Nuclear myocardial perfusion imaging with a cadmium-zinc-telluride detector technique: optimized protocol for scan time reduction

Keeping Up With ChatGPT: Evaluating Its Recognition and Interpretation of Nuclear Medicine Images

PURPOSE

The latest iteration of GPT4 (generative pretrained transformer) is a large multimodal model that can integrate both text and image input, but its performance with medical images has not been systematically evaluated. We studied whether ChatGPT with GPT-4V(ision) can recognize images from common nuclear medicine examinations and interpret them.

PATIENTS AND METHODS

Fifteen representative images (scintigraphy, 11; PET, 4) were submitted to ChatGPT with GPT-4V(ision), both in its Default and "Advanced Data Analysis (beta)" version. ChatGPT was asked to name the type of examination and tracer, explain the findings and whether there are abnormalities. ChatGPT should also mark anatomical structures or pathological findings. The appropriateness of the responses was rated by 3 nuclear medicine physicians.

RESULTS

The Default version identified the examination and the tracer correctly in the majority of the 15 cases (60% or 53%) and gave an "appropriate" description of the findings or abnormalities in 47% or 33% of cases, respectively. The Default version cannot manipulate images. "Advanced Data Analysis (beta)" failed in all tasks in >90% of cases. A "major" or "incompatible" inconsistency between 3 trials of the same prompt was observed in 73% (Default version) or 87% of cases ("Advanced Data Analysis (beta)" version).

CONCLUSIONS

Although GPT-4V(ision) demonstrates preliminary capabilities in analyzing nuclear medicine images, it exhibits significant limitations, particularly in its reliability (ie, correctness, predictability, and consistency).

Immediate recruitment of dormant coronary collaterals can provide more than half of normal resting perfusion during coronary occlusion in patients with coronary artery disease

BACKGROUND

Dormant coronary collaterals are highly prevalent and clinically beneficial in cases of coronary occlusion. However, the magnitude of myocardial perfusion provided by immediate coronary collateral recruitment during acute occlusion is unknown. We aimed to quantify collateral myocardial perfusion during balloon occlusion in patients with coronary artery disease (CAD).

METHODS

Patients without angiographically visible collaterals undergoing elective percutaneous transluminal coronary angioplasty (PTCA) to a single epicardial vessel underwent two scans with 99mTc-sestamibi myocardial perfusion single-photon emission computed tomography (SPECT). All subjects underwent at least three minutes of angiographically verified complete balloon occlusion, at which time an intravenous injection of the radiotracer was administered, followed by SPECT imaging. A second radiotracer injection followed by SPECT imaging was performed 24 h after PTCA.

RESULTS

The study included 22 patients (median [interquartile range] age 68 [54-72] years. The perfusion defect extent was 19 [11-38] % of the LV, and the collateral perfusion at rest was 64 [58-67]% of normal.

CONCLUSION

This is the first study to describe the magnitude of short-term changes in coronary microvascular collateral perfusion in patients with CAD. On average, despite coronary occlusion and an absence of angiographically visible collateral vessels, collaterals provided more than half of the normal perfusion.

Stress-First Myocardial Perfusion Imaging

Stress-first approaches to myocardial perfusion imaging provide diagnostically and prognostically accurate perfusion data equivalent to a full rest-stress study while saving time in the imaging laboratory and reducing the radiation exposure to patients and laboratory staff. Unfortunately, implementing a stress-first approach in a nuclear cardiology laboratory involves significant challenges such as the need for attenuation correction, triage of patients to an appropriate protocol, real-time review of stress images, and consideration of differential reimbursement. Despite it being best practice for both the patient and the laboratory, these impediments have kept the proportions of studies performed stress-first relatively unchanged in North America and world-wide in the last 10 years.

Comparison of diabetes to other prognostic predictors among patients referred for cardiac stress testing: A contemporary analysis from the REFINE SPECT Registry

BACKGROUND

Diabetes mellitus (DM) is increasingly prevalent among contemporary populations referred for cardiac stress testing, but its potency as a predictor for major adverse cardiovascular events (MACE) vs other clinical variables is not well delineated.

METHODS AND RESULTS

From 19,658 patients who underwent SPECT-MPI, we identified 3122 patients with DM without known coronary artery disease (CAD) (DM+/CAD-) and 3564 without DM with known CAD (DM-/CAD+). Propensity score matching was used to control for the differences in characteristics between DM+/CAD- and DM-/CAD+ groups. There was comparable MACE in the matched DM+/CAD- and DM-/CAD+ groups (HR 1.15, 95% CI 0.97-1.37). By Chi-square analysis, type of stress (exercise or pharmacologic), total perfusion deficit (TPD), and left ventricular function were the most potent predictors of MACE, followed by CAD and DM status. The combined consideration of mode of stress, TPD, and DM provided synergistic stratification, an 8.87-fold (HR 8.87, 95% CI 7.27-10.82) increase in MACE among pharmacologically stressed patients with DM and TPD > 10% (vs non-ischemic, exercised stressed patients without DM).

CONCLUSIONS

Propensity-matched patients with DM and no known CAD have similar MACE risk compared to patients with known CAD and no DM. DM is synergistic with mode of stress testing and TPD in predicting the risk of cardiac stress test patients.

Differences in Prognostic Value of Myocardial Perfusion Single-Photon Emission Computed Tomography Using High-Efficiency Solid-State Detector Between Men and Women in a Large International Multicenter Study

BACKGROUND

Semiquantitative assessment of stress myocardial perfusion defect has been shown to have greater prognostic value for prediction of major adverse cardiac events (MACE) in women compared with men in single-center studies with conventional single-photon emission computed tomography (SPECT) cameras. We evaluated sex-specific difference in the prognostic value of automated quantification of ischemic total perfusion defect (ITPD) and the interaction between sex and ITPD using high-efficiency SPECT cameras with solid-state detectors in an international multicenter imaging registry (REFINE SPECT [Registry of Fast Myocardial Perfusion Imaging With Next-Generation SPECT]).

METHODS

Rest and exercise or pharmacological stress SPECT myocardial perfusion imaging were performed in 17 833 patients from 5 centers. MACE was defined as the first occurrence of death or myocardial infarction. Total perfusion defect (TPD) at rest, stress, and ejection fraction were quantified automatically by software. ITPD was given by stressTPD-restTPD. Cox proportional hazards model was used to evaluate the association between ITPD versus MACE-free survival and expressed as a hazard ratio.

RESULTS

In 10614 men and 7219 women, with a median follow-up of 4.75 years (interquartile range, 3.7-6.1), there were 1709 MACE. In a multivariable Cox model, after adjusting for revascularization and other confounding variables, ITPD was associated with MACE (hazard ratio, 1.08 [95% CI, 1.05-1.1]; P<0.001). There was an interaction between ITPD and sex (P<0.001); predicted survival for ITPD<5% was worse among men compared to women, whereas survival among women was worse than men for ITPD≥5%, P<0.001.

CONCLUSIONS

In the international, multicenter REFINE SPECT registry, moderate and severe ischemia as quantified by ITPD from high-efficiency SPECT is associated with a worse prognosis in women compared with men.

Transluminal attenuation gradient derived from coronary CT angiography to predict ischemia in SPECT myocardial perfusion imaging: Effect of coronary cross-sectional area

BACKGROUND

Coronary computed tomography angiography (CCTA)-based transluminal attenuation gradient (TAG) was suggested to determine the functional significance of a stenosis. However, evidence that TAG acquired by wide-volume scanners can assess the hemodynamic significance of stenosis assessed by single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is lacking. Moreover, coronary cross-sectional area may influence TAG. Hence, we aimed at assessing the diagnostic value of TAG to predict ischemia in SPECT-MPI and the correlation between TAG and the transluminal cross-sectional area gradient (TCG).

