Radiation dose reduction method combining the ECG-Edit function and high helical pitch in retrospectively-gated CT angiography

INTRODUCTION

The purpose of this study was to demonstrate that dose reduction does not compromise image quality when combining high helical pitch (HP) and the ECG-Edit function during low HP retrospectively gated computed tomography angiography (CTA).

METHODS

This study made use of a pulsating cardiac phantom (ALPHA 1 VTPC). The heart rate (HR) of the cardiac phantom was changed in five intervals, every 5 beats per minute (bpm), from 40 to 60 bpm. Evaluation of a range of HR was important because data loss might occur when combining a low HR and high HP. We performed retrospectively gated CTA scans five times using a low HP (0.16) and high HP (0.24), for each of the five HR intervals, using a 64-detector row CT scanner. The CT volume dose index (CTDI_vol) was recorded from the CT console of each scan. For the images with data loss, data were repaired using the ECG-Edit function. We compared the CTDI_vol, estimated cardiac phantom volume, and the visualization of the coronary ladder phantom between HP 0.16, with or without repaired HP 0.24, using the ECG-Edit function.

RESULTS

Data loss occurred with a HR of 40 bpm and 45 bpm when using HP 0.24. The CTDI_vol was reduced by approximately 33% with HP 0.24 when compared with HP 0.16. There were no significant differences in the mean cardiac motion phantom volume and visualization scores between HP 0.16 and with and without repaired HP 0.24 using the ECG-Edit function (p < 0.05).

CONCLUSION

The ECG-Edit function is potential useful for repairing the lost data in patients with a low HR, and when combined with a high HP, it is possible to reduce the radiation dose by approximately 33%.

IMPLICATIONS FOR PRACTICE

The ECG-Edit function and high HP may be a viable option in pediatric CTA studies.

Smoking and obesity predict high-risk plaque by coronary CTA in low coronary artery calcium score (CACS)

BACKGROUND

The AHA recommends statins in patients with CACS>100 AU. However in patients with low CACS (1-99 AU), no clear statement is provided, leaving the clinician in a grey-zone. High-risk plaque (HRP) criteria by coronary CTA are novel imaging biomarkers indicating a higher a-priori cardiovascular (CV) risk, which could help for decision-making. Therefore the objective of our study was to identify which CV-risk factors predict HRP in patients with low CACS 1-99.

METHODS

1003 symptomatic patients with low-to-intermediate risk, a clinical indication for coronary computed tomography angiography (CCTA) and who had a coronary artery calcium score (CACS) between 1 and 99 AU, were enrolled. CCTA analysis included: stenosis severity and HRP-criteria: low-attenuation plaque (LAP <30HU, <60HU and <90HU) napkin-ring-sign, spotty calcification and positive remodeling. Multivariate regression models were created for predicting HRP-criteria by the major 5 cardiovascular risk factors (CVRF) (smoking, arterial hypertension, positive family history, dyslipidemia, diabetes) and obesity (BMI>25 ​kg/m²).

RESULTS

304 (33.5%) were smokers. 20.4% of smokers had HRP compared with only 14.9% of non-smokers (p ​= ​0.045). Male gender was associated with HRP (p ​< ​0.001). Smoking but not the other 5 CVRF had the most associations with HRP-criteria (LAP<60HU/≥2 criteria:OR 1.59; 95%CI:1.07-2.35), LAP<90HU (OR 1.57; 95%CI:1.01-2.43), Napkin-Ring-Sign (OR 1.78; 95%CI:1.02-3.1) and positive remodelling (OR 1.54; 95%CI:1.09-2.19). Smoking predicted fibrofatty LAP<90HU in males only. Obesity predicted LAP<60HU in both females and males.

CONCLUSIONS

In patients with low CACS 1-99AU, male gender, smoking and obesity, but not the other CVRF predict HRP. These patients would rather benefit from intensification of primary CV-prevention measures such as statins.

Coronary atherosclerosis characteristics in HIV-infected patients on long-term antiretroviral therapy: insights from coronary computed tomography-angiography

OBJECTIVE

The aim of the study was to assess coronary artery disease (CAD) characteristics by coronary computed tomography-angiography (CCTA) in individuals with HIV infection on long-term antiretroviral therapy (ART) DESIGN:: Retrospective case-controlled matched cohort study.

