An ICRP-based Chinese adult male voxel model and its absorbed dose for idealized photon exposures--the skeleton

Individualized dose calculation for internal exposure on radionuclide intake: GPU acceleration approach

Objective. The rapid and accurate assessment of internal exposure dose is a crucial safeguard for personnel health and safety. This study aims to investigate a precise and efficient GPU Monte Carlo simulation approach for internal exposure dose calculation. It directly calculates doses from common radioactive nuclides intake, like60Co for occupational exposure, allowing personalized assessments.Approach. This study developed a GPU-accelerated Monte Carlo program for internal exposure on radionuclide intake, successfully realizing photoelectronic coupled transport, nuclide simulation, and optimized acceleration. The generation of internal irradiation sources and sampling methods were achieved, along with the establishment of a personalized phantom construction process. Three irradiation scenarios were simulated to assess computational accuracy and efficiency, and to investigate the influence of posture variations on internal dose estimations.Main results. Using the International Commission on Radiological Protection (ICRP) voxel-type phantom, the internal dose of radionuclides in individual organs was calculated, exhibiting relative deviation of less than 3% in comparison to organ dose results interpolated by Specific Absorbed Fractions in ICRP Publication 133. Employing the Chinese reference phantom for calculating internal irradiation dose from the intake of various radionuclides, the use of GPU Monte Carlo program significantly shortened the simulation time compared to using CPU programs, by a factor of 150-500. Internal dose estimation utilizing a seated Chinese phantom revealed up to a 75% maximum difference in organ dose compared to the same phantom in a standing posture.Significance. This study presents a rapid GPU-based simulation method for internal irradiation doses, capable of directly simulating dose outcomes from nuclide intake and accommodating individualized phantoms for more realistic and expeditious calculations tailored to specific internal irradiation scenarios. It provides an effective and feasible tool for precisely calculating internal irradiation doses in real-world scenarios.

Development of Chinese mesh-type pediatric reference phantom series and application in dose assessment of Chinese undergoing computed tomography scanning

Pediatric patients are in a growing stage with more dividing cells than adults. Therefore, they are more sensitive to the radiation dose when undergoing computed tomography (CT) scanning. It is necessary and essential to assess the organ absorbed dose and effective dose to children. Monte Carlo simulation with computational phantoms is one of the most used methods for dose calculation in medical imaging and radiotherapy. Because of the vast change of the pediatric body with age increasing, many research groups developed series pediatric phantoms for various ages. However, most of the existing pediatric reference phantoms were developed based on Caucasian populations, which is not conformable to Chinese pediatric patients. The use of different phantoms can contribute to a difference in the dose calculation. To assess the CT dose of Chinese pediatric patients more accurately, we developed the Chinese pediatric reference phantoms series, including the 3-month (CRC3m), 1-year-old (CRC01), 5-year-old (CRC05), 10-year-old (CRC10), 15-year-old male (CRCM15), and a 15-year-old female (CRCF15) phantoms. Furthermore, we applied them to dose assessment of patients undergoing CT scanning. The GE LightSpeed 16 CT scanner was simulated and the paper presents the detailed process of phantoms development and the establishment of the CT dose database (with x-ray tube voltages of 120, 100 and 80 kVp, with collimators of 20, 10, and 5 mm width, with filters for head and body), compares for the 1-year-old results with other results based on different phantoms and analyzes the CT dose calculation results. It was found that the difference in phantoms' characteristics, organ masses and positions had a significant impact on the CT dose calculation outcomes. For the 1-year-old phantom, the dose results of organs fully covered by the x-ray beam were within 10% difference from the results of other studies. For organs partially covered and not covered by the scan range, the maximum differences came up to 84% (stomach dose, chest examinations) and 463% (gonads dose, chest examinations) respectively. The findings are helpful for the dose optimization of Chinese pediatric patients undergoing CT scanning. The developed phantoms could be applied in dose estimation of other medical modalities.

Advances in Computational Human Phantoms and Their Applications in Biomedical Engineering - A Topical Review

Over the past decades, significant improvements have been made in the field of computational human phantoms (CHPs) and their applications in biomedical engineering. Their sophistication has dramatically increased. The very first CHPs were composed of simple geometric volumes, e.g., cylinders and spheres, while current CHPs have a high resolution, cover a substantial range of the patient population, have high anatomical accuracy, are poseable, morphable, and are augmented with various details to perform functionalized computations. Advances in imaging techniques and semi-automated segmentation tools allow fast and personalized development of CHPs. These advances open the door to quickly develop personalized CHPs, inherently including the disease of the patient. Because many of these CHPs are increasingly providing data for regulatory submissions of various medical devices, the validity, anatomical accuracy, and availability to cover the entire patient population is of utmost importance. The article is organized into two main sections: the first section reviews the different modeling techniques used to create CHPs, whereas the second section discusses various applications of CHPs in biomedical engineering. Each topic gives an overview, a brief history, recent developments, and an outlook into the future.