METHODS

Patients undergoing CCTA and SPECT-MPI for suspected coronary artery disease were included. TAG and TCG were calculated measuring the mean vessel attenuation and the cross-sectional area along major coronary vessels at 5-mm intervals.

RESULTS

A total of 255 coronary arteries of 87 patients were included. TAG and TCG did not discriminate between coronary arteries with or without ischemia as assessed by SPECT-MPI (p = .44 and p = .25, respectively). The area under the curve to predict ischemia was not increased by adding TAG (0.88, 95% CI 0.83-0.92) or TCG (0.87, 95% CI 0.81-0.90) to CCTA alone (0.85, 95% CI 0.80-0.89). There was a significant correlation between TAG and TCG (r = 0.43; p < .001).

CONCLUSIONS

CCTA-derived TAG and TCG do not offer any value in predicting ischemia assessed by SPECT-MPI. TAG is partly affected by differences in the coronary luminal area.

Serial change in perfusion-metabolism mismatch after coronary artery bypass grafting

OBJECTIVE

Myocardial ischemia is known to suppress fatty acid metabolism and favor glucose metabolism. However, changes in myocardial metabolism after coronary revascularization are not fully elucidated.

METHODS

Thirty-eight patients with coronary artery disease were retrospectively enrolled. These patients had undergone stress perfusion single photon emission computed tomography (SPECT) and ¹²³I-BMIPP SPECT in both the short-term (6.4 ± 4.7 months) and mid-term (29.9 ± 7.2 months) after isolated coronary artery bypass grafting. Tracer uptake was graded using a 17-segment, 5-point scoring model. Serial changes in SRS (summed rest score), SDS (summed difference score), the BMIPP score (total defect score of BMIPP), and the mismatch score (BMIPP score-SRS) were evaluated. In addition, persistent perfusion-metabolism mismatch (PM) was defined as mismatch score minus SDS of 3 or more during the mid-term postoperative period. The clinical parameters associated with PM were examined.

RESULTS

From short- to mid-term postoperative period, the extent of infarcted myocardium (SRS) did not change significantly (7.8 ± 8.0 to 7.1 ± 7.0, P = 0.117). The extent of ischemic myocardium (SDS), the BMIPP score and the mismatch score, which reflects perfusion-metabolism mismatch, were significantly improved (2.0 ± 2.8 to 0.7 ± 1.0, P = 0.010; 12.2 ± 9.0 to 9.5 ± 7.9, P < 0.001; 4.4 ± 3.7 to 2.5 ± 2.6, P < 0.001; respectively). Remarkably, perfusion-metabolism mismatch persisted in 13 patients (34%) even in the mid-term postoperative period. eGFR and SYNTAX score were independent predictors of persistent perfusion-metabolic mismatch in multivariable analysis (OR = 0.951, 95% CI 0.898-0.985, P = 0.010 and OR = 1.126, 95% CI 1.011-1.254, P = 0.031, respectively). The mismatch score both in the short- and mid-term significantly correlated with SYNTAX score (r = 0.400 and r = 0.472, respectively).

CONCLUSIONS

Fatty acid metabolism disturbance improved from short- to mid-term postoperative period in patients with successful reperfusion by coronary artery bypass grafting. However, in patients with severe atherosclerosis, impaired fatty acid metabolism was sustained until the mid-term postoperative period, even though ischemia had resolved.

Capabilities of Modern Semiconductor Gamma Cameras in Radionuclide Diagnosis of Coronary Artery Disease

This paper presents a review of the literature concerning the clinical application of modern semiconductor (CZT) gamma cameras in the radioinuclide diagnosis of coronary artery disease. It contains information on the diagnostic efficacy of myocardial perfusion studies performed with those cameras compared with the widely used scintillation (Anger) cameras, an overview of their effectiveness in comparison with coronary angiography (also fractional flow reserve) and currently available clinical results of a myocardial flow reserve measured with a dynamic SPECT study. Introduction of this imaging modality to the measurement of a myocardial flow reserve aims to facilitate access to this type of study compared to the less available and more expensive PET method used so far.

The effect of body mass index on high versus low administered activity protocol myocardial perfusion imaging scan time and effective dose using a cadmium zinc telluride camera in clinical practice

Cadmium Zinc Telluride (CZT) crystal-based myocardial perfusion imaging (MPI) cameras have increased count sensitivity compared to Anger cameras and can be used to lower either the injected activity or the image acquisition time. Institutions adopting CZT cameras need to decide whether to lower the injected activity or imaging time or attempt to lower both with a compromise. The aim of our study was to compare the scan time required to obtain similar count images using high activity protocol (HAP) versus low activity protocol (LAP) stratified by body mass index (BMI) and assess the impact on effective dose and our clinic workflow. Using a CZT camera, a cohort of 100 consecutive clinical patients imaged with LAP rest-stress MPI with approximately 185 MBq and 555 MBq activity was retrospectively compared to a similar cohort of 100 consecutive clinical patients imaged with HAP rest-stress MPI using approximately 370 MBq and 1110 MBq. Administered activity and BMI both had a statistically significant effect on scan time and radiation effective dose. LAP scans took an average of 9 min longer than HAP scans overall, P < 0.0001 and larger BMIs took longer than smaller BMIs, P < 0.0001. In addition, scan times were longer in men than women, P = 0.007. Effective dose was inversely proportional to BMI with an overall decrease of approximately 50% comparing LAP to HAP. For the same CZT camera, the LAP increased scan time while lowering the radiation effective dose when compared to HAP. The increase in scan time increased proportionally to BMI. The effective dose was inversely proportional to BMI. This increase in time did not have a significant impact on our local workflow, but its implications should be considered in the setting of LAP implementation, especially in obese or high patient volume practices.

Head-to-head comparison of a CZT-based all-purpose SPECT camera and a dedicated CZT cardiac device for myocardial perfusion and functional analysis

PURPOSE

To compare the outputs of a novel all-purpose SPECT camera equipped with CZT detectors (Discovery NM/CT 670) with the state-of-the-art represented by a dedicated CZT (Alcyone, Discovery 530c) cardiac camera in patients submitted to myocardial perfusion imaging (MPI).

METHODS

We included 19 patients that underwent sequential low-dose 99mTc-tetrofosmin (148-185 MBq during stress and 296-370 MBq at rest) MPI with Alcyone and Discovery 670 cameras. Quantitative (% tracer's uptake) and semi-quantitative analyses of perfusion data were performed for each scan. Moreover, major left ventricular (LV) functional and structural parameters were derived from each camera and compared.

RESULTS

The two cameras showed excellent correlation for segmental myocardial % uptake at stress (R = 0.90; P < 0.001) and at rest (R = 0.88; P < 0.001) with narrow Bland-Altman limits of agreement. The level of diagnostic agreement of Discovery 670 and Alcyone cameras regarding perfusion analysis was excellent (Cohen's κ 0.85). Similarly, the two cameras showed excellent correlation in the evaluation of LV ejection fraction (R = 0.95), peak filling rate (R = 0.97), and mass (R = 0.98).

CONCLUSIONS

Our preliminary results suggest that MPI with an all-purpose Discovery 670 CZT-SPECT camera is feasible, comparing well with the current state-of-the-art technology.

