Prospectively ECG-triggered sequential dual-source coronary CT angiography in patients with atrial fibrillation: comparison with retrospectively ECG-gated helical CT

Diagnosis of coronary artery disease in patients with atrial fibrillation using low tube voltage coronary CT angiography with isotonic low-concentration contrast agent

This prospective study evaluated the image quality and accuracy of coronary computed tomography angiography (CCTA) for diagnosing coronary artery disease (CAD) in patients with atrial fibrillation (AF), in which CCTA used adaptive iterative dose reduction (AIDR) with a low tube voltage and low concentration of isotonic contrast agent. Sixty-eight consecutive patients with AF and suspected CAD were equally and randomly apportioned to two groups and underwent CCTA. In the experimental group, the contrast agent was iodixanol (270 mg I/mL), patients were scanned with 100 kV, and reconstruction was by AIDR. In the conventional scanning (control) group, the contrast agent was iopromide (370 mg I/mL), patients were scanned with 120 kV, and reconstruction was by filtered back projection. The image quality, effective radiation dose (E), and total iodine intake of the groups were compared. Thirty-nine patients with coronary artery stenosis later were given invasive coronary angiography (ICA). The groups were similar with regard to mean CT value, noise, and signal-to-noise and contrast-to-noise ratios. The figure of merit of the experimental group was significantly higher than that of the control group, while the E and total iodine were significantly lower. Using ICA as the diagnostic reference, the groups shared similar sensitivity, specificity, and false positive and false negative rates for diagnosing coronary artery stenosis. For determining CAD in patients with AF, CCTA with isotonic low-concentration contrast agent and low-voltage scanning is a feasible alternative that improves accuracy and reduces radiation dose and iodine intake.

Low-Dose Coronary CT Angiography in Patients with Atrial Fibrillation: Comparison of Image Quality and Radiation Exposure with Two Different Approaches

RATIONALE AND OBJECTIVES

To evaluate image quality, coronary interpretability and radiation exposure of coronary CT angiography (CCTA) performed in patients with atrial fibrillation (AF) with the latest scanner generation, comparing two different technical approaches. A new scanner that combines a 0.23 mm spatial resolution, a new generation of iterative reconstruction, fast gantry rotation time and the intracycle motion-correction algorithm to improve the temporal resolution was recently introduced in the clinical field.

MATERIALS AND METHODS

We enrolled 105 consecutive patients with chronic AF who performed CCTA with a whole-heart coverage high-definition CT scanner (16-cm z-axis coverage with 256 detector rows, 0.28 s gantry rotation time). Five of them were excluded for impaired renal function. Patients were randomized between a double acquisition protocol (50 patients, group 1) or a single acquisition protocol (50 patients, group 2). The image quality, coronary segment interpretability and effective dose (ED) of CCTA were assessed.

RESULTS

The mean HR during the scan was 85.6±21 bpm in group 1 vs. 83.7±23 bpm in Group 2, respectively (p < ns). In group 2, overall image quality was high and comparable with that of group 1 (Likert scale =3.2 ± 1.4 vs. 3.3 ± 1.2, p = ns, in group 1 and 2, respectively). Coronary interpretability was high and similar between the two groups (97.5% and 97.1% in group 1 and 2, p = ns, respectively). Mean ED was significantly higher in group 1 than in group 2 (5.3 ± 1.8 mSv vs. 2.7 ± 0.7 mSv, p < 0.001).

CONCLUSION

The novel whole-heart coverage CT scanner allows to perform CCTA with a single-acquisition protocol with high image quality and low radiation exposure in AF patients.

Coronary CT angiography radiation dose trends: A 10-year analysis to develop institutional diagnostic reference levels

PURPOSE

To develop institutional diagnostic reference levels (IDRL) for coronary CT angiography (CCTA) according to patient size by analyzing radiation dose changes over the past 10 years.

