High-dose erythropoietin for tissue protection

DEFF Research Database (Denmark)

Lund, Anton; Lundby, Carsten; Olsen, Niels Vidiendal

2014-01-01

BACKGROUND: The discovery of potential anti-apoptotic and cytoprotective effects of recombinant human erythropoietin (rHuEPO) has led to clinical trials investigating the use of high-dose, short-term rHuEPO therapy for tissue protection in conditions such as stroke and myocardial infarction....... Experimental studies have been favourable, but the clinical efficacy has yet to be validated. MATERIALS AND METHODS: We have reviewed clinical studies regarding the use of high-dose, short-term rHuEPO therapy for tissue protection in humans with the purpose to detail the safety and efficacy of r...... no effect of rHuEPO therapy on measures of tissue protection. Five trials including 1025 patients reported safety concerns in the form of increased mortality or adverse event rates. No studies reported reduced mortality. CONCLUSIONS: Evidence is sparse to support a tissue-protective benefit of r...

Assessment of a new p-Mosfet usable as a dose rate insensitive gamma dose sensor

International Nuclear Information System (INIS)

Vettese, F.; Donichak, C.; Bourgeault, P.

1995-01-01

Dosimetric response of unbiased MOS devices has been assessed at dose rates greater than 2000 cGy/h. Application have been made to a personal dosemeter / dose rate meter to measure the absorbed tissue dose received in the case of acute external irradiation. (D.L.)

A generalised formulation of the 'incomplete-repair' model for cell survival and tissue response to fractionated low dose-rate irradiation

International Nuclear Information System (INIS)

Nilsson, P.; Joiner, M.C.

1990-01-01

A generalized equation for cell survival or tissue effects after fractionated low dose-rate irradiations, when there is incomplete repair between fractions and significant repair during fractions, is derived in terms of the h- and g-functions of the 'incomplete-repair' (IR) model. The model is critically dependent on α/β, repair half-time, treatment time and interfraction interval, and should therefore be regarded primarily as a tool for the analysis of fractionation and dose-rate effects in carefully designed radiobiological experiments, although it should also be useful in exploring, in a general way, the feasibility of clinical treatment protocols using fractionated low dose-rate treatments. (author)

Radiobiological influence of megavoltage electron pulses of ultra-high pulse dose rate on normal tissue cells.

Science.gov (United States)

Laschinsky, Lydia; Karsch, Leonhard; Leßmann, Elisabeth; Oppelt, Melanie; Pawelke, Jörg; Richter, Christian; Schürer, Michael; Beyreuther, Elke

2016-08-01

Regarding the long-term goal to develop and establish laser-based particle accelerators for a future radiotherapeutic treatment of cancer, the radiobiological consequences of the characteristic short intense particle pulses with ultra-high peak dose rate, but low repetition rate of laser-driven beams have to be investigated. This work presents in vitro experiments performed at the radiation source ELBE (Electron Linac for beams with high Brilliance and low Emittance). This accelerator delivered 20-MeV electron pulses with ultra-high pulse dose rate of 10(10) Gy/min either at the low pulse frequency analogue to previous cell experiments with laser-driven electrons or at high frequency for minimizing the prolonged dose delivery and to perform comparison irradiation with a quasi-continuous electron beam analogue to a clinically used linear accelerator. The influence of the different electron beam pulse structures on the radiobiological response of the normal tissue cell line 184A1 and two primary fibroblasts was investigated regarding clonogenic survival and the number of DNA double-strand breaks that remain 24 h after irradiation. Thereby, no considerable differences in radiation response were revealed both for biological endpoints and for all probed cell cultures. These results provide evidence that the radiobiological effectiveness of the pulsed electron beams is not affected by the ultra-high pulse dose rates alone.

Radiobiological influence of megavoltage electron pulses of ultra-high pulse dose rate on normal tissue cells

International Nuclear Information System (INIS)

Laschinsky, Lydia; Karsch, Leonhard; Schuerer, Michael; Lessmann, Elisabeth; Beyreuther, Elke; Oppelt, Melanie; Pawelke, Joerg; Richter, Christian

2016-01-01

Regarding the long-term goal to develop and establish laser-based particle accelerators for a future radiotherapeutic treatment of cancer, the radiobiological consequences of the characteristic short intense particle pulses with ultra-high peak dose rate, but low repetition rate of laser-driven beams have to be investigated. This work presents in vitro experiments performed at the radiation source ELBE (Electron Linac for beams with high Brilliance and low Emittance). This accelerator delivered 20-MeV electron pulses with ultra-high pulse dose rate of 10"1"0 Gy/min either at the low pulse frequency analogue to previous cell experiments with laser-driven electrons or at high frequency for minimizing the prolonged dose delivery and to perform comparison irradiation with a quasi-continuous electron beam analogue to a clinically used linear accelerator. The influence of the different electron beam pulse structures on the radiobiological response of the normal tissue cell line 184A1 and two primary fibroblasts was investigated regarding clonogenic survival and the number of DNA double-strand breaks that remain 24 h after irradiation. Thereby, no considerable differences in radiation response were revealed both for biological endpoints and for all probed cell cultures. These results provide evidence that the radiobiological effectiveness of the pulsed electron beams is not affected by the ultra-high pulse dose rates alone. (orig.)

Dose rates from a C-14 source using extrapolation chamber and MC calculations

International Nuclear Information System (INIS)

Borg, J.

1996-05-01

The extrapolation chamber technique and the Monte Carlo (MC) calculation technique based on the EGS4 system have been studied for application for determination of dose rates in a low-energy β radiation field e.g., that from a 14 C source. The extrapolation chamber measurement method is the basic method for determination of dose rates in β radiation fields. Applying a number of correction factors and the stopping power ratio, tissue to air, the measured dose rate in an air volume surrounded by tissue equivalent material is converted into dose to tissue. Various details of the extrapolation chamber measurement method and evaluation procedure have been studied and further developed, and a complete procedure for the experimental determination of dose rates from a 14 C source is presented. A number of correction factors and other parameters used in the evaluation procedure for the measured data have been obtained by MC calculations. The whole extrapolation chamber measurement procedure was simulated using the MC method. The measured dose rates showed an increasing deviation from the MC calculated dose rates as the absorber thickness increased. This indicates that the EGS4 code may have some limitations for transport of very low-energy electrons. i.e., electrons with estimated energies less than 10 - 20 keV. MC calculations of dose to tissue were performed using two models: a cylindrical tissue phantom and a computer model of the extrapolation chamber. The dose to tissue in the extrapolation chamber model showed an additional buildup dose compared to the dose in the tissue model. (au) 10 tabs., 11 ills., 18 refs

[Dose rate-dependent cellular and molecular effects of ionizing radiation].

Science.gov (United States)

Przybyszewski, Waldemar M; Wideł, Maria; Szurko, Agnieszka; Maniakowski, Zbigniew

2008-09-11

The aim of radiation therapy is to kill tumor cells while minimizing damage to normal cells. The ultimate effect of radiation can be apoptotic or necrotic cell death as well as cytogenetic damage resulting in genetic instability and/or cell death. The destructive effects of radiation arise from direct and indirect ionization events leading to peroxidation of macromolecules, especially those present in lipid-rich membrane structures as well as chromatin lipids. Lipid peroxidative end-products may damage DNA and proteins. A characteristic feature of radiation-induced peroxidation is an inverse dose-rate effect (IDRE), defined as an increase in the degree of oxidation(at constant absorbed dose) accompanying a lower dose rate. On the other hand, a low dose rate can lead to the accumulation of cells in G2, the radiosensitive phase of the cell cycle since cell cycle control points are not sensitive to low dose rates. Radiation dose rate may potentially be the main factor improving radiotherapy efficacy as well as affecting the intensity of normal tissue and whole-body side effects. A better understanding of dose rate-dependent biological effects may lead to improved therapeutic intervention and limit normal tissue reaction. The study reviews basic biological effects that depend on the dose rate of ionizing radiation.

Neutron dose rate for {sup 252} Cf AT source in medical applications

Energy Technology Data Exchange (ETDEWEB)

Paredes, L.; Balcazar, M. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico); Azorin, J. [UAM-I, 09340 Mexico D.F. (Mexico); Francois, J.L. [FI-UNAM, 04510 Mexico D.F. (Mexico)

2006-07-01

The AAPM TG-43 modified protocol was used for the calculation of the neutron dose rate of {sup 252}Cf sources for two tissue substitute materials, five normal tissues and six tumours. The {sup 252}Cf AT source model was simulated using the Monte Carlo MCNPX code in spherical geometry for the following factors: a) neutron air kerma strength conversion factor, b) dose rate constant, c) radial dose function, d) geometry factor, e) anisotropy function and f) neutron dose rate. The calculated dose rate in water at 1 cm and 90 degrees from the source long axis, using the Watt fission spectrum, was D{sub n}(r{sub 0}, {theta}{sub 0})= 1.9160 cGy/h-{mu}g. When this value is compared with Rivard et al. calculation using MCNP4B code, 1.8730 cGy/h-{mu}g, a difference of 2.30% is obtained. The results for the reference neutron dose rate in other media show how small variations in the elemental composition between the tissues and malignant tumours, produce variations in the neutron dose rate up to 12.25%. (Author)

Estimates of Health Detriments and Tissue Weighting Factors for Hong Kong Populations from Low Dose, Low Dose Rate and Low LET Ionising Radiation Exposure

International Nuclear Information System (INIS)

Lee, S.K.

1998-01-01

The total health detriments and the tissue weighting factors for the Hong Kong populations from low dose, low dose rate and low LET ionising radiation exposure are obtained according to the methodology recommended in ICRP Publication 60. The probabilities of fatal cancers for the general (ages 0-90) and working (ages 20-64) populations due to lifetime exposure at low dose and low dose rate are 4.9 x 10 -2 Sv -1 and 3.6 x 10 -2 Sv -1 respectively, comparing with the ICRP 60 estimates of 5.0 x 10 -2 Sv -1 and 4.0 x 10 -2 Sv -1 . The corresponding total health detriments for the general and working populations are 6.9 x 10 -2 Sv -1 and 4.9 x 10 -2 Sv -1 respectively comparing with the ICRP 60 estimates of 7.3 x 10 -2 Sv -1 and 5.6 x 10 -2 Sv -1 . Tissue weighting factors for the general population are 0.01 (bone surface and skin), 0.02 (liver, oesophagus and thyroid), 0.04 (bladder and breast), 0.08 (remainder), 0.10 (stomach), 0.11 (bone marrow), 0.15 (colon), 0.19 (lung) and 0.21 (gonads) and for the working population are 0.01 (bone surface and skin), 0.03 (liver, oesophagus and thyroid), 0.04 (breast), 0.06 (remainder), 0.07 (bladder), 0.08 (colon), 0.14 (bone marrow and stomach), 0.16 (lung) and 0.20 (gonads). (author)

Comparison of the predictions of the LQ and CRE models for normal tissue damage due to biologically targeted radiotherapy with exponentially decaying dose rates

International Nuclear Information System (INIS)

O'Donoghue, J.A.; West of Schotland Health Boards, Glasgow

1989-01-01

For biologically targeted radiotherapy organ dose rates may be complex functions of time, related to the biodistribution kinetics of the delivery vehicle and radiolabel. The simples situation is where dose rates are exponentially decaying functions of time. Two normal tissue isoeffect models enable the effects of exponentially decaying dose rates to be addressed. These are the extension of the linear-quadratic model and the cumulative radiation effect model. This communication will compare the predictions of these models. (author). 14 refs.; 1 fig

Dose optimization of intra-operative high dose rate interstitial brachytherapy implants for soft tissue sarcoma

Directory of Open Access Journals (Sweden)

Jamema Swamidas

2009-01-01

Full Text Available Objective : A three dimensional (3D image-based dosimetric study to quantitatively compare geometric vs. dose-point optimization in combination with graphical optimization for interstitial brachytherapy of soft tissue sarcoma (STS. Materials and Methods : Fifteen consecutive STS patients, treated with intra-operative, interstitial Brachytherapy, were enrolled in this dosimetric study. Treatment plans were generated using dose points situated at the "central plane between the catheters", "between the catheters throughout the implanted volume", at "distances perpendicular to the implant axis" and "on the surface of the target volume" Geometrically optimized plans had dose points defined between the catheters, while dose-point optimized plans had dose points defined at a plane perpendicular to the implant axis and on the target surface. Each plan was graphically optimized and compared using dose volume indices. Results : Target coverage was suboptimal with coverage index (CI = 0.67 when dose points were defined at the central plane while it was superior when the dose points were defined at the target surface (CI=0.93. The coverage of graphically optimized plans (GrO was similar to non-GrO with dose points defined on surface or perpendicular to the implant axis. A similar pattern was noticed with conformity index (0.61 vs. 0.82. GrO were more conformal and less homogeneous compared to non-GrO. Sum index was superior for dose points defined on the surface of the target and relatively inferior for plans with dose points at other locations (1.35 vs. 1.27. Conclusions : Optimization with dose points defined away from the implant plane and on target results in superior target coverage with optimal values of other indices. GrO offer better target coverage for implants with non-uniform geometry and target volume.

Review of low dose-rate epidemiological studies and biological mechanisms of dose-rate effects on radiation induced carcinogenesis

International Nuclear Information System (INIS)

Iwasaki, Toshiyasu; Otsuka, Kensuke; Yoshida, Kazuo

2015-01-01

Radiation protection system adopts the linear non-threshold model with using dose and dose-rate effectiveness factor (DDREF). The dose-rate range where DDREF is applied is below 100 mGy per hour, and it is regarded that there are no dose-rate effects at very low dose rate, less than of the order of 10 mGy per year, even from the biological risk evaluation model based on cellular and molecular level mechanisms for maintenance of genetic integrity. Among low dose-rate epidemiological studies, studies of residents in high natural background areas showed no increase of cancer risks at less than about 10 mGy per year. On the other hand, some studies include a study of the Techa River cohort suggested the increase of cancer risks to the similar degree of Atomic bomb survivor data. The difference of those results was supposed due to the difference of dose rate. In 2014, International Commission on Radiological Protection opened a draft report on stem cell biology for public consultations. The report proposed a hypothesis based on the new idea of stem cell competition as a tissue level quality control mechanism, and suggested that it could explain the dose-rate effects around a few milligray per year. To verify this hypothesis, it would be needed to clarify the existence and the lowest dose of radiation-induced stem cell competition, and to elucidate the rate of stem cell turnover and radiation effects on it. As for the turnover, replenishment of damaged stem cells would be the important biological process. It would be meaningful to collect the information to show the difference of dose rates where the competition and the replenishment would be the predominant processes. (author)

Development of Real-Time Measurement of Effective Dose for High Dose Rate Neutron Fields

International Nuclear Information System (INIS)

Braby, L. A.; Reece, W. D.; Hsu, W. H.

2003-01-01

Studies of the effects of low doses of ionizing radiation require sources of radiation which are well characterized in terms of the dose and the quality of the radiation. One of the best measures of the quality of neutron irradiation is the dose mean lineal energy. At very low dose rates this can be determined by measuring individual energy deposition events, and calculating the dose mean of the event size. However, at the dose rates that are normally required for biology experiments, the individual events can not be separated by radiation detectors. However, the total energy deposited in a specified time interval can be measured. This total energy has a random variation which depends on the size of the individual events, so the dose mean lineal energy can be calculated from the variance of repeated measurements of the energy deposited in a fixed time. We have developed a specialized charge integration circuit for the measurement of the charge produced in a small ion chamber in typical neutron irradiation experiments. We have also developed 4.3 mm diameter ion chambers with both tissue equivalent and carbon walls for the purpose of measuring dose mean lineal energy due to all radiations and due to all radiations except neutrons, respectively. By adjusting the gas pressure in the ion chamber, it can be made to simulate tissue volumes from a few nanometers to a few millimeters in diameter. The charge is integrated for 0.1 seconds, and the resulting pulse height is recorded by a multi channel analyzer. The system has been used in a variety of photon and neutron radiation fields, and measured values of dose and dose mean lineal energy are consistent with values extrapolated from measurements made by other techniques at much lower dose rates. It is expected that this technique will prove to be much more reliable than extrapolations from measurements made at low dose rates because these low dose rate exposures generally do not accurately reproduce the attenuation and

Dose rate effectiveness in radiation-induced teratogenesis in mice

International Nuclear Information System (INIS)

Kato, F.; Ootsuyama, A.; Norimura, T.

2000-01-01

To investigate the role of p53 gene in tissue repair of teratogenic injury, we compared incidence of radiation-induced malformations in homozygous p53(-/-) mice, heterozygous p53(+/-) mice and wild-type p53(+/+) mice. After X-irradiation with 2 Gy at high dose rate on 9.5 days of gestation, p53(-/-) mice showed higher incidences of anomalies and higher resistance to prenatal deaths than p53(+/+) mice. This reciprocal relationship of radiosensitivity to anomalies and deaths supports the notion that embryos or fetuses have a p53-dependent 'guardian' that aborts cells bearing radiation-induced teratogenic DNA damage. In fact, after X-irradiation, the number of apoptotic cells was greatly increased in p53(+/+) fetuses but not in p53(-/-) fetuses. The same dose of γ-ray exposure at low dose rate on 9.5-10.5 day of gestation produced significant reduction of radiation-induced malformation in p53(+/+) and p53(+/-) mice, remained teratogenic for p53(-/-) mice. These results suggest that complete elimination of teratogenic damage from irradiated tissues requires the concerted cooperation of two mechanisms; proficient DNA repair and the p53-dependent apoptotic tissue repair. When concerted DNA repair and apoptosis functions efficiently, there is a threshold dose-rate for radiation-induced malformations. (author)

Radiobiological modelling of dose-gradient effects in low dose rate, high dose rate and pulsed brachytherapy

International Nuclear Information System (INIS)

Armpilia, C; Dale, R G; Sandilos, P; Vlachos, L

2006-01-01

This paper presents a generalization of a previously published methodology which quantified the radiobiological consequences of dose-gradient effects in brachytherapy applications. The methodology uses the linear-quadratic (LQ) formulation to identify an equivalent biologically effective dose (BED eq ) which, if applied uniformly to a specified tissue volume, would produce the same net cell survival as that achieved by a given non-uniform brachytherapy application. Multiplying factors (MFs), which enable the equivalent BED for an enclosed volume to be estimated from the BED calculated at the dose reference surface, have been calculated and tabulated for both spherical and cylindrical geometries. The main types of brachytherapy (high dose rate (HDR), low dose rate (LDR) and pulsed (PB)) have been examined for a range of radiobiological parameters/dimensions. Equivalent BEDs are consistently higher than the BEDs calculated at the reference surface by an amount which depends on the treatment prescription (magnitude of the prescribed dose) at the reference point. MFs are closely related to the numerical BED values, irrespective of how the original BED was attained (e.g., via HDR, LDR or PB). Thus, an average MF can be used for a given prescribed BED as it will be largely independent of the assumed radiobiological parameters (radiosensitivity and α/β) and standardized look-up tables may be applicable to all types of brachytherapy treatment. This analysis opens the way to more systematic approaches for correlating physical and biological effects in several types of brachytherapy and for the improved quantitative assessment and ranking of clinical treatments which involve a brachytherapy component

Applicability of the tissue stem cell turnover concept on the validity of cumulative dose based radiation risk evaluation

International Nuclear Information System (INIS)

Otsuka, Kensuke; Hamada, Nobuyuki; Iwasaki, Toshiyasu; Yoshida, Kazuo

2011-01-01

The radiation protection system adopts the linear no-threshold model to achieve proper radiation protection for considering cancer risks resulting from radiation exposure. This model uses cumulative dose to a tissue for risk evaluation in which cumulative dose is related to the amount of DNA damage and consequential induction of gene mutation. In this concept, gene mutation accumulates in tissue stem cells, the putative target of carcinogenesis, with total dose given to the tissue. Unlike high-dose-rate exposure, epidemiological studies in high radiation background areas, such as Kerala in India, revealed that cancer risks is not elevated by the dose to the inhabitants, suggesting that there exists some mechanisms to eliminate the damage/mutation in the exposed tissue under extremely low-dose-rate exposure situations. In this report, the dynamics of tissue stem cell turnover is evaluated as a possible mechanism under extremely low-dose-rate exposure situations. To this end, we reviewed recent literatures studying tissue stem cell turnover, and found that great advances in stem cell research have made it possible to trace a fate of stem cells in tissues. Furthermore, turnover of tissue stem cells is found to occur after irradiation, due to competition of stem cells within tissues. This raises a possibility that radiation effects may not accumulate in a tissue depending on the dose-rate and duration of exposure period. (author)

Carcinogenesis in mice after low doses and dose rates

International Nuclear Information System (INIS)

Ullrich, R.L.

1979-01-01

The results from the experimental systems reported here indicate that the dose-response curves for tumor induction in various tissues cannot be described by a single model. Furthermore, although the understanding of the mechanisms involved in different systems is incomplete, it is clear that very different mechanisms for induction are involved. For some tumors the mechanism of carcinogenesis may be mainly a result of direct effects on the target cell, perhaps involving one or more mutations. While induction may occur, in many instances, through such direct effects, the eventual expression of the tumor can be influenced by a variety of host factors including endocrine status, competence of the immune system, and kinetics of target and interacting cell populations. In other tumors, indirect effects may play a major role in the initiation or expression of tumors. Some of the hormone-modulated tumors would fall into this class. Despite the complexities of the experimental systems and the lack of understanding of the types of mechanisms involved, in nearly every example the tumorigenic effectiveness per rad of low-LET radiation tends to decrease with decreasing dose rate. For some tumor types the differences may be small or may appear only with very low dose rates, while for others the dose-rate effects may be large

An energy-independent dose rate meter for beta and gamma radiation

International Nuclear Information System (INIS)

Heinzelmann, M.; Keller, M.

1986-01-01

An easy to handle dose rate meter has been developed at the Juelich Nuclear Research Centre with a small probe for the energy-independent determination of the dose rate in mixed radiation fields. The dose rate meter contains a small ionisation chamber with a volume of 15.5 cm 3 . The window of the ionisation chamber consists of an aluminised plastic foil of 7 mg.cm -2 . The dose rate meter is suitable for determining the dose rate in skin. With a supplementary depth dose cap, the dose rate can be determined in tissue at a depth of 1 cm. The dose rate meter is energy-independent within +-20% for 147 Pm, 204 Tl and 90 Sr/ 90 Y beta radiation and for gamma radiation in the energy range above 35 keV. (author)

In vitro and in vivo effects of low dose HTO contamination modulated by dose rate

International Nuclear Information System (INIS)

Petcu, I.; Savu, D.; Moisoi, N.; Koeteles, G.J.

1997-01-01

The experiment performed in vitro intended to examine whether an adaptive response could be elicited on lymphocytes by low-level contamination of whole blood with tritiated water and if the modification of the dose rate has any influence on it. Lymphocytes pre-exposed to 3 HOH (0.2 - 6.6 MBq/ml) and subsequently irradiated with I Gy γ-rays showed micronuclei frequency significantly lower (40% - 45%) than the expected member (sum of the yields induced by 3 HOH and γ-rays separately). The degree of the radioresistance induced by HTO pre-treatments became higher with decreasing dose-rate for a rather similar total adapting dose. In vivo, the aim of the study was to investigate if different dose rates are inducing modulation of the lipid peroxidation level and of the thymidine uptake in different tissues of animals contaminated by HTO ingestion. The total doses varied between 5 and 20 cGy and were delivered as chronic (100 days) or acute contamination (5 days). It was observed that only doses about 20 cGy caused a dose-rate dependent increase of the lipid peroxidation level in the tissues of small intestine, kidney and spleen. Both chronic and acute contamination did produce reduced incorporation of thymidine in the cells of bone marrow. The most effective decrease of thymidine uptake was induced by the acute contamination in the lower dose domain (approx. 5 cGy). Our hypothesis is that in this dose domain the modification of thymidine uptake could be due to changes at the level of membrane transport. (author)

Dose rate considerations in brachytherapy: biological equivalence of LDR and HDR

International Nuclear Information System (INIS)

Orton, C.G.

1994-01-01

The linear-quadratic model for cell survival and bioeffect doses is discussed and equations for low dose rate (LDR), high dose rate (HDR) and intermediate situations are presented. The model, when used to define LDR and single fractions of HDR, shows, that these correspond to irradiations lasting longer than about 14 hours or shorter than about 0.7 hours, respectively. It is shown that, for HDR to be as safe and effective as LDR, the dose-rate effect of LDR has to be replaced by the fractionation-effect of HDR. This is necessary in order to take advantage of the differential repair characteristics between late-reacting normal tissue and tumor cells at low doses and low dose rates. Using the linear-quadratic model to simulate repair mathematically, it is shown that the number of fractions required is highly dependent upon what parameters are assumed for normal tissues and tumor, as well as whether or not there is any physical advantage gained by conversion from LDR to HDR. (author). 20 refs., 7 figs

The Contribution of Tissue Level Organization to Genomic Stability Following Low Dose/Low Dose Rate Gamma and Proton Irradiation

Energy Technology Data Exchange (ETDEWEB)

Cheryl G. Burrell, Ph.D.

2012-05-14

The formation of functional tissue units is necessary in maintaining homeostasis within living systems, with individual cells contributing to these functional units through their three-dimensional organization with integrin and adhesion proteins to form a complex extra-cellular matrix (ECM). This is of particular importance in those tissues susceptible to radiation-induced tumor formation, such as epithelial glands. The assembly of epithelial cells of the thyroid is critical to their normal receipt of, and response to, incoming signals. Traditional tissue culture and live animals present significant challenges to radiation exposure and continuous sampling, however, the production of bioreactor-engineered tissues aims to bridge this gap by improve capabilities in continuous sampling from the same functional tissue, thereby increasing the ability to extrapolate changes induced by radiation to animals and humans in vivo. Our study proposes that the level of tissue organization will affect the induction and persistence of low dose radiation-induced genomic instability. Rat thyroid cells, grown in vitro as 3D tissue analogs in bioreactors and as 2D flask grown cultures were exposed to acute low dose (1, 5, 10 and 200 cGy) gamma rays. To assess immediate (6 hours) and delayed (up to 30 days) responses post-irradiation, various biological endpoints were studied including cytogenetic analyses, apoptosis analysis and cell viability/cytotoxicity analyses. Data assessing caspase 3/7 activity levels show that, this activity varies with time post radiation and that, overall, 3D cultures display more genomic instability (as shown by the lower levels of apoptosis over time) when compared to the 2D cultures. Variation in cell viability levels were only observed at the intermediate and late time points post radiation. Extensive analysis of chromosomal aberrations will give further insight on the whether the level of tissue organization influences genomic instability patterns after

Low-dose-rate intraoperative brachytherapy combined with external beam irradiation in the conservative treatment of soft tissue sarcoma

International Nuclear Information System (INIS)

Delannes, M.; Thomas, L.; Martel, P.; Bonnevialle, P.; Stoeckle, E.; Chevreau, Ch.; Bui, B.N.; Daly-Schveitzer, N.; Pigneux, J.; Kantor, G.

2000-01-01

Purpose: Conservative treatment of soft tissue sarcomas most often implies combination of surgical resection and irradiation. The aim of this study was to evaluate low-dose-rate intraoperative brachytherapy, delivered as a boost, in the local control of primary tumors, with special concern about treatment complications. Methods and Materials: Between 1986 and 1995, 112 patients underwent intraoperative implant. This report focuses on the group of 58 patients with primary sarcomas treated by combination of conservative surgery, intraoperative brachytherapy, and external irradiation. Most of the tumors were located in the lower limbs (46/58--79%). Median size of the tumor was 10 cm, most of the lesions being T2-T3 (51/58--88%), Grade 2 or 3 (48/58--83%). The mean brachytherapy dose was 20 Gy and external beam irradiation dose 45 Gy. In 36/58 cases, iridium wires had to be placed on contact with neurovascular structures. Results: With a median follow-up of 54 months, the 5-year actuarial survival was 64.9%, with a 5-year actuarial local control of 89%. Of the 6 patients with local relapse, 3 were salvaged. Acute side effects, essentially wound healing problems, occurred in 20/58 patients, late side effects in 16/58 patients (7 neuropathies G2 to G4). No amputation was required. The only significant factor correlated with early side effects was the location of the tumor in the lower limb (p = 0.003), and with late side effects the vicinity of the tumor with neurovascular structures (p = 0.009). Conclusion: Brachytherapy allows early delivery of a boost dose in a reduced volume of tissue, precisely mapped by the intraoperative procedure. Combined with external beam irradiation, it is a safe and efficient treatment technique leading to high local control rates and limited functional impairment

Organ or tissue doses, effective dose and collective effective dose from X-ray diagnosis, in Japan

International Nuclear Information System (INIS)

Murayama, Takashi; Nishizawa, Kanae; Noda, Yutaka; Kumamoto, Yoshikazu; Iwai, Kazuo.

1996-01-01

Effective doses and collective effective doses from X-ray diagnostic examinations were calculated on the basis of the frequency of examinations estimated by a nationwide survey and the organ or tissue doses experimentally determined. The average organ or tissue doses were determined with thermoluminescence dosimeters put at various sites of organs or tissues in an adult and a child phantom. Effective doses (effective dose equivalents) were calculated as the sum of the weighted equivalent doses in all the organs or tissues of the body. As the examples of results, the effective doses per radiographic examination were approximately 7 mGy for male, and 9 mGy for female angiocardiography, and about 3 mGy for barium meal. Annual collective effective dose from X-ray diagnostic examinations in 1986 were about 104 x 10 3 person Sv from radiography and 118 x 10 3 person Sv from fluoroscopy, with the total of 222 x 10 3 person Sv. (author)

Probability distribution of dose rates in the body tissue as a function of the rhytm of Sr90 administration and the age of animals

International Nuclear Information System (INIS)

Rasin, I.M.; Sarapul'tsev, I.A.

1975-01-01

The probability distribution of tissue radiation doses in the skeleton were studied in experiments on swines and dogs. When introducing Sr-90 into the organism from the day of birth till 90 days dose rate probability distribution is characterized by one, or, for adult animals, by two independent aggregates. Each of these aggregates correspond to the normal distribution law

Gamma-ray dose-rates to human tissues from natural external sources in Great Britain

International Nuclear Information System (INIS)

Spiers, F.W.

1960-01-01

The information on environmental gamma radiation given in the last report (Spiers, 1956) was limited by the small amount of experimental data then available. Considerably more information has been accumulated since then and a summary has been published in the Report of the United Nations Scientific Committee on te Effects of Atomic Radiation 1958). The data reported from Austria, France, Sweden and the U.S.A. show that in general dose-rates out-of-doors range from about 0 mrads per year over sedimentary rocks to about 200 mrads per year in granite districts. In houses a similar range of doserates is indicated, the rates in individual houses depending upon the nature of the building materials. In some parts of the world, however, very much higher dose-rates have been observed. On the extensive area of monazite sand in the Kerala State of India dose-rates of up to 4000 mrads per year have been recorded and the mean dose-rate for 10 villages with a total population of 52,000 has been estimated to be 1270 mrads per year. Mean dose-rates of 500 and 1600 mrads per year have also been reported from two localities in Brazil

Gamma-ray dose-rates to human tissues from natural external sources in Great Britain

Energy Technology Data Exchange (ETDEWEB)

Spiers, F W

1960-12-01

The information on environmental gamma radiation given in the last report (Spiers, 1956) was limited by the small amount of experimental data then available. Considerably more information has been accumulated since then and a summary has been published in the Report of the United Nations Scientific Committee on te Effects of Atomic Radiation 1958). The data reported from Austria, France, Sweden and the U.S.A. show that in general dose-rates out-of-doors range from about 0 mrads per year over sedimentary rocks to about 200 mrads per year in granite districts. In houses a similar range of doserates is indicated, the rates in individual houses depending upon the nature of the building materials. In some parts of the world, however, very much higher dose-rates have been observed. On the extensive area of monazite sand in the Kerala State of India dose-rates of up to 4000 mrads per year have been recorded and the mean dose-rate for 10 villages with a total population of 52,000 has been estimated to be 1270 mrads per year. Mean dose-rates of 500 and 1600 mrads per year have also been reported from two localities in Brazil.

Estimation of the transit dose component in high dose rate brachytherapy

International Nuclear Information System (INIS)

Garcia Romero, A.; Millan Cebrian, E.; Lozano Flores, F.J.; Lope Lope, R.; Canellas Anoz, M.

2001-01-01

Current high dose rate brachytherapy (HDR) treatment planning systems usually calculate dose only from source stopping positions (stationary component), but fails to account for the administered dose when the source is moving (dynamic component or transit dose). Numerical values of this transit dose depends upon the source velocity, implant geometry, source activity and prescribed dose. In some HDR treatments using particular geometry the transit dose cannot be ignored because it increases the dose at the prescriptions points and also could increase potential late tissue complications as predicted by the linear quadratic model. International protocols recommend to verify this parameter. The aim of this paper has been to establish a procedure for the transit dose calculation for the Gammamed 12i equipment at the RT Department in the Clinical University Hospital (Zaragoza-Spain). A numeric algorithm was implemented based on a dynamic point approximation for the moving HDR source and the calculated results for the entrance-exit transit dose was compared with TLD measurements made in some discrete points. (author) [es

Consequences of the exposure at low dose rates-contribution of animal experimentation

International Nuclear Information System (INIS)

Masse, R.

1990-01-01

The exposure of laboratory animals to the various types of radiations will induce cancers in relation with the tissue absorbed doses. The shape of the dose-effet relationship is most variable. It is important to distinguish which tumours are comparable to human tumours. Those showing more analogies answer but seldom to the classical lineo-quadratic relationship; however, a strong attenuation of induction is demonstrated at low dose rates. Quasi-threshold relationships are seen after the exposure of some tissues to high-LET radiations. These observations question the validity of generalizing the radiobiologists' dual action theory, setting the origin of the dose-effect relationship in the induction of events within the DNA molecule. There is an alternative in the cellular collaboration events; it assumes that the effectiveness per dose unit decreases constantly as an inverse function of the dose rate [fr

Late change of normal tissue treated either by high dose rate or low dose rate interstitial brachytherapy. A retrospective comparative study on oral and oropharyngeal mucosa

International Nuclear Information System (INIS)

Nose, Takayuki; Koizumi, Masahiko; Nishiyama, Kinji; Inoue, Toshihiko

2002-01-01

The purpose of this study was to compare late changes of normal tissue treated either by high dose rate (HDR) or low dose rate (LDR) interstitial brachytherapy. For HDR group, 22 oropharynx cancer patients who were treated by HDR Ir-192 interstitial brachytherapy with/without external beam radiotherapy in Osaka (Osaka Medical Center for Cancer and Cardiovascular Diseases and Osaka University Hospital) during June 1994 through April 2000 and came to the follow-up clinics during July 2000 through December 2000 were studied. For LDR group, 26 oropharynx cancer patients who were treated by LDR Ir-192 interstitial brachytherapy with/without external beam radiotherapy in Nancy (Centre Alexis Vautrin) during February 1989 through July 1998 and came to the follow-up clinics during April 1999 through July 1999 were studied. The standard HDR schedules were 54 Gy/9 fr/5-6 days for monotherapy and 18-24 Gy/3-4 fr/2-3 days following 45 Gy external beam radiotherapy. The standard LDR schedules were 65 Gy/5-6 days for monotherapy and 15-25 Gy/2-3 days following 50 Gy external beam radiotherapy. For evaluation of the late changes, we scored the mucosal and muscular changes inside the treated volume using the modified Dische score system and the RTOG/EORTC late radiation morbidity scoring scheme. For 6 items of the modified Dische score system, no significant difference was found between HDR and LDR groups. For the remaining 2 items (pallor, mobility impairment of faucial pillars), LDR group showed higher scores (p=0.010, 0.002). LDR group showed a trend toward higher scores for the RTOG/EORTC scheme (p=0.059). Some predict late effects by HDR interstitial brachytherapy to be severer than by LDR because no dose-rate effects can be expected. Our study, however, showed at least equivalent or even milder late changes by HDR. Appropriate fractionation schedule and extra geometrical sparing effects by optimized dose distribution of HDR group might result in milder late changes. With our

Tumour alpha/beta ratios and dose-rate selection in brachytherapy

International Nuclear Information System (INIS)

Duchesne, G.M.

2003-01-01

Traditionally brachytherapy employed low dose rate (LDR) techniques. Recent adoption of high dose rate (HDR) applications, addressing radiation protection concerns, has sparked debate over possible reductions in therapeutic ratio. The radiobiological characteristics of two contrasting examples, prostate cancer and cervical cancer, are examined. Both in-vitro and clinical observations of prostate cancer suggest a low α/β ratio. Labelling indices are below 2.5%, translating into long potential doubling times (Tpot ) of 16 to 61 days or more. Clinical PSA doubling times are in the order of years. Analysis of clinical endpoints in prostate cancer treated with either LDR or HDR techniques indicates that its α/β ratio may lie between 1 - 4 Gy, similar to slowly proliferating late reacting tissues. As such, therapeutic gain may arise from the use of hypofractionated HDR treatments, exploiting the sensitivity to large fraction sizes, effectively escalating dose. The slow proliferative rate also gives credence to the use of LDR, although several tumour doublings may occur during the effective treatment time, and analysis of the clinical data using a low α/β ratio suggests that LDR doses are only equivalent to 70 Gy with conventional fractionation. Cervical carcinoma is a rapidly proliferating tumour with Tpot values of 3-6 days. LDR implants were delivered over relatively short treatment times, negating repopulation effects, and the 'hyperfractionation' effect of LDR was suited to the high α/β ratio. HDR, although also preventing significant repopulation, has the potential to decrease the therapeutic ratio if low α/β , late-reacting tissues are not protected. Clinical data however show improved outcomes and reduced morbidity with HDR through reduced doses to normal tissues. Choosing the optimal dose rate in brachytherapy depends on tumour behaviour and achievable accuracy. HDR offers some advantages even for high α/β ratio tumours, and may be the technique of

Dose rate constants for new dose quantities

International Nuclear Information System (INIS)

Tschurlovits, M.; Daverda, G.; Leitner, A.

1992-01-01

Conceptual changes and new quantities made is necessary to reassess dose rate quantities. Calculations of the dose rate constant were done for air kerma, ambient dose equivalent and directional dose equivalent. The number of radionuclides is more than 200. The threshold energy is selected as 20 keV for the dose equivalent constants. The dose rate constant for the photon equivalent dose as used mainly in German speaking countries as a temporary quantity is also included. (Author)

Low dose X -ray effects on catalase activity in animal tissue

Science.gov (United States)

Focea, R.; Nadejde, C.; Creanga, D.; Luchian, T.

2012-12-01

This study was intended to investigate the effect of low-dose X ray-irradiation upon the activity of catalase (CAT) in freshly excised chicken tissues (liver, kidney, brain, muscle). The tissue samples were irradiated with 0.5Gy and 2Gy respectively, in a 6 MV photon beam produced by a clinical linear accelerator (VARIAN CLINAC 2100SC). The dose rate was of 260.88cGy/min. at 100 cm source to sample distance. The catalase level was assayed spectrophotometrically, based on reaction kinetics, using a catalase UV assay kit (SIGMA). Catalase increased activity in various tissue samples exposed to the studied X ray doses (for example with 24 % in the liver cells, pbonds that ensure the specificity of CAT active site) but the resulted balance of the two concurrent processes indicates the cell ability of decomposing the hydrogen peroxide-with benefits for the cell physiology restoration for the chosen low dose radiation.

Limb sparing surgery and boost with high dose rate interstitial brachytherapy in treatment of soft tissue sarcoma

International Nuclear Information System (INIS)

Koike, P.; Miziara, M.; Soares, C.; Fogaroli, R.; Baraldi, H.; Pellizoni, A.; Borba, G.

2003-01-01

Soft tissue sarcoma, a rare neoplasia with high aggressively, accounts for approximately 0,7% of the malignant tumors and occurs more often with youngest. Because of the potential risk of local recurrence, theoretically surgical resection, encompassing macroscopic tumor with a margin of macroscopically noninvolved tissue is the right way to perform, with a wide 'en bloc' resection, amputation, with bad functional results. The aim of conservative treatment is combined modality therapy as surgical resection and irradiation to obtain a local control rate as high as possible while preserving functional results. A retrospective review of 31 patients treated with high dose rate (HDR) Brachytherapy in the Radiotherapy Department Arnaldo Vieira de Carvalho Cancer Institute. Methods: Between April 1995 and August 1999, 31 patients who underwent a combine therapy; examined the results on multivariate analysis of conservative surgery and brachytherapy follow/or not by external beam radiation (EBRT). The 31 patients treated, 17 ( 54,8%) females and 14(45,2%) males have a median age of 48 years ( range,19 to 77 years). Most of the tumors was located in the lower limb (17/31 - 54,8%) . The other sites were the upper limb (10/31-32,3%), thoracic wall and abdomen (3/31-9,7%).Classification of the tumors, according to the International Union Against Cancer (UICC) staging was T1 5 patients (16%), T2 (24/31-77%). Median size of the tumors was 9,2cm ( ranged, 2,5 to 24cm). Most of the tumors being malignant fibrous histiocytomas (9/31-29%) and the histological grade II (14/31-45%). Twenty-two (71%) patients had intraoperative implants and the insertion of the radioactive source was delayed 24 to 120 hours. Eight patients (25,8%) had postoperative and received HDRB 45 to 60 days after the surgery . Guide needles were placed in the tumor bed, perpendicular to the scar, systematically in a single plane, the implant volume being defined by radiotherapist . A minimum safety margin of 2 cm

Dosimetric and radiobiological comparison of volumetric modulated arc therapy, high-dose rate brachytherapy, and low-dose rate permanent seeds implant for localized prostate cancer

Energy Technology Data Exchange (ETDEWEB)

Yang, Ruijie, E-mail: ruijyang@yahoo.com; Zhao, Nan; Liao, Anyan; Wang, Hao; Qu, Ang

2016-10-01

To investigate the dosimetric and radiobiological differences among volumetric modulated arc therapy (VMAT), high-dose rate (HDR) brachytherapy, and low-dose rate (LDR) permanent seeds implant for localized prostate cancer. A total of 10 patients with localized prostate cancer were selected for this study. VMAT, HDR brachytherapy, and LDR permanent seeds implant plans were created for each patient. For VMAT, planning target volume (PTV) was defined as the clinical target volume plus a margin of 5 mm. Rectum, bladder, urethra, and femoral heads were considered as organs at risk. A 78 Gy in 39 fractions were prescribed for PTV. For HDR and LDR plans, the dose prescription was D{sub 90} of 34 Gy in 8.5 Gy per fraction, and 145 Gy to clinical target volume, respectively. The dose and dose volume parameters were evaluated for target, organs at risk, and normal tissue. Physical dose was converted to dose based on 2-Gy fractions (equivalent dose in 2 Gy per fraction, EQD{sub 2}) for comparison of 3 techniques. HDR and LDR significantly reduced the dose to rectum and bladder compared with VMAT. The D{sub mean} (EQD{sub 2}) of rectum decreased 22.36 Gy in HDR and 17.01 Gy in LDR from 30.24 Gy in VMAT, respectively. The D{sub mean} (EQD{sub 2}) of bladder decreased 6.91 Gy in HDR and 2.53 Gy in LDR from 13.46 Gy in VMAT. For the femoral heads and normal tissue, the mean doses were also significantly reduced in both HDR and LDR compared with VMAT. For the urethra, the mean dose (EQD{sub 2}) was 80.26, 70.23, and 104.91 Gy in VMAT, HDR, and LDR brachytherapy, respectively. For localized prostate cancer, both HDR and LDR brachytherapy were clearly superior in the sparing of rectum, bladder, femoral heads, and normal tissue compared with VMAT. HDR provided the advantage in sparing of urethra compared with VMAT and LDR.

Dosimetric and radiobiological comparison of volumetric modulated arc therapy, high-dose rate brachytherapy, and low-dose rate permanent seeds implant for localized prostate cancer

International Nuclear Information System (INIS)

Yang, Ruijie; Zhao, Nan; Liao, Anyan; Wang, Hao; Qu, Ang

2016-01-01

To investigate the dosimetric and radiobiological differences among volumetric modulated arc therapy (VMAT), high-dose rate (HDR) brachytherapy, and low-dose rate (LDR) permanent seeds implant for localized prostate cancer. A total of 10 patients with localized prostate cancer were selected for this study. VMAT, HDR brachytherapy, and LDR permanent seeds implant plans were created for each patient. For VMAT, planning target volume (PTV) was defined as the clinical target volume plus a margin of 5 mm. Rectum, bladder, urethra, and femoral heads were considered as organs at risk. A 78 Gy in 39 fractions were prescribed for PTV. For HDR and LDR plans, the dose prescription was D 90 of 34 Gy in 8.5 Gy per fraction, and 145 Gy to clinical target volume, respectively. The dose and dose volume parameters were evaluated for target, organs at risk, and normal tissue. Physical dose was converted to dose based on 2-Gy fractions (equivalent dose in 2 Gy per fraction, EQD 2 ) for comparison of 3 techniques. HDR and LDR significantly reduced the dose to rectum and bladder compared with VMAT. The D mean (EQD 2 ) of rectum decreased 22.36 Gy in HDR and 17.01 Gy in LDR from 30.24 Gy in VMAT, respectively. The D mean (EQD 2 ) of bladder decreased 6.91 Gy in HDR and 2.53 Gy in LDR from 13.46 Gy in VMAT. For the femoral heads and normal tissue, the mean doses were also significantly reduced in both HDR and LDR compared with VMAT. For the urethra, the mean dose (EQD 2 ) was 80.26, 70.23, and 104.91 Gy in VMAT, HDR, and LDR brachytherapy, respectively. For localized prostate cancer, both HDR and LDR brachytherapy were clearly superior in the sparing of rectum, bladder, femoral heads, and normal tissue compared with VMAT. HDR provided the advantage in sparing of urethra compared with VMAT and LDR.

Influence of dose, dose rate, and radiation quality on radiation carcinogenesis and life shortening in RFM and BALB/C mice

International Nuclear Information System (INIS)

Ullrich, R.L.; Storer, J.B.

1978-01-01

The effects produced by 137 Cs gamma rays delivered at a high (45 rads/min) or intermediate (8.2 rads/day) dose rate and the effect of fission neutrons at a high (25 rads/min) and low (1 rad/day) rate in a population of nearly 30,000 RFM and 11,000 BALB/c mice have been studied. Gamma ray doses ranged from 10 to 400 rads with the RFM's and from 50-400 rads with the BALB/c's, while neutron doses ranged from 5 to 200 rads with both strains. The present paper will present an overview of these data and the general findings while subsequent publications will present detailed analyses of each aspect. A variety of neoplasms were sensitive to induction after radiation exposure, including tumors of both reticular tissue origin (leukemia, lymphoma, etc.) and solid tumors. For the RFM, thymic lymphomas were the dominant reticular tissue neoplasm while the majority of solid tumors were either lung adenomas or fit into the broad category of endocrine related tumors, including ovarian, pituitary, harderian, and uterine tumors. The BALB/c was much less sensitive to induction of reticular tissue neoplasms. The tumors that were most sensitive to induction included malignant lung carcinomas, mammary adenocarcinomas and ovarian tumors. In general for both life shortening and tumor induction after gamma ray exposures, when the low to intermediate dose range was sufficiently defined, linearity could be rejected and a dose squared or linear-dose squared relationship adequately fit the data. For neutron exposures, on the other hand, linear relationships were the general finding. The RBE for neutrons varied with tumor type and total dose level. For gamma ray irradiation, the intermediate dose rate resulted in a decreased effectiveness in all cases, while for neutron exposures the dose rate relationships were more complex

Dose rate correction in medium dose rate brachytherapy for carcinoma cervix

International Nuclear Information System (INIS)

Patel, F.D.; Negi, P.S.; Sharma, S.C.; Kapoor, R.; Singh, D.P.; Ghoshal, S.

1998-01-01

Purpose: To establish the magnitude of brachytherapy dose reduction required for stage IIB and III carcinoma cervix patients treated by external radiation and medium dose rate (MDR) brachytherapy at a dose rate of 220±10 cGy/h at point A.Materials and methods: In study-I, at the time of MDR brachytherapy application at a dose rate of 220±10 cGy/h at point A, patients received either 3060 cGy, a 12.5% dose reduction (MDR-12.5), or 2450 cGy, a 30% dose reduction (MDR-30), to point A and they were compared to a group of previously treated LDR patients who received 3500 cGy to point A at a dose rate of 55-65 cGy/h. Study-II was a prospective randomized trial and patients received either 2450 cGy, a 30% dose reduction (MDR-II (30)) or 2800 cGy, a 20% dose reduction (MDR-II (20)), at point A. Patients were evaluated for local control of disease and morbidity. Results: In study-I the 5-year actuarial local control rate in the MDR-30 and MDR-12.5 groups was 71.7±10% and 70.5±10%, respectively, compared to 63.4±10% in the LDR group. However, the actuarial morbidity (all grades) in the MDR-12.5 group was 58.5±14% as against 34.9±9% in the LDR group (P 3 developed complication as against 62.5% of those receiving a rectal BED of (140 3 (χ 2 =46.43; P<0.001). Conclusion: We suggest that at a dose rate of 220±10 cGy/h at point A the brachytherapy dose reduction factor should be around 30%, as suggested by radiobiological data, to keep the morbidity as low as possible without compromising the local control rates. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

Pulsed dose rate and fractionated high dose rate brachytherapy: choice of brachytherapy schedules to replace low dose rate treatments

International Nuclear Information System (INIS)

Visser, Andries G.; Aardweg, Gerard J.M.J. van den; Levendag, Peter C.

1996-01-01

to be less need for strong fractionation in PDR schedules. If the overall time is at least as long as that of the LDR schedule and if the total physical dose is (slightly) adapted, PDR schedules can be designed using longer pulse intervals of up to 3 h. Schedules with sufficiently long intervals have significant logistic advantages in terms of patient care and treatment tolerance. However, in general, PDR schedules that apply more fractionation have a lower risk of overdosing normal tissues in comparison to fractionated HDR schedules. Applying probable ranges for the values of α/β and T (1(2)) , the model calculations indicate that the differences in effects between the proposed fractionated HDR and PDR schedules could be rather small. To detect the magnitude of these differences, (randomized) clinical studies with rather large patient groups might be needed. Conclusions: Pulsed dose rate treatment schedules with longer intervals of up to 3 h appear adequate to replace LDR treatment schedules. Whether PDR schedules can, indeed, replace LDR treatment schedules and whether they offer detectable advantages over schedules with less fractionation (fractionated HDR) should be tested in clinical studies

Beta particle dose rates to micro-organisms in soil

International Nuclear Information System (INIS)

Kabir, M.; Spiers, F.W.; Iinuma, Takeshi.

