The place of conformal radiotherapy in the routine work: national investigation of SFRO members'opinion

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Lagrange, J.L.; Lipinski, F.

2001-01-01

National French investigation of the using of conformal radiotherapy in routine work, has been made in 2001, in 180 radiotherapeutic centers. Eighty responses have been obtained and analyzed. Conformal radiotherapy is used in 88% and virtual simulation in 60% of these centers. There is a heterogeneity in the equipment of these institutions, most of them have one or two machines. The accelerator equipment differs, and the availability of multi-leaf collimators and electronic portal imaging is limited. Actually only eleven centers have IMRT, eight have projects to install. Only six centers have CT-scans, used mainly for simulation. In 75% of centers conformal radiotherapy have been used in the treatment of CNS-tumors, head and neck cancers, prostate, and non-small cell lung carcinoma. If there are more equipment and human facilities to use conformal radiotherapy, this treatment can be proposed to patients with breast cancer, rectal and gynecological tumors. According 90% of responses, all prostatic cancers need conformal radiotherapy. The analysis of routine use of conformal radiotherapy in France shows an important heterogeneity but it seems that there is an agreement with objectives of this treatment. (authors)

Conformity Index and Homogeneity Index of the Postoperative Whole Breast Radiotherapy.

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Petrova, Deva; Smickovska, Snezana; Lazarevska, Emilija

2017-10-15

The treatment of breast cancer involves a multidisciplinary approach in which radiotherapy plays a key role. The conformity index and the homogeneity index are two analysis tools of a treatment plan using conformal radiotherapy. The purpose of this article is an analysis of these two parameters in the assessment of the treatment plans in 58 patients undergoing postoperative radiotherapy of the whole breast. All 58 patients participating in the study had a conservatively treated early-stage breast cancer. The treatment was performed using a standard regimen of fractionation in 25 fractions up to a total dose of 50 Gy. Dose-volume histograms were generated for both plans with and without segmental fields. Pair samples t-test was used. The technique with segmental fields allowed us more homogeneity distribution when compared to standard two tangential field techniques. The HI values were 1.08 ± 0.01 and 1.09 ± 0.01 for segment and technique with two tangential fields (p conformity and the homogeneity index are important tools in the analysis of the treatment plans during radiation therapy in patients with early-stage breast cancer. Adding segment fields in the administration of radiotherapy in patients with conservatively treated breast cancer can lead to improved dosage homogeneity and conformity.

A Comparative Dosimetric Study of Adjuvant 3D Conformal Radiotherapy for Operable Stomach Cancer Versus AP-PA Conventional Radiotherapy in NCI-Cairo

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El-Hossiny, H.A.; Diab, N.A.; El-Taher, M.M.

2009-01-01

This study was to compare this multiple field conformal technique to the AP-PA technique with respect to target volume coverage and dose to normal tissues. Materials and Methods: Seventeen patients with stages II-III denocarcinoma of the stomach were treated with adjuvant postoperative chemoradiotherapy presented to radiotherapy department in National Cancer Institute, Cairo in period between February 2009 to March 2010 using 3D conformal radiotherapy technique that consisted of a mono isocentric arrangement employing 4-6 radiation fields. For each patient, a second radiotherapy treatment plan was done using an antroposterior (AP-PA) fields, the two techniques were then compared using dose volume histogram (DVH) analysis. Results: Comparing different DVHs, it was found that the planning target volume (PTV) was adequately covered in both (3D and 2D) plans while the left kidney and spinal cord demonstrate lower radiation doses on using the conformal technique. The liver doses is higher in the 3D tecq, but still well below liver tolerance. Conclusions: Both 3D conformal radiotherapy and AP-PA conventional techniques doses are within range of normal tissues tolerance. Regarding the left kidney and spinal cord the 3D conformal radiotherapy is superior than the AP-PA conventional techniques but with higher doses to the liver in the 3D conformal radiotherapy compared to the AP-PA conventional techniques

Bladder filling variation during conformal radiotherapy for rectal cancer

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Sithamparam, S.; Ahmad, R.; Sabarudin, A.; Othman, Z.; Ismail, M.

2017-05-01

Conformal radiotherapy for rectal cancer is associated with small bowel toxicity mainly diarrhea. Treating patients with a full bladder is one of the practical solutions to reduce small bowel toxicity. Previous studies on prostate and cervix cancer patients revealed that maintaining consistent bladder volume throughout radiotherapy treatment is challenging. The aim of this study was to measure bladder volume variation throughout radiotherapy treatment. This study also measured the association between bladder volume changes and diarrhea. Twenty two rectal cancer patients were recruited prospectively. Patients were planned for treatment with full bladder following departmental bladder filling protocol and the planning bladder volume was measured during CT-simulation. During radiotherapy, the bladder volume was measured weekly using cone-beam computed tomography (CBCT) and compared to planning bladder volume. Incidence and severity of diarrhea were recorded during the weekly patient review. There was a negative time trend for bladder volume throughout five weeks treatment. The mean bladder volume decreased 18 % from 123 mL (SD 54 mL) during CT-simulation to 101 mL (SD 71 mL) on the 5th week of radiotherapy, but the decrease is not statistically significant. However, there was a large variation of bladder volume within each patient during treatment. This study showed an association between changes of bladder volume and diarrhea (P = 0.045). In conclusion bladder volume reduced throughout radiotherapy treatment for conformal radiotherapy for rectal cancer and there was a large variation of bladder volume within patients.

Bladder filling variation during conformal radiotherapy for rectal cancer

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Sithamparam, S; Ahmad, R; Sabarudin, A; Othman, Z; Ismail, M

2017-01-01

Conformal radiotherapy for rectal cancer is associated with small bowel toxicity mainly diarrhea. Treating patients with a full bladder is one of the practical solutions to reduce small bowel toxicity. Previous studies on prostate and cervix cancer patients revealed that maintaining consistent bladder volume throughout radiotherapy treatment is challenging. The aim of this study was to measure bladder volume variation throughout radiotherapy treatment. This study also measured the association between bladder volume changes and diarrhea. Twenty two rectal cancer patients were recruited prospectively. Patients were planned for treatment with full bladder following departmental bladder filling protocol and the planning bladder volume was measured during CT-simulation. During radiotherapy, the bladder volume was measured weekly using cone-beam computed tomography (CBCT) and compared to planning bladder volume. Incidence and severity of diarrhea were recorded during the weekly patient review. There was a negative time trend for bladder volume throughout five weeks treatment. The mean bladder volume decreased 18 % from 123 mL (SD 54 mL) during CT-simulation to 101 mL (SD 71 mL) on the 5th week of radiotherapy, but the decrease is not statistically significant. However, there was a large variation of bladder volume within each patient during treatment. This study showed an association between changes of bladder volume and diarrhea (P = 0.045). In conclusion bladder volume reduced throughout radiotherapy treatment for conformal radiotherapy for rectal cancer and there was a large variation of bladder volume within patients. (paper)

Patterns of failure in children with medulloblastoma treated with 3D conformal radiotherapy

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Skowronska-Gardas, Anna; Chojnacka, Marzanna; Morawska-Kaczynska, Marzena; Perek, Danuta; Perek-Polnik, Marta

2007-01-01

Background and purpose: Craniospinal irradiation for medulloblastoma is one of the most complex techniques employed in radiotherapy. Many reports stress the impact of irradiation quality on survival in these patients. Our report presents the outcome and patterns of failure for 95 patients treated with 3D conformal radiotherapy (3D-CRT). Materials and methods: From 1998 to 2003, 95 children with medulloblastoma received 3D conformal radiotherapy. All of them were previously treated with surgery and chemotherapy. The brain and upper spinal cord were treated with two lateral 6 MV photon fields. In four patients, the cribriform plate was irradiated by the additional field. For primary tumour bed we applied two or three photon beams. Spinal cord was irradiated either with 18-20 MeV electron fields or with a mixed beam. Results: With a median follow-up of 48 months, 32/95 patients suffered a multifocal (21) or isolated (11) recurrence. We evaluated every primary site of failure. In all patients, the recurrence appeared within the isodose level of 95-100%. Conclusions: Patterns of failure in medulloblastoma patients treated with 3D conformal radiotherapy indicated that the relapse was mainly associated with poor response to pre-irradiation chemotherapy. We believe that 3D conformal radiotherapy allows avoiding failures, related to radiotherapy uncertainties

Transition from 2-D radiotherapy to 3-D conformal and intensity modulated radiotherapy

International Nuclear Information System (INIS)

2008-05-01

Cancer is one of the leading causes of death globally and radiotherapy is currently an essential component in the management of cancer patients, either alone or in combination with surgery or chemotherapy, both for cure or palliation. It is now recognized that safe and effective radiotherapy service needs not only substantial capital investment in radiotherapy equipment and specially designed facilities but also continuous investment in maintenance and upgrading of the equipment to comply with the technical progress, but also in training the staff. The recent IAEA-TECDOC publication 'Setting up a Radiotherapy Programme: Clinical, Medical Physics, Radiation Protection and Safety Aspects' provides general guidelines for designing and implementing radiotherapy services in Member States. Advances in computer technology have enabled the possibility of transitioning from basic 2- dimensional treatment planning and delivery (2-D radiotherapy) to a more sophisticated approach with 3-dimensional conformal radiotherapy (3-D CRT). Whereas 2-D radiotherapy can be applied with simple equipment, infrastructure and training, transfer to 3-D conformal treatments requires more resources in technology, equipment, staff and training. A novel radiation treatment approach using Intensity Modulated Radiation Therapy (IMRT) that optimizes the delivery of radiation to irregularly shaped tumour volumes demands even more sophisticated equipment and seamless teamwork, and consequentially more resources, advanced training and more time for treatment planning and verification of dose delivery than 3-D CRT. Whereas 3-D CRT can be considered as a standard, IMRT is still evolving. Due to the increased interest of Member States to the modern application of radiotherapy the IAEA has received a number of requests for guidance coming from radiotherapy departments that wish to upgrade their facilities to 3-D CRT and IMRT through Technical Cooperation programme. These requests are expected to increase

[Technique of complex mammary irradiation: Mono-isocentric 3D conformational radiotherapy and helical tomotherapy].

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Vandendorpe, B; Guilbert, P; Champagne, C; Antoni, T; Nguyen, T D; Gaillot-Petit, N; Servagi Vernat, S

2017-12-01

To evaluate the dosimetric contribution of helical tomotherapy for breast cancers compared with conformal radiotherapy in mono-isocentric technique. For 23 patients, the dosimetric results in mono-isocentric 3D conformational radiotherapy did not satisfy the constraints either of target volumes nor organs at risk. A prospective dosimetric comparison between mono-isocentric 3D conformational radiotherapy and helical tomotherapy was therefore carried out. The use of helical tomotherapy showed a benefit in these 23 patients, with either an improvement in the conformity index or homogeneity, but with an increase in low doses. Of the 23 patients, two had pectus excavatum, five had past thoracic irradiation and two required bilateral irradiation. The other 14 patients had a combination of morphology and/or indication of lymph node irradiation. For these patients, helical tomotherapy was therefore preferred to mono-isocentric 3D conformational radiotherapy. Tomotherapy appears to provide better homogeneity and tumour coverage. This technique of irradiation may be justified in the case of morphological situations such as pectus exavatum and in complex clinical situations. In other cases, conformal radiotherapy in mono-isocentric technique remains to be favoured. Copyright © 2017 Société française de radiothérapie oncologique (SFRO). Published by Elsevier SAS. All rights reserved.

The value of 18F-FDG PET in three-dimensional conformal radiotherapy of cancer

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Lv Huiqing; Zhang Zhongmin; Lv Zhonghong

2006-01-01

Three-dimensional conformal radiotherapy (3D-CRT) is based on an extensive use of modern medical imaging techniques. Delineation of the gross tumor volume and organs at risk constitutes one of the most important phases of conformal radiotherapy procedures. 18 F-fluorodeoxyglucose ( 18 F-FDG) PET possesses greater sensitivity and accuracy in detecting diseased lymph nodes, is an important staging examination for patients considered for radiation treatment with curative intent. 18 F-FDG PET has an important role in delineation of gross tumor volume for patients treated with three-dimensional conformal radiotherapy. (authors)

Acute and late side-effects of conventional and conformal pelvic radiotherapy for cervical and endometrial cancer

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Izmajlowicz, B.; Komafel, J.

2010-01-01

Aim of the study. The purpose of this prospective study was to analyze and compare acute and late side-effects observed in patients with cervical and endometrial cancer treated with conventional 2-dimensional (2D) and conformal 3-dimensional (3D) pelvic radiotherapy. Patients and method. 50 patients treated with conventional pelvic radiotherapy and 50 patients treated with conformal pelvic radiotherapy at the Clinical Department of Gynecological Radiotherapy of the Lower Silesian Oncology Center between November 2004 and October 2005 were entered into a prospective study. We assessed Radiotherapy side-effects according to EORTCIRTOG, performance status according to the WHO, Body Mass Index and hematologic parameters during radiotherapy and one year after treatment. Results. Performance status acc. to the WHO was significantly better in the conformal arm. Anemia and nausea were more frequent in the conventional arm. In both the study groups acute gastrointestinal and genitourinary morbidity was more frequent than late morbidity and performance status was better after than before radiotherapy. Mean BMI was lower after radiotherapy than before treatment. Conclusions. Conformal pelvic radiotherapy in patients with cervical and endometrial cancer is less toxic than conventional pelvic radiotherapy which is also confirmed by the performance status. (authors)

Analysis of the efficacy and safety of conventional radiotherapy of chest wall and clavicular field and three-dimensional conformal radiotherapy in patients after modified radical mastectomy

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Song-Lin Wang

2017-04-01

Full Text Available Objective: To explore the efficacy and safety of conventional radiotherapy of chest wall and clavicular field and three-dimensional conformal radiotherapy in patients after modified radical mastectomy. Methods: A total of 84 patients who were admitted in our hospital after modified radical mastectomy were included in the study and divided into the conventional radiotherapy group (n=42 and the three-dimensional conformal radiotherapy group (n=42 according to different radiotherapy methods. The patients in the conventional radiotherapy group were given conventional radiotherapy of chest wall and clavicular field, while the patients in the three-dimensional conformal radiotherapy group were given three-dimensional conformal radiotherapy. The serum tumor markers and peripheral blood T lymphocyte subsets 6-8 weeks after treatment in the two groups were detected. The clinical efficacy, and toxic and side effects in the two groups were evaluated. Results: The serum CA15-3, CA125, CEA, and CK19 levels after treatment in the two groups were significantly reduced when compared with before treatment, CD3 +,CD4 +, and CD4 +/CD8 + were significantly elevated, while CD8 + was significantly reduced when compared with before treatment, but the comparison of the above indicators between the two groups was not statistically significant. The occurrence rate of radioactive skin damage and pneumonia after treatment in the conventional radiotherapy group was significantly higher than that in the three-dimensional conformal radiotherapy group. Conclusions: The two kinds of radiotherapy schemes have an equal efficacy, but the toxic and side effects of three-dimensional conformal radiotherapy are significantly lower than those by the conventional radiotherapy, with a certain advantage.

3D Conformal radiotherapy for gastric cancer-results of a comparative planning study

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Leong, Trevor; Willis, David; Joon, Daryl Lim; Condron, Sara; Hui, Andrew; Ngan, Samuel Y.K.

2005-01-01

Background and purpose: Many radiation oncologists are reluctant to use anteroposterior-posteroanterior (AP-PA) field arrangements when treating gastric cancer with adjuvant postoperative radiotherapy due to concerns about normal tissue toxicity, particularly in relation to the kidneys and spinal cord. In this report, we describe a multiple-field conformal radiotherapy technique, and compare this technique to the more commonly used AP-PA technique that was used in the recently reported Intergroup study (INT0116). Materials and methods: Fifteen patients with stages II-IV adenocarcinoma of the stomach were treated with adjuvant postoperative chemoradiotherapy using a standardised 3D conformal radiotherapy technique that consisted of a 'split-field', mono-isocentric arrangement employing 6 radiation fields. For each patient, a second radiotherapy treatment plan was generated utilising AP-PA fields. The two techniques were then compared for target volume coverage and dose to normal tissues using dose volume histogram (DVH) analysis. Results: The conformal technique provides more adequate coverage of the target volume with 99% of the planning target volume (PTV) receiving 95% of the prescribed dose, compared to 93% using AP-PA fields. Comparative DVHs for the right kidney, left kidney and spinal cord demonstrate lower radiation doses using the conformal technique, and although the liver dose is higher, it is still well below liver tolerance. Conclusions: 3D conformal radiotherapy produces superior dose distributions and reduced radiation doses to the kidneys and spinal cord compared to AP-PA techniques, with the potential to reduce treatment toxicity

Doses to organs at cerebral risks: optimization by robotized stereotaxic radiotherapy and automatic segmentation atlas versus three dimensional conformal radiotherapy

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Bondiau, P.Y.; Thariat, J.; Benezery, K.; Herault, J.; Dalmasso, C.; Marcie, S.; Malandain, G.

2007-01-01

The stereotaxic radiotherapy robotized by 'Cyberknife fourth generation' allows a dosimetric optimization with a high conformity index on the tumor and radiation doses limited on organs at risk. A cerebral automatic anatomic segmentation atlas of organs at risk are used in routine in three dimensions. This study evaluated the superiority of the stereotaxic radiotherapy in comparison with the three dimensional conformal radiotherapy on the preservation of organs at risk in regard of the delivered dose to tumors justifying an accelerated hypo fractionation and a dose escalation. This automatic segmentation atlas should allow to establish correlations between anatomy and cerebral dosimetry; This atlas allows to underline the dosimetry optimization by stereotaxic radiotherapy robotized for organs at risk. (N.C.)

Dosimetry comparison of irradiation with conformal radiotherapy, intensity modulated radiotherapy, conformal radiotherapy in stereotactic conditions and robotic stereotactic radiotherapy for benign brain tumours

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Spasic, E.; Noel, A.; Buchheit, I.; Bernier, V.

2011-01-01

Purpose. - To compare several techniques in order to determine the best treatment for benign brain tumours. Methods and patients. - A retrospective study was performed for five patients who received 3D-conformal radiotherapy, intensity modulated radiotherapy or CyberKnife R . These patients had a meningioma, a pituitary tumour, a cranio-pharyngioma or a neurinoma. In each case, these treatment plans were optimised and compared with the three other dosimetries. Radiobiological or positioning parameters were evaluated, as well as dosimetric parameters, in order to compare treatments with different characteristics. Results. - The dosimetric parameters showed that the choice of treatment seemed to be determined mostly by tumour size, shape and proximity with organs at risk (not tumour localisation). Whereas the results showed no significant deviations with regards to the radiobiological parameters. Therefore, with these parameters, it was difficult to give priority to a treatment. Conclusions. - With regards to benign brain tumours of medium or large size, intensity modulated radiotherapy seemed the recommended treatment. It enabled to obtain a good ratio between efficacy and toxicity for tumours that are really close to organs at risk. Concerning small benign brain tumours, the CyberKnife R was probably the best treatment. (authors)

Pelvic Ewing sarcomas. Three-dimensional conformal vs. intensity-modulated radiotherapy

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Mounessi, F.S.; Lehrich, P.; Haverkamp, U.; Eich, H.T. [Muenster Univ. (Germany). Dept. of Radiation Oncology; Willich, N. [Muenster Univ. (Germany). Dept. of Radiation Oncology; Universitaetsklinikum Muenster (Germany). RiSK - Registry for the Evaluation of Late Side Effects after Radiotherapy in Childhood and Adolescence; Boelling, T. [Center for Radiation Oncology, Osnabrueck (Germany)

2013-04-15

The goal of the present work was to assess the potential advantage of intensity-modulated radiotherapy (IMRT) over three-dimensional conformal radiotherapy (3D-CRT) planning in pelvic Ewing's sarcoma. A total of 8 patients with Ewing sarcoma of the pelvis undergoing radiotherapy were analyzed. Plans for 3D-CRT and IMRT were calculated for each patient. Dose coverage of the planning target volume (PTV), conformity and homogeneity indices, as well as further parameters were evaluated. Results The average dose coverage values for PTV were comparable in 3D-CRT and IMRT plans. Both techniques had a PTV coverage of V{sub 95} > 98 % in all patients. Whereas the IMRT plans achieved a higher conformity index compared to the 3D-CRT plans (conformity index 0.79 {+-} 0.12 vs. 0.54 {+-} 0.19, p = 0.012), the dose distribution across the target volumes was less homogeneous with IMRT planning than with 3D-CRT planning. This difference was statistically significant (homogeneity index 0.11 {+-} 0.03 vs. 0.07 {+-} 0.0, p = 0.035). For the bowel, D{sub mean} and D{sub 1%}, as well as V{sub 2} to V{sub 60} were reduced in IMRT plans. For the bladder and the rectum, there was no significant difference in D{sub mean}. However, the percentages of volumes receiving at least doses of 30, 40, 45, and 50 Gy (V{sub 30} to V{sub 50}) were lower for the rectum in IMRT plans. The volume of normal tissue receiving at least 2 Gy (V{sub 2}) was significantly higher in IMRT plans compared with 3D-CRT, whereas at high dose levels (V{sub 30}) it was significantly lower. Compared to 3D-CRT, IMRT showed significantly better results regarding dose conformity (p = 0.012) and bowel sparing at dose levels above 30 Gy (p = 0.012). Thus, dose escalation in the radiotherapy of pelvic Ewing's sarcoma can be more easily achieved using IMRT. (orig.)

A survey on the state on the use of conformation radiotherapy units in Japan

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Tomaru, Teizo; Onai, Yoshio; Abe, Shunsuke

1985-01-01

A survey on the stage on the use of conformation radiotherapy units in Japan was performed by the Radiotherapy Equipments Committee of the Japanese Association for Radiotherapy Systems. The questionnaire was sent to 34 hospitals, which are all the hospitals equipped with these units, and 13 cancer and adult disease centers. The answers were collected from 42 hospitals, of which the 31 from formers and 11 from latters. In June, 1984, 27 conformation radiotherapy units (11 units with a pair of lower jaws and 16 units with multi-leaf collimators) were being used at 26 hospitals answered to questionnaire. During a month from May 16 to June 15 in 1984, conformation radiotherapy was performed at 10 hopsitals, and mean number of patients per day treated with these irradiation techniques was 3.7 +- 3.5. Fixed beam radiotherapy with irregular shape fields using multi-leaf collimators was also performed at 8 hospitals and mean number of patients per day treated with this fixed beam was 6.6 +- 3.9. Hollow-out irradiation technique was used at 4 hospitals, and 3.8 patients per day per hospital were treated with this technique. (author)

Cardiac Exposure in the Dynamic Conformal Arc Therapy, Intensity-Modulated Radiotherapy and Volumetric Modulated Arc Therapy of Lung Cancer.

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Xin Ming

Full Text Available To retrospectively evaluate the cardiac exposure in three cohorts of lung cancer patients treated with dynamic conformal arc therapy (DCAT, intensity-modulated radiotherapy (IMRT, or volumetric modulated arc therapy (VMAT at our institution in the past seven years.A total of 140 lung cancer patients were included in this institutional review board approved study: 25 treated with DCAT, 70 with IMRT and 45 with VMAT. All plans were generated in a same commercial treatment planning system and have been clinically accepted and delivered. The dose distribution to the heart and the effects of tumor laterality, the irradiated heart volume and the beam-to-heart distance on the cardiac exposure were investigated.The mean dose to the heart among all 140 plans was 4.5 Gy. Specifically, the heart received on average 2.3, 5.2 and 4.6 Gy in the DCAT, IMRT and VMAT plans, respectively. The mean heart doses for the left and right lung tumors were 4.1 and 4.8 Gy, respectively. No patients died with evidence of cardiac disease. Three patients (2% with preexisting cardiac condition developed cardiac disease after treatment. Furthermore, the cardiac exposure was found to increase linearly with the irradiated heart volume while decreasing exponentially with the beam-to-heart distance.Compared to old technologies for lung cancer treatment, modern radiotherapy treatment modalities demonstrated better heart sparing. But the heart dose in lung cancer radiotherapy is still higher than that in the radiotherapy of breast cancer and Hodgkin's disease where cardiac complications have been extensively studied. With strong correlations of mean heart dose with beam-to-heart distance and irradiated heart volume, cautions should be exercised to avoid long-term cardiac toxicity in the lung cancer patients undergoing radiotherapy.

Beam shaping for conformal fractionated stereotactic radiotherapy: a modeling study

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Hacker, Fred L.; Kooy, Hanne M.; Bellerive, Marc R.; Killoran, Joseph H.; Leber, Zachary H.; Shrieve, Dennis C.; Tarbell, Nancy J.; Loeffler, Jay S.

1997-01-01

Purpose: The patient population treated with fractionated stereotactic radiotherapy (SRT) is significantly different than that treated with stereotactic radiosurgery (SRS). Generally, lesions treated with SRT are larger, less spherical, and located within critical regions of the central nervous system; hence, they offer new challenges to the treatment planner. Here a simple, cost effective, beam shaping system has been evaluated relative to both circular collimators and an ideal dynamically conforming system for effectiveness in providing conformal therapy for these lesions. Methods and Materials: We have modeled a simple system for conformal arc therapy using four independent jaws. The jaw positions and collimator angle are changed between arcs but held fixed for the duration of each arc. Eleven previously treated SRT cases have been replanned using this system. The rectangular jaw plans were then compared to the original treatment plans which used circular collimators. The plans were evaluated with respect to tissue sparing at 100%, 80%, 50%, and 20% of the prescription dose. A plan was also done for each tumor in which the beam aperture was continuously conformed to the beams eye view projection of the tumor. This was used as an ideal standard for conformal therapy in the absence of fluence modulation. Results: For tumors with a maximum extent of over 3.5 cm the rectangular jaw plans reduced the mean volume of healthy tissue involved at the prescription dose by 57% relative to the circular collimator plans. The ideal conformal plans offered no significant further improvement at the prescription dose. The relative advantage of the rectangular jaw plans decreased at lower isodoses so that at 20% of the prescription dose tissue involvement for the rectangular jaw plans was equivalent to that for the circular collimator plans. At these isodoses the ideal conformal plans gave substantially better tissue sparing. Conclusion: A simple and economical field shaping

Clinical Studies on conformal radiotherapy combined with epidermal ...

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Purpose: To study the effect of conformal radiotherapy combined with epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) in the second-line treatment of non-small cell lung cancer (NSCLC). Methods: A total of 316 patients attending Shanghai Pulmonary Hospital affiliated to Tongji University, were divided ...

Salvage conformal radiotherapy for biochemical recurrent prostate cancer after radical prostatectomy

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Carlos R. Monti

2006-08-01

Full Text Available OBJECTIVE: Assess the results of salvage conformal radiotherapy in patients with biochemical failure after radical prostatectomy and identify prognostic factors for biochemical recurrence and toxicity of the treatment. MATERIALS AND METHODS: From June 1998 to November 2001, 35 patients were submitted to conformal radiotherapy for PSA > 0.2 ng/mL in progression after radical prostatectomy and were retrospectively analyzed. The mean dose of radiation in prostatic bed was of 77.4 Gy (68-81. Variables related to the treatment and to tumor were assessed to identify prognostic factors for biochemical recurrence after salvage radiotherapy. RESULTS: The median follow-up was of 55 months (17-83. The actuarial survival rates free of biochemical recurrence and free of metastasis at a distance of 5 years were 79.7% e 84.7%, respectively. The actuarial global survival rate in 5 years was 96.1%.The actuarial survival rate free of biochemical recurrence in 5 years was 83.3% with PSA pre-radiotherapy 1 and 2 (p = 0.023. Dose > 70 Gy in 30% of the bladder volume implied in more acute urinary toxicity (p = 0.035. The mean time for the development of late urinary toxicity was 21 months (12-51. Dose > 55 Gy in 50% bladder volume implied in more late urinary toxicity (p = 0.018. A patient presented late rectal toxicity of 2nd grade. CONCLUSIONS: Conformal radiotherapy showed to be effective for the control of biochemical recurrence after radical prostatectomy. Patients with pre-therapy PSA < 2 ng/mL have more biochemical control.

Parotid gland sparing radiotherapy technique using 3-D conformal radiotherapy for nasopharyngeal carcinoma

International Nuclear Information System (INIS)

Lim, Ji Hoon; Kim, Gwi Eon; Keum, Ki Chang; Suh, Chang Ok; Lee, Sang Wook; Park, Hee Chul; Cho, Jae Ho; Chang, Sei Kyung; Loh, Juhn Kyu

2000-01-01

Although using the high energy photon beam with conventional parallel-opposed beams radio-therapy for nasopgaryngeal carcinoma, radiation-induced xerostomia is a troublesome problem for patients. We conducted this study to explore a new parotid gland sparing technique in 3-D conformal radiotherapy (3-DCRT) in an effort to prevent the radiation-induced xerostomia. We performed three different planning for four clinically node-negative nasopharyngeal cancer patients with different location of tumor(intracranial extension, nasal cavity extension, oropharyngeal extension, parapharyngeal extension), and intercompared the plans. Total prescription dose was 70.2 Gy to the isocenter. For plan-A, 2-D parallel opposing fields, a conventional radiotherapy technique, were employed. For plan-B, 2-D parallel opposing fields were used up until 54 Gy and afterwards 3-D non-coplanar beams were used. For plan-C, the new technique, 54Gy was delivered by 3-D conformal 3-port beams (AP and both lateral ports with wedge compensator, shielding both superficial lobes of parotid glands at the AP beam using BEV) from the beginning of the treatment and early spinal cord block (at 36 Gy) was performed. And bilateral posterior necks were treated with electron after 36 Gy. After 54 Gy, non-coplanar beams were used for cone-down plan. We intercompared dose statistics (Dmax, Dmin, Dmean, D95, D05, V95, V05, Volume receiving 46 Gy) and dose volume histograms (DVH) of tumor and normal tissues and NTCP values of parotid glands for the above three plans. For all patients, the new technique (plan-C) was comparable or superior to the other plans in target volume isodose distribution and dose statistics and it has more homogenous target volume coverage. The new technique was most superior to the other plans in parotid glands sparing (volume receiving 46 Gy: 100, 98, 69% for each plan-A, B and C). And it showed the lowest NTCP value of parotid glands in all patients (range of NTCP; 96-100%, 79-99%, 51

Salvage conformal radiotherapy for biochemical recurrent prostate cancer after radical prostatectomy

International Nuclear Information System (INIS)

Monti, Carlos R.; Nakamura, Ricardo A.; Ferrigno, Robson; Rossi Junior, Aristides; Kawakami, Neusa S.; Trevisan, Felipe A.

2006-01-01

Objective: Assess the results of salvage conformal radiotherapy in patients with biochemical failure after radical prostatectomy and identify prognostic factors for biochemical recurrence and toxicity of the treatment. Materials and methods: From June 1998 to November 2001, 35 patients were submitted to conformal radiotherapy for PSA ≥ 0.2 ng/mL in progression after radical prostatectomy and were retrospectively analyzed. The mean dose of radiation in prostatic bed was of 77.4 Gy (68-81). Variables related to the treatment and to tumor were assessed to identify prognostic factors for biochemical recurrence after salvage radiotherapy. Results: The median follow-up was of 55 months (17-83). The actuarial survival rates free of biochemical recurrence and free of metastasis at a distance of 5 years were 79.7% e 84.7%, respectively. The actuarial global survival rate in 5 years was 96.1%.The actuarial survival rate free of biochemical recurrence in 5 years was 83.3% with PSA pre-radiotherapy ≤ 1, 100% when > 1 and ≤ 2, and 57.1% when > 2 (p = 0.023). Dose > 70 Gy in 30% of the bladder volume implied in more acute urinary toxicity (p = 0.035). The mean time for the development of late urinary toxicity was 21 months (12-51). Dose > 55 Gy in 50% bladder volume implied in more late urinary toxicity (p = 0.018). A patient presented late rectal toxicity of second grade. Conclusions: Conformal radiotherapy showed to be effective for the control of biochemical recurrence after radical prostatectomy. Patients with pre-therapy PSA < 2 ng/mL have more biochemical control. (author)

Prospective randomized trail on chrono-chemotherapy + late course three dimensional conformal radio-therapy and conventional chemotherapy plus radiotherapy for nasopharyngeal carcinoma

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Jin Feng; Ouyang Jinling; Dong Hongmin; Wu Weili; Chen Haixia; He Zhihui

2005-01-01

Objective: To compare the therapeutic effects, toxic side effects of late-course three dimensional conformal radiotherapy plus chrono-chemotherapy (DDP + 5-FU/CF) and conventional radiotherapy plus chemotherapy for nasopharyngeal carcinoma (NPC). Methods: Eighty -six NPC patients admitted from Feb. 2001 to Jan. 2002 were divided randomly into two groups: 1. Chrono-chemotherapy + late course three dimensional conformal radiotherapy(CCR) group-44 patients were treated by late course three dimensional conformal radio-therapy plus chrono-chemotherapy, and 2. Routine-chemotherapy-radiotherapy (RCR) group-42 patients were treated by routine chemotherapy plus radiotherapy. The patients in CCR and RCR group were comparable in age, KPS, stage and pathology. All patients were treated by combined chemotherapy and radiotherapy, with chemotherapy stared 2 weeks ahead of radiotherapy. Chemotherapy: Braun pump was used in all drug infusions; 1. CCR group-DDP 80 mg/ m 2 starting from 10:00 until 22:00, 5-Fu 750 mg/d/m 2 starting from 22:00 until 10:00 next day, CF 200 mg/d/m 2 starting from 10:00 every day, infused at normal speed. These drugs were given for 3 days, 14 days as one cycle, totally 2 cycle, and 2. RCR group-with the same drugs at the same total dose, only with the difference being DDP and CF given QD, starting from 10:00 but at the normal speed. 5-Fu was given through-out the day and continuously for 3 days, totally for 2 cycles. Radiotherapy: linear accelerator irradiation was given to either group. Composite facio-cervical field + anterior cervical tangential field to D T 40 Gy/4w, followed by the coned down per-auricular field plus anterior tangential field or β beam irradiation. In CCR group, after D T 40gy/4w, late course 3-dimensional conformal radiotherapy (3DCRT) was used to add D T 30Gy/3w. In RCR group, routine radiotherapy of 40 Gy/w was supplemented with 30 Gy/3w. The total dose in either group was 70 Gy/7w at the nasopharynx, D T 60-70 Gy/6-7w at the

Conformal Radiotherapy in the Treatment of Advanced Juvenile Nasopharyngeal Angiofibroma With Intracranial Extension: An Institutional Experience

International Nuclear Information System (INIS)

Chakraborty, Santam; Ghoshal, Sushmita; Patil, Vijay Maruti; Oinam, Arun Singh; Sharma, Suresh C.

2011-01-01

Purpose: To describe the results of conformal radiotherapy in advanced juvenile nasopharyngeal angiofibroma in a tertiary care institution. Methods and Materials: Retrospective chart review was conducted for 8 patients treated with conformal radiotherapy between 2006 and 2009. The median follow-up was 17 months. All patients had Stage IIIB disease with intracranial extension. Radiotherapy was considered as treatment because patients were deemed inoperable owing to extensive intracranial/intraorbital extension or proximity to optic nerve. All but 1 patient were treated with intensity-modulated radiotherapy using seven coplanar fields. Median (range) dose prescribed was 39.6 (30-46) Gy. Actuarial analysis of local control and descriptive analysis of toxicity profile was conducted. Results: Despite the large and complex target volume (median planning target volume, 292 cm 3 ), intensity-modulated radiotherapy achieved conformal dose distributions (median van't Reit index, 0.66). Significant sparing of the surrounding organs at risk was obtained. No significant Grade 3/4 toxicities were experienced during or after treatment. Actual local control at 2 years was 87.5%. One patient died 1 month after radiotherapy secondary to massive epistaxis. The remaining 7 patients had progressive resolution of disease and were symptom-free at last follow-up. Persistent rhinitis was the only significant toxicity, seen in 1 patient. Conclusions: Conformal radiotherapy results in good local control with minimal acute and late side effects in juvenile nasopharyngeal angiofibromas, even in the presence of advanced disease.

Chest wall desmoid tumours treated with definitive radiotherapy: a plan comparison of 3D conformal radiotherapy, intensity-modulated radiotherapy and volumetric-modulated arc radiotherapy

International Nuclear Information System (INIS)

Liu, Jia; Ng, Diana; Lee, James; Stalley, Paul; Hong, Angela

2016-01-01

Definitive radiotherapy is often used for chest wall desmoid tumours due to size or anatomical location. The delivery of radiotherapy is challenging due to the large size and constraints of normal surrounding structures. We compared the dosimetry of 3D conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT) to evaluate the best treatment option. Ten consecutive patients with inoperable chest wall desmoid tumours (PTV range 416–4549 cm 3 ) were selected. For each patient, 3DCRT, IMRT and VMAT plans were generated and the Conformity Index (CI), organ at risk (OAR) doses and monitor unit (MU) were evaluated. The Wilcoxon signed-rank test was used to compare dose delivered to both target and OARs. The mean number of fields for 3DCRT and IMRT were 6.3 ± 2.1, 7.2 ± 1.8. The mean number of arcs for VMAT was 3.7 ± 1.1. The mean conformity index of VMAT (0.98 ± 0.14) was similar to that of IMRT (1.03 ± 0.13), both of which were significantly better than 3DCRT (1.35 ± 0.20; p = 0.005). The mean dose to lung was significantly higher for 3DCRT (11.9Gy ± 7.9) compared to IMRT (9.4Gy ± 5.4, p = 0.014) and VMAT (8.9Gy ± 4.5, p = 0.017). For the 3 females, the low dose regions in the ipsilateral breast for VMAT were generally less with VMAT. IMRT plans required 1427 ± 532 MU per fraction which was almost 4-fold higher than 3DCRT (313 ± 112, P = 0.005). Compared to IMRT, VMAT plans required 60 % less MU (570 ± 285, P = 0.005). For inoperable chest wall desmoid tumours, VMAT delivered equivalent target coverage when compared to IMRT but required 60 % less MU. Both VMAT and IMRT were superior to 3DCRT in terms of better PTV coverage and sparing of lung tissue

Clinical Applications of 3-D Conformal Radiotherapy

Science.gov (United States)

Miralbell, Raymond

Although a significant improvement in cancer cure (i.e. 20% increment) has been obtained in the last 2-3 decades, 30-40% of patients still fail locally after curative radiotherapy. In order to improve local tumor control rates with radiotherapy high doses to the tumor volume are frequently necessary. Three-dimensional conformal radiation therapy (3-D CRT) is used to denote a spectrum of radiation planning and delivery techniques that rely on three-dimensional imaging to define the target (tumor) and to distinguish it from normal tissues. Modern, high-precision radiotherapy (RT) techniques are needed in order to implement the goal of optimal tumor destruction delivering minimal dose to the non-target normal tissues. A better target definition is nowadays possible with contemporary imaging (computerized tomography, magnetic resonance imaging, and positron emission tomography) and image registration technology. A highly precise dose distributions can be obtained with optimal 3-D CRT treatment delivery techniques such as stereotactic RT, intensity modulated RT (IMRT), or protontherapy (the latter allowing for in-depth conformation). Patient daily set-up repositioning and internal organ immobilization systems are necessary before considering to undertake any of the above mentioned high-precision treatment approaches. Prostate cancer, brain tumors, and base of skull malignancies are among the sites most benefitting of dose escalation approaches. Nevertheless, a significant dose reduction to the normal tissues in the vicinity of the irradiated tumor also achievable with optimal 3-D CRT may also be a major issue in the treatment of pediatric tumors in order to preserve growth, normal development, and to reduce the risk of developing radiation induced diseases such as cancer or endocrinologic disorders.

Conformal radiotherapy for 6 cases of bile duct carcinoma

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Kawasaki, Yoshiyuki; Suzuki, Takashi; Sugahara, Shinji

1998-01-01

Authors performed the conformal radiotherapy using the multileaf collimator for inoperable patients with bile duct carcinoma and examined the usefulness of this treatment. Forty one patients were examined, whose age was from 45 to 80 years (mean: 69.5 years), and whose ratio of men to women was 1 to 1.6. Patients in Group I (palliative irradiation, 30 cases) received bilateral irradiation using the linac with 4 MV-x-ray of total 50.0 Gy (2.0 Gy a dose, 5 times a week), those in Group II (palliative irradiation, 5 cases) using the microtron with 10 MV-x-ray of total 50.0 Gy (2.0 Gy a dose, 5 times a week). And those in Group III (radial irradiation, 6 cases) were first irradiated using the microtron with total 40.0 Gy (2.0 Gy a dose, 5 times a week) and secondly by the conformal radiotherapy with total 20.0 Gy (2.0 Gy a dose, 5 times a week). Patients in Group III were irradiated with total 60.0 Gy. Patients in all Groups showed mild side-effects including nausea and vomiting. And patients in Group III, who were irradiated 10 Gy more than other Group, showed no severe side-effects as alimentary bleeding, liver function disorders and cholangitis. In Group I, one year survivors were 3 (10.0%) and two years survivors were none. The median survival month was 7.2 months. In Group II, one year survivor was 1 (20.0%) and two years survivors were none. The median survival month was 8.1 months. In Group III, one year survivors were 2 (33.3%), and two years survivors were 2 (33.3%). The median survival month was 11.2 months. Two patients are survival at present (March, 1998), 2 years and 10 months, and 2 years and 9 months, respectively. The conformal radiotherapy gave better results than the ordinary radiotherapy. (K.H.)

Could 3-D conformal radiotherapy improve the overall survival for non-small cell lung cancer?

International Nuclear Information System (INIS)

Giraud, P.; Helfre, S.; Lavole, A.; Rosenwald, J.C.; Cosset, J.M.

2002-01-01

The conformal radiotherapy approach, three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT), is based on modern imaging modalities, efficient 3-D treatment planning systems, sophisticated immobilization devices and demanding quality assurance and treatment verification. The main goal of conformal radiotherapy is to ensure a high dose distribution tailored to the limits of the target volume while reducing exposure of healthy tissues. These techniques would then allow a further dose escalation increasing local control and survival. Non-small cell lung cancer (NSCLC) is one of the most difficult malignant tumors to be treated. It combines geometrical difficulties due to respiratory motion, and number of low tolerance neighboring organs, and dosimetric difficulties because of the presence of huge inhomogeneities. This localization is an attractive and ambitious example for the evaluation of new techniques. However, the published clinical reports in the last years described very heterogeneous techniques and, in the absence of prospective randomized trials, it is somewhat difficult at present to evaluate the real benefits drawn from those conformal radiotherapy techniques. After reviewing the rationale for 3DCRT for NSCLC, this paper will describe the main studies of 3DCRT, in order to evaluate its impact on lung cancer treatment Then the current state-of-the-art of IMRT and the last technical and therapeutic innovations in NSCL will be discussed. (authors)

Magnetic Resonance Imaging and conformal radiotherapy: Characterization of MRI alone simulation for conformal radiotherapy. Development and evaluation of an automatic volumes of interest segmentation tool for prostate cancer radiotherapy

International Nuclear Information System (INIS)

Pasquier, David

2006-01-01

Radiotherapy is a curative treatment of malignant tumours. Radiotherapy techniques considerably evolved last years with the increasing integration of medical images in conformal radiotherapy. This technique makes it possible to elaborate a complex ballistics conforming to target volume and sparing healthy tissues. The examination currently used to delineate volumes of interest is Computed Tomography (CT), on account of its geometrical precision and the information that it provides on electronic densities needed to dose calculation. Magnetic Resonance Imaging (MRI) ensures a more precise delineation of target volumes in many locations, such as pelvis and brain. For pelvic tumours, the use of MRI needs image registration, which complicates treatment planning and poses the problem of the lack of in vivo standard method of validation. The obstacles in the use of MRI alone in treatment planning were evaluated. Neither geometrical distortion linked with the system and the patient nor the lack of information on electronic densities represent stumbling obstacles. Distortion remained low even in edge of large field of view on modern machines. The assignment of electronic densities to bone structures and soft tissues in MR images permitted to obtain equivalent dosimetry to that carried out on the original CT, with a good reproducibility and homogeneous distribution within target volume. The assignment of electronic densities could not be carried out using 20 MV photons and suitable ballistics. The development of Image Guided Radiotherapy could facilitate the use of MRI alone in treatment planning. Target volumes and organ at risk delineation is a time consuming task in radiotherapy planning. We took part in the development and evaluated a method of automatic and semi automatic delineation of volumes of interest from MRI images for prostate cancer radiotherapy. For prostate and organ at risk automatic delineation an organ model-based method and a seeded region growing method

Extracranial stereotactic radiotherapy: Evaluation of PTV coverage and dose conformity

International Nuclear Information System (INIS)

Haedinger, U.; Thiele, W.; Wulf, J.

2002-01-01

During the past few years the concept of cranial sterotactic radiotherapy has been successfully extended to extracranial tumoral targets. In our department, hypofractionated treatment of tumours in lung, liver, abdomen, and pelvis is performed in the Stereotactic Body Frame (ELEKTA Instrument AB) since 1997. We present the evaluation of 63 consecutively treated targets (22 lung, 21 liver, 20 abdomen/pelvis) in 58 patients with respect to dose coverage of the planning target volume (PTV) as well as conformity of the dose distribution. The mean PTV coverage was found to be 96.3%±2.3% (lung), 95.0%±4.5% (liver), and 92.1%±5.2% (abdomen/pelvis). For the so-called conformation number we obtained values of 0.73±0.09 (lung), 0.77±0.10 (liver), and 0.70±0.08 (abdomen/pelvis). The results show that highly conformal treatment techniques can be applied also in extracranial stereotactic radiotherapy. This is primarily due to the relatively simple geometrical shape of most of the targets. Especially lung and liver targets turned out to be approximately spherically/cylindrically shaped, so that the dose distribution can be easily tailored by rotational fields. (orig.) [de

Conformal radiotherapy for locally advanced juvenile nasopharyngeal angio-fibroma

Directory of Open Access Journals (Sweden)

Supriya Mallick

2015-01-01

Full Text Available Purpose: To assess the efficacy of radiation in the treatment of juvenile nasopharyngeal angiofibroma (JNA. Materials and Methods: Data were retrieved for JNA treated with radiotherapy from 1987-2012. The demographics, treatment and outcome data were recorded in predesigned proforma. Results: Data of 32 patients were retrieved. Median age was 17 years (range: 12-33 years. All patients received radiation because of refractory, residual or unresectable locally advanced disease. All patients were planned with a three-dimensional conformal technique (3DCRT. The median radiation dose was 30 Gray (range: 30-45 Gray. Median follow-up was 129 months (range: 1-276 months. At the last follow-up, 13 patients were found to have a radiological complete response. Two patients progressed 38 and 43 months after completion of treatment and opted for alternative treatment. One patient developed squamous cell carcinoma of the nasal ale 15 years after radiation. Conclusion: Conformal radiotherapy shows promise as an alternative treatment approach for locally advanced JNA and confers long-term disease control with minimal toxicity.

A computer-controlled conformal radiotherapy system. III: graphical simulation and monitoring of treatment delivery

International Nuclear Information System (INIS)

Kessler, Marc L.; McShan, Daniel L.; Fraass, Benedick A.

1995-01-01

Purpose: Safe and efficient delivery of radiotherapy using computer-controlled machines requires new procedures to design and verify the actual delivery of these treatments. Graphical simulation and monitoring techniques for treatment delivery have been developed for this purpose. Methods and Materials: A graphics-based simulator of the treatment machine and a set of procedures for creating and manipulating treatment delivery scripts are used to simulate machine motions, detect collisions, and monitor machine positions during treatment. The treatment delivery simulator is composed of four components: a three-dimensional dynamic model of the treatment machine; a motion simulation and collision detection algorithm, user-interface widgets that mimic the treatment machine's control and readout devices; and an icon-based interface for creating and manipulating treatment delivery scripts. These components are used in a stand-alone fashion for interactive treatment delivery planning and integrated with a machine control system for treatment implementation and monitoring. Results: A graphics-based treatment delivery simulator and a set of procedures for planning and monitoring computer-controlled treatment delivery have been developed and implemented as part of a comprehensive computer-controlled conformal radiotherapy system. To date, these techniques have been used to design and help monitor computer-controlled treatments on a radiotherapy machine for more than 200 patients. Examples using these techniques for treatment delivery planning and on-line monitoring of machine motions during therapy are described. Conclusion: A system that provides interactive graphics-based tools for defining the sequence of machine motions, simulating treatment delivery including collision detection, and presenting the therapists with continual visual feedback from the treatment machine has been successfully implemented for routine clinical use as part of an overall system for computer

Brainstem tolerance to conformal radiotherapy of skull base tumors

International Nuclear Information System (INIS)

Debus, J.; Hug, E.B.; Munzenrider, J.E.; Liebsch, N.J.; O'Farrell, D.; Efird, J.; Daly, W.; Suit, H.D.

1996-01-01

Purpose/Objective: Brainstem tolerance to inhomogenous radiation doses applied by modern conformal radiotherapy has not yet been examined. The aim of this study was to analyse the incidence of brainstem toxicity in patients treated for skull base tumors with high dose conformal radiotherapy. Materials and Methods: Between 1974 and 1995, 367 patients with chordomas (n=195) and chondrosarcomas (n=172) of the base of skull have been treated with combined megavoltage photon and 160 MeV proton radiotherapy. All patients had previously undergone biopsy, subtotal or total tumor removal. 104 patients had two or more surgical procedures before radiotherapy. Following 3D treatment planning with delineation of target volumes and critical non-target structures, dose distributions and dose volume histograms were calculated [at the time of treatment delivery]. Radiotherapy was given once a day, 1.8 Gy or CGE (Cobalt Gy Equivalent: Proton Gy X 1.1) per fraction, 5 fractions per week, with prescribed target doses ranging from 63 CGE to 79.2 CGE (mean = 67.8 CGE). Doses to the brainstem surface were limited to ≤64 CGE and to the brainstem center to ≤53 CGE. Dose distributions were developed to limit dose to brainstem surface and center; current plans limit dose to surface and center to ≤64 CGE and ≤53 CGE, respectively. Brainstem toxicity was scored according to the RTOG grading system. Results: Follow-up ranged from 6 months to 21.4 years (mean = 42.5 months). Brainstem symptoms, attributable to the treatment, developed in 17 of 282 patients with local tumor control (6.0%), resulting in death of three patients. The mean time to onset of symptoms was 17 months (range: 4.5 to 177 months). These symptoms appeared in 89.5% within 3 years. Grading of the brainstem toxicity is listed in table 1. Actuarial rates of 5 and 10 year toxicity free survival were 87% and 82% respectively. Increased risk of brainstem toxicity was significantly associated with maximum brainstem dose

Accelerated partial breast irradiation using robotic radiotherapy: a dosimetric comparison with tomotherapy and three-dimensional conformal radiotherapy.

Science.gov (United States)

Rault, Erwann; Lacornerie, Thomas; Dang, Hong-Phuong; Crop, Frederik; Lartigau, Eric; Reynaert, Nick; Pasquier, David

2016-02-27

Accelerated partial breast irradiation (APBI) is a new breast treatment modality aiming to reduce treatment time using hypo fractionation. Compared to conventional whole breast irradiation that takes 5 to 6 weeks, APBI is reported to induce worse cosmetic outcomes both when using three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT). These late normal tissue effects may be attributed to the dose volume effect because a large portion of the non-target breast tissue volume (NTBTV) receives a high dose. In the context of APBI, non-coplanar beams could spare the NTBTV more efficiently. This study evaluates the dosimetric benefit of using the Cyberknife (CK) for APBI in comparison to IMRT (Tomotherapy) and three dimensional conformal radiotherapy (3D-CRT). The possibility of using surgical clips, implanted during surgery, to track target movements is investigated first. A phantom of a female thorax was designed in-house using the measurements of 20 patients. Surgical clips of different sizes were inserted inside the breast. A treatment plan was delivered to the mobile and immobile phantom. The motion compensation accuracy was evaluated using three radiochromic films inserted inside the breast. Three dimensional conformal radiotherapy (3D-CRT), Tomotherapy (TOMO) and CK treatment plans were calculated for 10 consecutive patients who received APBI in Lille. To ensure a fair comparison of the three techniques, margins applied to the CTV were set to 10 mm. However, a second CK plan was prepared using 3 mm margins to evaluate the benefits of motion compensation. Only the larger clips (VITALITEC Medium-Large) could be tracked inside the larger breast (all gamma indices below 1 for 1 % of the maximum dose and 1 mm). All techniques meet the guidelines defined in the NSABP/RTOG and SHARE protocols. As the applied dose volume constraints are very strong, insignificant dosimetric differences exist between techniques regarding the PTV

Accelerated partial breast irradiation using robotic radiotherapy: a dosimetric comparison with tomotherapy and three-dimensional conformal radiotherapy

International Nuclear Information System (INIS)

Rault, Erwann; Lacornerie, Thomas; Dang, Hong-Phuong; Crop, Frederik; Lartigau, Eric; Reynaert, Nick; Pasquier, David

2016-01-01

Accelerated partial breast irradiation (APBI) is a new breast treatment modality aiming to reduce treatment time using hypo fractionation. Compared to conventional whole breast irradiation that takes 5 to 6 weeks, APBI is reported to induce worse cosmetic outcomes both when using three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT). These late normal tissue effects may be attributed to the dose volume effect because a large portion of the non-target breast tissue volume (NTBTV) receives a high dose. In the context of APBI, non-coplanar beams could spare the NTBTV more efficiently. This study evaluates the dosimetric benefit of using the Cyberknife (CK) for APBI in comparison to IMRT (Tomotherapy) and three dimensional conformal radiotherapy (3D-CRT). The possibility of using surgical clips, implanted during surgery, to track target movements is investigated first. A phantom of a female thorax was designed in-house using the measurements of 20 patients. Surgical clips of different sizes were inserted inside the breast. A treatment plan was delivered to the mobile and immobile phantom. The motion compensation accuracy was evaluated using three radiochromic films inserted inside the breast. Three dimensional conformal radiotherapy (3D-CRT), Tomotherapy (TOMO) and CK treatment plans were calculated for 10 consecutive patients who received APBI in Lille. To ensure a fair comparison of the three techniques, margins applied to the CTV were set to 10 mm. However, a second CK plan was prepared using 3 mm margins to evaluate the benefits of motion compensation. Only the larger clips (VITALITEC Medium-Large) could be tracked inside the larger breast (all gamma indices below 1 for 1 % of the maximum dose and 1 mm). All techniques meet the guidelines defined in the NSABP/RTOG and SHARE protocols. As the applied dose volume constraints are very strong, insignificant dosimetric differences exist between techniques regarding the PTV

Dosimetric comparison of three-dimensional conformal and intensity modulated radiotherapy in brain glioma

International Nuclear Information System (INIS)

Lu Jie; Zhang Guifang; Bai Tong; Yin Yong; Fan Tingyong; Wu Chaoxia

2009-01-01

Objective: To investigate the dosimetry advantages of intensity modulated radiotherapy (IMRT)of brain glioma compared with that of three-dimensional conformal radiotherapy (SD CRT). Methods: Ten patients with brain glioma were enrolled in this study. Three-dimensional conf0rmal and intensity modulated radiotherapy plans were performed for each patient. The dose distributions of target volume and normal tissues, conformal index (CI) and heterogeneous index (HI) were analyzed using the dose-volume histogram (DVH). The prescription dose was 60 Gy in 30 fractions. Results: IMRT plans decrease the maximum dose and volume of brainstem, mean dose of affected side parotid and maximum dose of spinal-cord. The CI for PTV of IMRT was superior to that of SD CRT, the HI for PTV has no statistical significance of the two model plans. Conclusions: IMRT plans can obviously decrease the dose and volume of brainstem. IMRT is a potential method in the treatment of brain glioma, and dose escalation was possible in patients with brain glioma. (authors)

Tolerance and early outcome results of postprostatectomy three-dimensional conformal radiotherapy

International Nuclear Information System (INIS)

Zelefsky, Michael J.; Aschkenasy, Eric; Kelsen, Suzanne; Leibel, Steven A.

1997-01-01

Purpose: Three-dimensional conformal radiotherapy (3D-CRT) has been associated with a reduction in acute and late toxicity among patients treated for localized prostatic cancer. The purpose of this study is to assess the acute and late toxicity of 3D-CRT delivered to patients in the postprostatectomy setting and to analyze which factors predict for durable biochemical control in this group of patients. Methods and Materials: Between 1988 and 1994, 42 patients were treated after prostatectomy with three-dimensional conformal radiotherapy. The median time from prostatectomy to radiotherapy was 11 months. Indications for treatment included a rising serum PSA level in 28 patients (65%) and positive surgical margins without a rising PSA level in 14 (35%). Twenty-five patients (60%) had pathologic stage T3 disease, and 32 (74%) had tumor at or close to the surgical margins. The median dose was 64.8 Gy, and the median follow-up time was 2 years. Results: 3D-CRT in the postprostatectomy setting was well tolerated. Three patients (7%) experienced Grade II acute genitourinary toxicity and nine patients (21%) experienced Grade II acute gastrointestinal toxicity during treatment. No patient experienced Grade III or higher acute morbidity. The 2-year actuarial risk for Grade II late genitourinary and gastrointestinal late complications were 5 and 9%, respectively. In patients with existing incontinence, the incidence of worsening stress incontinence 6 months after treatment was 17%, which resolved within 12 months to its preradiotherapy level in four of six cases (66%). The overall 2-year postirradiation PSA relapse-free survival rate was 53%. The 2-year PSA relapse-free survival was 66% for patients with undetectable PSA levels in the immediate postoperative period compared to 26% for those with detectable levels of PSA after surgery (p 1.0 ng/ml (p 1 ng/ml (p < 0.002) was the most important covariate predicting for a rising PSA after radiotherapy. Conclusions: After

External beam radiotherapy of localized prostatic adenocarcinoma. Evaluation of conformal therapy, field number and target margins

International Nuclear Information System (INIS)

Lennernaes, B.; Rikner, G.; Letocha, H.; Nilsson, S.

1995-01-01

The purpose of the present study was to identify factors of importance in the planning of external beam radiotherapy of prostatic adenocarcinoma. Seven patients with urogenital cancers were planned for external radiotherapy of the prostate. Four different techniques were used, viz. a 4-field box technique and four-, five- or six-field conformal therapy set-ups combined with three different margins (1-3 cm). The evaluations were based on the doses delivered to the rectum and the urinary bladder. A normal tissue complication probability (NTCP) was calculated for each plan using Lyman's dose volume reduction method. The most important factors that resulted in a decrease of the dose delivered to the rectum and the bladder were the use of conformal therapy and smaller margins. Conformal therapy seemed more important for the dose distribution in the urinary bladder. Five- and six-field set-ups were not significantly better than those with four fields. NTCP calculations were in accordance with the evaluation of the dose volume histograms. To conclude, four-field conformal therapy utilizing reduced margins improves the dose distribution to the rectum and the urinary bladder in the radiotherapy of prostatic adenocarcinoma. (orig.)

An ill-conditioning conformal radiotherapy analysis based on singular values decomposition

International Nuclear Information System (INIS)

Lefkopoulos, D.; Grandjean, P.; Bendada, S.; Dominique, C.; Platoni, K.; Schlienger, M.

1995-01-01

Clinical experience in stereotactic radiotherapy of irregular complex lesions had shown that optimization algorithms were necessary to improve the dose distribution. We have developed a general optimization procedure which can be applied to different conformal irradiation techniques. In this presentation this procedure is tested on the stereotactic radiotherapy modality of complex cerebral lesions treated with multi-isocentric technique based on the 'associated targets methodology'. In this inverse procedure we use the singular value decomposition (SVD) analysis which proposes several optimal solutions for the narrow beams weights of each isocentre. The SVD analysis quantifies the ill-conditioning of the dosimetric calculation of the stereotactic irradiation, using the condition number which is the ratio of the bigger to smaller singular values. Our dose distribution optimization approach consists on the study of the irradiation parameters influence on the stereotactic radiotherapy inverse problem. The adjustment of the different irradiation parameters into the 'SVD optimizer' procedure is realized taking into account the ratio of the quality reconstruction to the time calculation. It will permit a more efficient use of the 'SVD optimizer' in clinical applications for real 3D lesions. The evaluation criteria for the choice of satisfactory solutions are based on the dose-volume histograms and clinical considerations. We will present the efficiency of ''SVD optimizer'' to analyze and predict the ill-conditioning in stereotactic radiotherapy and to recognize the topography of the different beams in order to create optimal reconstructed weighting vector. The planification of stereotactic treatments using the ''SVD optimizer'' is examined for mono-isocentrically and complex dual-isocentrically treated lesions. The application of the SVD optimization technique provides conformal dose distribution for complex intracranial lesions. It is a general optimization procedure

Intensity modulated conformal radiotherapy

International Nuclear Information System (INIS)

Noel, Georges; Moty-Monnereau, Celine; Meyer, Aurelia; David, Pauline; Pages, Frederique; Muller, Felix; Lee-Robin, Sun Hae; David, Denis Jean

2006-12-01

This publication reports the assessment of intensity-modulated conformal radiotherapy (IMCR). This assessment is based on a literature survey which focussed on indications, efficiency and safety on the short term, on the risk of radio-induced cancer on the long term, on the role in the therapeutic strategy, on the conditions of execution, on the impact on morbidity-mortality and life quality, on the impact on the health system and on public health policies and program. This assessment is also based on the opinion of a group of experts regarding the technical benefit of IMCR, its indications depending on the cancer type, safety in terms of radio-induced cancers, and conditions of execution. Before this assessment, the report thus indicates indications for which the use of IMCR can be considered as sufficient or not determined. It also proposes a technical description of IMCR and helical tomo-therapy, discusses the use of this technique for various pathologies or tumours, analyses the present situation of care in France, and comments the identification of this technique in foreign classifications

Patient repositioning in prostate conformal radiotherapy by image fusion

International Nuclear Information System (INIS)

Betrouni, Nacim

2004-01-01

This research thesis first proposes an overview of imaging modalities which are generally used in radiotherapy, and briefly presents operation principles for ultrasound scans, scanners and MRI. The issue of patient repositioning in radiotherapy is then introduced, and already proposed solutions are presented. In the next part, the author addresses space location and ultrasound-based location, with a brief overview of methods used to track the displacements of a mobile object, in this case an ultrasound probe, and calibration. Then, after a presentation of the adopted method, and a discussion of published works related to contour extraction and to filtering and noise reduction methods in ultrasound imagery, the author addresses the issue of prostate segmentation based on ultrasound images. The next part deals with image registration with an overview of available methods and tools. A method of registration of pre-operation images obtained by MRI or scanner, and of intra-operation ultrasound images is proposed for a real-time registration. This method is aimed at supporting patient repositioning during prostate conformal radiotherapy

Indications for quality assurance in conformal radiotherapy in Italy

International Nuclear Information System (INIS)

Banci Buonamici, F.; DE Angelis, C.; Rosi, A.; Tabocchini, M.A.; Iotti, C.; Olmi, P.

2008-01-01

Intensity-Modulated Radiation Therapy (IMRT) is an advanced and promising technique of external beam irradiation. IMRT is able to conform the dose distribution to the 3D tumour shape also for complex geometries, preserving surrounding normal tissues and reducing the probability of side effects. IMRT is a time consuming and complex technique and its use demands high level quality assurance. It is, therefore, very important to define conditions for its utilization. Professionals of Radiotherapy Centres, with experience in the IMRT use, have constituted a multidisciplinary working group with the aim of developing indications in this field. Purpose of the present document is to highlight relevant aspects of the technique, but also to underline the high complexity of the technique, whose implementation requires extreme attention of the staff of Radiotherapy Centres involved [it

Conformal intensity-modulated radiotherapy (IMRT) delivered by robotic linac-conformality versus efficiency of dose delivery

International Nuclear Information System (INIS)

Webb, Steve

2000-01-01

Intensity-modulated radiotherapy (IMRT) may be delivered with a high-energy-photon linac mounted on a robotic gantry and executing a complex trajectory. In a previous paper an inverse-planning technique was developed for such an application. Here the work is extended to demonstrate the dependence of conformality on the size of the elemental pencil beam, on the complexity of the trajectory and on the sampling of azimuth and elevation of the collimated source. The improved conformality of complex trajectories is demonstrated and benchmarked relative to simpler trajectories, more representative of existing non-robotic IMRT techniques. Specifically, by choosing a very fine pencil beam, exquisitely conformal dose distributions have been obtained. Important sampling considerations have been determined. Expressions have been derived for the dosimetry and monitor-unit efficiency of robotic IMRT. Equivalent trajectories were computed for executing the complex robotic trajectories instead by using a conventional linac. The work benchmarks an ideal in IMRT against which more practical and more common techniques may be measured. (author)

Results of three-dimensional conformal radiotherapy and thalidomide for advanced hepatocellular carcinoma

International Nuclear Information System (INIS)

Hsu, Wei-Chung; Chung, Na-Na; Wang, Po-Ming; Ying, Kung-Shih; Shin, Jeng-Shiann; Chao, Che-Jen; Lin, Gau-De; Chan, Sue-Ching; Ting, Lai-Lei

2006-01-01

The purpose of this study was to evaluate the effectiveness of three-dimensional conformal radiotherapy and thalidomide in the treatment of advanced hepatocellular carcinoma. Between 1999 and 2003, 121 patients (mean age, 54.4±12.4 years; range, 20-81 years) with advanced hepatocellular carcinoma received three-dimensional conformal radiotherapy and thalidomide. Radiation was delivered in 1.5 Gy fractions twice daily for 5 days a week, for a total dose of 45-75 Gy. Mean treatment volume was 429.52±408.50 cm 3 (range, 26.89-2284.82 cm 3 ). Thalidomide was given concomitantly: 200 mg/day in 109 patients, 300 mg/day in 8 patients and 400 mg/day in 4 patients. Treatment responses, survival rates and factors affecting survival were analyzed. Treatment responses were observed in 61% of the patients. Liver cirrhosis (P=0.001) and tumor size (P=0.001) significantly affected the tumor responses. Overall survival at 6, 12 and 24 months was 84.8, 60.0 and 44.6%, respectively. On univariate analysis, liver cirrhosis (P=0.003), Karnofsky performance status (P=0.007), tumor size (P<0.001), portal vein tumor thrombosis (P<0.001) and alpha-fetoprotein level (P=0.003) were shown to significantly affect survival. On multivariate analysis, only thrombosis (P=0.039) and alpha-fetoprotein level (P=0.006) were shown to be factors affecting survival. Three-dimensional conformal radiotherapy with thalidomide seems to be effective in the treatment of advanced hepatocellular carcinoma. (author)

Conformal radiotherapy by intensity modulation of pediatrics tumors

International Nuclear Information System (INIS)

Leseur, J.; Le Prise, E.; Carrie, C.; Bernier, V.; Beneyton, V.; Mahe, M.A.; Supiot, S.

2009-01-01

The objective of this study is to take stock on the validated and potential indications of the conformal radiotherapy with intensity modulation ( intensity modulated radiotherapy I.M.R.T.) in pediatrics and to propose recommendations for its use as well as the adapted dose constraints. About 40 to 50% of children treated for a cancer are irradiated. The I.M.R.T., by linear accelerator or helical tomo-therapy has for aim to give a homogenous dose to the target volume and to save organs at risk. Its use in pediatrics seems particularly interesting because of the complexity of target volumes and the closeness of organs at risk. In compensation for these positive elements, the importance of low doses irradiation given in big volumes makes fear event consequences on growth and an increased incidence of secondary cancers in children suffering from tumors with high cure rates and long life expectancy. (N.C.)

Nasopharynx carcinoma treatment: from the conventional radiotherapy to the conformal radiotherapy with intensity modulation; Traitement du carcinome du nasopharynx: de la radiotherapie conventionnelle a la radiotherapie conformationnelle avec modulation d'intensite

Energy Technology Data Exchange (ETDEWEB)

Mokaouim, K.; Grehange, G.; Truc, G.; Peingnaux, K.; Martin, E.; Zanetta, S.; Bruchon, Y.; Bonnetain, F.; Maingon, P. [Centre Georges-Francois Leclerc, 21 - Dijon (France)

2009-10-15

The objective of this study was to evaluate retrospectively the impact of factors linked to the radiotherapy realisation on the local and locoregional control, the global survival, the survival without disease of patients suffering of naso-pharynx carcinoma. Conclusion: the patients suffering of a nasopharynx carcinoma treated by irradiation associated to chemotherapy have an improved global survival and an improved survival without disease. The conformal radiotherapy with or without modulated intensity reduce the risk of serous otitis, trismus and xerostomia at long term. It seems necessary to realize multi centric studies with a longer period of follow up before asserting the advantages of the I.M.R.T. in comparison to the classical and conformal technique in the treatment of naso-pharynx carcinomas. (N.C.)

Comparison of Heart and Coronary Artery Doses Associated With Intensity-Modulated Radiotherapy Versus Three-Dimensional Conformal Radiotherapy for Distal Esophageal Cancer

Energy Technology Data Exchange (ETDEWEB)

Kole, Thomas P.; Aghayere, Osarhieme; Kwah, Jason [Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY (United States); Yorke, Ellen D. [Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY (United States); Goodman, Karyn A., E-mail: goodmank@mskcc.org [Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY (United States)

2012-08-01

Purpose: To compare heart and coronary artery radiation exposure using intensity-modulated radiotherapy (IMRT) vs. four-field three-dimensional conformal radiotherapy (3D-CRT) treatment plans for patients with distal esophageal cancer undergoing chemoradiation. Methods and Materials: Nineteen patients with distal esophageal cancers treated with IMRT from March 2007 to May 2008 were identified. All patients were treated to 50.4 Gy with five-field IMRT plans. Theoretical 3D-CRT plans with four-field beam arrangements were generated. Dose-volume histograms of the planning target volume, heart, right coronary artery, left coronary artery, and other critical normal tissues were compared between the IMRT and 3D-CRT plans, and selected parameters were statistically evaluated using the Wilcoxon rank-sum test. Results: Intensity-modulated radiotherapy treatment planning showed significant reduction (p < 0.05) in heart dose over 3D-CRT as assessed by average mean dose (22.9 vs. 28.2 Gy) and V30 (24.8% vs. 61.0%). There was also significant sparing of the right coronary artery (average mean dose, 23.8 Gy vs. 35.5 Gy), whereas the left coronary artery showed no significant improvement (mean dose, 11.2 Gy vs. 9.2 Gy), p = 0.11. There was no significant difference in percentage of total lung volume receiving at least 10, 15, or 20 Gy or in the mean lung dose between the planning methods. There were also no significant differences observed for the kidneys, liver, stomach, or spinal cord. Intensity-modulated radiotherapy achieved a significant improvement in target conformity as measured by the conformality index (ratio of total volume receiving 95% of prescription dose to planning target volume receiving 95% of prescription dose), with the mean conformality index reduced from 1.56 to 1.30 using IMRT. Conclusions: Treatment of patients with distal esophageal cancer using IMRT significantly decreases the exposure of the heart and right coronary artery when compared with 3D

Conformational dynamics data bank: a database for conformational dynamics of proteins and supramolecular protein assemblies.

Science.gov (United States)

Kim, Do-Nyun; Altschuler, Josiah; Strong, Campbell; McGill, Gaël; Bathe, Mark

2011-01-01

The conformational dynamics data bank (CDDB, http://www.cdyn.org) is a database that aims to provide comprehensive results on the conformational dynamics of high molecular weight proteins and protein assemblies. Analysis is performed using a recently introduced coarse-grained computational approach that is applied to the majority of structures present in the electron microscopy data bank (EMDB). Results include equilibrium thermal fluctuations and elastic strain energy distributions that identify rigid versus flexible protein domains generally, as well as those associated with specific functional transitions, and correlations in molecular motions that identify molecular regions that are highly coupled dynamically, with implications for allosteric mechanisms. A practical web-based search interface enables users to easily collect conformational dynamics data in various formats. The data bank is maintained and updated automatically to include conformational dynamics results for new structural entries as they become available in the EMDB. The CDDB complements static structural information to facilitate the investigation and interpretation of the biological function of proteins and protein assemblies essential to cell function.

Conformal radiotherapy for prostate cancer: contribution of pelvic immobilization and new fiducial markers

International Nuclear Information System (INIS)

Garcia, R.; Oozeer, R.; Le Thanh, H.; Chauvet, B.; Toy, B.J.; Reboul, F.

1997-01-01

To reduce errors in the positioning of patients treated with external conformal radiotherapy for prostate cancer, we evaluated both the use of an immobilization device and new fiducial markers. The immobilization device consisted of an individual mold made of polyurethane foam. Two sets of skin markers located on the anterior tibial surfaces were used to identify the pelvic isocenter. The patient's position was evaluated by orthogonal port film which were then compared with the original simulation film. Results are presented with respect to orthogonal axes. Comparison with classic procedures without immobilization showed that use of the mold and new fiducial markers led to a decrease in set-up errors which were less than 5 mm. With the use of an immobilization device and optimized techniques for patients' positioning, conformal radiotherapy of prostate cancer is more accurate. (authors)

Conventional and conformal technique of external beam radiotherapy in locally advanced cervical cancer: Dose distribution, tumor response, and side effects

Science.gov (United States)

Mutrikah, N.; Winarno, H.; Amalia, T.; Djakaria, M.

2017-08-01

The objective of this study was to compare conventional and conformal techniques of external beam radiotherapy (EBRT) in terms of the dose distribution, tumor response, and side effects in the treatment of locally advanced cervical cancer patients. A retrospective cohort study was conducted on cervical cancer patients who underwent EBRT before brachytherapy in the Radiotherapy Department of Cipto Mangunkusumo Hospital. The prescribed dose distribution, tumor response, and acute side effects of EBRT using conventional and conformal techniques were investigated. In total, 51 patients who underwent EBRT using conventional techniques (25 cases using Cobalt-60 and 26 cases using a linear accelerator (LINAC)) and 29 patients who underwent EBRT using conformal techniques were included in the study. The distribution of the prescribed dose in the target had an impact on the patient’s final response to EBRT. The complete response rate of patients to conformal techniques was significantly greater (58%) than that of patients to conventional techniques (42%). No severe acute local side effects were seen in any of the patients (Radiation Therapy Oncology Group (RTOG) grades 3-4). The distribution of the dose and volume to the gastrointestinal tract affected the proportion of mild acute side effects (RTOG grades 1-2). The urinary bladder was significantly greater using conventional techniques (Cobalt-60/LINAC) than using conformal techniques at 72% and 78% compared to 28% and 22%, respectively. The use of conformal techniques in pelvic radiation therapy is suggested in radiotherapy centers with CT simulators and 3D Radiotherapy Treatment Planning Systems (RTPSs) to decrease some uncertainties in radiotherapy planning. The use of AP/PA pelvic radiation techniques with Cobalt-60 should be limited in body thicknesses equal to or less than 18 cm. When using conformal techniques, delineation should be applied in the small bowel, as it is considered a critical organ according to RTOG

Conformal three dimensional radiotherapy treatment planning in Lund

International Nuclear Information System (INIS)

Knoos, T.; Nilsson, P.; Anders, A.

1995-01-01

The use of conformal therapy is based on 3-dimensional treatment planning as well as on methods and routines for 3-dimensional patient mapping, 3-dimensional virtual simulation and others. The management of patients at the Radiotherapy Department at the University Hospital in Lund (Sweden) is discussed. About 2100 new patients are annually treated with external radiotherapy using seven linear accelerators. Three of the accelerators have dual photon energies and electron treatment facilities. A multi-leaf collimator as well as an electronic portal imaging device are available on one machine. Two simulators and an in-house CT-scanner are used for treatment planning. From 1988 to 1992 Scandiplan (Umplan) was used. Since 1992, the treatment planning system is TMS (HELAX AB, Sweden), which is based on the pencil beam algorithm of Ahnesjo. The calculations use patient modulated accelerator specific energy fluence spectra which are compiled with pencil beams from Monte Carlo generated energy absorption kernels. Heterogeneity corrections are performed with results close to conventional algorithms. Irregular fields, either from standard or individual blocks and from multi-leaf collimators are handled by the treatment planning system. The field shape is determined conveniently using the beam's eye view. The final field shape is exported electronically to either the block cutting machine or the multileaf collimator control computer. All patient fields are checked against the beam's eye view during simulation using manual methods. Treatment verification is performed by portal films and in vivo dosimetry with silicon diodes or TL-dosimetry. Up to now, approximately 4400 patients have received a highly individualized 3-dimensional conformal treatment

Anal wall sparing effect of an endorectal balloon in 3D conformal and intensity-modulated prostate radiotherapy.

NARCIS (Netherlands)

Smeenk, R.J.; Lin, E.N.J.T. van; Kollenburg, P. van; Kunze-Busch, M.C.; Kaanders, J.H.A.M.

