CT images obtained using CT based attenuation correction

Journal of Nuclear Cardiology Volume 11, Number 4;S1-S18 0.001; kappa ⫽ 0.253 vs 0.341 p ⬍ 0.001). This trend persisted even when patients with resting ST-T wave abnormalities or Q-waves were excluded (Pearson’s R ⫽ 0.305 vs 0.363 p ⬍ 0.001; kappa ⫽ 0.298 vs 0.361 p ⬍ 0.001). The specificity of ST? to predict ischemia as defined by reversibility was almost identical PCABG and in the control group (67% vs 68%), but sensitivity was significantly reduced in the PCABG (61% vs 67%). In males, there were no significant differences between the positive predictive value (PPV) in the PCABG and in the control group (78% in both). The negative predictive value was much lower PCABG (46% vs 59%). In women, the PPV was higher PCABG (72% vs 65%), whereas the NPV was much lower (45% vs 69%). Conclusion: Following CABG, correlation and agreement between significant exercise-induced ST-segment shift and myocardial ischemia as defined by 201Tl-SPECT are worse than in the general population. In both genders, after CABG there is an increase of false negative exercise-ECG tests. 31.41 FOLLOW-UP OF PATIENTS WITH REVERSIBLE MYOCARDIAL PERFUSION DEFECTS AND HEMODYNAMICALLY NONSIGNIFICANT LESIONS ON CORONARY ANGIOGRAPHY R Petrovici, RM Iwanochko, M Husain Toronto Western Hospital-University Health Network Background: The prognostic value of stress-rest myocardial perfusion imaging (MPI) has been extensively studied in patients with hemodynamically significant coronary lesions. Few studies have explored the predictive value of reversible defects (RD) in patients with normal or near-normal coronary angiography (CA). We sought to examine the cardiac outcome in this group of patients were MPI is considered false positive. Methods: Our study group consisted of 52 patients (37 males) with suspected CAD, mean age 50 ⫾ 9, having CA described as either normal (40%), minor lesions (10%-50% stenosis) (54%) and intermediate lesions (50%-70% stenosis) (6%). Each patient had at least one RD on MPI performed 4.9 ⫾ 4.5 months from CA. SPECT MPI was performed with 99m-Tc Sestamibi (18), Thallium-201 (31) or dual isotope (1). Treadmill exercise was used in 36 and pharmacologic stress in 16 patients. Summed difference score (SDS), defined as the difference between the summed stress and rest perfusion scores on a 9-segment 4-point (0 –3) model (Min/Max score: 0/27), identified RD as stress-induced ischemia. Studies considered difficult to interpret (TDS) due to technical artefacts were reported as such. Patients were followed for 47 ⫾ 27 months (min 13, max 85). Results: During follow-up, 5 (10%) patients suffered cardiac events: 2 underwent CABG (1 male and 1 female, 13 and 4 months after MPI), 1 fatal myocardial infarction (male, 7 months after MPI), 2 were diagnosed with cardiomyopathy (1 male and 1 female, 25 and 26 months after MPI). On initial CA, all the three patients developing CAD had only minor lesions (20 –30% range), while those developing cardiomyopathy had normal coronaries. SDS was higher in the patients with events (2.8 ⫾ 1.1) than in those without (2.6 ⫾ 1.9), but this difference was not statistically significant. TDS represented 12 (26%) in the non-event group. No patients in the event-group had TDS. Conclusion: Reversible defects on MPI may identify a patients at risk for future cardiac events even in the presence of normal or near-normal coronary angiography. 31.42 COMPARABILITY OF CARDIAC RESULTS ACQUIRED USING A PET/CT SCANNER, TO THOSE OBTAINED BY DEDICATED PET, USING SEMI-QUANTITATIVE ANALYSIS AGAINST A COMMERCIALLY AVAILABLE NORMATIVE DATABASE (EMORY CARDIAC TOOLBOX) RC Brunken1, F DiFilippo1, DR Neumann 1, B Bybel1, B Herrington2, T Bruckbauer2, C Howe2, K Lohmann2, C Hayden2, C Chatterjee2, B Lathrop2 1 Cleveland Clinic Foundation, Cleveland, OH, 2CPS Innovations, Knoxville, TN Background: Cardiac PET/CT provides, on a single imaging platform, functional information from PET and morphological information from CT (e.g. coronary angiography). However, PET/CT employs a different technique to acquire information for attenuation correction (AC). PET scanners typically use radionuclide sources (511 keV) to acquire a 300 – 600 sec. transmission scan, thus imaging a composite of multiple respiratory and

