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. 2010 Feb;51(2):288-92.
doi: 10.2967/jnumed.109.068734. Epub 2010 Jan 15.

Fetal dose estimates for (18)F-fluoro-L-thymidine using a pregnant monkey model

Rachel M Bartlett  1 , Robert J Nickles, Todd E Barnhart, Bradley T Christian, James E Holden, Onofre T DeJesus
Affiliations

Fetal dose estimates for (18)F-fluoro-L-thymidine using a pregnant monkey model

Rachel M Bartlett et al. J Nucl Med. 2010 Feb.

Abstract

Estimating the radiation dose received by the fetus from nuclear medicine procedures is important because of the greater sensitivity of rapidly developing fetal tissues to ionizing radiation. (18)F-fluoro-L-thymidine (FLT) uptake is related to cellular proliferation and is currently used to monitor tumor progression and response to therapy. This study was undertaken to estimate-on the basis of biodistribution data obtained by PET/CT in pregnant rhesus monkeys-radiation absorbed dose to a human fetus administered (18)F-FLT.

Methods: Three pregnant rhesus macaques (gestational age, 113 +/- 8 d) were administered (18)F-FLT and imaged for 2 h on a PET/CT scanner. Time-activity curves for maternal and fetal organs were generated in anatomic regions of interest identified via CT. Doses were estimated using OLINDA/EXM and the 6-mo-pregnant human model.

Results: The extrapolated whole-body maternal dose obtained, 11.4 microGy/MBq, is similar to the previously reported adult female dose of 15.6 microGy/MBq. The estimated total-body dose to a human fetus is 24 microGy/MBq. Significant long-term (18)F-FLT accumulation in fetal liver resulted in a fetal liver dose of 53 microGy/MBq.

Conclusion: The fetal dose estimate in a 6-mo-pregnant human using (18)F-FLT is slightly greater than that reported for (18)F-FDG. (18)F-FLT trapping in the fetal liver should be considered in the risk-benefit analysis of (18)F-FLT PET examination in pregnant patients.

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Figures

FIGURE 1
FIGURE 1
Coronal images of pregnant monkey displaying average tracer distribution over early (0–3 min, first 10 frames), mid (6–12 min, 5 frames), and late (60–120 min, last 6 frames) time frames. B = brain; Bl = bladder; F = fetus; FL = fetal liver; K = kidney; L = liver; P = placenta; R = ribs.
FIGURE 2
FIGURE 2
Average time-activity curves (n = 3) extrapolated to 62-kg pregnant human model, normalized for injected dose and organ weight for maternal kidneys, liver, placenta, and fetus.
FIGURE 3
FIGURE 3
(A) PET/CT image of abdominal region of pregnant monkey showing placenta (P), fetal head (FH), and liver (FL). (B) Time-activity curve for fetal liver.
See this image and copyright information in PMC

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