Left ventricular (LV) segmentation, including accurate assignment of LV contours, is essential for the quantitative assessment of myocardial perfusion SPECT (MPS). Two major types of segmentation failures are observed in clinical practices: incorrect LV shape determination and incorrect valve-plane (VP) positioning. We have developed a technique to automatically detect these failures for both nongated and gated studies.
A standard Cedars-Sinai perfusion SPECT (quantitative perfusion SPECT [QPS]) algorithm was applied to derive LV contours in 318 consecutive 99mTc-sestamibi rest/stress MPS studies consisting of stress/rest scans with or without attenuation correction and gated stress/rest images (1,903 scans total). Two numeric parameters, shape quality control (SQC) and valve-plane quality control, were derived to categorize the respective contour segmentation failures. The results were compared with the visual classification of automatic contour adequacy by 3 experienced observers.
The overall success of automatic LV segmentation in the 1,903 scans ranged from 66% on nongated images (incorrect shape, 8%; incorrect VP, 26%) to 87% on gated images (incorrect shape, 3%; incorrect VP, 10%). The overall interobserver agreement for visual classification of automatic LV segmentation was 61% for nongated scans and 80% for gated images; the agreement between gray-scale and color-scale display for these scans was 86% and 91%, respectively. To improve the reliability of visual evaluation as a reference, the cases with intra- and interobserver discrepancies were excluded, and the remaining 1,277 datasets were considered (101 with incorrect LV shape and 102 with incorrect VP position). For the SQC, the receiver-operating-characteristic area under the curve (ROC-AUC) was 1.0 ± 0.00 for the overall dataset, with an optimal sensitivity of 100% and a specificity of 98%. The ROC-AUC was 1.0 in all specific datasets. The algorithm was also able to detect the VP position errors: VP overshooting with ROC-AUC, 0.91 ± 0.01; sensitivity, 100%; and specificity, 70%; and VP undershooting with ROC-AUC, 0.96 ± 0.01; sensitivity, 100%; and specificity, 70%.
A new automated method for quality control of LV MPS contours has been developed and shows high accuracy for the detection of failures in LV segmentation with a variety of acquisition protocols. This technique may lead to an improvement in the objective, automated quantitative analysis of MPS.
single photon emission computed tomography; quality control; myocardial perfusion imaging; left ventricle segmentation
To validate fast perfusion mapping techniques in a setting of coronary artery stenosis, and to further assess the relationship of absolute myocardial blood volume (MBV) and blood flow (MBF) to global myocardial oxygen demand.
A group of 27 mongrel dogs were divided into 10 controls and 17 with acute coronary stenosis. On 1.5-T MRI, first-pass perfusion imaging with a bolus injection of a blood-pool contrast agent was performed to determine myocardial perfusion both at rest and during either dipyridamole-induced vasodilation or dobutamine-induced stress. Regional values of MBF and MBV were quantified by using a fast mapping technique. Color microspheres and 99mTc-labeled red blood cells were injected to obtain respective gold standards.
Microsphere-measured MBF and 99mTc-measured MBV reference values correlated well with the MR results. Given the same changes in MBF, changes in MBV are twofold greater with dobutamine than with dipyridamole. Under dobutamine stress, MBV shows better association with total myocardial oxygen demand than MBF. Coronary stenosis progressively reduced this association in the presence of increased stenosis severity.
MR first-pass perfusion can rapidly estimate regional MBF and MBV. Absolute quantification of MBV may add additional information on stenosis severity and myocardial viability compared with standard qualitative clinical evaluations of myocardial perfusion.
Coronary stenosis; Myocardial blood flow; Myocardial blood volume
Gated myocardial perfusion single-photon emission computed tomography (GSPECT) has been established as an accurate and reproducible diagnostic and prognostic technique for the assessment of myocardial perfusion and function. Respiratory motion is among the major factors that may affect the quality of myocardial perfusion imaging (MPI) and consequently the accuracy of the examination. In this study, we have proposed a new approach for the tracking of respiratory motion and the correction of unwanted respiratory motion by the use of respiratory-cardiac gated-SPECT (RC-GSPECT). In addition, we have evaluated the use of RC-GSPECT for quantitative and visual assessment of myocardial perfusion and function.
Materials and Methods
Twenty-six patients with known or suspected coronary artery disease (CAD)-underwent two-day stress and rest 99mTc-Tetrofosmin myocardial scintigraphy using both conventional GSPECT and RC-GSPECT methods. The respiratory signals were induced by use of a CT real-time position management (RPM) respiratory gating interface. A PIO-D144 card, which is transistor-transistor logic (TTL) compatible, was used as the input interface for simultaneous detection of both ECG and respiration signals.
