Simplified normal limits and automated quantitative assessment for attenuation-corrected myocardial perfusion SPECT

Background  We aimed to compare normal limits and the detection of coronary artery disease (CAD) with attenuation-corrected (AC) and non-attenuation-corrected (NC) myocardial perfusion single photon emission computed tomography (MPS) by use of a recently improved automated quantification technique. Methods and Results  We acquired 415 rest/stress technetium 99m MPS studies on a Vertex dual-detector camera with a gadolinium 153 line source (Vantage Pro). Gender-specific NC, AC, and gender-combined AC normal limits were created from rest/stress images of 50 women and 50 men with a low likelihood of CAD (<5%) and a median body mass index (BMI) of 30 kg/m2 in each gender group. BMI-specific normal limits (<30 kg/m2 and >30 kg/m2) were also compared. Total perfusion deficit and 17-segment summed scores in 174 patients were compared with angiography, and normalcy rates were established from 141 studies of low-likelihood patients. There were no differences between low-BMI and high-BMI normal limits for AC or NC studies. Male and female normal limits differed in 12 of 17 segments for NC stress studies and in 3 of 17 segments for AC stress studies (P < .01). The sensitivity, specificity, and normalcy rates for stenoses with 70% narrowing or greater were 89%, 73%, and 91%, respectively, for NC studies and 87%, 80%, and 95%, respectively, for AC studies (P = not significant). Conclusion  Automated detection of CAD by AC and NC MPS demonstrated similar sensitivity, specificity, and normalcy rates. Some gender differences were noted for AC normal limits.     

Combined supine and prone quantitative myocardial perfusion SPECT: method development and clinical validation in patients with no known coronary artery disease.

Acquisition in the prone position has been demonstrated to improve the specificity of visually analyzed myocardial perfusion SPECT (MPS) for detecting coronary artery disease (CAD). However, the diagnostic value of prone imaging alone or combined acquisition has not been previously described using quantitative analysis. METHODS: A total of 649 patients referred for MPS comprised the study population. Separate supine and prone normal limits were derived from 40 males and 40 females with a low likelihood (LLk) of CAD using a 3 average-deviation cutoff for all pixels on the polar map. These limits were applied to the test population of 369 consecutive patients (65% males; age, 65 +/- 13 y; 49% exercise stress) without known CAD who had diagnostic coronary angiography within 3 mo of MPS. Total perfusion deficit (TPD), defined as a product of defect extent and severity scores, was obtained for supine (S-TPD), prone (P-TPD), and combined supine-prone datasets (C-TPD). The angiographic group was randomly divided into 2 groups for deriving and validating optimal diagnostic cutoffs. Normalcy rates were validated in 2 additional groups of consecutive LLk patients: unselected patients (n = 100) and patients with body mass index >30 (n = 100). RESULTS: C-TPD had a larger area under the receiver-operating-characteristic (ROC) curve than S-TPD or P-TPD for identification of stenosis >or=70% (0.86, 0.88, and 0.90 for S-TPD, P-TPD, and C-TPD, respectively; P < 0.05). In the validation group, sensitivity for P-TPD was lower than for S- or C-TPD (P < 0.05). C-TPD yielded higher specificity than S-TPD and a trend toward higher specificity than P-TPD (65%, 83%, and 86% for S-, P-, and C-TPD, respectively, P < 0.001; vs. S-TPD and P = 0.06 vs. P-TPD). Normalcy rates for C-TPD were higher than for S-TPD in obese LLk patients (78% vs. 95%, P < 0.001). CONCLUSION: Combined supine-prone quantification significantly improves the area under the ROC curve and specificity of MPS in the identification of obstructive CAD compared with quantification of supine MPS alone.     

