Novel solid-state-detector dedicated cardiac camera for fast myocardial perfusion imaging: multicenter comparison with standard dual detector cameras

Stress thallium-201/rest technetium-99m sequential dual-isotope high-speed myocardial perfusion imaging validation versus invasive coronary angiography

BACKGROUND

Recent advances in nuclear myocardial perfusion imaging (MPI) have made it possible to develop a dual-isotope protocol for high-speed acquisition with image quality and radiation delivery comparable to that obtained with conventional single isotope protocols. So far, no study has compared dual-isotope high-speed MPI to invasive coronary angiography (ICA) in a large cohort using a Cadmium-zinc-telluride SPECT system.

METHODS

Over a 1-year period (May 2011 to April 2012), 1366 patients underwent dual-isotope high-speed MPI. Patients with ICA within 3 months after dual-isotope high-speed MPI were included together with patients with a low likelihood of coronary artery disease (CAD) in order to assess normalcy rate. Global summed stress score (SSS) and summed rest score (SRS) were calculated, and ICA results were analyzed independently. The main end point was a patient-based assessment of the diagnostic performance of dual-isotope high-speed MPI in detecting or ruling out significant CAD (>70% reduction in lumen diameter).

RESULTS

Inclusion criteria were fulfilled for 214 patients (143 men; age 60 ± 14 years; ICA, n = 104; low likelihood for CAD, n = 110). An exercise stress test was performed in 62% of patients and a pharmacological stress test was performed with either dipyridamole (32%) or dobutamine (6%). Average examination duration was 22.4 ± 4.5 minutes. Mean SSS, SRS, and SDS were 8.0 ± 4.9, 3.1 ± 4.3, and 5.0 ± 3.2, respectively. Prevalence of angiographic CAD was 75%. ICA detected stenosis in the left main trunk, left anterior descending artery, left circumflex artery, and right coronary artery in 4, 33, 31, and 42 patients, respectively. Sensitivity of dual-isotope high-speed MPI was 94%, normalcy rate was 92%, and accuracy was 83% for detecting CAD.

CONCLUSION

Dual-isotope high-speed MPI is reliable at detecting or ruling out CAD. NCT01785589.

Flow-Dependent Uptake of ¹²³I-CMICE-013, a Novel SPECT Perfusion Agent, Compared with Standard Tracers

Rotenone derivatives have shown promise in myocardial perfusion imaging (MPI). CMICE-013 is a novel (123)I-labeled rotenone derivative developed for SPECT MPI. The objective of this study was to assess the image quality of CMICE-013 and compare its uptake with tetrofosmin, sestamibi, and (201)Tl in vivo in a porcine model of stress-induced myocardial ischemia.

METHODS

Microspheres were injected simultaneously with the radiotracer injections at rest and stress to measure blood flow. Mimicking a 1-d tetrofosmin protocol, stress imaging used 3 times as much activity and occurred 1 h after the rest injection. SPECT images were obtained at both rest and stress. After imaging, the heart was sectioned into 44-50 pieces. In each heart sample, the tracer uptake was measured in a γ counter. The images were aligned, and the decay-corrected ratio of the signals at rest and stress was used to separate the well-counter signal into rest and stress components. The uptake at rest and stress was compared with microsphere flow measurements.

RESULTS

The CMICE-013 images showed good contrast between the heart and surrounding organs, with heart-to-liver and heart-to-lung uptake ratios similar to those of the standard tracers. Uptake of CMICE-013 was 1.5% of the injected dose at rest and increased more rapidly with increased blood flow than did the standard SPECT tracers. The percentage injected dose of CMICE-013 taken up by the heart was greater (P < 0.05) than (201)Tl, tetrofosmin, or sestamibi at flows greater than 1.5 mL/min/g.

CONCLUSION

CMICE-013 is a promising new SPECT MPI agent.

Cardiac function changes with switching from the supine to prone position: analysis by quantitative semiconductor gated single-photon emission computed tomography

BACKGROUND

Prone positioning is required in certain operations such as spinal surgery. Changes in cardiac function in the prone position have been studied with various methodologies. Few studies have investigated changes in left ventricular diastolic function and rhythm in subjects turned prone.

METHODS AND RESULTS

Cardiac function was evaluated in the supine and prone positions in 90 patients without atrial fibrillation who underwent (99m)Tc-tetrofosmin quantitative gated single-photon emission computed tomography. Three groups of 30 patients each were classified as "no history of myocardial ischemia or cardiomyopathy" (Group A), "history of myocardial infarction" (Group B), and "ischemic heart disease without myocardial infarction history" (Group C). Upon assuming the prone position, the cardiac index and any dyssynchrony worsened in all groups. Ejection fraction changes occurred only in Group B, and diastolic function changes occurred in Groups B and C, but not in Group A. The changes caused by prone positioning were more severe in the patients with poor cardiac function.

CONCLUSIONS

Prone positioning induces significant changes in systolic and diastolic function, as well as dyssynchrony. The negative effects of prone positioning are more severe in patients with poor baseline cardiac function.

Scatter correction improves concordance in SPECT MPI with a dedicated cardiac SPECT solid-state camera

PURPOSE

Correction for photon attenuation and scatter improves image quality with conventional NaI-based gamma cameras but evaluation of these corrections for novel solid-state dedicated cardiac cameras is limited. In this study, we assess the accuracy of dual-energy-window (DEW) scatter correction (SC) applied to clinically acquired (99m)Tc-tetrofosmin myocardial perfusion images obtained on a dedicated multi-pinhole camera with cadmium-zinc-telluride (CZT) detectors (GE Discovery NM530) compared to DEW scatter-corrected images from our conventional SPECT camera (GE Infinia Hawkeye 4; INF).

METHODS

A modified DEW SC method was formulated to account for the detection of primary photons in the lower energy window (120 keV ± 5%) with CZT detectors, in addition to estimating the scattered photons detected in the photopeak window (140 keV ± 10%). Phantom experiments were used to estimate the DEW correction parameters. Data from 108 patients, acquired using a standard rest/stress Tc-99m-tetrofosmin SPECT/CT protocol on both cameras, were reconstructed with no correction (NC), attenuation correction (AC), and AC with DEW-SC. Images were compared based on the summed stress/rest/difference scores (SSS/SRS/SDS) calculated by clinical software.

