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Radiation Dosimetry Research Group
Ferdowsi University of Mashhad
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Home · Members · Projects |
Projects 1. Library of
Statistical Phantoms 2. Internal Dosimetry of Inhaled Iodine-131 4. Fortran code to transform voxel data into MCNP code geometry 5. Different Effective Dose Conversion
Coefficients 7. Specific Absorbed Fractions from internal photon sources in ORNL analytical adult phantom 8. Dose factors for ORNL adult phantom 1. Library of Statistical
Phantoms
1.1
Image acquisition and segmentation The CT images of chest-abdomen-pelvis and head-neck of
100 patients (50 males and 50 females) were provided and the contours of
their distinguishable organs were determined using 3D-DOCTOR software. The organ models
and exterior surface of body were then extracted and imported into Rhinoceros software for 3D modeling. 1.2
NURBS modeling The
segmented organs from chest-abdomen-pelvis and head-neck image series were
imported to Rhinoceros software and
placed in correct location with respect to each other. An appropriate surface
for exterior of the body was also created based on length of trunk and
perimeters of chest, abdomen and pelvis wall using MakeHuman
software. The skeletal structures in extremities were also constructed
using a template model which includes all cortical, spongiosa, and medullary
parts. 1.3
Voxelization It
is necessary to convert the BREP geometry into discrete voxels because the
dosimetric calculations cannot be performed using the polygon mesh and NURBS
surfaces directly. So, the essential process of voxelization for hybrid
phantoms was performed with an in-house FORTRAN code. This application can
only deal with OBJ files. The final version of NURBS surfaces should then be converted
into polygon mesh and exported as obj files. The
presented lectures in CP2015 in Seoul, Korea (https://www.cp2015.org/) The
presented lectures in CP2019 in Munich, Germany (https://cp2019.helmholtz-muenchen.de/) Ř
Virtual
calibration of whole-body counter using a library of statistical phantoms Ř The
first series of Iranian BREP phantoms 2. Internal Dosimetry of
Inhaled Iodine-131
ABSTRACT
Iodine-131
(131I) is an important contributor to the overall exposure in the
early period after a nuclear accident. Inhalation is one of the main pathways
of radioiodine exposure. The ICRP has published, among other dosimetric data,
the committed effective dose (CED) coefficients of the radioisotopes,
including radioiodine, inhaled as gas and particulates in sizes 1 and 5 µm.
Radioiodine, however, may be encountered in a variety of chemical and
physical forms, namely vapors/gases, and particulates in various sizes. The
dose assessment for the iodine inhalation exposure in 19 aerosol sizes as
well as three gas/vapor forms, performed in this study, could shed some light
on the health risks of radioiodine exposure. Two different modes of work
(light vs. heavy) and breathing (nose vs. mouth) for aerosol inhalation were
also investigated. With the latest set of biokinetic models the cumulated
activities per unit intake were calculated at three levels (0, 5, and ~27%)
of thyroid uptake. The S values for 131I were computed based on
the ICRP adult male and female reference voxel phantoms by the Monte
Carlo method. Then, the committed equivalent and committed effective dose
coefficients were obtained (The data are available here). In general, for
nonzero thyroid uptakes, the maximum cumulated activity was found in the
thyroid. When the thyroid is blocked, however, the maximum depends on the
work and breathing mode as well as radioisotope form. Overall, the maximum
CED coefficient was evaluated for the inhalation of elemental iodine at
thyroid uptake of ~27% (2.8×10-8 Sv/Bq). As for the particle inhalation per se, mouth
breathing AMTD 0.6 nm and AMAD 0.2 µm particles showed to have the maximum
(2.8×10-8 Sv/Bq)
and minimum (6.4×10-9 Sv/Bq) CED coefficients, respectively. Compared to the reference CED coefficients, the
authors found an increase of about 58% for inhalation of the aerosols with
AMAD 1 micron and 70% for 5 micron. Supplementary
Data This
paper is submitted to the Journal of Environmental Radioactivity. Its
Supplementary data is provided in appendixes A, B, and C. Appendix A.
Cumulated Activity This
appendix lists cumulated activities in the source regions following
inhalation of 1 Bq 131I in 19 aerosol
sizes (0.6 nm- 20 µm), and three gas/vapor forms (I2, CH3I,
and C2H5I).
Appendix B.
Committed Equivalent Dose Coefficients Appendix
B summarizes the committed equivalent dose coefficients (Sv/Bq) in male and female phantoms at three levels of
thyroid uptake following inhalation of 1 Bq 131I
in 19 aerosol sizes (0.6 nm- 20 µm), and three gas/vapor forms of iodine (I2,
CH3I, and C2H5I).
Appendix C.
