Topics of Interest

(1)

Cleveland Clinic, Emeritus Staff, Cleveland, OH, USA

Keywords

Absorbed doseTumor uptake ⁸²Sr–⁸²Rb generator

Estimated Absorbed Dose from Intravenous Administration of ¹⁸F-FDG and ⁸²Rb-RbCl in Humans

The dose estimate D in a human organ is made by using the following internal dosimetry equation (Saha 2013):

$D=\overset{\sim }{A}\times S,$

(14.1)

where Ã is the cumulated activity and S is the mean absorbed dose per cumulated activity. Ã is calculated from the initial administered activity and the biodistribution and residence time of the tracer in each organ and has the unit of μCi · h or MBq · h. S is calculated from the knowledge of physical characteristics of the radiation in question, the mass of the organ, and the absorption fraction of the radiation in the target organ and has the unit of rad/μCi · h or mGy/MBq · h. The values of S are available in literature for most common radiopharmaceuticals including ¹⁸F-FDG and ¹⁸Rb-RbCl. The experimental data for biodistribution and residence time are available in literature and used to calculate Ã. The following two tables give the absorbed doses per administered activity based on these calculations for ¹⁸F-FDG and ⁸²Rb-RbCl, respectively (Tables 14.1 and 14.2).

Table 14.1

Absorbed dose per unit administered activity of ¹⁸F-FDG^a

Target organ	mGy/MBq	rad/mCi
Brain	0.046 ± 0.012	0.17 ± 0.044
Heart wall	0.068 ± 0.036	0.25 ± 0.13
Kidneys	0.021 ± 0.0059	0.078 ± 0.022
Liver	0.024 ± 0.0085	0.088 ± 0.031
Lungs	0.015 ± 0.0084	0.056 ± 0.031
Pancreas	0.014 ± 0.0016	0.052 ± 0.0060
Red marrow	0.011 ± 0.0017	0.040 ± 0.0062
Spleen	0.015 ± 0.0021	0.056 ± 0.0078
Urinary bladder wall^b	0.073 ± 0.042	0.27 ± 0.16
Ovaries^c	0.011 ± 0.0015	0.041 ± 0.0055
Testes^c	0.011 ± 0.0016	0.041 ± 0.0057
Whole body^d	0.012 ± 0.00077	0.043 ± 0.0023
Effective dose^d,e	0.0190	0.070

^aReproduced with permission from Hays MT, Watson EE, Thomas ER, et al (2002). MIRD dose estimate report no.19: radiation absorbed dose estimates from ¹⁸F-FDG. J Nucl Med 43:210

^bDose to urinary bladder wall is based on 120-min void intervals, starting 120 min after dosing, using traditional static MIRD model

^cDoses to ovaries and testes include doses from residence times in urinary bladder and remainder of body as calculated from data in: Hays MT, Segall GM (1999) A mathematical model for the distribution of fluorodeoxyglucose in humans. J Nucl Med 40:1358

^dThe calculation of whole-body dose is based on total energy deposited in the body divided by its total mass, whereas the total effective dose reported by the ICRP is calculated by applying risk-based weighting factors to individual organ doses to estimate a uniform whole-body dose that in theory gives the same risk as the nonuniform pattern that actually occurred. The two values are based on different concepts and not comparable

^eFrom ICRP (1999) Publication No. 80. Pergamon Press, New York

Table 14.2

Absorbed dose per unit administered activity of ⁸²Rb-RbCl

Adult absorbed radiation doses^a
Organ	mGy/2220 MBq	rads/60 mCi
Adrenals	2.15	0.22
Stomach	1.91	0.19
Small intestine	3.11	0.32
Upper large intestine	1.91	0.19
Lower large intestine	1.91	0.19
Heart wall	4.22	0.42
Kidneys	19.1	1.92
Liver	1.91	0.19
Lungs	3.77	0.38
Ovaries	0.84	0.084 Only gold members can continue reading. Log In or Register to continue Share this: Click to share on Twitter (Opens in new window) Click to share on Facebook (Opens in new window) Related posts: Synthesis of PET Radiopharmaceuticals Sample Procedures for PET Studies Reimbursement for PET Procedures Image Reconstruction PET Scanning Systems Performance Characteristics of PET Scanners Stay updated, free articles. Join our Telegram channel Tags: Basics of PET Imaging Sep 9, 2016 \| Posted by admin in GENERAL RADIOLOGY \| Comments Off on Topics of Interest Full access? Get Clinical Tree Get Clinical Tree app for offline access Get Clinical Tree app for offline access