RESULTS

The correlation between SSS/SRS for the two cameras was excellent (r ≥ 0.94). The mean difference between cameras was <0.4 for SSS/SRS/SDS scores. Since datasets did not follow a normal distribution, non-parametric tests were used to show significant differences between datasets. Classification of disease (SSS) was highly correlated, as ranked by the two cameras (kendall's tau = 0.72, P < .001). AC significantly reduced the mean difference between the two cameras for SSS/SRS compared to NC. AC without SC on the CZT introduced a bias towards higher scores when compared to the INF, which was reduced after applying SC. Although SC increased noise, the scores for the AC/SC images were not significantly different between the two cameras (P > .1).

CONCLUSIONS

DEW-SC on the CZT camera was feasible and produced images that are not significantly different from those acquired on the INF camera. Although use of SC on CZT images does increase noise, the resultant noise does not introduce bias relative to the INF camera.

Approaches to reducing radiation dose from radionuclide myocardial perfusion imaging

Radionuclide myocardial perfusion imaging (MPI) plays a vital role in the evaluation and management of patients with coronary artery disease. However, because of a steep growth in MPI in the mid 2000s, concerns about inappropriate use of MPI and imaging-related radiation exposure increased. In response, the professional societies developed appropriate-use criteria for MPI. Simultaneously, novel technology, image-reconstruction software for traditional scanners, and dedicated cardiac scanners emerged and facilitated the performance of MPI with low-dose and ultra-low-dose radiotracers. This paper provides a practical approach to performing low-radiation-dose MPI using traditional and novel technologies.

A performance comparison of novel cadmium-zinc-telluride camera and conventional SPECT/CT using anthropomorphic torso phantom and water bags to simulate soft tissue and breast attenuation

PURPOSES

This study was aimed to compare the physical performances of cadmium-zinc-telluride (CZT) camera and conventional Anger camera. An anthropomorphic torso phantom and water bags to simulate breasts were used to evaluate artifacts arising from soft tissue attenuation.

MATERIALS AND METHODS

Linear source studies were performed to evaluate extrinsic resolution of CZT camera (Discovery NM 530c, GE) and conventional single-photon emission computed tomography (SPECT) Anger camera (Symbia T2, Siemens). Three sets of phantom experiments: cardiac phantom only (phantom H), anthropomorphic torso phantom added (phantom T), and torso phantom with water bags attached (phantom B), with Tc-99m were performed on both scanners. Imaging performances were evaluated through count sensitivity, contrast-to-noise ratio, quantitative sharpness profile, wall thickness, perfusion uniformity (measured by standard deviation of perfusion percentage of 20 segments using quantitative perfusion SPECT (QPS) software, Cedars-Sinai), and visual imaging quality (using 20-segment sum defect scores (SDS) of QPS) for CZT camera, conventional SPECT without and with computed tomography transmission attenuation correction (AC).

RESULTS

CZT cameras had higher extrinsic resolution than conventional SPECT. Myocardium count sensitivity of CZT camera is about threefold of conventional SPECT. Contrast-to-noise ratios and sharpness profiles are higher on CZT camera but degraded while extracardiac soft tissue presented. Myocardial walls measured on CZT images were thicker. Images of CZT had lower SDS, while AC reduced the differences of SDS between CZT and CC. Perfusion images from CZT had the better uniformity than SPECT without or with AC. Breast attenuation was less prominent on CZT camera than conventional SPECT, while inferior and inferolateral segments still suffer marked soft tissue attenuation on CZT camera.

CONCLUSIONS

CZT camera has better physical performance and image quality with less artificial perfusion defects than conventional SPECT. CZT camera also has less breast attenuation than conventional SPECT. However, extracardiac soft tissue may degrade the superior performance of CZT camera, and attenuation correction methods are still needed to solve the attenuation issues in inferior and inferolateral myocardium.

Assessment of a Monte-Carlo simulation of SPECT recordings from a new-generation heart-centric semiconductor camera: from point sources to human images

Geant4 application for tomographic emission (GATE), a Monte-Carlo simulation platform, has previously been used for optimizing tomoscintigraphic images recorded with scintillation Anger cameras but not with the new-generation heart-centric cadmium-zinc-telluride (CZT) cameras. Using the GATE platform, this study aimed at simulating the SPECT recordings from one of these new CZT cameras and to assess this simulation by direct comparison between simulated and actual recorded data, ranging from point sources to human images. Geometry and movement of detectors, as well as their respective energy responses, were modeled for the CZT 'D.SPECT' camera in the GATE platform. Both simulated and actual recorded data were obtained from: (1) point and linear sources of (99m)Tc for compared assessments of detection sensitivity and spatial resolution, (2) a cardiac insert filled with a (99m)Tc solution for compared assessments of contrast-to-noise ratio and sharpness of myocardial borders and (3) in a patient with myocardial infarction using segmented cardiac magnetic resonance imaging images. Most of the data from the simulated images exhibited high concordance with the results of actual images with relative differences of only: (1) 0.5% for detection sensitivity, (2) 6.7% for spatial resolution, (3) 2.6% for contrast-to-noise ratio and 5.0% for sharpness index on the cardiac insert placed in a diffusing environment. There was also good concordance between actual and simulated gated-SPECT patient images for the delineation of the myocardial infarction area, although the quality of the simulated images was clearly superior with increases around 50% for both contrast-to-noise ratio and sharpness index. SPECT recordings from a new heart-centric CZT camera can be simulated with the GATE software with high concordance relative to the actual physical properties of this camera. These simulations may be conducted up to the stage of human SPECT-images even if further refinement is needed in this setting.

Development and validation of a patient-tailored dose regime in myocardial perfusion imaging using CZT-SPECT

BACKGROUND

Guidelines for SPECT myocardial perfusion imaging (MPI) traditionally recommend a fixed tracer dose. Yet, clinical practice shows degraded image quality in heavier patients. The aim was to optimize and validate the tracer dose and scan time to obtain a constant image quality less dependent on patients' physical characteristics.

METHODS

125 patients underwent Cadmium Zinc Telluride (CZT)-SPECT stress MPI using a fixed Tc-99m-tetrofosmin tracer dose. Image quality was scored by three physicians on a 4-point grading scale and related to the number of photon counts normalized to tracer dose and scan time. Counts were correlated with various patient-specific parameters dealing with patient size and weight to find the best predicting parameter. From these data, a formula to provide constant image quality was derived, and subsequently tested in 92 new patients.

