Brief Article
Copyright ©2012 Baishideng Publishing Group Co., Limited. All rights reserved.
World J Radiol. Mar 28, 2012; 4(3): 102-108
Published online Mar 28, 2012. doi: 10.4329/wjr.v4.i3.102
Ablation margin assessment of liver tumors with intravenous contrast-enhanced C-arm computed tomography
Mi Sung Kim, Sarabjeet Singh, Elkan Halpern, Sanjay Saini, Mannudeep K Kalra
Mi Sung Kim, Myongji Hospital, Kwandong University, 522 Naegok-dong, Gangneung-si, Gangwon-do 220-801, South Korea
Sarabjeet Singh, Elkan Halpern, Sanjay Saini, Mannudeep K Kalra, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, United States
Author contributions: Kim MS helped in manuscript writing and editing, literature search; Singh S helped in organizing the study, literature search, manuscript writing; Kalra MK helped in overall study design and manuscript writing.
Supported by Research funding from GE Healthcare (Waukesha, Wis) (to Kalra MK)
Correspondence to: Dr. Sarabjeet Singh, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit St, Boston, MA 02114, United States.
Telephone: +617-643-4583 Fax: +617-643-0111
Received: January 18, 2011
Revised: February 28, 2012
Accepted: March 7, 2012
Published online: March 28, 2012

AIM: To determine the influence of anthropomorphic parameters on the relationship between patient centering, mean computed tomography (CT) numbers and quantitative image noise in abdominal CT.

METHODS: Our Institutional Review Board approved study included 395 patients (age range 21-108, years; male:female = 195:200) who underwent contrast-enhanced abdominal CT on a 16-section multi-detector row scanner (GE LightSpeed 16). Patient centering in the gantry isocenter was measured from the lateral localizer radiograph (off center S = patient off centered superior to isocenter; off center I = patient off centered inferior to isocenter). Mean CT numbers (Hounsfield Units: HU) and noise (standard deviation of CT numbers: SD) were measured in the anterior (aHU, aSD) and posterior (pHU, pSD) abdominal wall subcutaneous fat and liver parenchyma (LivHU, LivSD) at the level of the porta hepatis. Patients’ age, gender, weight, body mass index and maximal anteroposterior diameter were recorded. The data were analyzed using linear regression analysis.

RESULTS: Most patients (81%; 320/395) were not correctly centered in the gantry isocenter for abdominal CT scanning. Mean CT numbers in the abdominal wall increased significantly with an increase in the off-centering distance, regardless of the direction of the off-center (P < 0.05). There was a substantial increase in pSD (P = 0.01) and LivSD (P = 0.017) with off-centering. Change in mean CT numbers and image noise along the off-center distance was influenced by the patient size (P < 0.01).

CONCLUSION: Inappropriate patient centering for CT scanning adversely affects the reliability of mean CT numbers and image noise.

Keywords: Automatic exposure control, Computed tomography radiation dose reduction, Patient offcentering, Tube current modulation