PurposeThe goal of this study is to present the Discovery NM 530c (DNM), a cardiac SPECT camera, interfacing multi-pinhole collimators with solid-state modules, aiming at slashing acquisition time without jeopardizing quality. DNM resembles PET since it enables 3-D SPECT without detector motion. We further envision how these novel capabilities may help with current and future challenges of cardiac imaging.MethodsDNM sensitivity, spatial resolution (SR) and energy resolution (ER), count rate response, cardiac uniformity and cardiac defect contrast were measured and compared to a dedicated cardiac, dual-head standard SPECT (S-SPECT) camera.ResultsDNM sensitivity was more than threefold higher while SR was notably better. Significantly, SR was the same for 99mTc and 201Tl. ER was improved on DNM and allowed good separation of 99mTc and 123I spectral peaks. Count rate remained linear on DNM up to 612 kcps, while S-SPECT showed severe dead time limitations. Phantom studies revealed comparable uniformity and defect contrast, notwithstanding significantly shorter acquisition time for the DNM. First patient images, including dynamic SPECT, are also presented.ConclusionDNM is raising the bar for expedition and upgrade of practice. It features high sensitivity as well as improved SR, temporal resolution and ER. It enables reduction of acquisition time and fast protocols. Importantly, it is potentially capable of dynamic 3-D acquisition. The new technology is potentially upgradeable and may become a milestone in the evolution of nuclear cardiology as it assumes its key role in molecular imaging of the heart.

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Calibration and quality control (QC) of gamma cameras with fixed pinhole collimators presents unique challenges since the usual assumption of uniform flood intensity at the surface of the detector is violated. For the GE Discovery NM 530c * , a fast cardiac SPECT system with multiple pinholes and CZT detectors focused on the heart, the problem is further complicated by the fact that the plane of the pinhole may not be parallel to either the detector or the flood source. To address this, we derived an expression for the geometrical response to an ideal uniform flood source, then added further terms to approximate the attenuation and scatter behavior of a real flood source. The model was validated with Monte Carlo simulations for a range of angles for both flood and pinhole. Accurate knowledge of the flood source orientation is essential for good uniformity correction; we developed a jig that permits repeatable flood positioning for rapid daily QC. Alternatively we have shown that the angle of the flood can be calculated from observed systematic flood non-uniformity. Experimental measurements show that variations in pinhole penetration as a function of angle can be detected in the residual error of the floods; the magnitude of the effect agrees very well with predictions from a simple model of the knife edge collimator. Uniformity effects attributable to the finite stopping power of CZT were also observed.The methods described in this paper have been implemented in the GE Discovery NM 530c and Discovery NM/CT 570c imaging systems, and portions of the technology are patent pending.

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