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F J Wackers

Publications and source records attributed to F J Wackers.

161 records · Page 9Linked to original sources
PubMedDate not supplied

Diagnostic utility of tomographic myocardial perfusion imaging with technetium 99m furifosmin (Q12) compared with thallium 201: results of a phase III multicenter trial.

BACKGROUND: Based on physical properties, 99mTc-labeled perfusion agents offer several advantages over 201Tl for myocardial perfusion imaging. The results of in vivo and experimental studies, along with preliminary experience in human subjects, have shown 99mTc-labeled furifosmin to be a promising new perfusion tracer. The purpose of this study was to evaluate the safety of a new myocardial perfusion agent, 99mTc-labeled furifosmin (Q12), and determine the concordance of furifosmin perfusion scintigraphy to 201Tl imaging. In addition, we sought to determine the normalcy rate of myocardial scintigraphy with furifosmin. METHODS AND RESULTS: One hundred fifty patients constituted the study group in this multicenter trial. Patients underwent exercise testing with furifosmin injected at peak exercise, and tomographic imaging was begun 15 to 30 minutes afterward. After a separate injection, resting images were obtained 3 to 4 hours later. Thallium scintigraphy was performed within 2 weeks of the furifosmin scans, after a similar exercise workload. Patients with a low likelihood of coronary artery disease (n = 39) also underwent furifosmin imaging. All images were processed and displayed in uniform manner and interpreted by a panel of readers. No adverse effects or clinically important laboratory alterations were related to furifosmin imaging. Image quality was slightly better with furifosmin than with thallium. The overall concordance between the perfusion studies was 86% (kappa value = 0.669). The normalcy rate for furifosmin scintigraphy was 100%. CONCLUSIONS: 99mTc-labeled furifosmin is a promising new 99mTc-labeled myocardial perfusion agent, providing diagnostic results similar to those obtained with 201Tl.

Coronary Disease↗
PubMedDate not supplied

Quantification of technetium 99m-labeled sestamibi single-photon emission computed tomography based on mean counts improves accuracy for assessment of relative regional myocardial blood flow: experimental validation in a canine model.

BACKGROUND: Quantification of single-photon emission computed tomographic (SPECT) images is generally based on determination of maximal counts on radial sectors of short-axis slices. We hypothesized that analysis of mean counts may reduce estimation error. METHODS AND RESULTS: We compared quantitative 99mTc-labeled sestamibi (MIBI) SPECT based on maximal myocardial counts with that based on mean myocardial counts for accuracy of quantifying relative regional myocardial perfusion in a canine model of permanent left anterior descending coronary artery occlusion. MIBI and radiolabeled microspheres were injected during left anterior descending coronary artery occlusion. Relative microsphere myocardial blood flow was expressed as a percentage of normal (left circumflex coronary artery territory) blood flow. SPECT imaging was performed in vivo and ex vivo. Relative MIBI uptake on SPECT short-axis slices was quantified with normalized circumferential profiles based on maximal and mean counts. In vivo and ex vivo SPECT relative myocardial count density was compared to relative myocardial blood flow in six dogs. In the comparisons, percent errors in estimating the relative blood flow and relative flow deficit with MIBI SPECT imaging were calculated. There was an excellent correlation between absolute myocardial tissue MIBI activity and regional myocardial blood flow for each of the six dogs (r = 0.90 to 0.98). The correlations between relative myocardial count density on SPECT and relative blood flow for individual sectors were similar for maximal and mean count profiles (maximal, 0.79 to 0.83; mean, 0.77 to 0.82). Comparing the nadirs of in vivo and ex vivo circumferential count profiles, the correlations were slightly better (maximal, 0.82 to 0.91; mean, 0.87 to 0.91). Average percent errors in assessing relative blood flow and relative flow deficit were decreased significantly by use of mean count profiles (p < 0.05). CONCLUSIONS: Relative SPECT count density with either maximal or mean count profiles correlated well with relative myocardial blood flow. Compared with maximal count profiles, quantification with mean count profiles improved estimation of relative flow.

Animals↗
PubMedDate not supplied

Relationship of scar and ischemia to the results of programmed electrophysiological stimulation in patients with coronary artery disease.

