Male Phantom Research Articles

SU-D-103-06: Bismuth Shield Usage in MDCT Thoracic Scans: Organ Dose Vs. Image Quality

Purpose: To study Bismuth (Bi) shielding for the breast, organ dose and image quality were compared under the following conditions: (1) tube current modulation (TCM), (2) TCM with a Bi shield placed after topogram, and (3) manually reduced tube current (RTC) with no Bi. Methods: All measurements were performed with a 64‐slice scanner at 120 kVp. Organ dose was measured with MOSFETs using an adult male anthropomorphic phantom with supine breast attachments. The reference exposure and reduced exposure (with 4‐ply Bi shield) was measured with an ion chamber located at the level of the breast. The mA was reduced by normalizing the reference mA to the ratio of the reduced exposure to the reference exposure. Image quality was measured using a high contrast insert placed in the lung. Regions of Interest (ROIs) were drawn in thoracic organs to measure signal‐to‐noise ratio (SNR), percent contrast (%Contrast), noise, and HU values. Results: Organ doses (mGy) for the three scans (TCM, TCM with Bi, and RTC) were 11.1, 6.89, and 6.04 to the breast; 8.83, 8.01, and 7.62 to the lung; and 8.20, 7.36 and 8.40 to the heart, respectively. HU increase was greatest in the TCM with Bi scan for organs closest to the shield. The SNRs were 37.6, 34.1, and 43.3 and the %Contrast values were 349.2, 326.3, and 354.3 with TCM, TCM with Bi, and RTC, respectively. Conclusion: For thoracic CT, this RTC method provides a dose reduction to the breast similar to that of the TCM with Bi. Decrease in SNR and %Contrast in the TCM with Bi scan was expected due to decrease in photons reaching the detectors and beam hardening from the shield, respectively. Increased SNR in RTC scan was due to the increased mA compared to TCM scan at the level of measurement. U.S. NRC Health Physics Fellowship Grant No. NRC‐HQ‐12‐G‐38‐0022

SU-E-I-61: Modification of An Anthropomorphic Phantom to Accommodate OSL Dosimeters

Purpose: To modify an anthropomorphic (Rando) phantom designed for use with TLD dosimeter chips to accept OSL dosimeters. Methods: An adult male anthropomorphic phantom (Alderson Rando) has arrays of 5mm holes in each phantom slice that are designed to accept TLD dosimeter chips. Current OSL dosimeters are available in a small, 1 cm × 1 cm form factor that is convenient for external use clinically, but will not fit into the 5mm holes in Rando. The first (top) ten slices of an adult male Rando phantom (head and neck) were modified by machining 2mm slots 1.2 cm wide x 1.7 cm deep centered over the existing holes to allow placement of OSL dosimeters. Placing the slots coincident with the existing holes minimizes the amount of material removed from the phantom. Results: Each modified hole in the phantom required the removal of approximately 0.25 cmA3 of phantom material. The use of OSL dosimeters has greatly simplified the measurement process and reduced the total time required to load, unload, and read the dosimeters. For the head and neck, a total time of approximately 4 hours is required for loading, scanning, unloading, and reading OSL chips. With TLD dosimeters, the time for the equivalent data collection was 10‐12 hours. Conclusion: Total time for dosimetry measurements using TLD chips in Rando is significant due to the care required in handling TLDs, as well as the time required for the anneal and read processes. Modification of the Rando phantom has greatly increased the efficiency of making in‐phantom dose measurements. The total material removed from the phantom to accommodate the OSL dosimeters is less than 1% of the total material and so should have a negligible impact on overall phantom attenuation.