RESULTS

Degradation in image quality and photon counts was observed for heavier patients for all patients' specific parameters (P < .01). We found body weight to be the best-predicting parameter for image quality and derived a new dose formula. After applying this new body weight-depended tracer dose and scan time in a new group, image quality was found to be constant (P > .19) in all patients.

CONCLUSIONS

Also in CZT SPECT image quality decreases with weight. The use of a tracer dose and scan time that depends linearly on patient's body weight corrected for the varying image quality in CZT-SPECT MPI. This leads to better radiation exposure justification.

Effect of co-ligands on chemical and biological properties of (99m)Tc(III) complexes [(99m)Tc(L)(CDO)(CDOH)2BMe] (L=Cl, F, SCN and N3; CDOH2=cyclohexanedione dioxime)

INTRODUCTION

(99m)Tc-Teboroxime ([(99m)TcCl(CDO)(CDOH)2BMe]) is a member of the BATO (boronic acid adducts of technetium dioximes) class of (99m)Tc(III) complexes. This study sought to explore the impact of co-ligands on solution stability, heart uptake and myocardial retention of [(99m)Tc(L)(CDO)(CDOH)2BMe] ((99m)Tc-Teboroxime: L=Cl; (99m)Tc-Teboroxime(F): L=F; (99m)Tc-Teboroxime(SCN): L=SCN; and (99m)Tc-Teboroxime(N3): L=N3).

METHODS

Radiotracers (99m)Tc-Teboroxime(L) (L=F, SCN and N3) were prepared by reacting (99m)Tc-Teboroxime with NaF, NaSCN and NaN3, respectively. Biodistribution and imaging studies were carried out in Sprague-Dawley rats. Image quantification was performed to compare their heart retention and liver clearance kinetics.

RESULTS

Complexes (99m)Tc-Teboroxime(L) (L=F, SCN and N3) were prepared in high yield with high radiochemical purity. All new radiotracers were stable for >6h in the kit matrix. In its HPLC chromatogram, (99m)Tc-Teboroxime showed one peak at ~15.5 min, which was shorter than that of (99m)Tc-Teboroxime(F) (~16.4 min). There were two peaks for (99m)Tc-Teboroxime(SCN) at 16.5 and 18.3 min. (99m)Tc-Teboroxime(N3) appeared as a single peak at 18.4 min. Their heart retention and liver clearance curves were best fitted to the bi-exponential decay function. The half-times of fast/slow components were 1.6±0.4/60.7±8.9 min for (99m)Tc-Teboroxime, 0.8±0.2/101.7±20.7 min for (99m)Tc-Teboroxime(F), 1.2±0.3/84.8±16.6 min for (99m)Tc-Teboroxime(SCN), and 2.9±0.9/51.6±5.0 min for (99m)Tc-Teboroxime(N3). The 2-min heart uptake followed the order of (99m)Tc-Teboroxime (3.00±0.37%ID/g)>(99m)Tc-Teboroxime(N3) (2.66±0.01 %ID/g)≈(99m)Tc-Sestamibi (2.55±0.46 %ID/g)>(99m)TcN-MPO (2.38±0.15 %ID/g). (99m)Tc-Teboroxime remains the best in first-pass extraction. The best image acquisition window is 0-5 min for (99m)Tc-Teboroximine and 0-15 min for (99m)Tc-Teboroximine(N3).

CONCLUSION

Co-ligands had significant impact on the heart uptake and myocardial retention of complexes [(99m)Tc(L)(CDO)(CDOH)2BMe] (L=Cl, F, SCN and N3). Future studies should be directed towards minimizing the liver uptake and radioactivity accumulation in the blood vessels while maintaining their high heart uptake.

Diagnostic performance of a novel cadmium-zinc-telluride gamma camera system assessed using fractional flow reserve

BACKGROUND

Although the novel cadmium-zinc-telluride (CZT) camera system provides excellent image quality, its diagnostic value using thallium-201 as assessed on coronary angiography (CAG) and fractional flow reserve (FFR) has not been validated. METHODS AND RESULTS: To evaluate the diagnostic accuracy of the CZT ultrafast camera system (Discovery NM 530c), 95 patients underwent stress thallium-201 single-photon emission computed tomography (SPECT) and then CAG within 3 months. Image acquisition was performed in the supine and prone positions after stress for 5 and 3 min, respectively, and in the supine position at rest for 10 min. Significant stenosis was defined as ≥90% diameter narrowing on visual estimation, or a lesion with <90% and ≥50% stenosis and FFR ≤0.75. To detect individual coronary stenosis, the respective sensitivity, specificity, and accuracy were 90%, 64%, and 78% for left anterior descending coronary artery stenosis, 78%, 84%, and 81% for left circumflex stenosis, and 83%, 47%, and 60% for right coronary artery (RCA) stenosis. The combination of prone and supine imaging had a higher specificity for RCA disease than supine imaging alone (65% vs. 47%), with an improvement in accuracy from 60% to 72%.

CONCLUSIONS

Using thallium-201 with short acquisition time, combined with prone imaging, CZT SPECT had a high diagnostic yield in detecting significant coronary stenosis as assessed using FFR.

Segmental and global left ventricular function assessment using gated SPECT with a semiconductor Cadmium Zinc Telluride (CZT) camera: phantom study and clinical validation vs cardiac magnetic resonance

BACKGROUND

We evaluated gated-SPECT using a Cadmium-Zinc-Telluride (CZT) camera for assessing global and regional left ventricular (LV) function.

METHODS

A phantom study evaluated the accuracy of wall thickening assessment using systolic count increase on both Anger and CZT (Discovery 530NMc) cameras. The refillable phantom simulated variable myocardial wall thicknesses. The apparent count increase (%CI) was compared to the thickness increase (%Th). CZT gated-SPECT was compared to cardiac magnetic resonance (CMR) in 27 patients. Global and regional LV function (wall thickening and motion) were quantified and compared between SPECT and CMR data.

RESULTS

In the phantom study using a 5-mm object, the regression between %CI and %Th was significantly closer to the line of identity (y = x) with the CZT (R (2) = 0.9955) than the Anger (R (2) = 0.9995, P = .03). There was a weaker correlation for larger objects (P = .003). In patients, there was a high concordance between CZT and CMR for ESV, EDV, and LVEF (all CCC >0.80, P < .001). CZT underestimated %CI and wall motion (WM) compared to CMR (P < .001). The agreement to CMR was better for WM than wall thickening.

CONCLUSION

The Discovery 530NMc provided accurate measurements of global LV function but underestimated regional wall thickening, especially in patients with increased wall thickness.

