Assessment of inferior wall in 123I-metaiodobenzylguanidine myocardial SPECT in diabetic patients

A phantom experiment and a clinical assessment have been made with the purpose of investigating the causes of low accumulation and deficiency of the inferior wall in 123I-metaiodobenzylguanidine (MIBG) myocardial SPECT and the method for its evaluation. By the phantom experiment, assessments were made regarding (1) influence of the liver positioned adjacently; and (2) involvement of absorption and attenuation of the inferior wall. For the clinical assessment, 84 patients with diabetes in whom no abnormality was observed by exercise myocardial SPECT (201TlCl) and 5 cases of inferior myocardial infarction (OMI group) were adopted as subjects. The inferior walls were evaluated as visually deficient because of the adjacently-positioned liver, but no low value was exhibited by quantitative evaluation. By pulmonary mediastinal phantom (-), improvement of the inferior wall was observed visually and quantitatively, compared with pulmonary mediastinal phantom (+). By quantitative evaluation, the patients were classified into normal MIBG group (N group); segmentally deficient group (S group); and non-accumulated group (DH group). In addition, S group was classified by severity score into those from S1 to S4 groups. No significant difference was observed in Relative Regional Uptake (RRU) in the inferior wall between S4 group and OMI group. To sum up, we considered the causes for low accumulation and deficiency of the inferior wall, (1) adjacently-positioned liver; (2) absorption and attenuation; and (3) the lesion itself. Visual evaluation is not sufficient as the evaluating method. Quantitative evaluation becomes necessary. (author)