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Marlton, NJ, United States

Siegel J.A.,Nuclear Physics Enterprises | Silberstein E.B.,University of Cincinnati
Thyroid | Year: 2014

Background: Clinical and historical uncertainty exists surrounding the regulations of the Atomic Energy Commission/Nuclear Regulatory Commission (AEC/NRC) requiring patient hospitalization when 131I activities exceed mCi. This review investigates the sometimes disturbing regulatory and clinical origins and consequences of the use of this low, mCi dose as a prescription for thyroid remnant ablation. Summary: As early as in the 1940s, activities of 131I between 30 and 200mCi, often fractionated, were employed. The AEC deliberated from 1947 to the early 1960s before imposing as a license condition the requirement of hospitalizing patients until they contained Source

Stabin M.G.,Vanderbilt University | Siegel J.A.,Nuclear Physics Enterprises
Health Physics | Year: 2015

An analysis is presented of the possible dosimetric consequences of various potential contamination events involving 223Ra dichloride (Xofigo), the FDA-approved therapeutic agent used in the treatment of bone metastases in patients with castration-resistant prostate cancer. Three exposure scenarios are considered: inhalation dose to an individual due to the hypothetical inhalation of 219Rn and its progeny assumed to be released into the air from a liquid spill on the floor, external dose from direct photon exposure of an individual assigned to clean up a spill, and skin dose to an individual should the liquid material come into contact with their skin. Doses from the first two scenarios were very small; 2.8 × 10-3 mSv and 8.1 × 10-4 mSv, respectively. Using extremely conservative assumptions, the skin dose was estimated to be 72 mSv; in a realistic scenario, this dose would likely be an order of magnitude or more lower. These doses are very small compared to regulatory limits, and good health physics practices likely to be employed in such incidents would lower them still further. The authors conclude that the medical use of Xofigo does not pose any significant radiation safety issue with respect to potential contamination events, even if multiple incidents might occur during the course of a year, since all worst-case potential contamination events considered in this study will not result in significant radiation exposures to workers. © 2015 Lippincott Williams & Wilkins. Source

Gulec S.A.,Florida International University | Sztejnberg M.L.,Purdue University | Siegel J.A.,Nuclear Physics Enterprises | Jevremovic T.,Purdue University | Stabin M.,Vanderbilt University
Journal of Nuclear Medicine | Year: 2010

Selective internal radiation treatment (SIRT) via intrahepatic arterial administration of 90Y microspheres is an effective therapeutic modality. The conventional and generally applied MIRD schema is based on the premise that the distribution of microspheres in the liver parenchyma is uniform. In reality, however, the distribution of the microspheres follows a distinct pattern, requiring that a model be developed to more appropriately estimate radiation absorbed doses to the different structural/functional elements of the hepatic microanatomy. Methods: A systematic investigation was performed encompassing a conventional average absorbed dose assessment, a compartmental macrodosimetric approach that accounts for the anticipated higher tumor-to-normal liver activity concentration ratio, dose point-kernel convolution-derived estimates, and Monte Carlo dose estimates employing a spherical and 3-dimensional hexagonal liver model, including various subunits of the hepatic anatomy, down to the micrometer level. Results: Detailed specifics of the radiation dose deposition of 90Y microspheres demonstrated a rapid decrease in absorbed dose in and around the portal tracts where the microspheres are deposited. The model also demonstrated that the hepatocellular parenchymal and central vein doses could be at significant levels because of a cross-fire effect. Conclusion: The reported microstructural dosimetry models can help in the detailed assessment of the dose distributions in the hepatic functional subunits and in relating these doses to their effects. Thesemodels have also revealed that the there is a consistent relationship between the average liver dose as calculated byMIRDmacrodosimetry and the structural dosimetry estimates in support of the clinical utility of theMIRD methodology. This relationship could be used tomore realistically assess patterns of hepatic toxicity associated with the 90Y SIRT treatment. Copyright © 2010 by the Society of Nuclear Medicine, Inc. Source

Siegel J.A.,Nuclear Physics Enterprises | Stabin M.G.,Vanderbilt University | Sharkey R.M.,Center for Molecular Medicine and Immunology
Cancer Biotherapy and Radiopharmaceuticals | Year: 2010

This study evaluates the predictive value of absorbed dose, biological effective dose, and time-dose-fractionation factors for use in patients receiving peptide radionuclide receptor therapy treatments by reanalyzing data in two different patient populations that have been reported in the literature. The analysis suggested that the alternative time-dose-fractionation model is as good and, in some cases, may be better in predicting kidney toxicity in these two patient populations than biological effective dose. This study suggests that future investigations proceed with more critical evaluation of different dosimetric quantities that may be more clinically useful in providing optimal patient treatment prescriptions for peptide radionuclide receptor therapy, rather than rely solely on a single methodology derived from experience with external-beam therapy. Copyright 2010, Mary Ann Liebert, Inc. Source

Siegel J.A.,Nuclear Physics Enterprises | Welsh J.S.,Loyola University Chicago
Technology in Cancer Research and Treatment | Year: 2016

In the past several years, there has been a great deal of attention from the popular media focusing on the alleged carcinogenicity of low-dose radiation exposures received by patients undergoing medical imaging studies such as X-rays, computed tomography scans, and nuclear medicine scintigraphy. The media has based its reporting on the plethora of articles published in the scientific literature that claim that there is “no safe dose” of ionizing radiation, while essentially ignoring all the literature demonstrating the opposite point of view. But this reported “scientific” literature in turn bases its estimates of cancer induction on the linear no-threshold hypothesis of radiation carcinogenesis. The use of the linear no-threshold model has yielded hundreds of articles, all of which predict a definite carcinogenic effect of any dose of radiation, regardless of how small. Therefore, hospitals and professional societies have begun campaigns and policies aiming to reduce the use of certain medical imaging studies based on perceived risk:benefit ratio assumptions. However, as they are essentially all based on the linear no-threshold model of radiation carcinogenesis, the risk:benefit ratio models used to calculate the hazards of radiological imaging studies may be grossly inaccurate if the linear no-threshold hypothesis is wrong. Here, we review the myriad inadequacies of the linear no-threshold model and cast doubt on the various studies based on this overly simplistic model. © 2015, © The Author(s) 2015. Source

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