[Artificial defect on myocardial SPECT image due to extra-cardiac MIBI accumulation]

If 99mTc-methoxy isobutylisonitrile (MIBI) myocardial scintigraphy was performed on the rest-stress protocol, MIBI accumulated in extra-cardiac area, gallbladder or liver, on rest image significantly. The purpose of this study was to evaluate whether extra-cardiac MIBI accumulation influences the quality of myocardial images. Rest-stress MIBI myocardial scintigraphy was performed in 90 patients. Fifteen patients showed defects on rest image in spite of normal findings on stress image. Before and after removing the area of extra-cardiac MIBI accumulation on projection images, SPECT was reconstructed in the 15 patients. Perfusion defect on rest image improved in 66% of patients (10/15) and 37% of total segments (33/89) by removing the area of extra-cardiac MIBI accumulation. Furthermore, it was 21% (4/19), 38% (11/29), 43% (16/37) and 50% (2/4) in anterior, septum, posterior and lateral segments respectively. Significant MIBI extra-cardiac accumulation, especially in the gallbladder, is one of the causes of artificial defects on rest image. Thus, reconstruction of SPECT after removing area of MIBI extra-cardiac accumulation will be an appropriate method to improve the quality of MIBI images.