The value and practice of attenuation correction for myocardial perfusion SPECT imaging: a joint position statement from the American Society of Nuclear Cardiology and the Society of Nuclear Medicine

Validation of attenuation correction using transmission truncation compensation with a small field of view dedicated cardiac SPECT camera system

BACKGROUND

Although attenuation correction (AC) has been successfully applied to large field of view (LFOV) cameras, applicability to small field of view (SFOV) cameras is a concern due to truncation. This study compared perfusion images between a LFOV and SFOV camera with truncation compensation, using the same AC solution.

METHODS AND RESULTS

Seventy-eight clinically referred patients underwent rest-stress single-photon emission computed tomography (SPECT) using both a SFOV and LFOV camera in a randomized sequence. Blinded images were interpreted by a consensus of three experienced readers. The percentage of normal images for SFOV and LFOV was significantly higher with than without AC (72% vs 44% and 72% vs 49%, both P < .001). Interpretive agreement between cameras was better with than without AC (kappa = 0.736 to 0.847 vs 0.545 to 0.774). Correlation for the summed stress score was higher with than without AC (r (2) = 0.892 vs 0.851, both P < 0.001) while Bland Altman analysis demonstrated narrower limits with than without AC (4.0 to -4.3 vs 5.9 to -5.6).

CONCLUSION

Attenuation correction using truncation compensation with a SFOV camera yields similar results to a LFOV camera. The higher interpretive agreement between cameras after attenuation correction suggests that such images are preferable to non-attenuation-corrected images.

Complementary roles of low-dose SPECT-CT and high-resolution volume CT for detection of coronary artery disease

A 70-year-old woman with a high pretest likelihood of coronary artery disease (CAD) underwent a Tc-99m MIBI SPECT-CT study for myocardial perfusion imaging (MPI), which was complemented by a high-resolution volume CT (VCT) study. After attenuation correction, an MPI pattern of ischemia was detected in the lateral wall of the myocardium. The CT calcium score (CTCS) was above the 75th percentile. The CT angiography (CTA) demonstrated a 70% stenosis at the ostial part of the circumflex artery, and incidentally revealed a saccular aneurysm. In today's nuclear cardiology, low-dose SPECT-CT plus high-resolution VCT allows anatofunctional assessment of suspected CAD.

Single Tc99m Sestamibi injection, double acquisition gated SPECT after stress and during low-dose dobutamine infusion: a new suggested protocol for evaluation of myocardial perfusion

BACKGROUND

The ability of low dose dobutamine (LDD) has been established in exploiting the reserved contractility of ischemic myocardium. This study was designed to assess the value of a new protocol, with an additional stress imaging during LDD infusion instead of the rest images, for evaluation of coronary artery disease (CAD) and perfusion reversibility.

METHODS

A total of 51 patients (42 men, 9 women; 57.2 +/- 11.3 years) were included in the study and underwent three sequential steps of imaging; the first step-stress gated SPECT with Tc-99m sestamibi, immediately followed by the second step-gated SPECT during constant infusion of 7.5 microg/kg/min dobutamine and finally the third step-rest phase scan following trinitroglycerine administration in the next day. The findings were interpreted using the images in three sets of display; first vs. second step-single injection-double acquisition gated SPECT before and during LDD (SIDAGS-LDD), first vs. third step-standard stress/rest protocol, and only first step-gated stress-only SPECT. In all cases, the Visual perfusion index of each protocols were calculated by summating the premeditated 5-point scale (5: normal, 4: completely reversible, 3: partially reversible, 2: nontransmural fixed and 1: transmural fixed defects) of 17 standard myocardial segments. The accuracy as well as the correlation and agreement of protocols for detecting perfusion abnormality and corresponding reversibility were statistically analyzed.

RESULTS

Calculated sensitivity, specificity, positive predictive value, negative predictive value and accuracy regarding the presence of CAD in both SIDAGS-LDD and standard protocols were 90.9% (40/44), 71.4% (5/7), 95.2% (40/42), 55.6% (5/9) and 88.2% (45/51), respectively. The extent and localization of perfusion abnormality with the new protocol were correlated well with standard method. The estimation of reversibility, however, was considerably improved by SIDAGS-LDD, especially in those with history of previous myocardial infarction (MI).

CONCLUSION

Our proposed protocol demonstrates good correlation and agreement with standard method and even is superior in some cases especially for estimation of viability after MI. Regarding no need for the rest phase radiotracer injection and imaging, this protocol can be more convenient (except the need for close monitoring of the patient during LDD infusion), less time-consuming, less expensive and moreover with less radiation burden to the patients and personnel.

Identification and viability assessment of infarcted myocardium with late enhancement multidetector computed tomography: comparison with thallium single photon emission computed tomography and echocardiography

BACKGROUND

Recent studies revealed that multidetector computed tomography late enhancement (MDCT-LE) is a reliable technique for detecting necrotic and scarred myocardial tissue. The aims of the study were to identify infarcted myocardium using MDCT-LE protocol in patients after myocardial infarction (MI) and assess viability in resting wall motion abnormalities.

METHODS

One hundred one patients with previous MI (62 +/- 13 years, 1-6 months after MI) underwent MDCT-LE (15 minutes after contrast medium administration), rest-redistribution thallium single photon emission computed tomography (Tl-SPECT), and dobutamine echocardiography (DbE). In a 17-segment model, infarcted myocardium detected by MDCT-LE was categorized as none, 1%-25%, 26%-50%, 51%-75%, or >75% segmental extent and was compared with decreased uptake of Tl-SPECT and contractile function by DbE on per patient and segmental basis in a blinded fashion.

RESULTS

By per patient analysis, MDCT-LE identified the presence of infarcted myocardium in 97 patients (96%), and Tl-SPECT decreased uptake in 88 patients (87%), (P = .02). By per segment analysis, the concordance for detecting infarcted myocardium was good (kappa value = 0.792). In segments with resting wall motion abnormalities (N = 486), there was moderate concordance in assessing viability (kappa value between MDCT and Tl-SPECT = 0.555, MDCT and DbE = 0.498, Tl-SPECT and DbE = 0.478) with predefined MDCT-LE threshold of 50% segmental extent. Among segments with MDCT-LE >75% segmental extent, the proportion designated nonviable by Tl-SPECT and DbE reached 87.8% and 92.2%, respectively.

CONCLUSIONS

Multidetector computed tomography late enhancement is accurate in identifying the presence and extent of infarcted myocardium. Its segmental extent has good correlation with the magnitude of thallium decreased uptake and can predict contractile reserve. Multidetector computed tomography late enhancement can be an alternative to assess viability.

