Assessment of S Values in Stylized and Voxel-Based Rat Models for Positron-Emitting Radionuclides

Xie, Tianwu; Zaidi, Habib

doi:10.1007/s11307-013-0632-0

Cited by 8 publications

(12 citation statements)

References 35 publications

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“…23,24,[41][42][43]53 However, significant differences between the dosimetric characteristics of stylized and voxel-based models for the same subject are often reported. [44][45][46][47] In the case of the newborn, the variations of the estimated self-absorbed S-values for positron-emitting radionuclides may range from −78% to 132% between stylized and voxel-based phantoms in representative organs. Since some biological tissues in children may have substantially different physical characteristics and tissue chemical compositions and present with significantly different radiosensitivity and bioavailability for various radiotracers at different ages, the evaluation of age-dependent absorbed dose using realistic anatomical anthropomorphic pediatric phantoms is commended.…”

Section: Discussionmentioning

confidence: 99%

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Pediatric radiation dosimetry for positron‐emitting radionuclides using anthropomorphic phantoms

et al. 2013

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Purpose: Positron emission tomography (PET) plays an important role in the diagnosis, staging, treatment, and surveillance of clinically localized diseases. Combined PET/CT imaging exhibits significantly higher sensitivity, specificity, and accuracy than conventional imaging when it comes to detecting malignant tumors in children. However, the radiation dose from positron-emitting radionuclide to the pediatric population is a matter of concern since children are at a particularly high risk when exposed to ionizing radiation. Methods: The authors evaluate the absorbed fractions and specific absorbed fractions (SAFs) of monoenergy photons/electrons as well as S-values of 9 positron-emitting radionuclides in 48 source regions for 10 anthropomorphic pediatric hybrid models, including the reference newborn, 1-, 5-, 10-, and 15-yr-old male and female models, using the Monte Carlo N-Particle eXtended general purpose Monte Carlo transport code. Results: The self-absorbed SAFs and S-values for most organs were inversely related to the age and body weight, whereas the cross-dose terms presented less correlation with body weight. For most source/target organ pairs, Rb-82 and Y-86 produce the highest self-absorbed and cross-absorbed S-values, respectively, while Cu-64 produces the lowest S-values because of the low-energy and highfrequency of electron emissions. Most of the total self-absorbed S-values are contributed from nonpenetrating particles (electrons and positrons), which have a linear relationship with body weight. The dependence of self-absorbed S-values of the two annihilation photons varies to the reciprocal of 0.76 power of the mass, whereas the self-absorbed S-values of positrons vary according to the reciprocal mass. Conclusions: The produced S-values for common positron-emitting radionuclides can be exploited for the assessment of radiation dose delivered to the pediatric population from various PET radiotracers used in clinical and research settings. The mass scaling method for positron-emitters can be used to derive patient-specific S-values from data of reference phantoms.

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Section: Discussionmentioning

confidence: 99%

“…However, significant differences have been reported between dosimetric results of stylized and voxel-based models of the same subject. [44][45][46][47] Therefore, the assessment of radiation dose for commonly used positron-emitting radionuclides in new generation anthropomorphic pediatric phantoms is highly desired.…”

Section: Introductionmentioning

confidence: 99%

Pediatric radiation dosimetry for positron‐emitting radionuclides using anthropomorphic phantoms

et al. 2013

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“…The effect of model type and maternal physical changes during gestation on resulting S values from various radionuclides to the pregnant population was studied. A large difference between S values was observed for hollow organs when using the MIRD-type mathematic models and the voxel-based models (29,30). The S values of voxel-based models used in this work would be more accurate than those of mathematic models because the former preserves more anatomic details of the human body.…”

Section: Discussionmentioning

confidence: 89%

Fetal and Maternal Absorbed Dose Estimates for Positron-Emitting Molecular Imaging Probes