Attenuation corrected gated SPECT for the assessment of left ventricular ejection fraction and volumes

OBJECTIVE: The aim of this study was to evaluate the value of attenuation correction (AC) of Tc-99m tetrofosmin single-photon emission tomography (SPECT) imaging for the assessment of left ventricular ejection fraction (LVEF). METHODS: Attenuation corrected and non-attenuation corrected (NC) resting Tc-99m tetrofosmin SPECT were compared for the assessment of LVEF. Planar multigated radionuclide angiography (MUGA) served as the reference for LVEF assessment. Patients (n = 56) with left ventricular dysfunction who underwent MUGA and rest gated Tc-99m tetrofosmin SPECT within 1 month were included. RESULTS: The average LVEF on NC gated SPECT was 37.4 +/- 11.8% and on AC SPECT 38.5 +/- 13.4% (P = NS). The absolute mean difference of the LVEF between the MUGA and NC gated SPECT and AC gated SPECT was -0.2% (95% CI -1.7 to 1.3) and -1.3% (95% CI -2.7 to 0.03), respectively (P = NS both vs. MUGA). The correlation between NC gated SPECT and AC gated SPECT versus MUGA measurement was high with a correlation coefficient of 0.89 (P < 0.01) and 0.92 (P < 0.01), respectively. End-diastolic volumes (EDVs) and end-systolic volumes (ESVs) were significantly higher with AC gated SPECT when compared with NC gated SPECT (both P < 0.001). CONCLUSIONS: Profile AC gated Tc-99m tetrofosmin SPECT agrees well with MUGA and NC gated Tc-99m tetrofosmin SPECT for the assessment of LVEF. EDVs and ESVs are significantly higher with AC gated SPECT when compared with NC gated SPECT.     

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 (> or =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.     

Automated SPECT analysis compared with expert visual scoring for the detection of FFR-defined coronary artery disease

Purpose

Traditionally, interpretation of myocardial perfusion imaging (MPI) is based on visual assessment. Computer-based automated analysis might be a simple alternative obviating the need for extensive reading experience. Therefore, the aim of the present study was to compare the diagnostic performance of automated analysis with that of expert visual reading for the detection of obstructive coronary artery disease (CAD).

Methods

206 Patients (64% men, age 58.2?±?8.7 years) with suspected CAD were included prospectively. All patients underwent ^99mTc-tetrofosmin single-photon emission computed tomography (SPECT) and invasive coronary angiography with fractional flow reserve (FFR) measurements. Non-corrected (NC) and attenuation-corrected (AC) SPECT images were analyzed both visually as well as automatically by commercially available SPECT software. Automated analysis comprised a segmental summed stress score (SSS), summed difference score (SDS), stress total perfusion deficit (S-TPD), and ischemic total perfusion deficit (I-TPD), representing the extent and severity of hypoperfused myocardium. Subsequently, software was optimized with an institutional normal database and thresholds. Diagnostic performances of automated and visual analysis were compared taking FFR as a reference.

Results

Sensitivity did not differ significantly between visual reading and most automated scoring parameters, except for SDS, which was significantly higher than visual assessment (p?<?0.001). Specificity, however, was significantly higher for visual reading than for any of the automated scores (p?<?0.001 for all). Diagnostic accuracy was significantly higher for visual scoring (77.2%) than for all NC images scores (p?<?0.05), but not compared with SSS AC and S-TPD AC (69.8% and 71.2%, p?=?0.063 and p?=?0.134). After optimization of the automated software, diagnostic accuracies were similar for visual (73.8%) and automated analysis. Among the automated parameters, S-TPD AC showed the highest accuracy (73.5%).

Conclusion

Automated analysis of myocardial perfusion SPECT can be as accurate as visual interpretation by an expert reader in detecting significant CAD defined by FFR.

     

Transient ischemic dilation for coronary artery disease in quantitative analysis of same-day sestamibi myocardial perfusion SPECT

Background

Transient ischemic dilation (TID) of the left ventricle in myocardial perfusion SPECT (MPS) has been shown to be a clinically useful marker of severe coronary artery disease (CAD). However, TID has not been evaluated for 99mTc-sestamibi rest/stress protocols (Mibi-Mibi). We aimed to develop normal limits and evaluate diagnostic power of TID ratio for Mibi-Mibi scans.

Methods

TID ratios were automatically derived from static rest/stress MPS (TID) and gated rest/stress MPS from the end-diastolic phase (TID_ed) in 547 patients who underwent Mibi-Mibi scans [215 patients with correlating coronary angiography and 332 patients with low likelihood (LLk) of CAD]. Scans were classified as severe (??70% stenosis in proximal left anterior descending (pLAD) artery or left main (LM), or ??90% in ??2 vessels), mild to moderate (??90% stenosis in 1 vessel or ??70%-90% in ??1 vessel except pLAD or LM), and normal (<70% stenosis or LLk group). Another classification based on the angiographic Duke prognostic CAD index (DI) was also applied: DI????50, 30????DI?<?50 and DI?<?30 or LLk group.