Prognostic Value of Diastolic Dysfunction Derived From D-SPECT in Coronary Artery Disease Patients With Normal Ejection Fraction

Diastolic dysfunction (DD) with normal systolic function has been elucidated to be associated with heart failure and worse prognosis. The recently introduced single photon emission computed tomography (SPECT) with dedicated cardiac cadmium-zinc-telluride (CZT) cameras (D-SPECT) is a novel method to quantitate left ventricular functional parameters. We aimed to evaluate the prognostic value of DD derived from D-SPECT in coronary artery disease (CAD) patients with normal ejection fraction. All CAD patients who underwent D-SPECT and invasive coronary angiography within 3 months were considered. DD was defined as peak filling rate (PFR) <2.1 end diastolic volume (EDV, ml)/s according to the D-SPECT results. Patients were divided into three groups: group 1 (n = 226)-normal PFR; group 2 (n = 67)-ischemia-related DD (abnormal stress PFR and normal rest PFR); and group 3 (n = 106)-rest DD (abnormal rest PFR). The primary clinical endpoint of the present study was a composite of heart failure events (HFE). A total of 399 consecutive CAD patients with normal systolic function undergoing stress D-SPECT were analyzed. The incidence rates of HFE among the three groups were 4.0, 7.5, and 11.3%, respectively. Cox regression analysis showed that the multivariate predictors of HFE were rest PFR, diabetes mellitus, obesity, and old age. DD derived from D-SPECT in CAD patients with normal ejection fraction is predictive of HFE.

Charge Sharing and Charge Loss in High-Flux Capable Pixelated CdZnTe Detectors

Cadmium zinc telluride (CdZnTe) detectors are known to suffer from polarization effects under high photon flux due to poor hole transport in the crystal material. This has led to the development of a high-flux capable CdZnTe material (HF-CdZnTe). Detectors with the HF-CdZnTe material have shown promising results at mitigating the onset of the polarization phenomenon, likely linked to improved crystal quality and hole carrier transport. Better hole transport will have an impact on charge collection, particularly in pixelated detector designs and thick sensors (>1 mm). In this paper, the presence of charge sharing and the magnitude of charge loss were calculated for a 2 mm thick pixelated HF-CdZnTe detector with 250 μm pixel pitch and 25 μm pixel gaps, bonded to the STFC HEXITEC ASIC. Results are compared with a CdTe detector as a reference point and supported with simulations from a Monte-Carlo detector model. Charge sharing events showed minimal charge loss in the HF-CdZnTe, resulting in a spectral resolution of 1.63 ± 0.08 keV Full Width at Half Maximum (FWHM) for bipixel charge sharing events at 59.5 keV. Depth of interaction effects were shown to influence charge loss in shared events. The performance is discussed in relation to the improved hole transport of HF-CdZnTe and comparison with simulated results provided evidence of a uniform electric field.

Role of microvascular dysfunction in left ventricular dysfunction in type 2 diabetes mellitus

BACKGROUND

Although microvascular disease (mVD) has been linked to poor cardiovascular outcomes in diabetes mellitus, the contribution of mVD to diabetic cardiomyopathy (DC) is unexplored. We investigated whether LV systolic and diastolic dysfunction is associated with mVD in T2DM.

METHODS

We recruited 32 asymptomatic patients with T2DM (age 71 ± 4 years, 31% females) from a community-based population. All underwent a comprehensive echocardiogram at baseline including assessment of global longitudinal strain (GLS) and diastolic function. Adenosine stress perfusion on cardiac magnetic resonance imaging (CMR) was performed in all patients. Coronary sinus flow (CSF) was measured offline at rest and peak stress with coronary flow reserve (CFR) calculated as the ratio of global stress and rest CSF.

RESULTS

Resting CSF was reduced in 15 (47%) compared to 4 (13%) with adenosine-stress (p = 0.023). Overall, CFR was observed to be reduced in the cohort (2.38 [IQR 2.20]). Abnormal CFR was not associated with diabetes duration of ≥10 years or poor glycaemic control. CFR was not associated with abnormal GLS (OR 1.04 [95% CI 0.49, 2.20], p = 0.93). However, a modest negative correlation was observed with e' and CFR (r = -0.49, p = 0.004).

CONCLUSION

This pilot study did not show correlation between subclinical systolic dysfunction and a novel MRI biomarker of microvascular disease. However, there was a weak correlation with myocardial relaxation. Confirmation of these findings in larger studies is indicated.

Diagnostic performance of myocardial perfusion imaging with conventional and CZT single-photon emission computed tomography in detecting coronary artery disease: A meta-analysis

BACKGROUND

We performed a meta-analysis to compare the diagnostic performance of conventional SPECT (C-SPECT) and cadmium-zinc-telluride (CZT)-SPECT systems in detecting angiographically proven coronary artery disease (CAD).

METHODS

Studies published between January 2000 and February 2018 were identified by database search. We included studies assessing C-SPECT or CZT-SPECT as a diagnostic test to evaluate patients for the presence of CAD, defined as at least 50% diameter stenosis on invasive coronary angiography. A study was eligible regardless of whether patients were referred for suspected or known CAD.

RESULTS

We identified 40 eligible articles (25 C-SPECT and 15 CZT-SPECT studies) including 7334 patients (4997 in C-SPECT and 2337 in CZT-SPECT studies). The pooled sensitivity and specificity were 85% and 66% for C-SPECT and 89% and 69% for CZT-SPECT imaging studies. The area under the curve was slightly higher for CZT-SPECT (0.89) compared to C-SPECT (0.83); accordingly, the summary diagnostic OR was 17 for CZT-SPECT and 11 for C-SPECT. The accuracy of the two tests slightly differs between C-SPECT and CZT-SPECT (chi-square 11.28, P < .05). At meta-regression analysis, no significant association between both sensitivity and specificity and demographical and clinical variables considered was found for C-SPECT and CZT-SPECT studies.

CONCLUSIONS

C-SPECT and CZT-SPECT have good diagnostic performance in detecting angiographic proven CAD, with a slightly higher accuracy for CZT-SPECT. This result supports the use of the novel gamma cameras in clinical routine practices also considering the improvements in acquisition time and radiation exposure reduction.

Paediatric Molecular Radiotherapy: Challenges and Opportunities

The common contemporary indications for paediatric molecular radiotherapy (pMRT) are differentiated thyroid cancer and neuroblastoma. It may also have value in neuroendocrine cancers, and it is being investigated in clinical trials for other diseases. pMRT is the prototypical biomarker-driven, precision therapy, with a unique mode of delivery and mechanism of action. It is safe and well tolerated, compared with other treatments. However, its full potential has not yet been achieved, and its wider use faces a number of challenges and obstacles. Paradoxically, the success of radioactive iodine as a curative treatment for metastatic thyroid cancer has led to a 'one size fits all' approach and limited academic enquiry into optimisation of the conventional treatment regimen, until very recently. Second, the specialised requirements for the delivery of pMRT are available in only a very limited number of centres. This limited capacity and geographical coverage results in reduced accessibility. With few enthusiastic advocates for this treatment modality, investment in research to improve treatments and broaden indications from both industry and national and charitable research funders has historically been suboptimal. Nonetheless, there is now an increasing interest in the opportunities offered by pMRT. Increased research funding has been allocated, and technical developments that will permit innovative approaches in pMRT are available for exploration. A new portfolio of clinical trials is being assembled. These studies should help to move at least some paediatric treatments from simply palliative use into potentially curative protocols. Therapeutic strategies require modification and optimisation to achieve this. The delivery should be personalised and tailored appropriately, with a comprehensive evaluation of tumour and organ-at-risk dosimetry, in alignment with the external beam model of radiotherapy. This article gives an overview of the current status of pMRT, indicating the barriers to progress and identifying ways in which these may be overcome.

