Qualitative analysis (Table 2):
Out of 96 patients of group A (bolus tracking in the left atrium),
the image quality was rated in 41 cases with a total score of 5 (42.7%),
in 39 cases with a total score of 4 (40.6%),
in 15 cases with a total score of 3 (15.6%) and in one case with a total score of 2 (1.1%).
Out of 96 patients of group B (bolus tracking in the ascending aorta),
the image quality was rated in 44 cases with a total score of 5 (45.8%),
in 36 cases with a total score of 4 (37.5%) and in 16 cases with a total score of 3 (16.7%).
Table 2: Overall qualitative scores depending on the bolus tracking position (left atrium (LA) or ascending aorta (AA)). The following scores were used: 5 = perfect; 4 = very good; 3 = good; 2 = poor; 1 = insufficient.
In summary,
image quality scores did not differ significantly between patients with bolus tracking in the left atrium and those with bolus tracking in the ascending aorta (p = 0.648).
Interrater reliability (Table 3):
Both radiologists assigned identical scores in 139 of 192 cases (72.4%) and different scores in 53 of 192 cases (27.6%),
but they never differed by more than one grade.
Table 3: Interrater agreement in regard to qualitative image scores.
The resulting Cohen´s kappa was κ = 0.654,
indicating substantial interrater agreement.
Quantitative analysis (Fig. 4; Table 4):
In the area of the ascending aorta (AA) the mean value of the SNR (signal-to-noise ratio) for group A (bolus tracking in the left atrium) was 14.92 (± 3.75) and for group B (bolus tracking in the ascending aorta) was 15.46 (± 3.85).
In the area of the left main coronary artery (LM) the mean value of the SNR for group A was 19.80 (± 8.36) and for group B was 20.30 (± 8.34).
In the area of the proximal right coronary artery (RCA) the mean value of the SNR for group A was 24.34 (± 11.04) and for group B was 24.30 (± 12.73).
Fig. 4: Signal-to-noise ratios (SNR) in the ascending aorta (AA), left main coronary artery (LM) and proximal right coronary artery (RCA) depending on the bolus tracking position (left atrium (LA) or ascending aorta (AA)).
Table 4: Mean signal-to-noise ratios (SNR) in the ascending aorta (AA), left main coronary artery (LM) and proximal right coronary artery (RCA) depending on the bolus tracking position (left atrium (LA) or ascending aorta (AA)).
In summary,
there was no significant difference between both patient groups regarding SNR in the ascending aorta (p = 0.273),
left main coronary artery (p = 0.653) and proximal right coronary artery (p = 0.983).
Radiation exposure (Table 5):
The mean dose-length product was 229.23 (± 177.24) mGycm in patients with bolus tracking in the left atrium and 229.31 (± 141.63) mGycm in patients with bolus tracking in the ascending aorta.
The corresponding mean effective doses were 4.13 (± 3.19) mSv and 4.13 (± 2.55) mSv.
Table 5: Radiation exposure for both groups of patients (bolus tracking in the left atrium (LA) or in the ascending aorta (AA)).
Thus there was also no significant difference regarding radiation exposure between the two groups (p = 0.997).