2009-01-01

BACKGROUND AND PURPOSE: To investigate the anal wall (Awall) sparing effect of an endorectal balloon (ERB) in 3D conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) for prostate cancer. MATERIALS AND METHODS: In 24 patients with localized prostate carcinoma, two planning

Initiation of conformal radiotherapy with a multileaf-collimator - An approach to clinical routine

International Nuclear Information System (INIS)

Bannach, B.; Doll, Th.; Pape, H.; Schmitt, G.

1995-01-01

The implementation of a three-dimensional conformal radiotherapy facility in the radiotherapy department of the Heinrich Heine University is described. Complex radiotherapy techniques with commercially available networked systems are introduced to improve clinical work. Over 18 month we have gained clinical experience with a PHILIPS Multileaf Collimator (MLC) mounted on a SL 25 linear accelerator. For a limited period the MLC was used as a conventional blocking device. The standard MLC-shapes are controlled with a stand-alone computer system. In addition, a three-dimensional treatment planning system (3-D-TPS / TMS-Radix, Helax AB) based on convolution/superposition algorithms was recently installed. Treatment optimization is achieved using static field arrangements with complete volumetric computerized tomographic patient data for 3-D-TPS. Conformal adaptation of the 95%-isodose to the Planning Target Volume (PTV, ICRU 50) results in MLC-field-shaping concerning size, position and contour to PTV-projection in beams-eye-view (BEV). Field prescription with defined leaf positions of the MLC-setting for geometrical beam shaping is transferred from TPS via TCP/IP. Patient treatment with complex coplanar and non-coplanar field arrangements is performed with an automatic set-up for gantry and collimator angle position contolled by a verification system. Quality assurance for treatment set-up is gained with a mega-voltage imaging device (MVI / PHILIPS SRI 100). Actual treatment outcome and accurate dose delivery for conformal therapy is verified by intercomparison of geometrical field matching of MVI and digitally reconstructed radiographs (DRR) for each delivered beam in BEV

Conformal three dimensional radiotherapy treatment planning in Lund

Energy Technology Data Exchange (ETDEWEB)

Knoos, T; Nilsson, P [Lund Univ. (Sweden). Dept. of Radiation Physics; Anders, A [Lund Univ. (Sweden). Dept. of Oncology

1995-12-01

The use of conformal therapy is based on 3-dimensional treatment planning as well as on methods and routines for 3-dimensional patient mapping, 3-dimensional virtual simulation and others. The management of patients at the Radiotherapy Department at the University Hospital in Lund (Sweden) is discussed. About 2100 new patients are annually treated with external radiotherapy using seven linear accelerators. Three of the accelerators have dual photon energies and electron treatment facilities. A multi-leaf collimator as well as an electronic portal imaging device are available on one machine. Two simulators and an in-house CT-scanner are used for treatment planning. From 1988 to 1992 Scandiplan (Umplan) was used. Since 1992, the treatment planning system is TMS (HELAX AB, Sweden), which is based on the pencil beam algorithm of Ahnesjo. The calculations use patient modulated accelerator specific energy fluence spectra which are compiled with pencil beams from Monte Carlo generated energy absorption kernels. Heterogeneity corrections are performed with results close to conventional algorithms. Irregular fields, either from standard or individual blocks and from multi-leaf collimators are handled by the treatment planning system. The field shape is determined conveniently using the beam`s eye view. The final field shape is exported electronically to either the block cutting machine or the multileaf collimator control computer. All patient fields are checked against the beam`s eye view during simulation using manual methods. Treatment verification is performed by portal films and in vivo dosimetry with silicon diodes or TL-dosimetry. Up to now, approximately 4400 patients have received a highly individualized 3-dimensional conformal treatment.

High precision conformal radiotherapy employing conservative margins in childhood benign and low-grade brain tumours

International Nuclear Information System (INIS)

Jalali, Rakesh; Budrukkar, Ashwini; Sarin, Rajiv; Sharma, Dayananda S.

2005-01-01

Background and purpose: To report local control and follow up outcome data of high precision conformal radiotherapy in childhood brain tumours. Materials and methods: Between December 1999 and December 2002, 26 children (17 boys and 9 girls, median age 11.5 years) with incompletely excised or recurrent benign and low-grade brain tumours [13 craniopharyngiomas, 11 low-grade gliomas (LGG) and 2 others] were treated with three-dimensional (3D) conformal radiotherapy (CRT) (12 patients) and stereotactic conformal radiotherapy (SCRT) (14 patients). Gross tumour volume (GTV) included neuro-imaging based visible tumour and/or resected tumour bed. Clinical target volume (CTV) consisted of GTV + 5 mm margin and planning target volume (PTV) consisted of additional 5 mm margin for CRT and 2 mm for SCRT. Treatment was delivered with 3-9 conformal fixed fields to a median dose of 54 Gy/30 fractions. Results: The actuarial 2 and 3 year disease free and overall survival was 96 and 100%, respectively (median follow up: 25 months, range 12-47 months). Radiological follow up available in 25 patients revealed complete response in 1, partial regression in 10, stable disease in 13 and progression in 1 patient (within the CTV). One patient with craniopharyngioma on a routine imaging revealed a mild asymptomatic cyst enlargement, which resolved with conservative management. A patient with chiasmatic glioma developed cystic degeneration and hydrocephalus 9 months after SCRT requiring cyst drainage and placement of a ventriculoperitoneal shunt. Conclusion: High-precision conformal techniques delivering irradiation to a computer generated target volume employing 7-10 mm 3D margins beyond the visible tumour and/or resected tumour bed appear to be safe in children with incompletely resected or recurrent benign and low-grade brain tumours, based on these data

Implementation of intensity-modulated conformational radiotherapy for cervical cancers at the Alexis Vautrin Centre

International Nuclear Information System (INIS)

Renard-Oldrini, Sophie

2010-01-01

As platinum salt based concomitant conformational radiotherapy and chemotherapy have been used as a standard treatment for cervical cancers but resulted in digestive and haematological toxicities, this research thesis reports the application of intensity-modulated conformational radiation therapy. After having recalled some epidemiological, anatomical aspects, diagnosis and treatments aspects regarding cervical cancer, the author presents this last treatment technique (principles, benefits, practical implementation). The author discusses results obtained by an experiment during which seven patients have been treated by simple conformational radiation therapy, and four by intensity-modulated conformational radiation therapy. Results are discussed in terms of volumes (clinical target volume, growth target volume, planned target volume), dosimetric results, toxicities (urine and skin), weight loss [fr

Phase I study of conformal radiotherapy with concurrent gemcitabine in locally advanced bladder cancer

International Nuclear Information System (INIS)

Sangar, Vijay K.; McBain, Catherine A.; Lyons, Jeanette; Ramani, Vijay; Logue, John; Wylie, James; Clarke, Noel W.; Cowan, Richard A.

2005-01-01

Purpose: A prospective phase I trial was conducted to determine the maximal tolerated dose of gemcitabine given once weekly during hypofractionated conformal radiotherapy to patients with locally advanced transitional cell carcinoma of the bladder. Eight male patients, median age 69 years, with Stage T2 (n = 4) or T3 (n = 4) N0M0, were enrolled in cohorts of 3. Treatment comprised conformal radiotherapy (52.5 Gy in 20 fractions) within 4 weeks, with concurrent gemcitabine once weekly for four cycles. The weekly gemcitabine dose was escalated from 100 mg/m 2 in increments of 50 mg/m 2 per cohort. Dose-limiting toxicity was defined as any acute Radiation Therapy Oncology Group (RTOG) toxicity Grade 3 or greater arising in >1 of 3 patients in each cohort. Tumor response was assessed cystoscopically and radiologically at 3 months. Results: All 8 patients completed radiotherapy, and 6 of 8 completed chemoradiotherapy. No acute toxicity greater than RTOG Grade 1 was seen with gemcitabine at 100 mg/m 2 . Dose-limiting toxicity was observed at 150 mg/m 2 with Grade 3 toxicity seen in 2 of 2 patients (one bladder, one bowel). An additional 3 patients received 100 mg/m 2 with minimal toxicity. No hematologic toxicity was encountered. A complete response was seen in 7 (87.5%) of 8 patients, all of whom were disease free at a median follow-up of 19.5 months (range, 14-23 months). No late toxicity (greater than RTOG Grade 0) has been observed. Conclusion: The maximal tolerated dose for gemcitabine given once weekly with concurrent hypofractionated conformal bladder radiotherapy was 150 mg/m 2 , with a maximal recommended dose of 100 mg/m 2 . This dose regimen has now entered Phase II clinical trials

Hyperfractionated 3D conformal radiotherapy and concurrent chemotherapy for unresectable stage III non-small cell lung cancer

International Nuclear Information System (INIS)

Choi, E.K.; Ahn, S.D.; Yi, B.Y.; Chang, H.S.; Lee, J.H.; Suh, C.W.; Lee, J.S.; Kim, S.H.; Koh, Y.S.; Kim, W.S.; Kim, D.S.; Kim, W.D.; Sohn, K.H.

1997-01-01

Purpose/Objective: This phase II study has been conducted to determine the feasibility, toxicity, response rate, local control, distant metastasis, and survival of hyperfractionated 3D conformal radiotherapy and concurrent chemotherapy with mitomycin C, vinblastine, and cisplatin in unresectable stage III non-small cell lung cancer (NSCLC), and also to find the most ideal 3D conformal radiotherapy technique. Materials and Methods: From Aug 1993, 173 patients with unresectable stage III NSCLC were entered into this trial and 146 (84%) completed the treatment. Hyperfractionated radiotherapy was given to a total dose of 65-70 Gy (120 cGy/fx, bid) with concurrent 2 cycles of MVP chemotherapy (Mitomycin C 6 mg/m 2 d2 and d29, Vinblastine 6 mg/m 2 d2 and d29, Cisplatin 60 mg/m 2 d1 and d28). Of these 146 patients who completed the treatment, 78 received noncoplanar 3D conformal radiotherapy using 4-6 fields and 17 received coplanar segmented conformal radiotherapy. Clinical tumor response was assessed one month after the completion of radiotherapy by computerized tomography (CT) scan. Toxicity was graded by RTOG and SWOG criteria. Normal tissue complication probability (NTCP) for lung was calculated to find the correlation with radiation pneumonitis. Results: Nineteen (13%) had stage IIIa and 127 (87%) had IIIb disease including 16 with pleural effusion and 20 with supraclavicular lymph node metastases. Response rate was 74%, including 20% complete response and 54% partial response. With a minimum follow up of 12 months, overall survival was 60% at 1 year, 30% at 2 years and median survival was 15 months. Patients achieving a complete response (n=29) had a 2-year overall survival of 46.5% compared to 28.7% for partial responders (n=79) (p=.001). Actuarial local control was 66.7% at 1 year and 43.7% at 2 years. Actuarial distant free survival was 52.3% at 1 year and 39.8% at 2 years. Major hematologic toxicity (Gr 3-4) occurred in 33% of the patients but treatment delay

Efficient CT simulation of the four-field technique for conformal radiotherapy of prostate carcinoma

International Nuclear Information System (INIS)

Valicenti, Richard K.; Waterman, Frank M.; Croce, Raymond J.; Corn, Benjamin; Suntharalingam, Nagalingam; Curran, Walter J.

1997-01-01

Purpose: Conformal radiotherapy of prostate carcinoma relies on contouring of individual CT slices for target and normal tissue localization. This process can be very time consuming. In the present report, we describe a method to more efficiently localize pelvic anatomy directly from digital reconstructed radiographs (DRRs). Materials and Methods: Ten patients with prostate carcinoma underwent CT simulation (the spiral mode at 3 mm separation) for conformal four-field 'box' radiotherapy. The bulbous urethra and bladder were opacified with iodinated contrast media. On lateral and anteroposterior DRRs, the volume of interest (VOI) was restricted to 1.0-1.5 cm tissue thickness to optimize digital radiograph reconstruction of the prostate and seminal vesicles. By removing unessential voxel elements, this method provided direct visualization of those structures. For comparison, the targets of each patient were also obtained by contouring CT axial slices. Results: The method was successfully performed if the target structures were readily visualized and geometrically corresponded to those generated by contouring axial images. The targets in 9 of 10 patients were reliable representations of the CT-contoured volumes. One patient had 18 mm variation due to the lack of bladder opacification. Using VOIs to generate thin tissue DRRs, the time required for target and normal tissue localization was on the average less than 5 min. Conclusion: In CT simulation of the four-field irradiation technique for prostate carcinoma, thin-tissue DRRs allowed for efficient and accurate target localization without requiring individual axial image contouring. This method may facilitate positioning of the beam isocenter and provide reliable conformal radiotherapy

Geometric accuracy of field alignment in fractionated stereotactic conformal radiotherapy of brain tumors

International Nuclear Information System (INIS)

Kortmann, Rolf D.; Becker, Gerd; Perelmouter, Jury; Buchgeister, Markus; Meisner, Christoph; Bamberg, Michael

1999-01-01

Purpose: To assess the accuracy of field alignment in patients undergoing three-dimensional (3D) conformal radiotherapy of brain tumors, and to evaluate the impact on the definition of planning target volume and control procedures. Methods and Materials: Geometric accuracy was analyzed in 20 patients undergoing fractionated stereotactic conformal radiotherapy for brain tumors. Rigid head fixation was achieved by using cast material. Transfer of stereotactic coordinates was performed by an external positioning device. The accuracy during treatment planning was quantitatively assessed by using repeated computed tomography (CT) examinations in treatment position (reproducibility of isocenter). Linear discrepancies were measured between treatment plan and CT examination. In addition, for each patient, a series of 20 verifications were taken in orthogonal projections. Linear discrepancies were measured between first and all subsequent verifications (accuracy during treatment delivery). Results: For the total group of patients, the distribution of deviations during treatment setup showed mean values between -0.3-1.2 mm, with standard deviations (SD) of 1.3-2.0 mm. During treatment delivery, the distribution of deviations revealed mean values between 0.7-0.8 mm, with SDs of 0.5-0.6 mm, respectively. For all patients, deviations for the transition to the treatment machine were similar to deviations during subsequent treatment delivery, with 95% of all absolute deviations between less than 2.8 and 4.6 mm. Conclusion: Random fluctuations of field displacements during treatment planning and delivery prevail. Therefore, our quantitative data should be considered when prescribing the safety margins of the planning target volume. Repeated CT examination are useful to detect operator errors and large random or systematic deviations before start of treatment. Control procedures during treatment delivery appear to be of limited importance. In addition, our findings should help to

Minimising contralateral breast dose in post-mastectomy intensity-modulated radiotherapy by incorporating conformal electron irradiation

NARCIS (Netherlands)

van der Laan, Hans Paul; Korevaar, Erik W; Dolsma, Willemtje; Maduro, John H; Langendijk, Johannes A

PURPOSE: To assess the potential benefit of incorporating conformal electron irradiation in intensity-modulated radiotherapy (IMRT) for loco-regional post-mastectomy RT. PATIENTS AND METHODS: Ten consecutive patients that underwent left-sided mastectomy were selected for this comparative planning

Radiotherapy for Adult Medulloblastoma: Evaluation of Helical Tomotherapy, Volumetric Intensity Modulated Arc Therapy, and Three-Dimensional Conformal Radiotherapy and the Results of Helical Tomotherapy Therapy

Directory of Open Access Journals (Sweden)

Sun Zong-wen

2018-01-01

Full Text Available Introduction. All adult medulloblastoma (AMB patients should be treated with craniospinal irradiation (CSI postoperatively. Because of the long irradiation range, multiple radiation fields must be designed for conventional radiotherapy technology. CSI can be completed in only one session with helical tomotherapy (HT. We evaluated the dose of HT, volumetric intensity modulated arc therapy (VMAT, and three-dimensional conformal radiotherapy (3D-CRT of AMB and the results of 5 cases of AMB treated with HT. Methods. Complete craniospinal and posterior cranial fossa irradiation with HT, VMAT, and 3D-CRT and dose evaluation were performed. And results of 5 cases of AMB treated with HT were evaluated. Results. A large volume of tissue was exposed to low dose radiation in the organs at risk (OAR, while a small volume was exposed to high dose radiation with HT. The conformity and uniformity of the targets were good with HT and VMAT, and the volume of targets exposed to high dose with VMAT was larger than that of HT. The uniformity of 3D-CRT was also good, but the dose conformity was poor. The main toxicity was hematologic toxicity, without 4th-degree bone marrow suppression. There was 3rd-degree inhibition in the white blood cells, hemoglobin, and platelets. The three female patients suffered menstrual disorders during the course of radiation. Two female patients with heavy menstruation suffered 3rd-degree anemia inhibition, and 2 patients suffered amenorrhea after radiotherapy. Although menstrual cycle was normal, the third patient was not pregnant. Conclusion. CSI with HT is convenient for clinical practice, and the side effects are mild. With good conformity and uniformity, VMAT can also be used for selection in CSI. For poor conformity, 3D-CRT should not be the priority selection for CSI. In female patients, the ovaries should be protected.

Conformal fields in prostate radiotherapy: A comparison between measurement, calculation and simulation

Directory of Open Access Journals (Sweden)

Seied R Mahdavi

2012-01-01

Full Text Available Aims: The objective of this study is to evaluate the accuracy of a treatment planning system (TPS for calculating the dose distribution parameters in conformal fields (CF. Dosimetric parameters of CF′s were compared between measurement, Monte Carlo simulation (MCNP4C and TPS calculation. Materials and Methods: Field analyzer water phantom was used for obtaining percentage depth dose (PDD curves and beam profiles (BP of different conformal fields. MCNP4C was used to model conformal fields dose specification factors and head of linear accelerator varian model 2100C/D. Results: Results showed that the distance to agreement (DTA and dose difference (DD of our findings were well within the acceptance criteria of 3 mm and 3%, respectively. Conclusions: According to this study it can be revealed that TPS using equivalent tissue air ratio calculation method is still convenient for dose prediction in non small conformal fields normally used in prostate radiotherapy. It was also showed that, since there is a close correlation with Monte Carlo simulation, measurements and TPS, Monte Carlo can be further confirmed for implementation and calculation dose distribution in non standard and complex conformal irradiation field for treatment planning systems.

Hyperfractionated conformal radiotherapy in locally advanced prostate cancer: results of a dose escalation study

International Nuclear Information System (INIS)

Forman, Jeffrey D.; Duclos, Marie; Shamsa, Falah; Porter, Arthur T.; Orton, Colin

1996-01-01

Purpose: This study was initiated to assess the incidence of chronic complications and histologic and biochemical control following hyperfractionated conformal radiotherapy in patients with locally advanced prostate cancer. Methods and Materials: Between October 1991 and October 1994, 49 patients with locally advanced prostate cancer were entered on the first two dose levels of a prospective dose-escalation study using hyperfractionated three dimensional conformal radiotherapy. The first 25 patients received a minimum tumor dose of 78 Gy to the prostate and seminal vesicles in 6 weeks at 1.3 Gy, b.i.d. No increase in chronic toxicity compared with conventional radiotherapy was noted; therefore, an additional 24 patients were treated to a minimum tumor dose of 82.8 Gy to the prostate and seminal vesicles in 7 weeks at 1.15 Gy, b.i.d. Toxicity was scored according to the Radiation Therapy Oncology Group morbidity grading scale. Efficacy was assessed through scheduled postradiation prostate specific antigen values and ultrasound-guided biopsies. The median follow-up for the entire group was 20 months. Results: The hyperfractionated external radiation was well tolerated with minimal acute morbidity. At 30 months, the actuarial probability of Grade 2 gastrointestinal toxicity was 17%. At 30 months, the actuarial probability of Grade 2 genitourinary toxicity was 16%. There was no statistically significant difference between the two dose levels. No Grade 3 or 4 gastrointestinal or genitourinary toxicity was noted. At 12 months, 84% of patients had a prostate specific antigen ≤ 4; and 53%; ≤ 1 ng/ml. At 12 months, 71% of patients had post radiation biopsies that were either negative (55%) or showed a marked therapeutic effect (16%). Conclusion: The use of hyperfractionated conformal radiotherapy facilitated dose escalation with no increase in chronic toxicity compared to standard doses. The initial tumor response based on prostate specific antigen measurements and

Effects of three-dimensional conformal radiotherapy, indensity modulated radiotherapy, and conventional radiotherapy ON treatment of esophageal cancer

Directory of Open Access Journals (Sweden)

Jian-Jun Han

2016-07-01

Full Text Available Objective: To compare the irradiation volume, short-term and long-term efficacy of conventional radiotherapy (CR, three-dimensional conformal radiotherapy (3D-CRT, and indensity modulated radiotherapy (IMRT in the treatment of esophageal cancer. Methods: A retrospective analysis method was adopted. The patients were divided into CR group (n=42, 3D-CRT group (n=45, and IMRT group (n=40. A follow-up visit was paid to collect the short-term and long-term efficacy, and the occurrence of adverse reactions. The gross tumor voluem (GTV, clinical target volume (CTV, planning target volume (PTV, and irradiation volume of organs (bilateral lungs, spinal cord, and heart at risk (OAR in the three groups were compared. Results: It was found by target volume comparison that the mean values of GTV, CTV, and PTV in the three groups were significantly increased (P0.05. The occurrence rate of adverse reactions in 3D-CRT group and IMRT group was significantly lower than that in CR group (P0.05. The difference of 1-year survival rate among the three groups was not statistically significant (P=0.144, but 3-year and 5-year survival rates in 3D-CRT group and IMRT group were significantly higher than those in CR group (P<0.05. Conclusions: 3D-CRT and IMRT can significantly enhance the short-term and long-term efficacy for esophageal cancer patients, and alleviate the radioactive damage; therefore, they are deserved to be widely recommended in the clinic.

Dosimetric comparison of field in field intensity-modulated radiotherapy technique with conformal radiotherapy techniques in breast cancer

International Nuclear Information System (INIS)

Ercan, T.; Alco, G.; Zengin, F.; Atilla, S.; Dincer, M.; Igdem, S.; Okkan, S.

2010-01-01

The aim of this study was to be able to implement the field-in-field intensity-modulated radiotherapy (FiF) technique in our daily practice for breast radiotherapy. To do this, we performed a dosimetric comparison. Treatment plans were produced for 20 consecutive patients. FiF plans and conformal radiotherapy (CRT) plans were compared for doses in the planning target volume (PTV), the dose homogeneity index (DHI), doses in irradiated soft tissue outside the target volume (SST), ipsilateral lung and heart doses for left breast irradiation, and the monitor unit counts (MU) required for treatment. Averaged values were compared using Student's t-test. With FiF, the DHI is improved 7.0% and 5.7%, respectively (P<0.0001) over the bilateral and lateral wedge CRT techniques. When the targeted volumes received 105% and 110% of the prescribed dose in the PTV were compared, significant decreases are found with the FiF technique. With the 105% dose, the SST, heart, and ipsilateral lung doses and the MU counts were also significantly lower with the FiF technique. The FiF technique, compared to CRT, for breast radiotherapy enables significantly better dose distribution in the PTV. Significant differences are also found for soft tissue volume, the ipsilateral lung dose, and the heart dose. Considering the decreased MUs needed for treatment, the FiF technique is preferred over tangential CRT. (author)

Intensity-Modulated Radiotherapy versus 3-Dimensional Conformal Radiotherapy Strategies for Locally Advanced Non-Small-Cell Lung Cancer

Directory of Open Access Journals (Sweden)

Uğur Selek

2014-12-01

Full Text Available Chemoradiotherapy is the current standard of care in patients with advanced inoperable stage IIIA or IIIB non-small cell lung cancer (NSCLC. Three-dimensional radiotherapy (3DCRT has been a trusted method for a long time and has well-known drawbacks, most of which could be improved by Intensity Modulated Radiotherapy (IMRT. IMRT is not currently the standard treatment of locally advanced NSCLC, but almost all patients could benefit to a degree in organ at risk sparing, dose coverage conformality, or dose escalation. The most critical step for a radiation oncology department is to strictly evaluate its own technical and physical capabilities to determine the ability of IMRT to deliver an optimal treatment plan. This includes calculating the internal tumor motion (ideally 4DCT or equivalent techniques, treatment planning software with an up-to-date heterogeneity correction algorithm, and daily image guidance. It is crucial to optimise and individualise the therapeutic ratio for each patient during the decision of 3DCRT versus IMRT. The current literature rationalises the increasing use of IMRT, including 4D imaging plus PET/CT, and encourages the applicable knowledge-based and individualised dose escalation using advanced daily image-guided radiotherapy.

Dynamic electron arc radiotherapy (DEAR): a feasibility study

International Nuclear Information System (INIS)

Rodrigues, Anna; Yin, Fang-Fang; Wu, Qiuwen

2014-01-01

Compared to other radiation therapy modalities, clinical electron beam therapy has remained practically unchanged for the past few decades even though electron beams with multiple energies are widely available on most linacs. In this paper, we present the concept of dynamic electron arc radiotherapy (DEAR), a new conformal electron therapy technique with synchronized couch motion. DEAR utilizes combination of gantry rotation, couch motion, and dose rate modulation to achieve desirable dose distributions in patient. The electron applicator is kept to minimize scatter and maintain narrow penumbra. The couch motion is synchronized with the gantry rotation to avoid collision between patient and the electron cone. In this study, we investigate the feasibility of DEAR delivery and demonstrate the potential of DEAR to improve dose distributions on simple cylindrical phantoms. DEAR was delivered on Varian's TrueBeam linac in Research Mode. In conjunction with the recorded trajectory log files, mechanical motion accuracies and dose rate modulation precision were analyzed. Experimental and calculated dose distributions were investigated for different energies (6 and 9 MeV) and cut-out sizes (1×10 cm 2  and 3×10 cm 2  for a 15×15 cm 2  applicator). Our findings show that DEAR delivery is feasible and has the potential to deliver radiation dose with high accuracy (root mean square error, or RMSE of <0.1 MU, <0.1° gantry, and <0.1 cm couch positions) and good dose rate precision (1.6 MU min −1 ). Dose homogeneity within ±2% in large and curved targets can be achieved while maintaining penumbra comparable to a standard electron beam on a flat surface. Further, DEAR does not require fabrication of patient-specific shields. These benefits make DEAR a promising technique for conformal radiotherapy of superficial tumors. (paper)

Brainstem tolerance to conformal radiotherapy of skull base tumors

International Nuclear Information System (INIS)

Debus, J.; Hug, E.B.; Liebsch, N.J.; O'Farrel, D.; Finkelstein, D.; Efird, J.; Munzenrider, J.E.

1997-01-01

Purpose: The aim of this study was to analyze the long-term incidence of brainstem toxicity in patients treated for skull base tumors with high dose conformal radiotherapy. Methods and Materials: Between 1974 and 1995, 367 patients with chordomas (n = 195) and chondrosarcomas (n = 172) of the base of skull have been treated with combined megavoltage photon and 160 MeV proton radiotherapy. Following 3D treatment planning with delineation of target volumes and critical nontarget structures dose distributions and dose-volume histograms were calculated. Radiotherapy was given an 1.8 Gy or CGE (=Cobalt Gray Equivalent) dose per fraction, with prescribed target doses ranging from 63 CGE to 79.2 CGE (mean = 67.8 CGE). Doses to the brainstem surface were limited to ≤64 CGE and to the brainstem center to ≤53 CGE. Results: Follow-up time ranged from 6 months to 21.4 years (mean = 42.5 months). Brainstem toxicity was observed in 17 of 367 patients attributable to treatment, resulting in death of three patients. Actuarial rates of 5 and 10-year high-grade toxicity-free survival were 94 and 88%, respectively. Increased risk of brainstem toxicity was significantly associated with maximum dose to brainstem, volume of brainstem receiving ≥50 CGE, ≥55 CGE, and ≥60 CGE, number of surgical procedures, and prevalence of diabetes or high blood pressure. Multivariate analysis identified three independent factors as important prognosticators: number of surgical procedures (p < 0.001), volume of the brainstem receiving 60 CGE (p < 0.001), and prevalence of diabetes (p < 0.01). Conclusions: Tolerance of brainstem to fractionated radiotherapy appears to be a steep function of tissue volume included in high dose regions rather than the maximum dose of brainstem alone. In addition, presence of predisposing factors as well as extent of surgical manipulation can significantly lower brainstem tolerance in the individual patient

Bladder radiotherapy treatment: A retrospective comparison of 3-dimensional conformal radiotherapy, intensity-modulated radiation therapy, and volumetric-modulated arc therapy plans

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Pasciuti, Katia, E-mail: k.pasciuti@virgilio.it [Department of Radiotherapy Physics, Royal Free Hospital, London (United Kingdom); Kuthpady, Shrinivas [Department of Radiotherapy, Royal Free Hospital, London (United Kingdom); Anderson, Anne; Best, Bronagh [Department of Radiotherapy Physics, Royal Free Hospital, London (United Kingdom); Waqar, Saleem; Chowdhury, Subhra [Department of Radiotherapy, Royal Free Hospital, London (United Kingdom)

2017-04-01

To examine tumor's and organ's response when different radiotherapy plan techniques are used. Ten patients with confirmed bladder tumors were first treated using 3-dimensional conformal radiotherapy (3DCRT) and subsequently the original plans were re-optimized using the intensity-modulated radiation treatment (IMRT) and volumetric-modulated arc therapy (VMAT)-techniques. Targets coverage in terms of conformity and homogeneity index, TCP, and organs' dose limits, including integral dose analysis were evaluated. In addition, MUs and treatment delivery times were compared. Better minimum target coverage (1.3%) was observed in VMAT plans when compared to 3DCRT and IMRT ones confirmed by a statistically significant conformity index (CI) results. Large differences were observed among techniques in integral dose results of the femoral heads. Even if no statistically significant differences were reported in rectum and tissue, a large amount of energy deposition was observed in 3DCRT plans. In any case, VMAT plans provided better organs and tissue sparing confirmed also by the normal tissue complication probability (NTCP) analysis as well as a better tumor control probability (TCP) result. Our analysis showed better overall results in planning using VMAT techniques. Furthermore, a total time reduction in treatment observed among techniques including gantry and collimator rotation could encourage using the more recent one, reducing target movements and patient discomfort.

CONSERVATIVE TREATMENT IN LOCALLY AND LOCALLY-ADVANCED PROSTATE CANCER USING CONFORMAL RADIOTHERAPY

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Tkachev Sergey Ivanovich

2013-01-01

Full Text Available The combination of androgen deprivation and radiotherapy increase the probability of diseases full regresses and survival rate. Modern technical and technological opportunities of 3D CRT allow to increase total dose to prostate up to 72-76Gy vs. radiotherapy of 66-70Gy. In this study we compare the rates of post radiation toxicity and the efficiency of treatment for the patients receiving conventional radiotherapy and 3D CRT. The use of 3D CRT has not only result to increase of 10-years recurrence free survival rate from 74% (I grope to 86,5% (II grope, р=0,01, but also to increase of 10-years overall survival, 70% versus 78,4% (р=0,04. The proposed version of conformal 3D CRT radiation therapy made ​​it possible compared to conventional 2D RT radiation therapy by increasing SOD radiation to the tumor, accuracy and compliance with the quality assurance of radiation therapy significantly reduce rates of recurrence and significantly increase the performance of 10-year overall and disease-free survival.

Accelerated Deformable Registration of Repetitive MRI during Radiotherapy in Cervical Cancer

DEFF Research Database (Denmark)

Noe, Karsten Østergaard; Tanderup, Kari; Kiritsis, Christian

2006-01-01

Tumour regression and organ deformations during radiotherapy (RT) of cervical cancer represent major challenges regarding accurate conformation and calculation of dose when using image-guided adaptive radiotherapy. Deformable registration algorithms are able to handle organ deformations, which can...... be useful with advanced tools such as auto segmentation of organs and dynamic adaptation of radiotherapy. The aim of this study was to accelerate and validate deformable registration in MRI-based image-guided radiotherapy of cervical cancer.    ...

Comparison between conventional and three-dimensional conformal treatment planning for radiotherapy of cerebral tumors

International Nuclear Information System (INIS)

Caudrelier, J.M.; Auliard, A.; Sarrazin, T.; Gibon, D.; Coche-Dequeant, B.; Castelain, B.

2001-01-01

Comparison between conventional and three-dimensional conformal treatment planning for radiotherapy of cerebral tumors. Purpose. - We prospectively compared a conventional treatment planning (PT2D) and 3-dimensional conformal treatment planning (PT3D) for radiotherapy of cerebral tumours. Patients and methods.- Patients treated between 1/10/98 and 1/4/99 by irradiation for cerebral tumours were analysed. For each case, we planned PT2D using conventional orthogonal x-ray films, and afterward, PT3D using CT scan. Gross tumor volume, planning target volume and normal tissue volumes were defined. Dose was prescribed according to report 50 of the International Commission on Radiation Units and Measurements (ICRU). We compared surfaces of sagittal view targets defined on PT2D and PT3D and called them S2D and S3D, respectively. Irradiated volumes by 90% isodoses (VE-90%) and normal tissue volumes irradiated by 20, 50, 90% isodoses were calculated and compared using Student's paired t-test. Results. -There was a concordance of 84% of target surfaces defined on PT2D and PT3D. Percentages of target surface under- or-over defined by PT2D were 16 and 13% respectively. VE-90% was decreased by 15% (p = 0.07) with PT3D. Normal brain volume irradiated by 90% isodose was decreased by 27% with PT3D (p = 0.04). Conclusion.- For radiotherapy of cerebral tumors using only coplanar beams, PT3D leads to a reduction of normal brain tissue irradiated. We recommend PT3D for radiotherapy of cerebral tumors, particularly for low-grade or benign tumors (meningiomas, neuromas, etc.). (authors)

Therapeutic effect analysis of three dimensional conformal radiotherapy non-small cell lung cancer

International Nuclear Information System (INIS)

Yao Zhijun; Cao Yongzhen; Zhang Wenxue; Liang Feng

2012-01-01

Objective: To analyse the treatment effect of non-small cell lung cancer of three dimensional conformal radiotherapy (3D-CRT) and to study the effect of patient survival related factors. Methods: Retrospective analysis was mack for 136 cases of non-small cell lung cancer, all accept 3D-CRT, through the case data collection and long-term follow-up, using the single factor and multiple factor analysis survival time and its influencing factors. Results: The recent curative effects of 136 cases of patients with three dimensional conformal radiotherapy: Complete response (CR) 14.7% (20/136), partial response (PR) 60.3 (82/136), stable disease(SD) 19.9% (27/136), progression disease (PD) 5.1% (7/136), total effective rate is 75% (102/136). One, two, three, five year survival rate is 79.4%, 45.4%, 22.1%, 12.5%. Side effects: Class 1 radiated esophagitis 35 cases, Class 2 radiated esophagitis 16 cases, Class 3 and above radiated esophagitis 0 case. Class I radiated pneumonia 20 cases, Class 2 radiated pneumonia 9 cases, Class 3 radiated pneumonia 0 case. Single factor analysis shows the influence of gender, age, pathology, phase, dose, and first-phase curative effect to the survival time are of a statistical significance, Multiple factor analysis showed KPS score, phase, dose, first-phase curative effect are the survival time independent factors. Conclusion: 3D-CRT for patients with non-small cell lung carcinoma is a safe, effective treatment method, Side effects are relatively low, and the patients survival time is long after radiotherapy. (authors)

Intensity-modulated radiotherapy (IMRT) and conventional three-dimensional conformal radiotherapy for high-grade gliomas: Does IMRT increase the integral dose to normal brain?

International Nuclear Information System (INIS)

Hermanto, Ulrich; Frija, Erik K.; Lii, MingFwu J.; Chang, Eric L.; Mahajan, Anita; Woo, Shiao Y.

2007-01-01

Purpose: To determine whether intensity-modulated radiotherapy (IMRT) treatment increases the total integral dose of nontarget tissue relative to the conventional three-dimensional conformal radiotherapy (3D-CRT) technique for high-grade gliomas. Methods and Materials: Twenty patients treated with 3D-CRT for glioblastoma multiforme were selected for a comparative dosimetric evaluation with IMRT. Original target volumes, organs at risk (OAR), and dose-volume constraints were used for replanning with IMRT. Predicted isodose distributions, cumulative dose-volume histograms of target volumes and OAR, normal tissue integral dose, target coverage, dose conformity, and normal tissue sparing with 3D-CRT and IMRT planning were compared. Statistical analyses were performed to determine differences. Results: In all 20 patients, IMRT maintained equivalent target coverage, improved target conformity (conformity index [CI] 95% 1.52 vs. 1.38, p mean by 19.8% and D max by 10.7%), optic chiasm (D mean by 25.3% and D max by 22.6%), right optic nerve (D mean by 37.3% and D max by 28.5%), and left optic nerve (D mean by 40.6% and D max by 36.7%), p ≤ 0.01. This was achieved without increasing the total nontarget integral dose by greater than 0.5%. Overall, total integral dose was reduced by 7-10% with IMRT, p < 0.001, without significantly increasing the 0.5-5 Gy low-dose volume. Conclusions: These results indicate that IMRT treatment for high-grade gliomas allows for improved target conformity, better critical tissue sparing, and importantly does so without increasing integral dose and the volume of normal tissue exposed to low doses of radiation

Estimating the costs of intensity-modulated and 3-dimensional conformal radiotherapy in Ontario.

Science.gov (United States)

Yong, J H E; McGowan, T; Redmond-Misner, R; Beca, J; Warde, P; Gutierrez, E; Hoch, J S

2016-06-01

Radiotherapy is a common treatment for many cancers, but up-to-date estimates of the costs of radiotherapy are lacking. In the present study, we estimated the unit costs of intensity-modulated radiotherapy (imrt) and 3-dimensional conformal radiotherapy (3D-crt) in Ontario. An activity-based costing model was developed to estimate the costs of imrt and 3D-crt in prostate cancer. It included the costs of equipment, staff, and supporting infrastructure. The framework was subsequently adapted to estimate the costs of radiotherapy in breast cancer and head-and-neck cancer. We also tested various scenarios by varying the program maturity and the use of volumetric modulated arc therapy (vmat) alongside imrt. From the perspective of the health care system, treating prostate cancer with imrt and 3D-crt respectively cost $12,834 and $12,453 per patient. The cost of radiotherapy ranged from $5,270 to $14,155 and was sensitive to analytic perspective, radiation technique, and disease site. Cases of head-and-neck cancer were the most costly, being driven by treatment complexity and fractions per treatment. Although imrt was more costly than 3D-crt, its cost will likely decline over time as programs mature and vmat is incorporated. Our costing model can be modified to estimate the costs of 3D-crt and imrt for various disease sites and settings. The results demonstrate the important role of capital costs in studies of radiotherapy cost from a health system perspective, which our model can accommodate. In addition, our study established the need for future analyses of imrt cost to consider how vmat affects time consumption.

Prospective longitudinal assessment of parotid gland function using dynamic quantitative pertechnate scintigraphy and estimation of dose–response relationship of parotid-sparing radiotherapy in head-neck cancers

International Nuclear Information System (INIS)

Gupta, Tejpal; Hotwani, Chandni; Kannan, Sadhana; Master, Zubin; Rangarajan, Venkatesh; Murthy, Vedang; Budrukkar, Ashwini; Ghosh-Laskar, Sarbani; Agarwal, Jai Prakash

2015-01-01

To estimate dose–response relationship using dynamic quantitative 99m Tc-pertechnate scintigraphy in head-neck cancer patients treated with parotid-sparing conformal radiotherapy. Dynamic quantitative pertechnate salivary scintigraphy was performed pre-treatment and subsequently periodically after definitive radiotherapy. Reduction in salivary function following radiotherapy was quantified by salivary excretion fraction (SEF) ratios. Dose–response curves were modeled using standardized methodology to calculate tolerance dose 50 (TD50) for parotid glands. Salivary gland function was significantly affected by radiotherapy with maximal decrease in SEF ratios at 3-months, with moderate functional recovery over time. There was significant inverse correlation between SEF ratios and mean parotid doses at 3-months (r = −0.589, p < 0.001); 12-months (r = −0.554, p < 0.001); 24-months (r = −0.371, p = 0.002); and 36-months (r = −0.350, p = 0.005) respectively. Using a post-treatment SEF ratio <45% as the scintigraphic criteria to define severe salivary toxicity, the estimated TD50 value with its 95% confidence interval (95% CI) for the parotid gland was 35.1Gy (23.6-42.6Gy), 41.3Gy (34.6-48.8Gy), 55.9Gy (47.4-70.0Gy) and 64.3Gy (55.8-70.0Gy) at 3, 12, 24, and 36-months respectively. There is consistent decline in parotid function even after conformal radiotherapy with moderate recovery over time. Dynamic quantitative pertechnate scintigraphy is a simple, reproducible, and minimally invasive test of major salivary gland function. The online version of this article (doi:10.1186/s13014-015-0371-2) contains supplementary material, which is available to authorized users

Conformal radiotherapy of locally advanced bile duct carcinoma

International Nuclear Information System (INIS)

Bouras, N.; Caudry, M.; Bonnel, C.; Trouette, R.; Demeaux, H.; Maire, J.P.; Saric, J.; Rullier, E.

2002-01-01

Purpose. - Retrospective study of 23 patients treated with conformal radiotherapy for a locally advanced bile duct carcinoma. Patients and methods. - Eight cases were irradiated after a radical resection (RO), because they were N+; seven after microscopically incomplete resection (R1) ; seven were not resected (R2). A dose of 45 of 50 Gy was delivered, followed by a boost up to 60 Gy in R1 and R2 groups. Concomitant chemotherapy was given in 15 cases. Results.-Late toxicity included a stenosis of the duodenum, and one of the biliary anastomosis. Two patients died from cholangitis, the mechanism of which remains unclear. Five patients are in complete remission, six had a local relapse, four developed a peritoneal carcinosis, and six distant metastases. Actuarial survival rate is 75%, 28% and 7% at 1, 3 and 5 years, respectively (median: 16.5 months). Seven patients are still alive with a 4 to 70 months follow-up. Survival is similar in the 3 small subgroups. The poor local control among RON+ cases might be related to the absence of a boost to the 'tumor bed'. In R1 patients, relapses were mainly distant metastases, where'as local and peritoneal recurrences predominated in R2. Conclusion. - Conformal radio-chemotherapy delivering 60 Gy represents a valuable palliative approach in locally advanced biliary carcinoma. (authors)

Intensity-modulated radiotherapy vs. parotid-sparing 3D conformal radiotherapy. Effect on outcome and toxicity in locally advanced head and neck cancer

Energy Technology Data Exchange (ETDEWEB)

Lambrecht, M.; Nevens, D.; Nuyts, S. [University Hospitals Leuven (Belgium). Dept. of Radiation Oncology

2013-03-15

Background and purpose: Intensity-modulated radiotherapy (IMRT) has rapidly become standard of care in the management of locally advanced head and neck squamous cell carcinoma (HNSCC). In this study, our aim was to retrospectively investigate the effect of the introducing IMRT on outcome and treatment-related toxicity compared to parotid-sparing 3D conformal radiotherapy (3DCRT). Material and methods: A total of 245 patients with stage III and IV HNSCC treated with primary radiotherapy between January 2003 and December 2010 were included in this analysis: 135 patients were treated with 3DCRT, 110 patients with IMRT. Groups were compared for acute and late toxicity, locoregional control (LRC), and overall survival (OS). Oncologic outcomes were estimated using Kaplan-Meier analysis and compared using a log-rank test. Acute toxicity was analyzed according to the Common Terminology Criteria for Adverse Events v3.0 and late toxicity was scored using the RTOG/EORTC late toxicity scoring system. Results: Median follow-up was 35 months in the IMRT group and 68 months in the 3DCRT group. No significant differences were found in 3-year LRC and OS rates between the IMRT group and 3DCRT group. Significantly less acute mucositis {>=} grade 3 was observed in the IMRT group (32% vs. 44%, p = 0.03). There was significantly less late xerostomia {>=} grade 2 in the IMRT group than in the 3DCRT group (23% vs. 68%, p < 0.001). After 24 months, there was less dysphagia {>=} grade 2 in the IMRT group although differences failed to reach statistical significance. Conclusion: The introduction of IMRT in the radiotherapeutic management of locally advanced head and neck cancer significantly improved late toxicity without compromising tumor control compared to a parotid-sparing 3D conformal radiotherapy technique. (orig.)

Health-Related Quality of Life in Patients With Locally Advanced Prostate Cancer After 76 Gy Intensity-Modulated Radiotherapy vs. 70 Gy Conformal Radiotherapy in a Prospective and Longitudinal Study

International Nuclear Information System (INIS)

Lips, Irene; Dehnad, Human; Kruger, Arto Boeken; Moorselaar, Jeroen van; Heide, Uulke van; Battermann, Jan; Vulpen, Marco van

2007-01-01

Purpose: To compare quality of life (QoL) after 70 Gy conformal radiotherapy with QoL after 76 Gy intensity-modulated radiotherapy (IMRT) in patients with locally advanced prostate carcinoma. Methods and Materials: Seventy-eight patients with locally advanced prostate cancer were treated with 70 Gy three-field conformal radiotherapy, and 92 patients received 76 Gy IMRT with fiducial markers for position verification. Quality of life was measured by RAND-36, the European Organization for Research and Treatment of Cancer core questionnaire (EORTC QLQ-C30(+3)), and the prostate-specific EORTC QLQ-PR25, before radiotherapy (baseline) and 1 month and 6 months after treatment. Quality of life changes in time (baseline vs. 1 month and baseline vs. 6 months) of ≥10 points were considered clinically relevant. Results: Differences between the treatment groups for QoL changes over time occurred in several QoL domains. The 76-Gy group revealed no significant deterioration in QoL compared with the 70-Gy group. The IMRT 76-Gy group even demonstrated a significantly better change in QoL from baseline to 1 month in several domains. The conformal 70-Gy group revealed temporary deterioration in pain, role functioning, and urinary symptoms; for the IMRT 76-Gy group a better QoL in terms of change in health existed after 1 month, which persisted after 6 months. For both treatment groups temporary deterioration in physical role restriction occurred after 1 month, and an improvement in emotional role restriction occurred after 6 months. Sexual activity was reduced after treatment for both groups and remained decreased after 6 months. Conclusions: Intensity-modulated radiotherapy and accurate position verification seem to provide a possibility to increase the radiation dose for prostate cancer without deterioration in QoL

Conformal radiotherapy by intensity modulation of pediatrics tumors; Radiotherapie conformationnelle par modulation d'intensite des tumeurs pediatriques

Energy Technology Data Exchange (ETDEWEB)

Leseur, J.; Le Prise, E. [Centre Eugene-Marquis, 35 - Rennes (France); Carrie, C. [Centre Leon Berard, 69 - Lyon (France); Bernier, V. [Centre Alexis-Vautrin, 54 - Nancy (France); Beneyton, V. [Centre Paul-Strauss, 67 - Strasbourg (France); Mahe, M.A.; Supiot, S. [Centre Rene-Gauducheau, 44 - Nantes (France)

2009-10-15

The objective of this study is to take stock on the validated and potential indications of the conformal radiotherapy with intensity modulation ( intensity modulated radiotherapy I.M.R.T.) in pediatrics and to propose recommendations for its use as well as the adapted dose constraints. About 40 to 50% of children treated for a cancer are irradiated. The I.M.R.T., by linear accelerator or helical tomo-therapy has for aim to give a homogenous dose to the target volume and to save organs at risk. Its use in pediatrics seems particularly interesting because of the complexity of target volumes and the closeness of organs at risk. In compensation for these positive elements, the importance of low doses irradiation given in big volumes makes fear event consequences on growth and an increased incidence of secondary cancers in children suffering from tumors with high cure rates and long life expectancy. (N.C.)

Clinical variability of target volume description and treatment plans in conformal radiotherapy in muscle invasive bladder cancer

International Nuclear Information System (INIS)

Logue, John P; Sharrock, Carole L; Cowan, Richard A.; Read, Graham; Marrs, Julie; Mott, David

1996-01-01

Purpose/Objective: The delineation of tumor and the production of a treatment plan to encompass this is the prime step in radiotherapy planning. Conformal radiotherapy is developing rapidly and although plentiful research has addressed the implementation of the radiotherapy prescription, scant attention has been made to the fundamental step of production, by the clinician, of an appropriate target volume. As part of an ongoing randomized trial of conformal radiotherapy, in bladder cancer, we have therefore assessed the interphysician variability of radiologists and radiation oncologists (RO) in assessing Gross Tumor Volume(GTV) (ICRU 50) and the adherence of the radiation oncologists to the study protocol of producing a Planning Target Volume (PTV). Materials and Methods: Four patients with T3 carcinoma of bladder who had been entered into the trial were identified. The clinical details, MR scans and CT scans were made available. Eight RO and 3 dedicated diagnostic oncology radiologists were invited to directly outline the GTV onto CT images on a planning computer consul. The RO in addition created a PTV following the trial protocol of 15mm margin around the GTV. Three RO sub-specialized in Urological radiotherapy; all RO had completed training. Volumes were produced, for each clinician, and comparison of these volumes and their isocenters were analyzed. In addition the margins allowed were measured and compared. Results: There was a maximum variation ratio (largest to smallest volume outlined) of the GTV in the four cases of 1.74 among radiologists and 3.74 among oncologists. There was a significant difference (p=0.01) in mean GTV between RO and the radiologists. The mean GTV of the RO exceeded the radiologists by a factor of 1.29 with a mean difference of 13.4 cm 3 The between observer variance within speciality comprised only 9.9% of the total variance in the data having accounted for case and observers speciality. The variation ratio in PTV among oncologists

Ras conformational switching: simulating nucleotide-dependent conformational transitions with accelerated molecular dynamics.

Directory of Open Access Journals (Sweden)

Barry J Grant

2009-03-01

Full Text Available Ras mediates signaling pathways controlling cell proliferation and development by cycling between GTP- and GDP-bound active and inactive conformational states. Understanding the complete reaction path of this conformational change and its intermediary structures is critical to understanding Ras signaling. We characterize nucleotide-dependent conformational transition using multiple-barrier-crossing accelerated molecular dynamics (aMD simulations. These transitions, achieved for the first time for wild-type Ras, are impossible to observe with classical molecular dynamics (cMD simulations due to the large energetic barrier between end states. Mapping the reaction path onto a conformer plot describing the distribution of the crystallographic structures enabled identification of highly populated intermediate structures. These structures have unique switch orientations (residues 25-40 and 57-75 intermediate between GTP and GDP states, or distinct loop3 (46-49, loop7 (105-110, and alpha5 C-terminus (159-166 conformations distal from the nucleotide-binding site. In addition, these barrier-crossing trajectories predict novel nucleotide-dependent correlated motions, including correlations of alpha2 (residues 66-74 with alpha3-loop7 (93-110, loop2 (26-37 with loop10 (145-151, and loop3 (46-49 with alpha5 (152-167. The interconversion between newly identified Ras conformations revealed by this study advances our mechanistic understanding of Ras function. In addition, the pattern of correlated motions provides new evidence for a dynamic linkage between the nucleotide-binding site and the membrane interacting C-terminus critical for the signaling function of Ras. Furthermore, normal mode analysis indicates that the dominant collective motion that occurs during nucleotide-dependent conformational exchange, and captured in aMD (but absent in cMD simulations, is a low-frequency motion intrinsic to the structure.

A strategy to correct for intrafraction target translation in conformal prostate radiotherapy: Simulation results

International Nuclear Information System (INIS)

Keall, P. J.; Lauve, A. D.; Hagan, M. P.; Siebers, J. V.

2007-01-01

simulated internal motion shifts. Dose increases for adjacent organs at risk were rare. D 33 of the rectum and D 20 of the bladder were increased by more than 5% of the prescription dose in 9 and 1 instances of the 3600 sampled internal motion shifts, respectively. D mean of the right femoral head increased by more than 5% of the prescription dose in 651 (18%) internal motion shifts, predominantly due to the projection of the lateral beams through the femoral head for anterior prostate motion. However, D 2 was not increased by more than 5% for any of the internal motion shifts. These data demonstrate the robustness of the proposed dynamic compensation strategy for correction of internal motion in conformal prostate radiotherapy, with minimal deviation from the original treatment plans even for errors exceeding those commonly encountered in the clinic. The compensation strategy could be performed automatically with appropriate enhancements to available delivery software

Preservation of parotid function with uncomplicated conformal radiotherapy

International Nuclear Information System (INIS)

Maes, Annelies; Weltens, Caroline; Flamen, Patrick; Lambin, Philippe; Bogaerts, Ria; Liu, Xuan; Baetens, Jan; Hermans, Robert; Van den Bogaert, Walter

2002-01-01

Background and purpose: To evaluate (1) parotid function, (2) subjective xerostomia and (3) pattern of relapses after conformal parotid-sparing radiotherapy (RT) for head and neck cancer. (4) To study dose-response curves of parotid glands. Material and methods: From September 1999 to November 2000, 39 head and neck cancer patients requiring bilateral neck RT were treated with a fairly simple conformal RT technique (three-field set-up+anterior lower neck field; two opposed oblique boost fields). The contralateral parotid was spared. Parotid function was assessed by salivary gland scintigraphies performed before, early (median 4 weeks) and late (median 28 weeks) after RT. Xerostomia was monitored by visual analogue scales (VAS) and LENT SOMA scores. Location of locoregional recurrences was studied in relation to the radiation fields. A dose-response curve of parotids was created using logistic regression. Results: (1) Early after RT, on salivary gland scintigraphy, the mean loss of secretion function in the spared parotid was 67% and total in the non-spared. Late after RT, the mean loss remained 19% in the spared and total in the non-spared parotid. Normal excretion function was regained in 75% of the spared parotids. (2) Late after RT, 78% of patients had no, minimal or acceptable subjective xerostomia. (3) No recurrence was seen near the spared parotid (11/39 locoregional recurrences). (4) The dose-response curve of parotids showed that the mean parotid dose should preferentially be ≤20 Gy, to obtain a good chance (≥70%) for preservation of its function on scintigraphy. Conclusions: An easy conformal parotid-sparing RT technique prevents moderate or severe subjective xerostomia in 78% of patients. In the spared parotids, nearly complete to complete recovery is obtained after 6-12 months

Toxicity and cosmetic outcome of three-dimensional conformal radiotherapy for accelerated partial breast irradiation

International Nuclear Information System (INIS)

Gatti, M.; Bresciani, S.; Ponzone, R.; Panaia, R.; Salatino, A.; Stasi, M.; Gabriele, P.

2011-01-01

Full text of publication follows: Purpose.- To analyse the incidence and severity of acute and late normal tissue toxicity and cosmetic outcome using three - dimensional conformal radiotherapy to deliver accelerated partial breast irradiation. Patients and Methods.- 70 patients with stage I disease were treated with three-dimensional conformal radiotherapy for accelerated partial breast irradiation, in an approved protocol. The prescribed dose was 34 Gy in all patients delivered in 10 fractions over 5 consecutive days. On all CT scans gross tumor volume (GTV ) was defined around surgical clips. A 1.5 cm margin was added in order to account for clinical target volume (CTV) . A margin of 1 cm was added to CTI to define the planning target volume (PTV). The dose-volume constraints were followed in accordance with the specifications as dictated in the NSABP/RTOG protocol. After treatment, patients underwent a clinical and cosmetic evaluation every 3 months. Late toxicity was evaluated according to the RTOG grading schema. The cosmetic assessment was performed by the physicians using the controlateral untreated breast as the reference (Harvard scale). Results.- Median patient age was 66 years (range 51-80). Median follow-up was 15 months (range 6-46). Tumor size was 2 cm in 4(6%). The mean value of the ratio between the PTV and the whole ipsilateral breast volume was 38 % and the median percentage whole breast volume that received 95 % of prescribed dose was 34% (range 16%-55%). The rate of G1 and G2 acute skin toxicity was 28% and 2% respectively and the late toxicity was 17% (G1). G2 or greater toxicities were not observed. The most pronounced G1 late toxicity was subcutaneous fibrosis, developed in 3 patients. The cosmetic outcome was excellent in 83% and good in 17%. Conclusion.- Accelerated partial breast irradiation using three-dimensional conformal radiotherapy is technically feasible with very low acute and late toxicity. Long-term results are needed to assess

Gastro-intestinal and genito-urinary morbidity after 3D conformal radiotherapy of prostate cancer: observations of a randomized trial

International Nuclear Information System (INIS)

Koper, Peter C.; Jansen, Peter; Putten, Wim van; Os, Marjolein van; Wijnmaalen, Arend J.; Lebesque, Joos V.; Levendag, Peter C.

2004-01-01

Background and purpose: The late morbidity of a randomized study was analyzed after a follow up of 2 years. The difference in intestinal morbidity was analyzed as a function of the treatment arm and dose volume parameters. The correlation with acute toxicity and (pre-existing) bowel complaints was investigated. Patients and methods: 266 T1-4N0M0 prostate cancer patients were randomized for conventional (open fields) and 3D conformal radiotherapy using beams eye view blocked fields with the same dose (66 Gy) and gross target volume-planning target volume margin (15 mm). Apart from the RTOG toxicity scoring system a patient self-assessment questionnaire was used to obtain detailed information on morbidity. Results: At 2 years there is only a trend for less rectal toxicity (grade≥1) in favor of the conformal radiotherapy (grade 1, 47 versus 40% and grade 2, 10 versus 7% for conventional and conformal radiotherapy, respectively (P=0.1). A significant relation was found between late rectal toxicity (grade≥1) and the volume of the anus and rectum exposed to≥90% tumor dose (TD). A highly significant relationship is observed between acute rectum and anal toxicity and late rectal toxicity. The patient self-assessment questionnaire analysis revealed that patients are most bothered by compliance related symptoms like urgency, soiling and fecal loss. In a multivariate analysis, all other variables loose significance, when anal volume exposed to≥90% TD and pre-treatment defaecation frequency are accounted for. Late anal toxicity is low and related only to acute anal toxicity. Late bladder toxicity is related solely to pre-treatment frequency and overall urological symptoms. The incidence of grade 2 toxicity increases with a factor 2.5-4 when (stool or urine) frequency is unfavorable at the start of treatment. Conclusions: Conformal radiotherapy at the dose level of 66 Gy does not significantly decrease the incidence of rectal, anal and bladder toxicity compared to

Fractionated stereotactic conformal radiotherapy following conservative surgery in the control of craniopharyngiomas

International Nuclear Information System (INIS)

Minniti, Giuseppe; Saran, Frank; Traish, Daphne; Soomal, Rubin; Sardell, Susan; Gonsalves, Adam; Ashley, Susan; Warrington, Jim; Burke, Kevin; Mosleh-Shirazi, Amin; Brada, Michael

2007-01-01

Purpose: To describe the technique and results of stereotactically guided conformal radiotherapy (SCRT) in patients with craniopharyngioma after conservative surgery. Methods and materials: Thirty-nine patients with craniopharyngioma aged 3-68 years (median age 18 years) were treated with SCRT between June 1994 and January 2003. All patients were referred for radiotherapy after undergoing one or more surgical procedures. Treatment was delivered in 30-33 daily fractions over 6-6.5 weeks to a total dose of 50 Gy using 6 MV photons. Outcome was assessed prospectively. Results: At a median follow-up of 40 months (range 3-88 months) the 3- and 5-year progression-free survival (PFS) was 97% and 92%, and 3- and 5-year survival 100%. Two patients required further debulking surgery for progressive disease 8 and 41 months after radiotherapy. Twelve patients (30%) had acute clinical deterioration due to cystic enlargement of craniopharyngioma following SCRT and required cyst aspiration. One patient with severe visual impairment prior to radiotherapy had visual deterioration following SCRT. Seven out of 10 patients with a normal pituitary function before SCRT had no endocrine deficits following treatment. Conclusion: SCRT as a high-precision technique of localized RT is suitable for the treatment of incompletely excised craniopharyngioma. The local control, toxicity and survival outcomes are comparable to results reported following conventional external beam RT. Longer follow-up is required to assess long-term efficacy and toxicity, particularly in terms of potential reduction in treatment related late toxicity

Generative Models of Conformational Dynamics

Science.gov (United States)

Langmead, Christopher James

2014-01-01

Atomistic simulations of the conformational dynamics of proteins can be performed using either Molecular Dynamics or Monte Carlo procedures. The ensembles of three-dimensional structures produced during simulation can be analyzed in a number of ways to elucidate the thermodynamic and kinetic properties of the system. The goal of this chapter is to review both traditional and emerging methods for learning generative models from atomistic simulation data. Here, the term ‘generative’ refers to a model of the joint probability distribution over the behaviors of the constituent atoms. In the context of molecular modeling, generative models reveal the correlation structure between the atoms, and may be used to predict how the system will respond to structural perturbations. We begin by discussing traditional methods, which produce multivariate Gaussian models. We then discuss GAMELAN (GrAphical Models of Energy LANdscapes), which produces generative models of complex, non-Gaussian conformational dynamics (e.g., allostery, binding, folding, etc) from long timescale simulation data. PMID:24446358

Non small cells stage I bronchial cancers: three-dimensional radiotherapy and radiotherapy in stereotactic conditions; Cancers bronchiques non a petites cellules de stade I: radiotherapie tridimensionnelle et radiotherapie en conditions stereotaxiques

Energy Technology Data Exchange (ETDEWEB)

Schipman, B.; Bosset, J.F. [CHU, 25 - Besancon (France); Marchesi, V.; Beckendorf, V.; Desandes, E.; Peiffert, D. [CRLCC Alexis-Vautrin, 54 - Vandaeuvre-les-Nancy (France); Bosset, M. [CHU, 26 - Valence (France)

2010-10-15

The authors report a comparison between three-dimensional conformation radiotherapy and robotic irradiation in stereotactic conditions (with CyberKnife) for patients suffering from a bronchial cancer with no small cells of stage I. Acute and late toxicity have been recorded, and the monitoring comprised a clinic examination and a thoracic scanography. The external radiotherapy results in an important local control rate and an acceptable toxicity. Some prospective studies are still needed to compare three-dimensional conformation respiratory-gated radiotherapy and radiotherapy in stereotactic conditions. Short communication

Intensity-modulated three-dimensional conformal radiotherapy

International Nuclear Information System (INIS)

Mohan, Radhe

1996-01-01

Optimized intensity-modulated treatments one of the important advances in photon radiotherapy. Intensity modulation provides a greatly increased control over dose distributions. Such control can be maximally exploited to achieve significantly higher levels of conformation to the desired clinical objectives using sophisticated optimization techniques. Safe, rapid and efficient delivery of intensity-modulated treatments has become feasible using a dynamic multi-leaf collimator under computer control. The need for all other field shaping devices such as blocks, wedges and compensators is eliminated. Planning and delivery of intensity-modulated treatments is amenable to automation and development of class solutions for each treatment site and stage which can be implemented not only at major academic centers but on a wide scale. A typical treatment involving as many as 10 fields can be delivered in times shorter than much simpler conventional treatments. The main objective of the course is to give an overview of the current state of the art of planning and delivery methods of intensity-modulated treatments. Specifically, the following topics will be covered using representative optimized plans and treatments: 1. A typical procedure for planning and delivering an intensity-modulated treatment. 2. Quantitative definition of criteria (i.e., the objective function) of optimization of intensity-modulated treatments. Clinical relevance of objectives and the dependence of the quality of optimized intensity-modulated plans upon whether the objectives are stated purely in terms of simple dose or dose-volume criteria or whether they incorporate biological indices. 3. Importance of the lateral transport of radiation in the design of intensity-modulated treatments. Impact on dose homogeneity and the optimum choice of margins. 4. Use of intensity-modulated treatments in escalation of tumor dose for the same or lower normal tissue dose. Fractionation of intensity-modulated treatments

Intensity-modulated three-dimensional conformal radiotherapy

International Nuclear Information System (INIS)

Mohan, Radhe

1997-01-01

Optimized intensity-modulated treatments one of the important advances in photon radiotherapy. Intensity modulation provides a greatly increased control over dose distributions. Such control can be maximally exploited to achieve significantly higher levels of conformation to the desired clinical objectives using sophisticated optimization techniques. Safe, rapid and efficient delivery of intensity-modulated treatments has become feasible using a dynamic multi-leaf collimator under computer control. The need for all other field shaping devices such as blocks, wedges and compensators is eliminated. Planning and delivery of intensity-modulated treatments is amenable to automation and development of class solutions for each treatment site and stage which can be implemented not only at major academic centers but on a wide scale. A typical treatment involving as many as 10 fields can be delivered in times shorter than much simpler conventional treatments. The main objective of the course is to give an overview of the current state of the art of planning and delivery methods of intensity-modulated treatments. Specifically, the following topics will be covered using representative optimized plans and treatments: 1. A typical procedure for planning and delivering an intensity-modulated treatment. 2. Quantitative definition of criteria (i.e., the objective function) of optimization of intensity-modulated treatments. Clinical relevance of objectives and the dependence of the quality of optimized intensity-modulated plans upon whether the objectives are stated purely in terms of simple dose or dose-volume criteria or whether they incorporate biological indices. 3. Importance of the lateral transport of radiation in the design of intensity-modulated treatments. Impact on dose homogeneity and the optimum choice of margins. 4. Use of intensity-modulated treatments in escalation of tumor dose for the same or lower normal tissue dose. Fractionation of intensity-modulated treatments

Auto-optimisation for three-dimensional conformal radiotherapy of nasopharyngeal carcinoma

Energy Technology Data Exchange (ETDEWEB)

Wu, V.W.C. E-mail: orvinwu@polyu.edu.hk; Kwong, D.W.L.; Sham, J.S.T.; Mui, A.W.L

2003-08-01

Purpose: The purpose of this study was to evaluate the application of auto-optimisation in the treatment planning of three-dimensional conformal radiotherapy (3DCRT) of nasopharyngeal carcinoma (NPC). Methods: Twenty-nine NPC patients were planned by both forward planning and auto-optimisation methods. The forward plans, which consisted of three coplanar facial fields, were produced according to the routine planning criteria. The auto-optimised plans, which consisted of 5-15 (median 9) fields, were generated by the planning system after prescribing the dose requirements and the importance weightings of the planning target volume and organs at risk. Plans produced by the two planning methods were compared by the dose volume histogram, tumour control probability (TCP), conformity index and normal tissue complication probability (NTCP). Results: The auto-optimised plans reduced the average planner's time by over 35 min. It demonstrated better TCP and conformity index than the forward plans (P=0.03 and 0.04, respectively). Besides, the parotid gland and temporo-mandibular (TM) joint were better spared with the mean dose reduction of 31.8 and 17.7%, respectively. The slight trade off was the mild dose increase in spinal cord and brain stem with their maximum doses remaining within the tolerance limits. Conclusions: The findings demonstrated the potentials of auto-optimisation for improving target dose and parotid sparing in the 3DCRT of NPC with saving of the planner's time.

Auto-optimisation for three-dimensional conformal radiotherapy of nasopharyngeal carcinoma

International Nuclear Information System (INIS)

Wu, V.W.C.; Kwong, D.W.L.; Sham, J.S.T.; Mui, A.W.L.

2003-01-01

Purpose: The purpose of this study was to evaluate the application of auto-optimisation in the treatment planning of three-dimensional conformal radiotherapy (3DCRT) of nasopharyngeal carcinoma (NPC). Methods: Twenty-nine NPC patients were planned by both forward planning and auto-optimisation methods. The forward plans, which consisted of three coplanar facial fields, were produced according to the routine planning criteria. The auto-optimised plans, which consisted of 5-15 (median 9) fields, were generated by the planning system after prescribing the dose requirements and the importance weightings of the planning target volume and organs at risk. Plans produced by the two planning methods were compared by the dose volume histogram, tumour control probability (TCP), conformity index and normal tissue complication probability (NTCP). Results: The auto-optimised plans reduced the average planner's time by over 35 min. It demonstrated better TCP and conformity index than the forward plans (P=0.03 and 0.04, respectively). Besides, the parotid gland and temporo-mandibular (TM) joint were better spared with the mean dose reduction of 31.8 and 17.7%, respectively. The slight trade off was the mild dose increase in spinal cord and brain stem with their maximum doses remaining within the tolerance limits. Conclusions: The findings demonstrated the potentials of auto-optimisation for improving target dose and parotid sparing in the 3DCRT of NPC with saving of the planner's time

Dosimetric evaluation of tomography and four-box field conformal radiotherapy in locally advanced rectal cancer

International Nuclear Information System (INIS)

Yu, Mina; Lee, Hyo Chun; Chung, Mi Joo; Kim, Sung Hwan; Lee, Jong Hoon; Jang, Hong Seok; Jeon, Dong Min; Cheon, Geum Seong

2013-01-01

To report the results of dosimetric comparison between intensity-modulated radiotherapy (IMRT) using Tomotherapy and four-box field conformal radiotherapy (CRT) for pelvic irradiation of locally advanced rectal cancer. Twelve patients with locally advanced rectal cancer who received a short course preoperative chemoradiotherapy (25 Gy in 5 fractions) on the pelvis using Tomotherapy, between July 2010 and December 2010, were selected. Using their simulation computed tomography scans, Tomotherapy and four-box field CRT plans with the same dose schedule were evaluated, and dosimetric parameters of the two plans were compared. For the comparison of target coverage, we analyzed the mean dose, Vn Gy, Dmin, Dmax, radical dose homogeneity index (rDHI), and radiation conformity index (RCI). For the comparison of organs at risk (OAR), we analyzed the mean dose. Tomotherapy showed a significantly higher mean target dose than four-box field CRT (p 0.001). But, V26.25 Gy and V27.5 Gywere not significantly different between the two modalities. Tomotherapy showed higher Dmax and lower Dmin. The Tomotherapy plan had a lower rDHI than four-box field CRT (p = 0.000). Tomotherapy showed better RCI than four-box field CRT (p = 0.007). For OAR, the mean irradiated dose was significantly lower in Tomotherapy than four-box field CRT. In locally advanced rectal cancer, Tomotherapy delivers a higher conformal radiation dose to the target and reduces the irradiated dose to OAR than four-box field CRT.

Dosimetric evaluation of tomography and four-box field conformal radiotherapy in locally advanced rectal cancer

Energy Technology Data Exchange (ETDEWEB)

Yu, Mina; Lee, Hyo Chun; Chung, Mi Joo; Kim, Sung Hwan; Lee, Jong Hoon [Dept. of Radiation Oncology, St. Vincent' s Hospital, The Catholic University of Korea College of Medicine, Suwon (Korea, Republic of); Jang, Hong Seok; Jeon, Dong Min; Cheon, Geum Seong [Dept. of Radiation Oncology, Seoul St. Mary' s Hospital, The Catholic University of Korea College of Medicine, Seoul (Korea, Republic of)

2013-12-15

To report the results of dosimetric comparison between intensity-modulated radiotherapy (IMRT) using Tomotherapy and four-box field conformal radiotherapy (CRT) for pelvic irradiation of locally advanced rectal cancer. Twelve patients with locally advanced rectal cancer who received a short course preoperative chemoradiotherapy (25 Gy in 5 fractions) on the pelvis using Tomotherapy, between July 2010 and December 2010, were selected. Using their simulation computed tomography scans, Tomotherapy and four-box field CRT plans with the same dose schedule were evaluated, and dosimetric parameters of the two plans were compared. For the comparison of target coverage, we analyzed the mean dose, Vn Gy, Dmin, Dmax, radical dose homogeneity index (rDHI), and radiation conformity index (RCI). For the comparison of organs at risk (OAR), we analyzed the mean dose. Tomotherapy showed a significantly higher mean target dose than four-box field CRT (p 0.001). But, V26.25 Gy and V27.5 Gywere not significantly different between the two modalities. Tomotherapy showed higher Dmax and lower Dmin. The Tomotherapy plan had a lower rDHI than four-box field CRT (p = 0.000). Tomotherapy showed better RCI than four-box field CRT (p = 0.007). For OAR, the mean irradiated dose was significantly lower in Tomotherapy than four-box field CRT. In locally advanced rectal cancer, Tomotherapy delivers a higher conformal radiation dose to the target and reduces the irradiated dose to OAR than four-box field CRT.

Three dimensional-conformal radiotherapy combined with capecitabine chemotherapy for locally advanced (unresectable) rectal cancer

International Nuclear Information System (INIS)

Zhu Yaqun; Tian Ye; Zhang Junning; Wang Bin

2010-01-01

Objective: To evaluate the compliance and efficacy of chemoradiotherapy for locally advanced (unresectable) rectal cancer. Methods: Thirty eight patients with locally advanced (T4 or recurred) rectal cancer received three dimensional-conformal radiotherapy (for 46 ∼ 50Gy/5 weeks and was boosted to the tumor 16 ∼ 18Gy/2 weeks, 2Gy/fraction, 5 days/week) in combination with capecitabine 1 650mg · m -2 · d -1 , day 1-14, every 3 weeks. Results: The overall response rate was 57.9%, with CR 5 (13.2%), PR 17(44.7%), SD 10 (26.3%), PD 6 (15.8%), median survival time, the 1-year overall survival rate and the 2-year overall survival rate were 18 months, 64.43%, 18.78%, respectively. The remission rate of pain and improvement rate of performance status were 100% and 52.8%. Treatment-related toxicity mainly showed at diarrhea, neutrocytopenia and hand-foot syndrome, the incidence of grade 3 toxicity were 15.8%, 15.8%, 7.9%, respectively. there were no grade 4 toxicity and treatment-related death. Conclusion: Combination of three dimensional-conformal radiotherapy with capecitabine is active in advanced rectal cancer, It is a well-tolerated regimen. (authors)

Revealing time bunching effect in single-molecule enzyme conformational dynamics.

Science.gov (United States)

Lu, H Peter

2011-04-21

In this perspective, we focus our discussion on how the single-molecule spectroscopy and statistical analysis are able to reveal enzyme hidden properties, taking the study of T4 lysozyme as an example. Protein conformational fluctuations and dynamics play a crucial role in biomolecular functions, such as in enzymatic reactions. Single-molecule spectroscopy is a powerful approach to analyze protein conformational dynamics under physiological conditions, providing dynamic perspectives on a molecular-level understanding of protein structure-function mechanisms. Using single-molecule fluorescence spectroscopy, we have probed T4 lysozyme conformational motions under the hydrolysis reaction of a polysaccharide of E. coli B cell walls by monitoring the fluorescence resonant energy transfer (FRET) between a donor-acceptor probe pair tethered to T4 lysozyme domains involving open-close hinge-bending motions. Based on the single-molecule spectroscopic results, molecular dynamics simulation, a random walk model analysis, and a novel 2D statistical correlation analysis, we have revealed a time bunching effect in protein conformational motion dynamics that is critical to enzymatic functions. Bunching effect implies that conformational motion times tend to bunch in a finite and narrow time window. We show that convoluted multiple Poisson rate processes give rise to the bunching effect in the enzymatic reaction dynamics. Evidently, the bunching effect is likely common in protein conformational dynamics involving in conformation-gated protein functions. In this perspective, we will also discuss a new approach of 2D regional correlation analysis capable of analyzing fluctuation dynamics of complex multiple correlated and anti-correlated fluctuations under a non-correlated noise background. Using this new method, we are able to map out any defined segments along the fluctuation trajectories and determine whether they are correlated, anti-correlated, or non-correlated; after which, a

Dosimetric Evaluation of Intensity Modulated Radiotherapy and 4-Field 3-D Conformal Radiotherapy in Prostate Cancer Treatment

Directory of Open Access Journals (Sweden)

Bora Uysal

2013-03-01

Full Text Available Objective: The purpose of this dosimetric study is the targeted dose homogeneity and critical organ dose comparison of 7-field Intensity Modulated Radiotherapy (IMRT and 3-D 4-field conformal radiotherapy. Study Design: Cross sectional study. Material and Methods: Twenty patients with low and moderate risk prostate cancer treated at Gülhane Military Medical School Radiation Oncology Department between January 2009 and December 2009 are included in this study. Two seperate dosimetric plans both for 7-field IMRT and 3D-CRT have been generated for each patient to comparatively evaluate the dosimetric status of both techniques and all the patients received 7-field IMRT. Results: Dose-comparative evaluation of two techniques revealed the superiority of IMRT technique with statistically significantly lower femoral head doses along with reduced critical organ dose-volume parameters of bladder V60 (the volume receiving 60 Gy and rectal V40 (the volume receiving 40 Gy and V60. Conclusion: It can be concluded that IMRT is an effective definitive management tool for prostate cancer with improved critical organ sparing and excellent dose homogenization in target organs of prostate and seminal vesicles.

Conventional (2D) Versus Conformal (3D) Techniques in Radiotherapy for Malignant Pediatric Tumors: Dosimetric Perspectives

International Nuclear Information System (INIS)

Ahmad, N.; Attia, G.; Radwan, A.; El-Badawy, S.; El-Ghoneimy, E.