Adaptive bayesian iterative transmission reconstruction for attenuation correction in myocardial perfusion imaging with SPECT/slow-rotation low-output CT systems

Objectives. SPECT/slow-rotation low-output CT systems can produce streak artifacts in filtered backprojection (FBP) attenuation maps, impacting attenuation correction (AC) in myocardial perfusion imaging. This paper presents an adaptive Bayesian iterative transmission reconstruction (ABITR) algorithm for more accurate AC. Methods. In each iteration, ABITR calculated a three-dimensional prior containing the pixels with attenuation coefficients similar to water, then used it to encourage these pixels to the water value. ABITR was tested with a cardiac phantom and 4 normal patients acquired by a GE Millennium VG/Hawkeye system. Results. FBP AC and ABITR AC produced similar phantom results. For the patients, streak artifacts were observed in the FBP and ordered-subsets expectation-maximization (OSEM) maps but not in the ABITR maps, and ABITR AC produced more uniform images than FBP AC and OSEM AC. Conclusion. ABITR can improve the quality of the attenuation map, producing more uniform images for normal studies.

CT-based attenuation correction versus prone imaging to decrease equivocal interpretations of rest/stress Tc-99m tetrofosmin SPECT MPI

BACKGROUND

The purpose of this study was to compare stress supine single photon emission computed tomography (SPECT) imaging with attenuation correction (AC) via computed tomography-based attenuation maps with stress prone SPECT imaging with regard to the rate of equivocal interpretation of rest/stress myocardial perfusion imaging.

METHODS AND RESULTS

Interpretations for 324 consecutive patients referred for rest/stress myocardial perfusion imaging were performed by use of the following sets of poststress SPECT images: supine with no AC (NC), supine NC/AC, supine NC/prone, and all images. The number of equivocal studies decreased with additional imaging: supine NC, 40%; supine NC/prone, 18%; supine NC/AC, 11%; and all images, 8%. The supine NC/AC sets of images reduced the number of defects to a greater extent than the supine NC/prone images for all patients (P = .01), men (P = .002), and women (P = .425). For the inferior (but not the anterior) wall, the percent decrease in defects with supine NC/AC images was lower as compared with supine NC/prone images.

CONCLUSION

Interpretation with all images resulted in the fewest equivocal studies. The supine NC/AC images reduced the number of equivocal studies to a greater extent than the supine NC/prone images. AC and prone imaging were more helpful in men than women and were more helpful to resolve inferior than anterior wall defects. Adding prone imaging to supine imaging without and with AC does not significantly alter the number of equivocal interpretations.

SPECT attenuation correction: an essential tool to realize nuclear cardiology's manifest destiny

Single photon emission computed tomography (SPECT) myocardial perfusion imaging has attained widespread clinical acceptance as a standard of care for cardiac patients. Yet, physical phenomena degrade the accuracy of how our cardiac images are visually interpreted or quantitatively analyzed. This degradation results in cardiac images in which brightness or counts are not necessarily linear with tracer uptake or myocardial perfusion. Attenuation correction (AC) is a methodology that has evolved over the last 30 years to compensate for this degradation. Numerous AC clinical trials over the last 10 years have shown increased diagnostic accuracy over non-AC SPECT for detecting and localizing coronary artery disease, particularly for significantly increasing specificity and normalcy rate. This overwhelming evidence has prompted our professional societies to issue a joint position statement in 2004 recommending the use of AC to maximize SPECT diagnostic accuracy and clinical usefulness. Phantom and animal studies have convincingly shown how SPECT AC recovers the true regional myocardial activity concentration, while non-AC SPECT does not. Thus, AC is also an essential tool for extracting quantitative parameters from all types of cardiac radionuclide distributions, and plays an important role in establishing cardiac SPECT for flow, metabolic, innervation, and molecular imaging, our manifest destiny.

Diagnostic Value of Contrast-Enhanced Magnetic Resonance Imaging and Single-Photon Emission Computed Tomography for Detection of Myocardial Necrosis Early After Acute Myocardial Infarction

OBJECTIVES

This study sought to evaluate the diagnostic value of contrast-enhanced magnetic resonance imaging (CMR) and single-photon emission computed tomography (SPECT) for detection of myocardial necrosis after acute myocardial infarction (AMI).

BACKGROUND

Single-photon emission computed tomography is widely accepted in the clinical setting for detection and estimation of myocardial infarction. Contrast-enhanced magnetic resonance imaging offers technical advantages and is therefore a promising new method for identification of infarcted tissue.

METHODS

Seventy-eight patients with AMI were examined by CMR and SPECT 7 days after percutaneous coronary intervention. Contrast-enhanced magnetic resonance imaging and SPECT images were scored for presence and location of infarction using a 17-segment model. Results were compared with the peak troponin T level, electrocardiographic, and angiographic findings.

RESULTS

Acute myocardial infarction was detected significantly more often by CMR than SPECT (overall sensitivity: 97% vs. 87%; p = 0.008). Sensitivity of CMR was superior to SPECT in detecting small infarction as assessed by the peak troponin T level <3.0 ng/ml (92 vs. 69%; p = 0.03), and infarction in non-anterior location (98% vs. 84%; p = 0.03). Non-Q-wave infarctions were more likely to be detected by CMR (sensitivity 85% vs. 46%; p = 0.06). While CMR offered high sensitivity for detection of AMI irrespective of the infarct-related artery, SPECT was less sensitive, particularly within the left circumflex artery territory.

CONCLUSIONS

Contrast-enhanced magnetic resonance imaging is superior to SPECT in detecting myocardial necrosis after reperfused AMI because CMR detects small infarcts that were missed by SPECT independent of the infarct location. Thus, CMR is attractive for accurate detection and assessment of the myocardial infarct region in patients early after AMI.

Prediction of functional recovery after revascularization in patients with coronary artery disease and left ventricular dysfunction by gated FDG-PET

BACKGROUND

Traditionally, cardiac fluorodeoxyglucose (FDG) uptake is combined with regional perfusion for optimal evaluation of viability. Gated FDG-positron emission tomography (PET) may be an alternative technique for detection of viability because it permits combined assessment of glucose metabolism uptake and wall thickening (WT). In this study the value of FDG uptake and WT (analyzed from a stand-alone gated FDG-PET study) for the prediction of recovery of regional and global left ventricular (LV) function in patients with coronary artery disease undergoing revascularization is studied.

