Windows Setting for Low kVp Abdominal CT: Comparison to 120-kVp CT Images

• Main Authors: Jun Sung Kim, Joon-Il Choi, Moon Hyung Choi, Michael Yong Park, Sung Eun Rha, Soon Nam Oh, Seung Eun Jung, Jae Young Byun
• Format: Article
• Language: English
• Published: The Korean Society of Radiology 2017-10-01
• Series: 대한영상의학회지
• Subjects: tomography; x-ray computed; radiation dosage; body image; picture archiving and communication systems
• Online Access: https://doi.org/10.3348/jksr.2017.77.4.211
• ISSN: 1738-2637; 2288-2928

Purpose: The purpose of the study is to identify the optimal window level (WL) and window width (WW) to maximize visualization of the findings for low kVp abdominal CT images utilizing the automated tube voltage selection (ATVS) (which producesbrightness and contrast very similar to that produced by a 120-kVp CT scanner). Materials and Methods: We enrolled 61 patients who underwent: 1) dynamic abdominal CT scanning using ATVS technique (in 2015) and 2) a second CT scan, on this occasion implementing a 120-kVp protocol (in 2014). With ATVS, all scans were performed using 80-kVp for the arterial phase. For the portal phase, 80-kVp and 100-kVp were applied in 27 and 34 patients, respectively. Two radiologists then over-read and compared the ATVS images to the 120-kVp images, assessing brightness and contrast. After the over-read and comparison, they selected the WL and WW for ATVS because they produced brightness and contrast very similar to that appreciated in the 120-kVp images. Results: The WL and the WW for the arterial phase (mode/mean) were 130 Hounsfield unit (HU)/120.7 HU and 230 HU/259.6 HU, respectively. For the portal phase, the WL and the WW (mode/mean) were 90 HU/109.6 HU and 450 HU/450.0 HU for 80-kVp, and 40 HU/63.5 HU and 400 HU/382.4 HU for 100-kVp, respectively. The mean values of WL and WW for 80-kVp were significantly higher than those for 100-kVp (p < 0.001). Conclusion: Based upon the findings, it was determined that WL and WW with ATVS should be higher than those used for 120-kVp protocol in order to obtain comparable brightness and contrast in the images produced by abdominal CT scanning.