A new method for quantification of pulmonary thallium uptake in myocardial SPECT studies

Quantified pulmonary thallium 201 (Tl) uptake was assessed in 32 normal subjects and 66 patients with suspected coronary artery disease (CAD) by a new method utilizing SPECT acquisition data. In 26 subjects pulmonary uptake was assessed with both SPECT and planar techniques. Pulmonary/myocardial (PM) ratios for the whole right lung (PM1) and for the upper left lung (PM2) were computed and compared with stress test, coronary angiography, radionuclide angiography (ERNA), and quantified Tl single photon emission computed tomography (SPECT) results. Excellent correlation between pulmonary uptake assessed by planar and SPECT technique was disclosed (r = 0.92). The PM ratios (PM1/PM2) sensitivity and specificity in patients with CAD were 88%/92% and 60%/70%, for predicting perfusion abnormalities 90%/87% and 88%/88%, and an inverse correlation to left ventricular ejection fraction (LVEF) was found (r = -0.40/r = -0.37, P less than 0.01). Significant correlations to coronary angiography findings (r = 0.54/r = 0.49, P less than 0.001) and to number of vessel territories with abnormal perfusion (r = 0.70/r = 0.69, P less than 0.001) were seen. Thus, pulmonary Tl uptake can be assessed in SPECT studies. The new method's discriminative ability seems higher than that of the standard planar techniques currently employed. Positive correlations to coronary angiography findings and even stronger ones to perfusion abnormalities were observed.     

Spatial distribution and temporal changes of pulmonary thallium uptake in myocardial perfusion studies

Spatial distribution and temporal changes in pulmonary thallium uptake were assessed in 24 normal subjects and 35 patients with coronary artery disease (CAD). In studies carried out directly after stress and 3 h later, pulmonary T1 uptake was assessed as body surface area corrected absolute pulmonary uptake in the upper, middle and lower right lung regions, and in the total right lung and upper left lung. Pulmonary/myocardial (PM) uptake ratios for these 5 regions were calculated as mean pulmonary/mean background-corrected myocardial uptake. Additionally, wash-out was assessed for each region and for the myocardium. In normal subjects, the inital pulmonary T1 uptake, the PM ratios and T1 wash-out were greater in the lower lung regions than in the upper. In the late studies, no significant differences in T1 content or PM ratios were found among the regions. In patients with CAD, initial pulmonary T1 uptake and PM ratios were greater in the lower than in the upper regions, and higher than for the normal subjects in all pulmonary regions (P<0.001). T1 wash-out was significantly higher in the low and middle regions versus the upper region (P < 0.001) and higher in all regions than in normal subjects (P<0.001). In the late studies no significant differences in T1 content or PM ratios were found between any pulmonary regions. Pulmonary T1 content was, in all regions, higher in CAD than in normal subjects (P<0.01), as were the PM ratios (P<0.001). In conclusion, in normal subjects as well as in patients with CAD, pulmonary T1 uptake is greatest in the lower lung regions. Absolute pulmonary T1 uptake, PM ratios and pulmonary wash-out are greater in all lung regions in patients with CAD. Lower myocardial uptake may be the more important factor in producing the increased PM ratios in patients with CAD. Pulmonary redistribution is complete after 3–4 h. These characteristics strongly affect pulmonary T1 uptake ratios and wash-out assessments.     

Identification of advanced coronary artery disease with exercise myocardial perfusion imaging: the clinical value of a novel approach for assessing lung thallium-201 uptake

