Tumor oximetry: Demonstration of an enhanced dynamic mapping procedure using fluorine-19 echo planar magnetic resonance imaging in the Dunning prostate R3327-AT1 rat tumor

Purpose: We have developed an enhanced approach to measuring regional oxyge n tension (pO(2)) dynamics in tumors. The technique is demonstrated in a gr oup of 8 Dunning prostate rat tumors (R3327-AT1) with respect to respirator y challenge. Methods and Materials: Hexafluorobenzene was injected directly into the tum ors of anesthetized rats. F-19 nuclear magnetic resonance echo planar imagi ng relaxometry was performed to obtain maps of regional tumor oxygenation u nder baseline conditions and when the inhaled gas was changed to oxygen or carbogen, Results: Sequential pO(2) maps required 8 min, with a typical precision of 1-3 torr at 30-100 individual regions across a tumor. When rats breathed 33 % oxygen, distinct heterogeneity was observed for baseline oxygenation in e ach tumor with pO(2) values ranging from hypoxic to greater than 100 torr, Larger tumors showed significantly lower baseline pO(2). Respiratory challe nge with oxygen or carbogen produced significant increases in tumor oxygena tion with a close correlation between the response to each gas at individua l locations. Regions of both small and large tumors responded to respirator y challenge, but the rate was generally much faster in initially well-oxyge nated regions, Conclusions: Regional pO(2) was assessed quantitatively and the response of multiple individual tumor regions observed simultaneously with respect to interventions. (C) 2001 Elsevier Science Inc.