Usefulness of second-generation motion correction algorithm in improving delineation and reducing motion artifact of coronary computed tomography angiography

BACKGROUND

The purpose of this study was to investigate the usefulness of second-generation intra-cycle motion correction algorithm (SnapShot Freeze 2, GE Healthcare, MC2) in improving the delineation and interpretability of coronary arteries in coronary computed tomography angiography (CCTA) compared to first-generation intra-cycle motion correction algorithm (SnapShot Freeze, GE Healthcare, MC1).

METHODS

Fifty consecutive patients with known or suspected coronary artery disease who underwent CCTA on a 256-slice CT scanner were retrospectively studied. CCTA were reconstructed with three different algorithms: no motion correction (NMC), MC1, and MC2. The delineation of coronary arteries on CCTA was qualitatively rated on a 5-point scale from 1 (nondiagnostic) to 5 (excellent) by two radiologists blinded to the reconstruction method and the patient information.

RESULTS

On a per-vessel basis, the delineation scores of coronary arteries were significantly higher on MC2 images compared to MC1 images (median [interquartile range], right coronary artery, 5.0 [4.5-5.0] vs 4.5 [4.0-5.0]; left anterior descending artery, 5.0 [4.5-5.0] vs 4.5 [3.5-5.0]; left circumflex artery, 5.0 [4.5-5.0] vs 4.5 [3.9-5.0]; all p ​< ​0.05). On a per-segment basis, for both 2 observers, the delineation scores on segment 1, 2, 8, 9, 10, 12 and 13 on MC2 images were significantly better than those on MC1 images (p ​< ​0.05). The percentage of interpretable segments (rated score 3 or greater) on NMC, MC1, and MC2 images was 90.5-91.9%, 97.4-97.9%, and 100.0%, respectively.

CONCLUSION

Second-generation intra-cycle motion correction algorithm improves the delineation and interpretability of coronary arteries in CCTA compared to first-generation algorithm.

Association Between Aortic Wall Parameters on Multidetector Computed Tomography and Ruptured Plaques By Nonobstructive General Angioscopy

BACKGROUND

Nonobstructive general angioscopy (NOGA) can identify vulnerable plaques in the aortic lumen that serve as potential risk factors for cardiovascular events such as embolism. However, the association between computed tomography (CT) images and vulnerable plaques detected on NOGA remains unknown.

METHODS AND RESULTS

We investigated 101 patients (67±11 years; women, 13.8%) who underwent NOGA and contrast-enhanced CT before or after 90 days in our hospital. On CT images, the aortic wall thickness, aortic wall area (AWA), and AWA in the vascular area were measured at the thickest point from the 6th to the 12th thoracic vertebral levels. Furthermore, the association between these measurements and the presence or absence of NOGA-derived aortic plaque ruptures (PRs) at the same vertebral level was assessed. NOGA detected aortic PRs in the aortic lumens at 145 (22.1%) of the 656 vertebral levels. The presence of PRs was significantly associated with greater aortic wall thickness (3.3±1.7 mm versus 2.1±1.2 mm), AWA (1.33±0.68 cm2 versus 0.89±0.49 cm2), and AWA in the vascular area (23.2%±9.3% versus 17.2%±7.6%) (P<0.001 for all) on the CT scans compared with the absence of PRs. The frequency of PRs significantly increased as the aortic wall thickness increased. Notably, a few NOGA-derived PRs were detected on CT in near-normal intima.

CONCLUSIONS

The presence of NOGA-derived PRs was strongly associated with increased aortic wall thickness, AWA, and AWA in the vascular area, measured using CT. NOGA can detect PRs in the intima that appear almost normal on CT scans.

Evaluation of Image Quality for High Heart Rates for Coronary Computed Tomographic Angiography with Advancement in CT Technology: The CONVERGE Registry

OBJECTIVE

This study aims to evaluate image quality in patients with heart rates above or equal to 70 beats per minute (bpm), performed on a 16 cm scanner (256-slice General Electric Revolution) in comparison to a CT scanner with only 4 cm of coverage (64 slice Volume CT).

