Prognostic value of one millisievert exercise myocardial perfusion imaging in patients without known coronary artery disease

Economic and healthcare resource utilization assessments of PET imaging in Coronary Artery Disease diagnosis: a systematic review and discussion of opportunities for future economic evaluations

AIMS

This systematic literature review (SLR) consolidated economic and healthcare resource utilization (HCRU) evidence for positron emission tomography (PET) and single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) to inform future economic evaluations.

MATERIALS AND METHODS

An electronic search was conducted in MEDLINE, Embase, and Cochrane databases from 2012-2022. Economic and HCRU studies in adults who underwent PET- or SPECT-MPI for coronary artery disease (CAD) diagnosis were eligible. A qualitative methodological assessment of existing economic evaluations, HCRU, and downstream cardiac outcomes was completed. Exploratory meta-analyses of clinical outcomes were performed.

RESULTS

The search yielded 13,439 results, with 71 records included. Economic evaluations and comparative clinical trials were limited in number and outcome types (HCRU, downstream cardiac outcomes, and diagnostic performance) assessed. No studies included all outcome types and only one economic evaluation linked diagnostic performance to HCRU. The meta-analyses of comparative studies demonstrated significantly higher rates of early- and late-invasive coronary angiography and revascularization for PET- compared to SPECT-MPI; however, the rate of repeat testing was lower with PET-MPI. The rate of acute myocardial infarction was lower, albeit non-significant with PET- vs. SPECT-MPI.

LIMITATIONS AND CONCLUSIONS

This SLR identified economic and HCRU evaluations following PET- and SPECT-MPI for CAD diagnosis and determined that existing studies do not capture all pertinent outcome parameters or link diagnostic performance to downstream HCRU and cardiac outcomes, thus, resulting in simplified assessments of CAD burden. A limitation of this work relates to heterogeneity in study designs, patient populations, and follow-up times of existing studies. Resultingly, it was challenging to pool data in meta-analyses. Overall, this work provides a foundation for the development of comprehensive economic models for PET- and SPECT-MPI in CAD diagnosis, which should link diagnostic outcomes to HCRU and downstream cardiac events to capture the full CAD scope.

Reduced acquisition time for thallium myocardial perfusion imaging with large field cadmium-zinc-telluride SPECT/CT cameras: An equivalence study

BACKGROUND

Cadmium-zinc-telluride (CZT) SPECT/CT cameras with large field of view offer a higher sensitivity than conventional Anger cameras. This prospective study aimed to determine the equivalence between a conventional protocol and a reduced acquisition time protocol for 201-Thallium myocardial perfusion imaging (MPI) using a whole-body CZT SPECT camera.

METHODS AND RESULTS

Stress MPI was obtained for 103 consecutive patients on a DISCOVERY-CZT camera. Images were anonymized and post-processed to simulate a 25% (D75 dataset) and 50% (D50 dataset) decrease in total recorded counts. Concerning the number of segments displaying a tracer uptake < 70% of maximum intensity per patient, equivalence was demonstrated for both count-reduced datasets with a good inter-observer agreement (between 0.90 and 0.88). When comparing the full-vs-D75 datasets and full-vs-D50 datasets, mean difference was 0.06 segment (CI95: [- 0.15;0.27], P < 0.001) and 0.518 segment (CI95: [0.28;0.76], P < 0.001) respectively. Inter-observer agreement was also moderate to good concerning the number of pathological segments (between 0.6 and 0.7) and excellent for functional parameters.

CONCLUSION

Whole-body CZT SPECT/CT cameras allow to reduce 201-Thallium MPI injected activity or acquisition time by 50% with an equivalence in the number of segments displaying a tracer uptake < 70% of maximum intensity and with a good inter-observer agreement.

Feasibility of simultaneous dual isotope acquisition for myocardial perfusion imaging with a cadmium zinc telluride camera

BACKGROUND

We studied the impact of technetium-99m (99mTc) in the thallium-201 (201Tl) energy window (70 keV) to determine if CZT cardiac cameras allow us to perform simultaneous dual-isotope acquisition for myocardial perfusion imaging.

METHODS

We included 117 consecutive patients. We injected 0.7 MBq/kg of 201Tl at stress, performed the first scan (image T1), then injected at rest 2 MBq/kg of 99mTc-tetrofosmin and immediately acquired a second scan with reconstruction in the energy window of thallium (image T2). A corrected thallium image was created by the subtraction of 99mTc downscattered photons (image TS). We compared spectra, image quality, and semiquantitative scores on T1, T2, and TS images.

RESULTS

Though T2 images were of worse quality, TS images were of equal quality compared to T1 images in most cases. Scores show an underestimation of abnormalities in 20% of patients on T2 images and in 10% on TS images.

CONCLUSIONS

Despite the improved energy resolution of CZT cameras, downscatter of technetium in the 201Tl window leads to an underestimation of the pathological territory in 10% to 20% of cases. It does not allow us to use simultaneous dual-isotope acquisition in clinical practice without additional tools for scatter correction.

