In the constantly evolving landscape of nuclear cardiology, technological advancements and novel imaging protocols hold the potential to transform the way to diagnose and manage cardiovascular diseases. The recently published article titled "Accurate and Efficient Rapid Acquisition Early Post-Injection Stress-First CZT SPECT Myocardial Perfusion Imaging with Tetrofosmin and Attenuation Correction”1 introduces an approach that support and reinforce the traditional paradigms of myocardial perfusion scintigraphy (MPS). The study explores the utilization of an early post-injection, stress-first single-photon emission computed tomography (SPECT) protocol with cadmium zinc telluride (CZT) technology and attenuation correction for Tc-99m tetrofosmin imaging. One of the most significant advantages of the early post-injection stress-first imaging is its substantial reduction in imaging time and total duration of the diagnostic exam.

The findings of this study help to establish a robust groundwork for the CZT nuclear cardiology techniques, supporting operational efficiency without compromising diagnostic accuracy and image quality.

The conventional approach to MPS has remained relatively unchanged despite significant technological advancements. As a result, there has been a transition of evidence from conventional Anger camera techniques to CZT technology. Among these methodological approaches in MPS with Anger camera, the well-known "fast" or "early imaging" protocol has also been adapted to CZT. For Tc-99m tetrofosmin imaging, this protocol involves an interval of 15 minutes (on average) between the post-stress test injection and the image acquisition.

This study addresses this issue by capitalizing on CZT SPECT technology and CT attenuation correction, the authors sought to improve patient throughput, decrease imaging time, and maintain image quality. Their efforts are commendable as this type of research is still crucial in the ongoing pursuit of optimizing nuclear cardiology practices.

In the comparison of early post-stress and standard 1-hour delayed imaging, the blinded readers demonstrated consistent interpretations for the need for rest imaging in the majority of studies. Moreover, the overall interpretation of the images was concordant in nearly 90% of cases, indicating that early post-injection stress-first imaging provides results comparable to the standard protocol.

The confidence of the readers in their interpretations was found to be high, with minimal variation between the two imaging protocols. This finding is paramount, as it underscores the reliability and robustness of the early post-injection approach. Additionally, image quality, a crucial aspect of any diagnostic imaging modality, was evaluated and demonstrated comparable performance between the early post-stress and standard delayed imaging. Though the difference in image quality did not reach statistical significance, the trend towards equivalence is noteworthy. The time from patient check-in to the end of stress imaging was remarkably shortened in the early post-injection group, compared to the standard delayed imaging protocol. This substantial time-saving streamlines clinical workflows, enhance patient convenience, and optimize resource utilization, ultimately benefitting both patients and healthcare facilities.

The feasibility of obtaining high-quality tetrofosmin SPECT MPS images as early as 15 minutes post-injection has been demonstrated in a recent systematic review.2 However, most of the evidence supporting this approach has been derived from studies employing conventional gamma cameras.

In light of this knowledge gap, it becomes essential to validate the potential application of early imaging using Cadmium Zinc Telluride (CZT) cameras, as they offer distinct advantages over conventional gamma cameras. CZT cameras are known for their superior spatial and energy resolution, leading to enhanced image quality and potentially reducing the imaging time needed for accurate results.

The study conducted by Case et al, plays a crucial role in this context, as it specifically examines the early stress imaging approach using CZT cameras.1 This investigation is significant because it aims to eliminate the empirical assumption of a hypothetical overlap between early imaging using conventional SPECT and CZT cameras. Until now, only one study has endorsed the utilization of CZT cameras for perfusion early imaging, comparing early and delayed stress-rest acquisition,3 highlighting the lack of research in this field. This study was also referenced in the EANM procedural guidelines for MPS using cardiac-centered gamma cameras,4 emphasizing how the high-energy resolution of CZT crystals enables a reduction in scatter signals from the liver and digestive tract on MPS, thereby maintaining image quality in early acquisitions. Consequently, the two studies reach a consensus on stress early imaging as previously explored using conventional SPECT. Despite this agreement, there is still a lack of evidence regarding the timing of rest early acquisition. The recent ASNC SPECT imaging guidelines,5 underline how the rest acquisition should be delayed compared to the stress acquisition: "The standard delay between the injection of 99mTc sestamibi or tetrofosmin and the scan is 30 to 60 minutes for rest and 15 to 60 minutes for stress (the former for exercise stress)". Thesis supported also by Askew et al6, despite the contrasting results of the stress-rest comparison found in the study by Meyers et al3. The study6 has suggested that delayed rest images are superior to images acquired 8 to 12 minutes after injection. In this context, Case et al article didn't analyze the early rest acquisition since it was beyond the aim of the study. This leaves the contrast unresolved, as described in previous CZT early acquisition comparison studies.

Furthermore, While the study highlights the potential of early post-injection stress-first CZT SPECT MPI, it is essential to recognize its limitations. The sample size was modest, and additional research on a larger cohort is warranted to further validate these results. Additionally, a thorough cost-effectiveness analysis should accompany future investigations to assess the economic implications of adopting this novel imaging approach. One missed opportunity lies in the investigation of the relationship between early acquisition and CT attenuation-corrected images in terms of added value and image quality compared to standard imaging at 1 hour. While the study provides valuable insights into the feasibility and diagnostic efficacy of early post-injection stress-first imaging, it does not delve deep into the potential benefits of attenuation correction in this context, as described by the authors, this study considers the AC as a support and did not explore the additional benefits of it. Attenuation correction has been shown to improve image quality and reduce artifacts,7 particularly in obese patients and those with significant breast attenuation. By not thoroughly exploring the added value of attenuation correction in the context of early post-injection stress-first CZT SPECT imaging, the study leaves this question unanswered.

Nevertheless, the current proposal by Case et al1 aims to provide evidences supporting the efficacy of stress early imaging with CZT cameras in tetrofosmin SPECT MPS and address a piece of the puzzle of the research gap about CZT, MPS and early imaging. The study confirms CZT cameras can offer comparable or improved results compared to conventional gamma cameras in the context of early imaging. In conclusion, the implementation of early post-injection stress-first CZT SPECT imaging with Tc-99m tetrofosmin demonstrated comparable image quality, diagnostic confidence, and need for rest imaging when compared to the traditional 1-hour delayed imaging. Moreover, the substantial reduction in imaging time could lead to improved patient care and resource optimization in nuclear cardiology departments.