INVESTIGATION OF DWI TO EVALUATE PROSTATE THERMAL AND CRYO LESIONS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Introduction: Thermal ablation and cryoablation are promising methods for the minimally treatment of prostate cancer. MRI provides the ability to guide the position of treatment applicator, to measure the tissue temperature during treatment, and to evaluate the tissue after the treatment. Contrast-enhanced imaging and diffusion-weighted imaging both demonstrate the thermal lesion, but the advantage to DWI is repeatability since it does not require an injection of contrast agent. The goal of this work is to evaluate DWI as a method to estimate tissue viability immediately after the treatment. Methods: All animal experiments were approved by the Administrative Panel on Laboratory Animal Care. Diffusion weighted imaging was performed in six canine prostates with MRI-guided high intensity ultrasound thermal therapy (3 cases) or cryoablation (3 cases). All MR imaging were acquired on the 0.5T Signa SP open MRI system (GE, Milwaukee, WI). The body coil was used as the transmitter. A 2-channel phase array coil consisting of an anterior surface coil and an endorectal coil was used as the receiver. Line scan diffusion weighted images (LSDI) (TE/TR = 70/150 ms, matrix = 256¿63, field of view = 24¿6 cm, LSDI inclination angle = 70¿, band width = 7.91 kHz, slice thickness = 5 mm, b = 10, 360 seconds/mm2) were acquired before the therapy and after the prostates returned to body temperature. Diffusion trace data were calculated and compared to the triphenyl tetrazolium chloride (TTC) staining result. The apparent diffusion coefficient (ADC) values were measured in both the necrotic and viable tissues.