From: Proceedings 10th World Congress of Cryosurgery
X-ray CT: an attractive alternative for monitoring iceball growth

November 1998
GA Sandison, JC Rewcastle, LJ Hahn Departments of Oncology, Medical Physics and Surgery, Tom Baker Cancer Centre, Calgary, Canada, T2N 4N2; Department of Physics and Astronomy, University of Calgary, Calgary, Canada, T2N 2N4; Department of Diagnostic Imaging, Foothills Hospital, Calgary, Canada, T2N 2T7

Real time ultrasound and MR imaging cannot image tissues within cryosurgical iceballs. The ability of X-ray CT to both resolve the ice interface and continue to image tissue within a cryosurgical iceball has, for the most part, been ignored in the literature. Phantom studies of the change in Houndsfield unit with temperature for distilled water, saline-gelatin mixture and calf liver-gelatin suspension have been performed. We found a decrease in HU upon freezing with no drop with further cooling. This change occurred over a range of -7 and was found to be approximately 85 HU upon freezing, regardless of the initial (prefreeze) value. We observed no correlation between HU and temperature deep within the iceball. X-ray CT should be considered for the monitoring of iceball growth during cryosurgery, since it is able to resolve the three-dimensional geometry of the iceball and image the anatomy within it.


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