Feasibility of simultaneous 99mTc-tetrofosmin and 123I-BMIPP dual-tracer imaging with cadmium-zinc-telluride detectors in patients undergoing primary coronary intervention for acute myocardial infarction

BACKGROUND

Simultaneous dual-tracer imaging using isotopes with close photo-peaks may benefit from improved properties of cadmium-zinc-telluride (CZT)-based scanners.

METHODS

Thirty patients having undergone primary percutaneous coronary intervention for acute myocardial infarction underwent single-(99mTc-tetrofosmin (TF) or 123I-BMIPP first) followed by simultaneous 99mTc-TF /123I-BMIPP dual-tracer imaging using a Discovery NM/CT 670 CZT. The values for the quantitative gated-SPECT (QGS) and the quantitative perfusion SPECT (QPS) were assessed.

RESULTS

The intra-class correlation (ICC) coefficients between the single- and dual-tracer imaging were high in all the QGS and QPS data (Summed motion score: 0.95, summed thickening score: 0.94, ejection fraction: 0.98, SRS for 99mTc-TF: 0.97/ for 123I-BMIPP: 0.95). Wall motion, wall thickening and rest scores per coronary-territory-based regions were also comparable between the single- and dual imaging (ICC coefficient > 0.91). The interrater concordance in the visual analysis for the infarction and perfusion-metabolism mismatch was significant for the global and regional left ventricle (P < 0.001).

CONCLUSION

The quantitative/semi-quantitative values for global and regional left-ventricular function, perfusion, and fatty acid metabolism were closely comparable between the dual-tracer imaging and the single-tracer mode. These data suggests the feasibility of the novel CZT-based scanner for the simultaneous 99mTc-TF /123I-BMIPP dual-tracer acquisitions in clinical settings.

SPECT/CT: Standing on the Shoulders of Giants, It Is Time to Reach for the Sky!

Twenty years ago, SPECT/CT became commercially available, combining the strengths of both techniques: the diagnostic sensitivity of SPECT and the anatomic detail of CT. Other benefits initially included attenuation correction of SPECT reconstructions, ultimately evolving to correction techniques that would enable absolute tracer uptake quantification. Recent developments in SPECT hardware include solid-state digital systems with higher sensitivity and resolution, using novel collimator designs based on tungsten. Similar advances in CT technology have been introduced in hybrid SPECT/CT systems, replacing low-end x-ray tubes with high-end multislice CT scanners equipped with iterative reconstruction, metal artifact reduction algorithms, and dual-energy capabilities. More recently, the design of whole-body SPECT/CT systems has taken another major leap with the introduction of a ring-shaped gantry equipped with multiple movable detectors surrounding the patient. These exciting developments have fueled efforts to develop novel SPECT radiopharmaceuticals, creating new chelators and prosthetic groups for radiolabeling. Innovative SPECT radionuclide pairs have now become available for radiolabeling with the potential for use as theranostic agents. The growth of precision medicine and the associated need for accurate radionuclide treatment dosimetry will likely drive the use of SPECT/CT in the near future. In addition, expanding clinical applications of SPECT/CT in other areas such as orthopedics offer exciting opportunities. Although it is true that the SPECT/CT ecosystem has seen several challenges during its development over the past 2 decades, it is now a feature-rich and mature tool ready for clinical prime time.

Rationale and design of the REgistry of Fast Myocardial Perfusion Imaging with NExt generation SPECT (REFINE SPECT)

BACKGROUND

We aim to establish a multicenter registry collecting clinical, imaging, and follow-up data for patients who undergo myocardial perfusion imaging (MPI) with the latest generation SPECT scanners.

METHODS

REFINE SPECT (REgistry of Fast Myocardial Perfusion Imaging with NExt generation SPECT) uses a collaborative design with multicenter contribution of clinical data and images into a comprehensive clinical-imaging database. All images are processed by quantitative software. Over 290 individual imaging variables are automatically extracted from each image dataset and merged with clinical variables. In the prognostic cohort, patient follow-up is performed for major adverse cardiac events. In the diagnostic cohort (patients with correlating invasive angiography), angiography and revascularization results within 6 months are obtained.

RESULTS

To date, collected prognostic data include scans from 20,418 patients in 5 centers (57% male, 64.0 ± 12.1 years) who underwent exercise (48%) or pharmacologic stress (52%). Diagnostic data include 2079 patients in 9 centers (67% male, 64.7 ± 11.2 years) who underwent exercise (39%) or pharmacologic stress (61%).

CONCLUSION

The REFINE SPECT registry will provide a resource for collaborative projects related to the latest generation SPECT-MPI. It will aid in the development of new artificial intelligence tools for automated diagnosis and prediction of prognostic outcomes.

Current Status of Myocardial Perfusion Imaging With New SPECT/CT Cameras

Myocardial perfusion imaging (MPI) with Single-Photon Emission Computed Tomography (SPECT) has a major role in the management of coronary artery disease. Recent technological advances regarding SPECT detectors with the use of solid-state detectors has allowed for improved imaging quality since a decade with dramatic dose and/or time reduction of imaging protocols due to improved sensitivity and spatial resolution, and is now performed as a routine exam. Interestingly, this new technology has modified our everyday practice, from acquisition protocols (low dose and ultra-fast protocols) to image semiology. Numerous studies have shown how these technical advances have allowed for improved patient management, with similar or improved diagnostic and prognostic information derived from MPI. These improvements have also led to the straightforward implementation of myocardial blood flow measurement. This article reviews the current status of MPI using new SPECT and SPECT/CT cameras.

Clinical quantitative cardiac imaging for the assessment of myocardial ischaemia

Cardiac imaging has a pivotal role in the prevention, diagnosis and treatment of ischaemic heart disease. SPECT is most commonly used for clinical myocardial perfusion imaging, whereas PET is the clinical reference standard for the quantification of myocardial perfusion. MRI does not involve exposure to ionizing radiation, similar to echocardiography, which can be performed at the bedside. CT perfusion imaging is not frequently used but CT offers coronary angiography data, and invasive catheter-based methods can measure coronary flow and pressure. Technical improvements to the quantification of pathophysiological parameters of myocardial ischaemia can be achieved. Clinical consensus recommendations on the appropriateness of each technique were derived following a European quantitative cardiac imaging meeting and using a real-time Delphi process. SPECT using new detectors allows the quantification of myocardial blood flow and is now also suited to patients with a high BMI. PET is well suited to patients with multivessel disease to confirm or exclude balanced ischaemia. MRI allows the evaluation of patients with complex disease who would benefit from imaging of function and fibrosis in addition to perfusion. Echocardiography remains the preferred technique for assessing ischaemia in bedside situations, whereas CT has the greatest value for combined quantification of stenosis and characterization of atherosclerosis in relation to myocardial ischaemia. In patients with a high probability of needing invasive treatment, invasive coronary flow and pressure measurement is well suited to guide treatment decisions. In this Consensus Statement, we summarize the strengths and weaknesses as well as the future technological potential of each imaging modality.

