Differentiation of focal intrahepatic lesions with 99mTc-red blood cell imaging.

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Abstract
The appearance of focal hepatic lesions on 99mTc-sulfur colloid images is nonspecific. Since it is important to distinguish hemangiomas from other lesions prior to biopsy, a prospective study was performed using 99PmTc-labeled red blood cells. Dynamic perfusion and delayed blood-pool images (1-2 h)were obtained and lesion activity categorized as increased, equal or decreased compared with the liver. Of 21 patients studied, 9 (43%) had 1 or more hepatic hemangiomas and 8 of these 9 patients (89%) demonstrated increased blood-pool activity. The 12 nonhemangiomatous lesions consisted of 7 metastatic tumors, 2 hepatomas, 1 cirrhotic nodule and 2 hepatic cysts. None of these 12 patients had increased activity on delayed blood-pool images. Early dynamic images of hepatic hemangiomas demonstrated variable activity (vascularity) and were not useful in differentiating hemangiomas from other lesions. Sensitivity was 89% and specificity 100%. Although liver enzymes are usually normal with hepatic hemangiomas, they may also be normal in metastatic disease. It is recommended that delayed blood-pool imaging should apparently be perfomred prior to biopsy, particularly in patients without a known primary tumor or those with normal liver enzyme levels.