Concentration of 123I-metaiodobenzylguanidine in left and right liver lobes. Findings indicate regional differences in function in the normal liver

• Purpose: Normal radioactivity in the liver is often shown to be higher in the left lobe than in the right lobe at clinical examination by single photon emission computed tomography (SPECT) with 123I-metaiodobenzylguanidine (123I-MIBG). Our objective was to determine whether this represents a pathological condition. Material and Methods: The distribution of 123I-MIBG in the liver was retrospectively studied in clinical patients who had normal CT examinations of the liver and spleen. In the SPECT sections of 27 123I-MIBG examinations, we determined the activity ratios between the left and right lobes. The control group comprised 33 examinations with 111In-pentetreotide (OctreoScan) and 23 examinations with 99mTc-antigranulocyte antibody. Results: The mean activity ratio between left and right lobes for 123I-MIBG was 1.24, and for 111In-pentetreotide 0.87. These figures differed significantly both from each other and from 1.00. The mean ratio for 99mTc-antibody at the early examinations was 0.99, and at the late examinations 0.95. These figures differed significantly from the values for 123I-MIBG and 111In-pentetreotide. Conclusion: The increased concentration of 123I-MIBG in the left lobe of the liver compared to the right lobe is a normal finding. The reason for this cannot be explained. The difference in the way in which the left and right lobes deal with the three radiopharmaceuticals is a new finding and indicates a regional difference in liver function that has not been reported previously.

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