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Sample records for absorbed dose distributions

  1. Study of absorbed dose distribution to high energy electron beams

    The depth absorbed dose distribution by electron beams was studied. The influence of the beam energy, the energy spread, field size and design characteristics of the accelerator was relieved. Three accelerators with different scattering and collimation systems were studied leading todifferent depth dose distributions. A theoretical model was constructed in order to explain the increase in the depth dose in the build-up region with the increase of the energy. The model utilizes a three-dimensional formalism based on the Fermi-Eyges multiple scattering theory, with the introduction of modifications that takes into account the criation of secondary electrons. (Author)

  2. Absorbed Dose Distribution in a Pulse Radiolysis Optical Cell

    Miller, Arne; McLaughlin, W. L.

    1975-01-01

    When a liquid solution in an optical cell is irradiated by an intense pulsed electron beam, it may be important in the chemical analysis of the solution to know the distribution of energy deposited throughout the cell. For the present work, absorbed dose distributions were measured by thin...... radiochromic dye film dosimeters placed at various depths in a quartz glass pulse radiolysis cell. The cell was irradiated with 30 ns pulses from a field-emission electron accelerator having a broad spectrum with a maximum energy of ≈MeV. The measured three-dimensional dose distributions showed sharp gradients...

  3. Space radiation absorbed dose distribution in a human phantom.

    Badhwar, G D; Atwell, W; Badavi, F F; Yang, T C; Cleghorn, T F

    2002-01-01

    The radiation risk to astronauts has always been based on measurements using passive thermoluminescent dosimeters (TLDs). The skin dose is converted to dose equivalent using an average radiation quality factor based on model calculations. The radiological risk estimates, however, are based on organ and tissue doses. This paper describes results from the first space flight (STS-91, 51.65 degrees inclination and approximately 380 km altitude) of a fully instrumented Alderson Rando phantom torso (with head) to relate the skin dose to organ doses. Spatial distributions of absorbed dose in 34 1-inch-thick sections measured using TLDs are described. There is about a 30% change in dose as one moves from the front to the back of the phantom body. Small active dosimeters were developed specifically to provide time-resolved measurements of absorbed dose rates and quality factors at five organ locations (brain, thyroid, heart/lung, stomach and colon) inside the phantom. Using these dosimeters, it was possible to separate the trapped-proton and the galactic cosmic radiation components of the doses. A tissue-equivalent proportional counter (TEPC) and a charged-particle directional spectrometer (CPDS) were flown next to the phantom torso to provide data on the incident internal radiation environment. Accurate models of the shielding distributions at the site of the TEPC, the CPDS and a scalable Computerized Anatomical Male (CAM) model of the phantom torso were developed. These measurements provided a comprehensive data set to map the dose distribution inside a human phantom, and to assess the accuracy and validity of radiation transport models throughout the human body. The results show that for the conditions in the International Space Station (ISS) orbit during periods near the solar minimum, the ratio of the blood-forming organ dose rate to the skin absorbed dose rate is about 80%, and the ratio of the dose equivalents is almost one. The results show that the GCR model dose

  4. Space radiation absorbed dose distribution in a human phantom

    Badhwar, G. D.; Atwell, W.; Badavi, F. F.; Yang, T. C.; Cleghorn, T. F.

    2002-01-01

    The radiation risk to astronauts has always been based on measurements using passive thermoluminescent dosimeters (TLDs). The skin dose is converted to dose equivalent using an average radiation quality factor based on model calculations. The radiological risk estimates, however, are based on organ and tissue doses. This paper describes results from the first space flight (STS-91, 51.65 degrees inclination and approximately 380 km altitude) of a fully instrumented Alderson Rando phantom torso (with head) to relate the skin dose to organ doses. Spatial distributions of absorbed dose in 34 1-inch-thick sections measured using TLDs are described. There is about a 30% change in dose as one moves from the front to the back of the phantom body. Small active dosimeters were developed specifically to provide time-resolved measurements of absorbed dose rates and quality factors at five organ locations (brain, thyroid, heart/lung, stomach and colon) inside the phantom. Using these dosimeters, it was possible to separate the trapped-proton and the galactic cosmic radiation components of the doses. A tissue-equivalent proportional counter (TEPC) and a charged-particle directional spectrometer (CPDS) were flown next to the phantom torso to provide data on the incident internal radiation environment. Accurate models of the shielding distributions at the site of the TEPC, the CPDS and a scalable Computerized Anatomical Male (CAM) model of the phantom torso were developed. These measurements provided a comprehensive data set to map the dose distribution inside a human phantom, and to assess the accuracy and validity of radiation transport models throughout the human body. The results show that for the conditions in the International Space Station (ISS) orbit during periods near the solar minimum, the ratio of the blood-forming organ dose rate to the skin absorbed dose rate is about 80%, and the ratio of the dose equivalents is almost one. The results show that the GCR model dose

  5. Scaling neutron absorbed dose distributions from one medium to another

    Central axis depth dose (CADD) and off-axis absorbed dose ratio (OAR) measurements were made in water, muscle and whole skeletal bone TE-solutions, mineral oil and glycerin with a clinical neutron therapy beam. These measurements show that, for a given neutron beam quality and field size, there is a universal CADD distribution at infinity if the depth in the phantom is expressed in terms of appropriate scaling lengths. These are essentially the kerma-weighted neutron mean free paths in the media. The method used in ICRU No. 26 to scale the CADD by the ratio of the densities is shown to give incorrect results. the OAR's measured in different media at depths proportional to the respective mean free paths were also found to be independent of the media to a good approximation. It is recommended that relative CADD and OAR measurements be performed in water because of its universality and convenience. A table of calculated scaling lengths is given for various neutron energy spectra and for various tissues and materials of practical importance in neutron dosimetry

  6. Radiochromic Plastic Films for Accurate Measurement of Radiation Absorbed Dose and Dose Distributions

    McLaughlin, W. L.; Miller, Arne; Fidan, S.;

    1977-01-01

    Thin radiochromic dye films are useful for measuring large radiation absorbed doses (105–108 rads) and for high-resolution imaging of dose patterns produced by penetrating radiation beams passing through non-homogeneous media. Certain types of amino-substituted triarylmethane cyanides dissolved in...... polymeric solutions can be cast into flexible free-standing thin films of uniform thickness and reproducible response to ultraviolet and ionizing radiation. The increase in optical density versus energy deposited by radiation is linear over a wide range of doses and is for practical purposes independent of...... dose rate (1–1014 rad s−1). Upon irradiation of the film, the profile of the radiation field is registered as a permanent colored image of the dose distribution. Unlike most other types of dyed plastic dose meters, the optical density produced by irradiation is in most cases stable for periods of at...

  7. Absorbed dose distribution analyses in irradiation with adjacent fields

    Because the special irradiation technique with adjacent fields is the most used in the case of medulloblastoma treatment, we consider very important to specify some general information about medulloblastoma. This malignant disease has a large incidence in children with age between 5-7 years. This tumor usually originates in the cerebellum and is referred to as primitive undifferentiated tumor. It may spread contiguously to the cerebellar peduncle, floor of the fourth ventricle, into the cervical spine. In addition, it may spread via the cerebrospinal fluid intracranially and/or to the spinal cord. For this purpose it is necessary to perform a treatment technique with cranial tangential fields combined with adjacent fields for the entire spinal cord to achieve a perfect coverage of the zones with malignant cells. The treatment in this case is an association between surgery-radio-chemotherapy, where the radiotherapy has a very important roll and a curative purpose. This is due to the fact that the migration of malignant cells in the body can't be controlled by surgery. Because of this special irradiation technique used in medulloblastoma treatment, we chase to describe in this paper this complex type of irradiation where the implications of the beams divergence in doses distribution are essentials

  8. Axial distribution of absorbed doses in fast neutron field at the RB reactor

    The coupled fast thermal system CFTS at the RB reactor is created for obtaining fast neutron fields. The axial distribution of fast neutron flux density in its second configuration (CFTS-2) is measured. The axial distribution of absorbed doses is computed on the basis of mentioned experimental results. At the end these experimental and computed results are given. (Author)

  9. Relationship between biologic tissue heterogeneity and absorbed dose distribution in therapy of oncologic patients with cyclotron U-120 fast neutrons

    Effect of biological tissue heterogeneity on the absorbed dose distribution of U-120 cyclotron fast neutron beam was studied by estimation and experimental method. It was found that adipose and bone tissues significantly changes the pattern of neutron absorbed dose distribution in patient body. Absorbed dose in adipose layer increase by 20% as compared to the dose in soft biological tissue. Approximation method for estimation of the absorbed dose distribution of fast neutrons in heterogeneities was proposed which could be applied in the dosimetric planning of U-120 cyclotron neutron therapy of neoplasms

  10. Evaluation of the distribution of absorbed dose in child phantoms exposed to diagnostic medical x rays

    The purpose of this study was to determine, by theoretical calculation and experimental measurement, the absorbed dose distributions in two heterogeneous phantoms representing one-year- and five-year-old children from typical radiographic examinations for those ages. Theoretical work included the modification of an existing internal dose code which uses Monte Carlo methods to determine doses within the Snyder-Fisher mathematical phantom. A Ge(Li) detector and a pinhole collimator were used to measure x-ray spectra which served as input to the modified Monte Carlo codes which were used to calculate organ doses in children. The calculated and measured tissue-air values were compared for a number of organs. For most organs, the results of the calculated absorbed doses agreed with the measured absorbed doses within twice the coefficient of variation of the calculated value. The absorbed dose to specific organs for several selected radiological examinations are given for one-year-old, five-year-old, and adult phantoms

  11. Evaluation of the distribution of absorbed dose in child phantoms exposed to diagnostic medical x rays

    Chen, W. L.; Poston, J. W.; Warner, G. G.

    1978-04-01

    The purpose of this study was to determine, by theoretical calculation and experimental measurement, the absorbed dose distributions in two heterogeneous phantoms representing one-year- and five-year-old children from typical radiographic examinations for those ages. Theoretical work included the modification of an existing internal dose code which uses Monte Carlo methods to determine doses within the Snyder-Fisher mathematical phantom. A Ge(Li) detector and a pinhole collimator were used to measure x-ray spectra which served as input to the modified Monte Carlo codes which were used to calculate organ doses in children. The calculated and measured tissue-air values were compared for a number of organs. For most organs, the results of the calculated absorbed doses agreed with the measured absorbed doses within twice the coefficient of variation of the calculated value. The absorbed dose to specific organs for several selected radiological examinations are given for one-year-old, five-year-old, and adult phantoms.

  12. Radiochromic Plastic Films for Accurate Measurement of Radiation Absorbed Dose and Dose Distributions

    McLaughlin, W. L.; Miller, Arne; Fidan, S.; Pejtersen, K.; Pedersen, Walther Batsberg

    1977-01-01

    dose rate (1–1014 rad s−1). Upon irradiation of the film, the profile of the radiation field is registered as a permanent colored image of the dose distribution. Unlike most other types of dyed plastic dose meters, the optical density produced by irradiation is in most cases stable for periods of at...... of many polymeric systems in industrial radiation processing. The result is that errors due to energy dependence of response of the radiation sensor are effectively reduced, since the spectral sensitivity of the dose meter matches that of the polymer of interest, over a wide range of photon and...

  13. Exposure distribution, absorbed doses, and energy imparted for panoramic radiography using Orthopantomograph model OP 5

    The absorbed doses and energy imparted for the Orthopantomograph model OP 5 using two different collimators (0.9-1.3 X 33 mm2 and 0.6-0.9 X 39.5 mm2, respectively) were examined at 70 and 75 kV. The absorbed doses were estimated by thermoluminescence dosimetry in a sectioned phantom and by the energy imparted from measurements of areal exposure using a plane parallel transmission ionization chamber. The exposure distribution was surveyed on radiographic film. The anterior part of the parotid glands received the highest absorbed doses (2.4-3.2 mGy) when the wider collimator was used, with a decrease of two to three times when the narrower collimator was used. Other areas received absorbed doses of about 1.0 to 1.5 mGy or below. An increase of the kV from 70 to 75 had a minor influence. The energy imparted for the wider collimator was 0.6-0.8 and for the narrower collimator, 0.4-0.6 mJ

  14. Distribution of absorbed dose in human eye simulated by SRNA-2KG computer code

    Rapidly increasing performances of personal computers and development of codes for proton transport based on Monte Carlo methods will allow, very soon, the introduction of the computer planning proton therapy as a normal activity in regular hospital procedures. A description of SRNA code used for such applications and results of calculated distributions of proton-absorbed dose in human eye are given in this paper. (author)

  15. An absorbed dose microcalorimeter

    A graphite microcalorimeter is described for use as a primary standard of ionising radiation absorbed dose; its place in the hierarchy of Australian ionising radiation standards is discussed. A disc shaped absorber is supported on pins within three nested graphite jackets and an insulated vacuum vessel. Calibration heating is by thermistor, the feasibility of this was verified by computer modelling. Adiabatic and heat-flow modes of operation are described, and calculations of heat transfer between the various graphite parts are summarised. Carbon and water phantoms were built for the evaluation of correction factors for the microcalorimeter, and for the calibration of radiotherapy dosemeters. The microcalorimeter will be used as a working standard for the calibration of dosemeters in terms of absorbed dose for the x-ray, gamma-ray and electron radiotherapy beams commonly used in Australia today

  16. Measurements of spatial distribution of absorbed dose in proton therapy with Gafchromic EBT3

    Gambarini, G.; Regazzoni, V.; Grisotto, S.; Artuso, E.; Giove, D. [Universita degli Studi di Milano, Department of Physics, via Celoria 16, 20133 Milano (Italy); Borroni, M.; Carrara, M.; Pignoli, E. [Fondazione IRCCS, Istituto Nazionale dei Tumori di Milano, Medical Physics Unit, via Giacomo Venezian 16, 20133 Milano (Italy); Mirandola, A.; Ciocca, M., E-mail: grazia.gambarini@mi.infn.it [Centro Nazionale Adroterapia Oncologica, Medical Physics Unit, Strada Campeggi 53, 27100 Pavia (Italy)

    2014-08-15

    A study of the response of EBT3 films has been carried out. Light transmittance images (around 630 nm) were acquired by means of a Ccd camera. The difference of optical density was assumed as dosimeter response. Calibration was performed by means of {sup 60}Co photons, at a radiotherapy facility. A study of the response variation during the time after exposure has been carried out. EBT3 films were exposed, in a solid-water phantom, to proton beams of various energies and the obtained depth-dose profiles were compared with those measured with a ionization chamber. As expected, in the Bragg peak region the values obtained with EBT3 films were lower than those obtained with the ionization chamber. The ratio of such values was evaluated, along dose profiles, for each utilized energy. A method for correcting the data measured with EBT3 has been proposed and tested. The results confirm that the method can be advantageously applied for obtaining spatial distribution of the absorbed dose in proton therapy. (author)

  17. Measurements of 2D distributions of absorbed dose in protontherapy with Gafchromic EBT3 films.

    Gambarini, G; Regazzoni, V; Artuso, E; Giove, D; Mirandola, A; Ciocca, M

    2015-10-01

    A study of the response of EBT3 films to protons has been carried out with the aim of finding a simple modality to achieve dose images in which the effect of the film sensitivity dependence on radiation LET is amended. Light transmittance images (around 630 nm) were acquired by means of a CCD camera and the difference of optical density was assumed as dosimeter response. The calibration of EBT3 film was performed by means of protons of 173.61 MeV. Some EBT3 films were exposed, in a solid-water phantom, to proton beams of three different energies (89.17 MeV, 110.96 MeV and 130.57 MeV) and the obtained depth-dose profiles were compared with the calculated profiles. From the ratios of calculated and measured Bragg peaks, a trend of the decrease in EBT3 sensitivity with increasing peak depth has been deduced. A method for correcting the data measured with EBT3 films, utilizing the file of irradiation planning data, has been proposed and tested. The results confirm that the method can be advantageously applied for obtaining spatial distribution of the absorbed dose in proton therapy. PMID:26188464

  18. Measurements of spatial distribution of absorbed dose in proton therapy with Gafchromic EBT3

    A study of the response of EBT3 films has been carried out. Light transmittance images (around 630 nm) were acquired by means of a Ccd camera. The difference of optical density was assumed as dosimeter response. Calibration was performed by means of 60Co photons, at a radiotherapy facility. A study of the response variation during the time after exposure has been carried out. EBT3 films were exposed, in a solid-water phantom, to proton beams of various energies and the obtained depth-dose profiles were compared with those measured with a ionization chamber. As expected, in the Bragg peak region the values obtained with EBT3 films were lower than those obtained with the ionization chamber. The ratio of such values was evaluated, along dose profiles, for each utilized energy. A method for correcting the data measured with EBT3 has been proposed and tested. The results confirm that the method can be advantageously applied for obtaining spatial distribution of the absorbed dose in proton therapy. (author)

  19. Measurements of 2D distributions of absorbed dose in protontherapy with Gafchromic EBT3 films

    A study of the response of EBT3 films to protons has been carried out with the aim of finding a simple modality to achieve dose images in which the effect of the film sensitivity dependence on radiation LET is amended. Light transmittance images (around 630 nm) were acquired by means of a CCD camera and the difference of optical density was assumed as dosimeter response. The calibration of EBT3 film was performed by means of protons of 173.61 MeV. Some EBT3 films were exposed, in a solid-water phantom, to proton beams of three different energies (89.17 MeV, 110.96 MeV and 130.57 MeV) and the obtained depth-dose profiles were compared with the calculated profiles. From the ratios of calculated and measured Bragg peaks, a trend of the decrease in EBT3 sensitivity with increasing peak depth has been deduced. A method for correcting the data measured with EBT3 films, utilizing the file of irradiation planning data, has been proposed and tested. The results confirm that the method can be advantageously applied for obtaining spatial distribution of the absorbed dose in proton therapy. - Highlights: • EBT3 films were calibrated with a proton pencil beam of 173.61 MeV. • In-phantom depth-dose image in the SOBP region was measured with EBT3. • A method to compensate for the EBT3 under-response, utilizing the file of irradiation planning data, was tested. • The central depth-dose profile extracted from the image was compared with that calculated by the TPS. • The inter-comparison of measured and calculated profiles has proven that satisfactory correction can be achieved with the proposed methods

  20. Gamma-Absorbed Dose Rate and Distribution of Natural Radionuclides in Songkhla Beach Sands

    Full text: Specific activities and distribution of natural radionuclide γ-ray activities, produced by 40K, 226Ra and 232Th, were determined in 80 sand samples collected along Chalatat and Samila beaches in Songkhla province. The derivation of 40K, 226Ra and 232Th gamma-ray specific activities of sand samples was performed using the high-purity germanium (HPGe) detector, gamma spectroscopy analysis system and the Eu-152 radioactive standard source at the Office of Atoms for Peace (OAP) laboratory. The beach sand specific activity ranges from 89 to 963 Bq/kg for 40K, 0 to 120 Bq/kg for 226Ra and 0 to 319 Bq/kg for 232Th with mean values of 248 ± 44 Bq/kg, 41 ± 5 Bq/kg and 64 ± 7 Bq/kg, respectively. The specific activities of these radionuclides were compared with some global radioactivity measurements and evaluations. Moreover, gamma to absorbed dose rates and radium equivalent activities were calculated for the analyzed samples to assess the radiation hazards arising. All the beach sand samples had the mean value of radium equivalent activities lower than 370 Bq/kg, which is the limit set by OECD

  1. Absorbed dose distributions in patients with bone metastases from hormone refractory prostate cancer treated with Re-186 HEDP

    Full text of publication follows. Aim: intravenous administration of Re-186 hydroxyethylidene-diphosphonate (HEDP) is used for metastatic bone pain palliation in hormone refractory prostate cancer patients. Dosimetry for bone seeking radionuclides is challenging due to the complex structure with osteoblastic, osteolytic and mixed lesions. The aim of this study was to perform image-based patient-specific 3D convolution dosimetry to obtain a distribution of the absorbed doses to each lesion and estimate inter- and intra-patient variations. Materials and methods: 28 patients received a fixed 5 GBq activity of Re-186 HEDP followed by peripheral blood stem cell rescue at 14 days in a phase II trial. A FORTE dual-headed gamma camera was used to acquire sequential Single-Photon-Emission Computed Tomography (SPECT) data of the thorax and pelvis area at 1, 4, 24, 48 and 72 hours following administration. The projection data were reconstructed using filtered-back projection and were corrected for attenuation and scatter. Voxelised cumulated activity distributions were obtained with two different methods. First, the scans were co-registered and the time-activity curves were obtained on a voxel-by-voxel basis. Second, the clearance curve was obtained from the mean number of counts in each individual lesion and used to scale the uptake distribution taken at 24 hours. The calibration factors required for image quantification were obtained from a phantom experiment. An in-house developed EGSnrc Monte Carlo code was used for the calculation of dose voxel kernels for soft-tissue and cortical/trabecular bone used to perform convolution dosimetry. Cumulative dose-volume histograms were produced and mean absorbed doses calculated for each spinal and pelvic lesion. Results: preliminary results show that the lesion mean absorbed doses ranged from 25 to 55 Gy when the medium was soft tissue and decreased by 40% if bone was considered. The use of the cumulated activity distribution

  2. Absorbed dose distributions in a tissue-equivalent absorber for Bremsstrahlung produced at the beamlines of the European Synchrotron Radiation Facility

    Pisharody, M; Berkvens, P; Colomp, P

    2000-01-01

    The absorbed-dose distributions for Bremsstrahlung, incident on a tissue-equivalent phantom, were measured with LiF : Mg,Ti thermoluminescent dosimeters at two insertion device beamlines of the European Synchrotron Radiation Facility (ESRF). The measurements were carried out for two different electron beam energies of 4 and 6 GeV. The corresponding Bremsstrahlung spectra and power were measured using a high-resolution lead glass total absorption calorimeter. The results are compared with similar measurements carried out at other facilities. The normalized Bremsstrahlung absorbed dose in a cross-sectional area of 100 mm sup sup 2 , at a depth of 150 mm of the phantom, was measured as 6.1 and 3.6 kGy h sup sup - sup sup 1 W sup sup - sup sup 1 for the corresponding Bremsstrahlung spectra of 4 and 6 GeV.

  3. Ion chamber absorbed dose calibration coefficients, ND,w, measured at ADCLs: Distribution analysis and stability

    Purpose: To analyze absorbed dose calibration coefficients, ND,w, measured at accredited dosimetry calibration laboratories (ADCLs) for client ionization chambers to study (i) variability among ND,w coefficients for chambers of the same type calibrated at each ADCL to investigate ion chamber volume fluctuations and chamber manufacturing tolerances; (ii) equivalency of ion chamber calibration coefficients measured at different ADCLs by intercomparing ND,w coefficients for chambers of the same type; and (iii) the long-term stability of ND,w coefficients for different chamber types by investigating repeated chamber calibrations. Methods: Large samples of ND,w coefficients for several chamber types measured over the time period between 1998 and 2014 were obtained from the three ADCLs operating in the United States. These are analyzed using various graphical and numerical statistical tests for the four chamber types with the largest samples of calibration coefficients to investigate (i) and (ii) above. Ratios of calibration coefficients for the same chamber, typically obtained two years apart, are calculated to investigate (iii) above and chambers with standard deviations of old/new ratios less than 0.3% meet stability requirements for accurate reference dosimetry recommended in dosimetry protocols. Results: It is found that ND,w coefficients for a given chamber type compared among different ADCLs may arise from differing probability distributions potentially due to slight differences in calibration procedures and/or the transfer of the primary standard. However, average ND,w coefficients from different ADCLs for given chamber types are very close with percent differences generally less than 0.2% for Farmer-type chambers and are well within reported uncertainties. Conclusions: The close agreement among calibrations performed at different ADCLs reaffirms the Calibration Laboratory Accreditation Subcommittee process of ensuring ADCL conformance with National Institute of

  4. The MIRD method of estimating absorbed dose

    Weber, D.A.

    1991-01-01

    The estimate of absorbed radiation dose from internal emitters provides the information required to assess the radiation risk associated with the administration of radiopharmaceuticals for medical applications. The MIRD (Medical Internal Radiation Dose) system of dose calculation provides a systematic approach to combining the biologic distribution data and clearance data of radiopharmaceuticals and the physical properties of radionuclides to obtain dose estimates. This tutorial presents a review of the MIRD schema, the derivation of the equations used to calculate absorbed dose, and shows how the MIRD schema can be applied to estimate dose from radiopharmaceuticals used in nuclear medicine.

  5. The study of space and energy distribution of personal absorbed dose of neutron from H-bomb

    Nowadays, many work have been done on the measurement and calculation of the space and energy distribution of neutron from H-bomb explosion. However, the established air and soil medium models are rough in the study of theoretical calculation before. The author established three air-soil mediums, and chose explosion height and space radial distance which have military meaning. The results of space and energy distribution of neutron personal absorbed dose from H-bomb are obtained through calculation. Many conclusion on radiation protection and nuclear monitoring have made

  6. Study of the spatial distribution of the absorbed dose in blood volumes irradiated using a teletherapy unit

    Blood irradiation can be performed using a dedicated blood irradiator or a teletherapy unit. A thermal device providing appropriate storage conditions during blood components irradiation with a teletherapy unit has been recently proposed. However, the most appropriated volume of the thermal device was not indicated. The goal of this study was to indicate the most appropriated blood volume for irradiation using a teletherapy unit in order to minimize both the dose heterogeneity in the volume and the blood irradiation time using these equipments. Theoretical and experimental methods were used to study the dose distribution in the blood volume irradiated using a linear accelerator and a cobalt-60 therapy machine. The calculation of absorbed doses in the middle plane of cylindrical acrylic volumes was accomplished by a treatment planning system. Experimentally, we also used cylindrical acrylic phantoms and thermoluminescent dosimeters to confirm the calculated doses. The data obtained were represented by isodose curves. We observed that an irradiation volume should have a height of 28 cm and a diameter of 28 cm and a height of 35 cm and a diameter of 35 cm, when the irradiation is to be performed by a linear accelerator and a cobalt-60 teletherapy unit, respectively. Calculated values of relative doses varied from 93% to 100% in the smaller volume, and from 66% to 100% in the largest one. A difference of 5.0%, approximately, was observed between calculated and experimental data. The size of these volumes permits the irradiation of blood bags in only one bath without compromising the homogeneity of the absorbed dose over the irradiated volume. Thus, these irradiation volumes can be recommend to minimize the irradiation time when a teletherapy unit is used to irradiate blood.

  7. The distribution of absorbed dose from x-rays as a function of depth

    Cummings, Frederick

    2000-08-01

    Organizations responsible for monitoring the occupational exposure to radiation workers in the U.S. are directed to measure the dose to specific depths in tissue. The knowledge of the depth distribution of energy deposited by radiation in materials is essential to the interpretation of devices used to measure occupational exposure In this work, the quantities used to convert the reference transfer quantity for x-ray fields, air kerma, to the regulatory quantity, dose equivalent, for mono- energetic x-ray fields and poly-energetic x-ray fields specified by the National Institute of Standards and Technology are cogenerated for European x-ray fields are indicated and consistent conversion factors for use in the U.S. are recommended. For the mono-energetic x-ray beams conversion factors ranged from 0.9 to 1.7 at the 7 mg/cm2 depth and from 0.03 to 1.9 at the 1000 mg/cm2 depth in tissue specified by the International Commission of Radiation Units and Measurements. The conversion factors for the NIST x-ray fields were reasonably consistent with values in an unpublished draft standard by the American National Standards Institute, but exhibited sufficient disagreement to warrant a re-evaluation of the factors in that document prior to publication.

  8. Contrast-enhanced radiotherapy: feasibility and characteristics of the physical absorbed dose distribution for deep-seated tumors

    Radiotherapy using kilovoltage x-rays in conjunction with contrast agents incorporated into the tumor, gold nanoparticles in particular, could represent a potential alternative to current techniques based on high-energy linear accelerators. In this paper, using the voxelized Zubal phantom in conjunction with the Monte Carlo code PENELOPE to model a prostate cancer treatment, it is shown that in combination with a 360 deg. arc delivery technique, tumoricidal doses of radiation can be delivered to deep-seated tumors while still providing acceptable doses to the skin and other organs at risk for gold concentrations in the tumor within the range of 7-10 mg-Au per gram of tissue. Under these conditions and using a x-ray beam with 90% of the fluence within the range of 80-200 keV, a 72 Gy physical absorbed dose to the prostate can be delivered, while keeping the rectal wall, bladder, skin and femoral heads below 65 Gy, 55 Gy, 40 Gy and 30 Gy, respectively. However, it is also shown that non-uniformities in the contrast agent concentration lead to a severe degradation of the dose distribution and that, therefore, techniques to locally quantify the presence of the contrast agent would be necessary in order to determine the incident x-ray fluence that best reproduces the dosimetry obtained under conditions of uniform contrast agent distribution.

  9. Contrast-enhanced radiotherapy: feasibility and characteristics of the physical absorbed dose distribution for deep-seated tumors

    Garnica-Garza, H M [Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional Unidad Monterrey, Via del Conocimiento 201 Parque de Investigacion e Innovacion Tecnologica, Apodaca NL C.P. 66600 (Mexico)], E-mail: hgarnica@cinvestav.mx

    2009-09-21

    Radiotherapy using kilovoltage x-rays in conjunction with contrast agents incorporated into the tumor, gold nanoparticles in particular, could represent a potential alternative to current techniques based on high-energy linear accelerators. In this paper, using the voxelized Zubal phantom in conjunction with the Monte Carlo code PENELOPE to model a prostate cancer treatment, it is shown that in combination with a 360 deg. arc delivery technique, tumoricidal doses of radiation can be delivered to deep-seated tumors while still providing acceptable doses to the skin and other organs at risk for gold concentrations in the tumor within the range of 7-10 mg-Au per gram of tissue. Under these conditions and using a x-ray beam with 90% of the fluence within the range of 80-200 keV, a 72 Gy physical absorbed dose to the prostate can be delivered, while keeping the rectal wall, bladder, skin and femoral heads below 65 Gy, 55 Gy, 40 Gy and 30 Gy, respectively. However, it is also shown that non-uniformities in the contrast agent concentration lead to a severe degradation of the dose distribution and that, therefore, techniques to locally quantify the presence of the contrast agent would be necessary in order to determine the incident x-ray fluence that best reproduces the dosimetry obtained under conditions of uniform contrast agent distribution.

  10. Distribution of absorbed dose rate in air because of terrestrial gamma radiation in Miyako-jima, Okinawa Prefecture, Japan

    The absorbed dose rate in air because of terrestrial gamma radiation in Miyako-jima, an island that is part of Okinawa Prefecture in the subtropical region of Japan, was estimated at 637 points by in situ measurements with spectrometers equipped with 3''φ x 3''NaI(Tl) and 1''φ x 2''NaI(TL) scintillation detectors. The mean, minimum, and maximum dose rates were calculated to be about 79 nGy/h, 3 nGy/h, and 165 nGy/h, respectively. The correlation of the dose rate and geology showed that the high-rate areas (>100 nGy/h) and the distribution of the Holocene red soils (Onokoshi Clay) overlap each other. On the other hand, the low dose rates (<30 nGy/h) were mainly found in an outcrop of the Pleistocene Ryukyu Limestone, the main geologic element in the foundation of the red soils. Recent studies (e.g., Inoue et al., 1993) concluded that most of the red soils were not residuals from the base rocks, but of eolian dust ''Kosa (Yellow Sand)'' origin. These results strongly indicate that the dose rate in Miyako-jima has been enhanced as a result of eolian deposits transported mainly from the arid region of China since the last glacial epoch. (author)

  11. The analysis of impact of irregularity in radionuclide coating of scaffold on the distribution of absorbed dose produced by grid of microsources

    N. A. Nerosin

    2015-01-01

    Full Text Available The impact of irregularity in radionuclide coating of scaffold on the distribution of absorbed dose produced by grid of microsources was analyzed. On engineering software MATHCAD the program for calculation of absorbed dose produced by grid of microsources was created. To verify this algorithm the calculation model for MCNP code was established and represented the area consisted of soft biological tissue or any other tissue in which the grid of microsources was incorporated. Using the developed system the value of possible systematic irregular coating of radioactivity on the microsource’s core was analyzed. The distribution of activity along the surface of microsource was simulated to create distribution of absorbed dose rate corresponding to experimental data on radiation injury. The obtained model of microsource with irregular distribution of activity was compared to conventional microsource with core coated regularly along the entire area of the silver stem by main dosimetry characteristics. The results showed that even for extremely irregular distribution of activity the distribution of dose rate produced by microsource in the tumor area was not substantially different from dose-rate field obtained for microsource with regularly coated activity. The differences in dose rates (up to 10% in areas which were the nearest to the center of the grid were significantly lower than its decline from center to periphery of the grid. For spatial distribution of absorbed dose for specific configuration of microsource set and tracing of curves of equal level by selected cut-off the program SEEDPLAN was developed. The developed program represents precisely enough the spatial distribution of selected configuration set of microsources using results of calculation data for absorbed dose around the single microsource as basic data and may be used for optimal planning of brachytherapy with microsources. 

  12. CALCULATION STUDIES OF SPATIAL DISTRIBUTION OF THE ABSORBED DOSE RATE FOR VARIOUS SEEDS

    N. A. Nerozin

    2015-01-01

    Full Text Available Purpose. Conducting computational studies of dosimetric characteristics of microsources with the radionuclide I‑125, pilot production of which is established in the research and production complex of isotope and radiopharmaceuticals, JSC “State Scientific Centre of the Russian Federation — Institute for Physics and Power Engineering named after A. I. Leypunsky” (SSC RF IPPE. Sources of production IPPE are similar to the model 6711 of the company Nicomed Amersham, dosimetric characteristics of which are standardized in accordance with the TG43 AAPM formalism.Materials and methods. Microsourse «SEED No. 6711» (model of the company Nicomed Amersham is hermetically sealed in a titanium capsule silver rod covered with a thin layer of radioactive I‑125. The half-life of iodine‑125 is 59,43 days. In the process of decay of I‑125 is converted into the Te‑125.Calculation of parameters of microsources and their comparison with the standard model 6711 is carried out with use of the computer code MCNP.Results. The method of calculation of the basic dosimetric characteristics of the microsourse SSC RF-IPPE in accordance with the TG43 formalism is developed. A comparative analysis of experimental data and calculated results by MCNP code, which allowed to identify possible reasons for differences, is performed. The estimated dose characteristics and recommended standard data for dose characteristics of micro «SEED No. 6711» are compared.Conclusions. There are two possible reasons for the differences between experimental and calculated results. The first one may be the roughness of the surface of a silver rod or diffusion of radioactive iodine in silver. The second reason might be the difference of the cross sections of the characteristic radiation of silver used in MCNP code. In the comparison of calculated dose characteristics and recommended standard the role of the application activity is very important. In compliance with the standard

  13. Absorbed dose distribution patterns in the beagle thorax after inhalation of 90Sr--90Y fused clay particles. II

    This experiment was designed to examine absorbed dose patterns in the Beagle dog thorax after inhalation of polydisperse fused montmorillonite clay particles labeled with 90Sr-90Y. Sixteen dogs were exposed nose-only to achieve initial lung burdens of 91 to 200 μCi. Dogs are being serially sacrificed and photographic data and autoradiographic data produced for a series of parallel planes approximately 1 cm apart through the thorax. Data analysis will include definition of absorbed dose patterns in the Beagle thorax at 8 days, 64 days, 1 year, 2 years, and 3 years post-exposure. To date, 8-day, 64-day, and 1-year animals have been sacrificed and partially analyzed. The result of this experiment will be a better understanding of deposition and absorbed dose patterns and allow a better correlation between absorbed dose and biological response for Beagle dogs exposed to relatively insoluble aerosols contaminated by energetic beta-emitting radionuclides. In addition, results will allow quantitating anomalies in deposition patterns, such as the striated pattern near ribs previously observed in this laboratory. (U.S.)

