Visibility of the origin and proximal course of coronary arteries on non-ECG-gated heart CT in patients with congenital heart disease

Computed tomography angiography features of children with ectopia cordis

Ectopia cordis is a rare congenital defect with high mortality, and it remains challenging to radiologists, neonatologists and surgeons. CT angiography provides key information that aids in the decision-making process for possible surgical intervention. This pictorial essay describes CT angiography features in six neonates with ectopia cordis.

[Coronary Artery Visualization by Using the 64-row MDCT in Pediatric Patients]

PURPOSE

We retrospectively evaluated the visualization of pediatric coronary computed tomography angiography (CCTA) images by using the 64-detector row CT scanner between the electrocardiogram-gated helical scan and non-electrocardiogram-gated helical scan.

METHODS

From January 2015 to March 2019, 100 children who underwent CT angiography examination were retrospectively enrolled. Group A consisted of 50 patients with electrocardiogram-gated helical scan. Group B consisted of 50 patients with non-electrocardiogram-gated helical scan. All patients were scanned using a 64-detector row CT scanner (LightSpeed VCT), and helical scans were acquired. The CT scanning parameters were 0.4-s rotation, 0.625-mm slice thickness, 0.24 (group A) helical pitch (beam pitch), 1.375 (group B) helical pitch (beam pitch), 80 kVp, and 50-300 mA (noise index 40). A retrospective method was used for electrocardiogram gated. To compare the radiation dose, CT volume dose index (CTDI_vol) and dose length product (DLP) displayed on the console were recorded. The visualization scores of the coronary artery images were compared between each group.

RESULTS

In group A, CTDI_vol and DLP values were 6.74 (1.05-11.97) mGy and 79.87 (15.90-146.65) mGy·cm, respectively. In group B, CTDI_vol and DLP values were 0.51 (0.39-0.95) mGy and 8.15 (6.30-17.50) mGy·cm, respectively. There were significant differences in CTDI_vol and DLP values between both groups (p<0.05). The visualization rates for the proximal and distal coronary arteries were 88% and 54% for the right coronary artery, 84% and 58% for the left anterior descending artery, and 66% and 30% for the left circumflex branch in group A, respectively. The visualization rates for the proximal and distal coronary arteries were 52% and 0% for the right coronary artery, 56% and 0% for the left anterior descending artery, and 32% and 0% for the left circumflex branch in group B.

CONCLUSION

In 64-row multidetector computed tomography (MDCT), the visualization rates for the proximal and distal coronary arteries were significantly higher in the electrocardiogram-gated scan, but the exposure dose was several times higher in the pediatric CCTA. For accurate diagnosis in pediatric coronary arteries, electrocardiogram-gated helical scan should be performed.

Coronary artery anomalies in tetralogy of Fallot patients evaluated by multi slice computed tomography; myocardial bridge is not a rare finding

Based on coronary angiography and interoperative inspection, anomalous origin of coronary artery crossing the right ventricular outflow tract (RVOT) is common in tetralogy of Fallot (TOF) patients. However, other coronary anomalies may be underestimated due to the overlying myocardium, epicardial fat, or adhesions due to previous palliative surgery. Currently, coronary artery visibility dramatically improved by multislice computed tomography (MSCT). We performed this study to assess the coronary arteries anatomy in TOF patients using MSCT.All TOF patients underwent MSCT examination at our centre from 2013 till 2019 were included. Assessment of the coronary arteries' origin and course were performed. Presence of myocardial bridge were assessed, and indexed RV mass was calculated.318 TOF patients were included, median age 2 years (range 1 month-46 years), 175 males (55%). The abnormal coronary artery origin and course were detected in 20 patients (6%); coronary artery crossed RVOT in 13 patients (65%), 5 patients (25%) had a retro-aortic course and 2 patient (10%) had inter-arterial course. Myocardial bridges of left anterior descending artery or/and right coronary artery were reported in 100 patients (36%), no myocardial bridge of left circumflex was reported. RV mass was 29.0 ± 21.1 g/m2. There was no correlation between RV mass and presence of myocardial bridges.MSCT is a useful imaging modality for detection of coronary arteries anomalies in TOF patients. Coronary artery crossing RVOT is not the only abnormal course and myocardial bridging is not a rare finding. Further studies are needed to demonstrate the clinical significance of these observations.

Diastolic and systolic right ventricular diameters for predicting pulmonary hypertension in children with congenital heart disease

Prospective electrocardiography (ECG)-gated cardiac computed tomography angiography (CTA) is widely used for pediatric patients with congenital heart disease (CHD) due to the lower radiation dose compared with the ECG-gated technique. However, functional parameters acquired using ECG-gated cardiac CT to predict pulmonary hypertension (PH) in children with CHD have not yet been reported. This study aimed to investigate the potential of diastolic and systolic right ventricular diameters (RVD) on prospective ECG-gated cardiac CTA to predict PH in children with CHD. A total of 44 children with CHD were divided into two groups: CHD with PH (n = 22) and CHD without PH (n = 22). The association between ECG-gated CTA parameters and PH was evaluated by logistic regression. The receiver operating characteristic curve (ROC) was used to find the best cut-off point for the parameters measured by Youden's index. Patients with higher RVD-BSA [aOR (95% CI) diastolic: 2.76 (1.23-6.23); systolic: 6.15 (1.72-22.06)] had higher risk of PH after adjusting for age and patent ductus arteriosus. The area under the curve (AUC) of D-RVD-BSA was 0.907 and the AUC of S-RVD-BSA was 0.917. Logistic regression showed that patients with D-RVD-BSA over 6.86 or S-RVD-BSA over 5.87 had significantly higher risk of PH after adjustments (aOR = 23.52, 95% CI = 2.89-191.03; aOR = 31.14, 95% CI = 2.75-352.85). In conclusion, in children with CHD, measurements of diastolic or systolic BSA-modified RVDs on prospective ECG-gated CTA are non-invasive markers of PH. BSA-modified D-RVD of 6.86 or BSA-modified S-RVD of 5.87 may be used to identify PH in children with CHD.

