Accuracy Of Myocardial Perfusion Imaging Research Articles

Diagnostic accuracy of stress myocardial perfusion imaging compared to invasive coronary angiography with fractional flow reserve meta-analysis.

Hemodynamically significant coronary artery disease is an important indication for revascularization. Stress myocardial perfusion imaging is a noninvasive alternative to invasive fractional flow reserve for evaluating hemodynamically significant coronary artery disease. The aim was to determine the diagnostic accuracy of myocardial perfusion imaging by single-photon emission computed tomography, echocardiography, MRI, positron emission tomography, and computed tomography compared with invasive coronary angiography with fractional flow reserve for the diagnosis of hemodynamically significant coronary artery disease. The meta-analysis adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. PubMed, EMBASE, and Web of Science were searched until May 2014. Thirty-seven studies, reporting on 4721 vessels and 2048 patients, were included. Meta-analysis yielded pooled sensitivity, pooled specificity, pooled likelihood ratios (LR), pooled diagnostic odds ratio, and summary area under the receiver operating characteristic curve. The negative LR (NLR) was chosen as the primary outcome. At the vessel level, MRI (pooled NLR, 0.16; 95% confidence interval [CI], 0.13-0.21) was performed similar to computed tomography (pooled NLR, 0.22; 95% CI, 0.12-0.39) and positron emission tomography (pooled NLR, 0.15; 95% CI, 0.05-0.44), and better than single-photon emission computed tomography (pooled NLR, 0.47; 95% CI, 0.37-0.59). At the patient level, MRI (pooled NLR, 0.14; 95% CI, 0.10-0.18) performed similar to computed tomography (pooled NLR, 0.12; 95% CI, 0.04-0.33) and positron emission tomography (pooled NLR, 0.14; 95% CI, 0.02-0.87), and better than single-photon emission computed tomography (pooled NLR, 0.39; 95% CI, 0.27-0.55) and echocardiography (pooled NLR, 0.42; 95% CI, 0.30-0.59). Stress myocardial perfusion imaging with MRI, computed tomography, or positron emission tomography can accurately rule out hemodynamically significant coronary artery disease and can act as a gatekeeper for invasive revascularization. Single-photon emission computed tomography and echocardiography are less suited for this purpose.

Differential impact of multi-focus fan beam collimation with L-mode and conventional systems on the accuracy of myocardial perfusion imaging: Quantitative evaluation using phantoms.

A novel IQ-SPECT™ method has become widely used in clinical studies. The present study compares the quality of myocardial perfusion images (MPI) acquired using the IQ-SPECT™ (IQ-mode), conventional (180° apart: C-mode) and L-mode (90° apart: L-mode) systems. We assessed spatial resolution, image reproducibility and quantifiability using various physical phantoms. SPECT images were acquired using a dual-headed gamma camera with C-mode, L-mode, and IQ-mode acquisition systems from line source, pai and cardiac phantoms containing solutions of (99m)Tc. The line source phantom was placed in the center of the orbit and at ± 4.0, ± 8.0, ± 12.0, ± 16.0 and ± 20.0 cm off center. We examined quantifiability using the pai phantom comprising six chambers containing 0.0, 0.016, 0.03, 0.045, 0.062, and 0.074 MBq/mL of 99m-Tc and cross-calibrating the SPECT counts. Image resolution and reproducibility were quantified as myocardial wall thickness (MWT) and %uptake using polar maps. The full width at half maximum (FWHM) of the IQ-mode in the center was increased by 11% as compared with C-mode, and FWHM in the periphery was increased 41% compared with FWHM at the center. Calibrated SPECT counts were essentially the same when quantified using IQ-and C-modes. IQ-SPECT images of MWT were significantly improved (P<0.001) over L-mode, and C-mode SPECT imaging with IQ-mode became increasingly inhomogeneous, both visually and quantitatively (C-mode vs. L-mode, ns; C-mode vs. IQ-mode, P<0.05). Myocardial perfusion images acquired by IQ-SPECT were comparable to those acquired by conventional and L-mode SPECT, but with significantly improved resolution and quality. Our results suggest that IQ-SPECT is the optimal technology for myocardial perfusion SPECT imaging.