  14. The Effects on Absorbed Dose Distribution in Intraoral X-ray Imaging When Using Tube Voltages of 60 and 70 kV for Bitewing Imaging

    Kristina Hellén-Halme

    2013-10-01

    Full Text Available Objectives: Efforts are made in radiographic examinations to obtain the best image quality with the lowest possible absorbed dose to the patient. In dental radiography, the absorbed dose to patients is very low, but exposures are relatively frequent. It has been suggested that frequent low-dose exposures can pose a risk for development of future cancer. It has previously been reported that there was no significant difference in the diagnostic accuracy of approximal carious lesions in radiographs obtained using tube voltages of 60 and 70 kV. The aim of this study was, therefore, to evaluate the patient dose resulting from exposures at these tube voltages to obtain intraoral bitewing radiographs.Material and Methods: The absorbed dose distributions resulting from two bitewing exposures were measured at tube voltages of 60 and 70 kV using Gafchromic® film and an anatomical head phantom. The dose was measured in the occlusal plane, and ± 50 mm cranially and caudally to evaluate the amount of scattered radiation. The same entrance dose to the phantom was used. The absorbed dose was expressed as the ratio of the maximal doses, the mean doses and the integral doses at tube voltages of 70 and 60 kV.Results: The patient receives approximately 40 - 50% higher (mean and integral absorbed dose when a tube voltage of 70 kV is used.Conclusions: The results of this study clearly indicate that 60 kV should be used for dental intraoral radiographic examinations for approximal caries detection.

  15. Quality assurance technique for absorbed dose distribution in external radiation therapy with non-physical wedges in consideration of the character of the imaging plate

    The film dose distribution method is used for profile measurements of non-physical wedges, because three-dimensional automatic control water phantoms cannot be used. Recently, many hospitals have adopted computed radiography (CR) systems in preference to automatic developing processors and films. This may allow use of automatic processors to be discontinued. In this study, a beam was irradiated to an Imaging Plate (IP), and then IP was exposed to a fixed amount of light with fading, and we then measured the off-center ratio (OCR) absorbed dose distribution in external radiation therapy with non-physical wedge. This was compared with the OCR measured with an ionization chamber dosimeter. It was consequently possible for IP to approximate the value measured by the ionization chamber dosimeter by using a metal filter. This method offers a simple quality assurance technique for absorbed dose distribution in external radiation therapy with non-physical wedges in consideration of the character of the IP. (author)

  16. Determination of Absorbed Dose Using a Dosimetric Film

    This paper presents the absorbed dose measurements by means of the irradiated dosimetric reference films. The dose distributions were made by MULTIDATA film densitometer using RTD-4 software, in INFLPR Linear Accelerator Department

  17. [Absorbed doses in dental radiology].

    Bianchi, S D; Roccuzzo, M; Albrito, F; Ragona, R; Anglesio, S

    1996-01-01

    The growing use of dento-maxillo-facial radiographic examinations has been accompanied by the publication of a large number of studies on dosimetry. A thorough review of the literature is presented in this article. Most studies were carried out on tissue equivalent skull phantoms, while only a few were in vivo. The aim of the present study was to evaluate in vivo absorbed doses during Orthopantomography (OPT). Full Mouth Periapical Examination (FMPE) and Intraoral Tube Panoramic Radiography (ITPR). Measurements were made on 30 patients, reproducing clinical conditions, in 46 anatomical sites, with 24 intra- and 22 extra-oral thermoluminiscent dosimeters (TLDS). The highest doses were measured, in orthopantomography, at the right mandibular angle (1899 mu Gy) in FMPE on the right naso-labial fold (5640 mu Gy and in ITPR on the palatal surface of the left second upper molar (1936 mu Gy). Intraoral doses ranged from 21 mu Gy, in orthopantomography, to 4494 mu Gy in FMPE. Standard errors ranged from 142% in ITPR to 5% in orthopantomography. The highest rate of standard errors was found in FMPE and ITPR. The data collected in this trial are in agreement with others in major literature reports. Disagreements are probably due to different exam acquisition and data collections. Such differences, presented comparison in several sites, justify lower doses in FMPE and ITPR. Advantages and disadvantages of in vivo dosimetry of the maxillary region are discussed, the former being a close resemblance to clinical conditions of examination and the latter the impossibility of collecting values in depth of tissues. Finally, both ITPR and FMPE required lower doses than expected, and can be therefore reconsidered relative to their radiation risk. PMID:8966249

  18. Absorbed Dose Distributions in Small Copper Wire Insulation due to Multiple-Sided Irradiations by 0.4 MeV Electrons

    Miller, Arne; McLaughlin, W. L.; Pedersen, Walther Batsberg; Pejtersen, K.

    When scanned electron beams are used to crosslink polymeric insulation of wire and cable, an important goal is to achieve optimum uniformity of absorbed dose distributions. Accurate measurements of dose distributions in a plastic dosimeter simulating a typical insulating material (polyethylene...... insulation thicknesses between 0.4 and 0.8 mm. The plastic dosimeter simulating polyethylene insulations was a thin radiochromic polyvinyl butyral film wrapped several times around the copper wire, such that when unwrapped and analyzed optically on a scanning microspectrophotometer, high-resolution radial...

  19. The role of nuclear reactions in Monte Carlo calculations of absorbed and biological effective dose distributions in hadron therapy

    Brons, S; Elsässer, T; Ferrari, A; Gadioli, E; Mairani, A; Parodi, K; Sala, P; Scholz, M; Sommerer, F

    2010-01-01

    Monte Carlo codes are rapidly spreading among hadron therapy community due to their sophisticated nuclear/electromagnetic models which allow an improved description of the complex mixed radiation field produced by nuclear reactions in therapeutic irradiation. In this contribution results obtained with the Monte Carlo code FLUKA are presented focusing on the production of secondary fragments in carbon ion interaction with water and on CT-based calculations of absorbed and biological effective dose for typical clinical situations. The results of the simulations are compared with the available experimental data and with the predictions of the GSI analytical treatment planning code TRiP.

  20. Development and verification of an analytical algorithm to predict absorbed dose distributions in ocular proton therapy using Monte Carlo simulations

    Proton beam radiotherapy is an effective and non-invasive treatment for uveal melanoma. Recent research efforts have focused on improving the dosimetric accuracy of treatment planning and overcoming the present limitation of relative analytical dose calculations. Monte Carlo algorithms have been shown to accurately predict dose per monitor unit (D/MU) values, but this has yet to be shown for analytical algorithms dedicated to ocular proton therapy, which are typically less computationally expensive than Monte Carlo algorithms. The objective of this study was to determine if an analytical method could predict absolute dose distributions and D/MU values for a variety of treatment fields like those used in ocular proton therapy. To accomplish this objective, we used a previously validated Monte Carlo model of an ocular nozzle to develop an analytical algorithm to predict three-dimensional distributions of D/MU values from pristine Bragg peaks and therapeutically useful spread-out Bragg peaks (SOBPs). Results demonstrated generally good agreement between the analytical and Monte Carlo absolute dose calculations. While agreement in the proximal region decreased for beams with less penetrating Bragg peaks compared with the open-beam condition, the difference was shown to be largely attributable to edge-scattered protons. A method for including this effect in any future analytical algorithm was proposed. Comparisons of D/MU values showed typical agreement to within 0.5%. We conclude that analytical algorithms can be employed to accurately predict absolute proton dose distributions delivered by an ocular nozzle.

  1. Experimental and theoretical determination of absorbed microwave dose rate distributions in phantom heads irradiated by an aperture source

    A thermographic technique is used to determine absorbed microwave energy distribution in phantom monkey and human heads irradiated by an aperture source. The phantom heads are brain equivalent tissue spheres and a bone and brain tissue geometric model of a monkey head. The results of the experiment are compared to patterns obtained from theoretical calculations, indicating good general agreement between experimental and theoretical data. The penetration of microwave energy is less for the phantom human head than for the monkey head. The overall poor penetration of the radiation due to the 2450 MHz aperture source used in this experiment indicates a need for further research using frequency and aperture dimensions as parameters to obtain desired microwave absorption patterns for both biological experiments and therapeutic applications. (author)

  2. On the definition of absorbed dose

    Purpose: The quantity absorbed dose is used extensively in all areas concerning the interaction of ionizing radiation with biological organisms, as well as with matter in general. The most recent and authoritative definition of absorbed dose is given by the International Commission on Radiation Units and Measurements (ICRU) in ICRU Report 85. However, that definition is incomplete. The purpose of the present work is to give a rigorous definition of absorbed dose. Methods: Absorbed dose is defined in terms of the random variable specific energy imparted. A random variable is a mathematical function, and it cannot be defined without specifying its domain of definition which is a probability space. This is not done in report 85 by the ICRU, mentioned above. Results: In the present work a definition of a suitable probability space is given, so that a rigorous definition of absorbed dose is possible. This necessarily includes the specification of the experiment which the probability space describes. In this case this is an irradiation, which is specified by the initial particles released and by the material objects which can interact with the radiation. Some consequences are discussed. Specific energy imparted is defined for a volume, and the definition of absorbed dose as a point function involves the specific energy imparted for a small mass contained in a volume surrounding the point. A possible more precise definition of this volume is suggested and discussed. Conclusions: The importance of absorbed dose motivates a proper definition, and one is given in the present work. No rigorous definition has been presented before. - Highlights: • A stringent definition of absorbed dose is given. • This requires the definition of an irradiation and a suitable probability space. • A stringent definition is important for an understanding of the concept absorbed dose

  3. Estimation of Absorbed Dose in Occlusal Radiography

    The purpose of this study was to estimate absorbed dose of each important anatomic site of phantom (RT-210 Head and Neck Section R, Humanoid Systems Co., U.S.A.) head in occlusal radiography. X-radiation dosimetry at 12 anatomic sites in maxillary anterior topography, maxillary posterior topography, mandibular anterior cross-section, mandibular posterior cross-section, mandibular anterior topographic, mandibular posterior topographic occlusal projection was performed with calcium sulfate thermoluminescent dosimeters under 70 Kvp and 15 mA, 1/4 second (8 inch cone ) and 1 second (16 inch cone) exposure time. The results obtained were as follows: Skin surface produced highest absorbed dose ranged between 3264 mrad and 4073 mrad but there was little difference between projections. In maxillary anterior topographic occlusal radiography, eyeballs, maxillary sinuses, and pituitary gland sites produced higher absorbed doses than those of other sites. In maxillary posterior topographic occlusal radiography, exposed eyeball site and exposed maxillary sinus site produced high absorbed doses. In mandibular anterior cross-sectional occlusal radiography, all sites were produced relatively low absorbed dose except eyeball sites. In Mandibular posterior cross-sectional occlusal radiography, exposed eyeball site and exposed maxillary sinus site were produced relatively higher absorbed doses than other sites. In mandibular anterior topographic occlusal radiography, maxillary sinuses, submandibular glands, and thyroid gland sites produced high absorbed doses than other sites. In mandibular posterior topographic occlusal radiography, submandibular gland site of the exposed side produced high absorbed dose than other sites and eyeball site of the opposite side produced relatively high absorbed dose.

  4. Estimation of Absorbed Dose in Occlusal Radiography

    Yoo, Young Ah; Choi, Karp Shick [Dept. of Oral Radiology, College of Dentistry, Kyungpuk National University, Daegu (Korea, Republic of); Lee, Sang Han [Dept. of Oral and Maxillofacial Surgery, College of Dentistry, Kyungpook National University, Daegu (Korea, Republic of)

    1990-02-15

    The purpose of this study was to estimate absorbed dose of each important anatomic site of phantom (RT-210 Head and Neck Section R, Humanoid Systems Co., U.S.A.) head in occlusal radiography. X-radiation dosimetry at 12 anatomic sites in maxillary anterior topography, maxillary posterior topography, mandibular anterior cross-section, mandibular posterior cross-section, mandibular anterior topographic, mandibular posterior topographic occlusal projection was performed with calcium sulfate thermoluminescent dosimeters under 70 Kvp and 15 mA, 1/4 second (8 inch cone) and 1 second (16 inch cone) exposure time. The results obtained were as follows: Skin surface produced highest absorbed dose ranged between 3264 mrad and 4073 mrad but there was little difference between projections. In maxillary anterior topographic occlusal radiography, eyeballs, maxillary sinuses, and pituitary gland sites produced higher absorbed doses than those of other sites. In maxillary posterior topographic occlusal radiography, exposed eyeball site and exposed maxillary sinus site produced high absorbed doses. In mandibular anterior cross-sectional occlusal radiography, all sites were produced relatively low absorbed dose except eyeball sites. In Mandibular posterior cross-sectional occlusal radiography, exposed eyeball site and exposed maxillary sinus site were produced relatively higher absorbed doses than other sites. In mandibular anterior topographic occlusal radiography, maxillary sinuses, submandibular glands, and thyroid gland sites produced high absorbed doses than other sites. In mandibular posterior topographic occlusal radiography, submandibular gland site of the exposed side produced high absorbed dose than other sites and eyeball site of the opposite side produced relatively high absorbed dose.

  5. Determination of absorbed dose in water

    This report describes the experimental work carried out for the determination of absorbed dose in water in the energy of X-rays generated at potentials of 100 kV to 250 kV. Two small cavity ionization chambers were used for this experiment. The results of these measurements were compared with the results obtained by using NPL Secondary Standard Therapy level X-ray exposure meter. The related problems of converting an exposure quantity into absorbed dose in water an absorbed dose in water have also been discussed. (Orig./A.B.)

  6. Absorbed dose by a CMOS in radiotherapy

    Borja H, C. G.; Valero L, C. Y.; Guzman G, K. A.; Banuelos F, A.; Hernandez D, V. M.; Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico); Paredes G, L. C., E-mail: candy_borja@hotmail.com [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2011-10-15

    Absorbed dose by a complementary metal oxide semiconductor (CMOS) circuit as part of a pacemaker, has been estimated using Monte Carlo calculations. For a cancer patient who is a pacemaker carrier, scattered radiation could damage pacemaker CMOS circuits affecting patient's health. Absorbed dose in CMOS circuit due to scattered photons is too small and therefore is not the cause of failures in pacemakers, but neutron calculations shown an absorbed dose that could cause damage in CMOS due to neutron-hydrogen interactions. (Author)

  7. Aerial gamma spectrometry of the uranium province of Lagoa Real (Caetite, BA, Brazil): go environmental aspects and distribution of the absorbed dose in the air

    In the present study, it was analyzed the surface concentrations of the natural radioelements K, U and Th, as well as the absorbed dose rate in air caused by gamma radiation from the Lagoa Real uranium province, which is located at the center southern portion of Bahia State and comprises an area of approximately 4.600 Km2. Data from the airborne gamma ray spectrometric survey of the region (Sao Timoeo Project) carried out in 1979, was used in this study. Besides, recent data of U, Th and absorbed dose rates from the Environmental Monitoring Program of the uranium concentration plant (URA), operated in the region by the Brazilian Nuclear Industries (INB), were used with the aim of inter compare the sampling points in the same geo referenced area. Imaging geo processing software's give support to frame maps of surface concentrations and ternary maps, as well as allow the integration of these with other themes (e.g. hydrology, geology, pedology) favouring the interpretation of geo environmental process from the radioactive cartography. Considering the whole study area, it was obtained the following mean values: absorbed dose rate in air (61,08 nGy.h-1), Potassium (1,65 % K) , Uranium (3,02 ppm eU) and thorium (18,26 ppm eTh). The geological unities bounding the uranium anomalies were placed in the areas characterized by the highest values of radioelements and, as expected, the major dose levels. The use of ternary maps coupled with the geology and hydrology allowed distinguishing the relationship between the surface distribution of natural radioelements and the geo environmental aspects, including the influence of the catchment in their transport and migration. (author)

  8. The Effects on Absorbed Dose Distribution in Intraoral X-ray Imaging When Using Tube Voltages of 60 and 70 kV for Bitewing Imaging

    Kristina Hellén-Halme; Mats Nilsson

    2013-01-01

    ABSTRACT Objectives Efforts are made in radiographic examinations to obtain the best image quality with the lowest possible absorbed dose to the patient. In dental radiography, the absorbed dose to patients is very low, but exposures are relatively frequent. It has been suggested that frequent low-dose exposures can pose a risk for development of future cancer. It has previously been reported that there was no significant difference in the diagnostic accuracy of approximal carious lesions in ...

  9. On the definition of absorbed dose

    Grusell, Erik

    2015-02-01

    Purpose: The quantity absorbed dose is used extensively in all areas concerning the interaction of ionizing radiation with biological organisms, as well as with matter in general. The most recent and authoritative definition of absorbed dose is given by the International Commission on Radiation Units and Measurements (ICRU) in ICRU Report 85. However, that definition is incomplete. The purpose of the present work is to give a rigorous definition of absorbed dose. Methods: Absorbed dose is defined in terms of the random variable specific energy imparted. A random variable is a mathematical function, and it cannot be defined without specifying its domain of definition which is a probability space. This is not done in report 85 by the ICRU, mentioned above. Results: In the present work a definition of a suitable probability space is given, so that a rigorous definition of absorbed dose is possible. This necessarily includes the specification of the experiment which the probability space describes. In this case this is an irradiation, which is specified by the initial particles released and by the material objects which can interact with the radiation. Some consequences are discussed. Specific energy imparted is defined for a volume, and the definition of absorbed dose as a point function involves the specific energy imparted for a small mass contained in a volume surrounding the point. A possible more precise definition of this volume is suggested and discussed. Conclusions: The importance of absorbed dose motivates a proper definition, and one is given in the present work. No rigorous definition has been presented before.

  10. Definition of spatial distribution of the absorbed dose of γ-radiation source 60Co for installation URI

    The study of energy distribution among different objects (as well as forms of energy absorption in them) being researched in radiation chemistry, radiobiology and micro-dosimetry has become one of the actual problems recently. Impossibility of practical parameters definition makes the theoretical solution of the problem one of the major tasks in this field. The most probable primary processes of interaction the γ-radiation with subjects of inquiry are Compton dispersion and photoeffect. Therefore in this work on the base of Compton dispersion and photoeffect an entire spectrum of dispersive γ-quanta and δ-electrons formed in the result of monoenergetic γ-quanta interaction with different media (gaseous, liquid, solid) is calculated. The flux density of γ-quanta in any part of cylindrical working volume is determined. Section of interaction of monoenergetic γ-quanta with the medium is calculated by the equation of Klein-Nishina-Tamm and Bete. Depending on energy spectrum of δ-electrons obtained in the result of the interaction their average energy is determined by means of stepping method. Interaction process cross-sectional of δ-electrons with the medium is determined by the equation of Grizinsky. The account proceeded up to value of δ-electrons energy approached to value of medium ionization energy. Dose rate received by a calculation way on the formula: P = k·φi (k - the constant of transition from density of a flow to a dose) to within ±5 % coincides with experimental values. The account was carried out on the basis of installations available in Section of Radiation Researches National Academy of Science of Azerbaijan, and on the basis of the mathematical program Mathcad

  11. Specification of absorbed dose for reporting a therapeutic irradiation

    The problem of dose specification in external beam therapy with photons and electrons has been dealt with in ICRU Report 29 (1978). This problem arises from the fact that the absorbed dose distribution is usually not uniform in the target volume and that for the purpose of treatment reporting a nominal absorbed dose - which will be called target absorbed dose - has to be selected. When comparing the clinical results obtained between radiotherapy centres, the differences in the reported target absorbed doses which can be introduced by differences in the methods of dose specification often are much larger than the differences related to the dosimetric procedures themselves. This shows the importance of the problem. In this paper, some definitions of terms and concepts currently used in radiotherapy are first recalled: tumour volume, target volume, treatment volume, etc. These definitions have been proposed in ICRU Report 29 for photon and electron beams; they can be extended to any kind of irradiation. For external beam therapy with photons and electrons, the target absorbed dose is defined as the absorbed dose at selected point(s) (specification point(s)) having a meaningful relation to the target volume and/or the irradiation beams. Examples are discussed for typical cases. As far as interstitial and intracavitary therapy is concerned, the problem is more complex and no recommendations have so far been made by the ICRU Commission. A major difficulty arises from the sharp dose gradient as a function of the distance to the sources. The particular case of the treatment of cervix carcinoma is considered and some possible methods of specification are discussed: (1) the indication of the sources (in adequate units) and the duration of the application, (2) the absorbed doses at selected reference points (bladder, rectum, bony structures) and (3) the description of the tissue volume (height, width, thickness) encompassed by a given isodose surface (60Gy). (author)

  12. Absorbed Doses to Patients in Nuclear Medicine

    The work with a Swedish catalogue of radiation absorbed doses to patients undergoing nuclear medicine investigations has continued. After the previous report in 1999, biokinetic data and dose estimates (mean absorbed dose to various organs and tissues and effective dose) have been produced for a number of substances: 11C- acetate, 11C- methionine, 18F-DOPA, whole antibody labelled with either 99mTc, 111In, 123I or 131I, fragment of antibody, F(ab')2 labelled with either 99mTc, 111In, 123I or 131I and fragment of antibody, Fab' labelled with either 99mTc, 111In, 123I or 131I. The absorbed dose estimates for these substances have been made from published biokinetic information. For other substances of interest, e.g. 14C-urea (children age 3-6 years), 14C-glycocholic acid, 14C-xylose and 14C-triolein, sufficient literature data have not been available. Therefore, a large number of measurements on patients and volunteers have been carried out, in order to determine the biokinetics and dosimetry for these substances. Samples of breast milk from 50 mothers, who had been subject to nuclear medicine investigations, have been collected at various times after administration of the radiopharmaceutical to the mother. The activity concentration in the breast milk samples has been measured. The absorbed dose to various organs and tissues and the effective dose to the child who ingests the milk have been determined for 17 different radiopharmaceuticals. Based on these results revised recommendations for interruption of breast-feeding after nuclear medicine investigations are suggested

  13. Evaluation and comparison of human absorbed dose of 90Y-DOTA-Cetuximab in various age groups based on distribution data in rats

    The organ radiation-absorbed doses have been evaluated for humans in six age groups and both genders based on animal data. After intravenous administration of 90Y-DOTA-Cetuximab to five groups of rats, they were sacrificed at exact time intervals (2, 24, 48, 72, and 96 h) and the percentage of injected dose per gram of each organ was calculated by direct counting from rat data. By using the formulation that Medical Internal Radiation Dose suggests, radiation-absorbed doses for all organs were calculated and extrapolated from rat to human. The total body absorbed dose for all groups was >22 mGy due to pure β-emission of the applied radiopharmaceutical. The effective dose resulting from an intravenously injected activity of 100 MBq is 56.7 mSv for a 60-kg female adult and 60.3 mSv for a 73-kg male adult. The results demonstrated the usefulness of this method for estimation of β-absorbed dose in humans. (author)

  14. Absorbed doses from temporomandibular joint radiography

    Brooks, S.L.; Lanzetta, M.L.

    1985-06-01

    Thermoluminescent dosimeters were used in a tissue-equivalent phantom to measure doses of radiation absorbed by various structures in the head when the temporomandibular joint was examined by four different radiographic techniques--the transcranial, transorbital, and sigmoid notch (Parma) projections and the lateral tomograph. The highest doses of radiation occurred at the point of entry for the x-ray beam, ranging from 112 mrad for the transorbital view to 990 mrad for the sigmoid notch view. Only the transorbital projection a radiation dose to the lens of the eye. Of the four techniques evaluated, the lateral tomograph produced the highest doses to the pituitary gland and the bone marrow, while the sigmoid notch radiograph produced the highest doses to the parotid gland.

  15. Absorbed doses from temporomandibular joint radiography

    Thermoluminescent dosimeters were used in a tissue-equivalent phantom to measure doses of radiation absorbed by various structures in the head when the temporomandibular joint was examined by four different radiographic techniques--the transcranial, transorbital, and sigmoid notch (Parma) projections and the lateral tomograph. The highest doses of radiation occurred at the point of entry for the x-ray beam, ranging from 112 mrad for the transorbital view to 990 mrad for the sigmoid notch view. Only the transorbital projection a radiation dose to the lens of the eye. Of the four techniques evaluated, the lateral tomograph produced the highest doses to the pituitary gland and the bone marrow, while the sigmoid notch radiograph produced the highest doses to the parotid gland

  16. Photon absorbed dose: the UK standard

    Since 1988, the primary standard for megavoltage photon dosimetry in the UK has been a graphite calorimeter. The routine calibration of secondary standard ionisation chambers has been provided by NPL directly in terms of absorbed dose to water since then, with users following the 1990 IPSM Code of Practice. Comparisons of the primary standard with NPL's reference ionisation chambers have been carried out annually, and the calibration service has been offered in the spring and autumn each year, for 60Co γ-rays and 4 MV to 19 MV X-rays. The data generated have been analysed and the results of this analysis are presented here. The long-term stability of the NE 2561 chamber, and its value in maintaining the standard of absorbed dose is demonstrated. The utility of TPR as a beam quality parameter is discussed, and the resulting ambiguity in chamber calibration is quantified. The conversion of dose from graphite to water is summarized, and changes in the basis of the NPL absorbed dose standard over the last seven years are described

  17. Problems in radiation absorbed dose estimation from positron emitters

    The positron emitters commonly used in clinical imaging studies for the most part are short-lived, so that when they are distributed in the body the radiation absorbed dose is low even though most of the energy absorbed is from the positrons themselves rather than the annihilation radiation. These considerations do not apply to the administration pathway for a radiopharmaceutical where the activity may be highly concentrated for a brief period rather than distributed in the body. Thus, high local radiation absorbed doses to the vein for an intravenous administration and to the upper airways during administration by inhalation can be expected. For these geometries, beta point source functions (FPS's) have been employed to estimate the radiation absorbed dose in the present study. Physiologic measurements were done to determine other exposure parameters for intravenous administration of O-15 and Rb-82 and for administration of O-15-CO2 by continuous breathing. Using FPS's to calculate dose rates to the vein wall from O-15 and Rb-82 injected into a vein having an internal radius of 1.5 mm yielded dose rates of 0.51 and 0.46 (rad x g/μCi x h), respectively. The dose gradient in the vein wall and surrounding tissues was also determined using FPS's. Administration of O-15-CO2 by continuous breathing was also investigated. Using ultra-thin thermoluninescent dosimeters (TLD's) having the effective thickness of normal tracheal mucosa, experiments were performed in which 6 dosimeters were exposed to known concentrations of O-15 positrons in a hemicylindrical tracheal phantom having an internal radius of 0.96 cm and an effective length of 14 cm. The dose rate for these conditions was 3.4 (rads/h)/(μCi/cm3). 15 references, 7 figures, 6 tables

  18. Specific absorbed fractions and S-factors for calculating absorbed dose to embryo and fetus

    The variation of specific absorbed fractions from maternal tissues to embryo/fetus is investigated for four different target masses and geometries. S-factors are calculated for selected radionuclides assumed to be distributed uniformly in fetal tissues represented by spheres from 1 mg to 4 kg. As an example, the dose to fetal tissues for iodine-131 and iron-59 is estimated based on human biokinetic data for various stages of pregnancy. 24 references, 4 tables

  19. Determination of absorbed dose in reactors

    There are many areas in the use and operation of research reactors where the absorbed dose and the neutron fluence are required. These include work on the determination of the radiolytic stability of the coolant and moderator and on the determination of radiation damage in structural materials, and reactor experiments involving radiation chemistry and radiation biology. The requirements range from rough estimates of the total heating due to radiation to precise values specifying the contributions of gamma rays, thermal neutrons and fast neutrons. To meet all these requirements a variety of experimental measurements and calculations as well as a knowledge of reactor radiations and their interactions is necessary. Realizing the complexity and importance of this field, its development at widely separated laboratories and the need to bring the experts in this work together, the IAEA has convened three panel meetings. These were: 'In-pile dosimetry', held in July 1964 (published by the Agency as Technical Reports Series No. 46); 'Neutron fluence measurements', in October 1965; and 'In-pile dosimetry', in November 1966. The recommendations of these three panels led the Agency to form a Working Group on Reactor Radiation Measurements and to commission the writing of this book and a book on Neutron Fluence Measurements. The latter was published in May 1970 (Technical Reports Series No. 107). The material on neutron fluence and absorbed dose measurements is widely scattered in reports and reviews. It was considered that it was time for all relevant information to be evaluated and put together in the form of a practical guide that would be valuable both to experienced workers and beginners in the field

  20. Análise da distribuição espacial de dose absorvida em próton terapia ocular Spatial distribution analysis of absorbed dose in ocular proton radiation therapy

    Marília Tavares Christóvão

    2010-08-01

    of proton therapy were performed based on preexisting facilities. RESULTS: Simulation data were integrated into SISCODES on the eye's model generating spatial dose distributions. Dose depth profiles reproducing the pure and modulated Bragg peaks are presented. Relevant aspects of proton beam radiotherapy planning are considered such as material absorber, modulation, collimator dimensions, incident proton energy and isodose generation. CONCLUSION: The conclusion is that proton therapy when properly modulated and directed can reproduce the ideal conditions for the dose deposition in the treatment of ocular tumors.

  1. Uncertainty analysis for absorbed dose from a brain receptor imaging agent

    Aydogan, B.; Miller, L.F. [Univ. of Tennessee, Knoxville, TN (United States). Nuclear Engineering Dept.; Sparks, R.B. [Oak Ridge Inst. for Science and Education, TN (United States); Stubbs, J.B. [Radiation Dosimetry Systems of Oak Ridge, Inc., Knoxville, TN (United States)

    1999-01-01

    Absorbed dose estimates are known to contain uncertainties. A recent literature search indicates that prior to this study no rigorous investigation of uncertainty associated with absorbed dose has been undertaken. A method of uncertainty analysis for absorbed dose calculations has been developed and implemented for the brain receptor imaging agent {sup 123}I-IPT. The two major sources of uncertainty considered were the uncertainty associated with the determination of residence time and that associated with the determination of the S values. There are many sources of uncertainty in the determination of the S values, but only the inter-patient organ mass variation was considered in this work. The absorbed dose uncertainties were determined for lung, liver, heart and brain. Ninety-five percent confidence intervals of the organ absorbed dose distributions for each patient and for a seven-patient population group were determined by the ``Latin Hypercube Sampling`` method. For an individual patient, the upper bound of the 95% confidence interval of the absorbed dose was found to be about 2.5 times larger than the estimated mean absorbed dose. For the seven-patient population the upper bound of the 95% confidence interval of the absorbed dose distribution was around 45% more than the estimated population mean. For example, the 95% confidence interval of the population liver dose distribution was found to be between 1.49E+0.7 Gy/MBq and 4.65E+07 Gy/MBq with a mean of 2.52E+07 Gy/MBq. This study concluded that patients in a population receiving {sup 123}I-IPT could receive absorbed doses as much as twice as large as the standard estimated absorbed dose due to these uncertainties.

  2. Simultaneous measurements of absorbed dose and linear energy transfer in therapeutic proton beams

    Granville, Dal A.; Sahoo, Narayan; Sawakuchi, Gabriel O.

    2016-02-01

    The biological response resulting from proton therapy depends on both the absorbed dose in the irradiated tissue and the linear energy transfer (LET) of the beam. Currently, optimization of proton therapy treatment plans is based only on absorbed dose. However, recent advances in proton therapy delivery have made it possible to vary the LET distribution for potential therapeutic gain, leading to investigations of using LET as an additional parameter in plan optimization. Having a method to measure and verify both absorbed dose and LET as part of a quality assurance program would be ideal for the safe delivery of such plans. Here we demonstrated the potential of an optically stimulated luminescence (OSL) technique to simultaneously measure absorbed dose and LET. We calibrated the ratio of ultraviolet (UV) to blue emission intensities from Al2O3:C OSL detectors as a function of LET to facilitate LET measurements. We also calibrated the intensity of the blue OSL emission for absorbed dose measurements and introduced a technique to correct for the LET-dependent dose response of OSL detectors exposed to therapeutic proton beams. We demonstrated the potential of our OSL technique by using it to measure LET and absorbed dose under new irradiation conditions, including patient-specific proton therapy treatment plans. In the beams investigated, we found the OSL technique to measure dose-weighted LET within 7.9% of Monte Carlo-simulated values and absorbed dose within 2.5% of ionization chamber measurements.

  3. Absorbed dose determination in photon fields using the tandem method

    The purpose of this work is to develop an alternative method to determine the absorbed dose and effective energy of photons with unknown spectral distributions. It includes a 'tandem' system that consists of two thermoluminescent dosemeters with different energetic dependence. LiF: Mg, Ti, CaF2: Dy thermoluminescent dosemeters and a Harshaw 3500 reading system are employed. Dosemeters are characterized with 90Sr-90Y, calibrated with the energy of 60Co and irradiated with seven different qualities of x-ray beams, suggested by ANSI No. 13 and ISO 4037. The answers of each type of dosemeter are adjusted to a function that depends on the effective energy of photons. The adjustment is carried out by means of the Rosenbrock minimization algorithm. The mathematical model used for this function includes five parameters and has a gauss and a straight line. Results show that the analytical functions reproduce the experimental data of the answers, with a margin of error of less than 5%. The reason of the answers of the CaF2: Dy and LiF: Mg, Ti, according to the energy of the radiation, allows us to establish the effective energy of photons and the absorbed dose, with a margin of error of less than 10% and 20% respectively

  4. Evaluation of absorbed dose in Gadolinium neutron capture therapy

    Abdullaeva Gayane; Djuraeva Gulnara; Kim Andrey; Koblik Yuriy; Kulabdullaev Gairatulla; Rakhmonov Turdimukhammad; Saytjanov Shavkat

    2015-01-01

    Gadolinium neutron capture therapy (GdNCT) is used for treatment of radioresistant malignant tumors. The absorbed dose in GdNCT can be divided into four primary dose components: thermal neutron, fast neutron, photon and natural gadolinium doses. The most significant is the dose created by natural gadolinium. The amount of gadolinium at the irradiated region is changeable and depends on the gadolinium delivery agent and on the structure of the location where the agent i...