METHODS AND RESULTS

Thirty-eight patients with chronic coronary artery disease and LV dysfunction were included. Patients underwent gated FDG-PET to assess viability. Magnetic resonance imaging was performed before and 6 months after revascularization to assess regional and global LV function and LV volumes. Of the 213 revascularized dysfunctional segments, 133 (62%) exhibited functional recovery on follow-up magnetic resonance imaging. Receiver operating characteristic curve analysis indicated that a cutoff level for FDG uptake of 50% or greater yielded a sensitivity and specificity of 93% and 85%, respectively, on gated FDG-PET for prediction of improvement in regional function. Similarly, a cutoff level of 10% or greater for WT was optimal with a sensitivity and specificity of 89% and 78%, respectively. Improvement in LV ejection fraction was best predicted by the number of viable segments. Reverse LV remodeling could be predicted with a sensitivity and specificity of 89% and 65%, respectively, by use of FDG uptake of 50% or greater and 78% and 70%, respectively, by use of WT of 10% or greater.

CONCLUSION

Accurate prediction of outcome after revascularization (including improvement in regional and global LV function and reverse remodeling) is possible with gated FDG-PET by use of a threshold of 50% or greater for FDG uptake or a threshold of 10% or greater for WT.

Use of coronary calcium score scans from stand-alone multislice computed tomography for attenuation correction of myocardial perfusion SPECT

PURPOSE

To evaluate the use of CT attenuation maps, generated from coronary calcium scoring (CCS) scans at in- and expiration with a 64-slice CT scanner, for attenuation correction (AC) of myocardial perfusion SPECT images.

METHODS

Thirty-two consecutive patients underwent( 99m)Tc-tetrofosmin gated adenosine stress/rest SPECT scan on an Infinia Hawkeye SPECT-CT device (GE Medical Systems) followed by CCS and CT angiography on a 64-slice CT. AC of the iteratively reconstructed images was performed with AC maps obtained: (a) from the "Hawkeye" low-resolution X-ray CT facility attached to the Infinia camera (IRAC); (b) from the CCS scan acquired on a 64-slice CT scanner during maximal inspiration (AC(INSP)) and (c) during normal expiration (AC(EXP)). Automatically determined uptake values of stress scans (QPS, Cedars Medical Sinai) from AC(INSP) and AC(EXP) were compared with IRAC. Agatston score (AS) values using AC(INSP)versus AC(EXP) were also compared.

RESULTS

AC(INSP) and AC(EXP) resulted in identical findings versus IRAC by visual analysis. A good correlation for uptake values between IRAC and AC(INSP) was found (apex, r=0.92; anterior, r=0.85; septal, r=0.91; lateral, r=0.86; inferior, r=0.90; all p<0.0001). The correlation was even closer between IRAC and AC(EXP) (apex, r=0.97; anterior, r=0.91; septal, r=0.94; lateral, r=0.92; inferior, r=0.97; all p<0.0001). The mean AS during inspiration (319+/-737) and expiration(317+/-778) was comparable (p=NS).

CONCLUSION

Attenuation maps from CCS allow accurate AC of SPECT MPI images. AC(EXP) proved superior to AC(INSP), suggesting that in hybrid scans CCS may be performed during normal expiration to allow its additional use for AC of SPECT MPI.

Prediction of functional recovery after revascularization in patients with chronic ischaemic left ventricular dysfunction: head-to-head comparison between 99mTc-sestamibi/18F-FDG DISA SPECT and 13N-ammonia/18F-FDG PET

PURPOSE

(18)F-FDG PET is an important modality for myocardial viability assessment in patients with left ventricular (LV) dysfunction. Dual-isotope simultaneous acquisition (DISA) SPECT may be an alternative to PET. The aim of this study was to compare the diagnostic performance of PET and DISA SPECT for the prediction of improvement in regional and global LV function as well as LV reverse remodelling after revascularization.

METHODS

Patients (n=47) with chronic coronary artery disease and LV dysfunction underwent DISA SPECT (with (99m)Tc-sestamibi and (18)F-FDG) and PET (with (13)N-ammonia and (18)F-FDG) on the same day to assess viability. All patients underwent revascularization and recovery of function was derived from serial magnetic resonance imaging studies.

RESULTS

Of 264 revascularized, dysfunctional segments, 143 (54%) improved in function. For prediction of improvement in regional LV function, PET and DISA SPECT had similar sensitivity (90% versus 89%, NS) and specificity (86% versus 86%, NS). For prediction of improvement in global LV function, sensitivity was 83% for DISA SPECT and 86% for PET (p=NS), whereas both modalities had a specificity of 100%. Finally, sensitivity and specificity for the prediction of LV reverse remodelling were also similar for DISA SPECT and PET.

CONCLUSION

In patients undergoing revascularization, DISA SPECT and PET predict the improvement in regional and global LV function and LV remodelling equally well post revascularization.

Diagnostic accuracy of gated Tc-99m sestamibi stress myocardial perfusion SPECT with combined supine and prone acquisitions to detect coronary artery disease in obese and nonobese patients

BACKGROUND

The diagnostic value of gated myocardial perfusion single-photon emission computed tomography (MPS) with combined supine and prone acquisitions to detect coronary artery disease (CAD) in obese and nonobese patients has not been defined.

METHODS AND RESULTS

We studied 1511 patients without prior myocardial infarction or coronary revascularization who either had coronary angiography within 3 months of MPS (n = 785) or had a low pretest likelihood of CAD (n = 726). All patients underwent rest thallium 201/gated exercise or adenosine stress technetium 99m sestamibi MPS in both the supine and prone positions. According to body mass index (BMI), patients were categorized as normal weight (BMI of 18.5-24.9 kg/m2), overweight (BMI of 25.0-29.9 kg/m2), or obese (BMI > or = 30.0 kg/m2). There were no significant differences in stress, fixed, or ischemic defects among patients in different weight categories. The sensitivity of MPS was 85%, 86%, and 89% for detecting patients with 50% or greater coronary stenosis and 89%, 91%, and 92% for detecting those with 70% or greater coronary stenosis in the normal-weight, overweight, and obese groups, respectively. Normalcy rates were nearly identical among the 3 weight groups (99%, 98%, and 99%, respectively). Multivariate logistic regression analysis further confirmed that BMI was a nonsignificant predictor for the detection of CAD. In a subset of 290 patients, automated quantitative MPS analysis confirmed that combined supine and prone MPS increased specificity (86%) in identifying CAD, without a significant reduction in sensitivity (83% for > or = 50% stenosis and 88% for > or = 70% stenosis).