Computed tomography attenuation correction improves the risk stratification accuracy of myocardial perfusion imaging

Computed tomography attenuation correction (CT-AC) may improve the image quality and diagnostic accuracy of myocardial perfusion imaging. We evaluated the prognostic value of single-photon emission computed tomography (SPECT) myocardial perfusion imaging with CT-AC. Technetium-99m sestamibi stress/rest myocardial perfusion imaging was performed with SPECT and CT-AC in 935 patients. Images without and with AC were rated using the summed stress score (SSS) and classified as normal (SSS, 0-3), mildly abnormal (SSS, 4-8), or moderately or severely abnormal (SSS>8). All patients were followed up for a major adverse cardiac event (MACE). At the end of a mean follow-up period of 2.2 ± 0.8 years, there had occurred 42 MACEs [17 all-cause deaths (2%) and 25 nonfatal myocardial infarctions (3%)]. The annual frequency of MACEs in patients with normal SSS was 0.5%, that in patients with mildly abnormal SSS was 2%, and in patients with moderately or severely abnormal SSS was 8%. With AC, more studies were categorized as definitely normal, and the number of patients with moderately to severely abnormal perfusion on CT-AC was reduced (κ=0.32, P ≤ 0.001). The annual frequency of MACEs was similar between studies without AC and those with CT-AC for patients with normal or mildly abnormal SSS, whereas for the moderately to severely abnormal group the annual frequency increased significantly after CT-AC (4.5 vs. 8.1%, P=0.03). Cumulative survival without MACE was highest among patients who had normal CT-AC studies (SSS<4) and was the least among patients who had moderately to severely abnormal studies (SSS>8; P ≤ 0.01). CT-AC allows improved risk stratification for MACEs because there is a more clear separation between low risk and moderately to severely abnormal findings.

Absolute Quantification of Left Ventricular Global and Regional Function at Nuclear MPI Using Ultrafast CZT SPECT: Initial Validation Versus Cardiac MR

We sought to evaluate the accuracy of myocardial perfusion imaging (MPI) using cadmium-zinc-telluride (CZT) SPECT cameras for the measurement of left ventricular (LV) global and regional function, and the performance of absolute wall motion (WM) and wall thickness (WT) measurements for the detection of myocardial scarring, using cardiac MR as a reference. Sixty patients with known or suspected coronary artery disease underwent MPI using a CZT SPECT camera, as well as cine and delayed enhanced cardiac MR. Gated MPI data were processed using quantitative gated SPECT software. LV global function was assessed by measuring LV end-diastolic volume (EDV), end-systolic volume (ESV), and ejection fraction (EF). Regional function was assessed by quantifying segmental WM and WT according to the 17-segment model. Myocardial scarring was quantified on each segment using delayed enhanced cardiac MR. Agreement between SPECT and cardiac MR was assessed using Pearson correlation and Bland-Altman analyses. The influence of measurement magnitude on the agreement was analyzed using Spearman correlation coefficients between the mean and SD of measurements. The performance of WM and WT for the detection of segments with more than 25% scar transmurality was assessed using receiver-operating-characteristic analysis. Correlation between methods was excellent for EF (R = 0.81, P < 0.0001) and ESV (R = 0.88, P < 0.0001) and was good for EDV (R = 0.71, P < 0.0001). Agreement was good for EF (bias, -2.7%; limits of agreement, -15.5 to +10.1) but was lower for EDV (bias, -29.7 mL; limits of agreement, -68.3 to +8.9) and ESV (bias, -9.9 mL; limits of agreement, -30.7 to +10.9). Correlation between methods was fair for WM (R = 0.49, P < 0.0001) and WT (R = 0.48, P < 0.0001). SPECT underestimated WT (bias, -41%; limits of agreement, -108 to +26), with an error depending on thickening magnitude (ρ = 0.70, P < 0.0001). The agreement in WM measurement was higher (bias, -1.4 mm; limits of agreement, -6.9 to +4) and independent of motion magnitude (ρ = 0.006, P = 0.86). WM and WT were equally able to identify scarred segments (area under the receiver-operating-characteristic curve, 0.74 ± 0.03 and 0.74 ± 0.03, respectively). MPI using CZT SPECT cameras and quantitative gated SPECT analysis accurately quantifies EF but still underestimates LV volumes. WM shows a higher agreement with cardiac MR than does WT, with errors in WT measurement increasing at greater thicknesses. Absolute quantification of segmental WM and WT can equally be used to identify myocardial scarring.

