Low-dose Coronary Computed Tomography Angiography Research Articles

Performance evaluation of using shorter contrast injection and 70 kVp with deep learning image reconstruction for reduced contrast medium dose and radiation dose in coronary CT angiography for children: a pilot study.

Iterative reconstruction algorithms are often used to reduce image noise in low-dose coronary computed tomography angiography (CCTA) but encounter limitations. The newly introduced deep learning image reconstruction (DLIR) algorithm may provide new opportunities. We assessed the image quality and diagnostic performance of DLIR in low radiation dose and contrast medium dose CCTA of pediatric patients with 70 kVp and a shortened injection protocol. This was a prospective study. A total of 27 consecutive arrhythmic pediatric patients were enrolled in the study group and underwent CCTA using a prospective ECG-triggered single-beat protocol: tube voltage 70 kVp, automatic tube current modulation for a noise index (NI) of 22, and contrast dose of 0.4-0.6 mL/kg. Images were reconstructed with DLIR. They were compared with 27 matched patients in the control group scanned with 80 kVp, a lower NI setting (NI =19), and a higher contrast dose (0.8-1.2 mL/kg). The images in the control group were reconstructed using the adaptive statistical iterative reconstruction (ASIR-V) algorithm. The image contrast, image quality, and diagnostic confidence were assessed by 2 experienced radiologists using a 5-point scale (1: nondiagnostic and 5: excellent). The CT value and standard deviation of the aorta and perivascular tissue were measured, and the contrast-to-noise ratio (CNR) for the aorta was calculated. The contrast medium and radiation doses were compared. The study and control groups had similar image contrast scores (4.75±0.57 vs. 4.78±0.42), image quality scores (3.67±0.47 vs. 3.44±0.51), and diagnostic confidence (4.74±0.44 vs. 4.74±0.45) (all P>0.05). There was an adequate enhancement in the aorta (614.74±127.73 vs. 705.89±111.20 HU) and similar CNR (20.34±4.64 vs. 20.99±4.14) in both groups. The image noise of the study group was lower in the aorta (30.61±3.88 vs. 34.77±3.49) and similar in perivascular tissue (27.66±6.24 vs. 27.55±3.33) compared with the control group. The study group reduced the total contrast medium dose by 53% to 15.07±3.68 mL and radiation dose by 36% to 0.57±0.31 mSv. The DLIR algorithm in CCTA for children using 70 kVp tube voltage with a shortened contrast medium injection protocol maintains image quality and diagnostic confidence while significantly reducing contrast medium dose and radiation dose compared with the use of the conventional CCTA protocol.

Coronary artery disease (CAD) extension-derived risk stratification for asymptomatic diabetic patients: usefulness of low-dose coronary computed tomography angiography (CCTA) in detecting high-risk profile patients.

As one of the most frequent risk factors for cardiovascular disease, type 2 diabetes mellitus (T2DM) is one of the largest causes of death. However, an acute cardiac presentation is not uncommon in diabetic patients, and the current investigative approach remains often inadequate. The aim of our study was to retrospectively stratify the risk of asymptomatic T2DM patients using low-dose 640-slice coronary computed tomography angiography (CCTA). CCTA examinations of 62 patients (mean age, 65years) with previous diagnosis of type 2 diabetes and without cardiac symptoms were analyzed. Image acquisition was performed using a 640-slice CT. Per-patient, per-vessel and per-plaque analyses were performed. Stratification risk was evaluated according to the ESC guidelines. The patients were followed up after 2.21 ± 0.56years from CCTA examination. Coronary artery disease (CAD) was found in 58 patients (93.55%) presenting 290 plaques. Analysis of all samples showed severe-to-occlusive atherosclerosis in 24 patients (38.7% of cases). However, over the degree of stenosis, 23 patients were evaluated at high risk considering the extension of CAD. Good agreement was shown by the correlation of CAD extension/risk estimation and MACE incidence, according to a Kaplan-Meier survival analysis (p value = 0.001), with a 7.25-fold increased risk (HR 7.25 CI 2.13-24.7; p value = 0.002). Our study confirms the high capability of CCTA to properly stratify the CV risk of asymptomatic T2DM patients. Its use could be recommended if we consider how current investigative strategies to correctly assess these patients often seem inadequate.