A total of 26 patients with known or suspected CAD were examined in this study. Stress and rest myocardial respiratory motion in the vertical direction was 8.8-16.6 mm (mean, 12.4 ± 2.9 mm) and 7.8-11.8 mm (mean, 9.5 ± 1.6 mm), respectively. The percentages of tracer intensity in the inferior, inferoseptal and septal walls as well as the inferior to lateral (I/L) uptake ratio was significantly higher with the use of RC-GSPECT as compared to the use of GSPECT (p < 0.01). In a left ventricular ejection fraction (LVEF) correlation analysis between the use of rest GSPECT and RC-GSPECT with echocardiography, better correlation was noted between RC-GSPECT and echocardiography as compared with the use of GSPECT (y = 0.9654x + 1.6514; r = 0.93, p < 0.001 versus y = 0.8046x + 5.1704; r = 0.89, p < 0.001). Nineteen (19/26) patients (73.1%) showed abnormal myocardial perfusion scans with reversible regional myocardial defects; of the 19 patients, 14 (14/26) patients underwent coronary angiography.
Respiratory induced motion can be successfully corrected simultaneously with the use of ECG-gated SPECT in MPI studies using this proposed technique. Moreover, the use of ECG-gated SPECT improved image quality, especially in the inferior and septal regions that are mostly affected by diaphragmatic attenuation. However, the effect of respiratory correction depends mainly on the patient respiratory pattern and may be clinically relevant in certain cases.
Respiratory correction; ECG-Gated SPECT; Myocardial perfusion imaging; 99mTC-Tetrofosmin
Simultaneous rest perfusion/fatty-acid metabolism studies have the potential to replace sequential rest/stress perfusion studies for the assessment of cardiac function. Simultaneous acquisition has the benefits of increased signal and lack of need for patient stress, but is complicated by cross-talk between the two radionuclide signals. We consider a simultaneous rest 99mTc-sestamibi/123I-BMIPP imaging protocol in place of the commonly-used sequential rest/stress 99mTc-sestamibi protocol. The theoretical precision with which the severity of a cardiac defect and the transmural extent of infarct can be measured is computed for simultaneous and sequential SPECT imaging, and their performance is compared for discriminating (1) degrees of defect severity, and (2) sub-endocardial from transmural defects. We consider cardiac infarcts, for which reduced perfusion and metabolism are observed. From an information perspective, simultaneous imaging is found to yield comparable or improved performance compared with sequential imaging for discriminating both severity of defect and transmural extent of infarct, for three defects of differing location and size.
Ideal estimation; simultaneous SPECT imaging; cardiac defects
The aim of this study was to compare the diagnostic performance of the three software packages 4DMSPECT (4DM), Emory Cardiac Toolbox (ECTb), and Cedars Quantitative Perfusion SPECT (QPS) for quantification of myocardial perfusion scintigram (MPS) using a large group of consecutive patients.
We studied 1,052 consecutive patients who underwent 2-day stress/rest 99mTc-sestamibi MPS studies. The reference/gold-standard classifications for the MPS studies were obtained from three physicians, with more than 25 years each of experience in nuclear cardiology, who re-evaluated all MPS images. Automatic processing was carried out using 4DM, ECTb, and QPS software packages. Total stress defect extent (TDE) and summed stress score (SSS) based on a 17-segment model were obtained from the software packages. Receiver-operating characteristic (ROC) analysis was performed.
A total of 734 patients were classified as normal and the remaining 318 were classified as having infarction and/or ischemia. The performance of the software packages calculated as the area under the SSS ROC curve were 0.87 for 4DM, 0.80 for QPS, and 0.76 for ECTb (QPS vs. ECTb p = 0.03; other differences p < 0.0001). The area under the TDE ROC curve were 0.87 for 4DM, 0.82 for QPS, and 0.76 for ECTb (QPS vs. ECTb p = 0.0005; other differences p < 0.0001).
There are considerable differences in performance between the three software packages with 4DM showing the best performance and ECTb the worst. These differences in performance should be taken in consideration when software packages are used in clinical routine or in clinical studies.
myocardial perfusion imaging; SPECT; automatic quantification; software; coronary artery disease
Nuclear cardiology practitioners have several new technologies available with which to perform myocardial perfusion single photon emission CT (MPS). These include dedicated small-footprint cardiac scanners, new stationary or semi-stationary three-dimensional detectors, and advanced software algorithms for optimal image reconstruction. These new technologies have been employed to reduce imaging time and radiation exposure. They require less technologist and camera time and offer improved patient comfort. They have potential for the overall cost reduction of MPS and at the same time for improved accuracy by increased resolution, or accurate attenuation correction. Furthermore, these new technologies offer potential for new protocols such as simultaneous dual isotope, new combinations of isotopes, stress only MPS, or dynamic first-pass imaging. In addition, new imaging technologies in coronary CT angiography (CCTA) allow novel hybrid stress only MPS/CCTA protocols with reduced radiation burden. Additional developments further improving efficiency and diagnostic accuracy of MPS are on the horizon.