  5. An international intercomparison of absorbed dose measurements for radiation therapy

    Dose intercomparison on an international basis has become an important component of quality assurance measurement i.e. to check the performance of absorbed dose measurements in radiation therapy. The absorbed dose to water measurements for radiation therapy at the SSDL, MINT have been regularly compared through international intercomparison programmes organised by the IAEA Dosimetry Laboratory, Seibersdorf, Austria such as IAEA/WHO TLD postal dose quality audits and the Intercomparison of therapy level ionisation chamber calibration factors in terms of air kerma and absorbed dose to water calibration factors. The results of these intercomparison in terms of percentage deviations for Cobalt 60 gamma radiation and megavoltage x-ray from medical linear accelerators participated by the SSDL-MINT during the year 1985-2001 are within the acceptance limit. (Author)

  6. Absorbed doses to patients from angioradiology

    The aim of study was to know patients doses exposes when three different procedures of angioradiology were carried out. The explorations considered were drainage biliary, varicocele embolization and dacriocistography made in the Radiodiagnostic Service at the University Hospital of Canary Islands, Tenerife (Spain). In total 14 patients were studied. The measurements were made using large area transmission ionisation chamber which gives the values of Dose Area Product (DAP). In addition, thermoluminescent dosimeters type TLD-100 were used in anthropomorphic phantom in order to obtain values of organ doses when the phantom was submitted to the same procedures rather than the actual patients. Furthermore, the Effdose program was used to estimate the effective doses in the procedures conditions. The values for DAP were in the range of 70-300 for drainage biliary, 43-180 for varicocele embolization and 1.4-9 for dacriocistography. The organ doses measured with TLD-100 were higher than the corresponding values estimated by Effdose program. The results for varicocele embolization were higher than other published data. In the case of drainage biliary procedure, the values were closed to other published results. It was not possible to find data for dacriocistography from other authors. (author)

  7. Direct MC conversion of absorbed dose to graphite to absorbed dose to water for 60Co radiation.

    Lye, J E; Butler, D J; Franich, R D; Harty, P D; Oliver, C P; Ramanathan, G; Webb, D V; Wright, T

    2013-06-01

    The ARPANSA calibration service for (60)Co gamma rays is based on a primary standard graphite calorimeter that measures absorbed dose to graphite. Measurements with the calorimeter are converted to the absorbed dose to water using the calculation of the ratio of the absorbed dose in the calorimeter to the absorbed dose in a water phantom. ARPANSA has recently changed the basis of this calculation from a photon fluence scaling method to a direct Monte Carlo (MC) calculation. The MC conversion uses an EGSnrc model of the cobalt source that has been validated against water tank and graphite phantom measurements, a step that is required to quantify uncertainties in the underlying interaction coefficients in the MC code. A comparison with the Bureau International des Poids et Mesures (BIPM) as part of the key comparison BIPM.RI(I)-K4 showed an agreement of 0.9973 (53). PMID:23152147

  8. In vivo dosimetry for head and neck carcinoma: determination of target absorbed dose from entrance and exit absorbed dose measurements

    Farhat, L.; Daoud, J. [Service de radiotherapie carcinologique, CHU Habib-Bourguiba, 3029 Sfax (Tunisia); Besbes, M. [Service de radiotherapie carcinologique, Institut Salah-Azaiz, Boulevard du 9-avril-Bab-Saadoun, 1006 Tunis (Tunisia); Bridier, A. [Service de radiophysique, Institut Gustave-Roussy, 39 rue Camille-Desmoulins, 94805 Villejuif Cedex (France)

    2011-04-15

    The aims of this work were to measure the entrance and exit dose for patient treated for head and neck tumors. The target absorbed dose was determined from the exit and entrance dose measurement. Twenty patients were evaluated. The results were compared to the calculated values and the midline dose was determinate and compared with the prescribed dose. 80 entrance doses and 80 exit doses measurements were performed. The average difference from expected values was 1.93% for entrance dose (SD 1.92%) and -0.34% for exit dose (SD 4.1%). The target absorbed dose differed from prescribed dose values by 2.94% (1.97%) for the results using the Noel method and 3.34% (SD: 2.29%) with the Rizzotti method. The total uncertainty budget in the measurement of the absorbed entrance and exit dose with diode, including diode reading, correction factors and diode calibration coefficient, is determined as 3.02% (1 s). Simple in vivo dose measurements are an additional safeguard against major setup errors and calculation or transcription errors that were missed during pre-treatment chart check. (authors)

  9. Evaluation of the absorbed dose in odontological computerized tomography

    This paper evaluated the absorbed dose at the surface entry known as 'cone beam computed tomography' (CBCT) in odontological computerized tomography. Examination were simulated with CBCT for measurements of dose. A phantom were filled with water, becoming scatter object of radiation. Thermoluminescent dosemeters were positioned on points correspondent to eyes and salivary glands

  10. Phantoms for calculations of absorbed organ dose

    We have developed a computer code IDES (Internal Dose Estimation System). In this code, MIRD Transformation Method is used and photon simulation by Monte Carlo method is also possible. We have studied Japanese phantoms in two procedures, mathematical phantom and 'symbol phantoms'. Our mathematical phantoms realize their height and body weights but does not hold some of organ weights, which were measured by TANAKA and KAWAMURA. The symbol phantom can solve this discrepancy and realize a realistic phantom, although it remains problems of authorization and normalization. Errors were estimated for internal dose calculations and it was pointed out that to use realistic organ weights and parameters of kinetics was important competitively to reduce uncertainty of the results. (author)

  11. Electron scattering effects on absorbed dose measurements with LiF-dosemeters

    The investigation deals with absorbed dose measurements with solid wall-less dosemeters. Electron scattering complicates both measurement of absorbed dose and its theoretical interpretation. The introduction of the dosemeter in a medium causes perturbations of the radiation field. This perturbation and its effect on the distribution of the absorbed dose inside the dosemeter is studied. Plane-parallel LiF-teflon dosemeters (0.005 - 0.1 g.cm-2) are irradiated by a photon beam (137Cs) in different media. The investigation shows that corrections must be made for perturbations caused by electron scattering phenomena. Correction factors are given for use in accurate absorbed dose determinations with thermoluminescent dosemeters. (Auth.)

  12. Thyroid absorbed dose using TLDs during mammography

    Gonzalez A, M.; Melendez L, M. [IPN, Centro de Investigacion y de Estudios Avanzados, Av. IPN 2508, Col. San Pedro Zacatenco, 07360 Mexico D. F. (Mexico); Davila M, P., E-mail: biomedica.sst@gmail.com [UNEME-DEDICAM de Ciudad Victoria, Circuito Medico s/n, 87087 Ciudad Victoria, Tamaulipas (Mexico)

    2015-10-15

    Full text: In this study, the mean glandular dose (MGD) and the thyroid dose (D Thy) were measured in 200 women screened with mammography in Cranio caudal (Cc) and mediolateral oblique projections. All mammograms were performed with Giotto-Ims (6000-14-M2 Model) equipment, which was verified to meet the criteria of quality of NOM-229-Ssa-2002. During audits performance and HVL, for each anode filter combinations was measured with the camera Radcal mammography equipment 10 X 6-6M (HVL = 0.26 mm Al). D Thy measurements were performed with TLD dosimeters (LiF:Mn) , that were read with the Harshaw 3500 TLD reader. The MGD, was obtained according to the UK and European protocols for mammographic dosimetry using a plane parallel chamber (Standard Imaging, Model A-600) calibrated by a radiation beam UW-23-Mo (= 0.279 mm Al HVL). A comparative statistical analysis was carried out with the measured MGD and D thy. The thyroid mean dose was 0.063 mGy and 0.078 mGy for Cc and mediolateral oblique respectively. There is a linear correlation between the MGD and the D Thy slightly influenced by the anode-filter combination. Using a 95% for the confidence interval in MGD (1.07 mGy), the 90% of measurements are in agreement with the established uncertainty limits. The D Thy are lower than the MGD. There is no risk for cancer induction in thyroid in women due to mammography screening. (Author)

  13. Thyroid absorbed dose using TLDs during mammography

    Full text: In this study, the mean glandular dose (MGD) and the thyroid dose (D Thy) were measured in 200 women screened with mammography in Cranio caudal (Cc) and mediolateral oblique projections. All mammograms were performed with Giotto-Ims (6000-14-M2 Model) equipment, which was verified to meet the criteria of quality of NOM-229-Ssa-2002. During audits performance and HVL, for each anode filter combinations was measured with the camera Radcal mammography equipment 10 X 6-6M (HVL = 0.26 mm Al). D Thy measurements were performed with TLD dosimeters (LiF:Mn) , that were read with the Harshaw 3500 TLD reader. The MGD, was obtained according to the UK and European protocols for mammographic dosimetry using a plane parallel chamber (Standard Imaging, Model A-600) calibrated by a radiation beam UW-23-Mo (= 0.279 mm Al HVL). A comparative statistical analysis was carried out with the measured MGD and D thy. The thyroid mean dose was 0.063 mGy and 0.078 mGy for Cc and mediolateral oblique respectively. There is a linear correlation between the MGD and the D Thy slightly influenced by the anode-filter combination. Using a 95% for the confidence interval in MGD (1.07 mGy), the 90% of measurements are in agreement with the established uncertainty limits. The D Thy are lower than the MGD. There is no risk for cancer induction in thyroid in women due to mammography screening. (Author)

  14. Absorbed dose simulations in near-surface regions using high dose rate Iridium-192 sources applied for brachytherapy

    Brachytherapy treatment with Iridium-192 high dose rate (HDR) sources is widely used for various tumours and it could be developed in many anatomic regions. Iridium-192 sources are inserted inside or close to the region that will be treated. Usually, the treatment is performed in prostate, gynaecological, lung, breast and oral cavity regions for a better clinical dose coverage compared with other techniques, such as, high energy photons and Cobalt-60 machines. This work will evaluate absorbed dose distributions in near-surface regions around Ir-192 HDR sources. Near-surface dose measurements are a complex task, due to the contribution of beta particles in the near-surface regions. These dose distributions should be useful for non-tumour treatments, such as keloids, and other non-intracavitary technique. For the absorbed dose distribution simulations the Monte Carlo code PENELOPE with the general code penEasy was used. Ir-192 source geometry and a Polymethylmethacrylate (PMMA) tube, for beta particles shield were modelled to yield the percentage depth dose (PDD) on a cubic water phantom. Absorbed dose simulations were realized at the central axis to yield the Ir-192 dose fall-off along central axis. The results showed that more than 99.2% of the absorbed doses (relative to the surface) are deposited in 5 cm depth but with slower rate at higher distances. Near-surface treatments with Ir-192 HDR sources yields achievable measurements and with proper clinical technique and accessories should apply as an alternative for treatment of lesions where only beta sources were used. - Highlights: ► A PMMA (polymethylmethacrylate) tube was used to surround the HDR Ir-192 to shield the beta particles. ► 99.2% of the absorbed doses (relative to the surface) are deposited in 5 cm depth. ► Near-surface treatments with Ir-192 HDR sources yields achievable measurements

  15. Electron absorbed dose measurements in LINACs by thermoluminescent dosimeters

    In this work, electron absorbed doses measurements in radiation therapy (RT) were obtained. Radiation measurements were made using thermoluminescent dosimeters of calcium sulfate doped with dysprosium (CaSO4:Dy) and zirconium oxide (ZrO2). TL response calibration was obtained by irradiating TLDs and a Farmer cylindrical ionization chamber PTW 30013 at the same time. Each TL material showed a typical glow curve according to each material. Both calcium sulfate doped with dysprosium and zirconium oxide exhibited better light intensity to high energy electron beam compared with lithium fluoride. TL response as a function of absorbed dose was analyzed. TL response as a function of high energy electron beam was also studied. - Highlights: • Experimental results of ZrO2 irradiated by high energy electron beam. • Dosimetric characteristics of CaSO4:Dy were obtained under high energy electron effect. • Absorbed dose in electron beam was determined by TL phosphors. • Absorbed dose could be measured by TL phosphors and the results suggest that phosphors are good candidate for absorbed dose determining

  16. Calculus of spatial distribution of absorbed dose to cellular level by Monte Carlo simulation for a radio-labelled peptide with 188Re and with nuclear internalization : preliminary results

    The 188Re is a radionuclide of radiation gamma emitter, useful in obtaining of gamma-graphic images, but it is also emitter of beta radiations and Auger electrons. A bio-molecule directed to a specific receptor of a cancer cell labeled with a emitter radionuclide of beta particles and Auger electrons, as the 188Re-Tat-Bombesin, it has the potential to be used in radiotherapy of molecular targets for its capacity to penetrate to cellular nucleus. In this system, the radiation dose is distributed in way located at microscopic levels in sub cellular specific places, where Auger emissions contributes of significant way in absorbed dose. The cellular dosimetry is realized in most of cases, using analytic or semi analytical methods, for example the cellular MIRD methodology. However, it is required to complement these calculations simulating the electrons transport and considering experimental bio kinetics data. Therefore, in this work preliminary results are presented of dosimetric calculation to sub cellular level for 188Re-Tat-Bombesin by Monte Carlo simulation, using the 2008 version of PENELOPE: PENEASY code. The spatial distribution of absorbed dose in membrane, cytoplasm and nucleus, was calculated with geometry of a cell of 10 μm of diameter, a nucleus of 2 μm of ratio and membrane of 0.2 μm of thickness, considering elementary constitution for each cellular compartment proposal in literature. The total number of disintegrations at sub cellular level was evaluated integrating the activity in function of time starting from experimental bio kinetics data in mamma cancer cells MDA-MB231. The preliminary results show that 46.4% of total disintegrations for unit of captured activity by cell occurs in nucleus, 38.4% in membrane and 15.2% in cytoplasm. The due absorbed dose to Auger electrons for 1 Bq of 188Re located in cellular membrane were respectively of 1.32E-1 and 1.43E-1 Gy in cytoplasm and nucleus. (Author)

  17. Patient absorbed radiation doses estimation related to irradiation anatomy

    Developed a direct equation to estimate the absorbed dose to the patient in x-ray examinations, using electric, geometric parameters and filtering combined with data from irradiated anatomy. To determine the absorbed dose for each examination, the entrance skin dose (ESD) is adjusted to the thickness of the patient's specific anatomy. ESD is calculated from the estimated KERMA greatness in the air. Beer-Lambert equations derived from power data mass absorption coefficients obtained from the NIST / USA, were developed for each tissue: bone, muscle, fat and skin. Skin thickness was set at 2 mm and the bone was estimated in the central ray of the site, in the anteroposterior view. Because they are similar in density and attenuation coefficients, muscle and fat are treated as a single tissue. For evaluation of the full equations, we chose three different anatomies: chest, hand and thigh. Although complex in its shape, the equations simplify direct determination of absorbed dose from the characteristics of the equipment and patient. The input data is inserted at a single time and total absorbed dose (mGy) is calculated instantly. The average error, when compared with available data, is less than 5% in any combination of device data and exams. In calculating the dose for an exam and patient, the operator can choose the variables that will deposit less radiation to the patient through the prior analysis of each combination of variables, using the ALARA principle in routine diagnostic radiology sector

  18. Absorbed dose to water reference dosimetry using solid phantoms in the context of absorbed-dose protocols

    For reasons of phantom material reproducibility, the absorbed dose protocols of the American Association of Physicists in Medicine (AAPM) (TG-51) and the International Atomic Energy Agency (IAEA) (TRS-398) have made the use of liquid water as a phantom material for reference dosimetry mandatory. In this work we provide a formal framework for the measurement of absorbed dose to water using ionization chambers calibrated in terms of absorbed dose to water but irradiated in solid phantoms. Such a framework is useful when there is a desire to put dose measurements using solid phantoms on an absolute basis. Putting solid phantom measurements on an absolute basis has distinct advantages in verification measurements and quality assurance. We introduce a phantom dose conversion factor that converts a measurement made in a solid phantom and analyzed using an absorbed dose calibration protocol into absorbed dose to water under reference conditions. We provide techniques to measure and calculate the dose transfer from solid phantom to water. For an Exradin A12 ionization chamber, we measured and calculated the phantom dose conversion factor for six Solid WaterTM phantoms and for a single Lucite phantom for photon energies between 60Co and 18 MV photons. For Solid WaterTM of certified grade, the difference between measured and calculated factors varied between 0.0% and 0.7% with the average dose conversion factor being low by 0.4% compared with the calculation whereas for Lucite, the agreement was within 0.2% for the one phantom examined. The composition of commercial plastic phantoms and their homogeneity may not always be reproducible and consistent with assumed composition. By comparing measured and calculated phantom conversion factors, our work provides methods to verify the consistency of a given plastic for the purpose of clinical reference dosimetry

  19. DETERMINATION OF SUPERFICIAL ABSORBED DOSE FROM EXTERNAL EXPOSURE OF WEAKLY PENETRATING RADIATIONS

    陈丽姝

    1994-01-01

    The methods of determining the superficial absorbed dose distributions in a water phantom by means of the experiments and available theories have been reported.The distributions of beta dose were measured by an extrapolation ionization chamber at definite depthes corresponding to some superficial organs and tissues such as the radiosensitive layer of the skin,cornea,sclera,anterior chamber and lens of eyeball.The ratios among superficial absorbed dose D(0.07) and average absorbed doses at the depthes 1,2,3,4,5 and 6mm are also obtained with Cross's methods.They can be used for confining the deterministic effects of some superficial tissues and organs such as the skin and the components of eyeball for weakly penetrating radiations.

  20. The effect of the male-female body-size difference on absorbed dose-rate distributions in humans from natural gamma rays

    Previous calculations of the natural gamma dose to human organs and tissues were based on the MIRD phantom, a 70 kg hermaphrodite model representing both sexes. This phantom was scaled down to 58 kg, the weight of the ICRP reference female. The effective dose to the reference male and female, based on the unaltered phantom and the scaled phantom respectively, were calculated and averaged to give revised doses to the U.S. population. The dose to females tends to be higher than to males. The over-all effect is about 10%. For most tissues the use of the hermaphrodite model results in a 5% underestimate in population dose values. Hence the correction for the male-female body size difference is to add 1-2 mrad/yr to the estimate of the gamma-ray dose rate to the U.S. population. On this basis, the average annual natural gamma-ray doses to the population are 33 +- 0.1 mrad/yr to the active marrow. The respective body-shielding factors are 0.598 +- 0.009 and 0.608 +- 0.0002 rad/R. (author)

  1. Effects of body and organ size on absorbed dose: there is no standard patient

    The problem of estimating the absorbed dose to organs and tissues of the human body due to the presence of a radiopharmaceutical in one or more organs is discussed. Complications are introduced by the fact that the body is not homogeneous and in many cases the organ shapes are not regular. Publications of the MIRD Committee have provided a direct means of estimating the absorbed dose (or absorbed fraction) for a number of radioisotopes. These estimates are based on Monte Carlo calculations for monoenergetic photons distributed uniformly in organs of an adult phantom. The medical physicist finds that his patient does not resemble the adult phantom. In addition, the absorbed fractions for the adult are not reasonable values for the child. This paper examines how these absorbed fraction estimates apply to a nonstandard patient

  2. Eye lens dosimetry for interventional procedures – Relation between the absorbed dose to the lens and dose at measurement positions

    This study investigated the relationship between the absorbed dose to the lens of the eye and the absorbed dose at different measurement positions near the eye of interventional radiologists. It also visualised the dose distribution inside the head, both when protective eyewear were used and without such protection. The best position for an eye lens dosimeter was found to be at the side of the head nearest to the radiation source, close to the eye. Positioning the dosimeter at the eyebrow could lead to an underestimation of the lens dose of as much as 45%. The measured dose distribution showed that the absorbed dose to the eye lenses was high compared to the other parts of the head, which stresses the importance of wearing protective eyewear. However, many models of eyewear were found to be deficient as the radiation could slip through at several places, e.g. at the cheek. The relationship between the absorbed dose to the lens and the kerma-area-product (PKA) delivered to the patient was also studied.

  3. Application of cytogenetic methods for estimation of absorbed dose

    Accumulated data on the practical application of cytogenetic technique to evaluate the absorbed dose for men involved in activities to eliminate the effects of the Chernobyl NPP accident were analyzed. Those data were compared with the results of cytogenetic studies conducted in other Russia regions affected by radiation impacts (Muslyumovo settle., Chelyabinsk Region, the Altay Territory settlements near the Semipalatinsk test range) and with the examination results of population of the territory of the Three Mile Island NPP (Island, Pennsylvania, USA) where in 1975 the nuclear accident took place. The cytogenetic studies were carried out using the standard analysis technique evaluating the frequency of unstable aberrations of chromosomes (UA) and using FISH-technique designed to evaluate the frequency of stable aberrations of chromosomes. It was pointed out that UA-technique could not be used efficiently for the retrospective evaluation of the absorbed doses with no clear idea correlating the nature and the rate of elimination with cell life time, especially, in case of small doses of irradiation. Analysis of the stable translocation using FISH-technique enabled to evaluate the absorbed dose within 8-9 years following the accident. The range of the absorbed doses of the examined persons varied from the background ones up to 1 Gy

  4. Data correction in ESR dosimetry for the average absorbed dose of teeth exposed to external photon

    A data-correction technique for the electron spin resonance (ESR) dosimetry was discussed in order to estimate an average absorbed dose of teeth exposed to external photon. Fourteen TLDs (thermoluminescent dosimeters) were used in the experiments to obtain the dose distribution in the human mouth. Each TLD was installed on the backside of the teeth in a female rando-phantom in order to estimate the absorbed dose of each tooth. The rando-phantom was exposed to photon beams of 137Cs (0.66 MeV) and 60Co (1.2/1.3 MeV) to investigate the influence of the energy on the dose distribution. The direction of the photons that hit the surface of the face could also affect the distribution of the dose in the phantom mouth. The incident angles of the photon beam were changed at 45-degree intervals around the longitudinal axis of the rando-phantom at the same height as the teeth. The largest difference among the measured doses, depending on the position of the teeth and photon energy, was in excess of 40% in the case of the exposure due to the beam direction from the backside of the phantom head at the energy of 662 keV. A sample of tooth enamel would be valuable for estimating the effective dose (Sv) calculated from the absorbed dose with ESR dosimetry. However, this study shows that the position of a tooth in the mouth affects the estimated value of an average absorbed dose of teeth. A simple technique to correct the ESR dosimetric results is suggested in this paper. The average absorbed dose of a tooth can be adequately estimated by using a simple formula that takes into consideration the position of the tooth, photon beam direction, and photon energy. (author)

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

    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)

  6. Sensors of absorbed dose of ionizing radiation based on mosfet

    Perevertaylo V. L.

    2010-01-01

    The requirements to technology and design of p-channel and n-channel MOS transistors with a thick oxide layer designed for use in the capacity of integral dosimeters of absorbed dose of ionizing radiation are defined. The technology of radiation-sensitive MOS transistors with a thick oxide in the p-channel and n-channel version is created.

  7. Absorbed dose simulations in near-surface regions using high dose rate Iridium-192 sources applied for brachytherapy

    Moura, E. S.; Zeituni, C. A.; Sakuraba, R. K.; Gonçalves, V. D.; Cruz, J. C.; Júnior, D. K.; Souza, C. D.; Rostelato, M. E. C. M.

    2014-02-01

    Brachytherapy treatment with Iridium-192 high dose rate (HDR) sources is widely used for various tumours and it could be developed in many anatomic regions. Iridium-192 sources are inserted inside or close to the region that will be treated. Usually, the treatment is performed in prostate, gynaecological, lung, breast and oral cavity regions for a better clinical dose coverage compared with other techniques, such as, high energy photons and Cobalt-60 machines. This work will evaluate absorbed dose distributions in near-surface regions around Ir-192 HDR sources. Near-surface dose measurements are a complex task, due to the contribution of beta particles in the near-surface regions. These dose distributions should be useful for non-tumour treatments, such as keloids, and other non-intracavitary technique. For the absorbed dose distribution simulations the Monte Carlo code PENELOPE with the general code penEasy was used. Ir-192 source geometry and a Polymethylmethacrylate (PMMA) tube, for beta particles shield were modelled to yield the percentage depth dose (PDD) on a cubic water phantom. Absorbed dose simulations were realized at the central axis to yield the Ir-192 dose fall-off along central axis. The results showed that more than 99.2% of the absorbed doses (relative to the surface) are deposited in 5 cm depth but with slower rate at higher distances. Near-surface treatments with Ir-192 HDR sources yields achievable measurements and with proper clinical technique and accessories should apply as an alternative for treatment of lesions where only beta sources were used.

  8. Absorbed Doses to Patients in Nuclear Medicine; Doskatalogen foer nukleaermedicin

    Leide-Svegborn, Sigrid; Mattsson, Soeren; Nosslin, Bertil [Universitetssjukhuset MAS, Malmoe (Sweden). Avd. foer radiofysik; Johansson, Lennart [Norrlands Universitetssjukhus, Umeaa (Sweden). Avd. foer radiofysik

    2004-09-01

    The work with a Swedish catalogue of radiation absorbed doses to patients undergoing nuclear medicine investigations has continued. After the previous report in 1999, biokinetic data and dose estimates (mean absorbed dose to various organs and tissues and effective dose) have been produced for a number of substances: {sup 11}C- acetate, {sup 11}C- methionine, {sup 18}F-DOPA, whole antibody labelled with either {sup 99m}Tc, {sup 111}In, {sup 123}I or {sup 131}I, fragment of antibody, F(ab'){sub 2} labelled with either {sup 99m}Tc, {sup 111}In, {sup 123}I or {sup 131}I and fragment of antibody, Fab' labelled with either {sup 99m}Tc, {sup 111}In, {sup 123}I or {sup 131}I. The absorbed dose estimates for these substances have been made from published biokinetic information. For other substances of interest, e.g. {sup 14}C-urea (children age 3-6 years), {sup 14}C-glycocholic acid, {sup 14}C-xylose and {sup 14}C-triolein, sufficient literature data have not been available. Therefore, a large number of measurements on patients and volunteers have been carried out, in order to determine the biokinetics and dosimetry for these substances. Samples of breast milk from 50 mothers, who had been subject to nuclear medicine investigations, have been collected at various times after administration of the radiopharmaceutical to the mother. The activity concentration in the breast milk samples has been measured. The absorbed dose to various organs and tissues and the effective dose to the child who ingests the milk have been determined for 17 different radiopharmaceuticals. Based on these results revised recommendations for interruption of breast-feeding after nuclear medicine investigations are suggested.

  9. Influence of gamma radiation of indoor radon decay products on absorbed dose

    A survey of absorbed dose rate and indoor radon concentration in multi storey houses was carried out. The main source of radon in such houses is construction materials. There is a relationship between absorbed dose rate and indoor radon concentration. This relationship is rather complicated and different for different premises. It depends on the geometry of premises and other characteristics which influence the distribution of indoor radon daughters. Increment of absorbed dose rate per unit of increment of indoor radon concentration depends on the concentration of indoor radon, floor where premises are situated, geometry of premises. The results of this study might help to assess the dose due to indoor radon which originates from construction materials. (author)

  10. Monte Carlo simulations of absorbed dose in a mouse phantom from 18-fluorine compounds

    The purpose of this study was to calculate internal absorbed dose distribution in mice from preclinical small animal PET imaging procedures with fluorine-18 labeled compounds (18FDG, 18FLT, and fluoride ion). The GATE Monte Carlo software and a realistic, voxel-based mouse phantom that included a subcutaneous tumor were used to perform simulations. Discretized time-activity curves obtained from dynamic in vivo studies with each of the compounds were used to set the activity concentration in the simulations. For 18FDG, a realistic range of uptake ratios was considered for the heart and tumor. For each simulated time frame, the biodistribution of the radionuclide in the phantom was considered constant, and a sufficient number of decays were simulated to achieve low statistical uncertainty. Absorbed dose, which was scaled to take into account radioactive decay, integration with time, and changes in biological distribution was reported in mGy per MBq of administered activity for several organs and uptake scenarios. The mean absorbed dose ranged from a few mGy/MBq to hundreds of mGy/MBq. Major organs receive an absorbed dose in a range for which biological effects have been reported. The effects on a given investigation are hard to predict; however, investigators should be aware of potential perturbations especially when the studied organ receives high absorbed dose and when longitudinal imaging protocols are considered

  11. Bone marrow and thyroid absorbed doses from mammography

    Breast dose from mammography has been estimated by various investigators, because of the established effectiveness of mammography in early screening for breast cancer and the relatively high sensitivity of the breast to radiation carcinogenesis. Nevertheless, to our knowledge, there is no available information in the literature about absorbed doses from mammography to organs other than the breast. The absorbed doses to the red bone marrow in the sternum and to the thyroid, due to scattered radiation from mammographic examinations, have been measured using a Plexiglas upper-body phantom and thermoluminescent dosemeters. Their dependence on several parameters has also been examined. It is necessary to emphasize that this work is still in progress. (author)

  12. Photon spectrum and absorbed dose in brain tumor

    Using Monte Carlo methods a BOMAB phantom inside a treatment hall with a brain tumor nearby the pituitary gland was treated with photons produced by a Varian 6 MV linac. The photon spectrum and the absorbed dose were calculated in the tumor, pituitary gland and the head. The treatment beam was collimated to illuminate only the tumor volume; however photons were noticed in the gland. Photon fluence reaching the tumor is 78.1 times larger than the fluence in the pituitary gland, on the other hand the absorbed dose in the tumor is 188 times larger than the dose in the gland because photons that reach the pituitary gland are scattered, by the head and the tumor, through Compton effect. (Author)

  13. Photon spectrum and absorbed dose in brain tumor

    Silva S, A. [General Electric Healthcare, Antonio Dovali Jaime 70, Torre A 3er. piso, Col. Santa Fe, 01210 Mexico D. F. (Mexico); Vega C, H. R. [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico); Rivera M, T. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria No. 694, 11500 Mexico D. F. (Mexico)

    2015-10-15

    Using Monte Carlo methods a BOMAB phantom inside a treatment hall with a brain tumor nearby the pituitary gland was treated with photons produced by a Varian 6 MV linac. The photon spectrum and the absorbed dose were calculated in the tumor, pituitary gland and the head. The treatment beam was collimated to illuminate only the tumor volume; however photons were noticed in the gland. Photon fluence reaching the tumor is 78.1 times larger than the fluence in the pituitary gland, on the other hand the absorbed dose in the tumor is 188 times larger than the dose in the gland because photons that reach the pituitary gland are scattered, by the head and the tumor, through Compton effect. (Author)

  14. Determination of absorbed dose distribution in water for COC ophthalmic applicator of {sup 106}Ru/{sup 106}Rh using Monte Carlo code-MCNPX; Determinacao da distribuicao de dose absorvida na agua para o aplicador oftalmico COC de {sup 106}Ru/{sup 106}Rh utilizando o codigo de Monte Carlo - MCNPX

    Barbosa, Nilseia A.; Rosa, Luiz A. Ribeiro da, E-mail: nilseia@ird.gov.br, E-mail: lrosa@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ),Rio de Janeiro, RJ (Brazil); Braz, Delson, E-mail: delson@nuclear.ufrj.br [Coordenacao dos programas de Pos-Graduacao em Engenharia (PEN/COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Nuclear

    2014-07-01

    The COC ophthalmic applicators using beta radiation source of {sup 106}Ru/{sup 106}Rh are used in the treatment of intraocular tumors near the optic nerve. In this type of treatment is very important to know the dose distribution in order to provide the best possible delivery of prescribed dose to the tumor, preserves the optic nerve region extremely critical, that if damaged, can compromise the patient's visual acuity, and cause brain sequelae. These dose distributions are complex and doctors, who will have the responsibility on the therapy, only have the source calibration certificate provided by the manufacturer Eckert and Ziegler BEBIG GmbH. These certificates provide 10 absorbed dose values at water depth along the central axis applicator with the uncertainties of the order of 20% isodose and in a plane located 1 mm from the applicator surface. Thus, it is important to know with more detail and precision the dose distributions in water generated by such applicators. To this end, the Monte Carlo simulation was used using MCNPX code. Initially, was validated the simulation by comparing the obtained results to the central axis of the applicator with those provided by the certificate. The different percentages were lower than 5%, validating the used method. Lateral dose profile was calculated for 6 different depths in intervals of 1 mm and the dose rates in mGy.min{sup -1} for the same depths.

  15. Absorbed dose evaluation by SISCODES code, kerma and fluence deviations

    Radiotherapy is a common treatment of cancer. Radiotherapy exposes the patient to a radiation field, producing ionization, and absorbed dose. A precise dose calculation and the ability to execute the irradiation on the patient are necessary in order to avoid serious injuries on the surrounding health tissue, thus, the maximum acceptable absorbed dose error from the prescribed and applied is about 5%. The doses on radiotherapy are usually calculated by superimposition experimental dose profile, namely PDP, which is experimentally measured in a water simulator. Moreover, the radiation interaction with human body tissues depends on the chemical composition and the tissue density, which means the anthropomorphism and anthropometric of the human being. This paper evaluates the deviation of calculated value of kerma, induced by human body heterogeneities. To do this job two thorax voxel models created on SISCODES (one filled with various tissues other filled with water) were applied. The result of simulations permits two different comparisons. One is the ratio between tissues kermas and water kerma. Another is the ratio between human phantom fluence, where exists radiation scatter and reflection, and water phantom fluence. The reconstructed pictures of studied regions showing the calculated ratios, and graphs of the ratios versus energy of each tissue are shown. The dose ratio deviations obtained are, in some situations, larger than the acceptable 5% point out serious miscalculation of doses for some spatial regions on the human body. (author)

  16. Absorbed dose determination in photon fields using the tandem method

    Marques-Pachas, J F

    1999-01-01

    The purpose of this work is to develop an alternative method to determine the absorbed dose and effective energy of photons with unknown spectral distributions. It includes a 'tandem' system that consists of two thermoluminescent dosemeters with different energetic dependence. LiF: Mg, Ti, CaF sub 2 : Dy thermoluminescent dosemeters and a Harshaw 3500 reading system are employed. Dosemeters are characterized with sup 9 sup 0 Sr- sup 9 sup 0 Y, calibrated with the energy of sup 6 sup 0 Co and irradiated with seven different qualities of x-ray beams, suggested by ANSI No. 13 and ISO 4037. The answers of each type of dosemeter are adjusted to a function that depends on the effective energy of photons. The adjustment is carried out by means of the Rosenbrock minimization algorithm. The mathematical model used for this function includes five parameters and has a gauss and a straight line. Results show that the analytical functions reproduce the experimental data of the answers, with a margin of error of less than ...

  17. The Monte Carlo simulation of the absorbed dose in quartz

    Chen Shaowen [School of Physics Science and Engineering, Sun Yat-Sen University, Guangzhou, Guangdong 510275 (China) and Electron Engineering Department, Dongguan University of Technology, Dongguan 523808 (China)], E-mail: siumon@163.com; Liu Xiaowei; Zhang Chunxiang; Tang Qiang [School of Physics Science and Engineering, Sun Yat-Sen University, Guangzhou, Guangdong 510275 (China)

    2009-05-15

    Regeneration irradiation is a necessary procedure in TL or OSL dating protocol. The accuracy of measuring the absorbed dose is one of the important factors in dating. Since a beta source is often used in the regeneration irradiation process, the size of the quartz sample, pressure of nitrogen gas and the material of the sample holder may cause significant uncertainties in delivering the absorbed dose. In this work, the effects of the size of the quartz sample, the pressure of nitrogen gas and the material of the sample holder are simulated using the Monte Carlo method, and the uncertainties are discussed in these cases. The results show that they need to be considered in the dating.

  18. Some comments on the concept of absorbed dose

    The main physical quantity for the evaluation of the induced effects by radiation ionizing is absorbed dose. ICRU report 51 defines this concept as quantity dε divided by dm, where dε is the mean energy imparted by radiation ionizing to matter of mass dm. However, nothing is said about the average operation concerning the stochastic energy imparted ε. Nevertheless, because considers the sum of all changes of rest mass of the involved nuclei and elementary particles in all interactions which occur within the mass (i.e. nuclear reactions and transformations of elementary particles), the average operation can not be done with an equilibrium statistical operator, rather, this has to be defined with a non-equilibrium statistical operator, therefore, absorbed dose is a function dependent on time. Furthermore, we present a discussion to clarify the equilibrium radiation and charged particle equilibrium within the context of thermodynamic equilibrium. (Author)

  19. Dose distributions around selectron applicators

    Measured and calculated dose distributions around selectron applicators, loaded with 60Co high dose rate pellets, are presented. The effect of the stopping screw, spacers, pellets themselves and the applicator wall on the dose distribution is discussed. The measured dose distribution is in almost perfect agreement with the calculated distribution in planes perpendicular to the applicator axis and containing a source. On the applicator axis directly below the applicator the measured dose amounts to about 75% of the calculated value, when only the stopping screw attenuates the beam from a pellet. When the beam is attenuated by spacers in addition to the stopping screw, the discrepancy between the calculated and measured dose may exceed 50%. Clinically relevant source geometries are also discussed. It is shown that for most regions around the applicator the method of a simple addition of dose contributions from individual point sources is an acceptable approximation for the calculation of dose distributions around the selectron applicators

  20. Sensors of absorbed dose of ionizing radiation based on mosfet

    Perevertaylo V. L.