Coronary computed tomography angiography and echocardiography in children with homozygous familial hypercholesterolemia

Background and aimsHomozygous familial hypercholesterolemia (hoFH) is a rare genetic disease, hallmarked by a lifelong exposure to very high levels of low-density lipoprotein cholesterol (LDL-C). Untreated, patients can experience a cardiovascular event in the first decade of life. Early detection and monitoring of subclinical atherosclerosis in these patients is therefore extremely important. We set out to assess the diagnostic yield of low-dose coronary computed tomography angiography (cCTA) compared to echocardiography in detecting subclinical atherosclerosis. MethodsFor this single-center cross-sectional study, we included all pediatric hoFH patients treated with lipoprotein-apheresis (LA) in Amsterdam UMC. We performed both cCTA and echocardiography in all patients as part of routine follow-up. ResultsSix hoFH patients were included. Median ages at diagnosis, onset of LA and cardiovascular assessment (cCTA and echocardiography) were 2.6, 6.5, 10.8 and 11.1 years, respectively. Echocardiography revealed no signs of atherosclerosis in any of the six patients. In two patients, mild dilatation of the cardiac chambers was detected and two patients showed signs of mitral or aortic insufficiency. On cCTA, however, non-calcified plaques without stenosis were detected in four patients. In two patients calcified coronary plaques were found at the ostia of the right coronary artery or the left main coronary artery. Aortic root calcifications were found in two patients. ConclusionsOur findings suggest that in hoFH children, low-dose cCTA is superior to echocardiography for the detection of subclinical coronary and aortic root atherosclerosis and should therefore be considered in the routine cardiovascular monitoring of these high-risk children.

Non-inferior low-dose coronary computed tomography angiography image quality with knowledge-based iterative model reconstruction for overweight patients.

We investigated the feasibility of low-dose coronary computed tomography angiography (CCTA), using a prospective electrocardiogram (ECG)-triggered axial scan protocol, knowledge-based iterative model reconstruction (IMR), and fixed tube current, in overweight subjects. Forty non-overweight (group A; body-mass index [BMI] < 25 kg/m2) and 40 overweight individuals (group B; BMI = 25–30 kg/m2), who underwent CCTA for coronary artery disease screening, were retrospectively and consecutively enrolled. A 64-slice CT scanner was used at 100-kVp tube voltage and 150-mA tube current, and images were reconstructed using IMR techniques. Image noise, attenuation at the aorta, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) at the proximal right and left main coronary arteries (pRCA and LMCA) were calculated. CCTA images were qualitatively evaluated using a four-point scale (1, poor; 4, excellent) and analyzed using a non-inferiority test with a pre-defined non-inferiority margin of -0.2. The mean CCTA radiation dose (Group A: 1.33 ± 0.02 mSv; Group B: 1.35 ± 0.10 mSv; p = 0.151) and mean aortic root CT attenuation values (Group A: 447.9 ± 81.6 HU; Group B: 439.5 ± 63.6 HU; p = 0.571) did not differ significantly between the two groups. The mean noise in groups A and B was 26.0 ± 4.8 HU and 29.2 ± 4.4 HU, respectively (p = 0.005). The noise reduction ratio in the groups, compared to filtered back projection, was 65.0% and 68.1%, respectively. The mean grade of image quality did not differ significantly (3.75 ± 0.04 vs. 3.71 ± 0.04, p = 0.478). Group B CCTA image quality was non-inferior (mean difference = -0.043, 95% CI = -0.162–0.077) to that of Group A. We concluded that low-dose CCTA with prospective ECG-triggering and IMR might be applied to overweight subjects, as well as to normal-weight subjects, by using a fixed tube current without an increase in tube current based on the patient’s body size.

Feasibility of ultra low-dose coronary computed tomography angiography

There is an urgent need to develop new protocols to reduce radiation dose of coronary computed tomography angiography (CTA). The aim of this pilot study was to demonstrate the feasibility of an ultra-low dose CTA scanning.

Long-term prognostic performance of low-dose coronary computed tomography angiography with prospective electrocardiogram triggering.