Introduction The precise clinical utility of lung ²⁰¹Tl uptake in exercise SPECT myocardial perfusion imaging remains open to research. This study validates an optimal index for lung ²⁰¹Tl uptake measurement and assesses its value in the prediction of higher-risk coronary artery disease (CAD). Method Three hundred and ninety-eight patients underwent exercise SPECT myocardial perfusion imaging. They were separated into derivation (n = 217) and validation (n = 186) groups, both including sub-populations of lower- and higher-risk CAD, according to coronary angiography. Another 56 individuals with a low probability of CAD comprised the control group. From a planar, anterior, post-exercise acquisition, the lung (L) to heart (H) maximal (L/H_max), total (L/H_mean) and background-subtracted total (L/H_net) ratios were calculated. These were also adjusted for confounding variables, as assessed from the control group. ROC analysis was used to compare the L/H ratios and define thresholds of abnormality. The performance of the optimal index was assessed in the derivation group and was then tested in the validation population. Subsequently, it was compared with other scintigraphic, exercise electrocardiography and clinical variables. Results In the derivation group L/H_net was a better discriminator for higher-risk CAD than both L/H_max and L/H_mean. Similarly, the adjusted L/H_net was a better discriminator than both the adjusted L/H_max and the adjusted L/H_mean. No significant difference was attained between L/H_net and the adjusted L/H_net. At the upper defined threshold of abnormality, sensitivity and specificity of L/H_net in the detection of higher-risk CAD in the derivation and the validation cohorts were 52% and 92% versus 47% and 94%, respectively (p =  ns). The results were similar at other defined thresholds. Moreover, L/H_net was found to be a significant predictor of higher-risk CAD, superior to myocardial perfusion images, transient ventricular dilation measurements, and clinical and exercise testing variables (ROC analysis and logistic regression). By raising the threshold of abnormality of L/H_net, specificity and positive predictive value increased, whereas sensitivity and negative predictive value decreased. Conclusion Lung ²⁰¹Tl assessment assists substantially in the identification of higher-risk CAD in exercise SPECT myocardial perfusion imaging and this is best achieved by L/H_net. This index is a significant predictor of higher-risk CAD, superior to myocardial perfusion images, and its value is associated with the probability of a disease state.     

Validation of a new cardiac image fusion software for three-dimensional integration of myocardial perfusion SPECT and stand-alone 64-slice CT angiography

Purpose Combining the functional information of SPECT myocardial perfusion imaging (SPECT-MPI) and the morphological information of coronary CT angiography (CTA) may allow easier evaluation of the spatial relationship between coronary stenoses and perfusion defects. The aim of the present study was the validation of a novel software solution for three-dimensional (3D) image fusion of SPECT-MPI and CTA. Methods SPECT-MPI with adenosine stress/rest ^99mTc-tetrofosmin was fused with 64-slice CTA in 15 consecutive patients with a single perfusion defect and a single significant coronary artery stenosis (≥50% diameter stenosis). 3D fused SPECT/CT images were analysed by two independent observers with regard to superposition of the stenosed vessel onto the myocardial perfusion defect. Interobserver variability was assessed by recording the X, Y, Z coordinates for the origin of the stenosed coronary artery and the centre of the perfusion defect and measuring the distance between the two landmarks. Results SPECT-MPI revealed a fixed defect in seven patients, a reversible defect in five patients and a mixed defect in three patients and CTA documented a significant stenosis in the respective subtending coronary artery. 3D fused SPECT/CT images showed a match of coronary lesion and perfusion defect in each patient and the fusion process took less than 15 min. Interobserver variability was excellent for landmark detection (r = 1.00 and r = 0.99, p < 0.0001) and very good for the 3D distance between the two landmarks (r = 0.94, p < 0.001). Conclusion 3D SPECT/CT image fusion is feasible, reproducible and allows correct superposition of SPECT segments onto cardiac CT anatomy.     

Global and regional left ventricular function: a comparison between gated SPECT, 2D echocardiography and multi-slice computed tomography

Purpose Global and regional left ventricular (LV) function are important indicators of the cardiac status in patients with coronary artery disease (CAD). Therapy and prognosis are to a large extent dependent on LV function. Multi-slice computed tomography (MSCT) has already earned its place as an imaging modality for non-invasive assessment of the coronary arteries, but since retrospective gating to the patient’s ECG is performed, information on LV function can be derived. Methods In 49 patients with known or suspected CAD, coronary angiography with MSCT imaging was performed, in addition to gated SPECT and 2D echocardiography. LV end-diastolic and LV end-systolic volumes and LV ejection fraction were analysed with dedicated software (CMR Analytical Software System, Medis, Leiden, The Netherlands for MSCT; gated SPECT by QGS, Cedars-Sinai Medical Center, Los Angeles, CA, USA), and by the biplane Simpson’s rule for 2D echocardiography. Regional wall motion was evaluated according to a 17-segment model and a three-point score system. Results Correlations were fairly good between gated SPECT and MSCT (LVEDV: r=0.65; LVESV: r=0.63; LVEF: r=0.60), and excellent between 2D echocardiography and MSCT (LVEDV: r=0.92; LVESV: r=0.93; LVEF: r=0.80). Agreement for regional wall motion was 95% (κ=0.66) between gated SPECT and MSCT, and 96% (κ=0.73) between 2D echocardiography and MSCT. Conclusion Global and regional LV function and LV volumes can be adequately assessed with MSCT. Correlations with 2D echocardiography are stronger than with gated SPECT.     