Accuracy of Myocardial Perfusion Imaging to Diagnose Coronary Artery Disease in Patients Undergoing Liver Transplantation

Accuracy of Myocardial Perfusion Imaging to Diagnose Coronary Artery Disease in Patients Undergoing Liver Transplantation Assessing cardiac risk in patients with advanced liver disease is complex due to difficulties in evaluating patient’s functional capacity. The purpose of this study was to evaluate the accuracy of Myocardial Perfusion Imaging (MPI) to identify Coronary Artery Disease (CAD) in this group of patients. Cardiovascular disease is a common cause of death in patients with advanced liver disease pre- and posttransplantation. Myocardial perfusion imaging is a useful test to detect CAD. However, it does not add diagnostic value in the presence of normal or mildly positive results.

Comparative Analysis between SPECT Myocardial Perfusion Imaging and CT Coronary Angiography for Diagnosis of Coronary Artery Disease

The study aims to discuss the relationship and difference between myocardial perfusion imaging (MPI) using SPECT and CT coronary angiography (CTCA) for diagnosis of coronary artery disease (CAD). Five hundred and four cases undergoing MPI and CTCA were comparatively analyzed, including fifty six patients undergoing invasive coronary angiography in the same period. Among patients with negative MPI results, negative or positive CTCA occupied 84.7% or 15.3%, respectively. Among patients with positive MPI, positive or negative CTCA occupied 67.2% or 32.8%, respectively. Among patients with negative CTCA, negative or positive MPI occupied 94.4% or 5.6%, respectively. Among patients with positive CTCA, positive or negative MPI occupied 40.2% or 59.8%, respectively. Negative predictive value was relatively higher than the positive predictive value for positive CTCA eliminating or predicting abnormal haemodynamics. And there was no significant difference for sensitivity, specificity, and accuracy of MPI or CTCA in diagnosing CAD. Both MPI and CTCA have good diagnostic performance for CAD. They provide different and complementary information for diagnosis and evaluation of CAD, namely, detection of ischemia versus detection of atherosclerosis, which are quite different but have a definite internal link for each other.

Yield of a novel ultra-low-dose computed tomography device mounted on a dedicated cardiac SPECT system in improving the accuracy of myocardial perfusion imaging and the detection of chest abnormalities

To examine the yield of an ultra-low-dose computed tomography (CT) transmission module for attenuation-correction (AC) on a dedicated cardiac camera in evaluation of SPECT-myocardial perfusion imaging (MPI) in the diagnosis of CAD and for additional chest abnormalities. The study group included 150 patients with known or suspected CAD referred for technetium sestamibi SPECT MPI. CT transmission scanning (effective radiation 0.17 mSv) was performed after each gated SPECT scan. AC and non-corrected (NC) SPECT scans were evaluated on a 5-point scale using a 17-segment model, and the sum stress score (SSS) and sum rest score (SRS) were calculated for each condition. Overall image quality, sensitivity and normalcy rate (51 patients) and processing of 28 CT slices were screened for chest findings. CT-based AC significantly improved image quality (P = .01). Mean SSS was 3.8 ± 5.8 with AC and 6.1 ± 7.1 with NC (P < .001); the respective SRS values were 2.6 ± 6.3 and 3.9 ± 7.7 (P < .001). The sensitivity of detecting ≥70% stenosis was 71% and 86% (P = NS) and the normalcy rate was 30% and 89% (P < .0001) in NC and AC SPECT MPI, respectively. Chest CT: lung abnormalities in 31%, aortic calcifications in 27%, and hiatus hernia in 5%. Ultra-low-dose CT for AC of SPECT-MPI improves image quality, diagnostic accuracy and suggests detection of chest findings.