BACKGROUND

Recent advancements in image acquisition, such as whole-heart coverage in a single rotation and post-processing methods in coronary computed tomographic angiography (CCTA), include motion-correction algorithms, such as SnapShot Freeze (SSF), which improve temporal resolution and allow for the assessment of coronary artery disease (CAD) with lower motion scores and better image qualities. Studies from the comprehensive evaluation of high temporal- and spatial-resolution cardiac CT using a wide coverage system (CONVERGE) registry (a multicenter registry at four centers) have shown the 16 cm CT scanner having a better image quality in comparison to the 4 cm scanner. However, these studies failed to include patients with undesirable or high heart rates due to well-documented poor image acquisition on prior generations of CCTA scanners.

METHODS

A prospective, observational, multicenter cohort study comparing image quality, quantitively and qualitatively, on scans performed on a 16 cm CCTA in comparison to a cohort of images captured on a 4 cm CCTA at four centers. Participants were recruited based on broad inclusion criteria, and each patient in the 16 cm CCTA arm of the study received a CCTA scan using a 256-slice, whole-heart, single-beat scanner. These patients were then matched by age, gender, and heart rate to patients who underwent CCTA scans on a 4 cm CT scanner. Image quality was graded based on the signal-to-noise ratio, contrast-to-noise ratio, and on a Likert scale of 0-4: 0, very poor-4, excellent.

RESULTS

104 patients were evaluated for this study. The mean heart rate was 75 ± 7 in the 4 cm scanner and 75 ± 7 in the 16 cm one (p = 0.426). The signal-to-noise and contrast-to-noise ratios were higher in the 16 cm scanner (p = 0.0001). In addition, more scans were evaluated as having an excellent quality on the 16 cm scanner than on the 4 cm scanner (p < 0.0001) based on a 4-point Likert scale.

CONCLUSIONS

The 16 cm scanner has a superior image quality for fast heart rates compared to the 4 cm scanner. This study shows that there is a significantly higher frequency of excellent and good studies showing better contrast-to-noise and signal-to-noise ratios with the 16 cm scanner compared to the 4 cm scanner.

Subtraction coronary CT angiography in patients with high heart rate

All the previous subtraction coronary CT angiography (CCTA) had strict heart rate (HR) inclusion criteria. In this study, a new subtraction method was applied to patients with various HR. The post-contrast scan time was respectively 3.5 s after ascending aorta peak enhancement while HR >80 bpm, 4 s while 65≤ HR ≤80 bpm and 4.5 s while HR <65 bpm. Forty-six patients who underwent the new subtraction protocol were enrolled and patients were stratified into the high HR group (≥70 bpm) and low HR group (<70 bpm). Eighteen patients with 15 severe calcification segments and 25 stent segments further received invasive coronary angiography (ICA). In all included patients, the coronary artery enhancement was compared between the high and low HR groups. In patients with ICA performed, the image quality improvement and diagnostic effectiveness for detection of significant coronary segments stenosis (>50%) were compared between the conventional CCTA and subtraction CCTA and between the high HR group and low HR group, respectively. All enrolled patients got sufficient coronary artery enhancement. In patients with ICA performed, receiver operating characteristic (ROC) curve analysis showed that the area under the curve (AUC) for the diagnosis of significant stenosis was 0.93 in subtraction CCTA and 0.73 in conventional CCTA (p < 0.05). Furthermore, there were no significant differences in image quality improvement, specificity, positive predictive value and accuracy between the high HR group and low HR group. The new subtraction CCTA method broadened the clinical availability for patients with high HR.

Influence of Heart Rate on Image Quality and Radiation Dose Exposure in Coronary CT Angiography

See also the editorial by Schoepf and Decker in this issue.

Comparison of Whole Heart Computed Tomography Scanners for Image Quality Lower Radiation Dosing in Coronary Computed Tomography Angiography: The CONVERGE Registry

RATIONALE AND OBJECTIVES

Novel technology in coronary computed tomographic angiography allows assessment of coronary artery disease with high image quality (IQ). There are currently two wide detector "whole heart" coverage scanners available, which avoid misregistration artifacts. However, there are no data directly comparing IQ between the two scanners. The aim of the current study is to investigate if IQ is different between the most scanners of GE and Toshiba broad detector scanners.