Results

The upper normal limits were 1.19 for TID and 1.23 for TID_ed as established in 259 LLk patients. Both ratios increased with disease severity (P?<?.0001). Incidence of abnormal TID increased from 2% in normal patients to >36% in patients with severe CAD. Similarly, when DI was used to classify disease severity, the average ratios showed significant increasing trend with DI increase (P?<?.003); incidence of abnormal TID also increased with increasing DI. The incidence of abnormal TID in the group with high perfusion scores significantly increased compared to the group with low perfusion scores (stress total perfusion deficit, TPD?<?3%) (P?<?.0001). The sensitivity for detecting severe CAD improved for TID when added to mild to moderate perfusion abnormality (3%????TPD?<?10%): 71% vs 64%, P?<?.05; and trended to improve for TID_ed/TID_es: 69% vs 64%, P?=?.08, while the accuracy remained consistent if abnormal TID was considered as a marker in addition to stress TPD. Similar results were obtained when DI was used for the definition of severe CAD (sensitivity: 76% vs 66%, P?<?.05 when TID was combined with stress TPD).

Conclusion

TID ratios obtained from gated or ungated Mibi-Mibi MPS and are useful markers of severe CAD.     

Attenuation correction improves the detection of viable myocardium by thallium-201 cardiac tomography in patients with previous myocardial infarction and left ventricular dysfunction.

The aim of this study was to determine the influence of attenuation-corrected thallium-201 stress/redistribution/reinjection single-photon emission tomography (SPET) on the number of viable segments in patients with previous myocardial infarction and dysfunctional myocardium. Fifty-one patients with previous myocardial infarction and left ventricular dysfunction were included in the study. In all patients, 201Tl non-corrected (NC) and attenuation-corrected (AC) SPET was performed using a stress/redistribution/reinjection protocol followed by coronary angiography. A semiquantitative analysis was performed using polar maps for NC and AC stress, redistribution and reinjection short-axis and vertical long-axis (apex) slices. Severe (perfusion defect below 50%/maximal count rate: PD < 50), mild and moderate persistent defects for redistribution and reinjection were evaluated for both NC and AC studies. A total of 1581 segments were evaluated by semiquantitative segmental analysis for both NC and AC studies for each redistribution and reinjection map. In the redistribution maps, NC revealed a total of 352 segments and AC a total of 222 segments with impaired perfusion below 50% of the maximal count rate (PD < 50). The mean number of affected segments was 6.9 +/- 5.5 in the case of NC and 4.4 +/- 4.8 in the case of AC (P < 0.001). In the reinjection maps, NC revealed a total of 263 non-viable segments (PD < 50) and AC a total of 169 non-viable segments. The mean number of affected segments was 5.2 +/- 5.3 in the case of NC and 3.3 +/- 4.2 in the case of AC (P < 0.001). Recovery of function was better predicted by AC than by NC in 20% of patients in the follow-up group. Therefore, the use of attenuation correction influences the extent of viable segments by showing more viable segments in either redistribution or reinjection maps. 201Tl imaging without attenuation correction may underestimate the extent of tissue viability, which may contribute to the lower sensitivity compared to fluorine-18-fluorodeoxyglucose positron emission tomography, where attenuation correction is a routinely performed procedure.     

CT-based attenuation correction in Tl-201 myocardial perfusion scintigraphy is less effective than non-corrected SPECT for risk stratification

Background

Previous studies advocate the use of attenuation correction in myocardial perfusion scintigraphy (MPS) for patient risk stratification.

Methods

Six-hundred and thirty-seven unselected patients underwent Tl-201 MPS by a hybrid SPECT/CT system. Attenuation-corrected (AC) and non-corrected (NAC) images were interpreted blindly and summed stress scores (SSS) were calculated. Study endpoints were all-cause mortality and the composites of death/non-fatal acute myocardial infarction (AMI) and death/AMI/late revascularization.

