Count statistics of myocardial perfusion imaging using solid-state cadmium-zinc-telluride technology

Objectives Anger camera technology has been a mainstay in nuclear medicine, but it is relatively count inefficient. A new generation of cameras using high sensitivity, high resolution, solid-state detectors CZT (cadmium-zinc-telluride) with improved count detection efficiency is now available. This may offer a shorter imaging time and/or reduction of administered dose, however few data are available about the count statistics of such systems.

Methods We evaluated a cohort of 20 consecutive patients undergoing myocardial perfusion imaging on CZT. This cohort consisted of 10 male patients (mean age 57, range 43-76) and 10 female patients (mean age 49, range 30-66). For each patient, a region of interest (ROI) was placed around the myocardium (“target”), as well as in the superior mediastinum (“background”). Target to background ratios, target count density, and maximum counts per pixel were assessed for each patient, and compared to previously published data for dual headed SPECT gamma cameras.

Results Typical 30mCi 99mTc Sestamibi doses take 16 minutes acquisition on an Anger Camera to yield acceptable image quality and count density (100 max counts per pixel, or more). Similar studies on the CZT system with the same dose but a 3 minute acquisition yielded higher count densities (mean 588 max counts per pixel, range 438 - 956). Also “Low Dose” MIBI protocols (mean dose 9.8 mCi, range 9.0 to 12.0 mCi), the CZT camera imaged for 5 minutes which yielded a count density of (277.6 mean max counts per pixel, range 143 - 460). Background to target ratios were (mean 35.3 %, range 23.9 - 49.5). Image quality remained adequate and provided diagnostic images.

Conclusions Higher efficiency of the CZT system may allow us to develop shorter acquisition times or lower radiation dose to the patient while maintaining image quality