Importance of correct patient positioning in myocardial perfusion SPECT when using a CZT camera

INTRODUCTION

Myocardial perfusion single photon emission computed tomography (MPS) is one of the most widely used diagnostic methods in patients with suspected ischemic heart disease (IHD). Recently, a novel technique based on cadmium-zinc-telluride (CZT) detectors, pinhole collimators, and a stationary gantry was introduced for MPS. The aim of this work was to investigate how patient positioning affects the reconstructed MPS images using this novel technique.

MATERIALS AND METHODS

Eighteen patients referred for a clinical MPS due to suspected IHD were included in the study. All patients underwent MPS imaging on a GE Discovery NM 530c CZT camera. After image acquisition with the heart positioned in the center of the quality field of view (QFOV), the patients were re-imaged in different positions 5-20 mm off-center. The heart was still positioned within the limits of the QFOV during the off-center scans. The summed stress score and/or the summed rest score (SSS and/or SRS) for the acquisition performed in the center was compared to the same parameter for the acquisitions performed off-center.

RESULTS

There was a statistically significant increase in SSS and/or SRS when imaging was performed with the heart 5-20 mm outside the center of the QFOV compared to optimal positioning (7.7 ± 1.3 vs 6.6 ± 1.3, P = .006). The SSS and/or SRS increased with ≥2 U in 35% (14/40) of the off-center examinations.

CONCLUSION

It is important to carefully position the patient's heart within the center of the QFOV when performing MPS with the Discovery NM 530c CZT camera to avoid positioning-related image artifacts that could affect the diagnostic accuracy.

Development of kit formulations for (99m) TcN-MPO: a cationic radiotracer for myocardial perfusion imaging

The objective of this study was to develop a kit formulation for [(99m) TcN(mpo)(PNP5)](+) (MPO = 2-mercaptopyridine oxide), ((99m) TcN-MPO) to support its clinical evaluations as a SPECT radiotracer. Radiolabeling studies were performed using three different formulations (two-vial formulation and single-vial formulations with/without SnCl2 ) to explore the factors influencing radiochemical purity (RCP) of (99m) TcN-MPO. We found that the most important factor affecting the RCP of (99m) TcN-MPO was the purity of PNP5. (99m) TcN-MPO was prepared >98% RCP (n = 20) using the two-vial formulation. For single-vial formulations with/without SnCl2 , β-cyclodextrin (β-CD) is particularly useful as a stabilizer for PNP5. The RCP of (99m) TcN-MPO was 95-98% using β-CD, but its RCP was only 90-93% with γ-cyclodextrin (γ-CD). It seems that PNP5 fits better into the inner cavity of β-CD, which forms more stable inclusion complex than γ-CD in the single-vial formulations. The results from biodistribution and imaging studies in Sprague-Dawley rats clearly demonstrated biological equivalence of three different formulations. Single photon-emission computed tomography data suggested that high quality images could be obtained at 0-30-min post-injection without significant interference from the liver radioactivity. Considering the ease for (99m) Tc-labeling and high RCP of (99m) TcN-MPO, the non-SnCl2 single-vial formulation is an attractive choice for future clinical studies.

Depressive symptoms are associated with mental stress-induced myocardial ischemia after acute myocardial infarction

OBJECTIVES

Depression is an adverse prognostic factor after an acute myocardial infarction (MI), and an increased propensity toward emotionally-driven myocardial ischemia may play a role. We aimed to examine the association between depressive symptoms and mental stress-induced myocardial ischemia in young survivors of an MI.

METHODS

We studied 98 patients (49 women and 49 men) age 38-60 years who were hospitalized for acute MI in the previous 6 months. Patients underwent myocardial perfusion imaging at rest, after mental stress (speech task), and after exercise or pharmacological stress. A summed difference score (SDS), obtained with observer-independent software, was used to quantify myocardial ischemia under both stress conditions. The Beck Depression Inventory-II (BDI-II) was used to measure depressive symptoms, which were analyzed as overall score, and as separate somatic and cognitive depressive symptom scores.

RESULTS

There was a significant positive association between depressive symptoms and SDS with mental stress, denoting more ischemia. After adjustment for demographic and lifestyle factors, disease severity and medications, each incremental depressive symptom was associated with 0.14 points higher SDS. When somatic and cognitive depressive symptoms were examined separately, both somatic [β = 0.17, 95% CI: (0.04, 0.30), p = 0.01] and cognitive symptoms [β = 0.31, 95% CI: (0.07, 0.56), p = 0.01] were significantly associated with mental stress-induced ischemia. Depressive symptoms were not associated with ischemia induced by exercise or pharmacological stress.

CONCLUSION

Among young post-MI patients, higher levels of both cognitive and somatic depressive symptoms are associated with a higher propensity to develop myocardial ischemia with mental stress, but not with physical (exercise or pharmacological) stress.

Advances in SPECT in evaluating coronary disease

Myocardial perfusion scintigraphy is the longest established of the functional imaging investigations for patients with known or suspected coronary artery disease. This article describes recent technical and clinical advances that are ensuring that the technique remains relevant some 40 years after its first introduction.

Comparison of image quality, myocardial perfusion, and left ventricular function between standard imaging and single-injection ultra-low-dose imaging using a high-efficiency SPECT camera: the MILLISIEVERT study

SPECT myocardial perfusion imaging plays a central role in coronary artery disease diagnosis, but concerns exist regarding its radiation burden. Compared with standard Anger SPECT (A-SPECT) cameras, new high-efficiency (HE) cameras with specialized collimators and solid-state cadmium-zinc-telluride detectors offer potential to maintain image quality (IQ), while reducing administered activity and thus radiation dose to patients. No previous study has compared IQ, interpretation, total perfusion deficit (TPD), or ejection fraction (EF) in patients receiving both ultra-low-dose (ULD) imaging on an HE SPECT camera and standard low-dose (SLD) A-SPECT imaging.

METHODS

We compared ULD HE SPECT with SLD A-SPECT imaging by dividing the rest dose in 101 patients at 3 sites scheduled to undergo clinical A-SPECT myocardial perfusion imaging using a same day rest-stress (99m)Tc protocol. Patients underwent HE SPECT imaging after an initial approximately 130-MBq (3.5 mCi) dose and SLD-A-SPECT imaging after the remainder of the planned dose. Images were scored visually by 2 masked readers for IQ and summed rest score. TPD and EF were assessed quantitatively.