Visualization of proximal coronary arteries on high-pitch electrocardiogram-triggered computed tomography in pediatric congenital heart disease: effects of heart rate and body surface area

BACKGROUND

As CT technology has advanced, techniques for pediatric cardiac CT in congenital heart disease have evolved from retrospective electrocardiography (ECG)-gating with relatively high radiation doses to lower-dose prospective ECG-gating and even single-beat gated scans. Despite these advances, coronary artery imaging in children remains challenging because of their small vessel size and high heart rates, often necessitating retrospective gating.

OBJECTIVE

Evaluate coronary artery visualization in pediatric patients (<20 years) who underwent low-dose high-pitch ECG-triggered scans and stratify the probability of coronary artery visualization based upon heart rate and body surface area (BSA).

MATERIALS AND METHODS

Two hundred eleven high-pitch ECG-triggered studies from April 2014 to November 2017 were reviewed by two pediatric cardiac imagers in this retrospective study. Patient age, gender, BSA, average heart rate, heart rate variability and use of general anesthesia were recorded as well as dose-length product (DLP) and volumetric CT dose index (CTDI_vol). We assessed the coronary artery score using a 5-point scale, with score of ≥3 considered of diagnostic quality. We performed multivariate statistical analysis including logistic regression to analyze effects of heart rate and BSA.

RESULTS

Patient age range was 1 day to 19 years (median age 3 years). Heart rate range was 49-188 beats per minute (bpm; median 122 bpm) and BSA range was 0.15-2.07 m² (median 0.53 m²). The origin and proximal coronary arteries were confidently seen (score ≥3) in 61% of studies in this cohort. Coronary artery visualization scores further increased with increased BSA (P<0.002) and with decreased heart rate (P<0.001). At heart rates <100 bpm or in patients with BSA>0.58, adequate coronary artery visualization was present 72% of the time.

CONCLUSION

While in many patients the coronary artery origins are visualized using high-pitch ECG-triggered technique, the importance of coronary artery visualization needs to be weighed with the radiation dose penalty in individual patients to achieve optimal imaging.

User-Friendly Vendor-Specific Guideline for Pediatric Cardiothoracic Computed Tomography Provided by the Asian Society of Cardiovascular Imaging Congenital Heart Disease Study Group: Part 1. Imaging Techniques

Optimal performance of pediatric cardiothoracic computed tomography (CT) is technically challenging and may need different approaches for different types of CT scanners. To meet the technical demands and improve clinical standards, a practical, user-friendly, and vendor-specific guideline for pediatric cardiothoracic CT needs to be developed for children with congenital heart disease (CHD). In this article, we have attempted to describe such guideline based on the consensus of experts in the Asian Society of Cardiovascular Imaging CHD Study Group. This first part describes the imaging techniques of pediatric cardiothoracic CT, and it includes recommendations for patient preparation, scan techniques, radiation dose, intravenous injection protocol, post-processing, and vendor-specific protocols.

Submillisievert Multiphasic Coronary Computed Tomography Angiography for Pediatric Patients With Congenital Heart Diseases

BACKGROUND

The use of coronary computed tomography (CT) angiography in children with coronary artery anomalies is increasing. However, it remains technically demanding and the need to adapt acquisition parameters to a patient's cardiac characteristics has not yet been addressed. The aim of the study was to prospectively assess the feasibility of personalized multiphasic coronary CT angiography for pediatric patients.

METHODS

Fifty pediatric patients (mean age 6.1±4.9 years) with coronary artery anomalies underwent a coronary CT angiography on a wide detector single-source CT equipment. Fifteen different acquisition patterns were used to trigger the acquisition at the best theoretical moment within the cardiac cycle. The appropriate pattern was automatically selected based on the patient's heart rate and heart rate variability, derived from the patient's ECG. Two independent radiologists qualitatively evaluated images.

RESULTS

All acquisitions fully answered the clinical question for a mean effective dose of 0.97±0.34 mSv. Image quality qualified as good or excellent in 94% of cases (47/50). No examination was considered as not assessable but 6% (3/50) were scored as adequate for diagnosis. For these 3 patients, motion artifacts were the main cause of average image quality. No significant visual differences were reported between the different coronary arteries (mean score of 3.6 on a 4-point scale). No correlation between image quality and cardiac parameters were reported ( r=-0.19 and r=0.00, respectively for heart rate and heart rate variability).

CONCLUSIONS

Personalized multiphasic coronary CT angiography acquisitions could be performed with diagnostic quality for a dose equivalent of <4 months of natural background irradiation.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT03194763.

Depiction of the native coronary arteries during ECG-triggered High-Pitch Dual-Source Coronary Computed Tomography Angiography in children: Determinants of image quality

OBJECTIVE

Assess the image quality of ECG-triggered High-Pitch Dual-Source CTA for the evaluation of native coronaries in children.

MATERIALS AND METHODS

Between August 2014 and September 2017, 45 children with morphologically normal cardiac chambers had cardiac prospective ECG-triggered High-Pitch Dual-Source CTA. Two pediatric radiologists blinded to clinical data, independently reviewed each case. The coronary arteries were evaluated using a four-point scale quality score according to the coronary segment. Attenuation, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured using values from the air, inter-ventricular septum and ascending aorta at the level of the sinuses of Valsalva.

RESULTS

225 coronary segments were assessed showed a mean score of 2.40 ± 0.73, 94.2% had diagnostic image quality. The best and worst average quality were seen in segment 5 and 2, respectively. Inter-observer agreement was moderate for all segments except for segment 1, which was excellent. Worse quality scores were significantly associated with younger patients and low body mass index as well as with higher heart rates in all segments. The mean observed heart rate and BSA in patients with diagnostic image quality were below 77 bpm and over 1.4 m² respectively. There is no significant association between attenuation, SNR and CNR with image quality.

CONCLUSIONS

Prospective ECG-triggered High-Pitch Dual-Source Computed Tomography Angiography achieves consistent and diagnostic image quality for coronary artery assessment at a low effective dose in pediatric patients.

Identification of coronary artery anatomy on dual-source cardiac computed tomography before arterial switch operation in newborns and young infants: comparison with transthoracic echocardiography

BACKGROUND

Considering inherent limitations of transthoracic echocardiography, the diagnostic accuracy of cardiac CT in identifying coronary artery anatomy before arterial switch operation needs to be investigated with recently improved coronary artery visibility using electrocardiogram (ECG)-synchronized dual-source CT.