CED Coefficients This
appendix presents committed effective dose (CED) coefficients (Sv/Bq) during light and heavy
work following inhalation aerosols (0.6 nm- 20 µm) of 131I through
the nose and mouth at three levels of thyroid uptake. 3. The Influence of
Computational Phantoms on the Effective Dose and Two-Dosimeter Algorithm for
External Photon Beams. In
this study, the influence of computational phantoms on the effective dose (E),
dosimeter responses positioned on the front (chest) and back of phantom and
two-dosimeter algorithm was investigated for external photon beams. This
study was performed using Korean Typical MAN-2 (KTMAN-2), Chinese Reference
Adult Male (CRAM), ICRP male reference and Male Adult meSH
(MASH) reference phantoms. Calculations were done
for beam directions in different polar and azimuthal angles using the Monte
Carlo code of MCNP at energies of 0.08 MeV, 0.3 MeV and 1 MeV. Results show
that the body shape significantly affects E and the both dosimeter responses,
when dosimeters are indirectly irradiated. The acquired two-dosimeter
algorithms are almost the same for mentioned phantoms except for KTMAN-2.
Comparisons between E and estimated E (Eest),
obtained from two- dosimeter algorithm, illustrate that the overestimation of
Eest occur in OverHead
(OH) and UnderFoot (UF) directions. The effect of
using one algorithm for all phantoms was also investigated. According to the results,
to apply one algorithm for all reference phantom is possible. Comparisons of
organ absorbed doses In
order to validate organ absorbed doses in this study, results obtained for
KTMAN-2, CRAM, ICRP and MASH3 phantoms were compared with reported results by
other authors for AP, PA , LLAT and RLAT irradiation geometries. The figures
of these comparisons are ready here.
Table 1 also indicates these comparisons for AP at 0.08 MeV as an example (Table1 is available here). Comparisons of
Effective doses According
to ICRP, E is calculated using sex-averaged results for male and female, but
effective doses of present study were limited to calculations of male
phantom. Especially, gender-specific organs of male phantom (breast and
gonad) were considered for E estimations. Table 2 shows E values calculated
for KTMAN-2, CRAM, ICRP and MASH3 phantoms in AP, RLAT, PA, LLAT, OH and UF
irradiation geometries. In order to validate the results in this study, they
were compared with reported results by other authors (Table2 is available here). 4.
FORTRAN code voxel2MCNPinput A FORTRAN code was written by our research group to
transform the voxel data of adult male and female ICRP reference phantoms
into MCNP code geometry. Supplementary data files provided by the ICRP
represent two three-dimensional matrices of 254 × 127 × 222 and 299 × 137 ×
348 dimension with voxel resolutions of 2.137 × 2.137 × 8 mm3 and
1.775 × 1.775 × 4.84 mm3 for adult male (AM) and female (AF),
respectively. The procedure of voxel data transformation into the code
geometry is done via repeated structures representation. The size of arrays
was reduced using the repetition record feature (r command). 142 142 ...(12967 times)...
142 141 141 141 141 141 141 141 142 (291 times)... 142 12966r 141 6r 142 290r... To access the
FORTRAN code please contact: mirihakim@ferdowsi.um.ac.ir 5. Different Effective Dose Conversion Coefficients
for Monoenergetic Neutron Fluence from 10-9 MeV to
20 MeV - A Methodological Comparative Study- International Commission on Radiological Protection
(ICRP) introduced the effective dose as the basic quantity for determining
the acceptable dose and radiation risk. This study are presented of the
effective doses per unit neutron fluence according to the ICRP publications
60 and 103 (Tables are available here).You can also find
the comparison between these data here for different
irradiation conditions. Then ORNL data were compared with the results of
ICRP/ICRU reference computational phantoms. Comparisons with the results of
an analytical phantom (Medical Internal Radiation Dose (MIRD-5)) are ready
for use here and you can get
the results of comparisons between ORNL and ICRP/ICRU RVP phantoms with click
here for various
irradiation geometries. For each comparison, according to the used
calculation method, the gender of human model and common energy points
correspond data were selected from this study on ORNL phantoms. Also the
results, which were estimated on ORNL male phantom were compared with Visible
Human Project (VIPMAN) (Figures are present here). ORNL male and female data were compared with the
results of Asian voxel phantoms (TARO and HANAKO), respectively. The figures
of these comparisons are ready here. Direct measurement of the absorbed dose in a human body is not
possible. In external dosimetry, the conversion coefficient is a calculational link between physical quantities such as
absorbed dose and fluence and protection quantities such as effective
dose, or operational quantities such as personal dose equivalent. In this
project, Neutron fluence to absorbed dose conversion coefficients have
been evaluated for the analytical ORNL modified adult phantom in 26