2009-01-01

Objectives: In pediatric radiotherapy, the enhanced radiosensitivity of the developing tissues combined with the high overall survival, raise the possibility of late complications. The present study aims at comparing two dimensional (2D) and three dimensional (3D) planning regarding dose homogeneity within target volume and dose to organs at risk (OARs) to demonstrate the efficacy of 3D in decreasing dose to normal tissue. Material and Methods: Thirty pediatric patients (18 years or less) with different pediatric tumors were planned using 2D and 3D plans. All were CT scanned after proper positioning and immobilization. Structures were contoured; including the planning target volume (PTV) and organs at risk (OARs). Conformal beams were designed and dose distribution analysis was edited to provide the best dose coverage to the PTV while sparing OARs using dose volume histograms (DVHs) of outlined structures. For the same PTVs conventional plans were created using the conventional simulator data (2-4 coplanar fields). Conventional and 3D plans coverage and distribution were compared using the term of V95% (volume of PTV receiving 95% of the prescribed dose), V107% (volume of PTV receiving 107% of the prescribed dose), and conformity index (CI) (volume receiving 90% of the prescribed dose/PTV). Doses received by OARs were compared in terms of mean dose. In children treated for brain lesions, OAR volume received 90% of the dose (V 90%) and OAR score were calculated. Results: The PTV coverage showed no statistical difference between 2D and 3D radiotherapy in terms of V95% or V107%. However, there was more conformity in 3D planning with CI 1.43 rather than conventional planning with CI 1.86 (p-value <0.001). Regarding OARs, 3D planning shows large gain in healthy tissue sparing. There was no statistical difference in mean dose received by each OAR. However, for brain cases, brain stem mean dose and brain V 90% showed better sparing in 3D planning (brain stem mean dose was

Dynamical realizations of l-conformal Newton–Hooke group

International Nuclear Information System (INIS)

Galajinsky, Anton; Masterov, Ivan

2013-01-01

The method of nonlinear realizations and the technique previously developed in [A. Galajinsky, I. Masterov, Nucl. Phys. B 866 (2013) 212, (arXiv:1208.1403)] are used to construct a dynamical system without higher derivative terms, which holds invariant under the l-conformal Newton–Hooke group. A configuration space of the model involves coordinates, which parametrize a particle moving in d spatial dimensions and a conformal mode, which gives rise to an effective external field. The dynamical system describes a generalized multi-dimensional oscillator, which undergoes accelerated/decelerated motion in an ellipse in accord with evolution of the conformal mode. Higher derivative formulations are discussed as well. It is demonstrated that the multi-dimensional Pais–Uhlenbeck oscillator enjoys the l=3/2 -conformal Newton–Hooke symmetry for a particular choice of its frequencies

Toxicity and cosmetic outcome of three-dimensional conformal radiotherapy for accelerated partial breast irradiation

Energy Technology Data Exchange (ETDEWEB)

Gatti, M.; Bresciani, S.; Ponzone, R.; Panaia, R.; Salatino, A.; Stasi, M.; Gabriele, P. [IRCC, Candiolo (Italy)

2011-10-15

Full text of publication follows: Purpose.- To analyse the incidence and severity of acute and late normal tissue toxicity and cosmetic outcome using three - dimensional conformal radiotherapy to deliver accelerated partial breast irradiation. Patients and Methods.- 70 patients with stage I disease were treated with three-dimensional conformal radiotherapy for accelerated partial breast irradiation, in an approved protocol. The prescribed dose was 34 Gy in all patients delivered in 10 fractions over 5 consecutive days. On all CT scans gross tumor volume (GTV ) was defined around surgical clips. A 1.5 cm margin was added in order to account for clinical target volume (CTV) . A margin of 1 cm was added to CTI to define the planning target volume (PTV). The dose-volume constraints were followed in accordance with the specifications as dictated in the NSABP/RTOG protocol. After treatment, patients underwent a clinical and cosmetic evaluation every 3 months. Late toxicity was evaluated according to the RTOG grading schema. The cosmetic assessment was performed by the physicians using the controlateral untreated breast as the reference (Harvard scale). Results.- Median patient age was 66 years (range 51-80). Median follow-up was 15 months (range 6-46). Tumor size was < 10 mm in 33 patients (53%) and > 2 cm in 4(6%). The mean value of the ratio between the PTV and the whole ipsilateral breast volume was 38 % and the median percentage whole breast volume that received 95 % of prescribed dose was 34% (range 16%-55%). The rate of G1 and G2 acute skin toxicity was 28% and 2% respectively and the late toxicity was 17% (G1). G2 or greater toxicities were not observed. The most pronounced G1 late toxicity was subcutaneous fibrosis, developed in 3 patients. The cosmetic outcome was excellent in 83% and good in 17%. Conclusion.- Accelerated partial breast irradiation using three-dimensional conformal radiotherapy is technically feasible with very low acute and late toxicity. Long

Three dimensional conformal postoperative radiotherapy for ...

African Journals Online (AJOL)

Introduction: Postoperative radiotherapy of the parotid gland could be achieved with various radiotherapy techniques. However they irradiate differently the surrounding organs at risk (OARs) in particular the cochlea, oral cavity & contralateral parotid causing significant increase in the risk of oral mucositis, xerostomia, and ...

Generative Models of Conformational Dynamics

OpenAIRE

Langmead, Christopher James

2014-01-01

Atomistic simulations of the conformational dynamics of proteins can be performed using either Molecular Dynamics or Monte Carlo procedures. The ensembles of three-dimensional structures produced during simulation can be analyzed in a number of ways to elucidate the thermodynamic and kinetic properties of the system. The goal of this chapter is to review both traditional and emerging methods for learning generative models from atomistic simulation data. Here, the term ‘generative’ refers to a...

Comparison of intensity-modulated radiotherapy and 3-dimensional conformal radiotherapy as adjuvant therapy for gastric cancer.

Science.gov (United States)

Minn, A Yuriko; Hsu, Annie; La, Trang; Kunz, Pamela; Fisher, George A; Ford, James M; Norton, Jeffrey A; Visser, Brendan; Goodman, Karyn A; Koong, Albert C; Chang, Daniel T

2010-08-15

The current study was performed to compare the clinical outcomes and toxicity in patients treated with postoperative chemoradiotherapy for gastric cancer using intensity-modulated radiotherapy (IMRT) versus 3-dimensional conformal radiotherapy (3D CRT). Fifty-seven patients with gastric or gastroesophageal junction cancer were treated postoperatively: 26 with 3D CRT and 31 with IMRT. Concurrent chemotherapy was capecitabine (n=31), 5-fluorouracil (5-FU) (n=25), or none (n=1). The median radiation dose was 45 Gy. Dose volume histogram parameters for kidney and liver were compared between treatment groups. The 2-year overall survival rates for 3D CRT versus IMRT were 51% and 65%, respectively (P=.5). Four locoregional failures occurred each in the 3D CRT (15%) and the IMRT (13%) patients. Grade>or=2 acute gastrointestinal toxicity was found to be similar between the 3D CRT and IMRT patients (61.5% vs 61.2%, respectively) but more treatment breaks were needed (3 vs 0, respectively). The median serum creatinine from before radiotherapy to most recent creatinine was unchanged in the IMRT group (0.80 mg/dL) but increased in the 3D CRT group from 0.80 mg/dL to 1.0 mg/dL (P=.02). The median kidney mean dose was higher in the IMRT versus the 3D CRT group (13.9 Gy vs 11.1 Gy; P=.05). The median kidney V20 was lower for the IMRT versus the 3D CRT group (17.5% vs 22%; P=.17). The median liver mean dose for IMRT and 3D CRT was 13.6 Gy and 18.6 Gy, respectively (P=.19). The median liver V30 was 16.1% and 28%, respectively (PCancer Society.

Dynamic neutron scattering from conformational dynamics. I. Theory and Markov models.

Science.gov (United States)

Lindner, Benjamin; Yi, Zheng; Prinz, Jan-Hendrik; Smith, Jeremy C; Noé, Frank

2013-11-07

The dynamics of complex molecules can be directly probed by inelastic neutron scattering experiments. However, many of the underlying dynamical processes may exist on similar timescales, which makes it difficult to assign processes seen experimentally to specific structural rearrangements. Here, we show how Markov models can be used to connect structural changes observed in molecular dynamics simulation directly to the relaxation processes probed by scattering experiments. For this, a conformational dynamics theory of dynamical neutron and X-ray scattering is developed, following our previous approach for computing dynamical fingerprints of time-correlation functions [F. Noé, S. Doose, I. Daidone, M. Löllmann, J. Chodera, M. Sauer, and J. Smith, Proc. Natl. Acad. Sci. U.S.A. 108, 4822 (2011)]. Markov modeling is used to approximate the relaxation processes and timescales of the molecule via the eigenvectors and eigenvalues of a transition matrix between conformational substates. This procedure allows the establishment of a complete set of exponential decay functions and a full decomposition into the individual contributions, i.e., the contribution of every atom and dynamical process to each experimental relaxation process.

Estimate of the damage in organs induced by neutrons in three-dimensional conformal radiotherapy

International Nuclear Information System (INIS)

Benites R, J. L.; Vega C, H. R.; Uribe, M. del R.

2014-08-01

By means of Monte Carlo methods was considered the damage in the organs, induced by neutrons, of patients with cancer that receive treatment in modality of three-dimensional conformal radiotherapy (3D-CRT) with lineal accelerator Varian Ix. The objective of this work was to estimate the damage probability in radiotherapy patients, starting from the effective dose by neutrons in the organs and tissues out of the treatment region. For that a three-dimensional mannequin of equivalent tissue of 30 x 100 x 30 cm 3 was modeled and spherical cells were distributed to estimate the Kerma in equivalent tissue and the absorbed dose by neutrons. With the absorbed dose the effective dose was calculated using the weighting factors for the organ type and radiation type. With the effective dose and the damage factors, considered in the ICRP 103, was considered the probability of damage induction in organs. (Author)

Localized field conformation radiotherapy combined with endocrine therapy for the treatment of prostate cancer

International Nuclear Information System (INIS)

Karasawa, Katsuyuki; Kaizu, Toshihide; Kurosaki, Hiromasa; Tanaka, Yoshiaki

1999-01-01

To improve the quality of life (QOL) of the patients with prostate cancer, we limit the radiotherapy target volume to the prostate and seminal vesicles while using endocrine therapy towards the disease outside the target volume. Radiotherapy technique was rotation conformation technique with computer-controlled multileaf collimators to the total doses of up to 66-70 Gy. Among 145 evaluable cases with the median age of 74, overall and cause-specific 5-year survival rates were 59.3% and 84.1%, respectively, and the relative survival rate of the Stage A-C cases was 100%. The two thirds (33/50) of the deaths were not of prostate cancer. The rate of severe complication was 1.4%. As for QOL, the rate of impotence was 90%, however, the patients' overall satisfaction towards the treatment was 90%. From this analysis, this combined treatment seems beneficial in the treatment of prostate cancer. (author)

Comparison of static conformal field with multiple noncoplanar arc techniques for stereotactic radiosurgery or stereotactic radiotherapy

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Hamilton, Russell J.; Kuchnir, Franca T.; Sweeney, Patrick; Rubin, Steven J.; Dujovny, Manuel; Pelizzari, Charles A.; Chen, George T. Y.

1995-01-01

Purpose: Compare the use of static conformal fields with the use of multiple noncoplanar arcs for stereotactic radiosurgery or stereotactic radiotherapy treatment of intracranial lesions. Evaluate the efficacy of these treatment techniques to deliver dose distributions comparable to those considered acceptable in current radiotherapy practice. Methods and Materials: A previously treated radiosurgery case of a patient presenting with an irregularly shaped intracranial lesion was selected. Using a three-dimensional (3D) treatment-planning system, treatment plans using a single isocenter multiple noncoplanar arc technique and multiple noncoplanar conformal static fields were generated. Isodose distributions and dose volume histograms (DVHs) were computed for each treatment plan. We required that the 80% (of maximum dose) isodose surface enclose the target volume for all treatment plans. The prescription isodose was set equal to the minimum target isodose. The DVHs were analyzed to evaluate and compare the different treatment plans. Results: The dose distribution in the target volume becomes more uniform as the number of conformal fields increases. The volume of normal tissue receiving low doses (> 10% of prescription isodose) increases as the number of static fields increases. The single isocenter multiple arc plan treats the greatest volume of normal tissue to low doses, approximately 1.6 times more volume than that treated by four static fields. The volume of normal tissue receiving high (> 90% of prescription isodose) and intermediate (> 50% of prescription isodose) doses decreases by 29 and 22%, respectively, as the number of static fields is increased from four to eight. Increasing the number of static fields to 12 only further reduces the high and intermediate dose volumes by 10 and 6%, respectively. The volume receiving the prescription dose is more than 3.5 times larger than the target volume for all treatment plans. Conclusions: Use of a multiple noncoplanar

Changes in Pulmonary Function After Three-Dimensional Conformal Radiotherapy, Intensity-Modulated Radiotherapy, or Proton Beam Therapy for Non-Small-Cell Lung Cancer

International Nuclear Information System (INIS)

Lopez Guerra, Jose L.; Gomez, Daniel R.; Zhuang Yan; Levy, Lawrence B.; Eapen, George; Liu, Hongmei; Mohan, Radhe; Komaki, Ritsuko; Cox, James D.; Liao Zhongxing

2012-01-01

Purpose: To investigate the extent of change in pulmonary function over time after definitive radiotherapy for non-small-cell lung cancer (NSCLC) with modern techniques and to identify predictors of changes in pulmonary function according to patient, tumor, and treatment characteristics. Patients and Methods: We analyzed 250 patients who had received ≥60 Gy radio(chemo)therapy for primary NSCLC in 1998–2010 and had undergone pulmonary function tests before and within 1 year after treatment. Ninety-three patients were treated with three-dimensional conformal radiotherapy, 97 with intensity-modulated radiotherapy, and 60 with proton beam therapy. Postradiation pulmonary function test values were evaluated among individual patients compared with the same patient’s preradiation value at the following time intervals: 0–4 (T1), 5–8 (T2), and 9–12 (T3) months. Results: Lung diffusing capacity for carbon monoxide (DLCO) was reduced in the majority of patients along the three time periods after radiation, whereas the forced expiratory volume in 1 s per unit of vital capacity (FEV1/VC) showed an increase and decrease after radiation in a similar percentage of patients. There were baseline differences (stage, radiotherapy dose, concurrent chemotherapy) among the radiation technology groups. On multivariate analysis, the following features were associated with larger posttreatment declines in DLCO: pretreatment DLCO, gross tumor volume, lung and heart dosimetric data, and total radiation dose. Only pretreatment DLCO was associated with larger posttreatment declines in FEV1/VC. Conclusions: Lung diffusing capacity for carbon monoxide is reduced in the majority of patients after radiotherapy with modern techniques. Multiple factors, including gross tumor volume, preradiation lung function, and dosimetric parameters, are associated with the DLCO decline. Prospective studies are needed to better understand whether new radiation technology, such as proton beam therapy

Conformal symmetry and non-relativistic second-order fluid dynamics

International Nuclear Information System (INIS)

Chao Jingyi; Schäfer, Thomas

2012-01-01

We study the constraints imposed by conformal symmetry on the equations of fluid dynamics at second order in the gradients of the hydrodynamic variables. At zeroth order, conformal symmetry implies a constraint on the equation of state, E 0 =2/3 P, where E 0 is the energy density and P is the pressure. At first order, conformal symmetry implies that the bulk viscosity must vanish. We show that at second order, conformal invariance requires that two-derivative terms in the stress tensor must be traceless, and that it determines the relaxation of dissipative stresses to the Navier–Stokes form. We verify these results by solving the Boltzmann equation at second order in the gradient expansion. We find that only a subset of the terms allowed by conformal symmetry appear. - Highlights: ► We derive conformal constraints for the stress tensor of a scale invariant fluid. ► We determine the relaxation time in kinetic theory. ► We compute the rate of entropy production in second-order fluid dynamics.

Development of model plans in three dimensional conformal radiotherapy for brain tumors

International Nuclear Information System (INIS)

Pyo, Hongryull; Kim, Gwieon; Keum, Kichang; Chang, Sekyung; Suh, Changok; Lee, Sanghoon

2002-01-01

Three dimensional conformal radiotherapy planning is being used widely for the treatment of patients with brain tumor. However, it takes much time to develop an optimal treatment plan, therefore, it is difficult to apply this technique to all patients. To increase the efficiency of this technique, we need to develop standard radiotherapy plans for each site of the brain. Therefore we developed several 3 dimensional conformal radiotherapy plans (3D plans) for tumors at each site of brain, compared them with each other, and with 2 dimensional radiotherapy plans. Finally model plans for each site of the brain were decided. Imaginary tumors, with sizes commonly observed in the clinic, were designed for each site of the brain and drawn on CT images. The planning target volumes (PTVs) were as follows; temporal tumor-5.7 x 8.2 x 7.6 cm, suprasellar tumor-3 x 4 x 4.1 cm, thalamic tumor-3.1 x 5.9 x 3.7 cm, frontoparietal tumor-5.5 x 7 x 5.5 cm, and occipitoparietal tumor-5 x 5.5 x 5 cm. Plans using parallel opposed 2-portals and/or 3 portals including fronto-vertex and 2 lateral fields were developed manually as the conventional 2D plans, and 3D noncoplanar conformal plans were developed using beam's eye view and the automatic block drawing tool. Total tumor dose was 54 Gy for a suprasellar tumor, 59.4 Gy and 72 Gy for the other tumors. All dose plans (including 2D plans) were calculated using 3D plan software. Developed plans were compared with each other using dose-volume histograms (DVH), normal tissue complication probabilities (NTCP) and variable dose statistic values (minimum, maximum and mean dose, D5, V83, V85 and V95). Finally a best radiotherapy plan for each site of brain was selected. 1) Temporal tumor; NTCPs and DVHs of the normal tissue of all 3D plans were superior to 2D plans and this trend was more definite when total dose was escalated to 72 Gy (NTCPs of normal brain 2D plans: 27%, 8% → 3D plans: 1%, 1%). Various dose statistic values did not show any

Dosimetry analysis on radiation-induced acute esophagitis after three-dimensional conformal radiotherapy for non-small cell lung cancer

International Nuclear Information System (INIS)

ZZhu Shuchai; Cui Yanli; Li Juan; Liu Zhikun; Shen Wenbin; Su Jingwei; Wang Yuxiang

2010-01-01

Objective: To analyze the related factors with radiation-induced esophagitis after threedimensional conformal radiotherapy for non-small cell lung cancer (NSCLC), in order to explore the predictors for optimizing the treatment planning of NSCLC. Methods: From Aug 2000 to Dec 2004, 104 NSCLC patients received radiotherapy and were eligible for this study, 45 cases squamous cell carcinoma, 20 cases adenocarcinoma, 33 cases carrying with cancer cells by test and 6 case with no definitive pathologic feature.46 patients were treated with three dimensional conformal radiotherapy (3DCRT), the other 58 patients conventional radiotherapy (CRT) before later-course 3DCRT. All the patients received the prescribed dose between 60-78 Gy and the median dose 66 Gy. The correlation of the variables were evaluated by Spearman relationship analysis. The morbidity of radiation-induced esophagitis was analyzed by X 2 test. The multivariate effect on radiation-induced esophagitis was statistically processed by Logistic regression model. Results: In 104 patients, the morbidity of radiation- induced esophagitis was 46.2%, including 32 cases at grade 1, 15 cases at grade 2, 1 case at grade 3. Univariate analysis showed the maximal and mean dose of esophagus, the volume of esophagus irradiated, the values of V 40 , V 45 , V 50 , V 55 , V 60 , LETT 45 , LETT 50 , LETT 55 , LETT 60 for the esophagus were correlated with radiation-induced esophagitis. Logistic regression model showed that the maximum dose received by the esophagus was the independent factor of ≥ 2 grade radiation-induced esophagitis. Conclusions: The maxmal dose of esophagus received might be the important factor of radiation-induced esophagitis. (authors)

Lipid Regulated Intramolecular Conformational Dynamics of SNARE-Protein Ykt6

Science.gov (United States)

Dai, Yawei; Seeger, Markus; Weng, Jingwei; Song, Song; Wang, Wenning; Tan, Yan-Wen

2016-08-01

Cellular informational and metabolic processes are propagated with specific membrane fusions governed by soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNARE). SNARE protein Ykt6 is highly expressed in brain neurons and plays a critical role in the membrane-trafficking process. Studies suggested that Ykt6 undergoes a conformational change at the interface between its longin domain and the SNARE core. In this work, we study the conformational state distributions and dynamics of rat Ykt6 by means of single-molecule Förster Resonance Energy Transfer (smFRET) and Fluorescence Cross-Correlation Spectroscopy (FCCS). We observed that intramolecular conformational dynamics between longin domain and SNARE core occurred at the timescale ~200 μs. Furthermore, this dynamics can be regulated and even eliminated by the presence of lipid dodecylphoshpocholine (DPC). Our molecular dynamic (MD) simulations have shown that, the SNARE core exhibits a flexible structure while the longin domain retains relatively stable in apo state. Combining single molecule experiments and theoretical MD simulations, we are the first to provide a quantitative dynamics of Ykt6 and explain the functional conformational change from a qualitative point of view.

Retrospective evaluation of dosimetric quality for prostate carcinomas treated with 3D conformal, intensity modulated and volumetric modulated arc radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Crowe, Scott B [Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland (Australia); Kairn, Tanya [Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland (Australia); Premion, Wesley Medical Centre, Brisbane, Queensland (Australia); Middlebrook, Nigel; Hill, Brendan; Christie, David R H; Knight, Richard T [Premion, Wesley Medical Centre, Brisbane, Queensland (Australia); Kenny, John [Australian Clinical Dosimetry Services, Australian Radiation Protection and Nuclear Safety Agency, Melbourne, Victoria (Australia); Langton, Christian M; Trapp, Jamie V [Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland (Australia)

2013-12-15

This study examines and compares the dosimetric quality of radiotherapy treatment plans for prostate carcinoma across a cohort of 163 patients treated across five centres: 83 treated with three-dimensional conformal radiotherapy (3DCRT), 33 treated with intensity modulated radiotherapy (IMRT) and 47 treated with volumetric modulated arc therapy (VMAT). Treatment plan quality was evaluated in terms of target dose homogeneity and organs at risk (OAR), through the use of a set of dose metrics. These included the mean, maximum and minimum doses; the homogeneity and conformity indices for the target volumes; and a selection of dose coverage values that were relevant to each OAR. Statistical significance was evaluated using two-tailed Welch's T-tests. The Monte Carlo DICOM ToolKit software was adapted to permit the evaluation of dose metrics from DICOM data exported from a commercial radiotherapy treatment planning system. The 3DCRT treatment plans offered greater planning target volume dose homogeneity than the other two treatment modalities. The IMRT and VMAT plans offered greater dose reduction in the OAR: with increased compliance with recommended OAR dose constraints, compared to conventional 3DCRT treatments. When compared to each other, IMRT and VMAT did not provide significantly different treatment plan quality for like-sized tumour volumes. This study indicates that IMRT and VMAT have provided similar dosimetric quality, which is superior to the dosimetric quality achieved with 3DCRT.

3-D conformal radiotherapy of localized prostate cancer: A subgroup analysis of rectoscopic findings prior to radiotherapy and acute/late rectal side effects

International Nuclear Information System (INIS)

Goldner, Gregor; Zimmermann, Frank; Feldmann, Horst; Glocker, Stefan; Wachter-Gerstner, Natascha; Geinitz, Hans; Becker, Gerd; Poetzi, Regina; Wambersie, Andre; Bamberg, Michael; Molls, Michael; Wachter, Stefan; Poetter, Richard

2006-01-01

Background and purpose: To identify endoscopic pathological findings prior to radiotherapy and a possible correlation with acute or chronic rectal side effects after three-dimensional conformal radiotherapy (3D-CRT) for prostate cancer. Patients and methods: Between 03/99 and 07/02, a total of 298 patients, who consented in a voluntary rectoscopy prior to radiotherapy were included into the analysis. Patients were treated with a total dose of either 70 or 74 Gy. Pathological rectoscopic findings like hemorrhoids, polyps or diverticula were documented. Acute and late rectal side effects were scored using the EORTC/RTOG score. Results: The most frequent pathological endosopic findings were hemorrhoids (35%), polyps (24%) and diverticula (13%). Rectal toxicity was mostly low to moderate. Grade 0/1 cumulative acute and late rectal side effects were 82 and 84%, grade 2 were 18 and 17%, respectively. We could not identify any correlation between preexisting pathological findings and rectal side effects by statistical analysis. Conclusions: There is no evidence that prostate cancer patients presenting with endoscopic verified pathological findings in the rectal mucosa at diagnosis are at an increased risk to develop rectal side effects when treated with 3D-CRT of the prostatic region

Dosimetric and Radiobiologic Comparison of 3D Conformal Versus Intensity Modulated Planning Techniques for Prostate Bed Radiotherapy

International Nuclear Information System (INIS)

Koontz, Bridget F.; Das, Shiva; Temple, Kathy; Bynum, Sigrun; Catalano, Suzanne; Koontz, Jason I.; Montana, Gustavo S.; Oleson, James R.

2009-01-01

Adjuvant radiotherapy for locally advanced prostate cancer improves biochemical and clinical disease-free survival. While comparisons in intact prostate cancer show a benefit for intensity modulated radiation therapy (IMRT) over 3D conformal planning, this has not been studied for post-prostatectomy radiotherapy (RT). This study compares normal tissue and target dosimetry and radiobiological modeling of IMRT vs. 3D conformal planning in the postoperative setting. 3D conformal plans were designed for 15 patients who had been treated with IMRT planning for salvage post-prostatectomy RT. The same computed tomography (CT) and target/normal structure contours, as well as prescription dose, was used for both IMRT and 3D plans. Normal tissue complication probabilities (NTCPs) were calculated based on the dose given to the bladder and rectum by both plans. Dose-volume histogram and NTCP data were compared by paired t-test. Bladder and rectal sparing were improved with IMRT planning compared to 3D conformal planning. The volume of the bladder receiving at least 75% (V75) and 50% (V50) of the dose was significantly reduced by 28% and 17%, respectively (p = 0.002 and 0.037). Rectal dose was similarly reduced, V75 by 33% and V50 by 17% (p = 0.001 and 0.004). While there was no difference in the volume of rectum receiving at least 65 Gy (V65), IMRT planning significant reduced the volume receiving 40 Gy or more (V40, p = 0.009). Bladder V40 and V65 were not significantly different between planning modalities. Despite these dosimetric differences, there was no significant difference in the NTCP for either bladder or rectal injury. IMRT planning reduces the volume of bladder and rectum receiving high doses during post-prostatectomy RT. Because of relatively low doses given to the bladder and rectum, there was no statistically significant improvement in NTCP between the 3D conformal and IMRT plans.

Dosimetric and radiobiologic comparison of 3D conformal versus intensity modulated planning techniques for prostate bed radiotherapy.

Science.gov (United States)

Koontz, Bridget F; Das, Shiva; Temple, Kathy; Bynum, Sigrun; Catalano, Suzanne; Koontz, Jason I; Montana, Gustavo S; Oleson, James R

2009-01-01

Adjuvant radiotherapy for locally advanced prostate cancer improves biochemical and clinical disease-free survival. While comparisons in intact prostate cancer show a benefit for intensity modulated radiation therapy (IMRT) over 3D conformal planning, this has not been studied for post-prostatectomy radiotherapy (RT). This study compares normal tissue and target dosimetry and radiobiological modeling of IMRT vs. 3D conformal planning in the postoperative setting. 3D conformal plans were designed for 15 patients who had been treated with IMRT planning for salvage post-prostatectomy RT. The same computed tomography (CT) and target/normal structure contours, as well as prescription dose, was used for both IMRT and 3D plans. Normal tissue complication probabilities (NTCPs) were calculated based on the dose given to the bladder and rectum by both plans. Dose-volume histogram and NTCP data were compared by paired t-test. Bladder and rectal sparing were improved with IMRT planning compared to 3D conformal planning. The volume of the bladder receiving at least 75% (V75) and 50% (V50) of the dose was significantly reduced by 28% and 17%, respectively (p = 0.002 and 0.037). Rectal dose was similarly reduced, V75 by 33% and V50 by 17% (p = 0.001 and 0.004). While there was no difference in the volume of rectum receiving at least 65 Gy (V65), IMRT planning significant reduced the volume receiving 40 Gy or more (V40, p = 0.009). Bladder V40 and V65 were not significantly different between planning modalities. Despite these dosimetric differences, there was no significant difference in the NTCP for either bladder or rectal injury. IMRT planning reduces the volume of bladder and rectum receiving high doses during post-prostatectomy RT. Because of relatively low doses given to the bladder and rectum, there was no statistically significant improvement in NTCP between the 3D conformal and IMRT plans.

Conformation analysis of trehalose. Molecular dynamics simulation and molecular mechanics

International Nuclear Information System (INIS)

Donnamaira, M.C.; Howard, E.I.; Grigera, J.R.

1992-09-01

Conformational analysis of the disaccharide trehalose is done by molecular dynamics and molecular mechanics. In spite of the different force fields used in each case, comparison between the molecular dynamics trajectories of the torsional angles of glycosidic linkage and energy conformational map shows a good agreement between both methods. By molecular dynamics it is observed a moderate mobility of the glycosidic linkage. The demands of computer time is comparable in both cases. (author). 6 refs, 4 figs

Dosimetric comparison of the related parameters between simultaneous integrated boost intensity-modulated radiotherapy and sequential boost conformal radiotherapy for postoperative malignant glioma of the brain

International Nuclear Information System (INIS)

Shao Qian; Lu Jie; Li Jianbin; Sun Tao; Bai Tong; Liu Tonghai; Yin Yong

2011-01-01

Objective: To compare the dosimetric of different parameter of simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) with sequential boost conformal radiotherapy (SB-CRT) for postoperative malignant glioma of the brain. Methods: Ten patients with malignant glioma of brain were selected to study. Each patient was simulated all by CT and MRI, and the imagings of CT and MRI were all sent to Pinnacle 3 planning system. The fusion technology with MR-CT imaging was used on Pinnacle 3 planning system. The target volume was delineated and defined based on MRI. The postoperative residual lesion and resection cavity were defined as gross tumor volume (GTV) and expanded GTV some scope was defined as clinical target volume (CTV). The margins of GTV expanded 10 mm and 25 mm were defined as CTV1 and CTV2 respectively. CTV1 and CTV2 all enlarged 5 mm were defined as PTV1 and PTV2 respectively. The plans of simultaneous integrated boost intensity-modulated radiotherapy and sequential boost conformal radiotherapy were respectively designed for each patient using Pinnacle 3 planning system and the dosimetric of different parameter was compared. The prescribe dose of SIB-IMRT was PTV1: 62.5 Gy/25 f, PTV2: 50.0 Gy/25 f; and SB-CRT was PTV1: 66.0 Gy/33 f, PTV2: 50.0 Gy/25 f. The dosimetries of different parameters of SIB-IMRT and SB-CRT were compared by using Paired-Samples T Test. Results: The maximum and mean dose of PTV1, PTV2, and brainstem were of significant difference (P 0.05). Conclusion: The SIB-IMRT plan is better than the SB-CRT plan. The CI and HI of SIB-IMRT are superior to SB-CRT. At the same time, it can preserve the important organs such as brainstem and reduce the mean dose of whole brain. On the other hand it can shorten the total period of therapy time. (authors)

Dynamics of the conformal factor in 4D gravity

International Nuclear Information System (INIS)

Antoniadis, I.

1993-01-01

We argue that 4D gravity is drastically modified at distances larger than the horizon scale, due to the large infrared quantum fluctuations of the conformal part of the metric. The infrared dynamics of the conformal factor is generated by an effective action, induced by the trace anomaly of matter in curved space, analogous to the Polyakov action in two dimensions. The resulting effective scalar theory is renormalizable, and possesses a non-trivial, infrared stable fixed point, characterized by an anomalous scaling dimension of the conformal factor. We argue that this theory describes a large distance scale invariant phase of 4D gravity and provides a framework for a dynamical solution of the cosmological constant problem (author). 12 refs

Computer controlled multi-leaf conformation radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Matsuda, T [Tokyo Metropolitan Komagome Hospital (Japan); Inamura, K

1981-10-01

A conformation radiotherapy system with 5-split collimators of which openings can be controlled symmetrically by computerized techniques during rotational irradiation by a linear accelerator has been developed. Outline of the system performance and its clinical applications are described as follows. 1. Profile of the system: The hardware is composed of three parts, namely, the multi-split collimator, the electronic data processor, and the interface between those two parts. 1) The multi-leaf collimator is composed of 5 pairs (10 leaves) diaphragms. It can be mounted to the X-ray head of a linear accelerator when used, and can be dismounted after its use. 2) The electronic data processor sends control signal to the collimator according to the 5-leaf target volume data which can be stored into a minifloppy disc through the curve digitizer previously. This part is composed of a) dedicated micro processor, b) I/O expansion unit, c) color CRT display with key board, d) dual mini-floppy disc unit, e) curve digitizer and f) digital plotter for recording and verification of resulted accuracy. 2. Performance of the system: 1) Maximum field size: 15 cm x 15 cm at isocenter. 2) Maximum elongation ratio of the target volume: 3 : 1 when the longer diameter is 15 cm. 3) Control accuracy: Within +-3 mm deviation from planned beam focus at isocenter. 3. Clinical application: The method of treatment planning and clinical advantages of this irradiation method are explained by raising clinical experiences such as treating brain tumor and rectal cancer.

Computer controlled multi-leaf conformation radiotherapy

International Nuclear Information System (INIS)

Matsuda, Tadayoshi; Inamura, Kiyonari.

1981-01-01

A conformation radiotherapy system with 5-split collimators of which openings can be controlled symmetrically by computerized techniques during rotational irradiation by a linear accelerator has been developed. Outline of the system performance and its clinical applications are described as follows. 1. Profile of the system: The hardware is composed of three parts, namely, the multi-split collimator, the electronic data processor, and the interface between those two parts. 1) The multi-leaf collimator is composed of 5 pairs (10 leaves) diaphragms. It can be mounted to the X-ray head of a linear accelerator when used, and can be dismounted after its use. 2) The electronic data processor sends control signal to the collimator according to the 5-leaf target volume data which can be stored into a minifloppy disc through the curve digitizer previously. This part is composed of a) dedicated micro processor, b) I/O expansion unit, c) color CRT display with key board, d) dual mini-floppy disc unit, e) curve digitizer and f) digital plotter for recording and verification of resulted accuracy. 2. Performance of the system: 1) Maximum field size: 15 cm x 15 cm at isocenter. 2) Maximum elongation ratio of the target volume: 3 : 1 when the longer diameter is 15 cm. 3) Control accuracy: Within +-3 mm deviation from planned beam focus at isocenter. 3. Clinical application: The method of treatment planning and clinical advantages of this irradiation method are explained by raising clinical experiences such as treating brain tumor and rectal cancer. (author)

A neurosurgery/stereotactic radiotherapy dedicated PACS for conformal radiotherapy

International Nuclear Information System (INIS)

Lefkopoulos, D.; Bocquiault, P.; Levrier, M.; Merienne, L.; Schlienger, M.

1995-01-01

To realise conformal cerebral stereotactic irradiations we use a Neurosurgery/stereotactic dedicated PACS between two distant hospitals. It connects the stereotactic neurosurgery planification imaging system NEUROAXIS (Sopelem-Sofretec/Ste Anne Hospital) with the dosimetric TPS ARTEMIS-3D/Dosigray (Tenon Hospital). NEUROAXIS is a computer aided stereotactic biopsies and stereo-electroencephalographies, used by surgeons in operating room. The system determines the precise location data for Talairach radiological equipment (X ray source at 5 meters from film) and the geometry of scanner and MRI stereotactical referentials. It provides a full set of features for lesion localization, geometrical computations, surgical planifications, picture archiving, stereotactic angiography, CT and MRI image processing and networking. It sends images through the French public digital network ISDN (NUMERIS/France Telecom : 2x64 Kbits/s) from Ste Anne to Tenon Hospital. Stereotactic angiographic and CT images are reformatted into the DOSIGRAY image processing environment where 3-D dose distributions, displays and DVHs are computed to determine the optimal treatment. ARTEMIS-3D/Dosigray is a TPS for stereotactic radiotherapy devised by the Tenon Hospital for clinical methodology and 3D dose calculations, optimization software development and the Dosigray company for multimodality imaging, (2D(3D)) computer graphics for dose and anatomical representation and data networking. Communication within the radiation oncology department is provided by local area ETHERNET network, linking heterogeneous systems (Vaxstations-3200; Decstation (5000(240))) by means of different protocols. The works in progress are to send back via the same network the 3-D dose matrix to Neurosurgery department NEUROAXIS system. Our PACS is used since six months to treat patients. It has permitted to improve the treatment quality in comparison with our first version TPS ARTEMIS-3D

Dosimetric comparison of intensity-modulated, conformal, and four-field pelvic radiotherapy boost plans for gynecologic cancer: a retrospective planning study

International Nuclear Information System (INIS)

Chan, Philip; Yeo, Inhwan; Perkins, Gregory; Fyles, Anthony; Milosevic, Michael

2006-01-01

To evaluate intensity-modulated radiation therapy (IMRT) as an alternative to conformal radiotherapy (CRT) or 4-field box boost (4FB) in women with gynecologic malignancies who are unsuitable for brachytherapy for technical or medical reasons. Dosimetric and toxicity information was analyzed for 12 patients with cervical (8), endometrial (2) or vaginal (2) cancer previously treated with external beam pelvic radiotherapy and a CRT boost. Optimized IMRT boost treatment plans were then developed for each of the 12 patients and compared to CRT and 4FB plans. The plans were compared in terms of dose conformality and critical normal tissue avoidance. The median planning target volume (PTV) was 151 cm 3 (range 58–512 cm 3 ). The median overlap of the contoured rectum with the PTV was 15 (1–56) %, and 11 (4–35) % for the bladder. Two of the 12 patients, both with large PTVs and large overlap of the contoured rectum and PTV, developed grade 3 rectal bleeding. The dose conformity was significantly improved with IMRT over CRT and 4FB (p ≤ 0.001 for both). IMRT also yielded an overall improvement in the rectal and bladder dose-volume distributions relative to CRT and 4FB. The volume of rectum that received the highest doses (>66% of the prescription) was reduced by 22% (p < 0.001) with IMRT relative to 4FB, and the bladder volume was reduced by 19% (p < 0.001). This was at the expense of an increase in the volume of these organs receiving doses in the lowest range (<33%). These results indicate that IMRT can improve target coverage and reduce dose to critical structures in gynecologic patients receiving an external beam radiotherapy boost. This dosimetric advantage will be integrated with other patient and treatment-specific factors, particularly internal tumor movement during fractionated radiotherapy, in the context of a future image-guided radiation therapy study

Limited Advantages of Intensity-Modulated Radiotherapy Over 3D Conformal Radiation Therapy in the Adjuvant Management of Gastric Cancer

International Nuclear Information System (INIS)

Alani, Shlomo; Soyfer, Viacheslav; Strauss, Natan; Schifter, Dan; Corn, Benjamin W.

2009-01-01

Purpose: Although chemoradiotherapy was considered the standard adjuvant treatment for gastric cancer, a recent Phase III trial (Medical Research Council Adjuvant Gastric Infusional Chemotherapy [MAGIC]) did not include radiotherapy in the randomization scheme because it was considered expendable. Given radiotherapy's potential, efforts needed to be made to optimize its use for treating gastric cancer. We assessed whether intensity-modulated radiotherapy (IMRT) could improve upon our published results in patients treated with three-dimensional (3D) conformal therapy. Methods and Materials: Fourteen patients with adenocarcinoma of the stomach were treated with adjuvant chemoradiotherapy using a noncoplanar four-field arrangement. Subsequently, a nine-field IMRT plan was designed using a CMS Xio IMRT version 4.3.3 module. Two IMRT beam arrangements were evaluated: beam arrangement 1 consisted of gantry angles of 0 deg., 53 deg., 107 deg., 158 deg., 204 deg., 255 deg., and 306 deg.. Beam arrangement 2 consisted of gantry angles of 30 deg., 90 deg., 315 deg., and 345 deg.; a gantry angle of 320 deg./couch, 30 deg.; and a gantry angle of 35 o /couch, 312 o . Both the target volume coverage and the dose deposition in adjacent critical organs were assessed in the plans. Dose-volume histograms were generated for the clinical target volume, kidneys, spine, and liver. Results: Comparison of the clinical target volumes revealed satisfactory coverage by the 95% isodose envelope using either IMRT or 3D conformal therapy. However, IMRT was only marginally better than 3D conformal therapy at protecting the spine and kidneys from radiation. Conclusions: IMRT confers only a marginal benefit in the adjuvant treatment of gastric cancer and should be used only in the small subset of patients with risk factors for kidney disease or those with a preexisting nephropathy.

Limited advantages of intensity-modulated radiotherapy over 3D conformal radiation therapy in the adjuvant management of gastric cancer.

Science.gov (United States)

Alani, Shlomo; Soyfer, Viacheslav; Strauss, Natan; Schifter, Dan; Corn, Benjamin W

2009-06-01

Although chemoradiotherapy was considered the standard adjuvant treatment for gastric cancer, a recent Phase III trial (Medical Research Council Adjuvant Gastric Infusional Chemotherapy [MAGIC]) did not include radiotherapy in the randomization scheme because it was considered expendable. Given radiotherapy's potential, efforts needed to be made to optimize its use for treating gastric cancer. We assessed whether intensity-modulated radiotherapy (IMRT) could improve upon our published results in patients treated with three-dimensional (3D) conformal therapy. Fourteen patients with adenocarcinoma of the stomach were treated with adjuvant chemoradiotherapy using a noncoplanar four-field arrangement. Subsequently, a nine-field IMRT plan was designed using a CMS Xio IMRT version 4.3.3 module. Two IMRT beam arrangements were evaluated: beam arrangement 1 consisted of gantry angles of 0 degrees , 53 degrees , 107 degrees , 158 degrees , 204 degrees , 255 degrees , and 306 degrees . Beam arrangement 2 consisted of gantry angles of 30 degrees , 90 degrees , 315 degrees , and 345 degrees ; a gantry angle of 320 degrees /couch, 30 degrees ; and a gantry angle of 35 degrees /couch, 312 degrees . Both the target volume coverage and the dose deposition in adjacent critical organs were assessed in the plans. Dose-volume histograms were generated for the clinical target volume, kidneys, spine, and liver. Comparison of the clinical target volumes revealed satisfactory coverage by the 95% isodose envelope using either IMRT or 3D conformal therapy. However, IMRT was only marginally better than 3D conformal therapy at protecting the spine and kidneys from radiation. IMRT confers only a marginal benefit in the adjuvant treatment of gastric cancer and should be used only in the small subset of patients with risk factors for kidney disease or those with a preexisting nephropathy.

Set-up error in supine-positioned patients immobilized with two different modalities during conformal radiotherapy of prostate cancer

International Nuclear Information System (INIS)

Fiorino, C.; Cattaneo, G.M.; Calandrino, R.; Reni, M.; Bolognesi, A.; Bonini, A.

1998-01-01

Background: Conformal radiotherapy requires reduced margins around the clinical target volume (CTV) with respect to traditional radiotherapy techniques. Therefore, high set-up accuracy and reproducibility are mandatory. Purpose: To investigate the effectiveness of two different immobilization techniques during conformal radiotherapy of prostate cancer with small fields. Materials and methods: 52 patients with prostate cancer were treated by conformal three- or four-field techniques with radical or adjuvant intent between November 1996 and March 1998. In total, 539 portal images were collected on a weekly basis for at least the first 4 weeks of the treatment on lateral and anterior 18 MV X-ray fields. The average number of sessions monitored per patient was 5.7 (range 4-10). All patients were immobilized with an alpha-cradle system; 25 of them were immobilized at the pelvis level (group A) and the remaining 27 patients were immobilized in the legs (group B). The shifts with respect to the simulation condition were assessed by measuring the distances between the same bony landmarks and the field edges. The global distributions of cranio-caudal (CC), posterior-anterior (PA) and left-right (LR) shifts were considered; for each patient random and systematic error components were assessed by following the procedure suggested by Bijhold et al. (Bijhold J, Lebesque JV, Hart AAM, Vijlbrief RE. Maximising set-up accuracy using portal images as applied to a conformal boost technique for prostatic cancer. Radiother. Oncol. 1992;24:261-271). For each patient the average isocentre (3D) shift was assessed as the quadratic sum of the average shifts in the three directions. Results 5 mm equal to 4.4% with respect to the 21.6% of group A (P<0.0001). This value was also better than the corresponding value found in a previously investigated group of 21 non-immobilized patients (Italia C, Fiorino C, Ciocca M, et al. Quality control by portal film analysis of the conformal radiotherapy

Monitoring conformational dynamics with solid-state R1ρ experiments

International Nuclear Information System (INIS)

Quinn, Caitlin M.; McDermott, Ann E.

2009-01-01

A new application of solid-state rotating frame (R 1ρ ) relaxation experiments to observe conformational dynamics is presented. Studies on a model compound, dimethyl sulfone (DMS), show that R 1ρ relaxation due to reorientation of a chemical shift anisotropy (CSA) tensor undergoing chemical exchange can be used to monitor slow-to-intermediate timescale conformational exchange processes. Control experiments used d 6 -DMS and alanine to confirm that the technique is monitoring reorientation of the CSA tensor rather than dipolar interactions or methyl group rotation. The application of this method to proteins could represent a new site-specific probe of conformational dynamics

Optimization of Stereotactic Radiotherapy Treatment Delivery Technique for Base-Of-Skull Meningiomas

International Nuclear Information System (INIS)

Clark, Brenda G.; Candish, Charles; Vollans, Emily; Gete, Ermias; Lee, Richard; Martin, Monty; Ma, Roy; McKenzie, Michael

2008-01-01

This study compares static conformal field (CF), intensity modulated radiotherapy (IMRT), and dynamic arcs (DA) for the stereotactic radiotherapy of base-of-skull meningiomas. Twenty-one cases of base-of-skull meningioma (median planning target volume [PTV] = 21.3 cm 3 ) previously treated with stereotactic radiotherapy were replanned with each technique. The plans were compared for Radiation Therapy Oncology Group conformity index (CI) and homogeneity index (HI), and doses to normal structures at 6 dose values from 50.4 Gy to 5.6 Gy. The mean CI was 1.75 (CF), 1.75 (DA), and 1.66 (IMRT) (p 3 , the CI (IMRT) was always superior to CI (DA) and CI (CF). At PTV sizes below 25 cm 3 , there was no significant difference in CI between each technique. There was no significant difference in HI between plans. The total volume of normal tissue receiving 50.4, 44.8, and 5.6 Gy was significantly lower when comparing IMRT to CF and DA plans (p 3 , due to improved conformity and normal tissue sparing, in particular for the brain stem and ipsilateral temporal lobe

A FAST MORPHING-BASED INTERPOLATION FOR MEDICAL IMAGES: APPLICATION TO CONFORMAL RADIOTHERAPY

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Hussein Atoui

2011-05-01

Full Text Available A method is presented for fast interpolation between medical images. The method is intended for both slice and projective interpolation. It allows offline interpolation between neighboring slices in tomographic data. Spatial correspondence between adjacent images is established using a block matching algorithm. Interpolation of image intensities is then carried out by morphing between the images. The morphing-based method is compared to standard linear interpolation, block-matching-based interpolation and registrationbased interpolation in 3D tomographic data sets. Results show that the proposed method scored similar performance in comparison to registration-based interpolation, and significantly outperforms both linear and block-matching-based interpolation. This method is applied in the context of conformal radiotherapy for online projective interpolation between Digitally Reconstructed Radiographs (DRRs.

Conformal radiotherapy in the adjuvant treatment of gastric cancer: Review of 82 cases

International Nuclear Information System (INIS)

Kassam, Zahra; Lockwood, Gina; O'Brien, Catherine; Brierley, James; Swallow, Carol; Oza, Amit; Siu, Lillian; Knox, Jennifer J.; Wong, Rebecca; Cummings, Bernard; Kim, John; Moore, Malcolm; Ringash, Jolie

2006-01-01

Background: The Intergroup 0116 study showed a survival benefit with adjuvant chemoradiotherapy (CRT) for resected gastric cancer. We report our experience using conformal radiotherapy (RT). Methods and Materials: Eighty-two patients with resected gastric or gastroesophageal junction (GEJ) adenocarcinoma, Stage IB to IV (M0), were treated with 45 Gy in 25 fractions using a 5-field conformal technique. Chemotherapy was in accordance with the Intergroup 0116 study, or infusional 5-fluorouracil and cisplatin in a phase I/II trial. Results: Mean age was 56.4 years. Median follow-up was 22.8 months. Grade 3 or greater acute toxicity (National Cancer Institute Common Terminology Criteria of Adverse Events, version 3.0) was noted in 57% of patients (upper gastrointestinal tract 34%, hematologic 33%). One patient died of neutropenic sepsis. Radiation Therapy Oncology Group Grade 3 late toxicity included esophageal strictures (3 patients) and small bowel obstruction (1 patient). Full course CRT was completed by 67% of patients. Of 26 patients who relapsed, 20 died. Site of first relapse was available on 23 patients: 8 locoregional and distant, 4 locoregional alone, 11 distant alone. Overall and relapse-free survival were 69% and 54% at 3 years. Conclusion: Adjuvant CRT for gastric cancer, even with conformal RT, is associated with significant toxicity. Survival was comparable to that reported in the Intergroup 0116 study

Animation and radiobiological analysis of 3D motion in conformal radiotherapy.

Science.gov (United States)

MacKay, R I; Graham, P A; Moore, C J; Logue, J P; Sharrock, P J

1999-07-01

To allow treatment plans to be evaluated against the range of expected organ motion and set up error anticipated during treatment. Planning tools have been developed to allow concurrent animation and radiobiological analysis of three dimensional (3D) target and organ motion in conformal radiotherapy. Surfaces fitted to structures outlined on CT studies are projected onto pre-treatment images or onto megavoltage images collected during the patient treatment. Visual simulation of tumour and normal tissue movement is then performed by the application of three dimensional affine transformations, to the selected surface. Concurrent registration of the surface motion with the 3D dose distribution allows calculation of the change in dose to the volume. Realistic patterns of motion can be applied to the structure to simulate inter-fraction motion and set-up error. The biologically effective dose for the structure is calculated for each fraction as the surface moves over the course of the treatment and is used to calculate the normal tissue complication probability (NTCP) or tumour control probability (TCP) for the moving structure. The tool has been used to evaluate conformal therapy plans against set up measurements recorded during patient treatments. NTCP and TCP were calculated for a patient whose set up had been corrected after systematic deviations from plan geometry were measured during treatment, the effect of not making the correction were also assessed. TCP for the moving tumour was reduced if inadequate margins were set for the treatment. Modelling suggests that smaller margins could have been set for the set up corrected during the course of the treatment. The NTCP for the rectum was also higher for the uncorrected set up due to a more rectal tissue falling in the high dose region. This approach provides a simple way for clinical users to utilise information incrementally collected throughout the whole of a patient's treatment. In particular it is possible to

Dynamics and diffusive-conformational coupling in polymer bulk samples and surfaces: a molecular dynamics study

International Nuclear Information System (INIS)

Vree, C; Mayr, S G

2010-01-01

The impact of free surfaces on the mobility and conformational fluctuations of model polymer chains is investigated with the help of classical molecular dynamics simulations over a broad temperature range. Below a critical temperature, T*, similar to the critical temperature of the mode coupling theory, the center-of-mass displacements and temporal fluctuations of the radius of gyration of individual chains-as a fingerprint of structural reconfigurations-reveal a strong enhancement close to surfaces, while this effect diminishes with increasing temperature and observation time. Interpreting conformational fluctuations as a random walk in conformational space, identical activation enthalpies for structural reconfigurations and diffusion are obtained within the error bars in the bulk and at the surfaces, thus indicating a coupling of diffusive and conformational dynamics.

A Comparison of Helical Intensity-Modulated Radiotherapy, Intensity-Modulated Radiotherapy, and 3D-Conformal Radiation Therapy for Pancreatic Cancer

International Nuclear Information System (INIS)

Poppe, Matthew M.; Narra, Venkat; Yue, Ning J.; Zhou Jinghao; Nelson, Carl; Jabbour, Salma K.

2011-01-01

We assessed dosimetric differences in pancreatic cancer radiotherapy via helical intensity-modulated radiotherapy (HIMRT), linac-based IMRT, and 3D-conformal radiation therapy (3D-CRT) with regard to successful plan acceptance and dose to critical organs. Dosimetric analysis was performed in 16 pancreatic cases that were planned to 54 Gy; both post-pancreaticoduodenectomy (n = 8) and unresected (n = 8) cases were compared. Without volume modification, plans met constraints 75% of the time with HIMRT and IMRT and 13% with 3D-CRT. There was no statistically significantly improvement with HIMRT over conventional IMRT in reducing liver V35, stomach V45, or bowel V45. HIMRT offers improved planning target volume (PTV) dose homogeneity compared with IMRT, averaging a lower maximum dose and higher volume receiving the prescription dose (D100). HIMRT showed an increased mean dose over IMRT to bowel and liver. Both HIMRT and IMRT offer a statistically significant improvement over 3D-CRT in lowering dose to liver, stomach, and bowel. The results were similar for both unresected and resected patients. In pancreatic cancer, HIMRT offers improved dose homogeneity over conventional IMRT and several significant benefits to 3D-CRT. Factors to consider before incorporating IMRT into pancreatic cancer therapy are respiratory motion, dose inhomogeneity, and mean dose.

Evaluation of dose coverage to target volume and normal tissue sparing in the adjuvant radiotherapy of gastric cancers: 3D-CRT compared with dynamic IMRT.

Science.gov (United States)

Murthy, Kk; Shukeili, Ka; Kumar, Ss; Davis, Ca; Chandran, Rr; Namrata, S

2010-01-01

To assess the potential advantage of intensity-modulated radiotherapy (IMRT) over 3D-conformal radiotherapy (3D-CRT) planning in postoperative adjuvant radiotherapy for patients with gastric carcinoma. In a retrospective study, for plan comparison, dose distribution was recalculated in 15 patients treated with 3D-CRT on the contoured structures of same CT images using an IMRT technique. 3D-conformal plans with three fields and four-fields were compared with seven-field dynamic IMRT plans. The different plans were compared by analyzing the dose coverage of planning target volume using TV(95), D(mean), uniformity index, conformity index and homogeneity index parameters. To assess critical organ sparing, D(mean), D(max), dose to one-third and two-third volumes of the OARs and percentage of volumes receiving more than their tolerance doses were compared. The average dose coverage values of PTV with 3F-CRT and 4F-CRT plans were comparable, where as IMRT plans achieved better target coverage(p3D-CRT plans. The doses to the liver and bowel reduced significantly (p3D-CRT plans. For all OARs the percentage of volumes receiving more than their tolerance doses were reduced with the IMRT plans. This study showed that a better target coverage and significant dose reduction to OARs could be achieved with the IMRT plans. The IMRT can be preferred with caution for organ motion. The authors are currently studying organ motion in the upper abdomen to use IMRT for patient treatment.

Late injury of the eye after conformation radiotherapy for carcinoma of the maxillary sinus

International Nuclear Information System (INIS)

Morita, Kozo

1975-01-01

Late injury of the eye after radiotherapy for 26 patients with carcinoma of the maxillary sinus was discussed. The conformation technique, a kind of improved rotational technique, was used as the method for radiotherapy. The eyes were shielded by a tungsten- or zinc-rod during irradiation. On the healthy-sided eye, which had received a total dose of 1000-1100 rads/6 weeks (max. 1460 rads/6 weeks), no impairment of vision was seen. On the ill-sided eye given a dose of more than 6000 rads/6 weeks, severe panophthalmopathy with corneal ulceration was observed within 1 year after irradiation. Serious deterioration of visual acuity alway occurred 1.5-2 years after on irradiation of the level of 4000 rads/6 weeks. At present the weakening of visual acuity is unlikely to occur after a dose of less than 3000 rads/6 weeks to the lens. From these results it is recommended that the total dose of the eye be reduced to less than 3000 rads/6 weeks. (author)

Molecular dynamics studies of the conformation of sorbitol

Science.gov (United States)

Lerbret, A.; Mason, P.E.; Venable, R.M.; Cesàro, A.; Saboungi, M.-L.; Pastor, R.W.; Brady, J.W.

2009-01-01

Molecular dynamics simulations of a 3 m aqueous solution of D-sorbitol (also called D-glucitol) have been performed at 300 K, as well as at two elevated temperatures to promote conformational transitions. In principle, sorbitol is more flexible than glucose since it does not contain a constraining ring. However, a conformational analysis revealed that the sorbitol chain remains extended in solution, in contrast to the bent conformation found experimentally in the crystalline form. While there are 243 staggered conformations of the backbone possible for this open-chain polyol, only a very limited number were found to be stable in the simulations. Although many conformers were briefly sampled, only eight were significantly populated in the simulation. The carbon backbones of all but two of these eight conformers were completely extended, unlike the bent crystal conformation. These extended conformers were stabilized by a quite persistent intramolecular hydrogen bond between the hydroxyl groups of carbon C-2 and C-4. The conformational populations were found to be in good agreement with the limited available NMR data except for the C-2–C-3 torsion (spanned by the O-2–O-4 hydrogen bond), where the NMR data supports a more bent structure. PMID:19744646

Is DNA a nonlinear dynamical system where solitary conformational ...

Indian Academy of Sciences (India)

Unknown

DNA is considered as a nonlinear dynamical system in which solitary conformational waves can be excited. The ... nonlinear differential equations and their soliton-like solu- .... structure and dynamics can be added till the most accurate.

Conformational analysis of oligosaccharides and polysaccharides using molecular dynamics simulations.

Science.gov (United States)

Frank, Martin

2015-01-01

Complex carbohydrates usually have a large number of rotatable bonds and consequently a large number of theoretically possible conformations can be generated (combinatorial explosion). The application of systematic search methods for conformational analysis of carbohydrates is therefore limited to disaccharides and trisaccharides in a routine analysis. An alternative approach is to use Monte-Carlo methods or (high-temperature) molecular dynamics (MD) simulations to explore the conformational space of complex carbohydrates. This chapter describes how to use MD simulation data to perform a conformational analysis (conformational maps, hydrogen bonds) of oligosaccharides and how to build realistic 3D structures of large polysaccharides using Conformational Analysis Tools (CAT).

Single-arc volumetric-modulated arc therapy (sVMAT) as adjuvant treatment for gastric cancer: Dosimetric comparisons with three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT)

International Nuclear Information System (INIS)

Wang, Xin; Li, Guangjun; Zhang, Yingjie; Bai, Sen; Xu, Feng; Wei, Yuquan; Gong, Youling

2013-01-01

To compare the dosimetric differences between the single-arc volumetric-modulated arc therapy (sVMAT), 3-dimensional conformal radiotherapy (3D-CRT), and intensity-modulated radiotherapy (IMRT) techniques in treatment planning for gastric cancer as adjuvant radiotherapy. Twelve patients were retrospectively analyzed. In each patient's case, the parameters were compared based on the dose-volume histogram (DVH) of the sVMAT, 3D-CRT, and IMRT plans, respectively. Three techniques showed similar target dose coverage. The maximum and mean doses of the target were significantly higher in the sVMAT plans than that in 3D-CRT plans and in the 3D-CRT/IMRT plans, respectively, but these differences were clinically acceptable. The IMRT and sVMAT plans successfully achieved better target dose conformity, reduced the V 20/30 , and mean dose of the left kidney, as well as the V 20/30 of the liver, compared with the 3D-CRT plans. And the sVMAT technique reduced the V 20 of the liver much significantly. Although the maximum dose of the spinal cord were much higher in the IMRT and sVMAT plans, respectively (mean 36.4 vs 39.5 and 40.6 Gy), these data were still under the constraints. Not much difference was found in the analysis of the parameters of the right kidney, intestine, and heart. The IMRT and sVMAT plans achieved similar dose distribution to the target, but superior to the 3D-CRT plans, in adjuvant radiotherapy for gastric cancer. The sVMAT technique improved the dose sparings of the left kidney and liver, compared with the 3D-CRT technique, but showed few dosimetric advantages over the IMRT technique. Studies are warranted to evaluate the clinical benefits of the VMAT treatment for patients with gastric cancer after surgery in the future

Dynamical interpretation of nonrelativistic conformal groups

International Nuclear Information System (INIS)

Andrzejewski, K.; Gonera, J.

2013-01-01

It is shown that N-Galilean conformal algebra with N odd and nontrivial central charge is the maximal symmetry algebra for higher derivative free theory both on classical and quantum levels. By maximal symmetry algebra the Lie algebra of the maximal group of space–time symmetry transformations is understood which preserves higher order free dynamics

Effect of Concurrent High-Dose Cisplatin Chemotherapy and Conformal Radiotherapy on Cervical Esophageal Cancer Survival

International Nuclear Information System (INIS)

Huang Shaohui; Lockwood, Gina; Brierley, James; Cummings, Bernard; Kim, John; Wong, Rebecca; Bayley, Andrew; Ringash, Jolie

2008-01-01

Purpose: To determine whether a change in treatment policy to conformal, elective nodal radiotherapy and concurrent high-dose cisplatin improved survival for cervical esophageal cancer patients. Methods and Materials: All cervical esophageal cancer patients treated between 1997 and 2005 were restaged (1983 American Joint Committee on Cancer criteria). Patients treated before 2001 (previous cohort [PC]) were compared with those treated from 2001 onward (recent cohort [RC]). The PC institutional chemoradiotherapy protocol was 54 Gy in 20 fractions within 4 weeks, with 5-fluorouracil (1,000 mg/m 2 ) on Days 1-4 and either mitomycin C (10 mg/m 2 ) or cisplatin (75 mg/m 2 ) on Day 1. The RC institutional chemoradiotherapy protocol was conformal radiotherapy, 70 Gy in 35 fractions within 7 weeks, to the primary tumor and elective nodes, with high-dose cisplatin (100 mg/m 2 ) on Days 1, 22, and 43. Results: The median follow-up was 3.1 years (PC, 8.1 and RC, 2.3). Of 71 patients (25 women and 46 men), 21 of 29 in the PC and 29 of 42 in the RC were treated curatively (curative subgroup, n = 50). Between the two groups, no differences in overall survival or locoregional relapse-free survival were seen. The overall survival rate at 2 and 5 years was 35% (range, 24-47%) and 21% (range, 12-32%) in the whole group and 46% (range 32-60%) and 28% (range, 15-42%) in the curative group, respectively. In the curative group, no statistically significant prognostic factors were found. Trends toward better locoregional relapse-free survival were seen in women (2-year rate, 73% vs. for men, 36%; p = 0.08) and in patients aged >64 years (2-year rate, 68% vs. age ≤64 years, 34%; p = 0.10). Conclusion: No survival improvement could be demonstrated after changing the treatment policy to high-dose cisplatin-based, conventionally fractionated conformal chemoradiotherapy. Female gender and older age might predict for better outcomes

Hypofractionated three-dimensional conformal radiotherapy for medically inoperable early stage

Energy Technology Data Exchange (ETDEWEB)

Lee, Joo Ho; Wu, Hong Gyun; KIm, Hak Jae; Park, Charn Il; Lee, Se Hoon; Kim, Dong Wan; Heo, Dae Seong [Seoul National University College of Medicine, Seou (Korea, Republic of)

2013-01-15

The purpose of this study was to assess the clinical outcomes of hypofractionated radiotherapy (HFRT) with three-dimensional conformal technique for medically inoperable patients with early stage non-small-cell lung cancer (NSCLC) and to evaluate prognostic factors. We performed a retrospective review of 26 patients who underwent HFRT for early stage NSCLC between September 2005 and August 2011. Only clinical stage T1-3N0 was included. The median RT dose was 70 Gy (range, 60 to 72 Gy) and the median biologically equivalent dose (BED) was 94.5 Gy (range, 78.0 to 100.8 Gy). In 84.6% of patients, 4 Gy per fraction was used. Neoadjuvant chemotherapy with paclitaxel and cisplatin was given to 2 of 26 patients. The median follow-up time for surviving patients was 21 months (range, 13 to 49 months). The overall response rate was 53.9%, and the initial local control rate was 100%. The median survival duration was 27.8 months. Rates of 2-year overall survival, progression-free survival (PFS), local control (LC), and locoregional-free survival (LRFS) were 54.3%, 61.1%, 74.6%, and 61.9%, respectively. Multivariate analysis showed that BED (>90 vs. {<=}90 Gy) was an independent prognostic factor influencing PFS, LC, and LRFS. Severe toxicities over grade 3 were not observed. Radical HFRT can yield satisfactory disease control with acceptable rates of toxicities in medically inoperable patients with early stage NSCLC. HFRT is a viable alternative for clinics and patients ineligible for stereotactic ablative radiotherapy. BED over 90 Gy and 4 Gy per fraction might be appropriate for HFRT.

Interactions Controlling the Slow Dynamic Conformational Motions of Ubiquitin

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Soichiro Kitazawa

2017-08-01

Full Text Available Rational mutation of proteins based on their structural and dynamic characteristics is a useful strategy for amplifying specific fluctuations in proteins. Here, we show the effects of mutation on the conformational fluctuations and thermodynamic stability of ubiquitin. In particular, we focus on the salt bridge between K11 and E34 and the hydrogen bond between I36 and Q41, which are predicted to control the fluctuation between the basic folded state, N1, and the alternatively folded state, N2, of the protein, using high-pressure NMR spectroscopy. The E34A mutation, which disrupts the salt bridge, did not alter picosecond–to–nanosecond, microsecond–to–millisecond dynamic motions, and stability of the protein, while the Q41N mutation, which destabilizes the hydrogen bond, specifically amplified the N1–N2 conformational fluctuation and decreased stability. Based on the observed thermodynamic stabilities of the various conformational states, we showed that in the Q41N mutant, the N1 state is more significantly destabilized than the N2 state, resulting in an increase in the relative population of N2. Identifying the interactions controlling specific motions of a protein will facilitate molecular design to achieve functional dynamics beyond native state dynamics.

Conformational and functional analysis of molecular dynamics trajectories by Self-Organising Maps

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Stella Fabio

2011-05-01

Full Text Available Abstract Background Molecular dynamics (MD simulations are powerful tools to investigate the conformational dynamics of proteins that is often a critical element of their function. Identification of functionally relevant conformations is generally done clustering the large ensemble of structures that are generated. Recently, Self-Organising Maps (SOMs were reported performing more accurately and providing more consistent results than traditional clustering algorithms in various data mining problems. We present a novel strategy to analyse and compare conformational ensembles of protein domains using a two-level approach that combines SOMs and hierarchical clustering. Results The conformational dynamics of the α-spectrin SH3 protein domain and six single mutants were analysed by MD simulations. The Cα's Cartesian coordinates of conformations sampled in the essential space were used as input data vectors for SOM training, then complete linkage clustering was performed on the SOM prototype vectors. A specific protocol to optimize a SOM for structural ensembles was proposed: the optimal SOM was selected by means of a Taguchi experimental design plan applied to different data sets, and the optimal sampling rate of the MD trajectory was selected. The proposed two-level approach was applied to single trajectories of the SH3 domain independently as well as to groups of them at the same time. The results demonstrated the potential of this approach in the analysis of large ensembles of molecular structures: the possibility of producing a topological mapping of the conformational space in a simple 2D visualisation, as well as of effectively highlighting differences in the conformational dynamics directly related to biological functions. Conclusions The use of a two-level approach combining SOMs and hierarchical clustering for conformational analysis of structural ensembles of proteins was proposed. It can easily be extended to other study cases and to

Conformational and functional analysis of molecular dynamics trajectories by Self-Organising Maps

Science.gov (United States)

2011-01-01

Background Molecular dynamics (MD) simulations are powerful tools to investigate the conformational dynamics of proteins that is often a critical element of their function. Identification of functionally relevant conformations is generally done clustering the large ensemble of structures that are generated. Recently, Self-Organising Maps (SOMs) were reported performing more accurately and providing more consistent results than traditional clustering algorithms in various data mining problems. We present a novel strategy to analyse and compare conformational ensembles of protein domains using a two-level approach that combines SOMs and hierarchical clustering. Results The conformational dynamics of the α-spectrin SH3 protein domain and six single mutants were analysed by MD simulations. The Cα's Cartesian coordinates of conformations sampled in the essential space were used as input data vectors for SOM training, then complete linkage clustering was performed on the SOM prototype vectors. A specific protocol to optimize a SOM for structural ensembles was proposed: the optimal SOM was selected by means of a Taguchi experimental design plan applied to different data sets, and the optimal sampling rate of the MD trajectory was selected. The proposed two-level approach was applied to single trajectories of the SH3 domain independently as well as to groups of them at the same time. The results demonstrated the potential of this approach in the analysis of large ensembles of molecular structures: the possibility of producing a topological mapping of the conformational space in a simple 2D visualisation, as well as of effectively highlighting differences in the conformational dynamics directly related to biological functions. Conclusions The use of a two-level approach combining SOMs and hierarchical clustering for conformational analysis of structural ensembles of proteins was proposed. It can easily be extended to other study cases and to conformational ensembles from

A comparison of conformal and intensity-modulated techniques for oesophageal radiotherapy

International Nuclear Information System (INIS)

Nutting, Christopher M.; Bedford, James L.; Cosgrove, Vivian P.; Tait, Diana M.; Dearnaley, David P.; Webb, Steve

2001-01-01

Background and purpose: To investigate the potential of intensity-modulated radiotherapy (IMRT) to reduce lung irradiation in the treatment of oesophageal carcinoma with radical radiotherapy. Materials and methods: A treatment planning study was performed to compare two-phase conformal radiotherapy (CFRT) with IMRT in five patients. The CFRT plans consisted of anterior, posterior and bilateral posterior oblique fields, while the IMRT plans consisted of either nine equispaced fields (9F), or four fields (4F) with orientations equal to the CFRT plans. IMRT plans with seven, five or three equispaced fields were also investigated in one patient. Treatment plans were compared using dose-volume histograms and normal tissue complication probabilities. Results: The 9F IMRT plan was unable to improve on the homogeneity of dose to the planning target volume (PTV), compared with the CFRT plan (dose range, 16.9±4.5 (1 SD) vs. 12.4±3.9%; P=0.06). Similarly, the 9F IMRT plan was unable to reduce the mean lung dose (11.7±3.2 vs. 11.0±2.9 Gy; P=0.2). Similar results were obtained for seven, five and three equispaced fields in the single patient studied. The 4F IMRT plan provided comparable PTV dose homogeneity with the CFRT plan (11.8±3.3 vs. 12.4±3.9%; P=0.6), with reduced mean lung dose (9.5±2.3 vs 11.0±2.9 Gy; P=0.001). Conclusions: IMRT using nine equispaced fields provided no improvement over CFRT. This was because the larger number of fields in the IMRT plan distributed a low dose over the entire lung. In contrast, IMRT using four fields equal to the CFRT fields offered an improvement in lung sparing. Thus, IMRT with a few carefully chosen field directions may lead to a modest reduction in pneumonitis, or allow tumour dose escalation within the currently accepted lung toxicity

Radiological response and dosimetry in physical phantom of head and neck for 3D conformational radiotherapy

International Nuclear Information System (INIS)

Thompson, Larissa

2013-01-01

Phantoms are tools for simulation of organs and tissues of the human body in radiology and radiotherapy. This thesis describes the development, validation and, most importantly, the use of a physical head and neck phantom in radiology and radiotherapy, with the purpose of evaluating dose distribution using Gafchromic EBT2 film in 15 MV 3D conformal radiotherapy. The work was divided in two stages, (1) development of new equivalent tissues and improvement of the physical phantom, and (2) use of the physical phantom in experimental dosimetry studies. In phase (1) parameters such as mass density, chemical composition of tissues, anatomical and biometric measurements were considered, as well as aspects of imaging by computed tomography (CT) and radiological response representation in Hounsfield Units (HU), which were compared with human data. Radiological experiments of in-phantom simulated brain pathologies were also conducted. All those results matched human-sourced data, therefore the physical phantom is a suitable simulator that may be used to enhance radiological protocols and education in medical imaging. The main objective in phase (2) was to evaluate the spatial dose distribution in a brain tumor simulator inserted inside the head and neck phantom developed by the Ionizing Radiation Research Group (NRI), exposed to 15 MV 3D conformal radiotherapy, for internal dose assessment. Radiation planning was based on CT images of the physical phantom with a brain tumor simulator made with equivalent material. The treatment planning system (TPS), CAT3D software, used CT images and prescribed a dose of 200 cGy, distributed in three fields of radiation, in a T-shaped pattern. The TPS covered the planning treatment volume (PTV) with 97% of the prescribed dose. A solid water phantom and radiochromic Gafchromic EBT2 film were used for calibration procedures, generating a dose response curve as a function of optical density (OD). After calibration and irradiation, the film

Selection of the optimal radiotherapy technique for locally advanced hepatocellular carcinoma

International Nuclear Information System (INIS)

Lee, Ik-Jae; Seong, Jinsil; Koom, Woong-Sub; Kim, Yong-Bae; Jeon, Byeong-Chul; Kim, Joo-Ho; Han, Kwang-Hyub

2011-01-01

Various techniques are available for radiotherapy of hepatocellular carcinoma, including three-dimensional conformal radiotherapy, linac-based intensity-modulated radiotherapy and helical tomotherapy. The purpose of this study was to determine the optimal radiotherapy technique for hepatocellular carcinoma. Between 2006 and 2007, 12 patients underwent helical tomotherapy for locally advanced hepatocellular carcinoma. Helical tomotherapy computerized radiotherapy planning was compared with the best computerized radiotherapy planning for three-dimensional conformal radiotherapy and linac-based intensity-modulated radiotherapy for the delivery of 60 Gy in 30 fractions. Tumor coverage was assessed by conformity index, radical dose homogeneity index and moderated dose homogeneity index. Computerized radiotherapy planning was also compared according to the tumor location. Tumor coverage was shown to be significantly superior with helical tomotherapy as assessed by conformity index and moderated dose homogeneity index (P=0.002 and 0.03, respectively). Helical tomotherapy showed significantly lower irradiated liver volume at 40, 50 and 60 Gy (V40, V50 and V60, P=0.04, 0.03 and 0.01, respectively). On the contrary, the dose-volume of three-dimensional conformal radiotherapy at V20 was significantly smaller than those of linac-based intensity-modulated radiotherapy and helical tomotherapy in the remaining liver (P=0.03). Linac-based intensity-modulated radiotherapy showed better sparing of the stomach compared with helical tomotherapy in the case of separated lesions in both lobes (12.3 vs. 24.6 Gy). Helical tomotherapy showed the high dose-volume exposure to the left kidney due to helical delivery in the right lobe lesion. Helical tomotherapy achieved the best tumor coverage of the remaining normal liver. However, helical tomotherapy showed much exposure to the remaining liver at the lower dose region and left kidney. (author)

3D-Conformal Versus Intensity-Modulated Postoperative Radiotherapy of Vaginal Vault: A Dosimetric Comparison

International Nuclear Information System (INIS)

Cilla, Savino; Macchia, Gabriella; Digesu, Cinzia; Deodato, Francesco; Romanella, Michele; Ferrandina, Gabriella; Padula, Gilbert; Picardi, Vincenzo; Scambia, Giovanni; Piermattei, Angelo; Morganti, Alessio Giuseppe

2010-01-01

We evaluated a step-and-shoot IMRT plan in the postoperative irradiation of the vaginal vault compared with equispaced beam arrangements (3-5) 3D-radiotherapy (RT) optimized plans. Twelve patients were included in this analysis. Four plans for each patient were compared in terms of dose-volume histograms, homogeneity index (HI), and conformity index (CI): (1) 3 equispaced beam arrangement 3D-RT; (2) 4 equispaced beam arrangement 3D-RT; (3) 5 equispaced beam arrangement 3D-RT; (4) step-and-shoot IMRT technique. CI showed a good discrimination between the four plans. The mean scores of CI were 0.58 (range: 0.38-0.67) for the 3F-CRT plan, 0.58 (range: 0.41-0.66) for 4F-CRT, 0.62 (range: 0.43-0.68) for 5F-CRT and 0.69 (range: 0.58-0.78) for the IMRT plan. A significant improvement of the conformity was reached by the IMRT plan (p mean , V90%, V95%, V100% was recorded for rectal and bladder irradiation with the IMRT plan. Surprisingly, IMRT supplied a significant dose reduction also for rectum and bladder V30% and V50%. A significant dosimetric advantage of IMRT over 3D-RT in the adjuvant treatment of vaginal vault alone in terms of treatment conformity and rectum and bladder sparing is shown.