Diagnostic accuracy of myocardial perfusion imaging and stress echocardiography for the diagnosis of left main and triple vessel coronary artery disease: a comparative meta-analysis

ObjectivesCompare the diagnostic performance of stress echocardiography (SE) and myocardial perfusion imaging (MPI) for the diagnosis of left main disease (LM) and triple vessel disease (TVD).BackgroundLimited comparative data on MPI...

Diagnostic accuracy of myocardial perfusion imaging with single photon emission computed tomography and positron emission tomography: a comparison with coronary angiography

The aim of this study was to compare the diagnostic accuracy of myocardial perfusion imaging (MPI) by positron emission tomography (PET) with the diagnostic accuracy of MPI by single photon emission computed tomography (SPECT) in two comparable patient cohorts, using coronary angiography (CA) as the standard of reference. A "SPECT-group" of 80 patients (15 female, 65 male; mean age 60+/-9 years) and a "PET-group" of 70 patients (14 female, 56 male; mean age 57+/-10 years) underwent a one day stress/rest examination either with attenuation-corrected (13)N-ammonia PET or attenuation-corrected (201)TlCl SPECT or (99m)Tc-hexakis-methoxy-isobutyl-isonitril (MIBI) SPECT. PET and SPECT results were semiquantitatively graded using a 6-segment heart model. All patients underwent CA, and stenoses were graded as a diameter reduction >or=50%. Coronary findings between both groups did not significantly differ at CA. For the SPECT-group overall sensitivity and specificity for localisation of stenoses was 77% and 84%. Respective values for the PET-group were 97% and 84%. The specificity of MPI by SPECT in the detection of ischemia was 74% and 91% for MPI by PET. The diagnostic accuracy of MPI improves when the individual coronary dominance and previous coronary revascularisations are taken into account. MPI by (13)N-ammonia PET is more sensitive in the detection and localisation of coronary stenoses, and more specific in the detection of ischemia than MPI by (201)TlCl/(99m)MIBI SPECT.

The expanding role of left ventricular functional assessment using gated myocardial perfusion SPECT: the supporting actor is stealing the scene

Gating of single-photon emission computed tomography (SPECT) has significantly improved the reliability and diagnostic accuracy of myocardial perfusion imaging. The functional parameters derived from this technique, mainly left ventricular volumes and ejection fraction, have been demonstrated to be accurate and reproducible. They are able to increase the detection of severe and extensive coronary artery disease and show a significant incremental prognostic power over perfusion abnormalities. Therefore, the importance given to gated SPECT functional data has progressively grown. This circumstance has further expanded the indications for myocardial perfusion imaging and strengthened its position among the different imaging modalities. Moreover, several studies show that the evaluation of ventricular function may have a leading part in justifying the execution of perfusion scintigraphy in various clinical conditions. Aim of this review is to describe this evolution of gated SPECT functional assessment from a supporting rank with respect to perfusion, to a main actor position in the field of cardiac imaging.

The ratio of the apex/anterior wall: A marker of breast attenuation artifact in women

Breast attenuation artifact is well known for reducing the accuracy of myocardial perfusion imaging in women. We have noticed the particular pattern of relative preservation of apical activity in women with breast attenuation and decreased anterior wall counts. This study was undertaken to see if this finding could be used to improve the accuracy of perfusion imaging in women. We identified 295 women referred for exercise stress testing using (201)Tl single photon emission computed tomography (SPECT) of whom 193 had less than 5% probability of coronary disease and 102 had coronary artery disease documented by catheterization within 60 days of stress testing (mean of 1.8+/-0.8 vessels with=50% stenosis). Patients with documented myocardial infarction, pathologic Q waves, left bundle branch block, non-ischaemic cardiomyopathy or prior bypass grafting were excluded. Volume-weighted bullseye plots were generated and normalized to 100; next, regions of interest were drawn over the anterior wall and apex in all patients and the ratio of the mean counts of each region was calculated. The normals were further divided into those with breast attenuation (defined as mean anterior counts <70% maximum) and those without. Defect scores of all patients were calculated; a formula to adjust the score for patients with breast attenuation was developed. Accuracy was assessed by calculating the area under the receiver operating curve. The normals, overall, had a mean ratio of 1.0+/-0.08 vs. 0.9+/-0.16 for those with coronary disease (P<0.0001). In normals with breast attenuation the ratio was 1.1+/-0.08 compared to 0.99+/-0.07 (P<0.0001) without. By adjusting the anterior wall defect score in patients with apex/anterior ratio >1 we were able to improve the accuracy from 0.808+/-0.028 to 0.826+/-0.027 (P<0.01). A ratio of the apex to the anterior wall >1 is not physiological and suggests the presence of significant breast attenuation artifact. This finding can be used to produce a small but statistically significant improvement in the accuracy of quantitative thallium SPECT in women who have not undergone coronary bypass grafting.

