Abstract
Changes in the blood oxygen level dependent (BOLD) enhancements in tumors (squamous cell carcinoma, (SCCVII)) implanted in mice maintained at core temperatures of 30°C or 37°C were measured using MRI and compared to tumor oxygen levels obtained using an oxygen‐sensitive Eppendorf electrode. Tumors were implanted in a hindleg of the mice intramuscularly. Tumor‐bearing mice were imaged by BOLD MRI, while first breathing air and then carbogen (95% O~2~, 5% CO~2~) for 15‐min intervals at a core temperature of 30°C. After an equilibration period, the identical regimen was conducted with the same animal maintained at 37°C. This procedure was repeated with additional mice starting at 37°C followed by imaging at 30°C. Likewise, oxygen electrode measurements of the tumor were determined at core temperatures of 30°C and 37°C. The Eppendorf measurements showed that tumors in animals maintained at 30°C were significantly more hypoxic than at 37°C. MRI studies demonstrated stronger BOLD enhancement at 30°C than at 37°C, suggesting significant changes in hypoxia and/or blood flow in tumors at these temperatures. The findings of the study stress the importance of maintaining normal core temperature when assessing tumor oxygen status using functional imaging modalities or oxygen‐sensitive electrodes. Magn Reson Med 51:389–393, 2004. Published 2004 Wiley‐Liss, Inc.