body organs using MCNP Monte Carlo code. The calculation used 20 monodirectional monoenergetic
neutron beams in the energy range 10−9-20 MeV, under six
irradiation conditions: anterior-posterior (AP), posterior-anterior (PA),
left-lateral (LLAT) , right-lateral (RLAT),
isotropic (ISO) and rotation (ROT) (these data are available here) . To design a diagnostic or therapeutic irradiation
program, there exists a need to estimate the absorbed dose. In this
investigation, Specific Absorbed Fractions (SAFs) were calculated based on Cristy and Eckerman-™s
analytical adult phantom, by MCNP4C Monte Carlo code. SAFs were estimated
with uncertainty less than 3%, for about 600 source organ - target organ
pairs at 12 photon energies. The SAF estimations, by F6 tally card, are
presented in some tables, each of which corresponds one of the source organs
(these data are available here). Then these results were compared with Cristy and Eckerman-™s which
were based on direct Monte Carlo, reciprocity principle and point source
kernel methods. Also, agreements and disagreements between them for different
states were discussed. You can find the comparison between ORNL and MCNP4C
estimations here. Each figure presents SAFs related to one of the
source-target pairs. 8. Dose factors for
ORNL adult phantom Mathematical models utilize mathematical equations
to describe the organs and tissues of the human body. These phantoms include
homogeneous slabs, cylinders and spheres such as MIRD-based phantoms which is
the ICRP reference mathematical phantom. The Medical Internal Radiation Dose
(MIRD) committee phantom had been created to calculate absorbed dose from
internal radiation by Snyder et al 1). Several years
later, this model had been modified to capacitate for using in calculation of
absorbed dose from external radiation. ICRP publication 74 2)
applied a hermaphrodite MIRD-5 phantom or modified MIRD-based phantoms (ADAM
and EVA) being distinct sex-specific.3) ADAM
and EVA have about 70.5 and 59.2kg in weight and 170 and 160cm in height,
respectively .3) In 1987, Cristy and Eckerman 4) of Oak Ridge National Laboratory
(ORNL) developed a series of phantoms representing adult male and children of
different ages. These phantoms followed the format of Snyder et al
5) and Cristy .6) Then Eckerman, Cristy and Ryman
7) revised the head region to include neck, added the esophagus, and
data of the extra thoracic airways. ORNL adult phantoms, simulated in this
work, are Eckerman and Cristy
phantoms in which thyroid were replaced by Ulanovsky
et al 8-9) and its overlaping
errors were removed in order to implement by MCNP code. Furthermore, it was
assumed that the female phantom has the same size and weight with male one
(73kg in weight and 168cm in height). On the basis of data in Table A-1 of
ORNL/TM-83814), the elemental composition and density of three
major body tissues (skeleton, lung, and soft tissue) were assigned to each of
the organs. The mass of each body organ and tissue was chosen from Table B-3
of ORNL/TM-8381 .4)
1. Snyder WS, Ford
MR, Warner GG. Estimates of absorbed fraction for monoenergetic
photon sources uniformly distributed in various organs and heterogeneous
phantom. Report ORNL-4979. Oak Ridge, TN: Oak Ridge National Laboratory;
1978. 2.
ICRP (International Commission on Radiological Protection) Publication 74.
Conversion Coefficients for use in Radiological Protection against External
Radiation 1995. (Oxford :Pergamon) 3.
Kramer R, Zankl M, Williams G, Drexler G et al.
The calculation of dose from external photon exposures using reference human
phantoms and Monte Carlo methods. Part I: the male (ADAM) and female (EVA)
adult mathematical phantoms GSF-Bericht S-885
(Munich: Gesellschaft fur Strahlen-
und Umweltforschung mbH);
1982. 4.
Cristy M, Eckerman KF.
Specific absorbed fractions of energy at various ages from internal photon sources.
Oak Ridge, TN: Oak Ridge National Laboratory. ORNL/TM-8381/V1. 1987. 5.
Snyder WS, Ford MR, Warner GG et al. A tabulation of dose equivalent per microcurie-day for source and target organs of an adult
for various radionuclides: Part1. Oak Ridge National Laboratory Rep.
ORNL-5000; 1974. 6.
Cristy M. Mathematical phantoms representing
children of various ages for use in estimates of internal dose.
ORNL/NUREG/TM-367 .Oak Ridge National Laboratory. Oak Ridge, TN; 1980. 7.
Eckerman KF, Cristy M, Ryman
JC. The ORNL mathematical phantom series, informal paper;ÂOakRidge, TN:Oak Ridge
National Laboratory. 1996; available at http://homer.hsr.ornl.gov/VLab/mird2.pdf 8.
Ulanovsky AV, Minenko VF,
Korneev SV. Influence of measurement geometry on
the estimate of 131I activity in the thyroid: Monte Carlo simulation of a
detector and a phantom. Health Phys 1997; 72: 34-41. 9.
Ulanovsky AV, Eckerman KF. Absorbed fractions for electron and photon
emissions in the developing thyroid fetus to five years old. Radiat Protect Dosim 1998;
79:419-424.
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Radiation
Dosimetry Research Group Physics department, Faculty of
Science, |
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