Shortened acquisition time in simultaneous 99mTc-tetrofosmin and 123I-β-methyl-p-iodophenyl pentadecanoic acid dual-tracer imaging with cadmium-zinc-telluride detectors in patients undergoing primary coronary intervention for acute myocardial infarction

OBJECTIVE

The use of cadmium-zinc-telluride-based scanners may increase the clinical feasibility of simultaneous dual-isotope imaging. In the current study, we sought to investigate a potential acquisition time in simultaneous Tc-tetrofosmin/I-β-methyl-p-iodophenyl pentadecanoic acid dual-isotope imaging using a Discovery NM/CT 670 cadmium-zinc-telluride.

METHODS

Simultaneous Tc-tetrofosmin/I-β-methyl-p-iodophenyl pentadecanoic acid dual-isotope imaging was performed in 29 patients who had undergone primary percutaneous coronary intervention for acute myocardial infarction. Referenced images with an acquisition time of 65 s/view (16.25 min) were reframed to produce images with acquisition times of 33, 16, and 8 s/view. The values for the quantitative-gated single-photon emission computed tomography (SPECT) and the quantitative perfusion SPECT were compared.

RESULTS

The quantitative-gated SPECT values for images with 33, 16, and 8 s/views showed good consistency with those for 65 s/view (the lower 95% confidence intervals for the intraclass correlation were ≥0.80). The quantitative perfusion SPECT values for Tc-tetrofosmin images with 33, 16, and 8 s/views also showed good consistency with those for 65 s/view; however, the quantitative perfusion SPECT values for I-β-methyl-p-iodophenyl pentadecanoic acid images with an acquisition time of 8 s/view were not consistent with the reference acquisition time of 65 s/view.

CONCLUSIONS

The quantitative-gated SPECT and quantitative perfusion SPECT values obtained from images with shorter acquisition times correlated with the values obtained from images with a reference acquisition time of 65 s/view; however, tracer-specific predisposition should be considered. These findings suggest that it is possible to reduce acquisition time when performing simultaneous Tc-tetrofosmin/I-β-methyl-p-iodophenyl pentadecanoic acid dual-tracer imaging with the novel cadmium-zinc-telluride scanner.

Myocardial Ischemic Burden and Differences in Prognosis Among Patients With and Without Diabetes: Results From the Multicenter International REFINE SPECT Registry

OBJECTIVE

Prevalence and prognostic impact of cardiovascular disease differ between patients with or without diabetes. We aimed to explore differences in the prevalence and prognosis of myocardial ischemia by automated quantification of total perfusion deficit (TPD) among patients with and without diabetes.

RESEARCH DESIGN AND METHODS

Of 20,418 individuals who underwent single-photon emission computed tomography myocardial perfusion imaging, 2,951 patients with diabetes were matched to 2,951 patients without diabetes based on risk factors using propensity score. TPD was categorized as TPD = 0%, 0% < TPD < 1%, 1% ≤ TPD < 5%, 5% ≤ TPD ≤ 10%, and TPD >10%. Major adverse cardiovascular events (MACE) were defined as a composite of all-cause mortality, myocardial infarction, unstable angina, or late revascularization.

RESULTS

MACE risk was increased in patients with diabetes compared with patients without diabetes at each level of TPD above 0 (P < 0.001 for interaction). In patients with TPD >10%, patients with diabetes had greater than twice the MACE risk compared with patients without diabetes (annualized MACE rate 9.4 [95% CI 6.7-11.6] and 3.9 [95% CI 2.8-5.6], respectively, P < 0.001). Patients with diabetes with even very minimal TPD (0% < TPD < 1%) experienced a higher risk for MACE than those with 0% TPD (hazard ratio 2.05 [95% CI 1.21-3.47], P = 0.007). Patients with diabetes with a TPD of 0.5% had a similar MACE risk as patients without diabetes with a TPD of 8%.

CONCLUSIONS

For every level of TPD >0%, even a very minimal deficit of 0% < TPD < 1%, the MACE risk was higher in the patients with diabetes compared with patients without diabetes. Patients with diabetes with minimal ischemia had comparable MACE risk as patients without diabetes with significant ischemia.

Differences in attenuation pattern in myocardial SPECT between CZT and conventional gamma cameras

BACKGROUND

In myocardial perfusion imaging (MPI), single-photon emission tomography (SPECT) soft-tissue attenuation by the abdomen, breasts, and lateral chest wall may create artifacts that mimic true perfusion defects. This may cause misdiagnosis of myocardial perfusion. The aim of the present study was to compare the localization, extent, and depth of attenuation artifacts in MPI SPECT for a multi-pinhole cadmium zinc telluride (CZT) camera vs a conventional gamma camera.

METHODS

Phantom and patient measurements were performed using a CZT camera (GE NM 530c) and a conventional gamma camera (GE Ventri). All images were attenuation corrected with externally acquired low-dose computed tomography. The localization, extent, and depth of the attenuation artifact were quantified by comparing attenuation-corrected and non-attenuation-corrected images.

RESULTS

Attenuation artifacts were shifted from the inferolateral wall to the lateral wall using the CZT camera compared to a conventional camera in both the patient and the phantom. The extent of the attenuation artifact was significantly larger for the CZT camera compared to the conventional camera (23 ± 5% vs 15 ± 5%, P < .001) for patients and the result was similar for the phantom (28% vs 19%). Furthermore, the depth of the attenuation artifact (percent of maximum counts) was less pronounced for the CZT camera than for the conventional camera, both for phantom measurements (73% vs 67%) and patients (72 ± 3% vs 68 ± 4%, P < .001).

CONCLUSIONS

Attenuation artifacts are found in different locations to different extents and depths when using a CZT camera vs a conventional gamma camera for MPI SPECT. This should be taken into consideration when evaluating MPI SPECT studies to avoid misinterpretation of myocardial perfusion distribution.

Gated SPECT myocardial perfusion imaging with cadmium-zinc-telluride detectors allows real-time assessment of dobutamine-stress-induced wall motion abnormalities

BACKGROUND

Left ventricular (LV) ejection fraction (EF) during high dobutamine stress (HD) by real-time gated-SPECT myocardial perfusion imaging (MPI) on a cadmium-zinc-telluride (CZT) gamma camera was validated versus cardiac magnetic resonance imaging (CMR).

METHODS AND RESULTS

After injecting 99mTc-tetrofosmin (320 MBq) in 50 patients (mean age 64 +/- 11 years), EF at rest and post-stress as well as relevant changes in EF at HD (ΔEF ≥ 5%) were assessed. CZT and CMR rest EF values yielded an excellent correlation and agreement (r = 0.96; P < 0.001; Bland-Altman limits of agreement (BA): + 0 to 14.8%). HD EF acquisition was feasible using CZT and correlated better to HD CMR EF than did post-stress CZT EF (r = 0.85 vs 0.76, respectively, all P < 0.001). Agreement in ΔEF detection between HD CMR and immediate post-stress CZT (reflecting standard acquisition using conventional SPECT camera unable to scan during stress) was 45%, while this increased to 85% with real-time HD CZT scan.

CONCLUSION

Real-time ultrafast dobutamine gated-SPECT MPI with a CZT device is feasible and provides accurate measurements of HD LV performance.

5-Year Prognostic Value of Quantitative Versus Visual MPI in Subtle Perfusion Defects: Results From REFINE SPECT

OBJECTIVES

This study compared the ability of automated myocardial perfusion imaging analysis to predict major adverse cardiac events (MACE) to that of visual analysis.

BACKGROUND

Quantitative analysis has not been compared with clinical visual analysis in prognostic studies.