CONCLUSION

The findings of this study suggest that MPS performed with gating and combined supine and prone acquisitions without attenuation correction had a similar diagnostic accuracy for the detection of CAD in normal-weight, overweight, and obese patients.

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

BACKGROUND

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.

METHODS AND RESULTS

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.

CONCLUSIONS

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.

Transmission scan truncation with small-field-of-view dedicated cardiac SPECT systems: impact and automated quality control

BACKGROUND

Small-field-of-view (FOV) dedicated cardiac single photon emission computed tomography (SPECT) systems will frequently exhibit severe transmission scan truncation that may degrade attenuation correction (AC). This study evaluated the impact of transmission scan truncation on AC and developed automated transmission scan truncation quality control (ATSTQC) for small-FOV systems.

METHODS AND RESULTS

Small-FOV data were simulated from the data of 10 patients acquired by a full-FOV Philips Vertex system. AC images of the full- and small-FOV data were compared by mean and maximum absolute differences of myocardial counts, and differences in stress and rest severity scores were calculated by use of the Emory Cardiac Toolbox.small-FOV systems. ATSTQC was developed to identify critical truncation that significantly increased these indices and then tested with 18 independent patients. Left-side truncation resulted in significant distortion of the quantitative indices. ATSTQC, developed on the condition that left-side truncation is critical, showed high concordance with the qualitative assessment in identification of critical truncation.

CONCLUSIONS

Identification of left-side truncation as critical truncation is necessary to judge whether accurate AC can be obtained. The developed ATSTQC can accurately detect critical truncation and will help clinicians decide whether to use AC in a particular study.

EANM/ESC procedural guidelines for myocardial perfusion imaging in nuclear cardiology

The European procedural guidelines for radionuclide imaging of myocardial perfusion and viability are presented in 13 sections covering patient information, radiopharmaceuticals, injected activities and dosimetry, stress tests, imaging protocols and acquisition, quality control and reconstruction methods, gated studies and attenuation-scatter compensation, data analysis, reports and image display, and positron emission tomography. If the specific recommendations given could not be based on evidence from original, scientific studies, we tried to express this state-of-art. The guidelines are designed to assist in the practice of performing, interpreting and reporting myocardial perfusion SPET. The guidelines do not discuss clinical indications, benefits or drawbacks of radionuclide myocardial imaging compared to non-nuclear techniques, nor do they cover cost benefit or cost effectiveness.

Color-encoded semiautomatic analysis of multi-slice first-pass magnetic resonance perfusion: comparison to tetrofosmin single photon emission computed tomography perfusion and X-ray angiography

BACKGROUND AND PURPOSE

Cardiovascular magnetic resonance (CMR) perfusion can accurately detect coronary artery disease (CAD). However, the absence of efficient, easy-to-use and reliable image analysis software is an obstacle to its introduction into clinical practice. The aim of this study was to evaluate new color-encoded semiautomatic software for analysis of first-pass CMR perfusion in comparison to tetrofosmin myocardial single photon emission computed tomography (SPECT), using X-ray angiography as the standard of truth for the detection of CAD.

METHODS

Thirty-two patients underwent both SPECT and CMR perfusion at rest and adenosine stress. Twenty of these patients also underwent X-ray angiography. Off-line CMR image analysis consisted of six steps to generate a color display of the myocardial perfusion reserve index (MPRI). The MPRI color-maps were analyzed visually and compared to SPECT.

RESULTS

In comparison to X-ray angiography overall accuracy was 87% for CMR and 77% for SPECT perfusion to detect significant CAD (stenosis > or =70%). In comparison with SPECT sensitivity was 80%, specificity 91%, and the overall agreement 89% for CMR.

CONCLUSIONS

Post-processing of CMR perfusion data using new semiautomatic software to generate and display the MPRI visually as color-encoded images is feasible and fast. In this study it yielded higher accuracy than SPECT to detect significant CAD on X-ray angiography. Correlation between SPECT and CMR accuracy for detection of perfusion defects was high. This method may accelerate the time-consuming analysis of CMR perfusion data, thus enabling a more widespread clinical utility.

Myocardial perfusion SPECT reconstruction: receiver operating characteristic comparison of CAD detection accuracy of filtered backprojection reconstruction with all of the clinical imaging information available to readers and solely stress slices iteratively reconstructed with combined compensation

BACKGROUND

Past receiver operating characteristic (ROC) studies have demonstrated that single photon emission computed tomography (SPECT) perfusion imaging by use of iterative reconstruction with combined compensation for attenuation, scatter, and detector response leads to higher area under the ROC curve (A(z)) values for detection of coronary artery disease (CAD) in comparison to the use of filtered backprojection (FBP) with no compensations. A new ROC study was conducted to investigate whether this improvement still holds for iterative reconstruction when observers have available all of the imaging information normally presented to clinical interpreters when reading FBP SPECT perfusion slices.

METHODS AND RESULTS

A total of 87 patient studies including 50 patients referred for angiography and 37 patients with a lower than 5% likelihood for CAD were included in the ROC study. The images from the two methods were read by 4 cardiology fellows and 3 attending nuclear cardiologists. Presented for the FBP readings were the short-axis, horizontal long-axis, and vertical long-axis slices for both the stress and rest images; cine images of both the stress and rest projection data; cine images of selected cardiac-gated slices; the CEQUAL-generated stress and rest polar maps; and an indication of patient gender. This was compared with reading solely the iterative reconstructed stress slices with combined compensation for attenuation, scatter, and resolution. With A(z) as the criterion, a 2-way analysis of variance showed a significant improvement in detection accuracy for CAD for the 7 observers (P = .018) for iterative reconstruction with combined compensation (A(z) of 0.895 +/- 0.016) over FBP even with the additional imaging information provided to the observers when scoring the FBP slices (A(z) of 0.869 +/- 0.030). When the groups of 3 attending physicians or 4 cardiology fellows were compared separately, the iterative technique was not statistically significantly better; however, the A(z) for each of the 7 observers individually was larger for iterative reconstruction than for FBP. Compared with results from our previous studies, the additional imaging information did increase the diagnostic accuracy of FBP for CAD but not enough to undo the statistically significantly higher diagnostic accuracy of iterative reconstruction with combined compensation.

CONCLUSIONS

We have determined through an ROC investigation that included two classes of observers (experienced attending physicians and cardiology fellows in training) that iterative reconstruction with combined compensation provides statistically significantly better detection accuracy (larger A(z)) for CAD than FBP reconstructions even when the FBP studies were read with all of the extra clinical nuclear imaging information normally available.