RESULTS

Mean activity was 134 MBq (3.62 mCi) for ULD HE SPECT (effective dose, 1.15 mSv) and 278 MBq (7.50 mCi, 2.39 mSv) for SLD A-SPECT. Overall IQ was superior for ULD HE SPECT (P < 0.0001), with twice as many studies graded excellent quality. Extracardiac activity and overall perfusion assessment were similar. Between-method correlations were high for summed rest score (r = 0.87), TPD (r = 0.91), and EF (r = 0.88).

CONCLUSION

ULD HE SPECT rest imaging correlates highly with SLD A-SPECT. It has improved image quality, comparable extracardiac activity, and achieves radiation dose reduction to 1 mSv for a single injection.

3D iteratively reconstructed spatial resolution map and sensitivity characterization of a dedicated cardiac SPECT camera

BACKGROUND

A solid-state cadmium zinc telluride (CZT) SPECT device provides ultrafast myocardial perfusion imaging (MPI) with a spherical field-of-view (FOV). This study aims at determining the spatial resolution and sensitivity throughout this FOV as a guide for patient positioning.

METHODS AND RESULTS

For this CZT camera (Discovery 570c, GE Healthcare), the iteratively reconstructed spatial resolution along 3 Cartesian axes was compared (average resolution 6.9 ± 1.0 mm full-width at half-maximum) using a 2 dimensional array of point sources in air which was aligned with a transverse plane shifted throughout the FOV. Sensitivity was plotted in the central transverse slice and axially in locations comparable to the placement of the heart in 266 rest/stress cardiac studies (M 78, age 63 ± 13 years). The average sensitivity was 0.46 ± 0.19 kc/s/MBq with a transverse gradient of 0.039 ± 0.001 kc/s/MBq/cm (8.9% of the sensitivity per cm). Reconstructed relative activity was uniform (uniformity <9%) and count rate was linear (R = 0.999) over 3 orders of magnitude.

CONCLUSIONS

The CZT SPECT camera offers good resolution, sensitivity, and uniformity, and provides linearity in count rate. A gradient of >8%/cm in sensitivity justifies the crucial role of patient positioning with the heart closest to the detector.

Sex differences in mental stress-induced myocardial ischemia in young survivors of an acute myocardial infarction

OBJECTIVES

Emotional stress may disproportionally affect young women with ischemic heart disease. We sought to examine whether mental stress-induced myocardial ischemia (MSIMI), but not exercise-induced ischemia, is more common in young women with previous myocardial infarction (MI) than in men.

METHODS

We studied 98 post-MI patients (49 women and 49 men) aged 38 to 60 years. Women and men were matched for age, MI type, and months since MI. Patients underwent technetium-99m sestamibi perfusion imaging at rest, after mental stress, and after exercise/pharmacological stress. Perfusion defect scores were obtained with observer-independent software. A summed difference score (SDS), the difference between stress and rest scores, was used to quantify ischemia under both stress conditions.

RESULTS

Women 50 years or younger, but not older women, showed a more adverse psychosocial profile than did age-matched men but did not differ for conventional risk factors and tended to have less angiographic coronary artery disease. Compared with age-matched men, women 50 years or younger exhibited a higher SDS with mental stress (3.1 versus 1.5, p = .029) and had twice the rate of MSIMI (SDS ≥ 3; 52% versus 25%), whereas ischemia with physical stress did not differ (36% versus 25%). In older patients, there were no sex differences in MSIMI. The higher prevalence of MSIMI in young women persisted when adjusting for sociodemographic and life-style factors, coronary artery disease severity, and depression.

CONCLUSIONS

MSIMI post-MI is more common in women 50 years or younger compared with age-matched men. These sex differences are not observed in post-MI patients who are older than 50 years.

Combined supine and prone myocardial perfusion single-photon emission computed tomography with a cadmium zinc telluride camera for detection of coronary artery disease

BACKGROUND

Myocardial perfusion SPECT (MPS) traditionally requires the patient to be in the supine position, but diaphragmatic attenuation of the inferior wall reduces test specificity. The aim of this study was to assess the feasibility of combined MPS in the supine and prone positions using a novel cadmium zinc telluride (CZT) camera.

METHODS AND RESULTS

A total of 276 consecutive patients with suspected/known coronary artery disease (CAD) who underwent single-day (99m)Tc-tetrofosmin or (99m)Tc-sestamibi stress/rest CZT SPECT, were enrolled in the study. Seventy-six underwent coronary angiography. Five-minute scan in the supine (S) position and thereafter in the prone (P) position produced images that were visually interpreted to obtain summed stress (SSS) and rest (SRS) scores. A combined stress score (C-SSS) was calculated by grouping anterior perfusion defects observed during supine imaging with inferior half segments observed during prone imaging. The SSS for the supine, prone, and combined protocols were 9±8, 7±8, and 7±8, respectively (P<0.0001). The SRS were 5±8, 4±7, and 6±7, respectively (P=0.005). The area under the ROC curve for the S-SSS, P-SSS, and C-SSS scores was 0.815 (95% CI: 0.713-0.917), 0.813 (0.711-0.914), and 0.872 (0.783-0.961), respectively. Corresponding sensitivities and specificities for detecting CAD were 87% and 50%, 80% and 77%, and 85% and 82%, respectively. C-SSS had significantly better specificity and accuracy than S-SSS (P<0.05).

CONCLUSIONS

Combined imaging with a CZT camera is suitable for routine clinical MPS and provides greater diagnostic accuracy than supine imaging alone.

Diagnostic performance of low-dose rest/stress Tc-99m tetrofosmin myocardial perfusion SPECT using the 530c CZT camera: quantitative vs visual analysis

BACKGROUND

We set out to develop normal databases and prospectively validate abnormality criteria for a low-dose Tc-99m tetrofosmin myocardial perfusion SPECT protocol using the 530c CZT camera.

METHODS

All patients received 6 mCi rest/20 mCi stress doses of Tc-99m tetrofosmin. Rest and stress images were obtained over 7-9 and 5-7 minutes according to the chest size. Low-dose CT of the chest was obtained on a standalone CT scanner. Forty patients with very low likelihood (LLK) of coronary artery disease (CAD) were used to define the normal count distributions. The abnormality criteria were prospectively validated in 55 patients who had coronary angiography and in 40 patients with LLK of CAD.

