ACUTE AND CRHRONIC MT RATIO OBSERVATIONS IN CANINE CRYOABLATION

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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 Prostate cancer is the most common invasive neoplasm in men in the United States; each year over 234,000 men are diagnosed with it. A potential minimally invasive treatment is cryoablation. With MR guidance, this treatment option could prove effective in locally ablating prostate tissue while preserving sensitive structures like the urethra or rectal wall. While iceball formation can be monitored with MR, assessment of tissue damage afterwards is less clear. Perfusion can be assessed with contrast enhanced (CE) imaging, but further tissue characterization of healing is desired. In previous studies, we noticed regions of low magnetization transfer (MT) contrast in cryolesions fourteen and fifty-three days after treatment. This current study follows the MT effect in cryolesions created in three canines, from immediately after treatment to weeks later when the dogs were sacrificed. The purpose of this work was to investigate if the lack of MT effect was evident immediately following treatment and to monitor how it progressed over time, comparing MT effect to CE and histology. Methods Three MRI-guided canine prostate cryoablations were performed in vivo on a 0.5T Signa SP scanner (GE Healthcare, Waukesha, WI). Each cryoablation procedure created multiple lesions within the prostate. After ablation, all dogs were imaged with MT pulse sequences, followed by Gadolinium CE imaging. The MT pulse sequences implemented on-resonance 1-2-1 binomial pulses alternating on and off per scan in both multislice 2D and 3D SPGR sequences. Two dogs (Dogs 1 and 2) were imaged with the same follow-up imaging protocol at seven days and at study termination - twenty-one days after treatment, while the third dog (Dog 3) was imaged at seven days and fourteen days (study termination). After the final imaging session, each dog was euthanized and the prostate harvested for histological analysis.