TU‐G‐103‐01: Monte Carlo Simulation and Dose Calculation of Chest CT Scan with Tube Current Modulation

Purpose: To establish the method of organ dose calculation through Monte Carlo simulations for patients taking CT scans with tube current modulation (TCM), and to give the dose results as well as the preliminary comparison of the dose with TCM and the dose without TCM. Methods: The MCNPX Monte Carlo code was used to simulate an armless adult male phantom taking a typical chest CT scan with TCM. The TCM output from a similar scan was provided by the manufacturer (GE Healthcare), and every specific tube current value corresponding to one of the total 15022 projections respectively. The 15022 projections throughout the entire scan were simplified into 274 projections in simulation, and the average tube current was calculated for each projection. With the organ dose per mAs for each projection simulated, the average current, and the rotation time, the organ doses for the entire scan were calculated. This dose simulation was compared to the dose from a constant tube current scan that preserves the same minimum image quality without TCM. Results: As expected, significantly lower dose for the CT scan with TCM was observed. Dose reduction with TCM was found to be from 59% to 72% for different organs, and it was as low as 28% of the dose to thyroid without TCM. Conclusion: The study successfully demonstrated the feasibility of performing Monte Carlo based organ dose calculations for TCM, and suggested the significant dose reduction capability of TCM. One member was funded by the 2012–2013 J. Newell Stannard Fellowship Award from Health Physics Society.

WE‐C‐108‐08: Organ Doses in a Male Phantom Undergoing High‐Dose‐Rate Brachytherapy Applied to the Prostate

Purpose: The aim of this study was to obtain equivalent doses to radiosensitive organs when applying high‐dose‐rate (HDR) brachytherapy to the prostate using60 Co or 192 Ir sources, and in comparison to external‐beam radiotherapy (EBRT) modalities. Methods: Monte Carlo simulations in Geant4 were performed using a voxelized adult reference man described in Publication 110 by the International Commission on Radiological Protection (ICRP). Point sources of 60Co or 192Ir with photon energy spectra corresponding to those exiting their capsules were placed in the center of the prostate. Equivalent doses per therapeutic absorbed dose to the prostate were obtained in several radiosensitive organs. Values were corrected to account for realistic source dwell times and positions throughout the prostate. This was repeated for a homogeneous water phantom to assess the adequacy of a homogeneous phantom for HDR brachytherapy dose calculations. Brachytherapy doses were compared to reported values from intensity‐modulated radiation therapy (IMRT) and proton therapy. Results: For the nearest organs considered (bladder, rectum, testes, small intestine, and colon), equivalent doses given by 60 Co source were smaller than from 192Ir. As the distance increased, 60Co delivered higher equivalent doses. Relative to 192Ir, the dose ratio increased up to a factor 5 for the brain. Differences between the heterogeneous and the water phantom became apparent at distances > 30 cm. For the closest organs, equivalent doses from the three EBRT modalities were within an order of magnitude to equivalent dosesdeposited by both brachytherapy sources. However, equivalent doses from brachytherapy to the farthest organs were up to two orders of magnitude smaller than EBRT doses. Conclusion: According to physical considerations, “ Co appears dosimetrically advantageous over 192Ir sources at close distances, but not for the farthest organs. Equivalent doses to distant healthy organs were lower for brachytherapy than the studied EBRT modalities.

Evaluation of specific absorbed fractions from internal photon sources in the ICRP Reference Male Phantom

In order to estimate the dose caused by internal radiation, it is necessary to know the specific absorbed fraction (SAF) values; through this work these values have been calculated using the Adult Male Reference Computational Phantom (RCP-AM) from the Publication 110 of the International Commission Radiologic Protection and the Monte Carlo transport code MCNPX. These values were calculated for a combination of 980 pairs of source and target organs, for a total of 12 energies. The results were validated and compared with the results reported by other authors: Hadid et al. (RCP-AM), Petoussi-Henss and Zankl (Golem) and the Oak Ridge National Laboratory (ORNL) stylised model reported by Cristy and Eckerman. Mostly, the SAF values calculated with the RCP-AM do not present significant differences in relation to its previous model Golem. When comparing the SAF values of RCP-AM with that of the ORNL stylised model, huge differences were found. These differences can be explained by the shape of the organs and their relative positions, which are more realistic in the voxelised phantoms.

