Whole-body Counting Research Articles

Monte Carlo modeling and simulation of a new 3D printed phantom for WBC calibration with ballistic gel as a tissue substitute

Whole-body counter (WBC) systems are used for in vivo monitoring in occupational internal dosimetry, typically calibrated using physical anthropomorphic phantoms. Our research group previously 3D-printed the Reference Female Phantom for Internal Dosimetry (RFPID) without internal organs specifically designed for WBC calibration. The RFPID and it is intended to fill it homogenously with ballistic gel, which is commonly used as a tissue equivalent in ballistic studies. However, comprehensive characterization of its physicochemical properties and radiological behavior as a tissue surrogate for dosimetry is limited. This study aims to evaluate the suitability of ballistic gel as a tissue substitute for physical phantoms in WBC system calibration and to analyze the RFPID as a model for WBC calibration. Ballistic gel tests determined its density and attenuation coefficients, comparing it to muscle, water, and PMMA. The RFPID was modeled and simulated using MCNP6.2 code and placed in an in vivo monitoring system using an 8”x4″ NaI(Tl) scintillator detector previously validated. The simulations were repeated with the RCP_AF of ICRP-110. Results indicate that ballistic gel has a density approximately 6% different from muscle and shows similar linear attenuation coefficients to muscle at intermediate and high energy levels (186–2200 keV). Simulations revealed a disparity of less than 9% in counting efficiency between RFPID and RCP_AF for energies from 100 to 3000 keV, confirming the phantom's suitability for WBC calibration and ballistic gel's viability as a tissue surrogate in internal dosimetry.

Usefulness and limitations of various detector systems for estimation of 131I thyroid activity following an RN event

Following a radiological or nuclear (RN) event, rapid measurement of131I in members of the public is of utmost importance, and much equipment is needed for a high throughput. In this study, three gamma cameras (GCs), two thyroid uptake meters (TUMs) and one whole-body counter (WBC) were calibrated for activity measurements of131I in the thyroid. Minimum detectable activity was derived for the GCs, the TUMs and the WBC giving that a committed effective dose (CED) in the interval 2.0-85μSv, 13-700μSv and 0.52-6.4μSv, and thyroid absorbed doses in the interval 0.075-2.1 mGy, 0.48-17 mGy, and 0.020-0.15 mGy, respectively, can be assessed for children, adolescents, and adults. These numbers are based on 10 min measurement, performed at 1, 3 and 7 d after intake, and the CED includes intake by ingestion and inhalation of aerosols Type F, with an activity median aerodynamic diameter of 1μm. For a fractional signal loss of 63% due to dead time, a CED up to 2.0, 84 and 3.6 Sv and thyroid absorbed dose up to 47 Gy, 2000 Gy and 88 Gy for the three systems, respectively, can be assessed for children and intake by ingestion as a worst-case scenario in terms of CED, measured 7 d after intake. This study demonstrates the potential and limitations of using equipment readily available at larger hospitals for estimation of131I content in thyroid, which could increase the measurement capability following an RN event.

Lung counting with a highly segmented HPGe detector

A highly segmented High-Purity Germanium (HPGe) detector was used to measure 241Am activity located inside the lungs of an anthropomorphic phantom with various active and passive shield configurations. It was found that the background suppression shield does not play a significant role in reducing the Minimum Detectable Activity (MDA) after veto, based on the segmentation in the depth direction of the HPGe, when measuring low-energy gamma rays. A reduction of up to 57% in the MDA was achieved. The MDA could be further improved by a thinner lateral segmentation and an optimized anti-Compton shield coupled with an active or passive backplate. The new detector application would be particularly useful in mobile whole-body counting units, where the natural background radiation poses a challenge when measuring low-energy gamma rays.

Internal dosimetry and biodistribution of indigenously prepared 177Lu-DOTA-rituximab in lymphoma and other hematological malignancies treated with rituximab.