Results

During a follow-up of 42.3 ± 12.8 months 24 deaths, 13 AMIs and 28 revascularizations were recorded. SSS groups formed according to event rate distribution across SSS values were: 0-4, 5-13, >13 for NAC and 0-2, 3-9, >9 for AC. Kaplan-Meier functions were statistically significant between NAC SSS groups for all study endpoints. AC discriminated only between SSS 0-2 and >9 for death/AMI and between 0-2 and 3-9 for death/AMI/revascularization. In the univariate Cox regression abnormal NAC (SSS > 4) was accompanied with much higher hazards ratios than abnormal AC (SSS > 2). In the multivariate model abnormal AC yielded no significance for either endpoint whereas abnormal NAC proved independent from other covariates for the composite endpoints.

Conclusion

Our results challenge the effectiveness of CT-based AC for risk stratification of patients referred for MPS.     

Automatic global and regional phase analysis from gated myocardial perfusion SPECT imaging: application to the characterization of ventricular contraction in patients with left bundle branch block

Although many patients with heart failure benefit from cardiac resynchronization therapy (CRT), predicting which patients will respond to CRT remains challenging. Recent evidence suggests that the analysis of mechanical dyssynchrony using gated myocardial perfusion SPECT (MPS) may be an effective tool. The aim of this study was to evaluate global and regional gated MPS dyssynchrony measurements by comparing parameters obtained from patients with a low likelihood (LLk) of conduction abnormalities and coronary artery disease and patients with left bundle branch block (LBBB). METHODS: A total of 86 consecutive patients with LLk and 72 consecutive patients with LBBB, all without prior myocardial infarction or sternotomy, were studied using gated MPS. Global (histogram SD [sigma], bandwidth [beta], and entropy [epsilon]) and regional (wall- and segment-based differences of means [Deltamicro(W) and Deltamicro(S), respectively] or modes [DeltaM(W) and DeltaM(S), respectively]) dyssynchrony measures were calculated by Fourier harmonic phase-angle analysis of local myocardial count variations over the cardiac cycle for each patient, and then unpaired t tests were used to determine which parameters were sex-specific and how well they discriminated between the LLk and LBBB populations. Receiver-operating-characteristic analysis was also performed to calculate the area under the curve (AUC), sensitivity (Ss), specificity (Sp), and optimal threshold (Th). RESULTS: Global parameters were found to be sex-specific, whereas regional differences were sex-independent. All parameters studied showed statistically significant differences between the groups (all global, P < 0.05; all regional, P < 0.0001). Receiver-operating-characteristic analysis yielded higher AUC, Ss, and Sp for epsilon and regional parameters (epsilon: AUC = 0.95/0.96, Ss = 94%/88%, Sp = 89%/91%, and Th = 53.9%/60.6% for women/men; Deltamicro(W): AUC = 0.93, Ss = 88%, Sp = 86%, and Th = 10.5 degrees ; Deltamicro(S): AUC = 0.94, Ss = 90%, Sp = 94%, and Th = 9.2 degrees ; DeltaM(W): AUC = 0.95, Ss = 90%, Sp = 94%, and Th = 15 degrees ; and DeltaM(S): AUC = 0.95, Ss = 88%, Sp = 90%, and Th = 10.5 degrees ) than for global parameters (sigma: AUC = 0.75/0.67, Ss = 81%/66%, Sp = 63%/64%, and Th = 16.5 degrees /22.2 degrees for women/men; beta: AUC = 0.80/0.72, Ss = 71%/71%, Sp = 79%/64%, and Th = 69 degrees /81 degrees for women/men). CONCLUSION: The computed parameters all discriminate effectively between LLk and LBBB populations. Measurements that are less dependent on the shape of the phase-angle distribution histogram provided higher sensitivity and specificity for this purpose. Further study is needed to evaluate these parameters for the purpose of predicting response to CRT.     

Improved accuracy of myocardial perfusion SPECT for detection of coronary artery disease by machine learning in a large population

Objective

We aimed to improve the diagnostic accuracy of myocardial perfusion SPECT (MPS) by integrating clinical data and quantitative image features with machine learning (ML) algorithms.