MATERIALS AND METHODS

This IRB approved retrospective investigation analyzed radiation dose data from CCTA between 2007 and 2016 at our institution. Annual trends in radiation dose were described for each scanner type and scanning mode. Radiation levels were analyzed for normorhythmic patients, patients with prior coronary artery bypass grafting (CABG), arrhythmia, and according to patient size and tube voltage. Median, and quartile values for volume CT dose index (CTDIvol), dose-length product (DLP), and size-specific dose estimate (SSDE) were calculated. Wilcoxon rank-sum test and Kruskal Wallis test were performed to assess the significance of quantitative data.

RESULTS

35,375 examinations from 33,317 patients (median age, 58 [50-66] years; male patients, 21,087 [58.7%]) were analyzed. CTDIvol, DLP, and SSDE significantly decreased by 9.0%, 30.8%, and 40.1% (all P < 0.05) for all examinations, respectively. All radiation dose metrics progressively decreased across scanning modes (especially retrospectively ECG-gated spiral and prospectively ECG-triggered high-pitch spiral acquisition mode), but did not significantly change across scanners in the last 6 years. CTDIvol and DLP increased with patient size when water-equivalent diameters were >19 cm for normorhythmic and CABG patients. In arrhythmic patients, CTDIvol increased progressively with water-equivalent diameters across all groups.

CONCLUSION

CCTA radiation dose has progressively decreased in the past decade except in patients with prior CABG and arrhythmia. Size-specific IDRLs may optimize radiation utilization in these patients going forward.

A Preliminary Study of Computed Tomography Coronary Angiography Within a Single Cardiac Cycle in Patients With Atrial Fibrillation Using 256-Row Detector Computed Tomography

OBJECTIVE

The purpose of this study was to evaluate the image quality and radiation dose of computed tomography (CT) coronary angiography using a 256-row detector CT scanner in a single cardiac cycle in patients with atrial fibrillation (AF).

METHODS

Seventy consecutive patients (41 men and 29 women; age range was from 37 to 84 years, mean age was 61.7 ± 10.2 years; body mass index range was from 15.08 to 36.45 kg/m, mean body mass index was 25.9 ± 3.5 kg/m) with persistent or paroxysmal AF during acquisition, who were not receiving any medications for heart rate (HR) regulation, were imaged with a 256-row detector CT scanner (Revolution CT, GE healthcare). According to the HR or HR variability (HRV) the patients were divided into 4 groups: group A (HR, ≥75 bpm; n = 36), group B (HR, <75 bpm; n = 34), group C (HRV, ≥50 bpm; n = 26), and group D (HRV, <50 bpm; n = 44). The snapshot freeze algorithm reconstruction was used to reduce motion artifacts whenever necessary. Two experienced radiologists, who were blinded to the electrocardiograph and reconstruction information, independently graded the CT images in terms of visibility and artifacts with a 4-grade rating scale (1, excellent; 2, good; 3, poor; 4, insufficient) using the 18-segment model. Subjective image quality scores and effective dose (ED) were calculated and compared between these groups.

RESULTS

The HR during acquisition ranged from 47 to 222 bpm (88.24 ± 36.80 bpm). A total of 917 in 936 coronary artery segments were rated as diagnostically evaluable (98.2 ± 0.04%). There was no significant linear correlation between mean image quality and HR or HRV (P > 0.05). Snapshot freeze reconstruction technique was applied in 28 patients to reduce motion artifacts and thus showed image quality was improved from 93.2% to 98.4%. The ED was 3.05 ± 2.23 mSv (0.49-11.86 mSv) for all patients, and 3.76 ± 2.22 mSv (0.92-11.17 mSv), 2.30 ± 2.02 mSv (0.49-11.86 mSv), 3.89 ± 2.35 mSv (1.18-11.86 mSv), and 2.56 ± 2.03 mSv (0.49-11.17 mSv) for groups A, B, C, and D, respectively. There were significant differences in mean ED between groups A and B, as well as C and D (P <0.05).

CONCLUSIONS

This study shows that CT coronary angiography with use of a new 256-row detector CT in single cardiac cycle achieves diagnostic image quality but with lower radiation dose in patients with AF. Heart rate or HRV has no significant effect on image quality.

Coronary CT angiography in patients with atrial fibrillation: Standard-dose and low-dose imaging with a high-resolution whole-heart CT scanner

OBJECTIVE

To compare image quality, observer confidence, radiation exposure in the standard-dose (SD-CCTA) and low-dose (LD-CCTA) protocols of coronary CT angiography (CCTA) in patients with atrial fibrillation (AF).