Dose conversion coefficients for ICRP110 voxel phantom in the Geant4 Monte Carlo code

The reference adult male voxel phantom recommended by International Commission on Radiological Protection no. 110 was implemented in the Geant4 Monte Carlo code. Geant4 was used to calculate Dose Conversion Coefficients (DCCs) expressed as dose deposited in organs per air kerma for photons, electrons and neutrons in the Annals of the ICRP. In this work the AP and PA irradiation geometries of the ICRP male phantom were simulated for the purpose of benchmarking the Geant4 code. Monoenergetic photons were simulated between 15keV and 10MeV and the results were compared with ICRP 110, the VMC Monte Carlo code and the literature data available, presenting a good agreement.

Effect of correction/calibration factors on accuracy of in vivo dose delivery with cylindrical n-type Isorad diode in conventional radiotherapy

AbstractPurposeThe main aim was to use pre-calculated correction factors and calibration factors for measurement of accuracy of dose delivery before implementation of such in vivo dosimetry on real patients visiting for first radiation treatment. These factors were verified by generating the most common treatment plans on human phantom except for breast and colon using cobalt-60 unit.Materials and methodsSix treatment plans were generated, i.e. nasopharynx, bladder, prostate, brain, larynx and lung of human phantom, total 18 fields were planned keeping in view the correction factors which are to be verified. MULTIDATA Decision Support System 2.5, Shimadzu simulator, Isorad diode-n type, electrometer patient dose monitor and ATOM Adult male human phantom were used.Results and conclusionFor 18 fields, the dose delivery was accurate in the range 0·29–6·74%. The deviation between measured and expected doses to nasopharynx, lung, bladder, prostate, brain and larynx cases of human phantom ranged from 1·44–3·89%, 0·29–0·54%, 0·44–6·18%, 0·54–5·16%, 0·33–4·90%, 5·58–6·74%, respectively. In 30 palliative patient cases, the first radiation treatment was also monitored. The accuracy of dosimety ranged from 1·05% to 5·35%. This study is helpful to identify areas of improvement in treatment of patients like quality control/quality assurance (QA) of treatment planning system, beam data modifications, machine repair maintenance, QA audit in radiotherapy.

A study of dosimetric characteristics for in vivo dosimetry with cylindrical n-type Isorad diode

AbstractBackground and purposeThe objective was to determine diode characteristics before actual dose verification on human phantom and patients.Materials and methodsThe reliability and stability of equipment, signal stability, precision, dose response linearity, field flatness, perturbation of radiation dose, plastic to water conversion factor (Kpl), ionisation chambers (ICs) and diode calibration were determined. Correction factors for tray (CFtray), wedge (CFwedge), field size (CFFS), SSD (CFSSD), angle (CFangle) and block (CFblock) were found. Patient dose monitor, Isorad diode (n-type) and IC (PTW Frieburg), Co-60 unit (Theratron), ATOM Adult male human phantom (Model 701-D, CIRS) were used.Results and conclusionGood signal stability, precise data, and linear dose response, variation of 0·500% and 5·000% in field flatness and perturbation tests, respectively, were noted. Kpl was 1·006 for IC PTW Frieburg TW30013, 0114. The diode calibration factor was 0·989. CFtray, CFFS, CFSSD, CFangle, CFblock were 1·001, 1·001, 0·997, 1·006 and 0·990, respectively. CFwedge were 1·024, 1·030 and 1·038 for 30°, 45° and 60° wedges, respectively. The verification of above correction factors (CFs) on Nasopharynx and lung of human phantom was also done.

