ECG-triggered Coronary CT Angiography Research Articles

Beta-blocker administration protocol for prospectively ECGtriggered coronary CT angiography

The aim of this article is to discuss the protocol of beta-blockers that is commonly used for prospectively ECG-triggered coronary computed tomography angiography (CCTA). It is essential to ensure a low and regular heart rate in patients undergoing prospectively ECG-triggered CCTA for optimal visualization of coronary arteries. Although early generations of computed tomographyscanners are not applicable to be tailored according to patients' heart rate, a low and regular heart rate is possible to be achieved by the administration of medications according to the beta-blocker protocol. Beta-blocker can be safely administered to reduce patients' heart rate for CCTA examination if patients are screened for certain contraindications.

Coronary CT angiography with single-source and dual-source CT: Comparison of image quality and radiation dose between prospective ECG-triggered and retrospective ECG-gated protocols

BackgroundThis study is conducted to investigate and compare image quality and radiation dose between prospective ECG-triggered and retrospective ECG-gated coronary CT angiography (CCTA) with the use of single-source CT (SSCT) and dual-source CT (DSCT). MethodsA total of 209 patients who underwent CCTA with suspected coronary artery disease scanned with SSCT (n=95) and DSCT (n=114) scanners using prospective ECG-triggered and retrospective ECG-gated protocols were recruited from two institutions. The image was assessed by two experienced observers, while quantitative assessment was performed by measuring the image noise, the signal-to-noise ratio (SNR) and the contrast-to-noise ratio (CNR). Effective dose was calculated using the latest published conversion coefficient factor. ResultsA total of 2087 out of 2880 coronary artery segments were assessable, with 98.0% classified as of sufficient and 2.0% as of insufficient image quality for clinical diagnosis. There was no significant difference in overall image quality between prospective ECG-triggered and retrospective gated protocols, whether it was performed with DSCT or SSCT scanners. Prospective ECG-triggered protocol was compared in terms of radiation dose calculation between DSCT (6.5±2.9mSv) and SSCT (6.2±1.0mSv) scanners and no significant difference was noted (p=0.99). However, the effective dose was significantly lower with DSCT (18.2±8.3mSv) than with SSCT (28.3±7.0mSv) in the retrospective gated protocol. ConclusionsProspective ECG-triggered CCTA reduces radiation dose significantly compared to retrospective ECG-gated CCTA, while maintaining good image quality.

Coronary CT angiography with prospective ECG-triggering: an effective alternative to invasive coronary angiography.

Despite the tremendous contributions of coronary CT angiography to coronary artery disease, radiation dose associated with coronary CT angiography has raised serious concerns in the literature, as the risk of developing radiation-induced malignancy is not negligible. Various dose-saving strategies have been implemented, with some of the strategies resulting in significant dose reduction. Of these strategies, prospective ECG-triggering is one of the most effective techniques with resultant effective radiation dose similar to or even lower than that of invasive coronary angiography. Prospective ECG-triggered coronary CT angiography has been reported to have high diagnostic accuracy in the diagnosis of coronary artery disease with image quality comparable to that of retrospective ECG-gating, but with significantly reduced radiation dose. Successful performance of prospective ECG-triggering is determined by strict exclusion criteria and careful patient preparation. The aim of this article is to provide an overview of the diagnostic applications of coronary CT angiography with prospective ECG-triggering with focus on radiation dose reduction. Radiation dose measurements are discussed with aim of allowing accurate dose estimation. Diagnostic value of prospective ECG-triggered coronary CT angiography in patients with different heart rate is discussed. Finally, current status and future directions are highlighted.

Reduction of radiation exposure and improvement of image quality with BMI-adapted prospective cardiac computed tomography and iterative reconstruction

PurposeTo assess the impact of body mass index (BMI)-adapted protocols and iterative reconstruction algorithms (iDose) on patient radiation exposure and image quality in patients undergoing prospective ECG-triggered 256-slice coronary computed tomography angiography (CCTA). MethodsImage quality and radiation exposure were systematically analyzed in 100 patients. 60 Patients underwent prospective ECG-triggered CCTA using a non-tailored protocol and served as a ‘control’ group (Group 1: 120kV, 200mAs). 40 Consecutive patients with suspected coronary artery disease (CAD) underwent prospective CCTA, using BMI-adapted tube voltage and standard (Group 2: 100/120kV, 100–200mAs) versus reduced tube current (Group 3: 100/120kV, 75–150mAs). Iterative reconstructions were provided with different iDose levels and were compared to filtered back projection (FBP) reconstructions. Image quality was assessed in consensus of 2 experienced observers and using a 5-grade scale (1=best to 5=worse), and signal- and contrast-to-noise ratios (SNR and CNR) were quantified. ResultsCCTA was performed without adverse events in all patients (n=100, heart rate of 47–87bpm and BMI of 19–38kg/m2). Patients examined using the non-tailored protocol in Group 1 had the highest radiation exposure (3.2±0.4mSv), followed by Group 2 (1.7±0.7mSv) and Group 3 (1.2±0.6mSv) (radiation savings of 47% and 63%, respectively, p<0.001). Iterative reconstructions provided increased SNR and CNR, particularly when higher iDose level 5 was applied with Multi-Frequency reconstruction (iDose5 MFR) (14.1±4.6 versus 21.2±7.3 for SNR and 12.0±4.2 versus 18.1±6.6 for CNR, for FBP versus iDose5 MFR, respectively, p<0.001). The combination of BMI adaptation with iterative reconstruction reduced radiation exposure and simultaneously improved image quality (subjective image quality of 1.4±0.4 versus 1.9±0.5 for Group 2 reconstructed using iDose5 MFR versus Group 1 reconstructed using FBP, p<0.05). ConclusionsProspective ECG-triggered 256-slice CCTA allows for visualization of the coronary artery tree with high image quality within a wide range of heart rates and BMIs. The combination of BMI-adapted protocols with iterative reconstruction algorithms can reduce radiation exposure for the patients and simultaneously improve image quality.

