EFFECTS OF MYOCARDIAL WALL THICKNESS ON SPECT QUANTIFICATION

The dependence of reconstructed counts on object thickness in PET and SPECT limits the accuracy with which regional distributions of activity can be derived in objects smaller than two full-widths-at-half-maximum of the point spread function. Myocardial wall thicknesses are well within this range for the resolutions of most SPECT systems. A cardiac phantom with varying wall thickness (9-23 mm) has been developed to characterize this effect on 201T1 myocardial SPECT images. Correction factors in the form of recovery coefficients have been developed with the use of a convolution simulation, and have been shown to substantially improve the agreement of counts extracted from SPECT images of the phantom with the actual 201Tl concentration. The degree of improvement, however, is markedly affected by external attenuation. Clinical application of this method will require corrections for attenuation and scatter or the development of regional recovery coefficients which include these effects. © 1990 IEEE