Effective and organ doses using helical 4DCT for thoracic and abdominal therapies

The capacity of 4DCT to quantify organ motion is beyond conventional 3DCT capability. Local control could be improved. However we are unaware of any reports of organ dose measurements for helical 4DCT imaging. We therefore quantified the radiation doses for helical 4DCT imaging. Organ and tissue dose was measured for thoracic and abdominal 4DCT in helical mode using an adult anthropomorphic phantom. Radiation doses were measured with thermoluminescence dosimeter chips inserted at various anatomical sites on the phantom. For the helical thoracic 4DCT, organ doses were 57.2 mGy for the lung, 76.7 mGy for the thyroids, 48.1 mGy for the breasts, and 10.86 mGy for the colon. The effective doses for male and female phantoms were very similar, with a mean value of 33.1 mSv. For abdominal 4DCT imaging, organ doses were 14.4 mGy for the lung, 0.78 mGy for the thyroids, 9.83 mGy for breasts, and 58.2 mGy for the colon (all obtained by using ICRP 103). We quantified the radiation exposure for thoracic and abdominal helical 4DCT. The doses for helical 4DCT were approximately 1.5 times higher than those for cine 4DCT, however the stepwise image artifact was reduced. 4DCT imaging should be performed with care in order to minimize radiation exposure, but the advantages of 4DCT imaging mandates its incorporation into routine treatment protocols.

Organ shielding and doses in Low-Earth orbit calculated for spherical and anthropomorphic phantoms

Humans in space are exposed to elevated levels of radiation compared to ground. Different sources contribute to the total exposure with galactic cosmic rays being the most important component. The application of numerical and anthropomorphic phantoms in simulations allows the estimation of dose rates from galactic cosmic rays in individual organs and whole body quantities such as the effective dose. The male and female reference phantoms defined by the International Commission on Radiological Protection and the hermaphrodite numerical RANDO phantom are voxel implementations of anthropomorphic phantoms and contain all organs relevant for radiation risk assessment. These anthropomorphic phantoms together with a spherical water phantom were used in this work to translate the mean shielding of organs in the different anthropomorphic voxel phantoms into positions in the spherical phantom. This relation allows using a water sphere as surrogate for the anthropomorphic phantoms in both simulations and measurements. Moreover, using spherical phantoms in the calculation of radiation exposure offers great advantages over anthropomorphic phantoms in terms of computational time.In this work, the mean shielding of organs in the different voxel phantoms exposed to isotropic irradiation is presented as well as the corresponding depth in a water sphere. Dose rates for Low-Earth orbit from galactic cosmic rays during solar minimum conditions were calculated using the different phantoms and are compared to the results for a spherical water phantom in combination with the mean organ shielding. For the spherical water phantom the impact of different aluminium shielding between 1g/cm2 and 100g/cm2 was calculated. The dose equivalent rates were used to estimate the effective dose rate.

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

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

2076 SPECIFIC ORGAN DOSES UTILIZING A NEW TECHNIQUE FOR IMAGING NEPHROLITHIASIS: DIGITAL TOMOSYNTHESIS

INTRODUCTION AND OBJECTIVES: Digital tomosynthesis (DT) is a novel imaging technique for the evaluation of patients of with nephrolithiasis. It consists of a plain abdominal radiograph (KUB) and one tomographic sweep. Software is used to recreate a series of coronal images from the tomographic sweep. We determined organ specific dose and effective dose (ED) for DT and compared it to our institutional “low dose” non contrast computed tomography (NCCT). METHODS: A validated anthropomorphic male phantom was placed supine on a GE Definium 8000 CT scanner. High sensitivity metal oxide semiconductor field effect transistors (MOSFET) dosimeters were placed at 20 organ locations and used to measure organ doses (OD). A routine DT study was performed consisting of two KUB (scout) images and one tomographic sweep in a 60 degree arc over the phantom. OD were determined as the sum of the doses for the study. Equivalent doses were calculated by multiplying OD and the appropriate tissue weighting factor. ED was calculated by the summation of the equivalent doses. OD and ED were determined in a similar fashion for a renal stone protocol NCCT and the doses were compared. RESULTS: Specific organ doses for DT (2 scouts and 1 tomographic sweep) and NCCT are shown in the table. The ED for NCCT is 3.04 ( 0.34) mSv. The calculated ED for digital tomosynthesis is 0.54 ( 0.07) mSv (2 scouts at 0.10mSv and 0.08mSv 1 sweep at 0.36mSv), p 0.0002. CONCLUSIONS: Digital tomosynthesis exposes patients to substantially less radiation than NCCT. This is particularly true for radiation sensitive organs. Further studies are needed to compare the sensitivity and specificity of DT as compared to NCCT. However, its low overall radiation dose make it an ideal study for the follow up of the recurrent stone former in the office setting.

