Proceedings Article | 8 February 2007
KEYWORDS: Prostate, Magnetic resonance imaging, Tissues, Cell death, Cancer, Oncology, Pathology, Visualization, Ultrasonography, Capillaries
Magnetic Resonance Imaging (MRI) is a promising tool for visualizing the delivery of minimally invasive cancer
treatments such as high intensity ultrasound (HUS) and cryoablation. We use an acute dog prostate model to correlate
lesion histopathology with contrast-enhanced (CE) T1 weighted MR images, to aid the radiologists in real time
interpretation of in vivo lesion boundaries and pre-existing lesions. Following thermal or cryo treatments, prostate glands
are removed, sliced, stained with the vital dye triphenyl tetrazolium chloride, photographed, fixed and processed in
oversized blocks for routine microscopy. Slides are scanned by Trestle Corporation at .32 microns/pixel resolution, the
various lesions traced using annotation software, and digital images compared to CE MR images. Histologically, HUS
results in discrete lesions characterized by a "heat-fixed" zone, in which glands subjected to the highest temperatures are
minimally altered, surrounded by a rim or "transition zone" composed of severely fragmented, necrotic glands,
interstitial edema and vascular congestion. The "heat-fixed" zone is non-enhancing on CE MRI while the "transition
zone" appears as a bright, enhancing rim. Likewise, the CE MR images for cryo lesions appear similar to thermally
induced lesions, yet the histopathology is significantly different. Glands subjected to prolonged freezing appear totally
disrupted, coagulated and hemorrhagic, while less intensely frozen glands along the lesion edge are partially fragmented
and contain apoptotic cells. In conclusion, thermal and cryo-induced lesions, as well as certain pre-existing lesions
(cystic hyperplasia - non-enhancing, chronic prostatitis - enhancing) have particular MRI profiles, useful for treatment
and diagnostic purposes.
