RT Journal Article
SR Electronic
T1 Image-Guided P<span class="sc">o</span><sub>2</sub> Probe Measurements Correlated with Parametric Images Derived from <sup>18</sup>F-Fluoromisonidazole Small-Animal PET Data in Rats
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1608
OP 1615
DO 10.2967/jnumed.112.103523
VO 53
IS 10
A1 Rachel M. Bartlett
A1 Bradley J. Beattie
A1 Manoj Naryanan
A1 Jens-Christoph Georgi
A1 Qing Chen
A1 Sean D. Carlin
A1 Gordon Roble
A1 Pat B. Zanzonico
A1 Mithat Gonen
A1 Joseph O’Donoghue
A1 Alexander Fischer
A1 John L. Humm
YR 2012
UL http://jnm.snmjournals.org/content/53/10/1608.abstract
AB 18F-fluoromisonidazole PET, a noninvasive means of identifying hypoxia in tumors, has been widely applied but with mixed results, raising concerns about its accuracy. The objective of this study was to determine whether kinetic analysis of dynamic 18F-fluoromisonidazole data provides better discrimination of tumor hypoxia than methods based on a simple tissue-to-plasma ratio. Methods: Eleven Dunning R3327-AT prostate tumor-bearing nude rats were immobilized in custom-fabricated whole-body molds, injected intravenously with 18F-fluoromisonidazole, and imaged dynamically for 105 min. They were then transferred to a robotic system for image-guided measurement of intratumoral partial pressure of oxygen (Po2). The dynamic 18F-fluoromisonidazole uptake data were fitted with 2 variants of a 2-compartment, 3-rate-constant model, one constrained to have K1 equal to k2 and the other unconstrained. Parametric images of the rate constants were generated. The Po2 measurements were compared with spatially registered maps of kinetic rate constants and tumor-to-plasma ratios. Results: The constrained pharmacokinetic model variant was shown to provide fits similar to that of the unconstrained model and did not introduce significant bias in the results. The trapping rate constant, k3, of the constrained model provided a better discrimination of low Po2 than the tissue-to-plasma ratio or the k3 of the unconstrained model. Conclusion: The use of kinetic modeling on a voxelwise basis can identify tumor hypoxia with improved accuracy over simple tumor-to-plasma ratios. An effective means of controlling noise in the trapping rate constant, k3, without introducing significant bias, is to constrain K1 equal to k2 during the fitting process.