Myocardial perfusion SPECT; Solid state detectors; Stress-only protocol; Hybrid imaging; Cardiac fusion; Simultaneous dual isotope; Fast cardiac SPECT; Dynamic imaging
The purpose of this study is to evaluate the feasibility, the image quality, and the clinical relevance of an early gated post-stress (GPS) single-photon emission computed tomography (SPECT) tetrofosmin (Myoview™—GE Healthcare) acquisition protocol. Time delay between myocardial technetium-labeled tracer administration and SPECT acquisition is usually about 30 minutes after stress, and 45 to 60 minutes at rest: because of the absence of significant redistribution, perfusion images are related to stress even 30 minutes after stress injection, while function and thickening data obtained with gated acquisition 30 minutes after stress are mainly related to rest conditions.
194 patients were prospectively included and analyzed, in a multicenter registry. Three gated-SPECT 99mTc-Tetrofosmin studies were performed per patient: GPS-SPECT, 30 minutes post-stress (GS30), and at rest (GR30).
GPS image quality was excellent/good (93.9%), and similar to GS30 images (96.6%). The presence of adjacent myocardial sub-diaphragmatic activity on GPS images was similar to GS30 images (24% vs 22%), and less frequent than on GR30 images (31%). For perfusion, thickening, and motion scores, there was no significant difference between early and 30 minute post-stress in the global patient population, but significant differences were observed between GPS and GS30 for LVEF (65% ± 15% vs 63% ± 14%). In the ischemic patients, with the stress-rest protocol, the perfusion score was 14.2 on GPS images and 12.4 on GS30 images (P = .002).
Tetrofosmin early GPS-SPECT is feasible without impairment of image quality (better count rate). Ischemic defect size on early post-stress images is slightly more pronounced than at 30 minutes: this could modify therapeutic decision. This technique produces reliable function information during early post-stress period, and might be useful for disclosing transient motion abnormalities.
Tetrofosmin; myocardial perfusion imaging; gated SPECT; early imaging
An important aspect of the diagnostic and prognostic work-up of patients with ischaemic cardiomyopathy is the assessment of myocardial viability. Patients with left ventricular dysfunction who have viable myocardium are the patients at highest risk because of the potential for ischaemia but at the same time benefit most from revascularisation. It is important to identify viable myocardium in these patients, and radionuclide myocardial scintigraphy is an excellent tool for this. Single-photon emission computed tomography perfusion scintigraphy (SPECT), whether using 201thallium, 99mTc-sestamibi, or 99mTc- tetrofosmin, in stress and/or rest protocols, has consistently been shown to be an effective modality for identifying myocardial viability and guiding appropriate management.
Metabolic and perfusion imaging with positron emission tomography radiotracers frequently adds additional information and is a powerful tool for predicting which patients will have an improved outcome from revascularisation. New techniques in the nuclear cardiology field, such as attenuation corrected SPECT, dual isotope simultaneous acquisition (DISA) SPECT and gated FDG PET are promising and will further improve the detection of myocardial viability. Also the combination of multislice computed tomography scanners with PET opens possibilities of adding coronary calcium scoring and noninvasive coronary angiography to myocardial perfusion imaging and quantification.
myocardial viability; LV dysfunction; new nuclear medicine techniques
We compared simultaneous dual-radionuclide stress and rest myocardial perfusion imaging (MPI) with a novel solid-state cardiac camera and a conventional SPECT camera with separate stress and rest acquisitions.
24 consecutive patients (64.5 ± 11.8 years, 16 men) were injected with 74 MBq of 201Tl (rest) and 250 MBq 99mTc-MIBI (stress). Conventional MPI acquisition times for stress and rest were 21 min and 16 min, respectively. A simultaneous dual-radionuclide (DR) 15 minute list mode gated acquisition was performed on D-SPECT (Spectrum-dynamics, Caesarea, Israel). The DR D-SPECT data were processed using a spillover and scatter correction method. We compared DR D-SPECT images with conventional SPECT images by visual analysis employing the 17-segment model and a 5-point scale (0=normal, 4=absent) to calculate the summed stress and rest scores (SSS and SRS, respectively) and the % visual perfusion defect (TPD) at stress and rest, by dividing the stress and rest scores, respectively, by 68 and multiplying by 100. TPD <5% was considered normal. Image quality was assessed on a 4-point scale (1=poor, 4=very good) and gut activity was assessed on a 4-point scale (0=none, 3=high).
Conventional MPI was abnormal at stress in 17 patients and at rest in 9 patients. In the 17 abnormal stress studies DR D-SPECT MPI was abnormal in 113 vs. 93 abnormal segments by conventional MPI. In the nine abnormal rest studies DR D-SPECT was abnormal in 45 vs. 48 segments abnormal by conventional MPI. SSS, SRS, TPD stress and TPD rest on conventional SPECT and DR D-SPECT highly correlated (r=0.9790, 0.9694, 0.9784, 0.9710, respectively; p<0.0001 for all). In addition, 6 patients had significantly larger perfusion defects on DR D-SPECT stress images, including five of 11 patients who were imaged earlier on D-SPECT than conventional SPECT.
