International Workshop on Semiconductor Pixel Detectors for Particles and Imaging (PIXEL2012)

Optimal Temporal Windows and Dose-reducing Strategy for Coronary Artery Bypass Graft Imaging with 256-Slice CT

6 Sept 2012, 15:10

1h

Hotel Listel Inawashiro, Inawashiro, Japan

POSTER X-ray imaging applications - Medicine Poster session

Speaker

YU-XIANG GUAN (National Yang-Ming University)

Description

Objective: To determine the optimal image reconstruction windows in the assessment of coronary artery bypass grafts (CABGs) with 256-slice CT, and to assess their associated optimal ECG pulsing windows for tube-current modulation (ETCM). Methods: We recruited 18 patients (three female; mean age 68.9 years) having mean heart rate (HR) of 66.3 bpm and a heart rate variability of 1.3 bpm for this study. A total of 36 CABGs with 168 segments were evaluated, including 12 internal mammary artery (33.3%) and 24 saphenous vein grafts (66.7%). We reconstructed 20 data sets in 5%-step through 0%-95% of the R-R interval. The image quality of the bypass grafts was assessed by a 5-point scale (1=excellent to 5=non-diagnostic) for each segment (proximal anastomosis, proximal, middle, distal course of graft body, and distal anastomosis). Two reviewers discriminated optimal reconstruction intervals for each CABG segment in each temporal window. Optimal windows for ETCM were also evaluated. Results: The determined optimal systolic and diastolic reconstruction intervals could be divided into 2 groups with threshold HR = 68. The determined best reconstruction intervals for low heart rate (HR < 68) and high heart rate (HR >68) were 76.0 ± 2.5% and 45.0 ± 0% respectively. Average image quality scores were 1.8 ± 0.6 with good inter-observer agreement (kappa=0.79). Image quality was significantly better for saphenous vein grafts versus arterial grafts (P < 0.001). The recommended windows of ETCM for low HR, high HR and all HR groups were 40-50%, 71-81% and 40-96% of R-R interval, respectively. The corresponding dose savings were about 60.8%, 58.7% and 22.7% in that order. Conclusions: We determined optimal reconstruction intervals and ETCM windows representing a good compromise between radiation and image quality for following bypass surgery using a 256-slice CT. Key Words: CT coronary angiograms; Coronary artery bypass graft; Image quality; ECG-based tube current modulation; Radiation dose