Rest-injected thallium-201 redistribution and resting technetium-99m methoxyisobutylisonitrile uptake in coronary artery disease: relation to the severity of coronary artery stenosis

To compare rest-injected thallium-201 (Tl) redistribution and resting technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) myocardial uptake in chronic coronary artery disease (CAD), 15 patients with angiographically proven CAD and left ventricular (LV) dysfunction (ejection fraction 34%±9%) were studied. All patients underwent rest-redistribution Tl and resting ^99mTc-MIBI cardiac imaging. Gated ^99mTc-MIBI images were also acquired to assess regional LV wall motion (WM). Myocardial segments (n=225) were divided into three groups on the basis of the degree of coronary artery stenosis: group 1 (total occlusion, n=82), group 2 (50%–99% of stenosis, n=84) and group 3 (<50% of stenosis, n=59). WM was significantly worse in groups 1 and 2 compared to group 3 (P<0.001), but no difference was observed between groups 1 and 2. TI and ^99mTc-MIBI uptake were significantly lower in groups 1 and 2 compared to group 3 (P < 0.001), and in group 1 compared to group 2 (P<0.001). When TI and ^99mTc-MIBI uptake were directly compared, TI uptake was higher than ^99mTc-MIBI uptake in group 1 (P<0.001), while no significant difference was observed in groups 2 and 3. Thus, both rest-injected TI redistribution and resting ^99mTc-MIBI uptake reflected the severity of coronary artery stenosis in CAD. However, in myocardial segments with total coronary occlusion T1 uptake was significantly higher than ^99mTc-MIBI uptake. Our data suggest that rest-injected Tl redistribution cardiac imaging may identify, more accurately than resting ^99mTc-MIBI imaging, the presence of viable myocardium in chronic CAD, particularly when the coronary blood flow is severely impaired.     

Left bundle branch block and coronary artery disease: Accuracy of dipyridamole thallium-201 single-photon emission computed tomography in patients with exercise anteroseptal perfusion defects

Background  Reduced septal or anteroseptal uptake of thallium-201 during exercise is frequently observed in patients with left bundle branch block (LBBB) even in the absence of left anterior descending (LAD) coronary artery disease. The purpose of this study was to evaluate prospectively the accuracy of dipyridamole²⁰¹TI single-photon emission computed tomography (SPECT) in detecting LAD coronary artery disease in patients with LBBB and septal or anteroseptal perfusion defects on exercise²⁰¹TI SPECT. Methods and Results  Twelve consecutive patients (10 men and two women) with complete LBBB and septal or anteroseptal perfusion defects on exercise²⁰¹TI SPECT underwent dipyridamole²⁰¹TI SPECT. The delay between dipyridamole and exercise was 2 to 30 days. Coronary angiography was performed during this period in all patients. Six (50%) of 12 patients with exercise perfusion defects showed normal perfusion after dipyridamole; all had normal coronary angiograms. The remaining six patients also had positive results of dipyridamole studies, two with moderate and four with severe septal or anteroseptal perfusion defects. Coronary angiography showed significant (>50%) LAD coronary artery stenosis in three patients; three patients with severe septal or anteroseptal perfusion defects after dipyridamole had normal coronary angiograms. Neither the evaluation of apical involvement nor the presence of dilated ventricles, decreased left ventricular ejection fraction, or wall motion abnormalities could help to identify (or explain) false-positive results. Conclusion  This study confirms that dipyridamole is more accurate than exercise in excluding LAD coronary artery disease. However, there are still false-positive results and the severity of the septal or anteroseptal perfusion defect does not add additional information to identify LAD coronary artery disease. Coronary angiography is thus necessary for positive dipyridamole study results to identify coronary artery disease as a major prognostic factor in patients with LBBB.     