MATERIALS AND METHODS

Prospective, observational, multicenter international cohort study comparing 236 consecutive patients who underwent coronary computed tomographic angiography using whole-heart scanners; 126 patients on scanner S1 ( Aquilion ONE Vision, Toshiba), and 110 patients on scanner S2 (Revolution CT, GE Healthcare). Hounsfield units were measured using regions of interest in the descending aorta at 6 points (cranial slice, level of the visualized first, second, third, and fourth spines, and the caudal slice). We also compared the coverage length (z-axis) of the full width field of view between a single rotation of the two scanners.

RESULTS

Evaluating mean CT attenuation values Hounsfield units through the scan range, are progressively reduced across the descending aorta in the S1 group, resulting in the larger difference of contrast brightness between the cranial and caudal slices compared to the S2 group (absolute difference: S2 13.0 ± 4.4 vs S1 141.9 ± 16.4, p < 0.0001; Percent difference: 19.3 ± 2.1 vs -3.4 ± 1.2, <0.0001). The standard deviation (SD) is similar at the cranial slice between the two scanners, however, the S1 group demonstrated higher SD-differential from cranial to caudal than S2 group. Median radiation exposure was significantly lower for the S2 scanner 1.50 ± 0.75 mSv vs the S1 system 1.9 mSv (IQR 1.7-2.7 mSv) (p = 0.01). Z-axis coverage was larger for the S2 scanner 152.5 mm (244 slices × 0.625 mm/slice) than 133 mm for S1 (266 slices × 0.5 mm/slice).

CONCLUSION

Although both "volume" scanners cover the whole heart z-axis with one beat, scans using the S1 scanner have a larger variability in attenuation values throughout the scan range, resulting in 20% increase in nonuniformity from cranial to caudal slice. Additionally, SD variation across the field of view, a metric of noise, is larger when using the S1 scanner vs the S2 scanner. These results indicate that the GE Revolution CT has more uniform contrast enhancement and more coverage, lower radiation and lower image noise compared to the Toshiba Aquilion ONE Vision system.

Comparative evaluation of image quality among different detector configurations using area detector computed tomography

The 320-detector row computed tomography (CT) system, i.e., the area detector CT (ADCT), can perform helical scanning with detector configurations of 4-, 16-, 32-, 64-, 80-, 100-, and 160-detector rows for routine CT examinations. This phantom study aimed to compare the quality of images obtained using helical scan mode with different detector configurations. The image quality was measured using modulation transfer function (MTF) and noise power spectrum (NPS). The system performance function (SP), based on the pre-whitening theorem, was calculated as MTF²/NPS, and compared between configurations. Five detector configurations, i.e., 0.5 × 16 mm (16 row), 0.5 × 64 mm (64 row), 0.5 × 80 mm (80 row), 0.5 × 100 mm (100 row), and 0.5 × 160 mm (160 row), were compared using a constant volume CT dose index (CTDI_vol) of 25 mGy, simulating the scan of an adult abdomen, and with a constant effective mAs value. The MTF was measured using the wire method, and the NPS was measured from images of a 20-cm diameter phantom with uniform content. The SP of 80-row configuration was the best, for the constant CTDI_vol, followed by the 64-, 160-, 16-, and 100-row configurations. The decrease in the rate of the 100- and 160-row configurations from the 80-row configuration was approximately 30%. For the constant effective mAs, the SPs of the 100-row and 160-row configurations were significantly lower, compared with the other three detector configurations. The 80- and 64-row configurations were adequate in cases that required dose efficiency rather than scan speed.

Incremental Prognostic Value of Coronary Computed Tomography Angiography: High-Risk Plaque Characteristics in Asymptomatic Patients

AIM

Coronary computed tomography angiography (CCTA) findings of positive remodeling (index ＞1.1) and low-attenuation plaque (＜30 Hounsfield units) are recognized as CT-verified high-risk plaque (CT-HRP). Therefore, we investigated the incremental prognostic value of evaluation of plaque characteristics using CCTA in asymptomatic patients.