BACKGROUND: Although myocardial perfusion imaging (MPI) is widely used in patients with coronary artery disease, few data are available concerning the relationship between myocardial scar and ischemia and arrhythmic potential. PATIENTS AND METHODS: One hundred forty-four patients with chronic coronary artery disease who underwent electrophysiological studies (EPS) and MPI within 3 months constituted the study population. By history, 26% of the patients had sustained ventricular tachycardia (VT), 21% had cardiac arrest with ventricular fibrillation, and 53% had nonsustained VT. Eighty-five percent had previous myocardial infarction. Standard EPS protocol with up to three extra stimuli was used. Patients with a response of sustained monomorphic VT were defined as inducible. Quantitative MPI was used to define stress perfusion defect size and reversibility. The relations of ischemia (reversible defect) and scar (fixed defect) to inducibility on EPS were assessed by univariate analysis. Multivariate analysis was used to compare MPI results with known clinical predictors of inducibility. RESULTS: Fifty-two percent of the patients had inducible monomorphic sustained VT. MPI showed scar alone in 33%, scar with additional ischemia in 53%, ischemia alone in 8%, and no abnormality in 6%. No relation was found between the scintigraphic presence or size of ischemia and the likelihood of inducibility or to the type of arrhythmia history. In contrast, scar size was related to the result of EPS; inducible patients had significantly larger resting defect integrals (27 +/- 23 vs 14 +/- 15) than noninducible patients (p < 0.0001). Of 37 patients with very large defects (defect integral > 30), 78% were inducible, whereas only 30% of 33 patients with defect integrals < 5 were inducible. On multivariate analysis resting defect integral was an independent predictor of inducibility. In comparison with left ventricular ejection fraction (available in 122 patients), perfusion defect size was a better independent predictor of sustained VT on EPS. CONCLUSION: The presence or size of potentially ischemic myocardium does not appear to be related to the inducibility during EPS. Size of scar as quantified by myocardial perfusion imaging correlates well and better than the global left ventricular function with inducibility of sustained VT on EPS.

Cardiac Pacing, Artificial↗
PubMedDate not supplied

Improved diagnostic accuracy of planar imaging with technetium 99m-labeled tetrofosmin compared with thallium-201 for the detection of coronary artery disease.

BACKGROUND: Receiver operating characteristic (ROC) curve analysis provides detailed information about the performance of a diagnostic test. METHODS AND RESULTS: As part of a multicenter phase III trial, 160 patients with known or suspected coronary artery disease underwent planar stress-rest 99mTc-labeled tetrofosmin and stress-redistribution 201Tl imaging within 14 days of each other, to compare the diagnostic accuracy of these imaging modalities by ROC curve analysis. Coronary arteriography was used as the reference standard and greater than 70% stenosis was considered significant. ROC curve analysis showed improved detection of coronary artery disease with 99mTc-labeled tetrofosmin compared with 201Tl, with ROC curve areas of 0.765 versus 0.644, respectively (p = 0.02). 99mTc-labeled tetrofosmin also better identified single-vessel disease in those without previous myocardial infarction (ROC curve areas of 0.684 vs 0.510 for 99mTc-labeled tetrofosmin and 201Tl, respectively; p = 0.04) and enhanced the detection of multivessel disease in those with previous myocardial infarction (ROC curve areas of 0.764 vs 0.638, respectively; p = 0.02). CONCLUSIONS: Detailed assessment of diagnostic performance by ROC curve analysis shows that, for planar imaging, 99mTc-labeled tetrofosmin enhances the detection of coronary artery disease compared with 201Tl.

Adult↗
PubMedDate not supplied

Exercise testing with myocardial perfusion imaging in patients with normal baseline electrocardiograms: cost savings with a stepwise diagnostic strategy.