The (F)utility of the thallium-201 quantitative lung/myocardial ratio in the detection of coronary artery disease

Exercise-induced increases in pulmonary uptake of thallium-201 (²⁰¹Tl) have been associated with exercise-induced myocardial dysfunction. To evaluate this phenomenon more replicably, a quantitative semi-automated computer program was used to generate, from anterior exercise and delayed views, lung-myocardial ratios (LMR) of²⁰¹Tl uptake in 78 patients [40 normal, 38 with coronary artery disease (CAD)]. Patients with CAD had a significantly higher mean exercise lung myocardial ratio (EXLMR) than normals (30.8 vs. 27.3;P < 0.003). In patients with adequate exercise (85% of an age-adjusted maximal heart rate), the EXLMRs of CAD patients were significantly higher than those of normals (29.7 vs. 25.5;P=0.003). However, this difference between CAD and normal patients was not apparent in a patient subgroup with submaximal exercise levels (< 85% of an age-adjusted maximal heart rate). In both normal and CAD patients, EXLMR decreased with increasing exercise levels (r=-0.555;P=0.007). In patients with²⁰¹Tl scans lacking visually defined perfusion defects (visually normal), an elevated LMR detected 60% of CAD cases with 81% specificity. A considerably elevated EXLMR in patients achieving adequate exercise should suggest the presence of CAD, even if there are no visually apparent cardiac perfusion defects. With submaximal exercise, however, the EXLMR is not a useful discriminator between CAD patients and normals.     

A normal stress SPECT scan is an effective gatekeeper for coronary angiography

Background  The effectiveness of stress single photon emission computed tomography (SPECT) as a gatekkeper for coronary angiography has not been extensively investigated. The characteristics of patients referred for carly angiography after a normal stress SPECT study have not been described. Methods and Results  Over a 10-year period, 14,273 patients without documented coronary artery disease (CAD) underwent stress SPECT. Images were abnormal in 47% and normal in 53%. The overall survival rate at 15 years was 55% for patients with abnormal images versus 71% for those with normal images (P<.001). Early coronary angiography (≤3 months) was performed in only 97 patients (1.3%) with normal SPECT studies versus 1,756 patients (26%) with abnormal SPECT studies (P<.001). Most patients with normal SPECT studies referred for carly angiography (85%) had clinical, exercise, or scintigraphic findings worrisome for CAD. Two thirds of these highly selected patients with normal SPECT studies who underwent angiography did not have significant CAD; the remining one third had primarily 1- and 2-vessel CAD. Conclusions  Stress SPECT is an effective gatekeeper for coronary angiography. The annual overall mortality rate for patients with normal images was 1.9%. Only 1.3% of patients with normal images were referred for early angiography. Dr Miller receives a research grant from Bristol Myers Squibb.     

Diagnostic impact of SPECT image display on assessment of obstructive coronary artery disease

Background  Diagnostic assessment of myocardial perfusion impacts the management of patients with suspected coronary artery disease (CAD). Although various image displays are available for single photon emission computed tomography (SPECT) interpretation, the effects of display differences on SPECT interpretation remain undetermined. Methods and Results  We studied 183 patients undergoing SPECT, including 131 consecutive patients referred for angiography and 52 at low CAD risk. Studies were visually interpreted by use of color and gray images, with readers blinded to the results of the other display. In accordance with established criteria, a summed stress score (SSS) of 4 or greater was considered abnormal. The prevalence of abnormal SPECT findings was higher with gray images than with color images (54% vs 48%, P<.001) based on a uniform criterion (SSS≥4). However, color images yielded equivalent sensitivity (79% vs 82%, P=.7) and improved specificity for global (50% vs 33%, P=.02) and vessel-specific CAD involving the right coronary artery (P<.01) and left anterior descending artery (P<.05). When the criterion for gray images was adjusted upward (SSS≥5) to reflect increased mean defect severity (SSS of 5.1 vs 4.4, P=.01), gray and color images provided equivalent sensitivity and specificity for global and vessel-specific CAD. Conclusions  SPECT interpretation can vary according to image display as a result of differences in perfusion defect severity. Adjustment of abnormality criteria for gray images to reflect minor increases in defect severity provides equivalent diagnostic performance of gray and color displays for CAD assessment. Dr Weinsaft was the recipient of a Doris Duke Clinical Scientist Development Award from the Doris Duke Charitable Foundation (New York, NY)     