Drivers of radiation dose reduction with myocardial perfusion imaging: A large health system experience

BACKGROUND

Despite increasing emphasis on reducing radiation exposure from myocardial perfusion imaging (MPI), the use of radiation-sparing practices (RSP) at nuclear laboratories remains limited. Defining real-world impact of RSPs on effective radiation dose (E) can potentially further motivate their adoption.

METHODS

MPI studies performed between 1/2010 and 12/2016 within a single health system were included. Mean E was compared between sites with 'basic' RSP (defined as elimination of thallium-based protocols and use of stress-only (SO) imaging on conventional single photon emission computed tomography (SPECT) cameras) and those with 'advanced' capabilities (sites that additionally used solid-state detector (SSD) SPECT cameras, advanced post-processing software (APPS) or positron emission tomography (PET) imaging), after matching patients by age, gender, and weight. Contributions of individual RSP to E reduction were determined using multiple linear regression after adjusting for factors affecting tracer dose.

RESULTS

Among 55,930 MPI studies performed, the use of advanced RSP was associated with significantly lower mean E compared to basic RSP (7 ± 5.6 mSv and 16 ± 5.4 mSv, respectively; P < 0.001), with a greater likelihood of achieving E < 9 mSv (65.7% vs. 10.8%, respectively; OR 15.8 [95% CI 14 to 17.8]; P < 0.0001). Main driver of E reduction was SO-SSD SPECT (mean reduction = 11.5 mSv), followed by use of SO-SPECT + APPS (mean reduction = 10.1 mSv), ;ET (mean reduction = 9.7 mSv); and elimination of thallium protocols (mean reduction = 9.1 mSv); P < 0.0001 for all comparisons.

CONCLUSION

In a natural experiment with implementation of radiation-saving practices at a large health system, stress-only protocols used in conjunction with modern SPECT technologies, the use of PET and elimination of thallium-based protocols were associated with greatest reductions in radiation dose. Availability of several approaches to dose reduction within a health system can facilitate achievement of targeted radiation benchmarks in a greater number of performed studies.

Ultra-low-dose computed tomography for attenuation correction of cadmium-zinc-telluride single photon emission computed tomography myocardial perfusion imaging

BACKGROUND

The applicability of ultra-low-dose computed tomography (CT) for attenuation correction (AC) of single-photon-emission computed tomography myocardial perfusion imaging (SPECT-MPI) remains elusive.

METHODS AND RESULTS

One-hundred patients underwent one-day 99mTc-tetrofosmin stress-rest MPI and non-contrast enhanced cardiac CT with 120, 80, and 70 kilovolt peak (kVp) tube voltage and tube current of 200 milliamperes for creation of AC maps. Normalized percent myocardial uptake from SPECT-MPI using 80 kVp scans for AC showed excellent correlation vs AC from 120 kVp scans for stress [intraclass correlation (ICC) = 0.988, 95% CI = 0.986-0.989, P < .001] and rest (ICC = 0.985, 95% CI = 0.983-0.987, P < .001) with narrow Bland-Altman limits of agreement (BA-LA) (- 5.3% to 4.5% and - 5.4% to 4.4%, respectively) and minimal bias (- 0.4% and - 0.5%, respectively). Correlation of AC SPECT-MPI based on 70 vs 120 kVp scans was excellent for stress (ICC = 0.988, 95% CI = 0.986-0.989, P < .001) and rest (ICC = 0.986, 95% CI = 0.984-0.987, P < .001) with narrow BA-LA (- 5.3% to 4.4% and - 5.2% to 4.5%, respectively) and small bias (- 0.4% and - 0.3%, respectively). Mean effective radiation dose for the 120, 80 and 70 kVp scans were 0.58 ± 0.07, 0.19 ± 0.02, and 0.12 ± 0.01 mSv, respectively.

CONCLUSIONS

Attenuation maps for MPI obtained from ultra-low radiation dose CT scans are interchangeable with attenuation maps from standard-dose CT while offering a substantial reduction in radiation dose exposure.

EANM procedural guidelines for myocardial perfusion scintigraphy using cardiac-centered gamma cameras

An increasing number of Nuclear Medicine sites in Europe are using cardiac-centered gamma cameras for myocardial perfusion scintigraphy (MPS). Three cardiac-centered gamma cameras are currently the most frequently used in Europe: the D-SPECT (Spectrum Dynamics), the Alcyone (Discovery NM 530c and Discovery NM/CT 570c; General Electric Medical Systems), and the IQ-SPECT (Siemens Healthcare). The increased myocardial count sensitivity of these three cardiac-centered systems has allowed for a decrease in the activities of radiopharmaceuticals injected to patients for myocardial perfusion imaging and, consequently, radiation exposure of patients. When setting up protocols for MPS, the overall objective should be to maintain high diagnostic accuracy of MPS, while injecting the lowest activities reasonably achievable to reduce the level of radiation exposure of patient and staff. These guidelines aim at providing recommendations for acquisition protocols and image interpretation using cardiac-centered cameras. As each imaging system has specific design and features for image acquisition and analysis, these guidelines have been separated into three sections for each gamma camera system. These recommendations have been written by the members of the Cardiovascular Committee of EANM and were based on their own experience with each of these systems and on the existing literature.