OBJECTIVE

To compare diagnostic accuracy between cardiac CT using a dual-source scanner and transthoracic echocardiography in identifying coronary artery anatomy before arterial switch operation in newborns and young infants.

MATERIALS AND METHODS

The study included 101 infants (median age 4 days, range 0 days to 10 months; M:F=78:23) who underwent ECG-synchronized cardiac dual-source CT and transthoracic echocardiography before arterial switch operation between July 2011 and December 2016. We evaluated and classified coronary artery anatomy on cardiac CT and transthoracic echocardiography. With the surgical findings as the reference standard, we compared the diagnostic accuracy for identifying coronary artery anatomy between cardiac CT and transthoracic echocardiography.

RESULTS

The most common coronary artery pattern was the usual pattern (left coronary artery from sinus 1 and right coronary artery from sinus 2; 64.4%, 65/101), followed by a single coronary artery from sinus 2 and a conal branch from sinus 1 (7.9%, 8/101), the inverted pattern (5.9%, 6/101), the right coronary artery and left anterior descending artery from sinus 1 and the left circumflex artery from sinus 2 (5.9%, 6/101), and others. In 96 infants with surgically proven coronary artery anatomy, the diagnostic accuracy of cardiac CT was significantly higher than that of transthoracic echocardiography (91.7%, 88/96 vs. 54.2%, 52/96; P<0.0001).

CONCLUSION

Diagnostic accuracy of cardiac CT is significantly higher than that of echocardiography in identifying coronary artery anatomy before arterial switch operation in newborns and young infants.

Image Quality of Coronary Arteries on Non-electrocardiography-gated High-Pitch Dual-Source Computed Tomography in Children with Congenital Heart Disease

This study aimed to evaluate image quality of coronary artery imaging on non-electrocardiography (ECG)-gated high-pitch dual-source computed tomography (DSCT) in children with congenital heart disease (CHD) and to assess factors affecting image quality. We retrospectively reviewed the records of 142 children with CHD who underwent non-ECG-gated high-pitch DSCT. The subjective image quality of the proximal coronary segments was graded using a five-point scale. A score <3 represented a non-diagnostic image. Age, body weight, and heart rate were compared between the two groups: patients with good diagnostic image quality in all four segments and patients with at least one segment with non-diagnostic image quality. Predictors of image quality were assessed by multivariate logistic regression, including age, body weight, and heart rate. Four-hundred-fifty-seven of the 568 segments (80.5%) had diagnostic image quality. Patients with non-diagnostic segments were significantly younger (21.6 ± 25.5 months), had lower body weight (7.82 ± 5.00 kg), and a faster heart rate (123 ± 23.7 beats/min) (each p < 0.05) than patients with diagnostic image quality in all four segments (30.6 ± 20.7 months, 10.3 ± 4.00 kg, and 113 ± 21.6 beats/min, respectively; each p < 0.05). The multivariate logistic regression revealed that body weight (odds ratio 1.228; p = 0.029) was a significant predictor of image quality. Non-ECG-gated high-pitch DSCT provided adequate image quality of the proximal coronary segments in children with CHD. Lower body weight was a factor that led to poorer image quality of the coronary arteries.

Image quality and radiation dose of dual-source CT cardiac angiography using prospective ECG-triggering technique in pediatric patients with congenital heart disease

Background

All studies involving use of ionizing radiation should be performed in accordance with the ALARA (As Low As Reasonably Achievable) principle, especially in children. In this study, the prospective ECG triggering technique with low voltage was used in dual-source computed tomography (DSCT) angiography to investigate if image quality with low radiation dose could be satisfactory in pediatric patients with congenital heart disease.

Methods

Sixty pediatric patients with suspected congenital cardiovascular anomalies were enrolled prospectively in the study. They were randomly assigned to two groups for DSCT angiography. Group A were scanned by prospective ECG-triggering computed tomography angiography (CTA) with 80 kV tube voltage, while group B by used non-ECG-gated CTA with the same tube voltage. The anomaly accuracy was evaluated based on the surgical and/or conventional cardiac angiography findings. The overall image quality was assessed on a five-point scale. And the diagnostic accuracy and radiation dose was evaluated in both groups.

Results

There were 127 cardiovascular anomalies in Group A and 108 in Group B. The mean subjective image quality and diagnostic accuracy between these two groups were significantly different (P = 0.007 and 0.011, respectively). The mean effective dose in Group A and Group B was 0.38 ± 0.13 mSv and 0.35 ± 0.17 mSv, respectively. But there was no significant difference between two groups (P = 0.197).

Conclusions

The prospective ECG triggering technique in DSCT scan can offer better image quality and diagnostic accuracy with low radiation exposure in pediatric patients with congenital heart diseases. This technique has potential to become a new clinical routine in pediatric cardiac computed tomography (CT) imaging.

Image Quality of Coronary Computed Tomography Angiography with 320-Row Area Detector Computed Tomography in Children with Congenital Heart Disease

The objective of this study was to assess factors affecting image quality of 320-row computed tomography angiography (CTA) of coronary arteries in children with congenital heart disease (CHD). We retrospectively reviewed 28 children up to 3 years of age with CHD who underwent prospective electrocardiography (ECG)-gated 320-row CTA with iterative reconstruction. We assessed image quality of proximal coronary artery segments using a five-point scale. Age, body weight, average heart rate, and heart rate variability were recorded and compared between two groups: patients with good diagnostic image quality in all four coronary artery segments and patients with at least one coronary artery segment with nondiagnostic image quality. Altogether, 96 of 112 segments (85.7 %) had diagnostic-quality images. Patients with nondiagnostic segments were significantly younger (10.0 ± 11.6 months) and had lower body weight (5.9 ± 2.9 kg) (each p < 0.05) than patients with diagnostic image quality of all four segments (20.6 ± 13.8 months and 8.4 ± 2.5 kg, respectively; each p < 0.05). Differences in heart rate and heart rate variability between the two imaging groups were not significant. Receiver operating characteristic analyses for predicting patients with nondiagnostic image quality revealed an optimal body weight cutoff of ≤5.6 kg and an optimal age cutoff of ≤12.5 months. Prospective ECG-gated 320-row CTA with iterative reconstruction provided feasible image quality of coronary arteries in children with CHD. Younger age and lower body weight were factors that led to poorer image quality of coronary arteries.