METHODS

Overall, 495 consecutive patients without any known coronary artery disease who underwent CCTA were included in this study. Patients who underwent revascularization within 30 days of CCTA or had scans with poor image quality were excluded. Clinical follow-up data (716.5±262.6 days) were available for 339 patients, who were analyzed for the current study. Framingham risk score (FRS), coronary artery calcium score (CACS), and CT-HRP were investigated as predictors of cardiac events by multivariable analysis using Cox proportional hazard model. Improvement of predictive accuracy by including CT findings was evaluated from reclassification [net reclassification indices (NRI) and integrated discrimination improvement (IDI)] standpoints.

RESULTS

During the follow-up period, 9 cardiac events (cardiac death: 0, nonfatal myocardial infarction: 2, hospitalization for unstable or progressive angina: 7) occurred. Multivariate Cox proportional hazard analysis demonstrated that CACS (HR, 13.23; 95% CI, 1.62-107.78, p＜0.0164) and CT-HRP (HR, 11.27; 95% CI, 1.24-102.12, p＜0.0321) were the independent predictors of cardiac events. NRI was 0.9556 (p＜0.0007) and IDI was 0.2582 (p＜0.0203), and the diagnostic performance improved by CT-HRP added to the combination of CACS and FRS.

CONCLUSION

Although the cardiac event rate was low, the evaluation of CCTA plaque characteristics may provide incremental prognostic value to CACS in asymptomatic patients.

Diagnostic Phase of Calcium Scoring Scan Applied as the Center of Acquisition Window of Coronary Computed Tomography Angiography Improves Image Quality in Minimal Acquisition Window Scan (Target CTA Mode) Using the Second Generation 320-Row CT

Objective. To compare the image quality of coronary computed tomography angiography (CCTA) acquired under two conditions: 75% fixed as the acquisition window center (Group 75%) and the diagnostic phase for calcium scoring scan as the center (CS; Group CS). Methods. 320-row cardiac CT with a minimal acquisition window (scanned using “Target CTA” mode) was performed on 81 patients. In Group 75% (n = 40), CS was obtained and reconstructed at 75% and the center of the CCTA acquisition window was set at 75%. In Group CS (n = 41), CS was obtained at 75% and the diagnostic phase showing minimal artifacts was applied as the center of the CCTA acquisition window. Image quality was evaluated using a four-point scale (4-excellent) and the mean scores were compared between groups. Results. The CCTA scan diagnostic phase occurred significantly earlier in CS (75.7 ± 3.2% vs. 73.6 ± 4.5% for Groups 75% and CS, resp., p = 0.013). The mean Group CS image quality score (3.58 ± 0.63) was also higher than that for Group 75% (3.19 ± 0.66, p < 0.0001). Conclusions. The image quality of CCTA in Target CTA mode was significantly better when the center of acquisition window is adjusted using CS.

Coronary artery calcium score and CT angiography in asymptomatic elderly patients with high pretest probability for coronary artery disease

PURPOSE

To evaluate the role of coronary artery calcium scoring (CACS) and/or coronary CT angiography (CCTA) in asymptomatic elderly patients with high pretest probability for coronary artery disease (CAD).

MATERIALS AND METHODS

Forty-eight consecutive asymptomatic elderly (>65 years) subjects who had a high pretest probability and underwent CACS/CCTA were included. Each CCTA was evaluated for adequacy for assessment of coronary stenosis. Significant stenosis (>50% diameter narrowing) was assessed on evaluable CT images and by invasive catheter angiography (ICA).

RESULTS

All subjects were men with mean CACS of 880 ± 1779. Among those with low (0-99), intermediate (100-399), and high (400-999) CACS, ICA-verified significant stenosis was present in 8% (1/13), 23% (2/13), and 67% (8/12), respectively. Among those with very high CACS (≥ 1000) (n = 10), 90% of CCTAs were not evaluable for stenosis.

