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

The associated factors for radiation dose variation in cardiac CT angiography

OBJECTIVE:

This study aimed to examine the associated factors for dose variation and influence cardiac CT angiography (CCTA) dose benchmarks in current CT imaging centres.

METHODS:

A questionnaire was distributed to CT centres across Australia and Saudi Arabia. All participating centres collected data for adults who underwent a CCTA procedure. The questionnaire gathered information about the examination protocol, scanning parameters, patient parameters, and volume CT dose index (CTDI vol) and dose-length product (DLP). A stepwise regression analysis was performed to assess the contribution of tube voltage (kV), padding time technique, cross-sectional area (CSA) of chest and weight to DLP.

RESULTS:

A total of 17 CT centres provided data for 423 CCTA examinations. The median CTDI_vol, DLP and effective dose were 18 mGy, 256 mGy.cm and 5.2 mSv respectively. There was a statistically significant difference in DLP between retrospective and prospective ECG-gating modes (p = 0.001). Median DLP from CCTA using padding technique was 61% higher than CCTA without padding (p = 0.001). The stepwise regression showed that kV was the most significant predictor of DLP followed by padding technique then CSA while patient weight did not statistically significantly predict DLP. Correlation analysis showed a strong positive correlation between weight and CSA (r = 0.78), and there was a moderate positive correlation between weight and DLP (r = 0.42), as well as CSA and DLP (r = 0.48).

CONCLUSION:

Findings show radiation dose variations for CCTA. The associated factors for dose variation found in this study are scanning mode, kV, padding time technique and CSA of the chest. This results support the need to include CSA measurements in future dose survey and for setting DRLs.

ADVANCES IN KNOWLEDGE:

The study provides baseline information that helps to understand the associated factors for dose variations and high doses within and between centres performing CCTA.

Second-generation motion correction algorithm improves diagnostic accuracy of single-beat coronary CT angiography in patients with increased heart rate

OBJECTIVE

To assess the effect of a second-generation motion correction algorithm on the diagnostic accuracy of coronary computed tomography angiography (CCTA) using a 256-detector row CT in patients with increased heart rates.

METHODS

Eighty-one consecutive symptomatic cardiac patients with increased heart rates (≥ 75 beats per min) were enrolled. All patients underwent CCTA and invasive coronary angiography (ICA). CCTA was performed with a 256-detector row CT using prospectively ECG-triggered single-beat protocol. Images were reconstructed using standard (STD) algorithm, first-generation intra-cycle motion correction (MC1) algorithm, and second-generation intra-cycle motion correction (MC2) algorithm. The image quality of coronary artery segments was assessed by two experienced radiologists using a 4-point scale (1: non-diagnostic and 4: excellent), according to the 18-segment model. Diagnostic performance for segments with significant lumen stenosis (≥ 50%) was compared between STD, MC1, and MC2 by using ICA as the reference standard.

RESULTS

The mean effective dose of CCTA was 1.0 mSv. On per-segment level, the overall image quality score and interpretability were improved to 3.56 ± 0.63 and 99.2% due to the use of MC2, as compared to 2.81 ± 0.85 and 92.5% with STD and 3.21 ± 0.79 and 97.2% with MC1. On per-segment level, compared to STD and MC1, MC2 improved the sensitivity (92.2% vs. 79.2%, 80.7%), specificity (97.8% vs. 82.1%, 90.8%), positive predictive value (89.9% vs. 48.4%, 65.1%), negative predictive value (98.3% vs. 94.9%, 95.7%), and diagnostic accuracy (96.8% vs. 81.5%, 89.0%).

CONCLUSION

A second-generation intra-cycle motion correction algorithm for single-beat CCTA significantly improves image quality and diagnostic accuracy in patients with increased heart rate.

KEY POINTS

• A second-generation motion correction (MC2) algorithm can further improve the image quality of all coronary arteries than a first-generation motion correction (MC1). • MC2 algorithm can significantly reduce the number of false positive segments compared to standard and MC1 algorithm.

Evaluate of the effect of low tube voltage on the radiation dosage using 640-slice coronary CT angiography

BACKGROUND

640-slice coronary CT angiography is becoming an accurate and reliable method of diagnosing coronary heart disease. However, how to reduce the radiation dosage while ensuring the clinically acceptable image quality remains a quite challenging issue.

OBJECTIVE

To evaluate the effect of low tube voltage on radiation dosage under 640-slice coronary CT angiography (CCTA).

METHODS

Four hundred patients (236 males, 164 females) with coronary heart disease and underwent CCTA using DCVT were classified into A1 (tube voltage: 120 kV; exposure phase window: 30-80%), B1 (120 kV; 70-80%), A2 (100 kV; 30-80%) and B2 group (100 kV; 70-80%), respectively. Image qualities and effective dose (ED) were assessed and compared.

RESULTS

No significant differences were observed among the groups in terms of age, height, weight and body mass index (BMI) (P > 0.05). ED were significantly lower in 100 kV group (P < 0.05). CT values of coronary artery in 100 kV groups were 13.5% and 17.3% higher than 120 kV group. ED in B1 group were 64.5% and 67.0% lower than A1 group. ED in B2 group were 65.4% and 65.2% lower than A2 group.

CONCLUSION

When using a 640-slice CCTA prospective ECG-gating scanning mode, it is preferable to use a 100 kV tube voltage setting because compared to 120 kV tube voltage protocol, it seems to significantly decrease the mean effective radiation dose, without significantly lowering both the subjective and objective image quality.