1977-01-01

Studies were made to estimate the beta-particle dose rates to micro-organisms of various sizes in soil. The small insects and organisms living in soil are constantly exposed to beta-radiation arising from naturally occuring radionuclides in soil as in this case no overlying tissue shields them. The technique of measuring beta-particle dose rate consisted of using of a thin plastic scintillator to measure the pulse height distribution as the beta particle traverses the scintillator. The integrated response was determined by the number and size of the photomultiplier pulses. From the data of soil analyses it was estimated that typically about 29% of the beta particles emitted per gm. of soil were contributed by the U/Ra series, 21% by the Th series and about 50% by potassium. By combining the individual spectra of these three radionuclides in the proportion found in a typical soil, a resultant spectrum was computed representing the energy distribution of the beta particles. The dose rate received by micro-organisms of different shape and size in soil was derived from the equilibrium dose rates combined with a 'Geometrical Factor' of the organisms. For small organisms, the dose rates did not vary between the spherical and cylindrical types, but in the case of larger organisms, the dose rates were found to be greater for the spherical types of the same diameter. (auth.)

Brachytherapy dose measurements in heterogeneous tissues

International Nuclear Information System (INIS)

Paiva F, G.; Luvizotto, J.; Salles C, T.; Guimaraes A, P. C.; Dalledone S, P. de T.; Yoriyaz, H.; Rubo, R.

2014-08-01

Recently, Beau lieu et al. published an article providing guidance for Model-Based Dose Calculation Algorithms (MBDCAs), where tissue heterogeneity considerations are addressed. It is well-known that T G-43 formalism which considers only water medium is limited and significant dose differences have been found comparing both methodologies. The aim of the present work is to experimentally quantify dose values in heterogeneous medium using different dose measurement methods and techniques and compare them with those obtained with Monte Carlo simulations. Experiments have been performed using a Nucletron micro Selectron-Hdr Ir-192 brachytherapy source and a heterogeneous phantom composed by PMMA and different tissue equivalent cylinders like bone, lungs and muscle. Several dose measurements were obtained using tissue equivalent materials with height 1.8 cm and 4.3 cm positioned between the radiation source and the detectors. Radiochromic films, TLDs and MOSFET S have been used for the dose measurements. Film dosimetry has been performed using two methodologies: a) linearization for dose-response curve based on calibration curves to create a functional form that linearize s the dose response and b) 177 multichannel analysis dosimetry where the multiple color channels are analyzed allowing to address not only disturbances in the measurements caused by thickness variation in the film layer, but also, separate other external influences in the film response. All experiments have been simulated using the MCNP5 Monte Carlo radiation transport code. Comparison of experimental results are in good agreement with calculated dose values with differences less than 6% for almost all cases. (Author)

Brachytherapy dose measurements in heterogeneous tissues

Energy Technology Data Exchange (ETDEWEB)

Paiva F, G.; Luvizotto, J.; Salles C, T.; Guimaraes A, P. C.; Dalledone S, P. de T.; Yoriyaz, H. [Instituto de Pesquisas Energeticas e Nucleares / CNEN, Av. Lineu Prestes 2242, Cidade Universitaria, 05508-000 Sao Paulo (Brazil); Rubo, R., E-mail: gabrielpaivafonseca@gmail.com [Hospital das Clinicas da Faculdade de Medicina da Universidade de Sao Paulo, 05403-900 Sao Paulo (Brazil)

2014-08-15

Recently, Beau lieu et al. published an article providing guidance for Model-Based Dose Calculation Algorithms (MBDCAs), where tissue heterogeneity considerations are addressed. It is well-known that T G-43 formalism which considers only water medium is limited and significant dose differences have been found comparing both methodologies. The aim of the present work is to experimentally quantify dose values in heterogeneous medium using different dose measurement methods and techniques and compare them with those obtained with Monte Carlo simulations. Experiments have been performed using a Nucletron micro Selectron-Hdr Ir-192 brachytherapy source and a heterogeneous phantom composed by PMMA and different tissue equivalent cylinders like bone, lungs and muscle. Several dose measurements were obtained using tissue equivalent materials with height 1.8 cm and 4.3 cm positioned between the radiation source and the detectors. Radiochromic films, TLDs and MOSFET S have been used for the dose measurements. Film dosimetry has been performed using two methodologies: a) linearization for dose-response curve based on calibration curves to create a functional form that linearize s the dose response and b) 177 multichannel analysis dosimetry where the multiple color channels are analyzed allowing to address not only disturbances in the measurements caused by thickness variation in the film layer, but also, separate other external influences in the film response. All experiments have been simulated using the MCNP5 Monte Carlo radiation transport code. Comparison of experimental results are in good agreement with calculated dose values with differences less than 6% for almost all cases. (Author)

Cancer radiotherapy based on femtosecond IR laser-beam filamentation yielding ultra-high dose rates and zero entrance dose.

Science.gov (United States)

Meesat, Ridthee; Belmouaddine, Hakim; Allard, Jean-François; Tanguay-Renaud, Catherine; Lemay, Rosalie; Brastaviceanu, Tiberius; Tremblay, Luc; Paquette, Benoit; Wagner, J Richard; Jay-Gerin, Jean-Paul; Lepage, Martin; Huels, Michael A; Houde, Daniel

2012-09-18

Since the invention of cancer radiotherapy, its primary goal has been to maximize lethal radiation doses to the tumor volume while keeping the dose to surrounding healthy tissues at zero. Sadly, conventional radiation sources (γ or X rays, electrons) used for decades, including multiple or modulated beams, inevitably deposit the majority of their dose in front or behind the tumor, thus damaging healthy tissue and causing secondary cancers years after treatment. Even the most recent pioneering advances in costly proton or carbon ion therapies can not completely avoid dose buildup in front of the tumor volume. Here we show that this ultimate goal of radiotherapy is yet within our reach: Using intense ultra-short infrared laser pulses we can now deposit a very large energy dose at unprecedented microscopic dose rates (up to 10(11) Gy/s) deep inside an adjustable, well-controlled macroscopic volume, without any dose deposit in front or behind the target volume. Our infrared laser pulses produce high density avalanches of low energy electrons via laser filamentation, a phenomenon that results in a spatial energy density and temporal dose rate that both exceed by orders of magnitude any values previously reported even for the most intense clinical radiotherapy systems. Moreover, we show that (i) the type of final damage and its mechanisms in aqueous media, at the molecular and biomolecular level, is comparable to that of conventional ionizing radiation, and (ii) at the tumor tissue level in an animal cancer model, the laser irradiation method shows clear therapeutic benefits.

Relative implications of protective responses versus damage induction at low dose and low-dose-rate exposures, using the microdose approach

Energy Technology Data Exchange (ETDEWEB)

Feinendegen, L.E

2003-07-01

In reviewing tissue effects of low-dose radiation (1) absorbed dose to tissue is replaced by the sum of energy deposited with track events in cell-equivalent tissue micromasses, i.e. with microdose hits, in the number of exposed micromasses and (2) induced cell damage and adaptive protection are related to microdose hits in exposed micromasses for a given radiation quality. DNA damage increases with the number of microdose hits. They also can induce adaptive protection, mainly against endogenous DNA damage. This protection involves cellular defenses, DNA repair and damage removal. With increasing numbers of low linear energy transfer (LET) microdose hits in exposed micromasses, adaptive protection first tends to outweigh damage and then (above 200 mGy) fails and largely disappears. These experimental data predict that cancer risk coefficients derived by epidemiology at high-dose irradiation decline at low doses and dose rates when adaptive protection outdoes DNA damage. The dose-risk function should include both linear and non-linear terms at low doses. (author)

Relative implications of protective responses versus damage induction at low dose and low-dose-rate exposures, using the microdose approach

International Nuclear Information System (INIS)

Feinendegen, L.E.

2003-01-01

In reviewing tissue effects of low-dose radiation (1) absorbed dose to tissue is replaced by the sum of energy deposited with track events in cell-equivalent tissue micromasses, i.e. with microdose hits, in the number of exposed micromasses and (2) induced cell damage and adaptive protection are related to microdose hits in exposed micromasses for a given radiation quality. DNA damage increases with the number of microdose hits. They also can induce adaptive protection, mainly against endogenous DNA damage. This protection involves cellular defenses, DNA repair and damage removal. With increasing numbers of low linear energy transfer (LET) microdose hits in exposed micromasses, adaptive protection first tends to outweigh damage and then (above 200 mGy) fails and largely disappears. These experimental data predict that cancer risk coefficients derived by epidemiology at high-dose irradiation decline at low doses and dose rates when adaptive protection outdoes DNA damage. The dose-risk function should include both linear and non-linear terms at low doses. (author)

Quantitative analysis of biological responses to low dose-rate γ-radiation, including dose, irradiation time, and dose-rate

International Nuclear Information System (INIS)

Magae, J.; Furukawa, C.; Kawakami, Y.; Hoshi, Y.; Ogata, H.

2003-01-01

Full text: Because biological responses to radiation are complex processes dependent on irradiation time as well as total dose, it is necessary to include dose, dose-rate and irradiation time simultaneously to predict the risk of low dose-rate irradiation. In this study, we analyzed quantitative relationship among dose, irradiation time and dose-rate, using chromosomal breakage and proliferation inhibition of human cells. For evaluation of chromosome breakage we assessed micronuclei induced by radiation. U2OS cells, a human osteosarcoma cell line, were exposed to gamma-ray in irradiation room bearing 50,000 Ci 60 Co. After the irradiation, they were cultured for 24 h in the presence of cytochalasin B to block cytokinesis, cytoplasm and nucleus were stained with DAPI and propidium iodide, and the number of binuclear cells bearing micronuclei was determined by fluorescent microscopy. For proliferation inhibition, cells were cultured for 48 h after the irradiation and [3H] thymidine was pulsed for 4 h before harvesting. Dose-rate in the irradiation room was measured with photoluminescence dosimeter. While irradiation time less than 24 h did not affect dose-response curves for both biological responses, they were remarkably attenuated as exposure time increased to more than 7 days. These biological responses were dependent on dose-rate rather than dose when cells were irradiated for 30 days. Moreover, percentage of micronucleus-forming cells cultured continuously for more than 60 days at the constant dose-rate, was gradually decreased in spite of the total dose accumulation. These results suggest that biological responses at low dose-rate, are remarkably affected by exposure time, that they are dependent on dose-rate rather than total dose in the case of long-term irradiation, and that cells are getting resistant to radiation after the continuous irradiation for 2 months. It is necessary to include effect of irradiation time and dose-rate sufficiently to evaluate risk

Prototype Operational Advances for Atmospheric Radiation Dose Rate Specification

Science.gov (United States)

Tobiska, W. K.; Bouwer, D.; Bailey, J. J.; Didkovsky, L. V.; Judge, K.; Garrett, H. B.; Atwell, W.; Gersey, B.; Wilkins, R.; Rice, D.; Schunk, R. W.; Bell, D.; Mertens, C. J.; Xu, X.; Crowley, G.; Reynolds, A.; Azeem, I.; Wiltberger, M. J.; Wiley, S.; Bacon, S.; Teets, E.; Sim, A.; Dominik, L.

2014-12-01

Space weather's effects upon the near-Earth environment are due to dynamic changes in the energy transfer processes from the Sun's photons, particles, and fields. The coupling between the solar and galactic high-energy particles, the magnetosphere, and atmospheric regions can significantly affect humans and our technology as a result of radiation exposure. Space Environment Technologies (SET) has developed innovative, new space weather observations that will become part of the toolset that is transitioned into operational use. One prototype operational system for providing timely information about the effects of space weather is SET's Automated Radiation Measurements for Aerospace Safety (ARMAS) system. ARMAS will provide the "weather" of the radiation environment to improve aircraft crew and passenger safety. Through several dozen flights the ARMAS project has successfully demonstrated the operation of a micro dosimeter on commercial aviation altitude aircraft that captures the real-time radiation environment resulting from Galactic Cosmic Rays and Solar Energetic Particles. The real-time radiation exposure is computed as an effective dose rate (body-averaged over the radiative-sensitive organs and tissues in units of microsieverts per hour); total ionizing dose is captured on the aircraft, downlinked in real-time via Iridium satellites, processed on the ground into effective dose rates, compared with NASA's Langley Research Center (LaRC) most recent Nowcast of Atmospheric Ionizing Radiation System (NAIRAS) global radiation climatology model runs, and then made available to end users via the web and smart phone apps. We are extending the dose measurement domain above commercial aviation altitudes into the stratosphere with a collaborative project organized by NASA's Armstrong Flight Research Center (AFRC) called Upper-atmospheric Space and Earth Weather eXperiment (USEWX). In USEWX we will be flying on the ER-2 high altitude aircraft a micro dosimeter for

The effect of continuous low dose-rate gamma irradiation on cell population kinetics of lymphoid tissue

Science.gov (United States)

Foster, B. R.

1974-01-01

Cellular response and cell population kinetics were studied during lymphopoiesis in the thymus of the mouse under continuous gamma irradiation using autoradiographic techniques and specific labeling with tritiated thymidine. On the basis of tissue weights, it is concluded that the response of both the thymus and spleen to continuous low dose-rate irradiation is multiphasic. That is, alternating periods of steady state growth, followed by collapse, which in turn is followed by another period of homeostasis. Since there are two populations of lymphocytes - short lived and long-lived, it may be that different phases of steady state growth are mediated by different lymphocytes. The spleen is affected to a greater extent with shorter periods of steady-state growth than exhibited by the thymus.

Post-operative high dose rate brachytherapy in patients with low to intermediate risk endometrial cancer

International Nuclear Information System (INIS)

Pearcey, R.G.; Petereit, D.G.

2000-01-01

This paper investigates the outcome using different dose/fractionation schedules in high dose rate (HDR) post-operative vaginal vault radiotherapy in patients with low to intermediate risk endometrial cancer. The world literature was reviewed and thirteen series were analyzed representing 1800 cases. A total of 12 vaginal vault recurrences were identified representing an overall vaginal control rate of 99.3%. A wide range of dose fractionation schedules and techniques have been reported. In order to analyze a dose response relationship for tumor control and complications, the biologically effective doses to the tumor and late responding tissues were calculated using the linear quadratic model. A threshold was identified for complications, but not vaginal control. While dose fractionation schedules that delivered a biologically effective dose to the late responding tissues in excess of 100 Gy 3 (LQED = 60 Gy) predicted for late complications, dose fractionation schedules that delivered a modest dose to the vaginal surface (50 Gy 10 or LQED = 30 Gy) appeared tumoricidal with vaginal control rates of at least 98%. By using convenient, modest dose fractionation schedules, HDR vaginal vault - brachytherapy yields very high local control and extremely low morbidity rates. (author)

Physics and quality assurance for brachytherapy - Part II: Low dose rate and pulsed dose rate

International Nuclear Information System (INIS)

Williamson, Jeffrey F.

1997-01-01

Purpose: A number of recent developments have revitalized brachytherapy including remote afterloading, implant optimization, increasing use of 3D imaging, and advances in dose specification and basic dosimetry. However, the core physical principles underlying the classical methods of dose calculation and arrangement of multiple sources remain unchanged. The purpose of this course is to review these principles and their applications to low dose-rate interstitial and intracavitary brachytherapy. Emphasis will be placed upon the classical implant systems along with classical and modern methods of dose specification. The level of presentation is designed for radiation oncology residents and beginning clinical physicists. A. Basic Principles (1) Radium-substitute vs. low-energy sealed sources (2) Dose calculation principles (3) The mysteries of source strength specification revealed: mgRaEq, mCi and air-kerma strength B. Interstitial Brachytherapy (1) Target volume, implanted volume, dose specification in implants and implant optimization criteria (2) Classical implant systems: Manchester Quimby and Paris a) Application of the Manchester system to modern brachytherapy b) Comparison of classical systems (3) Permanent interstitial implants a) Photon energy and half life b) Dose specification and pre-operative planning (4) The alphabet soup of dose specification: MCD (mean central dose), minimum dose, MPD (matched peripheral dose), MPD' (minimum peripheral dose) and DVH (dose-volume histogram) quality indices C. Intracavitary Brachytherapy for Carcinoma of the Cervix (1) Basic principles a) Manchester System: historical foundation of U.S. practice patterns b) Principles of applicator design (2) Dose specification and treatment prescription a) mg-hrs, reference points, ICRU Report 38 reference volume -- Point A dose vs mg-hrs and IRAK (Integrated Reference Air Kerma) -- Tissue volume treated vs mg-hrs and IRAK b) Practical methods of treatment specification and prescription

Physics and quality assurance for brachytherapy - Part II: Low dose rate and pulsed dose rate

International Nuclear Information System (INIS)

Williamson, Jeffrey F.

1996-01-01

Purpose: A number of recent developments have revitalized brachytherapy including remote afterloading, implant optimization, increasing use of 3D imaging, and advances in dose specification and basic dosimetry. However, the core physical principles underlying the classical methods of dose calculation and arrangement of multiple sources remain unchanged. The purpose of this course is to review these principles and their applications to low dose-rate interstitial and intracavitary brachytherapy. Emphasis will be placed upon the classical implant systems along with classical and modern methods of dose specification. The level of presentation is designed for radiation oncology residents and beginning clinical physicists. A. Basic Principles (1) Radium-substitute vs. low-energy sealed sources (2) Dose calculation principles (3) The mysteries of source strength specification revealed: mgRaEq, mCi and air-kerma strength B. Interstitial Brachytherapy (1) Target volume, implanted volume, dose specification in implants and implant optimization criteria (2) Classical implant systems: Manchester Quimby and Paris a) Application of the Manchester system to modern brachytherapy b) Comparison of classical systems (3) Permanent interstitial implants a) Photon energy and half life b) Dose specification and pre-operative planning (4) The alphabet soup of dose specification: MCD (mean central dose), minimum dose, MPD (matched peripheral dose), MPD' (minimum peripheral dose) and DVH (dose-volume histogram) quality indices C. Intracavitary Brachytherapy for Carcinoma of the Cervix (1) Basic principles a) Manchester System: historical foundation of U.S. practice patterns b) Principles of applicator design (2) Dose specification and treatment prescription a) mg-hrs, reference points, ICRU Report 38 reference volume --Point A dose vs mg-hrs and IRAK (Integrated Reference Air Kerma) --Tissue volume treated vs mg-hrs and IRAK b) Practical methods of treatment specification and prescription

Dosimetric systems of high dose, dose rate and dose uniformity in food and medical products

International Nuclear Information System (INIS)

Vargas, J.; Vivanco, M.; Castro, E.

2014-08-01

implants with a weight of 1393 g the maximum dose rate of 6.5276 kGy /h, the minimum dose rate of 3.5684 kGy /h and the dose uniformity of 1 83 were determined. Then, based on the minimum dose rate irradiation times were calculated for different doses to evaluate in the microbial decontamination of food (3, 5, 8 and 12 kGy) and the sterilization of medical material by radiation (15, 20, 25 and 40 kGy), corroborating the applied doses with routine dosimeters of ethanol chlorobenzene (1-100 kGy) and perspex network 4034 (5-50 kGy). Other routine dosimeters used in different applications according to the doses range are Gafchromic Hd (40-400 Gray) for induced mutation by radiation and the development of new varieties of plants, the sterile insect technique to eradicate pests, quarantine treatment to solve plant health problems. Ambar Perspex 3042 C (3-15 kGy) for microbial decontamination of dried foods, spices, aromatic herbs, medicinal plants, etc. GEX B-3000 (1-140 kGy) and FWT (0.5-200 kGy) for sterilization of medical and pharmaceutical material, cosmetics, biological tissues, etc. The minimum dose rate allowing to calculate the irradiation times to apply the desired dose for the research or industrial processes, taking into account the density and geometry of product. Is notorious the difference in dose uniformity in food (1, 16) and medical material (1, 83) due to the geometry and relative density of the products within the irradiation cylinder. (author)

Atmospheric radiation flight dose rates

Science.gov (United States)

Tobiska, W. K.

2015-12-01

Space weather's effects upon the near-Earth environment are due to dynamic changes in the energy transfer processes from the Sun's photons, particles, and fields. Of the domains that are affected by space weather, the coupling between the solar and galactic high-energy particles, the magnetosphere, and atmospheric regions can significantly affect humans and our technology as a result of radiation exposure. Space Environment Technologies (SET) has been conducting space weather observations of the atmospheric radiation environment at aviation altitudes that will eventually be transitioned into air traffic management operations. The Automated Radiation Measurements for Aerospace Safety (ARMAS) system and Upper-atmospheric Space and Earth Weather eXperiment (USEWX) both are providing dose rate measurements. Both activities are under the ARMAS goal of providing the "weather" of the radiation environment to improve aircraft crew and passenger safety. Over 5-dozen ARMAS and USEWX flights have successfully demonstrated the operation of a micro dosimeter on commercial aviation altitude aircraft that captures the real-time radiation environment resulting from Galactic Cosmic Rays and Solar Energetic Particles. The real-time radiation exposure is computed as an effective dose rate (body-averaged over the radiative-sensitive organs and tissues in units of microsieverts per hour); total ionizing dose is captured on the aircraft, downlinked in real-time, processed on the ground into effective dose rates, compared with NASA's Langley Research Center (LaRC) most recent Nowcast of Atmospheric Ionizing Radiation System (NAIRAS) global radiation climatology model runs, and then made available to end users via the web and smart phone apps. Flight altitudes now exceed 60,000 ft. and extend above commercial aviation altitudes into the stratosphere. In this presentation we describe recent ARMAS and USEWX results.

Dose specification for 192Ir high dose rate brachytherapy in terms of dose-to-water-in-medium and dose-to-medium-in-medium

International Nuclear Information System (INIS)

Fonseca, Gabriel Paiva; Yoriyaz, Hélio; Tedgren, Åsa Carlsson; Nilsson, Josef; Persson, Maria; Reniers, Brigitte; Verhaegen, Frank

2015-01-01

Dose calculation in high dose rate brachytherapy with 192 Ir is usually based on the TG-43U1 protocol where all media are considered to be water. Several dose calculation algorithms have been developed that are capable of handling heterogeneities with two possibilities to report dose: dose-to-medium-in-medium (D m,m ) and dose-to-water-in-medium (D w,m ). The relation between D m,m and D w,m for 192 Ir is the main goal of this study, in particular the dependence of D w,m on the dose calculation approach using either large cavity theory (LCT) or small cavity theory (SCT). A head and neck case was selected due to the presence of media with a large range of atomic numbers relevant to tissues and mass densities such as air, soft tissues and bone interfaces. This case was simulated using a Monte Carlo (MC) code to score: D m,m, D w,m (LCT), mean photon energy and photon fluence. D w,m (SCT) was derived from MC simulations using the ratio between the unrestricted collisional stopping power of the actual medium and water. Differences between D m,m and D w,m (SCT or LCT) can be negligible (<1%) for some tissues e.g. muscle and significant for other tissues with differences of up to 14% for bone. Using SCT or LCT approaches leads to differences between D w,m (SCT) and D w,m (LCT) up to 29% for bone and 36% for teeth. The mean photon energy distribution ranges from 222 keV up to 356 keV. However, results obtained using mean photon energies are not equivalent to the ones obtained using the full, local photon spectrum. This work concludes that it is essential that brachytherapy studies clearly report the dose quantity. It further shows that while differences between D m,m and D w,m (SCT) mainly depend on tissue type, differences between D m,m and D w,m (LCT) are, in addition, significantly dependent on the local photon energy fluence spectrum which varies with distance to implanted sources. (paper)

Low dose X –ray effects on catalase activity in animal tissue

International Nuclear Information System (INIS)

Focea, R; Nadejde, C; Creanga, D; Luchian, T

2012-01-01

This study was intended to investigate the effect of low-dose X ray-irradiation upon the activity of catalase (CAT) in freshly excised chicken tissues (liver, kidney, brain, muscle). The tissue samples were irradiated with 0.5Gy and 2Gy respectively, in a 6 MV photon beam produced by a clinical linear accelerator (VARIAN CLINAC 2100SC). The dose rate was of 260.88cGy/min. at 100 cm source to sample distance. The catalase level was assayed spectrophotometrically, based on reaction kinetics, using a catalase UV assay kit (SIGMA). Catalase increased activity in various tissue samples exposed to the studied X ray doses (for example with 24 % in the liver cells, p<0.05) suggested the stimulation of the antioxidant enzyme biosynthesis within several hours after exposure at doses of 0.5 Gy and 2 Gy; the putative enzyme inactivation could also occur (due to the injuries on the hydrogen bonds that ensure the specificity of CAT active site) but the resulted balance of the two concurrent processes indicates the cell ability of decomposing the hydrogen peroxide-with benefits for the cell physiology restoration for the chosen low dose radiation.

Life span and tumorigenesis in mice exposed to continuous low dose-rate gamma-rays

International Nuclear Information System (INIS)

Tanaka, Satoshi; Braga-Tanaka III, Ignacia; Takabatake, Takashi; Ichinohe, Kazuaki; Tanaka, Kimio; Matsumoto, Tsuneya; Sato, Fumiaki

2004-01-01

Two experiments were conducted to evaluate late biological effects of chronic low dose-rate radiation. 1: Late effects of chronic low dose-rate gamma-ray irradiation on SPF mice, using life span and pathological changes as parameters. Continuous irradiation for approximately 400 days was performed using 137 Cs gamma-rays at dose-rates of 20 mGy/day, 1 mGy/day and 0.05 mGy/day with accumulated doses equivalent to 8000 mGy, 400 mGy and 20 mGy, respectively. All mice were kept until their natural death. Statistical analyses show that the life spans of the both sexes irradiated at 20 mGy/day (p<0.0001) and of females irradiated at 1 mGy/day (p<0.05) were significantly shorter than those of the control group. There was no evidence of lengthened life span in mice continuously exposed to very low dose-rates of gama-rays. Pathodological examinations showed that the most frequently observed lethal neoplasms in males were malignant lymphomas, liver, lung, and soft tissue neoplasms, whereas, in females, malignant lymphomas and soft tissue neoplasms were common. No significant difference in the causes of death and mortality rates between groups. Hematopoietic neoplasms (malignant lymphoma and myeloid leukemia), liver, lung and soft tissue neoplasms, showed a tendency to appear at a younger age in both sexes irradiated at 20 mGy/day. Experiment 2: effects on the progeny of chronic low dose-rate gamma-ray irradiated SPF mice: preliminary study. No significant difference was observed between non-irradiated group and irradiated group with regards to litter size, sex ratio and causes of death in F1 and F2 mice. (author)

High dose rate brachytherapy for oral cancer.

Science.gov (United States)

Yamazaki, Hideya; Yoshida, Ken; Yoshioka, Yasuo; Shimizutani, Kimishige; Furukawa, Souhei; Koizumi, Masahiko; Ogawa, Kazuhiko

2013-01-01

Brachytherapy results in better dose distribution compared with other treatments because of steep dose reduction in the surrounding normal tissues. Excellent local control rates and acceptable side effects have been demonstrated with brachytherapy as a sole treatment modality, a postoperative method, and a method of reirradiation. Low-dose-rate (LDR) brachytherapy has been employed worldwide for its superior outcome. With the advent of technology, high-dose-rate (HDR) brachytherapy has enabled health care providers to avoid radiation exposure. This therapy has been used for treating many types of cancer such as gynecological cancer, breast cancer, and prostate cancer. However, LDR and pulsed-dose-rate interstitial brachytherapies have been mainstays for head and neck cancer. HDR brachytherapy has not become widely used in the radiotherapy community for treating head and neck cancer because of lack of experience and biological concerns. On the other hand, because HDR brachytherapy is less time-consuming, treatment can occasionally be administered on an outpatient basis. For the convenience and safety of patients and medical staff, HDR brachytherapy should be explored. To enhance the role of this therapy in treatment of head and neck lesions, we have reviewed its outcomes with oral cancer, including Phase I/II to Phase III studies, evaluating this technique in terms of safety and efficacy. In particular, our studies have shown that superficial tumors can be treated using a non-invasive mold technique on an outpatient basis without adverse reactions. The next generation of image-guided brachytherapy using HDR has been discussed. In conclusion, although concrete evidence is yet to be produced with a sophisticated study in a reproducible manner, HDR brachytherapy remains an important option for treatment of oral cancer.

Absorbed dose measurement by using tissue equivalent ionization chamber (pair ionization chamber) in the Yayoi reactor

International Nuclear Information System (INIS)

Sasuga, N.; Okamura, K.; Terakado, T.; Mabuchi, Y.; Nakagawa, T.; Sukegawa, Toshio; Aizawa, C.; Saito, I.; Oka, Yoshiaki

1998-01-01

Each dose rate of neutron and gamma ray in the thermal column of the Yayoi reactor, in which an epithermal neutron field will be used for the boron neutron capture therapy, was measured by using a tissue equivalent ionization chamber and a graphite chamber. The tissue equivalent ionization chamber has some response to both neutron and gamma ray, but the graphite chamber has a few response to the neutron, so called pair ionization chamber method. The epithermal neutron fluxes of the thermal column were calculated by ANISN (one dimensional neutron-gamma transport code). A measured value for gamma dose rate by the pair ionization chamber agrees relevantly with a calculated result. For neutron dose rate, however, the measured value was too much small in comparison with the calculated result. The discrepancy between the measured value and the calculated result for neutron dose rate is discussed in detail in the report. (M. Suetake)

Active specific immunotherapy using the immune reaction of a low-dose irradiated tumor tissue

International Nuclear Information System (INIS)

Ogawa, Y.; Imanaka, K.; Ashida, C.; Takashima, H.; Imajo, Y.; Kimura, S.

1983-01-01

Active specific immunotherapy using the immune reaction of a low-dose irradiated tumor tissue was studied on the transplanted MM46 tumor of female C3H/He mice after radiotherapy. MM46 tumor cells were inoculated into the right hind paws of mice. On the 5th day, irradiation with the dose irradiated tumor tissue (2000 rad on the fifth day), were injected into the left hind paws of the tumor-bearing mice. Effectiveness of this active specific immunotherapy against tumor was evaluated by the regression of tumor and survival rate of mice. Tumor was markedly regressed and survival rate was significantly increased by the active specific immunitherapy

Dose and dose rate monitor

International Nuclear Information System (INIS)

Novakova, O.; Ryba, J.; Slezak, V.; Svobodova, B.; Viererbl, L.

1984-10-01

The methods are discussea of measuring dose rate or dose using a scintillation counte. A plastic scintillator based on polystyrene with PBD and POPOP activators and coated with ZnS(Ag) was chosen for the projected monitor. The scintillators were cylindrical and spherical in shape and of different sizes; black polypropylene tubes were chosen as the best case for the probs. For the counter with different plastic scintillators, the statistical error 2σ for natural background was determined. For determining the suitable thickness of the ZnS(Ag) layer the energy dependence of the counter was measured. Radioisotopes 137 Cs, 241 Am and 109 Cd were chosen as radiation sources. The best suited ZnS(Ag) thickness was found to be 0.5 μm. Experiments were carried out to determine the directional dependence of the detector response and the signal to noise ratio. The temperature dependence of the detector response and its compensation were studied, as were the time stability and fatigue manifestations of the photomultiplier. The design of a laboratory prototype of a dose rate and dose monitor is described. Block diagrams are given of the various functional parts of the instrument. The designed instrument is easiiy portable, battery powered, measures dose rates from natural background in the range of five orders, i.e., 10 -2 to 10 3 nGy/s, and allows to determine a dose of up to 10 mGy. Accouracy of measurement in the energy range of 50 keV to 1 MeV is better than +-20%. (E.S.)

Review of techniques and detectors used in instruments for field measurement of beta doses and dose rates

International Nuclear Information System (INIS)

Jones, A.R.

1983-01-01

Generally, field measurements are required to assess the hazard from #betta#-rays before personnel are allowed to occupy a working space or perform a task. Occasionally, the measurements are required for an assessment after a #betta#-ray exposure is suspected to have occurred. Until recently the dose or dose rate have been the quantities of interest but there is now felt to be a need to characterize the energies and directions of the #betta#-rays as well. The purpose of #betta#-dosimetry is the assessment of hazard to superficial tissues (within approx. 10 mm of the surface) and that these tissues may also be exposed simultaneously to other ionizing radiations. The #betta#-dosimetry technique must take account of this. With these uses of field instruments in mind the following detectors, and associated techniques will be discussed in terms of the measurement principles, advantages and limitations: thin-walled ion chambers (sometimes in combination with thick-walled ones or with covers thick enough to prevent penetration of #betta#-particles); thin scintillators, nearly tissue equivalent, to provide a detector analogous to skin; scintillators, thick enough to absorb all the energy of the #betta#-particles (circuitry is required to count pulses according to size to permit calculation of dose or dose rate); silicon diodes with thin detection layers operated as photocurrent generators; silicon diodes, reversed biassed, with pulses counted according to size; and simple pulse counters (e.g., GM counters or silicon diodes with thin windows)

The usefulness of metal markers for CTV-based dose prescription in high-dose-rate interstitial brachytherapy

International Nuclear Information System (INIS)

Yoshida, Ken; Mitomo, Masanori; Nose, Takayuki; Koizumi, Masahiko; Nishiyama, Kinji; Yoshida, Mineo

2002-01-01

We employ a clinical target volume (CTV)-based dose prescription for high-dose-rate (HDR) interstitial brachytherapy. However, it is not easy to define CTV and organs at risk (OAR) from X-ray film or CT scanning. To solve this problem, we have utilized metal markers since October 1999. Moreover, metal markers can help modify dose prescription. By regulating the doses to the metal markers, refining the dose prescription can easily be achieved. In this research, we investigated the usefulness of the metal markers. Between October 1999 and May 2001, 51 patients were implanted with metal markers at Osaka Medical Center for Cancer and Cardiovascular Diseases (OMCC), Osaka National Hospital (ONH) and Sanda City Hospital (SCH). Forty-nine patients (head and neck: 32; pelvis: 11; soft tissue: 3; breast: 3) using metal markers were analyzed. During operation, we implanted 179 metal markers (49 patients) to CTV and 151 markers (26 patients) to OAR. At treatment planning, CTV was reconstructed judging from the metal markers, applicator position and operation records. Generally, we prescribed the tumoricidal dose to an isodose surface that covers CTV. We also planned to limit the doses to OAR lower than certain levels. The maximum normal tissue doses were decided 80%, 150%, 100%, 50% and 200% of the prescribed doses for the rectum, the urethra, the mandible, the skin and the large vessel, respectively. The doses to the metal markers using CTV-based dose prescription were generated. These were compared with the doses theoretically calculated with the Paris system. Treatment results were also investigated. The doses to the 158 metal markers (42 patients) for CTV were higher than ''tumoricidal dose''. In 7 patients, as a result of compromised dose prescription, 9 markers were lower than the tumoricidal dose. The other 12 markers (7%) were excluded from dose evaluation because they were judged as miss-implanted. The doses to the 142 metal markers (24 patients) for OAR were lower

Transport calculations of. gamma. -ray flux density and dose rate about implantable californium-252 sources

Energy Technology Data Exchange (ETDEWEB)

Shapiro, A; Lin, B I [Cincinnati Univ., Ohio (USA). Dept. of Chemical and Nuclear Engineering; Windham, J P; Kereiakes, J G

1976-07-01

..gamma.. flux density and dose rate distributions have been calculated about implantable californium-252 sources for an infinite tissue medium. Point source flux densities as a function of energy and position were obtained from a discrete-ordinates calculation, and the flux densities were multiplied by their corresponding kerma factors and added to obtain point source dose rates. The point dose rates were integrated over the line source to obtain line dose rates. Container attenuation was accounted for by evaluating the point dose rate as a function of platinum thickness. Both primary and secondary flux densities and dose rates are presented. The agreement with an independent Monte Carlo calculation was excellent. The data presented should be useful for the design of new source configurations.

Dose rate effect of 125I irradiation on normal rabbit eyes and experimental choroidal melanoma

International Nuclear Information System (INIS)

Yang, C.M.; Olsen, K.R.; Schwade, J.G.; Houdek, P.V.; Markoe, A.M.; Pisciotta, V.; Xiaodong Wu

1993-01-01

The dose rate effect of radiation by 125 I plaque on choroidal melanoma and normal intraocular tissue was studied. In the first part of the experiment, high activity plaques (HAP) and low activity plagues (LAP) were implanted on rabbit eyes with experimental Greene choroidal melanoma to deliver a total dose of 10 000 cGy to the tumor apex. The mean dose rate calculated at 0.5 mm from the inner sclera in eight eyes with high activity plaques was 3341.5 cGy hr -1 while that in ten eyes with low activity plaques was 239.9 cGy hr -1 . For tumors less than 1.0 mm in height, both groups showed complete tumor regression at the tumor implantation site after plaque treatment. For tumours more than 1.0 mm in height, two out of two eyes in the low activity plaque group and one of four eyes in the high activity plaque group failed to show complete tumor regression. In the second part of the experiment, 125 I plaques were implanted on the sclera of 12 normal rabbits' eyes. Six received high dose rate plaque treatment, while the other six received low dose rate plaque treatment. Clinical and histologic examinations demonstrated more damaging effects to the normal chorioretinal tissues at the plaque implantation site in the high dose rate plaque group. These results suggest that high dose rate plaques are more effective than low dose rate plaques when tumor height is statistically controlled. (Author)

Dose volume assessment of high dose rate 192IR endobronchial implants

International Nuclear Information System (INIS)

Cheng, B. Saw; Korb, Leroy J.; Pawlicki, Todd; Wu, Andrew

1996-01-01

Purpose: To study the dose distributions of high dose rate (HDR) endobronchial implants using the dose nonuniformity ratio (DNR) and three volumetric irradiation indices. Methods and Materials: Multiple implants were configured by allowing a single HDR 192 Ir source to step through a length of 6 cm along an endobronchial catheter. Dwell times were computed to deliver a dose of 5 Gy to points 1 cm away from the catheter axis. Five sets of source configurations, each with different dwell position spacings from 0.5 to 3.0 cm, were evaluated. Three-dimensional (3D) dose distributions were then generated for each source configuration. Differential and cumulative dose-volume curves were generated to quantify the degree of target volume coverage, dose nonuniformity within the target volume, and irradiation of tissues outside the target volume. Evaluation of the implants were made using the DNR and three volumetric irradiation indices. Results: The observed isodose distributions were not able to satisfy all the dose constraints. The ability to optimally satisfy the dose constraints depended on the choice of dwell position spacing and the specification of the dose constraint points. The DNR and irradiation indices suggest that small dwell position spacing does not result in a more homogeneous dose distribution for the implant. This study supports the existence of a relationship between the dwell position spacing and the distance from the catheter axis to the reference dose or dose constraint points. Better dose homogeneity for an implant can be obtained if the spacing of the dwell positions are about twice the distance from the catheter axis to the reference dose or dose constraint points

Investigation of the dose rate dependency of the PAGAT gel dosimeter at low dose rates

International Nuclear Information System (INIS)

Zehtabian, M.; Faghihi, R.; Zahmatkesh, M.H.; Meigooni, A.S.; Mosleh-Shirazi, M.A.; Mehdizadeh, S.; Sina, S.; Bagheri, S.

2012-01-01

Medical physicists need dosimeters such as gel dosimeters capable of determining three-dimensional dose distributions with high spatial resolution. To date, in combination with magnetic resonance imaging (MRI), polyacrylamide gel (PAG) polymers are the most promising gel dosimetry systems. The purpose of this work was to investigate the dose rate dependency of the PAGAT gel dosimeter at low dose rates. The gel dosimeter was used for measurement of the dose distribution around a Cs-137 source from a brachytherapy LDR source to have a range of dose rates from 0.97 Gy h −1 to 0.06 Gy h −1 . After irradiation of the PAGAT gel, it was observed that the dose measured by gel dosimetry was almost the same at different distances (different dose rates) from the source, although the points nearer the source had been expected to receive greater doses. Therefore, it was suspected that the PAGAT gel is dose rate dependent at low dose rates. To test this further, three other sets of measurements were performed by placing vials containing gel at different distances from a Cs-137 source. In the first two measurements, several plastic vials were exposed to equal doses at different dose rates. An ionization chamber was used to measure the dose rate at each distance. In addition, three TLD chips were simultaneously irradiated in order to verify the dose to each vial. In the third measurement, to test the oxygen diffusion through plastic vials, the experiment was repeated again using plastic vials in a nitrogen box and glass vials. The study indicates that oxygen diffusion through plastic vials for dose rates lower than 2 Gy h −1 would affect the gel dosimeter response and it is suggested that the plastic vials or (phantoms) in an oxygen free environment or glass vials should be used for the dosimetry of low dose rate sources using PAGAT gel to avoid oxygen diffusion through the vials.

High dose rate brachytherapy for oral cancer

International Nuclear Information System (INIS)

Yamazaki, Hideya; Yoshida, Ken; Yoshioka, Yasuo; Shimizutani, Kimishige; Koizumi, Masahiko; Ogawa, Kazuhiko; Furukawa, Souhei

2013-01-01

Brachytherapy results in better dose distribution compared with other treatments because of steep dose reduction in the surrounding normal tissues. Excellent local control rates and acceptable side effects have been demonstrated with brachytherapy as a sole treatment modality, a postoperative method, and a method of reirradiation. Low-dose-rate (LDR) brachytherapy has been employed worldwide for its superior outcome. With the advent of technology, high-dose-rate (HDR) brachytherapy has enabled health care providers to avoid radiation exposure. This therapy has been used for treating many types of cancer such as gynecological cancer, breast cancer, and prostate cancer. However, LDR and pulsed-dose-rate interstitial brachytherapies have been mainstays for head and neck cancer. HDR brachytherapy has not become widely used in the radiotherapy community for treating head and neck cancer because of lack of experience and biological concerns. On the other hand, because HDR brachytherapy is less time-consuming, treatment can occasionally be administered on an outpatient basis. For the convenience and safety of patients and medical staff, HDR brachytherapy should be explored. To enhance the role of this therapy in treatment of head and neck lesions, we have reviewed its outcomes with oral cancer, including Phase I/II to Phase III studies, evaluating this technique in terms of safety and efficacy. In particular, our studies have shown that superficial tumors can be treated using a non-invasive mold technique on an outpatient basis without adverse reactions. The next generation of image-guided brachytherapy using HDR has been discussed. In conclusion, although concrete evidence is yet to be produced with a sophisticated study in a reproducible manner, HDR brachytherapy remains an important option for treatment of oral cancer. (author)

Analysis of dose, dose-rate and treatment time in the production of injuries by radium treatment for cancer of the uterine cervix; and reply by K.H. Lee

International Nuclear Information System (INIS)

Saunders, J.E.

1977-01-01

The author of the first letter has detected several errors and inconsistencies in the treatment of the data in a recent paper (Lee, K.H., Kagan, A.R., Nussbaum, H., Wollin, M., Winkley, J.H., and Norman, A., 1976, Br. J. Radiol., vol. 49, 430). Valid conclusions about the relative importance of time or dose-rate could not be based on this data. The reply, from one of the authors of the original paper, accepts many of the errata, and enumerates the changes which should be made. Replotting dose-treatment time and dose-dose rate does not however invalidate the conclusion that dose-rate is more important than time in analysing the risk of normal tissue injury. It is not claimed that the Strandqvist separation line in the dose-dose rate plane is better than in the dose-time plane. An improved definition of a region of low injury risk is given by a horizontal line at 4500 rad maximum dose and a vertical line at 60 rad/h maximum dose-rate on the dose-dose rate plot. Dose-rate is expected to be more important than time as a modifying factor of dose, both on the basis of radiobiological data and of clinical experience. Radiotherapists must balance the risks of radiotherapy-tumour recurrence with those of normal tissue injury, and increased attention should therefore be paid to regions of high and low dose-rate. (U.K.)

Salvage high-dose-rate interstitial brachytherapy for locally recurrent rectal cancer

Energy Technology Data Exchange (ETDEWEB)

Pellizzon, Antonio Cassio Assis, E-mail: acapellizzon@hcancer.org.br [A.C. Camargo Cancer Center, Sao Paulo, SP (Brazil). Departamento de Radioterapia

2016-05-15

For tumors of the lower third of the rectum, the only safe surgical procedure is abdominal-perineal resection. High-dose-rate interstitial brachytherapy is a promising treatment for local recurrence of previously irradiated lower rectal cancer, due to the extremely high concentrated dose delivered to the tumor and the sparing of normal tissue, when compared with a course of external beam radiation therapy. (author)

Comparison of half-dose and full-dose gadolinium MR contrast on the enhancement of bone and soft tissue tumors

Energy Technology Data Exchange (ETDEWEB)

Costelloe, Colleen M. [University of Texas M. D. Anderson Cancer Center, Department of Diagnostic Radiology, Houston, Texas (United States); University of Texas M. D. Anderson Cancer Center, Houston, Texas (United States); Murphy, William A.; Haygood, Tamara M.; Kumar, Rajendra; McEnery, Kevin W.; Madewell, John E. [University of Texas M. D. Anderson Cancer Center, Department of Diagnostic Radiology, Houston, Texas (United States); Stafford, R.J. [University of Texas M. D. Anderson Cancer Center, Department of Imaging Physics, Houston, Texas (United States); Roy, Anjali [Cancer Treatment Centers of America Medical Diagnostic Imaging Group, Arizona (United States); Bassett, Roland L.; Harrell, Robyn K. [University of Texas M. D. Anderson Cancer Center, Department of Biostatistics, Houston, Texas (United States)

2011-03-15

To evaluate the effect of half-dose intravenous gadolinium contrast on the enhancement of bone and soft tissue tumors. This study is HIPAA compliant and informed consent was waived by the institutional review board. An institutional database search was performed over a 1-year period for patients with full- and half-dose MR examinations performed for musculoskeletal oncologic indications. Examination pairs that were identical with regard to field strength and presence or absence of fat saturation were included, resulting in 29 paired examinations. When multiple, the lesion that was best delineated and enhanced well on the first examination in the pair was chosen, yielding 17 bone and 12 soft tissue. Five musculoskeletal radiologists blinded to dosages were asked to assess for a difference in enhancement when comparing the lesion on both examinations and to rate the degree of difference on a three-point scale. They were also asked to identify the examination on which the lesion enhanced less (tallied as low dose). Results were analyzed with the exact binomial test. The readers perceived an enhancement difference in 41% (59/145) of studies (p = 0.03) and the majority were rated as ''mild'' (66%, 39/59). The readers did not accurately identify the low-dose examinations (54% correctly identified, 32/59, p = 0.60). Half-dose gadolinium enhancement of lesions could not be accurately distinguished from full-dose enhancement upon review of the same lesion imaged at both concentrations. (orig.)

Perioperative fractionated high-dose rate brachytherapy for malignant bone and soft tissue tumors

International Nuclear Information System (INIS)

Koizumi, Masahiko; Inoue, Takehiro; Yamazaki, Hideya; Teshima, Teruki; Tanaka, Eiichi; Yoshida, Ken; Imai, Atsushi; Shiomi, Hiroya; Kagawa, Kazufumi; Araki, Nobuto; Kuratsu, Shigeyuki; Uchida, Atsumasa; Inoue, Toshihiko

1999-01-01

Purpose: To investigate the viability of perioperative fractionated HDR brachytherapy for malignant bone and soft tissue tumors, analyzing the influence of surgical margin. Methods and Materials: From July 1992 through May 1996, 16 lesions of 14 patients with malignant bone and soft tissue tumors (3 liposarcomas, 3 MFHs, 2 malignant schwannomas, 2 chordomas, 1 osteosarcoma, 1 leiomyosarcoma, 1 epithelioid sarcoma, and 1 synovial sarcoma) were treated at the Osaka University Hospital. The patients' ages ranged from 14 to 72 years (median: 39 years). Treatment sites were the pelvis in 6 lesions, the upper limbs in 5, the neck in 4, and a lower limb in 1. The resection margins were classified as intracapsular in 5 lesions, marginal in 5, and wide in 6. Postoperative fractionated HDR brachytherapy was started on the 4th-13th day after surgery (median: 6th day). The total dose was 40-50 Gy/7-10 fr/ 4-7 day (bid) at 5 or 10 mm from the source. Follow-up periods were between 19 and 46 months (median: 30 months). Results: Local control rates were 75% at 1 year and 48% in 2 years, and ultimate local control was achieved in 8 (50%) of 16 lesions. Of the 8 uncontrolled lesions, 5 (63%) had intracapsular (macroscopically positive) resection margins, and all the 8 controlled lesions (100%) had marginal (microscopically positive) or wide (negative) margins. Of the total, 3 patients died of both tumor and metastasis, 3 of metastasis alone, 1 of tumor alone, and 7 showed no evidence of disease. Peripheral nerve palsy was seen in one case after this procedure, but no infection or delayed wound healing caused by tubing or irradiation has occurred. Conclusion: Perioperative fractionated HDR brachytherapy is safe, well tolerated, and applicable to marginal or wide surgical margin cases

Calculation of dose-rate conversion factors for external exposure to photons and electrons

International Nuclear Information System (INIS)

Kocher, D.C.

1978-01-01

Methods are presented for the calculation of dose-rate conversion factors for external exposure to photon and electron radiation from radioactive decay. A dose-rate conversion factor is defined as the dose-equivalent rate per unit radionuclide concentration. Exposure modes considered are immersion in contaminated air, immersion in contaminated water, and irradiation from a contaminated ground surface. For each radiation type and exposure mode, dose-rate conversion factors are derived for tissue-equivalent material at the body surface of an exposed individual. In addition, photon dose-rate conversion factors are estimated for 22 body organs. The calculations are based on the assumption that the exposure medium is infinite in extent and that the radionuclide concentration is uniform. The dose-rate conversion factors for immersion in contaminated air and water then follow from the requirement that all of the energy emitted in the radioactive decay is absorbed in the infinite medium. Dose-rate conversion factors for ground-surface exposure are calculated at a reference location above a smooth, infinite plane using the point-kernel integration method and known specific absorbed fractions for photons and electrons in air

Quantitative radiation dose-response relationships for normal tissues in man. II. Response of the salivary glands during radiotherapy

International Nuclear Information System (INIS)

Mossman, K.L.