The Diagnostic Accuracy of 64-Slice Computed Tomography Coronary Angiography Compared With Stress Nuclear Imaging in Emergency Department Low-Risk Chest Pain Patients

We compared the accuracy of multidetector computed tomography (CT) coronary angiography with stress nuclear imaging for the detection of an acute coronary syndrome or 30-day major adverse cardiac events in low-risk chest pain patients. This was a prospective study of the diagnostic accuracy of myocardial perfusion imaging and multidetector CT in low-risk chest pain patients. The target condition was an acute coronary syndrome (confirmed >70% coronary stenosis on coronary artery catheterization) or major adverse cardiac events within 30 days. Patients were low risk by Reilly/Goldman criteria and had negative serial ECGs and cardiac markers. All had both rest/stress sestamibi nuclear imaging and multidetector CT. Patients with abnormal stress nuclear imaging results (reversible perfusion defects) or multidetector CT results (stenosis >50% or calcium score >400) were considered for cardiac catheterization, and those with discordant results had a greater than 30-day reevaluation (including ECG) by a cardiologist. All were followed up for evidence of major adverse cardiac events within 30 days by review of hospital records and structured telephone interview. Primary outcomes were the accuracy of multidetector CT and myocardial perfusion imaging for the detection of an acute coronary syndrome and 30-day major adverse cardiac events. Of the 92 patients, 7 (8%) were excluded because of uninterpretable multidetector CT scans. Of the remaining 85 study patients (49+/-11 years, 53% men), 7 (8%) were found to have the target condition, with all having significant coronary stenosis (88%+/-9%) and none having myocardial infarction or major adverse cardiac events during 30 days. Stress nuclear imaging results were negative in 72 (85%) patients, and multidetector CT results were negative in 73 (86%) patients. The sensitivity of stress nuclear imaging was 71% (95% confidence interval [CI] 36% to 92%), and multidetector CT was 86% (95% CI 49% to 97%), and the specificity was 90% (95% CI 81% to 95%) and 92% (95% CI 84% to 96%), respectively. The negative predictive value of stress nuclear imaging and multidetector CT was 97% (95% CI 90% to 99%) and 99% (95% CI 93% to 100%), respectively, and the positive predictive value was 38% (95% CI 18% to 64%) and 50% (95% CI 25% to 75%), respectively. The accuracy of multidetector CT is at least as good as that of stress nuclear imaging for the detection and exclusion of an acute coronary syndrome in low-risk chest pain patients.

Diagnostic accuracy of myocardial perfusion imaging in a study population without post-test referral bias

Most previous studies on the accuracy of myocardial perfusion imaging (MPI) are hampered by post-test referral bias, in that referral for coronary angiography was influenced by the MPI result. In this way, patients with a normal MPI result less frequently underwent catheterization, a tendency supposed to cause an underestimation of test specificity and an overestimation of test sensitivity. MPI by use of a gated dual-isotope protocol was undertaken before angiography in 357 patients referred for angiography for suspected stable angina pectoris. The MPI reports were kept secret to prevent post-test referral bias. The MPI study was normal in 215 patients (60%) and showed reversible perfusion abnormalities in 118 (33%) and fixed defects in 24 (7%). Angiography was normal in 231 patients (65%) and revealed 1 or more significant stenoses in 126 (35%). With angiography as the reference, the sensitivity and specificity of MPI for detecting significant coronary artery stenosis were 75% and 79%, respectively. In this prospective study without post-test referral bias, we found a lower sensitivity and slightly higher specificity than in studies with post-test referral bias. The imperfect accuracy may reflect differences between anatomic and physiologic imaging.