Postexercise lung uptake of 99mTc-sestamibi determined by a new automatic technique: validation and application in detection of severe and extensive coronary artery disease and reduced left ventricular function.

This study validated a new automatic algorithm for assessment of lung-to-heart ratio (L/H) of radiotracers in myocardial perfusion SPECT and assessed the diagnostic value of (99m)Tc-sestamibi L/H after exercise. METHODS: The new technique extracts a left ventricular region of interest (ROI) from a summed anterior projection image and generates a lung ROI by reshaping and translating the left ventricular ROI. This algorithm was applied to 230 patients who underwent exercise (99m)Tc-sestamibi SPECT (gated SPECT, n = 88) with first-pass ventriculography. Normal values were established in 26 patients in whom the likelihood of coronary artery disease (CAD) was 5% or less. An abnormality threshold for detecting severe and extensive CAD was defined in a subgroup of 109 patients who underwent coronary angiography and was validated in a prospective group (n = 72). RESULTS: The success rate of the automatic algorithm was 97%. Excellent correlation was found between automatic and manual L/H values (r = 0.95; P < 0.001). The mean L/H was higher in patients with a peak exercise ejection fraction (EF) less than 40% versus 40% or more (0.51 +/- 0.07 versus 0.43 +/- 0.05, P < 0.001) and in patients with a poststress EF less than 40% versus 40% or more (0.50 +/- 0.07 versus 0.44 +/- 0.06, P < 0.01). A threshold of L/H greater than 0.44 yielded a sensitivity and specificity of 63% and 81%, respectively, for identifying severe and extensive CAD in the prospective group and a sensitivity of 86% in identifying stenosis of 90% or more in the proximal left anterior descending artery. CONCLUSION: The new automatic algorithm for assessing L/H correlated well with manually derived L/H for (99m)Tc-sestamibi as well as (201)TI SPECT. An increased postexercise (99m)Tc-sestamibi L/H adds significant diagnostic value to study myocardial perfusion SPECT as a marker of severe and extensive CAD and reduced ventricular function.     

Significance of increased right ventricular uptake on 99mTc-sestamibi SPECT in patients with coronary artery disease.

The significance of increased right ventricular (RV) tracer uptake in patients with coronary artery disease (CAD) without pulmonary or valvular heart disease is unclear. METHODS: Forty consecutive patients with increased RV uptake on SPECT myocardial perfusion imaging and right heart catheterization within 4 wk were studied prospectively. Thirty-five individuals with very low likelihood of CAD served as controls. Rest and stress SPECT myocardial perfusion data were obtained using a standard 99mTc-sestamibi 1-d imaging protocol. A quick and simple RV-to-left ventricular (LV) myocardial uptake ratio was calculated from the maximum counts per pixel detected in the right and left ventricles using the reconstructed coronal slices. RV end-systolic pressure (RV-ESP), mean pulmonary artery pressure (PAP) and pulmonary capillary wedge pressure were obtained by standard techniques. RESULTS: The RV/LV uptake ratio in the controls was 0.31+/-0.05. Thirty-six of the 40 (90%) CAD patients with increased RV tracer uptake had increased RV-ESP, and 39 (97.5%) had increased PAP. Highly significant positive correlations between the RV/LV uptake ratio and RV-ESP and PAP were found (r = 0.45, P = 0.003; and r = 0.52, P < 0.001, respectively). CONCLUSION: Increased RV uptake, assessed from standard myocardial perfusion studies, can identify RV pressure overload among patients with CAD. In the absence of pulmonary or valvular heart disease, increased RV uptake (i.e., RV pressure overload) indicates significant backward failure, a variable with known significant negative prognostic implications.     

