Yunseok Choi BS, Presenter: Nothing to Disclose

Yang-Kyun Park MS, Abstract Co-Author: Nothing to Disclose

Chang Heon Choi, Abstract Co-Author: Nothing to Disclose

Jae-Sung Kim MD, Abstract Co-Author: Nothing to Disclose

Sung-Joon Ye PhD, Abstract Co-Author: Nothing to Disclose

Pediatric CT scans at 90 kVp had advantages in radiation doses over 120 kVp scans. In the view of image quality, images at 90 kVp were much better than 120kVp in low contrast resolution and slightly worse in noise. Using 90kVp tube voltage is recommanded for pediatric CT for radiation treatment plan.

To find effect of technical factors (peak tube voltage and tube current) in radiation dose and image quality of pediatric CT in two tube voltage and various time-current product and to suggest an optimized technical factors for pediatric CT.

The AAPM CT performance phantom (Victoreen) was used for CT image analysis. The AAPM CT phantom was scanned by the Brilliance Big Bore Oncology (Philips). We can test some factors of CT image quality using AAPM phantom. Technical factors were set as follows. At the tube voltages of 90 kVp and 120 kVp, the tube current ranged from 60 to 500 mAs. A standard CT dosimetry phantom (FLUKE) and a 100 mm pencil chamber (Victoreen) were used to measure radiation doses from CT. The modulation transfer function (MTF) was used to asses the high contrast resolution. To evaluate uniformity, the maximum deviation of averaged HU of 4 ROIs was measured. The low contrast resolution of CT images was evaluated by contrast-to-noise ratio (CNR). Standard deviations in 4 ROIs on CT images were measured for noise evaluation. the weighted CT dose index (CTDIw) was assessed to check radiation dose according to each technical factors. Dose and noise of pediatric patient CT image was evaluated for verification.

CTDIw was linearly proportional to currernt-time product, and in the view of tube voltage, the inclination of CTDIw vs. mAs at 120 kVp was 2.2 times higher than that at 90 kVp. The noise was inversely proportional to CTDIw-0.5 as well as mAs, current-time product. In tube voltage of CT, the noise at 90 kVp was 10% higher than the value at 120 kVp. For the decrease in tube voltage from 120 to 90 kVp, the phantom had a 42% greater CNR on average, according to the linear regression. The spatial resolution and uniformity have no correlation with CT tube voltages and current-time products. The patient study confirmed the findings from the phantom study.

Choi, Y, Park, Y, Choi, C, Kim, J, Ye, S, Effect of Technical Factors in Radiation Dose and Image Quality of Pediatric CT.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11010296.html