The aim of this study was to evaluate the biodistribution and dosimetry of lutetium-177-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (177Lu-DOTA)-rituximab in CD20+ non-Hodgkin's lymphoma and other hematological malignancies treated with rituximab. The standard dosimetry protocol was used, with cold rituximab infusion, then a diagnostic activity of 177Lu-DOTA-rituximab. Planar images were acquired at multiple time points. Normal organs and tumor dosimetry were performed by using organ and tumor-specific regions of interest and whole-body counts were obtained serially after pixel matched, background, scatter, and attenuation correction. The mean radiation absorbed doses were obtained from OLINDA/EXM v2.1.1 and ORIGIN software. A total of 22 patients were included in this study. Prolonged blood pool clearance of 177Lu-DOTA-rituximab with long residence time in the blood pool and normal organs were observed. The whole body effective half-life was 104.5 ± 22 h. The mean total body radiation absorbed dose was 0.208 ± 0.03 mGy/MBq and the mean total body effective dose was 0.196 ± 0.05 mGy/MBq of 177Lu-DOTA-rituximab. The mean radiation absorbed doses of 0.613 ± 0.21, 1.68 ± 2, 1.01 ± 0.42, and 0.136 ± 0.02mGy/MBq were seen for the liver, spleen, kidneys, and bone marrow, respectively. Tumor lesion uptake was noticed in two patients with tumor radiation absorbed doses were 0.842 mGy/MBq in one and 9.9 mGy/MBq in the other patient. A strong correlation was obtained between the cumulative activities of radiation-absorbed doses derived from ORIGIN and OLINDA software methods at a significant P value less than 0.001. The results of our study demonstrated favorable biodistribution and dosimetry of indigenously produced 177Lu-DOTA-rituximab in patients with CD20+ lymphoma. These results can be used for future studies of radioimmunotherapy employing 177Lu-DOTA-rituximab.

RFPID: development and 3D-printing of a female physical phantom for whole-body counter

Whole-body counters (WBC) are used in internal dosimetry for in vivo monitoring in radiation protection. The calibration processes of a WBC set-up include the measurement of a physical phantom filled with a certificate radioactive source that usually is referred to a standard set of individuals determined by the International Commission on Radiological Protection (ICRP). The aim of this study was to develop an anthropomorphic and anthropometric female physical phantom for the calibration of the WBC systems. The reference female computational phantom of the ICRP, now called RFPID (Reference Female Phantom for Internal Dosimetry) was printed using PLA filament and with an empty interior. The goal is to use the RFPID to reduce the uncertainties associated with in vivo monitoring system. The images which generated the phantom were manipulated using ImageJ®, Amide®, GIMP® and the 3D Slicer® software. RFPID was split into several parts and printed using a 3D printer in order to print the whole-body phantom. The newly printed physical phantom RFPID was successfully fabricated, and it is suitable to mimic human tissue, anatomically similar to a human body i.e., size, shape, material composition, and density.

Improvement of internal exposure assessments of the inhalation of fuel-type hot particles during long-term outages

During outages at nuclear power plants, much more care for radiation workers against internal exposure should be ensured given that more hot particles exist relative to the amount during normal operation. If fuel-type hot particles (FTHP) are inhaled, they can cause more severe health risks compared to activation-type hot particles (ATHP), which contain 60Co, due to the alpha-emitting nuclides within FTHPs. The activities of difficult-to-measure nuclides within FTHPs inhaled by workers are inferred by the age-dating technique using a141Ce/144Ce ratio as measured by whole-body counters. However, this method may be limited to outages that last for only a few months due to the short half-life (32.5 days) of 141Ce. We studied the feasibility of utilizing 241Am, a nuclide with a long half-life of 432.6 years, as an alternative to 141Ce. Additionally, we improved the performance of a stand-type whole-body counter for low-energy gamma spectroscopy to meet the criterion (RMSE ≤0.25) specified in ANSI/HPS N13.30–2011 by employing an artificial neural network (ANN). This study can contribute to more rapid and accurate internal dose assessments for workers who have inhaled FTHPs during long-term outages at nuclear power plants.

Optimizing the Positioning of Detectors for Improved Counting Efficiencies Using Monte Carlo Simulations.