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

To assess feasibility, image quality, and radiation dose of prospectively ECG-triggered coronary CT angiography (CTA) in orthotopic heart transplant (OHT) recipients. 47 consecutive OHT recipients (40 men, mean age 62.1 ± 10.9 years, mean heart rate 86.3 ± 14.4 bpm) underwent dual-source CTA to rule out coronary allograft vasculopathy in a prospectively ECG-triggered mode with data acquisition during 35% to 45% of the cardiac cycle. Two independent observers blindly assessed image quality on a per-segment and per-vessel basis using a four-point scale (1-excellent, 4-not evaluable). Scores 1-3 were considered acceptable for diagnosis. Multivariate analysis was performed to evaluate differences between image quality scores obtained at different reconstruction intervals. Effective radiation doses were calculated. 671 coronary segments were evaluated. Interobserver agreement on the image quality was κ=0.75. Diagnostic image quality was observed in 93.9%, 95.5% and 93.3% of the segments at 35%, 40% and 45% reconstruction intervals. Mean image quality score was 1.5 ± 0.7 for the entire coronary tree, 1.4 ± 0.7 for the RCA, 1.6 ± 0.8 for the LCA and 1.6 ± 0.7 for the Cx at the best reconstruction interval. Estimated mean radiation dose was 4.5 ± 1.2 mSv. Systolic prospectively ECG-triggered CTA allows diagnostic image quality coronary angiograms in OHT recipients at low radiation doses.

Prognostic performance of low-dose coronary CT angiography with prospective ECG triggering

ObjectiveTo assess the prognostic value of low-dose 64-slice coronary CT angiography (CCTA) using prospective ECG triggering in a patient population with known or suspected coronary artery disease (CAD).DesignLongitudinal follow-up study.SettingTertiary...

Effect of Padding Duration on Radiation Dose and Image Interpretation in Prospectively ECG-Triggered Coronary CT Angiography

Prospectively ECG-triggered coronary CT angiography images are acquired during a window in middiastole. Additional surrounding x-ray beam on time, or padding, can be variably set, and the increased padding results in additional available phases for analysis. The purpose of this study was to assess the effect of padding duration on image interpretability and its incident effect on radiation dose. We prospectively evaluated imaging of 886 patients undergoing consecutive prospectively ECG-triggered coronary CT angiographic examinations at three centers and compared the findings in patients stratified by padding duration. We assessed the effect of padding duration on image interpretability and radiation dose. The mean patient age was 56 +/- 12 years, and 58% of the patients were men. The median heart rate was 55 beats/min (interquartile range, 50-61 beats/min). Padding duration was 0, 1-99, and 100-150 milliseconds for 268, 482, and 136 patients, respectively, with no difference in image interpretability rate between groups (per patient, 98.8%, 97.3%, and 97.1%; per artery, 99.2%, 99.2%, and 99.1%). The groups differed in median radiation dose (2.3 mSv [interquartile range, 1.5-3.2 mSv]; 3.8 mSv [interquartile range, 2.3-4.7 mSv]; 5.5 mSv [interquartile range, 3.8-6.1 mSv]; p < 0.001). Independent of patient and scan parameters, increased padding was associated with greater radiation dose (45% increase per 100-millisecond increase in padding, p < 0.001). In a large multicenter study of coronary CT angiography of patients with excellent heart rate control, the use of minimal padding was associated with a substantial reduction in radiation dose with preserved image interpretability. Use of no or reduced padding should be considered in dose-reduction strategies.