1983-01-01

A quantitative dose-response curve for salivary gland function in patients during radiotherapy is presented. Salivary-function data used in this study were obtained from four previously published reports. All patients were treated with 60 Co teletherapy to the head and neck using conventional treatment techniques. Salivary dysfunction was determined at specific dose levels by comparing salivary flow rates before therapy with flow rates at specific dose intervals during radiotherapy up to a total dose of 6000 cGy. Fifty percent salivary dysfunction occurred after 1000 cGy and eighty percent dysfunction was observed by the end of the therapy course (6000 cGy). The salivary-function curve was also compared to the previously published dose-response curve for taste function. Comparisons of the two curves indicate that salivary dysfunction precedes taste loss and that the shapes of the dose-response curves are different. A new term, tissue tolerance ratio, defined as the ratio of responses of two tissues given the same radiation dose, was used to make the comparisons between gustatory and salivary gland tissue effects. Measurements of salivary gland function and analysis of dose-response curves may be useful in evaluating chemical modifiers of radiation response

Neutron organ dose and the influence of adipose tissue

Science.gov (United States)

Simpkins, Robert Wayne

Neutron fluence to dose conversion coefficients have been assessed considering the influences of human adipose tissue. Monte Carlo code MCNP4C was used to simulate broad parallel beam monoenergetic neutrons ranging in energy from thermal to 10 MeV. Simulated Irradiations were conducted for standard irradiation geometries. The targets were on gender specific mathematical anthropomorphic phantoms modified to approximate human adipose tissue distributions. Dosimetric analysis compared adipose tissue influence against reference anthropomorphic phantom characteristics. Adipose Male and Post-Menopausal Female Phantoms were derived introducing interstitial adipose tissue to account for 22 and 27 kg additional body mass, respectively, each demonstrating a Body Mass Index (BMI) of 30. An Adipose Female Phantom was derived introducing specific subcutaneous adipose tissue accounting for 15 kg of additional body mass demonstrating a BMI of 26. Neutron dose was shielded in the superficial tissues; giving rise to secondary photons which dominated the effective dose for Incident energies less than 100 keV. Adipose tissue impact on the effective dose was a 25% reduction at the anterior-posterior incidence ranging to a 10% increase at the lateral incidences. Organ dose impacts were more distinctive; symmetrically situated organs demonstrated a 15% reduction at the anterior-posterior Incidence ranging to a 2% increase at the lateral incidences. Abdominal or asymmetrically situated organs demonstrated a 50% reduction at the anterior-posterior incidence ranging to a 25% increase at the lateral incidences.

Evaluation of dose components for healthy tissue tolerance studies on dogs at the HFR Petten

International Nuclear Information System (INIS)

Watkins, P.; Moss, R.L.; Siefert, A.; Huiskamp, R.; Gavin, P.; Konijnenberg, M.

1993-01-01

Before the start of clinical trails of BNCT on glioma patients at the Petten reactor, certain preconditions must be determined. In particular the tolerance of healthy brain tissue exposed to the epithermal neutron beam requires investigation. In these studies, beagle dogs have been subjected to different levels of irradiation and 10 B, the latter in the form of BSH. To support this work a treatment planning tool is being developed to predict the various dose components within the treatment volume. A Monte Carlo code, MCNP, has been used to simulate the particle transport and to predict the different dose rate distributions. The doses rates generated by MCNP are manipulated with a processing code, TREAT, to give irradiation times, peak dose positions and to display the required data in a graphical format. This paper explains the basic methodology used in the system and a practical case is presented for one of the healthy tissue tolerance dogs. Doses, both physical and RBE weighted, have been produced for pre-treatment planning studies

Tank Z-361 dose rate calculations

International Nuclear Information System (INIS)

Richard, R.F.

1998-01-01

Neutron and gamma ray dose rates were calculated above and around the 6-inch riser of tank Z-361 located at the Plutonium Finishing Plant. Dose rates were also determined off of one side of the tank. The largest dose rate 0.029 mrem/h was a gamma ray dose and occurred 76.2 cm (30 in.) directly above the open riser. All other dose rates were negligible. The ANSI/ANS 1991 flux to dose conversion factor for neutrons and photons were used in this analysis. Dose rates are reported in units of mrem/h with the calculated uncertainty shown within the parentheses

Bayesian estimation of dose rate effectiveness

International Nuclear Information System (INIS)

Arnish, J.J.; Groer, P.G.

2000-01-01

A Bayesian statistical method was used to quantify the effectiveness of high dose rate 137 Cs gamma radiation at inducing fatal mammary tumours and increasing the overall mortality rate in BALB/c female mice. The Bayesian approach considers both the temporal and dose dependence of radiation carcinogenesis and total mortality. This paper provides the first direct estimation of dose rate effectiveness using Bayesian statistics. This statistical approach provides a quantitative description of the uncertainty of the factor characterising the dose rate in terms of a probability density function. The results show that a fixed dose from 137 Cs gamma radiation delivered at a high dose rate is more effective at inducing fatal mammary tumours and increasing the overall mortality rate in BALB/c female mice than the same dose delivered at a low dose rate. (author)

Integral dose and evaluation of irradiated tissue volume

International Nuclear Information System (INIS)

Sivachenko, T.P.; Kalina, V.K.; Belous, A.K.; Gaevskij, V.I.

1984-01-01

Two parameters having potentialities of radiotherapy planning improvement are under consideration. One of these two parameters in an integral dose. An efficiency of application of special tables for integral dose estimation is noted. These tables were developed by the Kiev Physician Improvement Institute and the Cybernetics Institute of the Ukrainian SSR Academy of Science. The meaning of the term of ''irradiated tissue volume'' is specified, and the method of calculation of the irradiated tissue effective mass is considered. It is possible to evaluate with higher accuracy tolerance doses taking into account the irradiated mass

Dose/dose-rate responses of shrimp larvae to UV-B radiation

International Nuclear Information System (INIS)

Damkaer, D.M.

1981-01-01

Previous work indicated dose-rate thresholds in the effects of UV-B on the near-surface larvae of three shrimp species. Additional observations suggest that the total dose response varies with dose-rate. Below 0.002 Wm -2 sub([DNA]) irradiance no significant effect is noted in activity, development, or survival. Beyond that dose-rate threshold, shrimp larvae are significantly affected if the total dose exceeds about 85 Jm -2 sub([DNA]). Predictions cannot be made without both the dose-rate and the dose. These dose/dose-rate thresholds are compared to four-year mean dose/dose-rate solar UV-B irradiances at the experimental site, measured at the surface and calculated for 1 m depth. The probability that the shrimp larvae would receive lethal irradiance is low for the first half of the season of surface occurrence, even with a 44% increase in damaging UV radiation. (orig.)

Dose/dose-rate responses of shrimp larvae to UV-B radiation

Energy Technology Data Exchange (ETDEWEB)

Damkaer, D.M.; Dey, D.B.; Heron, G.A.

1981-01-01

Previous work indicated dose-rate thresholds in the effects of UV-B on the near-surface larvae of three shrimp species. Additional observations suggest that the total dose response varies with dose-rate. Below 0.002 Wm/sup -2/sub((DNA)) irradiance no significant effect is noted in activity, development, or survival. Beyond that dose-rate threshold, shrimp larvae are significantly affected if the total dose exceeds about 85 Jm/sup -2/sub((DNA)). Predictions cannot be made without both the dose-rate and the dose. These dose/dose-rate thresholds are compared to four-year mean dose/dose-rate solar UV-B irradiances at the experimental site, measured at the surface and calculated for 1 m depth. The probability that the shrimp larvae would receive lethal irradiance is low for the first half of the season of surface occurrence, even with a 44% increase in damaging UV radiation.

Non-uniform dwell times in line source high dose rate brachytherapy: physical and radiobiological considerations

International Nuclear Information System (INIS)

Jones, B.; Tan, L.T.; Freestone, G.; Bleasdale, C.; Myint, S.; Littler, J.

1994-01-01

The ability to vary source dwell times in high dose rate (HDR) brachytherapy allows for the use of non-uniform dwell times along a line source. This may have advantages in the radical treatment of tumours depending on individual tumour geometry. This study investigates the potential improvements in local tumour control relative to adjacent normal tissue isoeffects when intratumour source dwell times are increased along the central portion of a line source (technique A) in radiotherapy schedules which include a relatively small component of HDR brachytherapy. Such a technique is predicted to increase the local control for tumours of diameters ranging between 2 cm and 4 cm by up to 11% compared with a technique in which there are uniform dwell times along the line source (technique B). There is no difference in the local control rates for the two techniques when used to treat smaller tumours. Normal tissue doses are also modified by the technique used. Technique A produces higher normal tissue doses at points perpendicular to the centre of the line source and lower dose at points nearer the ends of the line source if the prescription point is not in the central plane of the line source. Alternatively, if the dose is prescribed at a point in the central plane of the line source, the dose at all the normal tissue points are lower when technique A is used. (author)

SU-E-T-501: Normal Tissue Toxicities of Pulsed Low Dose Rate Radiotherapy and Conventional Radiotherapy: An in Vivo Total Body Irradiation Study

Energy Technology Data Exchange (ETDEWEB)

Cvetkovic, D; Zhang, P; Wang, B; Chen, L; Ma, C [Fox Chase Cancer Center, Philadelphia, PA (United States)

2014-06-01

Purpose: Pulsed low dose rate radiotherapy (PLDR) is a re-irradiation technique for therapy of recurrent cancers. We have previously shown a significant difference in the weight and survival time between the mice treated with conventional radiotherapy (CRT) and PLDR using total body irradiation (TBI). The purpose of this study was to investigate the in vivo effects of PLDR on normal mouse tissues.Materials and Methods: Twenty two male BALB/c nude mice, 4 months of age, were randomly assigned into a PLDR group (n=10), a CRT group (n=10), and a non-irradiated control group (n=2). The Siemens Artiste accelerator with 6 MV photon beams was used. The mice received a total of 18Gy in 3 fractions with a 20day interval. The CRT group received the 6Gy dose continuously at a dose rate of 300 MU/min. The PLDR group was irradiated with 0.2Gyx20 pulses with a 3min interval between the pulses. The mice were weighed thrice weekly and sacrificed 2 weeks after the last treatment. Brain, heart, lung, liver, spleen, gastrointestinal, urinary and reproductive organs, and sternal bone marrow were removed, formalin-fixed, paraffin-embedded and stained with H and E. Morphological changes were observed under a microscope. Results: Histopathological examination revealed atrophy in several irradiated organs. The degree of atrophy was mild to moderate in the PLDR group, but severe in the CRT group. The most pronounced morphological abnormalities were in the immune and hematopoietic systems, namely spleen and bone marrow. Brain hemorrhage was seen in the CRT group, but not in the PLDR group. Conclusions: Our results showed that PLDR induced less toxicity in the normal mouse tissues than conventional radiotherapy for the same dose and regimen. Considering that PLDR produces equivalent tumor control as conventional radiotherapy, it would be a good modality for treatment of recurrent cancers.

Lymphoid cell kinetics under continuous low dose-rate gamma irradiation: A comparison study

Science.gov (United States)

Foster, B. R.

1975-01-01

A comparison study was conducted of the effects of continuous low dose-rate gamma irradiation on cell population kinetics of lymphoid tissue (white pulp) of the mouse spleen with findings as they relate to the mouse thymus. Experimental techniques employed included autoradiography and specific labeling with tritiated thymidine (TdR-(h-3)). The problem studied involved the mechanism of cell proliferation of lymphoid tissue of the mouse spleen and thymus under the stress of continuous irradiation at a dose rate of 10 roentgens (R) per day for 105 days (15 weeks). The aim was to determine whether or not a steady state or near-steady state of cell population could be established for this period of time, and what compensatory mechanisms of cell population were involved.

Four-dimensional dose distributions of step-and-shoot IMRT delivered with real-time tumor tracking for patients with irregular breathing: Constant dose rate vs dose rate regulation

International Nuclear Information System (INIS)

Yang Xiaocheng; Han-Oh, Sarah; Gui Minzhi; Niu Ying; Yu, Cedric X.; Yi Byongyong

2012-01-01

Purpose: Dose-rate-regulated tracking (DRRT) is a tumor tracking strategy that programs the MLC to track the tumor under regular breathing and adapts to breathing irregularities during delivery using dose rate regulation. Constant-dose-rate tracking (CDRT) is a strategy that dynamically repositions the beam to account for intrafractional 3D target motion according to real-time information of target location obtained from an independent position monitoring system. The purpose of this study is to illustrate the differences in the effectiveness and delivery accuracy between these two tracking methods in the presence of breathing irregularities. Methods: Step-and-shoot IMRT plans optimized at a reference phase were extended to remaining phases to generate 10-phased 4D-IMRT plans using segment aperture morphing (SAM) algorithm, where both tumor displacement and deformation were considered. A SAM-based 4D plan has been demonstrated to provide better plan quality than plans not considering target deformation. However, delivering such a plan requires preprogramming of the MLC aperture sequence. Deliveries of the 4D plans using DRRT and CDRT tracking approaches were simulated assuming the breathing period is either shorter or longer than the planning day, for 4 IMRT cases: two lung and two pancreatic cases with maximum GTV centroid motion greater than 1 cm were selected. In DRRT, dose rate was regulated to speed up or slow down delivery as needed such that each planned segment is delivered at the planned breathing phase. In CDRT, MLC is separately controlled to follow the tumor motion, but dose rate was kept constant. In addition to breathing period change, effect of breathing amplitude variation on target and critical tissue dose distribution is also evaluated. Results: Delivery of preprogrammed 4D plans by the CDRT method resulted in an average of 5% increase in target dose and noticeable increase in organs at risk (OAR) dose when patient breathing is either 10% faster or

HDRMC, an accelerated Monte Carlo dose calculator for high dose rate brachytherapy with CT-compatible applicators

Energy Technology Data Exchange (ETDEWEB)

Chibani, Omar, E-mail: omar.chibani@fccc.edu; C-M Ma, Charlie [Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111 (United States)

2014-05-15

Purpose: To present a new accelerated Monte Carlo code for CT-based dose calculations in high dose rate (HDR) brachytherapy. The new code (HDRMC) accounts for both tissue and nontissue heterogeneities (applicator and contrast medium). Methods: HDRMC uses a fast ray-tracing technique and detailed physics algorithms to transport photons through a 3D mesh of voxels representing the patient anatomy with applicator and contrast medium included. A precalculated phase space file for the{sup 192}Ir source is used as source term. HDRM is calibrated to calculated absolute dose for real plans. A postprocessing technique is used to include the exact density and composition of nontissue heterogeneities in the 3D phantom. Dwell positions and angular orientations of the source are reconstructed using data from the treatment planning system (TPS). Structure contours are also imported from the TPS to recalculate dose-volume histograms. Results: HDRMC was first benchmarked against the MCNP5 code for a single source in homogenous water and for a loaded gynecologic applicator in water. The accuracy of the voxel-based applicator model used in HDRMC was also verified by comparing 3D dose distributions and dose-volume parameters obtained using 1-mm{sup 3} versus 2-mm{sup 3} phantom resolutions. HDRMC can calculate the 3D dose distribution for a typical HDR cervix case with 2-mm resolution in 5 min on a single CPU. Examples of heterogeneity effects for two clinical cases (cervix and esophagus) were demonstrated using HDRMC. The neglect of tissue heterogeneity for the esophageal case leads to the overestimate of CTV D90, CTV D100, and spinal cord maximum dose by 3.2%, 3.9%, and 3.6%, respectively. Conclusions: A fast Monte Carlo code for CT-based dose calculations which does not require a prebuilt applicator model is developed for those HDR brachytherapy treatments that use CT-compatible applicators. Tissue and nontissue heterogeneities should be taken into account in modern HDR

Simple approximation for estimating centerline gamma absorbed dose rates due to a continuous Gaussian plume

International Nuclear Information System (INIS)

Overcamp, T.J.; Fjeld, R.A.

1987-01-01

A simple approximation for estimating the centerline gamma absorbed dose rates due to a continuous Gaussian plume was developed. To simplify the integration of the dose integral, this approach makes use of the Gaussian cloud concentration distribution. The solution is expressed in terms of the I1 and I2 integrals which were developed for estimating long-term dose due to a sector-averaged Gaussian plume. Estimates of tissue absorbed dose rates for the new approach and for the uniform cloud model were compared to numerical integration of the dose integral over a Gaussian plume distribution

High-dose-rate brachytherapy alone post-hysterectomy for endometrial cancer

International Nuclear Information System (INIS)

MacLeod, Craig; Fowler, Allan; Duval, Peter; D'Costa, Ieta; Dalrymple, Chris; Firth, Ian; Elliott, Peter; Atkinson, Ken; Carter, Jonathan

1998-01-01

Purpose: To evaluate the outcome of post-hysterectomy adjuvant vaginal high-dose-rate (HDR) brachytherapy. Methods and Materials: A retrospective analysis was performed on a series of 143 patients with endometrial cancer treated with HDR brachytherapy alone post-hysterectomy from 1985 to June 1993. Of these patients, 141 received 34 Gy in four fractions prescribed to the vaginal mucosa in a 2-week period. The median follow-up was 6.9 years. Patients were analyzed for treatment parameters, survival, local recurrence, distant relapse, and toxicity. Results: Five-year relapse free survival and overall survival was 100% and 88% for Stage 1A, 98% and 94% for Stage IB, 100% and 86% for Stage IC, and 92% and 92% for Stage IIA. The overall vaginal recurrence rate was 1.4%. The overall late-toxicity rate was low, and no RTOG grade 3, 4, or 5 complications were recorded. Conclusion: These results are similar to reported international series that have used either low-dose-rate or HDR brachytherapy. The biological effective dose was low for both acute and late responding tissues compared with some of the HDR brachytherapy series, and supports using this lower dose and possibly decreasing late side-effects with no apparent increased risk of vaginal recurrence

Tissue doses in X-ray examinations of osteoarticular system

International Nuclear Information System (INIS)

Rabkin, I.Kh.; Stavitskij, R.V.; Blinov, N.N.; Vasil'ev, Yu.D.

1985-01-01

The X-ray method in diagnosis of the osteoarticular system disease is described. Problems on tissue dose distribution in X-ray examinations of a skeleton, a skull, humeral articulation, cervical, thoracic and lumbar vertebrae, hip joint, hipbones are considered. The values of specific tissue doses in roentgenography of the osteoarticular system are given

Outdoor γ-ray dose rate in Shariki Village and environmental factors affecting outdoor γ-ray dose rate in IES

International Nuclear Information System (INIS)

Iyogi, Takashi; Hisamatsu, Shun'ichi; Inaba, Jiro

2000-01-01

Previously, we surveyed the outdoor γ-ray dose rate throughout Aomori Prefecture from 1992 to 1995, and found an annual mean dose rate of 51 nGy h -1 . Relatively high dose rates were also observed in several areas (municipalities) of the survey locations. In this study, we examined the detailed distribution of the γ-ray dose rate in one such high dose rate area, Shariki Village. Glass dosemeters were used for the monitoring of cumulative γ-ray dose rate at 10 locations in the village. The dose rate from each radioactive nuclide in the ground at the monitoring locations was measured by using an in situ γ-ray spectrometer with a Ge detector. The results obtained with the glass dosemeters showed that the γ-ray dose rates in Shariki Village varied from 49 to 55 nGy h -1 . Although the dose rates were generally higher than the mean dose in Aomori Prefecture (1992-1995), the rates were lower than other high dose rate areas which had already been measured. The in situ γ-ray spectrometry revealed that these relatively high dose rates were mainly caused by 40 K and Th series radionuclides in the village. The effect of meteorological conditions on the γ-ray dose rate was studied at a monitoring station in the IES site. The dose rate was continuously recorded by a DBM NaI(Tl) scintillation detector system. The mean dose rate obtained when precipitation was sensed was 27 nGy h -1 and higher than when no precipitation was sensed (25 nGy h -1 ). (author)

Outdoor γ-ray dose rate in Mutsu city and environmental factors affecting outdoor γ-ray dose rate in IES

International Nuclear Information System (INIS)

Iyogi, Takashi; Hisamatsu, Shun'ichi; Inaba, Jiro

2001-01-01

Previously, we surveyed outdoor γ-ray dose rates throughout Aomori Prefecture from 1992 to 1995, and found a mean annual dose rate of 28 nGy h -1 . Relatively high dose rates were also observed in several areas (municipalities) of the survey locations. In this study, we examined the detailed distribution of the γ-ray dose rate in one such high dose rate area, Mutsu City. Glass dosemeters were used for the monitoring of cumulative γ-ray dose rate at 10 locations in the city. The dose rate from each radioactive nuclide in the ground at the monitoring locations was measured by using an in situ γ-ray spectrometer with a Ge detector. The results obtained with the glass dosemeters showed that the γ-ray dose rates in Mutsu City varied from 17 to 32 nGy h -1 . Although the dose rates were almost the same as the mean dose in Aomori Prefecture (1992-1995), the rates were lower than other high dose rate areas which had already been measured. The in situ γ-ray spectrometry revealed that these relatively high dose rates were mainly caused by 40 K and Th series radionuclides in the local ground. The effect of meteorological conditions on the γ-ray dose rate was studied at a monitoring station in the IES site. The dose rate was continuously recorded by a DBM NaI(Tl) scintillation detector system. The mean dose rate obtained when precipitation was sensed was 26 nGy h -1 and higher than when no precipitation was sensed (24 nGy h -1 ). (author)

Spontaneous mutation rates and the rate-doubling dose

International Nuclear Information System (INIS)

Von Borstel, R.C.; Moustaccki, E.; Latarjet, R.

1978-01-01

The amount of radiation required to double the frequency of mutations or tumours over the rate of those that occur spontaneously is called the rate-doubling dose. An equivalent concept has been proposed for exposure to other environmental mutagens. The doubling dose concept is predicated on the assumption that all human populations have the same spontaneous mutation rate, and that this spontaneous mutation rate is known. It is now established for prokaryotes and lower eukaryotes that numerous genes control the spontaneous mutation rate, and it is likely that the same is true for human cells as well. Given that the accepted mode of evolution of human populatons is from small, isolated groups of individuals, it seems likely that each population would have a different spontaneous mutation rate. Given that a minimum of twenty genes control or affect the spontaneous mutation rate, and that each of these in turn is susceptible to spontaneously arising or environmentally induced mutations, it seems likely that every individual within a population (except for siblings from identical multiple births) will have a unique spontaneous mutation rate. If each individual in a population does have a different spontaneous mutation rate, the doubling dose concept, in rigorous terms, is fallacious. Therefore, as with other concepts of risk evaluation, the doubling dose concept is subject to criticism. Nevertheless, until we know individual spontaneous mutation rates with precision, and can evaluate risks based on this information, the doubling dose concept has a heuristic value and is needed for practical assessment of risks for defined populations. (author)

Effects of proton radiation dose, dose rate and dose fractionation on hematopoietic cells in mice

International Nuclear Information System (INIS)

Ware, J.H.; Rusek, A.; Sanzari, J.; Avery, S.; Sayers, C.; Krigsfeld, G.; Nuth, M.; Wan, X.S.; Kennedy, A.R.

2010-01-01

The present study evaluated the acute effects of radiation dose, dose rate and fractionation as well as the energy of protons in hematopoietic cells of irradiated mice. The mice were irradiated with a single dose of 51.24 MeV protons at a dose of 2 Gy and a dose rate of 0.05-0.07 Gy/min or 1 GeV protons at doses of 0.1, 0.2, 0.5, 1, 1.5 and 2 Gy delivered in a single dose at dose rates of 0.05 or 0.5 Gy/min or in five daily dose fractions at a dose rate of 0.05 Gy/min. Sham-irradiated animals were used as controls. The results demonstrate a dose-dependent loss of white blood cells (WBCs) and lymphocytes by up to 61% and 72%, respectively, in mice irradiated with protons at doses up to 2 Gy. The results also demonstrate that the dose rate, fractionation pattern and energy of the proton radiation did not have significant effects on WBC and lymphocyte counts in the irradiated animals. These results suggest that the acute effects of proton radiation on WBC and lymphocyte counts are determined mainly by the radiation dose, with very little contribution from the dose rate (over the range of dose rates evaluated), fractionation and energy of the protons.

Effects of proton radiation dose, dose rate and dose fractionation on hematopoietic cells in mice.

Science.gov (United States)

Ware, J H; Sanzari, J; Avery, S; Sayers, C; Krigsfeld, G; Nuth, M; Wan, X S; Rusek, A; Kennedy, A R

2010-09-01

The present study evaluated the acute effects of radiation dose, dose rate and fractionation as well as the energy of protons in hematopoietic cells of irradiated mice. The mice were irradiated with a single dose of 51.24 MeV protons at a dose of 2 Gy and a dose rate of 0.05-0.07 Gy/min or 1 GeV protons at doses of 0.1, 0.2, 0.5, 1, 1.5 and 2 Gy delivered in a single dose at dose rates of 0.05 or 0.5 Gy/min or in five daily dose fractions at a dose rate of 0.05 Gy/min. Sham-irradiated animals were used as controls. The results demonstrate a dose-dependent loss of white blood cells (WBCs) and lymphocytes by up to 61% and 72%, respectively, in mice irradiated with protons at doses up to 2 Gy. The results also demonstrate that the dose rate, fractionation pattern and energy of the proton radiation did not have significant effects on WBC and lymphocyte counts in the irradiated animals. These results suggest that the acute effects of proton radiation on WBC and lymphocyte counts are determined mainly by the radiation dose, with very little contribution from the dose rate (over the range of dose rates evaluated), fractionation and energy of the protons.

Dosimetric Coverage of the Prostate, Normal Tissue Sparing, and Acute Toxicity with High-Dose-Rate Brachytherapy for Large Prostate Volumes

Directory of Open Access Journals (Sweden)

George Yang

2015-06-01

Full Text Available ABSTRACTPurposeTo evaluate dosimetric coverage of the prostate, normal tissue sparing, and acute toxicity with HDR brachytherapy for large prostate volumes.Materials and MethodsOne hundred and two prostate cancer patients with prostate volumes >50 mL (range: 5-29 mL were treated with high-dose-rate (HDR brachytherapy ± intensity modulated radiation therapy (IMRT to 4,500 cGy in 25 daily fractions between 2009 and 2013. HDR brachytherapy monotherapy doses consisted of two 1,350-1,400 cGy fractions separated by 2-3 weeks, and HDR brachytherapy boost doses consisted of two 950-1,150 cGy fractions separated by 4 weeks. Twelve of 32 (38% unfavorable intermediate risk, high risk, and very high risk patients received androgen deprivation therapy. Acute toxicity was graded according to the Common Terminology Criteria for Adverse Events (CTCAE version 4.ResultsMedian follow-up was 14 months. Dosimetric goals were achieved in over 90% of cases. Three of 102 (3% patients developed Grade 2 acute proctitis. No variables were significantly associated with Grade 2 acute proctitis. Seventeen of 102 (17% patients developed Grade 2 acute urinary retention. American Urological Association (AUA symptom score was the only variable significantly associated with Grade 2 acute urinary retention (p=0.04. There was no ≥ Grade 3 acute toxicity.ConclusionsDosimetric coverage of the prostate and normal tissue sparing were adequate in patients with prostate volumes >50 mL. Higher pre-treatment AUA symptom scores increased the relative risk of Grade 2 acute urinary retention. However, the overall incidence of acute toxicity was acceptable in patients with large prostate volumes.

Dosimetric coverage of the prostate, normal tissue sparing, and acute toxicity with high-dose-rate brachytherapy for large prostate volumes

Energy Technology Data Exchange (ETDEWEB)

Yang, George; Strom, Tobin J.; Shrinath, Kushagra; Mellon, Eric A.; Fernandez, Daniel C.; Biagioli, Matthew C. [Department of Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL (United States); Wilder, Richard B., E-mail: mcbiagioli@yahoo.com [Cancer Treatment Centers of America, Newnan, GA (United States)

2015-05-15

Purpose: to evaluate dosimetric coverage of the prostate, normal tissue sparing, and acute toxicity with HDR brachytherapy for large prostate volumes. Materials and methods: one hundred and two prostate cancer patients with prostate volumes >50 mL (range: 5-29 mL) were treated with high-dose-rate (HDR) brachytherapy ± intensity modulated radiation therapy (IMRT) to 4,500 cGy in 25 daily fractions between 2009 and 2013. HDR brachytherapy monotherapy doses consisted of two 1,350-1,400 cGy fractions separated by 2-3 weeks, and HDR brachytherapy boost doses consisted of two 950-1,150 cGy fractions separated by 4 weeks. Twelve of 32 (38%) unfavorable intermediate risk, high risk, and very high risk patients received androgen deprivation therapy. Acute toxicity was graded according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4. Results: median follow-up was 14 months. Dosimetric goals were achieved in over 90% of cases. Three of 102 (3%) patients developed Grade 2 acute proctitis. No variables were significantly associated with Grade 2 acute proctitis. Seventeen of 102 (17%) patients developed Grade 2 acute urinary retention. American Urological Association (AUA) symptom score was the only variable significantly associated with Grade 2 acute urinary retention (p-0.04). There was no ≥ Grade 3 acute toxicity. Conclusions: dosimetric coverage of the prostate and normal tissue sparing were adequate in patients with prostate volumes >50 mL. Higher pre-treatment AUA symptom scores increased the relative risk of Grade 2 acute urinary retention. However, the overall incidence of acute toxicity was acceptable in patients with large prostate volumes. (author)

The difference of scoring dose to water or tissues in Monte Carlo dose calculations for low energy brachytherapy photon sources.

Science.gov (United States)

Landry, Guillaume; Reniers, Brigitte; Pignol, Jean-Philippe; Beaulieu, Luc; Verhaegen, Frank

2011-03-01

The goal of this work is to compare D(m,m) (radiation transported in medium; dose scored in medium) and D(w,m) (radiation transported in medium; dose scored in water) obtained from Monte Carlo (MC) simulations for a subset of human tissues of interest in low energy photon brachytherapy. Using low dose rate seeds and an electronic brachytherapy source (EBS), the authors quantify the large cavity theory conversion factors required. The authors also assess whether ap plying large cavity theory utilizing the sources' initial photon spectra and average photon energy induces errors related to spatial spectral variations. First, ideal spherical geometries were investigated, followed by clinical brachytherapy LDR seed implants for breast and prostate cancer patients. Two types of dose calculations are performed with the GEANT4 MC code. (1) For several human tissues, dose profiles are obtained in spherical geometries centered on four types of low energy brachytherapy sources: 125I, 103Pd, and 131Cs seeds, as well as an EBS operating at 50 kV. Ratios of D(w,m) over D(m,m) are evaluated in the 0-6 cm range. In addition to mean tissue composition, compositions corresponding to one standard deviation from the mean are also studied. (2) Four clinical breast (using 103Pd) and prostate (using 125I) brachytherapy seed implants are considered. MC dose calculations are performed based on postimplant CT scans using prostate and breast tissue compositions. PTV D90 values are compared for D(w,m) and D(m,m). (1) Differences (D(w,m)/D(m,m)-1) of -3% to 70% are observed for the investigated tissues. For a given tissue, D(w,m)/D(m,m) is similar for all sources within 4% and does not vary more than 2% with distance due to very moderate spectral shifts. Variations of tissue composition about the assumed mean composition influence the conversion factors up to 38%. (2) The ratio of D90(w,m) over D90(m,m) for clinical implants matches D(w,m)/D(m,m) at 1 cm from the single point sources, Given

Consequences of the exposure at low dose rates-contribution of animal experimentation. Consequences de l'exposition aux faibles debits de dose. Apport de l'experimentation animale

Energy Technology Data Exchange (ETDEWEB)

Masse, R. (CEA Centre d' Etudes de Fontenay-aux-Roses, 92 (FR). Direction des Sciences du Vivant)

1990-01-01

The exposure of laboratory animals to the various types of radiations will induce cancers in relation with the tissue absorbed doses. The shape of the dose-effet relationship is most variable. It is important to distinguish which tumours are comparable to human tumours. Those showing more analogies answer but seldom to the classical lineo-quadratic relationship; however, a strong attenuation of induction is demonstrated at low dose rates. Quasi-threshold relationships are seen after the exposure of some tissues to high-LET radiations. These observations question the validity of generalizing the radiobiologists' dual action theory, setting the origin of the dose-effect relationship in the induction of events within the DNA molecule. There is an alternative in the cellular collaboration events; it assumes that the effectiveness per dose unit decreases constantly as an inverse function of the dose rate.

RadNuc: a graphical user interface to deliver dose rate patterns encountered in nuclear medicine with a 137Cs irradiator.

Science.gov (United States)

Pasternack, Jordan B; Howell, Roger W

2013-02-01

The temporal variations in absorbed dose rates to organs and tissues in the body are very large in diagnostic and therapeutic nuclear medicine. The response of biological endpoints of relevance to radiation safety and therapeutic efficacy is generally modulated by dose rate. Therefore, it is important to understand how the complex dose rate patterns encountered in nuclear medicine impact relevant biological responses. Accordingly, a graphical user interface (GUI) was created to control a cesium-137 irradiator to deliver such dose rate patterns. Visual Basic 6.0 was used to create a user-friendly GUI to control the dose rate by varying the thickness of a mercury attenuator. The GUI facilitates the delivery of a number of dose rate patterns including constant, exponential increase or decrease, and multi-component exponential. Extensive visual feedback is provided by the GUI during both the planning and delivery stages. The GUI controlled irradiator can achieve a maximum dose rate of 40 cGy/h and a minimum dose rate of 0.01 cGy/h. Addition of machined lead blocks can be used to further reduce the minimum dose rate to 0.0001 cGy/h. Measured dose rate patterns differed from programmed dose rate patterns in total dose by 3.2% to 8.4%. The GUI controlled irradiator is able to accurately create dose rate patterns encountered in nuclear medicine and other related fields. This makes it an invaluable tool for studying the effects of chronic constant and variable low dose rates on biological tissues in the contexts of both radiation protection and clinical administration of internal radionuclides. Copyright © 2013 Elsevier Inc. All rights reserved.

Advanced Computational Approaches for Characterizing Stochastic Cellular Responses to Low Dose, Low Dose Rate Exposures

Energy Technology Data Exchange (ETDEWEB)

Scott, Bobby, R., Ph.D.

2003-06-27

applications of NEOTRANS2, indicate that nonlinear threshold-type, dose-response relationships for excess stochastic effects (problematic nonlethal mutations, neoplastic transformation) should be expected after exposure to low linear energy transfer (LET) gamma rays or gamma rays in combination with high-LET alpha radiation. Similar thresholds are expected for low-dose-rate low-LET beta irradiation. We attribute the thresholds to low-dose, low-LET radiation induced protection against spontaneous mutations and neoplastic transformations. The protection is presumed mainly to involve selective elimination of problematic cells via apoptosis. Low-dose, low-LET radiation is presumed to trigger wide-area cell signaling, which in turn leads to problematic bystander cells (e.g., mutants, neoplastically transformed cells) selectively undergoing apoptosis. Thus, this protective bystander effect leads to selective elimination of problematic cells (a tissue cleansing process in vivo). However, this protective bystander effects is a different process from low-dose stimulation of the immune system. Low-dose, low-LET radiation stimulation of the immune system may explain why thresholds for inducing excess cancer appear much larger (possibly more than 100-fold larger) than thresholds for inducing excess mutations and neoplastic transformations, when the dose rate is low. For ionizing radiation, the current risk assessment paradigm is such that the relative risk (RR) is always ¡Ý 1, no matter how small the dose. Our research results indicate that for low-dose or low-dose-rate, low-LET irradiation, RR < 1 may be more the rule than the exception. Directly tied to the current RR paradigm are the billion-dollar cleanup costs for radionuclide-contaminated DOE sites. Our research results suggest that continued use of the current RR paradigm for which RR ¡Ý 1 could cause more harm than benefit to society (e.g., by spreading unwarranted fear about phantom excess risks associated with low-dose low

A new tissue segmentation method to calculate 3D dose in small animal radiation therapy.

Science.gov (United States)

Noblet, C; Delpon, G; Supiot, S; Potiron, V; Paris, F; Chiavassa, S

2018-02-26

In pre-clinical animal experiments, radiation delivery is usually delivered with kV photon beams, in contrast to the MV beams used in clinical irradiation, because of the small size of the animals. At this medium energy range, however, the contribution of the photoelectric effect to absorbed dose is significant. Accurate dose calculation therefore requires a more detailed tissue definition because both density (ρ) and elemental composition (Z eff ) affect the dose distribution. Moreover, when applied to cone beam CT (CBCT) acquisitions, the stoichiometric calibration of HU becomes inefficient as it is designed for highly collimated fan beam CT acquisitions. In this study, we propose an automatic tissue segmentation method of CBCT imaging that assigns both density (ρ) and elemental composition (Z eff ) in small animal dose calculation. The method is based on the relationship found between CBCT number and ρ*Z eff product computed from known materials. Monte Carlo calculations were performed to evaluate the impact of ρZ eff variation on the absorbed dose in tissues. These results led to the creation of a tissue database composed of artificial tissues interpolated from tissue values published by the ICRU. The ρZ eff method was validated by measuring transmitted doses through tissue substitute cylinders and a mouse with EBT3 film. Measurements were compared to the results of the Monte Carlo calculations. The study of the impact of ρZ eff variation over the range of materials, from ρZ eff  = 2 g.cm - 3 (lung) to 27 g.cm - 3 (cortical bone) led to the creation of 125 artificial tissues. For tissue substitute cylinders, the use of ρZ eff method led to maximal and average relative differences between the Monte Carlo results and the EBT3 measurements of 3.6% and 1.6%. Equivalent comparison for the mouse gave maximal and average relative differences of 4.4% and 1.2%, inside the 80% isodose area. Gamma analysis led to a 94.9% success rate in the 10% isodose

High dose rate (HDR) and low dose rate (LDR) interstitial irradiation (IRT) of the rat spinal cord

International Nuclear Information System (INIS)

Pop, Lucas A.M.; Plas, Mirjam van der; Skwarchuk, Mark W.; Hanssen, Alex E.J.; Kogel, Albert J. van der

1997-01-01

Purpose: To describe a newly developed technique to study radiation tolerance of rat spinal cord to continuous interstitial irradiation (IRT) at different dose rates. Material and methods: Two parallel catheters are inserted just laterally on each side of the vertebral bodies from the level of Th 10 to L 4 . These catheters are afterloaded with two 192 Ir wires of 4 cm length each (activity 1-2.3 mCi/cm) for the low dose rate (LDR) IRT or connected to the HDR micro-Selectron for the high dose rate (HDR) IRT. Spinal cord target volume is located at the level of Th 12 -L 2 . Due to the rapid dose fall-off around the implanted sources, a dose inhomogeneity across the spinal cord thickness is obtained in the dorso-ventral direction. Using the 100% reference dose (rate) at the ventral side of the spinal cord to prescribe the dose, experiments have been carried out to obtain complete dose response curves at average dose rates of 0.49, 0.96 and 120 Gy/h. Paralysis of the hind-legs after 5-6 months and histopathological examination of the spinal cord of each irradiated rat are used as experimental endpoints. Results: The histopathological damage seen after irradiation is clearly reflected the inhomogeneous dose distribution around the implanted catheters, with the damage predominantly located in the dorsal tract of the cord or dorsal roots. With each reduction in average dose rate, spinal cord radiation tolerance is significantly increased. When the dose is prescribed at the 100% reference dose rate, the ED 50 (induction of paresis in 50% of the animals) for the HDR-IRT is 17.3 Gy. If the average dose rate is reduced from 120 Gy/h to 0.96 or 0.49 Gy/h, a 2.9- or 4.7-fold increase in the ED 50 values to 50.3 Gy and 80.9 Gy is observed; for the dose prescribed at the 150% reference dose rate (dorsal side of cord) ED 50 values are 26.0, 75.5 and 121.4 Gy, respectively. Using different types of analysis and in dependence of the dose prescription and reference dose rate, the �

HIGH-DOSE RATE BRACHYTHERAPY IN CARCINOMA CERVIX STAGE IIIB

Directory of Open Access Journals (Sweden)

Sathya Maruthavanan

2016-07-01

Full Text Available INTRODUCTION Radiotherapy is the standard treatment in locally advanced (IIB-IVA and early inoperable cases. The current standard of practice with curable intent is concurrent chemoradiation in which intracavitary brachytherapy is an integral component of radiotherapy. This study aims at assessing the efficacy of HDR ICBT (High-dose rate intracavitary brachytherapy in terms local response, normal tissue reactions, and feasibility. METHODS AND MATERIALS A total of 20 patients of stage IIIB cancer of the uterine cervix were enrolled in the study and were planned to receive concurrent chemotherapy weekly along with EBRT (external beam radiotherapy to a dose of 50 Gy/25 Fr. Suitability for ICBT was assessed at 40 Gy/20 Fr. 6/20 patients were suitable at 40 Gy and received HDR ICBT with a dose of 5.5 Gy to point A in 4 sessions (5.5 Gy/4 Fr. The remaining 14/20 patients completed 50 Gy and received HDR ICBT with a dose of 6 Gy to point A in 3 sessions (6 Gy/3 Fr. RESULTS A total of 66 intracavitary applications were done and only one application required dose modification due to high bladder dose, the pelvic control rate was 85% (17/20. 10% (2/20 had stable disease and 5% (1/20 had progressive disease at one year of follow up. When toxicity was considered only 15% developed grade I and grade II rectal complications. Patient compliance and acceptability was 100%. Patients were very comfortable with the short treatment time as compared with patients on LDR ICBT (low-dose rate intracavitary brachytherapy treatment interviewed during the same period. CONCLUSION This study proves that HDR brachytherapy is efficacious and feasible in carcinoma of cervix stage IIIB. It also proves that good dose distribution can be achieved with HDR intracavitary facility by the use of dose optimization. The short treatment time in HDR ICBT makes it possible to maintain this optimised dose distribution throughout the treatment providing a gain in the therapeutic ratio and

The effect of dose, dose rate, route of administration, and species on tissue and blood levels of benzene metabolites

International Nuclear Information System (INIS)

Henderson, R.F.; Sabourin, P.J.; Bechtold, W.E.; Griffith, W.C.; Medinsky, M.A.; Birnbaum, L.S.; Lucier, G.W.

1989-01-01

Studies were completed in F344/N rats and B6C3F 1 mice to determine the effect of dose, dose rate, route of administration, and rodent species on formation of total and individual benzene metabolites. Oral doses of 50 mg/kg or higher saturated the capacity for benzene metabolism in both rats and mice, resulting in an increased proportion of the administered dose being exhaled as benzene. The saturating air concentration for benzene metabolism during 6-hr exposures was between 130 and 900 ppm. At the highest exposure concentration, rats exhaled approximately half of the internal dose retained at the end of the 6-hr exposure as benzene; mice exhaled only 15% as benzene. Mice were able to convert more of the inhaled benzene to metabolites than were rats. In addition, mice metabolized more of the benzene by pathways leading to the putative toxic metabolites, benzoquinone and muconaldehyde, than did rats. In both rats and mice, the effect of increasing dose, administered orally or by inhalation, was to increase the proportion of the total metabolites that were the products of detoxification pathways relative to the products of pathways leading to putative toxic metabolites. This indicates low-affinity, high-capacity pathways for detoxification and high-affinity, low-capacity pathways leading to putative toxic metabolites. If the results of rodent studied performed at high doses were used to assess the health risk at low-dose exposures to benzene, the toxicity of benzene would be underestimated

Gamma dose rate effect on JFET transistors

International Nuclear Information System (INIS)

Assaf, J.

2011-04-01

The effect of Gamma dose rate on JFET transistors is presented. The irradiation was accomplished at the following available dose rates: 1, 2.38, 5, 10 , 17 and 19 kGy/h at a constant dose of 600 kGy. A non proportional relationship between the noise and dose rate in the medium range (between 2.38 and 5 kGy/h) was observed. While in the low and high ranges, the noise was proportional to the dose rate as the case of the dose effect. This may be explained as follows: the obtained result is considered as the yield of a competition between many reactions and events which are dependent on the dose rate. At a given values of that events parameters, a proportional or a non proportional dose rate effects are generated. No dependence effects between the dose rate and thermal annealing recovery after irradiation was observed . (author)

Biological influence from low dose and low-dose rate radiation

International Nuclear Information System (INIS)

Magae, Junji

2007-01-01

Although living organisms have defense mechanisms for radioadaptive response, the influence is considered to vary qualitatively and quantitatively for low dose and high dose, as well as for low-dose rate and high-dose rate. This article describes the bioresponse to low dose and low-dose rate. Among various biomolecules, DNA is the most sensitive to radiation, and accurate replication of DNA is an essential requirement for the survival of living organisms. Also, the influence of active enzymes resulted from the effect of radiation on enzymes in the body is larger than the direct influence of radiation on the body. After this, the article describes the carcinogenic risk by low-dose radiation, and then so-called Hormesis effect to create cancer inhibition effect by stimulating active physiology. (S.K.)

Dose rate measuring device and dose rate measuring method using the same

International Nuclear Information System (INIS)

Urata, Megumu; Matsushita, Takashi; Hanazawa, Sadao; Konno, Takahiro; Chiba, Yoshinori; Yumitate, Tadahiro

1998-01-01

The device of the present invention comprises a scintillation fiber scope having a shape elongated in the direction of the height of a pressure vessel and emitting light by incident of radiation to detect radiation, a radioactivity measuring device for measuring a dose rate based on the detection of the fiber scope and a reel means for dispensing and taking up the fiber scope, and it constituted such that the dose rate of the pressure vessel and that of a shroud are determined independently. Then, when the taken out shroud is contained in an container, excessive shielding is not necessary, in addition, this device can reliably be inserted to or withdrawn from complicated places between the pressure vessel and the shroud, and further, the dose rate of the pressure vessel and that of the shroud can be measured approximately accurately even when the thickness of them is different greatly. (N.H.)

Dose rate measuring device and dose rate measuring method using the same

Energy Technology Data Exchange (ETDEWEB)

Urata, Megumu; Matsushita, Takashi; Hanazawa, Sadao; Konno, Takahiro; Chiba, Yoshinori; Yumitate, Tadahiro

1998-11-13

The device of the present invention comprises a scintillation fiber scope having a shape elongated in the direction of the height of a pressure vessel and emitting light by incident of radiation to detect radiation, a radioactivity measuring device for measuring a dose rate based on the detection of the fiber scope and a reel means for dispensing and taking up the fiber scope, and it constituted such that the dose rate of the pressure vessel and that of a shroud are determined independently. Then, when the taken out shroud is contained in an container, excessive shielding is not necessary, in addition, this device can reliably be inserted to or withdrawn from complicated places between the pressure vessel and the shroud, and further, the dose rate of the pressure vessel and that of the shroud can be measured approximately accurately even when the thickness of them is different greatly. (N.H.)

Low dose rate and high dose rate intracavitary treatment for cervical cancer

International Nuclear Information System (INIS)

Hareyama, Masato; Oouchi, Atsushi; Shidou, Mitsuo

1997-01-01

From 1984 through 1993, 144 previous untreated patients with carcinoma of uterine cervix were treated with either low dose rate 137 Cs therapy (LDR) or high dose rate 60 Co therapy (HDR). The local failure rates for more than 2-years for the primary lesions were 11.8% (8 of 63 patients) for LDR and 18.0% (11 of 61 patients). Rectal complication rates were significantly lower for HDR versus LDR (14.3% VS. 32.8%. p<0.01). Also, bladder complication rates were significantly lower for HDR versus LDR (0% VS. 10.4%, p<0.005). Treatment results in term of local control were equivalent for HDR and LDR treatment. However, the incidence of complications was higher for the LDR group than for the HDR group. (author)

Brachytherapy optimization using radiobiological-based planning for high dose rate and permanent implants for prostate cancer treatment

Science.gov (United States)

Seeley, Kaelyn; Cunha, J. Adam; Hong, Tae Min

2017-01-01

We discuss an improvement in brachytherapy--a prostate cancer treatment method that directly places radioactive seeds inside target cancerous regions--by optimizing the current standard for delivering dose. Currently, the seeds' spatiotemporal placement is determined by optimizing the dose based on a set of physical, user-defined constraints. One particular approach is the ``inverse planning'' algorithms that allow for tightly fit isodose lines around the target volumes in order to reduce dose to the patient's organs at risk. However, these dose distributions are typically computed assuming the same biological response to radiation for different types of tissues. In our work, we consider radiobiological parameters to account for the differences in the individual sensitivities and responses to radiation for tissues surrounding the target. Among the benefits are a more accurate toxicity rate and more coverage to target regions for planning high-dose-rate treatments as well as permanent implants.

Evaluating the Application of Tissue-Specific Dose Kernels Instead of Water Dose Kernels in Internal Dosimetry : A Monte Carlo Study

NARCIS (Netherlands)

Moghadam, Maryam Khazaee; Asl, Alireza Kamali; Geramifar, Parham; Zaidi, Habib

2016-01-01

Purpose: The aim of this work is to evaluate the application of tissue-specific dose kernels instead of water dose kernels to improve the accuracy of patient-specific dosimetry by taking tissue heterogeneities into consideration. Materials and Methods: Tissue-specific dose point kernels (DPKs) and

DIANE, a simulation code for the interaction of neutrons with living tissues. Application to low doses of fast neutrons on human tumoral cells

International Nuclear Information System (INIS)

Nenot, M.L.

2003-07-01

Our work deals with the irradiation of cells and living tissues by 14 MeV neutrons at very low doses (a few 10 -2 Gy). Such experiments require an accurate knowledge of the values of neutron dose rates and fluences at the level of cell cultures. We have performed measurements of fluence rates through an activation method applied to gold and copper foils. The fluence rate is deduced from the gamma rays emitted by the irradiated foils. Neutron doses and dose rates have been measured through varied methods: PIN diodes, ionization tissue equivalent chambers, and Geiger-Mueller counters. We have designed the DIANE code to simulate the impact of energetic neutrons on cells. This code can be used with isolated cells or macroscopic tissues, it takes into account the roles of the ionisation electrons produced by recoil nuclei entering the cell. This point is all the more important since recent works have highlighted the impact of very low energy electrons on DNA. (A.C.)

Simple experimentally derived algorithm for computer calculated dose rates associated with 137Cs gynecologic insertions

International Nuclear Information System (INIS)

Wrede, D.E.; Dawalibi, H.

1980-01-01

A simple mathematical algorithm is derived from experimental data for dose rates from 137 Cs sources in a finite tissue equivalent medium corresponding to the female pelvis. An analytical expression for a point source of 137 Cs along with a simple numerical integration routine allows for rapid as well as accurate dose rate calculations at points of interest for gynecologic insertions. When compared with theoretical models assuming an infinite unit density medium, the measured dose rates are found to be systematically lower at distances away from a single source; 5 per cent at 2 cm and 10 per cent at 7 cm along the transverse axis. Allowance in the program for print out of dose rates from individual sources to a given point and the feature of source strength modification allows for optimization in terms of increasing the difference in dose rate between reference treatment points and sensitive structures such as the bladder, rectum and colon. (Auth.)