D-SPECT enables fast and high quality simultaneous DR MPI in a single imaging session with comparable diagnostic performance and image quality to conventional SPECT. Modifications of the injected doses and of the imaging protocol with DR D-SPECT may enable shortening of imaging time, reducing radiation exposure and shortening significantly patient stay in the department.
Myocardial perfusion imaging; simultaneous dual-radionuclide acquisition; early imaging; cardiac camera; solid state detectors
Changes in myocardial function signatures such as wall motion and thickening are typically computed separately from myocardial perfusion SPECT (MPS) stress and rest studies to assess for stress-induced function abnormalities. The standard approach may suffer from the variability in contour placements and image orientation when subtle changes between stress and rest scans in motion and thickening are being evaluated. We have developed a new measure of regional change of function signature (motion and thickening) computed directly from registered stress and rest gated MPS data. In our novel approach, endocardial surfaces at the end-diastolic and end-systolic frames for stress and rest studies were registered by matching ventricular surfaces. Furthermore, we propose a new global registration method based on finding the optimal rotation for myocardial best ellipsoid fit to minimize the indexing disparities between two surfaces between stress and rest studies. Myocardial stress-rest function changes were computed and normal limits of change were determined as the mean and standard deviation of the training set for each polar sample. Normal limits were utilized to quantify the stress-rest function change for each polar map sample and the accumulated quantified function signature values were used for abnormality assessments in territorial regions. To evaluate the effectiveness of our novel method, we examined the agreements of our results against visual scores for motion change on vessel territorial regions obtained by human experts on a test group with 623 cases and were able to show that our detection method has a improved sensitivity on per vessel territory basis, compared to those obtained by human experts utilizing gated MPS data.
Coronary artery disease; Regional wall motion; SPECT; Gated study
Transient arrhythmias can affect transient ischemic dilation (TID) ratios. This study was initiated to evaluate the frequency and effect of normal heart rate change on TID measures in routine clinical practice.
Consecutive patients undergoing stress/rest sestamibi gated myocardial perfusion scintigraphy were studied (N = 407). Heart rate at the time of stress and rest imaging were recorded. TID ratios were analyzed in relation to absolute change in heart rate (stress minus rest) for subjects with normal perfusion and systolic function (Group 1, N = 169) and those with abnormalities in perfusion and/or function (Group 2, N = 238).
In Group 1, mean TID ratio was inversely correlated with the change in heart rate (r = -0.47, P < 0.0001). For every increase of 10 BPM in heart rate change, the TID ratio decreased by approximately 0.06 (95% confidence interval 0.04–0.07). In Group 2, multiple linear regression demonstrated that the change in heart rate (beta = -0.25, P < 0.0001) and the summed difference score (beta = 0.36, P < 0.0001) were independent predictors of the TID ratio.
Normal variation in heart rate between the stress and rest components of myocardial perfusion scans is common and can influence TID ratios in patients with normal and abnormal cardiac scans.
The Tako-Tsubo syndrome is a reversible form of an acute stress-related cardiomyopathy that was reported during the last decade. It typically presents with a constellation of symptoms, electrocardiographic changes, and elevated cardiac enzyme levels consistent with an acute coronary syndrome. However, when the patient undergoes cardiac angiography, left ventricular apical ballooning finding is seen, but no significant coronary artery stenosis. This balloon-like morphology, being the hallmark of this entity, can be detected by imaging. We present a case report of a patient who was admitted to our hospital and met all the diagnostic criteria of the Tako-Tsubo syndrome. Myocardial perfusion imaging (MPI) showed an anteroapical perfusion defect at rest, moderated systolic dysfunction, and intraventricular asynchrony all assessed by gated-SPECT phase analysis. Two months later, all MPI findings returned to normal parameters.
Broken heart syndrome; left ventricular apical ballooning; left ventricle dysfunction; Tako-Tsubo cardiomyopathy
A comprehensive evaluation of myocardial ischemia requires measures of both oxygen supply and demand. Positron emission tomography (PET) is currently the gold standard for such evaluations, but its use is limited due to its ionizing radiation, limited availability, and high cost. A cardiac magnetic resonance imaging (MRI) method was developed for assessing myocardial oxygenation. The purpose of this study was to evaluate and validate this technique compared to PET during pharmacologic stress in a canine model of coronary artery stenosis.
Methods and Results
Twenty-one beagles and small mongrel dogs without coronary artery stenosis (controls), or with moderate to severe acute coronary artery stenosis underwent MRI and PET imaging at rest and during dipyridamole vasodilation or dobutamine stress to induce a wide range of changes in cardiac perfusion and oxygenation. MRI first-pass perfusion imaging was performed to quantify myocardial blood flow (MBF) and volume (MBV). The MRI blood-oxygen-level-dependent (BOLD) technique was used to determine the myocardial oxygen extraction fraction (OEF) during pharmacologic hyperemia. Myocardial oxygen consumption (MVO2) was determined by Fick’s law. In the same dogs, 15O-water and 11C-acetate were used to measure MBF and MVO2, respectively, by PET. Regional assessments were performed for both MR and PET. MRI data correlated nicely with PET values for MBF (R2 = 0.79, P < 0.001), MVO2 (R2 = 0.74, P < 0.001), and OEF (R2 = 0.66, P < 0.01).