Adenosine-stress dynamic myocardial volume perfusion imaging with second generation dual-source computed tomography: Concepts and first experiences

Recent research suggests that multidetector-row CT may have potential as a standalone modality for integrative imaging of coronary heart disease, including the assessment of the myocardial blood supply. However, the technical prerequisites for volumetric, time-resolved imaging of the passage of a contrast medium bolus through the myocardium have only been met with latest generation wide-detector CT scanners. Second-generation dual-source CT enables performing electrocardiographic (ECG)-synchronized dynamic myocardial perfusion imaging by a dedicated "shuttle" mode. With this acquisition mode, image data can be acquired during contrast medium infusion at 2 alternating table positions with the table shuttling back and forth between the 2 positions covering a 73-mm anatomic volume. We applied this acquisition technique for detecting differences in perfusion patterns between healthy and diseased myocardium and for quantifying myocardial blood flow under adenosine stress in 3 patients with coronary heart disease. According to our initial experience, the addition of adenosine stress volumetric dynamic CT perfusion to a cardiac CT protocol comprising coronary artery calcium quantification, prospectively ECG-triggered coronary CT angiography, and delayed acquisition appears promising for the comprehensive assessment of coronary artery luminal integrity, cardiac function, perfusion, and viability with a single modality.

Assessment of image quality and radiation dose in prospective ECG-triggered coronary CT angiography compared with retrospective ECG-gated coronary CT angiography

We sought to determine the cut-off point of the average heart rate (HR) and HR differences in obtaining diagnostic image quality using prospective electrocardiographically-triggered (PT) coronary computed tomographic angiography (CCTA) and to compare image quality and radiation dose for CCTA obtained with PT CCTA and retrospective electrocardiographically-gated (RG) CCTA. A total of 178 patients who were referred for CCTA were enrolled in the study. Two independent radiologists evaluated subjective image quality. The non-diagnostic coronary segments were 32 of 1,226 segments (2.6%) for PT CCTA and 12 of 1,346 segments (0.9%) for RG CCTA (P < 0.001). The mean image quality scores for PT CCTA and RG CCTA were 3.82 +/- 0.29 and 3.93 +/- 0.14, respectively. The mean radiation dose of patients that underwent PT CCTA was 3.83 +/- 0.84 mSv and RG CCTA 10.7 +/- 2.70 mSv. For patients who underwent PT CCTA, image quality was inversely related to HR (56.5 +/- 4.3 bpm; r = 0.38; P < 0.001) and HR differences (2.8 +/- 2.7 bpm; r = 0.49; P < 0.001). With the use of receiver operator characteristic analysis, a cut-off HR of 57 bpm (58% sensitivity, 67% specificity) and HR difference of 6 bpm (93% sensitivity, 46% specificity) were the best threshold for the prediction of diagnostic image quality. In patients with a regular, low HR, PT CCTA offers diagnostic image quality and substantially reduces effective radiation compared with the use of RG CCTA with dose modulation.

Low-Dose Coronary CT Angiography With Prospective ECG Triggering: Validation of a Contrast Material Protocol Adapted to Body Mass Index

The aim of the study was to validate a body mass index (BMI)-adapted contrast material protocol to compensate for the effect of BMI on coronary attenuation during low-dose coronary CT angiography with prospective ECG triggering. One hundred forty patients underwent prospectively ECG-triggered coronary CT angiography for clinical indications. The following BMI-adapted contrast material protocol was used for imaging of 70 consecutively registered patients: BMI < 17.5, 50 mL contrast material at 4.0 mL/s; 17.5-22.4, 55 mL at 4.0 mL/s; 22.5-24.9, 65 mL at 4.0 mL/s; 25.0-27.4, 80 mL at 4.5 mL/s; 27.5-29.9, 80 mL at 5.0 mL/s; 30.0-34.9, 85 mL at 5.0 mL/s; 35.0-40.0, 95 mL at 5.0 mL/s; > 40, 105 mL at 5.0 mL/s. Seventy patients matched for BMI who had previously undergone routine coronary CT angiography with a fixed contrast material dosage of 80 mL at 5 mL/s served as the reference group. Vessel attenuation in the left main and proximal right coronary arteries was measured and correlated with BMI, and the results in the two protocol groups were compared. The groups were well matched for BMI. The mean BMI in the nonadapted protocol group was 26.5 +/- 4.0 (standard deviation) (range, 18.9-36.5), and that in the BMI-adapted protocol group was 26.7 +/- 4.2 (range, 18.2-37.2) (p not significant). The mean amount of contrast material used was smaller in the BMI-adapted group (73.9 +/- 11.2 vs 80.0 +/- 0 mL; p < 0.01). Mean coronary artery attenuation did not differ significantly between the two groups (386 +/- 102 HU vs 385 +/- 64 HU; p not significant). Without BMI adaptation, coronary attenuation correlated strongly with BMI (r = -0.63; p < 0.001). With the BMI-adapted protocol, however, there was no correlation between BMI and coronary attenuation (r = -0.24; p not significant). We validated a BMI-adapted contrast material protocol that results in adequate coronary vessel attenuation independent of individual BMI despite a significant reduction in overall amount of contrast material used.