A computer-controlled high resolution micro-multi-leaf collimator for stereotactic conformal radio-therapy

International Nuclear Information System (INIS)

Schlegel, Wolfgang; Pastyr, Otto; Kubesch, Rudolf; Diemer, Torsten; Kuester, Gunnilla; Rhein, Bernhard; Hoever, Karl-Heinz

1997-01-01

Purpose/Objective In stereotactic conformal radiotherapy of irregularly shaped lesions, either multi-isocentric convergent beam treatment techniques with circular collimators or irregular shaped beams are being used. While the treatment technique with multiple isocenters has the disadvantage of producing inhomogeneous dose distributions, the use of irregular shaped fields is not yet satisfying from a technical point of view: Cerrobend blocking or the use of static micro MLCs need a long preparation time and only allow static treatment techniques, MLC collimators which are commercially available in connection with modern LINACs have leaf-thickness of at least 1 cm which is too coarse for stereotactic radiotherapy of lesions in the brain and head and neck area. For this reason, we developed a computer controlled micro-MLC with technical specifications matched to the needs of stereotactic radiotherapy and radiosurgery. Materials and Methods The mechanical specifications of the computer controlled micro-MLC were derived from our experience with stereotactic treatment techniques, from the requirement that the MLC has to be attachable as an external device to the accessory holders of standard LINACs, including cost considerations, dosimetric measurements as well as Monte Carlo calculations. The Micro-MLC is controlled by an electronic equipment consisting of a standard PC under Windows 95, an interface board, 14 Micro-controller boards, a verification system and 80 driving units equipped with DC motors and potentiometers. The control program has calibrating, operating, visualizing and test options. Irregular field data are transferred from the treatment planning computer to the control PC and distributed to the micro-controllers, which in parallel are driving three leaves each. Beside the special control unit, we are currently investigating whether the electronics of commercially available integrated large field MLCs can also be used for operating the Micro-MLC. Results

Parotid gland-sparing 3-dimensional conformal radiotherapy results in less severe dry mouth in nasopharyngeal cancer patients: A dosimetric and clinical comparison with conventional radiotherapy

International Nuclear Information System (INIS)

Jen, Y.-M.; Shih Rompin; Lin, Y.-S.; Su, W.-F.; Ku, C.-H.; Chang, C.-S.; Shueng, P.-W.; Hwang, J.-M.; Liu, D.-W.; Chao, H.-L.; Lin, H.-Y.; Chang, L.-P.; Shum, W.-Y.; Lin, C.-S.

2005-01-01

Background and purpose: This study examined the efficacy of parotid gland sparing of three-dimensional conformal radiotherapy (3DCRT) compared with conventional radiotherapy for NPC patients. Both the dose given to the parotids and clinical assessment of dry mouth were conducted. Materials and methods: Dry mouth was assessed for 108 patients treated with conventional technique and 72 treated with 3DCRT. Dose analysis was performed in 48 patients of the 3DCRT group. A dose of 70 Gy was given to the midplane in conventional radiotherapy and to 90% isodose volume in 3DCRT. Prognostic factors affecting the severity of dry mouth were analyzed using Generalized Estimating Equation (GEE). Results: In the 3DCRT group about 50% of the patients' parotid glands received less than 25 Gy. Parallel analysis of dry mouth shows a significant decrease in the incidence of severe xerostomia after 3DCRT. The proportion of patients without dry mouth was also significantly higher in the 3DCRT group than the conventional group at 1-3 years after completion of radiotherapy. Although 3DCRT delivered a higher dose to the tumor, it spared the parotid gland significantly better than the conventional treatment. Late toxicities were mostly similar between the 2 groups while local control in T4 patients and survival were improved for 3DCRT. Conclusion: Dosimetrically and clinically 3DCRT is better than conventional technique regarding parotid gland protection

Single Molecule Cluster Analysis Identifies Signature Dynamic Conformations along the Splicing Pathway

Science.gov (United States)

Blanco, Mario R.; Martin, Joshua S.; Kahlscheuer, Matthew L.; Krishnan, Ramya; Abelson, John; Laederach, Alain; Walter, Nils G.

2016-01-01

The spliceosome is the dynamic RNA-protein machine responsible for faithfully splicing introns from precursor messenger RNAs (pre-mRNAs). Many of the dynamic processes required for the proper assembly, catalytic activation, and disassembly of the spliceosome as it acts on its pre-mRNA substrate remain poorly understood, a challenge that persists for many biomolecular machines. Here, we developed a fluorescence-based Single Molecule Cluster Analysis (SiMCAn) tool to dissect the manifold conformational dynamics of a pre-mRNA through the splicing cycle. By clustering common dynamic behaviors derived from selectively blocked splicing reactions, SiMCAn was able to identify signature conformations and dynamic behaviors of multiple ATP-dependent intermediates. In addition, it identified a conformation adopted late in splicing by a 3′ splice site mutant, invoking a mechanism for substrate proofreading. SiMCAn presents a novel framework for interpreting complex single molecule behaviors that should prove widely useful for the comprehensive analysis of a plethora of dynamic cellular machines. PMID:26414013

Conformational Dynamics of apo-GlnBP Revealed by Experimental and Computational Analysis

KAUST Repository

Feng, Yitao

2016-10-13

The glutamine binding protein (GlnBP) binds l-glutamine and cooperates with its cognate transporters during glutamine uptake. Crystal structure analysis has revealed an open and a closed conformation for apo- and holo-GlnBP, respectively. However, the detailed conformational dynamics have remained unclear. Herein, we combined NMR spectroscopy, MD simulations, and single-molecule FRET techniques to decipher the conformational dynamics of apo-GlnBP. The NMR residual dipolar couplings of apo-GlnBP were in good agreement with a MD-derived structure ensemble consisting of four metastable states. The open and closed conformations are the two major states. This four-state model was further validated by smFRET experiments and suggests the conformational selection mechanism in ligand recognition of GlnBP. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Conformational Dynamics of apo-GlnBP Revealed by Experimental and Computational Analysis

KAUST Repository

Feng, Yitao; Zhang, Lu; Wu, Shaowen; Liu, Zhijun; Gao, Xin; Zhang, Xu; Liu, Maili; Liu, Jianwei; Huang, Xuhui; Wang, Wenning

2016-01-01

The glutamine binding protein (GlnBP) binds l-glutamine and cooperates with its cognate transporters during glutamine uptake. Crystal structure analysis has revealed an open and a closed conformation for apo- and holo-GlnBP, respectively. However, the detailed conformational dynamics have remained unclear. Herein, we combined NMR spectroscopy, MD simulations, and single-molecule FRET techniques to decipher the conformational dynamics of apo-GlnBP. The NMR residual dipolar couplings of apo-GlnBP were in good agreement with a MD-derived structure ensemble consisting of four metastable states. The open and closed conformations are the two major states. This four-state model was further validated by smFRET experiments and suggests the conformational selection mechanism in ligand recognition of GlnBP. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Association of anorectal dose-volume histograms and impaired fecal continence after 3D conformal radiotherapy for carcinoma of the prostate

International Nuclear Information System (INIS)

Vordermark, Dirk; Schwab, Michael; Ness-Dourdoumas, Rhea; Sailer, Marco; Flentje, Michael; Koelbl, Oliver

2003-01-01

Purpose: The late toxicity of fecal incontinence after pelvic radiotherapy is now frequently recognized but the etiology poorly understood. We therefore investigated associations between dose-volume histogram (DVH) parameters of the rectum and the anal canal with fecal continence as measured by an established 10-item questionnaire. Methods and materials: Forty-four patients treated for carcinoma of the prostate with 58-72 Gy of 3D conformal radiotherapy between 1995 and 1999 who completed the questionnaire formed the study population. Total continence scores of treated patients obtained 1.5 years (median) after radiotherapy were compared to a control group of 30 patients before radiotherapy. Median, mean, minimum and maximum doses as well as the volume (% and ml) treated to 40, 50, 60 and 70 Gy were determined separately for anal canal and rectum. DVH parameters were correlated with total continence score (Spearman rank test) and patients grouped according to observed continence were compared regarding DVH values (Mann-Whitney U-test). Results: Median fecal continence scores were significantly worse in the irradiated than in the control group (31 vs. 35 of a maximum 36 points). In treated patients, 59%/27%/14% were classified as fully continent, slightly incontinent and severely incontinent. Continence was similar in the 58-to-62-Gy, 66-Gy and 68-to-72-Gy dose groups. No DVH parameter was significantly correlated with total continence score, but severely incontinent patients had a significantly higher minimum dose to the anal canal than fully continent/slightly incontinent, accompanied by portals extending significantly further inferiorly with respect to the ischial tuberosities. Conclusions: Excluding the inferior part of the anal canal from the treated volume in 3D conformal therapy for carcinoma of the prostate appears to be a promising strategy to prevent radiation-induced fecal incontinence

Propensity Score-based Comparison of Long-term Outcomes With 3-Dimensional Conformal Radiotherapy vs Intensity-Modulated Radiotherapy for Esophageal Cancer

International Nuclear Information System (INIS)

Lin, Steven H.; Wang Lu; Myles, Bevan; Thall, Peter F.; Hofstetter, Wayne L.; Swisher, Stephen G.; Ajani, Jaffer A.; Cox, James D.; Komaki, Ritsuko; Liao Zhongxing

2012-01-01

Purpose: Although 3-dimensional conformal radiotherapy (3D-CRT) is the worldwide standard for the treatment of esophageal cancer, intensity modulated radiotherapy (IMRT) improves dose conformality and reduces the radiation exposure to normal tissues. We hypothesized that the dosimetric advantages of IMRT should translate to substantive benefits in clinical outcomes compared with 3D-CRT. Methods and Materials: An analysis was performed of 676 nonrandomized patients (3D-CRT, n=413; IMRT, n=263) with stage Ib-IVa (American Joint Committee on Cancer 2002) esophageal cancers treated with chemoradiotherapy at a single institution from 1998-2008. An inverse probability of treatment weighting and inclusion of propensity score (treatment probability) as a covariate were used to compare overall survival time, interval to local failure, and interval to distant metastasis, while accounting for the effects of other clinically relevant covariates. The propensity scores were estimated using logistic regression analysis. Results: A fitted multivariate inverse probability weighted-adjusted Cox model showed that the overall survival time was significantly associated with several well-known prognostic factors, along with the treatment modality (IMRT vs 3D-CRT, hazard ratio 0.72, P<.001). Compared with IMRT, 3D-CRT patients had a significantly greater risk of dying (72.6% vs 52.9%, inverse probability of treatment weighting, log-rank test, P<.0001) and of locoregional recurrence (P=.0038). No difference was seen in cancer-specific mortality (Gray's test, P=.86) or distant metastasis (P=.99) between the 2 groups. An increased cumulative incidence of cardiac death was seen in the 3D-CRT group (P=.049), but most deaths were undocumented (5-year estimate, 11.7% in 3D-CRT vs 5.4% in IMRT group, Gray's test, P=.0029). Conclusions: Overall survival, locoregional control, and noncancer-related death were significantly better after IMRT than after 3D-CRT. Although these results need

Applications of three-dimensional image correlation in conformal radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Van Herk, M; Gilhuijs, K; Kwa, S; Lebesque, J; Muller, S; De Munck, J; Touw, A [Nederlands Kanker Inst. ` Antoni van Leeuwenhoekhuis` , Amsterdam (Netherlands); Kooy, H [Harvard Medical School, Boston, MA (United States)

1995-12-01

The development of techniques for the registration of CT, MRI and SPECT creates new possibilities for improved target volume definition and quantitative image analysis. The discussed technique is based on chamfer matching and is suitable for automatic 3-D matching of CT with CT, CT with MRI, CT with SPECT and MRI with SPECT. By integrating CT with MRI, the diagnostic qualities of MRI are combined with the geometric accuracy of the planning CT. Significant differences in the delineation of the target volume for brain, head and neck and prostate tumors were demonstrated when using integrated CT and MRI compared with using CT alone. In addition, integration of the planning CT with pre-operative scans improves knowledge of possible tumor extents. By first matching scans based on the bony anatomy and subsequently matching on an organ of study, relative motion of the organ is quantified accurately. In a study with 42 CT scans of 11 patients, magnitude and causes of prostate motion were analysed. The most important motion of the prostate is a forward-backward rotation around a point near the apex caused by rectal volume difference. Significant correlations were also found between motion of the legs and the prostate. By integrating functional images made before and after radiotherapy with the planning CT, the relation between local change of lung function and delivered dose has been quantified accurately. The technique of chamfer matching is a convenient and more accurate alternative for the use of external markers in a CT/SPECT lung damage study. Also, damage visible in diagnostic scans can be related to radiation dose, thereby improving follow-up diagnostics. It can be concluded that 3-D image integration plays an important role in assessing and improving the accuracy of radiotherapy and is therefore indispensable for conformal therapy. However, user-friendly implementation of these techniques remains to be done to facilitate clinical application on a large scale.

Applications of three-dimensional image correlation in conformal radiotherapy

International Nuclear Information System (INIS)

Van Herk, M.; Gilhuijs, K.; Kwa, S.; Lebesque, J.; Muller, S.; De Munck, J.; Touw, A.; Kooy, H.

1995-01-01

The development of techniques for the registration of CT, MRI and SPECT creates new possibilities for improved target volume definition and quantitative image analysis. The discussed technique is based on chamfer matching and is suitable for automatic 3-D matching of CT with CT, CT with MRI, CT with SPECT and MRI with SPECT. By integrating CT with MRI, the diagnostic qualities of MRI are combined with the geometric accuracy of the planning CT. Significant differences in the delineation of the target volume for brain, head and neck and prostate tumors have been demonstrated when using integrated CT and MRI compared with using CT alone. In addition, integration of the planning CT with pre-operative scans improves knowledge of possible tumor extents. By first matching scans based on the bony anatomy and subsequently matching on an organ of study, relative motion of the organ is quantified accurately. In a study with 42 CT scans of 11 patients, magnitude and causes of prostate motion have been analysed. The most important motion of the prostate is a forward-backward rotation around a point near the apex caused by rectal volume difference. Significant correlations were also found between motion of the legs and the prostate. By integrating functional images made before and after radiotherapy with the planning CT, the relation between local change of lung function and delivered dose has been quantified accurately. The technique of chamfer matching is a convenient and more accurate alternative for the use of external markers in a CT/SPECT lung damage study. Also, damage visible in diagnostic scans can be related to radiation dose, thereby improving follow-up diagnostics. It can be concluded that 3-D image integration plays an important role in assessing and improving the accuracy of radiotherapy and is therefore indispensable for conformal therapy. However, user-friendly implementation of these techniques remains to be done to facilitate clinical application on a large

Visual Outcome and Tumor Control After Conformal Radiotherapy for Patients With Optic Nerve Sheath Meningioma

International Nuclear Information System (INIS)

Arvold, Nils D.; Lessell, Simmons; Bussiere, Marc; Beaudette, Kevin; Rizzo, Joseph F.; Loeffler, Jay S.; Shih, Helen A.

2009-01-01

Purpose: Optic nerve sheath meningioma (ONSM) is a rare tumor that almost uniformly leads to visual dysfunction and even blindness without intervention. Because surgical extirpation carries a high risk of postoperative blindness, vision-sparing treatment strategies are desirable. Methods and Materials: We retrospectively reviewed the outcomes of 25 patients (25 optic nerves) with ONSM, treated at a single institution with conformal fractionated radiotherapy by either stereotactic photon or proton radiation. Primary endpoints were local control and visual acuity. Results: The patients presented with symptoms of visual loss (21) or orbital pain (3) or were incidentally diagnosed by imaging (3). The mean age was 44 years, and 64% were female patients. The indication for treatment was the development or progression of symptoms. Of the patients, 13 were treated with photons, 9 were treated with protons, and 3 received a combination of photons and protons. The median dose delivered was 50.4 gray equivalents (range, 45-59.4 gray equivalents). Median follow-up after radiotherapy was 30 months (range, 3-168 months), with 3 patients lost to follow-up. At most recent follow-up, 21 of 22 patients (95%) had improved (14) or stable (7) visual acuity. One patient had worsened visual acuity after initial postirradiation improvement. Of the 22 patients, 20 (95%) had no radiographic progression. Three patients had evidence of asymptomatic, limited retinopathy on ophthalmologic examination, and one had recurrent ONSM 11 years after treatment. Conclusions: Highly conformal, fractionated radiation therapy for symptomatic primary ONSM provides tumor control and improvement in visual function in most cases, with minimal treatment-induced morbidity. Longer follow-up is needed to assess the durability of tumor control and treatment-related late effects.

Late xerostomia after intensity-modulated conformational radiotherapy of upper aero-digestive tract cancers: study 2004-03 by the head and neck oncology and radiotherapy Group (Gortec)

International Nuclear Information System (INIS)

Toledano, I.; Lapeyre, M.; Graff, P.; Serre, C.; Bensadoun, R.J.; Bensadoun, R.J.; Ortholan, C.; Calais, G.; Alfonsi, M.; Giraud, P.; Racadot, S.

2010-01-01

The authors report a retrospective assessment of late xerostomia according to the RTOG (Radiation Therapy Oncology Group) classification of the European Organization for Research and Treatment of Cancer (EORTC) among patients treated by intensity-modulated conformational radiotherapy (IMRT) and suffering from upper aero-digestive tract carcinomas of different stages. Some of these patients have bee operated, and some have been treated by chemotherapy. It appears that the IMRT results in a reduction of late xerostomia, and even in an absence of salivary toxicity. Short communication

Film dosimetry in conformal radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Danciu, C; Proimos, B S [Patras Univ. (Greece). Dept. of Medical Physics

1995-12-01

Dosimetry, through a film sandwiched in a transverse cross-section of a solid phantom, is a method of choice in Conformal Radiotherapy because: (a) the blackness (density) of the film at each point offers a measure of the total dose received at that point, and (b) the film is easily calibrated by exposing a film strip in the same cross-section, through a stationary field. The film must therefore have the following properties: (a) it must be slow, in order not to be overexposed, even at a therapeutic dose of 200 cGy, and (b) the response of the film (density versus dose curve) must be independent of the photon energy spectrum. A few slow films were compared. It was found that the Kodak X-Omat V for therapy verification was the best choice. To investigate whether the film response was independent of the photon energy, response curves for six depths, starting from the depth of maximum dose to the depth of 25 cm, in solid phantom were derived. The vertical beam was perpendicular to the anterior surface of the phantom, which was at the distance of 100 cm from the source and the field was 15x15 cm at that distance. This procedure was repeated for photon beams emitted by a Cobalt-60 unit, two 6 MV and 15 MV Linear Accelerators, as well as a 45 MV Betatron. For each of those four different beams the film response was the same for all six depths. The results, as shown in the diagrams, are very satisfactory. The response curve under a geometry similar to that actually applied, when the film is irradiated in a transverse cross-section of the phantom, was derived. The horizontal beam was almost parallel (angle of 85) to the plane of the film. The same was repeated with the central ray parallel to the film (angle 90) and at a distance of 1.5 cm from the horizontal film. The field size was again 15x15 at the lateral entrance surface of the beam. The response curves remained the same, as when the beam was perpendicular to the films.

The evolution of rectal and urinary toxicity and immune response in prostate cancer patients treated with two three-dimensional conformal radiotherapy techniques

Czech Academy of Sciences Publication Activity Database

Vránová, J.; Vinakurau, S.; Richter, J.; Starec, M.; Fišerová, Anna; Rosina, J.

2011-01-01

Roč. 2, č. 6 (2011), s. 1-13 ISSN 1748-717X R&D Projects: GA AV ČR IAA500200620 Institutional research plan: CEZ:AV0Z50200510 Keywords : 3-dimensional conformal radiotherapy (3DCRT) * gastrointestinal and genitourinary toxicity * prostate cancer Subject RIV: EC - Immunology Impact factor: 2.321, year: 2011

Conformal radiotherapy of locally advanced bile duct carcinoma; Radiotherapie conformationnelle des cholangiocarcinomes de la voie biliaire principale localement evolues

Energy Technology Data Exchange (ETDEWEB)

Bouras, N.; Caudry, M.; Bonnel, C.; Trouette, R.; Demeaux, H.; Maire, J.P. [Centre Hospitalier Universitaire, Hopital Saint-Andre, Service de Radiotherapie, 33 - Bordeaux (France); Saric, J.; Rullier, E. [Centre Hospitalier Universitaire, Hopital Saint-Andre, Service de Chirurgie Viscerale et de Transplantation Hepatique, 33 - Bordeaux (France)

2002-02-01

Purpose. - Retrospective study of 23 patients treated with conformal radiotherapy for a locally advanced bile duct carcinoma. Patients and methods. - Eight cases were irradiated after a radical resection (RO), because they were N+; seven after microscopically incomplete resection (R1) ; seven were not resected (R2). A dose of 45 of 50 Gy was delivered, followed by a boost up to 60 Gy in R1 and R2 groups. Concomitant chemotherapy was given in 15 cases. Results.-Late toxicity included a stenosis of the duodenum, and one of the biliary anastomosis. Two patients died from cholangitis, the mechanism of which remains unclear. Five patients are in complete remission, six had a local relapse, four developed a peritoneal carcinosis, and six distant metastases. Actuarial survival rate is 75%, 28% and 7% at 1, 3 and 5 years, respectively (median: 16.5 months). Seven patients are still alive with a 4 to 70 months follow-up. Survival is similar in the 3 small subgroups. The poor local control among RON+ cases might be related to the absence of a boost to the 'tumor bed'. In R1 patients, relapses were mainly distant metastases, where'as local and peritoneal recurrences predominated in R2. Conclusion. - Conformal radio-chemotherapy delivering 60 Gy represents a valuable palliative approach in locally advanced biliary carcinoma. (authors)

Comparison of Toxicity Between Intensity-Modulated Radiotherapy and 3-Dimensional Conformal Radiotherapy for Locally Advanced Non-small-cell Lung Cancer.

Science.gov (United States)

Ling, Diane C; Hess, Clayton B; Chen, Allen M; Daly, Megan E

2016-01-01

The role of intensity-modulated radiotherapy (IMRT) in reducing treatment-related toxicity for locally advanced non-small-cell lung cancer (NSCLC) remains incompletely defined. We compared acute toxicity and oncologic outcomes in a large cohort of patients treated with IMRT or 3-dimensional conformal radiotherapy (3-DCRT), with or without elective nodal irradiation (ENI). A single-institution retrospective review was performed evaluating 145 consecutive patients with histologically confirmed stage III NSCLC treated with definitive chemoradiotherapy. Sixty-five (44.8%) were treated with 3-DCRT using ENI, 43 (30.0%) with 3-DCRT using involved-field radiotherapy (IFRT), and 37 (25.5%) with IMRT using IFRT. All patients received concurrent chemotherapy. Comparison of acute toxicities by treatment technique (IMRT vs. 3-DCRT) and extent of nodal irradiation (3-DCRT-IFRT vs. 3-DCRT-ENI) was performed for grade 2 or higher esophagitis or pneumonitis, number of acute hospitalizations, incidence of opioid requirement, percutaneous endoscopic gastrostomy utilization, and percentage weight loss during treatment. Local control and overall survival were analyzed by the Kaplan-Meier method. We identified no significant differences in any measures of acute toxicity by treatment technique or extent of nodal irradiation. There was a trend toward lower rates of grade 2 or higher pneumonitis among IMRT patients compared to 3-DCRT patients (5.4% vs. 23.0%; P = .065). Local control and overall survival were similar between cohorts. Acute and subacute toxicities were similar for patients treated with IMRT and with 3-DCRT with or without ENI, with a nonsignificant trend toward a reduction in pneumonitis with IMRT. Larger studies are needed to better define which patients will benefit from IMRT. Copyright © 2016 Elsevier Inc. All rights reserved.

Molecular modeling of the conformational dynamics of the cellular prion protein

Science.gov (United States)

Nguyen, Charles; Colling, Ian; Bartz, Jason; Soto, Patricia

2014-03-01

Prions are infectious agents responsible for transmissible spongiform encephalopathies (TSEs), a type of fatal neurodegenerative disease in mammals. Prions propagate biological information by conversion of the non-pathological version of the prion protein to the infectious conformation, PrPSc. A wealth of knowledge has shed light on the nature and mechanism of prion protein conversion. In spite of the significance of this problem, we are far from fully understanding the conformational dynamics of the cellular isoform. To remedy this situation we employ multiple biomolecular modeling techniques such as docking and molecular dynamics simulations to map the free energy landscape and determine what specific regions of the prion protein are most conductive to binding. The overall goal is to characterize the conformational dynamics of the cell form of the prion protein, PrPc, to gain insight into inhibition pathways against misfolding. NE EPSCoR FIRST Award to Patricia Soto.

Simultaneous integrated boost intensity-modulated radiotherapy versus 3-dimensional conformal radiotherapy in preoperative concurrent chemoradiotherapy for locally advanced rectal cancer

Energy Technology Data Exchange (ETDEWEB)

Bae, Bong Kyung; Kang, Min Kyul; Kim, Jae Chul [Dept. of Radiation Oncology, Kyungpook National University School of Medicine, Daegu (Korea, Republic of); Kim, Min Young; Choi, Gyu Seog; Kim, Jong Gwang; Kang, Byung Woog; Kim, Hye Jin; Park, Soo Yeun [Kyungpook National University Chilgok Hospital, Kyungpook National University School of Medicine, Daegu (Korea, Republic of)

2017-09-15

To evaluate the feasibility of simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) for preoperative concurrent chemoradiotherapy (PCRT) in locally advanced rectal cancer (LARC), by comparing with 3-dimensional conformal radiotherapy (3D-CRT). Patients who were treated with PCRT for LARC from 2015 January to 2016 December were retrospectively enrolled. Total doses of 45 Gy to 50.4 Gy with 3D-CRT or SIB-IMRT were administered concomitantly with 5-fluorouracil plus leucovorin or capecitabine. Surgery was performed 8 weeks after PCRT. Between PCRT and surgery, one cycle of additional chemotherapy was administered. Pathologic tumor responses were compared between SIB-IMRT and 3D-CRT groups. Acute gastrointestinal, genitourinary, hematologic, and skin toxicities were compared between the two groups based on the RTOG toxicity criteria. SIB-IMRT was used in 53 patients, and 3D-CRT in 41 patients. After PCRT, no significant differences were noted in tumor responses, pathologic complete response (9% vs. 7%; p = 1.000), pathologic tumor regression Grade 3 or higher (85% vs. 71%; p = 0.096), and R0 resection (87% vs. 85%; p = 0.843). Grade 2 genitourinary toxicities were significantly lesser in the SIB-IMRT group (8% vs. 24%; p = 0.023), but gastrointestinal toxicities were not different across the two groups. SIB-IMRT showed lower GU toxicity and similar tumor responses when compared with 3D-CRT in PCRT for LARC.

On the analysis and comparison of conformer-specific essential dynamics upon ligand binding to a protein

International Nuclear Information System (INIS)

Grosso, Marcos; Kalstein, Adrian; Parisi, Gustavo; Fernandez-Alberti, Sebastian; Roitberg, Adrian E.

2015-01-01

The native state of a protein consists of an equilibrium of conformational states on an energy landscape rather than existing as a single static state. The co-existence of conformers with different ligand-affinities in a dynamical equilibrium is the basis for the conformational selection model for ligand binding. In this context, the development of theoretical methods that allow us to analyze not only the structural changes but also changes in the fluctuation patterns between conformers will contribute to elucidate the differential properties acquired upon ligand binding. Molecular dynamics simulations can provide the required information to explore these features. Its use in combination with subsequent essential dynamics analysis allows separating large concerted conformational rearrangements from irrelevant fluctuations. We present a novel procedure to define the size and composition of essential dynamics subspaces associated with ligand-bound and ligand-free conformations. These definitions allow us to compare essential dynamics subspaces between different conformers. Our procedure attempts to emphasize the main similarities and differences between the different essential dynamics in an unbiased way. Essential dynamics subspaces associated to conformational transitions can also be analyzed. As a test case, we study the glutaminase interacting protein (GIP), composed of a single PDZ domain. Both GIP ligand-free state and glutaminase L peptide-bound states are analyzed. Our findings concerning the relative changes in the flexibility pattern upon binding are in good agreement with experimental Nuclear Magnetic Resonance data

On the analysis and comparison of conformer-specific essential dynamics upon ligand binding to a protein

Energy Technology Data Exchange (ETDEWEB)

Grosso, Marcos; Kalstein, Adrian; Parisi, Gustavo; Fernandez-Alberti, Sebastian, E-mail: sfalberti@gmail.com [Universidad Nacional de Quilmes, Roque Saenz Peña 352, B1876BXD Bernal (Argentina); Roitberg, Adrian E. [Departments of Physics and Chemistry, University of Florida, Gainesville, Florida 32611 (United States)

2015-06-28

The native state of a protein consists of an equilibrium of conformational states on an energy landscape rather than existing as a single static state. The co-existence of conformers with different ligand-affinities in a dynamical equilibrium is the basis for the conformational selection model for ligand binding. In this context, the development of theoretical methods that allow us to analyze not only the structural changes but also changes in the fluctuation patterns between conformers will contribute to elucidate the differential properties acquired upon ligand binding. Molecular dynamics simulations can provide the required information to explore these features. Its use in combination with subsequent essential dynamics analysis allows separating large concerted conformational rearrangements from irrelevant fluctuations. We present a novel procedure to define the size and composition of essential dynamics subspaces associated with ligand-bound and ligand-free conformations. These definitions allow us to compare essential dynamics subspaces between different conformers. Our procedure attempts to emphasize the main similarities and differences between the different essential dynamics in an unbiased way. Essential dynamics subspaces associated to conformational transitions can also be analyzed. As a test case, we study the glutaminase interacting protein (GIP), composed of a single PDZ domain. Both GIP ligand-free state and glutaminase L peptide-bound states are analyzed. Our findings concerning the relative changes in the flexibility pattern upon binding are in good agreement with experimental Nuclear Magnetic Resonance data.

Anal wall sparing effect of an endorectal balloon in 3D conformal and intensity-modulated prostate radiotherapy.

Science.gov (United States)

Smeenk, Robert Jan; van Lin, Emile N J Th; van Kollenburg, Peter; Kunze-Busch, Martina; Kaanders, Johannes H A M

2009-10-01

To investigate the anal wall (Awall) sparing effect of an endorectal balloon (ERB) in 3D conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) for prostate cancer. In 24 patients with localized prostate carcinoma, two planning CT-scans were performed: with and without ERB. A prostate planning target volume (PTV) was defined, and the Awall was delineated, using two different methods. Three-field and 4-field 3D-CRT plans, and IMRT plans were generated with a prescription dose of 78Gy. In 144 treatment plans, the minimum dose (D(min)), maximum dose (D(max)), and mean dose (D(mean)) to the Awall were calculated, as well as the Awall volumes exposed to doses ranging from >or=20Gy to >or=70Gy (V(20)-V(70), respectively). In the 3D-CRT plans, an ERB significantly reduced D(mean), D(max), and V(30)-V(70). For IMRT all investigated dose parameters were significantly reduced by the ERB. The absolute reduction of D(mean) was 12Gy in 3D-CRT and was 7.5Gy in IMRT for both methods of Awall delineation. Application of an ERB showed a significant Awall sparing effect in both 3D-CRT and IMRT. This may lead to reduced late anal toxicity in prostate radiotherapy.

Langevin dynamics of conformational transformations induced by the charge-curvature interaction

DEFF Research Database (Denmark)

Gaididei, Yuri Borisovich; Gorria, C.; Christiansen, Peter Leth

2009-01-01

The role of thermal fluctuations in the conformational dynamics of a single closed filament is studied. It is shown that, due to the interaction between charges and bending degrees of freedom, initially circular chains may undergo transformation to polygonal shape.......The role of thermal fluctuations in the conformational dynamics of a single closed filament is studied. It is shown that, due to the interaction between charges and bending degrees of freedom, initially circular chains may undergo transformation to polygonal shape....

Three-Dimensional Conformal Simultaneously Integrated Boost Technique for Breast-Conserving Radiotherapy

International Nuclear Information System (INIS)

Laan, Hans Paul van der; Dolsma, Wil V.; Maduro, John H.; Korevaar, Erik W.; Hollander, Miranda; Langendijk, Johannes A.

2007-01-01

Purpose: To compare the target coverage and normal tissue dose with the simultaneously integrated boost (SIB) and the sequential boost technique in breast cancer, and to evaluate the incidence of acute skin toxicity in patients treated with the SIB technique. Methods and Materials: Thirty patients with early-stage left-sided breast cancer underwent breast-conserving radiotherapy using the SIB technique. The breast and boost planning target volumes (PTVs) were treated simultaneously (i.e., for each fraction, the breast and boost PTVs received 1.81 Gy and 2.3 Gy, respectively). Three-dimensional conformal beams with wedges were shaped and weighted using forward planning. Dose-volume histograms of the PTVs and organs at risk with the SIB technique, 28 x (1.81 + 0.49 Gy), were compared with those for the sequential boost technique, 25 x 2 Gy + 8 x 2 Gy. Acute skin toxicity was evaluated for 90 patients treated with the SIB technique according to Common Terminology Criteria for Adverse Events, version 3.0. Results: PTV coverage was adequate with both techniques. With SIB, more efficiently shaped boost beams resulted in smaller irradiated volumes. The mean volume receiving ≥107% of the breast dose was reduced by 20%, the mean volume outside the boost PTV receiving ≥95% of the boost dose was reduced by 54%, and the mean heart and lung dose were reduced by 10%. Of the evaluated patients, 32.2% had Grade 2 or worse toxicity. Conclusion: The SIB technique is proposed for standard use in breast-conserving radiotherapy because of its dose-limiting capabilities, easy implementation, reduced number of treatment fractions, and relatively low incidence of acute skin toxicity

Situation of radiotherapy in 2010 - context and methods, data for 2003/2010, synthesis

International Nuclear Information System (INIS)

2011-03-01

Illustrated by data tables and figures, this report first gives an overview of the status and situation of European and French radiotherapy centres, and of care activity authorizations regarding external radiotherapy. It gives an overview of equipment used for treatments and for treatment preparation and delivery, and of the different treatment techniques (three dimensional conformational, intensity-modulated conformational, stereotactic, whole body radiotherapy, proton-therapy). It comments the activity of radiotherapy centres: patients (age, sessions, and treated pathologies), comments data regarding medical and paramedical personnel involved in radiotherapy, and financial data regarding radiotherapy in 2009

Long-Term Results of Conformal Radiotherapy for Progressive Airway Amyloidosis

Energy Technology Data Exchange (ETDEWEB)

Truong, Minh Tam, E-mail: mitruong@bu.edu [Department of Radiation Oncology, Amyloid Treatment and Research Program, Boston University School of Medicine, Boston Medical Center, Boston, MA (United States); Kachnic, Lisa A. [Department of Radiation Oncology, Amyloid Treatment and Research Program, Boston University School of Medicine, Boston Medical Center, Boston, MA (United States); Grillone, Gregory A. [Department of Otolaryngology, Amyloid Treatment and Research Program, Boston University School of Medicine, Boston Medical Center, Boston, MA (United States); Bohrs, Harry K.; Lee, Richard [Department of Radiation Oncology, Amyloid Treatment and Research Program, Boston University School of Medicine, Boston Medical Center, Boston, MA (United States); Sakai, Osamu [Department of Radiology, Amyloid Treatment and Research Program, Boston University School of Medicine, Boston Medical Center, Boston, MA (United States); Berk, John L. [Department of Medicine, Amyloid Treatment and Research Program, Boston University School of Medicine, Boston Medical Center, Boston, MA (United States)

2012-06-01

Purpose: To evaluate the efficacy of conformal external beam radiotherapy (RT) for local control of progressive airway amyloidosis. Methods and Materials: We conducted a retrospective review of patients with biopsy-proven progressive airway amyloidosis treated with conformal RT between 2000 and 2006 at Boston Medical Center. The patients were evaluated for performance status and pulmonary function, with computed tomography and endoscopy after RT compared with the pretreatment studies. Local control was defined as the lack of progression of airway wall thickening on computed tomography imaging and stable endobronchial deposits by endoscopy. Results: A total of 10 symptomatic airway amyloidosis patients (3 laryngeal and 7 tracheobronchial) received RT to a median total dose of 20 Gy in 10 fractions within 2 weeks. At a median follow-up of 6.7 years (range, 1.5-10.3), 8 of the 10 patients had local control. The remaining 2 patients underwent repeat RT 6 and 8.4 months after initial RT, 1 for persistent bronchial obstruction and 1 for progression of subglottic amyloid disease with subsequent disease control. The Eastern Cooperative Oncology Group performance status improved at a median of 18 months after RT compared with the baseline values, from a median score of 2 to a median of 1 (p = .035). Airflow (forced expiratory volume in 1 second) measurements increased compared with the baseline values at each follow-up evaluation, reaching a 10.7% increase (p = .087) at the last testing (median duration, 64.8 months). Acute toxicity was limited to Grade 1-2 esophagitis, occurring in 40% of patients. No late toxicity was observed. Conclusions: RT prevented progressive amyloid deposition in 8 of 10 patients, resulting in a marginally increased forced expiratory volume in 1 second, and improved functional capacity, without late morbidity.

Application of biological dose concept in dose optimization for conformal radiotherapy of prostate carcinoma

International Nuclear Information System (INIS)

Li Yunhai; Liao Yuan; Zhou Lijun; Pan Ziqiang; Feng Yan

2003-01-01

Objective: On basis of physical dose optimization, LQ model was used to investigate the difference between the curves of biological effective dose and physical isodose. The influence of applying the biological dose concept on three dimensional conformal radiotherapy of prostate carcinoma was discussed. Methods: Four treatment plannings were designed for physical dose optimization: three fields, four-box fields, five fields and six fields. Target dose uniformity and protection of the critical tissue-rectum were used as the principal standard for designing the treatment planning. Biological effective dose (BED) was calculated by LQ model. The difference between the BED curve drawn in the central layer and the physical isodose curve was studied. The difference between the adjusted physical dose (APD) and the physical dose was also studied. Results: Five field planning was the best in target dose uniformity and protection of the critical tissue-rectum. The physical dose was uniform in the target, but the biological effective doses revealed great discrepancy in the biological model. Adjusted physical dose distribution also displayed larger discrepancy than the physical dose unadjusted. Conclusions: Intensified Modulated Radiotherapy (IMRT) technique with inversion planning using biological dose concept may be much more advantageous to reach a high tumor control probability and low normal tissue complication probability

Trajectory optimization for dynamic couch rotation during volumetric modulated arc radiotherapy

Science.gov (United States)

Smyth, Gregory; Bamber, Jeffrey C.; Evans, Philip M.; Bedford, James L.

2013-11-01

Non-coplanar radiation beams are often used in three-dimensional conformal and intensity modulated radiotherapy to reduce dose to organs at risk (OAR) by geometric avoidance. In volumetric modulated arc radiotherapy (VMAT) non-coplanar geometries are generally achieved by applying patient couch rotations to single or multiple full or partial arcs. This paper presents a trajectory optimization method for a non-coplanar technique, dynamic couch rotation during VMAT (DCR-VMAT), which combines ray tracing with a graph search algorithm. Four clinical test cases (partial breast, brain, prostate only, and prostate and pelvic nodes) were used to evaluate the potential OAR sparing for trajectory-optimized DCR-VMAT plans, compared with standard coplanar VMAT. In each case, ray tracing was performed and a cost map reflecting the number of OAR voxels intersected for each potential source position was generated. The least-cost path through the cost map, corresponding to an optimal DCR-VMAT trajectory, was determined using Dijkstra’s algorithm. Results show that trajectory optimization can reduce dose to specified OARs for plans otherwise comparable to conventional coplanar VMAT techniques. For the partial breast case, the mean heart dose was reduced by 53%. In the brain case, the maximum lens doses were reduced by 61% (left) and 77% (right) and the globes by 37% (left) and 40% (right). Bowel mean dose was reduced by 15% in the prostate only case. For the prostate and pelvic nodes case, the bowel V50 Gy and V60 Gy were reduced by 9% and 45% respectively. Future work will involve further development of the algorithm and assessment of its performance over a larger number of cases in site-specific cohorts.

Radiotherapy equipment for conformal radiotherapy and IMRT in the Czech Republic

International Nuclear Information System (INIS)

Horakova, I.; Irena Pavlikova, I.; Novotny, J. ml.

2005-01-01

The development of the equipment of radiotherapy departments in the Czech Republic is presented here. The data from the special questionnaire from 14 workplaces with linear accelerators with multi-leaf collimators (MLC) and electronic portal imaging device (EPID) are included. They show not only the equipment specification but also the application methods, the quality control, plans for future etc. In the Czech Republic, a great extension of modem irradiation techniques and accessories occurs at present. Together with it, it is necessary to develop quality assurance of the whole process of dose delivery to the patient. It is also necessary to assure further education and training of hospital staff. Modern radiotherapy techniques demand sufficient amount of all sources including personal sources. (authors)

A method of analyzing rectal surface area irradiated and rectal complications in prostate conformal radiotherapy

International Nuclear Information System (INIS)

Lu Yong; Song, Paul Y.; Li Shidong; Spelbring, Danny R.; Vijayakumar, Srinivasan; Haraf, Daniel J.; Chen, George T.Y.

1995-01-01

Purpose: To develop a method of analyzing rectal surface area irradiated and rectal complications in prostate conformal radiotherapy. Methods and Materials: Dose-surface histograms of the rectum, which state the rectal surface area irradiated to any given dose, were calculated for a group of 27 patients treated with a four-field box technique to a total (tumor minimum) dose ranging from 68 to 70 Gy. Occurrences of rectal toxicities as defined by the Radiation Therapy Oncology Group (RTOG) were recorded and examined in terms of dose and rectal surface area irradiated. For a specified end point of rectal complication, the complication probability was analyzed as a function of dose irradiated to a fixed rectal area, and as a function of area receiving a fixed dose. Lyman's model of normal tissue complication probability (NTCP) was used to fit the data. Results: The observed occurrences of rectal complications appear to depend on the rectal surface area irradiated to a given dose level. The patient distribution of each toxicity grade exhibits a maximum as a function of percentage surface area irradiated, and the maximum moves to higher values of percentage surface area as the toxicity grade increases. The dependence of the NTCP for the specified end point on dose and percentage surface area irradiated was fitted to Lyman's NTCP model with a set of parameters. The curvature of the NTCP as a function of the surface area suggests that the rectum is a parallel structured organ. Conclusions: The described method of analyzing rectal surface area irradiated yields interesting insight into understanding rectal complications in prostate conformal radiotherapy. Application of the method to a larger patient data set has the potential to facilitate the construction of a full dose-surface-complication relationship, which would be most useful in guiding clinical practice

Conkiss: Conformal Kidneys Sparing 3D Noncoplanar Radiotherapy Treatment for Pancreatic Cancer As an Alternative to IMRT

International Nuclear Information System (INIS)

Sebestyen, Zsolt; Kovacs, Peter; Gulyban, Akos; Farkas, Robert; Bellyei, Szabolcs; Liposits, Gabor; Szigeti, Andras; Esik, Olga; Derczy, Katalin; Mangel, Laszlo

2011-01-01

When treating pancreatic cancer using standard (ST) 3D conformal radiotherapy (3D-CRT) beam arrangements, the kidneys often receive a higher dose than their probable tolerance limit. Our aim was to elaborate a new planning method that-similarly to IMRT-effectively spares the kidneys without compromising the target coverage. Conformal kidneys sparing (CONKISS) 5-field, noncoplanar plans were compared with ST plans for 23 consecutive patients retrospectively. Optimal beam arrangements were used consisting of a left- and right-wedged beam-pair and an anteroposterior beam inclined in the caudal direction. The wedge direction determination (WEDDE) algorithm was developed to adjust the adequate direction of wedges. The aimed organs at risk (OARs) mean dose limits were: kidney <12 Gy, liver <25 Gy, small bowels <30 Gy, and spinal cord maximum <45 Gy. Conformity and homogeneity indexes with z-test were used to evaluate and compare the different planning approaches. The mean dose to the kidneys decreased significantly (p < 0.05): left kidney 7.7 vs. 10.7 Gy, right kidney 9.1 vs. 11.7 Gy. Meanwhile the mean dose to the liver increased significantly (18.1 vs. 15.0 Gy). The changes in the conformity, homogeneity, and in the doses to other OARs were not significant. The CONKISS method balances the load among the OARs and significantly reduces the dose to the kidneys, without any significant change in the conformity and homogeneity. Using 3D-CRT the CONKISS method can be a smart alternative to IMRT to enhance the possibility of dose escalation.

Phase II study of radiotherapy with three-dimensional conformal boost concurrent with paclitaxel and cisplatin for Stage IIIB non-small-cell lung cancer

International Nuclear Information System (INIS)

Kim, Young Seok; Yoon, Sang Min; Choi, Eun Kyung; Yi, Byong Yong; Kim, Jong Hoon; Ahn, Seung Do; Lee, Sang-wook; Shin, Seong Soo; Lee, Jung Shin; Suh, Cheolwon; Kim, Sang-We; Kim, Dong Soon; Kim, Woo Sung; Park, Heon Joo; Park, Charn Il

2005-01-01

Purpose: To evaluate the efficacy and toxicity of concurrent chemoradiotherapy with paclitaxel/cisplatin for Stage IIIB locally advanced non-small-cell lung cancer (NSCLC). Methods and Materials: Radiotherapy was administered to a total dose of 70.2 Gy (daily fraction of 1.8 Gy, 5 days/wk), over an 8-week period, combined with chemotherapy. The chemotherapy consisted of weekly 40 mg/m 2 of paclitaxel plus 20 mg/m 2 of cisplatin for 8 consecutive weeks. All patients received three-dimensional conformal radiotherapy (3D-CRT), based on computed tomography simulated planning after 41.4 Gy. The median follow-up period of survivors was 24 months. Results: Between January 2000 and October 2002, 135 patients with a median age of 60 years were enrolled and analyzed in this prospective trial. The overall response rate was 75% including 2 cases of complete response. The major patterns of failure were local failure and distant metastasis. The 2-year overall and progression-free survival rates were 37% and 18%, respectively. The median overall and progression-free survival times were 17 months and 9 months, respectively. Hematologic toxicity >Grade 2 was observed in 19% of patients and severe non-hematologic toxicity was infrequent. Conclusions: Three-dimensional conformal radiotherapy, combined with paclitaxel and cisplatin chemotherapy, was associated with a satisfactory outcome with manageable toxicity. Further investigations are needed to improve the local control

Improvement in toxicity in high risk prostate cancer patients treated with image-guided intensity-modulated radiotherapy compared to 3D conformal radiotherapy without daily image guidance.

Science.gov (United States)

Sveistrup, Joen; af Rosenschöld, Per Munck; Deasy, Joseph O; Oh, Jung Hun; Pommer, Tobias; Petersen, Peter Meidahl; Engelholm, Svend Aage

2014-02-04

Image-guided radiotherapy (IGRT) facilitates the delivery of a very precise radiation dose. In this study we compare the toxicity and biochemical progression-free survival between patients treated with daily image-guided intensity-modulated radiotherapy (IG-IMRT) and 3D conformal radiotherapy (3DCRT) without daily image guidance for high risk prostate cancer (PCa). A total of 503 high risk PCa patients treated with radiotherapy (RT) and endocrine treatment between 2000 and 2010 were retrospectively reviewed. 115 patients were treated with 3DCRT, and 388 patients were treated with IG-IMRT. 3DCRT patients were treated to 76 Gy and without daily image guidance and with 1-2 cm PTV margins. IG-IMRT patients were treated to 78 Gy based on daily image guidance of fiducial markers, and the PTV margins were 5-7 mm. Furthermore, the dose-volume constraints to both the rectum and bladder were changed with the introduction of IG-IMRT. The 2-year actuarial likelihood of developing grade > = 2 GI toxicity following RT was 57.3% in 3DCRT patients and 5.8% in IG-IMRT patients (p analysis, 3DCRT was associated with a significantly increased risk of developing grade > = 2 GI toxicity compared to IG-IMRT (p analysis there was no difference in biochemical progression-free survival between 3DCRT and IG-IMRT. The difference in toxicity can be attributed to the combination of the IMRT technique with reduced dose to organs-at-risk, daily image guidance and margin reduction.

FXG dosimeter response for three-dimensional conformal radiotherapy using different evaluation techniques

Energy Technology Data Exchange (ETDEWEB)

Cavinato, Christianne C.; Campos, Leticia L., E-mail: ccavinato@ipen.b, E-mail: lcrodri@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Souza, Benedito H.; Carrete Junior, Henrique; Daros, Kellen A.C.; Medeiros, Regina B., E-mail: bhsouza@unifesp.b, E-mail: daros.kellen@unifesp.b, E-mail: rbitel-li.ddi@epm.b [Universidade Federal de Sao Paulo (UNIFESP), SP (Brazil). Dept. de Diagnostico por Imagem; Giordani, Adelmo J. [Universidade Federal de Sao Paulo (UNIFESP), SP (Brazil). Servico de Radioterapia

2011-07-01

This work aims to compare the dose-response of the Fricke xylenol gel (FXG) dosimeter developed at IPEN using 270 Bloom gelatin from porcine skin made in Brazil evaluated using the magnetic resonance imaging (MRI) technique with the dosimetric response evaluated using the optical absorption (OA) spectrophotometry technique, in order to verify the possibility of quality assurance (QA) and reproducibility of FXG dosimeter to be carried out routinely using the OA technique for three-dimensional conformal radiotherapy (3DCRT) application using a 6 MV photons linear accelerator. The response in function of the absorbed dose of FXG dosimeter developed at IPEN presents linear behavior in clinical interest dose range when irradiated with Co-60 gamma radiation and 6 MV photons and evaluated using the MRI and OA techniques. The results indicate that the optical technique can be used for QA of FXG dosemeter when used in the possible application in QA of 3DCRT. (author)

FXG dosimeter response for three-dimensional conformal radiotherapy using different evaluation techniques

International Nuclear Information System (INIS)

Cavinato, Christianne C.; Campos, Leticia L.; Souza, Benedito H.; Carrete Junior, Henrique; Daros, Kellen A.C.; Medeiros, Regina B.; Giordani, Adelmo J.

2011-01-01

This work aims to compare the dose-response of the Fricke xylenol gel (FXG) dosimeter developed at IPEN using 270 Bloom gelatin from porcine skin made in Brazil evaluated using the magnetic resonance imaging (MRI) technique with the dosimetric response evaluated using the optical absorption (OA) spectrophotometry technique, in order to verify the possibility of quality assurance (QA) and reproducibility of FXG dosimeter to be carried out routinely using the OA technique for three-dimensional conformal radiotherapy (3DCRT) application using a 6 MV photons linear accelerator. The response in function of the absorbed dose of FXG dosimeter developed at IPEN presents linear behavior in clinical interest dose range when irradiated with Co-60 gamma radiation and 6 MV photons and evaluated using the MRI and OA techniques. The results indicate that the optical technique can be used for QA of FXG dosemeter when used in the possible application in QA of 3DCRT. (author)

Dosimetric Study of Current Treatment Options for Radiotherapy in Retinoblastoma

Energy Technology Data Exchange (ETDEWEB)

Eldebawy, Eman [Department of Radiation Oncology, McGill University Health Centre, Montreal, Quebec (Canada); Department of Radiation Oncology, Children' s Cancer Hospital, Cairo (Egypt); Parker, William, E-mail: william.parker@mcgill.ca [Department of Medical Physics, McGill University Health Centre, Montreal, Quebec (Canada); Abdel Rahman, Wamied [Department of Medical Physics, McGill University Health Centre, Montreal, Quebec (Canada); Freeman, Carolyn R. [Department of Radiation Oncology, McGill University Health Centre, Montreal, Quebec (Canada)

2012-03-01

Purpose: To determine the best treatment technique for patients with retinoblastoma requiring radiotherapy to the whole eye. Methods and Materials: Treatment plans for 3 patients with retinoblastoma were developed using 10 radiotherapy techniques including electron beams, photon beam wedge pair (WP), photon beam three-dimensional conformal radiotherapy (3D-CRT), fixed gantry intensity-modulated radiotherapy (IMRT), photon volumetric arc therapy (VMAT), fractionated stereotactic radiotherapy, and helical tomotherapy (HT). Dose-volume analyses were carried out for each technique. Results: All techniques provided similar target coverage; conformity was highest for VMAT, nine-field (9F) IMRT, and HT (conformity index [CI] = 1.3) and lowest for the WP and two electron techniques (CI = 1.8). The electron techniques had the highest planning target volume dose gradient (131% of maximum dose received [D{sub max}]), and the CRT techniques had the lowest (103% D{sub max}) gradient. The volume receiving at least 20 Gy (V{sub 20Gy}) for the ipsilateral bony orbit was lowest for the VMAT and HT techniques (56%) and highest for the CRT techniques (90%). Generally, the electron beam techniques were superior in terms of brain sparing and delivered approximately one-third of the integral dose of the photon techniques. Conclusions: Inverse planned image-guided radiotherapy delivered using HT or VMAT gives better conformity index, improved orbital bone and brain sparing, and a lower integral dose than other techniques.

Setup error in three-dimensional conformal radiotherapy for thoracic esophageal carcinoma

International Nuclear Information System (INIS)

Hong Jinsheng; Zhang Weijian; Chen Jinmei; Cai Chuanshu; Ke Chunlin; Chen Xiuying; Wu Bing; Guo Feibao

2009-01-01

Objective: To study the setup errors in three-dimensional conformal radiotherapy (3DCRT) for thoracic esophageal carcinoma using electronic portal imaging device(EPID) and calculate the margins from CTV to PTV. Methods: Forty-one patients with thoracic esophageal carcinoma who received 3DCRT were continuously enrolled into this study. The anterior and lateral electronic portal images (EPI) were aquired by EPID once a week. The setup errors were obtained through comparing the difference between EPI and digitally reconstructed radiographs (DRR). Then the setup margins from CTV to PTV were calculated. By using self paired design, 22 patients received definitive radiotherapy with different margins. Group A: the margins were 10 mm in all the three axes; Group B: the margins were aquired in this study. The difference were compared by Paired t-test or Wilcoxon signed-rank test. Results: The margins from CTV to PTV in x, y and z axes were 8.72 mm, 10.50 mm and 5.62 mm, respectively. Between the group A and group B, the difference of the maximum dose of the spinal cord was significant(4638.7 cGy ± 1449.6 cGy vs. 4310.2 cGy ± 1528.7 cGy; t=5.48, P=0.000), and the difference of NTCP for the spinal cord was also significant (4.82% ± 5.99% vs. 3.64% ± 4.70%; Z=-2.70, P=0.007). Conclusions: For patients with thoracic esophageal carcinoma who receive 3DCRT in author's department, the margins from CTV to PTV in x, y and z axes were 8.72 mm, 10.50 mm and 5.62 mm, respectively. The spinal cord could be better protected by using these setup margins than using 10 mm in each axis. (authors)

Three-dimensional conformal radiotherapy in the treatment of prostate cancer in Australia and New Zealand: Report on a survey of radiotherapy centres and the proceedings of a consensus workshop

International Nuclear Information System (INIS)

Tai, K.-H.; Duchesne, G.; See, A.; Berry, M.

2004-01-01

There is an increasing use of 3-D conformal radiotherapy (3DCRT) in the radiotherapeutic management of prostate cancer. The Faculty of Radiation Oncology Genito-Urinary Group carried out a survey of Australian and New Zealand radiotherapy centres in the preparation of a consensus workshop. Of the 19 centres that were represented, there were 24 radiation oncologists, 16 radiation therapists and 12 medical physicists. The survey collected demographic information and data on the practices undertaken at those centres when delivering curative radiotherapy in the treatment of prostate cancer. There was much variation in the delivery of treatment in the areas of patient set-up, contouring of target volumes and organs of interest during computer planning, the techniques and the dose constraints used in these techniques, the use of adjuvant androgen deprivation therapy and the quality assurance processes used in monitoring effects of treatment. This variability reflects the range of data in the published literature. Emerging trends of practices were also identified. This is a first report on a multi-disciplinary approach to the development of guidelines in 3DCRT of prostate cancer. Copyright (2004) Blackwell Science Pty Ltd

Anal wall sparing effect of an endorectal balloon in 3D conformal and intensity-modulated prostate radiotherapy

International Nuclear Information System (INIS)

Smeenk, Robert Jan; Lin, Emile N.J.Th. van; Kollenburg, Peter van; Kunze-Busch, Martina; Kaanders, Johannes H.A.M.

2009-01-01

Background and purpose: To investigate the anal wall (Awall) sparing effect of an endorectal balloon (ERB) in 3D conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) for prostate cancer. Materials and methods: In 24 patients with localized prostate carcinoma, two planning CT-scans were performed: with and without ERB. A prostate planning target volume (PTV) was defined, and the Awall was delineated, using two different methods. Three-field and 4-field 3D-CRT plans, and IMRT plans were generated with a prescription dose of 78 Gy. In 144 treatment plans, the minimum dose (D min ), maximum dose (D max ), and mean dose (D mean ) to the Awall were calculated, as well as the Awall volumes exposed to doses ranging from ≥20 Gy to ≥70 Gy (V 20 - V 70 , respectively). Results: In the 3D-CRT plans, an ERB significantly reduced D mean , D max , and V 30 - V 70 . For IMRT all investigated dose parameters were significantly reduced by the ERB. The absolute reduction of D mean was 12 Gy in 3D-CRT and was 7.5 Gy in IMRT for both methods of Awall delineation. Conclusions: Application of an ERB showed a significant Awall sparing effect in both 3D-CRT and IMRT. This may lead to reduced late anal toxicity in prostate radiotherapy.

Molecular dynamics of conformation-specific dopamine transporter-inhibitor complexes.

Science.gov (United States)

Jean, Bernandie; Surratt, Christopher K; Madura, Jeffry D

2017-09-01

The recreational psychostimulant cocaine inhibits dopamine reuptake from the synapse, resulting in excessive stimulation of postsynaptic dopamine receptors in brain areas associated with reward and addiction. Cocaine binds to and stabilizes the outward- (extracellular-) facing conformation of the dopamine transporter (DAT) protein, while the low abuse potential DAT inhibitor benztropine prefers the inward- (cytoplasmic-) facing conformation. A correlation has been previously postulated between psychostimulant abuse potential and preference for the outward-facing DAT conformation. The 3β-aryltropane cocaine analogs LX10 and LX11, however, differ only in stereochemistry and share a preference for the outward-facing DAT, yet are reported to vary widely in abuse potential in an animal model. In search of the molecular basis for DAT conformation preference, complexes of cocaine, benztropine, LX10 or LX11 bound to each DAT conformation were subjected to 100ns of all-atom molecular dynamics simulation. Results were consistent with previous findings from cysteine accessibility assays used to assess an inhibitor's DAT conformation preference. The respective 2β- and 2α-substituted phenyltropanes of LX10 and LX11 interacted with hydrophobic regions of the DAT S1 binding site that were inaccessible to cocaine. Solvent accessibility measurements also revealed subtle differences in inhibitor positioning within a given DAT conformation. This work serves to advance our understanding of the conformational selectivity of DAT inhibitors and suggests that MD may be useful in antipsychostimulant therapeutic design. Copyright © 2017 Elsevier Inc. All rights reserved.

Orientation and conformation of a lipase at an interface studied by molecular dynamics simulations

DEFF Research Database (Denmark)

Jensen, Morten Østergaard; Jensen, T.R.; Kjær, Kristian

2002-01-01

Electron density profiles calculated from molecular dynamics trajectories are used to deduce the orientation and conformation of Thermomyces lanuginosa lipase and a mutant adsorbed at an air-water interface. It is demonstrated that the profiles display distinct fine structures, which uniquely...... characterize enzyme orientation and conformation. The density profiles are, on the nanosecond timescale, determined by the average enzyme conformation. We outline a Computational scheme that from a single molecular dynamics trajectory allows for extraction of electron density profiles referring to different...

Individualized margins in 3D conformal radiotherapy planning for lung cancer: analysis of physiological movements and their dosimetric impacts.

Science.gov (United States)

Germain, François; Beaulieu, Luc; Fortin, André

2008-01-01

In conformal radiotherapy planning for lung cancer, respiratory movements are not taken into account when a single computed tomography (CT) scan is performed. This study examines tumor movements to design individualized margins to account for these movements and evaluates their dosimetric impacts on planning volume. Fifteen patients undergoing CT-based planning for radical radiotherapy for localized lung cancer formed the study cohort. A reference plan was constructed based on reference gross, clinical, and planning target volumes (rGTV, rCTV, and rPTV, respectively). The reference plans were compared with individualized plans using individualized margins obtained by using 5 serial CT scans to generate individualized target volumes (iGTV, iCTV, and iPTV). Three-dimensional conformal radiation therapy was used for plan generation using 6- and 23-MV photon beams. Ten plans for each patient were generated and dose-volume histograms (DVHs) were calculated. Comparisons of volumetric and dosimetric parameters were performed using paired Student t-tests. Relative to the rGTV, the total volume occupied by the superimposed GTVs increased progressively with each additional CT scans. With the use of all 5 scans, the average increase in GTV was 52.1%. For the plans with closest dosimetric coverage, target volume was smaller (iPTV/rPTV ratio 0.808) but lung irradiation was only slightly decreased. Reduction in the proportion of lung tissue that received 20 Gy or more outside the PTV (V20) was observed both for 6-MV plans (-0.73%) and 23-MV plans (-0.65%), with p = 0.02 and p = 0.04, respectively. In conformal RT planning for the treatment of lung cancer, the use of serial CT scans to evaluate respiratory motion and to generate individualized margins to account for these motions produced only a limited lung sparing advantage.

Individualized Margins in 3D Conformal Radiotherapy Planning for Lung Cancer: Analysis of Physiological Movements and Their Dosimetric Impacts

International Nuclear Information System (INIS)

Germain, Francois; Beaulieu, Luc; Fortin, Andre

2008-01-01

In conformal radiotherapy planning for lung cancer, respiratory movements are not taken into account when a single computed tomography (CT) scan is performed. This study examines tumor movements to design individualized margins to account for these movements and evaluates their dosimetric impacts on planning volume. Fifteen patients undergoing CT-based planning for radical radiotherapy for localized lung cancer formed the study cohort. A reference plan was constructed based on reference gross, clinical, and planning target volumes (rGTV, rCTV, and rPTV, respectively). The reference plans were compared with individualized plans using individualized margins obtained by using 5 serial CT scans to generate individualized target volumes (iGTV, iCTV, and iPTV). Three-dimensional conformal radiation therapy was used for plan generation using 6- and 23-MV photon beams. Ten plans for each patient were generated and dose-volume histograms (DVHs) were calculated. Comparisons of volumetric and dosimetric parameters were performed using paired Student t-tests. Relative to the rGTV, the total volume occupied by the superimposed GTVs increased progressively with each additional CT scans. With the use of all 5 scans, the average increase in GTV was 52.1%. For the plans with closest dosimetric coverage, target volume was smaller (iPTV/rPTV ratio 0.808) but lung irradiation was only slightly decreased. Reduction in the proportion of lung tissue that received 20 Gy or more outside the PTV (V20) was observed both for 6-MV plans (-0.73%) and 23-MV plans (-0.65%), with p = 0.02 and p = 0.04, respectively. In conformal RT planning for the treatment of lung cancer, the use of serial CT scans to evaluate respiratory motion and to generate individualized margins to account for these motions produced only a limited lung sparing advantage

Practical recommendations for breathing-adapted radiotherapy; Bonnes pratiques pour la radiotherapie asservie a la respiration

Energy Technology Data Exchange (ETDEWEB)

Simon, L.; Giraud, P.; Rosenwald, J.C. [Institut Curie, Dept. d' Oncologie-radiotherapie, 75 - Paris (France); Dumas, J.L.; Lorchel, F. [CHU de Besancon, Hopital Jean-Minjoz, Service Radiotherapie, 25 - Besancon (France); Marre, D. [Institut Claudius-Regaud, Dept. des Radiations, 31 - Toulouse (France); Dupont, S. [Hopital Europeen Georges-Pompidou, Service d' Oncoradiotherapie, 75 - Paris (France); Varmenot, N. [Centre Henri-Becquerel, UnitE de Physique Medicale, 76 - Rouen (France); Ginestet, C. [Centre Leon-Berard, Dept. de Radiotherapie, 69 - Lyon (France); Caron, J. [Institut Bergonie, Dept. de Radiotherapie, 33 - Bordeaux (France); Marchesi, V. [Centre Alexis-Vautrin, Dept. de Radiotherapie, 54 - Vandoeuvre-les-Nancy (France); Ferreira, I. [Institut Gustave-Roussy, Dept. d' Oncologie Radiotherapie, 94 - Villejuif (France); Garcia, R. [Institut Sainte-Catherine, Service de Radiotherapie, 84 - Avignon (France)

2007-06-15

Respiration-gated radiotherapy offers a significant potential for improvement in the irradiation of tumor sites affected by respiratory motion such as lung, breast and liver tumors. An increased conformality of irradiation fields leading to decreased complications rates of organs at risk (lung, heart) is expected. Respiratory gating is in line with the need for improved precision required by radiotherapy techniques such as 3D conformal radiotherapy or intensity modulated radiotherapy. Reduction of respiratory motion can be achieved by using either breath-hold techniques or respiration synchronized gating techniques. Breath-hold techniques can be achieved with active techniques, in which airflow of the patient is temporarily blocked by a valve, or passive techniques, in which the patient voluntarily holds his/her breath. Synchronized gating techniques use external devices to predict the phase of the respiration cycle while the patient breaths freely. This work summarizes the different experiences of the centers of the STIC 2003 project. It describes the different techniques, gives an overview of the literature and proposes a practice based on our experience. (authors)

SU-F-P-52: A Meta-Analysis of Controlled Clinical Trials Comparing Elective Nodal Irradiation with Involved-Field Irradiation for Conformal Or Intensity-Modulated Radiotherapy in Patients with Esophageal Cancer

Energy Technology Data Exchange (ETDEWEB)

Bai, W; Zhang, R; Zhou, Z; Qiao, X [The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei (China)

2016-06-15

Purpose: To compare elective nodal irradiation with involved-field irradiation for three-dimensional conformal radiotherapy or intensity-modulated radiotherapy in patients with esophageal cancer by a metaanalysis. Methods: Wanfang, CNKI, VIP, CBM databases, PubMed, Embase and Cochrane Library were searched to identify the controlled clinical trials of elective nodal irradiation with involved-field irradiation for three-dimensional conformal radiotherapy or intensity-modulated radiotherapy in patients with esophageal cancer. The obtained data were analyzed using Stata 11.0. The difference between two groups was estimated by calculating the odds ratio (OR) with 95% confidence interval (95% CI). Results: A total of 12 controlled clinical trials involving 1095 esophageal cancer patients, which were selected according to inclusion and exclusion criteria, were included in this meta-analysis. The meta-analysis showed that the elective nodal irradiation group reduced the rates of out-field failure comparing with involved-field irradiation group (OR=3.727, P=0.007). However, the rates of ≥grades 3 acute radiation pneumonitis and esophagitis were significantly higher in the elective nodal irradiation group than in the involved-field irradiation group (OR=0.348, P=0.001, OR=0.385, P=0.000). 1-, 2-, 3-year local control rates (OR=0.966, P=0.837, OR=0.946, P=0.781; OR=0.732P=0.098) and 1-, 3-, 5-year survival rates were similar in the two groups ( OR=0.966, P=0.837; OR=0.946, P=0.781; OR=0.732, P=0.098; OR=0.952, P=0.756; OR=1.149, P=0.422; OR=0.768, P=0.120). It is the same with the rates of distant metastasis (OR=0.986, P=0.937). Conclusion: Compared with involved-field irradiation, the elective nodal irradiation can reduce the rates of out-field failure for three-dimensional conformal radiotherapy or intensity-modulated radiotherapy in patients with esophageal cancer. However, its advantage of local control and survival rates is not obvious and it increases the incidence

The conformational dynamics of the mitochondrial Hsp70 chaperone.

Science.gov (United States)

Mapa, Koyeli; Sikor, Martin; Kudryavtsev, Volodymyr; Waegemann, Karin; Kalinin, Stanislav; Seidel, Claus A M; Neupert, Walter; Lamb, Don C; Mokranjac, Dejana

2010-04-09

Heat shock proteins 70 (Hsp70) represent a ubiquitous and conserved family of molecular chaperones involved in a plethora of cellular processes. The dynamics of their ATP hydrolysis-driven and cochaperone-regulated conformational cycle are poorly understood. We used fluorescence spectroscopy to analyze, in real time and at single-molecule resolution, the effects of nucleotides and cochaperones on the conformation of Ssc1, a mitochondrial member of the family. We report that the conformation of its ADP state is unexpectedly heterogeneous, in contrast to a uniform ATP state. Substrates are actively involved in determining the conformation of Ssc1. The J protein Mdj1 does not interact transiently with the chaperone, as generally believed, but rather is released slowly upon ATP hydrolysis. Analysis of the major bacterial Hsp70 revealed important differences between highly homologous members of the family, possibly explaining tuning of Hsp70 chaperones to meet specific functions in different organisms and cellular compartments. 2010 Elsevier Inc. All rights reserved.

Optimization of the primary collimator settings for fractionated IMRT stereotactic radiotherapy

International Nuclear Information System (INIS)

Tobler, Matt; Leavitt, Dennis D.; Watson, Gordon

2004-01-01

Advances in field-shaping techniques for stereotactic radiosurgery/radiotherapy have allowed dynamic adjustment of field shape with gantry rotation (dynamic conformal arc) in an effort to minimize dose to critical structures. Recent work evaluated the potential for increased sparing of dose to normal tissues when the primary collimator setting is optimized to only the size necessary to cover the largest shape of the dynamic micro multi leaf field. Intensity-modulated radiotherapy (IMRT) is now a treatment option for patients receiving stereotactic radiotherapy treatments. This multisegmentation of the dose delivered through multiple fixed treatment fields provides for delivery of uniform dose to the tumor volume while allowing sparing of critical structures, particularly for patients whose tumor volumes are less suited for rotational treatment. For these segmented fields, the total number of monitor units (MUs) delivered may be much greater than the number of MUs required if dose delivery occurred through an unmodulated treatment field. As a result, undesired dose delivered, as leakage through the leaves to tissues outside the area of interest, will be proportionally increased. This work will evaluate the role of optimization of the primary collimator setting for these IMRT treatment fields, and compare these results to treatment fields where the primary collimator settings have not been optimized

Dosimetric Comparison of Three Dimensional Conformal Radiation Radiotherapy and Helical Tomotherapy Partial Breast Cancer

International Nuclear Information System (INIS)

Kim, Dae Woong; Kim, Jong Won; Choi, Yun Kyeong; Kim, Jung Soo; Hwang, Jae Woong; Jeong, Kyeong Sik; Choi, Gye Suk

2008-01-01

The goal of radiation treatment is to deliver a prescribed radiation dose to the target volume accurately while minimizing dose to normal tissues. In this paper, we comparing the dose distribution between three dimensional conformal radiation radiotherapy (3D-CRT) and helical tomotherapy (TOMO) plan for partial breast cancer. Twenty patients were included in the study, and plans for two techniques were developed for each patient (left breast:10 patients, right breast:10 patients). For each patient 3D-CRT planning was using pinnacle planning system, inverse plan was made using Tomotherapy Hi-Art system and using the same targets and optimization goals. We comparing the Homogeneity index (HI), Conformity index (CI) and sparing of the organs at risk for dose-volume histogram. Whereas the HI, CI of TOMO was significantly better than the other, 3D-CRT was observed to have significantly poorer HI, CI. The percentage ipsilateral non-PTV breast volume that was delivered 50% of the prescribed dose was 3D-CRT (mean: 40.4%), TOMO (mean: 18.3%). The average ipsilateral lung volume percentage receiving 20% of the PD was 3D-CRT (mean: 4.8%), TOMO (mean: 14.2), concerning the average heart volume receiving 20% and 10% of the PD during treatment of left breast cancer 3D-CRT (mean: 1.6%, 3.0%), TOMO (mean: 9.7%, 26.3%) In summary, 3D-CRT and TOMO techniques were found to have acceptable PTV coverage in our study. However, in TOMO, high conformity to the PTV and effective breast tissue sparing was achieved at the expense of considerable dose exposure to the lung and heart.

Carbon-ion radiotherapy for marginal lymph node recurrences of cervical cancer after definitive radiotherapy: a case report

International Nuclear Information System (INIS)

Tamaki, Tomoaki; Nakano, Takashi; Ohno, Tatsuya; Kiyohara, Hiroki; Noda, Shin-ei; Ohkubo, Yu; Ando, Ken; Wakatsuki, Masaru; Kato, Shingo; Kamada, Tadashi

2013-01-01

Recurrences of cervical cancer after definitive radiotherapy often occur at common iliac or para-aortic lymph nodes as marginal lymph node recurrences. Patients with these recurrences have a chance of long-term survival by optimal re-treatment with radiotherapy. However, the re-irradiation often overlaps the initial and the secondary radiotherapy fields and can result in increased normal tissue toxicities in the bowels or the stomach. Carbon-ion radiotherapy, a form of particle beam radiotherapy using accelerated carbon ions, offers more conformal and sharp dose distribution than X-ray radiotherapy. Therefore, this approach enables the delivery of high radiation doses to the target while sparing its surrounding normal tissues. Marginal lymph node recurrences in common iliac lymph nodes after radiotherapy were treated successfully by carbon-ion radiotherapy in two patients. These two patients were initially treated with a combination of external beam radiotherapy and intracavitary and interstitial brachytherapy. However, the diseases recurred in the lymph nodes near the border of the initial radiotherapy fields after 22 months and 23 months. Because re-irradiation with X-ray radiotherapy may deliver high doses to a section of the bowels, carbon-ion radiotherapy was selected to treat the lymph node recurrences. A total dose of 48 Gy (RBE) in 12 fractions over 3 weeks was given to the lymph node recurrences, and the tumors disappeared completely with no severe acute toxicities. The two patients showed no evidence of disease for 75 months and 63 months after the initial radiotherapy and for 50 months and 37 months after the carbon-ion radiotherapy, respectively. No severe late adverse effects are observed in these patients. The two presented cases suggest that the highly conformal dose distribution of carbon-ion radiotherapy may be beneficial in the treatment of marginal lymph node recurrences after radiotherapy. In addition, the higher biological effect of carbon

Factors Influencing Neurocognitive Outcomes in Young Patients With Benign and Low-Grade Brain Tumors Treated With Stereotactic Conformal Radiotherapy

International Nuclear Information System (INIS)

Jalali, Rakesh; Mallick, Indranil; Dutta, Debnarayan

2010-01-01

Purpose: To present the effect of radiotherapy doses to different volumes of normal structures on neurocognitive outcomes in young patients with benign and low-grade brain tumors treated prospectively with stereotactic conformal radiotherapy (SCRT). Methods and Materials: Twenty-eight patients (median age, 13 years) with residual/progressive brain tumors (10 craniopharyngioma, 8 cerebellar astrocytoma, 6 optic pathway glioma and 4 cerebral low-grade glioma) were treated with SCRT to a dose of 54 Gy in 30 fractions over 6 weeks. Prospective neuropsychological assessments were done at baseline before RT and at subsequent follow-up examinations. The change in intelligence quotient (IQ) scores was correlated with various factors, including dose-volume to normal structures. Results: Although the overall mean full-scale IQ (FSIQ) at baseline before RT remained unchanged at 2-year follow-up after SCRT, one third of patients did show a >10% decline in FSIQ as compared with baseline. Logistic regression analysis demonstrated that patients aged 10% drop in FSIQ than older patients (53% vs. 10%, p = 0.03). Dosimetric comparison in patients showing a >10% decline vs. patients showing a 43.2 Gy to >13% of volume of the left temporal lobe were the ones to show a significant drop in FSIQ (p = 0.048). Radiotherapy doses to other normal structures, including supratentorial brain, right temporal lobe, and frontal lobes, did not reveal any significant correlation. Conclusion: Our prospectively collected dosimetric data show younger age and radiotherapy doses to left temporal lobe to be predictors of neurocognitive decline, and may well be used as possible dose constraints for high-precision radiotherapy planning.

Acute toxicity in pelvic radiotherapy; a randomised trial of conformal versus conventional treatment

International Nuclear Information System (INIS)

Tait, Diana M.; Nahum, Alan E.; Meyer, Lesley C.; Law, Matthew; Dearnaley, David P.; Horwich, Alan; Mayles, W. Philip; Yarnold, John R.

