Determination of the optimal energy level in spectral CT imaging for displaying abdominal vessels in pediatric patients.
OBJECTIVE
To determine the optimal energy level in contrast-enhanced spectral CT imaging for displaying abdominal vessels in pediatric patients.


METHODS
This retrospective study was institutional review board approved. 15 children (8 males and 7 females, age range, 6-15 years, mean age 10.1±3.1 years) underwent contrast-enhanced spectral CT imaging for diagnosing solid tumors in abdomen and pelvic areas were included. A single contrast-enhanced scan was performed using a dual energy spectral CT mode with a new split contrast injection scheme (iodixanol at 1-1.5 ml/kg dose. 2/3 first, 1/3 at 7-15 s after the first injection). 101 sets of monochromatic images with photon energies of 40-140 keV with 1 keV interval were reconstructed. Contrast-noise-ratio (CNR) for hepatic portal or vein were generated and compared at every energy level to determine the optimal energy level to maximize CNR. 2 board-certified radiologists interpreted the selected image sets independently for image quality scores.


RESULTS
CT values and CNR for the vessels increased as photon energy decreased from 140 to 40 keV: (CT value: 48.29-570.12 HU, CNR: 0.08-14.90) in the abdominal aorta, (58.48-369.73 HU, 0.64-5.87) in the inferior vena cava, and (58.48-369.73 HU, 0.06-6.96) in the portal vein. Monochromatic images at 40-50 keV (average 42.0±4.67 keV) could display vessels above three levels clearly, and with excellent image quality scores of 3.17±0.58 (of 4) (k=0.50). The CNR values at the optimal energy level were significantly higher than those at 70 keV, an average energy corresponding to the conventional 120 kVp for abdominal CT imaging.


CONCLUSIONS
Spectral CT imaging provides a set of monochromatic images to optimize image quality and enhance vascular visibility, especially in the hepatic portal and vein systems. The best CNR for displaying abdominal vessels in children was obtained at 42 keV photon energy level.
Beijing Children's Hospital, Capital Medical University, Imaging Center, No. 56, Nanlishi Road, Xicheng District, Beijing 100045, China. Electronic address: hudi0415@163.com.
Di
D
Hu
Beijing Children's Hospital, Capital Medical University, Imaging Center, No. 56, Nanlishi Road, Xicheng District, Beijing 100045, China. Electronic address: hemophilia@126.com.
Tong
T
Yu
Beijing Children's Hospital, Capital Medical University, Imaging Center, No. 56, Nanlishi Road, Xicheng District, Beijing 100045, China. Electronic address: potatocat@yeah.net.
Xiaomin
X
Duan
Beijing Children's Hospital, Capital Medical University, Imaging Center, No. 56, Nanlishi Road, Xicheng District, Beijing 100045, China. Electronic address: ppengyun@yahoo.com.
Yun
Y
Peng
Beijing Chaoyang Hospital, Capital Medical University, Imaging Center, No. 8, Gongti South Road, Chaoyang District, Beijing 100020, China. Electronic address: zhairenyou@163.com.
Renyou
R
Zhai
D000005:Abdomen / Q000098:blood supply; D000008:Abdominal Neoplasms / Q000000981:diagnostic imaging*; D000293:Adolescent; D000792:Angiography / Q000379:methods*; D002648:Child; D003626:Data Display; D005260:Female; D006499:Hepatic Artery / Q000000981:diagnostic imaging*; D006503:Hepatic Veins / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D011856:Radiographic Image Enhancement / Q000379:methods*; D011860:Radiography, Abdominal / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*
Abdominal vessels; Best energy level; Low radiation dose; Spectral CT