Attenuation correction single-photon emission computed tomography myocardial perfusion imaging

Clinicians now rely heavily on the results of single-photon emission computed tomography (SPECT) myocardial perfusion imaging for diagnosing coronary disease and for planning therapy. However, the technique is imperfect for these purposes, mainly because of technical limitations, the most prominent of which is the effect of soft-tissue attenuation on apparent tracer distribution. Providers have attempted to compensate for this by a number of indirect approaches. Recently, validated hardware and software solutions for directly correcting image data for soft-tissue attenuation have become widely available commercially. Optimal application requires an understanding of the technical details that differ somewhat from system to system, the quality control prerequisites, knowledge of the importance of the transmission map quality, and how dedicated SPECT and SPECT-computed tomography systems present different challenges. In addition, the clinical literature is expanding rapidly, including studies on diagnostic accuracy, image appearances, quantitative analysis, appropriate patients for attenuation correction, clinical utility, incremental value in relation to ECG-gating, and risk stratification.

Comparison of 99mTc-sestamibi/18FDG DISA SPECT with PET for the detection of viability in patients with coronary artery disease and left ventricular dysfunction

PURPOSE

Dual-isotope simultaneous acquisition (DISA) single-photon emission computed tomography (SPECT) is an attractive technique as it permits assessment of both myocardial glucose metabolism and perfusion within a single session, but few data on its accuracy for the assessment of viability are available as yet. In the present study, DISA SPECT was compared with positron emission tomography (PET) for the detection of myocardial viability in normal and dysfunctional left ventricular (LV) myocardium.

METHODS

Fifty-eight patients with chronic coronary artery disease and LV dysfunction (LV ejection fraction 33+/-12%) were studied. Patients underwent a 1-day dipyridamole stress 99mTc-sestamibi/18F-fluorodeoxyglucose (18FDG) DISA SPECT and 13N-ammonia/18FDG PET protocol. Within 1 week, resting MRI was performed to assess contractile function. Comparison of PET and SPECT data was performed using both visual and quantitative analysis.

RESULTS

The correlation of normalised activities of the flow tracers 99mTc-sestamibi and 13N-ammonia was good (r = 0.82; p < 0.001). The correlation between the two 18FDG studies was also good (r = 0.83; p < 0.001). The agreement for the assessment of viability for all segments between DISA SPECT and PET was 82%, with a kappa-statistic of 0.59 (95% CI 0.53-0.64), without a significant difference; in dysfunctional segments only, the agreement was 82%, with a kappa-statistic of 0.63 (95% CI 0.56-0.70), without a significant difference. When the DISA SPECT data were analysed visually, the agreement between DISA SPECT and PET was 83%, with a kappa-statistic of 0.58 (95% CI 0.52-0.63), without a significant difference. Moreover, there was no significant difference between visual and quantitative DISA SPECT analysis for the detection of viability.

CONCLUSION

This study shows an overall good agreement between 99mTc-sestamibi/18FDG DISA SPECT and PET for the assessment of myocardial viability in patients with severe LV dysfunction. Quantitative or visual analysis of the SPECT data did not influence the agreement with PET, suggesting that visual assessment may be sufficient for clinical purposes.

Cardiac positron emission tomography imaging

Cardiac positron emission tomography (PET) imaging has advanced from primarily a research tool to a practical, high-performance clinical imaging modality. The widespread availability of state-of-the-art PET gamma cameras, the commercial availability of perfusion and viability PET imaging tracers, reimbursement for PET perfusion and viability procedures by government and private health insurance plans, and the availability of computer software for image display of perfusion, wall motion, and viability images have all been a key to cardiac PET imaging becoming a routine clinical tool. Although myocardial perfusion PET imaging is an option for all patients requiring stress perfusion imaging, there are identifiable patient groups difficult to image with conventional single-photon emission computed tomography imaging that are particularly likely to benefit from PET imaging, such as obese patients, women, patients with previous nondiagnostic tests, and patients with poor left ventricular function attributable to coronary artery disease considered for revascularization. Myocardial PET perfusion imaging with rubidium-82 is noteworthy for high efficiency, rapid throughput, and in a high-volume setting, low operational costs. PET metabolic viability imaging continues to be a noninvasive standard for diagnosis of viability imaging. Cardiac PET imaging has been shown to be cost-effective. The potential of routine quantification of resting and stress blood flow and coronary flow reserve in response to pharmacologic and cold-pressor stress offers tantalizing possibilities of enhancing the power of PET myocardial perfusion imaging. This can be achieved by providing assurance of stress quality control, in enhancing diagnosis and risk stratification in patients with coronary artery disease, and expanding diagnostic imaging into the realm of detection of early coronary artery disease and endothelial dysfunction subject to risk factor modification. Combined PET and x-ray computed tomography imaging (PET-CT) results in enhanced patient throughput and efficiency. 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. Evaluation of the clinical role of these creative new possibilities warrants investigation.

Porous phantoms for PET and SPECT performance evaluation and quality assurance

Characterization of PET and SPECT imaging performance often requires phantoms with complex radionuclide distributions. For example, lesion detection studies use multiple spherical regions of specific target-to-background ratios to simulate cancerous lesions. Such complex distributions are typically created using phantoms with multiple fillable chambers. However, such phantoms are typically difficult and time-consuming to prepare accurately and reproducibly. A new approach using a single-chamber phantom with a porous core can overcome these difficulties.

METHODS

Prototypes of two designs of porous core phantoms were produced and evaluated. The "hot spheres" phantom contained a multitude of simulated spherical lesions with diameters ranging from 6.35 to 25.4 mm ("multi-resolution" slice) and with lesion-to-background ratios ranging from 1.6 to 4.4 ("multi-contrast" slice). The "multi-attenuation" phantom consisted of two halves. One half contained a porous core to produce regions of different attenuation but uniform activity. The other half mimicked the NEMA-94 design with cold inserts of different attenuation.

RESULTS

Both phantoms produced the expected radionuclide distributions while requiring the preparation of only a single radionuclide solution and with much reduced preparation time. In images taken on clinical PET and SPECT scanners, the porous core structures were found to contribute negligible background noise or artifact. The measured lesion-to-background ratios from the hot spheres phantom differed slightly from calculated values, with the differences attributed mainly to uncertainty in pore diameter. The measured attenuation coefficients from the multi-attenuation phantom agreed well with expected values. However, it was found that trapped air bubbles due to manufacturing defects in the porous core could potentially cause quantitative errors.