Dosimetric Considerations to Determine the Optimal Technique for Localized Prostate Cancer Among External Photon, Proton, or Carbon-Ion Therapy and High-Dose-Rate or Low-Dose-Rate Brachytherapy

Energy Technology Data Exchange (ETDEWEB)

Georg, Dietmar, E-mail: Dietmar.Georg@akhwien.at [Department of Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria); Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria); Hopfgartner, Johannes [Department of Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria); Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria); Gòra, Joanna [Department of Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria); Kuess, Peter [Department of Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria); Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria); Kragl, Gabriele [Department of Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria); Berger, Daniel [Department of Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria); Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria); Hegazy, Neamat [Department of Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria); Goldner, Gregor; Georg, Petra [Department of Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria); Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Medical University of Vienna/Allgemeines Krankenhaus der Stadt Wien, Vienna (Austria)

2014-03-01

Purpose: To assess the dosimetric differences among volumetric modulated arc therapy (VMAT), scanned proton therapy (intensity-modulated proton therapy, IMPT), scanned carbon-ion therapy (intensity-modulated carbon-ion therapy, IMIT), and low-dose-rate (LDR) and high-dose-rate (HDR) brachytherapy (BT) treatment of localized prostate cancer. Methods and Materials: Ten patients were considered for this planning study. For external beam radiation therapy (EBRT), planning target volume was created by adding a margin of 5 mm (lateral/anterior–posterior) and 8 mm (superior–inferior) to the clinical target volume. Bladder wall (BW), rectal wall (RW), femoral heads, urethra, and pelvic tissue were considered as organs at risk. For VMAT and IMPT, 78 Gy(relative biological effectiveness, RBE)/2 Gy were prescribed. The IMIT was based on 66 Gy(RBE)/20 fractions. The clinical target volume planning aims for HDR-BT ({sup 192}Ir) and LDR-BT ({sup 125}I) were D{sub 90%} ≥34 Gy in 8.5 Gy per fraction and D{sub 90%} ≥145 Gy. Both physical and RBE-weighted dose distributions for protons and carbon-ions were converted to dose distributions based on 2-Gy(IsoE) fractions. From these dose distributions various dose and dose–volume parameters were extracted. Results: Rectal wall exposure 30-70 Gy(IsoE) was reduced for IMIT, LDR-BT, and HDR-BT when compared with VMAT and IMPT. The high-dose region of the BW dose–volume histogram above 50 Gy(IsoE) of IMPT resembled the VMAT shape, whereas all other techniques showed a significantly lower high-dose region. For all 3 EBRT techniques similar urethra D{sub mean} around 74 Gy(IsoE) were obtained. The LDR-BT results were approximately 30 Gy(IsoE) higher, HDR-BT 10 Gy(IsoE) lower. Normal tissue and femoral head sparing was best with BT. Conclusion: Despite the different EBRT prescription and fractionation schemes, the high-dose regions of BW and RW expressed in Gy(IsoE) were on the same order of magnitude. Brachytherapy techniques

Dosimetric Considerations to Determine the Optimal Technique for Localized Prostate Cancer Among External Photon, Proton, or Carbon-Ion Therapy and High-Dose-Rate or Low-Dose-Rate Brachytherapy

International Nuclear Information System (INIS)

Georg, Dietmar; Hopfgartner, Johannes; Gòra, Joanna; Kuess, Peter; Kragl, Gabriele; Berger, Daniel; Hegazy, Neamat; Goldner, Gregor; Georg, Petra

2014-01-01

Purpose: To assess the dosimetric differences among volumetric modulated arc therapy (VMAT), scanned proton therapy (intensity-modulated proton therapy, IMPT), scanned carbon-ion therapy (intensity-modulated carbon-ion therapy, IMIT), and low-dose-rate (LDR) and high-dose-rate (HDR) brachytherapy (BT) treatment of localized prostate cancer. Methods and Materials: Ten patients were considered for this planning study. For external beam radiation therapy (EBRT), planning target volume was created by adding a margin of 5 mm (lateral/anterior–posterior) and 8 mm (superior–inferior) to the clinical target volume. Bladder wall (BW), rectal wall (RW), femoral heads, urethra, and pelvic tissue were considered as organs at risk. For VMAT and IMPT, 78 Gy(relative biological effectiveness, RBE)/2 Gy were prescribed. The IMIT was based on 66 Gy(RBE)/20 fractions. The clinical target volume planning aims for HDR-BT ( 192 Ir) and LDR-BT ( 125 I) were D 90% ≥34 Gy in 8.5 Gy per fraction and D 90% ≥145 Gy. Both physical and RBE-weighted dose distributions for protons and carbon-ions were converted to dose distributions based on 2-Gy(IsoE) fractions. From these dose distributions various dose and dose–volume parameters were extracted. Results: Rectal wall exposure 30-70 Gy(IsoE) was reduced for IMIT, LDR-BT, and HDR-BT when compared with VMAT and IMPT. The high-dose region of the BW dose–volume histogram above 50 Gy(IsoE) of IMPT resembled the VMAT shape, whereas all other techniques showed a significantly lower high-dose region. For all 3 EBRT techniques similar urethra D mean around 74 Gy(IsoE) were obtained. The LDR-BT results were approximately 30 Gy(IsoE) higher, HDR-BT 10 Gy(IsoE) lower. Normal tissue and femoral head sparing was best with BT. Conclusion: Despite the different EBRT prescription and fractionation schemes, the high-dose regions of BW and RW expressed in Gy(IsoE) were on the same order of magnitude. Brachytherapy techniques were clearly superior in

Dependence of total dose response of bipolar linear microcircuits on applied dose rate

International Nuclear Information System (INIS)

McClure, S.; Will, W.; Perry, G.; Pease, R.L.

1994-01-01

The effect of dose rate on the total dose radiation hardness of three commercial bipolar linear microcircuits is investigated. Total dose tests of linear bipolar microcircuits show larger degradation at 0.167 rad/s than at 90 rad/s even after the high dose rate test is followed by a room temperature plus a 100 C anneal. No systematic correlation could be found for degradation at low dose rate versus high dose rate and anneal. Comparison of the low dose rate with the high dose rate anneal data indicates that MIL-STD-883, method 1019.4 is not a worst-case test method when applied to bipolar microcircuits for low dose rate space applications

Tumor and normal tissue responses to fractioned non-uniform dose delivery

Energy Technology Data Exchange (ETDEWEB)

Kaellman, P; Aegren, A; Brahme, A [Karolinska Inst., Stockholm (Sweden). Dept. of Radiation Physics

1996-08-01

The volume dependence of the radiation response of a tumor is straight forward to quantify because it depends primarily on the eradication of all its clonogenic cells. A tumor therefore has a parallel organization as any surviving clonogen in principle can repopulate the tumor. The difficulty with the response of the tumor is instead to know the density and sensitivity distribution of the most resistant clonogenic cells. The increase in the 50% tumor control dose and the decrease in the maximum normalized slope of the dose response relation, {gamma}, in presence of small compartments of resistant tumor cells have therefore been quantified to describe their influence on the dose response relation. Injury to normal tissue is a much more complex and gradual process. It depends on earlier effects induced long before depletion of the differentiated and clonogenic cells that in addition may have a complex structural and functional organization. The volume dependence of the dose response relation of normal tissues is therefore described here by the relative seriality, s, of the infrastructure of the organ. The model can also be generalized to describe the response of heterogeneous tissues to non uniform dose distributions. The new model is compared with clinical and experimental data on normal tissue response, and shows good agreement both with regard to the shape of dose response relation and the volume dependence of the isoeffect dose. The response of tumors and normal tissues are quantified for arbitrary dose fractionations using the linear quadratic cell survival parameters {alpha} and {beta}. The parameters of the dose response relation are derived both for a constant dose per fraction and a constant number of dose fractions, thus in the latter case accounting also for non uniform dose delivery. (author). 26 refs, 4 figs.

Late effects of chronic low dose-rate γ-rays irradiation on mice

International Nuclear Information System (INIS)

Tanaka, Satoshi; Sasagawa, Sumiko; Ichinohe, Kazuaki; Matsumoto, Tsuneya; Otsu, Hiroshi; Sato, Fumiaki

2002-01-01

To evaluate late biological effects of chronic low dose-rate radiation, we are conducting two experiments. Experiment 1 - Late effects of chronic low dose-rate g-rays irradiation on SPF mice, using life-span and pathological changes as parameters. Continuous irradiation with g-rays for 400 days was performed using 137 Cs γ-rays at dose-rates of 20 mGy/day, 1 mGy/day and 0.05 mGy/day with accumulated doses equivalent to 8,000 mGy, 400 mGy and 20 mGy, respectively. All mice were kept until they died a natural death. As of 2002 March 31, 3,999 of the total 4,000 mice have died. Preliminary analyses of data show that 20 mGy/day suggested a shortened life span in both sexes. Partial results show that the most common lethal neoplasms in the pooled data of non-irradiated control and irradiated male mice, in order of frequency, were neoplasms of the lymphohematopoietic system, liver, and lung. In female mice, neoplasms of the lymphohematopoietic system, soft tissue, and endocrine system were common. Experiment 2 - Effects on the progeny of chronic low dose-rate g-ray irradiated SPF mice: pilot study, was started in 1999 and is currently in progress. (author)

Brachytherapy for early oral tongue cancer. Low dose rate to high dose rate

International Nuclear Information System (INIS)

Yamazaki, Hideya; Inoue, Takehiro; Yoshida, Ken; Yoshioka, Yasuo; Shimizutani, Kimishige; Inoue, Toshihiko; Furukawa, Souhei; Kakimoto, Naoya

2003-01-01

To examine the compatibility of low dose rate (LDR) with high dose rate (HDR) brachytherapy, we reviewed 399 patients with early oral tongue cancer (T1-2N0M0) treated solely by brachytherapy at Osaka University Hospital between 1967 and 1999. For patients in the LDR group (n=341), the treatment sources consisted of Ir-192 pin for 227 patients (1973-1996; irradiated dose, 61-85 Gy; median, 70 Gy), Ra-226 needle for 113 patients (1967-1986; 55-93 Gy; median, 70 Gy). Ra-226 and Ir-192 were combined for one patient. Ir-192 HDR (microSelectron-HDR) was used for 58 patients in the HDR group (1991-present; 48-60 Gy; median, 60 Gy). LDR implantations were performed via oral and HDR via a submental/submandibular approach. The dose rates at the reference point for the LDR group were 0.30 to 0.8 Gy/h, and for the HDR group 1.0 to 3.4 Gy/min. The patients in the HDR group received a total dose of 48-60 Gy (8-10 fractions) during one week. Two fractions were administered per day (at least a 6-h interval). The 3- and 5-year local control rates for patients in the LDR group were 85% and 80%, respectively, and those in the HDR group were both 84%. HDR brachytherapy showed the same lymph-node control rate as did LDR brachytherapy (67% at 5 years). HDR brachytherapy achieved the same locoregional result as did LDR brachytherapy. A converting factor of 0.86 is applicable for HDR in the treatment of early oral tongue cancer. (author)

Tissue-phantom dose ratio R(t, F) in irradiation planning. 2

International Nuclear Information System (INIS)

Hegewald, H.

1986-01-01

The principles for measuring doses are represented to complete the developed tissue-phantom dose ratio R(t, F). The functional dependence of the tissue-phantom dose ratio on the field size results from the different spectral energy distribution in the buildup range compared to greater depths. This once more illustrates the demand, to move the calibration and reference depths into greater depths than the dose maximum depth on account of a high precision. The scattering factors and their dependence on the type of collimator are represented and tables are made up for practical use. In a supplement the derivations of the equation systems are given, to find out the tissue-phantom dose ratio by computation and the correspondence is tested. The measurements are more relevant in the megavolt range since dose values typically for the equipment are measured in the buildup range and depth dose tables are not available in the required completeness. (author)

Effects of dose, dose-rate and fraction on radiation-induced breast and lung cancers

International Nuclear Information System (INIS)

Howe, G.R.

1992-01-01

Recent results from a large Canadian epidemiologic cohort study of low-LET radiation and cancer will be described. This is a study of 64,172 tuberculosis patients first treated in Canada between 1930 and 1952, of whom many received substantial doses to breast and lung tissue from repeated chest fluoroscopies. The mortality of the cohort between 1950 and 1987 has been determined by computerized record linkage to the National Mortality Data Base. There is a strong positive association between radiation and breast cancer risk among the females in the cohort, but in contrast very little evidence of any increased risk in lung cancer. The results of this and other studies suggest that the effect of dose-rate and/or fractionation on cancer risk may will differ depending upon the particular cancer being considered. (author)

Dose distribution around ion track in tissue equivalent material

International Nuclear Information System (INIS)

Zhang Wenzhong; Guo Yong; Luo Yisheng

2007-01-01

Objective: To study the energy deposition micro-specialty of ions in body-tissue or tissue equivalent material (TEM). Methods: The water vapor was determined as the tissue equivalent material, based on the analysis to the body-tissue, and Monte Carlo method was used to simulate the behavior of proton in the tissue equivalent material. Some features of the energy deposition micro-specialty of ion in tissue equivalent material were obtained through the analysis to the data from calculation. Results: The ion will give the energy by the way of excitation and ionization in material, then the secondary electrons will be generated in the progress of ionization, these electron will finished ions energy deposition progress. When ions deposited their energy, large amount energy will be in the core of tracks, and secondary electrons will devote its' energy around ion track, the ion dose distribution is then formed in TEM. Conclusions: To know biological effects of radiation , the research to dose distribution of ions is of importance(significance). (authors)

Gynecological brachytherapy - from low-dose-rate to high-tech. Gynaekologische Brachytherapie - von Low-dose-rate zu High-tech

Energy Technology Data Exchange (ETDEWEB)

Herrmann, T. (Abt. Strahlenthgerapie, Klinik und Poliklinik fuer Radiologie, Medizinische Akademie ' Carl Gustav Carus' , Dresden (Germany)); Christen, N. (Abt. Strahlenthgerapie, Klinik und Poliklinik fuer Radiologie, Medizinische Akademie ' Carl Gustav Carus' , Dresden (Germany)); Alheit, H.D. (Abt. Strahlenthgerapie, Klinik und Poliklinik fuer Radiologie, Medizinische Akademie ' Carl Gustav Carus' , Dresden (Germany))

1993-03-01

The transition from low-dose-rate (LDR) brachytherapy to high-dose-rate (HDR) afterloading treatment is in progress in most centres of radiation therapy. First reports of studies comparing HDR and LDR treatment in cervix cancer demonstrate nearly equal local control. In our own investigations on 319 patients with primary irradiated carcinoma of the cervix (125 HDR/194 LDR) we found the following control rates: Stage FIGO I 95.4%/82.9% (HDR versus LDR), stage FIGO II 71.4%/73.7%, stage FIGO III 57.9%/38.5%. The results are not significant. The side effects - scored after EORT/RTOG criteria - showed no significant differences between both therapies for serious radiogenic late effects on intestine, bladder and vagina. The study and findings from the literature confirm the advantage of the HDR-procedure for patient and radiooncologist and for radiation protection showing at least the same results as in the LDR-area. As for radiobiolgical point of view it is important to consider that the use of fractionation in the HDR-treatment is essential for the sparing of normal tissues and therefore a greater number of small fractionation doses in the brachytherapy should be desirable too. On the other hand the rules, which are true for fractionated percutaneous irradiation therapy (overall treatment time as short as possible to avoid reppopulation of tumor cells) should be taken into consideration in combined brachy-teletherapy regime in gynecologic tumors. The first step in this direction may be accelerated regime with a daily application of both treatment procedures. The central blocking of the brachytherapy region from the whole percutaneous treatment target volume should be critically reflected, especially in the case of advanced tumors. (orig.)

Dose Rate Effects in Linear Bipolar Transistors

Science.gov (United States)

Johnston, Allan; Swimm, Randall; Harris, R. D.; Thorbourn, Dennis

2011-01-01

Dose rate effects are examined in linear bipolar transistors at high and low dose rates. At high dose rates, approximately 50% of the damage anneals at room temperature, even though these devices exhibit enhanced damage at low dose rate. The unexpected recovery of a significant fraction of the damage after tests at high dose rate requires changes in existing test standards. Tests at low temperature with a one-second radiation pulse width show that damage continues to increase for more than 3000 seconds afterward, consistent with predictions of the CTRW model for oxides with a thickness of 700 nm.

Transcriptional Response in Mouse Thyroid Tissue after 211At Administration: Effects of Absorbed Dose, Initial Dose-Rate and Time after Administration.

Directory of Open Access Journals (Sweden)

Nils Rudqvist

Full Text Available 211At-labeled radiopharmaceuticals are potentially useful for tumor therapy. However, a limitation has been the preferential accumulation of released 211At in the thyroid gland, which is a critical organ for such therapy. The aim of this study was to determine the effect of absorbed dose, dose-rate, and time after 211At exposure on genome-wide transcriptional expression in mouse thyroid gland.BALB/c mice were i.v. injected with 1.7, 7.5 or 100 kBq 211At. Animals injected with 1.7 kBq were killed after 1, 6, or 168 h with mean thyroid absorbed doses of 0.023, 0.32, and 1.8 Gy, respectively. Animals injected with 7.5 and 100 kBq were killed after 6 and 1 h, respectively; mean thyroid absorbed dose was 1.4 Gy. Total RNA was extracted from pooled thyroids and the Illumina RNA microarray platform was used to determine mRNA levels. Differentially expressed transcripts and enriched GO terms were determined with adjusted p-value 1.5, and p-value <0.05, respectively.In total, 1232 differentially expressed transcripts were detected after 211At administration, demonstrating a profound effect on gene regulation. The number of regulated transcripts increased with higher initial dose-rate/absorbed dose at 1 or 6 h. However, the number of regulated transcripts decreased with mean absorbed dose/time after 1.7 kBq 211At administration. Furthermore, similar regulation profiles were seen for groups administered 1.7 kBq. Interestingly, few previously proposed radiation responsive genes were detected in the present study. Regulation of immunological processes were prevalent at 1, 6, and 168 h after 1.7 kBq administration (0.023, 0.32, 1.8 Gy.

Outcome of stroke patients receiving different doses of recombinant tissue plasminogen activator.

Science.gov (United States)

Ong, Cheung-Ter; Wong, Yi-Sin; Wu, Chi-Shun; Su, Yu-Hsiang

2017-01-01

Intravenous recombinant tissue plasminogen activator (tPA) at a dose of 0.9 mg/kg body weight is associated with a high hemorrhagic transformation (HT) rate. Low-dose tPA (0.6 mg/kg) may have a lower hemorrhage rate but the mortality and disability rates at 90 days cannot be confirmed as non-inferior to standard-dose tPA. Whether the doses 0.7 and 0.8 mg/kg have better efficacy and safety needs further investigation. Therefore, this study is to compare the efficacy and safety of each dose of tPA (0.6, 0.7, 0.8, and 0.9 mg/kg body weight) and to investigate the factors affecting early neurological improvement (ENI) and early neurological deterioration (END). For this observational study, data were obtained from 274 patients who received tPA thrombolytic therapy in Chia-Yi Christian Hospital stroke unit. The tPA dose was given at the discretion of each physician. The definition of ENI was a >8 point improvement (compared with baseline) at 24 h following thrombolytic therapy or an improvement in the National Institutes of Health Stroke Score (NIHSS) to 0 or 1 toward the end of tPA infusion. The definition of END was a >4 point increase in NIHSS (compared with baseline) within 24 h of tPA infusion. The primary objective was to investigate whether 0.7 and 0.8 mg/kg of tPA have higher ENI rate, lower END rate, and better outcome at 6 months. Poor outcome was defined as having a modified Rankin Scale of 3 to 6 (range, 0 [no symptoms] to 6 [death]). The secondary objective was to investigate whether low-dose tPA has a lower risk of intracerebral HT than that with standard-dose tPA. We also investigated the factors affecting ENI, END, HT, and 6-month outcome. A total of 274 patients were included during the study period, of whom 260 were followed up for >6 months. There was a trend for the HT rate to increase as the dose increased ( P =0.02). The symptomatic HT rate was not significantly different among the low-dose and standard-dose groups. The ENI and END ( P =0.52) were

Dose rate visualization of radioisotope thermoelectric generators

International Nuclear Information System (INIS)

Schwarz, R.A.; Kessler, S.F.; Tomaszewski, T.A.

1995-09-01

Advanced visualization techniques can be used to investigate gamma ray and neutron dose rates around complex dose rate intensive operations. A method has been developed where thousands of dose points are calculated using the MCNP(Monte Carlo N-Particle) computer code and then displayed to create color contour plots of the dose rate for complex geometries. Once these contour plots are created, they are sequenced together creating an animation to dynamically show how the dose rate changes with changes in the geometry or source over time

Biological responses to low dose rate gamma radiation

International Nuclear Information System (INIS)

Magae, Junji; Ogata, Hiromitsu

2003-01-01

Linear non-threshold (LNT) theory is a basic theory for radioprotection. While LNT dose not consider irradiation time or dose-rate, biological responses to radiation are complex processes dependent on irradiation time as well as total dose. Moreover, experimental and epidemiological studies that can evaluate LNT at low dose/low dose-rate are not sufficiently accumulated. Here we analyzed quantitative relationship among dose, dose-rate and irradiation time using chromosomal breakage and proliferation inhibition of human cells as indicators of biological responses. We also acquired quantitative data at low doses that can evaluate adaptability of LNT with statistically sufficient accuracy. Our results demonstrate that biological responses at low dose-rate are remarkably affected by exposure time, and they are dependent on dose-rate rather than total dose in long-term irradiation. We also found that change of biological responses at low dose was not linearly correlated to dose. These results suggest that it is necessary for us to create a new model which sufficiently includes dose-rate effect and correctly fits of actual experimental and epidemiological results to evaluate risk of radiation at low dose/low dose-rate. (author)

Simple experimentally derived algorithm for computer calculated dose rates associated with /sup 137/Cs gynecologic insertions

Energy Technology Data Exchange (ETDEWEB)

Wrede, D E; Dawalibi, H [King Faisal Specialist Hospital and Research Centre, Department of Medical Physics. Riyadh (Saudi Arabia)

1980-01-01

A simple mathematical algorithm is derived from experimental data for dose rates from /sup 137/Cs sources in a finite tissue equivalent medium corresponding to the female pelvis. An analytical expression for a point source of /sup 137/Cs along with a simple numerical integration routine allows for rapid as well as accurate dose rate calculations at points of interest for gynecologic insertions. When compared with theoretical models assuming an infinite unit density medium, the measured dose rates are found to be systematically lower at distances away from a single source; 5 per cent at 2 cm and 10 per cent at 7 cm along the transverse axis. Allowance in the program for print out of dose rates from individual sources to a given point and the feature of source strength modification allows for optimization in terms of increasing the difference in dose rate between reference treatment points and sensitive structures such as the bladder, rectum and colon.

Dose rate visualization of radioisotope thermoelectric generators

International Nuclear Information System (INIS)

Schwarz, R.A.; Kessler, S.F.; Tomaszewski, T.A.

1996-01-01

Advanced visualization techniques can be used to investigate gamma ray and neutron dose rates around complex dose rate intensive operations. A method has been developed where thousands of dose points are calculated using the MCNP (Monte Carlo N-Particle) computer code (Briesmeister 1993) and then displayed to create color contour plots of the dose rate for complex geometries. Once these contour plots are created, they are sequenced together creating an animation to dynamically show how the dose rate changes with changes in the geometry or source over time. copyright 1996 American Institute of Physics

Dose-rate dependence of thermoluminescence response

International Nuclear Information System (INIS)

McKeever, S.W.S.; Chen, R.; Groom, P.J.; Durrani, S.A.

1980-01-01

The previously observed dose-rate effect of thermoluminescence in quartz at high dose-rates is given at theoretical formulation. Computer calculations simulating the experimental conditions yield similar results to the experimental ones. (orig.)

A study of microscopic dose rate distribution of 99Tcm-MIBI in the liver of mice

International Nuclear Information System (INIS)

Wang Mingxi; Zhang Liang'an; Wang Yong; Dai Guangfu

2002-01-01

Objective: A microdosimetry model was tried to develop an accurate way to evaluate absorbed dose rates in target cell nuclei from radiopharmaceuticals. Methods: Microscopic frozen section autoradiography was used to determine the subcellular locations of 99 Tc m -MIBI relative to the tissue histology in the liver of mice after injection of 99 Tc m -MIBI via tail for two hours, and a mathematical model was developed to evaluate the microscopic dose rates in cell nuclei. The Medical Internal Radiation Dose (MIRD) schema was also used to evaluate the dose rates at the same time, and a comparison of the results of the two methods was conducted to determine which method is better to accurately estimate microscopic dose rates. Results: The spatial distribution of 99 Tc m -MIBI in the liver of mice at subcellular level was not uniform, and the differences between the microdosimetry model and MIRD schema were significant (P 99 Tc m -labeled pharmaceuticals at the microscopic level

Effects of trapped proton flux anisotropy on dose rates in low Earth orbit

International Nuclear Information System (INIS)

Badhwar, G.D.; Kushin, V.V.; Akatov, Yu A.; Myltseva, V.A.

1999-01-01

Trapped protons in the South Atlantic Anomaly (SAA) have a rather narrow pitch angle distribution and exhibit east-west anisotropy. In low Earth orbits, the E-W effect results in different amounts of radiation dose received by different sections of the spacecraft. This effect is best studied on missions in which the spacecraft flies in a fixed orientation. The magnitude of the effect depends on the particle energy and altitude through the SAA. In this paper, we describe a clear example of this effect from measurements of radiation dose rates and linear energy transfer spectra made on Space Shuttle flight STS-94 (28.5 deg. inclination x 296 km altitude). The ratio of dose rates from the two directions at this location in the mid-deck was 2.7. As expected from model calculations, the spectra from the two directions are different, that is the ratio is energy dependent. The data can be used to distinguish the anisotropy models. The flight carried an active tissue equivalent proportional counter (TEPC), and passive thermoluminscent detectors (TLDs), and two types of nuclear emulsions. Using nuclear emulsions, charged particles and secondary neutron energy spectra were measured. The combined galactic cosmic radiation+trapped charged particle lineal energy spectra measured by the TEPC and the linear energy transfer spectrum measured by nuclear emulsions are in good agreement. The charged particle absorbed dose rates varied from 112 to 175 μGy/day, and dose equivalent rates from 264.3 to 413 μSv/day. Neutrons in the 1-10 MeV contributed a dose rate of 3.7 μGy/day and dose equivalent rate of 30.8 μSv/day, respectively

Effects of trapped proton flux anisotropy on dose rates in low Earth orbit.

Science.gov (United States)

Badhwar, G D; Kushin, V V; Akatov YuA; Myltseva, V A

1999-06-01

Trapped protons in the South Atlantic Anomaly (SAA) have a rather narrow pitch angle distribution and exhibit east-west anisotropy. In low Earth orbits, the E-W effect results in different amounts of radiation dose received by different sections of the spacecraft. This effect is best studied on missions in which the spacecraft flies in a fixed orientation. The magnitude of the effect depends on the particle energy and altitude through the SAA. In this paper, we describe a clear example of this effect from measurements of radiation dose rates and linear energy transfer spectra made on Space Shuttle flight STS-94 (28.5 degree inclination x 296 km altitude). The ratio of dose rates from the two directions at this location in the mid-deck was 2.7. As expected from model calculations, the spectra from the two directions are different, that is the ratio is energy dependent. The data can be used to distinguish the anisotropy models. The flight carried an active tissue equivalent proportional counter (TEPC), and passive thermoluminscent detectors (TLDs), and two types of nuclear emulsions. Using nuclear emulsions, charged particles and secondary neutron energy spectra were measured. The combined galactic cosmic radiation+trapped charged particle lineal energy spectra measured by the TEPC and the linear energy transfer spectrum measured by nuclear emulsions are in good agreement. The charged particle absorbed dose rates varied from 112 to 175 microGy/day, and dose equivalent rates from 264.3 to 413 microSv/day. Neutrons in the 1-10 MeV contributed a dose rate of 3.7 microGy/day and dose equivalent rate of 30.8 microSv/day, respectively.

Responses of some normal tissues to low doses of γ-radiation

International Nuclear Information System (INIS)

Withers, H.R.

1975-01-01

The response of four normal tissues to low doses of γ-radiation was measured in mice using three indirect methods. The survival curves for cells of the tissues studied (colon, jejunum, testis and haemoleucopoietic system) may be exponential over an uncertain dose range (from zero to between 100 to 230 rad), the slope being about one third of that in the high-dose region. Some of the uncertainties in the data probably reflect variations in age-density distribution. (author)

External dose-rate conversion factors for calculation of dose to the public

Energy Technology Data Exchange (ETDEWEB)

1988-07-01

This report presents a tabulation of dose-rate conversion factors for external exposure to photons and electrons emitted by radionuclides in the environment. This report was prepared in conjunction with criteria for limiting dose equivalents to members of the public from operations of the US Department of Energy (DOE). The dose-rate conversion factors are provided for use by the DOE and its contractors in performing calculations of external dose equivalents to members of the public. The dose-rate conversion factors for external exposure to photons and electrons presented in this report are based on a methodology developed at Oak Ridge National Laboratory. However, some adjustments of the previously documented methodology have been made in obtaining the dose-rate conversion factors in this report. 42 refs., 1 fig., 4 tabs.

Evaluation of two intracavitary high-dose-rate brachytherapy devices for irradiating additional and irregularly shaped volumes of breast tissue

International Nuclear Information System (INIS)

Lu, Sharon M.; Scanderbeg, Daniel J.; Barna, Patrick; Yashar, William; Yashar, Catheryn

2012-01-01

The SAVI and Contura breast brachytherapy applicators represent 2 recent advancements in brachytherapy technology that have expanded the number of women eligible for accelerated partial breast irradiation in the treatment of early-stage breast cancer. Early clinical experience with these 2 single-entry, multichannel high-dose-rate brachytherapy devices confirms their ease of use and dosimetric versatility. However, current clinical guidelines for SAVI and Contura brachytherapy may result in a smaller or less optimal volume of treated tissue compared with traditional interstitial brachytherapy. This study evaluates the feasibility of using the SAVI and Contura to irradiate larger and irregularly shaped target volumes, approaching what is treatable with the interstitial technique. To investigate whether additional tissue can be treated, 17 patients treated with the SAVI and 3 with the Contura were selected. For each patient, the planning target volume (PTV) was modified to extend 1.1 cm, 1.3 cm, and 1.5 cm beyond the tumor bed cavity. To evaluate dose conformance to an irregularly shaped target volume, 9 patients treated with the SAVI and 3 with the Contura were selected from the original 20 patients. The following asymmetric PTV margin combinations were assessed for each patient: 1.5/0.3, 1.3/0.3, and 1.1/0.3 cm. For all patients, treatment planning was performed, adopting the National Surgical Adjuvant Breast and Bowel Project guidelines, and dosimetric comparisons were made. The 6–1 and 8–1 SAVI devices can theoretically treat a maximal tissue margin of 1.5 cm and an asymmetric PTV with margins ranging from 0.3 to 1.5 cm. The 10–1 SAVI and Contura can treat a maximal margin of 1.3 cm and 1.1 cm, respectively, and asymmetric PTV with margins ranging from 0.3–1.3 cm. Compared with the Contura, the SAVI demonstrated greater dosimetric flexibility. Risk of developing excessive hot spots increased with the size of the SAVI device. Both the SAVI and Contura

Dose rate effect on low-dose hyper-radiosensitivity with cells in vitro

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Kim, Geon-Min; Kim, Eun-Hee [Seoul National University, Seoul (Korea, Republic of)

2016-10-15

Low-dose hyper-radiosensitivity (HRS) is the phenomenon that mammalian cells exhibit higher sensitivity to radiation at low doses (< 0.5 Gy) than expected by the linear-quadratic model. At doses above 0.5Gy, the cellular response is recovered to the level expected by the linear-quadratic model. This transition is called the increased radio-resistance (IRR). HRS was first verified using Chinese hamster V79 cells in vitro by Marples and has been confirmed in studies with other cell lines including human normal and tumor cells. HRS is known to be induced by inactivation of ataxia telangiectasia-mutated (ATM), which plays a key role in repairing DNA damages. Considering the connection between ATM and HRS, one can infer that dose rate may affect cellular response regarding HRS at low doses. In this study, we quantitated the effect of dose rate on HRS by clonogenic assay with normal and tumor cells. The HRS of cells at low dose exposures is a phenomenon already known. In this study, we observed HRS of rat normal diencephalon cells and rat gliosarcoma cells at doses below 1 Gy. In addition, we found that dose rate mattered. HRS occurred at low doses, but only when total dose was delivered at a rate below certain level.

Pulsed dose rate brachytherapy – is it the right way?

Directory of Open Access Journals (Sweden)

Janusz Skowronek

2010-10-01

Full Text Available Pulsed dose rate (PDR-BT treatment is a brachytherapy modality that combines physical advantages of high-doserate (HDR-BT technology (isodose optimization, radiation safety with the radiobiological advantages of low-dose-rate (LDR-BT brachytherapy. Pulsed brachytherapy consists of using stronger radiation source than for LDR-BT and producing series of short exposures of 10 to 30 minutes in every hour to approximately the same total dose in the sameoverall time as with the LDR-BT. Modern afterloading equipment offers certain advantages over interstitial or intracavitaryinsertion of separate needles, tubes, seeds or wires. Isodose volumes in tissues can be created flexibly by a combinationof careful placement of the catheter and the adjustment of the dwell times of the computerized stepping source.Automatic removal of the radiation sources into a shielded safe eliminates radiation exposures to staff and visitors.Radiation exposure is also eliminated to the staff who formerly loaded and unloaded multiplicity of radioactive sources into the catheters, ovoids, tubes etc. This review based on summarized clinical investigations, analyses the feasibility and the background to introduce this brachytherapy technique and chosen clinical applications of PDR-BT.

Photon beam dose distributions for patients with implanted temporary tissue expanders

Science.gov (United States)

Asena, A.; Kairn, T.; Crowe, S. B.; Trapp, J. V.

2015-01-01

This study examines the effects of temporary tissue expanders (TTEs) on the dose distributions of photon beams in breast cancer radiotherapy treatments. EBT2 radiochromic film and ion chamber measurements were taken to quantify the attenuation and backscatter effects of the inhomogeneity. Results illustrate that the internal magnetic port present in a tissue expander causes a dose reduction of approximately 25% in photon tangent fields immediately downstream of the implant. It was also shown that the silicone elastomer shell of the tissue expander reduced the dose to the target volume by as much as 8%. This work demonstrates the importance for an accurately modelled high-density implant in the treatment planning system for post-mastectomy breast cancer patients.

Calculation of dose for β point and sphere sources in soft tissue

International Nuclear Information System (INIS)

Sun Fuyin; Yuan Shuyu; Tan Jian

1999-01-01

Objective: To compare the results of the distribution of dose rate calculated by three typical methods for point source and sphere source of β nuclide. Methods: Calculating and comparing the distributions of dose rate from 32 P β point and sphere sources in soft tissue calculated by the three methods published in references, [1]. [2] and [3], respectively. Results: For the point source of 3.7 x 10 7 Bq (1mCi), the variations of the calculation results of the three formulas are within 10% if r≤0.35 g/cm 2 , r being the distance from source, and larger than 10% if r > 0.35 g/cm 2 . For the sphere source whose volume is 50 μl and activity is 3.7 x 10 7 Bq(1 mCi), the variations are within 10% if z≤0.15 g/cm 2 , z being the distance from the surface of the sphere source to a point outside the sphere. Conclusion: The agreement of the distributions of the dose rate calculated by the three methods mentioned above for point and sphere β source are good if the distances from point source or the surface of sphere source to the points observed are small, and poor if they are large

Air dose rate in Aichi Prefecture

International Nuclear Information System (INIS)

Ohnuma, Shoko; Chaya, Kunio; Tomita, Banichi; Aoyama, Kan; Yamada, Naoki; Yamada, Masuo; Hamamura, Norikatsu

1985-01-01

We have carried out the observations of air dose rate during 1964--1983 at the fixed points of Aichi Prefecture and investigated the distribution of air dose rate in this prefecture during 1979--1983. The results of these researches are as follows. 1) The apparent half time of radiation dose from the earth and the atmosphere during the last 20 years was about 9.7 years and it was longer than the apparent half time of fallout total β radioactivity in every rainfall that was about 3.2 years. 2) The influence of nuclear explosion test in China on the measurements of air does rate did not existed directly during the latter half of 20 years, not so as during the former and it was keeping decreasing. It was expected that the air dose rate would begin to indicate the natural radiation dose from the earth and the atmosphere in the near future. 3) The distribution of air dose rate in this prefecture depended strongly on the geology. The maximum value was 5.6 μR/hr (except cosmic rays) in Fujioka Cho, the minimum value was 1.9 μR/hr (except cosmic rays) in Tahara Cho and the average in the whole prefecture was 3.5+-0.7 μR/hr (except cosmic rays). 4) It was estimated that the radiation dose which the inhabitants received from the earth and the atmosphere was 17--52 m rem a year and the average was 31 m rem a year. (author)

Air dose rate in Aichi Prefecture

Energy Technology Data Exchange (ETDEWEB)

Ohnuma, Shoko; Chaya, Kunio; Tomita, Banichi; Aoyama, Kan; Yamada, Naoki; Yamada, Masuo; Hamamura, Norikatsu

1985-03-01

We have carried out the observations of air dose rate during 1964-1983 at the fixed points of Aichi Prefecture and investigated the distribution of air dose rate in this prefecture during 1979-1983. The results of these researches are as follows. 1) The apparent half time of radiation dose from the earth and the atmosphere during the last 20 years was about 9.7 years and it was longer than the apparent half time of fallout total ..beta.. radioactivity in every rainfall that was about 3.2 years. 2) The influence of nuclear explosion test in China on the measurements of air does rate did not existed directly during the latter half of 20 years, not so as during the former and it was keeping decreasing. It was expected that the air dose rate would begin to indicate the natural radiation dose from the earth and the atmosphere in the near future. 3) The distribution of air dose rate in this prefecture depended strongly on the geology. The maximum value was 5.6 ..mu..R/hr (except cosmic rays) in Fujioka Cho, the minimum value was 1.9 ..mu..R/hr (except cosmic rays) in Tahara Cho and the average in the whole prefecture was 3.5 +- 0.7 ..mu..R/hr (except cosmic rays). 4) It was estimated that the radiation dose which the inhabitants received from the earth and the atmosphere was 17-52 m rem a year and the average was 31 m rem a year.

Dose rate and dose fractionation studies in total body irradiation of dogs

International Nuclear Information System (INIS)

Kolb, H.J.; Netzel, B.; Schaffer, E.; Kolb, H.

1979-01-01

Total body irradiation (TBI) with 800-900 rads and allogeneic bone marrow transplantation according to the regimen designated by the Seattle group has induced remissions in patients with otherwise refractory acute leukemias. Relapse of leukemia after bone marrow transplantation remains the major problem, when the Seattle set up of two opposing 60 Co-sources and a low dose rate is used in TBI. Studies in dogs with TBI at various dose rates confirmed observations in mice that gastrointestinal toxicity is unlike toxicity against hemopoietic stem cells and possibly also leukemic stem cells depending on the dose rate. However, following very high single doses (2400 R) and marrow infusion acute gastrointestinal toxicity was not prevented by the lowest dose rate studied (0.5 R/min). Fractionated TBI with fractions of 600 R in addition to 1200 R (1000 rads) permitted the application of total doses up to 300 R followed by marrow infusion without irreversible toxicity. 26 dogs given 2400-3000 R have been observed for presently up to 2 years with regard to delayed radiation toxicity. This toxicity was mild in dogs given single doses at a low dose rate or fractionated TBI. Fractionated TBI is presently evaluated with allogeneic transplants in the dog before being applied to leukemic patients

Biosynthesis of pyrimidine ribonucleotides and the level of high-energy compounds in tissues of dogs exposed to γ-radiation at low dose-rates and treated with exogenous ATF

International Nuclear Information System (INIS)

Koshcheenko, N.N.; Zhulanova, Z.I.; Tikhomirova, M.V.; Trebenok, Z.A.; Romantsev, E.F.

1979-01-01

It was established that total-body γ-irradiation of dogs in a dosage of 800 R at a dose-rate of 1R/min produces a considerable temporaty increase in the ability of liver and spleen extracts to synthesize uridine monophosphate (UMP) from 14 C-orotic acid. The processes of UMP formation from uracil and subsequent enzymatic phosphorylation of UMP undergo less pronounced postradiation changes. Preventive treatment with ATP in a radioprotective dose does not hinder the development of biochemical changes in tissues of exposed animals. A single injection of ATP to nonirradiated dogs temporarily increases the UMP biosynthesis from orotic acid in both tissues; decreases the activity of uracil phosphoribosyltransferase and increases the activity of UMP kinase in the spleen, but has no effect on these processes in the liver. The pool of energy-rich compounds (ATP+ADP) in the liver and spleen of dogs varies markedly during 72 h following prolonged exposure. Preventive treatment with ATP normalizes these changes

Dose-rate effects and chronological changes of chromosome aberration rates in spleen cells from mice that are chronically exposed to gamma-ray at low dose rates

International Nuclear Information System (INIS)

Tanaka, Kimio; Kohda, Atsushi; Ichinohe, Kazuaki; Matsumoto, Tsuneya; Oghiso, Yoichi

2006-01-01

Dose-rate effects have not been examined in the low dose-rate regions of less than 60-600 mGy/h. Mice were chronically exposed to gamma-ray at 20 mGy/day (approximately 1 mGy/h) up to 700 days and at 1 mGy/day (approximately 0.05 mGy/h) for 500 days under SPF conditions. Chronological changes of chromosome aberration rates in spleen cells were observed along with accumulated doses at both low dose-rates. Unstable aberrations increased in a biphasic manner within 0-2 Gy and 4-14 Gy in 20 mGy/day irradiation. They slightly increased up to 0.5 Gy in 1 mGy/day irradiation. Chromosome aberration rates at 20 mGy/day and 1 mGy/day were compared at the same total doses of 0.5 Gy and 0.25 Gy. They were 2.0 vs. 0.53, and 1.0 vs. 0.47 respectively. Thus, dose-rate effects were observed in these low dose-rate regions. (author)

A graphical review of radiogenic animal cancer data using the 'dose and dose-rate map'

International Nuclear Information System (INIS)

Yoshida, Kazuo; Hoshi, Yuko; Sakai, Kazuo

2008-01-01

We have been investigating the effects of low dose or low dose rate irradiation on mice, using our low dose-rate irradiation facilities. In these studies, we found that the effects were highly dependent on both total dose and dose rate. To show this visually, we proposed the 'dose/dose rate map', and plotted the results of our laboratory and our co-workers. The map demonstrated that dose/dose rate plane could be divided into three areas; 1) An area where harmful effects are observed, 2) An area where no harmful effects are observed, and 3) Another area, between previous two areas, where certain protective functions are enhanced. As this map would be a powerful tool to find some trend among the vast numbers of data relating the biological effects of ionizing radiation, we have developed a computer program which plots the collected data on the dose/dose rate map sorting by experimental conditions. In this study, we graphically reviewed and analyzed the data relating to the lifespan studies of animals with a view to determining the relationships between doses and dose rates of ionizing radiation and cancer incidence. The data contains about 800 sets of experiments, which concerns 187,000 animals exposed to gamma ray or X-ray and their 112,000 controls, and total of about 30,000 cancers in exposed animals and 14,000 cancers in controls. About 800 points of data were plotted on the dose/dose rate map. The plot showed that 1) The divided three areas in the dose/dose rate map were generally confirmed by these 800 points of data, and 2) In some particular conditions, e.g. sarcoma by X-rays, the biologically effective area is extended to relatively high dose/dose rate area. (author)

Low-Dose Radioactive Iodine Destroys Thyroid Tissue Left after Surgery

Science.gov (United States)

A low dose of radioactive iodine given after surgery for thyroid cancer destroyed (ablated) residual thyroid tissue as effectively as a higher dose, with fewer side effects and less exposure to radiation, according to two randomized controlled trials.

Changes in dose with segmentation of breast tissues in Monte Carlo calculations for low-energy brachytherapy

International Nuclear Information System (INIS)

Sutherland, J. G. H.; Thomson, R. M.; Rogers, D. W. O.

2011-01-01

Purpose: To investigate the use of various breast tissue segmentation models in Monte Carlo dose calculations for low-energy brachytherapy. Methods: The EGSnrc user-code BrachyDose is used to perform Monte Carlo simulations of a breast brachytherapy treatment using TheraSeed Pd-103 seeds with various breast tissue segmentation models. Models used include a phantom where voxels are randomly assigned to be gland or adipose (randomly segmented), a phantom where a single tissue of averaged gland and adipose is present (averaged tissue), and a realistically segmented phantom created from previously published numerical phantoms. Radiation transport in averaged tissue while scoring in gland along with other combinations is investigated. The inclusion of calcifications in the breast is also studied in averaged tissue and randomly segmented phantoms. Results: In randomly segmented and averaged tissue phantoms, the photon energy fluence is approximately the same; however, differences occur in the dose volume histograms (DVHs) as a result of scoring in the different tissues (gland and adipose versus averaged tissue), whose mass energy absorption coefficients differ by 30%. A realistically segmented phantom is shown to significantly change the photon energy fluence compared to that in averaged tissue or randomly segmented phantoms. Despite this, resulting DVHs for the entire treatment volume agree reasonably because fluence differences are compensated by dose scoring differences. DVHs for the dose to only the gland voxels in a realistically segmented phantom do not agree with those for dose to gland in an averaged tissue phantom. Calcifications affect photon energy fluence to such a degree that the differences in fluence are not compensated for (as they are in the no calcification case) by dose scoring in averaged tissue phantoms. Conclusions: For low-energy brachytherapy, if photon transport and dose scoring both occur in an averaged tissue, the resulting DVH for the entire

Changes in dose with segmentation of breast tissues in Monte Carlo calculations for low-energy brachytherapy

Energy Technology Data Exchange (ETDEWEB)

Sutherland, J. G. H.; Thomson, R. M.; Rogers, D. W. O. [Carleton Laboratory for Radiotherapy Physics, Department of Physics, Carleton University, Ottawa K1S 5B6 (Canada)

2011-08-15

Purpose: To investigate the use of various breast tissue segmentation models in Monte Carlo dose calculations for low-energy brachytherapy. Methods: The EGSnrc user-code BrachyDose is used to perform Monte Carlo simulations of a breast brachytherapy treatment using TheraSeed Pd-103 seeds with various breast tissue segmentation models. Models used include a phantom where voxels are randomly assigned to be gland or adipose (randomly segmented), a phantom where a single tissue of averaged gland and adipose is present (averaged tissue), and a realistically segmented phantom created from previously published numerical phantoms. Radiation transport in averaged tissue while scoring in gland along with other combinations is investigated. The inclusion of calcifications in the breast is also studied in averaged tissue and randomly segmented phantoms. Results: In randomly segmented and averaged tissue phantoms, the photon energy fluence is approximately the same; however, differences occur in the dose volume histograms (DVHs) as a result of scoring in the different tissues (gland and adipose versus averaged tissue), whose mass energy absorption coefficients differ by 30%. A realistically segmented phantom is shown to significantly change the photon energy fluence compared to that in averaged tissue or randomly segmented phantoms. Despite this, resulting DVHs for the entire treatment volume agree reasonably because fluence differences are compensated by dose scoring differences. DVHs for the dose to only the gland voxels in a realistically segmented phantom do not agree with those for dose to gland in an averaged tissue phantom. Calcifications affect photon energy fluence to such a degree that the differences in fluence are not compensated for (as they are in the no calcification case) by dose scoring in averaged tissue phantoms. Conclusions: For low-energy brachytherapy, if photon transport and dose scoring both occur in an averaged tissue, the resulting DVH for the entire

Cirurgia conservadora, radioterapia externa e reforço de dose com braquiterapia de alta taxa de dose: uma nova perspectiva no tratamento de sarcomas de partes moles do adulto Limb-sparing surgery, external beam radiotherapy and boost with high-dose rate brachytherapy: a new perspective for the treatment of soft tissue sarcomas in adults

Directory of Open Access Journals (Sweden)

Antonio Cássio Assis Pellizzon

2002-03-01

Full Text Available OBJETIVO: Avaliar a influência no controle local de pacientes adultos e portadores de sarcoma de partes moles em extremidades e submetidos a cirurgia conservadora do membro, com braquiterapia de alta taxa de dose (BATD como reforço para a radioterapia externa (RT. MATERIAL E MÉTODOS: Foram avaliados 16 pacientes tratados, de 1993 até 1999. A RT foi utilizada com finalidade pré ou pós-operatória (30--55 Gy e BATD com dose de 18--36 Gy (fx 3--6 Gy BID. Com base no modelo linear quadrático calculou-se a dose efetiva biológica ("biological effective dose" - BED para o tumor e comparou-se seu valor a dados da literatura internacional, que utiliza tratamentos com RT e braquiterapia de baixa taxa de dose (BBTD. RESULTADOS: Os valores médios e medianos da BED para os sarcomas de partes moles foram de 78,5 Gy7 e 80 Gy7. A análise univariada mostrou que a BED para o tumor, quando utilizada BATD, era semelhante ao valor de 83 Gy7 quando utilizada BBTD (p = 0,008. As taxas de controle local, sobrevida livre de doença e sobrevida global atuarial em cinco anos foram de 83,2%, 75% e 93,7%, respectivamente. CONCLUSÕES: A BATD, quando utilizada como método complementar no reforço de dose da RT no tratamento conservador dos sarcomas de partes moles, apresenta taxas de controle local equiparáveis às da literatura internacional; no entanto, estudos com número maior de pacientes e período maior de seguimento são ainda necessários para determinar o verdadeiro potencial da BATD em substituir a BBTD.PURPOSE: To evaluate the influence on local control in adult patients with soft tissue sarcomas of the limbs that underwent limb-sparing surgery and high-dose rate brachytherapy (HDRB in association with teletherapy. MATERIAL AND METHODS: Sixteen patients treated from 1993 to 1999 were reviewed. Teletherapy was used pre- or postoperatively (30--55 Gy in association with HDRB in a dose range of 18--36 Gy (fx 3--6 Gy BID. The linear quadratic model was

High Dose-Rate Versus Low Dose-Rate Brachytherapy for Lip Cancer

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Ghadjar, Pirus, E-mail: pirus.ghadjar@insel.ch [Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern (Switzerland); Bojaxhiu, Beat [Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern (Switzerland); Simcock, Mathew [Swiss Group for Clinical Cancer Research Coordinating Center, Bern (Switzerland); Terribilini, Dario; Isaak, Bernhard [Division of Medical Radiation Physics, Inselspital, Bern University Hospital, and University of Bern, Bern (Switzerland); Gut, Philipp; Wolfensberger, Patrick; Broemme, Jens O.; Geretschlaeger, Andreas; Behrensmeier, Frank; Pica, Alessia; Aebersold, Daniel M. [Department of Radiation Oncology, Inselspital, Bern University Hospital, and University of Bern (Switzerland)

2012-07-15

Purpose: To analyze the outcome after low-dose-rate (LDR) or high-dose-rate (HDR) brachytherapy for lip cancer. Methods and Materials: One hundred and three patients with newly diagnosed squamous cell carcinoma of the lip were treated between March 1985 and June 2009 either by HDR (n = 33) or LDR brachytherapy (n = 70). Sixty-eight patients received brachytherapy alone, and 35 received tumor excision followed by brachytherapy because of positive resection margins. Acute and late toxicity was assessed according to the Common Terminology Criteria for Adverse Events 3.0. Results: Median follow-up was 3.1 years (range, 0.3-23 years). Clinical and pathological variables did not differ significantly between groups. At 5 years, local recurrence-free survival, regional recurrence-free survival, and overall survival rates were 93%, 90%, and 77%. There was no significant difference for these endpoints when HDR was compared with LDR brachytherapy. Forty-two of 103 patients (41%) experienced acute Grade 2 and 57 of 103 patients (55%) experienced acute Grade 3 toxicity. Late Grade 1 toxicity was experienced by 34 of 103 patients (33%), and 5 of 103 patients (5%) experienced late Grade 2 toxicity; no Grade 3 late toxicity was observed. Acute and late toxicity rates were not significantly different between HDR and LDR brachytherapy. Conclusions: As treatment for lip cancer, HDR and LDR brachytherapy have comparable locoregional control and acute and late toxicity rates. HDR brachytherapy for lip cancer seems to be an effective treatment with acceptable toxicity.