Methods

1,181 rest ²⁰¹Tl/stress ^99mTc-sestamibi dual-isotope MPS studies [713 consecutive cases with correlating invasive coronary angiography (ICA) and suspected coronary artery disease (CAD) and 468 with low likelihood (LLk) of CAD <5%] were considered. Cases with stenosis <70% by ICA and LLk of CAD were considered normal. Total stress perfusion deficit (TPD) for supine/prone data, stress/rest perfusion change, and transient ischemic dilatation were derived by automated perfusion quantification software and were combined with age, sex, and post-electrocardiogram CAD probability by a boosted ensemble ML algorithm (LogitBoost). The diagnostic accuracy of the model for prediction of obstructive CAD ≥70% was compared to standard prone/supine quantification and to visual analysis by two experienced readers utilizing all imaging, quantitative, and clinical data. Tenfold stratified cross-validation was performed.

Results

The diagnostic accuracy of ML (87.3% ± 2.1%) was similar to Expert 1 (86.0% ± 2.1%), but superior to combined supine/prone TPD (82.8% ± 2.2%) and Expert 2 (82.1% ± 2.2%) (P < .01). The receiver operator characteristic areas under curve for ML algorithm (0.94 ± 0.01) were higher than those for TPD and both visual readers (P < .001). The sensitivity of ML algorithm (78.9% ± 4.2%) was similar to TPD (75.6% ± 4.4%) and Expert 1 (76.3% ± 4.3%), but higher than that of Expert 2 (71.1% ± 4.6%), (P < .01). The specificity of ML algorithm (92.1% ± 2.2%) was similar to Expert 1 (91.4% ± 2.2%) and Expert 2 (88.3% ± 2.5%), but higher than TPD (86.8% ± 2.6%), (P < .01).

Conclusion

ML significantly improves diagnostic performance of MPS by computational integration of quantitative perfusion and clinical data to the level rivaling expert analysis.     

Automated quantitative Rb-82 3D PET/CT myocardial perfusion imaging: Normal limits and correlation with invasive coronary angiography

Background

We aimed to characterize normal limits and to determine the diagnostic accuracy for an automated quantification of 3D 82-Rubidium (Rb-82) PET/CT myocardial perfusion imaging (MPI).

Methods

We studied 125 consecutive patients undergoing Rb-82 PET/CT MPI, including patients with suspected coronary artery disease (CAD) and invasive coronary angiography, and 42 patients with a low likelihood (LLk) of CAD. Normal limits for perfusion and function were derived from LLk patients. QPET software was used to quantify perfusion abnormality at rest and stress expressed as total perfusion deficit (TPD).

Results

Relative perfusion databases did not differ in any of the 17 segments between males and females. The areas under the receiver operating characteristic curve for detection of CAD were 0.86 for identification of ??50% and ??70% stenosis. The sensitivity/specificity was 86%/86% for detecting ??50% stenosis and 93%/77% for ??70% stenosis, respectively. In regard to normal limits, mean rest and stress left ventricular ejection fraction (LVEF) were 67%?±?10% and 75%?±?9%, respectively. Mean transient ischemic dilation ratio was 1.06?±?0.14 and mean increase in LVEF with stress was 7.4%?±?6.1% (95th percentile of 0%).

Conclusion

Normal limits have been established for 3D Rb-82 PET/CT analysis with QPET software. Fully automated quantification of myocardial perfusion PET data shows high diagnostic accuracy for detecting obstructive CAD.     

Motion-frozen myocardial perfusion SPECT improves detection of coronary artery disease in obese patients.

In this study, we compared the diagnostic performance of the standard SPECT with motion-frozen (MF) myocardial perfusion SPECT (MPS) in obese patients. METHODS: A total of 90 consecutive obese patients (body mass index, 30.1-46.8, average, 34.3 +/- 3.6; age, 63 +/- 12 y; 30% women) underwent standard supine rest (201)Tl/stress (99m)Tc dual-isotope gated MPS and cardiac catheterization within 3 mo. MF images were obtained by nonlinear warping of cardiac phases to the end-diastolic position. Total perfusion deficit (TPD) was obtained for summed (S-TPD) and motion-frozen (MF-TPD) datasets with sex-specific standard and MF normal limits. RESULTS: The area under the receiver-operating-characteristic (ROC) curve for detection of coronary artery disease (CAD) by MF-TPD was significantly larger than that for S-TPD (0.93 +/- 0.25 vs. 0.88 +/- 0.32, P < 0.05). MF-TPD had higher specificity (77% vs. 55%, P < 0.05) and accuracy (89% vs. 80%, P < 0.05) than did S-TPD. CONCLUSION: MF processing of MPS improves CAD detection in obese patients.     