CONCLUSION

The hot spheres and multi-attenuation porous phantoms exhibited a wide range of imaging features providing thorough tests of lesion detection and of attenuation and scatter correction accuracy. Because the local activity concentration is set by the relative volume of radionuclide solution in the porous core, the quantitative accuracy is limited mainly by mechanical tolerance, and strict quality control during manufacturing is essential. Nonetheless, the single-chamber design of the porous core phantoms is inherently more reproducible and more practical for routine use compared to conventional multi-chamber phantoms.

[Diagnostic accuracy of the SPECT of post-stress myocardial perfusion with attenuation and scatter correction]

OBJECTIVE

To evaluate the effect of attenuation and scatter correction (AC-SC) on the diagnostic accuracy of post-stress myocardial perfusion (MP) SPECT.

MATERIAL AND METHODS

The retrospective analysis included 121 patients who had a non-corrected (NC) and AC-SC 99mTc-Tetrofosmin MP SPECT after stress. The left ventricle was divided into 13 segments. Two observers performed a visual assessment of the MP on a scale from 0 (perfusion defect) to 3 (normal uptake). A consensus on concordances and discordances between the NC and AC-SC images was established. Final diagnosis of coronary artery disease (CAD) was established by coronary angiography (CANG) (stenosis > or = 70 %).

RESULTS

The combined analysis of NC and AC-SC images produced 93 concordances and 28 discordances. Of the 93 concordances, both studies were abnormal in 67 patients (abnormal CANG in 57) and normal in 26 patients (normal CANG in 20). Among the 28 discordances, 23 were abnormal NC/normal AC-SC (normal CANG in 18) and 5 normal NC/abnormal AC-SC. In these 5 patients AC-SC generated anterior perfusion defects but the CANG was normal. Overall, the appearance of NC and AC-SC images were in agreement with the CANG findings in the 72 % (87/121) and 78 % (95/121) of the patients, respectively. Sixty-seven of the 90 patients with abnormal NC had also abnormal AC-SC (abnormal CANG in 57) and the other 23 had normal AC-SC (normal CANG in 18). The appearance of AC-SC was in agreement with CANG finding in the 83 % (75/90) of patients with abnormal NC. MP abnormalities in NC normalized by AC-SC were more frequently located in inferior wall

CONCLUSION

AC-SC improves the diagnostic accuracy of post stress NC MP SPECT for the diagnosis of CAD. From these results we consider that AC-SC is of clinical value for the correction of attenuation artifacts, more frequently observed in the inferior wall. The presence of antero-apical perfusion defects in AC-SC with normal NC does not mean CAD. So it is necessary to adjust the normalcy pattern of MP SPECT when AC-SC is performed.

Acute Myocardial Infarction: Evaluation with First-Pass Enhancement and Delayed Enhancement MR Imaging Compared with201Tl SPECT Imaging

PURPOSE

To evaluate acute myocardial infarction by using first-pass enhancement (FPE) and delayed enhancement (DE) magnetic resonance (MR) imaging compared with thallium 201 ((201)Tl) single photon emission computed tomography (SPECT).

MATERIALS AND METHODS

Contrast material-enhanced FPE MR, inversion-recovery DE MR, and rest-redistribution (201)Tl SPECT images were obtained in 60 consecutive patients (53 men, seven women; mean age [+/- SD], 56 years +/- 13; range, 30-78 years) at 6 days +/- 3 after reperfused first myocardial infarction. Presence of microvascular obstruction was determined on FPE MR images. Infarct size was defined on DE MR images as percentage of left ventricular (LV) area and compared with uptake defect on redistribution (201)Tl SPECT images. Differences in continuous data were analyzed with Student t test. Linear regression and Bland-Altman analysis were used to compare measurements of infarct size.

RESULTS

Mean infarct size was not significantly different between DE MR imaging (20.7% +/- 11.5% of LV area) and (201)Tl SPECT (19.4% +/- 14.3% of LV area; P =.26); good correlation (r = 0.73; P <.001) and agreement were found, with a mean difference of +1.3% +/- 9.8% of LV area. (201)Tl SPECT failed to depict infarct in six (20%) of 30 patients with inferior myocardial infarction (mean size, 6.4% +/- 5.7% of LV area on DE MR images), whereas DE MR images showed the infarct in all patients (P <.01). FPE MR images depicted microvascular obstruction in 23 (38%) of 60 patients; these patients had larger infarctions at DE MR imaging than did patients without microvascular obstruction (30.4% +/- 9.0% vs 15.1% +/- 8.4% of LV area, P <.001). (201)Tl SPECT showed larger infarcts in patients with microvascular obstruction (26.7% +/- 16.2% vs 15.0% +/- 11.2% of LV area, P <.01).

CONCLUSION

Good correlation and agreement with (201)Tl SPECT indicate DE MR imaging may be used to estimate infarct size 6 days after reperfused acute myocardial infarction. DE MR imaging is more sensitive for detection of inferior infarction than is (201)Tl SPECT. Patients with microvascular obstruction on FPE MR images have larger infarcts.

Attenuation correction for single photon emission computed tomography myocardial perfusion imaging

The specificity of cardiac single photon emission computed tomography (SPECT) perfusion imaging is significantly affected by internal photon absorption. Commonly referred to as anterior wall breast and inferior wall diaphragm attenuation artifacts, even when following characteristic patterns in women and men, the reduced activity produced can be difficult to differentiate from real perfusion defects. Unfortunately, wide variations in body habitus result in unpredictable variations in tissue attenuation and the specificity of uncorrected SPECT is unacceptably low in many laboratories. This manuscript reviews recent developments in attenuation correction methods for cardiac SPECT. Several commercial methods are now available, and although the initial success using these methods varied widely, as these methods have been improved successful clinical reports are appearing with increasing frequency. Recent developments have yielded more robust validated methods and significant clinical advantages have been achieved in the diagnostic evaluation of coronary heart disease (sensitivity as well as specificity) and myocardial viability. As these methods continue to mature, further advances should be anticipated.

Cardiac imaging using nuclear medicine and postitron emission tomography

This article concentrates on specific issues that are of current interest in mainstream nuclear cardiology. These include developments in myocardial perfusion technique, the potential diagnostic benefits of ECG-gating and attenuation correction, nuclear imaging in the diagnosis of hibernating myocardium, and the cost-effectiveness of perfusion imaging in patients with suspected angina.

Quantitative Tc-99m sestamibi attenuation-corrected SPECT: development and multicenter trial validation of myocardial perfusion stress gender-independent normal database in an obese population

BACKGROUND

A gender-independent stress normal database and criteria for abnormality for attenuation-corrected rest-stress technetium 99m sestamibi same-day myocardial perfusion imaging were developed by evaluation of 112 patients, validated against an obese population of 95 patients from four different clinical sites, and compared with conventional gender-matched database quantification of non-attenuation-corrected studies.