Present dose limits and their relation to radiosensitivity of different organs and tissues

International Nuclear Information System (INIS)

Anon.

1987-01-01

Dose equivalent limits in relation to dose thresholds are considered for injury of various tissues and organs to evaluate the protection agains non-stochastic irradiation effects by the existing system of dose limitation for radiotherapeutic personnel. Data on tissue radiosensitivity in relation to non-stochastic effects, obtained from radiotherapeutic experience, are presented. Dose threshold values, derived for patients, with a correction in the direction of increase, may be applied to conditions of occupational exposure except for bone marrow, gonads and eye lens, where threshold doses are lower

Dose Response Model of Biological Reaction to Low Dose Rate Gamma Radiation

International Nuclear Information System (INIS)

Magae, J.; Furikawa, C.; Hoshi, Y.; Kawakami, Y.; Ogata, H.

2004-01-01

It is necessary to use reproducible and stable indicators to evaluate biological responses to long term irradiation at low dose-rate. They should be simple and quantitative enough to produce the results statistically accurate, because we have to analyze the subtle changes of biological responses around background level at low dose. For these purposes we chose micronucleus formation of U2OS, a human osteosarcoma cell line, as indicators of biological responses. Cells were exposed to gamma ray in irradiation rom bearing 50,000 Ci 60Co. After irradiation, they were cultured for 24 h in the presence of cytochalasin B to block cytokinesis, and cytoplasm and nucleus were stained with DAPI and prospidium iodide, respectively. the number of binuclear cells bearing micronuclei was counted under a fluorescence microscope. Dose rate in the irradiation room was measured with PLD. Dose response of PLD is linear between 1 mGy to 10 Gy, and standard deviation of triplicate count was several percent of mean value. We fitted statistically dose response curves to the data, and they were plotted on the coordinate of linearly scale response and dose. The results followed to the straight line passing through the origin of the coordinate axes between 0.1-5 Gy, and dose and does rate effectiveness factor (DDREF) was less than 2 when cells were irradiated for 1-10 min. Difference of the percent binuclear cells bearing micronucleus between irradiated cells and control cells was not statistically significant at the dose above 0.1 Gy when 5,000 binuclear cells were analyzed. In contrast, dose response curves never followed LNT, when cells were irradiated for 7 to 124 days. Difference of the percent binuclear cells bearing micronucleus between irradiated cells and control cells was not statistically significant at the dose below 6 Gy, when cells were continuously irradiated for 124 days. These results suggest that dose response curve of biological reaction is remarkably affected by exposure

On determining dose rate constants spectroscopically

International Nuclear Information System (INIS)

Rodriguez, M.; Rogers, D. W. O.

2013-01-01

Purpose: To investigate several aspects of the Chen and Nath spectroscopic method of determining the dose rate constants of 125 I and 103 Pd seeds [Z. Chen and R. Nath, Phys. Med. Biol. 55, 6089–6104 (2010)] including the accuracy of using a line or dual-point source approximation as done in their method, and the accuracy of ignoring the effects of the scattered photons in the spectra. Additionally, the authors investigate the accuracy of the literature's many different spectra for bare, i.e., unencapsulated 125 I and 103 Pd sources. Methods: Spectra generated by 14 125 I and 6 103 Pd seeds were calculated in vacuo at 10 cm from the source in a 2.7 × 2.7 × 0.05 cm 3 voxel using the EGSnrc BrachyDose Monte Carlo code. Calculated spectra used the initial photon spectra recommended by AAPM's TG-43U1 and NCRP (National Council of Radiation Protection and Measurements) Report 58 for the 125 I seeds, or TG-43U1 and NNDC(2000) (National Nuclear Data Center, 2000) for 103 Pd seeds. The emitted spectra were treated as coming from a line or dual-point source in a Monte Carlo simulation to calculate the dose rate constant. The TG-43U1 definition of the dose rate constant was used. These calculations were performed using the full spectrum including scattered photons or using only the main peaks in the spectrum as done experimentally. Statistical uncertainties on the air kerma/history and the dose rate/history were ⩽0.2%. The dose rate constants were also calculated using Monte Carlo simulations of the full seed model. Results: The ratio of the intensity of the 31 keV line relative to that of the main peak in 125 I spectra is, on average, 6.8% higher when calculated with the NCRP Report 58 initial spectrum vs that calculated with TG-43U1 initial spectrum. The 103 Pd spectra exhibit an average 6.2% decrease in the 22.9 keV line relative to the main peak when calculated with the TG-43U1 rather than the NNDC(2000) initial spectrum. The measured values from three different

Late effects of low doses and dose rates

International Nuclear Information System (INIS)

Paretzke, H.G.

1980-01-01

This paper outlines the spectrum of problems and approaches used in work on the derivation of quantitative prognoses of late effects in man of low doses and dose rates. The origins of principal problems encountered in radiation risks assessments, definitions and explanations of useful quantities, methods of deriving risk factors from biological and epidemiological data, and concepts of risk evaluation and problems of acceptance are individually discussed

Dose and dose rate extrapolation factors for malignant and non-malignant health endpoints after exposure to gamma and neutron radiation

Energy Technology Data Exchange (ETDEWEB)

Tran, Van; Little, Mark P. [National Cancer Institute, Radiation Epidemiology Branch, Rockville, MD (United States)

2017-11-15

Murine experiments were conducted at the JANUS reactor in Argonne National Laboratory from 1970 to 1992 to study the effect of acute and protracted radiation dose from gamma rays and fission neutron whole body exposure. The present study reports the reanalysis of the JANUS data on 36,718 mice, of which 16,973 mice were irradiated with neutrons, 13,638 were irradiated with gamma rays, and 6107 were controls. Mice were mostly Mus musculus, but one experiment used Peromyscus leucopus. For both types of radiation exposure, a Cox proportional hazards model was used, using age as timescale, and stratifying on sex and experiment. The optimal model was one with linear and quadratic terms in cumulative lagged dose, with adjustments to both linear and quadratic dose terms for low-dose rate irradiation (<5 mGy/h) and with adjustments to the dose for age at exposure and sex. After gamma ray exposure there is significant non-linearity (generally with upward curvature) for all tumours, lymphoreticular, respiratory, connective tissue and gastrointestinal tumours, also for all non-tumour, other non-tumour, non-malignant pulmonary and non-malignant renal diseases (p < 0.001). Associated with this the low-dose extrapolation factor, measuring the overestimation in low-dose risk resulting from linear extrapolation is significantly elevated for lymphoreticular tumours 1.16 (95% CI 1.06, 1.31), elevated also for a number of non-malignant endpoints, specifically all non-tumour diseases, 1.63 (95% CI 1.43, 2.00), non-malignant pulmonary disease, 1.70 (95% CI 1.17, 2.76) and other non-tumour diseases, 1.47 (95% CI 1.29, 1.82). However, for a rather larger group of malignant endpoints the low-dose extrapolation factor is significantly less than 1 (implying downward curvature), with central estimates generally ranging from 0.2 to 0.8, in particular for tumours of the respiratory system, vasculature, ovary, kidney/urinary bladder and testis. For neutron exposure most endpoints, malignant and

Quality control of 192Ir high dose rate after loading brachytherapy dose veracity

International Nuclear Information System (INIS)

Feng Zhongsu; Xu Xiao; Liu Fen

2008-01-01

Recently, 192 Ir high dose rate (HDR) afterloading are widely used in brachytherapy. The advantage of using HDR systems over low dose rate systems are shorter treatment time and higher fraction dose. To guarantee the veracity of the delivery dose, several quality control methods are deseribed in this work. With these we can improve the position precision, time precision and dose precision of the brachytherapy. (authors)

Radiation dose rate meter

International Nuclear Information System (INIS)

Kronenberg, S.; Siebentritt, C.R.

1981-01-01

A combined dose rate meter and charger unit therefor which does not require the use of batteries but on the other hand produces a charging potential by means of a piezoelectric cylinder which is struck by a manually triggered hammer mechanism. A tubular type electrometer is mounted in a portable housing which additionally includes a geiger-muller (Gm) counter tube and electronic circuitry coupled to the electrometer for providing multi-mode operation. In one mode of operation, an rc circuit of predetermined time constant is connected to a storage capacitor which serves as a timed power source for the gm tube, providing a measurement in terms of dose rate which is indicated by the electrometer. In another mode, the electrometer indicates individual counts

A study on gamma dose rate in Seoul (I)

International Nuclear Information System (INIS)

Kim, You Hyun; Kim, Chang Kyun; Choi, Jong Hak; Kim, Jeong Min

2001-01-01

This study was conducted to find out gamma dose rate in Seoul, from January to December in 2000, and the following results were achieved : The annual gamma dose rate in Seoul was 17.24 μR/hr as average. The annual gamma dose rate in subway of Seoul was 14.96 μR/hr as average. The highest annual gamma dose rate was Dong-daemon ku. Annual gamma dose rate in Seoul was higher autumn than winter

Radioactivities (dose rates) of rocks in Japan

International Nuclear Information System (INIS)

Matsuda, Hideharu; Minato, Susumu

1995-01-01

The radioactive distribution (radiation doses) of major rocks in Japan was monitored to clarify the factors influencing terrestrial gamma-ray absorbed dose rates. The rock samples were reduced to powder and analyzed by well-type NaI(Tl) scintillation detector and pulse height analyzer. Terrestrial gamma-ray dose rates were estimated in terms of gamma radiation dose rate 1 m above the ground. The radioactivity concentration was highest in acidic rock which contains much SiO 2 among igneous rock, followed by neutral rock, basic rock, and ultrabasic rock. The radioactive concentration was 30-40% lower in acidic and clastic rocks than those of the world average concentration. Higher radioactive concentration was observed in soils than the parent rocks of sedimentary rock and metamorphic rock. The gamma radiation dose rate was in proportion to the radioactive concentration of the rocks. To clarify the radioactive effect in the change course of rocks into soils, comparative measurement of outcrop and soil radioactive concentrations is important. (S.Y.)

Low doses effects and gamma radiations low dose rates

International Nuclear Information System (INIS)

Averbeck, D.

1999-01-01

This expose wishes for bringing some definitions and base facts relative to the problematics of low doses effects and low dose rates effects. It shows some already used methods and some actual experimental approaches by focusing on the effects of ionizing radiations with a low linear energy transfer. (N.C.)

Ageing effects of polymers at very low dose-rates

International Nuclear Information System (INIS)

Chenion, J.; Armand, X.; Berthet, J.; Carlin, F.; Gaussens, G.; Le Meur, M.

1987-10-01

The equipment irradiation dose-rate into the containment is variable from 10 -6 to 10 -4 gray per second for the most exposed materials. During qualification, safety equipments are submitted in France to dose-rates around 0.28 gray per second. This study purpose is to now if a so large irradiation dose-rate increase is reasonable. Three elastomeric materials used in electrical cables, o'rings seals and connectors, are exposed to a very large dose-rates scale between 2.1.10 -4 and 1.4 gray per second, to 49 KGy dose. This work was carried out during 3.5 years. Oxygen consumption measurement of the air in contact with polymer materials, as mechanical properties measurement show that: - at very low dose-rate, oxygen consumption is maximum at the same time (1.4 year) for the three elastomeric samples. Also, mechanical properties simultaneously change with oxygen consumption. At very low dose-rate, for the low irradiation doses, oxygen consumption is at least 10 times more important that it is showed when irradiation is carried out with usual material qualification dose-rate. At very low dose-rate, oxygen consumption decreases when absorbed irradiation dose by samples increases. The polymer samples irradiation dose is not still sufficient (49 KGy) to certainly determine, for the three chosen polymer materials, the reasonable irradiation acceleration boundary during nuclear qualification tests [fr

Recommended de minimis radiation dose rates for Canada

International Nuclear Information System (INIS)

1990-07-01

A de minimis dose or dose rate as used in this report represents a level of risk which is generally accepted as being of no significance to an individual, or in the case of a population, of no significance to society. The doses corresponding to these levels of risk are based on current scientific knowledge. Dose rates recommended in this report are as follows: a de minimis individual dose rate of 10 μSv a -1 , based on a risk level that would generally be regarded as negligible in comparison with other risks; and a de minimis collective dose rate of 1 person-Sv a -1 , based on an imperceptible increase above the normal incidences of cancer and genetic defects in the exposed population. The concept of de minimis is to be distinguished from 'exempt from regulation' (below regulatory concern). The latter involves broader social and economic factors which encompass but are not limited to the purely risk-based factors addressed by the de minimis dose. De minimis is one of the factors that determine the exemption of sources or practices that may result in doses below or above the de minimis level. Although these de minimis dose rates should be considered in developing criteria and guidelines for deriving quantities and concentrations of radioactive substances that may be exempted from regulation, this document is only concerned with establishing de minimis dose rates, not with exempting sources and practices

The calculation of dose rates from rectangular sources

International Nuclear Information System (INIS)

Hartley, B.M.

1998-01-01

A common problem in radiation protection is the calculation of dose rates from extended sources and irregular shapes. Dose rates are proportional to the solid angle subtended by the source at the point of measurement. Simple methods of calculating solid angles would assist in estimating dose rates from large area sources and therefore improve predictive dose estimates when planning work near such sources. The estimation of dose rates is of particular interest to producers of radioactive ores but other users of bulk radioactive materials may have similar interest. The use of spherical trigonometry can assist in determination of solid angles and a simple equation is derived here for the determination of the dose at any distance from a rectangular surface. The solid angle subtended by complex shapes can be determined by modelling the area as a patchwork of rectangular areas and summing the solid angles from each rectangle. The dose rates from bags of thorium bearing ores is of particular interest in Western Australia and measured dose rates from bags and containers of monazite are compared with theoretical estimates based on calculations of solid angle. The agreement is fair but more detailed measurements would be needed to confirm the agreement with theory. (author)

Estimation of dose from chromosome aberration rate

International Nuclear Information System (INIS)

Li Deping

1990-01-01

The methods and skills of evaluating dose from correctly scored shromsome aberration rate are presented, and supplemented with corresponding BASIC computer code. The possibility and preventive measures of excessive probability of missing score of the aberrations in some of the current routine score methods are discussed. The use of dose-effect relationship with exposure time correction factor G in evaluating doses and their confidence intervals, dose estimation in mixed n-γ exposure, and identification of high by nonuniform acute exposure to low LET radiation and its dose estimation are discussed in more detail. The difference of estimated dose due to whether the interaction between subleisoms produced by n and γ have been taken into account is examined. In fitting the standard dose-aberration rate curve, proper weighing of experiment points and comparison with commonly accepted values are emphasised, and the coefficient of variation σ y √y of the aberration rate y as a function of dose and exposure time is given. In appendix I and II, the dose-aberration rate formula is derived from dual action theory, and the time variation of subleisom is illustrated and in appendix III, the estimation of dose from scores of two different types of aberrations (of other related score) is illustrated. Two computer codes are given in appendix IV, one is a simple code, the other a complete code, including the fitting of standard curve. the skills of using compressed data storage, and the production of simulated 'data ' for testing the curve fitting procedure are also given

High Dose-Rate Versus Low Dose-Rate Brachytherapy for Lip Cancer

International Nuclear Information System (INIS)

Ghadjar, Pirus; Bojaxhiu, Beat; Simcock, Mathew; Terribilini, Dario; Isaak, Bernhard; Gut, Philipp; Wolfensberger, Patrick; Brömme, Jens O.; Geretschläger, Andreas; Behrensmeier, Frank; Pica, Alessia; Aebersold, Daniel M.

2012-01-01

Purpose: To analyze the outcome after low-dose-rate (LDR) or high-dose-rate (HDR) brachytherapy for lip cancer. Methods and Materials: One hundred and three patients with newly diagnosed squamous cell carcinoma of the lip were treated between March 1985 and June 2009 either by HDR (n = 33) or LDR brachytherapy (n = 70). Sixty-eight patients received brachytherapy alone, and 35 received tumor excision followed by brachytherapy because of positive resection margins. Acute and late toxicity was assessed according to the Common Terminology Criteria for Adverse Events 3.0. Results: Median follow-up was 3.1 years (range, 0.3–23 years). Clinical and pathological variables did not differ significantly between groups. At 5 years, local recurrence-free survival, regional recurrence-free survival, and overall survival rates were 93%, 90%, and 77%. There was no significant difference for these endpoints when HDR was compared with LDR brachytherapy. Forty-two of 103 patients (41%) experienced acute Grade 2 and 57 of 103 patients (55%) experienced acute Grade 3 toxicity. Late Grade 1 toxicity was experienced by 34 of 103 patients (33%), and 5 of 103 patients (5%) experienced late Grade 2 toxicity; no Grade 3 late toxicity was observed. Acute and late toxicity rates were not significantly different between HDR and LDR brachytherapy. Conclusions: As treatment for lip cancer, HDR and LDR brachytherapy have comparable locoregional control and acute and late toxicity rates. HDR brachytherapy for lip cancer seems to be an effective treatment with acceptable toxicity.

Radiobiological responses for two cell lines following continuous low dose-rate (CLDR) and pulsed dose rate (PDR) brachytherapy

International Nuclear Information System (INIS)

Hanisch, Per Henrik; Furre, Torbjoern; Olsen, Dag Rune; Pettersen, Erik O.

2007-01-01

The iso-effective irradiation of continuous low-dose-rate (CLDR) irradiation was compared with that of various schedules of pulsed dose rate (PDR) irradiation for cells of two established human lines, T-47D and NHIK 3025. Complete single-dose response curves were obtained for determination of parameters α and β by fitting of the linear quadratic formula. Sublethal damage repair constants μ and T 1/2 were determined by split-dose recovery experiments. On basis of the acquired parameters of each cell type the relative effectiveness of the two regimens of irradiation (CLDR and PDR) was calculated by use of Fowler's radiobiological model for iso-effect irradiation for repeated fractions of dose delivered at medium dose rates. For both cell types the predicted and observed relative effectiveness was compared at low and high iso-effect levels. The results indicate that the effect of PDR irradiation predicted by Fowler's model is equal to that of CLDR irradiation for both small and large doses with T-47D cells. With NHIK 3025 cells PDR irradiation induces a larger effect than predicted by the model for small doses, while it induces the predicted effect for high doses. The underlying cause of this difference is unclear, but cell-cycle parameters, like G2-accumulation is tested and found to be the same for the two cell lines

Effect of low-density lateral interfaces on soft-tissue doses

International Nuclear Information System (INIS)

Hunt, Margie A.; Desobry, Gregory E.; Fowble, Barbara; Coia, Lawrence R.

1997-01-01

Purpose: Doses at the interface between tissue and low-density inhomogeneities with the interface positioned perpendicular to the beam direction have been well studied. When the inhomogeneity lies parallel to the beam direction (i.e., a lateral interface), the resulting dose distribution is not as well known. Lateral lung--soft-tissue interfaces are common in many fields used to treat malignancies in the thorax region including tangential breast fields and anteroposterior fields for lung and esophageal cancer. The purpose of this study was to evaluate the dose distribution along lateral interfaces and to determine the implications for treatment. Methods and Materials: A polystyrene and cork slab phantom was irradiated from the side to simulate treatment fields with lateral lung--soft-tissue interfaces. The beam was positioned with the isocenter in polystyrene and the field edge in cork. Cork slabs (0.6-2.5 cm) were used to simulate different thicknesses of lung between the field edge and the target volume. Measurements were made using a parallel plate ionization chamber. With the chamber position held constant, polystyrene slabs were added between the cork and the chamber to study the dose distribution in the interface region. Interface doses were studied as a function of the amount of cork in the field, field size, beam energy (6-18 MV), and depth. Results: Doses in the interface region were lower by as much as 10% compared to doses in a homogeneous phantom. For a given cork width and field size, the magnitude of the underdose increased by several percent as the x-ray energy increased from 6 to 18 MV. The underdose at the interface was 5% for 6 MV and 8% for 18 MV X-rays with a 1-cm cork width. For a 2.5-cm cork width, underdoses of 2.5% and 3% at distances up to 2.5 and 4 mm lateral to the interface were observed for 6- and 18-MV X-rays, respectively. However, doses right at the interface were 1% greater for 6 MV and 3% less for 18 MV than doses in a homogeneous

Treatment Planning for Pulsed Reduced Dose-Rate Radiotherapy in Helical Tomotherapy

International Nuclear Information System (INIS)

Rong Yi; Paliwal, Bhudatt; Howard, Steven P.; Welsh, James

2011-01-01

Purpose: Pulsed reduced dose-rate radiotherapy (PRDR) is a valuable method of reirradiation because of its potential to reduce late normal tissue toxicity while still yielding significant tumoricidal effect. A typical method using a conventional linear accelerator (linac) is to deliver a series of 20-cGy pulses separated by 3-min intervals to give an effective dose-rate of just under 7 cGy/min. Such a strategy is fraught with difficulties when attempted on a helical tomotherapy unit. We investigated various means to overcome this limitation. Methods and Materials: Phantom and patient cases were studied. Plans were generated with varying combinations of field width (FW), pitch, and modulation factor (MF) to administer 200 cGy per fraction to the planning target in eight subfractions, thereby mimicking the technique used on conventional linacs. Plans were compared using dose-volume histograms, homogeneity indices, conformation numbers, and treatment time. Plan delivery quality assurance was performed to assess deliverability. Results: It was observed that for helical tomotherapy, intrinsic limitations in leaf open time in the multileaf collimator deteriorate plan quality and deliverability substantially when attempting to deliver very low doses such as 20-40 cGy. The various permutations evaluated revealed that the combination of small FW (1.0 cm), small MF (1.3-1.5), and large pitch (∼0.86), along with the half-gantry-angle-blocked scheme, can generate clinically acceptable plans with acceptable delivery accuracy (±3%). Conclusion: Pulsed reduced dose-rate radiotherapy can be accurately delivered using helical tomotherapy for tumor reirradiation when the appropriate combination of FW, MF, and pitch is used.

Dose and dose rate effects of whole-body gamma-irradiation: I. Lymphocytes and lymphoid organs

Science.gov (United States)

Pecaut, M. J.; Nelson, G. A.; Gridley, D. S.

2001-01-01

The major goal of part I of this study was to compare varying doses and dose rates of whole-body gamma-radiation on lymphoid cells and organs. C57BL/6 mice (n = 75) were exposed to 0, 0.5, 1.5, and 3.0 Gy gamma-rays (60Co) at 1 cGy/min (low-dose rate, LDR) and 80 cGy/min (high-dose rate, HDR) and euthanized 4 days later. A significant dose-dependent loss of spleen mass was observed with both LDR and HDR irradiation; for the thymus this was true only with HDR. Decreasing leukocyte and lymphocyte numbers occurred with increasing dose in blood and spleen at both dose rates. The numbers (not percentages) of CD3+ T lymphocytes decreased in the blood in a dose-dependent manner at both HDR and LDR. Splenic T cell counts decreased with dose only in HDR groups; percentages increased with dose at both dose rates. Dose-dependent decreases occurred in CD4+ T helper and CD8+ T cytotoxic cell counts at HDR and LDR. In the blood the percentages of CD4+ cells increased with increasing dose at both dose rates, whereas in the spleen the counts decreased only in the HDR groups. The percentages of the CD8+ population remained stable in both blood and spleen. CD19+ B cell counts and percentages in both compartments declined markedly with increasing HDR and LDR radiation. NK1.1+ natural killer cell numbers and proportions remained relatively stable. Overall, these data indicate that the observed changes were highly dependent on the dose, but not dose rate, and that cells in the spleen are more affected by dose rate than those in blood. The results also suggest that the response of lymphocytes in different body compartments may be variable.

MONTEC, an interactive fortran program to simulate radiation dose and dose-rate responses of populations

International Nuclear Information System (INIS)

Perry, K.A.; Szekely, J.G.

1983-09-01

The computer program MONTEC was written to simulate the distribution of responses in a population whose members are exposed to multiple radiation doses at variable dose rates. These doses and dose rates are randomly selected from lognormal distributions. The individual radiation responses are calculated from three equations, which include dose and dose-rate terms. Other response-dose/rate relationships or distributions can be incorporated by the user as the need arises. The purpose of this documentation is to provide a complete operating manual for the program. This version is written in FORTRAN-10 for the DEC system PDP-10

The limiting dose rate and its importance in radiation protection

International Nuclear Information System (INIS)

Bakkiam, D.; Sonwani, Swetha; Arul Ananthakumar, A.; Mohankumar, Mary N.

2012-01-01

The concept of defining a low dose of ionizing radiation still remains unclear. Before attempting to define a low dose, it is more important to define a low-dose rate since effects at low dose-rates are different from those observed at higher dose-rates. Hence, it follows that low dose-rates rather than a low dose is an important criteria to determine radio-biological effects and risk factors i.e. stochastic health effects. Chromosomal aberrations induced by ionizing radiations are well fitted by quadratic model Y= áD + âD 2 + C with the linear coefficient of dose predominating for high LET radiations and low doses of low LET. At higher doses and dose rates of sparsely ionizing radiation, break pairs produced by inter-track action leads to the formation of exchange type aberrations and is dependent on dose rate. Whereas at lower doses and dose rates, intra-track action produces break pairs and resulting aberrations are in direct proportion to absorbed dose and independent of dose rate. The dose rate at which inter-track ceases to be observable and where intra-track action effectively becomes the sole contributor of lesion-pair formation is referred to as limiting dose rate (LDR). Once the LDR is reached further reduction in dose rates will not affect the slope of DR since breaks produced by independent charged particle tracks are widely separated in time to interact with each other for aberration yield. This linear dependency is also noticed for acute exposures at very low doses. Existing reports emphasizes the existence of LDR likely to be e6.3cGyh -1 . However no systematic studies have been conducted so far to determine LDR. In the present investigation DR curves were constructed for the dose rates 0.002 and 0.003 Gy/min and to define LDR at which a coefficient approaches zero. Extrapolation of limiting low dose rate data can be used to predict low dose effects regardless of dose rate and its definition ought to serve as a useful index for studies pertaining

Problems in continuous dose rate measurement

International Nuclear Information System (INIS)

Yoshioka, Mitsuo

1983-01-01

The system of continuous dose rate measurement in Fukui Prefecture is described. A telemeter system was constructed in October, 1976, and it has been operated since 1977. Observation has been made at 11 observation stations in the Prefecture. In addition to the continuous measurement of dose rate by using NaI(T1)-DBM systems, the ionization chambers for high dose rate were installed, and also meteorological data have been collected. The detectors are covered with 1 mm thick aluminum designed so that the absorption of external radiation is kept as small as possible. To keep the environmental temperature of the detectors constant, constant temperature wind blow is made. With these consideration, the measurement of Xe-133 is possible, and the standard deviation of yearly dose is around 0.4 mR/Y. By measuring DBM transmission rate, the contribution of Xe-133, which comes from the exhaust pumps in power plants, can be detected. The problems of this system are as follows. First of all, the characteristics of the system must meet the purpose of dose monitoring. The system must detect the dose less than the target value to be achieved. The second is the selection of measuring systems to be set. The system is still not unified, and it is difficult to exchange data between different stations. Finally, the method of data analysis is not yet unified. Manuals or guide-books for this purpose are necessary for the mutual comparison of the data from the stations in different districts. (Kato, T.)

Radiation shielding and dose rate distribution for the building of the high dose rate accelerator

International Nuclear Information System (INIS)

Matsuda, Koji; Takagaki, Torao; Nakase, Yoshiaki; Nakai, Yohta.

1984-03-01

A high dose rate electron accelerator was established at Osaka Laboratory for Radiation Chemistry, Takasaki Establishment, JAERI in the fiscal year of 1975. This report shows the fundamental concept for the radiation shielding of the accelerator building and the results of their calculations which were evaluated through the model experiments. After the construction of the building, the leak radiation was measured in order to evaluate the calculating method of radiation shielding. Dose rate distribution of X-rays was also measured in the whole area of the irradiation room as a data base. (author)

Effects of low dose rate irradiation on life span prolongation of human premature-aging syndrome model mice

International Nuclear Information System (INIS)

Nomura, Takaharu

2006-01-01

We previously showed that Type II diabetes model mice prolonged of their life span by life long low dose rate irradiation. We also found that antioxidant function in variety tissues of some strain of mice were enhancement after low dose/low dose rate irradiation. The prolongation of life span might depend on certain damaged level of reactive oxygen species. We thought the effect of the prolongation was due to the enhancement of the antioxidant activities after irradiation. We investigated whether the enhancement of antioxidant activities after low dose rate irradiation had an effect on life span prolongation. Four-week-old female human premature-aging syndrome model mice, kl/kl (klotho) mice, which the life span of this model mouse is about 65 days, were irradiated with gamma rays at 0.35, 0.70 or 1.2 mGy/hr. The 0.70 mGy/hr-irradiated group remarkably effected on the prolongation of their life span. Some mice of the group were extremely survived for about and more 100 days. Antioxidant activities in the irradiated groups were enhancement by low dose rate irradiation, however the dependence of the dose rates were not clearly difference. These results suggest that the antioxidant activities in this model mouse were enhanced by the low dose rate irradiation, and may make it possible to prolong the life span of this mouse. (author)

Proposal of a high dose rate brachytherapy model for in vitro radiobiology studies

International Nuclear Information System (INIS)

Geraldo, Jony M.; Nogueira, Luciana B.; Andrade, Lidia M.; Trindade, Cassia; Furtado, Clascidia A.; Ladeira, Luiz Orlando

2016-01-01

The aim of this research was to develop an easy and reproducible approach for experimental HDR brachytherapy allowing in vitro irradiation studies based on clinical parameters. An acrylic platform was designed to attach T25 tissue culture flasks and multi-well tissue culture plates as well as kept the catheters in a fixed position during irradiation. CT images were taken and the irradiation was planned for 550cGy dose applied on adherent tumor cells. Dosimetric measurements were done and all relevant uncertainties were taken into account in order to figure out the correct dose range received by the cells. Tumor cells were irradiated two times over an interval of 24h between irradiations. Proof of concepts of this approach was carried out by biological effects analysis using a radioresistant human epidermoid carcinoma A431 cell line. Cellular proliferation and cell cycle phase were assessed by Trypan blue exclusion assay and DNA content analysis by flow cytometry, respectively. This approach allowed uniform dose distribution around the arrangement in all types of tissue culture plastics evaluated. Corrections due to uncertainties were managed. Regarding in vitro assays there was a significant (p<0.05) decreasing of cellular proliferation rate in irradiated cells. Moreover, increased percentage of cells arrested in G2/M phase (32.3 ± 1.5%) were observed for treated group compared with untreated cells. (author)

Estimated dose rates to members of the public from external exposure to patients with 131I thyroid treatment

International Nuclear Information System (INIS)

Dewji, S.; Bellamy, M.; Leggett, R.; Eckerman, K.; Hertel, N.; Sherbini, S.; Saba, M.

2015-01-01

Purpose: Estimated dose rates that may result from exposure to patients who had been administered iodine-131 ( 131 I) as part of medical therapy were calculated. These effective dose rate estimates were compared with simplified assumptions under United States Nuclear Regulatory Commission Regulatory Guide 8.39, which does not consider body tissue attenuation nor time-dependent redistribution and excretion of the administered 131 I. Methods: Dose rates were estimated for members of the public potentially exposed to external irradiation from patients recently treated with 131 I. Tissue attenuation and iodine biokinetics were considered in the patient in a larger comprehensive effort to improve external dose rate estimates. The external dose rate estimates are based on Monte Carlo simulations using the Phantom with Movable Arms and Legs (PIMAL), previously developed by Oak Ridge National Laboratory and the United States Nuclear Regulatory Commission. PIMAL was employed to model the relative positions of the 131 I patient and members of the public in three exposure scenarios: (1) traveling on a bus in a total of six seated or standing permutations, (2) two nursing home cases where a caregiver is seated at 30 cm from the patient’s bedside and a nursing home resident seated 250 cm away from the patient in an adjacent bed, and (3) two hotel cases where the patient and a guest are in adjacent rooms with beds on opposite sides of the common wall, with the patient and guest both in bed and either seated back-to-back or lying head to head. The biokinetic model predictions of the retention and distribution of 131 I in the patient assumed a single voiding of urinary bladder contents that occurred during the trip at 2, 4, or 8 h after 131 I administration for the public transportation cases, continuous first-order voiding for the nursing home cases, and regular periodic voiding at 4, 8, or 12 h after administration for the hotel room cases. Organ specific activities of 131 I

SU-E-T-154: Calculation of Tissue Dose Point Kernels Using GATE Monte Carlo Simulation Toolkit to Compare with Water Dose Point Kernel

Energy Technology Data Exchange (ETDEWEB)

Khazaee, M [shahid beheshti university, Tehran, Tehran (Iran, Islamic Republic of); Asl, A Kamali [Shahid Beheshti University, Tehran, Iran., Tehran, Tehran (Iran, Islamic Republic of); Geramifar, P [Shariati Hospital, Tehran, Iran., Tehran, Tehran (Iran, Islamic Republic of)

2015-06-15

Purpose: the objective of this study was to assess utilizing water dose point kernel (DPK)instead of tissue dose point kernels in convolution algorithms.to the best of our knowledge, in providing 3D distribution of absorbed dose from a 3D distribution of the activity, the human body is considered equivalent to water. as a Result tissue variations are not considered in patient specific dosimetry. Methods: In this study Gate v7.0 was used to calculate tissue dose point kernel. the beta emitter radionuclides which have taken into consideration in this simulation include Y-90, Lu-177 and P-32 which are commonly used in nuclear medicine. the comparison has been performed for dose point kernels of adipose, bone, breast, heart, intestine, kidney, liver, lung and spleen versus water dose point kernel. Results: In order to validate the simulation the Result of 90Y DPK in water were compared with published results of Papadimitroulas et al (Med. Phys., 2012). The results represented that the mean differences between water DPK and other soft tissues DPKs range between 0.6 % and 1.96% for 90Y, except for lung and bone, where the observed discrepancies are 6.3% and 12.19% respectively. The range of DPK difference for 32P is between 1.74% for breast and 18.85% for bone. For 177Lu, the highest difference belongs to bone which is equal to 16.91%. For other soft tissues the least discrepancy is observed in kidney with 1.68%. Conclusion: In all tissues except for lung and bone, the results of GATE for dose point kernel were comparable to water dose point kernel which demonstrates the appropriateness of applying water dose point kernel instead of soft tissues in the field of nuclear medicine.

SU-E-T-154: Calculation of Tissue Dose Point Kernels Using GATE Monte Carlo Simulation Toolkit to Compare with Water Dose Point Kernel

International Nuclear Information System (INIS)

Khazaee, M; Asl, A Kamali; Geramifar, P

2015-01-01

Purpose: the objective of this study was to assess utilizing water dose point kernel (DPK)instead of tissue dose point kernels in convolution algorithms.to the best of our knowledge, in providing 3D distribution of absorbed dose from a 3D distribution of the activity, the human body is considered equivalent to water. as a Result tissue variations are not considered in patient specific dosimetry. Methods: In this study Gate v7.0 was used to calculate tissue dose point kernel. the beta emitter radionuclides which have taken into consideration in this simulation include Y-90, Lu-177 and P-32 which are commonly used in nuclear medicine. the comparison has been performed for dose point kernels of adipose, bone, breast, heart, intestine, kidney, liver, lung and spleen versus water dose point kernel. Results: In order to validate the simulation the Result of 90Y DPK in water were compared with published results of Papadimitroulas et al (Med. Phys., 2012). The results represented that the mean differences between water DPK and other soft tissues DPKs range between 0.6 % and 1.96% for 90Y, except for lung and bone, where the observed discrepancies are 6.3% and 12.19% respectively. The range of DPK difference for 32P is between 1.74% for breast and 18.85% for bone. For 177Lu, the highest difference belongs to bone which is equal to 16.91%. For other soft tissues the least discrepancy is observed in kidney with 1.68%. Conclusion: In all tissues except for lung and bone, the results of GATE for dose point kernel were comparable to water dose point kernel which demonstrates the appropriateness of applying water dose point kernel instead of soft tissues in the field of nuclear medicine

Terrestrial gamma dose rate in Pahang state Malaysia

International Nuclear Information System (INIS)

Gabdo, H.T.; Federal College of Education, Yola; Ramli, A.T.; Sanusi, M.S.; Saleh, M.A.; Garba, N.N.; Ahmadu Bello University, Zaria

2014-01-01

Environmental terrestrial gamma radiations (TGR) were measured in Pahang state Malaysia between January and April 2013. The TGR dose rates ranged from 26 to 750 nGy h -1 . The measurements were done based on geology and soil types of the area. The mean TGR dose rate was found to be 176 ± 5 nGy h -1 . Few areas of relatively enhanced activity were located in Raub, Temerloh, Bentong and Rompin districts. These areas have external gamma dose rates of between 500 and 750 nGy h -1 . An Isodose map of the state was produced using ArcGIS9 software version 9.3. To evaluate the radiological hazard due to terrestrial gamma dose, the annual effective dose equivalent and the mean population weighted dose rate were calculated and found to be 0.22 mSv year -1 and 168 nGy h -1 respectively. (author)

Health effect of low dose/low dose rate radiation

International Nuclear Information System (INIS)

Kodama, Seiji

2012-01-01

The clarified and non-clarified scientific knowledge is discussed to consider the cause of confusion of explanation of the title subject. The low dose is defined roughly lower than 200 mGy and low dose rate, 0.05 mGy/min. The health effect is evaluated from 2 aspects of clinical symptom/radiation hazard protection. In the clinical aspect, the effect is classified in physical (early and late) and genetic ones, and is classified in stochastic (no threshold value, TV) and deterministic (with TV) ones from the radioprotection aspect. Although the absence of TV in the carcinogenic and genetic effects has not been proved, ICRP employs the stochastic standpoint from the safety aspect for radioprotection. The lowest human TV known now is 100 mGy, meaning that human deterministic effect would not be generated below this dose. Genetic deterministic effect can be observable only in animal experiments. These facts suggest that the practical risk of exposure to <100 mGy in human is the carcinogenesis. The relationship between carcinogenic risk in A-bomb survivors and their exposed dose are found fitted to the linear no TV model, but the epidemiologic data, because of restriction of subject number analyzed, do not always mean that the model is applicable even below the dose <100 mGy. This would be one of confusing causes in explanation: no carcinogenic risk at <100 mGy or risk linear to dose even at <100 mGy, neither of which is scientifically conclusive at present. Also mentioned is the scarce risk of cancer in residents living in the high background radiation regions in the world in comparison with that in the A-bomb survivors exposed to the chronic or acute low dose/dose rate. Molecular events are explained for the low-dose radiation-induced DNA damage and its repair, gene mutation and chromosome aberration, hypothesis of carcinogenesis by mutation, and non-targeting effect of radiation (bystander effect and gene instability). Further researches to elucidate the low dose

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

Science.gov (United States)

Shi, Chengyu; Guo, Bingqi; Cheng, Chih-Yao; Eng, Tony; Papanikolaou, Nikos

2010-09-01

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent™ x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V100 reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as compared to 95

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

Energy Technology Data Exchange (ETDEWEB)

Shi Chengyu; Guo Bingqi; Eng, Tony; Papanikolaou, Nikos [Cancer Therapy and Research Center, University of Texas Health Science Center at San Antonio, TX 78229 (United States); Cheng, Chih-Yao, E-mail: shic@uthscsa.ed [Radiation Oncology Department, Oklahoma University Health Science Center, Oklahoma, OK 73104 (United States)

2010-09-21

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent(TM) x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V{sub 100} reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

International Nuclear Information System (INIS)

Shi Chengyu; Guo Bingqi; Eng, Tony; Papanikolaou, Nikos; Cheng, Chih-Yao

2010-01-01

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent(TM) x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V 100 reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as compared to 95

A model for inverse dose-rate effects - low dose-rate hyper-sensibility in response to targeted radionuclide therapy

International Nuclear Information System (INIS)

Murray, I.; Mather, S.J.

2015-01-01

Full text of publication follows. The aim of this work was to test the hypothesis that the Linear-Quadratic (LQ) model of cell survival, developed for external beam radiotherapy (EBRT), could be extended to targeted radionuclide therapy (TRT) in order to predict dose-response relationships in a cell line exhibiting low dose hypersensitivity (LDH). Methods: aliquots of the PC-3 cancer cell line were treated with either EBRT or an in-vitro model of TRT (Irradiation of cell culture with Y-90 EDTA over 24, 48, 72 or 96 hours). Dosimetry for the TRT was calculated using radiation transport simulations with the Monte Carlo PENELOPE code. Clonogenic as well as functional biological assays were used to assess cell response. An extension of the LQ model was developed which incorporated a dose-rate threshold for activation of repair mechanisms. Results: accurate dosimetry for in-vitro exposures of cell cultures to radioactivity was established. LQ parameters of cell survival were established for the PC-3 cell line in response to EBRT. The standard LQ model did not predict survival in PC-3 cells exposed to Y 90 irradiation over periods of up to 96 hours. In fact cells were more sensitive to the same dose when irradiation was carried out over 96 hours than 24 hours. I.e. at a lower dose-rate. Deviations from the LQ predictions were most pronounced below a threshold dose-rate of 0.5 Gy/hr. These results led to an extension of the LQ model based upon a dose-rate dependent sigmoid model of single strand DNA repair. This extension to the model resulted in predicted cell survival curves that closely matched the experimental data. Conclusion: the LQ model of cell survival to radiation has been shown to be largely predictive of response to low dose-rate irradiation. However, in cells displaying LDH, further adaptation of the model was required. (authors)

Conditioned instrumental behaviour in the rat: Effects of prenatal irradiation with various low dose-rate doses

International Nuclear Information System (INIS)

Klug, H.

1986-01-01

4 groups of rats of the Wistar-strain were subjected to γ-irradiation on the 16th day of gestation. 5 rats received 0,6 Gy low dose rate irradiation, 5 animals received 0,9 Gy low dose and 6 high dose irradiation, 3 females were shamirradiated. The male offspring of these 3 irradiation groups and 1 control group were tested for locomotor coordination on parallel bars and in a water maze. The female offspring were used in an operant conditioning test. The locomotor test showed slight impairment of locomotor coordination in those animals irradiated with 0,9 Gy high dose rate. Swimming ability was significantly impaired by irradiation with 0,9 Gy high dose rate. Performance in the operant conditioning task was improved by irradiation with 0,9 Gy both low and high dose rate. The 0,9 Gy high dose rate group learned faster than all the other groups. For the dose of 0,9 Gy a significant dose rate effect could be observed. For the dose of 0,6 Gy a similar tendency was observed, differences between 0,6 Gy high and low dose rate and controls not being significant. (orig./MG) [de

High dose rate versus low dose rate interstitial radiotherapy for carcinoma of the floor of mouth

International Nuclear Information System (INIS)

Inoue, Takehiro; Inoue, Toshihiko; Yamazaki, Hideya; Koizumi, Masahiko; Kagawa, Kazufumi; Yoshida, Ken; Shiomi, Hiroya; Imai, Atsushi; Shimizutani, Kimishige; Tanaka, Eichii; Nose, Takayuki; Teshima, Teruki; Furukawa, Souhei; Fuchihata, Hajime

1998-01-01

Purpose: Patients with cancer of the floor of mouth are treated with radiation because of functional and cosmetic reasons. We evaluate the treatment results of high dose rate (HDR) and low dose rate (LDR) interstitial radiation for cancer of the floor of mouth. Methods and Materials: From January 1980 through March 1996, 41 patients with cancer of the floor of mouth were treated with LDR interstitial radiation using 198 Au grains, and from April 1992 through March 1996 16 patients with HDR interstitial radiation. There were 26 T1 tumors, 30 T2 tumors, and 1 T3 tumor. For 21 patients treated with interstitial radiation alone, a total radiation dose of interstitial therapy was 60 Gy/10 fractions/6-7 days in HDR and 85 Gy within 1 week in LDR. For 36 patients treated with a combination therapy, a total dose of 30 to 40 Gy of external radiation and a total dose of 48 Gy/8 fractions/5-6 days in HDR or 65 Gy within 1 week in LDR were delivered. Results: Two- and 5-year local control rates of patients treated with HDR interstitial radiation were 94% and 94%, and those with LDR were 75% and 69%, respectively. Local control rate of patients treated with HDR brachytherapy was slightly higher than that with 198 Au grains (p = 0.113). For late complication, bone exposure or ulcer occurred in 6 of 16 (38%) patients treated with HDR and 13 of 41 (32%) patients treated with LDR. Conclusion: HDR fractionated interstitial brachytherapy can be an alternative to LDR brachytherapy for cancer of the floor of mouth and eliminate radiation exposure for the medical staff

Toward endobronchial Ir-192 high-dose-rate brachytherapy therapeutic optimization

International Nuclear Information System (INIS)

Gay, H A; Allison, R R; Downie, G H; Mota, H C; Austerlitz, C; Jenkins, T; Sibata, C H

2007-01-01

A number of patients with lung cancer receive either palliative or curative high-dose-rate (HDR) endobronchial brachytherapy. Up to a third of patients treated with endobronchial HDR die from hemoptysis. Rather than accept hemoptysis as an expected potential consequence of HDR, we have calculated the radial dose distribution for an Ir-192 HDR source, rigorously examined the dose and prescription points recommended by the American Brachytherapy Society (ABS), and performed a radiobiological-based analysis. The radial dose rate of a commercially available Ir-192 source was calculated with a Monte Carlo simulation. Based on the linear quadratic model, the estimated palliative, curative and blood vessel rupture radii from the center of an Ir-192 source were obtained for the ABS recommendations and a series of customized HDR prescriptions. The estimated radius at risk for blood vessel perforation for the ABS recommendations ranges from 7 to 9 mm. An optimized prescription may in some situations reduce this radius to 4 mm. The estimated blood perforation radius is generally smaller than the palliative radius. Optimized and individualized endobronchial HDR prescriptions are currently feasible based on our current understanding of tumor and normal tissue radiobiology. Individualized prescriptions could minimize complications such as fatal hemoptysis without sacrificing efficacy. Fiducial stents, HDR catheter centering or spacers and the use of CT imaging to better assess the relationship between the catheter and blood vessels promise to be useful strategies for increasing the therapeutic index of this treatment modality. Prospective trials employing treatment optimization algorithms are needed

Dose rate effect in food irradiation

International Nuclear Information System (INIS)

Singh, H.

1991-08-01

It has been suggested that the minor losses of nutrients associated with radiation processing may be further reduced by irradiating foods at the high dose rates generally associated with electron beams from accelerators, rather than at the low dose rates typical of gamma irradiation (e.g. 60 Co). This review briefly examines available comparative data on gamma and electron irradiation of foods to evaluate these suggestions. (137 refs., 27 tabs., 11 figs.)

Dose and Dose-Rate Effectiveness Factor (DDREF); Der Dosis- und Dosisleistungs-Effektivitaetsfaktor (DDREF)

Energy Technology Data Exchange (ETDEWEB)

Breckow, Joachim [Fachhochschule Giessen-Friedberg, Giessen (Germany). Inst. fuer Medizinische Physik und Strahlenschutz

2016-08-01

For practical radiation protection purposes it is supposed that stochastic radiation effects a determined by a proportional dose relation (LNT). Radiobiological and radiation epidemiological studies indicated that in the low dose range a dependence on dose rates might exist. This would trigger an overestimation of radiation risks based on the LNT model. OCRP had recommended a concept to combine all effects in a single factor DDREF (dose and dose-Rate effectiveness factor). There is still too low information on cellular mechanisms of low dose irradiation including possible repair and other processes. The Strahlenschutzkommission cannot identify a sufficient scientific justification for DDREF and recommends an adaption to the actual state of science.

Dose rate-dependent marrow toxicity of TBI in dogs and marrow sparing effect at high dose rate by dose fractionation.

Science.gov (United States)

Storb, R; Raff, R F; Graham, T; Appelbaum, F R; Deeg, H J; Schuening, F G; Sale, G; Seidel, K

1999-01-01

We evaluated the marrow toxicity of 200 and 300 cGy total-body irradiation (TBI) delivered at 10 and 60 cGy/min, respectively, in dogs not rescued by marrow transplant. Additionally, we compared toxicities after 300 cGy fractionated TBI (100 cGy fractions) to that after single-dose TBI at 10 and 60 cGy/min. Marrow toxicities were assessed on the basis of peripheral blood cell count changes and mortality from radiation-induced pancytopenia. TBI doses studied were just below the dose at which all dogs die despite optimal support. Specifically, 18 dogs were given single doses of 200 cGy TBI, delivered at either 10 (n=13) or 60 (n=5) cGy/min. Thirty-one dogs received 300 cGy TBI at 10 cGy/min, delivered as either single doses (n=21) or three fractions of 100 cGy each (n=10). Seventeen dogs were given 300 cGy TBI at 60 cGy/min, administered either as single doses (n=5) or three fractions of 100 cGy each (n=10). Within the limitations of the experimental design, three conclusions were drawn: 1) with 200 and 300 cGy single-dose TBI, an increase of dose rate from 10 to 60 cGy/min, respectively, caused significant increases in marrow toxicity; 2) at 60 cGy/min, dose fractionation resulted in a significant decrease in marrow toxicities, whereas such a protective effect was not seen at 10 cGy/min; and 3) with fractionated TBI, no significant differences in marrow toxicity were seen between dogs irradiated at 60 and 10 cGy/min. The reduced effectiveness of TBI when a dose of 300 cGy was divided into three fractions of 100 cGy or when dose rate was reduced from 60 cGy/min to 10 cGy/min was consistent with models of radiation toxicity that allow for repair of sublethal injury in DNA.