MATERIAL AND METHODS

CCTA was performed in 303 patients using a CT scanner with 16-cm coverage (111 scans during sinus rhythm (SR); 192 during AF). LD-CCTA was used in 218 patients; SD-CCTA in 85 patients suspected of having coronary artery disease (CAD). Image quality and observer confidence were evaluated on 5-point scales. Radiation doses were recorded.

RESULTS

Image quality was superior in the SD-CCTA compared to the LD-CCTA (SR 1.45±0.40; AF 1.72±0.46; vs. SR 1.83±0.48; AF 1.92±0.50; p < 0.001). Observers were more confident with SD-CCTA than with LD-CCTA (SR 1.38±0.33; AF 1.61±0.43; vs. SR 1.70±0.45; AF 1.82±0.50; p < 0.001). Radiation doses in AF were significantly higher than in the SR (LD-CCTA, 1.68±0.71 mSv; SD-CCTA, 3.72±1.95 mSv; vs. LD-CCTA, 1.3 ±0.52 mSv; SD-CCTA, 2.67±1.47 mSv; p < 0.001).

CONCLUSION

Using a low-dose protocol in AF, radiation exposure can be decreased by 50 % at the expense of 20 % impaired image quality. A low-dose CCTA protocol can be considered in young patients, whereas the standard-dose protocol is recommended for older patients and those suspected of having CAD.

KEY POINTS

• Whole-heart CT allows visualization of the coronary arteries in atrial fibrillation. • Low-dose CT decreases radiation exposure by 50%, image quality by 20%. • Standard-dose CT seems advantageous when concomitant coronary artery disease is suspected.

Influence of irregular heart rhythm on radiation exposure, image quality and diagnostic impact of cardiac computed tomography angiography in 4,339 patients. Data from the German Cardiac Computed Tomography Registry

BACKGROUND

Coronary computed tomography angiography (coronary CTA) provides non-invasive evaluation of the coronary arteries with high precision for the detection of significant coronary artery disease (CAD).

AIM

To investigate whether irregular heart rhythm including atrial fibrillation and premature beats during data acquisition influences (i) radiation and contrast media exposure, (ii) number of non-evaluable coronary segments and (iii) diagnostic impact of coronary CTA.

METHODS

Twelve tertiary care centers with ≥64 slice CT scanners and ≥5 years of experience with cardiovascular imaging participated in this registry. Between 2009 and 2014, 4339 examinations were analysed in patients who underwent clinically indicated coronary CTA for suspected CAD. Clinical and epidemiologic data were gathered from all patients. In addition, clinical presentation, heart rate and rhythm during the scan, Agatston score, radiation and contrast media exposure and the diagnostic impact of coronary CTA were systematically analysed.

RESULTS

Of 4339 patients in total, 260 (6.0%) had irregular heart rhythm, whereas the remaining 4079 (94.0%) had stable sinus rhythm. Patients with irregular heart rhythm were older (63.2 ± 12.5yrs versus 58.6 ± 11.4yrs. p < 0.001), exhibited a higher rate of pathologic stress tests before CTA (37.1% versus 26.1%, p < 0.01) and higher heart rates during CTA compared to those with sinus rhythm (62.5 ± 11.6bpm versus 58.9 ± 8.5bpm, p < 0.001). Both contrast media exposure and radiation exposure were significantly higher in patients with irregular heart rhythm (90 mL (95%CI = 80-110 mL) versus 80 mL (95%CI = 70-90 mL) and 6.2 mSv (95%CI = 2.5-11.7) versus 3.3 mSv (95%CI = 1.7-6.9), p < 0.001 for both). Coronary CTA excluded significant CAD less frequently in patients with irregular heart rhythm (32.9% versus 44.8%, p < 0.001). This was attributed to the higher rate of examinations with at least one non-diagnostic coronary segment in patients with irregular heart rhythm (10.8% versus 4.6%, p < 0.001). Subsequent invasive angiography could be avoided in 47.2% of patients with irregular heart rhythm compared to 52.9% of patients with sinus rhythm (p = NS), whereas downstream stress testing was recommended in 3.2% of patients with irregular heart rhythm versus 4.0% of patients with sinus rhythm (p = NS).

