Abstract
Although there is considerable interest in gated cardiac ECT (Ref. 1), the large amount of data makes it difficult to use this technique clinically with existing computer systems. We have developed a clinically practical technique to acquire and analyze gated SPECT data of the cardiac blood pool by performing a buffered beat acquisition at each camera position, sorting and normalizing the images, serially reconstructing sets of transverse slices, and post-processing those slices for real-time review and analysis. Processing steps are designed so that a minimum of human interaction is required at the beginning, and the bulk of the processing is subsequently done automatically by the computer in the background. We acquire 64x64 word images over 180 degrees at 32 camera angular positions for 120 seconds per position, gating the R-R interval into 16 frames, yielding a total of 4 megabytes of raw data. Standard software (Siemens MicroDelta) was modified to automatically sort, normalize, and reconstruct all 16 frames with the same parameters following a standard reconstruction of the first. After 2 minutes of user interaction, the unattended reconstruction takes 1.5 minutes per frame. Studies are reviewed by displaying the moving transverse or oblique slices in either of two cine modes, and/or defining the blood pool surface for each chamber and viewing the moving surfaces from virtually any angle selected with a joy stick. The volume calculation is based on our previously reported technique for non-gated data. The first slice-cine mode displays one slice level, with interactive control of level and rate. The second displays all slices in a "spread stack" format. Surface definition requires 20 minutes of initial operator assistance to help separate the chambers. We have acquired and analyzed data from ten patients and a rotating phantom. Patients have tolerated the one hour acquisition time well. The automated processing makes this technique feasible for daily use in a busy clinic.
