Coded-aperture imaging of the heart.

Coded-aperture imaging of the heart combines the advantages of tomography with good sensitivity, high resolution, and accurate size scaling. Since the images are multiplexed, the method may be adapted to small, portable cameras for bed-side use without sacrificing image resolution. A new coded aperture designed especially for cardiac imaging has been constructed and tested. This aperture incorporates significant improvements over previous designs. Longitudinal tomograms are calculated at 1-cm intervals using a modified ART algorithm. Experimental lateral resulution at 140 keV with a portable scintillation camera is 3.8 mm FWHM at 4 cm, and 7.8 mm FWHM at 12 cm. Dpth resolution determined from a sloping line source is 1.1 cm FWHM at 4 cm, and 2.9 cm at 12 cm. The calculated point-source sensitivities in air at 4 cm and 12 cm, respectively, are 20 and 8 cps/microCi. Images of good diagnostic quality have been obtained in phantoms and in a dog model of acute myocardial infarction, using thallium-201, technetium-99m pyrophosphate, and gated ventricular blood-pool imaging with Tc-labeled red blood cells. Preliminary studies in humans confirm the good results in animals.