CONCLUSION

A significant number of patients scheduled for coronary CTA have irregular heart rhythm in a real-world clinical setting. In such patients, heart rate during coronary CTA is higher, possibly resulting in (i) higher radiation and contrast agent exposure and (ii) more frequent coronary CTA examinations with at least one non-diagnostic coronary artery segment. However, this does not seem to lead to increased downstream stress testing or subsequent invasive procedures.

Feasibility of low-dose coronary computed tomographic angiography used in atrial fibrillation patients

OBJECTIVE

The diagnosis of coronary artery disease (CAD) in atrial fibrillation (AF) patients using coronary computed tomography angiography (CCTA) requires a large exposure dosage or repeated examinations. This study evaluates the feasibility of using low-dose CCTA in the double prospectively ECG-triggered high-pitch spiral acquisition mode (Double Flash Spiral mode).

METHODS

Twenty-eight AF patients with suspected CAD were recruited. Double Flash Spiral mode (tube voltage 100 kVp) and iterative reconstruction was used for CCTA examination. Two radiologists cross-evaluated the CCTA image quality. The effective radiation dose was measured for each patient.

RESULTS

Twenty-eight AF patients (10 female, 18 male, mean age 68.8 ± 13.9 y, body mass index 24.3 ± 2.3 kg/cm²) were recruited and 337 artery segments were evaluated. In total, 98.5% (332/337) of the coronary artery segments and 96.4% (27/28) of the AF patients were rated as diagnostically evaluable. Of these 27 diagnosable patients, 17 patients (63%) were diagnosed with multi-vessel stenosis. Besides, 5 of 28 patients (17.9%) have left atrial appendage thrombus. The quality of the integrated image was significantly better than either of the individual first or the second scans, based on segments (P < 0.001) and patients (P < 0.05). The mean effective radiation dose was 1.5 mSv ±0.4 mSv.

CONCLUSIONS

Using the Double Flash Spiral mode at low radiation dose (mean 1.5 mSv), 98.5% of the coronary segments and 96.4% of the scans were of sufficient diagnostic quality.

Image Quality and Radiation Exposure Comparison of a Double High-Pitch Acquisition for Coronary Computed Tomography Angiography Versus Standard Retrospective Spiral Acquisition in Patients With Atrial Fibrillation

OBJECTIVE

The aim of this study was to compare image quality and radiation dose of coronary computed tomography (CT) angiography performed with dual-source CT scanner using 2 different protocols in patients with atrial fibrillation.

METHODS

Forty-seven patients with AF underwent 2 different acquisition protocols: double high-pitch (DHP) spiral acquisition and retrospective spiral acquisition. The image quality was ranked according to a qualitative score by 2 experts: 1, no evident motion; 2, minimal motion not influencing coronary artery luminal evaluation; and 3, motion with impaired luminal evaluation. A third expert solved any disagreement.

RESULTS

A total of 732 segments were evaluated. The DHP group (24 patients, 374 segments) showed more segments classified as score 1 than the retrospective spiral acquisition group (71.3% vs 37.4%). Image quality evaluation agreement was high between observers (κ = 0.8). There was significantly lower radiation exposure for the DHP group (3.65 [1.29] vs 23.57 [10.32] mSv).

CONCLUSIONS

In this original direct comparison, a DHP spiral protocol for coronary CT angiography acquisition in patients with atrial fibrillation resulted in lower radiation exposure and superior image quality compared with conventional spiral retrospective acquisition.

CT coronary angiography in atrial fibrillation: a comparison of radiation dose and diagnostic confidence with retrospective gating vs prospective gating with systolic acquisition

OBJECTIVE

To compare unmodulated, retrospective electrocardiographic (ECG) gating to prospective ECG gating with systolic acquisition for CT coronary angiography (CTCA) in patients with atrial fibrillation (AF), considering the radiation dose and the diagnostic confidence achieved with each technique.