Dose and dose-rate effects of ionizing radiation: a discussion in the light of radiological protection

Energy Technology Data Exchange (ETDEWEB)

Ruehm, Werner [Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Institute of Radiation Protection, Neuherberg (Germany); Woloschak, Gayle E. [Northwestern University, Department of Radiation Oncology, Feinberg School of Medicine, Chicago, IL (United States); Shore, Roy E. [Radiation Effects Research Foundation (RERF), Hiroshima City (Japan); Azizova, Tamara V. [Southern Urals Biophysics Institute (SUBI), Ozyorsk, Chelyabinsk Region (Russian Federation); Grosche, Bernd [Federal Office for Radiation Protection, Oberschleissheim (Germany); Niwa, Ohtsura [Fukushima Medical University, Fukushima (Japan); Akiba, Suminori [Kagoshima University Graduate School of Medical and Dental Sciences, Department of Epidemiology and Preventive Medicine, Kagoshima City (Japan); Ono, Tetsuya [Institute for Environmental Sciences, Rokkasho, Aomori-ken (Japan); Suzuki, Keiji [Nagasaki University, Department of Radiation Medical Sciences, Atomic Bomb Disease Institute, Nagasaki (Japan); Iwasaki, Toshiyasu [Central Research Institute of Electric Power Industry (CRIEPI), Radiation Safety Research Center, Nuclear Technology Research Laboratory, Tokyo (Japan); Ban, Nobuhiko [Tokyo Healthcare University, Faculty of Nursing, Tokyo (Japan); Kai, Michiaki [Oita University of Nursing and Health Sciences, Department of Environmental Health Science, Oita (Japan); Clement, Christopher H.; Hamada, Nobuyuki [International Commission on Radiological Protection (ICRP), PO Box 1046, Ottawa, ON (Canada); Bouffler, Simon [Public Health England (PHE), Centre for Radiation, Chemical and Environmental Hazards, Chilton, Didcot (United Kingdom); Toma, Hideki [JAPAN NUS Co., Ltd. (JANUS), Tokyo (Japan)

2015-11-15

The biological effects on humans of low-dose and low-dose-rate exposures to ionizing radiation have always been of major interest. The most recent concept as suggested by the International Commission on Radiological Protection (ICRP) is to extrapolate existing epidemiological data at high doses and dose rates down to low doses and low dose rates relevant to radiological protection, using the so-called dose and dose-rate effectiveness factor (DDREF). The present paper summarizes what was presented and discussed by experts from ICRP and Japan at a dedicated workshop on this topic held in May 2015 in Kyoto, Japan. This paper describes the historical development of the DDREF concept in light of emerging scientific evidence on dose and dose-rate effects, summarizes the conclusions recently drawn by a number of international organizations (e.g., BEIR VII, ICRP, SSK, UNSCEAR, and WHO), mentions current scientific efforts to obtain more data on low-dose and low-dose-rate effects at molecular, cellular, animal and human levels, and discusses future options that could be useful to improve and optimize the DDREF concept for the purpose of radiological protection. (orig.)

Mathematical model for evaluation of dose-rate effect on biological responses to low dose γ-radiation

International Nuclear Information System (INIS)

Ogata, H.; Kawakami, Y.; Magae, J.

2003-01-01

Full text: To evaluate quantitative dose-response relationship on the biological response to radiation, it is necessary to consider a model including cumulative dose, dose-rate and irradiation time. In this study, we measured micronucleus formation and [ 3 H] thymidine uptake in human cells as indices of biological response to gamma radiation, and analyzed mathematically and statistically the data for quantitative evaluation of radiation risk at low dose/low dose-rate. Effective dose (ED x ) was mathematically estimated by fitting a general function of logistic model to the dose-response relationship. Assuming that biological response depends on not only cumulative dose but also dose-rate and irradiation time, a multiple logistic function was applied to express the relationship of the three variables. Moreover, to estimate the effect of radiation at very low dose, we proposed a modified exponential model. From the results of fitting curves to the inhibition of [ 3 H] thymidine uptake and micronucleus formation, it was obvious that ED 50 in proportion of inhibition of [ 3 H] thymidine uptake increased with longer irradiation time. As for the micronuclei, ED 30 also increased with longer irradiation times. These results suggest that the biological response depends on not only total dose but also irradiation time. The estimated response surface using the three variables showed that the biological response declined sharply when the dose-rate was less than 0.01 Gy/h. These results suggest that the response does not depend on total cumulative dose at very low dose-rates. Further, to investigate the effect of dose-rate within a wider range, we analyzed the relationship between ED x and dose-rate. Fitted curves indicated that ED x increased sharply when dose-rate was less than 10 -2 Gy/h. The increase of ED x signifies the decline of the response or the risk and suggests that the risk approaches to 0 at infinitely low dose-rate

Concrete spent fuel storage casks dose rates

International Nuclear Information System (INIS)

Bace, M.; Jecmenica, R.; Trontl, K.

1998-01-01

Our intention was to model a series of concrete storage casks based on TranStor system storage cask VSC-24, and calculate the dose rates at the surface of the casks as a function of extended burnup and a prolonged cooling time. All of the modeled casks have been filled with the original multi-assembly sealed basket. The thickness of the concrete shield has been varied. A series of dose rate calculations for different burnup and cooling time values have been performed. The results of the calculations show rather conservative original design of the VSC-24 system, considering only the dose rate values, and appropriate design considering heat rejection.(author)

Radiation dose rates from UF{sub 6} cylinders

Energy Technology Data Exchange (ETDEWEB)

Friend, P.J. [Urenco, Capenhurst (United Kingdom)

1991-12-31

This paper describes the results of many studies, both theoretical and experimental, which have been carried out by Urenco over the last 15 years into radiation dose rates from uranium hexafluoride (UF{sub 6}) cylinders. The contents of the cylinder, its history, and the geometry all affect the radiation dose rate. These factors are all examined in detail. Actual and predicted dose rates are compared with levels permitted by IAEA transport regulations.

Dose escalation using conformal high-dose-rate brachytherapy improves outcome in unfavorable prostate cancer.

Science.gov (United States)

Martinez, Alvaro A; Gustafson, Gary; Gonzalez, José; Armour, Elwood; Mitchell, Chris; Edmundson, Gregory; Spencer, William; Stromberg, Jannifer; Huang, Raywin; Vicini, Frank

2002-06-01

To overcome radioresistance for patients with unfavorable prostate cancer, a prospective trial of pelvic external beam irradiation (EBRT) interdigitated with dose-escalating conformal high-dose-rate (HDR) prostate brachytherapy was performed. Between November 1991 and August 2000, 207 patients were treated with 46 Gy pelvic EBRT and increasing HDR brachytherapy boost doses (5.50-11.5 Gy/fraction) during 5 weeks. The eligibility criteria were pretreatment prostate-specific antigen level >or=10.0 ng/mL, Gleason score >or=7, or clinical Stage T2b or higher. Patients were divided into 2 dose levels, low-dose biologically effective dose 93 Gy (149 patients). No patient received hormones. We used the American Society for Therapeutic Radiology and Oncology definition for biochemical failure. The median age was 69 years. The mean follow-up for the group was 4.4 years, and for the low and high-dose levels, it was 7.0 and 3.4 years, respectively. The actuarial 5-year biochemical control rate was 74%, and the overall, cause-specific, and disease-free survival rate was 92%, 98%, and 68%, respectively. The 5-year biochemical control rate for the low-dose group was 52%; the rate for the high-dose group was 87% (p failure. The Radiation Therapy Oncology Group Grade 3 gastrointestinal/genitourinary complications ranged from 0.5% to 9%. The actuarial 5-year impotency rate was 51%. Pelvic EBRT interdigitated with transrectal ultrasound-guided real-time conformal HDR prostate brachytherapy boost is both a precise dose delivery system and a very effective treatment for unfavorable prostate cancer. We demonstrated an incremental beneficial effect on biochemical control and cause-specific survival with higher doses. These results, coupled with the low risk of complications, the advantage of not being radioactive after implantation, and the real-time interactive planning, define a new standard for treatment.

Estimated dose rates to members of the public from external exposure to patients with {sup 131}I thyroid treatment

Energy Technology Data Exchange (ETDEWEB)

Dewji, S., E-mail: dewjisa@ornl.gov; Bellamy, M.; Leggett, R.; Eckerman, K. [Oak Ridge National Laboratory, 1 Bethel Valley Road, MS-6335, Oak Ridge, Tennessee 37831 (United States); Hertel, N. [Oak Ridge National Laboratory, 1 Bethel Valley Road, MS-6335, Oak Ridge, Tennessee 37831 and Georgia Institute of Technology, 770 State Street, Atlanta, Georgia 30332-0745 (United States); Sherbini, S.; Saba, M. [United States Nuclear Regulatory Commission, Washington, DC 20555-0001 (United States)

2015-04-15

Purpose: Estimated dose rates that may result from exposure to patients who had been administered iodine-131 ({sup 131}I) as part of medical therapy were calculated. These effective dose rate estimates were compared with simplified assumptions under United States Nuclear Regulatory Commission Regulatory Guide 8.39, which does not consider body tissue attenuation nor time-dependent redistribution and excretion of the administered {sup 131}I. Methods: Dose rates were estimated for members of the public potentially exposed to external irradiation from patients recently treated with {sup 131}I. Tissue attenuation and iodine biokinetics were considered in the patient in a larger comprehensive effort to improve external dose rate estimates. The external dose rate estimates are based on Monte Carlo simulations using the Phantom with Movable Arms and Legs (PIMAL), previously developed by Oak Ridge National Laboratory and the United States Nuclear Regulatory Commission. PIMAL was employed to model the relative positions of the {sup 131}I patient and members of the public in three exposure scenarios: (1) traveling on a bus in a total of six seated or standing permutations, (2) two nursing home cases where a caregiver is seated at 30 cm from the patient’s bedside and a nursing home resident seated 250 cm away from the patient in an adjacent bed, and (3) two hotel cases where the patient and a guest are in adjacent rooms with beds on opposite sides of the common wall, with the patient and guest both in bed and either seated back-to-back or lying head to head. The biokinetic model predictions of the retention and distribution of {sup 131}I in the patient assumed a single voiding of urinary bladder contents that occurred during the trip at 2, 4, or 8 h after {sup 131}I administration for the public transportation cases, continuous first-order voiding for the nursing home cases, and regular periodic voiding at 4, 8, or 12 h after administration for the hotel room cases. Organ

The dose-rate effect

International Nuclear Information System (INIS)

Steel, G.G.

1989-01-01

This paper presents calculations that illustrate two conclusions; for any particular cell type there will be a critical radius at which tumor control breaks down, and the radius at which this occurs is strongly dependent upon the low-dose-rate radiosensitivity of the cells

A comparison of anti-tumor effects of high dose rate fractionated and low dose rate continuous irradiation in multicellular spheroids

International Nuclear Information System (INIS)

Kubota, Nobuo; Omura, Motoko; Matsubara, Sho.

1997-01-01

In a clinical experience, high dose rate (HDR) fractionated interstitial radiotherapy can be an alternative to traditional low dose rate (LDR) continuous interstitial radiotherapy for head and neck cancers. To investigate biological effect of HDR, compared to LDR, comparisons have been made using spheroids of human squamous carcinoma cells. Both LDR and HDR were delivered by 137 Cs at 37degC. Dose rate of LDR was 8 Gy/day and HDR irradiations of fraction size of 4, 5 or 6 Gy were applied twice a day with an interval time of more than 6 hr. We estimated HDR fractionated dose of 31 Gy with 4 Gy/fr to give the same biological effects of 38 Gy by continuous LDR for spheroids. The ratio of HDR/LDR doses to control 50% spheroids was 0.82. (author)

Modification of transmission dose algorithm for irregularly shaped radiation field and tissue deficit

Energy Technology Data Exchange (ETDEWEB)

Yun, Hyong Geon; Shin, Kyo Chul [Dankook Univ., College of Medicine, Seoul (Korea, Republic of); Huh, Soon Nyung; Woo, Hong Gyun; Ha, Sung Whan [Seoul National Univ., College of Medicine, Seoul (Korea, Republic of); Lee, Hyoung Koo [The Catholic Univ., College of Medicine, Seoul (Korea, Republic of)

2002-07-01

Algorithm for estimation of transmission dose was modified for use in partially blocked radiation fields and in cases with tissue deficit. The beam data was measured with flat solid phantom in various conditions of beam block. And an algorithm for correction of transmission dose in cases of partially blocked radiation field was developed from the measured data. The algorithm was tested in some clinical settings with irregular shaped field. Also, another algorithm for correction of transmission dose for tissue deficit was developed by physical reasoning. This algorithm was tested in experimental settings with irregular contours mimicking breast cancer patients by using multiple sheets of solid phantoms. The algorithm for correction of beam block could accurately reflect the effect of beam block, with error within {+-}1.0%, both with square fields and irregularly shaped fields. The correction algorithm for tissue deficit could accurately reflect the effect of tissue deficit with errors within {+-}1.0% in most situations and within {+-}3.0% in experimental settings with irregular contours mimicking breast cancer treatment set-up. Developed algorithms could accurately estimate the transmission dose in most radiation treatment settings including irregularly shaped field and irregularly shaped body contour with tissue deficit in transmission dosimetry.

Modification of transmission dose algorithm for irregularly shaped radiation field and tissue deficit

International Nuclear Information System (INIS)

Yun, Hyong Geon; Shin, Kyo Chul; Huh, Soon Nyung; Woo, Hong Gyun; Ha, Sung Whan; Lee, Hyoung Koo

2002-01-01

Algorithm for estimation of transmission dose was modified for use in partially blocked radiation fields and in cases with tissue deficit. The beam data was measured with flat solid phantom in various conditions of beam block. And an algorithm for correction of transmission dose in cases of partially blocked radiation field was developed from the measured data. The algorithm was tested in some clinical settings with irregular shaped field. Also, another algorithm for correction of transmission dose for tissue deficit was developed by physical reasoning. This algorithm was tested in experimental settings with irregular contours mimicking breast cancer patients by using multiple sheets of solid phantoms. The algorithm for correction of beam block could accurately reflect the effect of beam block, with error within ±1.0%, both with square fields and irregularly shaped fields. The correction algorithm for tissue deficit could accurately reflect the effect of tissue deficit with errors within ±1.0% in most situations and within ±3.0% in experimental settings with irregular contours mimicking breast cancer treatment set-up. Developed algorithms could accurately estimate the transmission dose in most radiation treatment settings including irregularly shaped field and irregularly shaped body contour with tissue deficit in transmission dosimetry

Dose Rate Determination from Airborne Gamma-ray Spectra

DEFF Research Database (Denmark)

Bargholz, Kim

1996-01-01

The standard method for determination of ground level dose rates from airborne gamma-ray is the integral count rate which for a constant flying altitude is assumed proportional to the dose rate. The method gives reasonably results for natural radioactivity which almost always has the same energy...

Cancer risk of low dose/low dose rate radiation: a meta-analysis of cancer data of mammals exposed to low doses of radiation

International Nuclear Information System (INIS)

Ogata, Hiromitsu; Magae, Junji

2008-01-01

Full text: Linear No Threshold (LNT) model is a basic theory for radioprotection, but the adaptability of this hypothesis to biological responses at low doses or at low dose rates is not sufficiently investigated. Simultaneous consideration of the cumulative dose and the dose rate is necessary for evaluating the risk of long-term exposure to ionizing radiation at low dose. This study intends to examine several numerical relationships between doses and dose rates in biological responses to gamma radiation. Collected datasets on the relationship between dose and the incidence of cancer in mammals exposed to low doses of radiation were analysed using meta-regression models and modified exponential (MOE) model, which we previously published, that predicts irradiation time-dependent biological response at low dose rate ionizing radiation. Minimum doses of observable risk and effective doses with a variety of dose rates were calculated using parameters estimated by fitting meta-regression models to the data and compared them with other statistical models that find values corresponding to 'threshold limits'. By fitting a weighted regression model (fixed-effects meta-regression model) to the data on risk of all cancers, it was found that the log relative risk [log(RR)] increased as the total exposure dose increased. The intersection of this regression line with the x-axis denotes the minimum dose of observable risk. These estimated minimum doses and effective doses increased with decrease of dose rate. The goodness of fits of MOE-model depended on cancer types, but the total cancer risk is reduced when dose rates are very low. The results suggest that dose response curve for cancer risk is remarkably affected by dose rate and that dose rate effect changes as a function of dose rate. For scientific discussion on the low dose exposure risk and its uncertainty, the term 'threshold' should be statistically defined, and dose rate effects should be included in the risk

Dose-rate effects of low-dropout voltage regulator at various biases

International Nuclear Information System (INIS)

Wang Yiyuan; Zheng Yuzhan; Gao Bo; Chen Rui; Fei Wuxiong; Lu Wu; Ren Diyuan

2010-01-01

A low-dropout voltage regulator, LM2941, was irradiated by 60 Co γ-rays at various dose rates and biases for investigating the total dose and dose rate effects. The radiation responses show that the key electrical parameters, including its output and dropout voltage, and the maximum output current, are sensitive to total dose and dose rates, and are significantly degraded at low dose rate and zero bias. The integrated circuits damage change with the dose rates and biases, and the dose-rate effects are relative to its electric field. (authors)

Risk of solid cancer in low dose-rate radiation epidemiological studies and the dose-rate effectiveness factor.

Science.gov (United States)

Shore, Roy; Walsh, Linda; Azizova, Tamara; Rühm, Werner

2017-10-01

Estimated radiation risks used for radiation protection purposes have been based primarily on the Life Span Study (LSS) of atomic bomb survivors who received brief exposures at high dose rates, many with high doses. Information is needed regarding radiation risks from low dose-rate (LDR) exposures to low linear-energy-transfer (low-LET) radiation. We conducted a meta-analysis of LDR epidemiologic studies that provide dose-response estimates of total solid cancer risk in adulthood in comparison to corresponding LSS risks, in order to estimate a dose rate effectiveness factor (DREF). We identified 22 LDR studies with dose-response risk estimates for solid cancer after minimizing information overlap. For each study, a parallel risk estimate was derived from the LSS risk model using matching values for sex, mean ages at first exposure and attained age, targeted cancer types, and accounting for type of dosimetric assessment. For each LDR study, a ratio of the excess relative risk per Gy (ERR Gy -1 ) to the matching LSS ERR risk estimate (LDR/LSS) was calculated, and a meta-analysis of the risk ratios was conducted. The reciprocal of the resultant risk ratio provided an estimate of the DREF. The meta-analysis showed a LDR/LSS risk ratio of 0.36 (95% confidence interval [CI] 0.14, 0.57) for the 19 studies of solid cancer mortality and 0.33 (95% CI 0.13, 0.54) when three cohorts with only incidence data also were added, implying a DREF with values around 3, but statistically compatible with 2. However, the analyses were highly dominated by the Mayak worker study. When the Mayak study was excluded the LDR/LSS risk ratios increased: 1.12 (95% CI 0.40, 1.84) for mortality and 0.54 (95% CI 0.09, 0.99) for mortality + incidence, implying a lower DREF in the range of 1-2. Meta-analyses that included only cohorts in which the mean dose was LDR data provide direct evidence regarding risk from exposures at low dose rates as an important complement to the LSS risk estimates used

Dose-rate conversion factors for external exposure to photon and electron radiation from radionuclides occurring in routine releases from nuclear fuel cycle facilities

International Nuclear Information System (INIS)

Kocher, D.C.

1980-01-01

Dose-rate conversion factors for external exposure to photon and electron radiation are calculated for 240 radionuclides of potential importance in routine releases from nuclear fuel cycle facilities. Exposure modes considered are immersion in contaminated air, immersion in contaminated water, and irradiation from a contaminated ground surface. For each exposure mode, dose-rate conversion factors for photons and electrons are calculated for tissue-equivalent material at the body surface of an exposed individual. Dose-rate conversion factors for photons only are calculated for 22 body organs. (author)

Analysis of the spatial rates dose rates during dental panoramic radiography

Energy Technology Data Exchange (ETDEWEB)

Ko, Jong Kyung [Dept. of Radiation Safety Management Commission, Daegu Health College, Daegu (Korea, Republic of); Park, Myeong Hwan [Dept. of Radiologic Technology, Daegu Health College, Daegu (Korea, Republic of); Kim, Yong Min [Dept. of Radiological Science, Catholic University of Daegu, Daegu (Korea, Republic of)

2016-12-15

A dental panoramic radiography which usually uses low level X-rays is subject to the Nuclear Safety Act when it is installed for the purpose of education. This paper measures radiation dose and spatial dose rate by usage and thereby aims to verify the effectiveness of radiation safety equipment and provide basic information for radiation safety of radiation workers and students. After glass dosimeter (GD-352M) is attached to direct exposure area, the teeth, and indirect exposure area, the eye lens and the thyroid, on the dental radiography head phantom, these exposure areas are measured. Then, after dividing the horizontal into a 45°, it is separated into seven directions which all includes 30, 60, 90, 120 cm distance. The paper shows that the spatial dose rate is the highest at 30 cm and declines as the distance increases. At 30 cm, the spatial dose rate around the starting area of rotation is 3,840 μSv/h, which is four times higher than the lowest level 778 μSv/h. Furthermore, the spatial dose rate was 408 μSv/h on average at the distance of 60 cm where radiation workers can be located. From a conservative point of view, It is possible to avoid needless exposure to radiation for the purpose of education. However, in case that an unintended exposure to radiation happens within a radiation controlled area, it is still necessary to educate radiation safety. But according to the current Medical Service Act, in medical institutions, even if they are not installed, the equipment such as interlock are obliged by the Nuclear Safety Law, considering that the spatial dose rate of the educational dental panoramic radiography room is low. It seems to be excessive regulation.

MCNP Code in Assessment of Variations of Effective Dose with Torso Adipose Tissue Thickness

International Nuclear Information System (INIS)

Massoud, E.

2005-01-01

The effective dose is the unite used in the field of radiation protection. It is a well defined doubly weighted uantity involving both physical and biological variables. Several factors may induce variation in the effective dose in different individuals of similar exposure data. One of these factors is the variation of adipose tissue thickness in different exposed individuals. This study essentially concenrs the assessment of the possible variation in the effective dose due to variation in the thickness of adipose tissue. The study was done using MCNP4b code to perform mathematical model of the human body depending on that given to the reference man developed by International Commission of Radiological Protection (ICRP), and calculate the effective dose with different thicknessess of adipose tissues. The study includes a comprehensive appraisal of the Monte Cario simulation, the Medical Internal Radiation Dose (MIRD) model for the human body, and the various mathematical considerations involved in the radiation dose calculations for the various pertinent parts of the human body. The radiation energies considered were 80 KeV, 300 KeV and I MeV, applying two exposure positions; anteroposterior (AP), postero-anterior (PA) with different adipose tissue thickness. This study is a theoretical approach based on detailed mathematical calculations of great precision that deals with all considerations involved in the mechanisms of radiation energy absorption in biological system depending on the variation in the densities of the particular in biological system depending on the variation in the densities of the particular tissues. The results obtained indicate that maximum decrease in effective dose occures with the lowest energy at 5cm adipose tissues thickeness for both AP and PA exposure positions. The results obtained were compared to similar work previsouly done using MCNP4 b showing very good agreement

Macroarray analysis of gene expression in hematopoietic tissues from mice continuously irradiated by low dose-rate ionizing radiation

Energy Technology Data Exchange (ETDEWEB)

Saitou, Mikio; Nakamura, Shingo; Shirata, Katsutoshi; Yanai, Takanori; Izumi, Jun; Sugihara, Takashi; Tanaka, Satoshi; Tanaka, Kimio; Otsu, Hiroshi; Sato, Fumiaki [Inst. for Environmental Sciences, Rokkasho, Aomori (Japan)

2002-07-01

We found that the number of hematopoietic progenitor cells in bone marrow and spleen from 4 - 8 Gy-irradiated mice decreased about 50%, in spite of no change in the number of peripheral blood cells. To evaluate the effects of chronic irradiation by low dose-rate ionizing radiation on the gene expression in mice hematopoietic cells from bone marrow and spleen, the RNA expressions of more than 500 genes such as cytokine genes and oncogenes were measured on the membranes by the RNA macroarray analysis method at accumulated doses at 4.7 and 8 Gy in specific-pathogen-free (SPF) C3H/HeN female mice irradiated by {sup 137}Cs {gamma}-rays with the dose rate of 20 mGy/day. The RNA macroarray analysis in spleens from 8 Gy-irradiated mice showed that the expressions in 16 genes including noggin were more than 1.5 times larger than that of control, while those in 64 genes including shh (sonic hedgehog) and BMP-4 (bone morphogenesis protein 4) were more than 1.5 times smaller than that of control. (author)

Spatial accuracy of 3D reconstructed radioluminographs of serial tissue sections and resultant absorbed dose estimates

Energy Technology Data Exchange (ETDEWEB)

Petrie, I.A.; Flynn, A.A.; Pedley, R.B.; Green, A.J.; El-Emir, E.; Dearling, J.L.J.; Boxer, G.M.; Boden, R.; Begent, R.H.J. [Cancer Research UK Targeting and Imaging Group, Department of Oncology, Royal Free and University College Medical School, Royal Free Campus, London (United Kingdom)

2002-10-21

Many agents using tumour-associated characteristics are deposited heterogeneously within tumour tissue. Consequently, tumour heterogeneity should be addressed when obtaining information on tumour biology or relating absorbed radiation dose to biological effect. We present a technique that enables radioluminographs of serial tumour sections to be reconstructed using automated computerized techniques, resulting in a three-dimensional map of the dose-rate distribution of a radiolabelled antibody. The purpose of this study is to assess the reconstruction accuracy. Furthermore, we estimate the potential error resulting from registration misalignment, for a range of beta-emitting radionuclides. We compare the actual dose-rate distribution with that obtained from the same activity distribution but with manually defined translational and rotational shifts. As expected, the error produced with the short-range {sup 14}C is much larger than that for the longer range {sup 90}Y; similarly values for the medium range {sup 131}I are between the two. Thus, the impact of registration inaccuracies is greater for short-range sources. (author)

Fractionation in normal tissues: the (α/β)eff concept can account for dose heterogeneity and volume effects.

Science.gov (United States)

Hoffmann, Aswin L; Nahum, Alan E

2013-10-07

The simple Linear-Quadratic (LQ)-based Withers iso-effect formula (WIF) is widely used in external-beam radiotherapy to derive a new tumour dose prescription such that there is normal-tissue (NT) iso-effect when changing the fraction size and/or number. However, as conventionally applied, the WIF is invalid unless the normal-tissue response is solely determined by the tumour dose. We propose a generalized WIF (gWIF) which retains the tumour prescription dose, but replaces the intrinsic fractionation sensitivity measure (α/β) by a new concept, the normal-tissue effective fractionation sensitivity, [Formula: see text], which takes into account both the dose heterogeneity in, and the volume effect of, the late-responding normal-tissue in question. Closed-form analytical expressions for [Formula: see text] ensuring exact normal-tissue iso-effect are derived for: (i) uniform dose, and (ii) arbitrary dose distributions with volume-effect parameter n = 1 from the normal-tissue dose-volume histogram. For arbitrary dose distributions and arbitrary n, a numerical solution for [Formula: see text] exhibits a weak dependence on the number of fractions. As n is increased, [Formula: see text] increases from its intrinsic value at n = 0 (100% serial normal-tissue) to values close to or even exceeding the tumour (α/β) at n = 1 (100% parallel normal-tissue), with the highest values of [Formula: see text] corresponding to the most conformal dose distributions. Applications of this new concept to inverse planning and to highly conformal modalities are discussed, as is the effect of possible deviations from LQ behaviour at large fraction sizes.

Assessment of radioactive residues arising from radiolabel instability in a multiple dose tissue distribution study in rats

International Nuclear Information System (INIS)

Slatter, J.G.; Sams, J.P.; Easter, J.A.

2003-01-01

Our study objectives were to quantitatively determine the effect of radiolabel instability on terminal phase radioactive tissue residues in a multiple dose tissue distribution study, to quantitatively compare tissue residue artifacts (non drug-related radioactivity) from two chemically-distinct radiolabel locations, and to conduct a definitive multiple dose tissue distribution study using the better of the two radiolabeled compounds. We compared the excretion and tissue distribution in rats of [ 14 C]linezolid, radiolabeled in two different locations, after 7 consecutive once daily [ 14 C] oral doses. The radiolabels were in the acetamide (two carbon) and oxazolidinone (isolated carbon) functional groups. Terminal phase tissue residue and excretion data were compared to data from rats dosed orally with [ 14 C]sodium acetate. Drug-related radioactivity was excreted rapidly over 24 h. After a single dose, the acetamide and oxazolidinone radiolabel sites both gave 3% of dose as exhaled 14 CO 2 . After 7 daily [ 14 C] oral doses, terminal phase radioactive tissue residues were higher from the acetamide radiolabel, relative to the oxazolidinone radiolabel, and were primarily not drug-related. In the definitive tissue distribution study, low concentrations of drug-related radioactivity in skin and thyroid were observed. We conclude that although small amounts of radiolabel instability do not significantly affect single dose tissue radioactivity C max and area under the curve (AUC), artifacts arising from radiolabel instability can prolong the apparent terminal phase half life and complicate study data interpretation. When possible, it is always preferable to use a completely stable radiolabel site. (author)

Assessment of radioactive residues arising from radiolabel instability in a multiple dose tissue distribution study in rats

Energy Technology Data Exchange (ETDEWEB)

Slatter, J.G. [Pharmacia Corp., Peapack, NJ (United States); Sams, J.P.; Easter, J.A. [Pharmacia Corp., Kalamazoo, MI (United States)] [and others

2003-05-01

Our study objectives were to quantitatively determine the effect of radiolabel instability on terminal phase radioactive tissue residues in a multiple dose tissue distribution study, to quantitatively compare tissue residue artifacts (non drug-related radioactivity) from two chemically-distinct radiolabel locations, and to conduct a definitive multiple dose tissue distribution study using the better of the two radiolabeled compounds. We compared the excretion and tissue distribution in rats of [{sup 14}C]linezolid, radiolabeled in two different locations, after 7 consecutive once daily [{sup 14}C] oral doses. The radiolabels were in the acetamide (two carbon) and oxazolidinone (isolated carbon) functional groups. Terminal phase tissue residue and excretion data were compared to data from rats dosed orally with [{sup 14}C]sodium acetate. Drug-related radioactivity was excreted rapidly over 24 h. After a single dose, the acetamide and oxazolidinone radiolabel sites both gave 3% of dose as exhaled {sup 14}CO{sub 2}. After 7 daily [{sup 14}C] oral doses, terminal phase radioactive tissue residues were higher from the acetamide radiolabel, relative to the oxazolidinone radiolabel, and were primarily not drug-related. In the definitive tissue distribution study, low concentrations of drug-related radioactivity in skin and thyroid were observed. We conclude that although small amounts of radiolabel instability do not significantly affect single dose tissue radioactivity C{sub max} and area under the curve (AUC), artifacts arising from radiolabel instability can prolong the apparent terminal phase half life and complicate study data interpretation. When possible, it is always preferable to use a completely stable radiolabel site. (author)

ESR signal features of 60Co γ-ray irradiated bone tissue and its dose response relationship

International Nuclear Information System (INIS)

Wu Ke; Sun Zunpu; Shi Yuanming

1993-01-01

Electron spin resonance (ESR) technique was used to study the radiation-induced ESR signal features of different paramagnetic species of 60 Co γ-ray irradiated bone tissue. The results showed that the intensity of an ESR signal at that the intensity of an ESR signal at g 2.0022 of human bones exposed to a dose range of 0-50 Gy had linear dose response relationships. The lower limit of detectable dose was about 2 Gy and the detecting error was about 10%. The signal was stable at room temperature during 60 days, and the effect of radiation dose rate of 0.5-8.0 Gy/min could be neglected. This signal was insensitive to microwave power and temperature, which was suitable for rapid and direct detection with ESR technique. These features suggest that human bones could be used for radiation accident dose evaluation by ESR

Alpha-particle doses to human organs and tissues from internally-deposited 226Ra and 228Ra

International Nuclear Information System (INIS)

Keane, A.T.; Schlenker, R.A.

1981-01-01

Estimation of radiation doses to the soft tissues from internally-deposited 226 Ra and 228 Ra is relevant to an investigation of soft-tissue malignancies in radium-exposed persons being conducted at the Center for Human Radiobiology. Alpha-particle doses in a 50-year period following a single injection of 226 Ra or 228 Ra are presented for 31 soft tissues and organs of the adult human. The dose estimates were derived from the ICRP alkaline earth model fitted to data on retention of 226 Ra in soft tissues and bone, combined with reported ratios of 226 Ra to Ca in soft tissue and bone at natural levels and the distribution of Ca in the tissues of Reference Man (ICRP23). The median of the 31 organ and tissue doses from the α-particles of 226 Ra itself is 0.08 rad per injected μCi. An additional average dose of 0.01 rad per μCi 226 Ra daughter products produced in soft tissue or transferred from bone to soft tissue. Soft-tissue doses from α-particles of the 228 Ra decay series are about six times those from 226 Ra α-particles for equal injected activities of 228 Ra and 226 Ra, with the assumption that 228 Ra daughter products do not transfer from the organ in which they are produced. The 50-year dose to the red marrow of bone from α-particles originating in bone is 0.55 rad per μCi 226 Ra injected and 1.0 rad per μCi 228 Ra injected. For ingestion by dial painters of luminous compound containg 226 Ra or 228 Ra with a daughter-to-parent activity ratio of 0.5, the dose to the mucosal alyer of the lower large intestine from α-particles originating in the gut contents is about 0.1 rad per μCi systemic intake of 226 Ra or 228 Ra

Dose response relationship for unstable-type chromosome aberration rate of spleen cells from mice continuously exposed to low-dose-rate gamma-rays

International Nuclear Information System (INIS)

Tanaka, Kimio; Khoda, Atsushi; Ichinohe, Kazuaki; Oghiso, Yoichi

2007-01-01

It has been reported that people who are chronically exposed to radiation such as nuclear facility workers and medical radiologists have slightly higher incidences of chromosome aberrations than non-exposed people. However, chronological changes of chromosome aberration rates related to accumulated doses and dose-rates for low dose-rate radiation exposures have not been well studied. Precise analyses of human populations are quite limited because confounding factors influence the results. For this reason, animal experiments are important for analyses. Mice were continuously exposed to gamma-rays at 400 mGy/22 hr/day for 10 days, 20 mGy/22 hr/day for about 400 days, and 1 mGy/22 hr/day for about 615 days under SPF conditions. Chronological changes of unstable-type chromosome aberration rates of spleen cells were observed along with accumulated doses at the middle dose rate and the two low-dose rates by conventional Giemsa-staining method. Aberrations such as dicentric chromosome, ring chromosome and fragment increased in a two-phase manner within 0-1.2 Gy and 2-8 Gy at 20 mGy/22 hr/day. They slightly increased up to 0.5 Gy at 1 mGy/22 hr/day. Aberration rates for 1, 2, 8 Gy at the 20 mGy/22 hr/day and for 0.5 Gy at 1 mGy/22 hr/day were 5.1, 9.6, 13.9 and 2.2 times higher than those of age-matched, non-irradiated control mice, respectively. Chromosome aberration rates at 400 mGy/22 hr/day were 2.7 times higher than that of 20 mGy/22 hr/day for the same total dose of 1.2 Gy. The results that unstable-type chromosome aberrations increased with accumulated dose of the low-dose rate radiation will be important to establish biological dosimetry for people who are chronically exposed to radiation. (author)

Dose escalation using conformal high-dose-rate brachytherapy improves outcome in unfavorable prostate cancer

International Nuclear Information System (INIS)

Martinez, Alvaro A.; Gustafson, Gary; Gonzalez, Jose; Armour, Elwood; Mitchell, Chris; Edmundson, Gregory; Spencer, William; Stromberg, Jannifer; Huang, Raywin; Vicini, Frank

2002-01-01

Purpose: To overcome radioresistance for patients with unfavorable prostate cancer, a prospective trial of pelvic external beam irradiation (EBRT) interdigitated with dose-escalating conformal high-dose-rate (HDR) prostate brachytherapy was performed. Methods and Materials: Between November 1991 and August 2000, 207 patients were treated with 46 Gy pelvic EBRT and increasing HDR brachytherapy boost doses (5.50-11.5 Gy/fraction) during 5 weeks. The eligibility criteria were pretreatment prostate-specific antigen level ≥10.0 ng/mL, Gleason score ≥7, or clinical Stage T2b or higher. Patients were divided into 2 dose levels, low-dose biologically effective dose 93 Gy (149 patients). No patient received hormones. We used the American Society for Therapeutic Radiology and Oncology definition for biochemical failure. Results: The median age was 69 years. The mean follow-up for the group was 4.4 years, and for the low and high-dose levels, it was 7.0 and 3.4 years, respectively. The actuarial 5-year biochemical control rate was 74%, and the overall, cause-specific, and disease-free survival rate was 92%, 98%, and 68%, respectively. The 5-year biochemical control rate for the low-dose group was 52%; the rate for the high-dose group was 87% (p<0.001). Improvement occurred in the cause-specific survival in favor of the brachytherapy high-dose level (p=0.014). On multivariate analysis, a low-dose level, higher Gleason score, and higher nadir value were associated with increased biochemical failure. The Radiation Therapy Oncology Group Grade 3 gastrointestinal/genitourinary complications ranged from 0.5% to 9%. The actuarial 5-year impotency rate was 51%. Conclusion: Pelvic EBRT interdigitated with transrectal ultrasound-guided real-time conformal HDR prostate brachytherapy boost is both a precise dose delivery system and a very effective treatment for unfavorable prostate cancer. We demonstrated an incremental beneficial effect on biochemical control and cause

Retrospective Dosimetric Comparison of Low-Dose-Rate and Pulsed-Dose-Rate Intracavitary Brachytherapy Using a Tandem and Mini-Ovoids

International Nuclear Information System (INIS)

Mourtada, Firas; Gifford, Kent A.; Berner, Paula A.; Horton, John L.; Price, Michael J.; Lawyer, Ann A.; Eifel, Patricia J.

2007-01-01

The purpose of this study was to compare the dose distribution of Iridium-192 ( 192 Ir) pulsed-dose-rate (PDR) brachytherapy to that of Cesium-137 ( 137 Cs) low-dose-rate (LDR) brachytherapy around mini-ovoids and an intrauterine tandem. Ten patient treatment plans were selected from our clinical database, all of which used mini-ovoids and an intrauterine tandem. A commercial treatment planning system using AAPM TG43 formalism was used to calculate the dose in water for both the 137 Cs and 192 Ir sources. For equivalent system loadings, we compared the dose distributions in relevant clinical planes, points A and B, and to the ICRU bladder and rectal reference points. The mean PDR doses to points A and B were 3% ± 1% and 6% ± 1% higher than the LDR doses, respectively. For the rectum point, the PDR dose was 4% ± 3% lower than the LDR dose, mainly because of the 192 Ir PDR source anisotropy. For the bladder point, the PDR dose was 1% ± 4% higher than the LDR dose. We conclude that the PDR and LDR dose distributions are equivalent for intracavitary brachytherapy with a tandem and mini-ovoids. These findings will aid in the transfer from the current practice of LDR intracavitary brachytherapy to PDR for the treatment of gynecologic cancers

Allograft tissue irradiation and failure rate after anterior cruciate ligament reconstruction: A systematic review.

Science.gov (United States)

Dashe, Jesse; Parisien, Robert L; Cusano, Antonio; Curry, Emily J; Bedi, Asheesh; Li, Xinning

2016-06-18

To evaluate whether anterior cruciate ligament (ACL) allograft irradiation is effective for sterility without compromising graft integrity and increasing failure rate. A literature search was conducted using PubMed, Cochrane, and Google. The following search terms were used: "Gamma irradiation AND anterior cruciate ligament AND allograft" with a return of 30 items. Filters used included: English language, years 1990-2015. There were 6 hits that were not reviewed, as there were only abstracts available. Another 5 hits were discarded, as they did not pertain to the topic of interest. There were 9 more articles that were excluded: Three studies were performed on animals and 6 studies were meta-analyses. Therefore, a total of 10 articles were applicable to review. There is a delicate dosing crossover where gamma irradiation is both effective for sterility without catastrophically compromising the structural integrity of the graft. Of note, low dose irradiation is considered less than 2.0 Mrad, moderate dose is between 2.1-2.4 Mrad, and high dose is greater than or equal to 2.5 Mrad. Based upon the results of the literature search, the optimal threshold for sterilization was found to be sterilization at less than 2.2 Mrad of gamma irradiation with the important caveat of being performed at low temperatures. The graft selection process also must include thorough donor screening and testing as well as harvesting the tissue in a sterile fashion. Utilization of higher dose (≥ 2.5 Mrad) of irradiation causes greater allograft tissue laxity that results in greater graft failure rate clinically in patients after ACL reconstruction. Allograft ACL graft gamma irradiated with less than 2.2 Mrad appears to be a reasonable alternative to autograft for patients above 25 years of age.

Dose and dose rate effects of whole-body gamma-irradiation: II. Hematological variables and cytokines

Science.gov (United States)

Gridley, D. S.; Pecaut, M. J.; Miller, G. M.; Moyers, M. F.; Nelson, G. A.

2001-01-01

The goal of part II of this study was to evaluate the effects of gamma-radiation on circulating blood cells, functional characteristics of splenocytes, and cytokine expression after whole-body irradiation at varying total doses and at low- and high-dose-rates (LDR, HDR). Young adult C57BL/6 mice (n = 75) were irradiated with either 1 cGy/min or 80 cGy/min photons from a 60Co source to cumulative doses of 0.5, 1.5, and 3.0 Gy. The animals were euthanized at 4 days post-exposure for in vitro assays. Significant dose- (but not dose-rate-) dependent decreases were observed in erythrocyte and blood leukocyte counts, hemoglobin, hematocrit, lipopolysaccharide (LPS)-induced 3H-thymidine incorporation, and interleukin-2 (IL-2) secretion by activated spleen cells when compared to sham-irradiated controls (p < 0.05). Basal proliferation of leukocytes in the blood and spleen increased significantly with increasing dose (p < 0.05). Significant dose rate effects were observed only in thrombocyte counts. Plasma levels of transforming growth factor-beta 1 (TGF-beta 1) and splenocyte secretion of tumor necrosis factor-alpha (TNF-alpha) were not affected by either the dose or dose rate of radiation. The data demonstrate that the responses of blood and spleen were largely dependent upon the total dose of radiation employed and that an 80-fold difference in the dose rate was not a significant factor in the great majority of measurements.

Beta induced Bremsstrahlung dose rate in concrete shielding

International Nuclear Information System (INIS)

Manjunatha, H.C.

2013-01-01

Dosimetric study of beta-induced Bremsstrahlung in concrete is importance in the field of radiation protection. The efficiency, intensity and dose rate of beta induced Bremsstrahlung by 113 pure beta nuclides in concrete shielding is computed. The Bremsstrahlung dosimetric parameters such as the efficiency (yield), Intensity and dose rate of Bremsstrahlung are low for 199 Au and high for 104 Tc in concrete. The efficiency, Intensity and dose rate of Bremsstrahlung increases with maximum energy of beta nuclide (Emax) and modified atomic number (Zmod) of the target. The estimated Bremsstrahlung efficiency, Intensity and dose rate are useful in the calculations photon track-length distributions. These parameters are useful to determine the quality and quantity of the radiation (known as the source term). Precise estimation of this source term is very important in planning of radiation shielding. (author)

Radiation dose rate affects the radiosensitization of MCF-7 and HeLa cell lines to X-rays induced by dextran-coated iron oxide nanoparticles.

Science.gov (United States)

Khoshgard, Karim; Kiani, Parvaneh; Haghparast, Abbas; Hosseinzadeh, Leila; Eivazi, Mohammad Taghi

2017-08-01

The aim of radiotherapy is to deliver lethal damage to cancerous tissue while preserving adjacent normal tissues. Radiation absorbed dose of the tumoral cells can increase when high atomic nanoparticles are present in them during irradiation. Also, the dose rate is an important aspect in radiation effects that determines the biological results of a given dose. This in vitro study investigated the dose-rate effect on the induced radiosensitivity by dextran-coated iron oxide in cancer cells. HeLa and MCF-7 cells were cultured in vitro and incubated with different concentrations of dextran-coated iron oxide nanoparticles. They were then irradiated with 6 MV photons at dose rates of 43, 185 and 370 cGy/min. The MTT test was used to obtain the cells' survival after 48 h of irradiations. Incubating the cells with the nanoparticles at concentrations of 10, 40 and 80 μg/ml showed no significant cytotoxicity effect. Dextran-coated iron oxide nanoparticles showed more radiosensitivity effect by increasing the dose rate and nanoparticles concentration. Radiosensitization enhancement factors of MCF-7 and HeLa cells at a dose-rate of 370 cGy/min and nanoparticles' concentration of 80 μg/ml were 1.21 ± 0.06 and 1.19 ± 0.04, respectively. Increasing the dose rate of 6 MV photons irradiation in MCF-7 and HeLa cells increases the radiosensitization induced by the dextran-coated iron nanoparticles in these cells.

Dose rate analysis for Tank 101 AZ (Project W151)

International Nuclear Information System (INIS)

Schwarz, R.A.; Hillesland, K.E.; Carter, L.L.

1994-11-01

This document describes the expected dose rates for modification to tank 101 AZ including modifications to the steam coil, mixer pump, and temperature probes. The thrust of the effort is to determine dose rates from: modification of a steam coil and caisson; the installation of mixer pumps; the installation of temperature probes; and estimates of dose rates that will be encountered while making these changes. Because the dose rates for all of these configurations depend upon the photon source within the supernate and sludge, comparisons were also made between measured dose rates within a drywell and the corresponding calculated dose rates. The calculational tool used is a Monte Carlo (MCNP 2 ) code since complicated three dimensional geometries are involved. A summary of the most important results of the entire study is given in Section 2. The basic calculational geometry model of the tank is discussed in Section 3, along with a tabulation of the photon sources that were used within the supernate and the sludge, and a discussion of uncertainties. The calculated dose rates around the steam coil and caisson before and after modification are discussed in Section 4. The configuration for the installation of the mixer pumps and the resulting dose rates are given in Section 5. The predicted changes in dose rates due to a possible dilution of the supernate source are given in Section 6. The calculational configuration used to model the installation of temperature probes and the resulting predicted dose rates are discussed in Section 7. Finally, comparisons of measured to calculated dose rates within a drywell are summarized in Section 8. Extended discussions of calculational models and Monte Carlo optimization techniques used are included in Appendix A

Dose-rate effects on mammalian cells exposed to ionizing radiation

International Nuclear Information System (INIS)

Mitchell, J.B.

1978-01-01

The effect of irradiation on the life cycle and on cell survival was studied for a range of different dose rates. Log phase, plateau phase and synchronized cultures of different mammalian cells were used. Cell cycle redistribution during the radiation exposure was found to be a very important factor in determining the overall dose-rate effect for log phase and synchronized cells. In fact, cell cycle redistribution during the exposure, in some instances, resulted in a lower dose rate being more effective in cell killing per unit dose than a higher dose rate. For plateau phase cultures, where cell cycle times are greatly lengthened, the effects of redistribution in regard to cell killing was virtually eliminated. Both fed and unfed plateau phase cultures exhibited a dose-rate effect, but it was found that below dose rates of 154 rad/h there is no further loss in effectiveness

Dose-rate effects on the bulk etch-rate of CR-39 track detector exposed to low-LET radiations

CERN Document Server

Yamauchi, T; Oda, K; Ikeda, T; Honda, Y; Tagawa, S

1999-01-01

The effect of gamma-rays and pulsed electrons has been investigated on the bulk etch rate of CR-39 detector at doses up to 100 kGy under various dose-rate between 0.0044 and 35.0 Gy/s. The bulk etch rate increased exponentially with the dose at every examined dose-rates. It was reveled to be strongly depend on the dose-rate: the bulk etch rate was decreased with increasing dose-rate at the same total dose. A primitive model was proposed to explain the dose-rate effect in which oxygen dissolved was assumed to dominate the damage formation process.

Mechanistic simulation of normal-tissue damage in radiotherapy-implications for dose-volume analyses

International Nuclear Information System (INIS)

Rutkowska, Eva; Baker, Colin; Nahum, Alan

2010-01-01

A radiobiologically based 3D model of normal tissue has been developed in which complications are generated when 'irradiated'. The aim is to provide insight into the connection between dose-distribution characteristics, different organ architectures and complication rates beyond that obtainable with simple DVH-based analytical NTCP models. In this model the organ consists of a large number of functional subunits (FSUs), populated by stem cells which are killed according to the LQ model. A complication is triggered if the density of FSUs in any 'critical functioning volume' (CFV) falls below some threshold. The (fractional) CFV determines the organ architecture and can be varied continuously from small (series-like behaviour) to large (parallel-like). A key feature of the model is its ability to account for the spatial dependence of dose distributions. Simulations were carried out to investigate correlations between dose-volume parameters and the incidence of 'complications' using different pseudo-clinical dose distributions. Correlations between dose-volume parameters and outcome depended on characteristics of the dose distributions and on organ architecture. As anticipated, the mean dose and V 20 correlated most strongly with outcome for a parallel organ, and the maximum dose for a serial organ. Interestingly better correlation was obtained between the 3D computer model and the LKB model with dose distributions typical for serial organs than with those typical for parallel organs. This work links the results of dose-volume analyses to dataset characteristics typical for serial and parallel organs and it may help investigators interpret the results from clinical studies.

Optimized dose distribution of a high dose rate vaginal cylinder

International Nuclear Information System (INIS)

Li Zuofeng; Liu, Chihray; Palta, Jatinder R.

1998-01-01

Purpose: To present a comparison of optimized dose distributions for a set of high-dose-rate (HDR) vaginal cylinders calculated by a commercial treatment-planning system with benchmark calculations using Monte-Carlo-calculated dosimetry data. Methods and Materials: Optimized dose distributions using both an isotropic and an anisotropic dose calculation model were obtained for a set of HDR vaginal cylinders. Mathematical optimization techniques available in the computer treatment-planning system were used to calculate dwell times and positions. These dose distributions were compared with benchmark calculations with TG43 formalism and using Monte-Carlo-calculated data. The same dwell times and positions were used for a quantitative comparison of dose calculated with three dose models. Results: The isotropic dose calculation model can result in discrepancies as high as 50%. The anisotropic dose calculation model compared better with benchmark calculations. The differences were more significant at the apex of the vaginal cylinder, which is typically used as the prescription point. Conclusion: Dose calculation models available in a computer treatment-planning system must be evaluated carefully to ensure their correct application. It should also be noted that when optimized dose distribution at a distance from the cylinder surface is calculated using an accurate dose calculation model, the vaginal mucosa dose becomes significantly higher, and therefore should be carefully monitored

Intraoperative high-dose-rate brachytherapy for the treatment of pediatric tumors: the Ohio State University experience

International Nuclear Information System (INIS)

Nag, Subir; Tippin, Douglas; Ruymann, Frederick B.