Attenuation correction by simultaneous emission-transmission myocardial single-photon emission tomography using a technetium-99m-labelled radiotracer: impact on diagnostic accuracy

Irregular photon attenuation may limit the diagnostic accuracy of myocardial single-photon emission tomography (SPET). The aim of this study was to quantify the potential benefit of attenuation correction by simultaneous emission and transmission imaging for the detection of coronary artery disease (CAD) of vessels supplying the inferoposterior wall segments. In 25 male patients with 50% stenoses of the right coronary artery and/or circumflex artery but without significant narrowing of the left anterior descending artery, stress studies using technetium-99m tetrofosmin (400 MBq) were carried out with and without attenuation correction. A dual-head camera with L-shaped detector positioning was equipped with two scanning gadolinium-153 line sources. Tomograms were reconstructed and quantified using circumferential count rate profiles of myocardial activity (two in each patient). The profiles were compared with the respective normal ranges obtained from a database of 25 male patients with a <10% likelihood of CAD. In patients without CAD, the maximal differences in count density of different wall segments were reduced from 29.0% in non-corrected (NC) studies to 9.5% in attenuation-corrected (AC) studies. In particular, the inferoposterior and septal wall segments were represented by significantly increased relative count densities after attenuation correction. The effects of attenuation correction proved independent of body mass. In patients with CAD, segmental count densities were abnormal in 84% of the NC studies and 100% of the AC studies. In single-vessel disease the stenotic vessel was identified in 66% of cases by NC studies and in 100% by AC studies. In AC studies, the extent and depth of defects exceeded those in NC studies. For the detection of CAD of the right coronary artery, the receiver operating characteristic (ROC) curves relating to the AC studies demonstrated improved discrimination capacity (P<0.05). ROC analysis of CAD detection yielded normalcy rates of 82% (NC) and 94% (AC) for the circumflex artery and 65% (NC) and 97% (AC) for the right coronary artery area at a sensitivity level of 95%. It is concluded that attenuation correction using the above system may enhance the diagnostic accuracy of myocardial SPET when inferoposterior wall segments are to be evaluated.     

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.     

"Motion-frozen" display and quantification of myocardial perfusion.

Gated myocadial perfusion SPECT (MPS) incorporates functional and perfusion information of the left ventricle (LV). To improve the image quality and accuracy of gated MPS we propose to eliminate the influence of cardiac LV motion in the display and quantification by a novel "motion-frozen" (MF) technique. METHODS: Three-dimensional LV contours were identified on images of the individual time phases. Three-dimensional phase-to-phase motion vectors were derived by sampling of the epi- and endocardial surfaces. A nonlinear image warping (thin-plate spline) was applied to warp all image phases to fit the end-diastolic (ED) phase. Warped images were created to provide the LV image in the ED phase but containing counts from an arbitrary number of time intervals. MF quantification has been performed using the same phase-to-phase motion vectors. MF normal perfusion limits were created from (99m)Tc sestamibi gated MPS studies of 40 females and 40 males with low likelihood (<5%) of coronary artery disease. All MF processing was completely automated. In the initial evaluation, we assessed the display quality and quantification of stress images using MF processing in 51 consecutive patients with 16-frame electrocardiographic gating and available coronary angiography. RESULTS: The display quality was significantly better for MF images as assessed visually. The MF images had the appearance of ED frames but were less noisy and of higher resolution than the summed images. MF images had higher maximum count values in the LV (116% +/- 6%) and higher contrast (12.5 +/- 7.7 vs. 9.5 +/- 3.2) than the corresponding summed images. The area under the receiver operator characteristic curve for prediction of stenoses > or = 70% by the MF method was 0.92 +/- 0.04 versus 0.89 +/- 0.04 by standard quantification (P = not significant). The computation time for automated MF quantification and warping was <25 s for each case. CONCLUSION: We have developed a novel technique for display and quantification of gated myocardial perfusion images, which retrospectively eliminates blur due to cardiac motion. Such processing of gated MPS appears to improve the effective resolution of images. Initial evaluation indicates that it may improve the accuracy of gated MPS in detection of coronary artery disease.     