1997-01-01

Background: A prospective, randomized clinical trial to assess the effect of reducing the volume of irradiated normal tissue on acute reactions in pelvic radiotherapy accrued 266 evaluable patients between 1988 and 1993. Purpose: This is the definitive analysis to assess the differences between the conformal and conventional arms of the trial. Materials and methods: In both arms, patients were treated with 6 MV X-rays using a 3-field technique (in all but 5 cases) consisting of an anterior and two wedged lateral or posterior oblique fields; in the conventional arm, rectangular fields were employed, whereas in the conformal arm, the fields were shaped with customized blocks drawn according to the beam's-eye-view of the target volume. The most common dosage was 65 Gy in 2-Gy fractions 5 times a week, although a subgroup (of ca. bladder patients) were treated with 30-36 Gy in once-a-week 6 Gy fractions. Each patient completed a comprehensive acute toxicity scoring questionnaire concentrating on bowel and bladder problems, tiredness and nausea, before the start of treatment, weekly during and for 3 weeks after the end of treatment and then monthly for a further 2 months. Compliance was excellent. Results: There were no differences between the patients in the two arms with respect to age, gender, tumour type (52% prostate, 41% bladder, 5% rectum, 2% other) fractionation/dosage, anterior field size, weight, or baseline symptoms. Substantial differences in normal-tissue volumes (rectum, bladder, etc.) were achieved: median high-dose volume (HDV) of 689 cm 3 for the conformal technique versus 792 cm 3 for the conventional. A clear pattern of an increase in symptoms during RT, followed by a decrease after RT, was observed for the patient group as a whole. However, a very extensive analysis has not revealed any (statistically) significant differences between the two arms in level of symptoms, nor in medication prescribed. The disparity between our findings and those of other

Strategies to evaluate the impact of rectal volume on prostate motion during three-dimensional conformal radiotherapy for prostate cancer

Energy Technology Data Exchange (ETDEWEB)

Poli, Ana Paula Diniz Fortuna, E-mail: anapaulafortuna@yahoo.com.br [Universidade Estadual de Campinas (CAISM/UNICAMP), Campinas, SP (Brazil). Centro de Atencao Integrada a Saude da Mulher. Divisao de Radioterapia; Dias, Rodrigo Souza; Giordani, Adelmo Jose; Segreto, Helena Regina Comodo; Segreto, Roberto Araujo [Universidade Federal de Sao Paulo (EPM/UNIFESP), Sao Paulo, SP (Brazil). Escola Paulista de Medicina. Divisao de Radioterapia

2016-01-15

Objective: To evaluate the rectal volume influence on prostate motion during three-dimensional conformal radiotherapy (3D-CRT) for prostate cancer. Materials and Methods: Fifty-one patients with prostate cancer underwent a series of three computed tomography scans including an initial planning scan and two subsequent scans during 3D-CRT. The organs of interest were outlined. The prostate contour was compared with the initial CT images considering the anterior, posterior, superior, inferior and lateral edges of the organ. Variations in the anterior limits and volume of the rectum were assessed and correlated with prostate motion in the anteroposterior direction. Results: The maximum range of prostate motion was observed in the superoinferior direction, followed by the anteroposterior direction. A significant correlation was observed between prostate motion and rectal volume variation (p = 0.037). A baseline rectal volume superior to 70 cm{sup 3} had a significant influence on the prostate motion in the anteroposterior direction (p = 0.045). Conclusion: The present study showed a significant interfraction motion of the prostate during 3D-CRT with greatest variations in the superoinferior and anteroposterior directions, and that a large rectal volume influences the prostate motion with a cutoff value of 70 cm{sup 3}. Therefore, the treatment of patients with a rectal volume > 70 cm{sup 3} should be re-planned with appropriate rectal preparation. Keywords: Rectal volume; Prostate cancer; Three-dimensional conformal radiotherapy. (author)

Physics aspects of recent and future concepts in radiotherapy

International Nuclear Information System (INIS)

Georg, D.

2001-01-01

Full text: The development of 3-D conformal radiotherapy (3D-CRT), in which the high dose volume matches as closely as possible the target volume and avoids therefore normal tissue irradiation as far as possible, has been a major theme in radiotherapy for improving the therapeutic window. Conformal radiotherapy is not a new concept but only the technological improvements of the last decade allow its clinical implementation. More recent and advanced forms of 3D-CRT are intensity modulated radiotherapy (IMRT) and stereotactic radiotherapy (SRT). IMRT uses an additional degree of freedom to achieve a new class of conformation: the variation of the primary beam intensity. SRT is based on a three dimensional stereotactic coordinate system which is correlated with the patient and the treatment facility through modern imaging technology. IMRT and SRT are related by common features, e.g. high dose gradients and small fields which require a high geometric precision. A high dosimetric and geometric precision can only be based on a detailed knowledge of the patient specific anatomy. Therefore, IMRT and SRT need to underlie multi-modality imaging studies. Both IMRT and SRT utilize photon beams and multiple field arrangements which increase the volumes of healthy tissue receiving low doses. Photons have a low selectivity along the beam direction implying that the sharp dose gradients are to be compromised. The increased low dose volume as well as the low selectivity of photon beams can be over-come by using proton or ions. Brachytherapy, a form of radiotherapy where encapsuled radioactive sources are placed directly in or in the vicinity of the tumor, is by definition conformal. Endovascular brachytherapy has become a promising new field in radiotherapy for the prevention of (re)stenosis after angioplasty. Although many clinical trials have been performed during the last years specific aspects related to endovascular brachytherapy have not been addressed clearly, such as the

Covalent dye attachment influences the dynamics and conformational properties of flexible peptides.

Directory of Open Access Journals (Sweden)

Manuel P Luitz

Full Text Available Fluorescence spectroscopy techniques like Förster resonance energy transfer (FRET and fluorescence correlation spectroscopy (FCS have become important tools for the in vitro and in vivo investigation of conformational dynamics in biomolecules. These methods rely on the distance-dependent quenching of the fluorescence signal of a donor fluorophore either by a fluorescent acceptor fluorophore (FRET or a non-fluorescent quencher, as used in FCS with photoinduced electron transfer (PET. The attachment of fluorophores to the molecule of interest can potentially alter the molecular properties and may affect the relevant conformational states and dynamics especially of flexible biomolecules like intrinsically disordered proteins (IDP. Using the intrinsically disordered S-peptide as a model system, we investigate the impact of terminal fluorescence labeling on the molecular properties. We perform extensive molecular dynamics simulations on the labeled and unlabeled peptide and compare the results with in vitro PET-FCS measurements. Experimental and simulated timescales of end-to-end fluctuations were found in excellent agreement. Comparison between simulations with and without labels reveal that the π-stacking interaction between the fluorophore labels traps the conformation of S-peptide in a single dominant state, while the unlabeled peptide undergoes continuous conformational rearrangements. Furthermore, we find that the open to closed transition rate of S-peptide is decreased by at least one order of magnitude by the fluorophore attachment. Our approach combining experimental and in silico methods provides a benchmark for the simulations and reveals the significant effect that fluorescence labeling can have on the conformational dynamics of small biomolecules, at least for inherently flexible short peptides. The presented protocol is not only useful for comparing PET-FCS experiments with simulation results but provides a strategy to minimize the

Preliminary results of three-dimensional conformal radiotherapy for non-small cell lung cancer

International Nuclear Information System (INIS)

Wang Yingjie; Wang Luhua; Wang Xin; Feng Qinfu; Zhang Hongxing; Xiao Zefen; Yin Weibo

2005-01-01

Objective: To evaluate the therapeutic effects and complications of three-dimensional conformal radiotherapy (3DCRT) for non-small cell lung cancer (NSCLC). Methods: Between March 1999 and September 2003, 91 NSCLC patients treated with 3DCRT were reviewed at the Cancer Hospital, Chinese Academy of Medical Sciences. This patient cohort consisted of 73 men and 18 women. The median age was 66 years. Radio-therapy was delivered at 2 Gy fraction, 5 fractions per week. The median total dose was 60 Gy. Results: With a median follow-up time of 17 months, the response rate after 3DCRT was 57.1%, with complete remission 11.0% (10/91) and partial remission 46.2%(42/91). The median survival time (MST) was 16 months, with 1- and 2- year overall survivals (OS) of 67.0% and 32.6%, 1- and 2-year local progression free survivals (LPFS) of 82.6% and 53.0%, respectively. The independent adverse prognostic factors by univariate analysis and multivariate analysis was weight loss ≥5%. Grade 2 acute radiation pneumonitis was observed in 2 patients and grade 3 in 4 patients. Late lung injury developed in 1 patient with grade 2, 1 patient with grade 3, respectively. Acute radiation esophagitis was observed in 8 patients with grade 2. Acute grade 2 hematologic toxicity developed in 5 patients. Conclusions: 3DCRT was feasible in the treatment of NSCLC with good immediate tumor response and acceptable normal tissue complication. The total dose may potentially be increased. (authors)

Self-assembly, Dynamics and Chirality of Conformational Switches on Metal Surfaces Studied by UHV-STM

DEFF Research Database (Denmark)

Nuermaimaiti, Ajiguli

2013-01-01

structures formed by the conformational switches and statistical analysis of conformational states, a detailed study of dynamic processes is performed by acquiring time-resolved STM data. Furthermore, one of the possible applications of conformational switches towards inducing chirality in surface assemblies...

Practical recommendations for breathing-adapted radiotherapy

International Nuclear Information System (INIS)

Simon, L.; Giraud, P.; Rosenwald, J.C.; Dumas, J.L.; Lorchel, F.; Marre, D.; Dupont, S.; Varmenot, N.; Ginestet, C.; Caron, J.; Marchesi, V.; Ferreira, I.; Garcia, R.

2007-01-01

Respiration-gated radiotherapy offers a significant potential for improvement in the irradiation of tumor sites affected by respiratory motion such as lung, breast and liver tumors. An increased conformality of irradiation fields leading to decreased complications rates of organs at risk (lung, heart) is expected. Respiratory gating is in line with the need for improved precision required by radiotherapy techniques such as 3D conformal radiotherapy or intensity modulated radiotherapy. Reduction of respiratory motion can be achieved by using either breath-hold techniques or respiration synchronized gating techniques. Breath-hold techniques can be achieved with active techniques, in which airflow of the patient is temporarily blocked by a valve, or passive techniques, in which the patient voluntarily holds his/her breath. Synchronized gating techniques use external devices to predict the phase of the respiration cycle while the patient breaths freely. This work summarizes the different experiences of the centers of the STIC 2003 project. It describes the different techniques, gives an overview of the literature and proposes a practice based on our experience. (authors)

A correspondence between solution-state dynamics of an individual protein and the sequence and conformational diversity of its family.

Directory of Open Access Journals (Sweden)

Gregory D Friedland

2009-05-01

Full Text Available Conformational ensembles are increasingly recognized as a useful representation to describe fundamental relationships between protein structure, dynamics and function. Here we present an ensemble of ubiquitin in solution that is created by sampling conformational space without experimental information using "Backrub" motions inspired by alternative conformations observed in sub-Angstrom resolution crystal structures. Backrub-generated structures are then selected to produce an ensemble that optimizes agreement with nuclear magnetic resonance (NMR Residual Dipolar Couplings (RDCs. Using this ensemble, we probe two proposed relationships between properties of protein ensembles: (i a link between native-state dynamics and the conformational heterogeneity observed in crystal structures, and (ii a relation between dynamics of an individual protein and the conformational variability explored by its natural family. We show that the Backrub motional mechanism can simultaneously explore protein native-state dynamics measured by RDCs, encompass the conformational variability present in ubiquitin complex structures and facilitate sampling of conformational and sequence variability matching those occurring in the ubiquitin protein family. Our results thus support an overall relation between protein dynamics and conformational changes enabling sequence changes in evolution. More practically, the presented method can be applied to improve protein design predictions by accounting for intrinsic native-state dynamics.

Study on the photoneutrons produced in 15 MV medical linear accelerators : Comparison of three dimensional conformal radiotherapy and intensity modulated radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Yang, Oh Nam [Gangneung Asan Hospital, Gangneung (Korea, Republic of); Yang, Oh Nam; Lim, Cheong Hwan [Hanseo Univ., Seosan (Korea, Republic of)

2012-12-15

Intensity-modulated radiotherapy(IMRT) have the ability to provide better dose conformity and sparing of critical normal tissues than three-dimensional radiotherapy(3DCRT). Especially, with the benefit of health insurance in 2011, its use now increasingly in many modern radiotherapy departments. Also the use of linear accelerator with high-energy photon beams over 10 MV is increasing. As is well known, these linacs have the capacity to produce photoneutrons due to photonuclear reactions in materials with a large atomic number such as the target, flattening filters, collimators, and multi-leaf collimators(MLC). MLC-based IMRT treatments increase the monitor units and the probability of production of photoneutrons from photon-induced nuclear reactions. The purpose of this study is to quantitatively evaluate the dose of photoneutrons produced from 3DCRT and IMRT technique for Rando phantom in cervical cancer. We performed the treatment plans with 3DCRT and IMRT technique using Rando phantom for treatment of cervical cancer. An Rando phantom placed on the couch in the supine position was irradiated using 15 MV photon beams. Optically stimulated luminescence dosimeters(OSLD) were attached to 4 different locations (abdomen, chest, head and neck, eyes) and from center of field size and measured 5 times each of locations. Measured neutron dose from IMRT technique increased by 9.0, 8.6, 8.8, and 14 times than 3DCRT technique for abdomen, chest, head and neck, and eyes, respectively. When using IMRT with 15 MV photon beams, the photoneutrons contributed a significant portion on out-of-field. It is difficult to prevent high energy photon beams to produce the photoneutrons due to physical properties, if necessary, It is difficult to prevent high energy photon beams to produce the photoneutrons due to physical properties, if necessary, it is need to provide the additional safe shielding on a linear accelerator and should therefore reduce the out-of-field dose.

Study on the photoneutrons produced in 15 MV medical linear accelerators : Comparison of three dimensional conformal radiotherapy and intensity modulated radiotherapy

International Nuclear Information System (INIS)

Yang, Oh Nam; Yang, Oh Nam; Lim, Cheong Hwan

2012-01-01

Intensity-modulated radiotherapy(IMRT) have the ability to provide better dose conformity and sparing of critical normal tissues than three-dimensional radiotherapy(3DCRT). Especially, with the benefit of health insurance in 2011, its use now increasingly in many modern radiotherapy departments. Also the use of linear accelerator with high-energy photon beams over 10 MV is increasing. As is well known, these linacs have the capacity to produce photoneutrons due to photonuclear reactions in materials with a large atomic number such as the target, flattening filters, collimators, and multi-leaf collimators(MLC). MLC-based IMRT treatments increase the monitor units and the probability of production of photoneutrons from photon-induced nuclear reactions. The purpose of this study is to quantitatively evaluate the dose of photoneutrons produced from 3DCRT and IMRT technique for Rando phantom in cervical cancer. We performed the treatment plans with 3DCRT and IMRT technique using Rando phantom for treatment of cervical cancer. An Rando phantom placed on the couch in the supine position was irradiated using 15 MV photon beams. Optically stimulated luminescence dosimeters(OSLD) were attached to 4 different locations (abdomen, chest, head and neck, eyes) and from center of field size and measured 5 times each of locations. Measured neutron dose from IMRT technique increased by 9.0, 8.6, 8.8, and 14 times than 3DCRT technique for abdomen, chest, head and neck, and eyes, respectively. When using IMRT with 15 MV photon beams, the photoneutrons contributed a significant portion on out-of-field. It is difficult to prevent high energy photon beams to produce the photoneutrons due to physical properties, if necessary, It is difficult to prevent high energy photon beams to produce the photoneutrons due to physical properties, if necessary, it is need to provide the additional safe shielding on a linear accelerator and should therefore reduce the out-of-field dose

Setup accuracy of stereoscopic X-ray positioning with automated correction for rotational errors in patients treated with conformal arc radiotherapy for prostate cancer

International Nuclear Information System (INIS)

Soete, Guy; Verellen, Dirk; Tournel, Koen; Storme, Guy

2006-01-01

We evaluated setup accuracy of NovalisBody stereoscopic X-ray positioning with automated correction for rotational errors with the Robotics Tilt Module in patients treated with conformal arc radiotherapy for prostate cancer. The correction of rotational errors was shown to reduce random and systematic errors in all directions. (NovalisBody TM and Robotics Tilt Module TM are products of BrainLAB A.G., Heimstetten, Germany)

Clinical results of conformal versus intensity-modulated radiotherapy using a focal simultaneous boost for muscle-invasive bladder cancer in elderly or medically unfit patients.

Science.gov (United States)

Lutkenhaus, Lotte J; van Os, Rob M; Bel, Arjan; Hulshof, Maarten C C M

2016-03-18

For elderly or medically unfit patients with muscle-invasive bladder cancer, cystectomy or chemotherapy are contraindicated. This leaves radical radiotherapy as the only treatment option. It was the aim of this study to retrospectively analyze the treatment outcome and associated toxicity of conformal versus intensity-modulated radiotherapy (IMRT) using a focal simultaneous tumor boost for muscle-invasive bladder cancer in patients not suitable for cystectomy. One hundred eighteen patients with T2-4 N0-1 M0 bladder cancer were analyzed retrospectively. Median age was 80 years. Treatment consisted of either a conformal box technique or IMRT and included a simultaneous boost to the tumor. To enable an accurate boost delivery, fiducial markers were placed around the tumor. Patients were treated with 40 Gy in 20 fractions to the elective treatment volumes, and a daily tumor boost up to 55-60 Gy. Clinical complete response was seen in 87 % of patients. Three-year overall survival was 44 %, with a locoregional control rate of 73 % at 3 years. Toxicity was low, with late urinary and intestinal toxicity rates grade ≥ 2 of 14 and 5 %, respectively. The use of IMRT reduced late intestinal toxicity, whereas fiducial markers reduced acute urinary toxicity. Radical radiotherapy using a focal boost is feasible and effective for elderly or unfit patients, with a 3-year locoregional control of 73 %. Toxicity rates were low, and were reduced by the use of IMRT and fiducial markers.

Hypo fractionated conformal irradiation of patients with malignant glioma

International Nuclear Information System (INIS)

Aboziada, M.A.; Abo-Kresha, A.E.

2012-01-01

Purpose: The aim of the study is to evaluate the effect of a conformal irradiation in short fractionation scheme of 49.5 Gy in 15 fractions in an overall time of 3 weeks, in terms of overall survival (OAS) and progression free survival (PFS) rates in brain glioma patients. Patients and methods: A prospective study was conducted on 54 brain glioma patients and was carried out in the Radiation Oncology Department, South Egypt Cancer Institute, Assiut University during the period from April 2006 till June 2009. Patients were treated by hypo fractionated conformal irradiation (49.5 Gy/15 fractions/3 weeks). Results: The median follow up was 23 months (range: 9-39 months). Two-year OAS and PFS rates were 68% and 60%, respectively. In univariate analysis, age > 50 years, poor performance status [Karnofasky score of >40- 50 years and glioblastoma pathology were the only independent prognostic factors that were associated with poor OAS (p = 0.003 and p = 0.004, respectively), and PFS (p = 0.027 and p = 0.011, respectively). Conclusion: Hypo fractionated conformal radiotherapy was as effective as the conventional radiotherapy, with time sparing for patients, and for radiation oncology centers. Hypo fractionated radiotherapy may be considered the radiotherapy regimen of choice in clinical practice for patients with gliomas

Comparison of mucous and cutaneous toxicity of IMRT and of conventional radiotherapy associated with cetuximab; Comparaison de la toxicite muqueuse et cutanee de la RCMI et de la radiotherapie classique associee au cetuximab

Energy Technology Data Exchange (ETDEWEB)

Kreps, S.; Tamby, E.; Dessard Diana, B.; Berges, O.; Botti, M.; Deberne, M.; Henni, M.; Durdux, C.; Housset, M.; Giraud, P. [Hopital europeen Georges-Pompidou, Paris (France)

2011-10-15

The authors report a retrospective assessment of acute, cutaneous and mucous toxicity resulting from an association of cetuximab and conventional conformational radiotherapy, and from an intensity-modulated conformational radiotherapy (IMRT). Seven patients presenting nasopharyngeal, oropharyngeal or hypopharyngeal tumours have been irradiated with intensity modulation, and seven without. It appears that the association of cetuximab and radiotherapy is not well tolerated and requires a close monitoring. Intensity-modulated radiotherapy allows a significant reduction of dose and of toxicity. However, mucous toxicity remains significant. Short communication

Characterization of conformational dynamics of bistable RNA by equilibrium and non-equilibrium NMR.

Science.gov (United States)

Fürtig, Boris; Reining, Anke; Sochor, Florian; Oberhauser, Eva Marie; Heckel, Alexander; Schwalbe, Harald

2014-12-19

Unlike proteins, a given RNA sequence can adopt more than a single conformation. The two (or more) conformations are long-lived and have similar stabilities, but interconvert only slowly. Such bi- or multistability is often linked to the biological functions of the RNA. This unit describes how nuclear magnetic resonance (NMR) spectroscopy can be used to characterize the conformational dynamics of bistable RNAs. Copyright © 2014 John Wiley & Sons, Inc.

The situation of radiotherapy in 2011

International Nuclear Information System (INIS)

2012-06-01

Published within the frame of the French 2009-2013 cancer plan, this report proposes an analysis of the situation of radiotherapy in France. More particularly, it analyses the French offer in terms of radiotherapy treatments and the French position in Europe. A second part analyses equipment (accelerators and other equipment) and techniques aimed at radiotherapy treatment preparation and delivery. The following techniques are addressed: three-dimensional conformational, intensity modulation, intracranial and extracranial stereotactic, image-guided, total body irradiation, hadron-therapy, and peri-operative radiotherapy. The last parts analyse the activity of radiotherapy centres in terms of treated patients, of patient age structure, of sessions and preparations, and of treated pathologies, the medical and paramedical personnel in charge of radiotherapy, and financial and cost aspects

Extracting Markov Models of Peptide Conformational Dynamics from Simulation Data.

Science.gov (United States)

Schultheis, Verena; Hirschberger, Thomas; Carstens, Heiko; Tavan, Paul

2005-07-01

A high-dimensional time series obtained by simulating a complex and stochastic dynamical system (like a peptide in solution) may code an underlying multiple-state Markov process. We present a computational approach to most plausibly identify and reconstruct this process from the simulated trajectory. Using a mixture of normal distributions we first construct a maximum likelihood estimate of the point density associated with this time series and thus obtain a density-oriented partition of the data space. This discretization allows us to estimate the transfer operator as a matrix of moderate dimension at sufficient statistics. A nonlinear dynamics involving that matrix and, alternatively, a deterministic coarse-graining procedure are employed to construct respective hierarchies of Markov models, from which the model most plausibly mapping the generating stochastic process is selected by consideration of certain observables. Within both procedures the data are classified in terms of prototypical points, the conformations, marking the various Markov states. As a typical example, the approach is applied to analyze the conformational dynamics of a tripeptide in solution. The corresponding high-dimensional time series has been obtained from an extended molecular dynamics simulation.

Metastatic breast cancer in the eye and orbit, use three-dimensional conformal radiotherapy. Our first experience

International Nuclear Information System (INIS)

Correa Pablos, Tamara; Caceres Toledo, Maria

2009-01-01

The eye and orbit metastases are a significant clinical problem, both by the inability and the deterioration in the quality of life that occur. The most common malignant tumors in the eye and orbit is metastasis. Cancer breast cancer is the most common tumor metastatic to the eye and orbit in a 40% and 50% of cases according to different series. With the introduction of Three-Dimensional Conformal Radiotherapy (3D-CRT) in our hospital from In 2007 we were able to treat patients with cancer different regions with the technique (2D) was impossible because caused irreparable damage to surrounding healthy tissue in this way thanks to potential of 3D technology to shape the planning volume will ensure greater protection for critical organs. (Author)

Conformity index: A review

International Nuclear Information System (INIS)

Feuvret, Loic; Noel, Georges; Mazeron, Jean-Jacques; Bey, Pierre

2006-01-01

We present a critical analysis of the conformity indices described in the literature and an evaluation of their field of application. Three-dimensional conformal radiotherapy, with or without intensity modulation, is based on medical imaging techniques, three-dimensional dosimetry software, compression accessories, and verification procedures. It consists of delineating target volumes and critical healthy tissues to select the best combination of beams. This approach allows better adaptation of the isodose to the tumor volume, while limiting irradiation of healthy tissues. Tools must be developed to evaluate the quality of proposed treatment plans. Dosimetry software provides the dose distribution in each CT section and dose-volume histograms without really indicating the degree of conformity. The conformity index is a complementary tool that attributes a score to a treatment plan or that can compare several treatment plans for the same patient. The future of conformal index in everyday practice therefore remains unclear

Rotational radiotherapy for prostate cancer in clinical practice

DEFF Research Database (Denmark)

Aznar, Marianne C; Petersen, Peter Meidahl; Logadottir, Ashildur

2010-01-01

Radiotherapy is the standard treatment in locally advanced prostate cancer. The latest technological improvement is modulated rotational radiotherapy, where one single rotation of the treatment machine is used to conform the dose delivery to the target and spare organs at risk, requiring less than...

Assessment of renal function after conformal radiotherapy and intensity-modulated radiotherapy by functional 1H-MRI and 23Na-MRI

International Nuclear Information System (INIS)

Haneder, S.; Michaely, H.J.; Schoenberg, S.O.; Konstandin, S.; Schad, L.R.; Siebenlist, K.; Wertz, H.; Wenz, F.; Lohr, F.; Boda-Heggemann, J.

2012-01-01

Purpose: Adjuvant radiochemotherapy (RCHT) improves survival of patients with locally advanced gastric cancer. Conventional three-dimensional conformal radiotherapy (3D-CRT) results in ablative doses to a significant amount of the left kidney, while image-guided intensity-modulated radiotherapy (IG-IMRT) provides excellent target coverage with improved kidney sparing. Few long-term results on IMRT for gastric cancer, however, have been published. Functional magnetic resonance imaging (fMRI) at 3.0 T including blood oxygenation-level dependent (BOLD) imaging, diffusion-weighted imaging (DWI) and, for the first time, 23 Na imaging was used to evaluate renal status after radiotherapy with 3D-CRT or IG-IMRT. Patients and methods Four disease-free patients (2 after 3D-CRT and 2 after IMRT; FU for all patients > 5 years) were included in this feasibility study. Morphological sequences, axial DWI images, 2D-gradient echo (GRE)-BOLD images, and 23 Na images were acquired. Mean values/standard deviations for ( 23 Na), the apparent diffusion coefficient (ADC), and R2 * values were calculated for the upper/middle/lower parts of both kidneys. Corticomedullary 23 Na-concentration gradients were determined. Results: Surprisingly, IG-IMRT patients showed no morphological alterations and no statistically significant differences of ADC and R2 * values in all renal parts. Values for mean corticomedullary 23 Na-concentration matched those for healthy volunteers. Results were similar in 3D-CRT patients, except for the cranial part of the left kidney. This was atrophic and presented significantly reduced functional parameters (p = 0.001 - p = 0.033). Reduced ADC values indicated reduced cell density and reduced extracellular space. Cortical and medullary R2 * values of the left cranial kidney in the 3D-CRT group were higher, indicating more deoxygenated hemoglobin due to reduced blood flow/oxygenation. ( 23 Na) of the renal cranial parts in the 3D-CRT group was significantly reduced

Comparison of mucous and cutaneous toxicity of IMRT and of conventional radiotherapy associated with cetuximab

International Nuclear Information System (INIS)

Kreps, S.; Tamby, E.; Dessard Diana, B.; Berges, O.; Botti, M.; Deberne, M.; Henni, M.; Durdux, C.; Housset, M.; Giraud, P.

2011-01-01

The authors report a retrospective assessment of acute, cutaneous and mucous toxicity resulting from an association of cetuximab and conventional conformational radiotherapy, and from an intensity-modulated conformational radiotherapy (IMRT). Seven patients presenting nasopharyngeal, oropharyngeal or hypopharyngeal tumours have been irradiated with intensity modulation, and seven without. It appears that the association of cetuximab and radiotherapy is not well tolerated and requires a close monitoring. Intensity-modulated radiotherapy allows a significant reduction of dose and of toxicity. However, mucous toxicity remains significant. Short communication

A comparison of swallowing dysfunction after three-dimensional conformal and intensity-modulated radiotherapy. A systematic review by the Italian Head and Neck Radiotherapy Study Group

International Nuclear Information System (INIS)

Ursino, Stefano; Morganti, Riccardo; Cristaudo, Agostino; Paiar, Fabiola; D'Angelo, Elisa; Lohr, Frank; Mazzola, Rosario; Merlotti, Anna; Russi, Elvio Grazioso; Musio, Daniela; Alterio, Daniela; Bacigalupo, Almalina

2017-01-01

Dysphagia is one of the most important treatment-related side effects in head and neck cancer (HNC), as it can lead to severe life-threating complications such as aspiration pneumonia and malnutrition. Intensity-modulated radiotherapy (IMRT) could reduce swallowing dysfunction by producing a concave dose distribution and reducing doses to the swallowing-related organs at risk (SWOARs). The aim of this study was to review the current literature in order to compare swallowing outcomes between IMRT and three-dimensional conformal radiotherapy (3DCRT). A search was conducted in the PubMed and Embase databases to identify studies on swallowing outcomes, both clinically and/or instrumentally assessed, after 3DCRT and IMRT. Dysphagia-specific quality of life and objective instrumental data are summarized and discussed. A total of 262 papers were retrieved from the searched databases. An additional 23 papers were retrieved by hand-searching the reference lists. Ultimately, 22 papers were identified which discussed swallowing outcomes after 3DCRT and IMRT for HNC. No outcomes from randomized trials were identified. Despite several methodological limitations, reports from the current literature seem to suggest better swallowing outcomes with IMRT compared to 3DCRT. Further improvements are likely to result from the increased use of IMRT plans optimized for SWOAR sparing. (orig.) [de

Radiotherapy and Brachytherapy : Proceedings of the NATO Advanced Study Institute on Physics of Modern Radiotherapy & Brachytherapy

CERN Document Server

Lemoigne, Yves

2009-01-01

This volume collects a series of lectures presented at the tenth ESI School held at Archamps (FR) in November 2007 and dedicated to radiotherapy and brachytherapy. The lectures focus on the multiple facets of radiotherapy in general, including external radiotherapy (often called teletherapy) as well as internal radiotherapy (called brachytherapy). Radiotherapy strategy and dose management as well as the decisive role of digital imaging in the associated clinical practice are developed in several articles. Grouped under the discipline of Conformal Radiotherapy (CRT), numerous modern techniques, from Multi-Leaf Collimators (MLC) to Intensity Modulated RadioTherapy (IMRT), are explained in detail. The importance of treatment planning based upon patient data from digital imaging (Computed Tomography) is also underlined. Finally, despite the quasi- totality of patients being presently treated with gamma and X-rays, novel powerful tools are emerging using proton and light ions (like carbon ions) beams, bound to bec...

Role of conformational dynamics in kinetics of an enzymatic cycle in a nonequilibrium steady state

Science.gov (United States)

Min, Wei; Xie, X. Sunney; Bagchi, Biman

2009-08-01

Enzyme is a dynamic entity with diverse time scales, ranging from picoseconds to seconds or even longer. Here we develop a rate theory for enzyme catalysis that includes conformational dynamics as cycling on a two-dimensional (2D) reaction free energy surface involving an intrinsic reaction coordinate (X) and an enzyme conformational coordinate (Q). The validity of Michaelis-Menten (MM) equation, i.e., substrate concentration dependence of enzymatic velocity, is examined under a nonequilibrium steady state. Under certain conditions, the classic MM equation holds but with generalized microscopic interpretations of kinetic parameters. However, under other conditions, our rate theory predicts either positive (sigmoidal-like) or negative (biphasic-like) kinetic cooperativity due to the modified effective 2D reaction pathway on X-Q surface, which can explain non-MM dependence previously observed on many monomeric enzymes that involve slow or hysteretic conformational transitions. Furthermore, we find that a slow conformational relaxation during product release could retain the enzyme in a favorable configuration, such that enzymatic turnover is dynamically accelerated at high substrate concentrations. The effect of such conformation retainment in a nonequilibrium steady state is evaluated.

Brownian dynamics simulation of the cross-talking effect among modified histones on conformations of nucleosomes

Science.gov (United States)

Duan, Zhao-Wen; Li, Wei; Xie, Ping; Dou, Shuo-Xing; Wang, Peng-Ye

2010-04-01

Using Brownian dynamics simulation, we studied the effect of histone modifications on conformations of an array of nucleosomes in a segment of chromatin. The simulation demonstrated that the segment of chromatin shows the dynamic behaviour that its conformation can switch between a state with nearly all of the histones being wrapped by DNA and a state with nearly all of the histones being unwrapped by DNA, thus involving the “cross-talking" interactions among the histones. Each state can stay for a sufficiently long time. These conformational states are essential for gene expression or gene silence. The simulation also shows that these conformational states can be inherited by the daughter DNAs during DNA replication, giving a theoretical explanation of the epigenetic phenomenon.

Esophageal perforation during or after conformal radiotherapy for esophageal carcinoma

International Nuclear Information System (INIS)

Chen Haiyan; Ma Xiumei; Ye Ming; Hou Yanli; Xie Huaying; Bai Yongrui

2014-01-01

The aim of this study was to analyze the risk factors and prognosis for patients with esophageal perforation occurring during or after radiotherapy for esophageal carcinoma. We retrospectively analyzed 322 patients with esophageal carcinoma. These patients received radiotherapy for unresectable esophageal tumors, residual tumors after operation, or local recurrence. Of these, 12 had radiotherapy to the esophagus before being admitted, 68 patients had concurrent chemoradiotherapy (CRT), and 18 patients had esophageal perforation after RT (5.8%). Covered self-expandable metallic stents were placed in 11 patients. Two patients continued RT after stenting and control of infection; one of these suffered a new perforation, and the other had a massive hemorrhage. The median overall survival was 2 months (0-3 months) compared with 17 months in the non-perforation group. In univariate analysis, the Karnofsky performance status (KPS) being ≤ 70, age younger than 60, T4 stage, a second course of radiotherapy to the esophagus, extracapsular lymph nodes (LN) involving the esophagus, a total dose > 100 Gy (biologically effective dose -10 ), and CRT were risk factors for perforation. In multivariate analysis, age younger than 60, extracapsular LN involving the esophagus, T4 stage, and a second course of radiotherapy to the esophagus were risk factors. In conclusion, patients with T4 stage, extracapsular LN involving the esophagus, and those receiving a second course of RT should be given particular care to avoid perforation. The prognosis after perforation was poor. (author)

SU-E-T-346: Effect of Jaw Position On Dose to Critical Structures in 3-D Conformal Radiotherapy Treatment of Pancreatic Cancer

Energy Technology Data Exchange (ETDEWEB)

Paudel, N; Han, E; Liang, X; Morrill, S; Zhang, X; Hardee, M; Penagaricano, J; Ratanatharathorn, V [Vaneerat, University of Arkansas for Medical Sciences, Little Rock, AR (United States)

2015-06-15

Purpose: Three-dimensional conformal therapy remains a valid and widely used modality for pancreatic radiotherapy treatment. It usually meets dose constraints on critical structures. However, careful positioning of collimation jaws can reduce dose to the critical structures. Here we investigate the dosimetric effect of jaw position in MLC-based 3-D conformal treatment planning on critical structures. Methods: We retrospectively selected seven pancreatic cancer patients treated with 3-D conformal radiotherapy. We started with treatment plans (Varian Truebeam LINAC, Eclipse TPS, AAA, 18MV) having both x and y jaws aligned with the farthest extent of the block outline (8mm around PTV). Then we subsequently moved either both x-jaws or all x and y jaws outwards upto 3 cm in 1 cm increments and investigated their effect on average and maximum dose to neighboring critical structures keeping the same coverage to treatment volume. Results: Lateral displacement of both x-jaws by 1cm each increased kidney and spleen mean dose by as much as 1.7% and 1.3% respectively and superior inferior displacement increased liver, right kidney, stomach and spleen dose by as much as 2.1%, 2%, 5.2% and 1.6% respectively. Displacement of all x and y-jaws away by 1cm increased the mean dose to liver, right kidney, left kidney, bowels, cord, stomach and spleen by as much as 4.9%, 5.9%, 2.1%, 2.8%, 7.4%, 10.4% and 4.2% respectively. Percentage increase in mean dose due to 2 and 3cm jaw displacement increased almost linearly with the displaced distance. Changes in maximum dose were much smaller (mostly negligible) than the changes in mean dose. Conclusion: Collimation jaw position affects dose mostly to critical structures adjacent to it. Though treatment plans with MLCs conforming the block margin usually meet dose constraints to critical structures, keeping jaws all the way in, to the edge of the block reduces dose to the critical structures during radiation treatment.

Conformational dynamics of ATP/Mg:ATP in motor proteins via data mining and molecular simulation

Science.gov (United States)

Bojovschi, A.; Liu, Ming S.; Sadus, Richard J.

2012-08-01

The conformational diversity of ATP/Mg:ATP in motor proteins was investigated using molecular dynamics and data mining. Adenosine triphosphate (ATP) conformations were found to be constrained mostly by inter cavity motifs in the motor proteins. It is demonstrated that ATP favors extended conformations in the tight pockets of motor proteins such as F1-ATPase and actin whereas compact structures are favored in motor proteins such as RNA polymerase and DNA helicase. The incorporation of Mg2+ leads to increased flexibility of ATP molecules. The differences in the conformational dynamics of ATP/Mg:ATP in various motor proteins was quantified by the radius of gyration. The relationship between the simulation results and those obtained by data mining of motor proteins available in the protein data bank is analyzed. The data mining analysis of motor proteins supports the conformational diversity of the phosphate group of ATP obtained computationally.

Clinical results of conformal versus intensity-modulated radiotherapy using a focal simultaneous boost for muscle-invasive bladder cancer in elderly or medically unfit patients

International Nuclear Information System (INIS)

Lutkenhaus, Lotte J.; Os, Rob M. van; Bel, Arjan; Hulshof, Maarten C. C. M.

2016-01-01

For elderly or medically unfit patients with muscle-invasive bladder cancer, cystectomy or chemotherapy are contraindicated. This leaves radical radiotherapy as the only treatment option. It was the aim of this study to retrospectively analyze the treatment outcome and associated toxicity of conformal versus intensity-modulated radiotherapy (IMRT) using a focal simultaneous tumor boost for muscle-invasive bladder cancer in patients not suitable for cystectomy. One hundred eighteen patients with T2-4 N0-1 M0 bladder cancer were analyzed retrospectively. Median age was 80 years. Treatment consisted of either a conformal box technique or IMRT and included a simultaneous boost to the tumor. To enable an accurate boost delivery, fiducial markers were placed around the tumor. Patients were treated with 40 Gy in 20 fractions to the elective treatment volumes, and a daily tumor boost up to 55–60 Gy. Clinical complete response was seen in 87 % of patients. Three-year overall survival was 44 %, with a locoregional control rate of 73 % at 3 years. Toxicity was low, with late urinary and intestinal toxicity rates grade ≥ 2 of 14 and 5 %, respectively. The use of IMRT reduced late intestinal toxicity, whereas fiducial markers reduced acute urinary toxicity. Radical radiotherapy using a focal boost is feasible and effective for elderly or unfit patients, with a 3-year locoregional control of 73 %. Toxicity rates were low, and were reduced by the use of IMRT and fiducial markers. The online version of this article (doi:10.1186/s13014-016-0618-6) contains supplementary material, which is available to authorized users

Dosimetric Comparison of Three-Dimensional Conformal Proton Radiotherapy, Intensity-Modulated Proton Therapy, and Intensity-Modulated Radiotherapy for Treatment of Pediatric Craniopharyngiomas

Energy Technology Data Exchange (ETDEWEB)

Boehling, Nicholas S. [Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States); Grosshans, David R., E-mail: dgrossha@mdanderson.org [Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States); Bluett, Jaques B. [Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States); Palmer, Matthew T. [Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States); Song, Xiaofei; Amos, Richard A.; Sahoo, Narayan [Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States); Meyer, Jeffrey J.; Mahajan, Anita; Woo, Shiao Y. [Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX (United States)

2012-02-01

Purpose: Cranial irradiation in pediatric patients is associated with serious long-term adverse effects. We sought to determine whether both three-dimensional conformal proton radiotherapy (3D-PRT) and intensity-modulated proton therapy (IMPT) compared with intensity-modulated radiotherapy (IMRT) decrease integral dose to brain areas known to harbor neuronal stem cells, major blood vessels, and other normal brain structures for pediatric patients with craniopharyngiomas. Methods and Materials: IMRT, forward planned, passive scattering proton, and IMPT plans were generated and optimized for 10 pediatric patients. The dose was 50.4 Gy (or cobalt Gy equivalent) delivered in 28 fractions with the requirement for planning target volume (PTV) coverage of 95% or better. Integral dose data were calculated from differential dose-volume histograms. Results: The PTV target coverage was adequate for all modalities. IMRT and IMPT yielded the most conformal plans in comparison to 3D-PRT. Compared with IMRT, 3D-PRT and IMPT plans had a relative reduction of integral dose to the hippocampus (3D-PRT, 20.4; IMPT, 51.3%{sup Asterisk-Operator }), dentate gyrus (27.3, 75.0%{sup Asterisk-Operator }), and subventricular zone (4.5, 57.8%{sup Asterisk-Operator }). Vascular organs at risk also had reduced integral dose with the use of proton therapy (anterior cerebral arteries, 33.3{sup Asterisk-Operator }, 100.0%{sup Asterisk-Operator }; middle cerebral arteries, 25.9%{sup Asterisk-Operator }, 100%{sup Asterisk-Operator }; anterior communicating arteries, 30.8{sup Asterisk-Operator }, 41.7%{sup Asterisk-Operator }; and carotid arteries, 51.5{sup Asterisk-Operator }, 77.6{sup Asterisk-Operator }). Relative reduction of integral dose to the infratentorial brain (190.7{sup Asterisk-Operator }, 109.7%{sup Asterisk-Operator }), supratentorial brain without PTV (9.6, 26.8%{sup Asterisk-Operator }), brainstem (45.6, 22.4%{sup Asterisk-Operator }), and whole brain without PTV (19.4{sup Asterisk

A custom made phantom for dosimetric audit and quality assurance of three-dimensional conformal radiotherapy

International Nuclear Information System (INIS)

Radaideh, K.M.; Matalqah, L.M.; Matalqah, L.M.; Tajuddin, A.A.; Luen, F.W.L.; Bauk, S.; Abdel Munem, E.M.E.

2012-01-01

The ultimate check of the actual dose delivered to a patient in radiotherapy can be achieved by using dosimetric measurements. The aims of this study were to develop and evaluate a custom handmade head and neck phantom for evaluation of Three-Dimensional Conformal Radiation Therapy (3D-CRT) dose planning and delivery. A phantom of head and neck region of a medium built male patient with nasopharyngeal cancer was constructed from Perspex material. Primary and secondary Planning Target Volume (PTV) and twelve Organs at Risk (OAR) were delineated using Treatment Planning System (TPS) guided by computed tomography printout transverse images. One hundred and seven (107) holes distributed among the organs were loaded with Rod-shaped Thermoluminescent dosimeters (LiF:Mg, Ti TLDs) after common and individual calibration. Head and neck phantom was imaged, planned and irradiated conformally (3D-CRT) by linear accelerator (LINAC Siemens Artiste). The planned predicted doses by TPS at PTV and OAR regions were obtained and compared with the TLD measured doses using the phantom. Repeated TLD measurements were reproducible with a percent standard deviation of < 3.5 %. Moreover, the average of dose discrepancies between TLDs reading and TPS predicted doses were found to be < 5.3 %. The phantom's preliminary results have proved to be a valuable tool for 3D-CRT treatment dose verification. (author)

Binding mechanism and dynamic conformational change of C subunit of PKA with different pathways.

Science.gov (United States)

Chu, Wen-Ting; Chu, Xiakun; Wang, Jin

2017-09-19

The catalytic subunit of PKA (PKAc) exhibits three major conformational states (open, intermediate, and closed) during the biocatalysis process. Both ATP and substrate/inhibitor can effectively induce the conformational changes of PKAc from open to closed states. Aiming to explore the mechanism of this allosteric regulation, we developed a coarse-grained model and analyzed the dynamics of conformational changes of PKAc during binding by performing molecular dynamics simulations for apo PKAc, binary PKAc (PKAc with ATP, PKAc with PKI), and ternary PKAc (PKAc with ATP and PKI). Our results suggest a mixed binding mechanism of induced fit and conformational selection, with the induced fit dominant. The ligands can drive the movements of Gly-rich loop as well as some regions distal to the active site in PKAc and stabilize them at complex state. In addition, there are two parallel pathways (pathway with PKAc-ATP as an intermediate and pathway PKAc-PKI as an intermediate) during the transition from open to closed states. By molecular dynamics simulations and rate constant analyses, we find that the pathway through PKAc-ATP intermediate is the main binding route from open to closed state because of the fact that the bound PKI will hamper ATP from successful binding and significantly increase the barrier for the second binding subprocess. These findings will provide fundamental insights of the mechanisms of PKAc conformational change upon binding.

Conformational dynamics of amyloid proteins at the aqueous interface

Science.gov (United States)

Armbruster, Matthew; Horst, Nathan; Aoki, Brendy; Malik, Saad; Soto, Patricia

2013-03-01

Amyloid proteins is a class of proteins that exhibit distinct monomeric and oligomeric conformational states hallmark of deleterious neurological diseases for which there are not yet cures. Our goal is to examine the extent of which the aqueous/membrane interface modulates the folding energy landscape of amyloid proteins. To this end, we probe the dynamic conformational ensemble of amyloids (monomer prion protein and Alzheimer's Ab protofilaments) interacting with model bilayers. We will present the results of our coarse grain molecular modeling study in terms of the existence of preferential binding spots of the amyloid to the bilayer and the response of the bilayer to the interaction with the amyloid. NSF Nebraska EPSCoR First Award

Hippocampal sparing radiotherapy for pediatric medulloblastoma: impact of treatment margins and treatment technique.

Science.gov (United States)

Brodin, N Patrik; Munck af Rosenschöld, Per; Blomstrand, Malin; Kiil-Berthlesen, Anne; Hollensen, Christian; Vogelius, Ivan R; Lannering, Birgitta; Bentzen, Søren M; Björk-Eriksson, Thomas

2014-04-01

We investigated how varying the treatment margin and applying hippocampal sparing and proton therapy impact the risk of neurocognitive impairment in pediatric medulloblastoma patients compared with current standard 3D conformal radiotherapy. We included 17 pediatric medulloblastoma patients to represent the variability in tumor location relative to the hippocampal region. Treatment plans were generated using 3D conformal radiotherapy, hippocampal sparing intensity-modulated radiotherapy, and spot-scanned proton therapy, using 3 different treatment margins for the conformal tumor boost. Neurocognitive impairment risk was estimated based on dose-response models from pediatric CNS malignancy survivors and compared among different margins and treatment techniques. Mean hippocampal dose and corresponding risk of cognitive impairment were decreased with decreasing treatment margins (P < .05). The largest risk reduction, however, was seen when applying hippocampal sparing proton therapy-the estimated risk of impaired task efficiency (95% confidence interval) was 92% (66%-98%), 81% (51%-95%), and 50% (30%-70%) for 3D conformal radiotherapy, intensity-modulated radiotherapy, and proton therapy, respectively, for the smallest boost margin and 98% (78%-100%), 90% (60%-98%), and 70% (39%-90%) if boosting the whole posterior fossa. Also, the distance between the closest point of the planning target volume and the center of the hippocampus can be used to predict mean hippocampal dose for a given treatment technique. We estimate a considerable clinical benefit of hippocampal sparing radiotherapy. In choosing treatment margins, the tradeoff between margin size and risk of neurocognitive impairment quantified here should be considered.

Brownian dynamics simulation of the cross-talking effect among modified histones on conformations of nucleosomes

International Nuclear Information System (INIS)

Zhao-Wen, Duan; Wei, Li; Ping, Xie; Shuo-Xing, Dou; Peng-Ye, Wang

2010-01-01

Using Brownian dynamics simulation, we studied the effect of histone modifications on conformations of an array of nucleosomes in a segment of chromatin. The simulation demonstrated that the segment of chromatin shows the dynamic behaviour that its conformation can switch between a state with nearly all of the histones being wrapped by DNA and a state with nearly all of the histones being unwrapped by DNA, thus involving the “cross-talking” interactions among the histones. Each state can stay for a sufficiently long time. These conformational states are essential for gene expression or gene silence. The simulation also shows that these conformational states can be inherited by the daughter DNAs during DNA replication, giving a theoretical explanation of the epigenetic phenomenon. (cross-disciplinary physics and related areas of science and technology)

Digital linear accelerator: The advantages for radiotherapy

International Nuclear Information System (INIS)

Andric, S.; Maksimovic, M.; Dekic, M.; Clark, T.

1998-01-01

Technical performances of Digital Linear Accelerator were presented to point out its advantages for clinical radiotherapy treatment. The accelerator installation is earned out at Military Medical Academy, Radiotherapy Department, by Medes and Elekta companies. The unit offers many technical advantages with possibility of introduction new conformal treatment techniques as stereotactic radiosurgery, total body and total skin irradiation. In the paper are underlined advantages in relation to running conventional accelerator units at Yugoslav radiotherapy departments, both from technical and medical point of view. (author)

Molecular Dynamics Simulations of Insulin: Elucidating the Conformational Changes that Enable Its Binding.

Directory of Open Access Journals (Sweden)

Anastasios Papaioannou

Full Text Available A sequence of complex conformational changes is required for insulin to bind to the insulin receptor. Recent experimental evidence points to the B chain C-terminal (BC-CT as the location of these changes in insulin. Here, we present molecular dynamics simulations of insulin that reveal new insights into the structural changes occurring in the BC-CT. We find three key results: 1 The opening of the BC-CT is inherently stochastic and progresses through an open and then a "wide-open" conformation--the wide-open conformation is essential for receptor binding, but occurs only rarely. 2 The BC-CT opens with a zipper-like mechanism, with a hinge at the Phe24 residue, and is maintained in the dominant closed/inactive state by hydrophobic interactions of the neighboring Tyr26, the critical residue where opening of the BC-CT (activation of insulin is initiated. 3 The mutation Y26N is a potential candidate as a therapeutic insulin analogue. Overall, our results suggest that the binding of insulin to its receptor is a highly dynamic and stochastic process, where initial docking occurs in an open conformation and full binding is facilitated through interactions of insulin receptor residues with insulin in its wide-open conformation.

Skin-sparing Helical Tomotherapy vs 3D-conformal Radiotherapy for Adjuvant Breast Radiotherapy: In Vivo Skin Dosimetry Study

International Nuclear Information System (INIS)

Capelle, Lisa; Warkentin, Heather; MacKenzie, Marc; Joseph, Kurian; Gabos, Zsolt; Pervez, Nadeem; Tankel, Keith; Chafe, Susan; Amanie, John; Ghosh, Sunita; Parliament, Matthew; Abdulkarim, Bassam

2012-01-01

Purpose: We investigated whether treatment-planning system (TPS)-calculated dose accurately reflects skin dose received for patients receiving adjuvant breast radiotherapy (RT) with standard three-dimensional conformal RT (3D-CRT) or skin-sparing helical tomotherapy (HT). Methods and Materials: Fifty patients enrolled in a randomized controlled trial investigating acute skin toxicity from adjuvant breast RT with 3D-CRT compared to skin-sparing HT, where a 5-mm strip of ipsilateral breast skin was spared. Thermoluminescent dosimetry or optically stimulated luminescence measurements were made in multiple locations and were compared to TPS-calculated doses. Skin dosimetric parameters and acute skin toxicity were recorded in these patients. Results: With HT there was a significant correlation between calculated and measured dose in the medial and lateral ipsilateral breast (r = 0.67, P V50 (1.4% vs 5.9%, respectively; P=.001) but higher skin V40 and skin V30 (71.7% vs 64.0%, P=.02; and 99.0% vs 93.8%, P=.001, respectively) than 3D-CRT plans. Conclusion: The 3D-CRT TPS more accurately reflected skin dose than the HT TPS, which tended to overestimate dose received by 14% in patients receiving adjuvant breast RT.

Dynamic and Progressive Control of DNA Origami Conformation by Modulating DNA Helicity with Chemical Adducts.

Science.gov (United States)

Chen, Haorong; Zhang, Hanyu; Pan, Jing; Cha, Tae-Gon; Li, Shiming; Andréasson, Joakim; Choi, Jong Hyun

2016-05-24

DNA origami has received enormous attention for its ability to program complex nanostructures with a few nanometer precision. Dynamic origami structures that change conformation in response to environmental cues or external signals hold great promises in sensing and actuation at the nanoscale. The reconfiguration mechanism of existing dynamic origami structures is mostly limited to single-stranded hinges and relies almost exclusively on DNA hybridization or strand displacement. Here, we show an alternative approach by demonstrating on-demand conformation changes with DNA-binding molecules, which intercalate between base pairs and unwind DNA double helices. The unwinding effect modulates the helicity mismatch in DNA origami, which significantly influences the internal stress and the global conformation of the origami structure. We demonstrate the switching of a polymerized origami nanoribbon between different twisting states and a well-constrained torsional deformation in a monomeric origami shaft. The structural transformation is shown to be reversible, and binding isotherms confirm the reconfiguration mechanism. This approach provides a rapid and reversible means to change DNA origami conformation, which can be used for dynamic and progressive control at the nanoscale.

Improvement in toxicity in high risk prostate cancer patients treated with image-guided intensity-modulated radiotherapy compared to 3D conformal radiotherapy without daily image guidance

International Nuclear Information System (INIS)

Sveistrup, Joen; Rosenschöld, Per Munck af; Deasy, Joseph O; Oh, Jung Hun; Pommer, Tobias; Petersen, Peter Meidahl; Engelholm, Svend Aage

2014-01-01

Image-guided radiotherapy (IGRT) facilitates the delivery of a very precise radiation dose. In this study we compare the toxicity and biochemical progression-free survival between patients treated with daily image-guided intensity-modulated radiotherapy (IG-IMRT) and 3D conformal radiotherapy (3DCRT) without daily image guidance for high risk prostate cancer (PCa). A total of 503 high risk PCa patients treated with radiotherapy (RT) and endocrine treatment between 2000 and 2010 were retrospectively reviewed. 115 patients were treated with 3DCRT, and 388 patients were treated with IG-IMRT. 3DCRT patients were treated to 76 Gy and without daily image guidance and with 1–2 cm PTV margins. IG-IMRT patients were treated to 78 Gy based on daily image guidance of fiducial markers, and the PTV margins were 5–7 mm. Furthermore, the dose-volume constraints to both the rectum and bladder were changed with the introduction of IG-IMRT. The 2-year actuarial likelihood of developing grade > = 2 GI toxicity following RT was 57.3% in 3DCRT patients and 5.8% in IG-IMRT patients (p < 0.001). For GU toxicity the numbers were 41.8% and 29.7%, respectively (p = 0.011). On multivariate analysis, 3DCRT was associated with a significantly increased risk of developing grade > = 2 GI toxicity compared to IG-IMRT (p < 0.001, HR = 11.59 [CI: 6.67-20.14]). 3DCRT was also associated with an increased risk of developing GU toxicity compared to IG-IMRT. The 3-year actuarial biochemical progression-free survival probability was 86.0% for 3DCRT and 90.3% for IG-IMRT (p = 0.386). On multivariate analysis there was no difference in biochemical progression-free survival between 3DCRT and IG-IMRT. The difference in toxicity can be attributed to the combination of the IMRT technique with reduced dose to organs-at-risk, daily image guidance and margin reduction

Conformity of LINAC-Based Stereotactic Radiosurgery Using Dynamic Conformal Arcs and Micro-Multileaf Collimator

International Nuclear Information System (INIS)

Hazard, Lisa J.; Wang, Brian; Skidmore, Thomas B.; Chern, Shyh-Shi; Salter, Bill J.; Jensen, Randy L.; Shrieve, Dennis C.

2009-01-01

Purpose: To assess the conformity of dynamic conformal arc linear accelerator-based stereotactic radiosurgery and to describe a standardized method of isodose surface (IDS) selection. Methods and Materials: In 174 targets, the conformity index (CI) at the prescription IDS used for treatment was calculated as CI = (PIV/PVTV)/(PVTV/TV), where TV is the target volume, PIV (prescription isodose volume) is the total volume encompassed by the prescription IDS, and PVTV is the TV encompassed by the IDS. In addition, a 'standardized' prescription IDS (sIDS) was chosen according to the following criteria: 95% of the TV was encompassed by the PIV and 99% of TV was covered by 95% of the prescription dose. The CIs at the sIDS were also calculated. Results: The median CI at the prescription IDS and sIDS was 1.63 and 1.47, respectively (p < 0.001). In 132 of 174 cases, the volume of normal tissue in the PIV was reduced by the prescription to the sIDS compared with the prescription IDS, in 20 cases it remained unchanged, and in 22 cases it was increased. Conclusion: The CIs obtained with linear accelerator-based stereotactic radiosurgery are comparable to those previously reported for gamma knife stereotactic radiosurgery. Using a uniform method to select the sIDS, adequate target coverage was usually achievable with prescription to an IDS greater than that chosen by the treating physician (prescription IDS), providing sparing of normal tissue. Thus, the sIDS might aid physicians in identifying a prescription IDS that balances coverage and conformity

Questionnaire based quality assurance for the RT01 trial of dose escalation in conformal radiotherapy for prostate cancer (ISRCTN 47772397)

International Nuclear Information System (INIS)

Mayles, W.; Moore, A.Rollo; Aird, Edwin G.A.; Bidmead, A. Margaret; Dearnaley, David P.; Griffiths, Sue E.; Stephens, Richard J.; Warrington, A.P. Jim

2004-01-01

Background and purpose: In order to ensure the validity of the outcome of the Medical Research Council's 'RT01 trial' of dose escalation in conformal radiotherapy for prostate cancer it was considered important that the quality of treatment delivery should meet an adequate standard across all contributing centres. A questionnaire was therefore devised to ensure that all aspects of the planning and delivery process were adequately covered. Patients and methods: The questionnaire considered each step in the planning and delivery process and drew the attention of the participants to the specific requirements of the trial. Before entering patients into the trial each participating centre had to complete the questionnaire and an outlining exercise (reported elsewhere). Results: It was not practicable to define a detailed universally acceptable protocol for the whole process of delivery of conformal radiotherapy, not least because of the different equipment available for planning and treatment in different centres. The questionnaire identified some areas of difference in practice between centres where there may be a need for the development of a consensus as to best practice, particularly in the area of patient set-up. Occasionally it was necessary to follow up responses to questions that had been misunderstood or inadequately answered, but in most cases these issues proved to be easily resolved. Conclusions: The questionnaire proved to be a useful self-assessment tool as well as enabling the quality assurance group to ensure that the standards of the trial were being met. Subsequent follow-up visits confirmed the usefulness and validity of this self assessment process

Real-time observation of the conformational dynamics of mitochondrial Hsp70 by spFRET.

Science.gov (United States)

Sikor, Martin; Mapa, Koyeli; von Voithenberg, Lena Voith; Mokranjac, Dejana; Lamb, Don C

2013-05-29

The numerous functions of the important class of molecular chaperones, heat shock proteins 70 (Hsp70), rely on cycles of intricate conformational changes driven by ATP-hydrolysis and regulated by cochaperones and substrates. Here, we used Förster resonance energy transfer to study the conformational dynamics of individual molecules of Ssc1, a mitochondrial Hsp70, in real time. The intrinsic dynamics of the substrate-binding domain of Ssc1 was observed to be uncoupled from the dynamic interactions between substrate- and nucleotide-binding domains. Analysis of the fluctuations in the interdomain separation revealed frequent transitions to a nucleotide-free state. The nucleotide-exchange factor Mge1 did not induce ADP release, as expected, but rather facilitated binding of ATP. These results indicate that the conformational cycle of Ssc1 is more elaborate than previously thought and provide insight into how the Hsp70s can perform a wide variety of functions.

Prone Hypofractionated Whole-Breast Radiotherapy Without a Boost to the Tumor Bed: Comparable Toxicity of IMRT Versus a 3D Conformal Technique

Energy Technology Data Exchange (ETDEWEB)

Hardee, Matthew E.; Raza, Shahzad; Becker, Stewart J.; Jozsef, Gabor; Lymberis, Stella C. [Department of Radiation Oncology, New York University School of Medicine, New York, NY (United States); Hochman, Tsivia; Goldberg, Judith D. [Division of Biostatistics, New York University School of Medicine, New York, NY (United States); DeWyngaert, Keith J. [Department of Radiation Oncology, New York University School of Medicine, New York, NY (United States); Formenti, Silvia C., E-mail: silvia.formenti@nyumc.org [Department of Radiation Oncology, New York University School of Medicine, New York, NY (United States)

2012-03-01

Purpose: We report a comparison of the dosimetry and toxicity of three-dimensional conformal radiotherapy (3D-CRT) vs. intensity-modulated radiotherapy (IMRT) among patients treated in the prone position with the same fractionation and target of the hypofractionation arm of the Canadian/Whelan trial. Methods and Materials: An institutional review board-approved protocol identified a consecutive series of early-stage breast cancer patients treated according to the Canadian hypofractionation regimen but in the prone position. Patients underwent IMRT treatment planning and treatment if the insurance carrier approved reimbursement for IMRT; in case of refusal, a 3D-CRT plan was used. A comparison of the dosimetric and toxicity outcomes during the acute, subacute, and long-term follow-up of the two treatment groups is reported. Results: We included 97 consecutive patients with 100 treatment plans in this study (3 patients with bilateral breast cancer); 40 patients were treated with 3D-CRT and 57 with IMRT. IMRT significantly reduced the maximum dose (Dmax median, 109.96% for 3D-CRT vs. 107.28% for IMRT; p < 0.0001, Wilcoxon test) and improved median dose homogeneity (median, 1.15 for 3D-CRT vs. 1.05 for IMRT; p < 0.0001, Wilcoxon test) when compared with 3D-CRT. Acute toxicity consisted primarily of Grade 1 to 2 dermatitis and occurred in 92% of patients. Grade 2 dermatitis occurred in 13% of patients in the 3D-CRT group and 2% in the IMRT group. IMRT moderately decreased rates of acute pruritus (p = 0.03, chi-square test) and Grade 2 to 3 subacute hyperpigmentation (p = 0.01, Fisher exact test). With a minimum of 6 months' follow-up, the treatment was similarly well tolerated in either group, including among women with large breast volumes. Conclusion: Hypofractionated breast radiotherapy is well tolerated when treating patients in the prone position, even among those with large breast volumes. Breast IMRT significantly improves dosimetry but yields only a modest

Dynamics of DNA conformations and DNA-protein interaction

DEFF Research Database (Denmark)

Metzler, R.; Ambjörnsson, T.; Lomholt, Michael Andersen

2005-01-01

Optical tweezers, atomic force microscopes, patch clamping, or fluorescence techniques make it possible to study both the equilibrium conformations and dynamics of single DNA molecules as well as their interaction with binding proteins. In this paper we address the dynamics of local DNA...... denaturation (bubble breathing), deriving its dynamic response to external physical parameters and the DNA sequence in terms of the bubble relaxation time spectrum and the autocorrelation function of bubble breathing. The interaction with binding proteins that selectively bind to the DNA single strand exposed...... in a denaturation bubble are shown to involve an interesting competition of time scales, varying between kinetic blocking of protein binding up to full binding protein-induced denaturation of the DNA. We will also address the potential to use DNA physics for the design of nanosensors. Finally, we report recent...

Characterizing highly dynamic conformational states: The transcription bubble in RNAP-promoter open complex as an example

Science.gov (United States)

Lerner, Eitan; Ingargiola, Antonino; Weiss, Shimon

2018-03-01

Bio-macromolecules carry out complicated functions through structural changes. To understand their mechanism of action, the structure of each step has to be characterized. While classical structural biology techniques allow the characterization of a few "structural snapshots" along the enzymatic cycle (usually of stable conformations), they do not cover all (and often fast interconverting) structures in the ensemble, where each may play an important functional role. Recently, several groups have demonstrated that structures of different conformations in solution could be solved by measuring multiple distances between different pairs of residues using single-molecule Förster resonance energy transfer (smFRET) and using them as constrains for hybrid/integrative structural modeling. However, this approach is limited in cases where the conformational dynamics is faster than the technique's temporal resolution. In this study, we combine existing tools that elucidate sub-millisecond conformational dynamics together with hybrid/integrative structural modeling to study the conformational states of the transcription bubble in the bacterial RNA polymerase-promoter open complex (RPo). We measured microsecond alternating laser excitation-smFRET of differently labeled lacCONS promoter dsDNA constructs. We used a combination of burst variance analysis, photon-by-photon hidden Markov modeling, and the FRET-restrained positioning and screening approach to identify two conformational states for RPo. The experimentally derived distances of one conformational state match the known crystal structure of bacterial RPo. The experimentally derived distances of the other conformational state have characteristics of a scrunched RPo. These findings support the hypothesis that sub-millisecond dynamics in the transcription bubble are responsible for transcription start site selection.

Emerging paradigm in radiobiology in concept and practices of hypo fractionated conformal radiotherapy

International Nuclear Information System (INIS)

Mishra, S.P.; Srivastava, Anoop Kumar; Rastogi, Madhup; Khurana, Rohini; Pawaskar, Asawari

2016-01-01

This study has been performed in clinical setting by creating the treatment plan in dynamic conformal arc mode as the treatment delivery technique; with add on collimator APEX system having 56 pairs of 2.5 mm each as treatment unit. Photon beam energy selected for the study was 6 MV. Various number of treatment arcs were applied depending upon the location of the PTV. The PTV was prescribed a total dose of 60 Gy in five fractions

Couplings between hierarchical conformational dynamics from multi-time correlation functions and two-dimensional lifetime spectra: Application to adenylate kinase

Energy Technology Data Exchange (ETDEWEB)

Ono, Junichi [Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Okazaki 444-8585 (Japan); Takada, Shoji [Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Okazaki 444-8585 (Japan); Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan); Saito, Shinji, E-mail: shinji@ims.ac.jp [Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, Okazaki 444-8585 (Japan); The Graduate University for Advanced Studies, Okazaki 444-8585 (Japan)

2015-06-07

An analytical method based on a three-time correlation function and the corresponding two-dimensional (2D) lifetime spectrum is developed to elucidate the time-dependent couplings between the multi-timescale (i.e., hierarchical) conformational dynamics in heterogeneous systems such as proteins. In analogy with 2D NMR, IR, electronic, and fluorescence spectroscopies, the waiting-time dependence of the off-diagonal peaks in the 2D lifetime spectra can provide a quantitative description of the dynamical correlations between the conformational motions with different lifetimes. The present method is applied to intrinsic conformational changes of substrate-free adenylate kinase (AKE) using long-time coarse-grained molecular dynamics simulations. It is found that the hierarchical conformational dynamics arise from the intra-domain structural transitions among conformational substates of AKE by analyzing the one-time correlation functions and one-dimensional lifetime spectra for the donor-acceptor distances corresponding to single-molecule Förster resonance energy transfer experiments with the use of the principal component analysis. In addition, the complicated waiting-time dependence of the off-diagonal peaks in the 2D lifetime spectra for the donor-acceptor distances is attributed to the fact that the time evolution of the couplings between the conformational dynamics depends upon both the spatial and temporal characters of the system. The present method is expected to shed light on the biological relationship among the structure, dynamics, and function.

Intensity modulated radiotherapy and 3D conformal radiotherapy for whole breast irradiation: a comparative dosimetric study and introduction of a novel qualitative index for plan evaluation, the normal tissue index

Energy Technology Data Exchange (ETDEWEB)

Yim, Jackie; Suttie, Clare; Bromley, Regina; Morgia, Marita; Lamoury, Gillian [Department of Radiation Oncology, Royal North Shore Hospital, St Leonards, New South Wales (Australia)

2015-09-15

We report on a retrospective dosimetric study, comparing 3D conformal radiotherapy (3DCRT) and hybrid intensity modulated radiotherapy (hIMRT). We evaluated plans based on their planning target volume coverage, dose homogeneity, dose to organs at risk (OARs) and exposure of normal tissue to radiation. The Homogeneity Index (HI) was used to assess the dose homogeneity in the target region, and we describe a new index, the normal tissue index (NTI), to assess the dose in the normal tissue inside the tangent treatment portal. Plans were generated for 25 early-stage breast cancer patients, using a hIMRT technique. These were compared with the 3DCRT plans of the treatment previously received by the patients. Plan quality was evaluated using the HI, NTI and dose to OARs. The hIMRT technique was significantly more homogenous than the 3DCRT technique, while maintaining target coverage. The hIMRT technique was also superior at minimising the amount of tissue receiving D{sub 105%} and above (P < 0.0001). The ipsilateral lung and contralateral breast maximum were significantly lower in the hIMRT plans (P < 0.05 and P < 0.005), but the 3DCRT technique achieved a lower mean heart dose in left-sided breast cancer patients (P < 0.05). Hybrid intensity modulated radiotherapy plans achieved improved dose homogeneity compared to the 3DCRT plans and superior outcome with regard to dose to normal tissues. We propose that the addition of both HI and NTI in evaluating the quality of intensity modulated radiotherapy (IMRT) breast plans provides clinically relevant comparators which more accurately reflect the new paradigm of treatment goals and outcomes in the era of breast IMRT.

Intensity modulated radiotherapy and 3D conformal radiotherapy for whole breast irradiation: a comparative dosimetric study and introduction of a novel qualitative index for plan evaluation, the normal tissue index

International Nuclear Information System (INIS)

Yim, Jackie; Suttie, Clare; Bromley, Regina; Morgia, Marita; Lamoury, Gillian

2015-01-01

We report on a retrospective dosimetric study, comparing 3D conformal radiotherapy (3DCRT) and hybrid intensity modulated radiotherapy (hIMRT). We evaluated plans based on their planning target volume coverage, dose homogeneity, dose to organs at risk (OARs) and exposure of normal tissue to radiation. The Homogeneity Index (HI) was used to assess the dose homogeneity in the target region, and we describe a new index, the normal tissue index (NTI), to assess the dose in the normal tissue inside the tangent treatment portal. Plans were generated for 25 early-stage breast cancer patients, using a hIMRT technique. These were compared with the 3DCRT plans of the treatment previously received by the patients. Plan quality was evaluated using the HI, NTI and dose to OARs. The hIMRT technique was significantly more homogenous than the 3DCRT technique, while maintaining target coverage. The hIMRT technique was also superior at minimising the amount of tissue receiving D 105% and above (P < 0.0001). The ipsilateral lung and contralateral breast maximum were significantly lower in the hIMRT plans (P < 0.05 and P < 0.005), but the 3DCRT technique achieved a lower mean heart dose in left-sided breast cancer patients (P < 0.05). Hybrid intensity modulated radiotherapy plans achieved improved dose homogeneity compared to the 3DCRT plans and superior outcome with regard to dose to normal tissues. We propose that the addition of both HI and NTI in evaluating the quality of intensity modulated radiotherapy (IMRT) breast plans provides clinically relevant comparators which more accurately reflect the new paradigm of treatment goals and outcomes in the era of breast IMRT

Radiotherapy gel dosimetry

International Nuclear Information System (INIS)

Baldock, C.

2002-01-01

In radiotherapy, the primary objective is to deliver a prescribed dose of radiation to a tumour or lesion within a patient while minimising the dose delivered to the surrounding healthy tissue. Traditional radiotherapy treatments usually involve simple external or internal irradiations of a tumour. External irradiations are normally achieved in the clinic with photon or electron beams produced by high energy linear accelerators. The photon or electron beams are collimated into regular shapes as they emerge from the treatment head of the unit which is supported by a gantry that can be rotated isocentrically to any position. A discrete number of photon or electron beams with different angles of incidence that intersect at the iso-centre are used to produce a region of high dose around the tumour volume (positioned at the iso-centre). Internal irradiations are normally achieved in the clinic by implanting radioactive sources in and around the tumour or lesion. Such irradiations are characterised by very high doses local to the tumour. Radioactive sources are also used to prevent post-angioplasty restenosis by inserting sources into arteries. Usually when treating a tumour, a compromise is made between tumour control and complications arising from normal tissue damage. One measure of this compromise, the therapeutic ratio, is defined as the radiation dose producing complications in 50% of patients divided by the dose providing tumour control in 50% of the patients. The therapeutic ratio depends on the radiobiological characteristics of the cancerous tissue and surrounding healthy tissues and on the radiation dose distribution achieved by the radiotherapy treatment. It is generally believed that the therapeutic ratio can be minimised by optimising the conformation of the radiation dose distribution to the target volume. This is difficult with traditional radiotherapy techniques since they do not produce dose distributions that adequately cover tumour volumes of complex

Neuropsychological status in children and young adults with benign and low-grade brain tumors treated prospectively with focal stereotactic conformal radiotherapy

International Nuclear Information System (INIS)

Jalali, Rakesh; Goswami, Savita; Sarin, Rajiv; More, Niteen; Siddha, Manish; Kamble, Rashmi

2006-01-01

Purpose: To present prospective neuropsychological data at baseline and follow-up in children and young adults with benign and low-grade gliomas treated with focal stereotactic conformal radiotherapy (SCRT). Methods and Materials: A total of 22 patients (age 4-25 years) with residual/progressive benign and low-grade brain tumors considered suitable for SCRT underwent detailed and in-depth neuropsychological and cognitive testing at baseline before SCRT. The test battery included measurement of age-adjusted intelligence quotients (IQs) and cognitive parameters of visual, spatial, visuomotor, and attention concentrations. Anxiety was measured using the State-Trait Anxiety Inventory for Children and Hamilton Anxiety Rating Scale for patients >16 years old. Patients were treated with high-precision conformal radiotherapy under stereotactic guidance to a dose of 54 Gy in 30 fractions. All neuropsychological assessments were repeated at 6 and 24 months after SCRT completion and compared with the baseline values. Results: The baseline mean full-scale IQ before starting RT for patients 16 years, the corresponding value was 72 (range, 64-129). Of 20 evaluable patients, 14 (70%) had less than average IQs at baseline, even before starting radiotherapy. The verbal IQ, performance IQ, and full-scale IQ, as well as other cognitive scores, did not change significantly at the 6- and 24-month follow-up assessments for all patients. The memory quotient in older children and young adults was maintained at 6 and 24 months after SCRT, with a mean value of 93 and 100, respectively, compared with a mean baseline value of 81 before RT. The mean anxiety score in children measured by the C1 and C2 components of the State-Trait Anxiety Inventory for Children (STAIC) was 48 and 40, respectively, which improved significantly to mean values of 30 and 26, respectively, at the 24-month follow-up assessment (p = 0.005). The mean depression score in patients >16 years old was 23 at baseline and had

Conformational Dynamics of Thermus aquaticus DNA Polymerase I during Catalysis

Science.gov (United States)

Suo, Zucai

2014-01-01

Despite the fact that DNA polymerases have been investigated for many years and are commonly used as tools in a number of molecular biology assays, many details of the kinetic mechanism they use to catalyze DNA synthesis remain unclear. Structural and kinetic studies have characterized a rapid, pre-catalytic open-to-close conformational change of the Finger domain during nucleotide binding for many DNA polymerases including Thermus aquaticus DNA polymerase I (Taq Pol), a thermostable enzyme commonly used for DNA amplification in PCR. However, little has been done to characterize the motions of other structural domains of Taq Pol or any other DNA polymerase during catalysis. Here, we used stopped-flow Förster resonance energy transfer (FRET) to investigate the conformational dynamics of all five structural domains of the full-length Taq Pol relative to the DNA substrate during nucleotide binding and incorporation. Our study provides evidence for a rapid conformational change step induced by dNTP binding and a subsequent global conformational transition involving all domains of Taq Pol during catalysis. Additionally, our study shows that the rate of the global transition was greatly increased with the truncated form of Taq Pol lacking the N-terminal domain. Finally, we utilized a mutant of Taq Pol containing a de novo disulfide bond to demonstrate that limiting protein conformational flexibility greatly reduced the polymerization activity of Taq Pol. PMID:24931550

The study of treatment value of concurrent chemotherapy for patients with esophageal carcinoma received three-dimensional conformal radiotherapy or intensity modulated radiotherapy

International Nuclear Information System (INIS)

Wang Lan; Wang Jun; Han Chun; Zhang Jing; Li Xiaoning; Gao Chao

2011-01-01

Objective: To observe the acute side effects, local control rate and survival rate of concurrent chemoradiotherapy (CC) and radiotherapy alone (R) for patients with esophageal carcinoma. Methods: From June 2006 to February 2009, 209 patients with esophageal carcinoma were observed, 105 of them were treated with CC. Of all the patients, 117 received three-dimensional conformal radiotherapy, 92 received intensity modulated radiotherapy, the median prescription dose was 60 Gy. The regimen of LFP (5-FU, cisplatin and calcium folinate) was selected for this study, side effects, local control rate and survival rate were observed and subsets analysis were performed. Results: The overall follow-up rate was 99.0%,there were 99 and 44 patients whose follow-up time was more than 2 and 3 years, respectively;for the CC group, the data were 45 and 14, respectively; and for the R group, 54 and 30, respectively. The 1-, 2-, 3-year local control rates of CC group and R group were 88.1%, 69.2%, 66.2% and 81.0%, 64.0%, 54.9% (χ 2 =2.31, P=0.128), respectively. The 1-, 2-, 3-year overall survival rates of CC group and R group were 84.4%, 52.9%, 45.6% and 75.2%, 50.7%, 37.0%(χ 2 =1.57, P=0.210), respectively. Subset analysis indicated that for the patients of N 0 group and whose length of GTV >7 cm, the local control rate of CC was significantly higher than that of radiotherapy alone (χ 2 =5.11, 7.66; P=0.024, 0.006). For N 0 group, the survival rate of CC was higher than that of R alone. (χ 2 =5.07, P=0.024). The incidence of WBC, PLT and HGB reduction for the two groups were 81.9% and 49.0% (χ 2 =36.45, P=0.000), 14.3% and 1.9% (χ 2 =10.54, P=0.006), and 24.8% and 2.9% (χ 2 =22.95, P=0.000), respectively. The incidence of nausea, vomiting and constipation for the two groups were 63.8% and 7.7% (χ 2 =71.52, P=0.000), respectively. The incidence of ≥2 grade esophagitis of CC group and R group were 48.57% and 38.46% (χ 2 =2.17, P=0.141), respectively. The incidence of ≥2

Selection and determination of beam weights based on genetic algorithms for conformal radiotherapy treatment planning

International Nuclear Information System (INIS)

Xingen Wu; Zunliang Wang

2000-01-01

A genetic algorithm has been used to optimize the selection of beam weights for external beam three-dimensional conformal radiotherapy treatment planning. A fitness function is defined, which includes a difference function to achieve a least-square fit to doses at preselected points in a planning target volume, and a penalty item to constrain the maximum allowable doses delivered to critical organs. Adjustment between the dose uniformity within the target volume and the dose constraint to the critical structures can be achieved by varying the beam weight variables in the fitness function. A floating-point encoding schema and several operators, like uniform crossover, arithmetical crossover, geometrical crossover, Gaussian mutation and uniform mutation, have been used to evolve the population. Three different cases were used to verify the correctness of the algorithm and quality assessment based on dose-volume histograms and three-dimensional dose distributions were given. The results indicate that the genetic algorithm presented here has considerable potential. (author)

Study of conformation and dynamic of surfactant molecules in graphite oxide via NMR

Energy Technology Data Exchange (ETDEWEB)

Ai, X.Q. [Jiangsu Second Normal University, College of Physics and Electronic Engineering, Nanjing (China); Ma, L.G. [Nanjing Xiaozhuang University, School of Electronic Engineering, Nanjing (China)

2016-08-15

The conformation and dynamic of surfactant in graphite oxide (GO) was investigated by solid-state {sup 13}C magic-angle-spinning NMR and {sup 1}H-{sup 13}C cross-polarization/magic-angle-spinning NMR spectra. The conformation ordering of the alkyl chains in the confined system shows strong dependence on its orientation. While the alkyl chains parallel to the GO layer in lateral monolayer arrangement are in gauche conformation in addition to a small amount of all-trans conformation, those with orientation radiating away from the GO in paraffin bilayer arrangement is in all-trans conformation in addition to some gauche conformation even though high-order diffraction peaks appears. NMR results suggest that the least mobile segment is located at the GO-surfactant interface corresponding to the N-methylene group. Further from it, the mobility of the alkyl chain increases. The terminal methyl and N-methyl carbon groups have the highest mobile. The chains in all-trans conformational state are characterized as more rigid than chains with gauche conformation; each segment of the confined alkyl chains with the lateral monolayer arrangement exhibits less mobility as compared to that with the paraffin bilayer arrangement. (orig.)