BACKGROUND: It has been suggested that in patients with a normal resting electrocardiogram (ECG), exercise radionuclide myocardial perfusion imaging (MPI) does not add significant incremental diagnostic information to exercise ECG. METHODS AND RESULTS: Of 840 consecutive patients referred for physical exercise MPI, 313 (37%) had normal resting ECGs. There were 189 men and 124 women with a mean age of 54+/-11.9 years. Exercise MPI was performed with either TI-201 or 99mTc-labeled sestamibi. Overall concordance between exercise ECG result and MPI result was 79% (kappa agreement = .54). One hundred eighty-four patients had normal exercise ECG; 181 (98.4%) of these also had normal exercise MPI. In 271 patients with low (< or =20%) to intermediate (21% to 70%) pre-exercise likelihood of coronary artery disease (CAD), concordance between normal exercise ECG and normal MPI was 100%. In the high likelihood (> or =71%) group 3 (15 %) patients with normal exercise ECG had abnormal exercise MPI. Of 129 patients with abnormal exercise ECG, 67 (52%) patients also had abnormal MPI, but 62 (48%) patients had normal MPI. Complete follow-up was obtained in 89% of patients at 9 months. Only 1 hard cardiac event occurred: nonfatal myocardial infarction. Twenty-one (8%) patients had subsequent coronary revascularization or admission with unstable angina. Although both abnormal stress ECG and abnormal exercise MPI were significantly (P < .0001) associated with hard and "soft" events, the association of abnormal exercise MPI was significantly stronger. Because all patients with a low and intermediate likelihood of CAD who had normal exercise ECG also had normal exercise MPI, we propose a stepwise diagnostic testing strategy whereby exercise MPI imaging is performed only in patients with a low to intermediate likelihood of CAD when the exercise ECG is abnormal. When the exercise ECG is performed first, and exercise MPI is performed only when the exercise ECG is abnormal, substantial (38%) cost savings can be achieved. In patients with a high likelihood of CAD, the exercise ECG may be falsely negative, and exercise MPI is preferred. CONCLUSION: In patients with normal resting ECGs a stepwise diagnostic strategy can reduce costs of exercise testing without compromising diagnostic yield when pretest likelihood of coronary artery disease is taken into consideration.

Adult↗
PubMedDate not supplied

Quantification of SPECT myocardial perfusion images: methodology and validation of the Yale-CQ method.

BACKGROUND: Quantification of single photon emission computed tomography (SPECT) images is important for reproducible and accurate image interpretation. In addition, SPECT quantification provides important prognostic information. The purpose of this study was to validate the Yale circumferential quantification (Yale-CQ) method in phantom studies. METHODS: Myocardial perfusion defects of varying extent and severities were simulated in a cardiac phantom with fillable defect inserts. Forty-five different phantom configurations simulated 45 different myocardial perfusion defect sizes, ranging from 1.6% to 32% of the cardiac phantom volume. Automatic processing was compared with manual processing in the phantom SPECT studies. RESULTS: The automatic Yale-CQ algorithm performed well in all phantom studies. Compared with manual processing, the mean absolute error for automatically determined center of short axis slices was 0.27 pixel in the x direction, 0.45 pixel in the y direction, and 0.15 pixel in radius. Quantification of phantom defects with the Yale-CQ method correlated well with actual defect sizes (R = 0.99), but there was a systematic underestimation (mean error = -7.9%). With derived correction factors the overall correlation between 45 phantom defects and actual defect sizes was excellent, and the estimation error was significantly improved (R = 0.98, mean error = -0.82% for manual method and -0.95% for automatic method). CONCLUSION: The automatic processing algorithm performs well for the phantom studies. Myocardial perfusion abnormalities can be quantified accurately by use of the Yale-CQ method. Quantified SPECT defect size can be expressed as a percentage of the left ventricle.

Algorithms↗
PubMedDate not supplied

Quantification of regional myocardial wall thickening on electrocardiogram-gated SPECT imaging.