Coronary artery imaging in children

Coronary artery problems in children usually have a significant impact on both short-term and long-term outcomes. Early and accurate diagnosis, therefore, is crucial but technically challenging due to the small size of the coronary artery, high heart rates, and limited cooperation of children. Coronary artery visibility on CT and MRI in children is considerably improved with recent technical advancements. Consequently, CT and MRI are increasingly used for evaluating various congenital and acquired coronary artery abnormalities in children, such as coronary artery anomalies, aberrant coronary artery anatomy specific to congenital heart disease, Kawasaki disease, Williams syndrome, and cardiac allograft vasculopathy.

Current trends in cardiac CT in children

Cardiac CT is increasingly utilized in children thanks to advanced scan techniques reducing cardiac and respiratory motion artifacts. Consequently, clinical indications of cardiac CT are not confined to the extracardiac evaluation and extended further to the assessment of intracardiac structures, coronary arteries, ventricular volumetry, and ventricular function. In addition, dual-energy CT allows the assessment of regional lung perfusion and ventilation. Four-dimensional airway evaluation is also useful and may be added to cardiac CT protocols. At the same time, a favorable risk-benefit ratio of cardiac CT can be achieved by means of various dose-saving techniques. Therefore, flexible scan techniques with minimal motion artifacts, low dose techniques without compromising excellent image quality, and extended clinical applications towards truly cardiac assessments constitute current trends in cardiac CT in children.

Coronary artery abnormalities in Kawasaki disease: comparison between CT and MR coronary angiography

BACKGROUND

Although CT coronary angiography (CTCA) and MR coronary angiography (MRCA) are increasingly used in patients with Kawasaki disease, comparison of coronary artery assessibility and diagnostic performance between the two imaging modalities has been rarely performed.

PURPOSE

To investigate which imaging modality, CTCA or MRCA, is better for evaluating coronary artery abnormalities in patients with Kawasaki disease.

MATERIAL AND METHODS

Between 2003 and 2011, 56 patients (38 boys/men; age range, 1-24 years) with Kawasaki disease underwent CTCA or MRCA (group A). Of these, 17 underwent both CTCA and MRCA (group B). Visibility of 11 coronary arterial segments in each patient was graded on a four-point scale. Coronary artery aneurysm, stenosis, and occlusion were evaluated by CTCA and MRCA, based on a reference standard obtained from cardiac catheterization, echocardiography, follow-up CTCA and MRCA, and clinical history. Coronary artery assessibility and diagnostic performance were compared between CTCA and MRCA.

RESULTS

In per-segment analysis, more segments were assessable on CTCA than on MRCA in both groups. In per-patient analysis of group B, no significant difference in the assessibility was found between CTCA (95.0%, 128.3/135 segments) and MRCA (92.4%, 124.8/135 segments) (P > 0.05). Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of CTCA vs. MRCA were 93.1% vs. 77.9% (P < 0.001), 99.2% vs. 99.7% (P = 0.65), 96.8% vs. 98.7% (P = 0.65), 98.2% vs. 94.1% (P < 0.001), and 98.0% vs. 94.9% (P = 0.008), respectively, in group A, and 91.8% vs. 70.4% (P < 0.001), 99.5% vs. 99.5% (P = 1.000), 98.5% vs. 98.0% (P = 1.000), 97.2% vs. 91.1% (P = 0.006), and 97.6% vs. 92.3% (P = 0.004), respectively, in group B.

CONCLUSION

Although CTCA and MRCA show comparable assessibility in per-patient analysis, CTCA shows higher diagnostic performance than MRCA for evaluating coronary artery abnormalities in patients with Kawasaki disease.

Infant cardiac CT angiography with 64-slice and 256-slice CT: comparison of radiation dose and image quality using a pediatric phantom

Background

The aims of this study were to investigate the image quality and radiation exposure of pediatric protocols for cardiac CT angiography (CTA) in infants under one year of age.

Methodology/Principal Findings

Cardiac CTA examinations were performed using an anthropomorphic phantom representing a 1-year-old child scanned with non-electrocardiogram-gated (NG), retrospectively electrocardiogram-gated helical (RGH) and prospectively electrocardiogram-gated axial (PGA) techniques in 64-slice and 256-slice CT scanners. The thermoluminescent dosimeters (TLD) were used for direct organ dose measurement, while dose-length product and effective mAs were also used to estimate the patient dose. For image quality, noise and signal-to-noise-ratio (SNR) were assessed based on regions-of-interest drawn on the reconstructed CT images, and were compared with the proposed cardiac image quantum index (CIQI). Estimated dose results were in accordant to the measured doses. The NG scan showed the best image quality in terms of noise and SNR. The PGA scan had better image quality than the RGH scan with 83.70% dose reduction. Noise and SNR were also corresponded to the proposed CIQI.

Conclusions/Significance

The PGA scan protocol was a good choice in balancing radiation exposure and image quality for infant cardiac CTA. We also suggested that the effective mAs and the CIQI were suitable in assessing the tradeoffs between radiation dose and image quality for cardiac CTA in infants. These results are useful for future implementation of dose reduction strategies in pediatric cardiac CTA protocols.

An initial randomised study assessing free-breathing CCTA using 320-detector CT

OBJECTIVES

To evaluate the feasibility of free-breathing coronary computed tomography angiography (CCTA) in adults using with a 320-detector multidetector CT (MDCT).

METHODS

In 74 patients who underwent CCTA, 37 CCTA examinations were performed during free-breathing, and the remaining 37 CCTA examinations were produced with the standard breath-holding method. The quality scores for 16 segments of all coronary arteries were analysed and defined as: 1 (excellent), 2 (good), and 3 (poor). The signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and effective radiation dose of each image were compared between the two methods.

