Real-time gated-SPECT myocardial perfusion imaging with CZT detectors: A promising tool for monitoring left ventricular function

Excerpt

The use of stress single-photon emission computed tomography (SPECT) cardiac imaging for the assessment of myocardial perfusion has become one of the most used noninvasive approaches for the management of patients with known or suspected coronary artery disease (CAD).1 The possibility to perform gated-SPECT as a routine part of clinical protocols offers the advantage to add to perfusion data functional parameters, such as left ventricular (LV) volumes, ejection fraction (EF), and regional wall motion, increasing the diagnostic accuracy and clinical utility of cardiac SPECT imaging.2,3 The assessment of LV volumes and EF represents a powerful and reliable method for the prediction of long-term prognosis and for clinical decision making in patients with heart diseases.4,5 There are many automated algorithms for quantification of SPECT parameters of myocardial perfusion and LV function, which have demonstrated accuracy and reproducibility.6 For the assessment of LV volumes and function, cardiac magnetic resonance (CMR) is considered the reference standard noninvasive method for validation of other imaging techniques. It is due to the characteristics of CMR imaging, a method that does not depend on geometric assumptions of LV shape.7 This approach is characterized by high reproducibility, excellent temporal and spatial resolution, and low interobserver and intraobserver variability.8 A good agreement of LV functional parameters between gated-SPECT by conventional Anger camera and CMR imaging has been demonstrated both at rest and post-stress. However, it has also been shown that gated-SPECT LV volumes and functional parameters may be underestimated by using standard cameras compared to CMR, showing high variability.9,10 Probably, the underestimation of end-diastolic and end-systolic volumes may be mainly explained by the limited SPECT temporal and spatial resolution. Other factors that may contribute to the discrepancies between these two modalities include the use of different algorithms and the possibility that in patients with large perfusion defects, severe reduction or absence of photon counts in a myocardial region may lead to an underestimation of regional wall motion, due to inadequate visualization.11 Using conventional Anger camera with waiting periods after stress tracer injection of at least 15 minutes, but sometimes also up to 60 minutes, post-stress LV function and volumes may be underestimated and early ischemic functional changes after stress test might be not identifiable. In addition, acquisition time with conventional cameras is very long and this may lead to a resolution of the LV function during this long time. All these characteristics do not allow to identifying post-stress LV function and wall motion abnormalities, which have been demonstrated to be correlated with severe obstructive CAD.12 …