REDUCED IODINATED CONTRAST VOLUME AND RADIATION DOSE IN THE NEW PROTOCOL FOR CT CORONARY ANGIOGRAPHY USING DUAL-SOURCE IMAGING WITH LOW TUBE VOLTAGE COMPARED WITH THE CONVENTIONAL PROTOCOL

Abstract

Objective: To assess the effectiveness and utility of a low-contrastvolume, coronary computed tomography angiography (CCTA) protocol that leverages a lower tube peak voltage (80 kVp) compared to the conventionally employed 120 kVp in patients referred for diagnostic coronary CT angiography.
 Materials and Methods: 120 patients (60 males, between 23 to 86 years) were randomly assigned to two groups (n=60) who were scanned with either the 80 kVp (“Group A”) or the 120 kVp (“Group B”) protocols using retrospective ECG gating. All patients had body mass index (BMI) under 25 kg/m2 and heart rates under 120 beats per minute. On a patient-by-patient and segment-by-segment basis, the signal-to-noise (S/N) and contrast-to-noise (C/N) ratios, effective radiation dose given in mSv, and diagnostic confidence (DC) were assessed for both groups by two independent readers with 8 and 7 years experience in coronary CT angiography.
 Results: Patients in group A received a significantly reduced radiation dose of 2.57 mSv compared with 7.07 mSv in group B (p < 0.001). The total administered amount of Iodine per scan was also significantly lower in Group A (17.5g) than in Group B (24.5g). A significant reduction in image noise with higher S/N and C/N ratios in coronary vessels was seen in group B (p < 0.001). S/N ratios in group A were 18.7, 18.6, 18.7, and 18.6 for left main, proximal left anterior descending, proximal left circumflex arteries, and proximal right coronary, respectively, and 16.7, 17.4, and 18.3 for distal left anterior descending, distal left circumflex, distal right coronary arteries, respectively, in group A. Conversely, in group B the S/R values were 22.5, 22.0, 22.0, 21.4,19.0, 18.8, and 21.7 in group B patients. C/N ratios were 22.2, 22.1, 21.9, 22.1, 20.5, 21.0, and 21.9 in group A compared with group B patients, who had ratios of 26.6, 26.1, 25.9, 25.5,23.2, 23.0 and 25.6 (in a vessel-by-vessel assessment, each vessel in group B had p < 0.001). No significant difference in DC per patient was seen between the groups (ICC 1.0 for Group A and 0.9 for Group B).
 Conclusion: The retrospective ECG-gated low-kVp low-volume contrast coronary CT angiography protocol provides angiograms without penalty in diagnostic confidence in patients with BMI up to 25 kg/m2 and heart rates of less than 120 beats/min. It is beneficial for patients whose kidney functions are not good and for those who increased risk for extravasations to diminish the risk of compartment syndrome in severe cases.