RESULTS

No significant differences were observed in the quality scores between the breath-holding and free-breathing methods (1.10 ± 0.31 vs. 1.12 ± 0.33; P = 0.443). The SNR and CNR were not significantly different between the two methods. The overall mean effective radiation dose revealed no significant difference between the two methods (P = 0.585).

CONCLUSIONS

Free-breathing CCTA using 320-detector MDCT showed no significant difference in image quality compared with standard breath-holding CCTA. For patients with difficulties of breath-holding or non-negligible apnoea-related heart rate variability, free-breathing CCTA can be an alternative solution for coronary artery evaluation.

KEY POINTS

• Cardiac CT is becoming widely used and some patients are inevitably breathless. • Multidetector CT (e.g. 320) offers new opportunities for the breathless patient. • Free breathing images yielded similar image quality to those obtained using breath-holding. • However, a possibility of higher radiation dose precludes its routine application.

Coronary imaging techniques with emphasis on CT and MRI

Coronary artery imaging in children is challenging, with high demands both on temporal and spatial resolution due to high heart rates and smaller anatomy. Although invasive conventional coronary angiography remains the benchmark technique, over the past 10 years, CT and MRI have emerged in the field of coronary imaging. The choice of hardware is important. For CT, the minimum requirement is a 64-channel scanner. The temporal resolution of the scanner is most important for optimising image quality and minimising radiation dose. Manufacturers have developed several modes of electrocardiographic (ECG) triggering to facilitate dose reduction. Recent technical advances have opened new possibilities in MRI coronary imaging. As a non-ionising radiation technique, MRI is of great interest in paediatric imaging. It is currently recommended in centres with appropriate expertise for the screening of patients with suspected congenital coronary anomalies. However, MRI is still not feasible in infants. This review describes and discusses the technical requirements and the pros and cons of all three techniques.

Cardiac MDCT in children: CT technology overview and interpretation

Cardiac multidetector computed tomography (MDCT) for congenital heart disease is a useful, rapid, and noninvasive imaging technique bridging the gaps between echocardiography, cardiac catheterization, and cardiac MRI. Fast scan speed and greater anatomic coverage, combined with flexible ECG-synchronized scans and a low radiation dose, are critical for improving the image quality of cardiac MDCT and minimizing patient risk. Current MDCT techniques can accurately evaluate extracardiac great vessels, lungs, and airways, as well as coronary arteries and intracardiac structures. Radiologists who perform cardiac MDCT in children should be familiarized with optimal cardiac computed tomography (CT) scan techniques and characteristic cardiac CT scan imaging findings.

Evaluation of image quality and radiation dose at prospective ECG-triggered axial 256-slice multi-detector CT in infants with congenital heart disease

BACKGROUND

There are a limited number of reports on the technical and clinical feasibility of prospective electrocardiogram (ECG)-gated multi-detector computed tomography (MDCT) in infants with congenital heart disease (CHD).

OBJECTIVE

To evaluate image quality and radiation dose at weight-based low-dose prospectively gated 256-slice MDCT angiography in infants with CHD.

MATERIALS AND METHODS

From November 2009 to February 2010, 64 consecutive infants with CHD referred for pre-operative or post-operative CT were included. All were scanned on a 256-slice MDCT system utilizing a low-dose protocol (80 kVp and 60-120 mAs depending on weight: 60 mAs for ≤ 3 kg, 80 mAs for 3.1-6 kg, 100 mAs for 6.1-10 kg, 120 mAs for 10.1-15 kg).

RESULTS

No serious adverse events were recorded. A total of 174 cardiac deformities, confirmed by surgery or heart catheterization, were studied. The sensitivity of MDCT for cardiac deformities was 97.1%; specificity, 99.4%; accuracy, 95.9%. The mean heart rate during scan was 136.7 ± 14.9/min (range, 91-160) with a corresponding heart rate variability of 2.8 ± 2.2/min (range, 0-8). Mean scan length was 115.3 ± 11.7 mm (range, 93.6-143.3). Mean volume CT dose index, mean dose-length product and effective dose were 2.1 ± 0.4 mGy (range, 1.5-2.8), 24.7 ± 5.9 mGy·cm (range, 14.7-35.8) and 1.6 ± 0.3 mSv (range, 1.1-2.5), respectively. Diagnostic-quality images were achieved in all cases. Satisfactory diagnostic quality for visualization of all/proximal/distal coronary artery segments was achieved in 88.4/98.8/80.0% of the scans.

CONCLUSION

Low-dose prospectively gated axial 256-slice CT angiography is a valuable tool in the routine clinical evaluation of infants with CHD, providing a comprehensive three-dimensional evaluation of the cardiac anatomy, including the coronary arteries.

Haemodynamic findings on cardiac CT in children with congenital heart disease

In patients with congenital heart disease, haemodynamic findings demonstrated on cardiac CT might provide useful hints for understanding the haemodynamics of cardiac defects. In contrast to morphological features depicted on cardiac CT, such haemodynamic findings on cardiac CT have not been comprehensively reviewed in patients with congenital heart disease. This article describes normal haemodynamic phenomena of cardiovascular structures and various abnormal haemodynamic findings with their mechanisms and clinical significance on cardiac CT in patients with congenital heart disease.

Radiation dose for thoracic and coronary step-and-shoot CT using a 128-slice dual-source machine in infants and small children with congenital heart disease

BACKGROUND

For coronary artery visualization, retrospective ECG-gated acquisition by dual-source computed tomography (DSCT) was superior to spiral non-ECG-gated acquisition in a paediatric population of congenital heart disease (CHD) patients. However, retrospective cardiac CT is associated with substantial radiation doses to the patient. Recently, DSCT with end-systolic reconstruction was found to be robust for imaging the coronary arteries in patients with high heart rates.

OBJECTIVE

To evaluate step-and-shoot DSCT with end-systolic reconstruction for evaluating the heart, coronary arteries and other thoracic structures in young children with CHD.

MATERIALS AND METHODS

All neonates and children younger than 6 years of age who were referred to our institution for CHD evaluation between September and October 2009 were included in the study. ECG-gated DSCT was performed in sequential prospective mode centred on the systolic phase identified by ECG analysis. To assess the radiation dose, we recorded the dose-length product (DLP) in mGy·cm and the effective dose in mSv estimated from the DLP. Overall image quality was evaluated using a 5-grade scoring system and was assessed by looking at cardiac and vascular structures. The image quality for the proximal and middle segments of the right and left coronary arteries was also evaluated using a 5-grade scale.