Conformational dynamics of a protein in the folded and the unfolded state

Energy Technology Data Exchange (ETDEWEB)

Fitter, Joerg

2003-08-01

In a quasielastic neutron scattering experiment, the picosecond dynamics of {alpha}-amylase was investigated for the folded and the unfolded state of the protein. In order to ensure a reasonable interpretation of the internal protein dynamics, the protein was measured in D{sub 2}O-buffer solution. The much higher structural flexibility of the pH induced unfolded state as compared to the native folded state was quantified using a simple analytical model, describing a local diffusion inside a sphere. In terms of this model the conformational volume, which is explored mainly by confined protein side-chain movements, is parameterized by the radius of a sphere (folded state, r=1.2 A; unfolded state, 1.8 A). Differences in conformational dynamics between the folded and the unfolded state of a protein are of fundamental interest in the field of protein science, because they are assumed to play an important role for the thermodynamics of folding/unfolding transition and for protein stability.

Conformal dynamics for electroweak symmetry breaking, from LHC to cosmology

International Nuclear Information System (INIS)

Sannino, Francesco

2009-01-01

Full text. I will first introduce dynamical electroweak symmetry breaking and then present how to resolve some of the long-standing problems using (near) conformal dynamics. In order to construct sensible extension of DEWSB I will then review the state-of-the-art of the phase diagram of gauge theories of fundamental interactions as function of the number of colors, flavors and matter representation. Finally I will introduce recent models known as minimal walking models and show how they lead to natural candidates of dark matter. (author)

A Retrospective Comparison of Robotic Stereotactic Body Radiotherapy and Three-Dimensional Conformal Radiotherapy for the Reirradiation of Locally Recurrent Nasopharyngeal Carcinoma

International Nuclear Information System (INIS)

Ozyigit, Gokhan; Cengiz, Mustafa; Yazici, Gozde; Yildiz, Ferah; Gurkaynak, Murat; Zorlu, Faruk; Yildiz, Demet; Hosal, Sefik; Gullu, Ibrahim; Akyol, Fadil

2011-01-01

Purpose: We assessed therapeutic outcomes of reirradiation with robotic stereotactic radiotherapy (SBRT) for locally recurrent nasopharyngeal carcinoma (LRNPC) patients and compared those results with three-dimensional conformal radiotherapy (CRT) with or without brachytherapy (BRT). Methods and Materials: Treatment outcomes were evaluated retrospectively in 51 LRNPC patients receiving either robotic SBRT (24 patients) or CRT with or without BRT (27 patients) in our department. CRT was delivered with a 6-MV linear accelerator, and a median total reirradiation dose of 57 Gy in 2 Gy/day was given. Robotic SBRT was delivered with CyberKnife (Accuray, Sunnyvale, CA). Patients in the SBRT arm received 30 Gy over 5 consecutive days. We calculated actuarial local control and cancer-specific survival rates for the comparison of treatment outcomes in SBRT and CRT arms. The Common Terminology Criteria for Adverse Events v3.0 was used for toxicity evaluation. Results: The median follow-up was 24 months for all patients. Two-year actuarial local control rates were 82% and 80% for SBRT and CRT arms, respectively (p = 0.6). Two-year cancer-specific survival rates were 64% and 47% for the SBRT and CRT arms, respectively (p = 0.4). Serious late toxicities (Grade 3 and above) were observed in 21% of patients in the SBRT arm, whereas 48% of patients had serious toxicity in the CRT arm (p = 0.04). Fatal complications occurred in three patients (12.5%) of the SBRT arm, and four patients (14.8%) of the CRT arm (p = 0.8). T stage at recurrence was the only independent predictor for local control and survival. Conclusion: Our robotic SBRT protocol seems to be feasible and less toxic in terms of late effects compared with CRT arm for the reirradiation of LRNPC patients.

Conformational changes in acetylcholine binding protein investigated by temperature accelerated molecular dynamics.

Directory of Open Access Journals (Sweden)

Zeynab Mohammad Hosseini Naveh

Full Text Available Despite the large number of studies available on nicotinic acetylcholine receptors, a complete account of the mechanistic aspects of their gating transition in response to ligand binding still remains elusive. As a first step toward dissecting the transition mechanism by accelerated sampling techniques, we study the ligand-induced conformational changes of the acetylcholine binding protein (AChBP, a widely accepted model for the full receptor extracellular domain. Using unbiased Molecular Dynamics (MD and Temperature Accelerated Molecular Dynamics (TAMD simulations we investigate the AChBP transition between the apo and the agonist-bound state. In long standard MD simulations, both conformations of the native protein are stable, while the agonist-bound structure evolves toward the apo one if the orientation of few key sidechains in the orthosteric cavity is modified. Conversely, TAMD simulations initiated from the native conformations are able to produce the spontaneous transition. With respect to the modified conformations, TAMD accelerates the transition by at least a factor 10. The analysis of some specific residue-residue interactions points out that the transition mechanism is based on the disruption/formation of few key hydrogen bonds. Finally, while early events of ligand dissociation are observed already in standard MD, TAMD accelerates the ligand detachment and, at the highest TAMD effective temperature, it is able to produce a complete dissociation path in one AChBP subunit.

Bystander effects and radiotherapy.

Science.gov (United States)

Marín, Alicia; Martín, Margarita; Liñán, Olga; Alvarenga, Felipe; López, Mario; Fernández, Laura; Büchser, David; Cerezo, Laura

2015-01-01

Radiation-induced bystander effects are defined as biological effects expressed after irradiation by cells whose nuclei have not been directly irradiated. These effects include DNA damage, chromosomal instability, mutation, and apoptosis. There is considerable evidence that ionizing radiation affects cells located near the site of irradiation, which respond individually and collectively as part of a large interconnected web. These bystander signals can alter the dynamic equilibrium between proliferation, apoptosis, quiescence or differentiation. The aim of this review is to examine the most important biological effects of this phenomenon with regard to areas of major interest in radiotherapy. Such aspects include radiation-induced bystander effects during the cell cycle under hypoxic conditions when administering fractionated modalities or combined radio-chemotherapy. Other relevant aspects include individual variation and genetics in toxicity of bystander factors and normal tissue collateral damage. In advanced radiotherapy techniques, such as intensity-modulated radiation therapy (IMRT), the high degree of dose conformity to the target volume reduces the dose and, therefore, the risk of complications, to normal tissues. However, significant doses can accumulate out-of-field due to photon scattering and this may impact cellular response in these regions. Protons may offer a solution to reduce out-of-field doses. The bystander effect has numerous associated phenomena, including adaptive response, genomic instability, and abscopal effects. Also, the bystander effect can influence radiation protection and oxidative stress. It is essential that we understand the mechanisms underlying the bystander effect in order to more accurately assess radiation risk and to evaluate protocols for cancer radiotherapy.

[Doses to organs at risk in conformational radiotherapy and stereotaxic irradiation: The heart].

Science.gov (United States)

Vandendorpe, B; Servagi Vernat, S; Ramiandrisoa, F; Bazire, L; Kirova, Y M

2017-10-01

Radiation therapy of breast cancer, Hodgkin lymphoma, lung cancer and others thoracic irradiations induce an ionizing radiation dose to the heart. Irradiation of the heart, associated with patient cardiovascular risk and cancer treatment-induced cardiotoxicity, increase cardiovascular mortality. The long survival after breast or Hodgkin lymphoma irradiation requires watching carefully late treatment toxicity. The over-risk of cardiac events is related to the dose received by the heart and the irradiated cardiac volume. The limitation of cardiac irradiation should be a priority in the planning of thoracic irradiations. Practices have to be modified, using modern techniques to approach of the primary objective of radiotherapy which is to optimize the dose to the target volume, sparing healthy tissues, in this case the heart. We have reviewed the literature on cardiac toxicity induced by conformational tridimensional radiation therapy, intensity-modulated radiation therapy or stereotactic body radiation therapy, in order to evaluate the possibilities to limit cardiotoxicity. Finally, we summarise the recommendations on dose constraints to the heart and coronary arteries. Copyright © 2017 Société française de radiothérapie oncologique (SFRO). Published by Elsevier SAS. All rights reserved.

Time-resolved infrared studies of protein conformational dynamics

Energy Technology Data Exchange (ETDEWEB)

Woodruff, W.H.; Causgrove, T.P.; Dyer, R.B. [Los Alamos National Laboratory, NM (United States); Callender, R.H. [Univ. of New York, NY (United States)

1994-12-01

We have demonstrated that TRIR in the amide I region gives structural information regarding protein conformational changes in realtime, both on processes involved in the development of the functional structure (protein folding) and on protein structural changes that accompany the functional dynamics of the native structure. Assignment of many of the amide I peaks to specific amide or sidechain structures will require much additional effort. Specifically, the congestion and complexity of the protein vibrational spectra dictate that isotope studies are an absolute requirement for more than a qualitative notion of the structural interpretation of these measurements. It is clear, however, that enormous potential exists for elucidating structural relaxation dynamics and energetics with a high degree of structural specificity using this approach.

Respiratory gated radiotherapy: current techniques and potential benefits

International Nuclear Information System (INIS)

Giraud, P.; Campana, F.; Rosenwald, J.C.; Cosset, J.M.; Reboul, F.; Garcia, R.; Clippe, S.; Carrie, C.; Dubray, B.

2003-01-01

Respiration-gated radiotherapy offers a significant potential for improvement in the irradiation of tumor sites affected by respiratory motion such as lung, breast and liver tumors. An increased conformality of irradiation fields leading to decreased complications rates of organs at risk (lung, heart...) is expected. Respiratory gating is in line with the need for improved precision required by radiotherapy techniques such as 3D conformal radiotherapy or intensity modulated radiotherapy. Reduction of respiratory motion can be achieved by using either breath hold techniques or respiration synchronized gating techniques. Breath-hold techniques can be achieved with active, in which airflow of the patient is temporarily blocked by a valve, or passive techniques, in which the patient voluntarily breath-hold. Synchronized gating techniques use external devices to predict the phase of the respiration cycle while the patient breaths freely. These techniques presently investigated in several medical centers worldwide. Although promising, the first results obtained in lung and liver cancer patients require confirmation. Physical, technical and physiological questions still remain to be answered. This paper describes the most frequently used gated techniques and the main published clinical reports on the use of respiration-gated radiotherapy in order to evaluate the impact of these techniques. (author)

Three-Dimensional Non-Coplanar Conformal Radiotherapy Yields Better Results Than Traditional Beam Arrangements for Adjuvant Treatment of Gastric Cancer

International Nuclear Information System (INIS)

Soyfer, Viacheslav; Corn, Benjamin W.; Melamud, Alex B.S.; Alani, Shlomi; Tempelhof, Haim; Agai, Reuben; Shmueli, Anat; Figer, Arie; Kovner, Felix

2007-01-01

Purpose: The current standard of adjuvant treatment for gastric cancer after curative resection is concurrent administration of radiotherapy and 5-fluorouracil-based chemotherapy. The radiation fields are often arranged as anterioposterior-posteroanterior opposed parallel fields with general recommendations for sparing at least two-thirds of one kidney. We investigated whether a better radiation distribution would be achievable with three-dimensional conformal approaches compared with the classic anterioposterior-posteroanterior fields. Methods and Materials: A total of 19 patients with adenocarcinoma of the stomach were treated with adjuvant chemoradiotherapy using a non-coplanar four-field arrangement. In each case, parallel planning using an anterioposterior-posteroanterior arrangement and a four-field 'box' was performed, and the generated plans were subsequently compared for coverage of target volumes and doses to irradiated organs next to the tumor bed. A separate analysis was performed for kidneys exposed to greater and lower doses in each patient. The mean radiation dose and percentage of kidney volume receiving a dose >20 Gy were registered. Statistical analysis was performed using the two-tailed t test. Results: The clinical target volume was adequately covered in all three plans. In the greater-dose kidney group, all the differences were statistically significant with a benefit for the three-dimensional plan. In the lower-dose kidney group, the differences in the mean radiation dose did not reach the level of statistical significance, and the differences in the kidney volume receiving a dose >20 Gy showed a statistically significant benefit for the three-dimensional plan. Conclusion: Non-coplanar three-dimensional-based conformal planning for postoperative radiotherapy for gastric cancer provided the best results regarding kidney and spinal cord exposure with adequate clinical target volume coverage. This technique was readily implemented in clinical

Three-dimensional non-coplanar conformal radiotherapy yields better results than traditional beam arrangements for adjuvant treatment of gastric cancer.

Science.gov (United States)

Soyfer, Viacheslav; Corn, Benjamin W; Melamud, Alex; Alani, Shlomi; Tempelhof, Haim; Agai, Reuben; Shmueli, Anat; Figer, Arie; Kovner, Felix

2007-10-01

The current standard of adjuvant treatment for gastric cancer after curative resection is concurrent administration of radiotherapy and 5-fluorouracil-based chemotherapy. The radiation fields are often arranged as anterioposterior-posteroanterior opposed parallel fields with general recommendations for sparing at least two-thirds of one kidney. We investigated whether a better radiation distribution would be achievable with three-dimensional conformal approaches compared with the classic anterioposterior-posteroanterior fields. A total of 19 patients with adenocarcinoma of the stomach were treated with adjuvant chemoradiotherapy using a non-coplanar four-field arrangement. In each case, parallel planning using an anterioposterior-posteroanterior arrangement and a four-field "box" was performed, and the generated plans were subsequently compared for coverage of target volumes and doses to irradiated organs next to the tumor bed. A separate analysis was performed for kidneys exposed to greater and lower doses in each patient. The mean radiation dose and percentage of kidney volume receiving a dose >20 Gy were registered. Statistical analysis was performed using the two-tailed t test. The clinical target volume was adequately covered in all three plans. In the greater-dose kidney group, all the differences were statistically significant with a benefit for the three-dimensional plan. In the lower-dose kidney group, the differences in the mean radiation dose did not reach the level of statistical significance, and the differences in the kidney volume receiving a dose >20 Gy showed a statistically significant benefit for the three-dimensional plan. Non-coplanar three-dimensional-based conformal planning for postoperative radiotherapy for gastric cancer provided the best results regarding kidney and spinal cord exposure with adequate clinical target volume coverage. This technique was readily implemented in clinical practice.

TH-EF-BRB-04: 4π Dynamic Conformal Arc Therapy Dynamic Conformal Arc Therapy (DCAT) for SBRT

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Chiu, T; Long, T; Tian, Z.; Yan, Y; Jiang, S; Gu, X [UT Southwestern Medical Center, Dallas, TX (United States); Modiri, A; Sawant, A [University of Maryland in Baltimore, Baltimore, MD (United States)

2016-06-15

Purpose: To develop an efficient and effective trajectory optimization methodology for 4π dynamic conformal arc treatment (4π DCAT) with synchronized gantry and couch motion; and to investigate potential clinical benefits for stereotactic body radiation therapy (SBRT) to breast, lung, liver and spine tumors. Methods: The entire optimization framework for 4π DCAT inverse planning consists of two parts: 1) integer programming algorithm and 2) particle swarm optimization (PSO) algorithm. The integer programming is designed to find an optimal solution for arc delivery trajectory with both couch and gantry rotation, while PSO minimize a non-convex objective function based on the selected trajectory and dose-volume constraints. In this study, control point interaction is explicitly taken into account. Beam trajectory was modeled as a series of control points connected together to form a deliverable path. With linear treatment planning objectives, a mixed-integer program (MIP) was formulated. Under mild assumptions, the MIP is tractable. Assigning monitor units to control points along the path can be integrated into the model and done by PSO. The developed 4π DCAT inverse planning strategy is evaluated on SBRT cases and compared to clinically treated plans. Results: The resultant dose distribution of this technique was evaluated between 3D conformal treatment plan generated by Pinnacle treatment planning system and 4π DCAT on a lung SBRT patient case. Both plans share the same scale of MU, 3038 and 2822 correspondingly to 3D conformal plan and 4π DCAT. The mean doses for most of OARs were greatly reduced at 32% (cord), 70% (esophagus), 2.8% (lung) and 42.4% (stomach). Conclusion: Initial results in this study show the proposed 4π DCAT treatment technique can achieve better OAR sparing and lower MUs, which indicates that the developed technique is promising for high dose SBRT to reduce the risk of secondary cancer.

Benchmarking Dosimetric Quality Assessment of Prostate Intensity-Modulated Radiotherapy

International Nuclear Information System (INIS)

Senthi, Sashendra; Gill, Suki S.; Haworth, Annette; Kron, Tomas; Cramb, Jim; Rolfo, Aldo; Thomas, Jessica; Duchesne, Gillian M.; Hamilton, Christopher H.; Joon, Daryl Lim; Bowden, Patrick; Foroudi, Farshad

2012-01-01

Purpose: To benchmark the dosimetric quality assessment of prostate intensity-modulated radiotherapy and determine whether the quality is influenced by disease or treatment factors. Patients and Methods: We retrospectively analyzed the data from 155 consecutive men treated radically for prostate cancer using intensity-modulated radiotherapy to 78 Gy between January 2007 and March 2009 across six radiotherapy treatment centers. The plan quality was determined by the measures of coverage, homogeneity, and conformity. Tumor coverage was measured using the planning target volume (PTV) receiving 95% and 100% of the prescribed dose (V 95% and V 100% , respectively) and the clinical target volume (CTV) receiving 95% and 100% of the prescribed dose. Homogeneity was measured using the sigma index of the PTV and CTV. Conformity was measured using the lesion coverage factor, healthy tissue conformity index, and the conformity number. Multivariate regression models were created to determine the relationship between these and T stage, risk status, androgen deprivation therapy use, treatment center, planning system, and treatment date. Results: The largest discriminatory measurements of coverage, homogeneity, and conformity were the PTV V 95% , PTV sigma index, and conformity number. The mean PTV V 95% was 92.5% (95% confidence interval, 91.3–93.7%). The mean PTV sigma index was 2.10 Gy (95% confidence interval, 1.90–2.20). The mean conformity number was 0.78 (95% confidence interval, 0.76–0.79). The treatment center independently influenced the coverage, homogeneity, and conformity (all p 95% only, with it being better at the start (p = .013). Risk status, T stage, and the use of androgen deprivation therapy did not influence any aspect of plan quality. Conclusion: Our study has benchmarked measures of coverage, homogeneity, and conformity for the treatment of prostate cancer using IMRT. The differences seen between centers and planning systems and the coverage

Modelling normal tissue isoeffect distribution in conformal radiotherapy of glioblastoma provides an alternative dose escalation pattern through hypofractionation without reducing the total dose

International Nuclear Information System (INIS)

Mangel, L.; Skriba, Z.; Major, T.; Polgar, C.; Fodor, J.; Somogyi, A.; Nemeth, G.

2002-01-01

The purpose of this study was to prove that by using conformal external beam radiotherapy (RT) normal brain structures can be protected even when applying an alternative approach of biological dose escalation: hypofractionation (HOF) without total dose reduction (TDR). Traditional 2-dimensional (2D) and conformal 3-dimensional (3D) treatment plans were prepared for 10 gliomas representing the subanatomical sites of the supratentorial brain. Isoeffect distributions were generated by the biologically effective dose (BED) formula to analyse the effect of conventionally fractionated (CF) and HOF schedules on both the spatial biological dose distribution and biological dose-volume histograms. A comparison was made between 2D-CF (2.0 Gy/day) and 3D-HOF (2.5 Gy/day) regimens, applying the same 60 Gy total doses. Integral biologically effective dose (IBED) and volumes received biologically equivalent to a dose of 54 Gy or more (V-BED54) were calculated for the lower and upper brain stem as organs of risk. The IBED values were lower with the 3D-HOF than with the 2D-CF schedule in each tumour location, means 22.7±17.1 and 40.4±16.9 in Gy, respectively (p<0.0001). The V-BED54 values were also smaller or equal in 90% of the cases favouring the 3D-HOF scheme. The means were 2.7±4.8 ccm for 3D-HOF and 10.7±12.7 ccm for 2D-CF (p=0.0006). Our results suggest that with conformal RT, fraction size can gradually be increased. HOF radiotherapy regimens without TDR shorten the treatment time and seem to be an alternative way of dose escalation in the treatment of glioblastoma

Modelling normal tissue isoeffect distribution in conformal radiotherapy of glioblastoma provides an alternative dose escalation pattern through hypofractionation without reducing the total dose

Energy Technology Data Exchange (ETDEWEB)

Mangel, L.; Skriba, Z.; Major, T.; Polgar, C.; Fodor, J.; Somogyi, A.; Nemeth, G. [National Research Inst. for Radiobiology and Radiohygiene, Budapest (Hungary)

2002-04-01

The purpose of this study was to prove that by using conformal external beam radiotherapy (RT) normal brain structures can be protected even when applying an alternative approach of biological dose escalation: hypofractionation (HOF) without total dose reduction (TDR). Traditional 2-dimensional (2D) and conformal 3-dimensional (3D) treatment plans were prepared for 10 gliomas representing the subanatomical sites of the supratentorial brain. Isoeffect distributions were generated by the biologically effective dose (BED) formula to analyse the effect of conventionally fractionated (CF) and HOF schedules on both the spatial biological dose distribution and biological dose-volume histograms. A comparison was made between 2D-CF (2.0 Gy/day) and 3D-HOF (2.5 Gy/day) regimens, applying the same 60 Gy total doses. Integral biologically effective dose (IBED) and volumes received biologically equivalent to a dose of 54 Gy or more (V-BED54) were calculated for the lower and upper brain stem as organs of risk. The IBED values were lower with the 3D-HOF than with the 2D-CF schedule in each tumour location, means 22.7{+-}17.1 and 40.4{+-}16.9 in Gy, respectively (p<0.0001). The V-BED54 values were also smaller or equal in 90% of the cases favouring the 3D-HOF scheme. The means were 2.7{+-}4.8 ccm for 3D-HOF and 10.7{+-}12.7 ccm for 2D-CF (p=0.0006). Our results suggest that with conformal RT, fraction size can gradually be increased. HOF radiotherapy regimens without TDR shorten the treatment time and seem to be an alternative way of dose escalation in the treatment of glioblastoma.

The comparison of 5-field conformal radiotherapy techniques for the treatment of prostate cancer: The best for femoral head sparing

International Nuclear Information System (INIS)

Zare, Mahkameh; Lashkari, Marzieh; Ghalehtaki, Reza; Ghasemi, Arash; Dehghan Manshadi, Hamidreza; Mir, Ali; Noorollahi, Somayeh; Alamolhoda, Mahboobeh

2016-01-01

External radiotherapy is a standard treatment procedure for localized prostate cancer. Given the relatively high long term survival treatment complications have been brought in center of attention. In this planning study, between 2012 and 2014, CT simulation data of 90 consecutive high-risk prostate cancer patients were collected. In the first phase, all were planned for whole pelvis irradiation up to 46Gy in 23 daily fractions. In the second phase, only the prostate gland was the target of radiation. Next, the subjects were divided randomly into three groups and each received a unique 5field conformal radiation plan including Plan A (Gantry angle: 0, 60, 120, 240, and 300), Plan B (Gantry angles: 0, 90, 120, 240, and 270) and Plan C (Gantry angles: 0, 60, 90, 270, and 300). The total dose was 70Gy. For each patient, the rectum, bladder, and both femoral heads were contoured as the at risk organs (OAR). From dose volume histograms, the proportional dose of PTV V100, the bladder and rectum V80 and V90 and femoral head V50 and V100 were calculated in all subjects and compared across plans. A statistically significant difference in the femoral head V50 and V100 was found between our studied 5field plans so that in Plan A (beam angles: 0, 60, 120, 240 and 300) less dose was received by both heads of femur. This study suggests that 5 field treatment planning including an anterior, two anterior oblique and two posterior oblique portals to be more proper for 3D conformal radiotherapy in order to spare femoral head with acceptable PTV coverage, and bladder and rectal doses.

Effects of carbon nanofiller characteristics on PTT chain conformation and dynamics: A computational study

Energy Technology Data Exchange (ETDEWEB)

Asadinezhad, Ahmad, E-mail: asadinezhad@cc.iut.ac.ir; Kelich, Payam

2017-01-15

Highlights: • Poly (trimethylene terephthalate) (PTT) conformation adopts a folded shape near nanofiller surface. • Graphene and carbon nanotube with different size and chemistry were simulated. • Graphene functionalization induces stronger confinement on PTT chain conformation. • PTT chain motion alters in dynamics mode as it becomes adsorbed onto nanofillers. • PTT reveals further changes near graphene than carbon nanotube surface. - Abstract: The effects of nanofiller chemistry and geometry on static and dynamic properties of an aromatic polyester, poly (trimethylene terephthalate), were addressed thanks to long-run classical molecular dynamics simulation. Two carbon nanofillers, graphene and carbon nanotube, were employed, where graphene was used in pristine and functionalized forms and carbon nanotube was used in two different diameters. The nanofiller geometry and chemistry were found to exert significant effects on conformation and dynamic behavior of PTT chain at the interface within the time scale the simulation was performed. It was found that PTT chain underwent interaction of van der Waals type with nanofiller via two subsequent phases, adsorption and orientation. The former stage, with definite characteristic time, involved translation of polymer chain toward interface while the latter was controlled by vibrational motions of chain atoms. The consequence of interaction was an increase in conformational order of polymer chain by transition to folded shape being favorable for any subsequent structural ordering (crystallization). The interaction of polymer with nanofiller gave rise to a reduction in overall mobility of polymer chain characterized by crossover from normal diffusive motion to subdiffusive mode.

Effects of carbon nanofiller characteristics on PTT chain conformation and dynamics: A computational study

International Nuclear Information System (INIS)

Asadinezhad, Ahmad; Kelich, Payam

2017-01-01

Highlights: • Poly (trimethylene terephthalate) (PTT) conformation adopts a folded shape near nanofiller surface. • Graphene and carbon nanotube with different size and chemistry were simulated. • Graphene functionalization induces stronger confinement on PTT chain conformation. • PTT chain motion alters in dynamics mode as it becomes adsorbed onto nanofillers. • PTT reveals further changes near graphene than carbon nanotube surface. - Abstract: The effects of nanofiller chemistry and geometry on static and dynamic properties of an aromatic polyester, poly (trimethylene terephthalate), were addressed thanks to long-run classical molecular dynamics simulation. Two carbon nanofillers, graphene and carbon nanotube, were employed, where graphene was used in pristine and functionalized forms and carbon nanotube was used in two different diameters. The nanofiller geometry and chemistry were found to exert significant effects on conformation and dynamic behavior of PTT chain at the interface within the time scale the simulation was performed. It was found that PTT chain underwent interaction of van der Waals type with nanofiller via two subsequent phases, adsorption and orientation. The former stage, with definite characteristic time, involved translation of polymer chain toward interface while the latter was controlled by vibrational motions of chain atoms. The consequence of interaction was an increase in conformational order of polymer chain by transition to folded shape being favorable for any subsequent structural ordering (crystallization). The interaction of polymer with nanofiller gave rise to a reduction in overall mobility of polymer chain characterized by crossover from normal diffusive motion to subdiffusive mode.

FDG-PET/CT Imaging for Staging and Target Volume Delineation in Preoperative Conformal Radiotherapy of Rectal Cancer

International Nuclear Information System (INIS)

Bassi, Maria Chiara; Turri, Lucia; Sacchetti, Gianmauro; Loi, Gianfranco; Cannillo, Barbara; La Mattina, Pierdaniele; Brambilla, Marco; Inglese, Eugenio; Krengli, Marco

2008-01-01

Purpose: To investigate the potential impact of using 18 F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) on staging and target volume delineation for patients affected by rectal cancer and candidates for preoperative conformal radiotherapy. Methods and Materials: Twenty-five patients diagnosed with rectal cancer T3-4 N0-1 M0-1 and candidates for preoperative radiotherapy underwent PET/CT simulation after injection of 5.18 MBq/kg of FDG. Clinical stage was reassessed on the basis of FDG-PET/CT findings. The gross tumor volume (GTV) and the clinical target volume (CTV) were delineated first on CT and then on PET/CT images. The PET/CT-GTV and PET/CT-CTV were analyzed and compared with CT-GTV and CT-CTV, respectively. Results: In 4 of 25 cases (24%), PET/CT affected tumor staging or the treatment purpose. In 3 of 25 cases (12%) staged N0 M0, PET/CT showed FDG uptake in regional lymph nodes and in a case also in the liver. In a patient with a single liver metastasis PET/CT detected multiple lesions, changing the treatment intent from curative to palliative. The PET/CT-GTV and PET/CT-CTV were significantly greater than the CT-GTV (p = 0.00013) and CT-CTV (p = 0.00002), respectively. The mean difference between PET/CT-GTV and CT-GTV was 25.4% and between PET/CT-CTV and CT-CTV was 4.1%. Conclusions: Imaging with PET/CT for preoperative radiotherapy of rectal cancer may lead to a change in staging and target volume delineation. Stage variation was observed in 12% of cases and a change of treatment intent in 4%. The GTV and CTV changed significantly, with a mean increase in size of 25% and 4%, respectively

The therapeutic effect of three-dimensional conformal radiation therapy combined with conventional radiotherapy for nasopharyngeal carcinoma

International Nuclear Information System (INIS)

Liang Feng; Lu Zhonghong; Yao Zhijun; Cao Yongzhen

2011-01-01

Objective: To observe the therapeutic effect of three-dimensional conformal radiation therapy (3DCRT) for nasopharyngeal carcinoma (NPC). Methods: 78 patients with NPC was treated by radiation schedule in two phases. In the first phase, nasopharyngeal lesions and metastases of all patients were treated by three-dimensional conformal radiation therapy (3DCRT) with a fraction of 2-5 Gy daily, 5 day per weeks, total dose 30 Gy. The second phase T1N0 or parts of T2N0 patients were done by Conventional radiotherapy with total dose 55 Gy on two small lateral opposing fields + with total dose 50 Gy on neck on tangential field,adding a 3 cm block. Patients with lymph node metastasis were given 55 Gy on the dacio-neck field (After 40 Gy, two small lateral opposing fields were used to boost the primary tumor while the spinal cord shielded) + with total dose 55 Gy on lower neck on tangential field. The upper bound of designed therapeutic field was set to connect with lower bound of main therapeutic field. Results: Three months after treatment,the rate of CR, PR, SD, PD were 38.5%, 55.1%, 5.1%, 1.3%, Total effective rate (CR+PR) were 93.6%. The 1-year, 2-year, 3-year and 5-year local-regional control rates were 92.3%, 88.5%, 78.2%, 70.5%.The 1-year, 2-year , 3-year and 5-year overall survival rate were 96.2%, 89.7%, 83.3%, 71.8%. Appearing early radiation response is well tolerated and no obviously mouth difficulties and cranial nerve damage observed. Conclusion: Clinical result of early-course three-dimensional conformal radiation therapy (3DCRT) for nasopharyngeal carcinoma (NPC) is good. (authors)

Probing the conformational dynamics of photosystem I in unconfined and confined spaces.

Science.gov (United States)

Das, Gaurav; Chattoraj, Shyamtanu; Nandi, Somen; Mondal, Prasenjit; Saha, Abhijit; Bhattacharyya, Kankan; Ghosh, Surajit

2017-12-20

The fluorescence dynamics of Photosystem I (PSI) in bulk water and inside a confined environment like a liposome have been investigated using time resolved confocal microscopy. In bulk water, PSI exhibits a major emission peak at ∼680 nm, while in the liposome it exhibits a markedly blue shifted emission maximum at ∼485 nm. This is indicative of conformational changes due to entrapment and emergence of a stressed conformation of PSI inside the liposome. The observed time constants for the fluorescence lifetime of PSI inside the liposome are significantly high as opposed to PSI in bulk water. More interestingly, the fluorescence intensity of PSI in bulk water exhibits strong fluctuations with many high intensity jumps and these are anti-correlated with the fluorescence lifetime of PSI. In contrast, inside the liposome, no such anti-correlated behaviour is observed. We further demonstrated that PSI exhibits at least two conformational states in bulk water, whereas a single conformation is observed inside the liposome, indicating the conformational rigidity and locking of the PSI complex inside a liposome.

Stereotactic body radiotherapy for lung cancer: how much does it really cost?

Science.gov (United States)

Lievens, Yolande; Obyn, Caroline; Mertens, Anne-Sophie; Van Halewyck, Dries; Hulstaert, Frank

2015-03-01

Despite the lack of randomized evidence, stereotactic body radiotherapy (SBRT) is being accepted as superior to conventional radiotherapy for patients with T1-2N0 non-small-cell lung cancer in the periphery of the lung and unfit or unwilling to undergo surgery. To introduce SBRT in a system of coverage with evidence development, a correct financing had to be determined. A time-driven activity-based costing model for radiotherapy was developed. Resource cost calculation of all radiotherapy treatments, standard and innovative, was conducted in 10 Belgian radiotherapy centers in the second half of 2012. The average cost of lung SBRT across the 10 centers (6221&OV0556;) is in the range of the average costs of standard fractionated 3D-conformal radiotherapy (5919&OV0556;) and intensity-modulated radiotherapy (7379&OV0556;) for lung cancer. Hypofractionated 3D-conformal radiotherapy and intensity-modulated radiotherapy schemes are less costly (3993&OV0556; respectively 4730&OV0556;). The SBRT cost increases with the number of fractions and is highly dependent of personnel and equipment use. SBRT cost varies more by centre than conventional radiotherapy cost, reflecting different technologies, stages in the learning curve and a lack of clear guidance in this field. Time-driven activity-based costing of radiotherapy is feasible in a multicentre setup, resulting in real-life resource costs that can form the basis for correct reimbursement schemes, supporting an early yet controlled introduction of innovative radiotherapy techniques in clinical practice.

Intensity-Modulated Radiotherapy for Sinonasal Cancer: Improved Outcome Compared to Conventional Radiotherapy

International Nuclear Information System (INIS)

Dirix, Piet; Vanstraelen, Bianca; Jorissen, Mark; Vander Poorten, Vincent; Nuyts, Sandra

2010-01-01

Purpose: To evaluate clinical outcome and toxicity of postoperative intensity-modulated radiotherapy (IMRT) for malignancies of the nasal cavity and paranasal sinuses. Methods and Materials: Between 2003 and 2008, 40 patients with cancer of the paranasal sinuses (n = 34) or nasal cavity (n = 6) received postoperative IMRT to a dose of 60 Gy (n = 21) or 66 Gy (n = 19). Treatment outcome and toxicity were retrospectively compared with that of a previous patient group (n = 41) who were also postoperatively treated to the same doses but with three-dimensional conformal radiotherapy without intensity modulation, from 1992 to 2002. Results: Median follow-up was 30 months (range, 4-74 months). Two-year local control, overall survival, and disease-free survival were 76%, 89%, and 72%, respectively. Compared to the three-dimensional conformal radiotherapy treatment, IMRT resulted in significantly improved disease-free survival (60% vs. 72%; p = 0.02). No grade 3 or 4 toxicity was reported in the IMRT group, either acute or chronic. The use of IMRT significantly reduced the incidence of acute as well as late side effects, especially regarding skin toxicity, mucositis, xerostomia, and dry-eye syndrome. Conclusions: Postoperative IMRT for sinonasal cancer significantly improves disease-free survival and reduces acute as well as late toxicity. Consequently, IMRT should be considered the standard treatment modality for malignancies of the nasal cavity and paranasal sinuses.

Evaluation of conformal radiotherapy techniques through physics and biologic criteria

International Nuclear Information System (INIS)

Bloch, Jonatas Carrero

2012-01-01

In the fight against cancer, different irradiation techniques have been developed based on technological advances and aiming to optimize the elimination of tumor cells with the lowest damage to healthy tissues. The radiotherapy planning goal is to establish irradiation technical parameters in order to achieve the prescribed dose distribution over the treatment volumes. While dose prescription is based on radiosensitivity of the irradiated tissues, the physical calculations on treatment planning take into account dosimetric parameters related to the radiation beam and the physical characteristics of the irradiated tissues. To incorporate tissue's radiosensitivity into radiotherapy planning calculations can help particularize treatments and establish criteria to compare and elect radiation techniques, contributing to the tumor control and the success of the treatment. Accordingly, biological models of cellular response to radiation have to be well established. This work aimed to study the applicability of using biological models in radiotherapy planning calculations to aid evaluating radiotherapy techniques. Tumor control probability (TCP) was studied for two formulations of the linear-quadratic model, with and without repopulation, as a function of planning parameters, as dose per fraction, and of radiobiological parameters, as the α/β ratio. Besides, the usage of biological criteria to compare radiotherapy techniques was tested using a prostate planning simulated with Monte Carlo code PENELOPE. Afterwards, prostate planning for five patients from the Hospital das Clinicas da Faculdade de Medicina de Ribeirao Preto, USP, using three different techniques were compared using the tumor control probability. In that order, dose matrices from the XiO treatment planning system were converted to TCP distributions and TCP-volume histograms. The studies performed allow the conclusions that radiobiological parameters can significantly influence tumor control

The Conformational Dynamics of Cas9 Governing DNA Cleavage Are Revealed by Single-Molecule FRET

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Mengyi Yang

2018-01-01

Full Text Available Summary: Off-target binding and cleavage by Cas9 pose major challenges in its application. How the conformational dynamics of Cas9 govern its nuclease activity under on- and off-target conditions remains largely unknown. Here, using intra-molecular single-molecule fluorescence resonance energy transfer measurements, we revealed that Cas9 in apo, sgRNA-bound, and dsDNA/sgRNA-bound forms spontaneously transits among three major conformational states, mainly reflecting significant conformational mobility of the catalytic HNH domain. We also uncovered surprising long-range allosteric communication between the HNH domain and the RNA/DNA heteroduplex at the PAM-distal end to ensure correct positioning of the catalytic site, which demonstrated that a unique proofreading mechanism served as the last checkpoint before DNA cleavage. Several Cas9 residues were likely to mediate the allosteric communication and proofreading step. Modulating interactions between Cas9 and heteroduplex at the PAM-distal end by introducing mutations on these sites provides an alternative route to improve and optimize the CRISPR/Cas9 toolbox. : Yang et al. revealed significant conformational dynamics of Cas9 at global and local scales using single-molecule FRET. They uncovered surprising long-range allosteric communication between the HNH nuclease domain and the RNA/DNA heteroduplex at the PAM-distal end that serves as a proofreading checkpoint to govern the nuclease activity and specificity of Cas9. Keywords: CRISPR, Cas9, single-molecule, FRET, conformational dynamics, proofreading, off-target, allosteric communication, genome editing

Dosimetric and clinical results of three-dimensional conformal radiotherapy for locally recurrent nasopharyngeal carcinoma

International Nuclear Information System (INIS)

Zheng Xiaokang; Ma Jun; Chen Longhua; Xia Yunfei; Shi Yusheng

2005-01-01

Purpose: To assess the dosimetric and clinical results of three-dimensional conformal radiotherapy (3D CRT) for locally recurrent nasopharyngeal carcinoma (NPC). Methods: A total of 86 patients with locally recurrent NPC were retreated with 3D CRT. The median prescribed dose was 68 Gy with 2 Gy per fractionation. Dosimetric quality was evaluated with dose distribution in planning target volume (PTV) and specified organs at risk (OAR), dose conformity index (CI) and dose homogeneity index (HI). The actuarial rate of local failure-free (LFF), overall survival (OS) and major late toxicities (MLT) were estimated with Kaplan-Meier method. Multivariate analysis for prognosis was performed using the Cox regression proportional hazards model. Results: The mean dose to PTV averaged 66.8 Gy, and the dose to specified OAR was acceptable. The average value of CI and HI was 0.59 and 9.1%. The 5-year actuarial rate of LFF and OS was 71 and 40%, respectively. The 5-year actuarial incidence of MLT≥Grade 3 and ≥Grade 4 were 100 and 49%, respectively. The major prognostic factors were T stage and the size of gross tumor volume (GTV). Advanced T stage and large GTV volume were associated with poor LFF and OS and high risk of MLT. Conclusion: The dosimetric quality of 3D CRT for locally recurrent NPC is generally excellent. A relatively high local control was achieved with this technique. However, the incidence of late toxicities were not found to decrease as originally expected. Early diagnosis of the recurrence and reasonable definition of the target volume are crucial to achieve a better outcome

Adjuvant Chemoradiation for Gastric Cancer Using Epirubicin, Cisplatin, and 5-Fluorouracil Before and After Three-Dimensional Conformal Radiotherapy With Concurrent Infusional 5-Fluorouracil: A Multicenter Study of the Trans-Tasman Radiation Oncology Group

International Nuclear Information System (INIS)

Leong, Trevor; Joon, Daryl Lim; Willis, David; Jayamoham, Jayasingham; Spry, Nigel; Harvey, Jennifer; Di Iulio, Juliana; Milner, Alvin; Mann, G. Bruce; Michael, Michael

2011-01-01

Purpose: The INT0116 study has established postoperative chemoradiotherapy as the standard of care for completely resected gastric adenocarcinoma. However, the optimal chemoradiation regimen remains to be defined. We conducted a prospective, multicenter study to evaluate an alternative chemoradiation regimen that combines more current systemic treatment with modern techniques of radiotherapy delivery. Methods and Materials: Patients with adenocarcinoma of the stomach who had undergone an R0 resection were eligible. Adjuvant therapy consisted of one cycle of epirubicin, cisplatin, and 5-FU (ECF), followed by radiotherapy with concurrent infusional 5-FU, and then two additional cycles of ECF. Radiotherapy was delivered using precisely defined, multiple-field, three-dimensional conformal techniques. Results: A total of 54 assessable patients were enrolled from 19 institutions. The proportion of patients commencing Cycles 1, 2, and 3 of ECF chemotherapy were 100%, 81%, and 67% respectively. In all, 94% of patients who received radiotherapy completed treatment as planned. Grade 3/4 neutropenia occurred in 66% of patients with 7.4% developing febrile neutropenia. Most neutropenic episodes (83%) occurred in the post-radiotherapy period during cycles 2 and 3 of ECF. Grade 3/4 gastrointestinal toxicity occurred in 28% of patients. In all, 35% of radiotherapy treatment plans contained protocol deviations that were satisfactorily amended before commencement of treatment. At median follow-up of 36 months, the 3-year overall survival rate was estimated at 61.6%. Conclusions: This adjuvant regimen using ECF before and after three-dimensional conformal chemoradiation is feasible and can be safely delivered in a cooperative group setting. A regimen similar to this is currently being compared with the INT0116 regimen in a National Cancer Institute-sponsored, randomized Phase III trial.

IMRT and 3D conformal radiotherapy with or without elective nodal irradiation in locally advanced NSCLC: A direct comparison of PET-based treatment planning.

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Fleckenstein, Jochen; Kremp, Katharina; Kremp, Stephanie; Palm, Jan; Rübe, Christian

2016-02-01

The potential of intensity-modulated radiation therapy (IMRT) as opposed to three-dimensional conformal radiotherapy (3D-CRT) is analyzed for two different concepts of fluorodeoxyglucose positron emission tomography (FDG PET)-based target volume delineation in locally advanced non-small cell lung cancer (LA-NSCLC): involved-field radiotherapy (IF-RT) vs. elective nodal irradiation (ENI). Treatment planning was performed for 41 patients with LA-NSCLC, using four different planning approaches (3D-CRT-IF, 3D-CRT-ENI, IMRT-IF, IMRT-ENI). ENI included a boost irradiation after 50 Gy. For each plan, maximum dose escalation was calculated based on prespecified normal tissue constraints. The maximum prescription dose (PD), tumor control probability (TCP), conformal indices (CI), and normal tissue complication probabilities (NTCP) were analyzed. IMRT resulted in statistically significant higher prescription doses for both target volume concepts as compared with 3D-CRT (ENI: 68.4 vs. 60.9 Gy, p ENI, there was a considerable theoretical increase in TCP (IMRT: 27.3 vs. 17.7 %, p ENI: 12.3 vs. 30.9 % p < 0.0001; IF: 15.9 vs. 24.1 %; p < 0.001). The IMRT technique and IF target volume delineation allow a significant dose escalation and an increase in TCP. IMRT results in an improved sparing of OARs as compared with 3D-CRT at equivalent dose levels.

Simultaneous optimization of beam orientations and beam weights in conformal radiotherapy

International Nuclear Information System (INIS)

Rowbottom, Carl Graham; Khoo, Vincent S.; Webb, Steve

2001-01-01

A methodology for the concurrent optimization of beam orientations and beam weights in conformal radiotherapy treatment planning has been developed and tested on a cohort of five patients. The algorithm is based on a beam-weight optimization scheme with a downhill simplex optimization engine. The use of random voxels in the dose calculation provides much of the required speed up in the optimization process, and allows the simultaneous optimization of beam orientations and beam weights in a reasonable time. In the implementation of the beam-weight optimization algorithm just 10% of the original patient voxels are used for the dose calculation and cost function evaluation. A fast simulated annealing algorithm controls the optimization of the beam arrangement. The optimization algorithm was able to produce clinically acceptable plans for the five patients in the cohort study. The algorithm equalized the dose to the optic nerves compared to the standard plans and reduced the mean dose to the brain stem by an average of 4.4% (±1.9, 1 SD), p value=0.007. The dose distribution to the PTV was not compromised by developing beam arrangements via the optimization algorithm. In conclusion, the simultaneous optimization of beam orientations and beam weights has been developed to be routinely used in a realistic time. The results of optimization in a small cohort study show that the optimization can reliably produce clinically acceptable dose distributions and may be able to improve dose distributions compared to those from a human planner

Structure-activity relationships of pyrethroid insecticides. Part 2. The use of molecular dynamics for conformation searching and average parameter calculation

Science.gov (United States)

Hudson, Brian D.; George, Ashley R.; Ford, Martyn G.; Livingstone, David J.

1992-04-01

Molecular dynamics simulations have been performed on a number of conformationally flexible pyrethroid insecticides. The results indicate that molecular dynamics is a suitable tool for conformational searching of small molecules given suitable simulation parameters. The structures derived from the simulations are compared with the static conformation used in a previous study. Various physicochemical parameters have been calculated for a set of conformations selected from the simulations using multivariate analysis. The averaged values of the parameters over the selected set (and the factors derived from them) are compared with the single conformation values used in the previous study.

Conformational dynamism for DNA interaction in the Salmonella RcsB response regulator.

Science.gov (United States)

Casino, Patricia; Miguel-Romero, Laura; Huesa, Juanjo; García, Pablo; García-Del Portillo, Francisco; Marina, Alberto

2018-01-09

The RcsCDB phosphorelay system controls an extremely large regulon in Enterobacteriaceae that involves processes such as biofilm formation, flagella production, synthesis of extracellular capsules and cell division. Therefore, fine-tuning of this system is essential for virulence in pathogenic microorganisms of this group. The final master effector of the RcsCDB system is the response regulator (RR) RcsB, which activates or represses multiple genes by binding to different promoter regions. This regulatory activity of RcsB can be done alone or in combination with additional transcriptional factors in phosphorylated or dephosphorylated states. The capacity of RcsB to interact with multiple promoters and partners, either dephosphorylated or phosphorylated, suggests an extremely conformational dynamism for this RR. To shed light on the activation mechanism of RcsB and its implication on promoter recognition, we solved the crystal structure of full-length RcsB from Salmonella enterica serovar Typhimurium in the presence and absence of a phosphomimetic molecule BeF3-. These two novel structures have guided an extensive site-directed mutagenesis study at the structural and functional level that confirms RcsB conformational plasticity and dynamism. Our data allowed us to propose a β5-T switch mechanism where phosphorylation is coupled to alternative DNA binding ways and which highlights the conformational dynamism of RcsB to be so pleiotropic. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

Benchmarking Dosimetric Quality Assessment of Prostate Intensity-Modulated Radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Senthi, Sashendra, E-mail: sasha.senthi@petermac.org [Division of Radiation Oncology, Peter MacCallum Cancer Center, East Melbourne, VIC (Australia); Gill, Suki S. [Division of Radiation Oncology, Peter MacCallum Cancer Center, East Melbourne, VIC (Australia); Haworth, Annette; Kron, Tomas; Cramb, Jim [Department of Physical Sciences, Peter MacCallum Cancer Center, East Melbourne, VIC (Australia); Rolfo, Aldo [Radiation Therapy Services, Peter MacCallum Cancer Center, East Melbourne, VIC (Australia); Thomas, Jessica [Biostatistics and Clinical Trials, Peter MacCallum Cancer Center, East Melbourne, VIC (Australia); Duchesne, Gillian M. [Division of Radiation Oncology, Peter MacCallum Cancer Center, East Melbourne, VIC (Australia); Hamilton, Christopher H.; Joon, Daryl Lim [Radiation Oncology Department, Austin Repatriation Hospital, Heidelberg, VIC (Australia); Bowden, Patrick [Radiation Oncology Department, Tattersall' s Cancer Center, East Melbourne, VIC (Australia); Foroudi, Farshad [Division of Radiation Oncology, Peter MacCallum Cancer Center, East Melbourne, VIC (Australia)

2012-02-01

Purpose: To benchmark the dosimetric quality assessment of prostate intensity-modulated radiotherapy and determine whether the quality is influenced by disease or treatment factors. Patients and Methods: We retrospectively analyzed the data from 155 consecutive men treated radically for prostate cancer using intensity-modulated radiotherapy to 78 Gy between January 2007 and March 2009 across six radiotherapy treatment centers. The plan quality was determined by the measures of coverage, homogeneity, and conformity. Tumor coverage was measured using the planning target volume (PTV) receiving 95% and 100% of the prescribed dose (V{sub 95%} and V{sub 100%}, respectively) and the clinical target volume (CTV) receiving 95% and 100% of the prescribed dose. Homogeneity was measured using the sigma index of the PTV and CTV. Conformity was measured using the lesion coverage factor, healthy tissue conformity index, and the conformity number. Multivariate regression models were created to determine the relationship between these and T stage, risk status, androgen deprivation therapy use, treatment center, planning system, and treatment date. Results: The largest discriminatory measurements of coverage, homogeneity, and conformity were the PTV V{sub 95%}, PTV sigma index, and conformity number. The mean PTV V{sub 95%} was 92.5% (95% confidence interval, 91.3-93.7%). The mean PTV sigma index was 2.10 Gy (95% confidence interval, 1.90-2.20). The mean conformity number was 0.78 (95% confidence interval, 0.76-0.79). The treatment center independently influenced the coverage, homogeneity, and conformity (all p < .0001). The planning system independently influenced homogeneity (p = .038) and conformity (p = .021). The treatment date independently influenced the PTV V{sub 95%} only, with it being better at the start (p = .013). Risk status, T stage, and the use of androgen deprivation therapy did not influence any aspect of plan quality. Conclusion: Our study has benchmarked measures

Conformal house

DEFF Research Database (Denmark)

Ryttov, Thomas Aaby; Sannino, Francesco

2010-01-01

fixed point. As a consistency check we recover the previously investigated bounds of the conformal windows when restricting to a single matter representation. The earlier conformal windows can be imagined to be part now of the new conformal house. We predict the nonperturbative anomalous dimensions...... at the infrared fixed points. We further investigate the effects of adding mass terms to the condensates on the conformal house chiral dynamics and construct the simplest instanton induced effective Lagrangian terms...

Comparing conformal, arc radiotherapy and helical tomotherapy in craniospinal irradiation planning.

Science.gov (United States)

Myers, Pamela A; Mavroidis, Panayiotis; Papanikolaou, Nikos; Stathakis, Sotirios

2014-09-08

Currently, radiotherapy treatment plan acceptance is based primarily on dosimetric performance measures. However, use of radiobiological analysis to assess benefit in terms of tumor control and harm in terms of injury to normal tissues can be advantageous. For pediatric craniospinal axis irradiation (CSI) patients, in particular, knowing the technique that will optimize the probabilities of benefit versus injury can lead to better long-term outcomes. Twenty-four CSI pediatric patients (median age 10) were retrospectively planned with three techniques: three-dimensional conformal radiation therapy (3D CRT), volumetric-modulated arc therapy (VMAT), and helical tomotherapy (HT). VMAT plans consisted of one superior and one inferior full arc, and tomotherapy plans were created using a 5.02cm field width and helical pitch of 0.287. Each plan was normalized to 95% of target volume (whole brain and spinal cord) receiving prescription dose 23.4Gy in 13 fractions. Using an in-house MATLAB code and DVH data from each plan, the three techniques were evaluated based on biologically effective uniform dose (D=), the complication-free tumor control probability (P+), and the width of the therapeutically beneficial range. Overall, 3D CRT and VMAT plans had similar values of D= (24.1 and 24.2 Gy), while HT had a D= slightly lower (23.6 Gy). The average values of the P+ index were 64.6, 67.4, and 56.6% for 3D CRT, VMAT, and HT plans, respectively, with the VMAT plans having a statistically significant increase in P+. Optimal values of D= were 28.4, 33.0, and 31.9 Gy for 3D CRT, VMAT, and HT plans, respectively. Although P+ values that correspond to the initial dose prescription were lower for HT, after optimizing the D= prescription level, the optimal P+ became 94.1, 99.5, and 99.6% for 3D CRT, VMAT, and HT, respectively, with the VMAT and HT plans having statistically significant increases in P+. If the optimal dose level is prescribed using a radiobiological evaluation method, as

Historical review of radiotherapy

International Nuclear Information System (INIS)

Onai, Yoshio

1993-01-01

The techniques of radiotherapy have been improved by development of particle accelerators, radionuclides and computers. This paper presents a historical review of the physical and technical aspects of radiotherapy in Japan. Changes in the kinds of radiation, such as X-rays, gamma rays, electrons, neutrons and protons used for external radiotherapy, and the equipment involved are described chronologically, and historical changes in the quality of radiotherapy apparatus are outlined. Patient data acquisition equipment, such as X-ray simulator and X-ray CT, beam modifying devices, patient setup devices, and devices to verify treatment fields and patient doses are reviewed historically. Radiation sources for brachytherapy and internal radiotherapy, and remotely controlled afterloading systems are reviewed chronologically. Historical changes in methods to evaluate absorbed doses, dose monitor systems and beam data acquisition systems are outlined. Changes in methods of calculating dose distributions for external X-ray and electron therapy, brachytherapy and internal radiotherapy by unsealded radionuclides are described and calculation techniques for treatment planning system are reviewed. Annual figures in the numbers of radiotherapy equipment, such as telecobalt and telecesium units, linear accelerators, betatrons, microtrons, stereotactic gamma units, conformation radiotherapy units, remotely controlled afterloading systems, and associated equipment such as X-ray simulators and treatment planning systems are provided, as are changes in the number of accelerators by maximum X-ray energy and maximum electron energy, and in the number of licensed hospitals and clinics using small sealed sources. Changes in techniques of external radiotherapy and brachytherapy are described briefly from the point of view of dose distributions. (author)

Intensity modulated radiotherapy (IMRT) in bilateral retinoblastoma

International Nuclear Information System (INIS)

Atalar, Banu; Ozyar, Enis; Gunduz, Kaan; Gungor, Gorkem

2010-01-01

External beam radiotherapy (EBRT) for retinoblastoma has traditionally been done with conventional radiotherapy techniques which resulted high doses to the surrounding normal tissues. A 20 month-old girl with group D bilateral retinoblastoma underwent intensity modulated radiotherapy (IMRT) to both eyes after failing chemoreduction and focal therapies including cryotherapy and transpupillary thermotherapy. In this report, we discuss the use of IMRT as a method for reducing doses to adjacent normal tissues while delivering therapeutic doses to the tumour tissues compared with 3-dimensional conformal radiotherapy (3DCRT). At one year follow-up, the patient remained free of any obvious radiation complications. Image guided IMRT provides better dose distribution than 3DCRT in retinoblastoma eyes, delivering the therapeutic dose to the tumours and minimizing adjacent tissue damage

Sonographic Assessment of Parotid and Submandibular Glands in Patients Undergoing 3D Conformal Radiotherapy

Directory of Open Access Journals (Sweden)

Johari M

2016-06-01

Full Text Available The aim of this study was to evaluate sonographic changes in parotid and submandibular salivary glands in patients undergoing radiotherapy for head and neck malignancies. In addition, salivary changes subsequent to radiotherapy were evaluated objectively and subjectively. Twenty patients(13males and 7females with head and neck malignancies, who had been referred to the Radiotherapy/Oncology Department of the Shahid Madani Hospital in Tabriz, Iran, were included in the study. Length, width, echotexture, echogenicity and margins of parotid and submandibular glands were evaluated before and after radiotherapy using sonography. Peak-systolic velocity(PSV,end-diastolic velocity(EDV and resistive index(RI were also assessed by Doppler sonography. Xerostomia subsequent to radiotherapy was evaluated with the use of two techniques: patients’ self-reported scoring and objective measurement of resting saliva. There was a significant decrease in the width of the parotid gland after radiotherapy compared to baseline(P=0.005.Although the length of the parotid gland and the dimensions of submandibular gland decrease, the differences were not significant. In addition, the echogenicity, echotexture and the margin of the glands change to hypoechoic, heterogenic and irregular, respectively, subsequent to radiotherapy. The Doppler technique showed decrease in PSV and RI and an increase in EDV; however, only the decrease in RI in the submandibular gland was statistically significant(P=0.002.The results showed a significant decrease in salivary flow after radiotherapy(P<0.001.In addition, based on the patients reports, the severity of xerostomia increased significantly after radiotherapy(P<0.001. Songraphic changes of parotid and submandibular glands after radiotherapy should be considered in ultrasound examinations. The damages to the parotid and submandibular glands had significant influence in patient post 3D-CRT.

Conformal radiotherapy of urinary bladder cancer

International Nuclear Information System (INIS)

Muren, Ludvig Paul; Smaaland, Rune; Dahl, Olav

2004-01-01

Recent advances in radiotherapy (RT) are founded on the enhanced tumour visualisation capabilities of new imaging modalities and the precise deposition of individualised radiation dose distributions made possible with the new systems for RT planning and delivery. These techniques have a large potential to also improve the results of RT of urinary bladder cancer. Major challenges to take full advantage of these advances in the management of bladder cancer are to control, and, as far as possible, reduce bladder motion, and to reliably account for the related intestine and rectum motion. If these obstacles are overcome, it should be possible in the near future to offer selected patients with muscle invading bladder cancer an organ-sparing, yet effective combined-modality treatment as an alternative to radical surgery

Secondary effects of radiotherapy on the orofacial sphere

International Nuclear Information System (INIS)

Guillaume, Nicolas

2012-01-01

The objective of this research is to determine the role of the dental surgeon in the taking into care of patients treated by head and neck radiotherapy. It also aims at giving information to the patient on secondary effects which radiotherapy may induce, and at determining which therapeutic behaviour to adopt to prevent or at least mitigate the appearance of complications. The author first presents some generalities on radiotherapy: presentation of upper aero-digestive tract cancers (surgery, radiotherapy, and chemotherapy), description of the different radiotherapy techniques (external radiotherapy, brachytherapy), discussion of factors influencing local secondary effects of radiotherapy. The second part addresses the specific case of early orofacial secondary effects, discusses their origin, clinic signs and prevention means: cutaneous effect, mucositis, xerostomia, candidiasis, taste disorders, relationship between early local reactions and anti-tumour treatment efficiency. The third part addresses late orofacial secondary effects: cervix sclerosis, limitation of mouth opening, dental effects, periodontal diseases, osteoradionecrosis. The last part discusses the evolution of radiotherapy: intensity modulated conformational radiotherapy, targeted therapeutics [fr

Integral Dose and Radiation-Induced Secondary Malignancies: Comparison between Stereotactic Body Radiation Therapy and Three-Dimensional Conformal Radiotherapy

Directory of Open Access Journals (Sweden)

Stefano G. Masciullo

2012-11-01

Full Text Available The aim of the present paper is to compare the integral dose received by non-tumor tissue (NTID in stereotactic body radiation therapy (SBRT with modified LINAC with that received by three-dimensional conformal radiotherapy (3D-CRT, estimating possible correlations between NTID and radiation-induced secondary malignancy risk. Eight patients with intrathoracic lesions were treated with SBRT, 23 Gy × 1 fraction. All patients were then replanned for 3D-CRT, maintaining the same target coverage and applying a dose scheme of 2 Gy × 32 fractions. The dose equivalence between the different treatment modalities was achieved assuming α/β = 10Gy for tumor tissue and imposing the same biological effective dose (BED on the target (BED = 76Gy10. Total NTIDs for both techniques was calculated considering α/β = 3Gy for healthy tissue. Excess absolute cancer risk (EAR was calculated for various organs using a mechanistic model that includes fractionation effects. A paired two-tailed Student t-test was performed to determine statistically significant differences between the data (p ≤ 0.05. Our study indicates that despite the fact that for all patients integral dose is higher for SBRT treatments than 3D-CRT (p = 0.002, secondary cancer risk associated to SBRT patients is significantly smaller than that calculated for 3D-CRT (p = 0.001. This suggests that integral dose is not a good estimator for quantifying cancer induction. Indeed, for the model and parameters used, hypofractionated radiotherapy has the potential for secondary cancer reduction. The development of reliable secondary cancer risk models seems to be a key issue in fractionated radiotherapy. Further assessments of integral doses received with 3D-CRT and other special techniques are also strongly encouraged.

A deterministic iterative least-squares algorithm for beam weight optimization in conformal radiotherapy

International Nuclear Information System (INIS)

Chen Yan; Michalski, Darek; Houser, Christopher; Galvin, James M.

2002-01-01

Currently, inverse treatment planning in conformal radiotherapy is, in part, a trial-and-error process due to the interplay of many competing criteria for obtaining a clinically acceptable dose distribution. A new method is developed for beam weight optimization that incorporates clinically relevant nonlinear and linear constraints. The process is driven by a nonlinear, quasi-quadratic objective function and the solution space is defined by a set of linear constraints. At each step of iteration, the optimization problem is linearized by a self-consistent approximation that is local to the existing dose distribution. The dose distribution is then improved by solving a series of constrained least-squares problems using an established method until all prescribed constraints are satisfied. This differs from the current approaches in that it does not rely on the search for the global minimum of a specific objective function. Essentially, our proposed objective function can be construed as a functional that comprises a class of dose-based quadratic objective functions. Empirical adjustment for appropriate model parameters in the construction of objective function is minimized, since these parameters are in effect adaptively adjusted during optimization. The method is robust in solving difficult clinical cases using either aperture or pencil beam based planning techniques for intensity-modulated radiation therapy. (author)

Cranial radiotherapy guided by computed tomography with or without fields conformation in pediatric

International Nuclear Information System (INIS)

Fernandez, Diego; Caussa, Lucas; Murina, Patricia; Zunino, Silvia

2007-01-01

Many malignancies in children can be cured by radiotherapy, acute toxicity and the significant effect of delayed treatment are worrying for the patient, family and society. Therefore, the end of the pediatric radiotherapy is to maintain or improve the cure rate of cancer, diminishing the aftermath of treatment. The goal of this study is to measure differences in doses to the healthy tissue of the central nervous system with two radiotherapy techniques, both guided by computed tomography [es

Conformal intensity-modulated radiotherapy (IMRT) delivered by robotic linac - testing IMRT to the limit?

International Nuclear Information System (INIS)

Webb, S.

1999-01-01

In this paper it is proposed that intensity-modulated radiotherapy (IMRT) could be delivered optimally by a short-length linac mounted on a robotic arm. The robot would allow the linac to 'plant' narrow pencils of photon radiation with any orientation (excluding zones within which the linac and couch might collide) relative to the planning target volume (PTV). The treatment is specified by the trajectory of the robot and by the number of monitor units (MUs) delivered at each robotic orientation. An inverse-planning method to determine the optimum robotic trajectory is presented. It is shown that for complex PTVs, specifically those with concavities in their outline, the conformality of the treatment is improved by the use of a complex trajectory in comparison with a less complex constrained trajectory and this improvement is quantified. It is concluded that robotic linac delivery would lead to a great flexibility in those IMRT treatments requiring very complicated dose distributions with complex 3D shapes. However, even using very fast computers, the goal of determining whether robotic linac delivery is the ultimate IMRT cannot be conclusively reached at present. (author)

Status of Radiotherapy around the World: Radiotherapy in China. Chapter 25.6

International Nuclear Information System (INIS)

Zhu, Ci; Yin, Wei Bo; Chen, Bo; Zhang, Chun Li; Zhang, Hong Zhi; Li, Ye Xiong

2017-01-01

China’s experience of using radiotherapy to treat cancer began with the installation of the first superficial X ray machine at Peking Union Medical College Hospital in early 1920, followed by the first 200 kV deep X ray machine installed at the French Hospital in Shanghai in 1923, and the first Chinese radiotherapy department established at the Affiliated Hospital of Peking University in 1932. However, the field of radiotherapy in China was still in its infancy between the 1930s and 1960s, as all operating machines were imported from foreign countries, making radiotherapy very difficult to access for cancer patients. Progress was slow until the mid-1970s, when the first batch of megavoltage machines (cobalt-60 machines and linacs) was produced by Chinese manufacturers. Owing to the efforts of radiotherapy pioneers such as Wu Huanxing, Gu Xianzhi, Liu Taifu, and Yin Weibo, who brought radiotherapy to China and shaped how Chinese patients would be treated today, radiotherapy was installed as one of the mainstream modalities of cancer treatment. In 1986, the China Society for Radiation Oncology (CSTRO) was founded, indicating that a network advancing radiation oncology practice in China was taking shape. One year later, the first issue of the Chinese Journal of Radiation Oncology was published, offering a platform for the timely exchange and sharing of laboratory and clinical research outcomes among radiation oncology professions across the country. During the past two decades, with the introduction of the gamma knife and stereotactic radiotherapy, 3-D conformal radiotherapy, IMRT, IGRT and other advanced techniques, China experienced not only a big jump in its radiotherapy equipment and facilities, but also a dramatic growth in the excellence of radiation oncology specialist staff nationwide

Conformal Field Theory as Microscopic Dynamics of Incompressible Euler and Navier-Stokes Equations

International Nuclear Information System (INIS)

Fouxon, Itzhak; Oz, Yaron

2008-01-01

We consider the hydrodynamics of relativistic conformal field theories at finite temperature. We show that the limit of slow motions of the ideal hydrodynamics leads to the nonrelativistic incompressible Euler equation. For viscous hydrodynamics we show that the limit of slow motions leads to the nonrelativistic incompressible Navier-Stokes equation. We explain the physical reasons for the reduction and discuss the implications. We propose that conformal field theories provide a fundamental microscopic viewpoint of the equations and the dynamics governed by them

Conformal field theory as microscopic dynamics of incompressible Euler and Navier-Stokes equations.

Science.gov (United States)

Fouxon, Itzhak; Oz, Yaron

2008-12-31

We consider the hydrodynamics of relativistic conformal field theories at finite temperature. We show that the limit of slow motions of the ideal hydrodynamics leads to the nonrelativistic incompressible Euler equation. For viscous hydrodynamics we show that the limit of slow motions leads to the nonrelativistic incompressible Navier-Stokes equation. We explain the physical reasons for the reduction and discuss the implications. We propose that conformal field theories provide a fundamental microscopic viewpoint of the equations and the dynamics governed by them.

Assessment of renal function after conformal radiotherapy and intensity-modulated radiotherapy by functional {sup 1}H-MRI and {sup 23}Na-MRI

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Haneder, S.; Michaely, H.J.; Schoenberg, S.O. [Universitaetsmedizin Mannheim, Heidelberg Univ., Mannheim (Germany). Inst. of Clinical Radiology and Nuclear Medicine; Konstandin, S.; Schad, L.R. [Universitaetsmedizin Mannheim, Heidelberg Univ., Mannheim (Germany). Computer-Assisted Clinical Medicine; Siebenlist, K.; Wertz, H.; Wenz, F.; Lohr, F.; Boda-Heggemann, J. [Universitaetsmedizin Mannheim, Heidelberg Univ., Mannheim (Germany). Dept. of Radiation Oncology

2012-12-15

Purpose: Adjuvant radiochemotherapy (RCHT) improves survival of patients with locally advanced gastric cancer. Conventional three-dimensional conformal radiotherapy (3D-CRT) results in ablative doses to a significant amount of the left kidney, while image-guided intensity-modulated radiotherapy (IG-IMRT) provides excellent target coverage with improved kidney sparing. Few long-term results on IMRT for gastric cancer, however, have been published. Functional magnetic resonance imaging (fMRI) at 3.0 T including blood oxygenation-level dependent (BOLD) imaging, diffusion-weighted imaging (DWI) and, for the first time, {sup 23}Na imaging was used to evaluate renal status after radiotherapy with 3D-CRT or IG-IMRT. Patients and methods Four disease-free patients (2 after 3D-CRT and 2 after IMRT; FU for all patients > 5 years) were included in this feasibility study. Morphological sequences, axial DWI images, 2D-gradient echo (GRE)-BOLD images, and {sup 23}Na images were acquired. Mean values/standard deviations for ({sup 23}Na), the apparent diffusion coefficient (ADC), and R2{sup *} values were calculated for the upper/middle/lower parts of both kidneys. Corticomedullary {sup 23}Na-concentration gradients were determined. Results: Surprisingly, IG-IMRT patients showed no morphological alterations and no statistically significant differences of ADC and R2{sup *} values in all renal parts. Values for mean corticomedullary {sup 23}Na-concentration matched those for healthy volunteers. Results were similar in 3D-CRT patients, except for the cranial part of the left kidney. This was atrophic and presented significantly reduced functional parameters (p = 0.001 - p = 0.033). Reduced ADC values indicated reduced cell density and reduced extracellular space. Cortical and medullary R2{sup *} values of the left cranial kidney in the 3D-CRT group were higher, indicating more deoxygenated hemoglobin due to reduced blood flow/oxygenation. ({sup 23}Na) of the renal cranial parts in

Molecular dynamics simulations of conformation changes of HIV-1 regulatory protein on graphene

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Zhao, Daohui; Li, Libo; He, Daohang; Zhou, Jian, E-mail: jianzhou@scut.edu.cn

2016-07-30

Graphical abstract: Preferential adsorption of Vpr13-33 on graphene accompanied by early conformational change from α-helix to β-sheet structures was observed by molecular simulations. This work presents the molecular mechanism of graphene-induced peptide conformational alteration and sheds light on developing graphene-based materials to inhibit HIV. - Highlights: • Graphene induced early structural transition of Vpr13-33 is studied by MD simulations. • Both π-π stacking and hydrophobic interactions orchestrate the peptide adsorption. • Vpr has an increased propensity of β-sheet content on graphene surface. • To develop graphene-based materials to inhibit HIV is possible. - Abstract: The fragment of viral protein R (Vpr), Vpr13-33, plays an important role in regulating nuclear importing of HIV genes through channel formation in which it adopts a leucine-zipper-like alpha-helical conformation. A recent experimental study reported that helical Vpr13-33 would transform to β-sheet or random coil structures and aggregate on the surface of graphene or graphene oxide through hydrophobic interactions. Due to experimental limitations, however, there is still a considerable lack of understanding on the adsorption dynamics at the early stage of the conformational transition at water-graphene interface and the underlying driving force at molecular level. In this study, atomistic molecular dynamics simulations were used to explore the conformation transition phenomena. Vpr13-33 kept α-helical structure in solution, but changed to β-sheet structure when strongly adsorbed onto graphene. Preferential adsorption of Vpr13-33 on graphene is dominated by hydrophobic interactions. The cluster analysis identified the most significant populated conformation and the early stage of structure conversion from α-helical to β-sheet was found, but the full β-sheet propagation was not observed. Free energy landscape analysis further complemented the transformation analysis of

Molecular dynamics simulations of conformation changes of HIV-1 regulatory protein on graphene

International Nuclear Information System (INIS)

Zhao, Daohui; Li, Libo; He, Daohang; Zhou, Jian

2016-01-01

Graphical abstract: Preferential adsorption of Vpr13-33 on graphene accompanied by early conformational change from α-helix to β-sheet structures was observed by molecular simulations. This work presents the molecular mechanism of graphene-induced peptide conformational alteration and sheds light on developing graphene-based materials to inhibit HIV. - Highlights: • Graphene induced early structural transition of Vpr13-33 is studied by MD simulations. • Both π-π stacking and hydrophobic interactions orchestrate the peptide adsorption. • Vpr has an increased propensity of β-sheet content on graphene surface. • To develop graphene-based materials to inhibit HIV is possible. - Abstract: The fragment of viral protein R (Vpr), Vpr13-33, plays an important role in regulating nuclear importing of HIV genes through channel formation in which it adopts a leucine-zipper-like alpha-helical conformation. A recent experimental study reported that helical Vpr13-33 would transform to β-sheet or random coil structures and aggregate on the surface of graphene or graphene oxide through hydrophobic interactions. Due to experimental limitations, however, there is still a considerable lack of understanding on the adsorption dynamics at the early stage of the conformational transition at water-graphene interface and the underlying driving force at molecular level. In this study, atomistic molecular dynamics simulations were used to explore the conformation transition phenomena. Vpr13-33 kept α-helical structure in solution, but changed to β-sheet structure when strongly adsorbed onto graphene. Preferential adsorption of Vpr13-33 on graphene is dominated by hydrophobic interactions. The cluster analysis identified the most significant populated conformation and the early stage of structure conversion from α-helical to β-sheet was found, but the full β-sheet propagation was not observed. Free energy landscape analysis further complemented the transformation analysis of

Modality comparison for small animal radiotherapy: A simulation study

Energy Technology Data Exchange (ETDEWEB)

Bazalova, Magdalena, E-mail: bazalova@stanford.edu; Nelson, Geoff; Noll, John M.; Graves, Edward E. [Department of Radiation Oncology, Molecular Imaging Program at Stanford, Stanford University, Stanford, California 94305 (United States)

2014-01-15

Purpose: Small animal radiation therapy has advanced significantly in recent years. Whereas in the past dose was delivered using a single beam and a lead shield for sparing of healthy tissue, conformal doses can be now delivered using more complex dedicated small animal radiotherapy systems with image guidance. The goal of this paper is to investigate dose distributions for three small animal radiation treatment modalities. Methods: This paper presents a comparison of dose distributions generated by the three approaches—a single-field irradiator with a 200 kV beam and no image guidance, a small animal image-guided conformal system based on a modified microCT scanner with a 120 kV beam developed at Stanford University, and a dedicated conformal system, SARRP, using a 220 kV beam developed at Johns Hopkins University. The authors present a comparison of treatment plans for the three modalities using two cases: a mouse with a subcutaneous tumor and a mouse with a spontaneous lung tumor. A 5 Gy target dose was calculated using the EGSnrc Monte Carlo codes. Results: All treatment modalities generated similar dose distributions for the subcutaneous tumor case, with the highest mean dose to the ipsilateral lung and bones in the single-field plan (0.4 and 0.4 Gy) compared to the microCT (0.1 and 0.2 Gy) and SARRP (0.1 and 0.3 Gy) plans. The lung case demonstrated that due to the nine-beam arrangements in the conformal plans, the mean doses to the ipsilateral lung, spinal cord, and bones were significantly lower in the microCT plan (2.0, 0.4, and 1.9 Gy) and the SARRP plan (1.5, 0.5, and 1.8 Gy) than in single-field irradiator plan (4.5, 3.8, and 3.3 Gy). Similarly, the mean doses to the contralateral lung and the heart were lowest in the microCT plan (1.5 and 2.0 Gy), followed by the SARRP plan (1.7 and 2.2 Gy), and they were highest in the single-field plan (2.5 and 2.4 Gy). For both cases, dose uniformity was greatest in the single-field irradiator plan followed by

Toxicity and dosimetric analysis of non-small cell lung cancer patients undergoing radiotherapy with 4DCT and image-guided intensity modulated radiotherapy: a regional centre's experience.

