Adaptive prospective ECG-triggered sequence coronary angiography in dual-source CT without heart rate control: Image quality and diagnostic performance

Dual-source computed tomography coronary artery imaging in children

Computed tomography (CT) has a well-established diagnostic role in the assessment of coronary arteries in adults. However, its application in a pediatric setting is still limited and often impaired by several technical issues, such as high heart rates, poor patient cooperation, and radiation dose exposure. Nonetheless, CT is becoming crucial in the noninvasive approach of children affected by coronary abnormalities and congenital heart disease. In some circumstances, CT might be preferred to other noninvasive techniques such as echocardiography and MRI for its lack of acoustic window influence, shorter acquisition time, and high spatial resolution. The introduction of dual-source CT has expanded the role of CT in the evaluation of pediatric cardiovascular anatomy and pathology. Furthermore, technical advances in the optimization of low-dose protocols represent an attractive innovation. Dual-source CT can play a key role in several clinical settings in children, namely in the evaluation of children with suspected congenital coronary artery anomalies, both isolated and in association with congenital heart disease. Moreover, it can be used to assess acquired coronary artery abnormalities, as in children with Kawasaki disease and after surgical manipulation, especially in case of transposition of the great arteries treated with arterial switch operation and in case of coronary re-implantation.

Submillisievert coronary CT angiography with adaptive prospective ECG-triggered sequence acquisition and iterative reconstruction in patients with high heart rate on the dual-source CT

PURPOSE

To assess the application value of submillisievert coronary CT angiography (CCTA) in patients with a high heart rate (HR) acquired with adaptive prospective ECG-triggered sequence acquisition and iterative reconstruction on the secondary generation dual-source CT.

MATERIALS AND METHODS

A total of 120 consecutive high-HR patients suspected with coronary artery disease underwent CCTA and invasive coronary angiography (ICA) within two weeks. Patients were randomly assigned into three groups: group A (n = 40), where the patients underwent retrospectively ECG-triggered acquisition CCTA at 100 kVp; group B (n = 40), where the patients received adaptive prospective ECG-triggered sequence acquisition at 100 kVp; and group C (n = 40), where the patients performed adaptive prospective ECG-triggered sequence acquisition at 80 kVp with iterative reconstruction. The mean CT values, signal noise ratios (SNR) and contrast noise ratios (CNR) in the ascending aorta and coronary arteries of the three groups were measured and compared. The image quality and radiation dose among the three groups were compared. The consistency of displaying the coronary stenosis of each group was assessed compared with the results of ICA as the gold standard.

RESULTS

There was no significant difference in gender, age and body mass index (BMI) (all P > 0.05). The mean attenuations, SNRs and CNRs in the ascending aorta and coronary artery were not significantly different between group A and group B (P > 0.05). The mean attenuations of group C were significantly higher than group A and group B (P < 0.01), but the image noise and CNR were significantly lower in group C (P < 0.01). The number of appreciable segments among the three groups was not significantly different on a per-segment and per-vessel basis (P > 0.05). The subjective image quality among the three groups was not significantly different (P > 0.05). With the ICA result as a reference standard, there was good consistency in the evaluation of the coronary stenosis degree between CCTA and ICA (r > 0.75), as well as in the assessment of the coronary stenosis rate using the Bland- Altman analysis. The mean radiation dose in group B was half of that in group A. Moreover, the mean radiation dose in group C was less than one sixth of that in group A and less than 1 mSv (0.7±0.2 mSv).

CONCLUSIONS

For patients with high HR, adaptive prospective ECG-triggered sequence acquisition on the FLASH dual-source CT results in equal image quality and half of the radiation dose reduction compared with retrospectively ECG-triggered spiral acquisition at the same tube voltage (100 kVp) and same R-R interval of exposure. In addition, adaptive prospective ECG-triggered sequence acquisition combined with low tube voltage and iterative reconstruction can further reduce the radiation dose to the submillisievert level without compromising image quality and the accuracy of assessing the coronary stenosis degree, and can be popularized as a routine technique.

Age-related differences in image quality of prospectively ECG-triggered axial and helical scans for coronary CT angiography

We investigated the underlying reasons for the occurrence of misalignment artifacts in prospectively ECG-triggered axial coronary CT angiography scans. In this study we analyzed 56 consecutive patients scanned in axial mode and 66 consecutive patients scanned in helical mode. Predictors for the occurrence of misalignment artifacts were evaluated by multivariable logistic regression analysis for those patients scanned in the axial mode; advanced age was identified as the sole independent predictor (odds ratio: 1.088; 95 % CI: 1.012-1.170; p = 0.0228). In a comparison with the patients scanned in the helical mode, the image quality score for patients aged 65 years or older was significantly higher in helical mode than in axial mode (2.6 ± 0.5 and 2.4 ± 0.7, respectively; p = 0.0313). Misalignment artifacts in the image are more common in the elderly than in younger. Helical mode should be preferred in this older patient population to allow for good diagnostic image quality.

Single- versus multi-phase acquisition protocol for prospective-triggered sequential dual-source CT coronary angiography: comparison of image quality and radiation dose

OBJECTIVE

To investigate image quality and radiation dose of single- versus multi-phase acquisition protocol for prospective-triggered sequential dual-source computed tomography (CT) coronary angiography.

MATERIALS AND METHODS

A total of 140 patients were randomly assigned to single- or multi-phase group. Image quality and radiation dose were compared.

RESULTS

No significant difference was found in image quality between the two groups. Effective dose of single-phase group was 21.6% lower than that of multi-phase group (P<.001).

CONCLUSIONS

Prospective-triggered sequential dual-source CT coronary angiography using single-phase protocol can reduce radiation dose without sacrifice of image quality in diastole compared with multi-phase protocol.

Effects of two different anesthetic protocols on 64-MDCT coronary angiography in dogs

Heart rate is a major factor influencing diagnostic image quality in computed tomographic coronary artery angiography (MDCT-CA), with an ideal heart rate of 60-65 beats/min in humans. The purpose of this prospective study was to compare effects of two different clinically applicable anesthetic protocols on cardiovascular parameters and 64-MDCT-CA quality in 10 healthy dogs. Scan protocols and bolus volumes were standardized. Image evaluations were performed in random order by a board-certified veterinary radiologist who was unaware of anesthetic protocols used. Heart rate during image acquisition did not differ between protocols (P = 1), with 80.6 ± 7.5 bpm for protocol A and 79.2 ± 14.2 bpm for protocol B. Mean blood pressure was significantly higher (P > 0.05) using protocol B (protocol A 62.9 ± 9.1 vs. protocol B 72.4 ± 15.9 mmHg). The R-R intervals allowing for best depiction of individual coronary artery segments were found in the end diastolic period and varied between the 70% and 95% interval. Diagnostic quality was rated excellent, good, and moderate in the majority of the segments evaluated, with higher scores given for more proximal segments and lower for more distal segments, respectively. Blur was the most commonly observed artifact and mainly affected the distal segments. No significant differences were identified between the two protocols for optimal reconstruction interval, diagnostic quality and measured length individual segments, or proximal diameter of the coronary arteries (P = 1). Findings indicated that, when used with a standardized bolus volume, both of these anesthetic protocols yielded diagnostic quality coronary 64-MDCT-CA exams in healthy dogs.