To assess long-term prognosis after low-dose 64-slice coronary computed tomography angiography (CCTA) using prospective electrocardiogram-triggering. We included434 consecutive patients with suspected or known coronary artery disease referred for low-dose CCTA. Patients were classified as normal, with non-obstructive or obstructive lesions, or previously revascularized. Coronary artery calcium score (CACS) was assessed in 223 patients. Follow-up was obtained regarding major adverse cardiac events (MACE): cardiac death, myocardial infarction and elective revascularization. We performed Kaplan-Meier analysis and Cox regressions. Mean effective radiation dose was 1.7 ± 0.6mSv. At baseline, 38% of patients had normal arteries, 21% non-obstructive lesions, 32% obstructive stenosis and 8% were revascularized. Twenty-nine patients (7%)were lost to follow-up. After a median follow-up of 6.1 ± 0.6years, MACE occurred in 0% of patients with normal arteries, 6% with non-obstructive lesions, 30% with obstructive stenosis and 39% of those revascularized. MACE occurrence increased with increasingCACS (P < 0.001), but 4% of patients with CACS = 0 experienced MACE. Multivariate Cox regression identified obstructive stenosis, lesion burden in CCTA and CACS as independent MACE predictors (P ≤ 0.001). Low-dose CCTA with prospective electrocardiogram-triggering has an excellent long-term prognostic performance with a warranty period >6years for patients with normal coronary arteries. • Coronary CT angiography (CCTA) has an excellent long-term prognostic performance. • CCTA can accurately stratify cardiac risk according to coronary lesion severity. • A normal CCTA predicts freedom from cardiac events for >6years. • Patients with a coronary calcium score of 0 may experience cardiac events. • CCTA allows for reclassification of cardiac risk compared with ESC SCORE.

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.

Assessment of Coronary Artery Calcium on Low-Dose Coronary Computed Tomography Angiography With Iterative Reconstruction.

This study aims to evaluate whether coronary calcium scoring (CCS) is also feasible using low-radiation-dose coronary computed tomography angiography (CCTA) in combination with iterative reconstruction. Forty-three individuals without known coronary artery disease underwent both noncontrast CCS (±1 mSv) for reference Agatston scores and low-dose CCTA (±3 mSv). Raw CCTA data were reconstructed with filtered back projection (FBP), hybrid iterative reconstruction (HIR), and model-based iterative reconstruction (MIR). Calcification volumes were derived with thresholds of >351 and >600 Hounsfield units (HU) and converted to proxy Agatston scores with linear regression analysis. Intraclass correlation coefficients for Agatston scores versus CCTA volumes with FBP and iterative reconstruction were excellent (ranges 0.94-0.99 and 0.96-0.99 for >351 HU and >600 HU thresholds, respectively). The >351 HU threshold resulted in higher CCTA volume scores ranging from 65.9 (15.1-347.0) for HIR to 94.8 (42.0-423.0) for MIR (P = 0.001 and <0.001, respectively). The >600 HU threshold scores ranged from 14.1 (0.0-159.3) for HIR to 28.6 (0.0-215.6) for MIR (P = 0.003 and 0.027, respectively). At >351 HU, reclassification occurred in 21 individuals (49%) for FBP and HIR and 25 individuals (58%) for MIR. Reclassifications decreased with >600 HU to 10 (HIR, 23%), 8 (FBP, 19%), and 4 (MIR, 9%). The CCS is feasible using iteratively reconstructed low-dose CCTA with a calcium threshold of >600 HU. Using MIR, only 9% of individuals were reclassified.

Impact of a New Motion-Correction Algorithm on Image Quality of Low-Dose Coronary CT Angiography in Patients with Insufficient Heart Rate Control

Prospective electrocardiogram (ECG) triggering allows coronary computed tomography angiography (CCTA) scanning with low radiation dose but requires heart rates below 63 beats/min. We assessed the impact of a novel vendor-specific motion-correction algorithm on image quality and interpretability of low-dose CCTA acquired despite insufficient heart rate control. In 40 patients undergoing CCTA for the assessment of known or suspected coronary artery disease who did not reach the target heart rate below 63 beats/min despite β-blockade before prospective low-dose scanning, the temporal acquisition window was increased (80 ms additional padding). The new algorithm detects and integrates vessel path and velocity from adjacent cardiac phases for motion correction. Two blinded observers assessed image quality on a 4-point Likert scale (1, nonevaluative; 2, reduced but evaluative; 3, good; and 4, excellent) and the fraction of interpretable segments (score 2 or more) using motion correction versus standard reconstruction. Image reconstruction with motion correction resulted in an increased median coronary artery image quality score (excellent interobserver agreement, κ = 0.85) compared to standard reconstruction (3.4 vs. 3.0, P < .001). Consequently, motion-corrected reconstruction significantly improved the overall interpretability of coronary arteries (from 78% to 88%, P < .001). Estimated mean effective radiation dose was 2.3 ± 0.8 mSv. A novel, vendor-specific, motion-corrected, reconstruction algorithm improves image quality and interpretability of prospectively ECG-triggered low-dose CCTA despite insufficient heart rate control.