The role of myocardial perfusion imaging in the diagnosis of patients with coronary artery disease: developments over the past year

The role of myocardial perfusion imaging in the diagnosis of coronary artery disease in various patient populations has been expanding. Recent literature from March 2004 to February 2005 has advanced the concept of attenuation correction and electrocardiographic gating in improving the diagnosis of coronary artery disease. The American Heart Association encourages the use of electrocardiographic-gated single photon emission computerized tomography in women. Asymptomatic diabetic patients may benefit from screening with myocardial perfusion imaging. Dobutamine stress perfusion imaging is an important diagnostic tool in elderly patients who are unable to exercise. In patients with chest pain, acute imaging may decrease unnecessary admissions. Vasodilator stress imaging has high sensitivity and specificity in patients with left bundle branch block. Patients undergoing endovascular stent grafting may benefit from risk stratification with vasodilator myocardial perfusion imaging. The American Society of Nuclear Cardiology and the Society of Nuclear Medicine have recognized the role of attenuation correction in increasing the diagnostic accuracy of myocardial perfusion imaging. Multiple studies emphasize the importance of electrocardiographic gating in myocardial perfusion imaging. Recent developments have resulted in an important statement by the American Heart Association that assigns a larger role for myocardial perfusion imaging in the diagnosis of coronary artery disease in women. The role of myocardial perfusion imaging is also expanding in various other patient populations. The literature has validated the concept of attenuation correction for the accurate assessment of attenuation artifacts as well as electrocardiographic gating in enhancing the diagnosis and risk stratification for coronary artery disease.

Initial experience with X-ray ct based attenuation correction in myocardial perfusion spect imaging using a combined spect/ct system

Attenuation artifacts adversely affect the diagnostic accuracy of myocardial perfusion imaging. We assessed the clinical usefulness of X-ray CT based attenuation correction (AC) in patients undergoing myocardial perfusion imaging by comparing their myocardial AC- and non-corrected (NC) SPECT images with the coronary angiography (CAG). We retrospectively reviewed the myocardial SPECT images of 30 patients (18 men, 12 women; mean age 68 years). Thirteen of 30 patients with coronary artery disease (CAD) and 17 without CAD were confirmed by CAG. They underwent sequential CT and myocardial SPECT imaging with thallium-201 (111 MBq) under an exercise or pharmacological stress protocol using our combined SPECT/ CT system. Two readers reviewed the myocardial SPECT images for the presence of CAD on a 4-point scale where 1 = normal, 2 = probably normal, 3 = probably abnormal, and 4 = abnormal. Two reading sessions were held. First, non-corrected (NC)-SPECT and second, AC-SPECT images using X-ray CT images were interpreted. Interobserver variability was assessed with kappa statistics. Diagnostic performance (accuracy) of coronary arterial stenosis was compared between AC- and NC-images. Interobserver agreement for visual assessment was substantial or almost perfect. For AC-images, the observer consensus for analysis was 0.84 for the LAD-, 0.87 for the LCX-, and 0.71 for the RCA-territory. For NC-images, it was 0.91, 0.71, and 0.78. AC resulted in statistically significant improvements in overall diagnostic accuracy (sensitivity/ specificity/accuracy = 76%/93%/89%, 67%/86%/81%, respectively, for AC- and NC-images). Because of an increase in the specificity, diagnostic accuracy was significantly increased on AC-images. These preliminary data suggest that X-ray CT based AC in myocardial SPECT imaging has the potential to develop into a reliable clinical technique.

The predictive accuracy of myocardial perfusion imaging (MPI) of single defects in the detection of coronary artery disease in a clinical practice setting

