Systolic prospectively ECG-triggered dual-source CT angiography for evaluation of the coronary arteries in heart transplant recipients

Systolic High-Pitch Coronary CT Angiography for Evaluation of the Coronary Arteries in Heart Transplant Recipients

OBJECTIVE. The purpose of this study was to evaluate the feasibility, image quality, and radiation dose of high-pitch coronary CT angiography (CCTA) in orthotopic heart transplant (OHT) recipients. SUBJECTS AND METHODS. Twenty-two consecutive OHT recipients (16 men, six women; median age, 66.5 years [interquartile range, 51.3-70.3 years]; median heart rate, 91 beats/min [interquartile range, 79.3-97.3 beats/min]) underwent CCTA with a third-generation dual-source CT scanner in high-pitch mode to rule out coronary allograft vasculopathy. Data acquisition was triggered at 30% of the R-R interval. Two independent observers blindly assessed image quality on a per-segment, per-vessel, and per-patient basis using a 4-point scale (4, excellent; 1, not evaluative). Scores 2-4 indicated diagnostic quality. Studies were compared with previously performed retrospective ECG-gated examinations, when available. Interobserver agreement on the image quality was assessed with kappa statistics. Radiation dose was recorded. RESULTS. A total of 322 coronary segments were evaluated. Diagnostic image quality was observed in 97.5% of the segments. Interobserver agreement for image quality assessment was very good on a per-patient (κ = 0.82), per-vessel (κ = 0.83), and per-segment basis (κ = 0.89). The median per-patient image quality score was 4.0 (3.0-4.0) for the entire coronary tree. A comparison of image quality scores between high-pitch and retrospective ECG-gated CCTA examinations showed no significant differences, but the estimated mean radiation dose was significantly lower for the high-pitch mode (median dose-length product, 31.6 mGy × cm [interquartile range, 23.1-38.8 mGy × cm] vs 736.5 mGy × cm [interquartile range, 655.5-845.7 mGy × cm], p < 0.001). CONCLUSION. Performing single-heartbeat high-pitch CCTA during the systolic phase of the cardiac cycle in OHT recipients results in diagnostic image quality in coronary angiograms at very low radiation dose.

Coronary computed tomography in heart transplant patients: detection of significant stenosis and cardiac allograft vasculopathy, image quality, and radiation dose

Background Cardiac allograft vasculopathy (CAV) is an accelerated form of atherosclerosis unique to heart transplant (HTX) patients. Purpose To investigate the detection of significant coronary artery stenosis and CAV, determinants of image quality, and the radiation dose in coronary computed tomography angiography (CCTA) of HTX patients with 64-slice multidetector CT (64-MDCT). Material and Methods Fifty-two HTX recipients scheduled for invasive coronary angiography (ICA) were prospectively enrolled and underwent CCTA before ICA with intravascular ultrasound (IVUS). Results Interpretable CCTA images were acquired in 570 (95%) coronary artery segments ≥2 mm in diameter. Sensitivity, specificity, and positive and negative predictive values of CCTA for the detection of segments with significant stenosis (lumen reduction ≥50%) on ICA were 100%, 98%, 7.7%, and 100%, respectively. Twelve significant stenoses were located in segments with uninterpretable image quality or vessel diameter <2 mm; only one was eligible for intervention. IVUS detected CAV (maximal intimal thickness ≥0.5 mm) in 33/41 (81%) patients; CCTA and ICA identified CAV (any wall or luminal irregularity) in 18 (44%) and 14 (34%) of these 33 patients, respectively. The mean estimated radiation dose was 19.0 ± 3.4 mSv for CCTA and 5.7 ± 3.3 mSv for ICA ( P < 0.001). Conclusion CCTA with interpretable image quality had a high negative predictive value for ruling out significant stenoses suitable for intervention. The modest detection of CAV by CCTA implied a limited value in identifying subtle CAV. The high estimated radiation dose for 64-MDCT is of concern considering the need for repetitive examinations in the HTX population.