BACKGROUND: Current assessment of regional left ventricular function with electrocardiogram (ECG)-gated single photon emission computed tomography (SPECT) imaging is generally performed by visual inspection. The objective of this study was to develop and validate a new computer algorithm for quantifying regional left ventricular wall thickening on ECG-gated SPECT images. METHODS: Regional wall thickening was measured from count density changes during the cardiac cycle observed in 24-sector circumferential count distribution profiles generated from each of 8 frames of an ECG-gated SPECT study. Wall thickening was expressed as the percent count increase during systole relative to end diastole. The program was tested in a phantom simulation and in patient studies consisting of a pilot study (n = 40) and a validation study (n = 33). In the phantom study varying degrees of wall thickening were simulated. The pilot study included 20 normal subjects with low likelihood (<3%) of coronary disease and 20 patients with prior myocardial infarction. Mean wall thickening - 2 standard deviations, measured in normal subjects, defined the lower limit of normal wall thickening. This criterion was tested in the validation study in 13 normal subjects and 20 patients with prior myocardial infarction. Abnormal wall thickening was characterized by extent (percent of circumferential profile) and severity (minimal thickening). RESULTS: The phantom study showed excellent linear correlation between wall thickening computed by the new software and actual wall thickening (r = 0.98). Interobserver and intraobserver reproducibility of quantitative assessment of minimal wall thickening were excellent (r = 0.98 and 0.99, P < .001). Regional wall thickening varied considerably from apex to base in the same ventricle among normal subjects. The average lower limit of normal wall thickening was 25% to 30% at the apex, 19% to 24% in the mid-ventricle, and 13% to 20% at the base of the left ventricle. In the validation study 11 of 13 normal subjects had wall thickening profiles within the pre-defined normal range. All 20 patients with prior myocardial infarction had abnormal regional wall thickening. Minimal regional wall thickening in the infarct areas was 5.4% +/- 5.5%, compared with 30.1% +/- 9.1% wall thickening in comparable anatomic areas in normal subjects (P < .001). CONCLUSION: Regional wall thickening can be quantified reliably from regional count density changes during the cardiac cycle on ECG-gated SPECT images. The new software measured the extent and severity of abnormal regional wall thickening relative to normal files. The method is highly reproducible. Clinical validation showed good differentiation between normal subjects and patients with prior infarction. Quantification of regional wall thickening may enhance diagnostic accuracy and reproducibility of interpretation of gated SPECT imaging.

Algorithms↗
PubMedDate not supplied

Assessment of left ventricular ejection fraction with quantitative gated SPECT: accuracy and correlation with first-pass radionuclide angiography.

BACKGROUND: Quantitative gated single photon emission computed tomography (SPECT [QGS]) software is widely used for the assessment of left ventricular ejection fraction (LVEF). Potentially confounding variables that may affect the accuracy of quantitative analysis of LVEF remain undefined. This study evaluated the accuracy of QGS as a means of determining LVEF in a wide range of LVEF values; evaluated the effect of extracardiac activity, count statistics, heart size, and perfusion defects on the accuracy of QGS LVEF; and compared QGS LVEF obtained at rest with that obtained after stress. METHODS AND RESULTS: QGS-derived LVEF was compared with rest first-pass radionuclide angiography (FPRNA) LVEF in 400 electrocardiographic-gated SPECT studies. The overall correlation between QGS and FPRNA LVEF was only fair (r = 0.66, SEE = 11.85%). In 35 of the patient studies (9%) with high extracardiac activity, the automated software failed, and no correlation was obtained. In the remaining 365 patient studies (91%), left ventricular contours were successfully identified. In these studies, correlation was better (r = 0.74, SEE = 9.77%). Agreement was better for images with high counts (r = 0.81, SEE = 8.66%) than for images with low counts (r = 0.61, SEE = 11.17%). Patient studies with abnormal LVEF had better correlation (r = 0.77, SEE = 6.4%) than studies with normal LVEF (r = 0.46, SEE = 10.2%). Agreement between QGS LVEF and FPRNA LVEF was better in hearts with large end diastolic volumes (>104 mL) than in hearts with small volumes. Overall, mean QGS LVEF was lower than mean FPRNA LVEF (54%+/-14% vs. 58%+/-14%, P<.0001). There was no difference between mean rest and stress QGS LVEF in the same patients, even in patients with stress-induced ischemia. CONCLUSIONS: QGS is a valuable method for assessing resting LVEF. However, QGS LVEF is often lower than FPRNA LVEF. Accuracy is affected by high extracardiac activity, low count density, and small size of the left ventricle.

Adult↗