Background: It is well known that extensive and severe reversible perfusion defects are highly correlated with CAD. Less is known about the predictive accuracy of MPI in the detection of CAD involving single perfusion defects. The purpose of this study is to examine the positive predictive value of MPI with diagnostic cardiac catheterization for the detection of CAD in a clinical practice setting in patients with single, mild, moderate or severe perfusion defects. Methods: Retrospective data was collected on 231 patients seen by a suburban cardiology practice (Eleven physician readers at multiple clinical offices) for MPI between March 2002 and September 2003. MPI defects were categorized by location, reversibility and severity (mild, moderate, severe). The accuracy of MPI interpretation was correlated with subsequent clinically-indicated diagnostic catheterization in all patients (CAD ≥50% stenosis). Results: Analysis of 231 MPI cases revealed 110 (48%) single perfusion defects (mild=49, moderate=52, severe=9). The positive predictive values for mild, moderate, and severe single defects were 0.59, 0.83 and 0.89 respectively. Conclusions: The predictive accuracy of MPI in the detection of CAD in moderate or severe, single defects is acceptable but is suboptimal in patients with mild defects. This low rate of predictive accuracy may be explained by the selection bias of patients in angiographically verified groups, by variations in patterns of referral to catheterization, coronary flow dynamics, and/or imaging artifact. Further studies are needed to assess the predictive accuracy and prognosis of single mild defects in clinical practice. These analyses will assist clinical practices in developing interventions to improve the accuracy of diagnostic MPI and subsequently quality of care.

Spect myocardial perfusion imaging in the morbidly obese: Prognosis and diagnostic value

Background: Obesity is a growing epidemic in the US. As little is known about the diagnostic accuracy of myocardial perfusion imaging (MPI) in the morbidly obese (BMI ≥ 40), we set out to evaluate the correlation of MPI with coronary angiography and the prognostic value of normal studies. Methods: We retrospectively studied 433 consecutive morbidly obese patients without known coronary artery disease presenting for a clinically indicated Tc-99m SPECT MPI study over a 42 months period. A subset of 43 subjects subsequently underwent coronary angiography whose results were compared to MPI. Hospital records and the Social Security Death Index were searched to assess all-cause mortality. Results: Of the 433 patients reviewed 139 (32%) had abnormal MPI results and 294 (68%) normal results. Comparing the patients with abnormal MPI results to normal MPI, the average age was 55 ± 12 versus 53 ± 11 years, BMI 46.9 ± 7 versus 47.5 ± 8 kg/m 2, weight 285 ± 58 versus 275 ± 63 lbs, and Tc99m dose of 36.2 ± 4.3 versus 35.3 ± 5.9 mCi (all p=NS). Of the 43 patients who underwent angiography, performed a median of 15 days later, 5 were performed on patients with normal MPI studies and 38 on patients with abnormal studies. Stress MPI had a sensitivity of 95%, specificity of 17%, positive predictive value of 50%, and negative predictive value of 80% for the detection of > 50% epicardial vessel stenosis. At one year of follow-up, 9 of the 295 patients (3.1%) with a normal MPI died during the follow-up (669 ± 307 days) yielding a 96.9% 1 year survival. Of the 139 patients with an abnormal MPI, 9 (6.5%) died during follow-up (719 ± 318 days) yielding a 93.5% 1 year survival. Conclusion: In the morbidly obese population, stress SPECT MPI imaging has high sensitivity and poor positive predictive value when compared to coronary angiography. One year mortality of the morbidly obese with a normal MPI study (3.1%) exceeds published expected mortality of patients with normal MPI results, as well as diabetic patients with normal MPI results.

Quantitative assessment of the effect of x-ray CT attenuation correction on myocardial perfusion in patients with single vessel coronary artery disease

Background: Attenuation artifacts diminish the diagnostic accuracy of myocardial perfusion imaging (MPI). Little quantitative data exist regarding the effect of x-ray CT based attenuation correction (AC) on regional tracer distribution. The purpose of this study is to quantitatively evaluate the effect of AC on MPI in individual vascular territories. Methods: In this study we selected patients with known single vessel disease who had stress technetium-99m sestamibi SPECT testing with and without AC and cardiac catheterization within 6 months. Coronary stenoses were considered significant if ≥ 70% of the mean luminal diameter. Patients with previous coronary bypass or acute myocardial infarction were excluded. Perfusion stress images were analyzed using automated bulls-eye 20 segment quantitative software. Segments below the 75% maximum threshold were considered abnormal. Specific vascular territories were evaluated. The basal anteroseptum and inferoseptum were excluded due to membranous septum variability. Results: Twenty nine patients were selected (8 LAD, 10LCX, 11RCA). Stress imaging showed more abnormal segments in the non-AC compared to the AC images (mean 13.45 vs. 11.41 p=0.0005). When considering specific vascular territories, there were more false positive segments in the RCA (inferior) territory in the non-AC images in all CAD patients (see table) likely representing diaphragmatic attenuation artifact. Abnormally Perfused Regions During Stress (mean) Patient's known CAD LAD AC/Non-AC LCX AC/Non-AC RCA AC/Non-AC LAD 5.3/4.8 p = NS 1.5/2.0 p = NS 3.6/5.3 p = 0.01 LCX 2.9/2.4 NS 3.2/3.1 NS 3.3/5.0 0.008 RCA 3.2/3.0 NS 2.2/3.3 p = 0.02 3.8/5.7 0.0004 Conclusions: Myocardial perfusion imaging using x-ray CT based attenuation correction is an accurate means of detecting single vessel CAD with improved visualization of the inferior wall and less diaphragmatic artifact compared to non-corrected imaging.

