IN VIVO ASSESSMENT OF CANINE PROSTATE CRYOABLATIONS WITH MMTU

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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. 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 to be effective in locally ablating prostate tissue while preserving sensitive tissues like the urethra or rectal wall. However, while iceball formation can be easily monitored under MR guidance, assessment of tissue treatment is less clear. Perfusion can be assessed with contrast enhanced imaging, but further tissue characterization as the tissue is remodeled is desired. There is a strong magnetization transfer (MT) effect in prostate tissue [2], and the purpose of this work was to investigate whether MT imaging could provide additional information in the assessment of cryoablation lesions in vivo many weeks after treatment. Methods Two imaging experiments were performed in in vivo canine prostate on a 0.5T Signa SP scanner (General Electric, Milwaukee, WI). Two beagles were cryoablated and imaged and later sacrificed at 14 days and 53 days after treatment. On-resonance magnetization transfer imaging was performed with a 3D SPGR pulse sequence, alternating the MT pulse on and off from scan to scan. The on-resonance pulses were 1-2-1 binomial pulses. Magnetization ratio images were created using MATLAB (The Mathworks, Natick, MA) using equation 1 and clipped to between zero and one. Also, Gadolinium contrast enhanced images were acquired through the created lesions for comparison.