L. Imbert

Compared Performance of High-Sensitivity Cameras Dedicated to Myocardial Perfusion SPECT: A Comprehensive Analysis of Phantom and Human Images

Differences in the performance of cadmium-zinc-telluride (CZT) cameras or collimation systems that have recently been commercialized for myocardial SPECT remain unclear. In the present study, the performance of 3 of these systems was compared by a comprehensive analysis of phantom and human SPECT images. Methods: We evaluated the Discovery NM 530c and DSPECT CZT cameras, as well as the Symbia Anger camera equipped with an astigmatic (IQ⋅SPECT) or parallel-hole (conventional SPECT) collimator. Physical performance was compared on reconstructed SPECT images from a phantom and from comparable groups of healthy subjects. Results: Classifications were as follows, in order of performance. For count sensitivity on cardiac phantom images (counts⋅s−1⋅MBq−1), DSPECT had a sensitivity of 850; Discovery NM 530c, 460; IQ⋅SPECT, 390; and conventional SPECT, 130. This classification was similar to that of myocardial counts normalized to injected activities from human images (respective mean values, in counts⋅s−1⋅MBq−1: 11.4 ± 2.6, 5.6 ± 1.4, 2.7 ± 0.7, and 0.6 ± 0.1). For central spatial resolution: Discovery NM 530c was 6.7 mm; DSPECT, 8.6 mm; IQ⋅SPECT, 15.0 mm; and conventional SPECT, 15.3 mm, also in accordance with the analysis of the sharpness of myocardial contours on human images (in cm−1: 1.02 ± 0.17, 0.92 ± 0.11, 0.64 ± 0.12, and 0.65 ± 0.06, respectively). For contrast-to-noise ratio on the phantom: Discovery NM 530c had a ratio of 4.6; DSPECT, 4.1; IQ⋅SPECT, 3.9; and conventional SPECT, 3.5, similar to ratios documented on human images (5.2 ± 1.0, 4.5 ± 0.5, 3.9 ± 0.6, and 3.4 ± 0.3, respectively). Conclusion: The performance of CZT cameras is dramatically higher than that of Anger cameras, even for human SPECT images. However, CZT cameras differ in that spatial resolution and contrast-to-noise ratio are better with the Discovery NM 530c, whereas count sensitivity is markedly higher with the DSPECT.

CZT cameras: A technological jump for myocardial perfusion SPECT

In the past few years, myocardial perfusion imaging has significantly evolved with the development of semiconductor cadmium-zinc-telluride (CZT) cameras, leading to a technological jump in this setting. The hopes raised by this new technology have been substantial because of the potential to improve energy resolution and image quality, compared to conventional Anger cameras. Unlike the latter cameras, these CZT cameras use a principle of direct detection where the interaction of a gamma photon of 140 keV produces approximately 30,000 electrons, a level 20-fold higher than that produced by a sparkling NaI(Tl) crystal. One of the most significant consequences is that energy resolution is improved by a factor of 2, compared with conventional Anger cameras. However, the new CZT cameras were also designed to optimize the acquisition and reconstruction processes with original software and collimation systems, leading to a marked enhancement in count sensitivity and spatial resolution, as confirmed by the article by Zoccarato et al, in this issue of the Journal of Nuclear Cardiology. Two semiconductor cameras are currently commercialized: the Discovery NM530c camera (GE Healthcare, Haifa, Israel) and the D.SPECT camera (Spectrum Dynamics, Caesarea, Israel). Both have a limited field of view, due to the substantial cost of semiconductors, and are thus mainly dedicated to cardiology applications. These two cameras use the same type of squared CZT-pixel detector with a surface area of 2.5 9 2.5 mm and a thickness of 5 mm. Consequently, the energy resolution is the same for both cameras and much better than that of conventional cameras. These CZT detectors provide a dramatic improvement in image quality and, in addition, facilitate dual isotope recordings such as those involving Tl and Tc-labeled tracers. However, the two CZT cameras are based on clearly different collimation systems. This constitutes the main reason why the characteristics of the myocardial perfusion images provided by these two cameras are significantly different, as confirmed by the study of Zoccarato et al. The Discovery NM530c camera is based on a stationary multi-pinhole collimation system. Each pinhole has an effective aperture diameter of only 5.1 mm that is likely to advantage spatial resolution and to disadvantage count sensitivity. However, a high count sensitivity may be achieved in this instance, by the simultaneous recording of the heart area through the 19 pinhole-detector blocks. The D.SPECT camera uses a very different system of rotational parallel-hole collimation. It involves 9 rotating columns associated with a wide-angle squarehole tungsten collimator. This collimator is likely to advantage count sensitivity although a high level of spatial resolution can be reached owing to an original reconstruction method. In addition to energy resolution, the main parameters allowing to characterize a gamma camera are (1) Reprint requests: Laetitia Imbert, PhD, CRAN, UMR 7039, Université de Lorraine CNRS, 54500 Vandoeuvre, France; l.imbert@nancy. unicancer.fr J Nucl Cardiol 2016;23:894–6. 1071-3581/

Compared vulnerabilities to small cardiac motions between different cameras used for myocardial perfusion imaging

34.00 Copyright 2015 American Society of Nuclear Cardiology.

Article originalImpact d’une réduction d’activité sur la mesure de la fraction d’éjection du ventricule gauche sur caméra D-SPECTImpact of a decrease in recorded counts on the left ventricular ejection fraction measurement from the D-SPECT camera

This phantom-based study was aimed to determine whether cardiac CZT-cameras, which provide an enhanced spatial resolution and image contrast compared to Anger cameras, are similarly affected by small cardiac motions. Translations of a left ventricular (LV) insert at half-SPECT acquisitions through six possible orthogonal directions and with 5- or 10-mm amplitude were simulated on the Discovery NM-530c and DSPECT CZT-cameras and on an Anger Symbia T2 camera equipped with an astigmatic (IQ.SPECT) or conventional parallel-hole collimator (Conv.SPECT). SPECT images were initially reconstructed as currently recommended for clinical routine. The heterogeneity in recorded activity from the 17 LV segments gradually increased between baseline and motions simulated at 5- and 10-mm amplitudes with all cameras, although being higher for Anger- than CZT-cameras at each step and resulting in a higher mean number of artifactual abnormal segments (at 10-mm amplitude, Conv.SPECT: 3.7; IQ.SPECT: 1.8, Discovery: 0.7, DSPECT: 0). However, this vulnerability to motion was markedly (1) decreased for Conv.SPECT reconstructed without the recommended Resolution Recovery algorithm and (2) increased for DSPECT reconstructed without the recommended cardiac model. CZT-cameras and especially the DSPECT appear less vulnerable to small cardiac motions than Anger-cameras although these differences are strongly dependent on reconstruction parameters.

Stress-first protocol for myocardial perfusion SPECT imaging with semiconductor cameras: high diagnostic performances with significant reduction in patient radiation doses.

Introduction Radionuclide ventriculography provides a reproducible measurement of the left ventricular fraction ejection (LVEF) but with a significant body radiation (effective dose of 5,9 mSv for the injection of 850 Mbq of 99mTc). The highly sensitive semi-conductor (CZT) cameras could allow decreasing the injected activity by a factor 3, similarly to that of myocardial perfusion imaging. Our study was aimed to determine whether the LVEF measurement provided by radionuclide ventriculography on the CZT D-SPECT camera is impacted by a 70% reduction in recorded counts.