RESULTS

Images of diagnostic quality (grade ≥ 3) were obtained in all 30 children with a mean image quality grade of 4.7 ± 0.6 (range, 3-5). Mean DLP was 5.7 ± 4.8 mGy*cm (range, 1-22 mGy cm) and mean effective radiation dose was 0.26 ± 0.16 mSv (range, 0.05-0.8 mSv).

CONCLUSION

Prospective ECG-gated thoracic DSCT at end-systole usually provides adequate thoracic and coronary artery image quality in neonates, infants and young children with CHD, independent of heart rate. This new method is associated with lower radiation doses compared to previous literature (mean effective dose, 0.26 mSv).

Paediatric cardiac computed tomography: a review of imaging techniques and radiation dose consideration

The significant challenges involved in imaging the heart in small children (<15 kg) have been addressed by, and partially resolved with improvement in temporal and spatial resolution secondary to the advent of new multi-detector CT technology. This has enabled both retrospective and prospective ECG-gated imaging in children even at high heart rates (over 100 bpm) without the need for beta blockers. Recent studies have highlighted that the radiation burden associated with cardiac CT can be reduced using prospective ECG-gating. Our experience shows that the resultant dose reduction can be optimised to a level equivalent to that of a non-gated study. This article reviews the different aspects of ECG-gating and the preferred technique for cardiac imaging in the young child (<15 kg). We summarize our evidenced based recommendations for readers, referencing recent articles and using our in house data, protocols and dose measurements discussing the various methods available for dose calculations and their inherent bias.

Coronary artery visibility in free-breathing young children with congenital heart disease on cardiac 64-slice CT: dual-source ECG-triggered sequential scan vs. single-source non-ECG-synchronized spiral scan

BACKGROUND

The potential impact of dual-source ECG-triggered sequential CT scan on coronary artery visibility has not been evaluated in free-breathing young children.

OBJECTIVE

To compare coronary artery visibility in free-breathing young children with congenital heart disease on cardiac 64-slice CT between dual-source ECG-triggered sequential (DSET) scan and single-source non-ECG-synchronized spiral (SSNE) scan.

MATERIALS AND METHODS

In 93 young children, 108 cardiac 64-slice CT examinations were performed during free-breathing. Visibility of coronary arteries and side branches was compared between SSNE and DSET scans. Heart rates and trigger delays for DSET scan were recorded. Effective dose of each scan technique was calculated.

RESULTS

Visual grades were significantly higher (P<0.001 or =0.011) on DSET scan than on SSNE scan except for the distal left anterior descending artery. Coronary arteries were traceable in 79.3% on DSET scan and 54.3% on SSNE scan in the overlapped scan range (P<0.0001), and 97.1% and 71.9% for the origins and proximal segments (P<0.0001). Visibility of side branches was improved on DSET scan by a factor of 2.0. Heart rates and trigger delays for DSET scan were 131±24 beats per min and 199±44 ms, respectively. Effective doses of DSET and SSNE scans were 0.36±0.12 mSv and 0.99±0.23 mSv, respectively.

CONCLUSION

DSET scan improves visibility of coronary arteries on cardiac 64-slice CT in free-breathing young children with congenital heart disease, compared with SSNE scan.

Multidetector CT for congenital heart patients: what a paediatric radiologist should know

Multidetector CT (MDCT) is increasingly used for imaging congenital heart disease (CHD) patients in addition to echocardiography, due to its ability to provide high quality three-dimensional images, giving a comprehensive evaluation of complex heart malformations. Using 4-slice or 16-slice CT, diagnostic information in CHD patients is limited to extra-cardiac anatomy, mainly the pulmonary arteries, aorta and venous connections. Due to high heart rates in babies however, coronary evaluation and intra-cardiac analysis were not reliable with the first generations of MDCT. Larger detector size with 64-slice CT and faster acquisition time, up to 75 ms for one slice, has progressively improved coronary and intra-cardiac visualization. Because radiation dose is the main concern, especially in children, every attempt to minimize dose whilst preserving image quality is important: the ALARA concept should always be applied in this population. The 80 kVp setting is now well accepted as a standard for more and more radiological teams involved in CT of children. Different acquisition strategies are now possible for childhood coronary imaging, using retrospective or even prospective gating. Using the latest technology, sub-mSv acquisitions are now attainable for scanning a whole thorax, providing a complete analysis of any 3-D cardiac malformation, including coronary artery course visualisation. This review will describe how technological developments have improved image quality with continuous reduction of radiation dose.

State-of-the-art CT imaging techniques for congenital heart disease

CT is increasingly being used for evaluating the cardiovascular structures and airways in the patients with congenital heart disease. Multi-slice CT has traditionally been used for the evaluation of the extracardiac vascular and airway abnormalities because of its inherent high spatial resolution and excellent air-tissue contrast. Recent developments in CT technology primarily by reducing the cardiac motion and the radiation dose usage in congenital heart disease evaluation have helped expand the indications for CT usage. Tracheobronchomalacia associated with congenital heart disease can be evaluated with cine CT. Intravenous contrast injection should be tailored to unequivocally demonstrate cardiovascular abnormalities. Knowledge of the state-of-the-art CT imaging techniques that are used for evaluating congenital heart disease is helpful not only for planning and performing CT examinations, but also for interpreting and presenting the CT image findings that consequently guide the proper medical and surgical management.

Evaluation of image quality and radiation dose of thoracic and coronary dual-source CT in 110 infants with congenital heart disease

BACKGROUND

There are only a few reports on the diagnostic accuracy, and the technical and clinical feasibility, of multidetector CT (MDCT) in infants with congenital heart disease (CHD).

OBJECTIVE

To evaluate the image quality and radiation dose of DSCT in babies with CHD.