Imaging in patients after cardiac transplantation and in patients with ventricular assist devices

The field of cardiac imaging and the management of patients with severe heart failure have advanced substantially during the past 10 years. Cardiac transplantation offers the best long-term survival with high quality of life for the patients with end stage heart failure. However, acute cardiac rejection and cardiac allograft vasculopathy (CAV) can occur post cardiac transplantation and these problems necessitate regular surveillance. The short-term success of mechanical circulatory support devices (MCSD), such as ventricular assist devices (VADs), in improving survival and quality of life has led to a dramatic growth of the patient population with these devices. The development of optimal imaging techniques and algorithms to evaluate these advanced heart failure patients is evolving and multimodality non-invasive imaging approaches and invasive techniques are commonly employed. Most of the published studies done in the transplant and VAD population are small, and biased based on the strength of the particular program, and there is a relative lack of published protocols to evaluate these patient groups. Moreover, the techniques of echocardiography, computed tomography (CT), magnetic resonance imaging, and nuclear cardiology have all progressed rapidly in recent years. There is thus a knowledge gap for cardiologists, radiologists, and clinicians, especially regarding surveillance for CAV and ideal imaging approaches for patients with VADs. The purpose of this review article is to provide an overview of different noninvasive imaging modalities used to evaluate patients after cardiac transplantation and for patients with VADs. The review focuses on the role of echocardiography, CT, and nuclear imaging in surveillance for CAV and rejection and on the assessment of ventricular structure and function, myocardial remodeling and complications for VAD patients.

Single- versus multi-phase acquisition protocol for prospective-triggered sequential dual-source CT coronary angiography: comparison of image quality and radiation dose

OBJECTIVE

To investigate image quality and radiation dose of single- versus multi-phase acquisition protocol for prospective-triggered sequential dual-source computed tomography (CT) coronary angiography.

MATERIALS AND METHODS

A total of 140 patients were randomly assigned to single- or multi-phase group. Image quality and radiation dose were compared.

RESULTS

No significant difference was found in image quality between the two groups. Effective dose of single-phase group was 21.6% lower than that of multi-phase group (P<.001).

CONCLUSIONS

Prospective-triggered sequential dual-source CT coronary angiography using single-phase protocol can reduce radiation dose without sacrifice of image quality in diastole compared with multi-phase protocol.

Detection of coronary artery stenosis with sub-milliSievert radiation dose by prospectively ECG-triggered high-pitch spiral CT angiography and iterative reconstruction

OBJECTIVES

To evaluate the diagnostic accuracy of sub-milliSievert (mSv) coronary CT angiography (cCTA) using prospectively ECG-triggered high-pitch spiral CT acquisition combined with iterative image reconstruction.

METHODS

Forty consecutive patients (52.9 ± 8.7 years; 30 men) underwent dual-source cCTA using prospectively ECG-triggered high-pitch spiral acquisition. The tube current-time product was set to 50 % of standard-of-care CT examinations. Images were reconstructed with sinogram-affirmed iterative reconstruction. Image quality was scored and diagnostic performance for detection of ≥50 % stenosis was determined with catheter coronary angiography (CCA) as the reference standard.

RESULTS

CT was successfully performed in all 40 patients. Of the 601 assessable coronary segments, 543 (90.3 %) had diagnostic image quality. Per-patient sensitivity for detection of ≥50 % stenosis was 95.7 % [95 % confidence interval (CI), 76.0-99.8 %] and specificity was 94.1 % (95 % CI, 69.2-99.7 %). Per-vessel sensitivity was 89.5 % (95 % CI, 77.8-95.6 %) with 93.2 % specificity (95 % CI, 86.0-97.0 %). The area under the receiver-operating characteristic curve on per-patient and per-vessel levels was 0.949 and 0.913. Mean effective dose was 0.58 ± 0.17 mSv. Mean size-specific dose estimate was 3.14 ± 1.15 mGy.

CONCLUSIONS

High-pitch prospectively ECG-triggered cCTA combined with iterative image reconstruction provides high diagnostic accuracy with a radiation dose below 1 mSv for detection of coronary artery stenosis.

KEY POINTS

• Cardiac CT with sub-milliSievert radiation dose is feasible in many patients • High-pitch spiral CT acquisition with iterative reconstruction detects coronary stenosis accurately. • Iterative reconstruction increases who can benefit from low-radiation cardiac CT.

Cardiac allograft vasculopathy after heart transplantation: electrocardiographically gated cardiac CT angiography for assessment

PURPOSE

To evaluate the diagnostic accuracy of cardiac computed tomographic (CT) angiography without the use of β-blockers compared with that of invasive angiography for the detection of cardiac allograft vasculopathy (CAV) in heart transplant recipients.

MATERIALS AND METHODS

The study was approved by the research ethics committee and informed consent was obtained. Heart transplant recipients (n = 138) scheduled for routine invasive angiography were prospectively enrolled to undergo CT to evaluate coronary artery calcification and retrospectively gated cardiac CT angiography with a 64-section scanner. The cardiac CT angiographic images were systematically analyzed for image quality. Degree of CAV was assessed by using a 15-coronary segments model. The area under the receiver operating characteristic curve, sensitivity, specificity, and negative and positive predictive values of cardiac CT angiography for detection of CAV with any degree of stenosis and greater than or equal to 50% stenosis were calculated.

