Imaging technique for real-time temperature monitoring during cryotherapy of lesions

Noninvasive real-time temperature imaging during thermal therapies is able to significantly improve clinical outcomes. An optoacoustic (OA) temperature monitoring method is proposed for noninvasive real-time thermometry of vascularized tissue during cryotherapy. The universal temperature-dependent optoacoustic response (ThOR) of red blood cells (RBCs) is employed to convert reconstructed OA images to temperature maps. To obtain the temperature calibration curve for intensity-normalized OA images, we measured ThOR of 10 porcine blood samples in the range of temperatures from 40 degrees C to -16 degrees C and analyzed the data for single measurement variations. The nonlinearity (Delta T-max) and the temperature of zero OA response (T-0) of the calibration curve were found equal to 11.4 +/- 0.1 degrees C and -13.8 +/- 0.1 degrees C, respectively. The morphology of RBCs was examined before and after the data collection confirming cellular integrity and intracellular compartmentalization of hemoglobin. For temperatures below 0 degrees C, which are of particular interest for cryotherapy, the accuracy of a single temperature measurement was +/- 1 degrees C, which is consistent with the clinical requirements. Validation of the proposed OA temperature imaging technique was performed for slow and fast cooling of blood samples embedded in tissue-mimicking phantoms. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)