MATERIALS AND METHODS

From November 2006 to November 2007, 110 consecutive infants with CHD referred for pre- or postoperative CT evaluation were included. All these infants had a spiral angiothoracic DSCT scan after injection of 300 mg/ml iopromide at 0.5-1 ml/s with a power injector using a low-dose protocol (80 kVp and 10 mAs/kg). Of these infants, 34 also underwent an ECG-gated coronary CT scan for evaluation of the course of the coronary arteries.

RESULTS

No serious adverse events were recorded. The mean dose-length product was 8+/-6 mGy x cm (effective dose 0.5+/-0.2 mSv) and 21+/-9 mGy x cm (effective dose 1.3+/-0.6 mSv) during the non-ECG-gated spiral acquisition and ECG-gated acquisition, respectively. Diagnostic quality images were achieved with the spiral acquisition in 89% of cases. Compared to the spiral mode, ECG-gated acquisition significantly improved the visualization of the coronary arteries, with a diagnostic rate of 91% and 84% for the left and right coronary arteries, respectively.

CONCLUSION

DSCT together with iopromide at 300 mg/ml is a valuable tool for the routine clinical evaluation of infants with CHD. ECG-gated acquisition provides reliable visualization of the course of the coronary arteries.

Coronary artery anomalies and clinically important anatomy in patients with congenital heart disease: multislice CT findings

In patients with congenital heart disease, coronary artery anomalies are common and have different clinical importance from individuals with structurally normal hearts. Visibility of the coronary arteries by CT has markedly improved due to high temporal resolution and ECG-synchronized data acquisition. In this article we describe current multislice CT techniques for coronary artery imaging and illustrate coronary artery anomalies and clinically important coronary artery anatomy from the point of view of congenital heart disease.

Abnormal Matrix Remodeling in Adolescents and Young Adults with Kawasaki Disease Late after Onset

Background: Patients with a history of Kawasaki disease (KD), have been found to have pericoronary and myocardial fibrosis. Serum biomarkers of fibrosis may be sensitive indices for detection of these late cardiac complications in KD patients.

Methods: We studied a cohort of 60 adolescents and young adults comprising 10 KD patients with persistent coronary artery lesions (CAL) occurring at a mean (SD) time of 14.5 (4.4) years after disease onset, 25 KD patients with no CAL after disease onset, and 25 healthy age-matched volunteers. We compared laboratory data from the patients and volunteers, including lipid profile, liver function, amino-terminal propeptide of type III procollagen (PIIINP), matrix metalloproteinase 9 (MMP-9), tissue inhibitor of metalloproteinase 1 (TIMP-1), and MMP-9:TIMP-1 ratios. Severity of CAL was determined on the basis of computed tomography determinations of the frequency of aneurysms and the extent of coronary stenosis/occlusion, thrombosis, and calcification.

Results: Increased PIIINP and decreased MMP-9 and TIMP-1 concentrations and decreased MMP-9:TIMP-1 ratios were found not only in KD patients with persistent CAL but also in KD patients without CAL, although to a lesser extent in the latter group. In KD patients, the concentrations of PIIINP were positively associated with the severity of coronary stenosis/occlusion (r = 0.72, P = 0.011) and with the extent of coronary thrombus (r = 0.64, P = 0.014). The concentrations of high-sensitivity C-reactive protein, however, did not differ across groups.

Conclusions: Our results demonstrate alterations in extracellular matrix biomarkers in KD patients, suggesting enhanced collagen synthesis and ameliorated degradation in adolescents and young adults late after the onset of KD. We also observed an association between the concentrations of PIIINP and the extent of coronary stenosis/occlusion or thrombosis in KD patients, a finding that needs confirmation in further studies.

Multislice CT angiography of interrupted aortic arch

Interrupted aortic arch (IAA) is defined as complete luminal and anatomic discontinuity between the ascending and descending aorta. Because almost all patients with IAA become critically ill during the neonatal period, they should undergo urgent corrective surgery. This clinical urgency necessitates a fast and accurate noninvasive diagnostic method. Although echocardiography remains the primary imaging tool for this purpose, it is not always sufficient for planning surgical correction of IAA, principally due to a limited acoustic window and the inexperience of imagers. In this context, multislice CT angiography is regarded as an appropriate imaging technique complementary to echocardiography because it is fast, accurate, and objective for the diagnosis of IAA. In this article we describe what cardiac radiologists should know about IAA in their clinical practice, including clinicopathological features, CT features with contemporary surgical methods and postoperative complications, and differentiation from coarctation of the aorta and aortic arch atresia.

Coronary artery diameters in infants and children with congenital heart disease as determined by computed tomography

This study was conducted to establish reference curves and formulas for the diameters of the coronary arteries in infants and children using computed tomography. A total of 145 children (57 female, 88 male) ranging in age from 2 days to 19 years, 11 months (mean 5 years, 10 months), were retrospectively identified, and the diameters of their coronary arteries were quantified. The measurability of the coronary arteries, coronary arterial size differences between the genders, and relations of the diameters of the coronary arteries to age, height, weight, body surface area, and the diameter of the descending aorta were examined. Independent-samples Student's t tests, 2-tailed Pearson's correlations, and linear regression were used in statistical analysis. The measurability of all coronary arteries was 73.3%. No difference in coronary arterial size was found between the genders. The diameter of the descending aorta correlated most strongly with coronary arterial size. In conclusion, predictive formulas and reference curves for coronary arterial diameters in infants and children were obtained.

Visualization of neonatal coronary arteries on multidetector row CT: ECG-gated versus non-ECG-gated technique

BACKGROUND

Multidetector CT (MDCT) seems to be a promising tool for detection of neonatal coronary arteries, but whether the ECG-gated or non-ECG-gated technique should be used has not been established.

OBJECTIVE

To compare the detection rate and image quality of neonatal coronary arteries on MDCT using ECG-gated and non-ECG-gated techniques.

MATERIALS AND METHODS

Twelve neonates with complex congenital heart disease were included. The CT scan was acquired using an ECG-gated technique, and the most quiescent phase of the RR interval was selected to represent the ECG-gated images. The raw data were then reconstructed without the ECG signal to obtain non-ECG-gated images. The detection rate and image quality of nine coronary artery segments in the two sets of images were then compared. A two-tailed paired t test was used with P values <0.05 considered as statistically significant.