METHODS

A total of 19,495 patients from the multicenter REFINE SPECT (REgistry of Fast Myocardial Perfusion Imaging with NExt generation SPECT) study (64 ± 12 years of age, 56% males) undergoing stress Tc-99m-labeled single-photon emission computed tomography (SPECT) myocardial perfusion imaging were followed for 4.5 ± 1.7 years for MACE. Perfusion abnormalities were assessed visually and categorized as normal, probably normal, equivocal, or abnormal. Stress total perfusion deficit (TPD), quantified automatically, was categorized as TPD = 0%, TPD >0% to <1%, ≤1% to <3%, ≤3% to <5%, ≤5% to ≤10%, or TPD >10%. MACE consisted of death, nonfatal myocardial infarction, unstable angina, or late revascularization (>90 days). Kaplan-Meier and Cox proportional hazards analyses were performed to test the performance of visual and quantitative assessments in predicting MACE.

RESULTS

During follow-up examinations, 2,760 (14.2%) MACE occurred. MACE rates increased with worsening of visual assessments, that is, the rate for normal MACE was 2.0%, 3.2% for probably normal, 4.2% for equivocal, and 7.4% for abnormal (all p < 0.001). MACE rates increased with increasing stress TPD from 1.3% for the TPD category of 0% to 7.8% for the TPD category of >10% (p < 0.0001). The adjusted hazard ratio (HR) for MACE increased even in equivocal assessment (HR: 1.56; 95% confidence interval [CI]: 1.37 to 1.78) and in the TPD category of ≤3% to <5% (HR: 1.74; 95% CI: 1.41 to 2.14; all p < 0.001). The rate of MACE in patients visually assessed as normal still increased from 1.3% (TPD = 0%) to 3.4% (TPD ≥5%) (p < 0.0001).

CONCLUSIONS

Quantitative analysis allows precise granular risk stratification in comparison to visual reading, even for cases with normal clinical reading.

High efficiency gamma camera enables ultra-low fixed dose stress/rest myocardial perfusion imaging

Aims

We validated a 1-day myocardial perfusion imaging (MPI) protocol using an ultra low-dose(ULD) equal for stress and rest on a cadmium zinc telluride (CZT).

Methods and results

Fifty-six patients underwent a 1-day MPI protocol using a standard (SD) 99mTc-tetrofosmin dose at stress (320 MBq) and rest (960 MBq) with 5 min acquisition time each (SD). Within 2 weeks MPI was repeated using ULD 99mTc-tetrofosmin equal for stress and rest (160 MBq) with 15 min acquisition time each (ULD). All scans were performed on a CZT camera (DNM 570c, GE Healthcare). Background subtraction was applied on the rest MPI of the ULD using P-mod software. Presence and extent of perfusion defect were analysed. Pearson's correlation was used to compare ejection fraction (EF), end diastolic volume (EDV), and end systolic volume (ESV) between both protocols. SD revealed ischaemia in 23, scar in 3, and an equivocal finding in 1 patient, while normal findings were documented in 29 patients. ULD resulted in the following findings: ischaemia 23, scar 3, and 30 normal scans. Congruence of SD and ULD was 22/23 for ischaemia, 3/3 for scar, and 29/29 in normal patients; one patient with ischaemia in SD was classified as scar in ULD. Overall agreement of ULD with SD was 98%. The mean extent of defect was comparable between SD and ULD for the stress (10% vs. 11%, respectively, P = NS) and rest studies (5% vs. 7%, respectively, P = NS). An excellent correlation between SD and ULD was found for EF (r = 0.93), EDV (r = 0.95), and ESV (r = 0.97).

Conclusion

CZT cameras may enable reliable MPI scanning in patients with known or suspected coronary artery disease using protocols with about a factor 4-decrease in radiation dose exposure compared with traditional protocols.

Comparison of CZT SPECT and conventional SPECT for assessment of contractile function, mechanical synchrony and myocardial scar in patients with heart failure

AIM

The aim of this study was to compare CZT-SPECT (CZT SPECT) to conventional SPECT (C-SPECT) in the assessment of left ventricular myocardial scar, contractile function, and mechanical synchrony in patients with heart failure (HF).

METHODS

Fifty-nine patients with HF who were referred for myocardial perfusion/metabolism imaging were enrolled. All patients underwent resting 99mTc-MIBI gated myocardial perfusion imaging using a CZT SPECT camera and a C-SPECT camera, respectively, and 18F-FDG PET myocardial metabolism imaging within three days. Summed rest score (SRS) and total perfusion defect (TPD) (as indices of perfusion abnormality), left ventricular (LV), end diastolic volume (EDV), end systolic volume (ESV), and ejection fraction (EF) (as indices of LV systolic function), and histogram band width (BW) and standard deviation (SD) (as indices of mechanical synchrony) were analyzed by automated software while the perfusion/metabolism patterns were analyzed visually.

RESULTS

There was a good correlation between CZT SPECT and C-SPECT for SRS and TPD. CZT SPECT tended to underestimate SRS and TPD compared to C-SPECT. CZT-SPECT and C-SPECT showed excellent agreement in assessing the perfusion/metabolism pattern though a small proportion of normal segments (6.6%) identified by CZT/PET exhibited mismatch pattern on C-SPECT/PET. CZT SPECT also showed excellent correlation with C-SPECT in measuring EDV, ESV, and EF. Finally, BW and SD measured by CZT SPECT correlated well with C-SPECT but CZT SPECT tended to overestimate BW and SD compared to C-SPECT.

CONCLUSION

CZT SPECT provided comparable data to C-SPECT for measuring LV scar, function and synchrony at a considerable reduction in imaging time. CZT SPECT holds a promise for comprehensive evaluation of myocardial performance in patients with HF.

Diagnostic value of cadmium-zinc-telluride myocardial perfusion imaging versus coronary angiography in coronary artery disease: A PRISMA-compliant meta-analysis

BACKGROUND

Rapid progress has been made in research of cadmium-zinc-telluride (CZT) technology in the last few years, which might serve as a new method to diagnose coronary artery disease. However, compared with coronary angiography, the diagnostic value of CZT is still controversial. We aimed to evaluate diagnosis value of coronary angiography versus CZT in coronary artery disease.

METHODS

We searched the database for eligible researches associated with CZT- myocardial perfusion imaging (MPI) and invasive coronary angiography, extracted the relevant data, and rigorously screened it according to the inclusion and exclusion criteria. The accuracy indicators included sensitivity, specificity, accuracy, positive and negative likelihood ratios.

RESULTS

According to the inclusion and exclusion criteria, we finally found 20 studies containing 2350 patients in this search. Pooled results showed that sensitivity of CZT-MPI was 0.84% and 95% confidence interval (95% CI): 0.78 to 0.89, specificity was 0.72, 95% CI (0.62-0.76), the specificity was lower apparently. The positive likelihood ratio was 3.0, 95% CI (2.4-3.8), the negative likelihood ratio was 0.22, 95% CI (0.16-0.31), diagnostic odds ratio was 14, 95% CI (7.84-17.42).

CONCLUSION

This meta-analysis showed that CZT-MPI had satisfactory sensitivity and specificity for diagnosing coronary artery disease. Larger studies are required for further evaluation.

High-speed scanning of planar images showing 123I-MIBG uptake using a whole-body CZT camera: a phantom and clinical study

Background

The heart-to-mediastinum ratio (HMR) obtained in myocardial sympathetic innervation imaging using ¹²³I-metaiodobenzylguanidine (MIBG) is used for heart failure or Lewy body diseases (LBD). Discovery NM/CT 670 CZT, a novel whole-body scanner, enables direct HMR measurements in planar images, in contrast to cardiac-dedicated CZT-based cameras which require specific post-processing reconstruction. We sought to investigate the clinical utility of the Discovery NM/CT 670 CZT for myocardial innervation imaging and the potential time reduction.

