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Oncology-Clinical Diagnosis: Solid TumorsGI Cancers - Colorectal and Liver |
1 Radiology/Nuclear Medicine, Mt. Sinai Med. Ctr., New York, New York
444
Objectives: Prior to the Yttrium-90 microspheres (Y-90) therapy, the percentage of shunting to the lungs and the distribution in the liver is determined from a scan using technetium-99m labeled macroaggregated albumin (Tc-99m MAA). The Y-90 is a pure beta emitter and can be imaged by Bremsstrahlung. For Y-90 therapy, it is assumed that the Y-90 microspheres will follow the Tc-99m MAA distribution, which is not always the case. The purpose of our study was to compare visually assessed and computer calculated correlation between Y-90 and Tc-99m MAA images.
Methods: 22 patients have been investigated. 5 mCi of Tc-99m MAA was used for diagnostic studies and for Y-90 therapy studies activities ranged from 21 to 66 mCi. For both studies SPECT/CT acquisitions were the same; there were 60 views, 30 s/view; the reconstruction algorithm was OSEM. The visual assessment was done for each segment and summed up. In addition, the Spearman’s rank correlation and image distance (L2) were calculated between Y-90 and coregistrated MAA images. Coregistration was done in two steps. First, corresponding CT studies were coregistrated using a transformation based on normalized mutual information (1). The transformation was saved and used to match Y-90 and MAA SPECT images.
Results: The visual assessment of the Y-90 and MAA distributions showed reasonable match with the Spearman’s rank correlation values (r= 0.52) and poorer corelation with L2 distance between Y-90 and matched MAA images (r= 0.38).
Conclusions: Spearman’s rank correlation had better correlation with visual assessment than image distance and can be used as an objective parameter in correlating the Y-90 and Tc-99m MAA distributions.
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