CODED-APERTURE IMAGING OF THE HEART

Abstract

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 adapted to small, portable cameras for bedside use without sacrificing image resolution. A new coded aperture designed especially for cardiac imaging was constructed and tested. This aperture incorporated significant improvements over previous designs. Longitudinal tomograms were calculated at 1-cm intervals using a modified ART algorithm. Lateral resolution at 140 keV with a portable scintillation camera was 3.8 mm FWHM [depth and lateral resolution] at 4 cm, and 7.8 mm FWHM at 12 cm. Depth resolution determined from a sloping line source was 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, were 20 and 8 cps/.mu.Ci. Images of good diagnostic quality were obtained in phantoms and in a dog model of acute myocardial infarction, using 201Tl, 99mTc PPi and gated ventricular blood-pool imaging with Tc-labeled red blood cells. Preliminary studies in humans confirm the good results in animals.