Results

Following preliminary phantom examinations, ¹²³I-MIBG planar imaging was performed in 36 patients with suspected or known LBD to measure HMRs with a collection time of 300 s. Images for different collection times were subsequently reframed using already acquired data, and changes in HMRs were evaluated.

The HMRs for patients with versus without clinically diagnosed LBD were 1.63 ± 0.08 versus 2.21 ± 0.08 at early phase (p < 0.001) and 1.54 ± 0.09 versus 2.08 ± 0.09 at delayed phase (p < 0.001). The difference of HMRs (300 s − other collection time) became greater as the collection time became shorter. There was good consistency in HMRs between the 300-s images (reference) and the 200-s (intra-class correlation (ICC) coefficients > 0.99), 100-s (ICC coefficients > 0.97), and 50-s (ICC coefficients > 0.89) images.

Conclusions

In planar images with a whole-body CZT-based camera, the HMRs of patients with LBD were significantly lower than those without. HMRs with the collection time of 50 s and longer showed good consistency with those of 300 s in the ICC analysis. These findings indicate a clinical utility of this novel scanner for HMR measurements and potential time reductions.

Electronic supplementary material

The online version of this article (10.1186/s13550-019-0491-z) contains supplementary material, which is available to authorized users.

The effect of CT-based attenuation correction on the automatic perfusion score of myocardial perfusion imaging using a dedicated cardiac solid-state CZT SPECT/CT

BACKGROUND

Data regarding cardiac cadmium-zinc-telluride (CZT)-specific augmented databases and their impact on CT-based attenuation correction (AC) perfusion scores in myocardial perfusion imaging (MPI) were obtained on a multiple-pinhole CZT SPECT/CT.

METHODS AND RESULTS

Summed stress (SSS) and rest scores (SRS) were measured using automated software in three independent patient groups: group 1 (n = 80) underwent MPI on both CZT and conventional sodium iodide (NaI) devices, group 2 (n = 80) with low coronary artery disease likelihood and normal MPI provided reference CZT databases; and group 3 (n = 152) served to compare AC and non-AC (NAC) scores on CZT. Group 1 CZT and NaI scores gave a significant 1:1 linear correlation for CZT scores referenced to the custom database vs NaI scores referenced to the default database, but these were not concordant when CZT scores were referenced to the default database. AC significantly decreased average SSS and SRS in men vs NAC, 4.29 ± 6.30 vs 5.37 ± 7.26 (P < 0.001) and 2.37 ± 4.72 vs 3.13 ± 5.85 (P < 0.001), but not in women, 2.28 ± 3.42 vs 2.28 ± 3.08 (p NS) and 0.46 ± 1.51 vs 0.61 ± 1.86, (p NS), respectively.

CONCLUSIONS

Specifically designed databases for solid-state CZT cardiac SPECT provide accurate quantitation of perfusion scores concordant with those previously validated for conventional SPECT. AC and NAC CZT scores differed significantly, especially in men.

Feasibility study of a novel general purpose CZT-based digital SPECT camera: initial clinical results

Background

The performance of a prototype novel digital single-photon emission computed tomography (SPECT) camera with multiple pixelated CZT detectors and high sensitivity collimators (Digital SPECT; Valiance X12 prototype, Molecular Dynamics) was evaluated in various clinical settings.

Images obtained in the prototype system were compared to images from an analog camera fitted with high-resolution collimators. Clinical feasibility, image quality, and diagnostic performance of the prototype were evaluated in 36 SPECT studies in 35 patients including bone (n = 21), brain (n = 5), lung perfusion (n = 3), and parathyroid (n = 3) and one study each of sentinel node and labeled white blood cells. Images were graded on a scale of 1–4 for sharpness, contrast, overall quality, and diagnostic confidence.

Results

Digital CZT SPECT provided a statistically significant improvement in sharpness and contrast in clinical cases (mean score of 3.79 ± 0.61 vs. 3.26 ± 0.50 and 3.92 ± 0.29 vs. 3.34 ± 0.47 respectively, p < 0.001 for both). Overall image quality was slightly higher for the digital SPECT but not statistically significant (3.74 vs. 3.66).

Conclusion

CZT SPECT provided significantly improved image sharpness and contrast compared to the analog system in the clinical settings evaluated. Further studies will evaluate the diagnostic performance of the system in large patient cohorts in additional clinical settings.

Deep Learning for Prediction of Obstructive Disease From Fast Myocardial Perfusion SPECT: A Multicenter Study

OBJECTIVES

The study evaluated the automatic prediction of obstructive disease from myocardial perfusion imaging (MPI) by deep learning as compared with total perfusion deficit (TPD).

BACKGROUND

Deep convolutional neural networks trained with a large multicenter population may provide improved prediction of per-patient and per-vessel coronary artery disease from single-photon emission computed tomography MPI.

METHODS

A total of 1,638 patients (67% men) without known coronary artery disease, undergoing stress ^99mTc-sestamibi or tetrofosmin MPI with new generation solid-state scanners in 9 different sites, with invasive coronary angiography performed within 6 months of MPI, were studied. Obstructive disease was defined as ≥70% narrowing of coronary arteries (≥50% for left main artery). Left ventricular myocardium was segmented using clinical nuclear cardiology software and verified by an expert reader. Stress TPD was computed using sex- and camera-specific normal limits. Deep learning was trained using raw and quantitative polar maps and evaluated for prediction of obstructive stenosis in a stratified 10-fold cross-validation procedure.

RESULTS

A total of 1,018 (62%) patients and 1,797 of 4,914 (37%) arteries had obstructive disease. Area under the receiver-operating characteristic curve for disease prediction by deep learning was higher than for TPD (per patient: 0.80 vs. 0.78; per vessel: 0.76 vs. 0.73: p < 0.01). With deep learning threshold set to the same specificity as TPD, per-patient sensitivity improved from 79.8% (TPD) to 82.3% (deep learning) (p < 0.05), and per-vessel sensitivity improved from 64.4% (TPD) to 69.8% (deep learning) (p < 0.01).

CONCLUSIONS

Deep learning has the potential to improve automatic interpretation of MPI as compared with current clinical methods.

Effect of a patient-specific minimum activity in stress myocardial perfusion imaging using CZT-SPECT: Prognostic value, radiation dose, and scan outcome

BACKGROUND

SPECT Myocardial perfusion imaging (MPI) is associated with a relatively high radiation burden and decreasing image quality in heavy patients. Patient-specific low-activity protocols (PLAPs) are suggested but follow-up data is lacking. Our aim was to compare the use of a standard fixed-activity protocol (FAP) with a PLAP in cadmium zinc telluride (CZT)-SPECT MPI.

METHODS

We retrospectively included 1255 consecutive patients who underwent CZT-SPECT stress-optional rest MPI. 668 Patients were scanned using FAP (370 MBq) and 587 patients using PLAP (2.25 MBq·kg-1). Percentage of scans interpreted as normal, radiation dose, and 1-year follow-up including hard event rates (all-cause death or non-fatal myocardial infarction) were collected and compared.

RESULTS

The percentage of scans interpreted as normal was 67% in FAP and 70% in PLAP groups (P = .29). The annualized hard event rates in these patients were 1.0% in the FAP and 0.9% in the PLAP group (P = .86). However, the mean radiation dose decreased by 23% for stress-only and by 15% to 2.6 mSv for stress-optional rest MPI after introduction of the PLAP (p<0.001).