Planar and tomographic imaging with technetium 99m-labeled tetrofosmin: Correlation with thallium 201 and coronary angiography

This study compared the results of planar and single-photon emission computed tomographic (SPECT) imaging with tetrofosmin with those of²⁰¹Tl and coronary angiography. In three normal volunteers the images were normal by both²⁰¹Tl and tetrofosmin (planar and SPECT). In 23 patients with coronary artery disease, the images were abnormal in 20 patients by SPECT tetrofosmin, in 19 by planar tetrofosmin, in 20 by SPECT thallium, and in 18 by planar thallium (difference not significant). Both planar and SPECT images were divided into five segments per patient. There were 58 perfusion defects by SPECT tetrofosmin, 50 by planar tetrofosmin (difference not significant), 47 by SPECT thallium, and 42 by planar thallium (difference not significant). Perfusion defects were reversible in 47 segments (36%) by SPECT tetrofosmin, 35 (27%) by planar tetrofosmin, 31 (24%) by SPECT thallium (p<0.05 vs SPECT tetrofosmin), and 31 (24%) by planar thallium (difference not significant). Among the 23 patients with coronary artery disease, 19 underwent coronary angiography. In these patients there were 32 diseased coronary arteries. Perfusion defects were present in 21 territories (66%) by SPECT tetrofosmin, 19 (59%) by planar tetrofosmin, 20 (63%) by SPECT thallium, and 18 (56%) by planar thallium. There was agreement between thallium and tetrofosmin in 108 of 130 segments (κ statistics=0.69±0.06). The images, especially with SPECT, are better with tetrofosmin than with²⁰¹Tl. Thus myocardial imaging with tetrofosmin provides results that are at least as good as those of²⁰¹Tl. Slightly more abnormal segments and more reversible defects are detected by tetrofosmin than by thallium imaging, especially with SPECT imaging. Supported in part by Mediphysics, Inc., Arlington Heights, Ill.     

Dobutamine technetium-99m tetrofosmin SPECT imaging for the diagnosis of coronary artery disease in patients with limited exercise capacity

BACKGROUND: Technetium-99m tetrofosmin single photon emission computed tomography (SPECT) imaging is increasingly used in conjunction with exercise and vasodilator stress test as a means of evaluating coronary artery disease (CAD). Dobutamine stress test is an alternative in patients with limited exercise capacity. This study assessed the accuracy of dobutamine-atropine stress tetrofosmin SPECT as a means of diagnosing and localizing CAD. METHODS AND RESULTS: We studied 124 patients (mean age, 57+/-12 years; 88 men) with limited exercise capacity and suspected CAD with dobutamine (as much as 40 microg/kg/min)-atropine (as much as 1 mg) Tc-99m tetrofosmin SPECT. Resting images were acquired 24 hours after the stress test. Significant CAD was defined as 50% or greater luminal diameter stenosis in 1 or more major coronary arteries. Myocardial perfusion abnormalities (fixed and/or reversible defects) were detected in 70 of 88 patients with CAD and in 10 of the 36 patients without CAD (sensitivity = 80%, CI, 72 to 87; specificity = 72%, CI, 64 to 80; accuracy = 77%, CI, 70 to 85). Sensitivity and accuracy rates were higher by using the criterion of any defect than by using the criterion of reversible defects only (80% vs 51%, P<.0001; 77% vs 60%, P<.01, respectively). The sensitivity rate was higher in patients with multivessel CAD than in patients with single-vessel CAD (88% vs 63%, P<.05). Patients with multivessel CAD had a larger stress perfusion defect score (4.5+/-3.1 vs. 2.7+/-2.5, P<.01) than patients with single-vessel CAD. CONCLUSION: Dobutamine stress Tc-99m tetrofosmin SPECT is a useful method for the diagnosis and localization of CAD in patients with limited exercise capacity. Optimal accuracy of the technique is achieved by using both fixed and reversible perfusion abnormalities for the diagnosis of CAD in patients without an earlier myocardial infarction.     

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.     