CONCLUSION

In asymptomatic elderly subjects with high pretest probability, CACS followed by CCTA may be considered for those with intermediate to high CACS.

Assessment of coronary in-stent restenosis: value of subtraction coronary computed tomography angiography

In conventional coronary computed tomography angiography (CCTA), metal artifacts are frequently observed where stents are located, making it difficult to evaluate in-stent restenosis. This study was conducted to investigate whether subtraction CCTA can improve diagnostic accuracy in the evaluation of in-stent restenosis. Subtraction CCTA was performed using 320-row CT in 398 patients with previously placed stents who were able to hold their breath for 25 s and in whom mid-diastolic prospective one-beat scanning was possible. Among these patients, 126 patients (94 men and 32 women, age 74 ± 8 years) with 370 stents who also underwent invasive coronary angiography (ICA) were selected as the subjects of this study. With ICA findings considered the gold standard, conventional CCTA was compared against subtraction CCTA to determine whether subtraction can improve diagnostic accuracy in the evaluation of in-stent restenosis. When non-assessable stents were considered to be stenotic, the diagnostic accuracy in the evaluation of in-stent restenosis was 62.7 % for conventional CCTA and 89.5 % for subtraction CCTA. When the non-assessable stents were considered to be non-stenotic the diagnostic accuracy was 90.3 % for conventional CCTA and 94.31 % for subtraction CCTA. When subtraction CCTA was used to evaluate only the 138 stents that were judged to be non-assessable by conventional CCTA, 116 of these stents were judged to be assessable, and the findings for 109 of them agreed with those obtained by ICA. Even for stents with an internal diameter of 2.5-3 mm, the lumen can be evaluated in more than 80 % of patients. Subtraction CCTA provides significantly higher diagnostic accuracy than conventional CCTA in the evaluation of in-stent restenosis.

Incremental predictive value for obstructive coronary artery disease by combination of Duke Clinical Score and Agatston score

AIMS

Recent study suggests that algorithms such as the Duke Clinical score (DCS) may overestimate the pretest probability. The Agatston score representing the grade of coronary artery calcification can be simply calculated from low-radiation exposure ECG-gated plain CT. In this study, we investigated whether or not more superior diagnostic performance for obstructive coronary artery disease (CAD) can be obtained by combining DCS with the Agatston score.

METHODS AND RESULTS

Of 3939 consecutive patients suspected of having stable angina without known CAD who underwent Coronary Computed Tomography Angiography (CCTA) as well as calculation of the DCS and Agatston score at our hospital, 3688 patients were selected as subjects. Obstructive CAD was defined as >50% diameter stenosis on CCTA; we investigated the diagnostic performance based on the area under the curve (AUC) of a receiver operating characteristic (ROC) curve, Net Reclassification Improvement (NRI), and Integrated Discrimination Improvement (IDI). The AUCs of ROCs prepared using the DCS alone and combination of the DCS and Agatston score were 0.7137 and 0.8057, respectively, showing that the diagnostic performance of the combination was significantly superior to DCS alone (P < 0.001). NRI was 0.8132 and IDI was 0.1374, showing that the diagnostic performance was improved by the combination of the DCS and Agatston score compared with DCS alone (P < 0.001). NRI (0.3522) and IDI (0.0287) were improved compared with those of the Agatston score alone (P < 0.001).

CONCLUSION

The combination of the DCS and Agatston score improved the diagnostic performance for obstructive CAD compared with DCS alone and Agatston score.

Incremental prognostic value of coronary computed tomographic angiography high-risk plaque characteristics in newly symptomatic patients

BACKGROUND

The incremental prognostic value of the plaque features in coronary computed tomographic angiography (CTA) has not been well assessed. This study was designed to determine whether CTA high-risk plaques have prognostic value incremental to the Framingham risk score (FRS) and the severity of luminal obstruction.

METHODS

A total of 628 newly symptomatic patients without known coronary artery disease underwent CTA. They were followed for a median of 677 days during which there were 26 cardiac events, including cardiac death, acute myocardial infarction, and hospitalization for unstable angina. Incremental prognostic value of adding plaque characteristics to the number of diseased vessels and the FRS was evaluated using 3 Cox models and net reclassification indexes.