Improved detection of left main coronary artery disease with attenuation-corrected SPECT

Background. Myocardial perfusion imaging has demonstrated a limited sensitivity as a means of accurately identifying left main (LM) coronary disease. Because regional quantitative perfusion biases are eliminated with attenuation corrected (AC) single photon emission computed tomography (SPECT), as compared with uncorrected (NC) SPECT, we hypothesized that AC SPECT would demonstrate increased diagnostic accuracy for the detection of significant LM coronary stenosis. Methods and Results. We studied 28 patients (23 men, 5 women; mean age, 66 ± 9 years) with significant LM stenoses (≥50%) and 34 control patients (27 men, 7 women; mean age, 65 ± 11 years) with 2-vessel coronary disease. Rest thallium-201 and stress technetium 99m sestamibi SPECT imaging with and without AC were performed, as described earlier. Both AC and NC images were analyzed visually and quantitatively in comparison with corresponding normal databases. A greater sensitivity for detection of an LM defect pattern (64% vs 7%,P = .0009) with equivalent specificity (94% vs 100%, P = not significant) was demonstrated by means of visual analysis of AC SPECT images. More disease was demonstrated in a greater number of territories with AC SPECT images than with NC images (2.14 ± 0.97 for AC images vs 1.43 ± 0.84 for NC images, P = .0001). Similar improvement in the detection of LM disease was shown by means of automated quantitative analysis (57% for AC SPECT vs 14% for NC SPECT,P = .0005), again with no loss in specificity. Conclusions. AC SPECT with the University of Michigan method in consecutive patients with LM stenoses and a select control population with severity matched multivessel coronary disease significantly improved the diagnostic accuracy of myocardial perfusion imaging for the identification of LM coronary disease, compared with uncorrected SPECT. (J Nucl Cardiol 2000;7:639-48.)

Effect of patient obesity on the accuracy of thallium-201 myocardial perfusion imaging

The effects of patient habitus (e.g., breast attenuation in women and diaphragmatic attenuation in men) have long been recognized as factors that reduce the accuracy of myocardial perfusion imaging. Although it has long been assumed that patient obesity effects accuracy, this has never been formally evaluated. We studied the effects of patient obesity, defined as a body mass index (BMI) ≥30, on 607 patients who underwent exercise thallium-201 single-photon emission computed tomography (SPECT). Because the effects of obesity are most likely mediated through increased photon attenuation and scatter, we also evaluated the effects of other markers of patient size: body surface area (BSA) and patient weight. Accuracy was determined by performing quantitative analysis and measuring the area under the receiver operating characteristic curve (AUC). Obesity was associated with significantly lower accuracy (AUC 0.86 ± 0.03 vs 0.92 ± 0.02, p <0.05) despite similar estimates of maximal coronary blood flow (as estimated by heart rate and rate-pressure product at peak exercise) and severity of coronary disease. There were no significant differences attributable to either patient weight or BSA. Weight and BSA correlated significantly with left ventricular chamber size whereas BMI did not. We conclude that the accuracy of quantitative SPECT thallium-201 is significantly reduced by patient obesity and that although BSA and weight are also associated with increased attenuation, they have no effect on accuracy, which is most likely due to the compensating effects of increased chamber size.