METHODS AND RESULTS

These 95 validation patients (63 men) were used for prospective quantitative evaluation (mean weight, 213 +/- 57 lb; mean body mass index, 32 +/- 9 kg/m(2)). This group included 21 patients (12 men) with a lower than 5% likelihood of coronary artery disease (mean weight, 226 +/- 72 lb; mean body mass index, 34 +/- 13 kg/m(2)) and 74 who underwent cardiac catheterization within 2 months (35 with normal coronaries or coronary lesions <70%). These studies were processed twice, once by use of conventional reconstruction and gender-specific database quantification and a second time by use of attenuation correction and a single gender-independent attenuation-corrected normal database. The attenuation-corrected normal database and criteria for abnormality were developed by evaluation of 48 and 78 patients, respectively. No statistically significant differences were found when comparing attenuation-corrected perfusion distributions of normal men and women, whereas significant differences were found in the same uncorrected studies. Compared with quantitative analysis of the uncorrected studies, quantitative analysis of the attenuation-corrected studies by use of a gender-independent normal database demonstrated a significant improvement in normalcy rate (90% vs 52%, P =.006) and specificity (57% vs 29%, P =.015) in this obese population at no significant loss in sensitivity (90% vs 97%, P = not significant).

CONCLUSION

Attenuation-corrected studies can be quantified with a single gender-independent normal database and a single criterion for abnormality without loss of sensitivity and with significantly better specificity and normalcy rate.

Clinical value of attenuation correction in stress-only Tc-99m sestamibi SPECT imaging

BACKGROUND

Attenuation artifact remains a substantial limitation to confident interpretation of images and reduces laboratory efficiency by requiring comparison of stress and rest image sets. Attenuation-corrected stress-only imaging has the potential to ameliorate these limitations.

METHODS AND RESULTS

Ten experienced nuclear cardiologists independently interpreted 90 stress-only electrocardiography (ECG)-gated technetium 99m sestamibi images in a sequential fashion: myocardial perfusion imaging (MPI) alone, MPI plus ECG-gated data, and attenuation-corrected MPI with ECG-gated data. Images were interpreted for diagnostic certainty (normal, probably normal, equivocal, probably abnormal, abnormal, and perceived need for rest imaging). With stress MPI data alone, only 37% of studies were interpreted as definitely normal or abnormal, with a very high perceived need for rest imaging (77%). The addition of gated data did not alter the interpretations. However, attenuation-corrected data significantly increased the number of studies characterized as definitely normal or abnormal (84%, P <.005) and significantly reduced the perceived need for rest imaging (43%, P <.005). These results were confirmed by use of a nonsequential consensus interpretation of three readers.

CONCLUSION

Attenuation correction applied to studies with stress-only Tc-99m ECG-gated single photon emission computed tomography images significantly increases the ability to interpret studies as definitely normal or abnormal and reduces the need for rest imaging. These findings may improve laboratory efficiency and diagnostic accuracy.

Monte Carlo-based down-scatter correction of SPECT attenuation maps

Combined acquisition of transmission and emission data in single-photon emission computed tomography (SPECT) can be used for correction of non-uniform photon attenuation. However, down-scatter from a higher energy isotope (e.g. 99mTc) contaminates lower energy transmission data (e.g. 153Gd, 100 keV), resulting in underestimation of reconstructed attenuation coefficients. Window-based corrections are often not very accurate and increase noise in attenuation maps. We have developed a new correction scheme. It uses accurate scatter modelling to avoid noise amplification and does not require additional energy windows. The correction works as follows: Initially, an approximate attenuation map is reconstructed using down-scatter contaminated transmission data (step 1). An emission map is reconstructed based on the contaminated attenuation map (step 2). Based on this approximate 99mTc reconstruction and attenuation map, down-scatter in the 153Gd window is simulated using accelerated Monte Carlo simulation (step 3). This down-scatter estimate is used during reconstruction of a corrected attenuation map (step 4). Based on the corrected attenuation map, an improved 99mTc image is reconstructed (step 5). Steps 3-5 are repeated to incrementally improve the down-scatter estimate. The Monte Carlo simulator provides accurate down-scatter estimation with significantly less noise than down-scatter estimates acquired in an additional window. Errors in the reconstructed attenuation coefficients are reduced from ca. 40% to less than 5%. Furthermore, artefacts in 99mTc emission reconstructions are almost completely removed. These results are better than for window-based correction, both in simulation experiments and in physical phantom experiments. Monte Carlo down-scatter simulation in concert with statistical reconstruction provides accurate down-scatter correction of attenuation maps.

Recent advances in cardiac positron emission tomography in the clinical management of the cardiac patient

Despite being primarily a research tool, positron emission tomography (PET) has seen slow but steady growth in the clinical management of the cardiac patient. The two major clinical applications of cardiac PET are regional myocardial perfusion imaging to determine the presence and severity of coronary artery disease and metabolic imaging to differentiate viable from nonviable myocardium in patients with ischemic left ventricular dysfunction. Indeed, PET with either nitrogen 13 ammonia or rubidium 82 may offer advantages over current single photon emission computed tomography approaches to assess myocardial perfusion. PET with fluorine 18 fluorodeoxyglucose is considered the current gold standard for identifying viable myocardium. Finally, the use of PET to quantify myocardial perfusion, metabolism, and innervation has led to key insights into the role of altered microvascular function, substrate metabolism, and neuronal function in a variety of cardiac disease processes.

Clinical significance of apical thinning after attenuation correction

BACKGROUND

Apical thinning and other image changes at the apex have been described after attenuation correction of myocardial perfusion single photon emission computed tomography (SPECT) studies, but their clinical significance is unknown.

METHODS AND RESULTS

We studied 102 subjects from a multicenter trial of attenuation correction, 46 with angiographic coronary artery disease and 56 normal subjects. We graded the presence and magnitude (on a 4-point scale) of apical thinning (decrease in wall thickness, best assessed in the vertical long-axis view) in both noncorrected and attenuation-corrected images. In attenuation-corrected images, apical thinning of any degree was present in 78% of the abnormal patients and 63% of the normal subjects (P = not significant [NS]). However, moderate or severe apical thinning was present in 30% of the abnormal patients compared with 5% of the normal subjects (relative risk = 2.2, P <.001). In noncorrected images, apical thinning of any degree was present in 87% of the abnormal patients and 71% of the normal subjects (P = NS). However, moderate or severe apical thinning was present in 28% of the abnormal patients compared with 4% of the normal subjects (relative risk = 2.3, P <.001).

