Abstract
Twenty five cases of liver cell carcinoma were studied by subtraction technique using 67Ga-Citrate and 99mTc-Colloid. Ten cases were operated on, and 15 were not. Using computer processing system (Nova III), subtraction image were made by substracting 99mTc image from 67Ga image. They were very useful for detecting abnormal 66Ga accumulations in the primary liver cell carcinoma. Twenty-four of 25 cases (96%) were easily diagnosed. In the remaining one, 66Ga accumulation was recognized retrospectively on the substracted images. It was able to detect intrahepatic metastases even in the area where ordinary scintigram did not show any abnormality.
Setting regions of interest on the 80% substracted image, tumor to bone marrow ratio and lung to bone marrow ratio were calculated respectively. Average tumor to bone mar-row ratio was 2.56 whereas lung to bone marrow ratios were 0.73 in cases without cirrhosis and 1.07 with cirrhosis.
We found that subtraction scintigraphy was very useful not only for diagnosing prima-ry liver cell carcinoma but also for the dicision of operability on the basis of radioisotope imaging technique.