The Human Monitoring Laboratory (HML) at Health Canada updated its whole-body counter with four new electrically cooled HPGe detectors. To optimize the counting efficiency of the new system, Monte Carlo simulation was used to model the whole-body counter using a reference BOMAB male phantom. The resulting modeled counting efficiencies showed that the best position to install the four new detectors could be obtained without performing laborious real measurements, thereby reducing the cost of preparing the BOMAB phantoms and reconfiguring the detector arrays in multiple geometries, saving time and energy.

Relationship between the Residual Cesium Body Contents and Individual Behaviors among Evacuees from Municipalities near the Fukushima Daiichi Nuclear Power Plant.

To support estimations of early individual internal doses to residents who suffered from the 2011 accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP), we have sought to use whole-body counter (WBC) measurement results of subjects who lived in municipalities neighboring the FDNPP at the time of the accident. These WBC measurements started several months after the accident; the targeted radionuclides were 134Cs and 137Cs. Our previous study had analyzed the relationship between the residual Cs contents of individuals and evacuation behaviors in the period immediately after the accident for residents of Namie-town, one of the most radiologically affected municipalities. Those results suggested that the first major release event at the FDNPP on 12 March 2011 caused significant exposure, particularly to those who delayed evacuation on that day. The present study expanded its scope to include subjects from four towns neighboring the FDNPP (Namie, Futaba, Okuma, and Tomioka) to gather additional evidence of the exposure that took place on 12 March 2011. Additionally, we investigated the relationship between individual cesium doses and subjects' destinations following the largest release event on 15 March 2011. The study population was 1,145 adults. We first divided the subjects into two evacuation groups depending on the distance from the FDNPP and their evacuation whereabouts (25-km boundary) as of 15:00 on 12 March 2011: the G1 group (≥25 km) and the G2 group (<25 km). We further divided these two subject groups into seven subgroups based on the subjects' destinations as of 0:00 on 16 March 2011. Our four main findings are as follows. (1) The 137Cs detection rate was significantly different between the G1 and G2 groups of Namie-town and Futaba-town but not for those of Okuma-town and Tomioka-town. This result corresponds to the plume passage (flowing toward the northwest to the north) in the afternoon of 12 March 2011 and supports our previous study. (2) The upper-percentile committed effective doses (CEDs) of the G2 groups were higher than those of the G1 groups for all four towns, although the between-group difference varied with the town. The highest CEDs were found in the G2 group of Futaba-town, and the lowest CEDs were in the Namie-town G1 group: 0.16 mSv and 0.04 mSv at the 90th percentile, respectively. The CEDs for both the G1 and G2 groups were relatively high for Okuma-town and Tomioka-town compared to those of the G1 group of Namie-town, although the former subjects were expected to be less exposed on 12 March 2011 and then evacuated to remote places, as did the residents of the other towns. (3) The CEDs of the G1 subgroup that evacuated outside Fukushima Prefecture were extremely low, suggesting that these subjects were little exposed on both 12 and 15 March 2011. However, the CEDs of the same G1 subgroup were rather higher than those of the corresponding G2 subgroup for Futaba-town and Okuma-town. We thus speculate that the WBC measurements were likely to have been affected by the contamination occurring in the second-round temporary re-entry (except for the Namie-town residents). (4) The analyses of the Namie-town evacuees indicated that the area including the middle and northern parts of Fukushima Prefecture was relatively more affected by the major release event on 15 March 2011. In conclusion, the early cesium intake due to the FDNPP accident remained detectable in the WBC measurements of certain present subjects; however, further analyses of the available data are necessary for a full understanding of the WBC measurement results.