RESULTS

The results for quantitative non-attenuation-corrected (AC) and AC analysis and visual analysis were as follows: sensitivity of 79%, 85%, and 92% (P = NS) and specificity of 44%, 75%, and 56% (P = NS), respectively. The normalcy rates for quantitative non-AC and AC analyses and visual analysis were 95%, 98%, and 98% (P = NS).

CONCLUSIONS

We have developed non-AC and AC normal databases for low-dose rest/stress Tc-99m tetrofosmin myocardial perfusion SPECT protocol using the 530c CZT camera. The per-patient diagnostic performance of quantitative analyses is not significantly different from visual analysis by an experienced reader.

The origins of SPECT and SPECT/CT

Single photon emission computed tomography (SPECT) has a long history of development since its initial demonstration by Kuhl and Edwards in 1963. Although clinical utility has been dominated by the rotating gamma camera, there have been many technological innovations with the recent popularity of organ-specific dedicated SPECT systems. The combination of SPECT and CT evolved from early transmission techniques used for attenuation correction with the initial commercial systems predating the release of PET/CT. The development and acceptance of SPECT/CT has been relatively slow with continuing debate as to what cost/performance ratio is justified. Increasingly, fully diagnostic CT is combined with SPECT so as to facilitate optimal clinical utility.

High-efficiency SPECT MPI: comparison of automated quantification, visual interpretation, and coronary angiography

BACKGROUND

Recently introduced high-efficiency (HE) SPECT cameras with solid-state CZT detectors have been shown to decrease imaging time and reduce radiation exposure to patients. An automated, computer-derived quantification of HE MPI has been shown to correlate well with coronary angiography on one HE SPECT camera system (D-SPECT), but has not been compared to visual interpretation on any of the HE SPECT platforms.

METHODS

Patients undergoing a clinically indicated Tc-99m sestamibi HE SPECT (GE Discovery 530c with supine and prone imaging) study over a 1-year period followed by a coronary angiogram within 2 months were included. Only patients with a history of CABG surgery were excluded. Both MPI studies and coronary angiograms were reinterpreted by blinded readers. One hundred and twenty two very low (risk of CAD < 5%) or low (risk of CAD < 10%) likelihood subjects with normal myocardial perfusion were used to create normal reference limits. Computer-derived quantification of the total perfusion deficit at stress and rest was obtained with QPS software. The visual and automated MPI quantification were compared to coronary angiography (≥70% luminal stenosis) by receiver operating curve (ROC) analysis.

RESULTS

Of the 3,111 patients who underwent HE SPECT over a 1-year period, 160 patients qualified for the correlation study (66% male, 52% with a history of CAD). The ROC area under the curve (AUC) was similar for both the automated and the visual interpretations using both supine only and combined supine and prone images (0.69-0.74). Using thresholds determined from sensitivity and specificity curves, the automated reads showed higher specificity (59%-67% vs 27%-60%) and lower sensitivity (71%-72% vs 79%-93%) than the visual reads. By including prone images sensitivity decreased slightly but specificity increased for both. By excluding patients with known CAD and cardiomyopathies, AUC and specificity increased for both techniques (0.72-0.82). The use of a difference score to evaluate ischemic burden resulted in lower sensitivities but higher specificities for both automated and visual quantification. There was good agreement between the visual interpretation and automated quantification in the entire cohort of 160 unselected consecutive patients (r = 0.70-0.81, P < .0001).

CONCLUSIONS

Automated and visual quantification of high-efficiency SPECT MPI with the GE Discovery camera provides similar overall diagnostic accuracy when compared to coronary angiography. There was good correlation between the two methods of assessment. Combined supine and prone stress imaging provided the best diagnostic accuracy.

Taking the perfect nuclear image: quality control, acquisition, and processing techniques for cardiac SPECT, PET, and hybrid imaging

Nuclear Cardiology for the past 40 years has distinguished itself in its ability to non-invasively assess regional myocardial blood flow and identify obstructive coronary disease. This has led to advances in managing the diagnosis, risk stratification, and prognostic assessment of cardiac patients. These advances have all been predicated on the collection of high quality nuclear image data. National and international professional societies have established guidelines for nuclear laboratories to maintain high quality nuclear cardiology services. In addition, laboratory accreditation has further advanced the goal of the establishing high quality standards for the provision of nuclear cardiology services. This article summarizes the principles of nuclear cardiology single photon emission computed tomography (SPECT) and positron emission tomography (PET) imaging and techniques for maintaining quality: from the calibration of imaging equipment to post processing techniques. It also will explore the quality considerations of newer technologies such as cadmium zinc telleride (CZT)-based SPECT systems and absolute blood flow measurement techniques using PET.

Recent trends in nuclear cardiology practice

Over the past three decades, radionuclide myocardial perfusion scintigraphy (MPS) has become established as the main functional cardiac imaging technique for ischemic heart disease. It is currently appropriate for all aspects of detecting and managing ischemic heart disease, including diagnosis, risk assessment and stratification, assessment of myocardial viability, and evaluation of left ventricular function. The purpose of this article was to review recent trends in nuclear cardiology practice, excluding positron emission tomography. The past few years have brought several rapid developments that have increased photon sensitivity in nuclear cardiology scanner hardware. Additionally, software applying new methods of single photon emission tomography (SPECT) reconstruction on conventional and dedicated systems has preserved or even improved SPECT image quality with lower count statistics. On the other hand, much interest has been shown in lowering the radiation dose by the stakeholders of MPS.

Gated SPECT evaluation of left ventricular function using a CZT camera and a fast low-dose clinical protocol: comparison to cardiac magnetic resonance imaging

PURPOSE

CZT technology allows ultrafast low-dose myocardial scintigraphy but its accuracy in assessing left ventricular function is still to be defined.

METHODS

The study group comprised 55 patients (23 women, mean age 63 ± 9 years) referred for myocardial perfusion scintigraphy. The patients were studied at rest using a CZT camera (Discovery NM530c; GE Healthcare) and a low-dose (99m)Tc-tetrofosmin clinical protocol (mean dose 264 ± 38 MBq). Gated SPECT imaging was performed as a 6-min list-mode acquisition, 15 min after radiotracer injection. Images were reformatted (8-frame to 16-frame) using Lister software on a Xeleris workstation (GE Healthcare) and then reconstructed with a dedicated iterative algorithm. Analysis was performed using Quantitative Gated SPECT (QGS) software. Within 2 weeks patients underwent cardiac magnetic resonance imaging (cMRI, 1.5-T unit CVi; GE Healthcare) using a 30-frame acquisition protocol and dedicated software for analysis (MASS 6.1; Medis).