Science.gov (United States)

Livingston, Gareth C; Last, Andrew J; Shakespeare, Thomas P; Dwyer, Patrick M; Westhuyzen, Justin; McKay, Michael J; Connors, Lisa; Leader, Stephanie; Greenham, Stuart

2016-09-01

For patients receiving radiotherapy for locally advance non-small cell lung cancer (NSCLC), the probability of experiencing severe radiation pneumonitis (RP) appears to rise with an increase in radiation received by the lungs. Intensity modulated radiotherapy (IMRT) provides the ability to reduce planned doses to healthy organs at risk (OAR) and can potentially reduce treatment-related side effects. This study reports toxicity outcomes and provides a dosimetric comparison with three-dimensional conformal radiotherapy (3DCRT). Thirty curative NSCLC patients received radiotherapy using four-dimensional computed tomography and five-field IMRT. All were assessed for early and late toxicity using common terminology criteria for adverse events. All plans were subsequently re-planned using 3DCRT to the same standard as the clinical plans. Dosimetric parameters for lungs, oesophagus, heart and conformity were recorded for comparison between the two techniques. IMRT plans achieved improved high-dose conformity and reduced OAR doses including lung volumes irradiated to 5-20 Gy. One case each of oesophagitis and erythema (3%) were the only Grade 3 toxicities. Rates of Grade 2 oesophagitis were 40%. No cases of Grade 3 RP were recorded and Grade 2 RP rates were as low as 3%. IMRT provides a dosimetric benefit when compared to 3DCRT. While the clinical benefit appears to increase with increasing target size and increasing complexity, IMRT appears preferential to 3DCRT in the treatment of NSCLC.

Global conformational dynamics of a Y-family DNA polymerase during catalysis.

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Cuiling Xu

2009-10-01

Full Text Available Replicative DNA polymerases are stalled by damaged DNA while the newly discovered Y-family DNA polymerases are recruited to rescue these stalled replication forks, thereby enhancing cell survival. The Y-family DNA polymerases, characterized by low fidelity and processivity, are able to bypass different classes of DNA lesions. A variety of kinetic and structural studies have established a minimal reaction pathway common to all DNA polymerases, although the conformational intermediates are not well defined. Furthermore, the identification of the rate-limiting step of nucleotide incorporation catalyzed by any DNA polymerase has been a matter of long debate. By monitoring time-dependent fluorescence resonance energy transfer (FRET signal changes at multiple sites in each domain and DNA during catalysis, we present here a real-time picture of the global conformational transitions of a model Y-family enzyme: DNA polymerase IV (Dpo4 from Sulfolobus solfataricus. Our results provide evidence for a hypothetical DNA translocation event followed by a rapid protein conformational change prior to catalysis and a subsequent slow, post-chemistry protein conformational change. Surprisingly, the DNA translocation step was induced by the binding of a correct nucleotide. Moreover, we have determined the directions, rates, and activation energy barriers of the protein conformational transitions, which indicated that the four domains of Dpo4 moved in a synchronized manner. These results showed conclusively that a pre-chemistry conformational change associated with domain movements was too fast to be the rate-limiting step. Rather, the rearrangement of active site residues limited the rate of correct nucleotide incorporation. Collectively, the conformational dynamics of Dpo4 offer insights into how the inter-domain movements are related to enzymatic function and their concerted interactions with other proteins at the replication fork.

Can All Centers Plan Intensity-Modulated Radiotherapy (IMRT) Effectively? An External Audit of Dosimetric Comparisons Between Three-Dimensional Conformal Radiotherapy and IMRT for Adjuvant Chemoradiation for Gastric Cancer

International Nuclear Information System (INIS)

Chung, Hans T.; Lee, Brian; Park, Eileen; Lu, Jiade J.; Xia Ping

2008-01-01

Purpose: To compare dosimetric endpoints between three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT) at our center with limited IMRT experience, and to perform an external audit of the IMRT plans. Methods and Materials: Ten patients, who received adjuvant chemoradiation for gastric cancer, formed the study cohort. For standardization, the planning target volume (PTV) and organs at risk were recontoured with the assistance of a study protocol radiologic atlas. The cohort was replanned with CMS Xio to generate coplanar 3D-CRT and IMRT plans. All 10 datasets, including volumes but without the plans (i.e., blinded), were transmitted to an experienced center where IMRT plans were designed using Nomos Corvus (IMRT-C) and ADAC Pinnacle (IMRT-P). All IMRT plans were normalized to D95% receiving 45 Gy. Results: Intensity-modulated radiotherapy yielded higher PTV V45 (volume that receives ≥45 Gy) (p < 0.001) than 3D-CRT. No difference in V20 was seen in the right (p = 0.9) and left (p 0.3) kidneys, but the liver mean dose (p < 0.001) was superior with IMRT. For the external audit, IMRT-C (p = 0.002) and IMRT-P (p < 0.001) achieved significantly lower left kidney V20 than IMRT, and IMRT-P (p < 0.001) achieved lower right kidney V20 than IMRT. The IMRT-C (p = 0.003) but not IMRT-P (p = 0.6) had lower liver mean doses than IMRT. Conclusions: At our institution with early IMRT experience, IMRT improved PTV dose coverage and liver doses but not kidney doses. An external audit of IMRT plans showed that an experienced center can yield superior IMRT plans

Experimental dosimetry in conformal breast teletherapy compared with the planning system

International Nuclear Information System (INIS)

Nogueira, Luciana Batista; Silva, Hugo Leonardo Lemos; Passos Ribeiro de Campos, Tarcísio

2015-01-01

The objective of this study was to compare and analyse the absorbed dose profiles from the conformal radiotherapy planning and experimental dosimetry taken in a breast anthropomorphic and anthropometric phantom. Conformal radiotherapy planning was elaborated in the Treatment Planning System (TPS). EBT2 Gafchromic radiochromic films were applied as dosimeters, positioned internally and superficially in the breast phantom. The standard radiation protocol was applied in the breast phantom. The films were digitalised, and their responses were analysed in RGB. The optical densities were processed, reproducing the spatial dose distribution. - Highlights: • Distributions of absorbed doses were generated by the TPS and measured by radiochromic films. • The breast phantom simulated a human breast in position for treatment. • A large portion of the glandular tissue absorbed doses that were equivalent to the radiotherapy planning. • There were regions of hot spots and small areas of under dosage in deeper areas at the lung interface

Intensity-Modulated Radiotherapy Causes Fewer Side Effects than Three-Dimensional Conformal Radiotherapy When Used in Combination With Brachytherapy for the Treatment of Prostate Cancer

International Nuclear Information System (INIS)

Forsythe, Kevin; Blacksburg, Seth; Stone, Nelson; Stock, Richard G.

2012-01-01

Purpose: To measure the benefits of intensity-modulated radiotherapy (IMRT) compared with three-dimensional conformal radiotherapy (3D-CRT) when used in combination with brachytherapy for the treatment of prostate cancer. Methods and Materials: We conducted a retrospective review of all patients with localized prostate cancer who received external-beam radiotherapy (EBRT) in combination with brachytherapy with at least 1 year follow-up (n = 812). Combination therapy consisted of 103 Pd or 125 I implant, followed by a course of EBRT. From 1993 to March 2003 521 patients were treated with 3D-CRT, and from April 2003 to March 2009 291 patients were treated with IMRT. Urinary symptoms were prospectively measured with the International Prostate Symptom Score questionnaire with a single quality of life (QOL) question; rectal bleeding was assessed per the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer Late Radiation Morbidity Scoring Schema. The Pearson χ 2 test was used to compare toxicities experienced by patients who were treated with either IMRT or 3D-CRT. Logistic regression analyses were also performed to rule out possible confounding factors. Results: Within the first 3 months after treatment, patients treated with 3D-CRT scored their urinary symptoms as follows: 19% mild, 44% moderate, and 37% severe; patients treated with IMRT scored their urinary symptoms as follows: 36% mild, 47% moderate, and 17% severe (p < 0.001). The 3D-CRT patients rated their QOL as follows: 35% positive, 20% neutral, and 45% negative; IMRT patients rated their QOL as follows: 51% positive, 18% neutral, and 31% negative (p < 0.001). After 1 year of follow-up there was no longer any difference in urinary morbidity between the two groups. Logistic regression confirmed the differences in International Prostate Symptom Score and QOL in the acute setting (p < 0.001 for both). Grade ≥2 rectal bleeding was reported by 11% of 3D-CRT patients and 7

Visual Outcome in Meningiomas Around Anterior Visual Pathways Treated With Linear Accelerator Fractionated Stereotactic Radiotherapy

International Nuclear Information System (INIS)

Stiebel-Kalish, Hadas; Reich, Ehud; Gal, Lior; Rappaport, Zvi Harry; Nissim, Ouzi; Pfeffer, Raphael; Spiegelmann, Roberto

2012-01-01

Purpose: Meningiomas threatening the anterior visual pathways (AVPs) and not amenable for surgery are currently treated with multisession stereotactic radiotherapy. Stereotactic radiotherapy is available with a number of devices. The most ubiquitous include the gamma knife, CyberKnife, tomotherapy, and isocentric linear accelerator systems. The purpose of our study was to describe a case series of AVP meningiomas treated with linear accelerator fractionated stereotactic radiotherapy (FSRT) using the multiple, noncoplanar, dynamic conformal rotation paradigm and to compare the success and complication rates with those reported for other techniques. Patients and Methods: We included all patients with AVP meningiomas followed up at our neuro-ophthalmology unit for a minimum of 12 months after FSRT. We compared the details of the neuro-ophthalmologic examinations and tumor size before and after FSRT and at the end of follow-up. Results: Of 87 patients with AVP meningiomas, 17 had been referred for FSRT. Of the 17 patients, 16 completed >12 months of follow-up (mean 39). Of the 16 patients, 11 had undergone surgery before FSRT and 5 had undergone FSRT as first-line management. Tumor control was achieved in 14 of the 16 patients, with three meningiomas shrinking in size after RT. Two meningiomas progressed, one in an area that was outside the radiation field. The visual function had improved in 6 or stabilized in 8 of the 16 patients (88%) and worsened in 2 (12%). Conclusions: Linear accelerator fractionated RT using the multiple noncoplanar dynamic rotation conformal paradigm can be offered to patients with meningiomas that threaten the anterior visual pathways as an adjunct to surgery or as first-line treatment, with results comparable to those reported for other stereotactic RT techniques.

Three dimensional conformal radiotherapy for the treatment of prostate cancer: low risk of chronic rectal morbidity observed in a large series of patients

International Nuclear Information System (INIS)

Sandler, Howard M.; McLaughlin, P. William; Ten Haken, Randall K.; Addison, Heather; Forman, Jeffrey; Lichter, Allen

1995-01-01

Purpose: Three dimensional conformal radiotherapy (3D CRT) may provide a technique to increase the dose delivered to target tissues while sparing uninvolved normal structures. To evaluate the role of 3D treatment in reducing the treatment toxicity, we analyzed the chronic rectal morbidity observed in a large group of patients undergoing radiotherapy for prostate cancer. Methods and Materials: From 1987 through 1992, 721 prostate cancer patients were treated with 3D CRT at the University of Michigan or Providence Hospital. All had axial computed tomography (CT) specifically for RT planning, multiple structures contoured on the axial images, and beam's-eye-view conformal beams edited to provide 3D dose coverage. Using current American Joint Commission (AJCC) staging, 537 patients had T1-T2 tumors, 123 had T3-T4 tumors, and 60 were treated postprostatectomy. Pelvic lymph nodes were treated in 462 patients. Prostate boosts were delivered with four-field axial, six-field axial, or four-field oblique, nonaxial fields. The median dose was 68.40 Gy (range 59.4-80.4). Median follow-up was 20.4 months; 175 were followed more than 3 years. All complications have been graded conservatively using the RTOG system. Results: Using a Cox proportional hazard's model, patient age, T-stage, prescribed dose, pelvic treatment, and boost technique were analyzed. The factor most strongly related to risk of morbidity was dose (p = 0.05); however, the boost technique was also related: the four-field oblique field had the lowest relative risk. Most episodes of rectal morbidity have been mild: 82 Grade 1 or 2. There have been only 14 more serious complications including 12 Grade 3 and 2 Grade 4. The actuarial risk of a Grade 3 or 4 complication is 3% at 3 and 5 years. Conclusions: A very small proportion of patients treated with 3D CRT had significant rectal morbidity related to RT, supporting the use of conformal treatment planning and dose delivery as a mechanism to minimize complications

Quality of Life and Survival Outcome for Patients With Nasopharyngeal Carcinoma Receiving Three-Dimensional Conformal Radiotherapy vs. Intensity-Modulated Radiotherapy-A Longitudinal Study

International Nuclear Information System (INIS)

Fang, F.-M.; Chien, C.-Y.; Tsai, W.-L.; Chen, H.-C.; Hsu, H.-C.; Lui, C.-C.; Huang, T.-L.

2008-01-01

Purpose: To investigate the changes of quality of life (QoL) and survival outcomes for patients with nasopharyngeal carcinoma (NPC) treated by three-dimensional conformal radiotherapy (3D-CRT) vs. intensity-modulated radiotherapy (IMRT). Methods and Materials: Two hundred and three newly diagnosed NPC patients, who were curatively treated by 3D-CRT (n = 93) or IMRT (n = 110) between March 2002 and July 2004, were analyzed. The distributions of clinical stage according to American Joint Committee on Cancer 1997 were I: 15 (7.4%), II: 78 (38.4%), III: 74 (36.5%), and IV: 36 (17.7%). QoL was longitudinally assessed by the European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30 and the EORTC QLQ-H and N35 questionnaires at the five time points: before RT, during RT (36 Gy), and 3 months, 12 months, and 24 months after RT. Results: The 3-year locoregional control, metastasis-free survival, and overall survival rates were 84.8%, 76.7%, and 81.7% for the 3D-CRT group, respectively, compared with 84.2%, 82.6%, and 85.4% for the IMRT group (p value > 0.05). A general trend of maximal deterioration in most QoL scales was observed during RT, followed by a gradual recovery thereafter. There was no significant difference in most scales between the two groups at each time point. The exception was that patients treated by IMRT had a both statistically and clinically significant improvement in global QoL, fatigue, taste/smell, dry mouth, and feeling ill at the time point of 3 months after RT. Conclusions: The potential advantage of IMRT over 3D-CRT in treating NPC patients might occur in QoL outcome during the recovery phase of acute toxicity

A feasibility study of dynamic adaptive radiotherapy for nonsmall cell lung cancer

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Kim, Minsun, E-mail: mk688@uw.edu [Department of Radiation Oncology, University of Washington, Seattle, Washington 98195-6043 (United States); Phillips, Mark H. [Departments of Radiation Oncology and Neurological Surgery, University of Washington, Seattle, Washington 98195-6043 (United States)

2016-05-15

Purpose: The final state of the tumor at the end of a radiotherapy course is dependent on the doses given in each fraction during the treatment course. This study investigates the feasibility of using dynamic adaptive radiotherapy (DART) in treating lung cancers assuming CBCT is available to observe midtreatment tumor states. DART adapts treatment plans using a dynamic programming technique to consider the expected changes of the tumor in the optimization process. Methods: DART is constructed using a stochastic control formalism framework. It minimizes the total expected number of tumor cells at the end of a treatment course, which is equivalent to maximizing tumor control probability, subject to the uncertainty inherent in the tumor response. This formulation allows for nonstationary dose distributions as well as nonstationary fractional doses as needed to achieve a series of optimal plans that are conformal to the tumor over time, i.e., spatiotemporally optimal plans. Sixteen phantom cases with various sizes and locations of tumors and organs-at-risk (OAR) were generated using in-house software. Each case was planned with DART and conventional IMRT prescribing 60 Gy in 30 fractions. The observations of the change in the tumor volume over a treatment course were simulated using a two-level cell population model. Monte Carlo simulations of the treatment course for each case were run to account for uncertainty in the tumor response. The same OAR dose constraints were applied for both methods. The frequency of replanning was varied between 1, 2, 5 (weekly), and 29 times (daily). The final average tumor dose and OAR doses have been compared to quantify the potential dosimetric benefits of DART. Results: The average tumor max, min, mean, and D95 doses using DART relative to these using conventional IMRT were 124.0%–125.2%, 102.1%–114.7%, 113.7%–123.4%, and 102.0%–115.9% (range dependent on the frequency of replanning). The average relative maximum doses for the

Active Polymers — Emergent Conformational and Dynamical Properties: A Brief Review

Science.gov (United States)

Winkler, Roland G.; Elgeti, Jens; Gompper, Gerhard

2017-10-01

Active matter exhibits a wealth of emerging nonequilibrium behaviours. A paradigmatic example is the interior of cells, where active components, such as the cytoskeleton, are responsible for its structural organization and the dynamics of the various components. Of particular interest are the properties of polymers and filaments. The intimate coupling of thermal and active noise, hydrodynamic interactions, and polymer conformations implies the emergence of novel structural and dynamical features. In this article, we review recent theoretical and simulation developments and results for the structural and dynamical properties of polymers exposed to activity. Two- and three-dimensional filaments are considered propelled by different mechanisms such as active Brownian particles or hydrodynamically-coupled force dipoles.

Accuracy requirements in radiotherapy treatment planning

International Nuclear Information System (INIS)

Buzdar, S. A.; Afzal, M.; Nazir, A.; Gadhi, M. A.

2013-01-01

Radiation therapy attempts to deliver ionizing radiation to the tumour and can improve the survival chances and/or quality of life of patients. There are chances of errors and uncertainties in the entire process of radiotherapy that may affect the accuracy and precision of treatment management and decrease degree of conformation. All expected inaccuracies, like radiation dose determination, volume calculation, complete evaluation of the full extent of the tumour, biological behaviour of specific tumour types, organ motion during radiotherapy, imaging, biological/molecular uncertainties, sub-clinical diseases, microscopic spread of the disease, uncertainty in normal tissue responses and radiation morbidity need sound appreciation. Conformity can be increased by reduction of such inaccuracies. With the yearly increase in computing speed and advancement in other technologies the future will provide the opportunity to optimize a greater number of variables and reduce the errors in the treatment planning process. In multi-disciplined task of radiotherapy, efforts are needed to overcome the errors and uncertainty, not only by the physicists but also by radiologists, pathologists and oncologists to reduce molecular and biological uncertainties. The radiation therapy physics is advancing towards an optimal goal that is definitely to improve accuracy where necessary and to reduce uncertainty where possible. (author)

Practical application of the tool calculation Monte Carlo MCVerif for checking for radiotherapy treatment

International Nuclear Information System (INIS)

Laliena Bielsa, V. M.; Garcia Romero, A.; Villa Gazulla, D.; Ortega Pardilla, P.; Calvo Carrillo, S.; Millan Cebrian, E.; Hernandez Vitorial, A.; Canellas Aznoz, M.

2013-01-01

The object of this work is to verify a patient group representative of the usual techniques of 3D conformal radiotherapy and IMRT performed in the radiotherapy service our hospital and thus validate the algorithm used commercial planning system. (Author)

Radiation-induced esophagitis in local advanced non-small cell lung cancer after three-dimensional conformal radiotherapy

International Nuclear Information System (INIS)

Tian Dandan; Wang Yuxiang; Qiu Rong; Zhu Shuchai; Tian Xiuming; Qiao Xueying

2014-01-01

Objective: To explore radiation-induced esophagitis and its related factors in the patients with local advanced non-small cell lung cancer (NSCLC) which were treated with three-dimensional conformal radiation therapy (3D-CRT). Methods: From January 2001 to December 2008, 203 patients who suffered from stage Ⅲ NSCLC were achieved, including 163 males and 40 females, with a median age of 63 years old, while 79 cases were in stage Ⅲ_a and 124 in stage Ⅲ_b. The equivalent median dose of tumor was 62 Gy(range of 50-78 Gy). Among them, 74 cases were administered with radiotherapy alone, 45 with sequential radiotherapy and chemotherapy, 87 cases with concurrent radiochemotherapy. Radiation esophagitis was evaluated with RTOG standard. The dosimetric parameters was estimated from dose volume histogrma (DVH). The clinical and dosimetric parameters of radiation esophagitis were evaluated by spearman correlatived univariate and Logistic multivariable analysis.Results After radiotherapy, out of 203 patients, 87 had acute radiation esophagitis(RE), 47 in grade 1, 37 in grade 2, and 3 in grade 3 RE. According to spearman correlatived analysis, the correlatived factors included ages, chemotherapy, GTV, PTV, the mean doses of PTV and lung, the max and mean dose of esophagus, V_4_0, V_4_5, V_5_0, V_5_5, V_6_0, length of esophagus (total circumference) treated with 45 Gy (LETT_4_5), and LETT_5_0 (r = -0.162-0.235, P 0.05). There were 21 factors, such as gender, age, smoking, clinical stage, site of tumor, chemotherapy, GTV, PTV, mean dose of PTV and lung, max and mean dose of esophagus, V_4_0-V_6_0 of esophagus, LETT_4_5_-_6_0, incorporated into multivariable analysis, only chemotherapy and V_4_5 of esophagus were independent predicted factors(Wald = 4.626, 9.882, P < 0.05). Conclusions: In local advanced NSCLC after 3D-CRT, chemotherapy(especially concurrent radiochemotherapy) could increase radiation-induced esophagitis. The parameter of DVH could also be used to predict

Conformational Rigidity and Protein Dynamics at Distinct Timescales Regulate PTP1B Activity and Allostery.

Science.gov (United States)

Choy, Meng S; Li, Yang; Machado, Luciana E S F; Kunze, Micha B A; Connors, Christopher R; Wei, Xingyu; Lindorff-Larsen, Kresten; Page, Rebecca; Peti, Wolfgang

2017-02-16

Protein function originates from a cooperation of structural rigidity, dynamics at different timescales, and allostery. However, how these three pillars of protein function are integrated is still only poorly understood. Here we show how these pillars are connected in Protein Tyrosine Phosphatase 1B (PTP1B), a drug target for diabetes and cancer that catalyzes the dephosphorylation of numerous substrates in essential signaling pathways. By combining new experimental and computational data on WT-PTP1B and ≥10 PTP1B variants in multiple states, we discovered a fundamental and evolutionarily conserved CH/π switch that is critical for positioning the catalytically important WPD loop. Furthermore, our data show that PTP1B uses conformational and dynamic allostery to regulate its activity. This shows that both conformational rigidity and dynamics are essential for controlling protein activity. This connection between rigidity and dynamics at different timescales is likely a hallmark of all enzyme function. Copyright © 2017 Elsevier Inc. All rights reserved.

Nucleotide-induced conformational dynamics in ABC transporters from structure-based coarse grained modelling.

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Flechsig, Holger

2016-02-01

ATP-binding cassette (ABC) transporters are integral membrane proteins which mediate the exchange of diverse substrates across membranes powered by ATP molecules. Our understanding of their activity is still hampered since the conformational dynamics underlying the operation of such proteins cannot yet be resolved in detailed molecular dynamics studies. Here a coarse grained model which allows to mimic binding of nucleotides and follow subsequent conformational motions of full-length transporter structures in computer simulations is proposed and implemented. To justify its explanatory quality, the model is first applied to the maltose transporter system for which multiple conformations are known and we find that the model predictions agree remarkably well with the experimental data. For the MalK subunit the switching from open to the closed dimer configuration upon ATP binding is reproduced and, moreover, for the full-length maltose transporter, progression from inward-facing to the outward-facing state is correctly obtained. For the heme transporter HmuUV, for which only the free structure could yet be determined, the model was then applied to predict nucleotide-induced conformational motions. Upon binding of ATP-mimicking ligands the structure changed from a conformation in which the nucleotide-binding domains formed an open shape, to a conformation in which they were found in tight contact, while, at the same time, a pronounced rotation of the transmembrane domains was observed. This finding is supported by normal mode analysis, and, comparison with structural data of the homologous vitamin B12 transporter BtuCD suggests that the observed rotation mechanism may contribute a common functional aspect for this class of ABC transporters. Although in HmuuV noticeable rearrangement of essential transmembrane helices was detected, there are no indications from our simulations that ATP binding alone may facilitate propagation of substrate molecules in this transporter

Dynamic conformational change regulates the protein-DNA recognition: an investigation on binding of a Y-family polymerase to its target DNA.

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Xiakun Chu

2014-09-01

Full Text Available Protein-DNA recognition is a central biological process that governs the life of cells. A protein will often undergo a conformational transition to form the functional complex with its target DNA. The protein conformational dynamics are expected to contribute to the stability and specificity of DNA recognition and therefore may control the functional activity of the protein-DNA complex. Understanding how the conformational dynamics influences the protein-DNA recognition is still challenging. Here, we developed a two-basin structure-based model to explore functional dynamics in Sulfolobus solfataricus DNA Y-family polymerase IV (DPO4 during its binding to DNA. With explicit consideration of non-specific and specific interactions between DPO4 and DNA, we found that DPO4-DNA recognition is comprised of first 3D diffusion, then a short-range adjustment sliding on DNA and finally specific binding. Interestingly, we found that DPO4 is under a conformational equilibrium between multiple states during the binding process and the distributions of the conformations vary at different binding stages. By modulating the strength of the electrostatic interactions, the flexibility of the linker, and the conformational dynamics in DPO4, we drew a clear picture on how DPO4 dynamically regulates the DNA recognition. We argue that the unique features of flexibility and conformational dynamics in DPO4-DNA recognition have direct implications for low-fidelity translesion DNA synthesis, most of which is found to be accomplished by the Y-family DNA polymerases. Our results help complete the description of the DNA synthesis process for the Y-family polymerases. Furthermore, the methods developed here can be widely applied for future investigations on how various proteins recognize and bind specific DNA substrates.

Dosimetric study of volumetric arc modulation with RapidArc and intensity-modulated radiotherapy in patients with cervical cancer and comparison with 3-dimensional conformal technique for definitive radiotherapy in patients with cervical cancer

Energy Technology Data Exchange (ETDEWEB)

Guy, Jean-Baptiste [Department of Radiation Oncology, Institut de Cancérologie de la Loire Lucien Neuwirth, Saint-Priest en Jarez (France); Falk, Alexander T. [Department of Radiation Oncology, Centre Antoine Lacassagne, Nice (France); Auberdiac, Pierre [Department of Radiation Oncology, Clinique Claude Bernard, Albi (France); Cartier, Lysian; Vallard, Alexis [Department of Radiation Oncology, Institut de Cancérologie de la Loire Lucien Neuwirth, Saint-Priest en Jarez (France); Ollier, Edouard [Department of Pharmacology-Toxicology, Centre Hospitalier Universitaire de Saint-Etienne, Saint-Priest en Jarez (France); Trone, Jane-Chloé; Khodri, Moustapha [Department of Radiation Oncology, Institut de Cancérologie de la Loire Lucien Neuwirth, Saint-Priest en Jarez (France); Chargari, Cyrus [Department of Radiation Oncology, Hôpital d’instruction de Armées du Val-de-Grâce, Paris (France); Magné, Nicolas, E-mail: nicolas.magne@icloire.fr [Department of Radiation Oncology, Institut de Cancérologie de la Loire Lucien Neuwirth, Saint-Priest en Jarez (France)

2016-04-01

Introduction: For patients with cervical cancer, intensity-modulated radiation therapy (IMRT) improves target coverage and allows dose escalation while reducing the radiation dose to organs at risk (OARs). In this study, we compared dosimetric parameters among 3-dimensional conformal radiotherapy (3D-CRT), “step-and-shoot” IMRT, and volumetric intensity-modulated arc radiotherapy (VMAT) in a series of patients with cervical cancer receiving definitive radiotherapy. Computed tomography (CT) scans of 10 patients with histologically proven cervical cancer treated with definitive radiation therapy (RT) from December 2008 to March 2010 at our department were selected for this study. The gross tumor volume (GTV) and clinical target volume (CTV) were delineated following the guidelines of the Gyn IMRT consortium that included cervix, uterus, parametrial tissues, and the pelvic nodes including presacral. The median age was 57 years (range: 30 to 85 years). All 10 patients had squamous cell carcinoma with Federation of Gynecology and Obstetrics (FIGO) stage IB-IIIB. All patients were treated by VMAT. OAR doses were significantly reduced for plans with intensity-modulated technique compared with 3D-CRT except for the dose to the vagina. Between the 2 intensity-modulated techniques, significant difference was observed for the mean dose to the small intestine, to the benefit of VMAT (p < 0.001). There was no improvement in terms of OARs sparing for VMAT although there was a tendency for a slightly decreased average dose to the rectum: − 0.65 Gy but not significant (p = 0.07). The intensity modulation techniques have many advantages in terms of quality indexes, and particularly OAR sparing, compared with 3D-CRT. Following the ongoing technologic developments in modern radiotherapy, it is essential to evaluate the intensity-modulated techniques on prospective studies of a larger scale.

Designing molecular dynamics simulations to shift populations of the conformational states of calmodulin.

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Ayse Ozlem Aykut

Full Text Available We elucidate the mechanisms that lead to population shifts in the conformational states of calcium-loaded calmodulin (Ca(2+-CaM. We design extensive molecular dynamics simulations to classify the effects that are responsible for adopting occupied conformations available in the ensemble of NMR structures. Electrostatic interactions amongst the different regions of the protein and with its vicinal water are herein mediated by lowering the ionic strength or the pH. Amino acid E31, which is one of the few charged residues whose ionization state is highly sensitive to pH differences in the physiological range, proves to be distinctive in its control of population shifts. E31A mutation at low ionic strength results in a distinct change from an extended to a compact Ca(2+-CaM conformation within tens of nanoseconds, that otherwise occur on the time scales of microseconds. The kinked linker found in this particular compact form is observed in many of the target-bound forms of Ca(2+-CaM, increasing the binding affinity. This mutation is unique in controlling C-lobe dynamics by affecting the fluctuations between the EF-hand motif helices. We also monitor the effect of the ionic strength on the conformational multiplicity of Ca(2+-CaM. By lowering the ionic strength, the tendency of nonspecific anions in water to accumulate near the protein surface increases, especially in the vicinity of the linker. The change in the distribution of ions in the vicinal layer of water allows N- and C- lobes to span a wide variety of relative orientations that are otherwise not observed at physiological ionic strength. E31 protonation restores the conformations associated with physiological environmental conditions even at low ionic strength.

Conformational dynamics of dry lamellar crystals of sugar based lipids: an atomistic simulation study.

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Vijayan ManickamAchari

Full Text Available The rational design of a glycolipid application (e.g. drug delivery with a tailored property depends on the detailed understanding of its structure and dynamics. Because of the complexity of sugar stereochemistry, we have undertaken a simulation study on the conformational dynamics of a set of synthetic glycosides with different sugar groups and chain design, namely dodecyl β-maltoside, dodecyl β-cellobioside, dodecyl β-isomaltoside and a C12C10 branched β-maltoside under anhydrous conditions. We examined the chain structure in detail, including the chain packing, gauche/trans conformations and chain tilting. In addition, we also investigated the rotational dynamics of the headgroup and alkyl chains. Monoalkylated glycosides possess a small amount of gauche conformers (∼20% in the hydrophobic region of the lamellar crystal (LC phase. In contrast, the branched chain glycolipid in the fluid Lα phase has a high gauche population of up to ∼40%. Rotational diffusion analysis reveals that the carbons closest to the headgroup have the highest correlation times. Furthermore, its value depends on sugar type, where the rotational dynamics of an isomaltose was found to be 11-15% and more restrained near the sugar, possibly due to the chain disorder and partial inter-digitation compared to the other monoalkylated lipids. Intriguingly, the present simulation demonstrates the chain from the branched glycolipid bilayer has the ability to enter into the hydrophilic region. This interesting feature of the anhydrous glycolipid bilayer simulation appears to arise from a combination of lipid crowding and the amphoteric nature of the sugar headgroups.

Conformational dynamics of semiflexibly bridged electron donor-acceptor systems comprising long aliphatic tails

NARCIS (Netherlands)

Bleisteiner, B.; Marian, T.; Schneider, S.; Brouwer, A.M.; Verhoeven, J.W.

2001-01-01

In continuation of our previous work on the conformational dynamics (harpooning mechanism) of semiflexibly bridged electron donor-acceptor systems we have studied a derivative with two long aliphatic chains tethered to the donor and acceptor moieties, respectively. The fitting of the time- and

Conformal Killing horizons and their thermodynamics

Science.gov (United States)

Nielsen, Alex B.; Shoom, Andrey A.

2018-05-01

Certain dynamical black hole solutions can be mapped to static spacetimes by conformal metric transformations. This mapping provides a physical link between the conformal Killing horizon of the dynamical black hole and the Killing horizon of the static spacetime. Using the Vaidya spacetime as an example, we show how this conformal relation can be used to derive thermodynamic properties of such dynamical black holes. Although these horizons are defined quasi-locally and can be located by local experiments, they are distinct from other popular notions of quasi-local horizons such as apparent horizons. Thus in the dynamical Vaidya spacetime describing constant accretion of null dust, the conformal Killing horizon, which is null by construction, is the natural horizon to describe the black hole.

Dissecting the dynamic conformations of the metamorphic protein lymphotactin.

Science.gov (United States)

Harvey, Sophie R; Porrini, Massimiliano; Konijnenberg, Albert; Clarke, David J; Tyler, Robert C; Langridge-Smith, Patrick R R; MacPhee, Cait E; Volkman, Brian F; Barran, Perdita E

2014-10-30

A mass spectrometer provides an ideal laboratory to probe the structure and stability of isolated protein ions. Interrogation of each discrete mass/charge-separated species enables the determination of the intrinsic stability of a protein fold, gaining snapshots of unfolding pathways. In solution, the metamorphic protein lymphotactin (Ltn) exists in equilibrium between two distinct conformations, a monomeric (Ltn10) and a dimeric (Ltn40) fold. Here, we use electron capture dissociation (ECD) and drift tube ion mobility-mass spectrometry (DT IM-MS) to analyze both forms and use molecular dynamics (MD) to consider how the solution fold alters in a solvent-free environment. DT IM-MS reveals significant conformational flexibility for the monomer, while the dimer appears more conformationally restricted. These findings are supported by MD calculations, which reveal how salt bridges stabilize the conformers in vacuo. Following ECD experiments, a distinctive fragmentation pattern is obtained for both the monomer and dimer. Monomer fragmentation becomes more pronounced with increasing charge state especially in the disordered regions and C-terminal α-helix in the solution fold. Lower levels of fragmentation are seen in the β-sheet regions and in regions that contain salt bridges, identified by MD simulations. The lowest charge state of the dimer for which we obtain ECD data ([D+9H](9+)) exhibits extensive fragmentation with no relationship to the solution fold and has a smaller collision cross section (CCS) than charge states 10-13+, suggesting a "collapsed" encounter complex. Other charge states of the dimer, as for the monomer, are resistant to fragmentation in regions of β-sheets in the solution fold. This study provides evidence for preservation and loss of global fold and secondary structural elements, providing a tantalizing glimpse into the power of the emerging field of native top-down mass spectrometry.

Cosmological consequences of nearly conformal dynamics at the TeV scale

International Nuclear Information System (INIS)

Konstandin, Thomas; Servant, Géraldine

2011-01-01

Nearly conformal dynamics at the TeV scale as motivated by the hierarchy problem can be characterized by a stage of significant supercooling at the electroweak epoch. This has important cosmological consequences. In particular, a common assumption about the history of the universe is that the reheating temperature is high, at least high enough to assume that TeV-mass particles were once in thermal equilibrium. However, as we discuss in this paper, this assumption is not well justified in some models of strong dynamics at the TeV scale. We then need to reexamine how to achieve baryogenesis in these theories as well as reconsider how the dark matter abundance is inherited. We argue that baryonic and dark matter abundances can be explained naturally in these setups where reheating takes place by bubble collisions at the end of the strongly first-order phase transition characterizing conformal symmetry breaking, even if the reheating temperature is below the electroweak scale ∼ 100 GeV. In particular, non-thermal production of heavy WIMPs during bubble collisions becomes a well-motivated possibility. We also discuss inflation as well as gravity wave smoking gun signatures of this class of models

Dose conformation to the spine during palliative treatments using dynamic wedges

Energy Technology Data Exchange (ETDEWEB)

Ormsby, Matthew A., E-mail: Matthew.Ormsby@usoncology.com [West Texas Cancer Center at Medical Center Hospital, Odessa, TX (United States); Herndon, R. Craig; Kaczor, Joseph G. [West Texas Cancer Center at Medical Center Hospital, Odessa, TX (United States)

2013-07-01

Radiation therapy is commonly used to alleviate pain associated with metastatic disease of the spine. Often, isodose lines are manipulated using dynamic or physical wedges to encompass the section of spine needing treatment while minimizing dose to normal tissue. We will compare 2 methods used to treat the entire thoracic spine. The first method treats the thoracic spine with a single, nonwedged posterior-anterior (PA) field. Dose is prescribed to include the entire spine. Isodose lines tightly conform to the top and bottom vertebrae, but vertebrae between these 2 received more than enough coverage. The second method uses a combination of wedges to create an isodose line that mimics the curvature of the thoracic spine. This “C”-shaped curvature is created by overlapping 2 fields with opposing dynamic wedges. Machine constraints limit the treatment length and therefore 2 isocenters are used. Each of the 2 PA fields contributes a portion of the total daily dose. This technique creates a “C”-shaped isodose line that tightly conforms to the thoracic spine, minimizing normal tissue dose. Spinal cord maximum dose is reduced, as well as mean dose to the liver, esophagus, and heart.

SU-E-J-254: Utility of Pinnacle Dynamic Planning Module Utilizing Deformable Image Registration in Adaptive Radiotherapy

International Nuclear Information System (INIS)

Jani, S

2014-01-01

Purpose For certain highly conformal treatment techniques, changes in patient anatomy due to weight loss and/or tumor shrinkage can result in significant changes in dose distribution. Recently, the Pinnacle treatment planning system added a Dynamic Planning module utilizing Deformable Image Registration (DIR). The objective of this study was to evaluate the effectiveness of this software in adapting to altered anatomy and adjusting treatment plans to account for it. Methods We simulated significant tumor response by changing patient thickness and altered chin positions using a commercially-available head and neck (H and N) phantom. In addition, we studied 23 CT image sets of fifteen (15) patients with H and N tumors and eight (8) patients with prostate cancer. In each case, we applied deformable image registration through Dynamic Planning module of our Pinnacle Treatment Planning System. The dose distribution of the original CT image set was compared to the newly computed dose without altering any treatment parameter. Result was a dose if we did not adjust the plan to reflect anatomical changes. Results For the H and N phantom, a tumor response of up to 3.5 cm was correctly deformed by the Pinnacle Dynamic module. Recomputed isodose contours on new anatomies were within 1 mm of the expected distribution. The Pinnacle system configuration allowed dose computations resulting from original plans on new anatomies without leaving the planning system. Original and new doses were available side-by-side with both CT image sets. Based on DIR, about 75% of H and N patients (11/15) required a re-plan using new anatomy. Among prostate patients, the DIR predicted near-correct bladder volume in 62% of the patients (5/8). Conclusions The Dynamic Planning module of the Pinnacle system proved to be an accurate and useful tool in our ability to adapt to changes in patient anatomy during a course of radiotherapy

Accessing a hidden conformation of the maltose binding protein using accelerated molecular dynamics.

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Denis Bucher

2011-04-01

Full Text Available Periplasmic binding proteins (PBPs are a large family of molecular transporters that play a key role in nutrient uptake and chemotaxis in Gram-negative bacteria. All PBPs have characteristic two-domain architecture with a central interdomain ligand-binding cleft. Upon binding to their respective ligands, PBPs undergo a large conformational change that effectively closes the binding cleft. This conformational change is traditionally viewed as a ligand induced-fit process; however, the intrinsic dynamics of the protein may also be crucial for ligand recognition. Recent NMR paramagnetic relaxation enhancement (PRE experiments have shown that the maltose binding protein (MBP - a prototypical member of the PBP superfamily - exists in a rapidly exchanging (ns to µs regime mixture comprising an open state (approx 95%, and a minor partially closed state (approx 5%. Here we describe accelerated MD simulations that provide a detailed picture of the transition between the open and partially closed states, and confirm the existence of a dynamical equilibrium between these two states in apo MBP. We find that a flexible part of the protein called the balancing interface motif (residues 175-184 is displaced during the transformation. Continuum electrostatic calculations indicate that the repacking of non-polar residues near the hinge region plays an important role in driving the conformational change. Oscillations between open and partially closed states create variations in the shape and size of the binding site. The study provides a detailed description of the conformational space available to ligand-free MBP, and has implications for understanding ligand recognition and allostery in related proteins.

Treatment results of adjuvant radiotherapy and salvage radiotherapy after radical prostatectomy for prostate cancer

International Nuclear Information System (INIS)

Wadasaki, Koichi; Kaneyasu, Yuko; Kenjo, Masahiro; Matsuura, Kanji; Murakami, Yuji; Hashimoto, Yasutoshi; Ito, Katsuhide; Kiriu, Hiroshi; Ito, Atsushi

2007-01-01

The indications for and the efficacy of radiation therapy after radical operation for patients with prostate cancer are not clear. We analyzed the treatment results of adjuvant radiotherapy and salvage radiotherapy after radical prostatectomy. Between September 1997 and November 2004, 57 patients received adjuvant radiotherapy or salvage radiotherapy after radical prostatectomy. Fifteen patients received radiation therapy because of positive margins and/or extracapsular invasion in surgical specimens (adjuvant group). Forty-two patients received radiation therapy because of rising prostate-specific antigen (PSA) during follow-up (salvage group). Radiation therapy was delivered to the fossa of the prostate±seminal vesicles by a three-dimensional (3-D) conformal technique to a total dose of 60-66 Gy (median, 60 Gy). Biochemical control was defined as the maintenance of a PSA level of less than 0.2 ng/ml. The median follow-up period after radiation therapy was 33 months (range, 12-98 months). Three-year biochemical control rates were 87% for the adjuvant group and 61% for the salvage group. For patients in the salvage group treated without hormone therapy, the preradiation PSA value was the most significant factor for the biochemical control rate. The 3-year biochemical control rate was 93% in patients whose preradiation PSA was 0.5 ng/ml or less and 29% in patients whose preradiation PSA was more than 0.5 ng/ml. No severe adverse effects (equal to or more than grade 3) were seen in treated patients. Radiation therapy after radical prostatectomy seemed to be effective for adjuvant therapy and for salvage therapy in patients with a preradiation PSA of 0.5 ng/ml or less. Also, radiation to the fossa of the prostate±seminal vesicles, to a total dose of 60-66 Gy, using a three-dimensional (3-D) conformal technique, seemed to be safe. (author)

Dosimetric comparison between intensity-modulated with coplanar field and 3D conformal radiotherapy with noncoplanar field for postocular invasion tumor.

Science.gov (United States)

Wenyong, Tu; Lu, Liu; Jun, Zeng; Weidong, Yin; Yun, Li

2010-01-01

This study presents a dosimetric optimization effort aiming to compare noncoplanar field (NCF) on 3 dimensions conformal radiotherapy (3D-CRT) and coplanar field (CF) on intensity-modulated radiotherapy (IMRT) planning for postocular invasion tumor. We performed a planning study on the computed tomography data of 8 consecutive patients with localized postocular invasion tumor. Four fields NCF 3D-CRT in the transverse plane with gantry angles of 0-10 degrees , 30-45 degrees , 240-270 degrees , and 310-335 degrees degrees were isocentered at the center of gravity of the target volume. The geometry of the beams was determined by beam's eye view. The same constraints were prepared with between CF IMRT optimization and NCF 3D-CRT treatment. The maximum point doses (D max) for the different optic pathway structures (OPS) with NCF 3D-CRT treatment should differ in no more than 3% from those with the NCF IMRT plan. Dose-volume histograms (DVHs) were obtained for all targets and organ at risk (OAR) with both treatment techniques. Plans with NCF 3D-CRT and CF IMRT constraints on target dose in homogeneity were computed, as well as the conformity index (CI) and homogeneity index (HI) in the target volume. The PTV coverage was optimal with both NCF 3D-CRT and CF IMRT plans in the 8 tumor sites. No difference was noted between the two techniques for the average D(max) and D(min) dose. NCF 3D-CRT and CF IMRT will yield similar results on CI. However, HI was a significant difference between NCF 3D-CRT and CF IMRT plan (p 3D-CRT versus CF IMRT set-up is very slight. NCF3D-CRT is one of the treatment options for postocular invasion tumor. However, constraints for OARs are needed. 2010 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.

Dosimetric Comparison Between Intensity-Modulated with Coplanar Field and 3D Conformal Radiotherapy with Noncoplanar Field for Postocular Invasion Tumor

International Nuclear Information System (INIS)

Tu Wenyong; Liu Lu; Zeng Jun; Yin Weidong; Li Yun

2010-01-01

This study presents a dosimetric optimization effort aiming to compare noncoplanar field (NCF) on 3 dimensions conformal radiotherapy (3D-CRT) and coplanar field (CF) on intensity-modulated radiotherapy (IMRT) planning for postocular invasion tumor. We performed a planning study on the computed tomography data of 8 consecutive patients with localized postocular invasion tumor. Four fields NCF 3D-CRT in the transverse plane with gantry angles of 0-10 deg., 30-45 deg., 240-270 deg., and 310-335 deg. degrees were isocentered at the center of gravity of the target volume. The geometry of the beams was determined by beam's eye view. The same constraints were prepared with between CF IMRT optimization and NCF 3D-CRT treatment. The maximum point doses (D max) for the different optic pathway structures (OPS) with NCF 3D-CRT treatment should differ in no more than 3% from those with the NCF IMRT plan. Dose-volume histograms (DVHs) were obtained for all targets and organ at risk (OAR) with both treatment techniques. Plans with NCF 3D-CRT and CF IMRT constraints on target dose in homogeneity were computed, as well as the conformity index (CI) and homogeneity index (HI) in the target volume. The PTV coverage was optimal with both NCF 3D-CRT and CF IMRT plans in the 8 tumor sites. No difference was noted between the two techniques for the average D max and D min dose. NCF 3D-CRT and CF IMRT will yield similar results on CI. However, HI was a significant difference between NCF 3D-CRT and CF IMRT plan (p < 0.001). Physical endpoints for target showed the mean target dose to be low in the CF IMRT plan, caused by a large target dose in homogeneity (p < 0.001). The impact of NCF 3D-CRT versus CF IMRT set-up is very slight. NCF3D-CRT is one of the treatment options for postocular invasion tumor. However, constraints for OARs are needed.

Dynamic Conformations of Nucleosome Arrays in Solution from Small-Angle X-ray Scattering

Energy Technology Data Exchange (ETDEWEB)

Howell, Steven C. [George Washington Univ., Washington, DC (United States)

2016-01-31

We set out to determine quantitative information regarding the dynamic conformation of nucleosome arrays in solution using experimental SAXS. Toward this end, we developed a CG simulation algorithm for dsDNA which rapidly generates ensembles of structures through Metropolis MC sampling of a Markov chain.

Radiotherapy of intensity modulated VS conformational in the treatment of carcinoma of the prostate. A dosimetric comparison; Radioterapia de intensidad modulada VS conformacional en el tratamiento de carcinoma de prostata. Una camparacion dosimetrica

Energy Technology Data Exchange (ETDEWEB)

Rodriguez Martin, G.; Garcia Vicente, F.; Zapatero Laborda, A.; Bermudez Luna, R.; Roch Gonzalez, M.; Perez Gonzalez, L.; Torres Escobar, J. J.

2013-07-01

The intensity modulated (IMRT) radiation therapy is a technique of high conformation which, by its nature, has as one of its main directions prostate cancer radiotherapy treatment. The purpose of this work is presents results of the dosimetric indicators collected in our hospital a number of patients of carcinoma of the prostate with standard three-dimensional Conformal technique (3D-CRT) and IMRT. Aims to demonstrate and quantify with a statistical methodology that, establishing an adequate Protocol of IMRT, significant reductions in risk organ doses can be obtained by keeping the same prescription to the white volume. (Author)

Collective Dynamics of Belief Evolution under Cognitive Coherence and Social Conformity.

Science.gov (United States)

Rodriguez, Nathaniel; Bollen, Johan; Ahn, Yong-Yeol

2016-01-01

Human history has been marked by social instability and conflict, often driven by the irreconcilability of opposing sets of beliefs, ideologies, and religious dogmas. The dynamics of belief systems has been studied mainly from two distinct perspectives, namely how cognitive biases lead to individual belief rigidity and how social influence leads to social conformity. Here we propose a unifying framework that connects cognitive and social forces together in order to study the dynamics of societal belief evolution. Each individual is endowed with a network of interacting beliefs that evolves through interaction with other individuals in a social network. The adoption of beliefs is affected by both internal coherence and social conformity. Our framework may offer explanations for how social transitions can arise in otherwise homogeneous populations, how small numbers of zealots with highly coherent beliefs can overturn societal consensus, and how belief rigidity protects fringe groups and cults against invasion from mainstream beliefs, allowing them to persist and even thrive in larger societies. Our results suggest that strong consensus may be insufficient to guarantee social stability, that the cognitive coherence of belief-systems is vital in determining their ability to spread, and that coherent belief-systems may pose a serious problem for resolving social polarization, due to their ability to prevent consensus even under high levels of social exposure. We argue that the inclusion of cognitive factors into a social model could provide a more complete picture of collective human dynamics.

The evaluation of results and complications of radiotherapy in children treated for orbital rhabdomyosarcoma

International Nuclear Information System (INIS)

Skowronska-Gardas, A.; Pedziwiatr, K.; Chojnacka, M.

2002-01-01

To analyse treatment results and late complications of radiotherapy in children treated for orbital rhabdomyosarcoma. Between the years 1980 and 2000 34 children (median age 7 yrs. range: 1-15) with orbital RMS, were treated in the 1st Department of the MCCMCC in Warsaw. All but two of the patients received induction chemotherapy; 3 children were treated after ablative surgery (exenteration); 6 children were irradiated due to recurrence after chemotherapy. All the children were treated with megavoltage radiotherapy from a Co-60 unit or linear accelerator. We applied individual lens and lacrimal apparatus shielding in 16 patients. Five children, treated between 1996-2000, received conformal radiotherapy, with CT and 3-D treatment planning system.To obtain information about late side effects, we developed a questionnaire, including questions about the status of the affected eye, appearance of the orbit and facial structures.Thirty one patients (91%) are still living (between 24 and 264 months - median 138 mos) after completion of radiotherapy and 28 (82%) with no recurrence. In six patients treated due to recurrent tumour OS and DFS was 80% and 60%, respectively. Late complications were evaluated in 24 patients. We observed lacrimal duct stenosis in 33%, cataract in 29%, enophtalmos in 20% of patients. Retinopathy developed in 2 children, glaucoma in 2 pts, and facial asymmetry in 3 pts. In one case enucleation of blind eye was performed. Thirteen children have preserved adequate vision in the treated eye. In children treated with conformal radiotherapy we did not observe any late complications. Radiotherapy in orbital RMS allows to obtain good local control and excellent survival rate. Late complications could be limited with the application of individual treatment planning and conformal radiotherapy. (author)

External validation of three dimensional conformal radiotherapy based NTCP models for patient-rated xerostomia and sticky saliva among patients treated with intensity modulated radiotherapy

International Nuclear Information System (INIS)

Beetz, Ivo; Schilstra, Cornelis; Luijk, Peter van; Christianen, Miranda E.M.C.; Doornaert, Patricia; Bijl, Henk P.; Chouvalova, Olga; Heuvel, Edwin R. van den; Steenbakkers, Roel J.H.M.; Langendijk, Johannes A.

2012-01-01

Purpose: The purpose of this study was to investigate the ability of predictive models for patient-rated xerostomia (XER 6M ) and sticky saliva (STIC 6M ) at 6 months after completion of primary (chemo)radiation developed in head and neck cancer patients treated with 3D-conformal radiotherapy (3D-CRT) to predict outcome in patients treated with intensity modulated radiotherapy (IMRT). Methods and materials: Recently, we published the results of a prospective study on predictive models for patient-rated xerostomia and sticky saliva in head and neck cancer patients treated with 3D-CRT (3D-CRT based NTCP models). The 3D-CRT based model for XER 6M consisted of three factors, including the mean parotid dose, age, and baseline xerostomia (none versus a bit). The 3D-CRT based model for STIC 6M consisted of the mean submandibular dose, age, the mean sublingual dose, and baseline sticky saliva (none versus a bit). In the current study, a population consisting of 162 patients treated with IMRT was used to test the external validity of these 3D-CRT based models. External validity was described by the explained variation (R 2 Nagelkerke) and the Brier score. The discriminative abilities of the models were calculated using the area under the receiver operating curve (AUC) and calibration (i.e. the agreement between predicted and observed outcome) was assessed with the Hosmer–Lemeshow “goodness-of-fit” test. Results: Overall model performance of the 3D-CRT based predictive models for XER 6M and STIC 6M was significantly worse in terms of the Brier score and R 2 Nagelkerke among patients treated with IMRT. Moreover the AUC for both 3D-CRT based models in the IMRT treated patients were markedly lower. The Hosmer–Lemeshow test showed a significant disagreement for both models between predicted risk and observed outcome. Conclusion: 3D-CRT based models for patient-rated xerostomia and sticky saliva among head and neck cancer patients treated with primary radiotherapy or

Refining Markov state models for conformational dynamics using ensemble-averaged data and time-series trajectories

Science.gov (United States)

Matsunaga, Y.; Sugita, Y.

2018-06-01

A data-driven modeling scheme is proposed for conformational dynamics of biomolecules based on molecular dynamics (MD) simulations and experimental measurements. In this scheme, an initial Markov State Model (MSM) is constructed from MD simulation trajectories, and then, the MSM parameters are refined using experimental measurements through machine learning techniques. The second step can reduce the bias of MD simulation results due to inaccurate force-field parameters. Either time-series trajectories or ensemble-averaged data are available as a training data set in the scheme. Using a coarse-grained model of a dye-labeled polyproline-20, we compare the performance of machine learning estimations from the two types of training data sets. Machine learning from time-series data could provide the equilibrium populations of conformational states as well as their transition probabilities. It estimates hidden conformational states in more robust ways compared to that from ensemble-averaged data although there are limitations in estimating the transition probabilities between minor states. We discuss how to use the machine learning scheme for various experimental measurements including single-molecule time-series trajectories.

Modulation of the Conformational Dynamics of Apo-Adenylate Kinase through a π-Cation Interaction.

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Halder, Ritaban; Manna, Rabindra Nath; Chakraborty, Sandipan; Jana, Biman

2017-06-15

Large-scale conformational transition from open to closed state of adenylate kinase (ADK) is essential for its catalytic cycle. Apo-ADK undergoes conformational transition in a way that closely resembles an open-to-closed conformational transition. Here, equilibrium simulations, free-energy simulations, and quantum mechanics/molecular mechanics (QM/MM) calculations in combination with several bioinformatics approaches have been used to explore the molecular origin of this conformational transition in apo-ADK. In addition to its conventional open state, Escherichia coli apo-ADK adopts conformations that resemble a closed-like intermediate, the "half-open-half-closed" (HOHC) state, and a π-cation interaction can account for the stability of this HOHC state. Energetics and the electronic properties of this π-cation interaction have been explored using QM/MM calculations. Upon rescinding the π-cation interaction, the conformational landscape of the apo-ADK changes completely. The apo-ADK population is shifted completely toward the open state. This π-cation interaction is highly conserved in bacterial ADK; the cationic guanidinium moiety of a conserved ARG interacts with the delocalized π-electron cloud of either PHE or TYR. Interestingly, this study demonstrates the modulation of a principal protein dynamics by a conserved specific π-cation interaction across different organisms.

Postoperative radiotherapy for prostate cancer. Morbidity of local-only or local-plus-pelvic radiotherapy

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Waldstein, Cora; Poetter, Richard; Widder, Joachim; Goldner, Gregor; Doerr, Wolfgang

2018-01-01

The aim of this work was to characterise actuarial incidence and prevalence of early and late side effects of local versus pelvic three-dimensional conformal postoperative radiotherapy for prostate cancer. Based on a risk-adapted protocol, 575 patients received either local (n = 447) or local-plus-pelvic (n = 128) radiotherapy. Gastrointestinal (GI) and genitourinary (GU) side effects (≥grade 2 RTOG/EORTC criteria) were prospectively assessed. Maximum morbidity, actuarial incidence rate, and prevalence rates were compared between the two groups. For local radiotherapy, median follow-up was 68 months, and the mean dose was 66.7 Gy. In pelvic radiotherapy, the median follow-up was 49 months, and the mean local and pelvic doses were 66.9 and 48.3 Gy respectively. Early GI side effects ≥ G2 were detected in 26% and 42% of patients respectively (p < 0.001). Late GI adverse events were detected in 14% in both groups (p = 0.77). The 5-year actuarial incidence rates were 14% and 14%, while the prevalence rates were 2% and 0% respectively. Early GU ≥ G2 side effects were detected in 15% and 16% (p = 0.96), while late GU morbidity was detected in 18% and 24% (p = 0.001). The 5-year actuarial incidence rates were 16% and 35% (p = 0.001), while the respective prevalence rates were 6% and 8%. Despite the low prevalence of side effects, postoperative pelvic radiotherapy results in significant increases in the actuarial incidence of early GI and late GU morbidity using a conventional 4-field box radiotherapy technique. Advanced treatment techniques like intensity-modulated radiotherapy (IMRT) or volumetric modulated arc radiotherapy (VMAT) should therefore be considered in pelvic radiotherapy to potentially reduce these side effects. (orig.) [de

Activation of Hsp90 Enzymatic Activity and Conformational Dynamics through Rationally Designed Allosteric Ligands.

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Sattin, Sara; Tao, Jiahui; Vettoretti, Gerolamo; Moroni, Elisabetta; Pennati, Marzia; Lopergolo, Alessia; Morelli, Laura; Bugatti, Antonella; Zuehlke, Abbey; Moses, Mike; Prince, Thomas; Kijima, Toshiki; Beebe, Kristin; Rusnati, Marco; Neckers, Len; Zaffaroni, Nadia; Agard, David A; Bernardi, Anna; Colombo, Giorgio

2015-09-21

Hsp90 is a molecular chaperone of pivotal importance for multiple cell pathways. ATP-regulated internal dynamics are critical for its function and current pharmacological approaches block the chaperone with ATP-competitive inhibitors. Herein, a general approach to perturb Hsp90 through design of new allosteric ligands aimed at modulating its functional dynamics is proposed. Based on the characterization of a first set of 2-phenylbenzofurans showing stimulatory effects on Hsp90 ATPase and conformational dynamics, new ligands were developed that activate Hsp90 by targeting an allosteric site, located 65 Å from the active site. Specifically, analysis of protein responses to first-generation activators was exploited to guide the design of novel derivatives with improved ability to stimulate ATP hydrolysis. The molecules' effects on Hsp90 enzymatic, conformational, co-chaperone and client-binding properties were characterized through biochemical, biophysical and cellular approaches. These designed probes act as allosteric activators of the chaperone and affect the viability of cancer cell lines for which proper functioning of Hsp90 is necessary. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Side effects of radiotherapy in regime of dynamic dose multifractioning for local larynx cancer forms

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Slobina, E.L.

2000-01-01

A regime for dynamic multifractioning of radiotherapy dose used for treating larynx cancer was developed. The method favored reducing the side effects frequency as compared with the conventional fractioning in larynx mucosa from 70% to 46%, in neck skin being irradiated - from 60% to 48%

Hierarchical Conformational Analysis of Native Lysozyme Based on Sub-Millisecond Molecular Dynamics Simulations.

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Kai Wang

Full Text Available Hierarchical organization of free energy landscape (FEL for native globular proteins has been widely accepted by the biophysics community. However, FEL of native proteins is usually projected onto one or a few dimensions. Here we generated collectively 0.2 milli-second molecular dynamics simulation trajectories in explicit solvent for hen egg white lysozyme (HEWL, and carried out detailed conformational analysis based on backbone torsional degrees of freedom (DOF. Our results demonstrated that at micro-second and coarser temporal resolutions, FEL of HEWL exhibits hub-like topology with crystal structures occupying the dominant structural ensemble that serves as the hub of conformational transitions. However, at 100 ns and finer temporal resolutions, conformational substates of HEWL exhibit network-like topology, crystal structures are associated with kinetic traps that are important but not dominant ensembles. Backbone torsional state transitions on time scales ranging from nanoseconds to beyond microseconds were found to be associated with various types of molecular interactions. Even at nanoseconds temporal resolution, the number of conformational substates that are of statistical significance is quite limited. These observations suggest that detailed analysis of conformational substates at multiple temporal resolutions is both important and feasible. Transition state ensembles among various conformational substates at microsecond temporal resolution were observed to be considerably disordered. Life times of these transition state ensembles are found to be nearly independent of the time scales of the participating torsional DOFs.

Intensity-modulated conformal radiotherapy in the anal canal cancer. Report of technological assessment. Updating of the 2006 report

International Nuclear Information System (INIS)

2015-07-01

As intensity-modulated conformal radiotherapy (IMCR) has already been technologically assessed in 2006 with a positive opinion for some treatments and a negative one for others, and as this technique displays some interesting properties for the treatment of pelvic cancers (optimisation of dose distribution, preservation of sane tissues, reduction of secondary effects during irradiation), this report proposes an assessment of clinical safety and efficiency of IMCR in the treatment of an anal canal cancer. After a discussion of generalities, of histological and epidemiological data, and of knowledge regarding treatment and follow-up of this cancer, the report presents the IMCR technique, some regulatory aspects, and its applications to the considered cancer. The methodology adopted for this assessment is then presented. Based on various studies and clinical results, the IMCR clinical safety and efficiency in the treatment of the anal canal cancer are discussed and assessed. Recommendations produced by different medical professional bodies are reported. Opinion of experts and a synthesis of stakeholders are then proposed

3D-conformal radiotherapy treatment of high grade gliomas of malignancy

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Chon Rivas, Ivonne; Chi Ramirez, Daysi; Alert Silva, Jose; Roca Muchuli, Carlos; Leon Gonzalez, Roberto; Perez Penna, Lourdes

2009-01-01

Patients diagnosed with high grade gliomas of malignancy (A), have a high mortality rate, about 10% achieve survivals than one year due to poor local control resulting from the inability of high doses of radiation to tumor volume by dose-limiting provided by healthy peritumoral tissues and structures. 3D conformal radiotherapy (RT-3DC) achieves effective tumoricidal high doses with high precision on the tumor with minimal involvement of critical structures near the tumor target volume. From 2005 until 2008 at INOR, a total of 23 patients with histologically confirmed supratentorial gliomas location, histological subtypes of anaplastic astrocytoma (AA) in 8 patients (35%) and Glioblastoma Multiforme (GBM) in 15 patients (65%), aged between 18 and 65, Karnofski scale of 70 or more and total previous surgical resection in 10 patients (43%) or partial in 13 (57%) were included prospectively in this study. The total tumor dose of 66-70 Gy was prescribed with a daily fractionation of 1.8 Gy. All patients underwent CT images (CT) and MRI (MRI) cranial volumes were defined treatment planning according to the concepts of ICRU 50 and 62 with precise immobilization of the head by thermo deformed mask, CT 3mm cuts planning system and 3D treatment planning. Median survival was better in patients younger than 55 years, with high rates of Karnofski, histology of AA and higher percentage of surgical resection. Median survival (Kaplan-Meier method) obtained was 16 months. Survival at 1 and 2 years was 51% and 28% respectively. The RT-3DC can administer higher doses on the tumor with peritumoral healthy protection structures in selected patients with a diagnosis of AA or GBM, increasing local control and potentially overall survival without exacerbating toxicity, thus demonstrating the dose- response of malignant brain tumors. (Author)

Dynamics of organizational culture: Individual beliefs vs. social conformity.

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Ellinas, Christos; Allan, Neil; Johansson, Anders

2017-01-01

The complex nature of organizational culture challenges our ability to infer its underlying dynamics from observational studies. Recent computational studies have adopted a distinctly different view, where plausible mechanisms are proposed to describe a wide range of social phenomena, including the onset and evolution of organizational culture. In this spirit, this work introduces an empirically-grounded, agent-based model which relaxes a set of assumptions that describes past work-(a) omittance of an individual's strive for achieving cognitive coherence; (b) limited integration of important contextual factors-by utilizing networks of beliefs and incorporating social rank into the dynamics. As a result, we illustrate that: (i) an organization may appear to be increasingly coherent in terms of its organizational culture, yet be composed of individuals with reduced levels of coherence; (ii) the components of social conformity-peer-pressure and social rank-are influential at different aggregation levels.

Optimal hypofractionated conformal radiotherapy for large brain metastases in patients with high risk factors: a single-institutional prospective study

International Nuclear Information System (INIS)

Inoue, Hiroshi K; Sato, Hiro; Suzuki, Yoshiyuki; Saitoh, Jun-ichi; Noda, Shin-ei; Seto, Ken-ichi; Torikai, Kota; Sakurai, Hideyuki; Nakano, Takashi

2014-01-01

A single-institutional prospective study of optimal hypofractionated conformal radiotherapy for large brain metastases with high risk factors was performed based on the risk prediction of radiation-related complications. Eighty-eight patients with large brain metastases ≥10 cm 3 in critical areas treated from January 2010 to February 2014 using the CyberKnife were evaluated. The optimal dose and number of fractions were determined based on the surrounding brain volume circumscribed with a single dose equivalent (SDE) of 14 Gy (V14) to be less than 7 cm 3 for individual lesions. Univariate and multivariate analyses were conducted. As a result of optimal treatment, 92 tumors ranging from 10 to 74.6 cm 3 (median, 16.2 cm 3 ) in volume were treated with a median prescribed isodose of 57% and a median fraction number of five. In order to compare the results according to the tumor volume, the tumors were divided into the following three groups: 1) 10–19.9 cm 3 , 2) 20–29.9 cm 3 and 3) ≥30 cm 3 . The lesions were treated with a median prescribed isodose of 57%, 56% and 55%, respectively, and the median fraction number was five in all three groups. However, all tumors ≥20 cm 3 were treated with ≥ five fractions. The median SDE of the maximum dose in the three groups was 47.2 Gy, 48.5 Gy and 46.5 Gy, respectively. Local tumor control was obtained in 90.2% of the patients, and the median survival was nine months, with a median follow-up period of seven months (range, 3-41 months). There were no significant differences in the survival rates among the three groups. Six tumors exhibited marginal recurrence 7-36 months after treatment. Ten patients developed symptomatic brain edema or recurrence of pre-existing edema, seven of whom required osmo-steroid therapy. No patients developed radiation necrosis requiring surgical resection. Our findings demonstrate that the administration of optimal hypofractionated conformal radiotherapy based on the dose-volume prediction

Monte Carlo conformal treatment planning as an independent assessment

International Nuclear Information System (INIS)

Rincon, M.; Leal, A.; Perucha, M.; Carrasco, E.; Sanchez-Doblado, F.; Hospital Univ. Virgen Macarena, Sevilla; Arrans, R.; Sanchez-Calzado, J.A.; Errazquin, L.; Medrano, J.C.

2001-01-01

The wide range of possibilities available in Radiotherapy with conformal fields cannot be covered experimentally. For this reason, dosimetrical and planning procedures are based on approximate algorithms or systematic measurements. Dose distribution calculations based on Monte Carlo (MC) simulations can be used to check results. In this work, two examples of conformal field treatments are shown: A prostate carcinoma and an ocular lymphoma. The dose distributions obtained with a conventional Planning System and with MC have been compared. Some significant differences have been found. (orig.)

Three-dimensional treatment planning for postoperative radiotherapy in patients with node-positive cervical cancer. Comparison between a conventional and a conformal technique

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Olofsen-van Acht, M.J.J.; Quint, S.; Seven, M.; Berg, H.A. van den; Levendag, P.C. [University Hospital Rotterdam (Netherlands). Dept. of Radiation Oncology; Santvoort, J.P.C. van [University Hospital Rotterdam (Netherlands). Subdivision of Clinical Physics; Logmans, A. [University Hospital Rotterdam (Netherlands). Dept. of Gynecologic Oncology

1999-09-01

Purpose: Reduction of irradiated small bowel volume, using a conformal three-dimensional treatment planning technique in postoperative radiotherapy of cervical cancer patients. Patients and Methods: Large gynecological treatment fields including the para-aortic nodes were analyzed in 15 patients. A conventional treatment plan with anterior and posterior (AP-PA) parallel opposed fields and a 3D 4-field conformal radiotherapy plan with a central blocking of small bowel were compared for each patient. Dose-volume histograms and dose parameters were established. Because of the tolerance constraints of the small bowel, the cumulative dose applied to the target was 48.6 Gy. Results: The mean Tumor Control Probability (TCP) values for both the conventional and the conformal technique were 0.60 and 0.61, respectively, with ranges of 0.56 to 0.67 and 0.57 to 0.66, respectively. The mean volume receiving 95% or more of the prescribed dose (V95) of the small bowel was 47.6% (32.5 to 66.3%) in the AP-PA technique and 14.9% (7.0 to 22.5%) in the conformal technique (p<0.001), indicating a significant reduction in irradiated volume of small bowel in the higher dose range. The mean Normal Tissue Complication Probability (NTCP) decreased from 0.11 to 0.03 with the conformal plan. In patients who received a pedicled omentoplasty during surgery, the mean V95 for small bowel could be reduced to 8.5% (7.0 to 9.9%). The mean median dose to the kidneys was only slightly elevated in the conformal treatment. Especially the mean dose to the right kidney in conventional vs conformal treatment was 3.3 vs 7.9 Gy. The mean near-minimum dose (D95) to the rectosigmoid decreased from 48.4 to 30.1 Gy in the conformal plan compared to the conventional plan. Conclusion: The small bowel dose can be significantly reduced with 3D treatment planning, particularly if a predicled omentoplasty is performed. This allows dose escalation to the tumor region without unacceptable toxicity for the small bowel

Large-scale conformational changes of Trypanosoma cruzi proline racemase predicted by accelerated molecular dynamics simulation.

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César Augusto F de Oliveira

2011-10-01

Full Text Available Chagas' disease, caused by the protozoan parasite Trypanosoma cruzi (T. cruzi, is a life-threatening illness affecting 11-18 million people. Currently available treatments are limited, with unacceptable efficacy and safety profiles. Recent studies have revealed an essential T. cruzi proline racemase enzyme (TcPR as an attractive candidate for improved chemotherapeutic intervention. Conformational changes associated with substrate binding to TcPR are believed to expose critical residues that elicit a host mitogenic B-cell response, a process contributing to parasite persistence and immune system evasion. Characterization of the conformational states of TcPR requires access to long-time-scale motions that are currently inaccessible by standard molecular dynamics simulations. Here we describe advanced accelerated molecular dynamics that extend the effective simulation time and capture large-scale motions of functional relevance. Conservation and fragment mapping analyses identified potential conformational epitopes located in the vicinity of newly identified transient binding pockets. The newly identified open TcPR conformations revealed by this study along with knowledge of the closed to open interconversion mechanism advances our understanding of TcPR function. The results and the strategy adopted in this work constitute an important step toward the rationalization of the molecular basis behind the mitogenic B-cell response of TcPR and provide new insights for future structure-based drug discovery.

Treatment planning evaluation of non-coplanar techniques for conformal radiotherapy of the prostate

International Nuclear Information System (INIS)

Bedford, James L.; Henrys, Anthony J.; Dearnaley, David P.; Khoo, Vincent S.

2005-01-01

Background and purpose: To evaluate the benefit of using non-coplanar treatment plans for irradiation of two different clinical treatment volumes: prostate only (PO) and the prostate plus seminal vesicles (PSV). Material and methods: An inverse planning algorithm was used to produce three-field, four-field, five-field and six-field non-coplanar treatment plans without intensity-modulation in ten patients. These were compared against a three-field coplanar plan. A dose of 74 Gy was prescribed to the isocentre. Plans were compared using the minimum dose to the planning target volume (PTV), maximum dose to the small bowel, and irradiated volumes of rectum, bladder and femoral head. Biological indices were also evaluated. Results: For the PO group, volume of rectum irradiated to 60 Gy (V 60 ) was 22.5±3.7% for the coplanar plan, and 21.5±5.3% for the five-field non-coplanar plan, which was the most beneficial (p=0.3). For the PSV group, the five-field non-coplanar plan was again the most beneficial. Rectal V 60 was in this case reduced from 41.5±10.4% for the coplanar plan to 35.2±9.3% for the non-coplanar plan (p=0.02). Conclusions: The use of non-coplanar beams in conformal prostate radiotherapy provides a small increase in rectal sparing, more significantly with PSV volumes than for PO volumes

Concomitant chemo-radiotherapy for locally advanced bronchial cancer: impact of radiotherapy quality on global survival: results of a trial by the Thoracic Cancerology French-speaking Inter-group (IFCT) and Pneumo-Cancerology French Group (GFPC) 02.01

International Nuclear Information System (INIS)

Martel-Lafay, I.; Montella, A.; Pommier, P.; Clavere, P.; Labat, J.P.; Benchalal, M.; Teissier, E.; Talabard, J.N.; Fournel, P.; D'Hombres, A.

