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Quantification in Emission Tomography
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Brian F. Hutton, Kjell Erlandsson, Kris Thielemans
There are two main areas where quantification has application. The most obvious is internal dosimetry where one needs to know the actual distribution of activity in the body over time in order to estimate the cumulated activity and resultant radiation dose to tissue. It is clear that the absolute activity is essential for this to be feasible. With the surge of interest in radionuclide therapy and the current emphasis on patient-specific dosimetry there is an increasing demand for dose estimation in the individual, which has motivated the release of improved vendor software. Though historically mainly used in SPECT there is increasing application also in PET.
Peptide Receptor Radionuclide Therapy for Neuroendocrine Tumours
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Anna Sundlöv, Katarina Sjögreen Gleisner
The absorbed doses (ADs) delivered by internally distributed radioactive drugs are estimated by means of internal dosimetry. Parameters that govern the AD are the activity distribution in different organs and tissues over time, the radiation energy emitted in each radioactive decay, how this energy is transported between body regions, and the mass of the tissues in which the radiation energy is imparted. The expressions used for internal dosimetry calculations were, already in 1968, formalized by the committee on Medical Internal Radiation Dose (MIRD) of the Society of Nuclear Medicine and Molecular Imaging [9]. Following the more recent MIRD Pamphlet No. 21 [10] the mean absorbed dose to a target region is calculated from the time-integrated activity in a source region according to
Education and Training for Radiation Protection in Nuclear Power Plants
Published in Kenneth L. Miller, Handbook of Management of Radiation Protection Programs, 2020
Internal dosimetry and bioassay are important parts of a health physicist’s education. While internal radiation contributes relatively little to the occupational exposure at nuclear power plants, the health physicist must be prepared to cope effectively with that which does (or might) occur. It is particularly important to be able to handle the continuing pressures to accept substantial external doses or other risks to avoid trivial internal doses. It is also important to appreciate the differences between the dose models and the actual behavior of radionuclides in human bodies. A suitable text is hard to identify at this time because the field is in transition. Keith Eckerman’s work41 seems suitable as an internal dosimetry text with ICRP 242 and ICRP 3043 serving as references. NCRP 8744 is a good choice as a bioassay text with Lessard’s report45 constituting a principal outside reference. These documents are recommended in part because they concentrate on the topic of interest (humans) and partly because they are likely to be updated as the official models and assumptions change.
Updated mortality analysis of the Mallinckrodt uranium processing workers, 1942–2012
Published in International Journal of Radiation Biology, 2022
Ashley P. Golden, Elizabeth D. Ellis, Sarah S. Cohen, Michael T. Mumma, Richard W. Leggett, Phillip W. Wallace, David Girardi, Janice P. Watkins, Roy E. Shore, John D. Boice
The important internal emitters at MCW were all naturally occurring radionuclides, primarily members of the 238U and 235U chains and in particular the elevated concentrations of airborne 238U, 235U, 234U, 226Ra, 222Rn and its short-lived progeny. Detailed explanations for internal dose reconstructions are given by Ellis et al. (2018). Briefly, three sources of internal dosimetry were used to calculate organ/tissue-specific cumulative internal doses for MCW workers: 39,451 uranium urine samples available for 1925 workers from 1948 to 1966; 2341 radon breath samples available for 500 workers from 1948 to 1966, and 6846 ambient radon exposure measurements for 1392 workers available from 1944–1955. Workers without internal source records were considered unexposed. The biokinetic and dosimetric models used to estimate annual organ/tissue doses from internal sources in this study are those recommended in International Commission on Radiological Protection Publications 68 (ICRP 1994), 71 (ICRP 1995), 100 (ICRP 2006), 116 (ICRP 2010), and 137 (ICRP 2017). Dose to the thoracic lymph nodes was also based on ICRP models and dosimetry systems (ICRP 1994, 2006). It was assumed that all intakes of uranium or 226Ra were via inhalation of moderately soluble (Type M) material. Radon breath samples were used to estimate radium body burden. All organ/tissue-specific doses from each source were added together to obtain the total organ/tissue-specific internal dose for each worker for each calendar year.
Dosimetry and uncertainty approaches for the million person study of low-dose radiation health effects: overview of the recommendations in NCRP Report No. 178
Published in International Journal of Radiation Biology, 2022
Lawrence T. Dauer, André Bouville, Richard E. Toohey, John D. Boice, Harold L. Beck, Keith F. Eckerman, Derek Hagemeyer, Richard W. Leggett, Michael T. Mumma, Bruce Napier, Kathy H. Pryor, Marvin Rosenstein, David A. Schauer, Sami Sherbini, Daniel O. Stram, James L. Thompson, John E. Till, R. Craig Yoder, Cary Zeitlin
Estimates of organ dose obtained in a dose reconstruction have limitations and are uncertain. Limitations and lack of certainty in organ doses can result from factors such as:lack of complete knowledge of an exposure scenario;uncertainty in relevant measurements;lack of relevant data at locations and times of exposure;uncertainty in internal dosimetry; andconversion of externally measured quantities to organ doses.
A review of mammalian in vivo genotoxicity of hexavalent chromium: implications for oral carcinogenicity risk assessment
Published in Critical Reviews in Toxicology, 2021
Chad M. Thompson, Marilyn J. Aardema, Melissa M. Heintz, James T. MacGregor, Robert R. Young
Chromosomal damage has been reported in blood and bone marrow following i.p., i.v. and high dose oral gavage studies with Cr(VI). Importantly, pharmacokinetic data indicate that a large percentage of Cr(VI) escapes reduction in the stomach at high exposure concentrations such as those employed in the NTP 2-year bioassay (≥5 ppm; Supplemental Figure S1). This results in more Cr(VI) entering the intestinal lumen and damaging the mouse intestinal mucosa than would occur at typical exposure levels in humans. The estimated mg Cr(VI)/kg-day doses in the NTP (2008) bioassay from drinking water exposures of 5-180 ppm ranged from 0.4–9 mg/kg in mice and 0.2–7 mg/kg in rats. Many of the i.p. and p.o. bolus exposures in genotoxicity studies are within or exceed the range of the NTP bioassay, either based on mg/kg dose or test article concentration. While this arguably makes the doses in these studies “relevant”, the internal dosimetry is very different compared to drinking water ingestion and thus positive genotoxicity results from bolus dosing has uncertain relevance to real-world exposure to Cr(VI). In contrast, the genotoxicity results in drinking water studies are uniformly negative for MN induction with the exception of a small increase in MN in am3-C57BL/6 mice (NTP 2007) and a questionable effect reported by Elshazly et al. (2016).