A faster PISTOL for 1H MR‐based quantitative tissue oximetry

Quantitative mapping of oxygen tension (pO2), noninvasively, could potentially be beneficial in cancer and stroke therapy for monitoring therapy and predicting response to certain therapies. Intracellular pO2 measurements may also prove useful in tracking the health of labeled cells and understanding the dynamics of cell therapy in vivo. Proton Imaging of Siloxanes to map Tissue Oxygenation Levels (PISTOL) is a relatively new oximetry technique that measures the T1 of administered siloxanes such as hexamethyldisiloxane (HMDSO), to map the tissue pO2 at various locations with a temporal resolution of 3.5 minutes. We have now developed a siloxane‐selective Look‐Locker imaging sequence equipped with an echo planar imaging (EPI) readout to accelerate PISTOL acquisitions. The new tissue oximetry sequence, referred to as PISTOL‐LL, enables the mapping of HMDSO T1, and hence tissue pO2 in under one minute. PISTOL‐LL was tested and compared with PISTOL in vitro and in vivo. Both sequences were used to record dynamic changes in pO2 of the rat thigh muscle (healthy Fischer rats, n = 6), and showed similar results (P > 0.05) as the other, with each sequence reporting a significant increase in pO2 (P 0.05) at 3.5‐fold acceleration compared with PISTOL.