RESULTS

The discrimination index was significantly increased by adding the number of diseased vessels to the FRS (change in c-statistic from 65.8% to 78.6%, p=0.028) but not significantly by further adding plaque characteristics (change in c-statistic from 78.6% to 80.0%, p=0.812). However, improved model-fitting by adding plaque characteristics into the linear combination with risk score and the number of diseased vessels (p=0.007 from likelihood ratio test) and the lowest value of Akaike's information criteria of that model indicated that plaque characteristics improved both predictive accuracy and discrimination perspective. More subjects reclassified by plaque characteristics were moved to directions consistent with their subsequent cardiac event status than in an inconsistent direction.

CONCLUSIONS

Evaluation of CTA plaque characteristics may provide incremental prognostic value to the number of diseased vessels and the FRS.

Prognostic Value of Coronary Computed Tomography (CT) Angiography and Coronary Artery Calcium Score Performed Before Revascularization

BACKGROUND

Cardiac events after revascularization are equally attributable to recurrence at site of culprit lesions and development of nonculprit lesions. We evaluated the hypothesis that coronary computed tomography (CT) angiography and coronary artery calcium score (CACS) performed before revascularization predicts cardiac events after treatment.

METHODS AND RESULTS

Among 2238 consecutive patients without known coronary artery disease who underwent coronary CT angiography and CACS, 359 patients underwent revascularization within 30 days after CT; in 337 of 359 (93.9%) follow-up clinical information was available. In addition to known cardiac risk factors, CT findings were evaluated as predictors of cardiac events after revascularization: CACS and the presence of CT-verified high-risk plaque (CT-HRP). Improvement of predictive accuracy by including CT findings was evaluated from a discrimination (Harrell's C-statistics) standpoint. During the follow-up period (median: 673, interquartile range: 47 to 1529 days), a total of 98 cardiac events occurred. Cox proportional hazard model revealed that age, diabetes, triglyceride, CACS, and nonculprit CT-HRP were significant predictors of overall cardiac events. Although not statistically significant, discriminatory power was greater for the model with CACS (C-stat: 63.2%) and the model with both CACS and CT-HRP (65.8%) compared to the model including neither CACS nor CT-HRP (60.7%).

CONCLUSIONS

High CACS and the presence of nonculprit CT-HRP performed before revascularization are significant predictors of cardiac events after revascularization.

Comprehensive assessment of radiation dose estimates for the CORE320 study

OBJECTIVE. The purpose of this study was to comprehensively study estimated radiation doses for subjects included in the main analysis of the Combined Non-invasive Coronary Angiography and Myocardial Perfusion Imaging Using 320 Detector Computed Tomography (CORE320) study ( ClinicalTrials.gov identifier NCT00934037), a clinical trial comparing combined CT angiography (CTA) and perfusion CT with the reference standard catheter angiography plus myocardial perfusion SPECT. SUBJECTS AND METHODS. Prospectively acquired data on 381 CORE320 subjects were analyzed in four groups of testing related to radiation exposure. Radiation dose estimates were compared between modalities for combined CTA and perfusion CT with respect to covariates known to influence radiation exposure and for the main clinical outcomes defined by the trial. The final analysis assessed variations in radiation dose with respect to several factors inherent to the trial. RESULTS. The mean radiation dose estimate for the combined CTA and perfusion CT protocol (8.63 mSv) was significantly (p < 0.0001 for both) less than the average dose delivered from SPECT (10.48 mSv) and the average dose from diagnostic catheter angiography (11.63 mSv). There was no significant difference in estimated CTA-perfusion CT radiation dose for subjects who had false-positive or false-negative results in the CORE320 main analyses in a comparison with subjects for whom the CTA-perfusion CT findings were in accordance with the reference standard SPECT plus catheter angiographic findings. CONCLUSION. Radiation dose estimates from CORE320 support clinical implementation of a combined CT protocol for assessing coronary anatomy and myocardial perfusion.

