Dual-source CT coronary angiography in patients with atrial fibrillation: comparison with single-source CT.

OBJECTIVE: To evaluate the performance of dual-source computed tomography (DSCT) for the visualization of the coronary arteries in a population with atrial fibrillation (AF) compared to single-source CT (SSCT) and to explore the impact of patients' heart rate (HR) on image quality (IQ) and reconstruction timing. METHODS: Thirty consecutive patients (11 male, 19 female; 69.0+/-9.2 years old) with suspected coronary artery disease and permanent AF were examined on a DSCT scanner (120 kV, 400 mAs/rot, 0.33 s rotation time, 64 x 0.6 mm collimation, pitch 0.20-0.28, Siemens Somatom Definition). Patients were divided into two groups: low and medium HR group (HR80 bpm, n=16). Five of the patients also underwent conventional coronary angiography (CAG). The raw data from both tube detector arrays were reconstructed as DSCT data using a routine algorithm (temporal resolution of 83 ms). The raw data from one tube detector array was reconstructed separately on the same system using a routine single source algorithm (temporal resolution of 83-165 ms) and defined as virtual SSCT data. Image quality was assessed using a four-point grading scale from excellent (1) to non-assessable (4). RESULTS: IQ of the DSCT data was significantly better than that of the virtual SSCT data (mean score 1.33+/-0.61 vs. 1.80+/-1.02; Z=-8.755, P=0.000). 98.6% of the segments shown in DSCT were diagnostic, compared with 89.9% of the segments in virtual SSCT, chi(2)=32.595, P=0.000. In DSCT group, IQ of low HR group was also better than that of high HR group, although the difference was not as big (mean score 1.25+/-0.52 vs. 1.38+/-0.66; Z=-2.227, P=0.026). The mean HR of low HR group and high HR group were 67.4+/-8.5 beats per minute (bpm) and 94.2+/-8.8 bpm (t=-8.499, P=0.000). The range of the variation of HR was higher in high HR group than in low HR group (mean difference between maximum and minimum HR 79.5+/-21.0 vs. 49.9+/-21.1 bpm; t=-3.845, P=0.001). In 23 (77%) patients optimal IQ was achieved within one phase for all three main arteries. In low HR group, the optimal phase was distributed evenly between diastole and systole; but in high HR group, the optimal phase shifted to systole in most cases (92%). In five cases these results were compared to CAG results to look for the ability to identify stenosis with a diameter reduction of more than 50% of the lumen. With DSCT it was possible to diagnose 20 of 21 stenosis and 48 of 49 non-stenosed vessel segments correctly. With SSCT 19 of 21 stenosis and 45 of 49 non-stenosed vessel segments were diagnosed correctly according to CAG. CONCLUSION: Due to its high temporal resolution, DSCT provides images of full diagnostic image quality in patients with AF, which otherwise would be excluded from CT examinations. The number of assessable segments for DSCT is still somewhat less than in non-AF patients, but in opposition to SSCT still valid for routine diagnostic imaging. Patients' HR had impact on IQ and reconstruction timing.

Comparison of myocardial bridging by dual-source CT with conventional coronary angiography.

BACKGROUND: The diagnosis of myocardial bridging (MB) is of clinical importance because of the association between MB and compromised coronary flow. The aim of this study was to compare the ability of dual-source computed tomography (DSCT) and conventional coronary angiography (CAG) to detect MB. METHODS AND RESULTS: DSCT were performed in 53 patients and 4-dimensional (D) reconstruction was subsequently performed in 16 patients with MB for double-blinded comparison with the findings of CAG. The diameters at systole and diastole of the coronary segments proximal and distal to the MB and of the tunneled segment were measured. The relationship between the rate of stenosis of the tunneled artery and the "milking" effect on 4-D reconstruction was analyzed. Of the 53 patients, CAG and DSCT detected 4 MBs in 3 patients and 21 MBs in 16 patients, respectively (p<0.001). On a per-patient and per-MB basis, significant difference was found between both methods (p=0.001, p<0.001). The 4-D reconstruction showed the milking effect and abnormal blood flow, detecting more MBs than did CAG (p<0.001). The rate of stenosis of the tunneled artery was related to the milking effect on the 4-D reconstruction (r=0.640, p=0.006). CONCLUSIONS: In the present study, DSCT detected more MBs than CAG, suggesting its clinical application for diagnosis of this condition.

On simulating subjective evaluation using combined objective metrics for validation of 3D tumor segmentation.

In this paper, we present a new segmentation evaluation method that can simulate radiologist's subjective assessment of 3D tumor segmentation in CT images. The method uses a new metric defined as a linear combination of a set of commonly used objective metrics. The weighing parameters of the linear combination are determined by maximizing the rank correlation between radiologist's subjective rating and objective measurements. Experimental results on 93 lesions demonstrate that the new composite metric shows better performance in segmentation evaluation than each individual objective metric. Also, segmentation rating using the composite metric compares well with radiologist's subjective evaluation. Our method has the potential to facilitate the development of new tumor segmentation algorithms and assist large scale segmentation evaluation studies.