Single photon tomographic imaging of a standard heart phantom with 201T1: a gamma camera based system

A standard heart phantom (University of Iowa design), including discrete myocardial walls, a central blood pool, and a 24-cc transmural "cold" defect, was studied with both planar and transverse tomographic imaging. The heart phantom was filled with 201T1 and placed within a cylindrical tank containing water and 201T1 to simulate nonmyocardial background activity from the thorax. The tomographic imaging system used was a commercially available, rotating, large field-of-view gamma camera. Image reconstruction from 64 sampling angles was performed in a nuclear medicine minicomputer system. The percentage activity in the region of the defect (actual activity of 0) contrasted to the normal wall was compared between planar and 1.25-cm transaxial tomographic slices. Defect activity fell to between 65% and 85% of that of the opposing normal wall in planar images, whereas it fell to between 26% and 49% of that of the normal wall in the tomographic images. In most cases, tomographic defect activity was half or less than that in the planar image. The geographic extent of the defect was seen in an appropriate number of tomographic slices; i.e., the geographic 3.2-cm defect length was predominantly seen in three 1.25-cm transverse slices. We conclude that camera-based tomographic systems show promise for improved 201T1 myocardial defect detection and quantitation over conventional planar images.