Image quality of low-dose CCTA in obese patients: impact of high-definition computed tomography and adaptive statistical iterative reconstruction

The accuracy of coronary computed tomography angiography (CCTA) in obese persons is compromised by increased image noise. We investigated CCTA image quality acquired on a high-definition 64-slice CT scanner using modern adaptive statistical iterative reconstruction (ASIR). Seventy overweight and obese patients (24 males; mean age 57 years, mean body mass index 33 kg/m(2)) were studied with clinically-indicated contrast enhanced CCTA. Thirty-five patients underwent a standard definition protocol with filtered backprojection reconstruction (SD-FBP) while 35 patients matched for gender, age, body mass index and coronary artery calcifications underwent a novel high definition protocol with ASIR (HD-ASIR). Segment by segment image quality was assessed using a four-point scale (1 = excellent, 2 = good, 3 = moderate, 4 = non-diagnostic) and revealed better scores for HD-ASIR compared to SD-FBP (1.5 ± 0.43 vs. 1.8 ± 0.48; p < 0.05). The smallest detectable vessel diameter was also improved, 1.0 ± 0.5 mm for HD-ASIR as compared to 1.4 ± 0.4 mm for SD-FBP (p < 0.001). Average vessel attenuation was higher for HD-ASIR (388.3 ± 109.6 versus 350.6 ± 90.3 Hounsfield Units, HU; p < 0.05), while image noise, signal-to-noise ratio and contrast-to noise ratio did not differ significantly between reconstruction protocols (p = NS). The estimated effective radiation doses were similar, 2.3 ± 0.1 and 2.5 ± 0.1 mSv (HD-ASIR vs. SD-ASIR respectively). Compared to a standard definition backprojection protocol (SD-FBP), a newer high definition scan protocol in combination with ASIR (HD-ASIR) incrementally improved image quality and visualization of distal coronary artery segments in overweight and obese individuals, without increasing image noise and radiation dose.

Image quality in low-dose coronary computed tomography angiography with a new high-definition CT scanner

A new generation of high definition computed tomography (HDCT) 64-slice devices complemented by a new iterative image reconstruction algorithm-adaptive statistical iterative reconstruction, offer substantially higher resolution compared to standard definition CT (SDCT) scanners. As high resolution confers higher noise we have compared image quality and radiation dose of coronary computed tomography angiography (CCTA) from HDCT versus SDCT. Consecutive patients (n = 93) underwent HDCT, and were compared to 93 patients who had previously undergone CCTA with SDCT matched for heart rate (HR), HR variability and body mass index (BMI). Tube voltage and current were adapted to the patient's BMI, using identical protocols in both groups. The image quality of all CCTA scans was evaluated by two independent readers in all coronary segments using a 4-point scale (1, excellent image quality; 2, blurring of the vessel wall; 3, image with artefacts but evaluative; 4, non-evaluative). Effective radiation dose was calculated from DLP multiplied by a conversion factor (0.014 mSv/mGy × cm). The mean image quality score from HDCT versus SDCT was comparable (2.02 ± 0.68 vs. 2.00 ± 0.76). Mean effective radiation dose did not significantly differ between HDCT (1.7 ± 0.6 mSv, range 1.0-3.7 mSv) and SDCT (1.9 ± 0.8 mSv, range 0.8-5.5 mSv; P = n.s.). HDCT scanners allow low-dose 64-slice CCTA scanning with higher resolution than SDCT but maintained image quality and equally low radiation dose. Whether this will translate into higher accuracy of HDCT for CAD detection remains to be evaluated.

