Myocardial perfusion imaging with real-time respiratory triggering: Impact of inspiration breath-hold on left ventricular functional parameters

Background: The latest gamma-camera generation with cadmium-zinc-telluride (CZT) detectors allows myocardial perfusion imaging (MPI) with respiratory triggering at breath-hold. We assessed its impact on functional left ventricular (LV) parameters. Methods: Twenty-eight consecutive patients underwent a one-day 99mTc-tetrofosmin pharmacologic stress/rest imaging protocol on a novel CZT camera. Electrocardiogram-gated high-dose (rest) MPI was performed without and with real-time respiratory triggering by intermittent scanning confined to breath-hold at deep inspiration. We studied the effect of respiratory triggering at deep inspiration levels on LV wall motion, wall thickening, LV volumes and ejection fraction (LVEF) compared to regular MPI without respiratory triggering. Results: Compared to regular MPI without respiratory triggering, systolic and diastolic LV volumes and stroke volumes decreased significantly (P<0.05) when respiratory triggering was applied. By contrast, there was no significant change in LVEF, with a high correlation (r=.939, P<0.001) between the two measurements. Furthermore, respiratory triggering introduced a significant change (P<0.05) in regional LV wall motion. Conclusions: Respiratory-triggered MPI with breath-hold at deep inspiration levels introduces significant changes to the measured LV volumes, stroke volumes and regional wall motion but does not significantly affect global LVEF when compared to regular MPI with normal breathin

Impact of CT attenuation correction on the viability pattern assessed by 99mTc-tetrofosmin SPECT/18F-FDG PET

SPECT myocardial perfusion imaging (MPI) is commonly used for comprehensive interpretation of metabolic PET FDG imaging in ischemic dysfunctional myocardium. We evaluated the difference in scan interpretation introduced by CT attenuation correction (CTAC) of SPECT MPI in patients undergoing viability characterization by 99mTc SPECT MPI/PET FDG. In 46 consecutive patients (mean age 64, range 36-83 years) with dysfunctional myocardium, we analyzed viability from combined SPECT MPI and PET FDG scanning without attenuation correction (NC) and with CTAC for SPECT MPI. FDG uptake was classified in groups of percent uptake using the segment with maximum tracer in SPECT perfusion uptake as reference. Viability patterns were categorized as normal, mismatch, mild match and scar by relative comparison of SPECT and PET. Applying CTAC introduced a different reference segment for the normalization of PET FDG study in 57% of cases. As a result, the flow-metabolism pattern changed in 28% of segments, yielding a normal, mismatch, mild match and scar pattern in 462, 150, 123, and 47 segments with NC and 553, 86, 108, and 35 with CTAC, respectively (P=0.001). Thus, by introducing CTAC for SPECT MPI 25% of segments originally classified as scar were reclassified and the number of normal segments increased by 20%. Introducing CTAC decreased by 54% the number of patients with possible indication for revascularization, from 26/46 to 12/46 (P<0.001). Different interpretation of myocardial viability can be observed when using CTAC instead of NC SPECT MPI as reference for PET FDG scan

Coronary calcium score scans for attenuation correction of quantitative PET/CT 13N-ammonia myocardial perfusion imaging

Purpose: The aim of this study was to evaluate whether ECG-triggered coronary calcium scoring (CCS) scans can be used for attenuation correction (AC) to quantify myocardial blood flow (MBF) and coronary flow reserve (CFR) assessed by PET/CT with 13N-ammonia. Methods: Thirty-five consecutive patients underwent a 13N-ammonia PET/CT scan at rest and during standard adenosine stress. MBF values were calculated using AC maps obtained from the ECG-triggered CCS scan during inspiration and validated against MBF values calculated using standard non-gated transmission scans for AC. CFR was calculated as the ratio of hyperaemic over resting MBF. In all 35 consecutive patients intraobserver variability was assessed by blinded repeat analysis for both AC methods. Results: There was an excellent correlation between CT AC and CCS for global MBF values at rest (n = 35, r = 0.94, p < 0.001) and during stress (n = 35, r = 0.97, p < 0.001) with narrow Bland-Altman (BA) limits of agreement (−0.21 to 0.10ml/min per g and −0.41 to 0.30ml/min per g) as well as for global CFR (n = 35, r = 0.96, p < 0.001, BA −0.27 to 0.34). The excellent correlation was preserved on the segmental MBF analysis for both rest and stress (n = 1190, r = 0.93, p < 0.001, BA −0.60 to 0.50) and for CFR (n = 595, r = 0.87, p < 0.001, BA −0.71 to 0.74). In addition, reproducibility proved excellent for global CFR by CT AC (n = 35, r = 0.91, p < 0.001, BA −0.42-0.58) and CCS scans (n = 35, r = 0.94, p < 0.001, BA −0.34-0.45). Conclusion: Use of attenuation maps from CCS scans allows accurate quantitative MBF and CFR assessment with 13N-ammonia PET/C