Abstracts Friday, October 1, 2004

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cardiac cycles for AC. PET/CTs typically employ a more rapid acquisition acquired at a lower energy (⬃120 kVp). These differences in AC scans between PET and PET/CT raise questions about the validity of assessing PET/CT results using normative databases previously acquired using dedicated PET. Methods: A unique “Slow-CT” protocol (1.5 sec/rot, feed/rotation ⫽ 6.4mm) was developed to acquire PET/CT scans for attenuation correction (CTAC) during free breathing, to average the range of respiratory and cardiac motion. X-ray tube current and voltage were reduced to limit X-ray exposure to approximately 1/3rd the standard CT levels. An initial subset of 11 subjects received resting Rb-82 studies on both dedicated PET (ECAT HR⫹) and 16-slice PET/CT using CTAC (Biograph LSO). Results were processed independently by two experienced operators and analyzed against a normative database collected previously using dedicated PET (Emory Cardiac Toolbox). Summed Resting Scores (SRS) as well as scores of individual segment (ISS) were compared for all subjects. Results: The average SRS was 16.0 (⫾ 11.6) by PET and 15.36 (⫾ 11.2) by PET/CT. SRS from dedicated PET were highly correlated to PET/CT (r⫽0.91, PET ⫽ 1.01*PET/CT). The average difference in SRS between PET and PET/CT was 3.9 (⫾ 2.2). Out of a total of 187 ISS, 70.1% demonstrated complete agreement, and 96.3% were within a difference of 1 score per segment. Of the ISS, which were “Normal” by PET (n⫽75, ISS⫽0), corresponding scores by PET/CT were either normal or equivocal in 96.7% of segments. Conclusion: Initial results from PET/CT using CTAC appear to be highly correlated to those acquired using dedicated PET, both with respect to extent and severity, when compared against a gold standard normative database. Results need to be extended to a larger patient group, to assess sensitivity and specificity and to encompass variables in imaging associated with stress (i.e. increased respiration and heart rate). 31.43 LVEF MEASUREMENTS FROM CARDIAC PET/CT IMAGES OBTAINED USING CT BASED ATTENUATION CORRECTION RC Brunken, MS Chen, KA Lohmann, WC Howe, T Bruckbauer, T Kaczur, B Bybel, FP DiFilippo Departments of Molecular and Functional Imaging and Cardiology, The Cleveland Clinic Foundation, Cleveland, Ohio and CPS Innovations, Knoxville, TN Background: Rapid growth of oncologic PET imaging procedures is stimulating the use of PET/CT devices, and it would be desirable for imaging centers to also employ this technology for myocardial imaging. However, it is uncertain whether left ventricular ejection fraction (LVEF) measurements obtained from myocardial PET images using CT based attenuation correction are feasible. The goal of this study was to assess the feasibility of cardiac PET/CT imaging for LVEF determinations using a “slow CT” attenuation correction technique. Methods: Four patients underwent imaging (2 metabolic imaging with F-18 2-fluoro-2-deoxyglucose and 2 perfusion imaging with rubidium-82) on the Siemens Biograph16 PET/CT (LSO crystal, Pico 0 electronics), using a list mode acquisition. CT images acquired over 42 sec were used for attenuation correction. PET data were rebinned into either 8 or 16 frames per cardiac cycle. LVEF’s were then determined from the gated images using 4D MSPECT software. EF’s derived from 2-D echocardiography, using a Simpson’s approach to quantify left ventricular volumes, were used for comparison. Results: PET EF’s ranged from 18% to 59% and were highly correlated to echo values on linear regression analysis: PET⫽5.2 ⫹ 0.92*Echo (r⫽0.97, p⫽0.01, SEE⫽3.4). Conclusions: LVEF measurements are feasible using PET/CT myocardial images corrected for attenuation using the “slow CT” technique. Derived EF values are slightly higher than those of 2-D echo, likely reflecting differences between tomographic and planar imaging techniques. Determination of the accuracy of the PET measurements awaits comparison to a comparable tomographic imaging technique, such as MRI. 31.44 POST-ISCHEMIC LEFT VENTRICULAR DYSFUNCTION IS DETECTED ON ADENOSINE GATED SPECT IN PATIENTS WITH EXTENSIVE CORONARY ARTERY DISEASE RS Druz, OA Akinboboye, R Grimson, KJ Nichols, N Reichek