RESULTS

The ventricular volumes obtained with 8-frame QGS showed excellent correlations with the cMRI volumes (end-diastolic volume (EDV), r = 0.90; end-systolic volume (ESV), r = 0.94; p < 0.001). However, QGS significantly underestimated the ventricular volumes (mean differences: EDV, -39.5 ± 29 mL; ESV, -15.4 ± 22 mL; p < 0.001). Similarly, the ventricular volumes obtained with 16-frame QGS showed an excellent correlations with the cMRI volumes (EDV, r = 0.92; ESV, r = 0.95; p < 0.001) but with significant underestimations (mean differences: EDV, -33.2 ± 26 mL; ESV, -17.9 ± 20 mL; p < 0.001). Despite significantly lower values (47.9 ± 16 % vs. 51.2 ± 15 %, p < 0.008), 8-frame QGS mean ejection fraction (EF) was closely correlated with the cMRI values (r = 0.84, p < 0.001). The mean EF with 16-frame QGS showed the best correlation with the cMRI values (r = 0.91, p < 0.001) and was similar to the mean cMRI value (49.6 ± 16 %, p not significant). Regional analysis showed a good correlation between both 8-frame and 16-frame QGS and cMRI wall motion score indexes (8-frame WMSI, r = 0.85; 16-frame WMSI, r = 0.89; p < 0.01).

CONCLUSION

Low-dose gated SPECT with a CZT camera provides ventricular volumes that correlate well with cMRI results despite significant underestimation in the measure values. EF estimation appeared to be more accurate with 16-frame reformatted images than with 8-frame images.

Planar radionuclide angiography with a dedicated cardiac SPECT camera

BACKGROUND

We compared a dedicated cardiac camera with a traditional system for left ventricular (LV) functional measurements using gated blood-pool imaging.

METHODS

24-frame gated planar images were obtained from 48 patients in an LAO orientation for 6M counts/view on a standard gamma camera. Immediately thereafter, 24-frame ECG-gated data were obtained for 8 minutes on a dedicated cardiac SPECT camera. The gated SPECT image volumes were iteratively reconstructed and then transferred offline. In-house software was used to reproject the images into a 24-frame gated planar format. Both the original and the reprojected gated planar datasets were analyzed using semiautomated software to determine ejection fraction (EF), ventricular volume (end diastolic volume, EDV), peak ejection rate (PER), and peak filling rate (PFR).

RESULTS

The difference in EF values averaged 0.4% ± 4.4%. The correlation in EF was r ≥ 0.94 (P < .01) with a linear regression slope of 0.98. Correlation of the EDV was r ≥ 0.86 (P < .01), but the volumes from the dedicated cardiac camera were smaller (linear regression slope was 0.6). Correlation of PFR and PER were r = 0.91 and r ≥ 0.83, respectively (P < .01 for both).

CONCLUSIONS

Reprojection of 24-frame gated blood-pool SPECT images is an effective means of obtaining LV functional measurements with a dedicated cardiac SPECT camera using standard 2D-planar analysis tools.

Comparison of contemporaneous left ventricular ejection fraction (LVEF) obtained from planar gated cardiac blood pool scans (GCBPS) and Tl-201 gated myocardial perfusion scans (MPS) using a novel solid state dedicated cardiac camera

BACKGROUND

There is limited data on the concordance of left ventricular ejection fraction (LVEF) obtained via solid state dedicated cardiac cameras (SSD) and gated cardiac blood pool scans (GCBPS). This study aimed to examine the agreement of LVEF measured during GCBPS and Tl-201 myocardial perfusion scans (MPS) using SSD.

METHODS

Seventy six patients were enrolled. Following stress MPS with 0.8 Mbq/kg (0.022 mCi/kg) Tl-201 and 8-frame gated rest studies after additional 15 Mbq (0.41 mCi) Tl-201, LVEFs were obtained using ECToolbox (ECT) and quantitative gated SPECT (QGS) software. Same day 16-frame planar GCBPS were performed. Interobserver variability was compared and LVEF results were compared using paired t tests, Pearson's correlation and the differences of the LVEF were plotted against GCBPS values.

RESULTS

For GCBPS, ECT and QGS, the mean (±SD) LVEF was 52% ± 14%, 61% ± 18% and 48% ± 19%, respectively. When compared to GCBPS, ECT and QGS, LVEFs had similar R values of 0.85 and 0.83, respectively, and mean differences [95% limits of agreement (LA)] of -8.6% (-27.4% to +10.2%, P < .001) and 4.2% (-17.2% to +25.6%, P = .001), respectively.

CONCLUSION

While the LVEF obtained by ECT or QGS demonstrates a statistically significant correlation with GCBPS, they are significantly different and the wide 95% LA suggest that Tl-201 MPS LVEFs derived from either software package are not interchangeable with GCBPS results.

A tailored ML-EM algorithm for reconstruction of truncated projection data using few view angles

Dedicated cardiac single photon emission computed tomography (SPECT) systems have the advantage of high speed and sensitivity at no loss, or even a gain, in resolution. The potential drawbacks of these dedicated systems are data truncation by the small field of view (FOV) and the lack of view angles. Serious artifacts, including streaks outside the FOV and distortion in the FOV, are introduced to the reconstruction when using the traditional emission data maximum-likelihood expectation-maximization (ML-EM) algorithm to reconstruct images from the truncated data with a small number of views. In this note, we propose a tailored ML-EM algorithm to suppress the artifacts caused by data truncation and insufficient angular sampling by reducing the image updating step sizes for the pixels outside the FOV. As a consequence, the convergence speed for the pixels outside the FOV is decelerated. We applied the proposed algorithm to truncated analytical data, Monte Carlo simulation data and real emission data with different numbers of views. The computer simulation results show that the tailored ML-EM algorithm outperforms the conventional ML-EM algorithm in terms of streak artifacts and distortion suppression for reconstruction from truncated projection data with a small number of views.