Cardiac MRI methods may provide an alternative to radionuclide imaging in settings of myocardial ischemia. Our newly developed quantitative MRI oxygenation imaging technique may be a valuable non-invasive tool to directly evaluate myocardial energetics and efficiency.
magnetic resonance imaging; perfusion; ischemia; oxygen consumption
To compare gender-related normal limits for left ventricular (LV) ejection fraction (EF), end-diastolic and end-systolic volumes (EDV and ESV), obtained using two myocardial perfusion-gated single photon emission computed tomography (SPECT) quantification methods. A total of 185 patients were retrospectively selected from a consecutive series of patients examined for coronary artery disease (CAD) or for management of known CAD. Patients were included in the study group if they had normal or probably normal results with stress and rest perfusion imaging and if the combined interpretation of perfusion studies and gated rest studies showed no signs or suspicion of myocardial infarction. The gated SPECT studies were performed using a 2-day stress/gated rest Tc-99m sestamibi protocol. All patient studies were processed using CAFU and quantitative-gated SPECT (QGS), the two software packages for quantification of gated SPECT images. The lower normal limits for EF were higher for CAFU compared with QGS for both women (59% versus 53%) and men (54% versus 47%). The upper normal limits for EDV were also higher for CAFU compared with QGS for both women (133 versus 107 ml) and men (182 versus 161 ml). The differences between the software packages were small for ESV (women 44 versus 44 ml; men 69 versus 74 ml). Gender-specific normal limits need to be applied for LV EF and volumes determined by gated SPECT. Separate criteria for abnormal LV EF and EDV need to be used for women and men depending on the software package used.
computer-assisted; gender; heart function tests; radionuclide imaging; reference values
Background: The diagnostic value of myocardial perfusion scintigraphy in patients with left bundle branch block (LBBB) and previous acute myocardial infarction has not been evaluated.
Objective: To determine the utility of single photon emission computed tomography (SPECT) in patients with LBBB and previous acute myocardial infarction.
Methods: Seventy two consecutive patients with permanent LBBB and previous acute myocardial infarction were studied with stress-rest SPECT using 99mTc compounds. The same stress procedures were followed in all patients: (1) exercise alone when it was sufficient; (2) exercise plus simultaneous administration of dipyridamole if exercise was insufficient.
Results: In 26 of 28 patients (93%) who had a Q wave acute myocardial infarct before the development of LBBB, there was concordance between abnormal Q waves and rest SPECT in the localisation of myocardial necrosis (κ = 0.836; p = 0.0001). In 48 patients who had coronary angiography, the positive predictive value of exercise (+dipyridamole) myocardial SPECT for the diagnosis of left anterior descending coronary artery stenosis was 93%, for left circumflex coronary artery stenosis, 96%, and for right coronary artery stenosis, 89%. Specificity values were 83%, 91%, and 69%, respectively. However, sensitivity (69%, 64%, and 89%) and negative predictive values (48%, 46%, and 82%) were suboptimal.
Conclusions: Rest myocardial perfusion SPECT with technetium compounds is useful for localising healed myocardial infarction in patients with LBBB, and exercise (+dipyridamole) SPECT has a high positive predictive value and specificity for the diagnosis of coronary stenosis in these patients.
acute myocardial infarction; scintigraphy; conduction
We aimed to develop a Japanese normal database for specific acquisition conditions, to compare US and Japanese normal populations, and to examine effects of camera rotation angle range on the normal limits.
Methods and Results
Stress-rest 99mTc myocardial perfusion databases for 360° (Jp360) and 180° (Jp180) acquisitions were created by the working group activity of the Japanese Society of Nuclear Medicine using Japanese patients. A standard 180° database (US180) had been previously generated by the Cedars Sinai Medical Center based on American patients. Additionally, 90 Japanese patients underwent coronary arteriography and stress-rest 99mTc perfusion study with 360° acquisition for validation purposes, and quantitative evaluation was performed by QPS software using the above three normal database sets. Major differences between US180 and Jp360 databases were found in the apex and in the anterior wall in females and in the inferior wall in males. When the diagnostic performance was evaluated by receiver-operating characteristic analysis, area under the curve was the highest for Jp360 (0.842), followed by Jp180 (0.758) and US180 (0.728) databases (P = .019, Jp360 vs US180; P = .035, Jp360 vs Jp180). The coronary territory score at stress was highest with the Jp360 database in male patients with right coronary artery stenosis (n = 26, Jp360: 4.92 ± 4.61 [mean ± SD], Jp180: 4.23 ± 4.29, US180: 2.92 ± 3.53; P < .0001 between Jp360 and US180) and in female patients with left anterior descending artery stenosis (n = 12, Jp360: 6.33 ± 4.76, Jp180: 5.25 ± 4.83, US180: 4.50 ± 4.15; P = .0076 between Jp360 and US180).