The European intercomparison of in-vivo monitoring laboratories: the EIVIC-2020 project

The EIVIC project was launched in 2020, and the main goal was the organisation of a European intercomparison of in-vivo monitoring laboratories dealing with direct measurements of gamma-emitting radionuclides incorporated into the body of exposed workers. This project was organised jointly by members of EURADOS Working Group 7 on internal dosimetry (WG7), the Federal Office for Radiation Protection (BfS, Germany) and the Radioprotection and Nuclear Safety Institute (IRSN, France). The objective was to assess the implementation of individual-monitoring requirements in EU Member States on the basis of in-vivo measurements and to gain insight into the performance of in-vivo measurements using whole-body counters. In this context, a total of 41 in-vivo monitoring laboratories from 21 countries, together with JRC (EC) and IAEA participated. The results were submitted in terms of activity (Bq) of the radionuclides identified inside phantoms that were circulated to all participants. The measured data were compared with reference activity values to evaluate the corresponding bias according to the standards ISO 28218 and ISO 13528. In general, the results of the different exercises are good, and most facilities are in conformity with the criteria for the bias and z-scores in the ISO standards. Furthermore, information about technical and organisational characteristics of the participating laboratories was collected to test if they had a significant influence on the reported results.

Biodistribution and radiation dosimetry of 124I-mIBG in adult patients with neural crest tumours and extrapolation to paediatric models

AimPositron emission tomography (PET) using 124I-mIBG has been established for imaging and pretherapeutic dosimetry. Here, we report the first systematic analysis of the biodistribution and radiation dosimetry of 124I-mIBG in patients with neural crest tumours and project the results to paediatric patient models.MethodsAdult patients with neural crest tumours who underwent sequential 124I-mIBG PET were included in this retrospective single-center analysis. PET data were acquired 4, 24, 48, and/or 120 h after administration of a mean of 43 MBq 124I-mIBG. Whole-body counting and blood sampling were performed at 2, 4, 24, 48 and 120 h after administration. Absorbed organ dose and effective dose coefficients were estimated in OLINDA/EXM 2.2 according to the MIRD formalism. Extrapolation to paediatric models was performed based on mass-fraction scaling of the organ-specific residence times. Biodistribution data for adults were also projected to 123I-mIBG and 131I-mIBG.ResultsTwenty-one patients (11 females, 10 males) were evaluated. For adults, the organs exposed to the highest dose per unit administered activity were urinary bladder (1.54 ± 0.40 mGy/MBq), salivary glands (0.77 ± 0.28 mGy/MBq) and liver (0.65 ± 0.22 mGy/MBq). Mean effective dose coefficient for adults was 0.25 ± 0.04 mSv/MBq (male: 0.24 ± 0.03 mSv/MBq, female: 0.26 ± 0.06 mSv/MBq), and increased gradually to 0.29, 0.44, 0.69, 1.21, and 2.94 mSv/MBq for the 15-, 10-, 5-, 1-years-old, and newborn paediatric reference patients. Projected mean effective dose coefficients for 123I-mIBG and 131I-mIBG for adults were 0.014 ± 0.002 mSv/MBq and 0.18 ± 0.04 mSv/MBq, respectively.ConclusionPET-based derived radiation dosimetry data for 124I-mIBG from this study agreed well with historical projected data from ICRP 53. The effective dose coefficients presented here may aid in guidance for establishing weight-based activity administration protocols.

Effective methods for monitoring internal contamination among workers handling radioactive materials in various fields

This study aimed to develop effective methods for monitoring internal contamination among workers handling radioactive materials in various fields. A total of 160 workers from nuclear power plants, medical institutions, military units, and educational/research institutions were included in the study. The monitoring methods included urinalysis and whole-body counting (WBC) using a mobile radio bioassay laboratory (MRL). Gamma-emitting radionuclides were monitored using the MRL WBC system, and a separate pretreatment procedure was used for tritium measurement in urine samples. Gross beta-screening was performed using a liquid scintillation counting system. The results were evaluated on the basis of the established screening criteria and compared with the dose limits. Additionally, tritium concentrations in the bodies of workers in the vicinity of a heavy-water reactor was analysed to assess the association between tritium concentration and occupation. The results showed a wide distribution of tritium concentrations. Workers involved in fuel and maintenance tasks demonstrated the maximum exposure. Workers in medical facilities showed low levels of internal contamination, which was primarily related to tasks involving radioactive isotopes. Military personnel involved in equipment repair showed significant tritium contamination due to damage during repairs. Workers in educational and research institutions in general had low levels of internal contamination.

Development of a new integrated IN-VIVO counting system at the QST.