Low dose coronary CT angiography with 256-slice helical CT

Objective To compare the image quality and patient radiation dose of coronary computed tomography angiography (CCTA) received by prospectively-gated step-and-shoot (SAS) technique with those obtained by retrospectively-gated spiral (RGS) technique on a 256-slice CT scanner. Methods A total of 200 patients were enrolled in this study. One hundred patients underwent CCTA with SAS mode were subdivided into two groups: ( 1 ) 50 patients with an average heart rate (HR) ≤70 bpm were scanned with a data acquisition time window centered at the 75％ of the R-R cycle ( group A) and (2) 50 patients with HR ＞ 70 bpm were scanned with the data acquisition time window centered at the 45％ of the R-R cycle, including a phase tolerance of ±％ (group B). Other 100 patients underwent CCTA with RGS mode and ECG-based tube current modulation were also subdivided into two groups: (3) 50 patients with HR ≤70 bpm were scanned with cardiac dose right set to phase of 75％ (group C) and (4) 50 patients with HR ＞ 70 bpm were scanned with cardiac ose Rdight set to phases of 45％ and 75％ (group D). All patients were grouped in randomized order. The image quality of CCTA were evaluated using a rank scale from 1 to 4 ( 1 : excellent ; 4 : non-assessable ) . Radiation dose of the four groups received was also estimated. The image quality between groups was compared by Mann-Whitney U test. The radiation dose between groups was compared by t test. For the 100 patients received by prospective ECG-gated CCTA, the receiver operating characteristic curve (ROC) was used to analyze the CCTA image quality and average heart rate to determine the uppercutoff of HR for obtaining diagnostic coronary images with SAS mode. A spearman correlation analysis was also performed to analyze the correlation of HR and image quality in patients underwent CCTA with SAS mode. Results Of 2338 coronary artery segments, excellent or good image quality( score of 1 or 2) was achieved in 96. 5％ (585 of 606) in group A, 77.7％ (445 of 573 ) in B,96. 1％ (548 of 570) in C, and 85. 7％ (505/589) in D, with no significant difference for A vs C(Z ＝- 1. 351 ,P ＞0. 05) and with significant differenceS for B vs D (Z＝ -2. 236,P ＜0. 05). Linear correlation analysis indicated a significant degradation of image quality with the increase of heart rate using SAS mode (Spearman correlation, r ＝ 0. 577, P ＜0. 01 ). ROC analysis established an upper HR threshold of 78 bpm for obtaining diagnostic image quality using SAS mode( AUC ＝ 0. 827, P ＜ 0. 05 ). The average radiation dose in group A [ ( 2. 6 ± 0. 5 ) mSv]reduced 75 ％ comparing with that in group C [ ( 10. 6 ± 2. 3 ) mSy], and the average radiation dose in group B [ ( 4.0 ± 0. 7 ) mSy]reduced 69％ comparing with that in group D [ ( 13.0 ± 1. 4) mSv]. Conclusion Using SAS mode to perform low-dose CCTA with 256-slice helical CT could keep the image quality and reduce radiation dose significantly. Our preliminary experience suggests a good promise of this technique which could be applied to a wider group of patients such as with higher heart rates. Key words: Tomography, X-ray computed; Coronary vessels; Diagnostic imaging; Radiation dosage

Image Quality in Reduced-Dose Coronary CT Angiography

Concerns for patient's risk of radiation-induced cancer have increased demand for reduced-dose coronary computed tomography angiography (CCTA). Previous comparisons of full and reduced-dose CCTA were not conclusive, because results were compared in different groups of patients. Presented here are results in patients examined by a widely used full dose CCTA protocol and a new low-dose alternative. Standard full-dose and low-dose CCTA with tube voltages of 120/100 kV were applied on 70 patients with intermediate probability of coronary artery disease (CAD). Both protocols used prospective electrocardiogram-gated acquisition on a 320-detector row CT scanner, whereas at low-dose CCTA the phase window was increased from 10% to 75% of R-R interval. Despite a mean dose reduction of 80%, from 4.9 ± 0.98 to 0.98 ± 0.24 mSv, visual image quality was not significantly affected at the low-dose protocol. Contrast level, image noise, and CNR for both protocols were similar in the majority of coronary segments. CNR for standard and low-dose protocol were 23.7 ± 17.1 and 23.2 ± 26.8, P = NS. Correlation between visual image quality and heart rate variability was strong at low dose: r = -0.58, P = .01, and absent at full dose: r = -0.07, P = .77. Image quality of blood vasculature is generally not affected by 80% CCTA dose reduction applied to standard prospective electrocardiogram-gated acquisition. The performance at the low-dose protocol owes to the increased phase window, enhancing image quality at the cost of sensitivity to heart rate variability as compared with standard CCTA.

