We previously reported that single-head SPECT imaging with teboroxime is feasible. However, excessive hepatic uptake in some patients may interfere with image interpretation. This study examined the feasibility of improving image quality by use of a preprocessing masking technique to substract hepatic activity. A band of 10 pixels in width adjacent to the inferior cardiac silhouette was marked on the raw planar images, and then SPECT reconstruction was done with the Butterworth filter with a frequency cutoff of 0.3 cycles/cm and the power of 10. The stress and rest images were compared before and after masking in 10 patients who underwent SPECT teboroxime imaging during adenosine-induced coronary hyperemia (140 μg/kg/min for 6 minutes). SPECT imaging with a single-head detector was performed with the use of a 180-degree anterior arc (from the 45-degree left posterior oblique projection to the 45-degree right anterior oblique projection); 32 images at 8 seconds per stop were obtained (total imaging time = 6.8 minutes). All images were considered subjectively better after the masking technique was used, especially for assessment of inferior wall perfusion pattern. The maximum count in any pixel was in the hepatic region of interest before masking and in the cardiac region of interest after masking (303 ± 110 counts vs 166 ± 55 counts; p < 0.001). The difference was especially pronounced in the images that were obtained when patients were at rest (366 ± 102 counts vs 184 ± 64 counts; p < 0.001). When the polar maps were used quantitatively, the inferior counts were significantly lower after the processing (229 ± 115 counts vs 146 ± 79 counts; p < 0.001). Thus preprocessing masking of hepatic activity improves the quality of SPECT teboroxime images. This method requires only 5 additional minutes, is easy to perform, and should be routinely incorporated in image processing. © 1992.