    2010-10-01

    Full Text Available The requirements to technology and design of p-channel and n-channel MOS transistors with a thick oxide layer designed for use in the capacity of integral dosimeters of absorbed dose of ionizing radiation are defined. The technology of radiation-sensitive MOS transistors with a thick oxide in the p-channel and n-channel version is created.

  1. The accuracy of absorbed dose estimates in tumours determined by Quantitative SPECT: A Monte Carlo study

    Background. Dosimetry in radionuclide therapy estimates delivered absorbed doses to tumours and ensures that absorbed dose levels to normal organs are below tolerance levels. One procedure is to determine time-activity curves in volumes-of-interests from which the absorbed dose is estimated using SPECT with appropriate corrections for attenuation, scatter and collimator response. From corrected SPECT images the absorbed energy can be calculated by (a) assuming kinetic energy deposited in the same voxel where particles were emitted, (b) convolve with point-dose kernels or (c) use full Monte Carlo (MC) methods. A question arises which dosimetry method is optimal given the limitations in reconstruction- and quantification procedures. Methods. Dosimetry methods (a) and (c) were evaluated by comparing dose-rate volume histograms (DrVHs) from simulated SPECT of 111In, 177Lu, 131I and Bremsstrahlung from 90Y to match true dose rate images. The study used a voxel-based phantom with different tumours in the liver. SPECT reconstruction was made using an iterative OSEM method and MC dosimetry was performed using a charged-particle EGS4 program that also was used to determined true absorbed dose rate distributions for the same phantom geometry but without camera limitations. Results. The DrVHs obtained from SPECT differed from true DrVH mainly due to limited spatial resolution. MC dosimetry had a marginal effect because the SPECT spatial resolution is in the same order as the energy distribution caused by the electron track ranges. For 131I, full MC dosimetry made a difference due to the additional contribution from high-energy photons. SPECT-based DrVHs differ significantly from true DrVHs unless the tumours are considerable larger than the spatial resolution. Conclusion. It is important to understand limitations in quantitative SPECT images and the reasons for apparent heterogeneities since these have an impact on dose-volume histograms. A MC-based dosimetry calculation from

  2. Determination of Absorbed Dose in Large 60-Co Fields Radiotherapy

    Radiation in radiotherapy has selective impact on ill and healthy tissue. During the therapy the healthy tissue receives certain amount of dose. Therefore dose calculations in outer radiotherapy must be accurate because too high doses produce damage in healthy tissue and too low doses cannot ensure efficient treatment of cancer cells. A requirement on accuracy in the dose calculations has lead to improvement of detectors, and development of absolute and relative dosimetry. Determination of the dose distribution with use of computer is based on data provided by the relative dosimetry. This paper compares the percentage depth doses in cubic water phantoms of various dimensions with percentage depth doses calculated with use of Mayneord factor from the experimental depth doses measured in water phantom of large dimension. Depth doses in water phantoms were calculated by the model of empirical dosimetrical functions. The calculations were based on the assumption that large 60Co photon field exceeds the phantom's limits. The experimental basis for dose calculations by the model of empirical dosimetrical functions were exposure doses measured in air and dose reduction factors because of finite phantom dimensions. Calculations were performed by fortran 90 software. It was found that the deviation of dosimetric model was small in comparison to the experimental data. (author)

  3. Sediment Distribution Coefficients (KD) and Concentration Factors (CF) in fish for natural radionuclides in a pond of a tropical region and their contributions to estimations of internal absorbed dose rate in fish

    Attention has been paid only recently to the protection of biota against radiation effects. Protection is being considered through modeling of the calculation of absorbed dose rate. In these models, the inputs are the fluxes of radionuclides of environmental concern and their resulting distribution between environmental compartments. Such distribution is estimated for dispersion models. In freshwater systems and when fish is used as biomaker, relevant environmental transfer parameters are transfer between sediment and water (sediment distribution coefficients KD, in 1 kg-1), and between water and fish (concentration factor CF, in 1 kg-1). These coefficients are under the influence of a number o physical, chemical and biological factors, and display following the literature a great variability. The present work establishes the KD's and CF's for uranium, thorium, radium and lead for two ponds: one that receives treated effluents from an ore treatment unit (UTM) situated at Pocos de Caldas, Minas Gerais, Brazil and the other pond from the uranium concentration unit (URA) situated at Caetite, Bahia, Brazil, and for fish used as biomarker. It intends also to compare these parameters with the values recommended by IAEA. Depending on considered radionuclide and on the site, CF's (1 kg-1) observed values were of the same magnitude as, or one order of magnitude lower than recommended by IAEA. KD's (1 kg-1) observed values were found of the same magnitude as those recommended by IAEA, approximately 10 times lower or up to 100 times higher than recommended by IAEA, again depending on the radionuclides and on the site. It can be concluded that local parameters should be established in order to obtain a more accurate estimative of biota exposition from man activities. (author)

  4. Sediment distribution coefficients (KD) and concentration factors (CF) in fish for natural radionuclides in a pond of a tropical region and their contributions to estimations of internal absorbed dose rate in fish

    Attention has been paid only recently to the protection of biota against radiation effects. Protection is being considered through modeling of the calculation of absorbed dose rate. In these models, the inputs are the fluxes of radionuclides of environmental concern and their resulting distribution between environmental compartments. Such distribution is estimated for dispersion models. In freshwater systems and when fish is used as biomaker, relevant environmental transfer parameters are transfer between sediment and water (sediment distribution coefficients KD, in l kg-1), and between water and fish (concentration factor CF, in l kg-1). These coefficients are under the influence of a number o physical, chemical and biological factors, and display following the literature a great variability. The present work establishes the KD's and CF's for uranium, thorium, radium and lead for two ponds: one that receives treated effluents from an ore treatment unit (UTM) situated at Pocos de Caldas, Minas Gerais, Brazil and the other pond from the uranium concentration unit (URA) situated at Caetite, Bahia, Brazil, and for fish used as biomarker. It intends also to compare these parameters with the values recommended by IAEA. Depending on considered radionuclide and on the site, CF's (l kg-1) observed values were of the same magnitude as, or one order of magnitude lower than recommended by IAEA. KD's (l kg-1) observed values were found of the same magnitude as those recommended by IAEA, approximately 10 times lower or up to 100 times higher than recommended by IAEA, again depending on the radionuclides and on the site. It can be concluded that local parameters should be established in order to obtain a more accurate estimative of biota exposition from man activities. (author)

  5. Independent absorbed-dose calculation using the Monte Carlo algorithm in volumetric modulated arc therapy

    To report the result of independent absorbed-dose calculations based on a Monte Carlo (MC) algorithm in volumetric modulated arc therapy (VMAT) for various treatment sites. All treatment plans were created by the superposition/convolution (SC) algorithm of SmartArc (Pinnacle V9.2, Philips). The beam information was converted into the format of the Monaco V3.3 (Elekta), which uses the X-ray voxel-based MC (XVMC) algorithm. The dose distribution was independently recalculated in the Monaco. The dose for the planning target volume (PTV) and the organ at risk (OAR) were analyzed via comparisons with those of the treatment plan. Before performing an independent absorbed-dose calculation, the validation was conducted via irradiation from 3 different gantry angles with a 10- × 10-cm2 field. For the independent absorbed-dose calculation, 15 patients with cancer (prostate, 5; lung, 5; head and neck, 3; rectal, 1; and esophageal, 1) who were treated with single-arc VMAT were selected. To classify the cause of the dose difference between the Pinnacle and Monaco TPSs, their calculations were also compared with the measurement data. In validation, the dose in Pinnacle agreed with that in Monaco within 1.5%. The agreement in VMAT calculations between Pinnacle and Monaco using phantoms was exceptional; at the isocenter, the difference was less than 1.5% for all the patients. For independent absorbed-dose calculations, the agreement was also extremely good. For the mean dose for the PTV in particular, the agreement was within 2.0% in all the patients; specifically, no large difference was observed for high-dose regions. Conversely, a significant difference was observed in the mean dose for the OAR. For patients with prostate cancer, the mean rectal dose calculated in Monaco was significantly smaller than that calculated in Pinnacle. There was no remarkable difference between the SC and XVMC calculations in the high-dose regions. The difference observed in the low-dose regions may

  6. Methods to verify absorbed dose of irradiated containers and evaluation of dosimeters

    The research on dose distribution in irradiated food containers and evaluation of several methods to verify absorbed dose were carried out. The minimum absorbed dose of treated five orange containers was in the top of the highest or in the bottom of lowest container. Dmax/Dmin in this study was 1.45 irradiated in a commercial 60Co facility. The density of orange containers was about 0.391g/cm3. The evaluation of dosimeters showed that the PMMA-YL and clear PMMA dosimeters have linear relationship with dose response, and the word NOT in STERIN-125 and STERIN-300 indicators were covered completely at the dosage of 125 and 300 Gy respectively. (author)

  7. Variations in absorbed doses from 59Fe in different diseases

    The biokinetics of radiopharmaceuticals administered in vivo may vary considerably with changes in organ functions. They studied the variations in absorbed doses from 59Fe in 207 patients with different diseases, in whom ferrokinetic investigations were performed for diagnostic purposes. Radiation doses to the bone marrow were highest in patients with deserythropoietic anemias (mean 38 nSv/Bq, range 19 - 57 nSv/Bq) and in hemolytic anemias (mean 21 nSv/Bq, range 7 - 35 nSv/Bq), whereas lower and rather constant values were found in other diseases (mean values between 9 and 13 nSv/Bq). The highest organ doses, the greatest differences with respect to diagnosis and also the largest variations within each group of patients were found for liver and spleen (e. g. in aplastic anemia; liver: 66 nSv/Bq, range 29 - 104 nSv/Bq; spleen: 57 nSv/Bq, range 34 - 98 nSv/Bq. In iron deficiency; liver: 13 nSv/Bq range 12 - 14 nSv/q; spleen: 19 nSv/Bq, range 18 - 20 nSv/Bq). Lower organ doses and smaller variations within and between the groups of patients were found for the gonads (means 3 - 7 nSv/Bq), the kidneys (means 10 - 13 nSv/Bq), the bone (means 4 - 7 nSv/Bq), the lung (means 8 - 12 nSv/Bq), and the total body (means 6 - 8 nSv/Bq). In patients with chronic bleeding absorbed doses decrease concomitantly to the extent of blood loss. The D/sub E/ is not markedly affected by the variations in organ doses but is fairly constant for different diseases. 16 references, 1 figure, 3 tables

  8. Estimation of absorbed organ doses and effective dose based on body mass index in digital radiography

    With the introduction of digital radiography, patients undergoing radiographic procedures are subject to being overexposed to radiation. Therefore, it is necessary to estimate the absorbed organ dose and the effective dose, which are significant for patient health, along with body type. During chest radiographic examinations conducted in 899 patients for screening, the absorbed dose of the 13 major organs, the average whole-body dose, and two effective doses weighted by factors published in ICRP 60 and ICRP 103 were calculated on the basis of patient information such as height, weight and examination condition, including kilovolt potential, focus-skin distance and entrance surface dose (ESD), using a PC-based Monte Carlo program simulation. It was found that dose per unit ESD had a tendency to decrease with body mass index (BMI). In particular, the absorbed dose for most organs was larger at high voltages (140 kVp) than at low voltages (120 kVp, 100 kVp). In addition, the effective dose which was based on ICRP 60 and ICRP 103 also represented the same tendency in respect of BMI and tube voltage. (authors)

  9. Testing of the IAEA code: Absorbed dose determination at Co 60 gamma radiation

    At several Primary Standard Dosimetry Laboratories measurements of absorbed dose to water have been performed with ionization chambers of different types. These ionization chambers are calibrated against both, primary standards of air kerma and water absorbed dose. Using the formalism of the IAEA Code of Practice the absorbed dose to water in Co 60 gamma beams was derived and compared with direct measurements of water absorbed dose. This yields a very valid test of the IAEA Code. (author). 18 refs, 7 tabs

  10. Aerial gamma spectrometry of the uranium province of Lagoa Real (Caetite, BA, Brazil): go environmental aspects and distribution of the absorbed dose in the air; Espectrometria gama aerea da provincia uranifera de Lagoa Real (Caetite, BA): aspectos geoambientais e distribuicao da dose absorvida no ar

    Santos, Esau Francisco Sena

    2006-07-01

    In the present study, it was analyzed the surface concentrations of the natural radioelements K, U and Th, as well as the absorbed dose rate in air caused by gamma radiation from the Lagoa Real uranium province, which is located at the center southern portion of Bahia State and comprises an area of approximately 4.600 Km{sup 2}. Data from the airborne gamma ray spectrometric survey of the region (Sao Timoeo Project) carried out in 1979, was used in this study. Besides, recent data of U, Th and absorbed dose rates from the Environmental Monitoring Program of the uranium concentration plant (URA), operated in the region by the Brazilian Nuclear Industries (INB), were used with the aim of inter compare the sampling points in the same geo referenced area. Imaging geo processing software's give support to frame maps of surface concentrations and ternary maps, as well as allow the integration of these with other themes (e.g. hydrology, geology, pedology) favouring the interpretation of geo environmental process from the radioactive cartography. Considering the whole study area, it was obtained the following mean values: absorbed dose rate in air (61,08 nGy.h{sup -1}), Potassium (1,65 % K) , Uranium (3,02 ppm eU) and thorium (18,26 ppm eTh). The geological unities bounding the uranium anomalies were placed in the areas characterized by the highest values of radioelements and, as expected, the major dose levels. The use of ternary maps coupled with the geology and hydrology allowed distinguishing the relationship between the surface distribution of natural radioelements and the geo environmental aspects, including the influence of the catchment in their transport and migration. (author)

  11. Comparison of piezoelectronic networks acting as distributed vibration absorbers

    Maurini, Corrado; Dell'Isola, Francesco; Del Vescovo, Dionisio

    2004-01-01

    International audience Electric vibration absorbers made of distributed piezoelectric devices for the control of beam vibrations are studied. The absorbers are obtained by interconnecting an array of piezoelectric transducers uniformly distributed on a beam with different modular electric networks. Five different topologies are considered and their damping performance is analysed and compared.

  12. Red bone marrow doses, integral absorbed doses, and somatically effective dose equivalent from four maxillary occlusal projections

    Phantom measurements of red bone marrow (RBM) doses, integral absorbed doses, and somatically effective dose equivalent (SEDE) from four different maxillary occlusal projections are presented. For each projection, different combinations of focus-skin distances and tube potentials were compared with regard to the patient's radiation load. The axial incisal view produced the highest patient exposures, with a maximum red bone marrow dose of 122.5 microGy/exposure, integral absorbed dose of 8.6 mJ/exposure, and SEDE values of 39.6 microSv/exposure. The corresponding values from the frontal, lateral occlusal, and tuber views ranged between 4% and 44% of the axial incisal view values for the integral absorbed dose and SEDE values, and between 0.3% and 3% for the red bone marrow doses. Increasing the focus-skin distance from 17.5 cm to 27 cm is accompanied by a 24% to 30% reduction in integral absorbed dose. Increasing the tube potential from 50 kV to 65 kV likewise results in a 23% reduction in absorbed energy

  13. Red bone marrow doses, integral absorbed doses, and somatically effective dose equivalent from four maxillary occlusal projections

    Berge, T.I.; Wohni, T.

    1984-02-01

    Phantom measurements of red bone marrow (RBM) doses, integral absorbed doses, and somatically effective dose equivalent (SEDE) from four different maxillary occlusal projections are presented. For each projection, different combinations of focus-skin distances and tube potentials were compared with regard to the patient's radiation load. The axial incisal view produced the highest patient exposures, with a maximum red bone marrow dose of 122.5 microGy/exposure, integral absorbed dose of 8.6 mJ/exposure, and SEDE values of 39.6 microSv/exposure. The corresponding values from the frontal, lateral occlusal, and tuber views ranged between 4% and 44% of the axial incisal view values for the integral absorbed dose and SEDE values, and between 0.3% and 3% for the red bone marrow doses. Increasing the focus-skin distance from 17.5 cm to 27 cm is accompanied by a 24% to 30% reduction in integral absorbed dose. Increasing the tube potential from 50 kV to 65 kV likewise results in a 23% reduction in absorbed energy.

  14. Calculation of absorbed dose of anchorage-dependent cells from internal beta-rays irradiation

    Objective: To elicit the formula of internal dosimetry in anchorage-dependent cells by beta-emitting radionuclides from uniformly distributed volume sources. Methods: By means of the definition of absorbed dose and the MIRD (Medical International Radiation Dose) scheme the formula of internal dosimetry was reasonably deduced. Firstly, studying the systems of suspension culture cells. Then, taking account of the speciality of the systems of the anchorage-dependent cells and the directions of irradiation, the absorbed dose of anchorage -dependent cells was calculated by the accumulated radioactivity, beta-ray energy, and the volume of the cultured systems. Results: The formula of internal dosimetry of suspension culture cells and anchorage-dependent cells were achieved. At the same time, the formula of internal dosimetry of suspension culture cells was compared with that of MIRD and was confirmed accurate. Conclusion: The formula of internal dosimetry is concise, reliable and accurate

  15. Specific absorbed fraction in bone tissue and bone marrow resulting from photons distributed in the skeleton

    The computer code 'ALGAM: Monte Carlo Estimation of Internal Dose from Gamma -ray Sources in a Phanton Man' only provides for an average dose to bone marrow resulting from a photon source distributed in the human body. Since there is no realistic model for the separation of these doses in the present phantom, some modifications were performed in the ALGAM code in order to introduce an heterogeneous skeleton and through this new model it was possible to make the estimation of dose in bone marrow. The specific absorbed fraction resulting from running the new program for 12 monoenergetic photon sources distributed in three source organs - skeleton, red marrow and yellow marrow is presented. The results obtained show that for low photon energies, the old model overestimates the specific absorbed fraction in bone marrow up to a factor of 4; while in bone, it underestimates the specific absorbed fractions up to a factor of 1.6. (Author)

  16. The influence of mammographic X-ray spectra on absorbed energy distribution in breast: Monte Carlo simulation studies

    A mathematical model, based on Monte Carlo simulation, is proposed for deriving absorbed energy and dose distribution in mammography utilizing a mathematical water-like phantom. The model was validated for its accuracy against experimental and published data. The main factor discriminating absorbed energy distribution characteristics among different mammographic techniques was considered the X-ray spectrum. The absorbed energy distribution inside the phantom was investigated via percentage depth dose and isodose curves. The influence of the factors affecting X-ray spectrum (tube voltage, anode material, filter material and thickness) on absorbed energy distribution was examined. The hardness of the beam, due to increase of tube voltage or filtration, was found to be the major factor affecting absorbed energy distribution inside the phantom. In general, Mo and W anode systems demonstrated superior dosimetric characteristics against those of W-Mo or Rh. The model presented can be used for estimating absolute and relative breast dose values and their spatial distributions

  17. Magnetic Resonance Imaging-Based Radiation-Absorbed Dose Estimation of {sup 166}Ho Microspheres in Liver Radioembolization

    Seevinck, Peter R., E-mail: p.seevinck@umcutrecht.nl [Image Sciences Institute, University Medical Center Utrecht, Utrecht (Netherlands); Maat, Gerrit H. van de [Image Sciences Institute, University Medical Center Utrecht, Utrecht (Netherlands); Wit, Tim C. de [Department of Nuclear Medicine, Amsterdam Medical Centre, Amsterdam (Netherlands); Vente, Maarten A.D.; Nijsen, Johannes F.W. [Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht (Netherlands); Bakker, Chris J.G. [Image Sciences Institute, University Medical Center Utrecht, Utrecht (Netherlands); Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht (Netherlands)

    2012-07-01

    Purpose: To investigate the potential of magnetic resonance imaging (MRI) for accurate assessment of the three-dimensional {sup 166}Ho activity distribution to estimate radiation-absorbed dose distributions in {sup 166}Ho-loaded poly (L-lactic acid) microsphere ({sup 166}Ho-PLLA-MS) liver radioembolization. Methods and Materials: MRI, computed tomography (CT), and single photon emission CT (SPECT) experiments were conducted on an anthropomorphic gel phantom with tumor-simulating gel samples and on an excised human tumor-bearing liver, both containing known amounts of {sup 166}Ho-PLLA-MS. Three-dimensional radiation-absorbed dose distributions were estimated at the voxel level by convolving the {sup 166}Ho activity distribution, derived from quantitative MRI data, with a {sup 166}Ho dose point-kernel generated by MCNP (Monte Carlo N-Particle transport code) and from Medical Internal Radiation Dose Pamphlet 17. MRI-based radiation-absorbed dose distributions were qualitatively compared with CT and autoradiography images and quantitatively compared with SPECT-based dose distributions. Both MRI- and SPECT-based activity estimations were validated against dose calibrator measurements. Results: Evaluation on an anthropomorphic phantom showed that MRI enables accurate assessment of local {sup 166}Ho-PLLA-MS mass and activity distributions, as supported by a regression coefficient of 1.05 and a correlation coefficient of 0.99, relating local MRI-based mass and activity calculations to reference values obtained with a dose calibrator. Estimated MRI-based radiation-absorbed dose distributions of {sup 166}Ho-PLLA-MS in an ex vivo human liver visually showed high correspondence to SPECT-based radiation-absorbed dose distributions. Quantitative analysis revealed that the differences in local and total amounts of {sup 166}Ho-PLLA-MS estimated by MRI, SPECT, and the dose calibrator were within 10%. Excellent agreement was observed between MRI- and SPECT-based dose

  18. Standard Guide for Selection and Use of Mathematical Methods for Calculating Absorbed Dose in Radiation Processing Applications

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This guide describes different mathematical methods that may be used to calculate absorbed dose and criteria for their selection. Absorbed-dose calculations can determine the effectiveness of the radiation process, estimate the absorbed-dose distribution in product, or supplement or complement, or both, the measurement of absorbed dose. 1.2 Radiation processing is an evolving field and annotated examples are provided in Annex A6 to illustrate the applications where mathematical methods have been successfully applied. While not limited by the applications cited in these examples, applications specific to neutron transport, radiation therapy and shielding design are not addressed in this document. 1.3 This guide covers the calculation of radiation transport of electrons and photons with energies up to 25 MeV. 1.4 The mathematical methods described include Monte Carlo, point kernel, discrete ordinate, semi-empirical and empirical methods. 1.5 General purpose software packages are available for the calcul...

  19. Influence of radioactive contaminants on absorbed dose estimates for radiopharmaceuticals

    Several popular radiopharmaceutical products contain low levels of radioactive contaminants. These contaminants increase the radiation absorbed dose to the patient without any increased benefit and, in some cases, with a decrease in image quality. The importance of a contaminant to the radiation dosimetry picture is a function of 1) the contaminant level, 2) the physical half-life of the contaminant, 3) the organ uptake and the biological half-time of the contaminant in the various body systems, and 4) the decay mode, energy, etc. of the contaminant. The general influence of these parameters is discussed in this paper; families of curves are included that reflect the changing importance of contaminant dosimetry with respect to the primary radionuclide as a function of these variables. Several specific examples are also given of currently used radiopharmaceutical products which can contain radioactive contaminants (I-123, In-111, Tl-201, Ir-191m, Rb-82, Au-195m). 7 references, 8 figures, 4 tables

  20. Magnetic Resonance Imaging-Based Radiation-Absorbed Dose Estimation of 166Ho Microspheres in Liver Radioembolization

    Purpose: To investigate the potential of magnetic resonance imaging (MRI) for accurate assessment of the three-dimensional 166Ho activity distribution to estimate radiation-absorbed dose distributions in 166Ho-loaded poly (L-lactic acid) microsphere (166Ho-PLLA-MS) liver radioembolization. Methods and Materials: MRI, computed tomography (CT), and single photon emission CT (SPECT) experiments were conducted on an anthropomorphic gel phantom with tumor-simulating gel samples and on an excised human tumor-bearing liver, both containing known amounts of 166Ho-PLLA-MS. Three-dimensional radiation-absorbed dose distributions were estimated at the voxel level by convolving the 166Ho activity distribution, derived from quantitative MRI data, with a 166Ho dose point-kernel generated by MCNP (Monte Carlo N-Particle transport code) and from Medical Internal Radiation Dose Pamphlet 17. MRI-based radiation-absorbed dose distributions were qualitatively compared with CT and autoradiography images and quantitatively compared with SPECT-based dose distributions. Both MRI- and SPECT-based activity estimations were validated against dose calibrator measurements. Results: Evaluation on an anthropomorphic phantom showed that MRI enables accurate assessment of local 166Ho-PLLA-MS mass and activity distributions, as supported by a regression coefficient of 1.05 and a correlation coefficient of 0.99, relating local MRI-based mass and activity calculations to reference values obtained with a dose calibrator. Estimated MRI-based radiation-absorbed dose distributions of 166Ho-PLLA-MS in an ex vivo human liver visually showed high correspondence to SPECT-based radiation-absorbed dose distributions. Quantitative analysis revealed that the differences in local and total amounts of 166Ho-PLLA-MS estimated by MRI, SPECT, and the dose calibrator were within 10%. Excellent agreement was observed between MRI- and SPECT-based dose–volume histograms. Conclusions: Quantitative MRI was demonstrated

  1. Implementation of an absorbed dose postal QA programme for radiosurgery

    Radiosurgery is becoming a well accepted method for the treatment of small intra cranial benign lesions and neoplasic tumours. It can be delivered using multiple sources of 60Co gamma rays (i.e. Gamma knife) or using high energy photons, typically 6 MV, produced by clinical linear accelerators. The main objective of this work was to develop, test, and implement a Postal System of Quality Assurance of the absorbed dose applicable specifically to radiosurgery. Due to the specificity of the radiation field including the steep dose gradients, several measuring systems were necessary in order to guarantee the required dose accuracy. The ionization chamber (0,125 cm3/ PTW-Model 31010), thermoluminescent mini dosimeters (TLD), film, and mini Alanina dosimeters were selected. The dosimeters were calibrated against a PTW ionization dosimeter previously calibrated at the PTW secondary standards. The postal evaluation system consist of a main cylindrical acrylic phantom, with 16 cm of length and 21 cm of diameter, and four smaller cylindrical (C1-C4) inserts with 10 cm of length and 7 cm of diameter with the following specific characteristics: - C1 contains a small air volume with 2 cm of diameter that simulates the target with 3 air micro spheres with a diameter of 3 mm; - C2 contains five cylindrical rods where the mini TLDs with 2 mm of diameter and 0,5 mm of length were inserted and placed 5, 15, and 35 mm from the centre; - C3 contains five cylindrical rods where the alanine dosimeters with 1 mm of diameter and 2 mm of length were inserted at distances similar to those of the TLDs; - C4 contains an oncology film (X Omat-V) placed inside. In addition, a set of forms for data register and written procedures were sent to the participating institutions. A total dose of 25 Gy is requested to be delivered at the target. The overall management procedure is described, and the three main phases of the procedure are as follows: 1) An evaluation was made of the coordinate system of

  2. Measurement of absorbed dose by 7-GeV bremsstrahlung in a PMMA phantom

    Job, P K; Semones, E

    1999-01-01

    High-energy electron storage rings generate energetic bremsstrahlung photons through radiative interaction of the particle beam with the residual gas molecules and other components inside the storage ring. At synchrotron radiation facilities, where beamlines are channeled out of the storage ring, a continuous bremsstrahlung spectrum, with a maximum energy of the stored particle beam, will be present. At the advanced photon source (APS), where the stored beam energy is 7 GeV, bremsstrahlung generated in the straight sections of the insertion device beamlines, which are a total of 15.38 m in length, can be significant. The contribution from each bremsstrahlung interaction adds up to produce a narrow mono-directional bremsstrahlung beam that comes down through the insertion device beamlines. The resulting absorbed dose distributions by this radiation in a 300 mmx300 mmx300 mm tissue substitute cube phantom were measured with LiF:Mg,Ti (TLD-700) thermoluminescent dosemeters. The normalized absorbed dose, in a cro...

  3. The influence of the patient's posture on organ and tissue absorbed doses caused by radiodiagnostic examinations

    Due to the gravitational force, organ positions and subcutaneous fat distribution change when a standing person lies down on her/his back, which is called 'supine posture'. Both postures, standing and supine, are very common in X-ray diagnosis, however, phantoms used for the simulation of patients for organ and tissue absorbed dose assessments normally represent humans either in standing or in supine posture. Consequently, the exposure scenario simulated sometimes does not match the real X-ray examination with respect to the patient's posture. Using standing and supine versions of mesh-based female and male adult phantoms, this study investigates the 'posture-effect' on organ and tissue absorbed doses for radiographs of the pelvis and the lumbar spine in order to find out if the errors from simulating the false posture are significant. (author)

  4. Physiologically based pharmacokinetic modeling of inhaled radon to calculate absorbed doses in mice, rats, and humans

    This is the first report to provide radiation doses, arising from inhalation of radon itself, in mice and rats. To quantify absorbed doses to organs and tissues in mice, rats, and humans, we computed the behavior of inhaled radon in their bodies on the basis of a physiologically based pharmacokinetic (PBPK) model. It was assumed that radon dissolved in blood entering the gas exchange compartment is transported to any tissue by the blood circulation to be instantaneously distributed according to a tissue/blood partition coefficient. The calculated concentrations of radon in the adipose tissue and red bone marrow following its inhalation were much higher than those in the others, because of the higher partition coefficients. Compared with a previous experimental data for rats and model calculation for humans, the present calculation was proved to be valid. Absorbed dose rates to organs and tissues were estimated to be within the range of 0.04-1.4 nGy (Bqm-3)-1 day-1 for all the species. Although the dose rates are not so high, it may be better to pay attention to the dose to the red bone marrow from the perspective of radiation protection. For more accurate dose assessment, it is necessary to update tissue/blood partition coefficients of radon that strongly govern the result of the PBPK modeling. (author)

  5. Standard Guide for Absorbed-Dose Mapping in Radiation Processing Facilities

    American Society for Testing and Materials. Philadelphia

    2003-01-01

    1.1 This document provides guidance in determining absorbed-dose distributions in products, materials or substances irradiated in gamma, X-ray (bremsstrahlung) and electron beam facilities. Note 1—For irradiation of food and the radiation sterilization of health care products, other specific ISO and ISO/ASTM standards containing dose mapping requirements exist. For food irradiation, see ISO/ASTM 51204, Practice for Dosimetry in Gamma Irradiation Facilities for Food Processing and ISO/ASTM 51431, Practice for Dosimetry in Electron and Bremsstrahlung Irradiation Facilities for Food Processing. For the radiation sterilization of health care products, see ISO 11137: 1995, Sterilization of Health Care Products Requirements for Validation and Routine Control Radiation Sterilization. In those areas covered by ISO 11137, that standard takes precedence. ISO/ASTM Practice 51608, ISO/ASTM Practice 51649, and ISO/ASTM Practice 51702 also contain dose mapping requirements. 1.2 Methods of analyzing the dose map data ar...