Stress myocardial perfusion imaging in the emergency department--new techniques for speed and diagnostic accuracy

Emergency room evaluations of patients presenting with chest pain continue to rise, and these evaluations which often include cardiac imaging, are an increasing area of resource utilization in the current health system. Myocardial perfusion imaging from the emergency department remains a vital component of the diagnosis or exclusion of coronary artery disease as the etiology of chest pain. Recent advances in camera technology, and changes to the imaging protocols have allowed MPI to become a more efficient way of providing this diagnostic information. Compared with conventional SPECT, new high-efficiency CZT cameras provide a 3-5 fold increase in photon sensitivity, 1.65-fold improvement in energy resolution and a 1.7-2.5-fold increase in spatial resolution. With stress-only imaging, rest images are eliminated if stress images are normal, as they provide no additional prognostic or diagnostic value and cancelling the rest images would shorten the length of the test which is of particular importance to the ED population. The rapid but accurate triage of patients in an ED CPU is essential to their care, and stress-only imaging and new CZT cameras allow for shorter test time, lower radiation doses and lower costs while demonstrating good clinical outcomes. These changes to nuclear stress testing can allow for faster throughput of patients through the emergency department while providing a safe and efficient evaluation of chest pain.

Reduced administered activity, reduced acquisition time, and preserved image quality for the new CZT camera

BACKGROUND

For a 1-day myocardial perfusion SPECT (MPS) the recommendations for administered activity stated in the EANM guidelines results in an effective dose of up to 16 mSv per patient. Recently, a gamma camera system, based on cadmium zinc telluride (CZT) technology, was introduced. This technique has the potential to reduce the effective dose and scan time compared to the conventional NaI gamma camera. The aim of this study was to investigate if the effective dose can be reduced with a preserved image quality using CZT technology in MPS.

METHODS

In total, 150 patients were included in the study. All underwent a 1-day (99m)Tc-tetrofosmin stress-rest protocol and were divided into three subgroups (n = 50 in each group) with 4, 3, and 2.5 MBq/kg body weight of administered activity in the stress examination, respectively. The acquisition time was increased in proportion to the decrease in administered activity. All examinations were analyzed for image quality by visual grading on a 4-point scale (1 = poor, 2 = adequate, 3 = good, 4 = excellent), by two expert readers.

RESULTS

The total effective dose (stress + rest) decreased from 9.3 to 5.8 mSv comparing 4 to 2.5 MBq/kg body weight. For the patients undergoing stress examination only (35%) the effective dose, administrating 2.5 MBq/kg, was 1.4 mSv. The image acquisition times for 2.5 MBq/kg body weight were 475 and 300 seconds (stress and rest) compared to 900 seconds for each when using conventional MPS. The average image quality was 3.7 ± 0.5, 3.8 ± 0.5, and 3.8 ± 0.4 for the stress images and 3.5 ± 0.6, 3.6 ± 0.6, and 3.5 ± 0.6 for the rest images and showed no statistically significant difference (P = .62) among the 4, 3, and 2.5 MBq/kg groups.

CONCLUSIONS

The new CZT technology can be used to considerably decrease the effective dose and acquisition time for MPS with preserved high image quality.

Myocardial perfusion imaging with a solid-state camera: simulation of a very low dose imaging protocol

High-sensitivity dedicated cardiac camera systems provide an opportunity to lower the injected doses for SPECT myocardial perfusion imaging (MPI), but the exact limits for lowering doses have not been determined. List-mode data acquisition allows for reconstruction of various fractions of acquired counts, enabling a simulation of gradually lower administered dose. We aimed to determine the feasibility of very low dose MPI by exploring the minimal count level in the myocardium required for accurate MPI.

METHODS

Seventy-nine patients were studied (mean body mass index, 30.0 ± 6.6; range, 20.2-54.0 kg/m(2)) who underwent 1-d standard-dose (99m)Tc-sestamibi exercise or adenosine rest-stress MPI for clinical indications using a cadmium-zinc-telluride dedicated cardiac camera. The imaging time was 14 min, with averaged 803 ± 200 MBq (21.7 ± 5.4 mCi) of (99m)Tc injected at stress. To simulate clinical scans with a lower dose at that imaging time we reframed the list-mode raw data. Accordingly, 6 stress-equivalent datasets were reconstructed containing various count fractions of the original scan. Automated quantitative perfusion and gated SPECT software was used to quantify total perfusion deficit (TPD) and ejection fraction for all 553 datasets (7 × 79). The minimal acceptable left ventricular region counts were determined on the basis of a previous report with repeatability of same-day, same-injection Anger camera studies. Pearson correlation coefficients and the SD of differences in TPD for all scans were calculated.

RESULTS

The correlations of quantitative perfusion and function analysis were excellent for both global and regional analysis between original scans and all simulated low-count scans (all r ≥ 0.95, P < 0.0001). The minimal acceptable counts were determined to be 1.0 million for the left ventricular region. At this count level, the SD of differences was 1.7% for TPD and 4.2% for ejection fraction. This count level would correspond to a 92.5-MBq (2.5-mCi) injected dose for the 14-min acquisition or 125.8-MBq (3.4-mCi) injected dose for the 10-min acquisition.

CONCLUSION

1.0 million counts appear to be sufficient to produce myocardial images that agree well with 8.0-million-count images on quantitative perfusion and function parameters. With a dedicated cardiac camera, these images can be obtained over 10 min with an effective radiation dose of less than 1 mSv without significant sacrifice of accuracy.

Prognostic value of quantitative high-speed myocardial perfusion imaging

BACKGROUND

We studied the prognostic value of fully automated quantitative analysis software applied to new solid-state, high-speed (HS) SPECT-myocardial perfusion imaging (MPI).

METHODS

1,613 consecutive patients undergoing exercise or adenosine HS-MPI were followed for 2.6 ± 0.5 years for all-cause mortality (ACM). Automated quantitative software was used to compute stress total perfusion deficit (sTPD) and was compared to semi-quantitative visual analysis. MPI was characterized as 0% (normal), 1%-4% (minimal perfusion defect), 5%-10% (mildly abnormal), and >10% (moderately/severely abnormal).

RESULTS

During follow-up, 79 patients died (4.9%). Annualized ACM increased with progressively increasing sTPD; 0% (0.87%), 1%-4% (1.94%), 5%-10% (3.10%), and >10% (5.33%) (log-rank P < .0001). While similar overall findings were observed with visual analysis, only sTPD demonstrated increased risk in patients with minimal perfusion defects. In multivariable analysis, sTPD > 10% was a mortality predictor (HR 3.03, 95% CI 1.30-7.09, P = .01). Adjusted mortality rate was substantial in adenosine MPI, but low in exercise MPI (9.0% vs 1.0%, P < .0001).

CONCLUSIONS

By quantitative analysis, ACM increases with increasing perfusion abnormality among patients undergoing stress HS-MPI. These findings confirm previous results obtained with visual analysis using conventional Anger camera imaging systems.