Evaluation of absorbed and effective doses to patients from radiopharmaceuticals using the ICRP 110 reference computational phantoms and ICRP 103 formulation

In diagnostic nuclear medicine, mean absorbed doses to patients' organs and effective doses are published for standard stylised anatomic models. To provide more realistic and detailed geometries of the human morphology, the International Commission on Radiological Protection (ICRP) has recently adopted male and female voxel phantoms to represent the reference adult. This work investigates the impact of the use of these new computational phantoms. The absorbed doses were calculated for 11 different radiopharmaceuticals currently used in diagnostic nuclear medicine. They were calculated for the ICRP 110 reference computational phantoms using the OEDIPE software and the MCNP extended Monte Carlo code. The biokinetic models were issued from ICRP Publications 53, 80 and 106. The results were then compared with published values given in these ICRP Publications. To discriminate the effect of anatomical differences on organ doses from the effect of the calculation method, the Monte Carlo calculations were repeated for the reference adult stylised phantom. The voxel effect, the influence of the use of different densities and nuclear decay data were also investigated. Effective doses were determined for the ICRP 110 adult reference computational phantom with the tissue weighting factor of ICRP Publication 60 and the tissue weighting factors of ICRP Publication 103. The calculation method and, in particular, the simulation of the electron transport have a significant influence on the calculated doses, especially, for small and walled organs. Overestimates of >200 % were observed for the urinary bladder wall of the stylised phantom compared with the computational phantoms. The unrealistic organ topology of the stylised phantom leads to important dose differences, sometimes by an order of magnitude. The effective doses calculated using the new computational phantoms and the new tissue weighting factors are globally lower than the published ones, except for some radiopharmaceuticals, where the differences can reach 60 % higher than the published values. This study analyses the first set of absorbed and effective doses with the new ICRP male and female reference computational phantoms for different radiopharmaceuticals. It highlights the importance of taking into account the electron transport and the realism of the shape and inter-organ distances of the anthropomorphic model used.

PO-0974: Organ doses in a male phantom undergoing high-dose-rate brachytherapy applied to localized prostate carcinoma

PO-0974: Organ doses in a male phantom undergoing high-dose-rate brachytherapy applied to localized prostate carcinoma

Calculated organ doses using Monte Carlo simulations in a reference male phantom undergoing HDR brachytherapy applied to localized prostate carcinoma

The aim of this study was to obtain equivalent doses in radiosensitive organs (aside from the bladder and rectum) when applying high-dose-rate (HDR) brachytherapy to a localized prostate carcinoma using (60)Co or (192)Ir sources. These data are compared with results in a water phantom and with expected values in an infinite water medium. A comparison with reported values from proton therapy and intensity-modulated radiation therapy (IMRT) is also provided. Monte Carlo simulations in Geant4 were performed using a voxelized phantom described in International Commission on Radiological Protection (ICRP) Publication 110, which reproduces masses and shapes from an adult reference man defined in ICRP Publication 89. Point sources of (60)Co or (192)Ir with photon energy spectra corresponding to those exiting their capsules were placed in the center of the prostate, and equivalent doses per clinical absorbed dose in this target organ were obtained in several radiosensitive organs. Values were corrected to account for clinical circumstances with the source located at various positions with differing dwell times throughout the prostate. This was repeated for a homogeneous water phantom. For the nearest organs considered (bladder, rectum, testes, small intestine, and colon), equivalent doses given by (60)Co source were smaller (8%-19%) than from (192)Ir. However, as the distance increases, the more penetrating gamma rays produced by (60)Co deliver higher organ equivalent doses. The overall result is that effective dose per clinical absorbed dose from a (60)Co source (11.1 mSv/Gy) is lower than from a (192)Ir source (13.2 mSv/Gy). On the other hand, equivalent doses were the same in the tissue and the homogeneous water phantom for those soft tissues closer to the prostate than about 30 cm. As the distance increased, the differences of photoelectric effect in water and soft tissue, and appearance of other materials such as air, bone, or lungs, produced variations between both phantoms which were at most 35% in the considered organ equivalent doses. Finally, effective doses per clinical absorbed dose from IMRT and proton therapy were comparable to those from both brachytherapy sources, with brachytherapy being advantageous over external beam radiation therapy for the furthest organs. A database of organ equivalent doses when applying HDR brachytherapy to the prostate with either (60)Co or (192)Ir is provided. According to physical considerations, (192)Ir is dosimetrically advantageous over (60)Co sources at large distances, but not in the closest organs. Damage to distant healthy organs per clinical absorbed dose is lower with brachytherapy than with IMRT or protons, although the overall effective dose per Gy given to the prostate seems very similar. Given that there are several possible fractionation schemes, which result in different total amounts of therapeutic absorbed dose, advantage of a radiation treatment (according to equivalent dose to healthy organs) is treatment and facility dependent.