Attenuation correction reveals gender-related differences in the normal values of transient ischemic dilation index in rest-exercise stress sestamibi myocardial perfusion imaging

BACKGROUND: Transient ischemic dilation (TID) has been established as an important independent marker of severe and extensive coronary artery disease (CAD) in myocardial perfusion imaging (MPI). The accuracy of the TID index is dependent on a well-determined threshold (normal limits) between normal and abnormal values for each study protocol. To date, the effects of neither gender nor attenuation correction (AC) on TID normal limits have been established. Thus, the objectives of this study were to determine if AC processing changes the normal value of the TID index and if there were gender-related differences in the TID index of normal patients who had undergone rest/exercise-stress technetium-99m sestamibi MPI. METHODS AND RESULTS: Seventy-five patients (33 women, 42 men; mean age, 57.7 +/- 11.7 y and 55.9 +/- 10.0 y, respectively) with less than a 5% likelihood of CAD, who had undergone low-dose rest/high-dose exercise-stress Tc-99m sestamibi MPI, were studied. All studies were acquired using simultaneous emission/transmission scans and were corrected for attenuation, scatter, and resolution effects using the ExSPECT II method. Both the AC and non-AC studies were analyzed using the Emory Cardiac Toolbox (ECTb; Syntermed, Inc, Atlanta, Ga) quantitative software. The TID index was calculated automatically as the ratio of stress mean left ventricular volumes to rest mean left ventricular volumes by ECTb. Patients were grouped by gender and the TID indices from AC and non-AC studies were compared. Linear regressions of the TID index and body mass index were analyzed to exclude differences in body size between male and female patients as a confounding factor in gender-related differences in TID. The TID index upper normal limits were calculated as the mean value plus 2 standard deviations (SDs). AC processing did not change the TID index significantly whether the genders were combined or separated (AC TID = 0.97 +/- 0.14 vs non-AC TID = 0.98 +/- 0.12 for all patients). Female patients showed higher mean TID indices than male patients in both AC (1.01 +/- 0.15 vs 0.95 +/- 0.12) and non-AC studies (1.00 +/- 0.15 vs. 0.97 +/- 0.10), but this difference was statistically significant only in AC studies (p = .03). TID indices remained constant across the range of body mass index studied. The TID index upper normal limit was 1.31 for female and 1.18 for male patients. CONCLUSION: TID normal values for rest/exercise-stress Tc-99m sestamibi MPI are gender-dependent and not affected by AC processing. Thus, diagnosticians should take into account these gender-related differences, as compared with the traditional value generated from mostly male populations, to ensure both men and women have the same overall accuracy of using the TID index in the diagnosis and prognosis of CAD.     

Prognostic implications of combined prone and supine acquisitions in patients with equivocal or abnormal supine myocardial perfusion SPECT.

Although acquisition of (99m)Tc-sestamibi myocardial perfusion SPECT (MPS) with the patient in the prone position is commonly used to minimize attenuation artifacts, the impact of combined prone and supine imaging on the prognostic evaluation of coronary artery disease (CAD) has not been determined. The prognostic implications of MPS obtained in both prone and supine positions in patients with perfusion defects on supine MPS were evaluated. METHODS: We studied 3,834 patients who were monitored for 24.2 +/- 6.0 mo after rest (201)Tl/stress (99m)Tc-sestamibi MPS acquired during 1994-1995, when prone acquisition was performed only in patients with inferior wall perfusion defects that might represent attenuation or motion artifact. RESULTS: During follow-up, there were 132 hard events (cardiac death or myocardial infarction) and 375 total events (hard events or late myocardial revascularization). Overall, patients who underwent prone and supine acquisitions had similar characteristics to those who underwent supine-only imaging, with the exception of being more commonly male. In multivariable analysis, there were similar independent predictors for hard events and total events; the type of acquisition (prone and supine or supine-only) was not a significant predictor of either of these outcome events. After risk adjustment, the predicted event rates were nearly identical for patients undergoing prone and supine compared with supine-only studies. Both observed and predicted hard event rates of patients with normal prone and supine versus supine-only imaging were very low (observed, 0.7%/y and 0.5%/y, respectively; predicted, 1.5% over 24 mo for both). There was no reduction in the higher rates of events associated with abnormal scan results with the combination of prone and supine imaging. CONCLUSION: Patients with inferior wall defects on supine MPS that are not present on prone MPS have a low risk of subsequent cardiac events, similar to that of patients with normal supine-only studies.     