RESULTS

In all coronary segments the ECG-gated technique had a better detection rate and produced images of better quality. The difference between the two techniques ranged from 25% in the left main coronary artery to 100% in the distal right coronary artery.

CONCLUSION

For neonates referred for MDCT, if evaluation of coronary artery anatomy is important for the clinical management or surgical planning, the ECG-gated technique should be used because it can reliably detect the coronary arteries.

Strategies for reduction of radiation dose in cardiac multislice CT

Because cardiac computed tomography (CT) (mainly coronary CT angiography) is a very promising technique, used more and more for coronary artery evaluation, the benefits and risks of this new low-invasive technique must be balanced. Radiation dose is a major concern for coronary CT angiography, especially in case of repeated examinations or in particular subgroups of patients (for example young female patients). Radiation dose to patient tends to increase from 16- to 64-slice CT. Radiation exposure in ECG-gated acquisitions may reach up to 40 mSv; considerable differences are attributable to the performance of CT machines, to technical dose-sparing tools, but also to radiological habits. Setting radiation dose at the lowest level possible should be a constant goal for the radiologist. Current technological tools are detailed in regard to their efficiency. Optimisation is necessary, by a judicious use of technological tools and also by individual adaptation of kV or mAs. This paper reviews the different current strategies for radiation dose reduction, keeping image quality constant. Data from the literature are discussed, and future technological developments are considered in regards to radiation dose reduction. The particular case of paediatric patients with congenital heart disease is also addressed.

Using multidetector-row CT in neonates with complex congenital heart disease to replace diagnostic cardiac catheterization for anatomical investigation: initial experiences in technical and clinical feasibility

BACKGROUND

Echocardiography is the first-line modality for the investigation of neonatal congenital heart disease. Diagnostic cardiac catheterization, which has a small but recognized risk, is usually performed if echocardiography fails to provide a confident evaluation of the lesions.

OBJECTIVE

To verify the technical and clinical feasibilities of replacing diagnostic cardiac catheterization with multidetector-row CT (MDCT) in neonatal complex congenital heart disease.

MATERIALS AND METHODS

Over a 1-year period we prospectively enrolled all neonates with complex congenital heart disease referred for diagnostic cardiac catheterization after initial assessment by echocardiography. MDCT was performed using a 40-detector-row CT scanner with dual syringe injection. A multidisciplinary congenital heart disease team evaluated the MDCT images and decided if further diagnostic cardiac catheterization was necessary. The accuracy of MDCT in detecting separate cardiovascular anomalies and bolus geometry of contrast enhancement were calculated.

RESULTS

A total of 14 neonates were included in the study. No further diagnostic cardiac catheterization was needed in any neonate. The accuracy of MDCT in diagnosing separate cardiovascular anomalies was 98% (53/54) with only one atrial septal defect missed in a patient with coarctation syndrome. The average cardiovascular enhancement in evaluated chambers was 471 HU. No obvious beam-hardening artefact was observed.

CONCLUSION

The technical and clinical feasibility of MDCT in complex congenital heart disease in neonates is confirmed. After initial assessment with echocardiography, MDCT could probably replace diagnostic cardiac catheterization for further anatomical clarification in neonates.

Coronary CT angiography and MR angiography of Kawasaki disease

Although the incidence of coronary artery aneurysms has diminished in patients with Kawasaki disease, coronary artery involvement is still regarded as a major complication of the disease, significantly affecting morbidity and mortality. Recent technical advances in coronary CT angiography (CTA) and MR angiography (MRA) have led to the possibility of using these two imaging methods as minimally invasive alternatives to the more invasive diagnostic catheter angiography in evaluating coronary artery abnormalities, such as aneurysm, stenosis, and occlusion. In this article, we describe imaging techniques and findings of coronary CTA and MRA in Kawasaki disease.

Tube current reduction in pediatric non-ECG-gated heart CT by combined tube current modulation

BACKGROUND

Dose reduction by combined tube current modulation has not been evaluated in pediatric low-dose CT.

OBJECTIVE

This study was performed to evaluate tube current reduction in non-ECG-gated heart CT angiography in children by combined tube current modulation, and to assess the effects of body weight, age, sex, and scan direction on tube current reduction.

MATERIALS AND METHODS

From September 2004 to January 2005, non-ECG-gated heart CT examinations were performed with combined tube current modulation in 50 children (median age 1 year, range 1 month to 16 years; M/F 29/21) with congenital heart disease. Sixteen-slice spiral CT studies were obtained using a weight-based low-dose protocol (80 kVp, 50-160 effective mA). CT scans were obtained in the craniocaudal direction when leg veins (n=36) were used for IV injection of contrast agent and in the caudocranial direction when arm veins (n=13) were used. In one child who underwent a Fontan operation, both arm and leg veins were used. We calculated tube current reduction by combined tube current modulation and evaluated the effects of body weight, age, sex, and scan technique on tube current reduction. The quality of CT angiography images was visually evaluated by an experienced pediatric radiologist.

RESULTS

Overall tube current reduction by combined tube current modulation was 15.8+/-11.1%. The reduction was variable among five body weight groups (9.3+/-7.9% for <4.9 kg, 14.3+/-9.3% for 5.0-9.9 kg, 16.4+/-12.5% for 10.0-19.9 kg, 25.8+/-9.8% for 20.0-39.9 kg, 15.9+/-12.7% for 40.0-59.9 kg) and was significantly different among the five groups (P=0.017). When eight children in the 40.0-59.9-kg group were excluded, age showed a significant positive correlation with tube current reduction (gamma=0.4, P=0.003). There was no significant difference in tube current reduction between boys and girls. Tube current reduction was significantly greater for the caudocranial scan (21.2+/-9.2%) than for the craniocaudal scan (14.2+/-11.3%) (P=0.049). All CT angiography images were of diagnostic quality.

CONCLUSIONS

Combined tube current modulation reduced tube current in pediatric non-ECG-gated heart CT by 15.8% without degradation of image quality. With our CT protocol, for body weights up to 39.9 kg, age showed a significant positive correlation with tube current reduction, but there was a lower dose-saving effect in children heavier than 40 kg. Tube current reduction was not affected by sex, but was affected by scan direction.