A new in-vivo counting system that functions as both a whole-body counter (WBC) and a lung counter (LC) was developed at the QST to enhance its dose assessment capability. This paper presents an overview of this system and the results of its performance tests. For use of the system as a WBC, three high purity germanium (HPGe) detectors installed in a 20-cm-thick iron shielding chamber are linearly arrayed over a subject lying on the bed, whereas two of the three HPGe detectors are placed over the subject's chest from side to side when using the system as an LC. The new in-vivo system was calibrated using three de-facto phantoms owned by the QST: an adult-male BOttle Manikin ABsorption (BOMAB) phantom, a Lawrence Livermore National Laboratory (LLNL) phantom and a Japan Atomic Energy Research Institute (JAERI) phantom. Monte Carlo simulations were also performed to determine an optimum location for the three detector array in the WBC mode and revealed that the peak efficiency for the BOMAB phantom (662keV) was little varied as long as the middle detector was placed above the thorax and abdomen parts of the phantom. The calculated peak efficiencies agreed well with the observed peak efficiencies for photons with energies over 100keV. For lung counting, a tentative Minimum Detectable Activity of 241Am was evaluated as 9.5Bq for a counting time of 30minutes, and a Japanese male subject with an average chest wall thinness (2.27cm). The developed system is now ready for use.

Internal radiation exposure from 137Cs and its association with the dietary habits of residents from areas affected by the Chernobyl nuclear accident, Ukraine: 2016-2018.

The total annual effective dose has steadily decreased since the fallout of the Chernobyl Nuclear Power Plant. However, chronic internal exposure to 137Cs still persists and fluctuates in a complex and unpredictable manner. Recently, body contamination was found to primarily occur owing to the intake of forest foodstuffs that contain long-lived 137Cs. Forest foodstuffs may have up to 100 times higher concentration of cesium than does local milk and meat. The present study aimed to investigate the recent dietary habits of residents in the Zhytomyr region of Ukraine, and assess the effect of the intake of forest foodstuffs on the increase in internal radioactivity from 137Cs. We screened 1,612 participants, from July 2016 to February 2018 for internal radioactivity, using whole-body counter at Korosten Medical Center and surveyed their background and intake habits. We analyzed the association among food type, intake frequency, and internal exposure dose. The analysis revealed that nearly 90% of the participants regularly consumed one of the forest foodstuffs (mushrooms, berries, fish) or milk. Nearly 80% of the participants indicated that they consumed mushrooms or berries or both. Internal radioactivity was detected in 30% of the participants. The diet that included mushrooms exhibited the highest internal radioactivity. The lowest Bq/kg concentration was observed in the only-berry group, following the no-intake group. There was a significant correlation between the intake frequency and the magnitude of Bq/kg. Radioactivity detected in the mushroom-berry and only-mushroom group were 8.6 and 9.2 Bq/kg, respectively. The lowest and highest intake frequency showed a radioactivity of 2.4 and 7.5 Bq/kg, respectively. Radioactivity in the winter season was significantly higher than that in other seasons. In conclusion, our study revealed that internal radioactivity varies depending on the type of food, intake frequency, and season.

Establishment of a Medical System for Emergency Radiation Exposure (One local city in Japan)

Introduction:Japan is the only country to have experienced the atomic bombings and still has many nuclear power plants. In 2011, a nuclear power plant accident occurred during a major magnitude 9.0 earthquake, and there was a great deal of concern about radiation exposure medicine for the public. It is necessary to provide appropriate radiation exposure medicine.Method:The facility is located within the IAEA's UPZ, and in the event of an emergency, it is necessary to provide medical care for a large number of people exposed to radiation, so an advanced radiation exposure medical facility was built in 2015 (the surrounding population is approximately 300,000).Results:The basics of radiation exposure medicine are: 1) medical priority, 2) prevention of the spread of radioactive materials, and 3) protection of our responders from radiation exposure. Everything from whole body assessments, contamination examinations due to exposure, medical procedures (including advanced medical procedures), and decontamination were able to be performed. The facility is also equipped with WBC (whole body counter) that can assess internal exposure. A support system for other medical facilities was being developed in the region by forming a team that can respond to radiation exposure.Conclusion:With the current system, not only radiation exposure medicine will be handled, but also CBRNE and other such services in the future. For this reason, repeated training and human resource development are very important.