Meta-analysis: Diagnostic Performance of Low-Radiation-Dose Coronary Computed Tomography Angiography

A new radiation dose-saving technique for noninvasive coronary artery imaging with computed tomography (CT) is available. To summarize current evidence about the ability of low-dose coronary CT angiography to rule out coronary artery disease (CAD) in symptomatic adults. Online databases, including MEDLINE, EMBASE, and the Cochrane Library, from inception through 31 October 2010; abstract databases; gray literature; reference lists of identified articles; and experts. No language restrictions were applied. All investigators screened and selected studies that compared prospective electrocardiography-gated coronary CT angiography with catheter coronary angiography (the reference standard) in symptomatic patients with suspected CAD. Two investigators independently extracted patient and study protocol characteristics and rated methodological quality; differences were resolved by consensus or by a third reader. Multivariate random-effects models were used to obtain pooled estimates. 16 studies, comprising 960 patients, were found (7 studies of single-source, 64-slice CT; 4 of dual-source, 64-slice CT; 2 of single-source, 320-slice CT; 1 dual-source, 128-slice CT; 1 of single-source, 128-slice CT; and 1 of single-source, 256-slice CT). On average, 2.4% of the coronary arterial segments were of nondiagnostic image quality, and 1 or more segments were nondiagnostic in 9.5% of the patients. The patient-level sensitivity and specificity of CT angiography were 1.00 (95% CI, 0.98 to 1.00) and 0.89 (CI, 0.85 to 0.92), respectively. The pooled vessel- and segment-level estimates showed lower sensitivity and higher specificity than the patient-level estimates. Statistically significant heterogeneity was found between studies for vessel- and segment-level estimates, which seemed to be associated with body mass index and prevalence of CAD but not with CT scanner characteristics. The small number of studies, half of which were from a single tertiary center, limits generalizability. The potential harms of the imaging tests were not well-evaluated. Early evidence suggests that low-dose coronary CT angiography matches the sensitivity of catheter-based angiography, has low radiation exposure, and is a potentially valid alternative to catheter angiography for triaging symptomatic patients with a clinical suspicion of CAD. None.

Low-dose coronary computed tomography angiography using prospective ECG-triggering compared to invasive coronary angiography

To assess the diagnostic accuracy of prospective ECG-triggering 64-slice multidetector computed tomography (MDCT) coronary angiography for evaluation of coronary artery disease (CAD). Forty-two patients (31 males, 11 females, mean age 64 years) underwent cardiac CT and invasive coronary angiography (ICA). Patients with a heart rate of <65 beats/min with stable heart rhythm were included in the study sample. We used a prospective ECG-triggering protocol. Luminal narrowing over 50% was considered to be significant according to a modified 17-segment AHA model, using invasive coronary angiography (ICA) as the standard of reference. The mean radiation dose was 3.5 mSv ± 0.3 (range, 3.3-4.2 mSv), and 542 of 549 segments (98.7%) in the 42 patients were diagnostic. In contrast, 119 of 542 segments (22%) were diagnosed as significant by ICA. The sensitivity, specificity, accuracy, PPV and NPV were 95.0, 96.2, 96, 85.8 and 98.8%, respectively. False positive results were affected by densely calcified plaques, whereas false negatives were caused by motion artifact with poor vessel attenuation at the distal segments or near the bifurcation area of the coronary arteries. Prospective ECG-triggering MDCT is a useful method for evaluating CAD in patients with a lower heart rate with low radiation dose.

Prospectively gated low-dose CCTA: 24 months experience in more than 2,000 clinical cases

Cardiac CT exams have recently come under increased scrutiny because of their relatively high radiation dose. The most effective way to lower the dose of coronary computed tomography angiography (CCTA) exams is with the use of prospective gating. This allows for a significant reduction in effective radiation dose when compared to retrospective ECG gating while image quality is maintained or improved. We reviewed data from 2,124 consecutive cardiac CT exams, including 1,978 CCTA’s and 146 CCTA’s post CABG. With effective heart rate control, prospective gating was used for 92.1% of the CCTAs and 83.2% of CCTAs following CABG. The prospectively gated CCTAs had a mean effective dose of 3.1 ± 1.5 mSv, CCTAs following CABG had a mean dose of 6.4 ± 2.3 mSv. We review our experience using prospective gating in specific areas to include patient selection, patient preparation, use of β- and calcium-channel-blockers for heart rate control, selection of gating technique and scan parameters, radiation dose, and post-processing techniques.