METHODS

A retrospective service evaluation was conducted before and after prospective gating with systolic acquisition replaced retrospectively gated imaging for patients with AF undergoing CTCA at our institution. 25 consecutive patients were examined in each group. The scan parameters and radiation dose information had been collected in a prospective fashion. The image sets were read by blinded, expert readers who rated their diagnostic confidence using a 5-point Likert scale.

RESULTS

The radiation dose received by patients was significantly greater in the retrospectively gated group than those being scanned using prospective gating (21 vs 5.9 mSv, p < 0.01). The prospective gating technique was also associated with greater diagnostic confidence (mean, per-patient score 3.09 vs 3.78, p = 0.02).

CONCLUSION

Prospective gating with systolic acquisition appears to improve diagnostic confidence at a significantly reduced radiation dose compared with retrospective gating in patients with AF.

ADVANCES IN KNOWLEDGE

The use of prospective gating with systolic triggering significantly reduces the radiation exposure to patients in AF undergoing CTCA. The same protocol also appears to improve diagnostic confidence.

Prospectively ECG-Triggered Sequential Dual-Source Coronary CT Angiography in Patients with Atrial Fibrillation: Influence of Heart Rate on Image Quality and Evaluation of Diagnostic Accuracy

Objectives

To evaluate the effects of mean heart rate (HR) and heart rate variation (HRV) on image quality and diagnostic accuracy of prospectively ECG-triggered sequential dual-source coronary CT angiography (CCTA) in patients with atrial fibrillation (AF).

Methods

Eighty-five patients (49 women, 36 men; mean age 62.1±9.5 years) with persistent AF underwent prospectively ECG-triggered sequential second-generation dual-source CCTA. Tube current and voltage were adjusted according to body mass index (BMI) and iterative reconstruction was used. Image quality of coronary segments (four-point scale) and presence of significant stenosis (>50%) were evaluated. Diagnostic accuracy was analyzed in 30 of the 85 patients who underwent additional invasive coronary angiography (ICA).

Results

Only 8 of 1102 (0.7%) segments demonstrated poor image quality. No significant impact on image quality was found for mean HR (94.9±21.8 bpm; r=0.034, p=0.758; F=0.413, p=0.663) or HRV (67.5±22.8 bpm; r=0.097, p=0.377; F=0.111, p=0.895). On per-segment analysis, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 89.7% (26/29), 99.4% (355/357), 92.9% (26/28), and 99.2% (355/358), respectively, with excellent correlation (kappa=0.91) with ICA. Mean effective dose was 3.3±1.0 mSv.

Conclusions

Prospectively ECG-triggered sequential dual-source CCTA provides diagnostic image quality and good diagnostic accuracy for detection of coronary stenosis in AF patients without significant influence by HR or HRV.

State-of-the-Art Updates on Cardiac Computed Tomographic Angiography for Assessing Coronary Artery Disease

OPINION STATEMENT

Cardiac computed tomographic angiography (CCTA) is a noninvasive imaging modality that is increasingly useful for the evaluation of coronary artery disease (CAD). Over the past decade, CCTA has consistently demonstrated an excellent sensitivity for the detection and exclusion of coronary atherosclerosis in patients with stable or acute chest pain symptoms. Large prospective registries have repeatedly demonstrated the prognostic significance of the presence, extent, or absence of CAD by CCTA. In response to initial concerns, technical advances have permitted a dramatic reduction in patient radiation exposure with preserved image quality. For many patients, the radiation dose of CCTA is less than half of that with conventional myocardial perfusion imaging while providing significantly more anatomic information. Furthermore, CCTA's excellent spatial resolution is increasingly being used for noninvasive assessment of coronary plaque, including the detection of higher-risk vulnerable plaque and association between plaque characteristics and ischemia. Finally, new promising techniques that incorporate physiology with anatomy, such as CT-based fractional flow reserve (FFR-CT) and CT perfusion (CTP), are allowing for the noninvasive hemodynamic assessment of coronary stenoses and improvements in the specificity of CCTA findings. Such advances augur a coming transition when CCTA will be a first-line test for the detection, exclusion, and even management of CAD in many 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.