Assessment of the Body Radioactivity of I-131 Using Two Techniques

Iodine-131 has become an essential radionuclide used in nuclear medicine for clinical and research purposes. The increase use of this radionuclide in medicine for diagnostic and treatment of thyroid diseases creates a demand to obtain a feasible methodology for occupational or accidental monitoring of internal contamination. In this study, two techniques were employed to find an appropriate one of in vivo bioassay for evaluating Iodine-131 body content. A scanning Whole Body Counter (WBC) equipped with 6NaI (Tl) scintillation detector, an anthropomorphic phantom and point source were used. The results showed that the counter sensitivity, as a first approach (conventional method), had a logarithmic and significant correlation with neck weight. On the other hand, the counting rate in the Compton band was considered, which is a measure of gamma ray attenuation, and found to have a direct relationship with body weight. The new technique, which is considered the variation of the counter sensitivity with the Compton to photopeak counting rate ratio, had the same regression but less uncertainty than the conventional approach. Finally, the theoretical MDA with neck weight was calculated for all the phantom configurations.

The Validity of Extrinsic Stable Isotopic Labeling for Mineral Absorption Studies in Rats

The use of extrinsic stable and radioisotopic labels (Fe, Zn, Cu and Se) was compared with the use of intrinsic labels by measuring label retention in rats. Saccharomyces cerevisiae (Hansen strain CBS 1171) was prepared intrinsically enriched with a stable isotope of iron, zinc, copper or selenium, and unenriched freeze-dried yeast was extrinsically labeled with the appropriate stable and/or radioisotope. Male Wistar rats, weighing 80–100 g and fed a purified diet, were given a test meal of one of the above labeled yeasts. Isotopic retention was determined by fecal monitoring. Retention of the stable isotopes was determined by thermal ionization quadruple mass spectrometry (TIQMS) and retention of the radioisotopes by counting feces in a whole-body counter. The results indicated that the behavior of the labels differed among the minerals, with copper as the only one in which the intrinsic and extrinsic stable isotopes were comparably retained. With zinc, retention of the extrinsic radiolabel and intrinsic label was similar, but retention of the extrinsic stable isotope label was higher. With iron, the intrinsic label had a significantly lower retention than the two extrinsic labels; with selenium, retention of all three labels was different, but these differences were not of a sufficient magnitude to conclude that extrinsic stable isotopic labeling is not valid. These results demonstrate that an extrinsic stable isotope label can be used for copper, selenium and inorganic iron, but that such a label is not valid for studies on zinc.

Medical gamma cameras in radiological emergency preparedness: determination of calibration factors and MDA for the GE Discovery NM/CT 670 Pro

A survey was performed of the available gamma camera models and whole-body counters (WBCs) in Sweden, revealing that there are about 75 gamma cameras and 15 WBCs currently in operation in Sweden. One of the most common gamma camera models (GE Discovery NM/CT 670 Pro), with the collimators removed, was calibrated for 152Eu, 137Cs, 60Co and 40K in three different measurement geometries (supine, close-up sitting and distant sitting) for six different phantom sizes (12–110 kg). Minimum detectable activities (MDAs) were calculated for the gamma camera and a typical WBC, both at the Sahlgrenska University Hospital in Gothenburg, Sweden. An energy window of 30–510 keV was used to calibrate the gamma camera. The calibration factors for this gamma camera for supine and close-up sitting geometry, including all phantom sizes, were 138–208 cps kBq−1 for 152Eu, 63–83 cps kBq−1 for 137Cs and 99–126 cps kBq−1 for 60Co; the MDAs were 50–73 Bq for 152Eu, 125–198 Bq for 137Cs and 83–105 Bq for 60Co. The International Commission on Radiological Protection dose coefficients for members of the public were used to calculate the committed effective doses (CEDs) corresponding to the MDAs, showing that CEDs down to a few μSv can be estimated with this gamma camera for the inhalation of aerosols of absorption type M. The distant sitting geometry was used to enable the estimation of higher contamination levels, and a hypothetical maximum CED was calculated. This was shown to be 256–2000 mSv, depending on the radionuclide and phantom size. However, further investigations are needed into the dead time losses for higher activity levels for the radionuclides studied. The results show that the use of gamma cameras for radiological triage and, in some cases, to estimate the internal activity of relevant radionuclides in radiological and nuclear events, is feasible.