CONCLUSIONS

Introduction of a patient-specific low-activity protocol does not affect the percentage of scans interpreted as normal or prognosis but significantly lowers the radiation dose for CZT-SPECT MPI.

Hybrid Imaging in Ischemic Heart Disease

Hybrid imaging for ischemic heart disease refers to the fusion of information from a single or usually from multiple cardiovascular imaging modalities enabling synergistic assessment of the presence, the extent, and the severity of coronary atherosclerotic disease along with the hemodynamic significance of lesions and/or with evaluation of the myocardial function. A combination of coronary computed tomography angiography with myocardial perfusion imaging, such as single-photon emission computed tomography and positron emission tomography, has been adopted in several centers and implemented in international coronary artery disease management guidelines. Interest has increased in novel hybrid methods including coronary computed tomography angiography-derived fractional flow reserve and computed tomography perfusion and these techniques hold promise for the imminent diagnostic and management approaches of patients with coronary artery disease. In this review, we discuss the currently available hybrid noninvasive imaging modalities used in clinical practice, research approaches, and exciting potential future technological developments.

The radiation dose to overweighted patients undergoing myocardial perfusion SPECT can be significantly reduced: validation of a linear weight-adjusted activity administration protocol

BACKGROUND

Large body size can cause a higher proportion of emitted photons being attenuated within the patient. Therefore, clinical myocardial perfusion SPECT (MPS) protocols often include unproportionally higher radioisotope activity to obese patients. The aim was to evaluate if a linear weight-adjusted low-dose protocol can be applied to obese patients and thereby decrease radiation exposure.

METHODS AND RESULT

Two hundred patients (>110 kg, BMI 18-41, [n = 69], ≤ 110 kg, BMI 31-58, [n = 131]) underwent 99mTc-tetrofosmin stress examination on a Cadmium Zinc Telluride or a conventional gamma camera using new generations of reconstruction algorithm (Resolution Recovery). Patients <110 kg were administered 2.5 MBq/kg, patients between 110 and 120 kg received 430 MBq and patients >120 kg received 570 MBq according to clinical routine. Patients >110 kg had 130% total number of counts in the images compared to patients <110 kg. Recalculating the counts to correspond to an administered activity of 2.5 MBq/kg resulted in similar number of counts across the groups. Image analyses in a subgroup with images corresponding to high activity and 2.5 MBq/kg showed no difference in image quality or ischemia quantification.

CONCLUSION

Linear low-dose weight-adjusted protocol of 2.5 MBq/kg in MPS can be applied over a large weight span without loss of counts or image quality, resulting in a significant reduction in radiation exposure to obese patients.

Diagnostic value of thallium-201 myocardial perfusion IQ-SPECT without and with computed tomography-based attenuation correction to predict clinically significant and insignificant fractional flow reserve: A single-center prospective study

The aim of this study was to clarify the predictive value of fractional flow reserve (FFR) determined by myocardial perfusion imaging (MPI) using thallium (Tl)-201 IQ-SPECT without and with computed tomography-based attenuation correction (CT-AC) for patients with stable coronary artery disease (CAD).We assessed 212 angiographically identified diseased vessels using adenosine-stress Tl-201 MPI-IQ-SPECT/CT in 84 consecutive, prospectively identified patients with stable CAD. We compared the FFR in 136 of the 212 diseased vessels using visual semiquantitative interpretations of corresponding territories on MPI-IQ-SPECT images without and with CT-AC.FFR inversely correlated most accurately with regional summed difference scores (rSDS) in images without and with CT-AC (r = -0.584 and r = -0.568, respectively, both P < .001). Receiver-operating characteristics analyses using rSDS revealed an optimal FFR cut-off of <0.80 without and with CT-AC. Although the diagnostic accuracy of FFR <0.80 did not significantly differ, FFR ≥0.82 was significantly more accurate with, than without CT-AC. Regions with rSDS ≥2 without or with CT-AC predicted FFR <0.80, and those with rSDS ≤1 without and with CT-AC predicted FFR ≥0.81, with 73% and 83% sensitivity, 84% and 67% specificity, and 79% and 75% accuracy, respectively.Although limited by the sample size and the single-center design, these findings showed that the IQ-SPECT system can predict FFR at an optimal cut-off of <0.80, and we propose a novel application of CT-AC to MPI-IQ-SPECT for predicting clinically significant and insignificant FFR even in nonobese patients.

Myocardial ischemia in the absence of obstructive coronary lesion: The role of post-stress diastolic dysfunction in detecting early coronary atherosclerosis

BACKGROUND

The interactions between non-obstructive coronary atherosclerosis (<50% stenosis) and myocardial perfusion and functional parameters on myocardial perfusion imaging (MPI) have never been evaluated.

METHODS AND RESULTS

One-hundred and ninety-five patients were submitted to stress-rest MPI and invasive coronary angiography. The presence of obstructive coronary lesions (>50% stenosis) was excluded. The summed stress score (SSS) was calculated in every patient. Moreover, the left ventricular (LV) ejection fraction (EF) and peak filling rate (PFR) were computed from gated MPI images as measures of systolic and diastolic functions. Sixty/195 patients (31%) showed the presence of non-obstructive atherosclerosis (>20% and <50% diameter reduction). Interestingly, they presented a higher SSS than those with normal coronary arteries (P < 0.001) despite a similar myocardial scar burden. If compared to patients with normal coronary arteries, those with non-obstructive atherosclerosis showed more abnormal post-stress PFR values (2.5 ± 0.9 vs 2.9 ± 0.8, P = 0.004), despite a similar EF. On multivariate analysis, the presence non-obstructive atherosclerosis was the only significant predictor (P = 0.026) of post-stress LV diastolic impairment, independently from perfusion parameters.

CONCLUSIONS

In patients without anatomically significant coronary lesions, the development of post-stress LV diastolic dysfunction on MPI associates with the presence of non-obstructive atherosclerosis on coronary angiography.

Reducing the small-heart effect in pediatric gated myocardial perfusion single-photon emission computed tomography

BACKGROUND

We compared two reconstruction algorisms and two cardiac functional evaluation software programs in terms of their accuracy for estimating ejection fraction (EF) of small hearts (SH).

METHODS

The study group consisted of 66 pediatric patients. Data were reconstructed using a filtered back projection (FBP) method without the resolution correction (RC) and an iterative method based on an ordered subset expectation maximization (OSEM) algorithm with the RC. EF was evaluated using two software programs of quantitative gated single-photon emission computed tomography (SPECT) (QGS) and cardioREPO. We compared the EF of gated myocardial perfusion SPECT to echocardiographic measurement (Echo).

RESULTS

Forty-eight of 66 patients had an end-systolic volume < 20 mL which was used as the criterion for being included in the SH group, and the SH effect led to an overestimation of EF. While significant differences were observed between Echo (66.9 ± 5.0%) and QGS-FBP without RC (76.9 ± 8.4%, P < .0001), QGS-OSEM with RC (76.6 ± 8.6%, P < .0001), and cardioREPO-FBP without RC (72.1 ± 10.0%, P = .0011), no significant difference was observed between Echo and cardioREPO-OSEM with RC (67.4 ± 6.1%) in SH group.

CONCLUSIONS

In pediatric gated myocardial perfusion SPECT, the SH effect can be significantly reduced when an OSEM algorithm is used with RC in combination with the specific cardioREPO algorithm.