  6. Calculation of the internal radiation absorbed dose of 123I-Annexin V

    To estimate absorbed doses by 123I-Annexin V in human, 125I-Annexin V was used as a radiotracer for measuring the distribution of radiolabeled Annexin V in mice. The standard Medical Internal Radiation Dose (MIRD) method was used by Mirdose-3 software in dosimetry estimation. The results show that liver and kidney received 2.77 x 10-3 and 2.71 x 10-3 mGy/MBq, respectively. The red marrow received 1.78 x 10-5 mGy/MBq, and the other organs received doses between 1.5 x 10-4 and 10.5 x 10-4 mGy/MBq. The effective dose was estimated at 5.55 x 10-4 mSv/MBq. Human radiation dosimetry can be performed by the mice biodistribution data and important data for clinical safe trial of 123I-Annexin V are provided. (authors)

  7. Assessment of population absorbed dose from external penetrating radiation in Beijing

    Gonad mean annual absorbed dose from external penetrating radiation for Beijing residents is 73.4 mrad/y of which the annual absorbed dose from cosmic ray is 27.1 mrad/y and that from natural radioactivity in building materials is 37.6 mrad/y. The construction of buildings and roads makes the annual absorbed dose change. The construction of buildings brings about an increase of 19.7 per cent in the annual absorbed dose. The construction of roads results in a reduction of 2.4%

  8. Basic evaluation of absorbed dose in the 'mantle' field in radiotherapy for Hodgkin's disease

    Hodgkin's disease is one of the radiocurable disease. Avoiding overlap of dose from adjacent fields, megavoltage beams can be utilized at a treatment distance of 100 to 160 cm, making in possible to encompass all of the lymph node chains above the diaphragm in a single treatment field-the 'mantle' field. In the mantle field, we use a set of lead blocks designed individually to spare lager parts of normal lung tissue. We made blocks with beam divergence from low melting lead alloy using lead shot. With these blocks, we measured the absorbed dose in the mantle field in a human phantom, using a thermoluminescent dosimetry system. The results demonstrate that the absorbed dose distribution calculated by the computer system in the axial slices at + 60, 0 and -70 mm from the middle of the radiation field were in good agreements with our dosimetric results in the same slices. An integral dose volume histogram (DVH) obtained from the axial slice in the middle of the radiation field showed quantitatively the irradiated normal lung tissue. In conclusion: first, a dose calculation system using a computer was available in the large irregular shaped field utilizing a long treatment distance such as the 'mantle' field. Second, the DVH may be useful in the quantitative evaluation of lung injury resulting from radiotherapy using the 'mantle' field. (author)

  9. The therapeutic effects and absorbed dose of I-131 MIBG in patients with malignant pheochromocytoma

    High selective tumor uptake and retention of I-131 MIBG (MIBG) is known as a prerequisite for successful treatment of pheochromocytoma. We evaluated the relationship of absorbed dose of MIBG in tumor and therapeutic effects in twelve selected patients gained over a period of more than 5 years. All patients were diagnosed as malignant adrenal or extra-adrenal pheochromocytoma clinically. The metastases were identified in 10 patients on tracer dose images prior to therapy. Except for 4 patients, all others were symptomatic and had raised hormones indicative of tumor hyper-secretion at the time of enrolment. The number of doses of MIBG ranged from 1 to 3 times with 3.7 GBq per course and a cumulative activity from 3.7 to 11.1 GBq. The estimation of the therapeutic MIBG absorbed dose was performed on the basis of measurement after a therapy by using SPECT on day 1,3,and 5. The absorbed dose was calculated from MIRD data. None of the patients had a complete remission to I-131 MIBG therapy. In one patient, died with DIC 4 months after therapy. Of the 11 patients evaluated, a partial remission (PR) and stable disease was observed in one case individually. A dramatic improvement of the symptoms was noticed in this PR patient and maintained well condition now, 12.0 years after initial MIBG therapy. The cumulated absorbed dose with 11.1 GBq of MIBG calculated in lung and lymph node metastases was exceeded over 150Gy. MIBG uptake in each tumor was thought to be homogeneous. The other nine patients, however, showed little effects, and five were died with disease in 2.6 to 4.1 years after therapy. MIBG therapy is an effective palliative treatment for malignant pheochromocytoma, although a complete tumor response rate is low. It is sufficient in the therapy of these difficult tumors that response of tumors is partial remission or the tumor arrest. Criteria of patient selection with therapeutic modalities should be estimated including the absorbed dose and also the distribution

  10. Influence of elemental weight of human tissues estimated by ICCT software in absorbed dose calculation

    Massicano, Felipe; Possani, Rafael G.; Yoriyaz, Helio [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Sao Paulo, SP (Brazil). Centro de Engenharia Nuclear; Cintra, Felipe B.; Massicano, Adriana V.F., E-mail: massicano@gmail.com [Instituto de Pesquisas Energeticas e Nucleares (DIRF/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Diretoria de Radiofarmacia

    2011-07-01

    Therapeutic use of radiopharmaceuticals in Nuclear Medicine has been well established and presented good success rates against many forms of cancer. The biologic effects of radionuclide therapy are measured via a physical quantity, the absorbed dose, which is defined as per unit mass of tissue. Therefore, it is of great important an accurate dosimetry to assess the potential effects of treatment and to confirm or contradict the treatment predictions. The most common method used to estimate the absorbed dose at organ level was developed by Medical Internal Radiation Dose (MIRD) Committee, called MIRD system. However, this method does not have adequate patient data to obtain a dose estimate accurate in therapy. In recent years, internal radionuclide radiation dosimetry system evaluated spatial dose distribution. This system is based in Monte Carlo radiation transport codes with anatomical and functional information of the patient. The high accuracy is, at least in part, due to the Monte Carlo method allows human tissues to be characterized by elemental composition and mass density. Thus, a reliable estimation of human tissues (elemental composition and mass density) must be obtained. According to Schneider, Bortfield and Schlegel, the tissue parameters (mass densities ({rho}) and elemental weights ({omega}{sub i})) can be obtained using Hounsfield units provided from Computed Tomography (CT) images. Based on this, the Nuclear Engineer Center of IPEN developed the ICCT software (Image Converter Computed Tomography). It converts CT images in tissue parameters (mass densities ({rho}) and elemental weights ({omega}{sub i}). This work intended to verify if the estimate values by software ICCT of the tissue parameter and elemental weights ({omega}{sub i}) are plausible to estimate the absorbed dose with reasonable accuracy. (author)

  11. SU-E-I-85: Absorbed Dose Estimation for a Commercially Available MicroCT Scanner

    Purpose: To quantify the simulated absorbed dose delivered for a typical scan from a commercially available microCT scanner in order to aid in the dose estimation. Methods: The simulations were conducted using the Geant4 Monte Carlo Toolkit (version 10) with the standard electromagnetic classes. The Quantum FX microCT scanner (PerkinElmer, Waltham, MA) was modeled incorporating the energy fluence and angular distributions of generated photons, spatial dimensions of nominal source-to-object and source-to-detector distances. The energy distribution was measured using a spectrometer (X-123CdTe, Amptek Inc., Bedford, USA) with a 300 angular spread from the source for the 90 kVp X-ray beams with no additional filtration. The nominal distances from the source to object consisted of three setups: 154.0 mm, 104.0 mm, and 51.96 mm. Our simulations recorded the dose absorbed in a cylindrical phantom of PMMA with a fixed length of 2 cm and varying radii (10, 20, 30 and 40 mm) using 100 million incident photons. The averaged absorbed dose in the object was then quantified for all setups. An exposure measurement of 417 mR was taken using a Radcal 9095 system utilizing 10×9–180 ion chamber with the given technique of 90 kVp, 63 μA, and 12 s. The exposure rate was also simulated with same setup to calculate the conversion factor of the beam current and the number of incident photons. Results: For a typical cone-beam scan with non-filtered 90kVp, the dose coefficients (the absorbed dose per mAs) were 2.614, 2.549 and 2.467 μGy/mAs under source to object distance of 104 mm for the object diameters of 10 mm, 20 mm and 30 mm, respectively. Conclusion: A look-up table was developed where an investigator can estimate the delivered dose using this particular microCT given the scanning protocol (kVp and mAs) as well as the size of the scanned object

  12. Calibration procedure for thermoluminescent dosemeters in water absorbed doses for Iridium-192 high dose rate sources

    Thermoluminescent dosimeters are used in brachytherapy services quality assurance programs, with the aim of guaranteeing the correct radiation dose supplied to cancer patients, as well as with the purpose of evaluating new clinical procedures. This work describes a methodology for thermoluminescent dosimeters calibration in terms of absorbed dose to water for 192Ir high dose rate sources. The reference dose used is measured with an ionization chamber previously calibrated for 192Ir energy quality, applying the methodology proposed by Toelli. This methodology aims to standardizing the procedure, in a similar form to that used for external radiotherapy. The work evolves the adaptation of the TRS-277 Code of the International Atomic Energy Agency, for small and big cavities, through the introduction for non-uniform experimental factor, for the absorbed dose in the neighborhood of small brachytherapy sources. In order to simulate a water medium around the source during the experimental work, an acrylic phantom was used. It guarantees the reproducibility of the ionization chamber and the thermoluminescent dosimeter's location in relation to the radiation source. The values obtained with the ionization chamber and the thermoluminescent dosimeters, exposed to a 192Ir high dose rate source, were compared and correction factors for different source-detector distances were determined for the thermoluminescent dosimeters. A numeric function was generated relating the correction factors and the source-detector distance. These correction factors are in fact the thermoluminescent dosimeter calibration factors for the 192Ir source considered. As a possible application of this calibration methodology for thermoluminescent dosimeters, a practical range of source-detector distances is proposed for quality control of 192Ir high dose rate sources. (author)

  13. Cumulative lognormal distributions of dose-response vs. dose distributions

    A review of the author's findings over four decades will show that the lognormal probability density function can be fit to many types of positive-variate radiation measurement and response data. The cumulative lognormal plot on probability vs. logarithmic coordinate graph paper can be shown to be useful in comparing trends in exposure distributions or responses under differing conditions or experimental parameters. For variates that can take on only positive values, such a model is more natural than the 'normal' (Gaussian) model. Such modeling can also be helpful in elucidating underlying mechanisms that cause the observed data distributions. It is important, however, to differentiate between the cumulative plot of a dose distribution, in which successive percentages of data are not statistically independent, and the plots of dose-response data for which independent groups of animals or persons are irradiated or observed for selected doses or dose intervals. While independent response points can often be best fitted by appropriate regression methods, the density functions for cumulative dose or concentration distributions must be fit by particular maximum likelihood estimates from the data. Also, as indicated in the texts by D.J. Finney and by R.O. Gilbert, for example, a simple plot of such data on available probability (or probit) vs. log scale graph paper will quickly show whether an adequate representation of the data is a lognormal function. Processes that naturally generate lognormal variates are sometimes estimated by statistics that follow the lognormal straight line for a cumulative plot on a probability vs. log scale; on the other hand, sometimes the statistics of interpretation follow such a line only over a certain range. Reported examples of lognormal occupational exposure distributions include those in some facilities in which roundoff biases were removed for some years. However, for a number of exposure distributions at licensed facilities in the

  14. Absorbed XFEL dose in the components of the LCLS X-Ray Optics

    Hau-Riege, S

    2005-09-27

    We list the materials that are anticipated to be placed into the Linac Coherent Light Source (LCLS) x-ray free electron laser (XFEL) beam line, their positions, and the absorbed dose, and compare this dose with anticipated damage thresholds.

  15. Blood compounds irradiation process: assessment of absorbed dose using Fricke and Thermoluminescent dosimetric systems

    The assessment of gamma absorbed doses in irradiation facilities allows the quality assurance and control of the irradiation process. The liability of dose measurements is assign to the metrological procedures adopted including the uncertainty evaluation. Fricke and TLD 800 dosimetric systems were used to measure absorbed dose in the blood compounds using the methodology presented in this paper. The measured absorbed doses were used for evaluating the effectiveness of the irradiation procedure and the gamma dose absorption inside the irradiation room of a gamma irradiation facility. The radiation eliminates the functional and proliferative capacities of donor T-lymphocytes, preventing Transfusion associated graft-versus-host disease (TA-GVHD), a possible complication of blood transfusions. The results show the applicability of such dosimetric systems in quality assurance programs, assessment of absorbed doses in blood compounds and dose uniformity assign to the blood compounds irradiation process by dose measurements in a range between 25 Gy and 100 Gy. (author)

  16. Absorbed dose rate in air in metropolitan Tokyo before the Fukushima Daiichi Nuclear Power Plant accident

    The monitoring of absorbed dose rate in air has been carried out continually at various locations in metropolitan Tokyo after the accident of the Fukushima Daiichi Nuclear Power Plant. While the data obtained before the accident are needed to more accurately assess the effects of radionuclide contamination from the accident, detailed data for metropolitan Tokyo obtained before the accident have not been reported. A car-borne survey of the absorbed dose rate in air in metropolitan Tokyo was carried out during August to September 2003. The average absorbed dose rate in air in metropolitan Tokyo was 49±6 nGy h-1. The absorbed dose rate in air in western Tokyo was higher compared with that in central Tokyo. Here, if the absorbed dose rate indoors in Tokyo is equivalent to that outdoors, the annual effective dose would be calculated as 0.32 mSv y-1. (authors)

  17. Distribution of Doppler Redshifts of Associated Absorbers of SDSS Quasars

    Cai-Juan Pan; Zhi-Fu Chen

    2013-12-01

    Doppler redshifts of a sample of Mg II associated absorbers of SDSS DR7 quasars are analysed. We find that there might be three Gaussian components in the distribution of the Doppler redshift. The first Gaussian component, with the peak being located at Dopp = -0.0074, probably arises from absorbers with outflow histories observed in the direction close to jets of quasars. The second Gaussian component, with the peak being located at Dopp = -0.0017, possibly arises from absorbers with outflow histories observed in the direction far away from jets of quasars. Whereas, the third Gaussian component, with the peak being located at Dopp = -0.0004, might arise from the random motion of absorbers with respect to quasars.

  18. The estimation of absorbed dose rates for non-human biota: an extended intercomparison.

    Vives i Batlle, J; Beaugelin-Seiller, K; Beresford, N A; Copplestone, D; Horyna, J; Hosseini, A; Johansen, M; Kamboj, S; Keum, D-K; Kurosawa, N; Newsome, L; Olyslaegers, G; Vandenhove, H; Ryufuku, S; Vives Lynch, S; Wood, M D; Yu, C

    2011-05-01

    An exercise to compare 10 approaches for the calculation of unweighted whole-body absorbed dose rates was conducted for 74 radionuclides and five of the ICRP's Reference Animals and Plants, or RAPs (duck, frog, flatfish egg, rat and elongated earthworm), selected for this exercise to cover a range of body sizes, dimensions and exposure scenarios. Results were analysed using a non-parametric method requiring no specific hypotheses about the statistical distribution of data. The obtained unweighted absorbed dose rates for internal exposure compare well between the different approaches, with 70% of the results falling within a range of variation of ±20%. The variation is greater for external exposure, although 90% of the estimates are within an order of magnitude of one another. There are some discernible patterns where specific models over- or under-predicted. These are explained based on the methodological differences including number of daughter products included in the calculation of dose rate for a parent nuclide; source-target geometry; databases for discrete energy and yield of radionuclides; rounding errors in integration algorithms; and intrinsic differences in calculation methods. For certain radionuclides, these factors combine to generate systematic variations between approaches. Overall, the technique chosen to interpret the data enabled methodological differences in dosimetry calculations to be quantified and compared, allowing the identification of common issues between different approaches and providing greater assurance on the fundamental dose conversion coefficient approaches used in available models for assessing radiological effects to biota. PMID:21113609

  19. Assessment of out-of-field absorbed dose and equivalent dose in proton fields

    Clasie, Ben; Wroe, Andrew; Kooy, Hanne; Depauw, Nicolas; Flanz, Jay; Paganetti, Harald; Rosenfeld, Anatoly [Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States); Department of Radiation Medicine, Loma Linda University Medical Center, Loma Linda, California 92354 (United States) and Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, 2522 (Australia); Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States); Centre for Medical Radiation Physics, University of Wollongong, Wollongong, New South Wales, 2522 (Australia)

    2010-01-15

    Purpose: In proton therapy, as in other forms of radiation therapy, scattered and secondary particles produce undesired dose outside the target volume that may increase the risk of radiation-induced secondary cancer and interact with electronic devices in the treatment room. The authors implement a Monte Carlo model of this dose deposited outside passively scattered fields and compare it to measurements, determine the out-of-field equivalent dose, and estimate the change in the dose if the same target volumes were treated with an active beam scanning technique. Methods: Measurements are done with a thimble ionization chamber and the Wellhofer MatriXX detector inside a Lucite phantom with field configurations based on the treatment of prostate cancer and medulloblastoma. The authors use a GEANT4 Monte Carlo simulation, demonstrated to agree well with measurements inside the primary field, to simulate fields delivered in the measurements. The partial contributions to the dose are separated in the simulation by particle type and origin. Results: The agreement between experiment and simulation in the out-of-field absorbed dose is within 30% at 10-20 cm from the field edge and 90% of the data agrees within 2 standard deviations. In passive scattering, the neutron contribution to the total dose dominates in the region downstream of the Bragg peak (65%-80% due to internally produced neutrons) and inside the phantom at distances more than 10-15 cm from the field edge. The equivalent doses using 10 for the neutron weighting factor at the entrance to the phantom and at 20 cm from the field edge are 2.2 and 2.6 mSv/Gy for the prostate cancer and cranial medulloblastoma fields, respectively. The equivalent dose at 15-20 cm from the field edge decreases with depth in passive scattering and increases with depth in active scanning. Therefore, active scanning has smaller out-of-field equivalent dose by factors of 30-45 in the entrance region and this factor decreases with depth

  20. Dose rate distribution for products irradiated in a semi-industrial irradiation plant. 1st stage

    The model of the bulk product absorbed dose rate distribution in a semi industrial irradiation plant is presented. In this plant the products are subject to a dynamic irradiation process: single-plaque, single-direction, four-passes. The additional two passes, also one on each side of the plaque, serve to minimize the lateral dose variation as well as the depth-dose non-uniformity. The first stage of this model takes only into account the direct absorbed dose rate; the model outputs are the depth-dose distribution and the lateral-dose distribution. The calculated absorbed dose in the bulk product and its uniformity-ratio after the dynamic irradiation process for different products is compared. The model results are in good agreement with the experimental measurements in a bulk of irradiated product; and the air absorbed dose rate in the irradiation chamber behind the product subject to the dynamic irradiation process. (author)

  1. Status of air kerma and absorbed dose standards in India

    Exradin A2, NE 2571, NE2577, Victoreen 415 B, Victoreen 415, Exradin A3 and NE 2581 are maintained. These chambers have been calibrated against the primary standards and have been used in the international intercomparison experiments. The future programme of development of standards include i) Development of graphite/water calorimeters as absorbed dose standards, ii) Establishment of extrapolation chamber as primary standard for absorbed dose for beta and soft x-ray beams and iii) Development of energy-independent plastic scintillators as reference standard for low energy low activity brachytherapy sources. (author)

  2. Graphite calorimeter, the primary standard of absorbed dose at BNM-LNHB

    The graphite calorimeter is the standard for absorbed dose to water at BNM-LNHB. The transfer from absorbed dose to graphite to absorbed dose to water is then performed by means of chemical dosimeters and ionisation chamber measurements. Therefore the quality of graphite calorimeter measurements is essential. The present graphite calorimeter is described. The characteristics of this calorimeter are pointed out. Special attention is given to the thermal feedback of the core, which is the main difference with the Domen-type calorimeter. The repeatability and reproducibility of the mean absorbed dose in the calorimeter core are presented in detail. As an example, individual measurements in the 20 MV photon beam from our Saturne 43 linac are given. The y-axis quantity is the mean absorbed dose in the core divided by the reference ionisation chamber charge. Both are normalised to the monitor ionisation chamber charge. The standard deviation (of the distribution itself) is 0.12 % for the first set of measurements performed in 1999. In 2002, for each different series, the standard deviation is 0.03%. The improvement on the 2002 standard deviation is mainly due to the change of the ionisation chamber used for the beam monitoring of the linac. Some benefit also comes from changes on the thermal control and measuring systems (nanovoltmeters, Wheatstone bridges, power supplies, determination of the measuring bridge sensitivity (V/Ω.) ). The maximum difference between the means of the three series is 0.08%. This difference is due to the variation of not only the calorimetric measurements but also of the reference ionisation chamber response, of the position of the assembly and of the monitoring of the beam. The stability of the linac (electron energy, photon beam shape) has to be very good too in order to obtain this global performance. The correction factors necessary to determine the absorbed dose to graphite at the reference point in an homogeneous phantom from the

  3. Absorbed dose to the skin in radiological examinations of upper and lower gastrointestinal tract

    Absorbed doses to the skin in radiological examinations of the upper and lower gastronintestinal tract in conventional and digital radiology are evaluated and compared. Absorbed doses were measured with LiF thermoluminescence dosemeters placed on the lower pelvis, umbilicus and forehead of the patient to evaluate the absorbed dose in and outside the primary beam. On 10 patients a reduction in absorbed dose of about 34% for double contrast barium enema and of 66% for upper gastrointestinal tract examinations was revealed with digital radiography equipment. In our working conditions the lower dose requirement for digital radiography is mainly due to image intensifiers and television chains and also, due to our equipment settings, to the dose reduction with digital spot fluorography compared with conventional spot film radiography. (Author)

  4. Absorbed doses on patients undergoing tomographic exams for pre-surgery planning of dental implants

    The thermoluminescent (TL) dosimetry was used to measure entrance skin absorbed doses at anatomical points close to critical organs of patients undergoing tomographic techniques as part of a pre-surgery planning for dental implants. The dosimetric procedure was applied in 19 patients, and absorbed doses could be measured with a combined uncertainty down to 14%. Results showed that patient doses may be increased by a factor of 20 in the helical computed tomography compared to panoramic and spiral conventional tomographic exams

  5. Concentration activities of natural radionuclides in three fish species in Brazilian coast and their contributions to the absorbed doses

    Activity concentrations of U-238, Ra-226, Pb-210, Th-232 e Ra-228 were analysed in three fish species at the Brasilian Coast. The fish 'Cubera snapper' (Lutjanus cyanopterus, Cuvier, 1828), in the region of Ceara and 'Whitemouth croaker' (Micropogonias furnieri, Desmarest, 1823) and 'Lebranche mullet' (Mugil liza, Valenciennes, 1836) in the region of Rio de Janeiro. These concentrations were transformed in absorbed dose rate using a dose conversion factor in unit of gray per year (μGy y-1), per becquerel per kilogram (Bq kg-1). Only the absorbed dose due to intake of radionuclides was examined, and the contributions due to radionuclides present in water and sediment were disregarded. The radionuclides were considered to be uniformly distributed in the fish body. The limit of the dose rate used, proposed by the Department of Energy of the USA, is equal to 3.65 1003 mGy y-1. The average dose rate due to the studied radionuclides is equal to 6.09 1000 μGy y-1, a value minor than 0.1% than the limits indicated by DOE, and quite similar to that found in the literature for 'benthic' fish. The most important radionuclides were the alpha emitters Ra-226 having 61 % of absorbed dose rate. U-238 and Th-232, each contributes with approximately 20 % of the absorbed dose rate. These three radionuclides are responsible for almost 100% of the dose rate received by the studied organisms. The beta emitters Ra-228 and Pb-210 account for approximately 1 % of the absorbed dose rate. (author)

  6. Measurements of angular distributions of degraded protons in thick absorbers

    This chapter examines the behavior of a proton beam with a kinetic energy corresponding to the lower energy limit of the Low-Energy Antiproton Ring (LEAR), which is degraded by thick absorbers suffering an energy loss comparable to its initial energy. Angular distributions of protons are measured with an initial energy around 3.5 MeV, degraded by thick aluminium, polyethylene, and lead absorbers. Using the Erlangen Tandem accelerator, the measurements indicate that in all cases the variation of the width of the straggling distribution (fwhm) and of their mean energy as a function of the scattering angle was found to be small in the angular region between 00 and 150. It is concluded that degraders with low proton number are superior to those with high proton number, due to their narrower angular distributions

  7. Isoeffective dose: a concept for biological weighting of absorbed dose in proton and heavier-ion therapies

    Wambersie, A; Menzel, H G; Gahbauer, R; DeLuca, P M; Hendry, J H; Jones, D T L

    2011-01-01

    When reporting radiation therapy procedures, International Commission on Radiation Units and Measurements (ICRU) recommends specifying absorbed dose at/in all clinically relevant points and/or volumes. In addition, treatment conditions should be reported as completely as possible in order to allow full understanding and interpretation of the treatment prescription. However, the clinical outcome does not only depend on absorbed dose but also on a number of other factors such as dose per fraction, overall treatment time and radiation quality radiation biology effectiveness (RBE). Therefore, weighting factors have to be applied when different types of treatments are to be compared or to be combined. This had led to the concept of `isoeffective absorbed dose', introduced by ICRU and International Atomic Energy Agency (IAEA). The isoeffective dose D(IsoE) is the dose of a treatment carried out under reference conditions producing the same clinical effects on the target volume as those of the actual treatment. It i...

  8. Direct absorbed dose to water determination based on water calorimetry in scanning proton beam delivery

    Purpose: The aim of this manuscript is to describe the direct measurement of absolute absorbed dose to water in a scanned proton radiotherapy beam using a water calorimeter primary standard. Methods: The McGill water calorimeter, which has been validated in photon and electron beams as well as in HDR 192Ir brachytherapy, was used to measure the absorbed dose to water in double scattering and scanning proton irradiations. The measurements were made at the Massachusetts General Hospital proton radiotherapy facility. The correction factors in water calorimetry were numerically calculated and various parameters affecting their magnitude and uncertainty were studied. The absorbed dose to water was compared to that obtained using an Exradin T1 Chamber based on the IAEA TRS-398 protocol. Results: The overall 1-sigma uncertainty on absorbed dose to water amounts to 0.4% and 0.6% in scattered and scanned proton water calorimetry, respectively. This compares to an overall uncertainty of 1.9% for currently accepted IAEA TRS-398 reference absorbed dose measurement protocol. The absorbed dose from water calorimetry agrees with the results from TRS-398 well to within 1-sigma uncertainty. Conclusions: This work demonstrates that a primary absorbed dose standard based on water calorimetry is feasible in scattered and scanned proton beams.

  9. Secondary neutron dose measurement for proton eye treatment using an eye snout with a borated neutron absorber

    We measured and assessed ways to reduce the secondary neutron dose from a system for proton eye treatment. Proton beams of 60.30 MeV were delivered through an eye-treatment snout in passive scattering mode. Allyl diglycol carbonate (CR-39) etch detectors were used to measure the neutron dose in the external field at 0.00, 1.64, and 6.00 cm depths in a water phantom. Secondary neutron doses were measured and compared between those with and without a high-hydrogen–boron-containing block. In addition, the neutron energy and vertices distribution were obtained by using a Geant4 Monte Carlo simulation. The ratio of the maximum neutron dose equivalent to the proton absorbed dose (H(10)/D) at 2.00 cm from the beam field edge was 8.79 ± 1.28 mSv/Gy. The ratio of the neutron dose equivalent to the proton absorbed dose with and without a high hydrogen-boron containing block was 0.63 ± 0.06 to 1.15 ± 0.13 mSv/Gy at 2.00 cm from the edge of the field at depths of 0.00, 1.64, and 6.00 cm. We found that the out-of-field secondary neutron dose in proton eye treatment with an eye snout is relatively small, and it can be further reduced by installing a borated neutron absorbing material

  10. The changes in optical absorbance of ZrO2 thin film with the rise of the absorbed dose

    Abayli, D.; Baydogan, N.

    2016-03-01

    In this study, zirconium oxide (ZrO2) thin film samples prepared by sol-gel method were irradiated using Co-60 radioisotope as gamma source. Then, it was investigated the ionizing effect on optical properties of ZrO2 thin film samples with the rise of the absorbed dose. The changes in the optical absorbance of ZrO2 thin films were determined by using optical transmittance and the reflectance measurements in the range between 190 - 1100 nm obtained from PG Instruments T80 UV-Vis spectrophotometer.

  11. A Monte Carlo study of absorbed dose distributions in both the vapor and liquid phases of water by intermediate energy electrons based on different condensed-history transport schemes.

    Bousis, C; Emfietzoglou, D; Hadjidoukas, P; Nikjoo, H

    2008-07-21

    Monte Carlo transport calculations of dose point kernels (DPKs) and depth dose profiles (DDPs) in both the vapor and liquid phases of water are presented for electrons with initial energy between 10 keV and 1 MeV. The results are obtained by the MC4 code using three different implementations of the condensed-history technique for inelastic collisions, namely the continuous slowing down approximation, the mixed-simulation with delta-ray transport and the addition of straggling distributions for soft collisions derived from accurate relativistic Born cross sections. In all schemes, elastic collisions are simulated individually based on single-scattering cross sections. Electron transport below 10 keV is performed in an event-by-event mode. Differences on inelastic interactions between the vapor and liquid phase are treated explicitly using our recently developed dielectric response function which is supplemented by relativistic corrections and the transverse contribution. On the whole, the interaction coefficients used agree to better than approximately 5% with NIST/ICRU values. It is shown that condensed phase effects in both DPKs and DDPs practically vanish above 100 keV. The effect of delta-rays, although decreases with energy, is sizeable leading to more diffused distributions, especially for DPKs. The addition of straggling for soft collisions is practically inconsequential above a few hundred keV. An extensive benchmarking with other condensed-history codes is provided. PMID:18574312

  12. Importance of pre-treatment radiation absorbed dose estimation for radioimmunotherapy of non-Hodgkin's lymphoma

    Non-Hodgkin's lymphoma I-131 radioimmunotherapy data were analyzed to determine whether a predictive relationship exists between radiation absorbed doses calculated from biodistribution studies and doses derived from patient size. Radioactivity treatment administrations scaled to patient size (MBq/kg or MBq/m2) or fixed MBq doses do not produce consistent radiation absorbed dose to critical organs. Treatment trials that do not provide dose estimates for critical normal organs are less likely to succeed in identifying a clinical role for radioimmunotherapy

  13. Absorbed doses profiles vs Synovia tissue depth for the Y-90 and P-32 used in radiosynoviortesis treatment

    The radiosynoviortesis treatment has been used during more of 40 years as an alternative to the chemical and surgical synovectomy to alleviate the pain and to reduce the inflammation in suffered patients of rheumatic arthropathies, haemophilic arthropathies and other articulation disorders. It consists on the injection of radioactive isotopes inside a synovial cavity. For to evaluate the dosimetry of the radiosynoviortesis treatment is of great interest to know the absorbed dose in the volume of the target (synovia). The precise calculation of the absorbed dose in the inflamed synovia it is difficult, for numerous reasons, since the same one will depend on the thickness of the synovial membrane, the size of the articular space, the structure of the synovial membrane, the distribution in the articulation, the nature of the articular liquid, etc. Also the presence of the bone and the articular cartilage, components also of the articulation, it even complicated more the calculations. The method used to evaluate the dosimetry in radioactive synovectomy is known as the Monte Carlo method. The objective of our work consists on estimating with the Monte Carlo code MCNP4B the absorbed dose of the Y-90 and the P-32 in the depth of the synovial tissue. The results are presented as absorbed dose for injected millicurie (Gy/mCi) versus depth of synovial tissue. The simulation one carries out keeping in mind several synovia areas, of 50 cm2 to 250 cm2 keeping in mind three states of progression of the illness. Those obtained values of absorbed dose using the MCNP4B code will allow to introduce in our country an optimized method of dose prescription to the patient, to treat the rheumatic arthritis in medium and big articulations using the Y-90 and the P-32, eliminating the fixed doses and fixed radionuclides for each articulation like it happens in many clinics of Europe, as well as the empiric doses. (Author)

  14. Radioiodine Therapy of Hyperthyroidism. Simplified patient-specific absorbed dose planning

    Radioiodine therapy of hyperthyroidism is the most frequently performed radiopharmaceutical therapy. To calculate the activity of 131I to be administered for giving a certain absorbed dose to the thyroid, the mass of the thyroid and the individual biokinetic data, normally in the form of uptake and biologic half-time, have to be determined. The biologic half-time is estimated from several uptake measurements and the first one is usually made 24 hours after the intake of the test activity. However, many hospitals consider it time-consuming since at least three visits of the patient to the hospital are required (administration of test activity, first uptake measurement, second uptake measurement plus treatment). Instead, many hospitals use a fixed effective half-time or even a fixed administered activity, only requiring two visits. However, none of these methods considers the absorbed dose to the thyroid of the individual patient. In this work a simplified patient-specific method for treating hyperthyroidism is proposed, based on one single uptake measurement, thus requiring only two visits to the hospital. The calculation is as accurate as using the individual biokinetic data. The simplified method is as patient-convenient and time effective as using a fixed effective half-time or a fixed administered activity. The simplified method is based upon a linear relation between the late uptake measurement 4-7 days after intake of the test activity and the product of the extrapolated initial uptake and the effective half-time. Treatments not considering individual biokinetics in the thyroid result in a distribution of administered absorbed dose to the thyroid, with a range of -50 % to +160 % compared to a protocol calculating the absorbed dose to the thyroid of the individual patient. Treatments with a fixed administered activity of 370 MBq will in general administer 250 % higher activity to the patient, with a range of -30 % to +770 %. The absorbed dose to other organs

  15. Absorbed dose evaluations in retrospective dosimetry: Methodological developments using quartz

    Bailiff, I.K.; Bøtter-Jensen, L.; Correcher, V.; Delgado, A.; Goksu, H.Y.; Jungner, H.; Petrov, S.A.

    Dose evaluation procedures based on luminescence techniques were applied to 50 quartz samples extracted from bricks that had been obtained from populated or partly populated settlements in Russia and Ukraine downwind of the Chernobyl NPP. Determinations of accrued dose in the range similar to 30......-300 mGy were obtained using TL (210 degreesC TL and pre-dose) and OSL (single and multiple aliquot) procedures. Overall, good inter-laboratory concordance of dose evaluations was achieved, with a variance (1 sigma) of similar to+/-10 mGy for the samples examined. (C) 2000 Elsevier Science Ltd. All...... rights reserved....