Because of the differences between US and Japanese normal databases, it is essential to use population- and acquisition-specific databases when using quantitative perfusion SPECT software.
Myocardial perfusion imaging; quantification; normal database; Japanese Society of Nuclear Medicine database; coronary artery disease
A nuclear cardiology test is the most commonly performed non-invasive cardiac imaging test in patients with heart failure, and it plays a pivotal role in their assessment and management. Quantitative gated single positron emission computed tomography (QGS) is used to assess quantitatively cardiac volume, left ventricular ejection fraction (LVEF), stroke volume, and cardiac diastolic function. Resting and stress myocardial perfusion imaging, with exercise or pharmacologic stress, plays a fundamental role in distinguishing ischemic from non-ischemic etiology of heart failure, and in demonstrating myocardial viability. Diastolic heart failure also termed as heart failure with a preserved LVEF is readily identified by nuclear cardiology techniques and can accurately be estimated by peak filling rate (PFR) and time to PFR. Movement of the left ventricle can also be readily assessed by QGS, with newer techniques such as three-dimensional, wall thickening evaluation aiding its assessment. Myocardial perfusion imaging is also commonly used to identify candidates for implantable cardiac defibrillator and cardiac resynchronization therapies. Neurotransmitter imaging using 123I-metaiodobenzylguanidine offers prognostic information in patients with heart failure. Metabolism and function in the heart are closely related, and energy substrate metabolism is a potential target of medical therapies to improve cardiac function in patients with heart failure. Cardiac metabolic imaging using 123I-15-(p-iodophenyl)3-R, S-methylpentadecacoic acid is a commonly used tracer in clinical studies to diagnose metabolic heart failure. Nuclear cardiology tests, including neurotransmitter imaging and metabolic imaging, are now easily preformed with new tracers to refine heart failure diagnosis. Nuclear cardiology studies contribute significantly to guiding management decisions for identifying cardiac risk in patients with heart failure.
Quantitative gated single photon emission computed tomography; Metaiodobenzylguanidine; β-methyl-p-iodophenyl-pentadecanoic acid; Diastolic function; Prognosis
Purpose of this study was to assess the additional value of first pass myocardial perfusion imaging during peak dose of dobutamine stress Cardiac-MR (CMR). Dobutamine Stress CMR was performed in 115 patients with an inconclusive diagnosis of myocardial ischemia on a 1.5 T system (Magnetom Avanto, Siemens Medical Systems). Three short-axis cine and grid series were acquired during rest and at increasing doses of dobutamine (maximum 40 μg/kg/min). On peak dose dobutamine followed immediately by a first pass myocardial perfusion imaging sequence. Images were graded according to the sixteen-segment model, on a four point scale. Ninety-seven patients showed no New (Induced) Wall Motion Abnormalities (NWMA). Perfusion imaging showed absence of perfusion deficits in 67 of these patients (69%). Perfusion deficits attributable to known previous myocardial infarction were found in 30 patients (31%). Eighteen patients had NWMA, indicative for myocardial ischemia, of which 14 (78%) could be confirmed by a corresponding perfusion deficit. Four patients (22%) with NWMA did not have perfusion deficits. In these four patients NWMA were caused by a Left Bundle Branch Block (LBBB). They were free from cardiac events during the follow-up period (median 13.5 months; range 6–20). Addition of first-pass myocardial perfusion imaging during peak-dose dobutamine stress CMR can help to decide whether a NWMA is caused by myocardial ischemia or is due to an (inducible) LBBB, hereby preventing a false positive wall motion interpretation.
Heart; Ischemia; MRI; Myocardium; Stress
Spinal cord stimulation (SCS) and percutaneous myocardial laser revascularisation (PMR) are treatment modalities used to treat refractory angina pectoris, with the major aim of such treatment being the relief of disabling symptoms. This study compared the change in myocardial perfusion following SCS and PMR treatment.
Subjects with Canadian Cardiovascular Society class 3/4 angina and reversible perfusion defects as assessed by single-photon emission computed tomographic myocardial perfusion scintigraphy were randomised to SCS (34) or PMR (34). 28 subjects in each group underwent repeat myocardial perfusion imaging 12 months post intervention. Visual scoring of perfusion images was performed using a 20-segment model and a scale of 0 to 4.
The mean (standard deviation) baseline summed rest score (SRS) and stress scores (SSS) were 4.6 (5.7) and 13.6 (9.0) in the PMR group and 6.1 (7.4) and 16.8 (11.6) in the SCS group. At 12 months, SRS was 5.5 (6.0) and SSS 15.3 (11.3) in the PMR group and 6.9 (8.2) and 15.1 (10.9) in the SCS group. There was no significant difference between the two treatment groups adjusted for baseline (p = 1.0 for SRS, p = 0.29 for SSS).