METHODS

Sixty-nine HIV-positive patients who underwent 128-slice dual source CCTA (mean age 54.9 years, 26.1% women) with mean 17.8 ± 9.4 years of HIV infection and a mean duration on ART of 13 ± 7.3 years were propensity score-matched (1 : 1) for age, sex, BMI, and five cardiovascular risk factors with 69 controls. CCTA was evaluated for stenosis severity [according to Coronary Artery Disease - Reporting and Data System (CAD-RADS)], total plaque burden [segment involvement score (SIS) and mixed-noncalcified plaque burden (G-score)]. As inflammatory biomarkers, high-risk plaque (HRP) features (napkin-ring sign, low-attenuation plaque, spotty calcification, positive remodeling), perivascular fat attenuation index (FAI), and ectatic coronary arteries were assessed.

RESULTS

CAD-RADS was higher in HIV-positive participants as compared with controls (2.21 ± 1.4 vs. 1.69 ± 1.5, P = 0.031). A higher prevalence of CAD and G-score (P = 0.043 and P = 0.003) was found. HRP prevalence [23 (34.3%) vs. 8 (12.1%); P = 0.002] and the number of HRP (36 vs. 10, P < 0.001) were higher in HIV-positive individuals. A perivascular FAI greater than -70 Hounsfield units was present in 27.8% of HRP. Ectatic coronary arteries were found in 10 (14.5%) HIV-positive persons vs. 0% in controls (P = 0.003).

CONCLUSION

Noncalcified and HRP burden in HIV-infected individuals on long-term ART is higher and associated with higher cardiovascular risk. Moreover, HIV-positive individuals displayed a higher stenosis severity (CAD-RADS) and more ectatic coronary arteries compared with the control group.

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.

SCCT guidelines for the performance and acquisition of coronary computed tomographic angiography: A report of the society of Cardiovascular Computed Tomography Guidelines Committee: Endorsed by the North American Society for Cardiovascular Imaging (NASCI)

In response to recent technological advancements in acquisition techniques as well as a growing body of evidence regarding the optimal performance of coronary computed tomography angiography (coronary CTA), the Society of Cardiovascular Computed Tomography Guidelines Committee has produced this update to its previously established 2009 "Guidelines for the Performance of Coronary CTA" (1). The purpose of this document is to provide standards meant to ensure reliable practice methods and quality outcomes based on the best available data in order to improve the diagnostic care of patients. Society of Cardiovascular Computed Tomography Guidelines for the Interpretation is published separately (2). The Society of Cardiovascular Computed Tomography Guidelines Committee ensures compliance with all existing standards for the declaration of conflict of interest by all authors and reviewers for the purpose ofclarity and transparency.

256-Slice coronary computed tomographic angiography in patients with atrial fibrillation: optimal reconstruction phase and image quality

OBJECTIVES

To assess the optimal reconstruction phase and the image quality of coronary computed tomographic angiography (CCTA) in patients with atrial fibrillation (AF).

METHODS

We performed CCTA in 60 patients with AF and 60 controls with sinus rhythm. The images were reconstructed in multiple phases in all parts of the cardiac cycle, and the optimal reconstruction phase with the fewest motion artefacts was identified. The coronary artery segments were visually evaluated to investigate their assessability.

RESULTS

In 46 (76.7 %) patients, the optimal reconstruction phase was end-diastole, whereas in 6 (10.0 %) patients it was end-systole or mid-diastole, and in 2 (3.3 %) patients it was another cardiac phase. In 53 (88.3 %) of the controls, the optimal reconstruction phase was mid-diastole, whereas it was end-systole in 4 (6.7 %), and in 3 (5.0 %) it was another cardiac phase. There was a significant difference between patients with AF and the controls in the optimal phase (p < 0.01) but not in the visual image quality score (p = 0.06).

CONCLUSIONS

The optimal reconstruction phase in most patients with AF was the end-diastolic phase. The end-systolic phase tended to be optimal in AF patients with higher average heart rates.