2001-01-01

Purpose: To determine whether intraoperative high-dose-rate brachytherapy (IO-HDRBT) can be used to decrease the dose of external beam radiotherapy (EBRT) in the treatment of children with soft-tissue sarcomas and, thereby, reduce morbidity without compromising local control. Methods and Materials: From March 1992 through April 1999, 13 pediatric patients were treated with IO-HDRBT, low-dose EBRT, chemotherapy, and radical surgery at 21 sites that were not amenable to intraoperative electron beam therapy. The IO-HDRBT dose at 5 mm depth was 10 to 12.5 Gy for close margins/microscopic disease at 14 sites and 12.5 to 15 Gy for gross disease at 7 sites. The treatment volumes ranged from 4 to 96 cm 3 (mean 27). The EBRT dose was limited to 27-30 Gy in most cases to minimize growth retardation and preserve normal organ function. Results: After a median follow-up of 47 months (range 12-97), 11 patients were alive and without evidence of disease (overall survival rate 85%, 4-year actuarial survival rate 77%). Of the 2 who died, 1 had Stage III pulmonary blastoma with a sacral recurrence; the other had Stage IV undifferentiated synovial sarcoma with a pulmonary recurrence. One local failure occurred in a patient with gross residual disease after incomplete resection for Stage IV pulmonary blastoma. The local control rate was 95%, and morbidity was observed in 3 patients (23%). One patient developed impaired orbital growth with mild ptosis. Another patient required orthopedic pinning of her femoral subcapital epiphysis and construction of a neobladder secondary to urethral obstruction. The third patient required reimplantation of her autotransplanted kidney secondary to chronic urinary tract infection and ureteral reflux. Conclusions: IO-HDRBT allowed for reduction in EBRT without compromising local control or disease-free survival in children with soft-tissue sarcomas. Tumor beds inaccessible to electron beam methods could be satisfactorily encompassed with IO

Influence trend of temperature distribution in skin tissue generated by different exposure dose pulse laser

Science.gov (United States)

Shan, Ning; Wang, Zhijing; Liu, Xia

2014-11-01

Laser is widely applied in military and medicine fields because of its excellent capability. In order to effectively defend excess damage by laser, the thermal processing theory of skin tissue generated by laser should be carried out. The heating rate and thermal damage area should be studied. The mathematics model of bio-tissue heat transfer that is irradiated by laser is analyzed. And boundary conditions of bio-tissue are discussed. Three layer FEM grid model of bio-tissue is established. The temperature rising inducing by pulse laser in the tissue is modeled numerically by adopting ANSYS software. The changing trend of temperature in the tissue is imitated and studied under the conditions of different exposure dose pulse laser. The results show that temperature rising in the tissue depends on the parameters of pulse laser largely. In the same conditions, the pulse width of laser is smaller and its instant power is higher. And temperature rising effect in the tissue is very clear. On the contrary, temperature rising effect in the tissue is lower. The cooling time inducing by temperature rising effect in the tissue is longer along with pulse separation of laser is bigger. And the temperature difference is bigger in the pulse period.

Airborne and total gamma absorbed dose rates at Patiala - India

International Nuclear Information System (INIS)

Tesfaye, Tilahun; Sahota, H.S.; Singh, K.

1999-01-01

The external gamma absorbed dose rate due to gamma rays originating from gamma emitting aerosols in air, is compared with the total external gamma absorbed dose rate at the Physics Department of Punjabi University, Patiala. It has been found out that the contribution, to the total external gamma absorbed dose rate, of radionuclides on particulate matter suspended in air is about 20% of the overall gamma absorbed dose rate. (author)

Conversion Factors for Predicting Unshielded Dose Rates in Shielded Waste

International Nuclear Information System (INIS)

Clapham, M.; Seamans Jr, J.V.; Arbon, R.E.

2009-01-01

This document describes the methodology developed and used by the Advanced Mixed Waste Treatment Project for determining the activity content and the unshielded surface dose rate for lead lined containers contaminated with transuranic waste. Several methods were investigated: - Direct measurement of the dose rate after removing the shielding. - Use of a MicroShield R derived dose conversion factor, (mRem/hr unshielded )/(mRem/hr shielded ), applied to the measured surface dose rate to estimate the unshielded surface dose rate. - Use of a MicroShield R derived activity conversion factor, mRem/hr unshielded /Ci, applied to the measured activity to estimate the unshielded dose rate. - Use of an empirically derived activity conversion factor, mRem/hr unshielded /Ci, applied to the measured activity to estimate the unshielded dose rate. The last approach proved to be the most efficacious by using a combination of nondestructive assay and empirically defined dose rate conversion factors. Empirically derived conversion factors were found to be highly dependent upon the matrix of the waste. Use of conversion factors relied on activity values corrected to address the presence of a lead liner. (authors)

Quantitative radiation dose-response relationships for normal tissues in man - I. Gustatory tissues response during photon and neutron radiotherapy

International Nuclear Information System (INIS)

Mossman, K.L.

1982-01-01

Quantitative radiation dose-response curves for normal gustatory tissue in man were studied. Taste function, expressed as taste loss, was evaluated in 84 patients who were given either photon or neutron radiotherapy for tumors in the head and neck region. Patients were treated to average tumor doses of 6600 cGy (photon) or 2200 cGy intervals for photon patients and 320-cGy intervals for neutron patients during radiotherapy. The dose-response curves for photons and neutrons were analyzed by fitting a four-parameter logistic equation to the data. Photon and neutron curves differed principally in their relative position along the dose axis. Comparison of the dose-response curves were made by determination of RBE. At 320 cGy, the lowest neutron dose at which taste measurements were made, RBE = 5.7. If this RBE is correct, then the therapeutic gain factor may be equal to or less than 1, indicating no biological advantage in using neutrons over photons for this normal tissue. These studies suggest measurements of taste function and evaluation of dose-response relationships may also be useful in quantitatively evaluating the efficacy of chemical modifiers of radiation response such as hypoxic cell radiosensitizers and radioprotectors

Late complications after high-dose-rate interstitial brachytherapy for tongue cancer

International Nuclear Information System (INIS)

Shimizutani, Kimishige; Inoue, Takehiro; Inoue, Toshihiko; Yoshioka, Yasuo; Teshima, Teruki; Kakimoto, Naoya; Murakami, Shumei; Furukawa, Souhei; Fuchihata, Hajime

2005-01-01

The objectives of this study was to analyze the treatment results and late complications of high-dose-rate (HDR) interstitial brachytherapy (ISBT) for early (T1N0, T2N0) mobile tongue cancer using the microSelectron-HDR. From January 1993 through April 2001, a total of 72 patients with early squamous cell carcinomas of the mobile tongue were treated with microSelectron-HDR interstitial brachytherapy at the Department of Radiology, Osaka University Hospital. Of the patients, 18% were treated with a combination of prior external radiation and HDR-ISBT, and 82% were treated with HDR-ISBT alone. For HDR-ISBT alone, all cases were treated with a total dose of 54 Gy/9 fractions every 5 days or 60 Gy/10 fractions every 8 days. In combined therapy with an external dose of 30 to 40 Gy, HDR-ISBT was given at a total dose of 42-50 Gy. The Brinkman and alcohol indexes were used to analyze the incidence of late complications after HDR-ISBT. The 2- and 5-year local control rates were 85% and 82%, respectively. Fifteen of 72 patients (21%) treated with HDR-ISBT had late complications. Ten of 15 patients (67%) with late complications had a Brinkman index exceeding 600. HDR-ISBT is useful and easily applied under local anesthesia to early or superficial lesions of the mobile tongue. However, we found an increase in late complications, such as soft-tissue ulcers and bone exposure, after irradiation of tongue cancer with 60 Gy HDR-ISBT in patients with a Brinkman index greater than 600. (author)

Postoperative vaginal irradiation with high dose rate afterloading technique in endometrial carcinoma stage I

International Nuclear Information System (INIS)

Sorbe, B.G.; Smeds, A.C.

1990-01-01

A high dose rate ( 60 Co) afterloading technique was used for postoperative prophylactic vaginal irradiation in a series of 404 women with endometrial carcinoma Stage I. The total recurrence rate was 3.7% with 0.7% vaginal deposits. The crude 5-year survival rate for the complete series was 91.8% compared to 13.3% for those with recurrences. Depth of myometrial infiltration (greater than 1/3 of the uterine wall) and nuclear grade were the most important prognostic factors. Clinically significant late radiation reactions (bladder and/or rectum) were recorded in 6.9%. Dose per fraction and the size of the target volume were highly significantly related to the occurrence of both early and late radiation reactions. Vaginal shortening is closely related to the dose per fraction, length of the reference isodose, and the applicator diameter. The shape of the vaginal applicator versus the isodoses and the importance of the source train geometry and relative activity for dose gradient inhomogeneities within the target volume are discussed. Cumulative radiation effect (CRE) and linear-quadratic (LQ) calculations have been performed and related to tissue reactions within the target volume and in the risk organs. An alpha-beta quotient of 8.8 for vaginal shrinkage effect and 2.0 for late rectal complications are suggested on the basis of calculations using a maximum likelihood method for quantal radiation data

Gamma Low-Dose-Rate Ionizing Radiation Stimulates Adaptive Functional and Molecular Response in Human Aortic Endothelial Cells in a Threshold-, Dose-, and Dose Rate-Dependent Manner.

Science.gov (United States)

Vieira Dias, Juliana; Gloaguen, Celine; Kereselidze, Dimitri; Manens, Line; Tack, Karine; Ebrahimian, Teni G

2018-01-01

A central question in radiation protection research is whether low-dose and low-dose-rate (LDR) exposures to ionizing radiation play a role in progression of cardiovascular disease. The response of endothelial cells to different LDR exposures may help estimate risk of cardiovascular disease by providing the biological mechanism involved. We investigated the effect of chronic LDR radiation on functional and molecular responses of human aorta endothelial cells (HAoECs). Human aorta endothelial cells were continuously irradiated at LDR (6 mGy/h) for 15 days and analyzed at time points when the cumulative dose reached 0.05, 0.5, 1.0, and 2.0 Gy. The same doses were administered acutely at high-dose rate (HDR; 1 Gy/min). The threshold for the loss of angiogenic capacity for both LDR and HDR radiations was between 0.5 and 1.0 Gy. At 2.0 Gy, angiogenic capacity returned to normal only for HAoEC exposed to LDR radiation, associated with increased expression of antioxidant and anti-inflammatory genes. Pre-LDR, but not pre-HDR, radiation, followed by a single acute 2.0 Gy challenge dose sustained the expression of antioxidant and anti-inflammatory genes and stimulated angiogenesis. Our results suggest that dose rate is important in cellular response and that a radioadaptive response is involved for a 2.0 Gy dose at LDR.

Toxicity bioassay in mice exposed to low dose-rate radiation

Energy Technology Data Exchange (ETDEWEB)

Kim, Joog Sun; Gong, Eun Ji; Heo, Kyu; Yang, Kwang Mo [Research Center, Dongnam Institute of Radiological and Medical Sciences, Busan (Korea, Republic of)

2013-04-15

The systemic effect of radiation increases in proportion to the dose amount and rate. The association between accumulated radiation dose and adverse effects, which is derived according to continuous low dose-rate radiation exposure, is not clearly elucidated. Our previous study showed that low dose-rate radiation exposure did not cause adverse effects in BALB/c mice at dose levels of ≤2 Gy, but the testis weight decreased at a dose of 2 Gy. In this study, we studied the effects of irradiation at the low dose rate (3.49 mGy/h) in the testes of C57BL/6 mice. Mice exposed to a total dose of 0.02, 0.2, and 2 Gy were found to be healthy and did not show any significant changes in body weight and peripheral blood components. However, mice irradiated with a dose of 2 Gy had significantly decreased testis weight. Further, histological studies and sperm evaluation also demonstrated changes consistent with the findings of decreased testis weight. In fertile patients found to have arrest of sperm maturation, the seminiferous tubules lack the DNMT1 and HDAC1 protein. The decrease of DNMT1 and HDAC1 in irradiated testis may be the part of the mechanism via which low dose-rate irradiation results in teticular injury. In conclusion, despite a low dose-rate radiation, our study found that when mice testis were irradiated with 2 Gy at 3.49 mGy/h dose rate, there was significant testicular and sperm damage with decreased DNMT1 and HDAC1 expression.

In situ measurements of dose rates from terrestrial gamma rays

International Nuclear Information System (INIS)

Horng, M.C.; Jiang, S.H.

2002-01-01

A portable, high purity germanium (HPGe) detector was employed for the performance of in situ measurements of radionuclide activity concentrations in the ground in Taiwan, at altitudes ranging from sea level to 3900 m. The absolute peak efficiency of the HPGe detector for a gamma-ray source uniformly distributed in the semi-infinite ground was determined using a semi-empirical method. The gamma-ray dose rates from terrestrial radionuclides were calculated from the measured activity levels using recently published dose rate conversion factors. The absorbed dose rate in air due to cosmic rays was derived by subtracting the terrestrial gamma-ray dose rate from the overall absorbed dose rate in air measured using a high-pressure ionization chamber. The cosmic-ray dose rate calculated as a function of altitude, was found to be in good agreement with the data reported by UNSCEAR. (orig.)

Novel high dose rate lip brachytherapy technique to improve dose homogeneity and reduce toxicity by customized mold

International Nuclear Information System (INIS)

Feldman, Jon; Appelbaum, Limor; Sela, Mordechay; Voskoboinik, Ninel; Kadouri, Sarit; Weinberger, Jeffrey; Orion, Itzhak; Meirovitz, Amichay

2014-01-01

The purpose of this study is to describe a novel brachytherapy technique for lip Squamous Cell Carcinoma, utilizing a customized mold with embedded brachytherapy sleeves, which separates the lip from the mandible, and improves dose homogeneity. Seven patients with T2 lip cancer treated with a “sandwich” technique of High Dose Rate (HDR) brachytherapy to the lip, consisting of interstitial catheters and a customized mold with embedded catheters, were reviewed for dosimetry and outcome using 3D planning. Dosimetric comparison was made between the “sandwich” technique to “classic” – interstitial catheters only plan. We compared dose volume histograms for Clinical Tumor Volume (CTV), normal tissue “hot spots” and mandible dose. We are reporting according to the ICRU 58 and calculated the Conformal Index (COIN) to show the advantage of our technique. The seven patients (ages 36–81 years, male) had median follow-up of 47 months. Four patients received Brachytherapy and External Beam Radiation Therapy, 3 patients received brachytherapy alone. All achieved local control, with excellent esthetic and functional results. All patients are disease free. The Customized Mold Sandwich technique (CMS) reduced the high dose region receiving 150% (V150) by an average of 20% (range 1–47%), The low dose region (les then 90% of the prescribed dose) improved by 73% in average by using the CMS technique. The COIN value for the CMS was in average 0.92 as opposed to 0.88 for the interstitial catheter only. All differences (excluding the low dose region) were statistically significant. The CMS technique significantly reduces the high dose volume and increases treatment homogeneity. This may reduce the potential toxicity to the lip and adjacent mandible, and results in excellent tumor control, cosmetic and functionality

Endorectal high dose rate brachytherapy quality assurance

International Nuclear Information System (INIS)

Devic, S.; Vuong, T.; Evans, M.; Podgorsak, E.

2008-01-01

We describe our quality assurance method for preoperative high dose rate (HDR) brachytherapy of endorectal tumours. Reproduction of the treatment planning dose distribution on a daily basis is crucial for treatment success. Due to the cylindrical symmetry, two types of adjustments are necessary: applicator rotation and dose distribution shift along the applicator axis. (author)

Biological effects of low doses of radiation at low dose rate

International Nuclear Information System (INIS)

1996-05-01

The purpose of this report was to examine available scientific data and models relevant to the hypothesis that induction of genetic changes and cancers by low doses of ionizing radiation at low dose rate is a stochastic process with no threshold or apparent threshold. Assessment of the effects of higher doses of radiation is based on a wealth of data from both humans and other organisms. 234 refs., 26 figs., 14 tabs

The impact of the oxygen scavenger on the dose-rate dependence and dose sensitivity of MAGIC type polymer gels

Science.gov (United States)

Khan, Muzafar; Heilemann, Gerd; Kuess, Peter; Georg, Dietmar; Berg, Andreas

2018-03-01

Recent developments in radiation therapy aimed at more precise dose delivery along with higher dose gradients (dose painting) and more efficient dose delivery with higher dose rates e.g. flattening filter free (FFF) irradiation. Magnetic-resonance-imaging based polymer gel dosimetry offers 3D information for precise dose delivery techniques. Many of the proposed polymer gels have been reported to exhibit a dose response, measured as relaxation rate ΔR2(D), which is dose rate dependent. A lack of or a reduced dose-rate sensitivity is very important for dosimetric accuracy, especially with regard to the increasing clinical use of FFF irradiation protocols with LINACs at high dose rates. Some commonly used polymer gels are based on Methacrylic-Acid-Gel-Initiated-by-Copper (MAGIC). Here, we report on the dose sensitivity (ΔR2/ΔD) of MAGIC-type gels with different oxygen scavenger concentration for their specific dependence on the applied dose rate in order to improve the dosimetric performance, especially for high dose rates. A preclinical x-ray machine (‘Yxlon’, E  =  200 kV) was used for irradiation to cover a range of dose rates from low \\dot{D} min  =  0.6 Gy min-1 to high \\dot{D} max  =  18 Gy min-1. The dose response was evaluated using R2-imaging of the gel on a human high-field (7T) MR-scanner. The results indicate that all of the investigated dose rates had an impact on the dose response in polymer gel dosimeters, being strongest in the high dose region and less effective for low dose levels. The absolute dose rate dependence \\frac{(Δ R2/Δ D)}{Δ \\dot{D}} of the dose response in MAGIC-type gel is significantly reduced using higher concentrations of oxygen scavenger at the expense of reduced dose sensitivity. For quantitative dose evaluations the relative dose rate dependence of a polymer gel, normalized to its sensitivity is important. Based on this normalized sensitivity the dose rate sensitivity was reduced distinctly

Radiation dose rates from commercial PWR and BWR spent fuel elements

International Nuclear Information System (INIS)

Willingham, C.E.

1981-10-01

Data on measurements of gamma dose rates from commercial reactor spent fuel were collected, and documented calculated gamma dose rates were reviewed. As part of this study, the gamma dose rate from spent fuel was estimated, using computational techniques similar to previous investigations into this problem. Comparison of the measured and calculated dose rates provided a recommended dose rate in air versus distance curve for PWR spent fuel

Dose Rate of Environmental Gamma Radiation in Java Island

International Nuclear Information System (INIS)

Gatot Suhariyono; Buchori; Dadong Iskandar

2007-01-01

The dose rate Monitoring of environmental gamma radiation at some locations in Java Island in the year 2005 / 2006 has been carried out. The dose rate measurement of gamma radiation is carried out by using the peripheral of Portable Gamma of Ray Spectrometer with detector of NaI(Tl), Merck Exploranium, Model GR-130- MINISPEC, while to determine its geographic position is used by the GPS (Global Positioning System), made in German corporation of GPS III Plus type. The division of measurement region was conducted by dividing Java Island become 66 parts with same distance, except in Jepara area that will built PLTN (Nuclear Energy Power), distance between measurement points is more closed. The results of dose rate measurement are in 66 locations in Java Island the range of (19.24 ± 4.05) nSv/hour until (150.78 ± 12.26) nSv/hour with mean (51.93 ± 36.53) nSv/h. The lowest dose rate was in location of Garut, while highest dose rate was in Ujung Lemah Abang, Jepara location. The data can be used for base line data of dose rate of environmental gamma radiation in Indonesia, specially in Java Island. The mean level of gamma radiation in Java monitoring area (0.46 mSv / year) was still lower than worldwide average effective dose rate of terrestrial gamma rays 0.5 mSv / year (report of UNSCEAR, 2000). (author)

Reference Dose Rates for Fluoroscopy Guided Interventions

International Nuclear Information System (INIS)

Geleijns, J.; Broerse, J.J.; Hummel, W.A.; Schalij, M.J.; Schultze Kool, L.J.; Teeuwisse, W.; Zoetelief, J.

1998-01-01

The wide diversity of fluoroscopy guided interventions which have become available in recent years has improved patient care. They are being performed in increasing numbers, particularly at departments of cardiology and radiology. Some procedures are very complex and require extended fluoroscopy times, i.e. longer than 30 min, and radiation exposure of patient and medical staff is in some cases rather high. The occurrence of radiation-induced skin injuries on patients has shown that radiation protection for fluoroscopy guided interventions should not only be focused on stochastic effects, i.e. tumour induction and hereditary risks, but also on potential deterministic effects. Reference dose levels are introduced by the Council of the European Communities as an instrument to achieve optimisation of radiation protection in radiology. Reference levels in conventional diagnostic radiology are usually expressed as entrance skin dose or dose-area product. It is not possible to define a standard procedure for complex interventions due to the large inter-patient variations with regard to the complexity of specific interventional procedures. Consequently, it is not realistic to establish a reference skin dose or dose-area product for complex fluoroscopy guided interventions. As an alternative, reference values for fluoroscopy guided interventions can be expressed as the entrance dose rates on a homogeneous phantom and on the image intensifier. A protocol has been developed and applied during a nationwide survey of fluoroscopic dose rate during catheter ablations. From this survey reference entrance dose rates of respectively 30 mGy.min -1 on a polymethylmethacrylate (PMMA) phantom with a thickness of 21 cm, and of 0.8 μGy.s -1 on the image intensifier have been derived. (author)

DIANE, a simulation code for the interaction of neutrons with living tissues. Application to low doses of fast neutrons on human tumoral cells; DIANE, un code de simulation de l'interaction des neutrons avec la matiere vivante. Applications aux faibles doses de neutrons rapides sur des cellules tumorales humaines

Energy Technology Data Exchange (ETDEWEB)

Nenot, M.L

2003-07-15

Our work deals with the irradiation of cells and living tissues by 14 MeV neutrons at very low doses (a few 10{sup -2} Gy). Such experiments require an accurate knowledge of the values of neutron dose rates and fluences at the level of cell cultures. We have performed measurements of fluence rates through an activation method applied to gold and copper foils. The fluence rate is deduced from the gamma rays emitted by the irradiated foils. Neutron doses and dose rates have been measured through varied methods: PIN diodes, ionization tissue equivalent chambers, and Geiger-Mueller counters. We have designed the DIANE code to simulate the impact of energetic neutrons on cells. This code can be used with isolated cells or macroscopic tissues, it takes into account the roles of the ionisation electrons produced by recoil nuclei entering the cell. This point is all the more important since recent works have highlighted the impact of very low energy electrons on DNA. (A.C.)

Development of a high precision dosimetry system for the measurement of surface dose rate distribution for eye applicators

Energy Technology Data Exchange (ETDEWEB)

Eichmann, Marion; Fluehs, Dirk; Spaan, Bernhard [Fakultaet Physik, Technische Universitaet Dortmund, D 44221 Dortmund (Germany); Klinische Strahlenphysik, Universitaetsklinikum Essen, D 45122 Essen (Germany); Fakultaet Physik, Technische Universitaet Dortmund, D 44221 Dortmund (Germany)

2009-10-15

Purpose: The therapeutic outcome of the therapy with ophthalmic applicators is highly dependent on the application of a sufficient dose to the tumor, whereas the dose applied to the surrounding tissue needs to be minimized. The goal for the newly developed apparatus described in this work is the determination of the individual applicator surface dose rate distribution with a high spatial resolution and a high precision in dose rate with respect to time and budget constraints especially important for clinical procedures. Inhomogeneities of the dose rate distribution can be detected and taken into consideration for the treatment planning. Methods: In order to achieve this, a dose rate profile as well as a surface profile of the applicator are measured and correlated with each other. An instrumental setup has been developed consisting of a plastic scintillator detector system and a newly designed apparatus for guiding the detector across the applicator surface at a constant small distance. It performs an angular movement of detector and applicator with high precision. Results: The measurements of surface dose rate distributions discussed in this work demonstrate the successful operation of the measuring setup. Measuring the surface dose rate distribution with a small distance between applicator and detector and with a high density of measuring points results in a complete and gapless coverage of the applicator surface, being capable of distinguishing small sized spots with high activities. The dosimetrical accuracy of the measurements and its analysis is sufficient (uncertainty in the dose rate in terms of absorbed dose to water is <7%), especially when taking the surgical techniques in positioning of the applicator on the eyeball into account. Conclusions: The method developed so far allows a fully automated quality assurance of eye applicators even under clinical conditions. These measurements provide the basis for future calculation of a full 3D dose rate

Development of a high precision dosimetry system for the measurement of surface dose rate distribution for eye applicators.

Science.gov (United States)

Eichmann, Marion; Flühs, Dirk; Spaan, Bernhard

2009-10-01

The therapeutic outcome of the therapy with ophthalmic applicators is highly dependent on the application of a sufficient dose to the tumor, whereas the dose applied to the surrounding tissue needs to be minimized. The goal for the newly developed apparatus described in this work is the determination of the individual applicator surface dose rate distribution with a high spatial resolution and a high precision in dose rate with respect to time and budget constraints especially important for clinical procedures. Inhomogeneities of the dose rate distribution can be detected and taken into consideration for the treatment planning. In order to achieve this, a dose rate profile as well as a surface profile of the applicator are measured and correlated with each other. An instrumental setup has been developed consisting of a plastic scintillator detector system and a newly designed apparatus for guiding the detector across the applicator surface at a constant small distance. It performs an angular movement of detector and applicator with high precision. The measurements of surface dose rate distributions discussed in this work demonstrate the successful operation of the measuring setup. Measuring the surface dose rate distribution with a small distance between applicator and detector and with a high density of measuring points results in a complete and gapless coverage of the applicator surface, being capable of distinguishing small sized spots with high activities. The dosimetrical accuracy of the measurements and its analysis is sufficient (uncertainty in the dose rate in terms of absorbed dose to water is <7%), especially when taking the surgical techniques in positioning of the applicator on the eyeball into account. The method developed so far allows a fully automated quality assurance of eye applicators even under clinical conditions. These measurements provide the basis for future calculation of a full 3D dose rate distribution, which then can be used as input for

Dose and dose rate effects of whole-body gamma-irradiation: II. Hematological variables and cytokines

Science.gov (United States)

Gridley, D. S.; Pecaut, M. J.; Miller, G. M.; Moyers, M. F.; Nelson, G. A.

2001-01-01

The goal of part II of this study was to evaluate the effects of gamma-radiation on circulating blood cells, functional characteristics of splenocytes, and cytokine expression after whole-body irradiation at varying total doses and at low- and high-dose-rates (LDR, HDR). Young adult C57BL/6 mice (n = 75) were irradiated with either 1 cGy/min or 80 cGy/min photons from a 60Co source to cumulative doses of 0.5, 1.5, and 3.0 Gy. The animals were euthanized at 4 days post-exposure for in vitro assays. Significant dose- (but not dose-rate-) dependent decreases were observed in erythrocyte and blood leukocyte counts, hemoglobin, hematocrit, lipopolysaccharide (LPS)-induced 3H-thymidine incorporation, and interleukin-2 (IL-2) secretion by activated spleen cells when compared to sham-irradiated controls (p factor-beta 1 (TGF-beta 1) and splenocyte secretion of tumor necrosis factor-alpha (TNF-alpha) were not affected by either the dose or dose rate of radiation. The data demonstrate that the responses of blood and spleen were largely dependent upon the total dose of radiation employed and that an 80-fold difference in the dose rate was not a significant factor in the great majority of measurements.

Dose-rate determination by radiochemical analysis

International Nuclear Information System (INIS)

Mangini, A.; Pernicka, E.; Wagner, G.A.

1983-01-01

At the previous TL Specialist Seminr we had suggested that α-counting is an unsuitable technique for dose-rate determination due to overcounting effects. This is confirmed by combining α-counting, neutron activation analysis, fission track counting, α-spectrometry on various pottery samples. One result of this study is that disequilibrium in the uranium decay chain alone cannot account for the observed discrepancies between α-counting and chemical analysis. Therefore we propose for routine dose-rate determination in TL dating to apply chemical analysis of the radioactive elements supplemented by an α-spectrometric equilibrium check. (author)

Effective dose rate coefficients for exposure to contaminated soil

Energy Technology Data Exchange (ETDEWEB)

Veinot, K.G. [Easterly Scientific, Knoxville, TN (United States); Y-12 National Security Complex, Oak Ridge, TN (United States); Eckerman, K.F.; Easterly, C.E. [Easterly Scientific, Knoxville, TN (United States); Bellamy, M.B.; Hiller, M.M.; Dewji, S.A. [Oak Ridge National Laboratory, Center for Radiation Protection Knowledge, Oak Ridge, TN (United States); Hertel, N.E. [Oak Ridge National Laboratory, Center for Radiation Protection Knowledge, Oak Ridge, TN (United States); Georgia Institute of Technology, Atlanta, GA (United States); Manger, R. [University of California San Diego, Department of Radiation Medicine and Applied Sciences, La Jolla, CA (United States)

2017-08-15

The Oak Ridge National Laboratory Center for Radiation Protection Knowledge has undertaken calculations related to various environmental exposure scenarios. A previous paper reported the results for submersion in radioactive air and immersion in water using age-specific mathematical phantoms. This paper presents age-specific effective dose rate coefficients derived using stylized mathematical phantoms for exposure to contaminated soils. Dose rate coefficients for photon, electron, and positrons of discrete energies were calculated and folded with emissions of 1252 radionuclides addressed in ICRP Publication 107 to determine equivalent and effective dose rate coefficients. The MCNP6 radiation transport code was used for organ dose rate calculations for photons and the contribution of electrons to skin dose rate was derived using point-kernels. Bremsstrahlung and annihilation photons of positron emission were evaluated as discrete photons. The coefficients calculated in this work compare favorably to those reported in the US Federal Guidance Report 12 as well as by other authors who employed voxel phantoms for similar exposure scenarios. (orig.)

Dose rate of restroon in facilities using radioisotope

Energy Technology Data Exchange (ETDEWEB)

Cho, Yong Gwi [Dept. of uclear Medicine, Inha University hospital, Incheon (Korea, Republic of); An, Seong Min [Dept. of Radiology, Gachon University, Incheon (Korea, Republic of)

2016-06-15

This study is therefore aimed at measuring the surface dose rate and the spatial dose rate in and outside the radionuclide facility in order to ensure safety of the patients, radiation workers and family care-givers in their use of such equipment and to provide a basic framework for further research on radiation protection. The study was conducted at 4 restrooms in and outside the radionuclide facility of a general hospital in Incheon between May 1 and July 31, 2014. During the study period, the spatial contamination dose rate and the surface contamination dose rate before and after radiation use were measured at the 4 places−thyroid therapy room, PET center, gamma camera room, and outpatient department. According to the restroom use survey by hospitals, restrooms in the radionuclide facility were used not only by patients but also by family care-givers and some of radiation workers. The highest cumulative spatial radiation dose rate was 8.86 mSv/hr at camera room restroom, followed by 7.31 mSv/hr at radioactive iodine therapy room restroom, 2.29 mSv/hr at PET center restroom, and 0.26 mSv/hr at outpatient department restroom, respectively. The surface radiation dose rate measured before and after radiation use was the highest at toilets, which are in direct contact with patient's excretion, followed by the center and the entrance of restrooms. Unsealed radioactive sources used in nuclear medicine are relatively safe due to short half lives and low energy. A patient who received those radioactive sources, however, may become a mobile radioactive source and contaminate areas the patient contacts−camera room, sedation room, and restroom−through secretion and excretion. Therefore, patients administered radionuclides should be advised to drink sufficient amounts of water to efficiently minimize radiation exposure to others by reducing the biological half-life, and members of the public−family care-givers, pregnant women, and children−be as far away from

Iodine-131 dose dependent gene expression in thyroid cancers and corresponding normal tissues following the Chernobyl accident.

Directory of Open Access Journals (Sweden)

Michael Abend

Full Text Available The strong and consistent relationship between irradiation at a young age and subsequent thyroid cancer provides an excellent model for studying radiation carcinogenesis in humans. We thus evaluated differential gene expression in thyroid tissue in relation to iodine-131 (I-131 doses received from the Chernobyl accident. Sixty three of 104 papillary thyroid cancers diagnosed between 1998 and 2008 in the Ukrainian-American cohort with individual I-131 thyroid dose estimates had paired RNA specimens from fresh frozen tumor (T and normal (N tissue provided by the Chernobyl Tissue Bank and satisfied quality control criteria. We first hybridized 32 randomly allocated RNA specimen pairs (T/N on 64 whole genome microarrays (Agilent, 4×44 K. Associations of differential gene expression (log(2(T/N with dose were assessed using Kruskall-Wallis and trend tests in linear mixed regression models. While none of the genes withstood correction for the false discovery rate, we selected 75 genes with a priori evidence or P kruskall/P trend <0.0005 for validation by qRT-PCR on the remaining 31 RNA specimen pairs (T/N. The qRT-PCR data were analyzed using linear mixed regression models that included radiation dose as a categorical or ordinal variable. Eleven of 75 qRT-PCR assayed genes (ACVR2A, AJAP1, CA12, CDK12, FAM38A, GALNT7, LMO3, MTA1, SLC19A1, SLC43A3, ZNF493 were confirmed to have a statistically significant differential dose-expression relationship. Our study is among the first to provide direct human data on long term differential gene expression in relation to individual I-131 doses and to identify a set of genes potentially important in radiation carcinogenesis.

Absorbed dose thresholds and absorbed dose rate limitations for studies of electron radiation effects on polyetherimides

Science.gov (United States)

Long, Edward R., Jr.; Long, Sheila Ann T.; Gray, Stephanie L.; Collins, William D.

1989-01-01

The threshold values of total absorbed dose for causing changes in tensile properties of a polyetherimide film and the limitations of the absorbed dose rate for accelerated-exposure evaluation of the effects of electron radiation in geosynchronous orbit were studied. Total absorbed doses from 1 kGy to 100 MGy and absorbed dose rates from 0.01 MGy/hr to 100 MGy/hr were investigated, where 1 Gy equals 100 rads. Total doses less than 2.5 MGy did not significantly change the tensile properties of the film whereas doses higher than 2.5 MGy significantly reduced elongation-to-failure. There was no measurable effect of the dose rate on the tensile properties for accelerated electron exposures.

Radiation safety program in high dose rate brachytherapy facility at INHS Asvini

Directory of Open Access Journals (Sweden)

Kirti Tyagi

2014-01-01

Full Text Available Brachytherapy concerns primarily the use of radioactive sealed sources which are inserted into catheters or applicators and placed directly into tissue either inside or very close to the target volume. The use of radiation in treatment of patients involves both benefits and risks. It has been reported that early radiation workers had developed radiation induced cancers. These incidents lead to continuous work for the improvement of radiation safety of patients and personnel The use of remote afterloading equipment has been developed to improve radiation safety in the delivery of treatment in brachytherapy. The widespread adoption of high dose rate brachytherapy needs appropriate quality assurance measures to minimize the risks to both patients and medical staff. The radiation safety program covers five major aspects: quality control, quality assurance, radiation monitoring, preventive maintenance, administrative measures and quality audit. This paper will discuss the radiation safety program developedfor a high dose rate brachytherapy facility at our centre which may serve as a guideline for other centres intending to install a similar facility.

GARDEC, Estimation of dose-rates reduction by garden decontamination

International Nuclear Information System (INIS)

Togawa, Orihiko

2006-01-01

1 - Description of program or function: GARDEC estimates the reduction of dose rates by garden decontamination. It provides the effect of different decontamination Methods, the depth of soil to be considered, dose-rate before and after decontamination and the reduction factor. 2 - Methods: This code takes into account three Methods of decontamination : (i)digging a garden in a special way, (ii) a removal of the upper layer of soil, and (iii) covering with a shielding layer of soil. The dose-rate conversion factor is defined as the external dose-rate, in the air, at a given height above the ground from a unit concentration of a specific radionuclide in each soil layer

Dose rate effect on material aging due to radiation. [Gamma radiation

Energy Technology Data Exchange (ETDEWEB)

Okamoto, Shin-ichi (Radiation Center of Osaka Prefecture, Sakai (Japan)); Hayakawa, Chikara; Takeya, Chikashi

1982-12-01

Although many reports have been presented on the radiation aging of the organic materials for electric cables, those have been based on the experiments carried out at high dose rate near 1 x 10/sup 6/ rad/h, assuming that aging effect depends on only radiation dose. Therefore, to investigate the aging behaviour in low dose rate range is an important subject to predict their practical life time. In this report, the results of having investigated the aging behaviour of six types of materials are described, (polyethylene for general insulation purpose, chemically cross-linked polyethylene, fire-retardant chemically cross-linked polyethylene, fire-retardant ethylene-propylene rubber, fire-retardant chloro-sulfonated polyethylene for sheaths, and fire-retardant, low hydrochloric acid, special heat-resistant vinyl for insulation purpose or chloroclean). They were irradiated with /sup 60/Co ..gamma..-ray at the dose from 5 x 10/sup 3/ to 1 x 10/sup 6/ rad/h, and their deterioration was tested for the items of elongation, tensile strength, resistivity, dielectric tangent and gel fraction. The aging mechanism and dose rate effect were also considered. The dose rate effect appeared or did not appear depending on the types of materials and also their properties. The materials that showed the dose rate effect included the typical ones whose characteristics degraded with the decreasing dose rate, and the peculiar ones whose deterioration of characteristics did not appear constantly. Aging mechanism may vary in the case of high dose rate and low dose rate. Also, if the life time at respective dose rate in relatively higher dose rate region is clarified, the life time in low dose rate region may possibly be predicted.

Mapping the outdoor gamma dose rate in Indonesia

International Nuclear Information System (INIS)

Iskandar, Dadong; Syarbaini, Sutarman; Bunawas, Kusdiana

2008-01-01

Full text: Indonesia is the largest archipelago in the world, comprising five main islands - Java, Sumatra, Sulawesi, Kalimantan and Papua - as well as 30 archipelagoes totaling 17,508 islands with about 6000 of those inhabited. Mapping the outdoor gamma dose rate in Indonesia is a research project conducted by National Nuclear Energy Agency since 2005 aiming to produce a baseline data map as an overview for planning purposes. In these three years 4 main islands has been measured. The grid system has been used in the research. In Sumatra Island the grid is 50 x 50 km 2 , while in Java 40 x 40 km 2 , in Kalimantan 60 x 60 km 2 , and in Sulawesi 40 x 40 km 2 . The gamma dose rates have been measured by Mini Gamma Ray Spectrometer Model GR-130 made by Exploranium-Canada. Figure 1 shows the map of outdoor gamma dose rate in Indonesia. Range of dose rate are in Sumatra from 22,96 ± 0,46 n Sv/h to 186,08 ± 3,72 n Sv/h, in Java 11,32 ± 0,72 n Sv/h to 127,54 ± 6,14 n Sv/h, in Kalimantan 10.72 ± 8.32 n Sv/h to 349,48 ± 57,21 n Sv/h, and in Sulawesi 17.7 ± 11,5 n Sv/h to 467 ± 102 n Sv/h. The arithmetic and geometric mean of dose rate in Indonesia are 68 n Sv/h and 53 n Sv/h, respectively. In general, outdoor gamma dose rate in Indonesia is in a normal range. There are some regions have anomaly of gamma dose rate, for examples at North Sumatra 186.08 ± 3,72 n Sv/h (N 2.12727, E 99.80909), at West Kalimantan 349,48 ± 57,21 n Sv/h (S 1.39507, E 110.57584), at West Sulawesi 487 ± 103 n Sv/h (S 2.95781, E 118.86995), etc. These data is very useful as a radiation baseline in Indonesia. (author)

Standardization of high-dose measurement of electron and gamma ray absorbed doses and dose rates

International Nuclear Information System (INIS)

McLaughlin, W.L.

1985-01-01

Intense electron beams and gamma radiation fields are used for sterilizing medical devices, treating municipal wastes, processing industrial goods, controlling parasites and pathogens, and extending the shelf-life of foods. Quality control of such radiation processes depends largely on maintaining measurement quality assurance through sound dosimetry procedures in the research leading to each process, in the commissioning of that process, and in the routine dose monitoring practices. This affords documentation as to whether satisfactory dose uniformity is maintained throughout the product and throughout the process. Therefore, dosimetry at high doses and dose rates must in many radiation processes be standardized carefully, so that 'dosimetry release' of a product is verified. This standardization is initiated through preliminary dosimetry intercomparison studies such as those sponsored recently by the IAEA. This is followed by establishing periodic exercises in traceability to national or international standards of absorbed dose and dose rate. Traceability is achieved by careful selection of dosimetry methods and proven reference dosimeters capable of giving sufficiently accurate and precise 'transfer' dose assessments: (1) they must be calibrated or have well-established radiation-yield indices; (2) their radiation response characteristics must be reproducible and cover the dose range of interest; (3) they must withstand the rigours of back-and-forth mailing between a central standardizing laboratory and radiation processing facilities, without excessive errors arising due to instabilities, dosimeter batch non-uniformities, and environmental and handling stresses. (author)

Measurement of californium-252 gamma photons depth dose distribution in tissue equivalent material. Vol. 4

Energy Technology Data Exchange (ETDEWEB)

Fadel, M A; El-Fiki, M A; Eissa, H M; Abdel-Hafez, A; Naguib, S H [National Institute of Standards, Cairo (Egypt)

1996-03-01

Phantom of tissue equivalent material with and without bone was used measuring depth dose distribution of gamma-rays from californium-252 source. The source was positioned at center of perspex walled phantom. Depth dose measurements were recorded for X, Y and Z planes at different distances from source. TLD 700 was used for measuring the dose distribution. Results indicate that implantation of bone in tissue equivalent medium cause changes in the gamma depth dose distribution which varies according to variation in bone geometry. 9 figs.

Estimate of the absorbed dose in the mouse organs and tissues after tritium administration

International Nuclear Information System (INIS)

Saito, Masahiro

2000-01-01

Chronic and accidental release of tritium from future fusion facilities may cause some extent of hazardous effect to the public health. Various experiments using small animals such as mice have been performed to mimic the dose accumulation due to tritium intake by the human body. An difficulty in such animal experiments using small animals is that it is rather difficult to administer tritium orally and estimate the dose to small organs or tissues. In the course of our study, a simple method to administer THO and T-labeled amino acids orally to the mouse was dictated and dose accumulation in various organs and tissues was determined. The tritium retention in the bone marrow was also determined using the micro-centrifuge method. Throughout our experiment, colony-bred DDY mice were used. The 8-10 week old male mice were orally and intraperitoneally administered THO water or T-amino acids mixture solution. For the purpose of oral administration, a 10 μl aliquot of T-containing saline solution was placed on the tongue of the mice using an automatic micropipette. At various times after tritium administration, the animals were sacrificed and the amount of tritium in various tissues and organs including bone marrow was examined. Dose accumulation pattern after THO intake and T-amino acids was compared between intraperitoneal injection and oral administration. The accumulated dose after oral administration of THO exhibited a tendency to be 10-20% higher than after intraperitoneal injection. The bone marrow dose after oral intake of THO was found to be lower than the doses to urine, blood, liver and testis. In contrast, the blood dose gave a conservative estimate for the dose to the other tissues and organs. (author)

Electron dose rate and photon contamination in electron arc therapy

International Nuclear Information System (INIS)

Pla, M.; Podgorsak, E.B.; Pla, C.

1989-01-01

The electron dose rate at the depth of dose maximum dmax and the photon contamination are discussed as a function of several parameters of the rotational electron beam. A pseudoarc technique with an angular increment of 10 degrees and a constant number of monitor units per each stationary electron field was used in our experiments. The electron dose rate is defined as the electron dose at a given point in phantom divided by the number of monitor units given for any one stationary electron beam. For a given depth of isocenter di the electron dose rates at dmax are linearly dependent on the nominal field width w, while for a given w the dose rates are inversely proportional to di. The dose rates for rotational electron beams with different di are related through the inverse square law provided that the two beams have (di,w) combinations which give the same characteristic angle beta. The photon dose at the isocenter depends on the arc angle alpha, field width w, and isocenter depth di. For constant w and di the photon dose at isocenter is proportional to alpha, for constant alpha and w it is proportional to di, and for constant alpha and di it is inversely proportional to w. The w and di dependence implies that for the same alpha the photon dose at the isocenter is inversely proportional to the electron dose rate at dmax

Survey of environmental radiation dose rates in Tokushima prefecture

International Nuclear Information System (INIS)

Sakama, Minoru; Imura, Hiroyoshi; Akou, Natsuki; Takeuchi, Emi; Morihiro, Yukinori

2004-01-01

Survey of environmental radiation dose rates in Tokushima prefecture has been carried out using a portable NaI (Tl) scintillation survey meter and a CsI(Tl) pocket type one. To our knowledge, previous several surveys in Tokushima, for example by Abe et al. (1982) and Yoshino et al. (1991), have remained to report the environmental radiation dose rates merely about the major cities, that is Tokushima City and others along the Pacific. Up to now, there have been few efforts to survey the environmental radiation dose rates about mountain valleys in Tokushima. In this work, it is remarkable that we have for the first time made surveys of environmental radiation dose rates on the 6 routes across the Sanuki mountains and inside the pier of Onaruto Bridge, 'Naruto Uzu-no-michi', in the northern area of Tokushima. In the course of present surveys, the maximum value of the environmental radiation dose rates was 0.117±0.020 μGy/h at Higetouge in Sanuki City, and then it was found that the radiation dose rates across the Sanuki mountains tend to increase slightly with approaching Kagawa area from Tokushima one. Considering geological formation around the northern side of Sanuki mountains, there are mainly geological layers of granodiorite containing in the substantial amount of naturally occurring radionuclides, 40 K, U-series, and Th-series, than other geological rocks and it was found that the terrestrial gamma-rays have effect on the environmental radiation dose rates according to the geological formation. (author)

Braquiterapia de alta taxa de dose no Brasil High-dose rate brachytherapy in Brazil

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Sérgio Carlos Barros Esteves

2004-10-01

Full Text Available A braquiterapia de alta taxa de dose foi introduzida em nosso meio em janeiro de 1991. Desde então, houve uma mudança significativa na abordagem das neoplasias malignas em relação às vantagens do novo método, e também resolução da demanda reprimida de braquiterapia para as neoplasias ginecológicas. Nos primeiros dez anos de atividade, o Brasil tratou, em 31 serviços, 26.436 pacientes com braquiterapia, sendo mais de 50% das pacientes portadoras de neoplasias do colo uterino. Este estudo mostra o número e o perfil de pacientes tratados com esse método e a sua distribuição no território nacional, deixando explícito o benefício da braquiterapia de alta taxa de dose para o Brasil.High-dose rate brachytherapy was first introduced in Brazil in January 1991. Significant changes in the management of malignant neoplasms were observed since utilization of high-dose rate brachytherapy. The high number of gynecological patients awaiting for brachytherapy also decreased during this period. In the first ten years 26,436 patients were treated with high-dose rate brachytherapy. More than 50% of these patients presented neoplasms of the uterine cervix. In this study we present the number and profile of the patients treated with high-dose rate brachytherapy as well as the distribution of these patients in the Brazilian territory, proving the benefit of the use of high-dose rate brachytherapy in Brazil.

Dose-rate dependent stochastic effects in radiation cell-survival models

International Nuclear Information System (INIS)

Sachs, R.K.; Hlatky, L.R.

1990-01-01

When cells are subjected to ionizing radiation the specific energy rate (microscopic analog of dose-rate) varies from cell to cell. Within one cell, this rate fluctuates during the course of time; a crossing of a sensitive cellular site by a high energy charged particle produces many ionizations almost simultaneously, but during the interval between events no ionizations occur. In any cell-survival model one can incorporate the effect of such fluctuations without changing the basic biological assumptions. Using stochastic differential equations and Monte Carlo methods to take into account stochastic effects we calculated the dose-survival rfelationships in a number of current cell survival models. Some of the models assume quadratic misrepair; others assume saturable repair enzyme systems. It was found that a significant effect of random fluctuations is to decrease the theoretically predicted amount of dose-rate sparing. In the limit of low dose-rates neglecting the stochastic nature of specific energy rates often leads to qualitatively misleading results by overestimating the surviving fraction drastically. In the opposite limit of acute irradiation, analyzing the fluctuations in rates merely amounts to analyzing fluctuations in total specific energy via the usual microdosimetric specific energy distribution function, and neglecting fluctuations usually underestimates the surviving fraction. The Monte Carlo methods interpolate systematically between the low dose-rate and high dose-rate limits. As in other approaches, the slope of the survival curve at low dose-rates is virtually independent of dose and equals the initial slope of the survival curve for acute radiation. (orig.)

Calculation of normal tissue complication probability and dose-volume histogram reduction schemes for tissues with a critical element architecture

International Nuclear Information System (INIS)

Niemierko, Andrzej; Goitein, Michael

1991-01-01

The authors investigate a model of normal tissue complication probability for tissues that may be represented by a critical element architecture. They derive formulas for complication probability that apply to both a partial volume irradiation and to an arbitrary inhomogeneous dose distribution. The dose-volume isoeffect relationship which is a consequence of a critical element architecture is discussed and compared to the empirical power law relationship. A dose-volume histogram reduction scheme for a 'pure' critical element model is derived. In addition, a point-based algorithm which does not require precomputation of a dose-volume histogram is derived. The existing published dose-volume histogram reduction algorithms are analyzed. The authors show that the existing algorithms, developed empirically without an explicit biophysical model, have a close relationship to the critical element model at low levels of complication probability. However, it is also showed that they have aspects which are not compatible with a critical element model and the authors propose a modification to one of them to circumvent its restriction to low complication probabilities. (author). 26 refs.; 7 figs

Terrestrial Gamma Radiation Dose Rate of West Sarawak

Science.gov (United States)

Izham, A.; Ramli, A. T.; Saridan Wan Hassan, W. M.; Idris, H. N.; Basri, N. A.

2017-10-01

A study of terrestrial gamma radiation (TGR) dose rate was conducted in west of Sarawak, covering Kuching, Samarahan, Serian, Sri Aman, and Betong divisions to construct a baseline TGR dose rate level data of the areas. The total area covered was 20,259.2 km2, where in-situ measurements of TGR dose rate were taken using NaI(Tl) scintillation detector Ludlum 19 micro R meter NaI(Tl) approximately 1 meter above ground level. Twenty-nine soil samples were taken across the 5 divisions covering 26 pairings of 9 geological formations and 7 soil types. A hyperpure Germanium detector was then used to find the samples' 238U, 232Th, and 40K radionuclides concentrations producing a correction factor Cf = 0.544. A total of239 measured data were corrected with Cf resulting in a mean Dm of 47 ± 1 nGy h-1, with a range between 5 nGy h-1 - 103 nGy h-1. A multiple regression analysis was conducted between geological means and soil types means against the corrected TGR dose rate Dm, generating Dg,s= 0.847Dg+ 0.637Ds- 22.313 prediction model with a normalized Beta equation of Dg,s= 0.605Dg+ 0.395Ds. The model has an 84.6% acceptance of Whitney- Mann test null hypothesis when tested against the corrected TGR dose rates.