CONCLUSION

The presence of mild apical thinning is common in both noncorrected and attenuation-corrected SPECT images and does not imply coronary artery disease. Moderate or severe apical thinning is 7 times more common in patients than in normal subjects, but it is relatively uncommon and thus is not a generally useful clinical tool.

Advances in quantitative perfusion SPECT imaging

Quantitative software for myocardial perfusion single photon emission computed tomography (SPECT) has advanced significantly over the last 25 years. The strength and availability of quantitative tools for perfusion SPECT have in many ways provided a competitive advantage to nuclear cardiology compared with other higher-resolution noninvasive imaging modalities for the detection of coronary artery disease. The purpose of this report is to review the advances in quantitative diagnostic software for cardiac SPECT over the past 25 years. The time period ending with the 1980s ("the past") saw the origins of nuclear cardiology with the development of planar thallium 201 imaging and perfusion SPECT imaging without electrocardiographic gating. The period from 1990 to the present saw the development of gated SPECT imaging providing both perfusion and functional information and attenuation correction SPECT with improved perfusion information. The report concludes with a look into the future, where hybrid multimodality imaging systems may provide a comprehensive noninvasive evaluation with previously unmatched accuracy in a single imaging session.

Prospective clinical comparison of non-corrected and attenuation- and scatter-corrected myocardial perfusion SPECT in patients with suspicion of coronary artery disease

Attenuation artefacts decrease the specificity of myocardial perfusion single-photon emission computed tomography (SPECT). In this paper, the results of a prospective study evaluating the clinical applicability of attenuation and scatter correction in myocardial perfusion SPECT are presented. Of 607 patients in whom post-stress 99mTc-tetrofosmin myocardial perfusion SPECT was performed due to suspicion of coronary artery disease, 99 also underwent coronary angiography (CAG). A simultaneous emission/transmission acquisition was performed. A multiple linear array of 153Gd sources and four independent energy windows were used for attenuation and scatter correction. A blind separate analysis of non-corrected (NC) and attenuation- and scatter-corrected (AC-SC) images was performed with scores of zero (no uptake) to three (normal uptake). The final diagnosis was based on CAG findings, and stenoses of > or =70% were considered to be significant. NC images had a sensitivity of 92% and a specificity of 46%. In AC-SC images, the sensitivity decreased to 76%, but the specificity increased to 71%. The decrease in the sensitivity of AC-SC images was observed in all three coronary regions. Attenuation and scatter correction increased the specificity in the right coronary region, but decreased the specificity in the left anterior descending coronary region. In 13 of the 99 patients, AC-SC images showed false positive findings due to count deficiency in the anterior wall with normal CAG. The size of perfusion defects was decreased in AC-SC images (from 5.01 +/- 2.74 to 3.15 +/- 2.50 segments). The severity of perfusion defects was higher in NC (1.10 +/- 0.60) than in AC-SC (1.28 +/- 0.56) images. The combined evaluation of NC and AC-SC images was in agreement with the CAG findings in 79% of patients. It can be concluded that, when compared with NC images, AC-SC images improved the specificity in the right coronary region and decreased the sensitivity in all three coronary regions. Attenuation and scatter correction may generate anterior wall defects with normal CAG. The analysis of AC-SC images cannot be used alone for the diagnosis of coronary artery disease. In the clinical setting, combined NC and AC-SC images are recommended for the evaluation of post-stress myocardial perfusion SPECT.

Gated stress-only 99mTc myocardial perfusion SPECT imaging accurately assesses coronary artery disease

In today's cost containment environment it is important to consider changes to standard protocols which would reduce cost, particularly if there is no significant loss of diagnostic accuracy. The aim of the present study was to assess the usefulness of a gated stress-only Tc sestamibi protocol in comparison to conventional gated dual isotope rest-stress myocardial perfusion single photon emission computed tomography (SPECT) in the detection and localization of coronary artery disease (CAD). Sixty-five consecutive patients (65+/-10 years, 22 women) who had undergone conventional gated perfusion SPECT were chosen retrospectively. Fifty-three of these 65 patients had previous coronary arteriography, 45 with at least one stenosis, eight without stenosis, and 12 of these 65 patients had <5% likelihood of CAD. Three readers interpreted the gated stress-only and dual isotope studies in separate sessions blinded to (1). their previous readings, (2). the interpretation by others, and (3). the angiographic results. Readers used a five-point scale to score their visual and quantitative assessment of perfusion, function and compromised vascular territory. Their average score was used for determination of the accuracy by using receiver operating characteristic (ROC) analysis of the techniques. The areas under ROC curves were determined for the detection of CAD and localization of vascular territories. Fifty-four of these patients had 97 significant stress induced perfusion defects as determined by the CEqual quantitative program. The agreement between protocols for the assessment of reversibility in these 97 defects was analysed. There were no statistically significant differences between dual isotope rest/stress and gated stress-only studies for the detection and localization of CAD. The area under the dual isotope rest/stress ROC curve was 0.78+/-0.07 compared to the area under the gated stress-only ROC curve of 0.80+/-0.06, resulting in P=0.30. For the combined vessels comparison of the area under the dual isotope rest/stress ROC curve was 0.73+/-0.04 versus the area under the gated stress-only ROC curve of 0.74+/-0.04, resulting in P=0.27. Similar non-significant differences were obtained when comparing the area under the dual isotope versus gated stress-only ROC curves for the left anterior descending vascular territory (LAD, 0.61+/-0.08 vs 0.660.08, P=0.14), the left circumflex vascular territory (LCX, 0.82+/-0.07 vs 0.81+/-0.06, P =0.47) or the right coronary vascular territory (RCA, 0.80+/-0.06 vs 0.78+/-0.06, P=0.28). The analysis of the reversibility of stress induced perfusion defects yielded a global agreement between protocols of 93% (kappa=0.42). The differences were due to the expert readers, using the gated stress-only protocol, misinterpreting some patients with attenuation artefacts, subendocardial infarction and functional stunning. These results show that the lower cost gated stress-only myocardial Tc myocardial perfusion SPECT studies are comparable to the conventional dual isotope studies when the clinical question is the detection and localization of coronary artery disease. Nevertheless, we also showed that this approach is limited when attempting to interpret the reversibility of stress induced perfusion defects in patients who exhibit attenuation artefacts, subendocardial infarction and functional stunning.