Repeat coronary computed tomographic angiography in patients with a prior scan excluding significant stenosis

BACKGROUND

ACCF/SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 Appropriate Use Criteria for Cardiac Computed Tomography (AUC2010) does not incorporate prior coronary computed tomographic angiography (CCTA) results in the appropriateness of a CCTA examination. The purpose of this study was to explore the criteria for forgoing repeat CCTA among patients with clinical scenarios suggesting CCTA as appropriate after prior CCTA excluding coronary artery disease.

METHODS AND RESULTS

Among patients from a single center (February 2006 to April 2013) who underwent appropriate CCTA based on AUC2010, consecutive 555 CCTAs, which had a prior CCTA excluding significant stenosis (>50% stenosis in diameter), were selected. The median time difference between the studies was 34.2 (Q1-Q3, 22.9-50.1) months. Significant stenosis was detected at the time of repeat scan (by CCTA or subsequent catheter angiography) in 13.3% (74 of 555). A multivariable logistic model (C-statistic, 0.74; bootstrapped overfitting bias, 0.8%) identified 3 predictors of significant stenosis: time difference between the studies >3 years (adjusted odds ratio, 2.1; 95% confidence interval, 1.2-3.5), diabetes mellitus (odds ratio, 2.4; 95% confidence interval,1.4-4.3), and 26% to 50% stenosis on the initial CCTA (odds ratio, 5.6; 95% confidence interval, 3.2-9.6). When these 3 factors were all absent (corresponding to 31.9% of the population), the probability of significant stenosis was 4.5% (95% confidence interval, 2.7-7.4%), whereas 17.1% of patients had significant stenosis among those with at least 1 positive variable. When coronary arteries were completely normal at the initial scan, the prevalence of significant stenosis was only 1.8% irrespective of other factors, and no patient underwent revascularization.

CONCLUSIONS

Nondiabetic patients with a prior CCTA <3 years showing no or ≤25% stenosis had a <5% prevalence of significant stenosis. The value of repeat CCTA in this group is likely small, especially when the prior CCTA demonstrated normal coronaries, even if the clinical scenario considered a CCTA appropriate.

Simulated 50 % radiation dose reduction in coronary CT angiography using adaptive iterative dose reduction in three-dimensions (AIDR3D)

To compare the image quality of coronary CT angiography (CTA) studies between standard filtered back projection (FBP) and adaptive iterative dose reduction in three-dimensions (AIDR3D) reconstruction using CT noise additional software to simulate reduced radiation exposure. Images from 93 consecutive clinical coronary CTA studies were processed utilizing standard FBP, FBP with 50 % simulated dose reduction (FBP50 %), and AIDR3D with simulated 50 % dose reduction (AIDR50 %). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured within 5 regions-of-interest, and image quality for each reconstruction strategy was assessed by two independent readers using a 4-point scale. Compared to FBP, the SNR measured from the AIDR50 % images was similar or higher (airway: 38.3 ± 12.7 vs. 38.5 ± 14.5, p = 0.81, fat: 5.5 ± 1.9 vs. 5.4 ± 2.0, p = 0.20, muscle: 3.2 ± 1.2 vs. 3.1 ± 1.3, p = 0.38, aorta: 22.6 ± 9.4 vs. 20.2 ± 9.7, p < 0.0001, liver: 2.7 ± 1.0 vs. 2.3 ± 1.1, p < 0.0001), while the SNR of the FBP50 % images were all lower (p values < 0.0001). The CNR measured from AIDR50 % images was also higher than that from the FBP images for the aorta relative to muscle (20.5 ± 9.0 vs. 18.3 ± 9.2, p < 0.0001). The interobserver agreement in the image quality score was excellent (κ = 0.82). The quality score was significantly higher for the AIDR50 % images compared to the FBP images (3.6 ± 0.6 vs. 3.3 ± 0.7, p = 0.004). Simulated radiation dose reduction applied to clinical coronary CTA images suggests that a 50 % reduction in radiation dose can be achieved with adaptive iterative dose reduction software with image quality that is at least comparable to images acquired at standard radiation exposure and reconstructed with filtered back projection.