Comparison of 60Cobalt and 192Iridium sources in high dose rate afterloading brachytherapy

International Nuclear Information System (INIS)

Richter, J.; Baier, K.; Flentje, M.

2008-01-01

Purpose: 60 Co sources with dimensions identical to those of 192 Ir have recently been made available in clinical brachytherapy. A longer half time reduces demands on logistics and quality assurance and perhaps costs. Material and Methods: Comparison of the physical properties of 60 Co and 192 Ir with regard to brachytherapy. Results: Required activities for the same air kerma rate are lower by a factor of 2.8 for 60 Co. Differential absorption in tissues of different densities can be neglected. Monte Carlo calculations demonstrate that integral dose due to radial dose fall off is higher for 192 Ir in comparison to 60 Co within the first 22 cm from the source (normalization at 1 cm). At larger distances this relationship is reversed. Conclusion: Clinical examples for intracavitary and interstitial applications however, show practically identical dose distributions in the treatment volume. (orig.)

Genotoxic effects of high dose rate X-ray and low dose rate gamma radiation in ApcMin/+ mice.

Science.gov (United States)

Graupner, Anne; Eide, Dag M; Brede, Dag A; Ellender, Michele; Lindbo Hansen, Elisabeth; Oughton, Deborah H; Bouffler, Simon D; Brunborg, Gunnar; Olsen, Ann Karin

2017-10-01

Risk estimates for radiation-induced cancer in humans are based on epidemiological data largely drawn from the Japanese atomic bomb survivor studies, which received an acute high dose rate (HDR) ionising radiation. Limited knowledge exists about the effects of chronic low dose rate (LDR) exposure, particularly with respect to the application of the dose and dose rate effectiveness factor. As part of a study to investigate the development of colon cancer following chronic LDR vs. acute HDR radiation, this study presents the results of genotoxic effects in blood of exposed mice. CBAB6 F1 Apc +/+ (wild type) and Apc Min/+ mice were chronically exposed to estimated whole body absorbed doses of 1.7 or 3.2 Gy 60 Co-γ-rays at a LDR (2.2 mGy h -1 ) or acutely exposed to 2.6 Gy HDR X-rays (1.3 Gy min -1 ). Genotoxic endpoints assessed in blood included chromosomal damage (flow cytometry based micronuclei (MN) assay), mutation analyses (Pig-a gene mutation assay), and levels of DNA lesions (Comet assay, single-strand breaks (ssb), alkali labile sites (als), oxidized DNA bases). Ionising radiation (ca. 3 Gy) induced genotoxic effects dependent on the dose rate. Chromosomal aberrations (MN assay) increased 3- and 10-fold after chronic LDR and acute HDR, respectively. Phenotypic mutation frequencies as well as DNA lesions (ssb/als) were modulated after acute HDR but not after chronic LDR. The Apc Min/+ genotype did not influence the outcome in any of the investigated endpoints. The results herein will add to the scant data available on genotoxic effects following chronic LDR of ionising radiation. Environ. Mol. Mutagen. 58:560-569, 2017. © 2017 The Authors Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society. © 2017 The Authors Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.

Comparison of traditional low-dose-rate to optimized and nonoptimized high-dose-rate tandem and ovoid dosimetry

International Nuclear Information System (INIS)

Decker, William E.; Erickson, Beth; Albano, Katherine; Gillin, Michael

2001-01-01

Purpose: Few dose specification guidelines exist when attempting to perform high-dose-rate (HDR) dosimetry. The purpose of this study was to model low-dose-rate (LDR) dosimetry, using parameters common in HDR dosimetry, to achieve the 'pear-shape' dose distribution achieved with LDR tandem and ovoid applications. Methods and Materials: Radiographs of Fletcher-Suit LDR applicators and Nucletron 'Fletcher-like' HDR applicators were taken with the applicators in an idealized geometry. Traditional Fletcher loadings of 3M Cs-137 sources and the Theratronics Planning System were used for LDR dosimetry. HDR dosimetry was performed using the Nucletron Microselectron HDR UPS V11.22 with an Ir-192 source. Dose optimization points were initially located along a line 2 cm lateral to the tandem, beginning at the tandem tip at 0.5-cm intervals, ending at the sail, and optimized to 100% of the point A dose. A single dose optimization point was also placed laterally from the center of each ovoid equal to the radius of the ovoid (ovoid surface dose). For purposes of comparison, dose was also calculated for points A and B, and a point located 1 cm superior to the tandem tip in the plane of the tandem, (point F). Four- and 6-cm tandem lengths and 2.0-, 2.5-, and 3.0-cm ovoid diameters were used for this study. Based on initial findings, dose optimization schemes were developed to best approximate LDR dosimetry. Finally, radiographs were obtained of HDR applications in two patients. These radiographs were used to compare the optimization schemes with 'nonoptimized' treatment plans. Results: Calculated doses for points A and B were similar for LDR, optimized HDR, and nonoptimized HDR. The optimization scheme that used tapered dose points at the tandem tip and optimized a single ovoid surface point on each ovoid to 170% of point A resulted in a good approximation of LDR dosimetry. Nonoptimized HDR resulted in higher doses at point F, the bladder, and at points lateral to the tandem tip

Radiobiological equivalent of low/high dose rate brachytherapy and evaluation of tumor and normal responses to the dose.

Science.gov (United States)

Manimaran, S

2007-06-01

The aim of this study was to compare the biological equivalent of low-dose-rate (LDR) and high-dose-rate (HDR) brachytherapy in terms of the more recent linear quadratic (LQ) model, which leads to theoretical estimation of biological equivalence. One of the key features of the LQ model is that it allows a more systematic radiobiological comparison between different types of treatment because the main parameters alpha/beta and micro are tissue-specific. Such comparisons also allow assessment of the likely change in the therapeutic ratio when switching between LDR and HDR treatments. The main application of LQ methodology, which focuses on by increasing the availability of remote afterloading units, has been to design fractionated HDR treatments that can replace existing LDR techniques. In this study, with LDR treatments (39 Gy in 48 h) equivalent to 11 fractions of HDR irradiation at the experimental level, there are increasing reports of reproducible animal models that may be used to investigate the biological basis of brachytherapy and to help confirm theoretical predictions. This is a timely development owing to the nonavailability of sufficient retrospective patient data analysis. It appears that HDR brachytherapy is likely to be a viable alternative to LDR only if it is delivered without a prohibitively large number of fractions (e.g., fewer than 11). With increased scientific understanding and technological capability, the prospect of a dose equivalent to HDR brachytherapy will allow greater utilization of the concepts discussed in this article.

Contributions to indoor gamma dose rate from building materials

International Nuclear Information System (INIS)

Liu Xionghua; Li Guangming; Yang Xiangdong

1990-01-01

In the coures of construction of a building structured with bricks and concrets, the indoor gamma air absorbed dose rates were seperately measured from the floors, brick walls and prefabricated plates of concrets, etc.. It suggested that the indoor gamma dose rates from building materials are mainly attributed to the brick walls and the floors. A little contribution comes from other brilding materials. The dose rates can be calculated through a 4π-infinite thick model with a correction factor of 0.52

Method for retrospective estimation of absorbed dose in subsurface tissues when conducting works connected with the Chernobyl' NPP accident effect elimination (using experimental and calculated data)

International Nuclear Information System (INIS)

Panova, V.I.; Shaks, A.I.

1992-01-01

The method for retrospective estimation of doses in subsurface tissues at early time periods from the accident begin in the case, when gamma radiation dose rate values (radiation field cartogram) and a person irradiation conditions on contaminated territory (professional route) are known, is discussed

Dose rate effects during damage accumulation in silicon

Energy Technology Data Exchange (ETDEWEB)

Caturla, M.J.; Diaz de la Rubia, T.

1997-01-01

We combine molecular dynamics and Monte Carlo simulations to study damage accumulation and dose rate effects during irradiation of Silicon. We obtain the initial stage of the damage produced by heavy and light ions using classical molecular dynamics simulations. While heavy ions like As or Pt induce amorphization by single ion impact, light ions like B only produce point defects or small clusters of defects. The amorphous pockets generated by heavy ions are stable below room temperature and recrystallize at temperatures below the threshold for recrystallization of a planar amorphous-crystalline interface. The damage accumulation during light ion irradiation is simulated using a Monte Carlo model for defect diffusion. In this approach, we study the damage in the lattice as a function of dose and dose rate. A strong reduction in the total number of defects left in the lattice is observed for lower dose rates.

Dose rate effects during damage accumulation in silicon

International Nuclear Information System (INIS)

Caturla, M.J.; Diaz de la Rubia, T.

1997-01-01

The authors combine molecular dynamics and Monte Carlo simulations to study damage accumulation and dose rate effects during irradiation of silicon. They obtain the initial stage of the damage produced by heavy and light ions using classical molecular dynamics simulations. While heavy ions like As or Pt induce amorphization by single ion impact, light ions like B only produce point defects or small clusters of defects. The amorphous pockets generated by heavy ions are stable below room temperature and recrystallize at temperatures below the threshold for recrystallization of a planar amorphous-crystalline interface. The damage accumulation during light ion irradiation is simulated using a Monte Carlo model for defect diffusion. In this approach, the authors study the damage in the lattice as a function of dose and dose rate. A strong reduction in the total number of defects left in the lattice is observed for lower dose rates

External dose-rate conversion factors of radionuclides for air submersion, ground surface contamination and water immersion based on the new ICRP dosimetric setting.

Science.gov (United States)

Yoo, Song Jae; Jang, Han-Ki; Lee, Jai-Ki; Noh, Siwan; Cho, Gyuseong

2013-01-01

For the assessment of external doses due to contaminated environment, the dose-rate conversion factors (DCFs) prescribed in Federal Guidance Report 12 (FGR 12) and FGR 13 have been widely used. Recently, there were significant changes in dosimetric models and parameters, which include the use of the Reference Male and Female Phantoms and the revised tissue weighting factors, as well as the updated decay data of radionuclides. In this study, the DCFs for effective and equivalent doses were calculated for three exposure settings: skyshine, groundshine and water immersion. Doses to the Reference Phantoms were calculated by Monte Carlo simulations with the MCNPX 2.7.0 radiation transport code for 26 mono-energy photons between 0.01 and 10 MeV. The transport calculations were performed for the source volume within the cut-off distances practically contributing to the dose rates, which were determined by a simplified calculation model. For small tissues for which the reduction of variances are difficult, the equivalent dose ratios to a larger tissue (with lower statistical errors) nearby were employed to make the calculation efficient. Empirical response functions relating photon energies, and the organ equivalent doses or the effective doses were then derived by the use of cubic-spline fitting of the resulting doses for 26 energy points. The DCFs for all radionuclides considered important were evaluated by combining the photon emission data of the radionuclide and the empirical response functions. Finally, contributions of accompanied beta particles to the skin equivalent doses and the effective doses were calculated separately and added to the DCFs. For radionuclides considered in this study, the new DCFs for the three exposure settings were within ±10 % when compared with DCFs in FGR 13.

Dose rate determining factors of PWR primary water

International Nuclear Information System (INIS)

Terachi, Takumi; Kuge, Toshiharu; Nakano, Nobuo

2014-01-01

The relationship between dose rate trends and water chemistry has been studied to clarify the determining factors on the dose rates. Therefore dose rate trends and water chemistry of 11 PWR plants of KEPCO (Kansai Electric Power Co., Inc.) were summarized. It is indicated that the chemical composition of the oxide film, behaviour of corrosion products and Co-58/Co-60 ratio in the primary system have effected dose rate trends based on plant operation experiences for over 40 years. According to plant operation experiences, the amount of Co-58 has been decreasing with the increasing duration of SG (Steam Generator) usage. It is indicated that the stable oxide film formation on the inner surface of SG tubing, is a major beneficial factor for radiation sources reduction. On the other hand, the reduction of the amount of Co-60 for the long term has been not clearly observed especially in particular high dose plants. The primary water parameters imply that considering release and purification balance on Co-59 is important to prevent accumulation of source term in primary water. In addition, the effect of zinc injection, which relates to the chemical composition of oxide film, was also assessed. As the results, the amount of radioactive Co has been clearly decreased. The decreasing trend seems to correlate to the half-life of Co-60, because it is considered that the injected zinc prevents the uptake of radioactive Co into the oxide film on the inner surface of the components and piping. In this paper, the influence of water chemistry and the replacement experiences of materials on the dose rates were discussed. (author)

Dose rate calculations for a reconnaissance vehicle

International Nuclear Information System (INIS)

Grindrod, L.; Mackey, J.; Salmon, M.; Smith, C.; Wall, S.

2005-01-01

A Chemical Nuclear Reconnaissance System (CNRS) has been developed by the British Ministry of Defence to make chemical and radiation measurements on contaminated terrain using appropriate sensors and recording equipment installed in a land rover. A research programme is under way to develop and validate a predictive capability to calculate the build-up of contamination on the vehicle, radiation detector performance and dose rates to the occupants of the vehicle. This paper describes the geometric model of the vehicle and the methodology used for calculations of detector response. Calculated dose rates obtained using the MCBEND Monte Carlo radiation transport computer code in adjoint mode are presented. These address the transient response of the detectors as the vehicle passes through a contaminated area. Calculated dose rates were found to agree with the measured data to be within the experimental uncertainties, thus giving confidence in the shielding model of the vehicle and its application to other scenarios. (authors)

Postoperative vaginal irradiation by a high dose-rate afterloading technique in endometrial carcinoma stage I

International Nuclear Information System (INIS)

Sorbe, B.; Smeds, A.C.

1989-01-01

A high dose-rate (cobalt-60) afterloading technique was used for postoperative vaginal irradiation in a series of 404 women with endometrial carcinoma stage I. The total recurrence rate was 3.7% with 0.7% vaginal lesions. The crude 5-year survival rate for the complete series was 91.8% compared to 13.3% for those with recurrences. Depth of myometrical infiltration (>1/3 of the uterine wall) and nuclear grade were the most important prognostic factors. Clinically significant late radiation reactions (bladder and/or rectum) were recorded in 6.9%. The absorbed dose per fraction and the size of the treatment volume were significantly related to the occurrence of both early and late radiation reactions. Vaginal shortening was closely related to the dose per fraction, length of the referce isodose and the applicator diameter. The shape of the vaginal applicator versus the isodose contours and the importance of the source train geometry and relative activity for absorbed dose inhomogeneitis within the treatment volume are discussed. Cumulative radiation effect (CRE) and linear-quadratic (LQ) calculations have been performed and related to tissue reactions within the target volume and in the risk organs. An alpha-beta quotient of 8.8 Gy for vaginal shrinkage effect and 2.0 Gy for late rectal complications are suggested on the basis of calculations using a maximum likelihood method for quantal radiation data. (orig.)

Nuclear Enterprises portable dose rate meter type PDR 2

International Nuclear Information System (INIS)

Burgess, P.H.; Iles, W.J.

1978-06-01

This instrument is a portable battery powered dose rate meter covering the dose rate range from 0.05 to 500 mrad h -1 . It is designed to measure X- and γ-radiation dose rates over the energy range from 35 keV to 3 MeV. The radiation detector is an MX 164/S GM tube provided with a compensation sheath. The report describes the instrument under the headings: facilities and controls; radiation characteristics; electrical characteristics; environmental characteristics; mechanical characteristics; the manual; summary of performance. (U.K.)

Rectal dose assessment in patients submitted to high-dose-rate brachytherapy for uterine cervix cancer

International Nuclear Information System (INIS)

Oliveira, Jetro Pereira de; Batista, Delano Valdivino Santos; Bardella, Lucia Helena; Carvalho, Arnaldo Rangel

2009-01-01

Objective: The present study was aimed at developing a thermoluminescent dosimetric system capable of assessing the doses delivered to the rectum of patients submitted to high-dose-rate brachytherapy for uterine cervix cancer. Materials and methods: LiF:Mg,Ti,Na powder was the thermoluminescent material utilized for evaluating the rectal dose. The powder was divided into small portions (34 mg) which were accommodated in a capillary tube. This tube was placed into a rectal probe that was introduced into the patient's rectum. Results: The doses delivered to the rectum of six patients submitted to high-dose-rate brachytherapy for uterine cervix cancer evaluated by means of thermoluminescent dosimeters presented a good agreement with the planned values based on two orthogonal (anteroposterior and lateral) radiographic images of the patients. Conclusion: The thermoluminescent dosimetric system developed in the present study is simple and easy to be utilized as compared to other rectal dosimetry methods. The system has shown to be effective in the evaluation of rectal doses in patients submitted to high-dose-rate brachytherapy for uterine cervix cancer. (author)

Determination of dose equivalent with tissue-equivalent proportional counters

International Nuclear Information System (INIS)

Dietze, G.; Schuhmacher, H.; Menzel, H.G.

1989-01-01

Low pressure tissue-equivalent proportional counters (TEPC) are instruments based on the cavity chamber principle and provide spectral information on the energy loss of single charged particles crossing the cavity. Hence such detectors measure absorbed dose or kerma and are able to provide estimates on radiation quality. During recent years TEPC based instruments have been developed for radiation protection applications in photon and neutron fields. This was mainly based on the expectation that the energy dependence of their dose equivalent response is smaller than that of other instruments in use. Recently, such instruments have been investigated by intercomparison measurements in various neutron and photon fields. Although their principles of measurements are more closely related to the definition of dose equivalent quantities than those of other existing dosemeters, there are distinct differences and limitations with respect to the irradiation geometry and the determination of the quality factor. The application of such instruments for measuring ambient dose equivalent is discussed. (author)

Mammalian Tissue Response to Low Dose Ionizing Radiation: The Role of Oxidative Metabolism and Intercellular Communication

Energy Technology Data Exchange (ETDEWEB)

Azzam, Edouard I

2013-01-16

The objective of the project was to elucidate the mechanisms underlying the biological effects of low dose/low dose rate ionizing radiation in organs/tissues of irradiated mice that differ in their susceptibility to ionizing radiation, and in human cells grown under conditions that mimic the natural in vivo environment. The focus was on the effects of sparsely ionizing cesium-137 gamma rays and the role of oxidative metabolism and intercellular communication in these effects. Four Specific Aims were proposed. The integrated outcome of the experiments performed to investigate these aims has been significant towards developing a scientific basis to more accurately estimate human health risks from exposures to low doses ionizing radiation. By understanding the biochemical and molecular changes induced by low dose radiation, several novel markers associated with mitochondrial functions were identified, which has opened new avenues to investigate metabolic processes that may be affected by such exposure. In particular, a sensitive biomarker that is differentially modulated by low and high dose gamma rays was discovered.

Gustatory tissue injury in man: radiation dose response relationships and mechanisms of taste loss

International Nuclear Information System (INIS)

Mossman, K.L.

1986-01-01

In this report dose response data for gustatory tissue damage in patients given total radiation doses ranging from 3000 to 6000 cGy are presented. In order to evaluate direct radiation injury to gustatory tissues as a mechanism of taste loss, measurements of damage to specific taste structures in bovine and murine systems following radiation exposure in the clinical range are correlated to taste impairment observed in radiotherapy patients. (author)

Low-dose-rate total lymphoid irradiation: a new method of rapid immunosuppression

International Nuclear Information System (INIS)

Blum, J.E.; de Silva, S.M.; Rachman, D.B.; Order, S.E.

1988-01-01

Total Lymphoid Irradiation (TLI) has been successful in inducing immunosuppression in experimental and clinical applications. However, both the experimental and clinical utility of TLI are hampered by the prolonged treatment courses required (23 days in rats and 30-60 days in humans). Low-dose-rate TLI has the potential of reducing overall treatment time while achieving comparable immunosuppression. This study examines the immunosuppressive activity and treatment toxicity of conventional-dose-rate (23 days) vs low-dose-rate (2-7 days) TLI. Seven groups of Lewis rats were given TLI with 60Co. One group was treated at conventional-dose-rates (80-110 cGy/min) and received 3400 cGy in 17 fractions over 23 days. Six groups were treated at low-dose-rate (7 cGy/min) and received total doses of 800, 1200, 1800, 2400, 3000, and 3400 cGy over 2-7 days. Rats treated at conventional-dose-rates over 23 days and at low-dose-rate over 2-7 days tolerated radiation with minimal toxicity. The level of immunosuppression was tested using allogeneic (Brown-Norway) skin graft survival. Control animals retained allogeneic skin grafts for a mean of 14 days (range 8-21 days). Conventional-dose-rate treated animals (3400 cGy in 23 days) kept their grafts 60 days (range 50-66 days) (p less than .001). Low-dose-rate treated rats (800 to 3400 cGy total dose over 2-7 days) also had prolongation of allogeneic graft survival times following TLI with a dose-response curve established. The graft survival time for the 3400 cGy low-dose-rate group (66 days, range 52-78 days) was not significantly different from the 3400 cGy conventional-dose-rate group (p less than 0.10). When the total dose given was equivalent, low-dose-rate TLI demonstrated an advantage of reduced overall treatment time compared to conventional-dose-rate TLI (7 days vs. 23 days) with no increase in toxicity

Impact of Drug Therapy, Radiation Dose, and Dose Rate on Renal Toxicity Following Bone Marrow Transplantation

International Nuclear Information System (INIS)

Cheng, Jonathan C.; Schultheiss, Timothy E.; Wong, Jeffrey Y.C.

2008-01-01

Purpose: To demonstrate a radiation dose response and to determine the dosimetric and chemotherapeutic factors that influence the incidence of late renal toxicity following total body irradiation (TBI). Methods and Materials: A comprehensive retrospective review was performed of articles reporting late renal toxicity, along with renal dose, fractionation, dose rate, chemotherapy regimens, and potential nephrotoxic agents. In the final analysis, 12 articles (n = 1,108 patients), consisting of 24 distinct TBI/chemotherapy conditioning regimens were included. Regimens were divided into three subgroups: adults (age ≥18 years), children (age <18 years), and mixed population (both adults and children). Multivariate logistic regression was performed to identify dosimetric and chemotherapeutic factors significantly associated with late renal complications. Results: Individual analysis was performed on each population subgroup. For the purely adult population, the only significant variable was total dose. For the mixed population, the significant variables included total dose, dose rate, and the use of fludarabine. For the pediatric population, only the use of cyclosporin or teniposide was significant; no dose response was noted. A logistic model was generated with the exclusion of the pediatric population because of its lack of dose response. This model yielded the following significant variables: total dose, dose rate, and number of fractions. Conclusion: A dose response for renal damage after TBI was identified. Fractionation and low dose rates are factors to consider when delivering TBI to patients undergoing bone marrow transplantation. Drug therapy also has a major impact on kidney function and can modify the dose-response function

Comparison of high-dose-rate and low-dose-rate brachytherapy in the treatment of endometrial carcinoma

International Nuclear Information System (INIS)

Fayed, Alaa; Mutch, David G.; Rader, Janet S.; Gibb, Randall K.; Powell, Matthew A.; Wright, Jason D.; El Naqa, Issam; Zoberi, Imran; Grigsby, Perry W.

2007-01-01

Purpose: To compare the outcomes for endometrial carcinoma patients treated with either high-dose-rate (HDR) or low-dose-rate (LDR) brachytherapy. Methods and Materials: This study included 1,179 patients divided into LDR (1,004) and HDR groups (175). Patients with International Federation of Gynecology and Obstetrics (FIGO) surgical Stages I-III were included. All patients were treated with postoperative irradiation. In the LDR group, the postoperative dose applied to the vaginal cuff was 60-70 Gy surface doses to the vaginal mucosa. The HDR brachytherapy prescription was 6 fractions of 2 Gy each to a depth of 0.5 cm from the surface of the vaginal mucosa. Overall survival, disease-free survival, local control, and complications were endpoints. Results: For all stages combined, the overall survival, disease-free survival, and local control at 5 years in the LDR group were 70%, 69%, and 81%, respectively. For all stages combined, the overall survival, disease-free survival, and local control at 5 years in the HDR group were 68%, 62%, and 78%, respectively. There were no significant differences in early or late Grade III and IV complications in the HDR or LDR groups. Conclusion: Survival outcomes, pelvic tumor control, and Grade III and IV complications were not significantly different in the LDR brachytherapy group compared with the HDR group

Precedents For Authorization Of Contents Using Dose Rate Measurements

International Nuclear Information System (INIS)

Abramczyk, G.; Bellamy, S.; Nathan, S.; Loftin, B.

2012-01-01

For the transportation of Radioactive Material (RAM) packages, the requirements for the maximum allowed dose rate at the package surface and in its vicinity are given in Title 10 of the Code of Federal Regulations, Section 71.47. The regulations are based on the acceptable dose rates to which the public, workers, and the environment may be exposed. As such, the regulations specify dose rates, rather than quantity of radioactive isotopes and require monitoring to confirm the requirements are met. 10CFR71.47 requires that each package of radioactive materials offered for transportation must be designed and prepared for shipment so that under conditions normally incident to transportation the radiation level does not exceed 2 mSv/h (200 mrem/h) at any point on the external Surface of the package, and the transport index does not exceed 10. Before shipment, the dose rate of the package is determined by measurement, ensuring that it conforms to the regulatory limits, regardless of any analyses. This is the requirement for all certified packagings. This paper discusses the requirements for establishing the dose rates when shipping RAM packages and the precedents for meeting these requirements by measurement.

Comparison of radiosensitization by 41 deg. C hyperthermia during low dose rate irradiation and during pulsed simulated low dose rate irradiation in human glioma cells

International Nuclear Information System (INIS)

Raaphorst, G. Peter; Ng, Cheng E.; Shahine, Bilal

1999-01-01

Purpose: Long duration mild hyperthermia has been shown to be an effective radiosensitizer when given concurrently with low dose rate irradiation. Pulsed simulated low dose rate (PSLDR) is now being used clinically, and we have set out to determine whether concurrent mild hyperthermia can be an effective radiosensitizer for the PSLDR protocol. Materials and Methods: Human glioma cells (U-87MG) were grown to plateau phase and treated in plateau phase in order to minimize cell cycle redistribution during protracted treatments. Low dose rate (LDR) irradiation and 41 deg. C hyperthermia were delivered by having a radium irradiator inside a temperature-controlled incubator. PSLDR was given using a 150 kVp X-ray unit and maintaining the cells at 41 deg. C between irradiations. The duration of irradiation and concurrent heating depended on total dose and extended up to 48 h. Results: When 41 deg. C hyperthermia was given currently with LDR or PSLDR, the thermal enhancement ratios (TER) were about the same if the average dose rate for PSLDR was the same as for LDR. At higher average dose rates for PSLDR the TERs became less. Conclusions: Our data show that concurrent mild hyperthermia can be an effective sensitizer for PSLDR. This sensitization can be as effective as for LDR if the same average dose rate is used and the TER increases with decreasing dose rate. Thus mild hyperthermia combined with PSLDR may be an effective clinical protocol

Minimising the risk: reducing breast tissue dose in an adolescent female

International Nuclear Information System (INIS)

Thompson, Ann; Toe, Aimee; Ungureanu, Elena; Wolf, M.; Wirth, Andrew

2005-01-01

Breast cancer is amongst the leading radiation-associated, second malignancies that develop in patients after treatment for Hodgkin's disease. This risk is affected by two main factors: 1. The age of the patient at the time of radiotherapy; and 2. The dose received by the breast tissue The adolescent female thus faces an exceptionally high risk, as breast tissue at this age is undergoing rapid developmental growth and small doses of radiation exposure could be carcinogenic. This case report of a fifteen-year-old girl who received radiotherapy for Hodgkin's disease demonstrates how radiation therapists worked together with the radiation oncologists and medical physicists to provide an optimal treatment plan for a high-risk patient. Copyright (2005) Australian Institute of Radiography

Influence of nuclear interactions in body tissues on tumor dose in carbon-ion radiotherapy

Energy Technology Data Exchange (ETDEWEB)

Inaniwa, T., E-mail: taku@nirs.go.jp; Kanematsu, N. [Medical Physics Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Anagawa 4-9-1, Inage-ku, Chiba 263-8555 (Japan); Tsuji, H.; Kamada, T. [Hospital, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)

2015-12-15

Purpose: In carbon-ion radiotherapy treatment planning, the planar integrated dose (PID) measured in water is applied to the patient dose calculation with density scaling using the stopping power ratio. Since body tissues are chemically different from water, this dose calculation can be subject to errors, particularly due to differences in inelastic nuclear interactions. In recent studies, the authors proposed and validated a PID correction method for these errors. In the present study, the authors used this correction method to assess the influence of these nuclear interactions in body tissues on tumor dose in various clinical cases. Methods: Using 10–20 cases each of prostate, head and neck (HN), bone and soft tissue (BS), lung, liver, pancreas, and uterine neoplasms, the authors first used treatment plans for carbon-ion radiotherapy without nuclear interaction correction to derive uncorrected dose distributions. The authors then compared these distributions with recalculated distributions using the nuclear interaction correction (corrected dose distributions). Results: Median (25%/75% quartiles) differences between the target mean uncorrected doses and corrected doses were 0.2% (0.1%/0.2%), 0.0% (0.0%/0.0%), −0.3% (−0.4%/−0.2%), −0.1% (−0.2%/−0.1%), −0.1% (−0.2%/0.0%), −0.4% (−0.5%/−0.1%), and −0.3% (−0.4%/0.0%) for the prostate, HN, BS, lung, liver, pancreas, and uterine cases, respectively. The largest difference of −1.6% in target mean and −2.5% at maximum were observed in a uterine case. Conclusions: For most clinical cases, dose calculation errors due to the water nonequivalence of the tissues in nuclear interactions would be marginal compared to intrinsic uncertainties in treatment planning, patient setup, beam delivery, and clinical response. In some extreme cases, however, these errors can be substantial. Accordingly, this correction method should be routinely applied to treatment planning in clinical practice.

Relationships betwen mitotic delay and the dose rate of X radiation

International Nuclear Information System (INIS)

Yi, P.N.; Rha, C.K.; Evans, H.H.; Beer, J.Z.

1994-01-01

Upon exposure of cells to radiation delivered at a continuous low dose rate, cell proliferation may be sustained with the cells exhibiting a constant doubling time that is independent of the total dose. The doubling time or mitotic delay under these conditions has been shown to depend on the dose rate in HeLa, V79 and P388F cells. Reanalysis of the data for these particular cell lines shows that there is a threshold dose rate for mitotic delay, and that above the threshold there is a linear relationship between the length of mitotic delay and the logarithm of the dose rate which is referred to as the dose-rate response. We have observed the same relationships for L5178Y (LY)-R and LY-S cells exposed to low-dose-rate radiation. The threshold dose rates for LY-R, LY-S and P388F cells are similar (0.01-0.02 Gy/h) and are much lower than for V79 and HeLa cells. The slope of the dose-rate response curve is the greatest for HeLa cells, followed in order by LY-S, V79 and P388F cells, and finally by LY-R cells. The slopes for HeLa and LY-R cells differ by a factor of 35. 20 refs., 3 figs., 1 tab

Review of techniques and detectors used in instruments for field measurement of β doses and dose rates

International Nuclear Information System (INIS)

Jones, A.R.

1984-01-01

Generally, field measurements are required to assess the hazard from β-rays before personnel are allowed to occupy a working space or perform a task. Occasionally, the measurements are required for an assessment after a β-ray exposure is suspected to have occurred. With these uses of field instruments in mind, the following detectors and associated techniques will be discussed in terms of the measurement principles, advantages, and limitations: 1) thin-walled ion chambers (sometimes in combination with thick-walled ones or with covers thick enough to prevent penetration of β-particles); 2) thin scintillators, nearly tissue equivalent, to provide a detector analogous to skin; 3) scintillators, thick enough to absorb all the energy of the β-particles. Circuitry is required to count pulses according to size to permit calculation of dose or dose rate; 4) silicon diodes with thin detection layers operated as photocurrent generators; 5) silicon diodes, reversed biassed, with pulses counted according to size; 6) simple pulse counters (e.g., GM counters or silicon diodes with thin windows)

Investigations of DNA damage induction and repair resulting from cellular exposure to high dose-rate pulsed proton beams

International Nuclear Information System (INIS)

Renis, M.; Malfa, G.; Tomasello, B.; Borghesi, M.; Schettino, G.; Favetta, M.; Romano, F.; Cirrone, G. A. P.; Manti, L.

2013-01-01

Studies regarding the radiobiological effects of low dose radiation, microbeam irradiation services have been developed in the world and today laser acceleration of protons and heavy ions may be used in radiation therapy. The application of different facilities is essential for studying bystander effects and relating signalling phenomena in different cells or tissues. In particular the use of ion beams results advantageous in cancer radiotherapy compared to more commonly used X-rays, since the ability of ions in delivering lethal amount of doses into the target tumour avoiding or limiting damage to the contiguous healthy tissues. At the INFN-LNS in Catania, a multidisciplinary radiobiology group is strategically structured aimed to develop radiobiological research, finalised to therapeutic applications, compatible with the use of high dose laser-driven ion beams. The characteristic non-continuous dose rates with several orders of magnitude of laser-driven ion beams makes this facility very interesting in the cellular systems' response to ultra-high dose rates with non-conventional pulse time intervals cellular studies. Our group have projected to examine the effect of high dose laser-driven ion beams on two cellular types: foetal fibroblasts (normal control cells) and DU145 (prostate cancer cells), studying the modulation of some different bio-molecular parameters, in particular cell proliferation and viability, DNA damage, redox cellular status, morphological alterations of both the cytoskeleton components and some cell organelles and the possible presence of apoptotic or necrotic cell death. Our group performed preliminary experiments with high energy (60 MeV), dose rate of 10 Gy/min, doses of 1, 2, 3 Gy and LET 1 keV/μm on human foetal fibroblasts (control cells). We observed that cell viability was not influenced by the characteristics of the beam, the irradiation conditions or the analysis time. Conversely, DNA damage was present at time 0, immediately

Investigations of DNA damage induction and repair resulting from cellular exposure to high dose-rate pulsed proton beams

Energy Technology Data Exchange (ETDEWEB)

Renis, M.; Malfa, G.; Tomasello, B. [Drug Sciences Department, University of Catania, Catania (Italy); Borghesi, M.; Schettino, G. [Queen' s University Belfast, Northern Ireland (United Kingdom); Favetta, M.; Romano, F.; Cirrone, G. A. P. [National Institute for Nuclear Physics (INFN-LNS), Catania (Italy); Manti, L. [Physics Science Department, University of Naples Federico II, Naples, and National Institute for Nuclear Physics (INFN), Naples (Italy)

2013-07-26

Studies regarding the radiobiological effects of low dose radiation, microbeam irradiation services have been developed in the world and today laser acceleration of protons and heavy ions may be used in radiation therapy. The application of different facilities is essential for studying bystander effects and relating signalling phenomena in different cells or tissues. In particular the use of ion beams results advantageous in cancer radiotherapy compared to more commonly used X-rays, since the ability of ions in delivering lethal amount of doses into the target tumour avoiding or limiting damage to the contiguous healthy tissues. At the INFN-LNS in Catania, a multidisciplinary radiobiology group is strategically structured aimed to develop radiobiological research, finalised to therapeutic applications, compatible with the use of high dose laser-driven ion beams. The characteristic non-continuous dose rates with several orders of magnitude of laser-driven ion beams makes this facility very interesting in the cellular systems' response to ultra-high dose rates with non-conventional pulse time intervals cellular studies. Our group have projected to examine the effect of high dose laser-driven ion beams on two cellular types: foetal fibroblasts (normal control cells) and DU145 (prostate cancer cells), studying the modulation of some different bio-molecular parameters, in particular cell proliferation and viability, DNA damage, redox cellular status, morphological alterations of both the cytoskeleton components and some cell organelles and the possible presence of apoptotic or necrotic cell death. Our group performed preliminary experiments with high energy (60 MeV), dose rate of 10 Gy/min, doses of 1, 2, 3 Gy and LET 1 keV/μm on human foetal fibroblasts (control cells). We observed that cell viability was not influenced by the characteristics of the beam, the irradiation conditions or the analysis time. Conversely, DNA damage was present at time 0, immediately

Research on the dose of the tissues located outside the treatment field when breast cancer was irradiated by linear accelerator

International Nuclear Information System (INIS)

Tu Yu; Zhou Juying; Jiang Dezhi; Qin Songbing

1999-10-01

The purpose of study was to determine the dose of the tissues which located outside the treatment field, when breast cancer was irradiated by 9 MeV electron-beam and 6 MV-X ray after operation. A search for decreasing the dose of the tissues outside the treatment field was made. Clinically relevant treatment fields were simulated on a tissue-equivalent material phantom and subsequently irradiated with 9 MeV electron-beam and 6 MV-X ray. TLD were used to measure absorbed doses. The prescribed dose of breast cancer region was 50.0 Gy, region-lymph-nodes were 60.0 Gy, each exposure dose was 2.0 Gy. In breast cancer region, if only with 9 MeV electron-beam, the dose of the tissues located outside the treatment field were from 29.0 cGy to 295.5 cGy, when shielded with Pb lump, the doses of the tissues outside the treatment field may descended 9.4%-53.6%; if only with 6 MV-X ray, the doses of aforementioned tissues were from 32.0 cGy to 206.7 cGy, when shielded with Pb lump, the doses of the tissues outside the treatment field descended 19.7%-56.6%. In region-lymph-nodes, with 6 MV-X ray, the doses of aforementioned tissues were from 22.5 cGy to 1650.9 cGy, when shielded with Pb lump, the doses of the tissues outside the treatment field descended 19.7-65.6%. If mix-irradiation (9 MeV electron-beam vs. 6 MV-X ray 2:3) was used, the doses outside field would be lower than only used 9 MeV electron-beam or 6 MV-X ray were used

Analysis of ethyl acrylate (EA) and acrylic acid (AA) residues from rat tissues following oral ea dosing

International Nuclear Information System (INIS)

Udinsky, J.R.; Frederick, C.B.

1990-01-01

Gavage dosing of rats with EA at high dose levels (100 or 200 mg/kg) has resulted in tumors at the dosing site, forestomach (FST), but no lesions of the glandular stomach (GST) or other remote tissues. Since previous in vitro studies have demonstrated that EA is very rapidly metabolized to AA and glutathione conjugates, EA and AA residues were analyzed 0-24 hr following gavage dosing of non-fasted F-344/N male rats with [1- 14 C]EA in corn oil at 10, 50, and 200 mg/kg. Analysis of total 14 C indicated that the dose solution was primarily in the FST at ≥5 min after dosing, although 14 C was detected in the GST, duodenum, and small intestine (attributed to distension of the FST and leakage from the FST to the GST). HPLC analysis of the gut contents, gut wall, liver, kidneys, lungs, and blood indicated that EA and AA could only be detected at ≥15 min in the FST and GST contents, and in the FST tissue. AA alone was detected in the GST tissue, duodenum tissue and contents, and small intestine tissue and contents. The minimum level of detection was 0.0005% of the dose. The remaining 14 C was primarily attributed to binding to the gut contents or bioincorporation of AA. The detection of EA and AA residues only in the upper gastrointestinal tract following gavage dosing is consistent with rapid detoxification of EA by hydrolysis and conjugation which prevents toxicity at sites remote form the site of dosing

Comparison of the two different standard flux-to-dose rate conversion factors

International Nuclear Information System (INIS)

Metghalchi, M.; Ashrafi, R.

1983-01-01

A very useful and simple way of obtaining the dose rate associated with neutron or photon fluxes is to multiply these fluxes by the appropriate flux-to-dose rate conversion factors. Two basic standard flux-to-dose rate conversion factors. are being used in all over the world, those recommended by the International Commission on Radiation Protection (ICRP) and the American National Standars (ANS). The purpose of this paper is to compare these two standard with each other. The comparison proved that the dose rate associated with a specific neutron flux, obtained by the ANS flux-to-dose rate conversion factors is usually higher than those calculated by the ICRP's conversion factors. Whereas in the case of the photon, in all energies, the difference between the dose rates obtained by these two standard flux-to-dose rate conversion factors are noticeable, and the ANS results are higher than the ICRP ones. So, it should be noted that for a specific neutron or photon flux the dose rate obtained by the ANS flux-to-dose rate conversion factors are more conservative than those obtained by the ICRP's. Therefore, in order to establish a more reasonable new standard flux-to-dose rate conversion factors, more work should be done. (author)

Low dose irradiation reduces cancer mortality rates

International Nuclear Information System (INIS)

Luckey, T.D.

2000-01-01

Low doses of ionizing radiation stimulate development, growth, memory, sensual acuity, fecundity, and immunity (Luckey, T.D., ''Radiation Hormesis'', CRC Press, 1991). Increased immune competence reduces cancer mortality rates and provides increased average lifespan in animals. Decreased cancer mortality rates in atom bomb victims who received low dose irradiation makes it desirable to examine populations exposed to low dose irradiation. Studies with over 300,000 workers and 7 million person-years provide a valid comparison of radiation exposed and control unclear workers (Luckey, T.D., Nurture with Ionizing Radiation, Nutrition and Cancer, 34:1-11, 1999). Careful selection of controls eliminated any ''healthy worker effect''. The person-year corrected average indicated the cancer mortality rate of exposed workers was only 51% that of control workers. Lung cancer mortality rates showed a highly significant negative correlation with radon concentrations in 272,000 U.S. homes (Cohen, B.L., Health Physics 68:157-174, 1995). In contrast, radon concentrations showed no effect on lung cancer rates in miners from different countries (Lubin, J.H. Am. J. Epidemiology 140:323-332, 1994). This provides evidence that excessive lung cancer in miners is caused by particulates (the major factor) or toxic gases. The relative risk for cancer mortality was 3.7% in 10,000 Taiwanese exposed to low level of radiation from 60 Co in their steel supported homes (Luan, Y.C. et al., Am. Nuclear Soc. Trans. Boston, 1999). This remarkable finding needs further study. A major mechanism for reduced cancer mortality rates is increased immune competence; this includes both cell and humoral components. Low dose irradiation increases circulating lymphocytes. Macrophage and ''natural killer'' cells can destroy altered (cancer) cells before the mass becomes too large. Low dose irradiation also kills suppressor T-cells; this allows helper T-cells to activate killer cells and antibody producing cells

Changes of chromosome aberration rate and micronucleus frequency along with accumulated dose in continuously irradiated mice with a low dose rate of γ-rays

International Nuclear Information System (INIS)

Tanaka, Kimio; Izumi, Jun; Yanai, Takanori; Ichinohe, Kazuaki; Matsumoto, Tsuneya

2003-01-01

Chromosome aberrations in chronically exposed workers in nuclear facilities and medical radiologists have been reported. However chronological change of chromosome aberration rates along with accumulated dose has not been well studied. Chromosome aberrations and micronuclei in spleen lymphocytes were observed serially in mice continuously irradiated with a low dose rate of 20 mGy/day up to 400 days. Chromosome aberration rates were rapidly increased to 11.1% at 1 Gy, while micronucleus incidence increased at 5 Gy. After these doses their increase rates were saturated. Micronucleus incidence in bone marrow erythroblasts was higher than in spleen cells. These chronological changes of cytogenetic aberrations seem to be induced through a balance between developments of chromosome aberrations and micronuclei, and life span of spleen lymphocytes. These results will be helpful for risk assessment in low dose rate radiation exposure. (author)

Sensitivity of low energy brachytherapy Monte Carlo dose calculations to uncertainties in human tissue composition

Energy Technology Data Exchange (ETDEWEB)

Landry, Guillaume; Reniers, Brigitte; Murrer, Lars; Lutgens, Ludy; Bloemen-Van Gurp, Esther; Pignol, Jean-Philippe; Keller, Brian; Beaulieu, Luc; Verhaegen, Frank [Department of Radiation Oncology (MAASTRO), GROW-School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht 6201 BN (Netherlands); Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario M4N 3M5 (Canada); Departement de Radio-Oncologie et Centre de Recherche en Cancerologie, de l' Universite Laval, CHUQ, Pavillon L' Hotel-Dieu de Quebec, Quebec G1R 2J6 (Canada) and Departement de Physique, de Genie Physique et d' Optique, Universite Laval, Quebec G1K 7P4 (Canada); Department of Radiation Oncology (MAASTRO), GROW-School for Oncology and Developmental Biology, Maastricht University Medical Center, Maastricht 6201 BN (Netherlands) and Medical Physics Unit, McGill University, Montreal General Hospital, Montreal, Quebec H3G 1A4 (Canada)

2010-10-15

Purpose: The objective of this work is to assess the sensitivity of Monte Carlo (MC) dose calculations to uncertainties in human tissue composition for a range of low photon energy brachytherapy sources: {sup 125}I, {sup 103}Pd, {sup 131}Cs, and an electronic brachytherapy source (EBS). The low energy photons emitted by these sources make the dosimetry sensitive to variations in tissue atomic number due to the dominance of the photoelectric effect. This work reports dose to a small mass of water in medium D{sub w,m} as opposed to dose to a small mass of medium in medium D{sub m,m}. Methods: Mean adipose, mammary gland, and breast tissues (as uniform mixture of the aforementioned tissues) are investigated as well as compositions corresponding to one standard deviation from the mean. Prostate mean compositions from three different literature sources are also investigated. Three sets of MC simulations are performed with the GEANT4 code: (1) Dose calculations for idealized TG-43-like spherical geometries using point sources. Radial dose profiles obtained in different media are compared to assess the influence of compositional uncertainties. (2) Dose calculations for four clinical prostate LDR brachytherapy permanent seed implants using {sup 125}I seeds (Model 2301, Best Medical, Springfield, VA). The effect of varying the prostate composition in the planning target volume (PTV) is investigated by comparing PTV D{sub 90} values. (3) Dose calculations for four clinical breast LDR brachytherapy permanent seed implants using {sup 103}Pd seeds (Model 2335, Best Medical). The effects of varying the adipose/gland ratio in the PTV and of varying the elemental composition of adipose and gland within one standard deviation of the assumed mean composition are investigated by comparing PTV D{sub 90} values. For (2) and (3), the influence of using the mass density from CT scans instead of unit mass density is also assessed. Results: Results from simulation (1) show that variations

Microfluidic thrombosis under multiple shear rates and antiplatelet therapy doses.

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Melissa Li

Full Text Available The mainstay of treatment for thrombosis, the formation of occlusive platelet aggregates that often lead to heart attack and stroke, is antiplatelet therapy. Antiplatelet therapy dosing and resistance are poorly understood, leading to potential incorrect and ineffective dosing. Shear rate is also suspected to play a major role in thrombosis, but instrumentation to measure its influence has been limited by flow conditions, agonist use, and non-systematic and/or non-quantitative studies. In this work we measured occlusion times and thrombus detachment for a range of initial shear rates (500, 1500, 4000, and 10000 s(-1 and therapy concentrations (0-2.4 µM for eptifibatide, 0-2 mM for acetyl-salicylic acid (ASA, 3.5-40 Units/L for heparin using a microfluidic device. We also measured complete blood counts (CBC and platelet activity using whole blood impedance aggregometry. Effects of shear rate and dose were analyzed using general linear models, logistic regressions, and Cox proportional hazards models. Shear rates have significant effects on thrombosis/dose-response curves for all tested therapies. ASA has little effect on high shear occlusion times, even at very high doses (up to 20 times the recommended dose. Under ASA therapy, thrombi formed at high shear rates were 4 times more prone to detachment compared to those formed under control conditions. Eptifibatide reduced occlusion when controlling for shear rate and its efficacy increased with dose concentration. In contrast, the hazard of occlusion from ASA was several orders of magnitude higher than that of eptifibatide. Our results show similar dose efficacy to our low shear measurements using whole blood aggregometry. This quantitative and statistically validated study of the effects of a wide range of shear rate and antiplatelet therapy doses on occlusive thrombosis contributes to more accurate understanding of thrombosis and to models for optimizing patient treatment.

Radiation response of industrial materials: Dose-rate and morphology implications

International Nuclear Information System (INIS)

Berejka, Anthony J.

2007-01-01

Industrial uses of ionizing radiation mostly rely upon high current, high dose-rate (100 kGy/s) electron beam (EB) accelerators. To a lesser extent, industry uses low dose-rate (2.8 x 10 -3 kGy/s) radioactive Cobalt-60 as a gamma source, generally for some rather specific purposes, as medical device sterilization and the treatment of food and foodstuffs. There are nearly nine times as many (∼1400) high current EB units in commercial operation than gamma sources (∼160). However, gamma sources can be easily scaled-down so that much research on materials effects is conducted using gamma radiation. Likewise, laboratories are more likely to have very low beam current and consequently low dose-rate accelerators such as Van de Graaff generators and linear accelerators. With the advent of very high current EB accelerators, X-ray processing has become an industrially viable option. With X-rays from high power sources, dose-rates can be modulated based upon accelerator power and the attenuation of the X-ray by the distance of the material from the X-ray target. Dose and dose-rate dependence has been found to be of consequence in several commercial applications which can employ the use of ionizing radiation. The combination of dose and dose-rate dependence of the polymerization and crosslinking of wood impregnants and of fiber composite matrix materials can yield more economically viable results which have promising commercial potential. Monomer and oligomer structure also play an important role in attaining these desirable results. The influence of morphology is shown on the radiation response of olefin polymers, such as ethylene, propylene and isobutylene polymers and their copolymers. Both controlled morphology and controlled dose-rate have commercial consequences. These are also impacted both by the adroit selection of materials and through the possible use of X-ray processing

Radiation Parameters of High Dose Rate Iridium -192 Sources

Science.gov (United States)

Podgorsak, Matthew B.

A lack of physical data for high dose rate (HDR) Ir-192 sources has necessitated the use of basic radiation parameters measured with low dose rate (LDR) Ir-192 seeds and ribbons in HDR dosimetry calculations. A rigorous examination of the radiation parameters of several HDR Ir-192 sources has shown that this extension of physical data from LDR to HDR Ir-192 may be inaccurate. Uncertainty in any of the basic radiation parameters used in dosimetry calculations compromises the accuracy of the calculated dose distribution and the subsequent dose delivery. Dose errors of up to 0.3%, 6%, and 2% can result from the use of currently accepted values for the half-life, exposure rate constant, and dose buildup effect, respectively. Since an accuracy of 5% in the delivered dose is essential to prevent severe complications or tumor regrowth, the use of basic physical constants with uncertainties approaching 6% is unacceptable. A systematic evaluation of the pertinent radiation parameters contributes to a reduction in the overall uncertainty in HDR Ir-192 dose delivery. Moreover, the results of the studies described in this thesis contribute significantly to the establishment of standardized numerical values to be used in HDR Ir-192 dosimetry calculations.