Main pulmonary artery diameter from attenuation correction CT scans in cardiac SPECT accurately predicts pulmonary hypertension

Objectives: To establish the value of the main pulmonary artery (MPA) diameter assessed from unenhanced computer tomography (CT) scans used for attenuation correction (AC) of single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) to predict pulmonary hypertension (PHT). Background: In contrast-enhanced chest CT scans an MPA diameter of 29mm or greater is an established predictor of PHT. However, it is unknown, whether measurements from an unenhanced CT scan for AC may be used as predictor of PHT. Methods: 100 patients underwent SPECT MPI for assessment of coronary artery disease. PHT was defined as a right ventriculo-atrial gradient of 30mm Hg or greater by Doppler echocardiography. We compared MPA diameter from CT to SPECT findings (right ventricular hypertrophy/enlargement, septal wall motion abnormality/perfusion defect, and D-shape) to determine the best predictor of PHT. Results: PHT was found in 37 patients. An MPA diameter of 30mm or greater yielded a sensitivity, specificity, accuracy, positive, and negative predictive value of 78%, 91%, 86%, 83%, and 88%, respectively. This yielded an area under the ROC curve of 0.85. Conclusions: MPA diameter from low-dose unenhanced multi-slice CT reliably predicts PHT, providing an important added clinical value from AC for SPECT MP

Left ventricular dyssynchrony assessment by phase analysis from gated PET-FDG scans

Background: The outcome of patients with severe ischaemic left ventricular (LV) dysfunction is determined by the extent of myocardial viability and the presence of LV dyssynchrony. We aimed at assessing both parameters from the same imaging method, i.e. gated positron emission tomography (PET) F18-fluorodeoxyglucose (FDG) scans. Methods: Phase analysis from Emory Cardiac Toolbox was applied on gated PET-FDG scans to assess histogram bandwidth and standard deviation (SD) as a measure of LV dyssynchrony in 30 heart failure patients (mean ejection fraction: 30.2%±13.8%) referred for the evaluation of myocardial viability. Cut-off values from single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI) best predicting cardiac resynchronization therapy (CRT) response served as standard of reference (bandwidth<135°; phase SD<43°). Severe LV dyssynchrony was diagnosed if both SPECT-MPI values were above these limits. Intraclass correlation and clinical agreement in detection of severe LV dyssynchrony by PET vs SPECT were assessed. Results: There was a significant correlation between PET-FDG and SPECT-MPI for bandwidth (r=0.88, P<.001) and phase SD (r=0.88, P<.001) resulting in an excellent clinical agreement between the two methods of 93%. Conclusions: Accurate LV dyssynchrony assessment by phase analysis of gated PET-FDG scans is feasible, allowing assessing myocardial viability and severe LV dyssynchrony in one sca

Nuclear myocardial perfusion imaging with a novel cadmium-zinc-telluride detector SPECT/CT device: first validation versus invasive coronary angiography

Purpose: We evaluated the diagnostic accuracy of attenuation corrected nuclear myocardial perfusion imaging (MPI) with a novel hybrid single photon emission computed tomography (SPECT)/CT device consisting of an ultrafast dedicated cardiac gamma camera with cadmium-zinc-telluride (CZT) solid-state semiconductor detectors integrated onto a multislice CT scanner to detect coronary artery disease (CAD). Invasive coronary angiography served as the standard of reference. Methods: The study population included 66 patients (79% men; mean age 63 ± 11years) who underwent 1-day 99mTc-tetrofosmin pharmacological stress/rest examination and angiography within 3months. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) as well as accuracy of the CT X-ray based attenuation corrected CZT MPI for detection of CAD (≥50% luminal narrowing) was calculated on a per-patient basis. Results: The prevalence of angiographic CAD in the study population was 82%. Sensitivity, specificity, PPV, NPV and accuracy were 87, 67, 92, 53 and 83%, respectively. Conclusion: In this first report on CZT SPECT/CT MPI comparison versus angiography we confirm a high accuracy for detection of angiographically documented CA

Ultrafast assessment of left ventricular dyssynchrony from nuclear myocardial perfusion imaging on a new high-speed gamma camera