2010-01-01

The author report the assessment of the influence of radiotherapy quality and of its consequences on the future of 113 patients during a phase-II randomized trial of concomitant chemo-radiotherapy of bronchial cancers without stage-II non-resectable small cells. The patients have been submitted to a conformational radiotherapy and a concomitant induction of consolidation chemotherapy. Ten items are analysed: immobilisation, dose per fraction, total dose, ganglion radiotherapy, number of beams, images before and after radiotherapy, radiotherapy duration, duration without radiotherapy, dose-lung volume histogram. The study notably shows the deleterious effects of an interruption of the concomitant chemotherapy on the global survival. Short communication

Prognosis comparison of three-dimensional conformal radiotherapy/intensity modulated radiation therapy for esophageal carcinoma with local regional lymph node metastasis

International Nuclear Information System (INIS)

Wang Yuxiang; Wang Jun; Wang Yi; Tian Dandan; Yang Jie; Zhu Shuchai

2011-01-01

Objective: To explore the prognosis and related factor of esophageal carcinoma with locoregional lymph node metastasis (N 1 ) treated with three-dimensional conformal radiotherapy (3DCRT) or intensity modulated radiation therapy (IMRT). Methods: From January 2001 to December 2008, 60 patients of esophageal carcinoma with local regional lymph node metastasis were treated with 3DCRT and 52 with IMRT. For all patients,dose of tumor was 56 - 70 Gy/28 - 35 fraction/5.6 - 7.0 weeks. Among them, 58 cases was treated with chemotherapy including cisplatin and 5-fluorouracil; 40 with concurrent chemoradiotherapy and 18 with sequential radiotherapy and chemotherapy. Results: After radiotherapy,the total efficiency rate was 98.2%, 96.7% in 3DCRT and 100% in IMRT (χ 2 =1.77, P =0.184). The follow-up rate was 99.1%. The number of patients completed follow-up were 68 and 53, respectively at 2-year and 3-year. The 1 and 3-year overall survival rates were 62.5%, 23.7%, respectively; the median survival time was 17 months. The 1 and 3-year survival rates and median were 52%, 19% and 12.4 months in 3DCRT and 75%, 40% and 17 months in IMRT, respectively (χ 2 =4.74, P =0.030). The 1 and 3-year free-recurrence survival rates were 64%, 45% in 3DCRT and 72%, 59% in IMRT (χ 2 =2.27, P =0.132), respectively. With univariate analysis, for female, ages ≤ 65, tumor located in cervical and upper-thoracic, >5 cm lesion length in barium esophagogram, ≤4 cm the largest diameter of lesion in CT scanning image, T 4 stage, or semiliquid or liquid diet before radiotherapy, survival rate were higher in IMRT than in 3DCRT group (χ 2 =4.63, 5.56, 7.19, 5.08, 4.43, 4.48, 8.25; P=0.031, 0.018, 0.007, 0.025, 0.035, 0.034, 0.004, respectively); but for male, ages > 65, tumor located in middle and lower-thoracic, ≤5 cm lesion length in barium esophagogram, >4 cm the largest diameter of lesion in CT scanning image, T 1-3 stage, or normal diet before radiotherapy, chemotherapy and dose of radiotherapy

Dosimetry in radiotherapy. V.1

International Nuclear Information System (INIS)

1988-01-01

A series of symposia on dosimetry in medicine and biology have been held by the IAEA in co-operation with WHO. The present symposium was the first one focusing on ''Dosimetry in Radiotherapy''. The papers presented reflected the different steps in the calibration chain such as the calibration standards established by the National Standards Laboratories and the conversion of the reading of calibrated instruments to the desired quantity, i.e. absorbed dose to water at a reference point in the user's beam at the radiotherapy clinic. The programme further examined the procedures necessary for optimization of the treatment of the patient, such as treatment planning methods, dose distribution studies, new techniques of dose measurement, improvements in the physical dose distributions/conformation therapy and special problems involved in total body treatments. Results of quality assurance in radiotherapy were presented from local hospitals as well as from national and international studies. Refs, figs and tabs

Potential clinical efficacy of intensity-modulated conformal therapy

International Nuclear Information System (INIS)

Meeks, Sanford L.; Buatti, John M.; Bova, Francis J.; Friedman, William A.; Mendenhall, William M.; Zlotecki, Robert A.

1998-01-01

Purpose: The purpose of this study was to examine the potential benefit of using intensity-modulated conformal therapy for a variety of lesions currently treated with stereotactic radiosurgery or conventional radiotherapy. Methods and Materials: Intensity-modulated conformal treatment plans were generated for small intracranial lesions, as well as head and neck, lung, breast, and prostate cases, using the Peacock Plan[reg] treatment-planning system (Nomos Corporation). For small intracranial lesions, intensity-modulated conformal treatment plans were compared with stereotactic radiosurgery treatment plans generated for patient treatment at the University of Florida Shands Cancer Center. For other sites (head and neck, lung, breast, and prostate), plans generated using the Peacock Plan[reg] were compared with conventional treatment plans, as well as beam's-eye-view conformal treatment plans. Plan comparisons were accomplished through conventional qualitative review of two-dimensional (2D) dose distributions in conjunction with quantitative techniques, such as dose-volume histograms, dosimetric statistics, normal tissue complication probabilities, tumor control probabilities, and objective numerical scoring. Results: For small intracranial lesions, there is little difference between intensity-modulated conformal treatment planning and radiosurgery treatment planning in the conformation of high isodose lines with the target volume. However, stereotactic treatment planning provides a steeper dose gradient outside the target volume and, hence, a lower normal tissue toxicity index. For extracranial sites, objective numerical scores for beam's-eye-view and intensity-modulated conformal planning techniques are superior to scores for conventional treatment plans. The beam's-eye-view planning technique prevents geographic target misses and better excludes healthy tissues from the treatment portal. Compared with scores for the beam's-eye-view planning technique, scores for

Comparison of 3DCRT,VMAT and IMRT techniques in metastatic vertebra radiotherapy: A phantom Study

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Gedik Sonay

2017-01-01

Full Text Available Vertebra metastases can be seen during the prognosis of cancer patients. Treatment ways of the metastasis are radiotherapy, chemotherapy and surgery. Three-dimensional conformal therapy (3D-CRT is widely used in the treatment of vertebra metastases. Also, Intensity Modulated Radiotherapy (IMRT and Volumetric Arc Therapy (VMAT are used too. The aim of this study is to examine the advantages and disadvantages of the different radiotherapy techniques. In the aspect of this goal, it is studied with a randophantom in Uludag University Medicine Faculty, Radiation Oncology Department. By using a computerized tomography image of the phantom, one 3DCRT plan, two VMAT and three IMRT plans for servical vertebra and three different 3DCRT plans, two VMAT and two IMRT plans for lomber vertebra are calculated. To calculate 3DCRT plans, CMS XiO Treatment System is used and to calculate VMAT and IMRT plans Monaco Treatment Planning System is used in the department. The study concludes with the dosimetric comparison of the treatment plans in the spect of critical organ doses, homogeneity and conformity index. As a result of this study, all critical organ doses are suitable for QUANTEC Dose Limit Report and critical organ doses depend on the techniques which used in radiotherapy. According to homogeneity and conformity indices, VMAT and IMRT plans are better than one in 3DCRT plans in servical and lomber vertebra radiotherapy plans.

Physical and clinical aspects of the dynamic intensity-modulated radiotherapy of 21 patients

International Nuclear Information System (INIS)

Engler, Mark J.; Tsai, J.-S.; Ulin, Kenneth; Wu Julian; Ling, Marilyn N.; Fagundes, Marcio; Kramer, Bradley; Wazer, David E.

1996-01-01

(Rx) varied from 6 to 50.4, in fractions of 1.8 to 6 Gy. Results: Thus far 204 treatments have been well tolerated. Positional reproducibility among was ± 1 mm. Plan verification showed that for 18 of the 21 patients, delivered isodose surfaces were within 2 mm of planned surfaces, and delivered absolute doses, within ± 5 % of planned. Verifications of 3 patients with large and complex tumor geometry showed larger dose discrepancies that were believed to arise from imperfection in the dose calculation and verification procedures. Delivered distributions compared favorably to those of most other external beam treatment modalities. Improvements to external beam treatments offered by the IMR system are its abilities to provide highly conformal doses with detailed dose strategies for multiple ROI, and to irradiate multiple targets irrespective of their geometry and without having to change collimators as in radiosurgery. Recent replacement of the linac with a high dose rate linac and upgrades to the IMR system have increased dose calculation accuracy and ease of treatment. Conclusion: Heretofore unattainable conformity of dose distribution to large, complex, and convoluted targets is now a reality. The IMR system studied here made other external beam radiotherapy, including most radiosurgery with circular collimators, seem primitive. In conclusion, robust development of optimized dynamic photon pencil beam IMR is suggested

A comparison of morbidity following conformal versus intensity-modulated radiotherapy for urinary bladder cancer.

Science.gov (United States)

Søndergaard, Jimmi; Holmberg, Mats; Jakobsen, Annette Ross; Agerbæk, Mads; Muren, Ludvig Paul; Høyer, Morten

2014-10-01

In radiotherapy (RT) of urinary bladder cancer, the use of intensity-modulated RT (IMRT) opens for sparing of considerable intestinal volumes. The purpose of the present study was to investigate the acute and late toxicities following either conformal RT (CRT) or IMRT for bladder cancer, and to correlate the toxicities to dose-volume parameters. The study included 116 consecutively treated patients with muscle-invasive bladder cancer who received either CRT (n = 66) or IMRT (n = 50) during 2007-2010. Acute side effects were retrospectively collected whereas late effects were assessed by a cross-sectional evaluation by telephone interview of 44 recurrence-free patients. Acute and late toxicities were scored according to the Common Terminology Criteria for Adverse Event (CTCAE) version 3.0. Acute diarrhoea grade ≥ 2 was more frequent in patients treated by CRT (56%) compared to IMRT (30%) (p = 0.008). Logistic regression analysis showed a correlation between acute diarrhoea and bowel cavity dose-volume parameters in the 10-50 Gy range. Severe late toxicity (grade ≥ 3) was recorded in 10% of the total cohort, with no statistical difference between the IMRT and CRT groups. Patients treated with IMRT for bladder cancer had significantly less acute diarrhoea compared to those treated with CRT, but there was no significant difference in late morbidity between the groups. The risk of acute diarrhoea was related to the volume of bowel irradiated.

Evaluation of a mixed beam therapy for post-mastectomy breast cancer patients: bolus electron conformal therapy combined with intensity modulated photon radiotherapy and volumetric modulated photon arc therapy.

Science.gov (United States)

Zhang, Rui; Heins, David; Sanders, Mary; Guo, Beibei; Hogstrom, Kenneth

2018-05-10

The purpose of this study was to assess the potential benefits and limitations of a mixed beam therapy, which combined bolus electron conformal therapy (BECT) with intensity modulated photon radiotherapy (IMRT) and volumetric modulated photon arc therapy (VMAT), for left-sided post-mastectomy breast cancer patients. Mixed beam treatment plans were produced for nine post-mastectomy radiotherapy (PMRT) patients previously treated at our clinic with VMAT alone. The mixed beam plans consisted of 40 Gy to the chest wall area using BECT, 40 Gy to the supraclavicular area using parallel opposed IMRT, and 10 Gy to the total planning target volume (PTV) by optimizing VMAT on top of the BECT+IMRT dose distribution. The treatment plans were created in a commercial treatment planning system (TPS), and all plans were evaluated based on PTV coverage, dose homogeneity index (DHI), conformity index (CI), dose to organs at risk (OARs), normal tissue complication probability (NTCP), and secondary cancer complication probability (SCCP). The standard VMAT alone planning technique was used as the reference for comparison. Both techniques produced clinically acceptable PMRT plans but with a few significant differences: VMAT showed significantly better CI (0.70 vs. 0.53, p 0.5 cm and volume of tissue between the distal PTV surface and heart or lung approximately > 250 cm 3 ) between distal PTV surface and lung may benefit the most from mixed beam therapy. This work has demonstrated that mixed beam therapy (BECT+IMRT : VMAT = 4 : 1) produces clinically acceptable plans having reduced OAR doses and risks of side effects compared with VMAT. Even though VMAT alone produces more homogenous and conformal dose distributions, mixed beam therapy remains as a viable option for treating post-mastectomy patients, possibly leading to reduced normal tissue complications. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Development of radiation oncology learning system combined with multi-institutional radiotherapy database (ROGAD)

International Nuclear Information System (INIS)

Takemura, Akihiro; Iinuma, Masahiro; Kou, Hiroko; Harauchi, Hajime; Inamura, Kiyonari

1999-01-01

We have constructed and are operating a multi-institutional radiotherapy database ROGAD (Radiation Oncology Greater Area Database) since 1992. One of it's purpose is 'to optimize individual radiotherapy plans'. We developed Radiation oncology learning system combined with ROGAD' which conforms to that purpose. Several medical doctors evaluated our system. According to those evaluations, we are now confident that our system is able to contribute to improvement of radiotherapy results. Our final target is to generate a good cyclic relationship among three components: radiotherapy results according to ''Radiation oncology learning system combined with ROGAD.'; The growth of ROGAD; and radiation oncology learning system. (author)

Predictive factors of gastroduodenal toxicity in cirrhotic patients after three-dimensional conformal radiotherapy for hepatocellular carcinoma

International Nuclear Information System (INIS)

Kim, Haeyoung; Lim, Do Hoon; Paik, Seung Woon; Yoo, Byung Chul; Koh, Kwang Gheol; Lee, Joon Hyoek; Choi, Moon Seok; Park, Won; Park, Hee Chul; Huh, Seung Jae; Choi, Doo Ho; Ahn, Yong Chan

2009-01-01

Background and purpose: To identify predictive factors for the development of gastroduodenal toxicity (GDT) in cirrhotic patients treated with three-dimensional conformal radiotherapy (3D-CRT) for hepatocellular carcinoma (HCC). Materials and methods: We retrospectively analyzed dose-volume histograms (DVHs) and clinical records of 73 cirrhotic patients treated with 3D-CRT for HCC. The median radiation dose was 36 Gy (range, 30-54 Gy) with a daily dose of 3 Gy. The grade of GDT was defined by the Common Toxicity Criteria Version 2. The predictive factors of grade 3 GDT were identified. Results: Grade 3 GDT was found in 9 patients. Patient's age and the percentage of gastroduodenal volume receiving more than 35 Gy (V 35 ) significantly affected the development of grade 3 GDT. Patients over 50 years of age developed grade 3 GDT more frequently than patients under 50 years of age. The risk of grade 3 GDT grew exponentially as V 35 increased. The 1-year actuarial rate of grade 3 GDT in patients with V 35 35 ≥5% (4% vs. 48%, p 35 were the most predictive factors for the development of grade 3 GDT in patients treated with RT.

The early toxicity of escalated versus standard dose conformal radiotherapy with neo-adjuvant androgen suppression for patients with localised prostate cancer: Results from the MRC RT01 trial (ISRCTN47772397)

International Nuclear Information System (INIS)

Dearnaley, David P.; Sydes, Matthew R.; Langley, Ruth E.; Graham, John D.; Huddart, Robert A.; Syndikus, Isabel; Matthews, John H.L.; Scrase, Christopher D.; Jose, Chakiath C.; Logue, John; Stephens, Richard J.

2007-01-01

Background: Five-year disease-free survival rates for localised prostate cancer following standard doses of conventional radical external beam radiotherapy are around 80%. Conformal radiotherapy (CFRT) raises the possibility that radiotherapy doses can be increased and long-term efficacy outcomes improved, with safety an important consideration. Methods: MRC RT01 is a randomised controlled trial of 862 men with localised prostate cancer comparing Standard CFRT (64 Gy/32 f) versus Escalated CFRT (74 Gy/37 f), both administered with neo-adjuvant androgen suppression. Early toxicity was measured using physician-reported instruments (RTOG, LENT/SOM, Royal Marsden Scales) and patient-reported questionnaires (MOS SF-36, UCLA Prostate Cancer Index, FACT-P). Results: Overall early radiotherapy toxicity was similar, apart from increased bladder, bowel and sexual toxicity, in the Escalated Group during a short immediate post-radiotherapy period. Toxicity in both groups had abated by week 12. Using RTOG Acute Toxicity scores, cumulative Grade ≥2 bladder and bowel toxicity was 38% and 30% for Standard Group and 39% and 33% in Escalated Group, respectively. Urinary frequency (Royal Marsden Scale) improved in both groups from pre-androgen suppression to 6 months post-radiotherapy (p < 0.001), but bowel and sexual functioning deteriorated. This pattern was supported by patient-completed assessments. Six months after starting radiotherapy the incidence of RTOG Grade ≥2 side-effects was low (<1%); but there were six reports of rectal ulceration (6 Escalated Group), six haematuria (5 Escalated Group) and eight urethral stricture (6 Escalated Group). Conclusions: The two CFRT schedules with neo-adjuvant androgen suppression have broadly similar early toxicity profiles except for the immediate post-RT period. At 6 months and compared to before hormone therapy, bladder symptoms improved, whereas bowel and sexual symptoms worsened. These assessments of early treatment safety will be

Estimate of the damage in organs induced by neutrons in three-dimensional conformal radiotherapy; Estimacion del dano en organos inducido por neutrones en radioterapia conformada en 3D

Energy Technology Data Exchange (ETDEWEB)

Benites R, J. L. [Centro Estatal de Cancerologia de Nayarit, Servicio de Seguridad Radiologica, Calzada de la Cruz 118 sur, 63000 Tepic, Nayarit (Mexico); Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Uribe, M. del R., E-mail: jlbenitesr@prodigy.net.mx [Instituto Tecnico Superior de Radiologia, Calle Leon No. 129, 63000 Tepic, Nayarit (Mexico)

2014-08-15

By means of Monte Carlo methods was considered the damage in the organs, induced by neutrons, of patients with cancer that receive treatment in modality of three-dimensional conformal radiotherapy (3D-CRT) with lineal accelerator Varian Ix. The objective of this work was to estimate the damage probability in radiotherapy patients, starting from the effective dose by neutrons in the organs and tissues out of the treatment region. For that a three-dimensional mannequin of equivalent tissue of 30 x 100 x 30 cm{sup 3} was modeled and spherical cells were distributed to estimate the Kerma in equivalent tissue and the absorbed dose by neutrons. With the absorbed dose the effective dose was calculated using the weighting factors for the organ type and radiation type. With the effective dose and the damage factors, considered in the ICRP 103, was considered the probability of damage induction in organs. (Author)

Guidelines for primary radiotherapy of patients with prostate cancer

International Nuclear Information System (INIS)

Boehmer, Dirk; Maingon, Philippe; Poortmans, Philip; Baron, Marie-Helene; Miralbell, Raymond; Remouchamps, Vincent; Scrase, Christopher; Bossi, Alberto; Bolla, Michel

2006-01-01

Background and purposes: The appropriate application of 3-D conformal radiotherapy, intensity modulated radiotherapy or image guided radiotherapy for patients undergoing radiotherapy for prostate cancer requires a standardisation of target delineation as well as clinical quality assurance procedures. Patients and methods: Pathological and imaging studies provide valuable information on tumour extension. In addition, clinical investigations on patient positioning and immobilisation as well as treatment verification data offer an abundance of information. Results: Target volume definitions for different risk groups of prostate cancer patients based on pathological and imaging studies are provided. Available imaging modalities, patient positioning and treatment preparation studies as well as verification procedures are collected from literature studies. These studies are summarised and recommendations are given where appropriate. Conclusions: On behalf of the European Organisation for Research and Treatment of Cancer (EORTC) Radiation Oncology Group this article presents a common set of recommendations for external beam radiotherapy of patients with prostate cancer

A computer-controlled conformal radiotherapy system. IV: Electronic chart

International Nuclear Information System (INIS)

Fraass, Benedick A.; McShan, Daniel L.; Matrone, Gwynne M.; Weaver, Tamar A.; Lewis, James D.; Kessler, Marc L.

1995-01-01

Purpose: The design and implementation of a system for electronically tracking relevant plan, prescription, and treatment data for computer-controlled conformal radiation therapy is described. Methods and Materials: The electronic charting system is implemented on a computer cluster coupled by high-speed networks to computer-controlled therapy machines. A methodical approach to the specification and design of an integrated solution has been used in developing the system. The electronic chart system is designed to allow identification and access of patient-specific data including treatment-planning data, treatment prescription information, and charting of doses. An in-house developed database system is used to provide an integrated approach to the database requirements of the design. A hierarchy of databases is used for both centralization and distribution of the treatment data for specific treatment machines. Results: The basic electronic database system has been implemented and has been in use since July 1993. The system has been used to download and manage treatment data on all patients treated on our first fully computer-controlled treatment machine. To date, electronic dose charting functions have not been fully implemented clinically, requiring the continued use of paper charting for dose tracking. Conclusions: The routine clinical application of complex computer-controlled conformal treatment procedures requires the management of large quantities of information for describing and tracking treatments. An integrated and comprehensive approach to this problem has led to a full electronic chart for conformal radiation therapy treatments

Treatment Planning Study to Determine Potential Benefit of Intensity-Modulated Radiotherapy Versus Conformal Radiotherapy for Unresectable Hepatic Malignancies

International Nuclear Information System (INIS)

Eccles, Cynthia L.; Bissonnette, Jean-Pierre; Craig, Tim; Taremi, Mojgan; Wu Xia; Dawson, Laura A.

2008-01-01

Purpose: To compare intensity-modulated radiotherapy (IMRT) with conformal RT (CRT) for hypofractionated isotoxicity liver RT and explore dose escalation using IMRT for the same/improved nominal risk of liver toxicity in a treatment planning study. Methods and Materials: A total of 26 CRT plans were evaluated. Prescription doses (24-54 Gy within six fractions) were individualized on the basis of the effective liver volume irradiated maintaining ≤5% risk of radiation-induced liver disease. The dose constraints included bowel (0.5 cm 3 ) and stomach (0.5 cm 3 ) to ≤30 Gy, spinal cord to ≤25 Gy, and planning target volume (PTV) to ≤140% of the prescribed dose. Two groups were evaluated: (1) PTV overlapping or directly adjacent to serial functioning normal tissues (n = 14), and (2) the liver as the dose-limiting normal tissue (n = 12). IMRT plans using direct machine parameter optimization maintained the CRT plan beam arrangements, an estimated radiation-induced liver disease risk of 5%, and underwent dose escalation, if all normal tissue constraints were maintained. Results: IMRT improved PTV coverage in 19 of 26 plans (73%). Dose escalation was feasible in 9 cases by an average of 3.8 Gy (range, 0.6-13.2) in six fractions. Three of seven plans without improved PTV coverage had small gross tumor volumes (≤105 cm 3 ) already receiving 54 Gy, the maximal prescription dose allowed. In the remaining cases, the PTV range was 9.6-689 cm 3 ; two had overlapped organs at risk; and one had four targets. IMRT did not improve these plans owing to poor target coverage (n = 2) and nonliver (n = 2) dose limits. Conclusion: Direct machine parameter optimization IMRT improved PTV coverage while maintaining normal tissue tolerances in most CRT liver plans. Dose escalation was possible in a minority of patients

Two-dimensional NMR investigations of the dynamic conformations of phospholipids and liquid crystals

Energy Technology Data Exchange (ETDEWEB)

Hong, Mei [Univ. of California, Berkeley, CA (United States). Applied Science and Technology

1996-05-01

Two-dimensional 13C, 1H, and 31P nuclear magnetic resonance (NMR) techniques are developed and used to study molecular structure and dynamics in liquid-crystalline systems, primarily phospholipids and nematic liquid crystals. NMR spectroscopy characterizes molecular conformation in terms of orientations and distances of molecular segments. In anisotropically mobile systems, this is achieved by measuring motionally-averaged nuclear dipolar couplings and chemical shift anisotropies. The short-range couplings yield useful bond order parameters, while the long-range interactions constrain the overall conformation. In this work, techniques for probing proton dipolar local fields are further developed to obtain highlyresolved dipolar couplings between protons and rare spins. By exploiting variable-angle sample spinning techniques, orientation-sensitive NMR spectra are resolved according to sitespecific isotropic chemical shifts. Moreover, the signs and magnitudes of various short-range dipolar couplings are obtained. They are used in novel theoretical analyses that provide information about segmental orientations and their distributions. Such information is obtained in a model-independent fashion or with physically reasonable assumptions. The structural investigation of phospholipids is focused on the dynam

Concerted motions in HIV-1 TAR RNA may allow access to bound state conformations: RNA dynamics from NMR residual dipolar couplings.

Science.gov (United States)

Al-Hashimi, Hashim M; Gosser, Yuying; Gorin, Andrey; Hu, Weidong; Majumdar, Ananya; Patel, Dinshaw J

2002-01-11

Ground-state dynamics in RNA is a critical precursor for structural adaptation observed ubiquitously in protein-RNA recognition. A tertiary conformational analysis of the stem-loop structural element in the transactivation response element (TAR) from human immunodeficiency virus type 1 (HIV-I) RNA is presented using recently introduced NMR methods that rely on the measurement of residual dipolar couplings (RDC) in partially oriented systems. Order matrix analysis of RDC data provides evidence for inter-helical motions that are of amplitude 46(+/-4) degrees, of random directional character, and that are executed about an average conformation with an inter-helical angle between 44 degrees and 54 degrees. The generated ensemble of TAR conformations have different organizations of functional groups responsible for interaction with the trans-activator protein Tat, including conformations similar to the previously characterized bound-state conformation. These results demonstrate the utility of RDC-NMR for simultaneously characterizing RNA tertiary dynamics and average conformation, and indicate an avenue for TAR complex formation involving tertiary structure capture. Copyright 2001 Academic Press.

Quantifying polypeptide conformational space: sensitivity to conformation and ensemble definition.

Science.gov (United States)

Sullivan, David C; Lim, Carmay

2006-08-24

Quantifying the density of conformations over phase space (the conformational distribution) is needed to model important macromolecular processes such as protein folding. In this work, we quantify the conformational distribution for a simple polypeptide (N-mer polyalanine) using the cumulative distribution function (CDF), which gives the probability that two randomly selected conformations are separated by less than a "conformational" distance and whose inverse gives conformation counts as a function of conformational radius. An important finding is that the conformation counts obtained by the CDF inverse depend critically on the assignment of a conformation's distance span and the ensemble (e.g., unfolded state model): varying ensemble and conformation definition (1 --> 2 A) varies the CDF-based conformation counts for Ala(50) from 10(11) to 10(69). In particular, relatively short molecular dynamics (MD) relaxation of Ala(50)'s random-walk ensemble reduces the number of conformers from 10(55) to 10(14) (using a 1 A root-mean-square-deviation radius conformation definition) pointing to potential disconnections in comparing the results from simplified models of unfolded proteins with those from all-atom MD simulations. Explicit waters are found to roughen the landscape considerably. Under some common conformation definitions, the results herein provide (i) an upper limit to the number of accessible conformations that compose unfolded states of proteins, (ii) the optimal clustering radius/conformation radius for counting conformations for a given energy and solvent model, (iii) a means of comparing various studies, and (iv) an assessment of the applicability of random search in protein folding.

Evaluation of the dose distribution of dynamic conical conformal therapy using a C-arm mounted accelerator

International Nuclear Information System (INIS)

Nakagawa, Keiichi; Aoki, Yukimasa; Ohtomo, Kuni

2001-01-01

Conformal radiation therapy, which is widely utilized in Japan as a standard, highly precise technique has limited advantage in dose confinement because of its coplanar beam entry. An improved form of conformal therapy is delivered by a linac mounted on a C-arm rotatable gantry. The linac head was designed to move along the C-arm with a maximum angle of 60 degrees. Simultaneous rotation of the gantry creates a Dynamic Conical irradiation technique. Dynamic Conical Conformal Therapy (Dyconic Therapy) was developed by combining the technique with continuous MLC motion based on beam's eye views of the target volume. Dose distributions were measured in a phantom using film densitometry and compared with conventional conformal radiation therapy. The measurements showed that the dose distribution conformed to the target shape identified by CT. In addition, the dose distribution for a cancer patient was evaluated through the use of DVHs generated by a treatment planning system. These measurements showed that the dose distribution along the patient's long axis conformed to the shape of the target volume. DVH analysis, however, did not indicate superiority of the present technique over the conventional technique. Angulation of the C-arm gantry allowed the primary beam to strike a larger area of the therapy room. This necessitated adding shielding to the walls and ceiling of the treatment room. It was confirmed that the leakage radiation was reduced to a negligible level by adding an iron plate 20 cm thick to several places on the side walls, by adding an iron plate 9 cm thick to several places on the ceiling, and by increasing the thickness of the concrete ceiling from 70 to 140 cm. The possible usefulness of Dyconic Therapy was confirmed. (author)

A comparative dosimetric study of conventional, conformal and intensity-modulated radiotherapy in postoperative pelvic irradiation of cervical cancer

International Nuclear Information System (INIS)

Li Bin; An Jusheng; Wu Lingying; Huang Manni; Gao Juzhen; Xu Yingjie; Dai Jianrong

2008-01-01

Objective: To evaluate target-volume coverage and organ at risk (OAR) protection achieved with conventional radiotherapy (CRT), three dimensional conformal radiotherapy (3DCRT), and intensity-modulated radiotherapy(IMRT) through dosimetric comparison in patients with cervical cancer after hysterectomy. Methods: The planning CT scans of 10 patients treated with pelvic radiation after hysterectomy for cervical cancer were used to generate CRT, 3DCRT and IMRT plans for this study. Clinical target volume(CTV) was contoured on the individual axial CT slices of every patient. The CTV was then uniformly expanded by 1.0 cm to create the planning target volume (PTV). The small bowel, rectum, bladder, bone marrow, ovaries, and femoral heads were outlined for the organ at risk (OAR) evaluation. The CRT, 3DCRT and IMRT plans were generated using commercial planning software. CRT plan was prescribed to deliver 45 Gy to the reference point, while IMRT and 3DCRT plans were 45 Gy to 95% of the PTV. Isodose line and dose volume histograms(DVH) were used to evaluate the dose distribution in CTV and OAR. Results: For 10 patients, the average volume of CTV receiving the prescribed dose of CRT was significantly lower than 3DCRT(Q=8.27, P<0.01) and IMRT(Q=8.37, P<0.01), respectively. Comparing with the CRT plan, the 3DCRT and IMRT plans notably reduced the volume of bowel at 30 and 45 Gy levels. The IMRT plan significantly spared rectum and bladder at 30 and 45 Gy levels comparing with the CRT (P<0.01) and 3DCRT(P<0.05) plans, while the 3DCRT plan significantly spared rectum and bladder at 45 Gy level comparing with the CRT(P<0.01) plans. For 4 patients with ovarian transposition, the average doses of ovary over 3 Gy were 2 patients with the 3 DCRT and IMRT plans, and 2 with all three plans. Conclusions: IMRT and 3DCRT are superior to CRT in improving dose coverage of target volume and sparing of OAR, while IMRT being the best. The superiority of IMRT and 3DCRT is obvious in sparing

Acute and Late Toxicity in a Randomized Trial of Conventional Versus Hypofractionated Three-Dimensional Conformal Radiotherapy for Prostate Cancer

International Nuclear Information System (INIS)

Arcangeli, Giorgio; Fowler, Jack; Gomellini, Sara; Arcangeli, Stefano; Saracino, Biancamaria; Petrongari, Maria Grazia; Benassi, Marcello; Strigari, Lidia

2011-01-01

Purpose: To compare the toxicity between hypofractionation vs. conventional fractionation schedules in patients with high-risk prostate cancer. Methods and Materials: Between January 2003 and December 2007, 168 patients were randomized to receive either hypofractionated (62 Gy in 20 fractions within 5 weeks, 4 fractions/wk) or conventionally fractionated (80 Gy in 40 fractions within 8 weeks) three-dimensional conformal radiotherapy to the prostate and seminal vesicles. All patients had undergone a 9-month course of total androgen deprivation, with radiotherapy starting 2 months after initiation of the total androgen deprivation. Results: The median follow-up was 32 and 35 months in the hypofractionation and conventional fractionation arms, respectively. For the patients developing acute toxicity, no difference between the two fractionation groups was found in either severity or duration of gastrointestinal or genitourinary toxicity. Also, no difference was found in the incidence and severity of late gastrointestinal and genitourinary toxicity between the two treatment schedules, with a 3-year rate of Grade 2 or greater toxicity of 17% and 16% for the hypofractionation arm and 14% and 11% for the conventional fractionation arm, respectively. A statistically significant correlation between acute and late gastrointestinal toxicity was found only in the conventional fractionation group. Conclusion: Our findings suggest that the hypofractionation regimen used in our study is safe, with only a slight, nonsignificant increase in tolerable and temporary acute toxicity compared with the conventional fractionation schedule. The severity and frequency of late complications was equivalent between the two treatment groups.

De novo protein structure prediction by dynamic fragment assembly and conformational space annealing.

Science.gov (United States)

Lee, Juyong; Lee, Jinhyuk; Sasaki, Takeshi N; Sasai, Masaki; Seok, Chaok; Lee, Jooyoung

2011-08-01

Ab initio protein structure prediction is a challenging problem that requires both an accurate energetic representation of a protein structure and an efficient conformational sampling method for successful protein modeling. In this article, we present an ab initio structure prediction method which combines a recently suggested novel way of fragment assembly, dynamic fragment assembly (DFA) and conformational space annealing (CSA) algorithm. In DFA, model structures are scored by continuous functions constructed based on short- and long-range structural restraint information from a fragment library. Here, DFA is represented by the full-atom model by CHARMM with the addition of the empirical potential of DFIRE. The relative contributions between various energy terms are optimized using linear programming. The conformational sampling was carried out with CSA algorithm, which can find low energy conformations more efficiently than simulated annealing used in the existing DFA study. The newly introduced DFA energy function and CSA sampling algorithm are implemented into CHARMM. Test results on 30 small single-domain proteins and 13 template-free modeling targets of the 8th Critical Assessment of protein Structure Prediction show that the current method provides comparable and complementary prediction results to existing top methods. Copyright © 2011 Wiley-Liss, Inc.

Comparison of simple and complex liver intensity modulated radiotherapy

International Nuclear Information System (INIS)

Lee, Mark T; Purdie, Thomas G; Eccles, Cynthia L; Sharpe, Michael B; Dawson, Laura A

2010-01-01

Intensity-modulated radiotherapy (IMRT) may allow improvement in plan quality for treatment of liver cancer, however increasing radiation modulation complexity can lead to increased uncertainties and requirements for quality assurance. This study assesses whether target coverage and normal tissue avoidance can be maintained in liver cancer intensity-modulated radiotherapy (IMRT) plans by systematically reducing the complexity of the delivered fluence. An optimal baseline six fraction individualized IMRT plan for 27 patients with 45 liver cancers was developed which provided a median minimum dose to 0.5 cc of the planning target volume (PTV) of 38.3 Gy (range, 25.9-59.5 Gy), in 6 fractions, while maintaining liver toxicity risk <5% and maximum luminal gastrointestinal structure doses of 30 Gy. The number of segments was systematically reduced until normal tissue constraints were exceeded while maintaining equivalent dose coverage to 95% of PTV (PTVD95). Radiotherapy doses were compared between the plans. Reduction in the number of segments was achieved for all 27 plans from a median of 48 segments (range 34-52) to 19 segments (range 6-30), without exceeding normal tissue dose objectives and maintaining equivalent PTVD95 and similar PTV Equivalent Uniform Dose (EUD(-20)) IMRT plans with fewer segments had significantly less monitor units (mean, 1892 reduced to 1695, p = 0.012), but also reduced dose conformity (mean, RTOG Conformity Index 1.42 increased to 1.53 p = 0.001). Tumour coverage and normal tissue objectives were maintained with simplified liver IMRT, at the expense of reduced conformity

IMRT and 3D conformal radiotherapy with or without elective nodal irradiation in locally advanced NSCLC. A direct comparison of PET-based treatment planning

International Nuclear Information System (INIS)

Fleckenstein, Jochen; Kremp, Katharina; Kremp, Stephanie; Palm, Jan; Ruebe, Christian

2016-01-01

The potential of intensity-modulated radiation therapy (IMRT) as opposed to three-dimensional conformal radiotherapy (3D-CRT) is analyzed for two different concepts of fluorodeoxyglucose positron emission tomography (FDG PET)-based target volume delineation in locally advanced non-small cell lung cancer (LA-NSCLC): involved-field radiotherapy (IF-RT) vs. elective nodal irradiation (ENI). Treatment planning was performed for 41 patients with LA-NSCLC, using four different planning approaches (3D-CRT-IF, 3D-CRT-ENI, IMRT-IF, IMRT-ENI). ENI included a boost irradiation after 50 Gy. For each plan, maximum dose escalation was calculated based on prespecified normal tissue constraints. The maximum prescription dose (PD), tumor control probability (TCP), conformal indices (CI), and normal tissue complication probabilities (NTCP) were analyzed. IMRT resulted in statistically significant higher prescription doses for both target volume concepts as compared with 3D-CRT (ENI: 68.4 vs. 60.9 Gy, p < 0.001; IF: 74.3 vs. 70.1 Gy, p < 0.03). With IMRT-IF, a PD of at least 66 Gy was achieved for 95 % of all plans. For IF as compared with ENI, there was a considerable theoretical increase in TCP (IMRT: 27.3 vs. 17.7 %, p < 0.00001; 3D-CRT: 20.2 vs. 9.9 %, p < 0.00001). The esophageal NTCP showed a particularly good sparing with IMRT vs. 3D-CRT (ENI: 12.3 vs. 30.9 % p < 0.0001; IF: 15.9 vs. 24.1 %; p < 0.001). The IMRT technique and IF target volume delineation allow a significant dose escalation and an increase in TCP. IMRT results in an improved sparing of OARs as compared with 3D-CRT at equivalent dose levels. (orig.) [de

Conformal Gravity

International Nuclear Information System (INIS)

Hooft, G.

2012-01-01

The dynamical degree of freedom for the gravitational force is the metric tensor, having 10 locally independent degrees of freedom (of which 4 can be used to fix the coordinate choice). In conformal gravity, we split this field into an overall scalar factor and a nine-component remainder. All unrenormalizable infinities are in this remainder, while the scalar component can be handled like any other scalar field such as the Higgs field. In this formalism, conformal symmetry is spontaneously broken. An imperative demand on any healthy quantum gravity theory is that black holes should be described as quantum systems with micro-states as dictated by the Hawking-Bekenstein theory. This requires conformal symmetry that may be broken spontaneously but not explicitly, and this means that all conformal anomalies must cancel out. Cancellation of conformal anomalies yields constraints on the matter sector as described by some universal field theory. Thus black hole physics may eventually be of help in the construction of unified field theories. (author)

Development of radiation oncology learning system combined with multi-institutional radiotherapy database (ROGAD)

Energy Technology Data Exchange (ETDEWEB)

Takemura, Akihiro; Iinuma, Masahiro; Kou, Hiroko [Kanazawa Univ. (Japan). School of Medicine; Harauchi, Hajime; Inamura, Kiyonari

1999-09-01

We have constructed and are operating a multi-institutional radiotherapy database ROGAD (Radiation Oncology Greater Area Database) since 1992. One of it's purpose is 'to optimize individual radiotherapy plans'. We developed Radiation oncology learning system combined with ROGAD' which conforms to that purpose. Several medical doctors evaluated our system. According to those evaluations, we are now confident that our system is able to contribute to improvement of radiotherapy results. Our final target is to generate a good cyclic relationship among three components: radiotherapy results according to ''Radiation oncology learning system combined with ROGAD.'; The growth of ROGAD; and radiation oncology learning system. (author)

High-dose (70-78 GY) conformal radiotherapy for prostate cancer; the relation between observed late bladder and rectum complications and parameters derived from the dose volume histograms

International Nuclear Information System (INIS)

Lebesque, J.V.; Bruce, A.; Boersma, L.J.; Velde, A. te

1996-01-01

Purpose: To determine the incidence of late gastrointestinal (GI) and genitourinary (GU) complications after conformal radiotherapy for prostate cancer, and to investigate the relation between these observed incidences and parameters derived from the Dose Volume Histograms (DVHs) of rectum and bladder wall. Patients and Methods: Hundred and thirty patients with T 2-4 G 1-3 N 0 M 0 prostate cancer were treated with conformal radiotherapy with the simultaneous boost technique in a dose-escalating protocol; 78 patients received a total dose of 70 Gy, 11 patients 74 - 76 Gy and 41 patients 78 Gy, each with a dose of 2 Gy per fraction. DVHs of the rectal wall were used to calculate NTCPs according to the model of Kutcher et al. with the estimated parameter values (n = 0.12, m = 0.15, TD 50 = 80 Gy) according to Burman et al. The median follow-up was 17 months (range 6 - 72 months). The crude and actuarial incidence of late (> 6 months) GI and GU complications were determined using the RTOG/EORTC morbidity scoring system (Grade I to IV). Results: Neither for late GI nor for GU complaints, a grade IV complication was observed. GU complaints occurred in 90 patients (69%): 54 patients (42%) only experienced grade I toxicity, 26 patients (20%) had grade II toxicity, and 10 patients (8%) had grade III complications, of which 8 patients (6%) developed a urethral (7 pts) or ureteric stenosis (1 pt). The actuarial incidence of grade III GU complications was 10% at 2 years. Since bladder wall DVHs are unreliable and most grade III complications were not related to the bladder, the grade II and/or III complications were analyzed in terms of the total prescribed dose only, but no correlation could be demonstrated. GI complications occurred in 71 patients (55%): 59 patients (45%) developed a grade I complication, 11 a grade II complication and only 1 patient required laser treatment twice and blood transfusion because of rectal bleeding (grade III). The actuarial incidence of GI

Guidelines for target volume definition in post-operative radiotherapy for prostate cancer, on behalf of the EORTC Radiation Oncology Group

International Nuclear Information System (INIS)

Poortmans, Philip; Bossi, Alberto; Vandeputte, Katia; Bosset, Mathieu; Miralbell, Raymond; Maingon, Philippe; Boehmer, Dirk; Budiharto, Tom; Symon, Zvi; Bergh, Alfons C.M. van den; Scrase, Christopher; Poppel, Hendrik van; Bolla, Michel

2007-01-01

The appropriate application of 3-D conformal radiotherapy, intensity modulated radiotherapy or image guided radiotherapy for patients undergoing post-operative radiotherapy for prostate cancer requires a standardisation of the target volume definition and delineation as well as standardisation of the clinical quality assurance procedures. Recommendations for this are presented on behalf of the European Organisation for Research and Treatment of Cancer (EORTC) Radiation Oncology Group and in addition to the already published guidelines for radiotherapy as the primary treatment

Measuring side effects after radiotherapy for pharynx cancer

DEFF Research Database (Denmark)

Jensen, Kenneth

2007-01-01

Data on side effects after radiotherapy is needed to establish the benefits and drawbacks of new treatments, but side effects are not quantified as easily as survival or local control. Side effects may be quantified using physical measures. Unfortunately, only few endpoints exist where a physical...... measure is obtainable, and the case of a patient-relevant measure is even rarer. Radiotherapy is often followed by complex symptoms not easily quantifiable by the observer. Quantitative patient reported side effects can be retrieved using validated questionnaires, but this kind of data is often difficult...... to interpret and the correlation with clinically observable or measurable changes not straightforward. The exploitation of the possibilities of highly conformal radiotherapy and multimodality treatment depends on a better understanding of the correlation between dose, volume, modifying factors, and side...

Evaluation of Sentinel Lymph Node Dose Distribution in 3D Conformal Radiotherapy Techniques in 67 pN0 Breast Cancer Patients.

Science.gov (United States)

Witucki, Gerlo; Degregorio, Nikolaus; Rempen, Andreas; Schwentner, Lukas; Bottke, Dirk; Janni, Wolfgang; Ebner, Florian

2015-01-01

Introduction. The anatomic position of the sentinel lymph node is variable. The purpose of the following study was to assess the dose distribution delivered to the surgically marked sentinel lymph node site by 3D conformal radio therapy technique. Material and Method. We retrospectively analysed 70 radiotherapy (RT) treatment plans of consecutive primary breast cancer patients with a successful, disease-free, sentinel lymph node resection. Results. In our case series the SN clip volume received a mean dose of 40.7 Gy (min 28.8 Gy/max 47.6 Gy). Conclusion. By using surgical clip markers in combination with 3D CT images our data supports the pathway of tumouricidal doses in the SN bed. The target volume should be defined by surgical clip markers and 3D CT images to give accurate dose estimations.

Molecular dynamics coupled with a virtual system for effective conformational sampling.

Science.gov (United States)

Hayami, Tomonori; Kasahara, Kota; Nakamura, Haruki; Higo, Junichi

2018-07-15

An enhanced conformational sampling method is proposed: virtual-system coupled canonical molecular dynamics (VcMD). Although VcMD enhances sampling along a reaction coordinate, this method is free from estimation of a canonical distribution function along the reaction coordinate. This method introduces a virtual system that does not necessarily obey a physical law. To enhance sampling the virtual system couples with a molecular system to be studied. Resultant snapshots produce a canonical ensemble. This method was applied to a system consisting of two short peptides in an explicit solvent. Conventional molecular dynamics simulation, which is ten times longer than VcMD, was performed along with adaptive umbrella sampling. Free-energy landscapes computed from the three simulations mutually converged well. The VcMD provided quicker association/dissociation motions of peptides than the conventional molecular dynamics did. The VcMD method is applicable to various complicated systems because of its methodological simplicity. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

SU-F-T-604: Dosimetric Evaluation of Intracranial Stereotactic Radiotherapy Plans On a LINAC

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Sheth, N; Tabibian, A; Rose, J; Alvelo, M; Perel, C; Laiken, K; Kim, A [Bayonne Medical Center, Bayonne, NJ (United States)

2016-06-15

Purpose: To evaluate the dosimetry of cranial stereotactic radiotherapy (SRT) plans of varying techniques on linac that meets appropriate TG-142 tolerances using 1 cm leaf width multileaf collimator (MLC). Methods: Seventeen spherical targets were generated in the center of a head phantom with diameters ranging 8 mm to 40 mm. SRT plans used 100° non-coplanar arcs and 5 couch angles with 35° spacing. The field size was target plus 1 mm margin. Four plans were created for each target: symmetrical jaws blocking for 5 arcs with 0° collimator (J1C), symmetrical jaws blocking with 5 clockwise arcs with 0° collimator and 5 counter-clockwise arcs with 45° collimator (J2C), MLC blocking for 5 dynamic conformal arcs with 0° collimator (M1C), and MLC blocking for 5 clockwise dynamic conformal arcs with 0° collimators and 5 counter-clockwise dynamic conformal arcs with 45° collimator (M2C).Conformity was evaluated using a ratio of Rx to target volume (PITV). Heterogeneity was determined using a ratio of maximum dose to Rx dose. Falloff was scored using CGIg: difference of effective radii of spheres equal to half and full Rx volumes. Results: All plans met RTOG SRS criteria for conformity and heterogeneity. The mean PITV was 1.52±0.07, 1.49±0.08, 1.39±0.05, and 1.37±0.04 for J1C, J2C, M1C, and M2C plans respectively. The mean CGIg was 75.35±15.79, 74.19±16.66, 77.14±15.12, and 76.28±15.78 for J1C, J2C, M1C, and M2C plans respectively. The mean MDPD was 1.25±0.00 for all techniques. Conclusion: Clinically acceptable SRT plans for spherical targets were created on a linac with 1 cm MLC. Adding two collimator angles and MLC to arcs each improved conformity. The MLC improved the dose falloff while two collimator angles degraded it. This technique can expand the availability of SRT to patients especially to those who cannot travel to a facility with a dedicated stereotactic radiosurgery machine.

SU-F-T-604: Dosimetric Evaluation of Intracranial Stereotactic Radiotherapy Plans On a LINAC

International Nuclear Information System (INIS)

Sheth, N; Tabibian, A; Rose, J; Alvelo, M; Perel, C; Laiken, K; Kim, A

2016-01-01

Purpose: To evaluate the dosimetry of cranial stereotactic radiotherapy (SRT) plans of varying techniques on linac that meets appropriate TG-142 tolerances using 1 cm leaf width multileaf collimator (MLC). Methods: Seventeen spherical targets were generated in the center of a head phantom with diameters ranging 8 mm to 40 mm. SRT plans used 100° non-coplanar arcs and 5 couch angles with 35° spacing. The field size was target plus 1 mm margin. Four plans were created for each target: symmetrical jaws blocking for 5 arcs with 0° collimator (J1C), symmetrical jaws blocking with 5 clockwise arcs with 0° collimator and 5 counter-clockwise arcs with 45° collimator (J2C), MLC blocking for 5 dynamic conformal arcs with 0° collimator (M1C), and MLC blocking for 5 clockwise dynamic conformal arcs with 0° collimators and 5 counter-clockwise dynamic conformal arcs with 45° collimator (M2C).Conformity was evaluated using a ratio of Rx to target volume (PITV). Heterogeneity was determined using a ratio of maximum dose to Rx dose. Falloff was scored using CGIg: difference of effective radii of spheres equal to half and full Rx volumes. Results: All plans met RTOG SRS criteria for conformity and heterogeneity. The mean PITV was 1.52±0.07, 1.49±0.08, 1.39±0.05, and 1.37±0.04 for J1C, J2C, M1C, and M2C plans respectively. The mean CGIg was 75.35±15.79, 74.19±16.66, 77.14±15.12, and 76.28±15.78 for J1C, J2C, M1C, and M2C plans respectively. The mean MDPD was 1.25±0.00 for all techniques. Conclusion: Clinically acceptable SRT plans for spherical targets were created on a linac with 1 cm MLC. Adding two collimator angles and MLC to arcs each improved conformity. The MLC improved the dose falloff while two collimator angles degraded it. This technique can expand the availability of SRT to patients especially to those who cannot travel to a facility with a dedicated stereotactic radiosurgery machine.

Normalization of serum testosterone levels in patients treated with neoadjuvant hormonal therapy and three-dimensional conformal radiotherapy for prostate cancer

International Nuclear Information System (INIS)

Padula, Gilbert D.A.; Zelefsky, Michael J.; Venkatraman, Ennapadam S.; Fuks, Zvi; Lee, Henry J.; Natale, Linda; Leibel, Steven A.

2002-01-01

Purpose: To determine the expected time to serum testosterone normalization after short-course neoadjuvant androgen deprivation therapy (NAAD) and three-dimensional conformal radiotherapy for patients with localized prostate cancer and to identify pretreatment predictors that correlated with the time to testosterone normalization. Methods: Between 1993 and 1999, 88 patients with localized prostate cancer, treated with NAAD and external beam radiotherapy, were prospectively monitored after treatment with sequential testosterone levels. NAAD was administered before and during the entire course of radiotherapy and discontinued at the end of treatment. The median duration of NAAD was 6 months. The actuarial rate of serum testosterone normalization from the end of treatment was evaluated, and the presence or absence of androgen deprivation-related symptoms was correlated with serum testosterone levels. Symptoms assessed included weight gain, loss of libido, breast tenderness, breast enlargement, hot flashes, and fatigue. Results: Serum testosterone levels returned to the normal range in 57 (65%) of the 88 patients and failed to normalize in 31 patients (35%). The median time to normalization was 18.3 months. The actuarial rate of normalization at 3, 6, 12, and 24 months was 10%, 26%, 38%, and 59%, respectively. In a multivariate analysis, a pretreatment testosterone level in the lower range of normal was the only variable that predicted for delayed testosterone normalization after NAAD (p=0.00047). Among 45 patients with information concerning androgen deprivation-related symptoms recorded 1 year after cessation of NAAD, 24 (53%) had normalized testosterone levels, but in 21 patients (47%), the levels had not yet returned to normal. At 1 year, only 1 (4%) of 24 patients whose testosterone level had returned to normal experienced NAAD-related symptoms compared with 14 (67%) of 21 patients who did not have normal testosterone levels (p<0.001). Conclusion: Testosterone

Hadron spectroscopy and dynamics from light-front holography and conformal symmetry

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de Téramond Guy F.

2014-06-01

Full Text Available To a first semiclassical approximation one can reduce the multi-parton light-front problem in QCD to an effective one-dimensional quantum field theory, which encodes the fundamental conformal symmetry of the classical QCD Lagrangian. This procedure leads to a relativistic light-front wave equation for arbitrary spin which incorporates essential spectroscopic and non-perturbative dynamical features of hadron physics. The mass scale for confinement and higher dimensional holographic mapping to AdS space are also emergent properties of this framework.

Incidental irradiation of internal mammary lymph nodes in breast cancer: conventional two-dimensional radiotherapy versus conformal three-dimensional radiotherapy

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Leite, Elton Trigo Teixeira; Ugino, Rafael Tsuneki; Lopes, Mauricio Russo; Pelosi, Edilson Lopes; Silva, Joao Luis Fernandes da, E-mail: eltontt@gmail.com [Hospital Sirio-Libanes, Sao paulo, SP (Brazil). Departamento de Radiologia e Oncologia; Santana, Marco Antonio; Ferreira, Denis Vasconcelos; Carvalho, Heloisa de Andrade [Universidade de Sao Paulo (FM/USP), Sao Paulo, SP (Brazil). Faculdade de Medicina. Departamento de Radiologia e Oncologia

2016-05-15

Objective: to evaluate incidental irradiation of the internal mammary lymph nodes (IMLNs) through opposed tangential fields with conventional two-dimensional (2D) or three-dimensional (3D) radiotherapy techniques and to compare the results between the two techniques. Materials and Methods: This was a retrospective study of 80 breast cancer patients in whom radiotherapy of the IMLNs was not indicated: 40 underwent 2D radiotherapy with computed tomography for dosimetric control, and 40 underwent 3D radiotherapy. The total prescribed dose was 50.0 Gy or 50.4 Gy (2.0 or 1.8 Gy/day, respectively). We reviewed all plans and defined the IMLNs following the Radiation Therapy Oncology Group recommendations. For the IMLNs, we analyzed the proportion of the volume that received 45 Gy, the proportion of the volume that received 25 Gy, the dose to 95% of the volume, the dose to 50% of the volume, the mean dose, the minimum dose (Dmin), and the maximum dose (Dmax). Results: Left-sided treatments predominated in the 3D cohort. There were no differences between the 2D and 3D cohorts regarding tumor stage, type of surgery (mastectomy, breast-conserving surgery, or mastectomy with immediate reconstruction), or mean delineated IMLN volume (6.8 vs. 5.9 mL; p = 0.411). Except for the Dmin, all dosimetric parameters presented higher mean values in the 3D cohort (p < 0.05). The median Dmax in the 3D cohort was 50.34 Gy. However, the mean dose to the IMLNs was 7.93 Gy in the 2D cohort, compared with 20.64 Gy in the 3D cohort. Conclusion: Neither technique delivered enough doses to the IMLNs to achieve subclinical disease control. However, all of the dosimetric parameters were significantly higher for the 3D technique. (author)

Volumetric modulated arc therapy for delivery of hypofractionated stereotactic lung radiotherapy: A dosimetric and treatment efficiency analysis

International Nuclear Information System (INIS)

McGrath, Samuel D.; Matuszak, Martha M.; Yan Di; Kestin, Larry L.; Martinez, Alvaro A.; Grills, Inga S.

2010-01-01

Purpose/objective(s): Volumetric modulated arc therapy (VMAT) allows for intensity-modulated radiation delivery during gantry rotation with dynamic MLC motion, variable dose rates and gantry speed modulation. We compared VMAT plans with 3D-CRT for hypofractionated lung radiotherapy. Materials/methods: Twenty-one 3D-CRT plans for Stage IA lung cancer previously treated stereotactically were selected. VMAT plans were generated by optimizing machine aperture shape and radiation intensity at 10 deg. intervals. A partial arc range of 180 deg. was manually selected to coincide with tumor location. The arc was resampled down to 5 deg. intervals to ensure dose calculation accuracy. Identical planning objectives were used for VMAT/3D-CRT. Parameters assessed included dose to PTV and organs-at-risk (OAR), monitor units, and multiple conformity and homogeneity indices. Plans were delivered to a phantom for time comparison. Results: Lung V 20/12.5/10/5 were less with VMAT (relative reduction 4.5%, p = .02; 3.2%, p = .01; 2.6%, p = .01; 4.2%, p = .03, respectively). Mean/maximum-doses to PTV, dose to additional OARs, 95% isodose line conformity, and target volume homogeneity were equivalent. VMAT improved conformity at both the 80% (1.87 vs. 1.93, p = .08) and 50% isodose lines (5.19 vs. 5.65, p = .01). Treatment times were reduced significantly with VMAT (mean 6.1 vs. 11.9 min, p < .01). Conclusions: Single arc VMAT planning achieves highly conformal dose distributions while controlling dose to critical structures, including significant reduction in lung dose volume parameters. Employing a VMAT technique decreases treatment times by 37-63%, reducing the chance of error introduced by intrafraction variation. The quality and efficiency of VMAT is ideally suited for stereotactic lung radiotherapy delivery.

Optimisation of radiotherapy for carcinoma of the parotid gland: a comparison of conventional, three-dimensional conformal, and intensity-modulated techniques

International Nuclear Information System (INIS)

Nutting, Christopher M.; Rowbottom, Carl G.; Cosgrove, Vivian P.; Henk, J. Michael; Dearnaley, David P.; Robinson, Martin H.; Conway, John; Webb, Steve

2001-01-01

Background and purpose: To compare external beam radiotherapy techniques for parotid gland tumours using conventional radiotherapy (RT), three-dimensional conformal radiotherapy (3DCRT), and intensity-modulated radiotherapy (IMRT). To optimise the IMRT techniques, and to produce an IMRT class solution. Materials and methods: The planning target volume (PTV), contra-lateral parotid gland, oral cavity, brain-stem, brain and cochlea were outlined on CT planning scans of six patients with parotid gland tumours. Optimised conventional RT and 3DCRT plans were created and compared with inverse-planned IMRT dose distributions using dose-volume histograms. The aim was to reduce the radiation dose to organs at risk and improve the PTV dose distribution. A beam-direction optimisation algorithm was used to improve the dose distribution of the IMRT plans, and a class solution for parotid gland IMRT was investigated. Results: 3DCRT plans produced an equivalent PTV irradiation and reduced the dose to the cochlea, oral cavity, brain, and other normal tissues compared with conventional RT. IMRT further reduced the radiation dose to the cochlea and oral cavity compared with 3DCRT. For nine- and seven-field IMRT techniques, there was an increase in low-dose radiation to non-target tissue and the contra-lateral parotid gland. IMRT plans produced using three to five optimised intensity-modulated beam directions maintained the advantages of the more complex IMRT plans, and reduced the contra-lateral parotid gland dose to acceptable levels. Three- and four-field non-coplanar beam arrangements increased the volume of brain irradiated, and increased PTV dose inhomogeneity. A four-field class solution consisting of paired ipsilateral coplanar anterior and posterior oblique beams (15, 45, 145 and 170 degree sign from the anterior plane) was developed which maintained the benefits without the complexity of individual patient optimisation. Conclusions: For patients with parotid gland tumours

Estimation of the incidence of late bladder and rectum complications after high-dose (70-78 Gy) conformal radiotherapy for prostate cancer, using dose-volume histograms

International Nuclear Information System (INIS)

Boersma, Liesbeth J.; Brink, Mandy van den; Bruce, Allison M.; Shouman, Tarek; Gras, Luuk; Velde, Annet te; Lebesque, Joos V.

1998-01-01

Purpose: To investigate whether Dose-Volume Histogram (DVH) parameters can be used to identify risk groups for developing late gastrointestinal (GI) and genitourinary (GU) complications after conformal radiotherapy for prostate cancer. Methods and Materials: DVH parameters were analyzed for 130 patients with localized prostate cancer, treated with conformal radiotherapy in a dose-escalating protocol (70-78 Gy, 2 Gy per fraction). The incidence of late (>6 months) GI and GU complications was classified using the RTOG/EORTC and the SOMA/LENT scoring system. In addition, GI complications were divided in nonsevere and severe (requiring one or more laser treatments or blood transfusions) rectal bleeding. The median follow-up time was 24 months. We investigated whether rectal and bladder wall volumes, irradiated to various dose levels, correlated with the observed actuarial incidences of GI and GU complications, using volume as a continuous variable. Subsequently, for each dose level in the DVH, the rectal wall volumes were dichotomized using different volumes as cutoff levels. The impact of the total radiation dose, and the maximum radiation dose in the rectal and bladder wall was analyzed as well. Results: The actuarial incidence at 2 years for GI complications ≥Grade II was 14% (RTOG/EORTC) or 20% (SOMA/LENT); for GU complications ≥Grade III 8% (RTOG/EORTC) or 21% (SOMA/LENT). Neither for GI complications ≥Grade II (RTOG/EORTC or SOMA/LENT), nor for GU complications ≥Grade III (RTOG/EORTC or SOMA/LENT), was a significant correlation found between any of the DVH parameters and the actuarial incidence of complications. For severe rectal bleeding (actuarial incidence at 2 years 3%), four consecutive volume cutoff levels were found, which significantly discriminated between high and low risk. A trend was observed that a total radiation dose ≥ 74 Gy (or a maximum radiation dose in the rectal wall >75 Gy) resulted in a higher incidence of severe rectal bleeding (p

Conformational study of bovine lactoferricin in membrane-micking conditions by molecular dynamics simulation and circular dichroism.

Science.gov (United States)

Daidone, Isabella; Magliano, Alessandro; Di Nola, Alfredo; Mignogna, Giuseppina; Clarkson, Matilda Manuela; Lizzi, Anna Rita; Oratore, Arduino; Mazza, Fernando

2011-04-01

Lactoferricins are potent antimicrobial peptides released by pepsin cleavage of Lactoferrins. Bovine Lactoferricin (LfcinB) has higher activity than the intact bovine Lactoferrin, and is the most active among the other Lactoferricins of human, murine and caprine origin. In the intact protein the fragment corresponding to LfcinB is in an helical conformation, while in water LfcinB adopts an amphipathic β-hairpin structure. However, whether any of these structural motifs is the antibacterial active conformation, i.e., the one interacting with bacterial membrane components, remains to be seen. Here we present Circular Dichroism (CD) spectra and Molecular Dynamics (MD) simulations indicating that in membrane-mimicking solvents the LfcinB adopts an amphipathic β-hairpin structure similar to that observed in water, but differing in the dynamic behavior of the side-chains of the two tryptophan residues. In the membrane-mimicking solvent these side-chains show a high propensity to point towards the hydrophobic environment, rather than being in the hydrophobic core as seen in water, while the backbone preserves the hairpin conformation as found in water. These results suggest that the tryptophans might act as anchors pulling the stable, solvent-invariant hairpin structure into the membrane.

Conformity index for brain cancer patients

International Nuclear Information System (INIS)

Petkovska, Sonja; Tolevska, Cveta; Kraleva, Slavica; Petreska, Elena

2010-01-01

The purpose of this study is to present the level of conformity achieved by using 3D conformal radiotherapy for brain cancer patients. Conformity index is a helpful quantitative tool for assessing (evaluating) the quality of a treatment plan. Treatment plans made for ninety patients with brain tumor are worked on this paper. The patients are in supine position and immobilized with thermoplastic masks for the head. Computed tomography data sets with 5 mm scan thickness are used to create a 3D image. All structures of interest are contoured. In order to obtain an optimal dose distribution, treatment fields are fit around target volume with set-up margins of 7mm in each direction. The conformity index values are between 1.21 and 2.04. Value of 1.8 is exceeded in eighteen cases; nine of them are bigger than 1.9 and only three of them are above 2. The target volume for each of these extreme CI values is ideal covered (between 95% and 105% of the prescribed dose). The most acceptable conformity index value in this paper belongs to the plan with the lowest minimal dose (84.7%). It can be concluded that conformity index is necessary but not sufficient factor for assessing radiation treatment plan conformity. To be able to estimate the acceptability of some treatment plan in daily practice, additional information as minimal, maximal and mean dose into target volume, as well as health tissues coverage must be taken into account.(Author)

Evidence-based review of three-dimensional conformal radiotherapy for localized prostate cancer: An ASTRO outcomes initiative

International Nuclear Information System (INIS)

Morris, David E.; Emami, Bahman; Mauch, Peter M.; Konski, Andre A.; Tao, May L.; Ng, Andrea K.; Klein, Eric A.; Mohideen, Najeeb; Hurwitz, Mark D.; Fraas, Bendick A.; Roach, Mack; Gore, Elizabeth M.; Tepper, Joel E.

2005-01-01

Purpose: To perform a systematic review of the evidence to determine the efficacy and effectiveness of three-dimensional conformal radiotherapy (3D-CRT) for localized prostate cancer; provide a clear presentation of the key clinical outcome questions related to the use of 3D-CRT in the treatment of localized prostate cancer that may be answered by a formal literature review; and provide concise information on whether 3D-CRT improves the clinical outcomes in the treatment of localized prostate cancer compared with conventional RT. Methods and Materials: We performed a systematic review of the literature through a structured process developed by the American Society for Therapeutic Radiology and Oncology's Outcomes Committee that involved the creation of a multidisciplinary task force, development of clinical outcome questions, a formal literature review and data abstraction, data review, and outside peer review. Results: Seven key clinical questions were identified. The results and task force conclusions of the literature review for each question are reported. Conclusion: The technological goals of reducing morbidity with 3D-CRT have been achieved. Randomized trials and follow-up of completed trials remain necessary to address these clinical outcomes specifically with regard to patient subsets and the use of hormonal therapy

Small animal radiotherapy research platforms

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Verhaegen, Frank; Granton, Patrick [Department of Radiation Oncology (MAASTRO), GROW-School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht 6201 BN (Netherlands); Tryggestad, Erik, E-mail: frank.verhaegen@maastro.nl [Department of Radiation Oncology and Molecular Radiation Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD 21231 (United States)

2011-06-21

Advances in conformal radiation therapy and advancements in pre-clinical radiotherapy research have recently stimulated the development of precise micro-irradiators for small animals such as mice and rats. These devices are often kilovolt x-ray radiation sources combined with high-resolution CT imaging equipment for image guidance, as the latter allows precise and accurate beam positioning. This is similar to modern human radiotherapy practice. These devices are considered a major step forward compared to the current standard of animal experimentation in cancer radiobiology research. The availability of this novel equipment enables a wide variety of pre-clinical experiments on the synergy of radiation with other therapies, complex radiation schemes, sub-target boost studies, hypofractionated radiotherapy, contrast-enhanced radiotherapy and studies of relative biological effectiveness, to name just a few examples. In this review we discuss the required irradiation and imaging capabilities of small animal radiation research platforms. We describe the need for improved small animal radiotherapy research and highlight pioneering efforts, some of which led recently to commercially available prototypes. From this, it will be clear that much further development is still needed, on both the irradiation side and imaging side. We discuss at length the need for improved treatment planning tools for small animal platforms, and the current lack of a standard therein. Finally, we mention some recent experimental work using the early animal radiation research platforms, and the potential they offer for advancing radiobiology research. (topical review)

Small animal radiotherapy research platforms

Science.gov (United States)

Verhaegen, Frank; Granton, Patrick; Tryggestad, Erik

2011-06-01

Advances in conformal radiation therapy and advancements in pre-clinical radiotherapy research have recently stimulated the development of precise micro-irradiators for small animals such as mice and rats. These devices are often kilovolt x-ray radiation sources combined with high-resolution CT imaging equipment for image guidance, as the latter allows precise and accurate beam positioning. This is similar to modern human radiotherapy practice. These devices are considered a major step forward compared to the current standard of animal experimentation in cancer radiobiology research. The availability of this novel equipment enables a wide variety of pre-clinical experiments on the synergy of radiation with other therapies, complex radiation schemes, sub-target boost studies, hypofractionated radiotherapy, contrast-enhanced radiotherapy and studies of relative biological effectiveness, to name just a few examples. In this review we discuss the required irradiation and imaging capabilities of small animal radiation research platforms. We describe the need for improved small animal radiotherapy research and highlight pioneering efforts, some of which led recently to commercially available prototypes. From this, it will be clear that much further development is still needed, on both the irradiation side and imaging side. We discuss at length the need for improved treatment planning tools for small animal platforms, and the current lack of a standard therein. Finally, we mention some recent experimental work using the early animal radiation research platforms, and the potential they offer for advancing radiobiology research.

Small animal radiotherapy research platforms

International Nuclear Information System (INIS)

Verhaegen, Frank; Granton, Patrick; Tryggestad, Erik

2011-01-01

Advances in conformal radiation therapy and advancements in pre-clinical radiotherapy research have recently stimulated the development of precise micro-irradiators for small animals such as mice and rats. These devices are often kilovolt x-ray radiation sources combined with high-resolution CT imaging equipment for image guidance, as the latter allows precise and accurate beam positioning. This is similar to modern human radiotherapy practice. These devices are considered a major step forward compared to the current standard of animal experimentation in cancer radiobiology research. The availability of this novel equipment enables a wide variety of pre-clinical experiments on the synergy of radiation with other therapies, complex radiation schemes, sub-target boost studies, hypofractionated radiotherapy, contrast-enhanced radiotherapy and studies of relative biological effectiveness, to name just a few examples. In this review we discuss the required irradiation and imaging capabilities of small animal radiation research platforms. We describe the need for improved small animal radiotherapy research and highlight pioneering efforts, some of which led recently to commercially available prototypes. From this, it will be clear that much further development is still needed, on both the irradiation side and imaging side. We discuss at length the need for improved treatment planning tools for small animal platforms, and the current lack of a standard therein. Finally, we mention some recent experimental work using the early animal radiation research platforms, and the potential they offer for advancing radiobiology research. (topical review)

Optimization of stereotactically-guided conformal treatment planning of sellar and parasellar tumors, based on normal brain dose volume histograms

International Nuclear Information System (INIS)

Perks, Julian R.; Jalali, Rakesh; Cosgrove, Vivian P.; Adams, Elizabeth J.; Shepherd, Stephen F.; Warrington, Alan P.; Brada, Michael

1999-01-01

Purpose: To investigate the optimal treatment plan for stereo tactically-guided conformal radiotherapy (SCRT) of sellar and parasellar lesions, with respect to sparing normal brain tissue, in the context of routine treatment delivery, based on dose volume histogram analysis. Methods and Materials: Computed tomography (CT) data sets for 8 patients with sellar- and parasellar-based tumors (6 pituitary adenomas and 2 meningiomas) have been used in this study. Treatment plans were prepared for 3-coplanar and 3-, 4-, 6-, and 30-noncoplanar-field arrangements to obtain 95% isodose coverage of the planning target volume (PTV) for each plan. Conformal shaping was achieved by customized blocks generated with the beams eye view (BEV) facility. Dose volume histograms (DVH) were calculated for the normal brain (excluding the PTV), and comparisons made for normal tissue sparing for all treatment plans at ≥80%, ≥60%, and ≥40% of the prescribed dose. Results: The mean volume of normal brain receiving ≥80% and ≥60% of the prescribed dose decreased by 22.3% (range 14.8-35.1%, standard deviation σ = 7.5%) and 47.6% (range 25.8-69.1%, σ 13.2%), respectively, with a 4-field noncoplanar technique when compared with a conventional 3-field coplanar technique. Adding 2 further fields, from 4-noncoplanar to 6-noncoplanar fields reduced the mean normal brain volume receiving ≥80% of the prescribed dose by a further 4.1% (range -6.5-11.8%, σ = 6.4%), and the volume receiving ≥60% by 3.3% (range -5.5-12.2%, σ = 5.4%), neither of which were statistically significant. Each case must be considered individually however, as a wide range is seen in the volume spared when increasing the number of fields from 4 to 6. Comparing the 4- and 6-field noncoplanar techniques to a 30-field conformal field approach (simulating a dynamic arc plan) revealed near-equivalent normal tissue sparing. Conclusion: Four to six widely spaced, fixed-conformal fields provide the optimum class solution

A Monte Carlo dosimetric quality assurance system for dynamic intensity-modulated radiotherapy

International Nuclear Information System (INIS)

Takegawa, Hideki; Yamamoto, Tokihiro; Miyabe, Yuki; Teshima, Teruki; Kunugi, Tomoaki; Yano, Shinsuke; Mizowaki, Takashi; Nagata, Yasushi; Hiraoka, Masahiro

2005-01-01

We are developing a Monte Carlo (MC) dose calculation system, which can resolve dosimetric issues derived from multileaf collimator (MLC) design for routine dosimetric quality assurance (QA) of intensity-modulated radiotherapy (IMRT). The treatment head of the medical linear accelerator equipped with MLC was modeled using the EGS4 MC code. A graphical user interface (GUI) application was developed to implement MC dose computation in the CT-based patient model and compare the MC calculated results with those of a commercial radiotherapy treatment planning (RTP) system, Varian Eclipse. To reduce computation time, the EGS4 MC code has been parallelized on massive parallel processing (MPP) system using the message passing interface (MPI). The MC treatment head model and MLC model were validated by the measurement data sets of percentage depth dose (PDD) and off-center ratio (OCR) in the water phantom and the film measurements for the static and dynamic test patterns, respectively. In the treatment head model, the MC calculated results agreed with those of measurements for both of PDD and OCR. The MC could reproduce all of the MLC dosimetric effects. A quantitative comparison between the results of MC and Eclipse was successfully performed with the GUI application. Parallel speed-up became almost linear. An MC dosimetric QA system for dynamic IMRT has been developed, however there were large dose discrepancies between the MC and the measurement in the MLC model simulation, which are now being investigated. (author)

DOSE-ESCALATED EXTERNAL BEAM RADIOTHERAPY DURING HORMONO-RADIOTHERAPY FOR PROSTATE CANCER

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Yu. V. Gumenetskaya

2016-01-01

Full Text Available Introduction. The introduction of modern technologies of conformal external beam radiotherapy (EBRT into clinical practice for the treatment of prostate cancer requires proper quality assurance measures as well as a careful analysis of both the efficacy and toxicity data of treatments. The purpose of this study was to inves- tigate tolerance and the immediate efficacy of conformal dose-escalated EBRT during hormono-radiotherapy for prostate cancer. material and methods. The study involved 156 prostate cancer patients treated with EBRT. Among them, 30 patients received a total dose of 70 Gy, and in 126 patients the total dose was esca- lated to 72-76 Gy (median total dose - 74.0 Gy. Fifty-nine patients received intensity modulated radiation therapy. Results. The prescribed course of treatment was completed in all the patients with prostate cancer. Acute radiation-induced bladder reactions (RTOG were observed in 50 (32.1 % patients, of whom 48 (30.8 % experienced grade I reactions, and 2 (1.3 % experienced grade II reactions. Eighteen (11.5 % patients had radiation-induced rectum reactions, not above grade I. The development of grade II dysuric phenomena necessitated treatment interruption only in two patients. Of 9 (5.8 % patients who had late bladder complica- tions (RTOG/EORTC, 8 (5.1 % patients developed grade I complications, and one (0.6 % patient developed grade II complications. Of 11 (7.1 % patients who had rectum complications, 8 (5.1 % patients developed grade I complications, and 3 (1.9 % patients developed grade II complications. No patients experienced the increase in toxicity of treatment during dose escalation up to a total dose exceeding 70 Gy. During the follow-up period, only one patient developed recurrent disease. Conclusion. The results of our study suggest acceptable levels of toxicity following a continuous course of dose-escalated EBRT given in conjunction with hormono-radiotherapy to prostate cancer patients. Further

Simulating molecular mechanisms of the MDM2-mediated regulatory interactions: a conformational selection model of the MDM2 lid dynamics.

Directory of Open Access Journals (Sweden)

Gennady M Verkhivker

Full Text Available Diversity and complexity of MDM2 mechanisms govern its principal function as the cellular antagonist of the p53 tumor suppressor. Structural and biophysical studies have demonstrated that MDM2 binding could be regulated by the dynamics of a pseudo-substrate lid motif. However, these experiments and subsequent computational studies have produced conflicting mechanistic models of MDM2 function and dynamics. We propose a unifying conformational selection model that can reconcile experimental findings and reveal a fundamental role of the lid as a dynamic regulator of MDM2-mediated binding. In this work, structure, dynamics and energetics of apo-MDM2 are studied as a function of posttranslational modifications and length of the lid. We found that the dynamic equilibrium between "closed" and "semi-closed" lid forms may be a fundamental characteristic of MDM2 regulatory interactions, which can be modulated by phosphorylation, phosphomimetic mutation as well as by the lid size. Our results revealed that these factors may regulate p53-MDM2 binding by fine-tuning the thermodynamic equilibrium between preexisting conformational states of apo-MDM2. In agreement with NMR studies, the effect of phosphorylation on MDM2 interactions was more pronounced with the truncated lid variant that favored the thermodynamically dominant closed form. The phosphomimetic mutation S17D may alter the lid dynamics by shifting the thermodynamic equilibrium towards the ensemble of "semi-closed" conformations. The dominant "semi-closed" lid form and weakened dependence on the phosphorylation seen in simulations with the complete lid can provide a rationale for binding of small p53-based mimetics and inhibitors without a direct competition with the lid dynamics. The results suggested that a conformational selection model of preexisting MDM2 states may provide a robust theoretical framework for understanding MDM2 dynamics. Probing biological functions and mechanisms of MDM2

“Invisible” Conformers of an Antifungal Disulfide Protein Revealed by Constrained Cold and Heat Unfolding, CEST-NMR Experiments, and Molecular Dynamics Calculations

Science.gov (United States)

Fizil, Ádám; Gáspári, Zoltán; Barna, Terézia; Marx, Florentine; Batta, Gyula

2015-01-01

Transition between conformational states in proteins is being recognized as a possible key factor of function. In support of this, hidden dynamic NMR structures were detected in several cases up to populations of a few percent. Here, we show by two- and three-state analysis of thermal unfolding, that the population of hidden states may weight 20–40 % at 298 K in a disulfide-rich protein. In addition, sensitive 15N-CEST NMR experiments identified a low populated (0.15 %) state that was in slow exchange with the folded PAF protein. Remarkably, other techniques failed to identify the rest of the NMR “dark matter”. Comparison of the temperature dependence of chemical shifts from experiments and molecular dynamics calculations suggests that hidden conformers of PAF differ in the loop and terminal regions and are most similar in the evolutionary conserved core. Our observations point to the existence of a complex conformational landscape with multiple conformational states in dynamic equilibrium, with diverse exchange rates presumably responsible for the completely hidden nature of a considerable fraction. PMID:25676351