Lean Beef and Beef Fat Interact to Enhance Nonheme Iron Absorption in Rats

Nonheme iron absorption is enhanced when meat replaces non-meat protein sources in a meal. Our objective was to examine the hypothesis that both lean and fat fractions of meat contribute to this enhancement. Weanling rats were assigned, according to a 3 x 3 factorial design, to one of nine nutritionally complete diets formulated to contain various combinations of protein (lean beef, skim milk or egg white) and fat sources (beef fat, milk fat or partially hydrogenated vegetable fat). Diets contained 20% protein and 20% fat. After 4 d of consuming the assigned diets, the rats were deprived of food overnight and offered a meal of their respective diet labeled extrinsically with 59FeCl3. Feeding of the unlabeled diets was continued for 14 d. Iron absorption was estimated from 59Fe retention, monitored by whole-body counting over the 14-d period. Absorption was highest from diets containing beef regardless of the fat source, but the combination of beef and beef fat was highest of all. In the comparison of absorption from the lean beef and other diets, there was significant interaction between lean beef and fat source on iron absorption. These results suggest that the iron absorption-enhancing properties of meat may involve an interaction between the lean and fat fractions of meat.

Design and Development of Children's Calibration Phantoms for Whole and Mobile Body Counters

Abstract The experiences from several past radiological accidents (e.g., Fukushima Daiichi, Chernobyl, and Goiania) have shown that not only occupationally radiation-exposed adults but also children of all age groups can be affected by such an accident. Moreover, in asymmetric conflicts, children could possibly be affected by the explosion of a radiological dispersal device. Whole-body counting facilities all over the world are well prepared to measure children and adults but suffer in the case of newly born babies and toddlers owing to a lack of corresponding calibrations. A series of calibration phantoms representative of adult persons and larger children is commercially available or can be constructed from easily accessible materials, but for newly born and children up to 20 kg, only very few phantoms have been described which approximate the infantile body, and only very roughly. The aim of this work was to improve the current unsatisfactory situation. Two main steps toward achieving this aim included the compilation of anthropomorphic data for children and the construction of a modular set of calibration phantoms for the weight classes between 3 and 20 kg from simple, readily accessible, and cheap materials. The phantoms are made from commercially available freezer packs, which can be filled with a radionuclide solution. By using calibrations based on these purposely-built realistic weight class phantoms, internal radioactive contamination in children can be assessed more reliably than would be otherwise possible with the standard adult phantom calibrations.

Monte Carlo calculation of whole body counter efficiency factors for different computational phantoms

Individual monitoring can provide an estimate of the radioactivity present in the body of the exposed individuals. Periodic monitoring of occupationally exposed individuals is of great importance in case of accidental incorporation. Computational phantoms and Monte Carlo codes are often used to complement the calibration method of counting systems in internal dosimetry. Here, counting efficiency (CE) factors for a WBC system were calculated using MC simulations. The WBC system with a NaI(Tl) detector and the BOMAB phantom was modeled using three MC codes. After validation, the models were used to obtain CE values for a wide range of energies, and a CE curve was generated for the WBC system. To estimate the effects of anatomical differences on the measurement process, two anthropomorphic voxel phantoms were modeled using the VMC code. For the detector position with the highest CE value, the differences when comparing BOMAB results with the MaMP and Yale results were (-1 ± 6)% and (-1 ± 3)%, respectively. The results confirm that the use of the BOMAB phantom is a good approach for the calibration of the whole-body counter system. Measurements should be made at detector position with the highest CE values, and it is recommended to use the mean Monte Carlo CE values calculated in this work.