A comparison of99mTc-MIBI myocardial SPET with electron beam computed tomography in the assessment of coronary artery disease

We compared technetium-99m methoxyisobutylisonitrile (MIBI) myocardial perfusion single-photon emission tomography (SPET) (MPS) and electron beam computed tomography (EBCT) in order to assess their respective value in the detection of coronary artery disease (CAD).^99mTc-MIBI SPET (stress-resting) and EBCT studies were performed in 51 patients with suspected CAD who underwent coronary angiography (CAG). CAG showed that of the 51 patients, 36 had coronary stenosis 50% while 15 had normal results. A moderate positive rank correlation was found between coronary calcification detected by EBCT and MPS score (r _s=0.5283,P<0.01). The concordance between EBCT and MPS for the evaluation of CAD was 72.5% (37/51). The sensitivity of EBCT in detecting CAD in 51 patients was comparable to that of MPS (81% vs 94%, NS). However, the accuracy of EBCT was lower than that of MPS (78% vs 94%,P<0.025). As regards the detection of individual coronary artery disease, there was no significant difference in sensitivity between EBCT and MPS (65% vs 75%, NS); however, the specificity and accuracy of EBCT were lower than those of MPS (specificity: 77% vs 95%,P<0.005; accuracy 71% vs 85%,P<0.005). The sensitivity, specificity and accuracy of MPS in detecting single-vessel disease were higher than those of EBCT (sensitivity: 86% vs 42%,P<0.025; specificity: 96% vs 70%,P<0.025; accuracy: 93% vs 61%,P<0.005). However, no significant differences in the sensitivity, specificity and accuracy of MPS and EBCT were found in respect of multivessel disease. In conclusion:^99mTc-MIBI myocardial perfusion SPET and EBCT provide different information in the assessment of CAD. The sensitivity of EBCT for the detection of CAD is comparable with that of MPS; however, the specificity and accuracy of EBCT are lower than those of MPS. More reliable results will be obtained if both myocardial perfusion SPET and EBCT are performed.     

Attenuation-corrected thallium-201 single-photon emission tomography using a gadolinium-153 moving line source: clinical value and the impact of attenuation correction on the extent and severity of perfusion abnormalities

The aim of the study was to test the clinical value of attenuation-corrected (AC) thallium-201 single-photon emission tomography using a moving gadolinium-153 line source in a group of patients in whom coronary angiography was planned because of clinically suspected coronary artery disease (CAD). Furthermore, we wanted to test the impact of AC on assessment of the extent and severity of perfusion abnormalities. A total of 107 patients planned to undergo coronary angiography were included in the study. In each patient, AC and NC (non-corrected) ²⁰¹Tl SPET was performed. AC and NC images were evaluated visually as well as by a 31-segment semiquantitative analysis and the findings were correlated with angiographic results. Patients were assigned to two groups: group A with angina and no previous cardiac infarction or intervention and group B with known CAD because of previous myocardial infarction or intervention. With visual analysis, NC revealed a sensitivity of 88.9% in group A and 74.3% in group B, compared to 94.4% in group A and 94.3% in group B with AC. Specificity for NC was calculated to be 68.7% for group A and 91.3% for group B. AC demonstrated significantly higher specificity of 83.9% and 100%, respectively. This effect was particularly demonstrated for males and bicycle workload. The extent and severity of perfusion abnormalities were significantly influenced by the use of AC, in that significantly fewer abnormal and less severely abnormal segments were demonstrated in the segmental analysis as compared to NC; this was especially true for the vascular territory of the left anterior descending artery nd the right coronary artery. It is concluded that AC with a moving line source is feasible in patients with all degrees of probability of CAD. AC has a significant impact on the assessment of the severity and extent of myocardial ischaemia, especially in the posterior and septal wall. Received 23 September and in revised form 11 November 1997     

Combined quantitative analysis of attenuation corrected and non-corrected myocadial perfusion SPECT: Method development and clinical validation

Background  

Attenuation corrected myocardial perfusion SPECT (AC-MPS) has been demonstrated to improve the specificity of detecting coronary artery disease (CAD) by visual analysis which utilizes both non-corrected (NC) and AC data. However, the combined automated quantification of NC and AC-MPS has not been previously described. We aimed to develop a combined quantitative analysis from AC and NC data to improve the accuracy of automated detection of CAD from AC-MPS.