Purpose: To validate the ultrafast assessment of left ventricular (LV) dyssynchrony by phase analysis using high-speed nuclear myocardial perfusion imaging (MPI) on a new gamma camera with cadmium-zinc-telluride (CZT) solid-state detector technology. Methods: In 46 patients rest MPI with 960MBq 99mTc-tetrofosmin was acquired on a dual-head detector SPECT camera (Ventri, GE Healthcare) and an ultrafast CZT camera (Discovery NM 530c, GE Healthcare) with acquisition times of 15 and 5min, respectively. LV dyssynchrony was assessed using the Emory Cardiac Toolbox with established values for histogram bandwidth (male <62.4°; female <49.7°) and standard deviations (male <24.4°; female <22.1°) as the gold standard. Evaluating CZT scan times of 0.5, 1, 2, 3 and 5min (list mode) in 16 patients revealed the preferred scan time to be 5min, which was then applied in all 46 patients. Intraclass correlation and the level of agreement in dyssynchrony detection between the CZT and Ventri cameras were assessed. Results: In LV dyssynchrony the mean histogram bandwidths with the CZT camera (n = 8) and the Ventri camera (n = 9) were 123.3 ± 50.6° and 130.2 ± 43.2° (p not significant) and 42.4 ± 13.6° vs. 43.2 ± 12.7° (p not significant). Normal bandwidths and SD obtained with the CZT camera (35.9 ± 7.7°, 12.6 ± 3.5°) and the Ventri camera (34.8 ± 6.6°, 11.1 ± 2.1°, both p not significant) excluded dyssynchrony in 38 and 37 patients, respectively. Intraclass correlation and the level of agreement between the CZT camera with a 5-min scan time and the Ventri camera were 0.94 (p < 0.001, SEE 14.4) and 96% for histogram bandwidth and 0.96 (p < 0.001, SEE 3.9) and 98% for SD. Conclusion: This ultrafast CZT camera allows accurate assessment of LV dyssynchrony with a scan time of only 5min, facilitating repeat measurements which would potentially be helpful for parameter optimization for cardiac resynchronization therap

Non-invasive assessment of coronary artery disease with CT coronary angiography and SPECT: a novel dose-saving fast-track algorithm

Purpose: To validate a new low-dose and rapid stepwise individualized algorithm for non-invasive assessment of ischemic coronary artery disease by sequential use of prospectively ECG-triggered low-dose CT coronary angiography (CTCA) and low-dose single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI). Methods: Forty patients referred for elective invasive coronary angiography (CA) were prospectively enrolled to undergo a comprehensive non-invasive evaluation with low-dose CTCA and a dose-reduced stress/rest SPECT-MPI scan (using dedicated reconstruction algorithms for low count scans). The following algorithm was reviewed: CTCA first, followed by a stress-only MPI if a coronary stenosis (≥ 50% diameter narrowing) or equivocal findings were observed. Only abnormal stress MPI scans were followed by rest MPI. The accuracy of the individualized algorithm to predict coronary revascularization and its mean effective radiation dose were assessed. Results: CTCA documented CAD in 18 and equivocal findings in two patients, thus, requiring additional stress MPI scans. Of these, 16 were abnormal, therefore requiring a rest MPI scan, revealing ischemia in 15 patients. Sensitivity, specificity, negative and positive predictive value, and accuracy of the individualized algorithm for predicting coronary revascularization was 93.3%, 96.0%, 96.0%, 93.3% and 95.0% on a per-patient base. The mean effective radiation dose was significantly lower for the individualized (4.8 ± 3.4mSv) versus the comprehensive method (8.1 ± 1.5mSv) resulting in a total population radiation dose reduction of 132.6mSv. Conclusion: This new individualized low-dose algorithm allows rapid and accurate prediction of invasive CA findings and of treatment decision with minimized radiation dos

Prevalence of noncardiac findings on low dose 64-slice computed tomography used for attenuation correction in myocardial perfusion imaging with SPECT

Electrocardiogram (ECG)-triggered, low dose computed tomography (CT) is increasingly used for attenuation correction in myocardial perfusion imaging (MPI) with SPECT. The purpose of the study was to assess the prevalence of relevant noncardiac findings in the field-of-view of such attenuation correction CT scans. Five hundred and eighty-two consecutive patients (211 female, 371 male; mean age: 64±11years; BMI: 27.7±5.3kg/m2) underwent 64-slice, ECG-triggered CT scanning for attenuation correction of MPI with SPECT. Relevant findings were defined as abnormalities that required clinical or radiological follow-up. Noncardiac findings were detected in 400 patients (68.7%). In 196 patients (33.7%) 226 relevant findings were detected. Findings included noncalcified pulmonary nodules (n=156), interstitial lung disease (n=6), pleural effusion (n=20), pneumonia (n=1), aortic aneurysm (n=5), aortic dissection (n=4), enlarged mediastinal lymph nodes (n=5), mediastinal tumor (n=3), breast abnormalities (n=3), liver cirrhosis (n=5), liver mass (n=5), ascites (n=5), splenomegaly (n=2), renal mass (n=1), hydronephrosis (n=1), adrenal mass (n=3), and bone metastasis (n=1). As low dose 64-slice CT scans used for attenuation correction in MPI with SPECT reveal a high prevalence of noncardiac pathologic findings with potential clinical relevance, a systematic review of the CT scans appears mandator