Computational lymphatic node models in pediatric and adult hybrid phantoms for radiation dosimetry

We developed models of lymphatic nodes for six pediatric and two adult hybrid computational phantoms to calculate the lymphatic node dose estimates from external and internal radiation exposures. We derived the number of lymphatic nodes from the recommendations in International Commission on Radiological Protection (ICRP) Publications 23 and 89 at 16 cluster locations for the lymphatic nodes: extrathoracic, cervical, thoracic (upper and lower), breast (left and right), mesentery (left and right), axillary (left and right), cubital (left and right), inguinal (left and right) and popliteal (left and right), for different ages (newborn, 1-, 5-, 10-, 15-year-old and adult). We modeled each lymphatic node within the voxel format of the hybrid phantoms by assuming that all nodes have identical size derived from published data except narrow cluster sites. The lymph nodes were generated by the following algorithm: (1) selection of the lymph node site among the 16 cluster sites; (2) random sampling of the location of the lymph node within a spherical space centered at the chosen cluster site; (3) creation of the sphere or ovoid of tissue representing the node based on lymphatic node characteristics defined in ICRP Publications 23 and 89. We created lymph nodes until the pre-defined number of lymphatic nodes at the selected cluster site was reached. This algorithm was applied to pediatric (newborn, 1-, 5-and 10-year-old male, and 15-year-old males) and adult male and female ICRP-compliant hybrid phantoms after voxelization. To assess the performance of our models for internal dosimetry, we calculated dose conversion coefficients, called S values, for selected organs and tissues with Iodine-131 distributed in six lymphatic node cluster sites using MCNPX2.6, a well validated Monte Carlo radiation transport code. Our analysis of the calculations indicates that the S values were significantly affected by the location of the lymph node clusters and that the values increased for smaller phantoms due to the shorter inter-organ distances compared to the bigger phantoms. By testing sensitivity of S values to random sampling and voxel resolution, we confirmed that the lymph node model is reasonably stable and consistent for different random samplings and voxel resolutions.

전투원 신체 주변 통신기기의 인체 노출량 분석

본 논문에서는 전투원이 착용할 수 있는 무선기기에 의한 인체영향 분석을 위해 인체의 다양한 위치에 송신 안테나를 위치시키고, 각 위치별로 송신기에 의한 인체영향을 분석하였다. 다양한 송신 안테나의 위치에 대해 분석하였다. 송신 안테나의 위치에 대한 시나리오는 전장에서 전투원이 통신기기를 착용할 수 있는 위치를 고려하여 국방과학연구소와 협의 하에 도출하였으며, 인체 전신 모델은 한국전자통신연구원(ETRI: Electronics and Telecommunications Research Institute)의 한국인 성인 남성 표준 모델을 사용하여 송신 안테나의 위치에 따른 전자파 흡수율(SAR: Specific Absorption Rate)을 국내 및 국제비전리복사방호위원회(ICNIRP: International Commission on Non-Ionizing Radiation Protection)의 인체 보호 기준과 비교하였다. 또한, 전장에서 전투원이 취할 수 있는 자세를 고려하여, 2가지 전형적인 자세에 대해서도 인체 노출량을 분석하였다. In this paper, human exposure of wireless devices was analyzed for various positions of the transmitter. The scenario for the position of the transmitting antenna was decided after discussion with ADD(Agency for Defense Development), and Korean male phantom model developed by ETRI were used to conduct simulations. The SAR values were analyzed by changing the position of the transmitter, and compared with Korean EMF regulations and ICNIRP guidelines. Additionally, human exposure was also investigated for two typical postures which can be posed by war-fighter.