Clinical usefulness of novel cardiac MDCT/SPECT fusion image

Background  We evaluated the relationship between computed tomography angiography (CTA) and SPECT, and assessed to determine the clinical usefulness of the fusion image using CTA and myocardial perfusion imaging (MPI). Methods  Forty-one consecutive patients [after coronary artery bypass operation (n = 13) and suspected stenosis (n = 28)] underwent MPI and CTA. SPECT/CTA fused images were generated. Results  In total, 687 segments including bypass graft in 164 coronary arteries were analyzed. Myocardial ischemia on MPI was observed in 11 patients among 28 with CTA abnormalities, one had both ischemia and infarction, and 7 had only infarction. Segment-based analysis showed that ischemia was found in 14 segments (24%) among 59 stenoses on CTA. Forty stenotic segments (69%) were not associated with perfusion abnormality. The rest 5 stenotic segments were considered equivocal (8%). A fusion image made it possible to associate perfusion defects with its corresponding coronary artery in 4 out of 5 equivocal lesions on side-by-side analysis. Patients with incremental diagnostic information on SPECT/CTA fusion (n = 4) had significant smaller coronary diameter than that of not-improved coronary vessels (2.0 ± 0.4 vs. 3.9 ± 0.4 mm, p = 0.001). Conclusion  Cardiac fusion imaging accurately diagnosed functionally relevant coronary stenosis. SPECT/CTA fusion images in coronary artery disease may provide added diagnostic information on functional relevance of coronary artery disease.     

Quantitation of postexercise lung thallium-201 uptake during single photon emission computed tomography

To test the hypothesis that analysis of lung thallium uptake measured during single photon emission computed tomography (SPECT) yields supplementary clinical information as reported for planar imaging, quantitative analysis of lung thallium uptake following maximal exercise was performed in 40 clinically normal subjects (Group 1) and 15 angiographically normal subjects (Group 2). Lung thallium uptake was measured from anterior projection images using a ratio of heart-to-lung activities. Seventy subjects with coronary artery disease (CAD) (Group 3) determined by angiography (greater than or equal to 70% luminal stenosis) underwent thallium perfusion SPECT. Thirty-nine percent of these subjects had multivessel and 61% had single vessel CAD. Lung thallium uptake was elevated in 47 of 70 (67%) Group 3 subjects. Group 3 subjects with elevated lung thallium uptake did not differ from Group 3 subjects with normal lung thallium uptake with respect to extent or distribution of coronary artery disease, left ventricular function, or severity of myocardial ischemia as determined by exercise and redistribution thallium SPECT. Thus, the measurement of thallium lung uptake from anterior projection images obtained during SPECT frequently identifies patients with CAD, but it may not provide supplementary information regarding the extent of myocardial ischemia or ventricular dysfunction.     

Integrated assessment of coronary anatomy and myocardial perfusion using a retractable SPECT camera combined with 64-slice CT: initial experience

We evaluated a prototype SPECT system integrated with multidetector row CT (MDCT) for obtaining complementary information on coronary anatomy and hemodynamic lesion significance. Twenty-five consecutive patients with known or suspected coronary artery disease (CAD) underwent routine SPECT myocardial perfusion imaging (MPI). All patients also underwent repeat MPI with a mobile SPECT unit which could be attached to a 64-slice MDCT system. Coronary CT angiography (cCTA) was performed without repositioning the patient. Investigational MPI was compared with routine MPI for detection of myocardial perfusion defects (PD). Two observers diagnosed presence or absence of CAD based on MPI alone, cCTA alone, and based on combined MPI and cCTA with fused image display. In 22/24 patients investigative MPI corresponded with routine MPI (r = 0.80). Stenosis ≥ 50% at cCTA was detected in 6/24 patients. Six out of 24 patients had PD at regular MPI. Three of these six patients had no significant stenosis at cCTA. Three out of 19 patients with normal MPI studies had significant stenosis at cCTA. Our initial experience indicates that the integration of SPECT MPI with cCTA is technically feasible and enables the comprehensive evaluation of coronary artery anatomy and myocardial perfusion with a single instrumental setup. This study received research support from Siemens Medical Solutions (Malvern, Pa). UJS is a medical consultant to Bayer, Bracco, General Electric, Siemens, and TeraRecon and receives research support from Bayer, Bracco, General Electric, Medrad, and Siemens. LG is a medical consultant to Cytogen Corporation. PC is a medical consultant to Bracco and receives research support from Siemens.     