KEY POINTS

The optimal reconstruction phase in 76.7 % of patients with atrial fibrillation (AF) was end-diastole. The end-systolic phase was optimal in AF patients with higher heart rates. ECG and heart-rate control are necessary to obtain end-diastolic images with fewer motion artefacts.

Impact of β(1)- and β(2)-adrenergic receptor gene single nucleotide polymorphisms on heart rate response to metoprolol prior to coronary computed tomographic angiography

A slow, steady heart rate (HR) is necessary for optimal image quality during coronary computed tomographic angiography. Beta blockers are often used, but the goal HR is not achieved in some patients. The aim of this study was to examine the influence of single-nucleotide polymorphisms (SNPs) of the β(1) (codons 49 and 389) and β(2) (codons 16, 27, and 164) adrenergic receptor (AR) genes on HR response to metoprolol in 200 adults (mean age 56 ± 11 years) referred for coronary computed tomographic angiography (using a 64-slice scanner). Oral and intravenous (IV) metoprolol was given to achieve a goal HR of <60 beats/min. Overall, 37 patients (18.5%) did not reach the goal HR despite the administration of oral (181 ± 116 mg) and IV (4.2 ± 9.4 mg) metoprolol. Patients with the β(1)-AR Ser49Gly or Gly49Gly genotype (n = 49) more often failed to reach an optimal HR compared to those with the Ser49Ser genotype (n = 151) (29% vs 15%, p = 0.04), despite receiving higher doses of oral (210 ± 115 vs 172 ± 115 mg, p = 0.048) and IV (7 ± 13 vs 3 ± 8 mg, p = 0.02) metoprolol. Similarly, patients with the β(1)-AR Gly389Gly genotype (n = 11) more often failed to reach an optimal HR compared to those with the Arg389Arg and Arg389Gly genotypes (n = 189) (45% vs 17%, p = 0.02), despite receiving higher doses of IV (13 ± 15 vs 4 ± 9 mg, p = 0.002) but not oral (162 ± 105 vs 182 ± 117 mg, p = 0.50) metoprolol. Multivariate analysis identified β(1)-AR SNPs at codons 49 and 389 and β(2)-AR SNP at codon 27 as independent predictors of suboptimal HR response. In conclusion, these data indicate that the selected SNPs of β(1)-AR and β(2)-AR genes influence HR response to metoprolol in patients who undergo coronary computed tomographic angiography.

[Reconstruction of coronary 64-multidetector-row computed tomography angiography in patients with atrial fibrillation: delete short RR intervals using electorocardiogram]

BACKGROUND

The image qualities of coronary 64-multidetector-row computed tomography angiography (CCTA) in patients with atrial fibrillation (Afib) are often not enough. This study clarifies how to use electrocardiogram (ECG) -editing in Afib.

METHODS

We performed CCTA (Aquilion 64 with beam pitch: 0.125, 0.35 s/r) in 33 patients (M/F=24/9, age: 71±9 yr, mean heart rate: 71±12 bpm) with Afib. We injected 5 mg of verapamil into the vein when the mean HR was ≥80 bpm. First, we reconstructed images after deleting short RR (<800, 750, 700, 650, or 600). Second, we reconstructed images in 4 different methods: (1) end-systolic images with Phase Navi (automatically selecting an optimal phase) (ES-Navi), (2) Mid-diastolic images with Phase Navi (MD-Navi), (3) Mid-diastolic images reconstructed by the "R+absolute time method" [Edit-MD (R+)], and (4) Mid-diastolic images reconstructed by the "R-absolute time method" [Edit-MD (R-)]. We reconstructed 1 and 2 without ECG-editing, and 3 and 4 were reconstructed after ECG-editing without a data deficit. The quality of the images was classified into 3 ranks: no artifact (3), mild artifact (2), and severe artifact (1).

RESULTS

The image quality point of CCTA, reconstructed after deleting RR<750, was similar to RR<800, and RR<750 was even higher than that after deleting HR<600, 650, or 700. The mean image quality point of CCTA that was reconstructed by Edit-MD (R-) or Edit-MD (R+) was significantly higher than ES-Navi or MD-Navi.