There was no significant difference in myocardial perfusion one year post treatment with SCS or PMR.
In patients with suspected coronary heart disease, single-photon emission computed tomography (SPECT) is the most widely used test for the assessment of myocardial ischaemia, but its diagnostic accuracy is reported to be variable and it exposes patients to ionising radiation. The aim of this study was to establish the diagnostic accuracy of a multiparametric cardiovascular magnetic resonance (CMR) protocol with x-ray coronary angiography as the reference standard, and to compare CMR with SPECT, in patients with suspected coronary heart disease.
In this prospective trial patients with suspected angina pectoris and at least one cardiovascular risk factor were scheduled for CMR, SPECT, and invasive x-ray coronary angiography. CMR consisted of rest and adenosine stress perfusion, cine imaging, late gadolinium enhancement, and MR coronary angiography. Gated adenosine stress and rest SPECT used 99mTc tetrofosmin. The primary outcome was diagnostic accuracy of CMR. This trial is registered at controlled-trials.com, number ISRCTN77246133.
In the 752 recruited patients, 39% had significant CHD as identified by x-ray angiography. For multiparametric CMR the sensitivity was 86·5% (95% CI 81·8–90·1), specificity 83·4% (79·5–86·7), positive predictive value 77·2%, (72·1–81·6) and negative predictive value 90·5% (87·1–93·0). The sensitivity of SPECT was 66·5% (95% CI 60·4–72·1), specificity 82·6% (78·5–86·1), positive predictive value 71·4% (65·3–76·9), and negative predictive value 79·1% (74·8–82·8). The sensitivity and negative predictive value of CMR and SPECT differed significantly (p<0·0001 for both) but specificity and positive predictive value did not (p=0·916 and p=0·061, respectively).
CE-MARC is the largest, prospective, real world evaluation of CMR and has established CMR's high diagnostic accuracy in coronary heart disease and CMR's superiority over SPECT. It should be adopted more widely than at present for the investigation of coronary heart disease.
British Heart Foundation.
We aimed to improve the quantification of myocardial perfusion stress–rest changes in myocardial perfusion SPECT (MPS) studies for the optimal automatic detection of ischemia and coronary artery disease (CAD).
Rest–stress 99mTc MPS studies (997 cases; 651 consecutive cases with correlating angiography and 346 cases with less than 5% likelihood (low likelihood [LLK]) of CAD) were analyzed. Normal limits for stress–rest changes were derived from additional LLK patients (40 women, 40 men). We computed the global stress–rest change (C-SR) by integrating direct stress–rest changes for each polar map pixel. Additionally, stress–rest change and total perfusion deficit (TPD) at stress were combined in 1 variable (C-TPD) for the optimal detection of CAD.
The area under the receiver-operating-characteristic curve (AUC) for C-SR (0.92) was larger than that for stress TPD–rest TPD (0.88) for the identification of stenosis of 70% or more (P < 0.0001). AUC (0.94) and sensitivity (90%) for C-TPD were higher than those for stress TPD (0.91 and 83%, respectively) (P < 0.0001), whereas specificity remained the same (81%).
C-SR and C-TPD provide higher diagnostic performance than difference between stress and rest TPD or stress hypoperfusion analysis.
SPECT; normal limits; myocardial perfusion stress–rest change; quantification
The phenomenon of reversible impairment in left ventricular function has been well described and is known as myocardial stunning.
To assess myocardial stunning in patients with stress-induced ischemia by the use of Tl-201 myocardial perfusion-gated single-photon emission computed tomography (SPECT).
PATIENTS AND METHODS:
Fifty-six patients (63±11 years old) with coronary artery disease participated in the study. All patients underwent exercise thallium scintigraphy. Electrocardiographically gated SPECT was obtained after stress (10 min after the injection of 111 MBq of thallium at the time of peak exercise) and at rest (after 180 min). The left ventricular ejection fraction (LVEF) and end systolic and end diastolic (EDV) volumes were determined using a quantitative gated SPECT (QGS) program. Patients were angiographically classified into three groups: one-vessel disease (n=38), two-vessel disease (n=9) and three-vessel disease (n=9). In 56 patients, resting left ventricular parameters determined by QGS were compared with those obtained by contrast left ventriculography (LVG) to investigate the feasibility of using thallium-gated SPECT to evaluate left ventricular function.
Good correlation was obtained between LVEF measured by QGS and LVEF measured by LVG (r=0.893, P<0.01). EDV measured by QGS correlated well with EDV measured by LVG (r=0.067, P<0.001). There was a significant difference between poststress LVEF and resting LVEF in patients with three-vessel disease (P<0.05); the difference was not significant in either of the other groups. The magnitude of the depression of LVEF after stress relative to that at rest correlated with the severity of ischemia (P<0.05).
Thallium-gated SPECT determines left ventricular function as well as perfusion does. Impaired poststress LVEF was detected using thallium-gated SPECT in patients with three-vessel disease. Poststress functional data would provide further diagnostic information in patients with coronary artery disease.