Patient dose, gray level and exposure index with a computed radiography system

Computed radiography (CR) is gradually replacing conventional screen-film system in Brazil. To assess image quality, manufactures provide the calculation of an exposure index through the acquisition software of the CR system. The objective of this study is to verify if the CR image can be used as an evaluator of patient absorbed dose too, through a relationship between the entrance skin dose and the exposure index or the gray level values obtained in the image. The CR system used for this study (Agfa model 30-X with NX acquisition software) calculates an exposure index called Log of the Median (lgM), related to the absorbed dose to the IP. The lgM value depends on the average gray level (called Scan Average Level (SAL)) of the segmented pixel value histogram of the whole image. A Rando male phantom was used to simulate a human body (chest and head), and was irradiated with an X-ray equipment, using usual radiologic techniques for chest exams. Thermoluminescent dosimeters (LiF, TLD100) were used to evaluate entrance skin dose and exit dose. The results showed a logarithm relation between entrance dose and SAL in the image center, regardless of the beam filtration. The exposure index varies linearly with the entrance dose, but the angular coefficient is beam quality dependent. We conclude that, with an adequate calibration, the CR system can be used to evaluate the patient absorbed dose.

Calculation of Dose in Healthy Organs, during Radiotherapy 4-Field Box 3D Conformal for Prostate Cancer, Simulation of the Linac 2300, Radiotherapy Room and MAX Phantom

In men, prostate cancer is one of the most frequent types, and radiotherapy is adopted as a form of treatment. Although there are efforts to minimize the dose in the healthy organ and tissues adjacent to the tumor during radiotherapy, these organs are affected by the secondary scattered and leakage radiation originating from the therapeutic beam and these doses deposited in the healthy organs, can induce the appearance of new focal points of cancer. The aim of this study is to calculate the equivalent and effective doses, due to photons and neutrons, in healthy organs of a patient submitted to radiotherapy treatment for prostate cancer. Computed simulation of radiotherapy treatment for prostate cancer was used to perform the dose calculations, adopting the treatment protocol used at INCA (Brazilian National Cancer Institute). The MCNPX code was employed in the simulation radiation transport while the male voxel MAX phantom was used to represent the patient's human anatomy. The results obtained in this study indicate that the organs close to the irradiated region are predominantly affected by the dose due to photons, with an impact on organs from different systems of the body, such as the bladder, colon, and testicles, besides bone structures such as the femur, pelvis and spinal column. The results obtained from the doses deposited due to neutrons suggest that tibia and fibula, mandible, cranium, brain and thyroid, had the highest dose deposited due to neutrons in relation to photons. The result obtained from the effective dose was 31.47 mSv due to photons, while the dose due to neutrons was 0.42 mSv. Note that the effective dose due to photons is significantly higher than the effective dose due to neutrons. The values calculated in this study were compared with the experimental values obtained in the literature, presenting reasonable concordance. Additionally, as described in the literature, it was verified that the dose due to photons decreases considerably with the increase in the distance of the target organ, while the dose due to neutrons is distributed homogeneously in the organs. It is concluded that the contribution of neutrons to the appearance of secondary cancers is more relevant in the organs furthest from the target volume, and that organs close to the tumor, are affected predominantly by the dose due to photons.

中国数字人体男性数学模型建立及外辐射模拟

中国数字人体男性数学模型建立及外辐射模拟