A comparative regional analysis of coronary atherosclerosis and calcium score on multislice CT versus myocardial perfusion on SPECT.

For the noninvasive evaluation of coronary artery disease (CAD), both multislice CT and gated SPECT are available. How these 2 modalities relate, however, is yet unclear. The purpose of this study was to perform a head-to-head comparison of the results of multislice CT and gated SPECT on a regional basis (per vessel distribution territory) in patients with known or suspected CAD. METHODS: One hundred forty patients underwent both multislice CT for coronary calcium scoring and coronary angiography and gated SPECT for myocardial perfusion imaging. The coronary calcium score was determined for each coronary artery. Coronary arteries on multislice CT angiography were classified as having no CAD, insignificant stenosis (<50% luminal narrowing), significant stenosis, or total or subtotal occlusion (>/=90% luminal narrowing). Gated SPECT findings were classified as normal or abnormal (reversible or fixed defects) and were allocated to the territory of one of the various coronary arteries. RESULTS: In coronary arteries with a calcium score of 10 or less, the corresponding myocardial perfusion was normal in 87% (n = 194/224). In coronary arteries with extensive calcifications (score > 400), the percentage of vascular territories with normal myocardial perfusion was lower, 54% (n = 13/24). Similarly, in most of the normal coronary arteries on multislice CT angiography, the corresponding myocardial perfusion was normal on SPECT (156/175, or 89%). In contrast, the percentage of normal SPECT findings was significantly lower in coronary arteries with obstructive lesions (59%) or with total or subtotal occlusions (8%) (P < 0.01). Nonetheless, only 48% of vascular territories with normal perfusion corresponded to normal coronary arteries on multislice CT angiography, whereas insignificant and significant stenoses were present in, respectively, 40% and 12% of corresponding coronary arteries. CONCLUSION: Although a relationship exists between the severity of CAD on multislice CT and myocardial perfusion abnormalities on SPECT, analysis on a regional basis showed only moderate agreement between observed atherosclerosis and abnormal perfusion. Accordingly, multislice CT and gated SPECT provide complementary rather than overlapping information, and further studies should address how these 2 modalities can be integrated to optimize patient management.     

Assessment of systolic wall thickening using technetium-99m methoxyisobutylisonitrile in patients with coronary artery disease: relation to thallium-201 scintigraphy with re-injection

The results of resting planar ECG-gated technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) imaging were compared with those of thallium-201 (TI) reinjection after exercise-redistribution scintigraphy in 20 patients (19 men, 1 woman, mean age 53±10 years) with angiographically proven coronary artery disease. Eight normal subjects (seven men, one woman, mean age 50±8 years) constituted the control group. In these subjects, only resting^99mTc-MIBI imaging was performed. The standardized percent count increase from end-diastole to end-systole was calculated as an index of wall thickening in 13 segments for each study. Regional wall thickening index (WTI) and^99mTc-MIBI uptake were significantly different (P<0.05) among segments classified as normal, reversible defects, irreversible defects with increased tracer uptake after re-injection (Re+) or irreversible defects with unchanged tracer uptake after re-injection (Re-) on TI imaging. Furthermore, WTI and^99mTc-MIBI uptake were significantly higher (P<0.05) in Resegments with moderate reduction of T1 uptake (50% of peak activity) than in Re- segments with severe reduction of TI uptake (<50% of peak activity). A significant relationship between WTI and the results of TI scintigraphy was observed (rho=0.71,P<0.0001). The percentage of Re- segments with severe reduction of WTI was significantly higher compared to Re+ segments (64% vs 3%,P<0.01). Furthermore, compared with moderate Re- segments, a significantly higher percentage of severe Re- segments showed a severe reduction of WTI (86% vs 48%,P<0.01). Our data document a close relationship between^99mTc-MIBI regional wall thickening, myocardial perfusion and TI uptake after reinjection. The results of this study suggest that regional WTI decreased significantly as myocardial perfusion decreased. In addition, regional wall thickening was preserved in segments with exercise-induced ischaemia and enhanced TI uptake after re-injection.