  16. Measurement of absorbed dose to water for low and medium energy x-rays

    to graphite in a graphite phantom. A measurement of absorbed dose to graphite, traceable to the physical base quantities of length and charge, can be accomplished by means of a graphite extrapolation chamber. In the energy range considered and under conditions of secondary electron equilibrium, the absorbed dose to graphite is numerically identical to the graphite collision kerma. Thus, by making use of the spectral distribution of the photon fluence at the point of measurement, which can be obtained by Monte Carlo calculations, the graphite collision kerma can be converted to water collision kerma by means of the ratio of the mass-energy absorption coefficients averaged over the photon energy fluence spectrum. This allows the calibration of a transfer ionisation chamber in terms of water collision kerma inside the graphite phantom. This transfer chamber is then positioned at the reference point of a water phantom. On the assumption that the angular and spectral distributions of the photon fluence in the graphite and the water phantom are reasonably similar to each other, the ionisation chamber measures water collision kerma inside the water phantom, which, again under the conditions prevailing, is numerically identical to absorbed dose to water. Each of the two methods outlined above has its 'critical' steps. For the measurement based on air kerma calibration there are significant differences between the calibration conditions (essentially mono directional radiation) and the conditions of measurement characterised by abundant scattered radiation. This makes it difficult to find reliable values for the correction factors which have to be applied to take the difference in the response to the two radiation fields into account. On the other hand, for the measurements with the graphite extrapolation chamber the ratio of the mass-energy absorption coefficients graphite to water is to be determined. This factor depends quite strongly on photon energy. The accuracy of the

  17. Development of methodology for assessment of absorbed dose and stopping power for low energy conversion electrons

    The evaluation of absorbed dose in the case of external and internal contamination due to radionuclides is sometimes hard, because of the difficulties in the assessment of the absorbed dose caused by electrons with energy less than 100 KeV in mucous membrane. In this work, a methodology for assessment of absorbed dose and stopping power in VYNS (co-polymer of polivinyl chloride - acetate) absorbers, for the 62.5 KeV and 84-88 KeV energy 109 Cd conversion electrons, working with a 4 π proportional pressurized detector, is presented. In order to assure the reproducibility of measurement conditions, one of the detector halves has been used to obtain a spectrum of a thin 109 Cd source, without absorber. The other half of the detector was used in concomitance to obtain spectra with different thicknesses if absorber. The absorbed energy was obtained subtracting each spectrum with absorber from the spectrum without absorber, which were stored in a microcomputer connected to signal processing systems by ACE type interface. The VYNS weight and thickness were evaluated using common radionuclide metrology procedures. As VYNS has characteristics similar to a tissue equivalent material, the results obtained are consistent with dosimetric concepts and have a good agreement with those of the literature. (author)

  18. Estimation of terrestrial air-absorbed dose rate from the data of regional geochemistry database

    This paper presents an estimation of air-absorbed dose rate from the data of K2O, U and Th content from Chinese regional geochemical database. A total of 421 group original data of combined samples in Zhongshan City (ZSC), Guangdong Province and south China were extracted from the national geochemical database. Estimated average value of air-absorbed dose rate is 139.4 nGy h-1 in the granite area and 73.7 nGy h-1 in the sedimentary area. The level of air-absorbed dose rate is closely related with the surface lithology. Estimated mean air-absorbed dose rate approximates to the measured average value by a portable plastic scintillator dosemeter in Zhuhai City were bordered with ZSC. The results show that the pre-evaluation of ionizing radiation level using regional geochemical data is feasible. (author)

  19. Advances in absorbed dose measurement standards at the australian radiation laboratory

    The applications of ionising radiation in the medical and industrial fields require both an accurate knowledge of the amount of ionising radiation absorbed by the medium in question and the capability of relating this to National and International standards. The most useful measure of the amount of radiation is the absorbed dose which is defined as the energy absorbed per unit mass. For radiotherapy, the reference medium is water, even though the measurement of the absorbed dose to water is not straightforward. Two methods are commonly used to provide calibrations in absorbed dose to water. The first is the calibration of the chamber in terms of exposure in a Cobalt-60 beam, followed by the conversion by a protocol into dose to water in this and higher energy beams. The other route is via the use of a graphite calorimeter as a primary standard device, where the conversion from absorbed dose to graphite to absorbed dose in water is performed either by theoretical means making use of cavity ionisation theory, or by experiment where the graphite calorimeter and secondary standard ionisation chamber are placed at scaled distances from the source of the radiation beam (known as the Dose-Ratio method). Extensive measurements have been made at Cobalt-60 at ARL using both the exposure and absorbed dose to graphite routes. Agreement between the ARL measurements and those based on standards maintained by ANSTO and NPL is within ± 0.3%. Absorbed dose measurements have also been performed at ARL with photon beams of nominal energy 16 and 19 MeV obtained from the ARL linac. The validity of the protocols at high photon energies, the validity of the methods used to convert from absorbed dose in graphite to absorbed dose in water and the validity of the indices used to specify the beams are discussed. Brief mention will also be made of the establishment of a calibration facility for neutron monitors at ARL and of progress in the development of ERP dosimetry

  20. Development of standardized methods to verify absorbed dose of irradiated fresh and dried fruits, tree nuts in trade

    Investigations were carried out on standardization of desired process control parameters such as dose distribution in trade containers, container standardization and development of 'label' dosimeters. A prototype 'label' dose indicators Sterins for threshold doses of 125 Gy and 300 Gy was studied. Dose distribution was studied using fresh fruits and tree nuts in trade and standardized containers with varying product densities. The distribution of absorbed doses was measured by Fricke, Gammachrome YR, clear Polymethylmethacrylate (PMMA), EthanolChlorobenzene (ECB) and Sterin 300. These values are given as Dmax/Dmin ratios in relation to product bulk densities. It was observed that bulk densities varied greatly among different products depending on the types of fruits, containers and pattern of loading which also affected dose distribution. Dmax/Dmin obtained by proper dose mapping could be kept low by arranging proper irradiation conditions which ensured uniform dose distribution. Prototype 'label' dose indicators like Sterins and clear PMMA were used for dose mapping along with the standard primary and secondary dosimeters. Sterins and clear PMMA were also studied for their dosimetric properties, particularly for use in label dosimetry. Sterins 125 and 300 evaluated visually showed their integrity at their threshold doses. The word NOT on Sterin 125 eclipsed after 115 Gy and on Sterin 300 after 270 Gy dose. Clear PMMA samples of 410 mm thickness irradiated at 200-1000 Gy showed linear response and had postirradiation stability for over a month storage at normal temperatures (21-35 deg. C) and humidities. These could be investigated further for developing as 'label' dosimeters in insect control quarantine treatment. Other low dose indicators studied such as coloured perspex, dye solutions were not found useful at quarantine dose levels. Further investigations are required for developing a 'label' dosimeter for commercial use. (author)

  1. Radon Exposure and the Definition of Low Doses-The Problem of Spatial Dose Distribution.

    Madas, Balázs G

    2016-07-01

    Investigating the health effects of low doses of ionizing radiation is considered to be one of the most important fields in radiological protection research. Although the definition of low dose given by a dose range seems to be clear, it leaves some open questions. For example, the time frame and the target volume in which absorbed dose is measured have to be defined. While dose rate is considered in the current system of radiological protection, the same cancer risk is associated with all exposures, resulting in a given amount of energy absorbed by a single target cell or distributed among all the target cells of a given organ. However, the biological effects and so the health consequences of these extreme exposure scenarios are unlikely to be the same. Due to the heterogeneous deposition of radon progeny within the lungs, heterogeneous radiation exposure becomes a practical issue in radiological protection. While the macroscopic dose is still within the low dose range, local tissue doses on the order of Grays can be reached in the most exposed parts of the bronchial airways. It can be concluded that progress in low dose research needs not only low dose but also high dose experiments where small parts of a biological sample receive doses on the order of Grays, while the average dose over the whole sample remains low. A narrow interpretation of low dose research might exclude investigations with high relevance to radiological protection. Therefore, studies important to radiological protection should be performed in the frame of low dose research even if the applied doses do not fit in the dose range used for the definition of low doses. PMID:27218294

  2. Calculation of 131I-ortho-iodohippurate absorbed kidney dose: A literature review

    Extensive information has been made available relative to the physical aspects necessary for calculation of radiation absorbed dose from radiopharmaceuticals. A similar data base for the biological factors involved in these calculations has not been documented as thoroughly. The authors present an extensive literature review for the radiation absorbed dose of 131I-ortho-iodohippurate and discuss the rationale for adjusting previously accepted values with new biodistribution information

  3. Biological indicators for radiation absorbed dose: a review

    Biological dosimetry has an important role to play in assessing the cumulative radiation exposure of persons working with radiation and also in estimating the true dose received during accidents involving external and internal exposure. Various biodosimetric methods have been tried to estimate radiation dose for the above purposes. Biodosimetric methods include cytogenetic, immunological and mutational assays. Each technique has certain advantages and disadvantages. We present here a review of each technique, the actual method used for detection of dose, the sensitivity of detection and its use in long term studies. (author)

  4. Fetus absorbed dose evaluation in head and neck radiotherapy procedures of pregnant patients

    In this work the head and neck cancer treatment of a pregnant patient was experimentally simulated. A female anthropomorphic Alderson phantom was used and the absorbed dose to the fetus was evaluated protecting the patient's abdomen with a 7 cm lead layer and using no abdomen shielding. The target volume dose was 50 Gy. The fetus doses evaluated with and without the lead shielding were, respectively, 0.52±0.039 and 0.88±0.052 cGy. - Highlights: • Head and neck radiotherapy simulation. • Head and neck radiotherapy procedures for pregnant patients. • Shielded and unshielded fetus absorbed dose evaluation

  5. Absorbed dose measurements in the build-up region of flattened versus unflattened megavoltage photon beams.

    De Puysseleyr, Annemieke; Lechner, Wolfgang; De Neve, Wilfried; Georg, Dietmar; De Wagter, Carlos

    2016-06-01

    This study evaluated absorbed dose measurements in the build-up region of conventional (FF) versus flattening filter-free (FFF) photon beams. The absorbed dose in the build-up region of static 6 and 10MV FF and FFF beams was measured using radiochromic film and extrapolation chamber dosimetry for single beams with a variety of field sizes, shapes and positions relative to the central axis. Removing the flattening filter generally resulted in slightly higher relative build-up doses. No considerable impact on the depth of maximum dose was found. PMID:27020966

  6. Evaluation of the absorbed dose in odontological computerized tomography; Avaliacao da dose absorvida em tomografia computadorizada odontologica

    Legnani, Adriano; Schelin, Hugo R.; Rocha, Anna Silvia P.S. da, E-mail: schelin@utfpr.edu.b, E-mail: anna@utfpr.edu.b [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Khoury, Helen J., E-mail: khoury@ufpe.b [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil)

    2011-10-26

    This paper evaluated the absorbed dose at the surface entry known as 'cone beam computed tomography' (CBCT) in odontological computerized tomography. Examination were simulated with CBCT for measurements of dose. A phantom were filled with water, becoming scatter object of radiation. Thermoluminescent dosemeters were positioned on points correspondent to eyes and salivary glands

  7. Estimation of the absorbed dose in gamma irradiated food containing bone by electron spin resonance spectroscopy

    The use of electron spin resonance (ESR) spectroscopy to accurately evaluate the absorbed dose to radiationprocessed bones (and thus meats) is examined. The exposure of foodstuffs containing bone to a dose of ionizing radiation results in the formation of long lived free radicals which give rise to characteristics ESR signals. The yield of radicals was found to be proportional to absorbed dose. Additive re-irradiation of previously irradiated bone was used to estimate the absorbed dose in the irradiated chicken bone. Simple non-linear rational equation was found to fit to the data and yields good dose estimates for irradiated bone in the range of doses (1.0 - 5.0 kGy). Decay of the ESR signal intensity was monitored at different dose levels (2.0 and 7.0 kGy) up to 22 days. The absorbed dose in irradiated chicken (2.Om 3.0 and 6.0 kGy) was assessed at 2, 6 and 12 days after irradiation. Relatively good results were obtained when measurements were made within the following days (up to 12 days) after irradiation. The ability of the dose additive method to provide accurate dose assessments is tested here

  8. The absorbed dose in air of photons generated from secondary cosmic rays at sea level at Nagoya, Japan

    Investigations have been carried out to determine the absorbed dose in air of photons generated from secondary cosmic radiation at sea level at Nagoya, Japan. To isolate the contribution from cosmic photons, the pulse-height distributions due to μ particles and electrons were eliminated from the observed pulse-height distribution of a measurement with a 3'' diam. spherical NaI(Tl) detector. The pulse height due to μ particles and electrons was inferred from the coincidence technique using two types of scintillation detectors with different sensitivities to photons. To obtain the photon fluence rate for further dose calculation, the pulse-height distribution of cosmic photons was unfolded by the iterative method. The mean and its standard deviation of the absorbed dose in air and fluence rate due to cosmic photons calculated from a one year observation are 2.86±0.05 nGy.h-1 and 0.1342±0.0015 photons.cm-2.s-1, respectively. The absorbed dose in air from cosmic photons was 0.5% lower during autumn to winter and 0.6% higher during spring to summer than the mean taken over the year. (author)

  9. Evaluation of the absorbed dose to the lungs due to Xe133 and Tc99m (MAA)

    The absorbed dose in lungs of an adult patient has been evaluated using the biokinetics of radiopharmaceuticals containing Xe133 or Tc99m (MAA). The absorbed dose was calculated using the MIRD formalism, and the Cristy-and Eckerman lungs model. The absorbed dose in the lungs due to 133Xe is 0.00104 mGy/MBq. Here, the absorbed dose due to remaining tissue, included in the 133Xe biokinetics is not significant. The absorbed dose in the lungs, due Tc99m (MAA), is 0.065 mGy/MBq. Approximately, 4.6% of the absorbed dose is due to organs like liver, kidneys, bladder, and the rest of tissues, included in the Tc99m biokinetics. Here, the absorbed dose is very significant to be overlooked. The dose contribution is mainly due to photons emitted by the liver. (Author)

  10. Measurement of absorbed dose for high energy electron using CaSO4: Tm-PTFE TLD

    In this study, the highly sensitive CaSO4: Tm-PTFE TLDs has been fabricated for the purpose of measurement of high energy electron. CaSO4: Tm phosphor powder was mixed with polytetrafluoroethylene(PTFE) powder and moulded in a disk type(diameter 8.5mm, thickness 90mg/cm2) by cold pressing. The absorbed dose distribution and ranges for high energy electron were measured by using the CaSO4: Tm-PTFE TLDs. The ranges determined were R100=3D14.5mm, R50=3D24.1mm and Rp=3D31.8mm, respectively and the beam flatness, the variation of relative dose in 80% of the field size, was 4.5%. The fabricated CaSO4: Tm-PTFE TLDs may be utilized in radiation dosimetry for personal, absorbed dose and environmental monitoring.=20

  11. Absorbed dose measurement on disprin tablets by ESR technique

    In this investigation an attempt has been made to measure the dose from free radicals induced in medicine tables by ESR. About 60mg of powdered irradiated Disprin tablets (acetyl salicylic acid 72% calcium carbonate 21% anhydrous citric acid 7%) was loaded into quartz tube and free radical density was measured using Bruker ESP-300 spectrometer. A linear response of dose with peak to peak height was obtained in the range of 1Gy to 700Gy at g=1.9975. (author). 5 refs., 1 fig

  12. Plastic film materials for dosimetry of very large absorbed doses

    McLaughlin, W.L.; Miller, Arne; Abdel-Rahim, F.;

    1985-01-01

    Most plastic films have limited response ranges for dosimetry because of radiation-induced brittleness, degradation, or saturation of the signal used for analysis (e.g. spectrophotometry) at high doses. There are, however, a few types of thin plastic films showing linearity of response even up to...

  13. measurement of absorbed dose in mix-dp phantom irradiated by x and gamma rays

    It has been done of x-rays dan gamma rays absorbed dose measurement of mix-dp phantom of 70 kVp.90kvp and 110 kvp x rays kxo-12 medical exposure and cobalt-60 gamma (50 ci) by UD-170A BeO-TLD. Ionization chamber 12 cc NIRS-R2 as reference dosemeter, which was calibrated on primer dosemeter. In X-rays energy used, it was done of absorbed dose measurement on Mix-Dp phantom surface and depth (d= 10cm) beam field area 10 x 10 cm, focus distance (FSD), s=80 cm dose measurement of 90 kvp X-rays on Mix-Dp phantom surface, depth and scattering (d=15 cm) beam field area 12 x 12 cm, focus distance (FSD),s=79 cm and measurement of absorbed dose Co-60 gamma: 5 R, 10R, 20 R, 30R, 40R and 50R by dose rate 0.434 R/min. It was shown that in clinical, effective energy range of X-rays relative lower than dose range Co-60 gamma. BeO-TLD characteristic on energy dependence is low based on TI sensitivity ± 1.3 for energy below 100 keV. Relation between absorbed dose and TL response to 90 kVp X-rays shown that rperm=0.990, r ber=0.995 and r sact=0.962. In measurement of Co-60 gamma absorbed dose by BeO-TLD shown TI sensitivity decrease ± 0.900. The result still needed corrections to achieve optimum measurement of absorbed dose X-rays and gamma by UD-170A BeO-TLD, which were performed optimum fading time and anealling temperature

  14. Radiation absorbed dose estimate for rubidium-82 determined from in vivo measurements in human subjects

    Radiation absorbed doses from rubidium-82 injected intravenously were determined in two young men, aged 23 and 27, using a dynamic conjugate counting technique to provide data for the net organ integrated time-activity curves in five organs: kidneys, lungs, liver, heart, and testes. This technique utilized a tungsten collimated Anger camera and the accuracy was validated in a prestwood phantom. The data for each organ were compared with conjugate count rates of a reference Ge-68/Ga-68 standard which had been calibrated against the Rb-82 injected. The effects of attenuation in the body were eliminated. The MIRD method was used to calculate the organ self absorbed doses and the total organ absorbed doses. The mean total absorbed doses were as follows (mrads/mCi injected): kidneys 30.9, heart walls 7.5, lungs 6.0, liver 3.0, testes 2.0 (one subject only), red marrow 1.3, remainder of body 1.3 and, extrapolating to women, ovaries 1.2. This absorbed dose to the kidney is significantly less than the pessimistic estimate of 59.4 mrads/mCi, made assuming instantaneous uptake and complete extraction of activity with no excretion by the kidneys, which receive 20% of the cardiac output. Further, in a 68 year old man the renal self absorbed dose was approximately 40% less than the mean renal self absorbed dose of the younger men. This decrease is probably related to the decline in renal blood flow which occurs with advancing age but other factors may also contribute to the observed difference. 14 references, 4 figures, 2 tables

  15. Patient absorbed radiation doses estimation related to irradiation anatomy; Estimativa de dose absorvida pelo paciente relacionada a anatomia irradiada

    Soares, Flavio Augusto Penna; Soares, Amanda Anastacio; Kahl, Gabrielly Gomes, E-mail: prof.flavio@gmail.com, E-mail: amanda-a-soares@hotmail.com, E-mail: gabriellygkahl@gmail.com [Instituto Federal de Eduacao, Ciencia e Tecnologia de Santa Catarina (IFSC), Florianopolis, SC (Brazil)

    2014-07-01

    Developed a direct equation to estimate the absorbed dose to the patient in x-ray examinations, using electric, geometric parameters and filtering combined with data from irradiated anatomy. To determine the absorbed dose for each examination, the entrance skin dose (ESD) is adjusted to the thickness of the patient's specific anatomy. ESD is calculated from the estimated KERMA greatness in the air. Beer-Lambert equations derived from power data mass absorption coefficients obtained from the NIST / USA, were developed for each tissue: bone, muscle, fat and skin. Skin thickness was set at 2 mm and the bone was estimated in the central ray of the site, in the anteroposterior view. Because they are similar in density and attenuation coefficients, muscle and fat are treated as a single tissue. For evaluation of the full equations, we chose three different anatomies: chest, hand and thigh. Although complex in its shape, the equations simplify direct determination of absorbed dose from the characteristics of the equipment and patient. The input data is inserted at a single time and total absorbed dose (mGy) is calculated instantly. The average error, when compared with available data, is less than 5% in any combination of device data and exams. In calculating the dose for an exam and patient, the operator can choose the variables that will deposit less radiation to the patient through the prior analysis of each combination of variables, using the ALARA principle in routine diagnostic radiology sector.

  16. Norwegian system for implementing the IAEA code of practice based on absorbed dose to water

    In 2001 the Nordic secondary standards dosimetry laboratories (SSDLs) recommended the use of absorbed dose to water as the quantity for the calibration standard and code of practice in radiotherapy.The code of practice adopted was IAEA Technical Reports Series No. 398. The Norwegian system for implementation includes the 60Co calibration of SSDL and hospital dosimeters in terms of absorbed dose to water at the Norwegian SSDL and on-site visits to every clinic teaching the new code and performing dose measurements. Comparisons of the Norwegian Radiation Protection Authority 60Co absorbed dose to water calibration at the Finnish SSDL with the French primary standards dosimetry laboratory showed agreement within 0.4%.The on-site visit measuring system compared with the Finnish on-site equipment agreed within 0.6%.The on-site visits were welcomed, and demonstrated the need for external dosimetry audits to improve the local implementation of the code of practice. (author)

  17. Three dimensional measurements of absorbed dose in BNCT by Fricke-gel imaging

    A method has been studied for absorbed dose imaging and profiling in a phantom exposed to thermal or epithermal neutron fields, also discriminating between various contributions to the absorbed dose. The proposed technique is based on optical imaging of FriXy-gel phantoms, which are proper tissue-equivalent phantoms acting as continuous dosimeters. Convenient modifications in phantom composition allow, from differential measurements, the discrimination of various contributions to the absorbed dose. The dosimetry technique is based on a chemical dosimeter incorporated in a tissue-equivalent gel (Agarose). The chemical dosimeter is a ferrous sulphate solution (which is the main component of the standard Fricke dosimeter) added with a metal ion indicator (Xylenol Orange). The absorbed dose is measured by analysing the variation of gel optical absorption in the visible spectrum, imaged by means of a CCD camera provided with a suitable filter. The technique validity has been tested by irradiating and analysing phantoms in the thermal facility of the fast research reactor TAPIRO (ENEA, Casaccia, Italy). In a cylindrical phantom simulating a head, we have imaged the therapy dose from thermal neutron reactions with 10B and the dose in healthy tissue not containing boron. In tissue without boron, we have discriminated between the two main contributions to the absorbed dose, which comes from the 1H(n,γ)2H and 14N(n,p)14C reactions. The comparison with the results of other experimental techniques and of simulations reveals that the technique is very promising. A method for the discrimination of fast neutron contribution to the absorbed dose, still in an experimental stage, is proposed too. (author)

  18. New absorbed dose measurement with cylindrical water phantoms for multidetector CT

    The aim of this study was to develop new dosimetry with cylindrical water phantoms for multidetector computed tomography (MDCT). The ionization measurement was performed with a Farmer ionization chamber at the center and four peripheral points in the body-type and head-type cylindrical water phantoms. The ionization was converted to the absorbed dose using a 60Co absorbed-dose-to-water calibration factor and Monte Carlo (MC) -calculated correction factors. The correction factors were calculated from MDCT (Brilliance iCT, 64-slice, Philips Electronics) modeled with GMctdospp (IMPS, Germany) software based on the EGSnrc MC code. The spectrum of incident x-ray beams and the configuration of a bowtie filter for MDCT were determined so that calculated photon intensity attenuation curves for aluminum (Al) and calculated off-center ratio (OCR) profiles in air coincided with those measured. The MC-calculated doses were calibrated by the absorbed dose measured at the center in both cylindrical water phantoms. Calculated doses were compared with measured doses at four peripheral points and the center in the phantom for various beam pitches and beam collimations. The calibration factors and the uncertainty of the absorbed dose determined using this method were also compared with those obtained by CTDIair (CT dose index in air). Calculated Al half-value layers and OCRs in air were within 0.3% and 3% agreement with the measured values, respectively. Calculated doses at four peripheral points and the centers for various beam pitches and beam collimations were within 5% and 2% agreement with measured values, respectively. The MC-calibration factors by our method were 44–50% lower than values by CTDIair due to the overbeaming effect. However, the calibration factors for CTDIair agreed within 5% with those of our method after correction for the overbeaming effect. Our method makes it possible to directly measure the absorbed dose for MDCT and is more robust and accurate than the

  19. New absorbed dose measurement with cylindrical water phantoms for multidetector CT

    Ohno, Takeshi; Araki, Fujio; Onizuka, Ryota; Hioki, Kazunari; Tomiyama, Yuuki; Yamashita, Yusuke

    2015-06-01

    The aim of this study was to develop new dosimetry with cylindrical water phantoms for multidetector computed tomography (MDCT). The ionization measurement was performed with a Farmer ionization chamber at the center and four peripheral points in the body-type and head-type cylindrical water phantoms. The ionization was converted to the absorbed dose using a 60Co absorbed-dose-to-water calibration factor and Monte Carlo (MC) -calculated correction factors. The correction factors were calculated from MDCT (Brilliance iCT, 64-slice, Philips Electronics) modeled with GMctdospp (IMPS, Germany) software based on the EGSnrc MC code. The spectrum of incident x-ray beams and the configuration of a bowtie filter for MDCT were determined so that calculated photon intensity attenuation curves for aluminum (Al) and calculated off-center ratio (OCR) profiles in air coincided with those measured. The MC-calculated doses were calibrated by the absorbed dose measured at the center in both cylindrical water phantoms. Calculated doses were compared with measured doses at four peripheral points and the center in the phantom for various beam pitches and beam collimations. The calibration factors and the uncertainty of the absorbed dose determined using this method were also compared with those obtained by CTDIair (CT dose index in air). Calculated Al half-value layers and OCRs in air were within 0.3% and 3% agreement with the measured values, respectively. Calculated doses at four peripheral points and the centers for various beam pitches and beam collimations were within 5% and 2% agreement with measured values, respectively. The MC-calibration factors by our method were 44-50% lower than values by CTDIair due to the overbeaming effect. However, the calibration factors for CTDIair agreed within 5% with those of our method after correction for the overbeaming effect. Our method makes it possible to directly measure the absorbed dose for MDCT and is more robust and accurate than the

  20. DOSE-Analyzer. A computer program with graphical user interface to analyze absorbed dose inside a body of mouse and human upon external neutron exposure

    DOSE-Analyzer is a computer program to retrieve the dose information from a database and generate a graph through a graphical user interface (GUI). The database is constructed for absorbed dose, fluence, and energy distribution inside a body of mouse and human exposed upon external neutrons, which is calculated by our developed Monte-Carlo simulation method using voxel-based phantom and particle transport code PHITS. The input configurations of irradiation geometry, subject, and energy are set by GUI. The results are tabulated at particle types, i.e. electron, proton, deuteron, triton, and alpha particle, and target organs on a data sheet of Microsoft Office ExcelTM. Simple analysis to compare the output values for two subjects is also performed on DOSE-Analyzer. This report is a user manual of DOSE-Analyzer. (author)

  1. Absorbed Doses to Patients in Nuclear Medicine; Doskatalogen foer nukleaermedicin

    Leide-Svegborn, Sigrid; Mattsson, Soeren; Johansson, Lennart; Fernlund, Per; Nosslin, Bertil

    2007-04-15

    The Swedish radiation protection authority, (SSI), has supported work on estimates of radiation doses to patients from nuclear medicine examinations since more than 20 years. A number of projects have been reported. The results are put together and published under the name 'Doskatalogen' which contains data on doses to different organs and tissues from radiopharmaceuticals used for diagnostics and research. This new report contains data on: {sup 11}C-labelled substances (realistic maximum model), amino acids labelled with {sup 11}C, {sup 18}F or {sup 75}Se, {sup 99m}Tc-apcitide, {sup 123}I-labelled fatty acids ({sup 123}I- BMIPP and {sup 123}I-IPPA) and revised models for previously reported {sup 15}O-labelled water, {sup 99m}Tc-tetrofosmin (rest as well as exercise) and {sup 201}Tl-ion Data for almost 200 substances and radionuclides are included in the 'Doskatalogen' today. Since the year 2001 the 'Doskatalogen' is available on the authority's home page (www.ssi.se)

  2. In-phantom measurement of absorbed dose to water in medium energy x-ray beams

    Absorbed dose values in a water phantom derived by the formalism of the IAEA Code of Practice of Absorbed Dose Determination in Photon and Electron Beams are a few per cent higher than those based on the procedure following e.g. ICRU Report 23. The maximum deviation exceeds 10% at 100 kV tube potential. The correction factor needed to take into account the differences at the calibration in terms of air kerma free in air and at the measurement in the water phantom can be determined in different ways: In comparing the result of the absorbed dose measurement by means of the ionization chambers with an other, preferably fundamental method of measurement of absorbed dose in the water phantom or by evaluating all component parts of the correction factor separately. The values of the perturbation correction factor in the IAEA Code were determined in the former way by comparing against a graphite extrapolation chamber. A review is given on a recent re-evaluation using former values of the extrapolation chamber measurements and on new determinations using an absorbed dose water calorimeter, a method based on calculated and measured air kerma values and a method of combining the component factors to the overall correction factor. Recent results achieved by the different methods are compared and a change of the data of the IAEA Code is recommended. (author). 31 refs, 14 figs, 3 tabs

  3. National absorbed dose to water references for radiotherapy medium energy X-rays by water calorimetry

    LNE-LNHB current references for medium energy X-rays are established in terms of air kerma. Absorbed dose to water, which is the quantity of interest for radiotherapy, is obtained by transfer dosimetric techniques following a methodology described in international protocols. The aim of the thesis is to establish standards in terms of absorbed dose to water in the reference protocol conditions by water calorimetry. The basic principle of water calorimetry is to measure the absorbed dose from the rise in temperature of water under irradiation. A calorimeter was developed to perform measurements at a 2 cm depth in water according to IAEA TRS-398 protocol for medium energy x-rays. Absorbed dose rates to water measured by calorimetry were compared to the values established using protocols based on references in terms of air kerma. A difference lower than 2.1% was reported. Standard uncertainty of water calorimetry being 0.8%, the one associated to the values from protocols being around 3.0%, results are consistent considering the uncertainties. Thanks to these new standards, it will be possible to use IAEA TRS-398 protocol to determine absorbed dose to water: a significant reduction of uncertainties is obtained (divided by 3 by comparison with the application of the IAEA TRS-277 protocol). Currently, none of the counterparts' laboratories own such an instrument allowing direct determination of standards in the reference conditions recommended by the international radiotherapy protocols. (author)

  4. The Norwegian system for implementing the IAEA code of practice based on absorbed dose to water

    The Norwegian Radiation Protection Authority (NRPA) SSDL recommended in 2000 the use of absorbed dose to water as the quality for calibration and code of practice in radiotherapy. The absorbed dose to water standard traceable to BIPM was established in Norway in 1995. The international code of practice, IAEA TRS 398 was under preparation. As a part of the implementation of the new dosimetry system the SSDL went to radiotherapy departments in Norway in 2001. The aim of the visit was to: Prepare and support the users in the implementation of TRS 398 by teaching, discussions and measurements on-site; Gain experience for NRPA in the practical implementation of TRS 398 and perform comparisons between TRS 277 and TRS 398 for different beam qualities; Report experience from implementation of TRS 398 to IAEA. The NRPA 30x30x30 cm3 water phantom is equal to the BIPM calibration phantom. This was used for the photon measurements in 16 different beams. NRPA used three chambers: NE 2571, NE 2611 and PR06C for the photon measurements. As a quality control the set-up was compared with the Finnish site-visit equipment at University Hospital of Helsinki, and the measured absorbed dose to water agreed within 0.6%. The Finnish SSDL calibrated the Norwegian chambers and the absorbed dose to water calibration factors given by the two SSDLs for the three chambers agreed within 0.3%. The local clinical dosimetry in Norway was based on TRS 277. For the site-visit the absorbed dose to water was determined by NRPA using own equipment including the three chambers and the hospitals reference chamber. The hospital determined the dose the same evening using their local equipment. For the 16 photon beams the deviations between the two absorbed dose to water determinations for TRS 277 were in the range -1,7% to +4.0%. The uncertainty in the measurements was 1% (k=1). The deviation was explained in local implementation of TRS 277, the use of plastic phantoms, no resent calibration of thermometers

  5. On the suitability of ultrathin detectors for absorbed dose assessment in the presence of high-density heterogeneities

    Bueno Vizcarra, Marta; Carrasco, P. (Paula); Jornet, N.; Muñoz Montplet, C.; Duch Guillen, María Amor

    2014-01-01

    Purpose: The aim of this study was to evaluate the suitability of several detectors for the determination of absorbed dose in bone.; Methods: Three types of ultrathin LiF-based thermoluminescent dosimeters (TLDs) two LiF:Mg,Cu,P-based (MCP-Ns and TLD-2000F) and a Li-7-enriched LiF:Mg,Ti-based (MTS-7s)-as well as EBT2 Gafchromic films were used to measure percentage depth-dose distributions (PDDs) in a water-equivalent phantom with a bone-equivalent heterogeneity for 6 and 18 MV and a set of f...

  6. A study on absorbed dose in the breast tissue using geant4 simulation for mammography

    As the breast cancer rate is increasing fast in Korean women, people pay more attention to mammography and number of mammography have been increasing dramatically over the last few years. Mammography is the only means to diagnose breast cancer early, but harms caused by radiation exposure shouldn't be overlooked. Therefore, it is important to calculate the radiation dose being absorbed into the breast tissue during the process of mammography for a protective measure against radiation exposure. Because it is impossible to directly measure the radiation dose being absorbed into the human body, statistical calculation methods are commonly used, and most of them are supposed to simulate the interaction between radiation and matter by describing the human body internal structure with anthropomorphic phantoms. However, a simulation using Geant4 Code of Monte Carlo Method, which is well-known as most accurate in calculating the absorbed dose inside the human body, helps calculate exact dose by recreating the anatomical human body structure as it is through the DICOM file of CT. To calculate the absorbed dose in the breast tissue, therefore, this study carried out a simulation using Geant4 Code, and by using the DICOM converted file provided by Geant4, this study changed the human body structure expressed on the CT image data into geometry needed for this simulation. Besides, this study attempted to verify if the dose calculation of Geant4 interlocking with the DICOM file is useful, by comparing the calculated dose provided by this simulation and the measured dose provided by the PTW ion chamber. As a result, under the condition of 28kVp/190mAs, the Difference(%) between the measured dose and the calculated dose was found to be 0.08 %∼0.33 %, and at 28 kVp/70 mAs, the Difference(%) of dose was 0.01 %∼0.16 %, both of which showed results within 2%, the effective difference range. Therefore, this study found out that calculation of the absorbed dose using Geant4

  7. Absorbed XFEL Dose in the Components of the LCLS X-Ray Optics

    Hau-Riege, Stefan

    2010-12-03

    There is great concern that the short, intense XFEL pulse of the LCLS will damage the optics that will be placed into the beam. We have analyzed the extent of the problem by considering the anticipated materials and position of the optical components in the beam path, calculated the absorbed dose as a function of photon energy, and compared these doses with the expected doses required (i) to observe rapid degradation due to thermal fatigue, (ii) to reach the melting temperature, or (iii) to actually melt the material. We list the materials that are anticipated to be placed into the Linac Coherent Light Source (LCLS) x-ray free electron laser (XFEL) beam line, their positions, and the absorbed dose, and compare this dose with anticipated damage thresholds.

  8. Dose absorbed by technologists in positron emission tomography procedures with FDG

    The objective of this work was to evaluate radiation doses delivered to technologists engaged in different tasks involving positron emission tomography (PET) studies with FDG (fluorodeoxyglucose). This investigation was performed in two French nuclear medicine departments, which presented significant differences in their arrangements and radiation safety conditions. Both centers administered about 300 MBq per PET/CT study, although only one of them is a dedicated clinical PET center. Dose equivalent Hp(10) and skin dose Hp(0.07) were measured using Siemens electronic personnel dosimeters. For assessment dose absorbed by hands during drawing up of tracer and injection into the patient, a Polimaster wristwatch gamma dosimeter was employed. Absorbed dose and the time spent during each investigated task were recorded for a total of 180 whole-body PET studies. In this report, the methodology employed, the results and their radioprotection issues are presented as well as discussed. (author)

  9. The effect of latex maturity on the absorbed dose for preparing RVNRL of optimum tensile strength

    This paper present the results of the studies on the effects of using latex of different maturity periods, between 0 to 15 weeks on gamma irradiation dose require to prepare RVNRL of optimum tensile strength. Absorbed dose to prepare RVNRL of optimum tensile strength, molecular weight between cross-links and cross-link density were found to be influenced by the maturity of the latex used in the studies. With respect to optimum tensile strength and absorbed dose, latex of about six weeks maturity was found most suitable and economical for radiation vulcanization process. Using latex either with or without added secondary preservative the optimum tensile strength was determined at an absorbed of 8 kGy. However, the optimum tensile strength of RVNRL prepared from latex contained added secondary preservative was found to be higher than the optimum tensile strength of RVNRL prepared from latex without secondary preservative

  10. Peculiarities of absorbed dose forming in some wild animals in Chornobyl,y exclusion zone

    Based on field researches conducted in the exclusion zone of the Chernobyl nuclear power plant in the years after the accident, identified the peculiarities of formation absorbed doses in animals of different taxonomic and ecological groups that live in conditions of radioactive contamination of ecosystems. Was shown importance of consideration of radiation features on wild animals according to their life cycle, conditions and ways of life. Was displayed data about the importance of different types of irradiation according to the period of stay the animals in the ground, in burrows and nests. Was reviewed the questions about value of external and internal radiation in absorbed dose of different types of wildlife. Was shown the results of the calculation of the absorbed dose of bird embryos from egg shell

  11. On the Influence of Patient Posture on Organ and Tissue Absorbed Doses Caused by Radiodiagnostic Examinations

    Virtual human phantoms, frequently used for organ and tissue absorbed dose assessment in radiology, normally represent the human body either in standing or in supine posture. This raises the question as to whether it matters dosimetrically if the postures of the patient and of the phantom do not match. This study uses the recently developed FASH2sta (Female Adult meSH) and FASH2sup phantoms which represent female adult persons in standing and supine posture. The effect of the posture on organ and tissue absorbed doses will be studied using the EGSnrc Monte Carlo code for simulating abdominal radiographs and special attention will be directed to the influence of body mass on the results. For the exposure conditions considered here, posture-dependent absorbed dose differences by up to a factor of two were found. (author)

  12. Absorbed dose in the full-mouth periapical radiography, panoramic radiography, and zonography

    The objective of this study was to evaluate the possibility of substitution of the zonography for the full-mouth periapical radiography in aspect of radiation protection. Rando phantom and LiF TLD chips were used for dosimetry. The absorbed doses at brain, skin above the TMJ, parotid gland, bone marrow in the mandibular body, and thyroid gland during the full-mouth periapical radiography, panoramic radiography, and zonography were measured. From the zonography, the absorbed doses to the brain, the skin over the TMJ, and the parotid gland were relatively high, but the absorbed doses to the bone marrow in the mandibular body and, especially, the thyroid gland were very low. The zonography can be an alternative to the full-mouth periapical radiography in aspect of radiation protection.