CONCLUSION

The high image quality of CCTA could be reconstructed after deleting RR<750 in 76% or after deleting RR<800 in 70% of Afib. The reconstruction using Edit-MD (R-) or Edit-MD (R+) without a data deficit could provide a better quality CCTA than using PhaseNavi in Afib.

The effect of heart rhythm on patient radiation dose with dual-source cardiac computed tomography

BACKGROUND

To lower the radiation exposure associated with cardiac CT, it is essential to identify all factors that influence radiation dose.

OBJECTIVES

We explored the effect of heart rhythm during scan acquisition on radiation dose with a 64-slice dual-source cardiac CT.

METHODS

Patient and scan data were collected prospectively in 302 consecutive patients referred for a clinical dual-source cardiac CT. Electrocardiograms recorded during acquisition were interpreted by a cardiologist and categorized as (1) normal sinus rhythm (NSR), (2) premature atrial contraction (PAC) or premature ventricular contraction (PVC), or (3) atrial fibrillation or flutter.

RESULTS

Of the 302 patients, 227 (75.2%) were in NSR and had no ectopy, 55 (18.2%) had PAC/PVC, and 20 (6.6%) had atrial fibrillation or flutter during the scan. Patients with irregular rhythm (PAC/PVC and atrial fibrillation or flutter) were older than patients with regular rhythm (61.0 vs 54.8 years; P = 0.006). Patients with NSR had the lowest estimated radiation dose, followed by PAC/PVC and atrial fibrillation/flutter (9.4, 14.5, 20.9 mSv; P < 0.001). The difference remained significant after adjustments for differences in examination type, tube current and voltage, scan length, pitch, and use of tube current modulation (9.8, 14.1, 17.9 mSv; P < 0.001). No significant association was observed between heart rhythm and subjective image quality although scans with regular rhythm and no ectopy had higher signal-to-noise and contrast-to-noise ratios (P < 0.01).

CONCLUSION

Compared to patients with NSR, patients with atrial fibrillation/flutter had the highest radiation exposure, followed by those with PAC/PVC. Even after adjustment for factors associated with radiation exposure, a significant difference in radiation dose persisted. These findings can be used to identify patients who are more likely to receive higher radiation dose when undergoing cardiac CT and to develop future more-efficient scanner algorithms for use in patients with arrhythmias.

[Evaluation of 320-row area detector computed tomography (ADCT) coronary angiography for patients with atrial fibrillation]

The aim of this study was to evaluate 320-row area detector CT (ADCT) for patients with atrial fibrillation (Af) based on simulated exposure using electrocardiogram RR intervals and comparison with the findings of coronary CT angiography (CCTA) using 64-row multi slice CT (MSCT). The probability of including RR intervals of 900 ms or more was calculated when the acquisition time was varied from 1 to 4 beats. Overall, 51 patients with Af who underwent CCTA were examined. The exposure time for CCTA, the total dose length product (DLP) for the examination, and the image quality (scored 0 to 3: poor to excellent) were compared between ADCT and MSCT. The probability of including RR intervals of 900 ms or more was highly significantly increased at 3 beats of acquisition time. The exposure time using ADCT was reduced by 75% compared with MSCT (ADCT/MSCT: 2.8/11.3 s), and the total DLP was reduced by 40% (ADCT/MSCT: 1398/2277 mGy·cm). Moreover, ADCT provided diagnosable images in all cases, and the mean image quality score for ADCT was significantly higher than that for MSCT (ADCT/MSCT: 2.8/2.4). Thus, 320-row ADCT at 3 beats of acquisition time can provide CCTA images of acceptable quality for patients with Af.

Image quality of coronary 320-MDCT in patients with atrial fibrillation: initial experience

OBJECTIVE

Noninvasive coronary angiography has generally been contraindicated in patients with atrial fibrillation because of the difficulty in synchronizing an irregular heartbeat with table gantry movement. The objective of this study was to evaluate and compare the quality of 320-MDCT images obtained in patients with atrial fibrillation and in a control group of patients in sinus rhythm.

MATERIALS AND METHODS

Two reviewers were blinded to the patient groups and evaluated images of 15 coronary artery segments for each patient using 320-MDCT. The images were printed on glossy paper and scored subjectively as 1 or 2, meaning of diagnostic quality, or 3, meaning poor quality.