Xie

Zaidi

2014

J Nucl Med

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PET and hybrid (PET/CT and PET/MR) imaging currently play a pivotal role in clinical diagnosis, staging and restaging, treatment, and surveillance of several diseases. As such, limiting the radiation exposure of special patients, such as pregnant women, from PET procedures is an important challenge that needs to be appropriately addressed because of the high sensitivity of the developing embryo/ fetus to ionizing radiation. Therefore, accurate radiation dose calculation for the embryo/fetus and pregnant patient from common positron-emitting radiotracers is highly desired. Methods: To obtain representative estimates of radiation dose to the human body, realistic biologic and physical models should be used. In this work, we evaluate the S values of 9 positron-emitting radionuclides ( 11 C, 13 N, 15 O, 18 F, 64 Cu, 68 Ga, 82 Rb, 86 Y, and 124 I) and the absorbed and effective doses for 21 positron-emitting labeled radiotracers using realistic anthropomorphic computational phantoms of early pregnancy and at 3-, 6-, and 9-mo of gestation and the most recent biokinetic data available. The Monte Carlo N-Particle eXtended general-purpose Monte Carlo code was used for radiation transport simulation. Results: The absorbed dose to the pregnant model is less influenced by the gestation for most organs or tissues, but the anatomic changes of the maternal body increases the effective dose for some radiotracers. For 18 F-FDG, the estimated absorbed doses to the embryo/fetus are 3.05E−02, 2.27E−02, 1.50E−02, and 1.33E−02 mGy/MBq at early pregnancy and 3-, 6-, and 9-mo gestation, respectively. The absorbed dose is nonuniformly distributed in the fetus and would be 1.03-2 times higher in the fetal brain than in other fetal soft tissues. Conclusion: The generated S values can be exploited to estimate the radiation dose delivered to pregnant patients and the embryo/fetus from various PET radiotracers used in clinical and research settings. The generated dosimetric database of radiotracers using new-generation computational models can be used for the assessment of radiation risks to pregnant women and the embryo/fetus undergoing PET/CT imaging procedures. This work also contributes to a better understanding of the absorbed dose distribution in the fetus.

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“…The discrepancies between small animal dosimetric results when using stylized, voxel, and hybrid models were also studied and reported in numerous contributions. 5,109,110 Overall, the ratios of self-absorbed S-factors ranged between 0.6 and 1.0 when comparing hybrid and voxel-based models and between 0.2 and 1.6 when comparing stylized and voxelbased models. The input parameters used for the simulations, such as model resolution, organ segmentation, tissue density, and spatial sampling, proved to have a substantial influence on small animal absorbed dose calculations when using hybrid models.…”

Section: A Ionizing Radiation Dosimetrymentioning

confidence: 99%

Development of computational small animal models and their applications in preclinical imaging and therapy research

Xie

Zaidi

2015

Med. Phys.

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The development of multimodality preclinical imaging techniques and the rapid growth of realistic computer simulation tools have promoted the construction and application of computational laboratory animal models in preclinical research. Since the early 1990s, over 120 realistic computational animal models have been reported in the literature and used as surrogates to characterize the anatomy of actual animals for the simulation of preclinical studies involving the use of bioluminescence tomography, fluorescence molecular tomography, positron emission tomography, single-photon emission computed tomography, microcomputed tomography, magnetic resonance imaging, and optical imaging. Other applications include electromagnetic field simulation, ionizing and nonionizing radiation dosimetry, and the development and evaluation of new methodologies for multimodality image coregistration, segmentation, and reconstruction of small animal images. This paper provides a comprehensive review of the history and fundamental technologies used for the development of computational small animal models with a particular focus on their application in preclinical imaging as well as nonionizing and ionizing radiation dosimetry calculations. An overview of the overall process involved in the design of these models, including the fundamental elements used for the construction of different types of computational models, the identification of original anatomical data, the simulation tools used for solving various computational problems, and the applications of computational animal models in preclinical research. The authors also analyze the characteristics of categories of computational models (stylized, voxel-based, and boundary representation) and discuss the technical challenges faced at the present time as well as research needs in the future. C 2016 American Association of Physicists in Medicine. [http://dx

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Assessment of S Values in Stylized and Voxel-Based Rat Models for Positron-Emitting Radionuclides

Cited by 8 publications

References 35 publications

Pediatric radiation dosimetry for positron‐emitting radionuclides using anthropomorphic phantoms

Pediatric radiation dosimetry for positron‐emitting radionuclides using anthropomorphic phantoms

Fetal and Maternal Absorbed Dose Estimates for Positron-Emitting Molecular Imaging Probes

Development of computational small animal models and their applications in preclinical imaging and therapy research

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