  13. The standard absorbed dose in a medium ''M'' as a quantity to replace exposure

    In order to replace exposure, at least as a calibration value, a more general dosimetric quantity is here proposed, namely the standard dose absorbed in a medium M, defined at any point in a photon field as 'the dose absorbed at the centre of a sphere filled with a material M, having its centre at the point under consideration and a radius equal to the maximum range of any electron brought into motion within it or incident upon it, and corrected for perturbation, by the sphere, of the energy fluence of the photons present at the point under consideration.' From the practical point of view, the absorbed dose thus specified possesses the following main advantages: its definition does not fix the reference material and leaves the choice thereof free depending on the field of application (for purposes of biomedical dosimetry this material would, of course, be water and the concept then concerns the 'standard dose in water'); the close and simple relationship with exposure would make it possible for metrology laboratories to establish calibration services in terms of standard dose unambiguously linked to the present exposure standards; calibration of a dose meter in terms of standard dose, for example in a cobalt-60 photon beam, would make it possible - for purposes of proceeding to mean dose calibration in the cavity - to apply a procedure fully analogous to that at present based on exposure calibration. (author)

  14. Measuring the absorbed dose in critical organs during low rate dose brachytherapy with 137 Cs using thermoluminescent dosemeters

    Intracavitary Brachytherapy is one of the most used methods for the treatment of the cervical-uterine cancer. This treatment consists in the insertion of low rate dose 137Cs sources into the patient. The most used system for the treatment dose planning is that of Manchester. This planning is based on sources, which are considered fixed during the treatment. However, the experience has shown that, during the treatment, the sources could be displaced from its initial position, changing the dose from that previously prescribed. For this reason, it is necessary to make measurements of the absorbed dose to the surrounding organs (mainly bladder and rectum). This paper presents the results of measuring the absorbed dose using home-made LiF: Mg, Cu, P + Ptfe thermoluminescent dosimeters (TLD). Measurements were carried out in-vivo during 20 minutes at the beginning and at the end of the treatments. Results showed that the absorbed dose to the critical organs vary significantly due to the movement of the patient during the treatment. (Author)

  15. A study on the absolute measurement of β-ray absorbed dose in the skin depth

    The absolute measurement of β ray absorbed dose in the skin depth located at the certain distance from the radiation source (90Sr + 90Y, 204TI, 147Pm) recommended by the International Standardization Organization is performed by using an extrapolation chamber in the range of several mGy/h. Since one of critical points in measuring of absorbed dose is to make the environment in chamber similar to tissue, a new approach to the measurement of absorbed dose is proposed. The attenuation difference is minimized by deciding a window thickness such as the attenuation effect in chamber window becomes similar to that in the skin depth. A-150 tissue equivalent plastic, whose structure and density is very similar to tissue, is used for back material. The back scattering effect of both media is measured using the proposed method to calibrate the difference in back scattering effect between back material and tissue. For the measurement of back scattering effect of each material, an ionization chamber, whose structure is very similar to the extrapolation chamber and back material is replaceable, is made. Based on the results, β ray absorbed dose in the skin depth of 70 μm was measured as follows : 0.759 μGy/s (±3.78% ) for 90Sr + 90Y, 0.173 μGy/s (±4.17%) for 204TI and 0.088 μGy/s (±7.70%) for 147Pm. In order to evaluate the reliability of the proposed method, the absorbed dose measured in this study is compared to that measured in PTB (Physikalisch Technische Bundesanstalt) for the same β ray source. Although the proposed method gives slightly higher value, the difference is within 1%. In conclusion, the proposed method seems to make the measuring environment closer to tissue, even though the calibration factor yielded by the proposed method has a little effect on evaluation of absorbed dose

  16. Determination of maximum/minimum ratio of absorbed dose of dried figs

    In the framework of an FAO/IAEA project, the ECB dosimeter and STERIN-125 and STERIN-300 dosimeters have been used for dose measurement in the dried figs packs. They were irradiated in our Gamma Irradiation Plant and were given 6 kGy dose. It was observed that all Sterin label dose indicators became very dark after a 6 kGy dose and the absorbance could not be measured with UV spectrophotometer. Therefore these label dose indicators were separately irradiated between 10-700 Gy doses by gamma rays to establish the dose sensitive curve of these indicators. After the irradiation of ECB dosimeter which is located in dried fig packs, we found the Dose Uniformity Ratio as 1.4 according to bulk density of 0.62 gr/cc. (author)

  17. Study of natural radionuclide and absorbed gamma dose in Ukhimath area of Garhwal Himalaya, India.

    Rautela, B S; Yadav, M; Bourai, A A; Joshi, V; Gusain, G S; Ramola, R C

    2012-11-01

    Natural radiation is the largest contributor to the collective radiation dose of the world population. It is widely distributed in different geological formations such as soil, rocks, air and groundwater. In the present investigation, (226)Ra, (232)Th and (40)K were measured in soil samples of the Ukhimath region of Garhwal Himalaya, India using NaI(Tl) gamma-ray spectrometry. The activity concentrations of naturally occurring radionuclides (226)Ra, (232)Th and (40)K were found to vary from 38.4 ± 6.1 to 141.7 ± 11.9 Bq kg(-1) with an average of 80.5 Bq kg(-1), 57.0 ± 7.5 to 155.9 ± 12.4 Bq kg(-1) with an average of 118.9 Bq kg(-1) and 9.0 ± 3.0 to 672.8 ± 25.9 Bq kg(-1) with an average of 341 Bq kg(-1), respectively. The total absorbed gamma dose rate varies from 70.4 to 169.1 nGy h(-1) with an average of 123.4 nGy h(-1). This study is important to generate a baseline data of radiation exposure in the area. Health hazard effects due to natural radiation exposure are discussed in details. PMID:22908360

  18. Study of natural radionuclide and absorbed gamma dose in Ukhimath area of Garhwal Himalaya (India))

    Natural radiation is the largest contributor to the collective radiation dose of the world population. It is widely distributed in different geological formations such as soil, rocks, air and groundwater. In the present investigation, 226Ra, 232Th and 40K were measured in soil samples of the Ukhimath region of Garhwal Himalaya (India)) using NaI(Tl) gamma-ray spectrometry. The activity concentrations of naturally occurring radionuclides 226Ra, 232Th and 40K were found to vary from 38.4±6.1 to 141.7±11.9 Bq kg-1 with an average of 80.5 Bq kg-1, 57.0±7.5 to 155.9±12.4 Bq kg-1 with an average of 118.9 Bq kg-1 and 9.0±3.0 to 672.8±25.9 Bq kg-1 with an average of 341 Bq kg-1, respectively. The total absorbed gamma dose rate varies from 70.4 to 169.1 nGy h-1 with an average of 123.4 nGy h-1. This study is important to generate a baseline data of radiation exposure in the area. Health hazard effects due to natural radiation exposure are discussed in details. (authors)

  19. The 1997 determination of the Australian standards of exposure and absorbed dose at 60Co

    The arrangements for the maintenance of the Australian standards for 60Co are described in detail. The primary standards are a graphite cavity chamber for exposure/air kerma and a graphite calorimeter for absorbed dose. These secondary standards are described and their responses in corresponding 90Sr reference sources are reported. Accurate ratios between the Australian Radiation Laboratory (ARL) and Australian Nuclear Science and Technology (ANSTO) 90Sr reference sources are derived for use in future calibrations. The value of 28.8 years for the half-life of 90Sr is confirmed. The usefulness of 90Sr reference source measurements in quality assurance is discussed. The charge sensitivity and linearity of the ANSTO electrometers are reported by two different methods and are compared with previous results. Calibration factors for all the secondary standard ionization chambers are given, in terms of exposure, air kerma and absorbed dose to water. Calibration factors are also given for most of the chambers in terms of absorbed dose to graphite. The methods of deriving the calibration factors are explained in detail, including all the corrections applied to both the primary and secondary standard measurements. Three alternative methods of deriving the absorbed dose to water calibration factors are compared. The reported calibration factors are compared with previous results. Changes in the Australian units of exposure, air kerma and absorbed dose to graphite and water are derived from changes in the corresponding calibration factors. The Australian units of exposure and air kerma have not changed significantly since 1990. The Australian unit of absorbed dose to graphite is now 1.1 % smaller than in 1993 and 1.3 % smaller than in 1990. The Australian unit of absorbed dose to water is now 1.4 % smaller than in 1993, but is only 0.9 % smaller than in 1990. Comparisons of the Australian standards of exposure/air kerma and absorbed dose with those of the Bureau International

  20. Optical fibre temperature sensor technology and potential application in absorbed dose calorimetry

    Optical fibre based sensors are proposed as a potential alternative to the thermistors traditionally used as temperature sensors in absorbed dose calorimetry. The development of optical fibre temperature sensor technology over the last ten years is reviewed. The potential resolution of various optical techniques is assessed with particular reference to the requirements of absorbed dose calorimetry. Attention is drawn to other issues which would require investigation before the development of practical optical fibre sensors for this purpose could occur. 192 refs., 5 tabs., 4 figs

  1. The 1997 determination of the Australian standards of exposure and absorbed dose at {sup 60}Co

    Huntley, R.B.; Boas, J.F. [Australian Radiation Laboratory, Yallambie, VIC (Australia); Van der Gaast, H. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia)

    1998-05-01

    The arrangements for the maintenance of the Australian standards for {sup 60}Co are described in detail. The primary standards are a graphite cavity chamber for exposure/air kerma and a graphite calorimeter for absorbed dose. These secondary standards are described and their responses in corresponding {sup 90}Sr reference sources are reported. Accurate ratios between the Australian Radiation Laboratory (ARL) and Australian Nuclear Science and Technology (ANSTO) {sup 90}Sr reference sources are derived for use in future calibrations. The value of 28.8 years for the half-life of {sup 90}Sr is confirmed. The usefulness of {sup 90}Sr reference source measurements in quality assurance is discussed. The charge sensitivity and linearity of the ANSTO electrometers are reported by two different methods and are compared with previous results. Calibration factors for all the secondary standard ionization chambers are given, in terms of exposure, air kerma and absorbed dose to water. Calibration factors are also given for most of the chambers in terms of absorbed dose to graphite. The methods of deriving the calibration factors are explained in detail, including all the corrections applied to both the primary and secondary standard measurements. Three alternative methods of deriving the absorbed dose to water calibration factors are compared. The reported calibration factors are compared with previous results. Changes in the Australian units of exposure, air kerma and absorbed dose to graphite and water are derived from changes in the corresponding calibration factors. The Australian units of exposure and air kerma have not changed significantly since 1990. The Australian unit of absorbed dose to graphite is now 1.1 % smaller than in 1993 and 1.3 % smaller than in 1990. The Australian unit of absorbed dose to water is now 1.4 % smaller than in 1993, but is only 0.9 % smaller than in 1990. Comparisons of the Australian standards of exposure/air kerma and absorbed dose with

  2. Model of the absorbed dose on a small sphere into a gamma irradiation field

    Several models of the absorbed dose calculated as the energy deposited by the secondary electrons on a small volume sphere are presented. The calculations use the Compton scattering of a uniform photon beam in water, the photon attenuation and the electron stopping power are included. The sphere total absorbed dose is due to the stopping of the electrons generated in three regions: into the sphere volume, ahead and behind the sphere volume. Calculations are performed for spheres of different radius and placed at various depth of the vacuum - water interface. (author)

  3. Absorbed dose in molecular radiotherapy: a comparison study of Monte Carlo, dose voxel kernels and phantom based dosimetry

    Full text of publication follows. Aim: the aim of this study was to perform a critical comparison of 3 dosimetric approaches in Molecular Radiotherapy: phantom based dosimetry, Dose Voxel Kernels (DVKs) and full Monte Carlo (MC) dosimetry. The objective was to establish the impact of the absorbed dose calculation algorithm on the final result. Materials and Methods: we calculated the absorbed dose to various organs in six healthy volunteers injected with a novel 18F-labelled PET radiotracer from GE Healthcare. Each patient underwent from 8 to 10 whole body 3D PET/CT scans. The first 8 scans were acquired dynamically in order to limit co-registration issues. Eleven organs were segmented on the first PET/CT scan by a physician. We analysed this dataset using the OLINDA/EXM software taking into account actual patient's organ masses; the commercial software Stratos by Philips implementing a DVK approach; and performing full MC dosimetry on the basis of a custom application developed with Gate. The calculations performed with these three techniques were based on the cumulated activities calculated at the voxel level by Stratos. Results: all the absorbed doses calculated with Gate were higher than those calculated with OLINDA. The average ratios between the Gate absorbed dose and OLINDA's was 1.38±0.34 σ (from 0.93 to 2.23) considering all patients. The discrepancy was particularly high for the thyroid, with an average Gate/OLINDA ratio of 1.97±0.83 σ for the 6 patients. The lower absorbed doses in OLINDA may be explained considering the inter-organ distances in the MIRD phantom. These are in general overestimated, leading to lower absorbed doses in target organs. The differences between Stratos and Gate resulted to be the highest. The average ratios between Gate and Stratos absorbed doses were 2.51±1.21 σ (from 1.09 to 6.06). The highest differences were found for lungs (average ratio 4.76±2.13 σ), as expected, since Stratos considers unit density

  4. Determination of absorbed dose in the experimental animal irradiated on the Leksell gamma knife

    The purpose of this study was to evaluate and quantify inaccuracy of Leksell GammaPlan relative and absolute dose calculations for the experimental animal and to determine necessary corrections that must be applied. Both TLD and semiconductor detectors appeared to be suitable for measurement of absorbed dose in the rat brain irradiated on the Leksell gamma knife. Both detectors, due to their size, measured mean doses, nay doses to maximum. The Leksell GammaPlan treatment planning system can be employed for the calculation of absorbed doses even in such an extreme condition like irradiation of experimental animals. However, in our concrete case, it was necessary to apply correction factor of 1.0779 for the absolute absorbed dose to obtain reliable results. Comparison of dose profiles in all three axis calculated by the treatment planning system and measured ones by polymer gel dosimeter showed acceptable agreement. Results presented in this study are strictly related to the Leksell GammaPlan treatment planning system and the special fixation device developed in Na Homolce Hospital. (authors)

  5. Specification of absorbed dose to water using model-based dose calculation algorithms for treatment planning in brachytherapy

    Model-based dose calculation algorithms (MBDCAs), recently introduced in treatment planning systems (TPS) for brachytherapy, calculate tissue absorbed doses. In the TPS framework, doses have hereto been reported as dose to water and water may still be preferred as a dose specification medium. Dose to tissue medium Dmed then needs to be converted into dose to water in tissue Dw,med. Methods to calculate absorbed dose to differently sized water compartments/cavities inside tissue, infinitesimal (used for definition of absorbed dose), small, large or intermediate, are reviewed. Burlin theory is applied to estimate photon energies at which cavity sizes in the range 1 nm–10 mm can be considered small or large. Photon and electron energy spectra are calculated at 1 cm distance from the central axis in cylindrical phantoms of bone, muscle and adipose tissue for 20, 50, 300 keV photons and photons from 125I, 169Yb and 192Ir sources; ratios of mass-collision-stopping powers and mass energy absorption coefficients are calculated as applicable to convert Dmed into Dw,med for small and large cavities. Results show that 1–10 nm sized cavities are small at all investigated photon energies; 100 µm cavities are large only at photon energies w,med/Dmed is discussed in terms of the cavity size in relation to the size of important cellular targets. Free radicals from DNA bound water of nanometre dimensions contribute to DNA damage and cell killing and may be the most important water compartment in cells implying use of ratios of mass-collision-stopping powers for converting Dmed into Dw,med. (paper)

  6. Identification and absorbed dose determination in irradiated kiwi by electron paramagnetic resonance

    A methodology for identification and absorbed dose determination in irradiated Kiwi with doses between 200 and 1000 Gy is present. Measurement are performed by Electron Paramagetic Resonance (ESR) in the flesh of the fruit after alcohol extration that removes water and soluble substances. The signal used is the radial produced in cellulose by radiation that shows to be stable during the usefull life of the fruit and that is not present in non-irradiated samples. Reference samples are not necessary to dose determination and the results shows that 85% of the calculated values are found to be within ± 15% of the applied initial dose. (author). 9 refs., 5 figs., 2 tabs

  7. Multicriteria optimization of the spatial dose distribution

    Schlaefer, Alexander [Medical Robotics Group, Universität zu Lübeck, Lübeck 23562, Germany and Institute of Medical Technology, Hamburg University of Technology, Hamburg 21073 (Germany); Viulet, Tiberiu [Medical Robotics Group, Universität zu Lübeck, Lübeck 23562 (Germany); Muacevic, Alexander; Fürweger, Christoph [European CyberKnife Center Munich, Munich 81377 (Germany)

    2013-12-15

    Purpose: Treatment planning for radiation therapy involves trade-offs with respect to different clinical goals. Typically, the dose distribution is evaluated based on few statistics and dose–volume histograms. Particularly for stereotactic treatments, the spatial dose distribution represents further criteria, e.g., when considering the gradient between subregions of volumes of interest. The authors have studied how to consider the spatial dose distribution using a multicriteria optimization approach.Methods: The authors have extended a stepwise multicriteria optimization approach to include criteria with respect to the local dose distribution. Based on a three-dimensional visualization of the dose the authors use a software tool allowing interaction with the dose distribution to map objectives with respect to its shape to a constrained optimization problem. Similarly, conflicting criteria are highlighted and the planner decides if and where to relax the shape of the dose distribution.Results: To demonstrate the potential of spatial multicriteria optimization, the tool was applied to a prostate and meningioma case. For the prostate case, local sparing of the rectal wall and shaping of a boost volume are achieved through local relaxations and while maintaining the remaining dose distribution. For the meningioma, target coverage is improved by compromising low dose conformality toward noncritical structures. A comparison of dose–volume histograms illustrates the importance of spatial information for achieving the trade-offs.Conclusions: The results show that it is possible to consider the location of conflicting criteria during treatment planning. Particularly, it is possible to conserve already achieved goals with respect to the dose distribution, to visualize potential trade-offs, and to relax constraints locally. Hence, the proposed approach facilitates a systematic exploration of the optimal shape of the dose distribution.

  8. Absorbed dose estimation and prediction irradiation effects in tumor-bearing mice under radionuclide therapy

    Full text: As the sizes of mouse organ are comparable with the range of the high-energy beta particles emitted by the radionuclides commonly used in radionuclide therapy a significant amount of beta radiation emitted could be imparted to the adjacent tissues. The often assumption that beta particles are fully-absorbed at the emission site is not satisfied and cross-irradiation should be included into the dose estimation formulas. Keeping in mind that the radiation effects are correlated with the absorbed dose in the target the inclusion of cross-irradiation in the dose estimation must be evaluated. The MIRD's formulation was used to perform absorbed dose calculation in mice using absorbed fractions previously reported for 131I, 90Y and 177Lu. Two approaches were considered: a) cross irradiation when a fraction of beta particles emitted can escape from the organ source and, b) full self- irradiation when the beta particles are considered fully absorbed at the emission site. The formulation of linear-quadratic model was readapted to be used in the radionuclide therapy. Treatment with a single administration in mice was simulated and radiation effects on tumor, bone marrow and kidneys under the assumption of cross-irradiation were predicted. A biphasic repair kinetics was considered in the calculation of irradiation effects on kidneys. Typical published biokinetic data for radiopharmaceutical assayed in mice and radiobiological parameters were used in the calculations. The influence of cross irradiation condition was diverse for the tissues analyzed here. The absorbed dose values in kidneys calculated for both methods were no significantly different for low energies, but variations around to 40-50% (over or under-estimation) in absorbed dose were obtained for high energies. Approximately a 30% of the beta radiation emitted from bone will cross irradiates the bone marrow. For injected activities values higher than 10MBq (300μCi), as a single injection, the

  9. Evaluation of bismuth shielding effectiveness in reducing breast absorbed dose during thoracic CT scan

    Alonso, T. C.; Mourao, A. P.; Santana, P. C.; Silva, T. A. [Federal University of Minas Gerais, Program of Nuclear Science and Techniques, Av. Pte. Antonio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais (Brazil)

    2015-10-15

    Computed Tomography (CT) is an essential method for tracking neoplasia and efficiently diagnosing a wide variety of thoracic diseases. CT is generally considered the most accurate choice for lung examination. Due to the growing use of CT, breast and other superficial and radiosensitive organs are unnecessarily irradiated during radiological procedures, thus requiring the development of strategies appropriate to optimize and, if possible, to reduce the radiation dose. The use of bismuth shielding to reduce radiation dose absorbed by breast during thoracic CT examinations has been the subject of many studies recently published by Brazilian and foreign authors of various fields. The purpose of this paper is both to accurately determine the glandular dose when breast is exposed to radiation and to assess the reduction in absorbed dose during thoracic CT examinations, using a set of Thermoluminescent Dosimeters, an anthropomorphic phantom and bismuth shielding. (Author)

  10. Evaluation of bismuth shielding effectiveness in reducing breast absorbed dose during thoracic CT scan

    Computed Tomography (CT) is an essential method for tracking neoplasia and efficiently diagnosing a wide variety of thoracic diseases. CT is generally considered the most accurate choice for lung examination. Due to the growing use of CT, breast and other superficial and radiosensitive organs are unnecessarily irradiated during radiological procedures, thus requiring the development of strategies appropriate to optimize and, if possible, to reduce the radiation dose. The use of bismuth shielding to reduce radiation dose absorbed by breast during thoracic CT examinations has been the subject of many studies recently published by Brazilian and foreign authors of various fields. The purpose of this paper is both to accurately determine the glandular dose when breast is exposed to radiation and to assess the reduction in absorbed dose during thoracic CT examinations, using a set of Thermoluminescent Dosimeters, an anthropomorphic phantom and bismuth shielding. (Author)

  11. Estimation of eye absorbed doses in head & neck radiotherapy practices using thermoluminescent detectors

    Gh Bagheri

    2011-09-01

    Full Text Available  Determination of eye absorbed dose during head & neck radiotherapy is essential to estimate the risk of cataract. Dose measurements were made in 20 head & neck cancer patients undergoing 60Co radiotherapy using LiF(MCP thermoluminescent dosimeters. Head & neck cancer radiotherapy was delivered by fields using SAD & SSD techniques. For each patient, 3 TLD chips were placed on each eye. Head & neck dose was about 700-6000 cGy in 8-28 equal fractions. The range of eye dose is estimated to be (3.49-639.1 mGy with a mean of maximum dose (98.114 mGy, which is about 3 % of head & neck dose. Maximum eye dose was observed for distsnces of about 3 cm from edge of the field to eye.

  12. Diamond detector in absorbed dose measurements in high-energy linear accelerator photon and electron beams.

    Ravichandran, Ramamoorthy; Binukumar, John Pichy; Al Amri, Iqbal; Davis, Cheriyathmanjiyil Antony

    2016-01-01

    Diamond detectors (DD) are preferred in small field dosimetry of radiation beams because of small dose profile penumbras, better spatial resolution, and tissue-equivalent properties. We investigated a commercially available 'microdiamond' detector in realizing absorbed dose from first principles. A microdiamond detector, type TM 60019 with tandem electrometer is used to measure absorbed doses in water, nylon, and PMMA phantoms. With sensitive volume 0.004 mm3, radius 1.1mm, thickness 1 x10(-3) mm, the nominal response is 1 nC/Gy. It is assumed that the diamond detector could collect total electric charge (nC) developed during irradiation at 0 V bias. We found that dose rate effect is less than 0.7% for changing dose rate by 500 MU/min. The reproducibility in obtaining readings with diamond detector is found to be ± 0.17% (1 SD) (n = 11). The measured absorbed doses for 6 MV and 15 MV photons arrived at using mass energy absorption coefficients and stop-ping power ratios compared well with Nd, water calibrated ion chamber measured absorbed doses within 3% in water, PMMA, and nylon media. The calibration factor obtained for diamond detector confirmed response variation is due to sensitivity due to difference in manufacturing process. For electron beams, we had to apply ratio of electron densities of water to carbon. Our results qualify diamond dosimeter as a transfer standard, based on long-term stability and reproducibility. Based on micro-dimensions, we recommend these detectors for pretreatment dose verifications in small field irradiations like stereotactic treatments with image guidance. PMID:27074452

  13. A system for 3-D absorbed dose measurements with tissue-equivalence for thermal neutrons

    A ferrous sulphate gel with a proper composition to thermalise epithermal neutrons with tissue equivalence with brain tissue gives the possibility of making phantoms which act as a continuous dosimeter for the gamma radiation, with the possibility of 3-D dose determination. If in the phantom a volume of gel containing 10B (in the amount typical for BNCT) is set, information on the absorbed dose in the tumour site may also be drawn. ((orig.))

  14. Radiation-Induced Color Centers in LiF for Dosimetry at High Absorbed Dose Rates

    McLaughlin, W. L.; Miller, Arne; Ellis, S. C.;

    1980-01-01

    Color centers formed by irradiation of optically clear crystals of pure LiF may be analyzed spectrophotometrically for dosimetry in the absorbed dose range from 102 to 107 Gy. Routine monitoring of intense electron beams is an important application. Both 6LiF and 7LiF forms are commercially avail...... available, and when used with filters as albedo dosimeters in pairs, they provide discrimination of neutron and gamma-ray doses....

  15. Estimation of dose distribution in occupationally exposed individuals to FDG-18F

    The use of unsealed radiation sources in nuclear medicine can lead to important incorporation of radionuclides, especially for occupationally exposed individuals (OEIs) during production and handling of radiopharmaceuticals. In this study, computer simulation was proposed as an alternative methodology for evaluation of the absorbed dose distribution and for the effective dose value in OEIs. For this purpose, the Exposure Computational Model (ECM) which is named as FSUP (Female Adult Mesh - supine) were used. This ECM is composed of: voxel phantom FASH (Female Adult MeSH) in the supine position, the MC code EGSnrc and an algorithm simulator of general internal source. This algorithm was modified to adapt to specific needs of the positron emission from FDG-18F. The obtained results are presented as absorbed dose/accumulated activity. To obtain the absorbed dose distribution it was necessary to use accumulative activity data from the in vivo bioassay. The absorbed dose distribution and the value of estimated effective dose in this study did not exceed the limits for occupational exposure. Therefore, the creation of a database with the distribution of accumulated activity is suggested in order to estimate the absorbed dose in radiosensitive organs and the effective dose for OEI in similar environment. (author)

  16. Dynamic dose-shaping by gravity-oriented absorbers for total lymph node irradiation

    Rotational therapy with gravity-oriented absorbers is proposed for better total lymph node irradiation (TLI). Two metal semicylinders are joined coaxially (face to face) to form a radiation absorber that is centrally suspended in the beam. During rotation this absorber is kept parallel to itself by gravity, like the riders of a Ferris wheel. The vertebrae remain continuously protected under the absorber's shadow. The circular full-dose region, achieved by ordinary rotation, is now transformed into a horse-shoe region embracing the spine anteriorly. The abdominal lymph nodes are thus irradiated while the spine and most of the normal tissue around the spine are protected. A similar technique is applied for the selective irradiation of the pelvic lymph nodes, which are confined in the two legs of an inverted V region

  17. A method to efficiently simulate absorbed dose in radio-sensitive instrumentation components

    Components installed in tunnels of high-power accelerators are prone to radiation-induced damage and malfunction. Such machines are usually modeled in detail and the radiation cascades are transported through the three-dimensional models in Monte Carlo codes. Very often those codes are used to compute energy deposition in beam components or radiation fields to the public and the environment. However, sensitive components such as electronic boards or insulator cables are less easily simulated, as their small size makes dose scoring a (statistically) inefficient process. Moreover the process to decide their location is iterative, as in order to define where these will be safely installed, the dose needs to be computed, but to do so the location needs to be known. This note presents a different approach to indirectly asses the potential absorbed dose by certain components when those are installed within a given radiation field. The method consists first in finding the energy and particle-dependent absorbed dose to fluence response function, and then programming those in a radiation transport Monte Carlo code, so that fluences in vacuum/air can be automatically converted real-time into potential absorbed doses and then mapped in the same way as fluences or dose equivalent magnitudes

  18. Internal radiation absorbed dose estimation in human brain due to technetium-99m and iodine-131

    Internal dosimetry is a branch of medical physics that deals with the measurement of the internally absorbed dose by an organ after applying isotopes. In this study, internal radiation absorbed dose has been calculated for 99mTc and 131I, which are frequently used for functioning tests and therapeutic treatments of thyroid, respectively in these cases, some amount of isotopes are accumulated in other tissues like brain, which are very soft and cannot be regenerated if they are damaged. Using ionizing radiation inside the body and to ensure the safety of brain, the internal radiation absorbed dose has been calculated applying direct counting measurement. Accumulation of isotopes to target organ has been measured and this target organ is considered as primary target organ; also this organ is considered as source with respect to other organs. These organ counts have, been measured by computer-based scintillation system. The amount of exposure in brain has been measured with the help of the data obtained from the special set-up equipment, including NaI detector, radiation survey meter and water phantoms of various sizes. Absorbed dose in brain for each isotope has been calculated by applying time-activity curve analysis. Finally, these results have been compared with the data in ICRP l Reports 53 and 71. (author)

  19. Absorbed neutron doses in air holes of fast neutron fields at the RB reactor

    Different experimental fast neutron fields are created at the RB reactor. The absorbed neutron doses in their air holes are determined on the basis of intermediate and fast neutron spectra measurements. The obtained results are analyzed in connection with application of these fields. (author)

  20. Aquatic ecosystems of the Chernobyl NPP exclusion zone: dynamics of contamination, radiation absorbed doses, radiation effects

    The results of radioactive contamination dynamics in the main components of aquatic ecosystems and absorbed dose rate for hydrobionts within the Chernobyl accident exclusion zone has been analysed. Some cytogenetic and haematological effects of long-term irradiation on aquatic organisms as well as damage of higher aquatic plants by parasitic fungi and gall-producing arthropods have been considered. (authors)

  1. Simulation of absorbed dose in human blood with MCNP 4C code

    Biological dosimetry, based on the analysis of solid stained dicentric chromosomes, has been used since the mid 1960s. The intervening years have seen great improvements bringing the technique to a point where dicentric analysis has become a routine component of the radiological protection programs of many countries. Experience of its application in thousands of cases of actual or suspected overexposures has proved the worth of the method. The aberrations scored in the lymphocytes are interpreted in terms of absorbed dose by reference to a dose response calibration curve. This curve will have been produced by exposure of blood in vitro to doses of the appropriate quality of radiation. The doses given to the specimens should be traceable via a physical instrument such as an ionization chamber, to a primary or secondary standard. An alternative to obtain the information about absorbed dose in a specific blood volume is through the Monte Carlo method. The use of such technique is worldwide when physical measurements are inconvenient or impossible, and particularly useful for the solution of complex problems that cannot be modeled by codes that use deterministic methods. It is applied to particle systems as neutrons and electrons, as well as photons or still in mixed systems. Due to difficulties that involve the use of neutrons, this technique has shown extreme importance for preliminary research and experimental arrangements with neutron sources. In this study, the main objective was to simulate the dose absorbed by a blood sample in an experimental arrangement through the irradiation with sources of 241AmBe. It was used the code Monte Carlo N-Particle version 4C (MCNP 4C) whose data had been processed parallel in a computational structure in a cluster. This method allowed estimating the absorbed dose in a specific blood volume, making possible the experimental setup arrangement. (author)

  2. Measurement of absorbed dose with a bone-equivalent extrapolation chamber

    A hybrid phantom-embedded extrapolation chamber (PEEC) made of Solid Water trade mark sign and bone-equivalent material was used for determining absorbed dose in a bone-equivalent phantom irradiated with clinical radiation beams (cobalt-60 gamma rays; 6 and 18 MV x rays; and 9 and 15 MeV electrons). The dose was determined with the Spencer-Attix cavity theory, using ionization gradient measurements and an indirect determination of the chamber air-mass through measurements of chamber capacitance. The collected charge was corrected for ionic recombination and diffusion in the chamber air volume following the standard two-voltage technique. Due to the hybrid chamber design, correction factors accounting for scatter deficit and electrode composition were determined and applied in the dose equation to obtain absorbed dose in bone for the equivalent homogeneous bone phantom. Correction factors for graphite electrodes were calculated with Monte Carlo techniques and the calculated results were verified through relative air cavity dose measurements for three different polarizing electrode materials: graphite, steel, and brass in conjunction with a graphite collecting electrode. Scatter deficit, due mainly to loss of lateral scatter in the hybrid chamber, reduces the dose to the air cavity in the hybrid PEEC in comparison with full bone PEEC by 0.7% to ∼2% depending on beam quality and energy. In megavoltage photon and electron beams, graphite electrodes do not affect the dose measurement in the Solid Water trade mark sign PEEC but decrease the cavity dose by up to 5% in the bone-equivalent PEEC even for very thin graphite electrodes (<0.0025 cm). In conjunction with appropriate correction factors determined with Monte Carlo techniques, the uncalibrated hybrid PEEC can be used for measuring absorbed dose in bone material to within 2% for high-energy photon and electron beams

  3. The METAS absorbed dose to water calibration service for high energy photon and electron beam radiotherapy

    Full text: The Swiss Federal Office of Metrology and Accreditation (METAS) provides an absorbed dose to water calibration service for reference dosimeters using 60Co γ radiation, ten X-ray beam qualities between TPR20,10=0.639 and 0.802 and ten electron beam qualities between R50=1.75 gcm-2 and 8.54 gcm-2. A 22 MeV microtron accelerator with a conventional treatment head is used as radiation source for the high energy photon and electron beams. The treatment head produces clinical beams. The METAS absorbed dose calibration service for high energy photons is based on a primary standard sealed water calorimeter of the Domen type, that is used to calibrate several METAS transfer standards of type NE2611A and NE2571A in terms of absorbed dose to water in the energy range from 60Co to TPR20,10 = 0.802. User reference dosimeters are compared with the transfer standards to give calibration factors in absorbed dose to water with an uncertainty of 1.0% for 60Co γ radiation and 1.4% for higher energies (coverage factor k=2). The calibration service was launched in 1997. The calibration factors measured by METAS have been compared with those derived from the Code of Practice of the International Atomic Energy Agency using the calculated kQ factors listed in table 14. The comparison showed a maximum difference of 0.8% for the NE25611A and NE 2571A chambers. At 60Co γ radiation the METAS primary standard of absorbed dose to water was bilaterally compared with the primary standards of the Bureau International des Poids et Mesures BIPM (Sevres) as well as of the National Research Council NRC (Canada). In either case the standards were in agreement within the comparison uncertainties. The METAS absorbed dose calibration service for high energy electron beams is based on a primary standard chemical dosimeter. A monoenergetic electron beam of precisely known particle energy and beam charge is totally absorbed in Fricke solution (ferrous ammonium sulphate) of a given mass. This

  4. Absorbed 18F-FDG Dose to the Fetus During Early Pregnancy

    We describe a rare case of a woman who underwent 18F-FDG PET/CT during early pregnancy (fetus age, 10 wk). The fetal absorbed dose was calculated by taking into account the 18F-FDG fetal self-dose, photon dose coming from the maternal tissues, and CT dose received by both mother and fetus. Methods: The patient (weight, 71 kg) had received 296 MBq of 18F-FDG. Imaging started at 1 h, with unenhanced CT acquisition, followed by PET acquisition. From the standardized uptake value measured in fetal tissues, we calculated the total number of disintegrations per unit of injected activity. Monte Carlo analysis was then used to derive the fetal 18F-FDG self-dose, including positrons and self-absorbed photons. Photon dose from maternal tissues and CT dose were added to obtain the final dose. Results: The maximum standardized uptake value in fetal tissues was 4.5. Monte Carlo simulation showed that the fetal self-dose was 3.0 * 10-2 mGy/MBq (2.7 * 10-2 mGy/MBq from positrons and 0.3 * 10-2 mGy/MBq from photons). The estimated photon dose to the fetus from maternal tissues was 1.04*10-2 mGy/MBq. Accordingly, the specific 18F-FDG dose to the fetus was about 4.0 *10-2 mGy/MBq (11.8 mGy in this patient). The CT scan added a further 10 mGy. Conclusion: The dose to the fetus during early pregnancy can be as high as 4.0*10-2 mGy/MBq of 18F-FDG. Current dosimetric standards in early pregnancy may need to be revised. (authors)

  5. The Effect of Diagnostic Absorbed Doses from 131I on Human Thyrocytes in Vitro

    Zbigniew Adamczewski

    2015-06-01

    Full Text Available Background: Administration of diagnostic activities of 131I, performed in order to detect thyroid remnants after surgery and/or thyroid cancer recurrence/metastases, may lead to reduction of iodine uptake. This phenomenon is called “thyroid stunning”. We estimated radiation absorbed dose-dependent changes in genetic material, in particular in sodium iodide symporter (NIS gene promoter, and NIS protein level in human thyrocytes (HT. Materials and Methods: We used unmodified HT isolated from patients subjected to thyroidectomy exposed to 131I in culture. The different 131I activities applied were calculated to result in absorbed doses of 5, 10, and 20 Gy. Results: According to flow cytometry analysis and comet assay, 131I did not influence the HT viability in culture. Temporary increase of 8-oxo-dG concentration in HT directly after 24 h (p < 0.05 and increase in the number of AP-sites 72 h after termination of exposition to 20 Gy dose (p < 0.0001 were observed. The signs of dose-dependent DNA damage were not associated with essential changes in the NIS expression on mRNA and protein levels. Conclusions: Our observation constitutes a first attempt to evaluate the effect of the absorbed dose of 131I on HT. The results have not confirmed the theory that the “thyroid stunning” reduces the NIS protein synthesis.