RESULTS

Coronary artery calcification was absent in 82 patients, five (6%) of whom had CAV with 50% or more stenosis. Interpretable image quality was obtained in 130 (96%) of the 136 patients who completed the study and 1900 (98%) of 1948 segments. At the patient level, cardiac CT angiography had an area under the receiver operating characteristic curve, sensitivity, specificity, and positive and negative predictive values of 0.880 (95% confidence interval: 0.819, 0.941), 98%, 78%, 77%, and 98%, respectively, for diagnosis of CAV with any degree of stenosis, but for CAV with 50% or more stenosis, the corresponding values were 0.942 (95% confidence interval: 0.885, 1.000), 96%, 93%, 72%, and 99%, respectively. None of the 61 patients with normal cardiac CT angiographic results had CAV on the basis of invasive angiographic images.

CONCLUSION

The study results show that cardiac CT angiography compares favorably with invasive angiography in detecting CAV in heart transplant recipients and may be a preferable screening technique because of its noninvasive nature. The absence of coronary artery calcification alone is not reliable enough for excluding CAV.

Black-blood steady-state free precession (SSFP) coronary wall MRI for cardiac allografts: a feasibility study

PURPOSE

To assess the hypothesis that steady-state free procession (SSFP) allows for imaging of the coronary wall under the conditions of fast heart rate in heart transplantation (HTx) patients.

MATERIALS AND METHODS

With the approval of our Institutional Review Board, 28 HTx patients were scanned with a 1.5T scanner. Cross-sectional black-blood images of the proximal portions of the left main artery, left anterior descending artery, and right coronary artery were acquired with both a 2D, double inversion recovery (DIR) prepared turbo (fast) spin echo (TSE) sequence and a 2D DIR SSFP sequence. Image quality (scored 0-3), vessel wall area, thickness, signal-to-noise ratio (SNR, vessel wall), and contrast-to-noise ratio (CNR, wall-lumen) were compared between TSE and SSFP.

RESULTS

The overall image quality of SSFP was higher than TSE (1.23 ± 0.95 vs. 0.88 ± 0.69, P < 0.001). SSFP had a higher coronary wall SNR (20.1 ± 8.5 vs. 14.9 ± 4.8, P < 0.001) and wall-lumen CNR (8.2 ± 4.6 vs. 6.8 ± 3.7, P = 0.005) than TSE.

CONCLUSION

Black-blood SSFP coronary wall MRI provides higher image quality, SNR, and CNR than traditional TSE does in HTx recipients. It has the potential to become an alternative means to noninvasive imaging of cardiac allografts.

Radiation dose considerations by intra-individual Monte Carlo simulations in dual source spiral coronary computed tomography angiography with electrocardiogram-triggered tube current modulation and adaptive pitch

OBJECTIVES

To evaluate radiation dose levels in patients undergoing spiral coronary computed tomography angiography (CTA) on a dual-source system in clinical routine.

METHODS

Coronary CTA was performed for 56 patients with electrocardiogram-triggered tube current modulation (TCM) and heart-rate (HR) dependent pitch adaptation. Individual Monte Carlo (MC) simulations were performed for dose assessment. Retrospective simulations with constant tube current (CTC) served as reference. Lung tissue was segmented and used for organ and effective dose (ED) calculation.

RESULTS

Estimates for mean relative ED was 7.1 ± 2.1 mSv/100 mAs for TCM and 12.5 ± 5.3 mSv/100 mAs for CTC (P < 0.001). Relative dose reduction at low HR (≤60 bpm) was highest (49 ± 5%) compared to intermediate (60-70 bpm, 33 ± 12%) and high HR (>70 bpm, 29 ± 12%). However lowest ED is achieved at high HR (5.2 ± 1.5 mSv/100 mAs), compared with intermediate (6.7 ± 1.6 mSv/100 mAs) and low (8.3 ± 2.1 mSv/100 mAs) HR when automated pitch adaptation is applied.

CONCLUSIONS

Radiation dose savings up to 52% are achievable by TCM at low and regular HR. However lowest ED is attained at high HR by pitch adaptation despite inferior radiation dose reduction by TCM.

KEY POINTS

• Monte Carlo simulations allow for individual radiation dose calculations. • ECG-triggered tube current modulation (TCM) can effectively reduce radiation dose. • Slow and regular heart rates allow for highest dose reductions by TCM. • Adaptive pitch accounts for lowest radiation dose at high heart rates. • Women receive higher effective dose than men undergoing spiral coronary CT-angiography.