Calculation of conversion coefficients using Chinese adult reference phantoms for air submersion and ground contamination

The effective and organ equivalent dose coefficients have been widely used to provide assessment of doses received by adult members of the public and by workers exposed to environmental radiation from nuclear facilities under normal or accidental situations. Advancements in phantom types, weighting factors, decay data, etc, have led to the publication of newer results in this regard. This paper presents a new set of conversion coefficients for air submersion and ground contamination (with the use of Geant4) for photons from 15 keV to 10 MeV using the Chinese and International Commission on Radiological Protection (ICRP) adult reference male and female phantoms. The radiation fields, except for energy spectrum at low energies, were validated by the data obtained from the Monte Carlo code YURI. The effective dose coefficients of monoenergetic photons, obtained for the ICRP adult reference phantoms, agree well with recently published data for air submersion and ground contamination with a plane source at a depth of 0.5 g cm^-2 in soil, but an average difference of 36.5% is observed for ground surface contamination with the abovementioned radiation field. The average differences in organ equivalent dose coefficients between the Chinese and the ICRP adult reference phantoms are within 6% for most organs, but noticeable differences of up to 70% or even higher are found at photon energies below 30 keV under air submersion. The effective dose coefficients obtained with the Chinese adult reference phantoms are greater than those of the ICRP adult reference phantoms above 30 keV and 0.5 MeV for ground contamination and air submersion, respectively; the average differences from the Chinese adult reference phantoms are about 3.6% and 0.4% in the whole energy range with maximum differences of 31.8% and 27.6% at 15 keV for air submersion and ground contamination respectively. These differences are attributed to anatomical discrepancies in overlying tissue mass of an individual organ and the body mass between the Chinese and the ICRP adult reference phantoms. These monoenergetic photon conversion coefficients are subsequently used to evaluate radionuclides with decay data from ICRP publication 107.

Effects of computational phantoms on the effective dose and two-dosimeter algorithm for external photon beams

In this study, the effect 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 performed for beam directions in different polar and azimuthal angles using the Monte Carlo code of MCNP at energies of 0.08, 0.3, and 1MeV. Results show that the body shape significantly affects E and two-dosimeter responses when the dosimeters are indirectly irradiated. The acquired two-dosimeter algorithms are almost the same for all the mentioned phantoms except for KTMAN-2. Comparisons between the obtained E and estimated E (Eest), acquired from two-dosimeter algorithm, illustrate that the Eest is overestimated in overhead (OH) and underfoot (UF) directions. The effect of using one algorithm for all phantoms was also investigated. Results show that application of one algorithm to all reference phantoms is possible.

Development of Chinese reference man deformable surface phantom and its application to the influence of physique on electromagnetic dosimetry

A reference man is a theoretical individual that represents the average anatomical structure and physiological and metabolic features of a specific group of people and has been widely used in radiation safety research. With the help of an advantage in deformation, the present work proposed a Chinese reference man adult-male polygon-mesh surface phantom based on the Visible Chinese Human segment image dataset by surface rendering and deforming. To investigate the influence of physique on electromagnetic dosimetry in humans, a series of human phantoms with 10th, 50th and 90th body mass index and body circumference percentile physiques for Chinese adult males were further constructed by deforming the Chinese reference man surface phantom. All the surface phantoms were then voxelized to perform electromagnetic field simulation in a frequency range of 20 MHz to 3 GHz using the finite-difference time-domain method and evaluate the whole-body average and organ average specific absorption rate and the ratios of absorbed energy in skin, fat and muscle to the whole body. The results indicate thinner physique leads to higher WBSAR and the volume of subcutaneous fat, the penetration depth of the electromagnetic field in tissues and standing-wave occurrence may be the influence factors of physique on electromagnetic dosimetry.

Red bone marrow dose calculations in radiotherapy of prostate cancer based on the updated VCH adult male phantom

Red bone marrow (RBM) is an important dose-limiting tissue that has high radiosensitivity but is difficult to identify on clinical medical images. In this study, we investigated dose distribution in RBM for prostate cancer radiotherapy. Four suborgans were identified in the skeleton of the visible Chinese human phantom: cortical bone (CB), trabecular bone (TB), RBM, and yellow bone marrow (YBM). Dose distributions in the phantom were evaluated by the Monte Carlo method. When the left os coxae was taken as the organ-at-risk (OAR), the difference in absorbed dose between RBM and each CB and TB was up to 20%, but was much less (≤3.1%) between RBM and YBM. When the left os coxae and entire bone were both taken as OARs, RBM dose also increased with increasing planning target volume size. The results indicate the validity of using dose to homogeneous bone marrow mixture for estimating dose to RBM when RBM is not available in computational phantoms. In addition, the human skeletal system developed in this study provides a model for considering RBM dose in radiotherapy planning.