  6. Skin Absorbed Doses from Full Mouth Standard Intraoral Radiography in Bisecting Angle and Paralleling techniques

    This study was performed to measure the skin absorbed doses from full mouth standard intraoral radiography(14 exposures) in bisecting angle and paralleling techniques. Thermoluminescent dosimeters were used in a phantom. Circular tube collimator (60 mm in diameter, 20 cm in length) and rectangular collimator (35 mm X 44 mm, 40 cm in length) were set for bisecting angle and paralleling techniques respectively. All measurement sites were classified into 8 groups according to distance from each point of central rays. The results were as follows: 1. The skin absorbed doses from the paralleling technique were significantly decreased than those from the bisecting technique in both points at central ray and points away from central ray. The percentage rats of decrease were greater at points away from central ray than those at central ray. 2. The skin absorbed doses at the lens of eye, parotid gland, submandibular gland and thyroid region were significantly decreased in paralleling technique, but those of the midline of palate remained similar in both techniques. 3. The highest doses were measured at the site 20 mm above the point of central ray for the mandibular premolars in bisecting angle technique and at the point of central ray for the mandibular premolars in paralleling techniques. The lowest doses were measured at the thyroid region in both techniques.

  7. The METAS absorbed dose to water calibration service for high energy photon and electron beam radiotherapy

    The Swiss Federal Office of Metrology and Accreditation (METAS) provides an absorbed dose to water calibration service for reference dosimeters. The calibration service uses 60Co gamma radiation, ten high energy photon beam qualities between TPR20,10 = 0.639 and 0.802 and ten electron beam qualities between R50 = 1.75 g/cm2 and 8.54 g/cm2. The METAS absorbed dose calibration service for high energy photons is based on a primary standard sealed water calorimeter used to calibrate several METAS NE 2611A and NE 2571A type ionization chamber working standards in terms of absorbed dose to water in the energy range of 60Co to TPR20,10 = 0.802. The users' reference dosimeters are compared with the working standards to give calibration factors in absorbed dose to water with an uncertainty of 1.0% for 60Co radiation and 1.4% for higher energies (coverage factor k = 2). The calibration service was launched in 1997. The calibration factors measured by METAS have been compared with those derived from the IAEA Technical Reports Series No. 398 (TRS 398) code of practice and from Recommendations No. 4 of the Swiss Society of Radiobiology and Medical Physics (SSRMP). The comparisons showed a maximum difference of 1.2% for the NE 2561A and NE 2571A chambers. At 60Co gamma radiation the METAS primary standard of absorbed dose to water was bilaterally compared with the primary standards of the Bureau international des poids et mesures.The standards were in agreement within the comparison uncertainties. The METAS absorbed dose calibration service for high energy electron beams is based on a primary standard chemical dosimeter. A monoenergetic electron beam of known particle energy and beam charge is totally absorbed in Fricke solution. The experiment was carried out in the energy range of 5.3 MeV to 22.4 MeV, which allows the determination of the response of the Fricke dosimeter. Finally, the users' dosimeters are compared with the METAS working standards. The overall uncertainty in

  8. Adiabatic calorimeter for measuring absorbed dose of IHEP synchrotron secondary radiation

    An adiabatic calorimeter for measuring the value of absorbed dose of mixed radiation generated by 70 GeV proton synchrotron is described. The calorimetric system consists of a working body (a core) and a shell (a screen). The calorimeter adiabaticity is provided by the absence of the core-shell heat exchange by maintaining the shell temperature equal to the core temperature and, consequently, the whole energy generated in the core goes for its heating. The work showed the possibility of carrying out the adiabatic calorimetric measurements of absorbed dose of secondary radiation generated by un accelerated proton beam under the conditions of alternating magnetic and electric fields at the IHEP proton synchrotron at the average dose rate not less than 5x10-3 Wxkg-1

  9. Absorbed dose measurements on external surface of Kosmos-satellites with glass thermoluminescent detectors.

    Akatov YuA; Arkhangelsky, V V; Kovalev, E E; Spurny, F; Votochkova, I

    1989-01-01

    In this paper we present absorbed dose measurements with glass thermoluminescent detectors on external surface of satellites of Kosmos-serie flying in 1983-87. Experiments were performed with thermoluminescent aluminophosphate glasses of thicknesses 0.1, 0.3, 0.4, 0.5, and 1 mm. They were exposed in sets of total thickness between 5 and 20 mm, which were protected against sunlight with thin aluminized foils. In all missions, extremely high absorbed dose values were observed in the first layers of detectors, up to the thickness of 0.2 to 0.5 gcm-2. These experimental results confirm that, during flights at 250 to 400 km, doses on the surface of the satellites are very high, due to the low energy component of the proton and electron radiation. PMID:11537297

  10. Absorbed doses received by infants subjected to panoramic dental and cephalic radiographs

    The IAEA Report No. 115 recommends that each country or region can establish levels of absorbed doses for each radiographic technique employed in diagnostic. assuming the extended and expensive of this purpose, we have been to begin in a first step with the dentistry area, in order to estimate the dose levels received at crystalline and thyroid level in infants that go to an important public institution in our country to realize panoramic and cephalic radiographs. This work will serve to justify and impel a quality assurance program in Venezuela on the dentistry area which includes aspects such as training for the medical lap referring the justification of the radiological practice, optimization of X-ray units to produce an adequate image quality that delivers to patient an absorbed dose as much lower as reasonably it can be reached without diagnostic detriment. (Author)

  11. Absorbed radiation dose in plants of natural complexes in Belarus over the past 10 years following the Chernobyl accident

    An absorbed radiation dose in plant of the natural complexes in Belarus for 10 years following the Chernobyl accident was calculated. The data on dynamics of the exposure dose rate in the area for 10 years were used for calculating the absorbed dose due to external irradiation and the data on the specific activity of the plants due to incorporation of cesium 137 and strontium 90 were taken into consideration when calculating the absorbed dose due to internal irradiation. Maximal absorbed doses in plants (to 40 Gy) were fixed in the zone with the high density of contamination. It resulted in visible somatic damages of separated plant organs. The highest contribution to formation of absorbed doses of ionizing radiation in plants in the contaminated zones belongs to internal irradiation of plant organisms due to incorporated radionuclides, in particular cesium 137

  12. 1D non-uniform dose delivery by a single dynamic absorber

    A new technique for 1D non-uniform dose delivery has been recently proposed, using a single computer-controlled dynamic absorber, which is driven within the beam during irradiation. Analytical-iterative and convolution algorithms have been developed in order to optimize the movement of the absorber in creating wished beam modulations. The technique has been demonstrated to be suitable for many applications in the fields of dynamic wedging, tissue-deficit compensation and, in some cases, conformal therapy by non-uniform dose delivery. A first non-focused prototype has been shown to be able to reproduce a number of modulated beams with an acceptable accuracy (Phys.Med. Biol. 40: 221-240, 1995). A new focused prototype has been carried out at our Institute and it is under investigation: preliminary tests (by diodes array and film dosimetry) confirm the wide possibilities of clinical application. The apparatus, which can be inserted in the tray holder of our Clinac Varian 6/100, is connected through a mechanical transmission system to a computer where absorber's speed profiles (corresponding to wished fluence profiles) are stored. The operator can recall the wished profile and move the absorber in the due way, when the irradiation starts. The single-absorber dynamic modulation technique cannot modulate the beam fluence in any way one wishes, due to the physical constraint that the absorber can stay in the irradiation field for a time not larger than the total irradiation time: however it can create a large number of dynamically modulated beams clinically interesting. For this reason it should be considered as a valid 'low-cost' technique for dynamic beam modulation (also on Linacs which do not have complex computer-controlled options for non-uniform dose delivery such as dynamic collimators and multi leaves)

  13. Fetus absorbed dose evaluation in head and neck radiotherapy procedures of pregnant patients

    Camargo da C, E.; Ribeiro da R, L. A.; Santos B, D. V., E-mail: etieli@ird.gov.br [Instituto de Radioprotecao e Dosimetria / CNEN, Av. Salvador Allende s/n, Barra de Tijuca, 22783-127 Rio de Janeiro (Brazil)

    2014-08-15

    Each year a considerable amount of pregnant women needs to be submitted to radiotherapeutic procedures to combat malignant tumors. Radiation therapy is often a treatment of choice for these patients. It is possible to use shielding and beam positioning such that the potential dose to the fetus can be minimized. In this work the head and neck cancer treatment of a pregnant patient was experimentally simulated. The patient was simulated by an anthropomorphic Alderson phantom and the absorbed dose to the fetus was evaluated using micro-rod TLD-100 detectors in two conditions, namely protecting the patients abdomen with a 7 cm lead layer and using no abdomen shielding. The aim of this experiment was to evaluate the efficiency of the abdomen protection in reducing the fetus absorbed dose. Irradiations were performed with a Trilogy linear accelerator using x-rays of 6 MV. A total dose of 50 Gy to the target volume was delivered. The fetus doses evaluated with and without the lead shielding were, respectively, 0.52±0.039 and (0.88±0.052) c Gy, corresponding to a dose reduction of 59%. The dose (0.52±0.039) c Gy is within the zone of biological tolerance for the fetus. (Author)

  14. PHITS simulations of absorbed dose out-of-field and neutron energy spectra for ELEKTA SL25 medical linear accelerator

    Monte Carlo (MC) based calculation methods for modeling photon and particle transport, have several potential applications in radiotherapy. An essential requirement for successful radiation therapy is that the discrepancies between dose distributions calculated at the treatment planning stage and those delivered to the patient are minimized. It is also essential to minimize the dose to radiosensitive and critical organs. With MC technique, the dose distributions from both the primary and scattered photons can be calculated. The out-of-field radiation doses are of particular concern when high energy photons are used, since then neutrons are produced both in the accelerator head and inside the patients. Using MC technique, the created photons and particles can be followed and the transport and energy deposition in all the tissues of the patient can be estimated. This is of great importance during pediatric treatments when minimizing the risk for normal healthy tissue, e.g. secondary cancer. The purpose of this work was to evaluate 3D general purpose PHITS MC code efficiency as an alternative approach for photon beam specification. In this study, we developed a model of an ELEKTA SL25 accelerator and used the transport code PHITS for calculating the total absorbed dose and the neutron energy spectra infield and outside the treatment field. This model was validated against measurements performed with bubble detector spectrometers and Boner sphere for 18 MV linacs, including both photons and neutrons. The average absolute difference between the calculated and measured absorbed dose for the out-of-field region was around 11%. Taking into account a simplification for simulated geometry, which does not include any potential scattering materials around, the obtained result is very satisfactorily. A good agreement between the simulated and measured neutron energy spectra was observed while comparing to data found in the literature. (note)

  15. A fibre optic scintillator dosemeter for absorbed dose measurements of low-energy X-ray-emitting brachytherapy sources

    A newly developed dosemeter using a 0.5 mm diameter x 0.5 mm thick cylindrical plastic scintillator coupled to the end of a fibre optic cable is capable of measuring the absorbed dose rate in water around low-activity, low-energy X-ray emitters typically used in prostate brachytherapy. Recent tests of this dosemeter showed that it is possible to measure the dose rate as a function of distance in water from 2 to 30 mm of a 103Pd source of air-kerma strength 3.4 U (1 U = 1 μGy m2h-1), or 97 MBq (2.6 mCi) apparent activity, with good signal-to-noise ratio. The signal-to-noise ratio is only dependent on the integration time and background subtraction. The detector volume is enclosed in optically opaque, nearly water-equivalent materials so that there is no polar response other than that due to the shape of the scintillator volume chosen, in this case cylindrical. The absorbed dose rate very close to commercial brachytherapy sources can be mapped in an automated water phantom, providing a 3-D dose distribution with sub-millimeter spatial resolution. The sensitive volume of the detector is 0.5 mm from the end of the optically opaque waterproof housing, enabling measurements at very close distances to sources. The sensitive detector electronics allow the measurement of very low dose rates, as exist at centimeter distances from these sources. The detector is also applicable to mapping dose distributions from more complex source geometries such as eye applicators for treating macular degeneration. (authors)

  16. Absorbed radiation doses in women undergone to PET-CT exams for cancer diagnosis

    The absorbed dose in several organs and the effective dose in patients submitted to PET-CT exams with the radiopharmaceutical 18F-FDG were assessed. The ICRP-106 biokinetic model and thermoluminescent detectors in a anthropomorphic phantom were used. The use of the PET-CT image acquisition protocol, with the CT protocol for anatomical mapping, showed that 60% of effective dose was from the radiotracer administration, being the effective dose values for a female patient of (5.80 ± 1.57) mSv. In conclusion, patient doses can be reduced by using appropriate imaging acquisition in 18F-FDG PET-CT examinations and promoting the compliance with the radiation protection principles. (author)

  17. Radiation absorbed doses from iron-52, iron-55, and iron-59 used to study ferrokinetics

    Robertson, J.S.; Price, R.R.; Budinger, T.F.; Fairbanks, V.F.; Pollycove, M.

    1983-04-01

    Biological data obtained principally with Fe-59 citrate are used with physical data to calculate radiation absorbed doses for ionic or weak chelate forms of Fe-52, Fe-55, and Fe-59, administered by intravenous injection. Doses are calculated for normal subjects, primary hemochromatosis (also called idiopathic or hereditary hemochromatosis), pernicious anemia in relapse, iron-deficiency anemia, and polycythemia vera. The Fe-52 doses include the dose from the Mn-52m daughter generated after injection of Fe-52. Special attention has been given to the dose to the spleen, which has a relatively high concentration of RBCs and therefore of radioiron, and which varies significantly in size in both health and disease.

  18. Radiation absorbed doses from iron-52, iron-55, and iron-59 used to study ferrokinetics.

    Robertson, J S; Price, R R; Budinger, T F; Fairbanks, V F; Pollycove, M

    1983-04-01

    Biological data obtained principally with Fe-59 citrate are used with physical data to calculate radiation absorbed doses for ionic or weak chelate forms of Fe-52, Fe-55, and Fe-59, administered by intravenous injection. Doses are calculated for normal subjects, primary hemochromatosis (also called idiopathic or hereditary hemochromatosis), pernicious anemia in relapse, iron-deficiency anemia, and polycythemia vera. The Fe-52 doses include the dose from the Mn-52m daughter generated after injection of Fe-52. Special attention has been given to the dose to the spleen, which has a relatively high concentration of RBCs and therefore of radioiron, and which varies significantly in size in both health and disease. PMID:6339690

  19. Graves' disease radioiodine-therapy: Choosing target absorbed doses for therapy planning

    Willegaignon, J., E-mail: j.willegaignon@gmail.com; Sapienza, M. T.; Coura-Filho, G. B.; Buchpiguel, C. A. [Cancer Institute of São Paulo State (ICESP), Clinical Hospital, School of Medicine, University of São Paulo, Sao Paulo 01246-000 (Brazil); Nuclear Medicine Service, Department of Radiology, School of Medicine, University of São Paulo, Sao Paulo 01246-000 (Brazil); Watanabe, T. [Nuclear Medicine Service, Department of Radiology, School of Medicine, University of São Paulo, Sao Paulo 01246-000 (Brazil); Traino, A. C. [Unit of Medical Physics, Azienda Ospedaliero-Universitaria Pisana, Pisa 56126 (Italy)

    2014-01-15

    Purpose: The precise determination of organ mass (m{sub th}) and total number of disintegrations within the thyroid gland (A{sup ~}) are essential for thyroid absorbed-dose calculations for radioiodine therapy. Nevertheless, these parameters may vary according to the method employed for their estimation, thus introducing uncertainty in the estimated thyroid absorbed dose and in any dose–response relationship derived using such estimates. In consideration of these points, thyroid absorbed doses for Graves’ disease (GD) treatment planning were calculated using different approaches to estimating the m{sub th} and the A{sup ~}. Methods: Fifty patients were included in the study. Thyroid{sup 131}I uptake measurements were performed at 2, 6, 24, 48, 96, and 220 h postadministration of a tracer activity in order to estimate the effective half-time (T{sub eff}) of {sup 131}I in the thyroid; the thyroid cumulated activity was then estimated using the T{sub eff} thus determined or, alternatively, calculated by numeric integration of the measured time-activity data. Thyroid mass was estimated by ultrasonography (USG) and scintigraphy (SCTG). Absorbed doses were calculated with the OLINDA/EXM software. The relationships between thyroid absorbed dose and therapy response were evaluated at 3 months and 1 year after therapy. Results: The average ratio (±1 standard deviation) betweenm{sub th} estimated by SCTG and USG was 1.74 (±0.64) and that between A{sup ~} obtained by T{sub eff} and the integration of measured activity in the gland was 1.71 (±0.14). These differences affect the calculated absorbed dose. Overall, therapeutic success, corresponding to induction of durable hypothyroidism or euthyroidism, was achieved in 72% of all patients at 3 months and in 90% at 1 year. A therapeutic success rate of at least 95% was found in the group of patients receiving doses of 200 Gy (p = 0.0483) and 330 Gy (p = 0.0131) when m{sub th} was measured by either USG or SCTG and A

  20. Assessing dose rate distributions in VMAT plans

    Mackeprang, P.-H.; Volken, W.; Terribilini, D.; Frauchiger, D.; Zaugg, K.; Aebersold, D. M.; Fix, M. K.; Manser, P.

    2016-04-01

    Dose rate is an essential factor in radiobiology. As modern radiotherapy delivery techniques such as volumetric modulated arc therapy (VMAT) introduce dynamic modulation of the dose rate, it is important to assess the changes in dose rate. Both the rate of monitor units per minute (MU rate) and collimation are varied over the course of a fraction, leading to different dose rates in every voxel of the calculation volume at any point in time during dose delivery. Given the radiotherapy plan and machine specific limitations, a VMAT treatment plan can be split into arc sectors between Digital Imaging and Communications in Medicine control points (CPs) of constant and known MU rate. By calculating dose distributions in each of these arc sectors independently and multiplying them with the MU rate, the dose rate in every single voxel at every time point during the fraction can be calculated. Independently calculated and then summed dose distributions per arc sector were compared to the whole arc dose calculation for validation. Dose measurements and video analysis were performed to validate the calculated datasets. A clinical head and neck, cranial and liver case were analyzed using the tool developed. Measurement validation of synthetic test cases showed linac agreement to precalculated arc sector times within  ±0.4 s and doses  ±0.1 MU (one standard deviation). Two methods for the visualization of dose rate datasets were developed: the first method plots a two-dimensional (2D) histogram of the number of voxels receiving a given dose rate over the course of the arc treatment delivery. In similarity to treatment planning system display of dose, the second method displays the dose rate as color wash on top of the corresponding computed tomography image, allowing the user to scroll through the variation over time. Examining clinical cases showed dose rates spread over a continuous spectrum, with mean dose rates hardly exceeding 100 cGy min-1 for conventional

  1. Comparison of the standards of absorbed dose to water of the OMH and the BIPM for 60Co γ rays

    A comparison of the standards of absorbed dose to water of the Orszagos Meresugyi Hivatal (OMH), Budapest, Hungary and of the Bureau International des Poids et Mesures (BIPM) has been made in 60Co radiation. The results show that the OMH and the BIPM standards for absorbed dose to water are in close agreement, the difference being within the estimated uncertainty. (authors)

  2. Analysis of surface absorbed dose in X-ray grating interferometry

    Highlights: • Theoretical framework for dose estimation in X-ray grating interferometry. • Potential dose reduction of X-ray grating interferometry compared to conventional radiography. • Guidelines for optimization of X-ray grating interferometry for dose-sensitive applications. • Measure to compare various existing X-ray phase contrast imaging techniques. - Abstract: X-ray phase contrast imaging using grating interferometry has shown increased contrast over conventional absorption imaging, and therefore the great potential of dose reduction. The extent of the dose reduction depends on the geometry of grating interferometry, the photon energy, the properties of the sample under investigation and the utilized detector. These factors also determine the capability of grating interferometry to distinguish between different tissues with a specified statistical certainty in a single raw image. In this contribution, the required photon number for imaging and the resulting surface absorbed dose are determined in X-ray grating interferometry, using a two-component imaging object model. The presented results confirm that compared to conventional radiography, phase contrast imaging using grating interferometry indeed has the potential of dose reduction. And the extent of dose reduction is strongly dependent on the imaging conditions. Those results provide a theoretical framework for dose estimation under given imaging conditions before experimental trials, and general guidelines for optimization of grating interferometry for those dose-sensitive applications

  3. External Auditing on Absorbed Dose Using a Solid Water Phantom for Domestic Radiotherapy Facilities

    We report the results of an external audit on the absorbed dose of radiotherapy beams independently performed by third parties. For this effort, we developed a method to measure the absorbed dose to water in an easy and convenient setup of solid water phantom. In 2008, 12 radiotherapy centers voluntarily participated in the external auditing program and 47 beams of X-ray and electron were independently calibrated by the third party's American Association of Physicists in Medicine (AAPM) task group (TG)-51 protocol. Even though the AAPM TG-51 protocol recommended the use of water, water as a phantom has a few disadvantages, especially in a busy clinic. Instead, we used solid water phantom due to its reproducibility and convenience in terms of setup and transport. Dose conversion factors between solid water and water were determined for photon and electron beams of various energies by using a scaling method and experimental measurements. Most of the beams (74%) were within ±2% of the deviation from the third party's protocol. However, two of 20 X-ray beams and three of 27 electron beams were out of the tolerance (±3%), including two beams with a >10% deviation. X-ray beams of higher than 6 MV had no conversion factors, while a 6 MV absorbed dose to a solid water phantom was 0.4% less than the dose to water. The electron dose conversion factors between the solid water phantom and water were determined: The higher the electron energy, the less is the conversion factor. The total uncertainty of the TG-51 protocol measurement using a solid water phantom was determined to be ±1.5%. The developed method was successfully applied for the external auditing program, which could be evolved into a credential program of multi-institutional clinical trials. This dosimetry saved time for measuring doses as well as decreased the uncertainty of measurement possibly resulting from the reference setup in water.

  4. External Auditing on Absorbed Dose Using a Solid Water Phantom for Domestic Radiotherapy Facilities

    Choi, Chang Heon; Kim, Jung In; Park, Jong Min; Park, Yang Kyun; Ye, Sung Joon [Medical Research Center, Seoul National University College of Medicine, Seoul (Korea, Republic of); Cho, Kun Woo; Cho, Woon Kap [Radiation Research, Korean Institute of Nuclear Safety, Daejeon (Korea, Republic of); Lim, Chun Il [Korea Food and Drug Administration, Seoul (Korea, Republic of)

    2010-11-15

    We report the results of an external audit on the absorbed dose of radiotherapy beams independently performed by third parties. For this effort, we developed a method to measure the absorbed dose to water in an easy and convenient setup of solid water phantom. In 2008, 12 radiotherapy centers voluntarily participated in the external auditing program and 47 beams of X-ray and electron were independently calibrated by the third party's American Association of Physicists in Medicine (AAPM) task group (TG)-51 protocol. Even though the AAPM TG-51 protocol recommended the use of water, water as a phantom has a few disadvantages, especially in a busy clinic. Instead, we used solid water phantom due to its reproducibility and convenience in terms of setup and transport. Dose conversion factors between solid water and water were determined for photon and electron beams of various energies by using a scaling method and experimental measurements. Most of the beams (74%) were within {+-}2% of the deviation from the third party's protocol. However, two of 20 X-ray beams and three of 27 electron beams were out of the tolerance ({+-}3%), including two beams with a >10% deviation. X-ray beams of higher than 6 MV had no conversion factors, while a 6 MV absorbed dose to a solid water phantom was 0.4% less than the dose to water. The electron dose conversion factors between the solid water phantom and water were determined: The higher the electron energy, the less is the conversion factor. The total uncertainty of the TG-51 protocol measurement using a solid water phantom was determined to be {+-}1.5%. The developed method was successfully applied for the external auditing program, which could be evolved into a credential program of multi-institutional clinical trials. This dosimetry saved time for measuring doses as well as decreased the uncertainty of measurement possibly resulting from the reference setup in water.

  5. An international dosimetry exchange for boron neutron capture therapy. Part I: Absorbed dose measurements.

    Binns, P J; Riley, K J; Harling, O K; Kiger, W S; Munck af Rosenschöld, P M; Giusti, V; Capala, J; Sköld, K; Auterinen, I; Serén, T; Kotiluoto, P; Uusi-Simola, J; Marek, M; Viererbl, L; Spurny, F

    2005-12-01

    An international collaboration was organized to undertake a dosimetry exchange to enable the future combination of clinical data from different centers conducting neutron capture therapy trials. As a first step (Part I) the dosimetry group from the Americas, represented by MIT, visited the clinical centers at Studsvik (Sweden), VTT Espoo (Finland), and the Nuclear Research Institute (NRI) at Rez (Czech Republic). A combined VTT/NRI group reciprocated with a visit to MIT. Each participant performed a series of dosimetry measurements under equivalent irradiation conditions using methods appropriate to their clinical protocols. This entailed in-air measurements and dose versus depth measurements in a large water phantom. Thermal neutron flux as well as fast neutron and photon absorbed dose rates were measured. Satisfactory agreement in determining absorbed dose within the experimental uncertainties was obtained between the different groups although the measurement uncertainties are large, ranging between 3% and 30% depending upon the dose component and the depth of measurement. To improve the precision in the specification of absorbed dose amongst the participants, the individually measured dose components were normalized to the results from a single method. Assuming a boron concentration of 15 microg g(-1) that is typical of concentrations realized clinically with the boron delivery compound boronophenylalanine-fructose, systematic discrepancies in the specification of the total biologically weighted dose of up to 10% were apparent between the different groups. The results from these measurements will be used in future to normalize treatment plan calculations between the different clinical dosimetry protocols as Part II of this study. PMID:16475772

  6. A model study on the absorbed dose of radiation following respiratory intake of 238U3O8 aerosols

    Aerosols of depleted uranium oxides, formed upon high-energy impact of shells on hard targets during military operations, are able to disperse, reach the alveolar region of the lungs and be absorbed and distributed throughout various parts of the body. The absorbed particles are subjected to clearance in the upper respiratory tract, distribution to other body districts, dissolution and excretion. While the soluble forms of uranium are known to deliver a small dose of radiation to the body due to their homogeneous distribution and the low specific activity of 238U, ceramic particles exhibit a low dissolution rate and irradiate a limited volume of tissue for a long time with alpha particles with an energy of 4.267 MeV. The extent of the irradiated tissues depends on the radius of the particles and the total intake of uranium oxides. For the measured intake of U3O8 of a war veteran (15.51 μg) the number of particles ranges from 5.56x104 to 6.95x106 for sizes of 0.4-2.0 μm. Modelling the distribution of the particles between two compartments of the body, the averaged dose absorbed in 20 y by tissues surrounding the particles and within the range of the alpha particles varies from 6.8 mGy to 0.85 Gy for lungs and 8.1 mGy to 1.0 Gy for the lymph nodes, respectively. Correspondingly, due to the clearance and redistribution, the mass irradiated by 2.0-mm particles falls in 20 y from 6.06 mg to 0.94 μg in the lungs and grows from 0 to 1.0 mg in the lymph nodes. The estimated rate of formation of hydroxyl radicals upon radiolysis of water in the lungs and lymph nodes is 5.17x104 d-1 per cell after 1 y. (authors)

  7. Dose calculation and dosimetry tests for clinical implementation of 1D tissue-deficit compensation by a single dynamic absorber

    Background and purpose: In this study the possibilities for implementing 1D tissue-deficit compensation techniques by a dynamic single absorber were investigated. This research firstly involved a preliminary examination on the accuracy of a pencil beam-based algorithm, implemented for irregularly shaped photon beams in our 3D treatment planning system (TPS) (Cadplan 2.7, Varian-Dosetek Oy), in calculating dose distributions delivered in 1D non-uniform fields. Once the reliability of the pencil beam (PB) algorithm for dose calculations in non-uniform beams was verified, we proceeded to test the feasibility of tissue-deficit compensation using our single absorber modulator. As an example, we considered a mantle field technique. Materials and methods: To evaluate the accuracy of the method employed in calculating dose distributions delivered in 1D non-uniform fields, three different fluence profiles, which could be considered as a small sample representative of clinically relevant applications, were selected. The incident non-uniform fluences were simulated by the sum of simple blocked fields (i.e. with rectangular 'strip' blocks, one per beam) properly weighed by the 'modulation factors' Fi, defined in each interval of the subdivided profile as the ratio between the desired fluence and the open field fluence. Depth dose distributions in a cubic phantom were then calculated by the TPS and compared with the corresponding doses (at 5 and 10 cm acrylic depths) delivered by the single absorber modulation system. In the present application, the absorber speed profile able to compensate for the tissue deficit along the cranio-caudal direction and then homogenizing the dose distribution on a 'midline' isocentric plane with sufficient accuracy can be directly derived from anatomic data, such as the SSDs (source-skin distances) along the patient contour. The compensation can be verified through portal dosimetry techniques (using a traditional port film system). Results: The

  8. The Fricke dosimeter as an absorbed dose to water primary standard for Ir-192 brachytherapy

    The aim of this project was to develop an absorbed dose to water primary standard for Ir-192 brachytherapy based on the Fricke dosimeter. To achieve this within the framework of the existing TG-43 protocol, a determination of the absorbed dose to water at the reference position, D(r0,θ0), was undertaken. Prior to this investigation, the radiation chemical yield of the ferric ions (G-value) at the Ir-192 equivalent photon energy (0.380 MeV) was established by interpolating between G-values obtained for Co-60 and 250 kV x-rays.An irradiation geometry was developed with a cylindrical holder to contain the Fricke solution and allow irradiations in a water phantom to be conducted using a standard Nucletron microSelectron V2 HDR Ir-192 afterloader. Once the geometry and holder were optimized, the dose obtained with the Fricke system was compared to the standard method used in North America, based on air-kerma strength.Initial investigations focused on reproducible positioning of the ring-shaped holder for the Fricke solution with respect to the Ir-192 source and obtaining an acceptable type A uncertainty in the optical density measurements required to yield the absorbed dose. Source positioning was found to be reproducible to better than 0.3 mm, and a careful cleaning and control procedure reduced the variation in optical density reading due to contamination of the Fricke solution by the PMMA holder. It was found that fewer than 10 irradiations were required to yield a type A standard uncertainty of less than 0.5%.Correction factors to take account of the non-water components of the geometry and the volume averaging effect of the Fricke solution volume were obtained from Monte Carlo calculations. A sensitivity analysis showed that the dependence on the input data used (e.g. interaction cross-sections) was small with a type B uncertainty for these corrections estimated to be 0.2%.The combined standard uncertainty in the determination of absorbed dose to water at

  9. The Fricke dosimeter as an absorbed dose to water primary standard for Ir-192 brachytherapy

    El Gamal, Islam; Cojocaru, Claudiu; Mainegra-Hing, Ernesto; McEwen, Malcolm

    2015-06-01

    The aim of this project was to develop an absorbed dose to water primary standard for Ir-192 brachytherapy based on the Fricke dosimeter. To achieve this within the framework of the existing TG-43 protocol, a determination of the absorbed dose to water at the reference position, D(r0,θ0), was undertaken. Prior to this investigation, the radiation chemical yield of the ferric ions (G-value) at the Ir-192 equivalent photon energy (0.380 MeV) was established by interpolating between G-values obtained for Co-60 and 250 kV x-rays. An irradiation geometry was developed with a cylindrical holder to contain the Fricke solution and allow irradiations in a water phantom to be conducted using a standard Nucletron microSelectron V2 HDR Ir-192 afterloader. Once the geometry and holder were optimized, the dose obtained with the Fricke system was compared to the standard method used in North America, based on air-kerma strength. Initial investigations focused on reproducible positioning of the ring-shaped holder for the Fricke solution with respect to the Ir-192 source and obtaining an acceptable type A uncertainty in the optical density measurements required to yield the absorbed dose. Source positioning was found to be reproducible to better than 0.3 mm, and a careful cleaning and control procedure reduced the variation in optical density reading due to contamination of the Fricke solution by the PMMA holder. It was found that fewer than 10 irradiations were required to yield a type A standard uncertainty of less than 0.5%. Correction factors to take account of the non-water components of the geometry and the volume averaging effect of the Fricke solution volume were obtained from Monte Carlo calculations. A sensitivity analysis showed that the dependence on the input data used (e.g. interaction cross-sections) was small with a type B uncertainty for these corrections estimated to be 0.2%. The combined standard uncertainty in the determination of absorbed dose to water

  10. Deterministic absorbed dose estimation in computed tomography using a discrete ordinates method

    Norris, Edward T.; Liu, Xin, E-mail: xinliu@mst.edu [Nuclear Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409 (United States); Hsieh, Jiang [GE Healthcare, Waukesha, Wisconsin 53188 (United States)

    2015-07-15

    Purpose: Organ dose estimation for a patient undergoing computed tomography (CT) scanning is very important. Although Monte Carlo methods are considered gold-standard in patient dose estimation, the computation time required is formidable for routine clinical calculations. Here, the authors instigate a deterministic method for estimating an absorbed dose more efficiently. Methods: Compared with current Monte Carlo methods, a more efficient approach to estimating the absorbed dose is to solve the linear Boltzmann equation numerically. In this study, an axial CT scan was modeled with a software package, Denovo, which solved the linear Boltzmann equation using the discrete ordinates method. The CT scanning configuration included 16 x-ray source positions, beam collimators, flat filters, and bowtie filters. The phantom was the standard 32 cm CT dose index (CTDI) phantom. Four different Denovo simulations were performed with different simulation parameters, including the number of quadrature sets and the order of Legendre polynomial expansions. A Monte Carlo simulation was also performed for benchmarking the Denovo simulations. A quantitative comparison was made of the simulation results obtained by the Denovo and the Monte Carlo methods. Results: The difference in the simulation results of the discrete ordinates method and those of the Monte Carlo methods was found to be small, with a root-mean-square difference of around 2.4%. It was found that the discrete ordinates method, with a higher order of Legendre polynomial expansions, underestimated the absorbed dose near the center of the phantom (i.e., low dose region). Simulations of the quadrature set 8 and the first order of the Legendre polynomial expansions proved to be the most efficient computation method in the authors’ study. The single-thread computation time of the deterministic simulation of the quadrature set 8 and the first order of the Legendre polynomial expansions was 21 min on a personal computer