RESULTS

No statistical difference between the groups was noted in patient age: The mean age of the patients with atrial fibrillation was 67 years (age range, 52-82 years) and that of the patients in sinus rhythm was 59 years (36-86 years) (p = 0.3). Scores of 1 and 2 (diagnostic quality) were assigned to 100% in sinus rhythm and 96% in atrial fibrillation (p < 0.05). Scores of 3 were seen only in the atrial fibrillation group (7/175, 4%). Segment 15, the distal circumflex artery, was the segment that was most frequently assigned a score of 3 (2/7, 28.6%). A discrepancy in the two reviewers' scores was seen in 25 segments (7%), requiring joint consensus. The segments that most frequently required consensus reading were segments 12 and 15. The overall mean image quality score for all three coronary arteries in atrial fibrillation was 1.25 +/- 0.47 (SD) and 1.08 +/- 0.26 in sinus rhythm (p < 0.001). The median effective dose was 19.28 and 13.55 mSv in the atrial fibrillation and sinus rhythm groups, respectively.

CONCLUSION

The analysis of our initial experience shows that imaging in patients with atrial fibrillation is possible using 320-MDCT, with images of most segments obtained being of diagnostic quality. Segment 15 was the most difficult to see on 320-MDCT because of the small caliber of the vessel; poor visualization of that segment mostly occurred in the setting of a dominant right coronary arterial system.

64-MDCT coronary angiography of patients with atrial fibrillation: influence of heart rate on image quality and efficacy in evaluation of coronary artery disease

OBJECTIVE

The purpose of this study was to prospectively evaluate the effects of mean heart rate and heart rate variability on image quality at coronary 64-MDCT angiography of patients with atrial fibrillation and to determine the efficacy of coronary 64-MDCT angiography in the detection of significant (> 50%) coronary artery stenosis in patients with atrial fibrillation.

SUBJECTS AND METHODS

Sixty patients (37 women, 23 men; mean age, 58.7 years) underwent both coronary 64-MDCT angiography and conventional coronary angiography. Heart rate variability was calculated as the SD from the mean heart rate during scanning. Image quality (good, moderate, or poor) and the presence of significant (> 50%) stenosis at coronary CT angiography were evaluated by two radiologists blinded to the results of conventional coronary angiography. The sensitivity, specificity, positive predictive value, and negative predictive value of coronary CT angiography were calculated with conventional angiography as the reference standard. Pearson's correlation analysis and chi-square tests were performed to compare image quality with mean heart rate and heart rate variability in each patient. Differences in detection of coronary artery stenosis between coronary 64-MDCT angiography and conventional coronary angiography were evaluated with McNemar's test, and agreement between techniques was calculated with kappa statistics.

RESULTS

The mean heart rate was 90 +/- 13.1 beats/min with variability of 19.35 +/- 6.95 beats/min. Of 803 segments evaluated, 26 (3%) were considered to have poor image quality. Highly significant correlation was found between mean heart rate and image quality for all segments in each patient (r = 0.51, p < 0.001), for the right coronary artery (r = 0.43, p = 0.001), and for the distal portion of the coronary arteries (r = 0.50, p < 0.001). Heart rate variability also correlated in a highly significant way with image quality in all segments (r = 0.57, p < 0.001), the right coronary artery (r = 0.46, p < 0.001), and the middle (r = 0.44, p = 0.001) and distal (r = 0.41, p = 0.001) portions of the coronary arteries. The best diagnostic image quality was obtained in end systole (200-400 milliseconds). Image quality decreased significantly with a mean heart rate greater than 100 beats/min or with an SD of heart rate greater than 24 beats/min. The overall sensitivity, specificity, positive predictive value, and negative predictive value per segment level were 86.4%, 99.3%, 79.2%, and 99.6%. No significant difference was found between coronary 64-MDCT angiography and conventional coronary angiography in detection of significant stenosis. Excellent agreement between techniques was found.

CONCLUSION

Coronary 64-MDCT angiography has diagnostic image quality within a wide range of heart rates and in patients with atrial fibrillation. Reducing average heart rate and heart rate variability in patients with atrial fibrillation is beneficial in improving image quality.