Diagnostic implications of CZT SPECT and impact of CT attenuation correction

Journal of Nuclear Cardiology, Jun 2017

Andrew Peters MD, Jeevan Kumar MD, Pravin V. Patil MD

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Diagnostic implications of CZT SPECT and impact of CT attenuation correction

Received Jun Diagnostic implications of CZT SPECT and impact of CT attenuation correction Andrew Peters 0 1 Jeevan Kumar 0 1 Pravin V. Patil 0 0 agency in the public, commercial, or not-for-profit sectors. Reprint requests: Pravin V. Patil MD, Section of Cardiology, Department of Medicine, Lewis Katz School of Medicine at Temple University , 9th Floor Parkinson Pavilion, 3401 N. Broad Street, Philadelphia, PA 19140 , USA 1 Section of Cardiology, Department of Medicine, Lewis Katz School of Medicine at Temple University , Philadelphia, PA , USA In the current issue, Kennedy et al.1 further validate cadmium-zinc-telluride (CZT) SPECT, including the use of customized databases for automated perfusion scoring. They also demonstrate the utility of CT attenuation correction to reduce false positives and improve diagnostic accuracy. They examined three groups of patients, performing a comparison of CZT and conventional SPECT, establishing a customized database for automated perfusion scoring with CZT, and demonstrating the impact of CT attenuation correction (CTAC) in CZT SPECT. While there have been many studies comparing conventional SPECT to invasive angiography and CZT SPECT to invasive angiography, not many have directly compared them in the same population. CZT VERSUS CONVENTIONAL SPECT Single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is an important non-invasive tool for the evaluation of coronary artery disease (CAD). The relationship of functional ischemia on non-invasive testing and angiographic disease on invasive angiography has been debated heavily, but strong evidence supports the use of stress MPI for diagnosis and prognosis of CAD in certain patients. SPECT MPI has its limitations, such as attenuation artifact and image resolution, which can affect the predictive value and impact the clinical utility. Conventional SPECT consists of a scintillation detector of sodium iodide (NaI) crystals. These cameras have been validated with good sensitivity and specificity leading to widespread clinical use. Conventional SPECT MPI has a sensitivity ranging between 0.82 and 0.91, and specificity ranging between 0.70 and 0.90.2 During the first decade of the twenty first century, CZT SPECT systems emerged promising ultrafast acquisition, dose reduction, and similar diagnostic accuracy. The direct conversion of gamma radiation into signal by the semiconductor ensured improved image fidelity. CZT SPECT has been discussed extensively in the literature since cameras have a higher sensitivity compared to conventional cameras and reduced imaging time.2 Many of these studies have assessed the diagnostic performance of MPI with CZT cameras (Table 1).1,3–8 Further, in a meta-analysis by Nudi et al., the sensitivity of CZT SPECT was found to be range between 0.78 and 0.89 and the specificity ranged from 0.62 to 0.76.9 While the sensitivity is comparable to prior studies, the specificity is lower. Neill et al. further emphasized this with a direct comparison of CZT to conventional SPECT MPI in patients with correlative invasive angiography. CZT SPECT again had superior sensitivity but decreased specificity when compared to conventional SPECT.8 It is speculated that the lower specificity of CZT imaging is due to the practice of performing upright imaging, which may enhance patient comfort but results in more abdominal attenuation artifact, as well as the clinical tendency for use in an obese patient subgroup. Kennedy et al.1 demonstrate a reasonable correlation between CZT and conventional NaI scanners. Their data are in agreement with prior studies that indicate CZT could be associated with lower specificity and a higher number of false positives. Further, they provide low-intermediate risk patient data that support the use of Author Sensitivity (%) Specificity (%) N/A a separate custom database for CZT automated perfusion scoring, which potentially could improve specificity. It will be important for further research to be performed with a higher risk cohort. The authors also incorporated CTAC into their analysis, validating its use. ROLE FOR CT ATTENUATION CORRECTION SPECT MPI is susceptible to attenuation artifacts from tissues such as breast, diaphragm, abdomen, and lateral chest wall that reduce specificity.10,11 Numerous techniques have been shown to reduce attenuation artifact including breast binding, prone imaging, and attenuation maps created by external sources. External fixed line source attenuation correction (AC) using most frequently gadolinium-153 but also cobalt-57, barium-133, americium-241, and technetium-99m has been used.12 Nishiyama et al. demonstrated a technique involving combined supine and prone SPECT acquisition could reduce the false-positive rate associated with supine image acquisition.6 Supine and upright imaging with CZT in obese patients has also demonstrated diagnostic accuracy for CAD.13,14 Although these techniques have been used, more rece (...truncated)


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Andrew Peters MD, Jeevan Kumar MD, Pravin V. Patil MD. Diagnostic implications of CZT SPECT and impact of CT attenuation correction, Journal of Nuclear Cardiology, 2017, pp. 1-4, DOI: 10.1007/s12350-017-0961-5