Quantitative gated SPECT; Stunned myocardium; Thallium
We define the repeatability coefficients (RC) of key quantitative and visual perfusion and function parameters that can be derived by the QGS/QPS automated software and by expert visual observer from gated myocardial perfusion SPECT (MPS) scans.
Standard QGS/QPS algorithms have been applied to derive quantitative perfusion and function parameters in 200 99mTc-tetrofosmin rest/stress MPS scans, obtained in 100 consecutive patients who underwent 2 separate gated rest/stress scans on the same camera. Variables included stress, rest, and ischemic total perfusion deficit (TPD), ejection fraction, motion, and thickening. Visual perfusion/motion scores were derived by an expert reader using randomized scan order and normalized to % myocardium.
Quantitative and visual parameters were highly reproducible with smaller RC for some quantitative measures as compared to visual measures (P < .0001). RC for quantitative measures were 3.3% for stress TPD, 1.8% for rest TPD, and 3.2% for ischemic TPD and for visual scoring 4.8% for stress, 3.8% for rest, and 4.3% for ischemic (P ≤ .002). The results in each vessel territory showed that in the right coronary artery (RCA) territory the quantitative approach had improved reproducibility as compared to visual reading. Visual thickening scoring was more reproducible than motion scoring (P < .0001).
This study demonstrates that standard perfusion and function parameters derived from MPS by visual or quantitative analysis are highly reproducible with some advantages to the quantitative approach.
SPECT, myocardial perfusion imaging; SPECT, reproducibility
This study assessed the cross-sectional association between coronary artery calcification (CAC) and myocardial perfusion in an asymptomatic population.
Clinical studies showed that the prevalence of stress-induced ischemia increased with CAC burden among patients with coronary heart disease (CHD). Whether an association between CAC and myocardial perfusion exists in subjects without a history of CHD remains largely unknown.
A total of 222 men and women, ages 45 to 84 years old and free of CHD diagnosis, in the Minnesota field center of the MESA (Multi-Ethnic Study of Atherosclerosis) were studied. Myocardial blood flow (MBF) was measured using magnetic resonance imaging during rest and adenosine-induced hyperemia. Perfusion reserve was calculated as the ratio of hyperemic to resting MBF. Agatston CAC score was determined from chest multidetector computed tomography.
Mean values of hyperemic MBF and perfusion reserve, but not resting MBF, were monotonically lower across increasing CAC levels. After adjusting for age and gender, odds ratios (95% confidence intervals) of reduced perfusion reserve (<2.5) for subjects with CAC scores of 0, 0.1 to 99.9, 100 to 399, and ≥400 were 1.00 (reference), 2.16 (0.96 to 4.84), 2.81 (1.04 to 7.58), and 4.99 (1.73 to 14.4), respectively. Further adjustment for other coronary risk factors did not substantially modify the association. However, the inverse association between perfusion reserve and CAC attenuated with advancing age (p for interaction < 0.05).
Coronary vasodilatory response was associated inversely with the presence and severity of CAC in asymptomatic adults. Myocardial perfusion could be impaired by or manifest the progression to subclinical coronary atherosclerosis in the absence of clinical CHD.
We recently reported that motion-frozen (MF) computer technique improved image quality of myocardial perfusion SPECT without sacrificing count density by reconstruction of perfusion images with all counts shifted to end diastolic (ED) frame. In this study, we aimed to compare diagnostic performance of the standard and motion-frozen processing using quantitative analysis in obese patients.
Patients with known coronary artery disease (CAD) were excluded. We studied 90 consecutive obese patients (Body Mass Index 30.1–46.8, average 34.3±3.6), age 63±12 years, 30% female, who underwent both standard supine rest 201Tl/stress 99mTc dual isotope gated myocardial perfusion SPECT and cardiac catheterization within 3 months. Motion-frozen images were obtained from non-linear image warping of images from all phases to the ED position. Total perfusion deficit (TPD) was defined as a product of defect extent and severity for standard supine (S-TPD) and motion-frozen (MF-TPD) datasets with the use of gender-specific standard and MF normal limits. We compared the sensitivity, specificity and receiver operator characteristic curves (ROC) obtained from S-TPD and MF-TPD.
The area under the curve for MF-TPD was significantly larger than for S-TPD for the detection of CAD (≥70% stenosis) (0.93±0.25 vs 0.88±0.32, p<0.05). In 7/31 patients without CAD, MF analysis corrected false positive non-MF results. While sensitivity was the same [93% vs 95% for S-TPD and MF-TPD respectively (p=NS)], MF-TPD had higher specificity (77% vs. 55%) and accuracy (89% vs. 80%) (both p<0.05) than S-TPD.
Motion-frozen processing of myocardial SPECT imaging improves accuracy of CAD detection in obese patients.
gated SPECT; myocardial perfusion; image registration; image warping; coronary artery disease; motion correction