Abdominal multislice CT for obese patients: effect on image quality and radiation dose in a phantom study.
OBJECTIVE
To evaluate the effect of a modified abdominal multislice computed tomography (CT) protocol for obese patients on image quality and radiation dose.


METHODS
An adult female anthropomorphic phantom was used to simulate obese patients by adding one or two 4-cm circumferential layers of fat-equivalent material to the abdominal portion. The phantom was scanned with a subcutaneous fat thickness of 0, 4, and 8 cm using the following parameters (detector configuration/beam pitch/table feed per rotation/gantry rotation time/kV/mA): standard protocol A: 16 x 0.625 mm/1.75/17.5 mm/0.5 seconds/140/380, and modified protocol B: 16 x 1.25 mm/1.375/27.5 mm/1.0 seconds/140/380. Radiation doses to six abdominal organs and the skin, image noise values, and contrast-to-noise ratios (CNRs) were analyzed. Statistical analysis included analysis of variance, Wilcoxon rank sum, and Student's t-test (P < .05).


RESULTS
Applying the modified protocol B with one or two fat rings, the image noise decreased significantly (P < .05), and simultaneously, the CNR increased significantly compared with protocol A (P < .05). Organ doses significantly increased, up to 54.7%, comparing modified protocol B with one fat ring to the routine protocol A with no fat rings (P < .05). However, no significant change in organ dose was seen for protocol B with two fat rings compared with protocol A without fat rings (range -2.1% to 8.1%) (P > .05).


CONCLUSIONS
Using a modified abdominal multislice CT protocol for obese patients with 8 cm or more of subcutaneous fat, image quality can be substantially improved without a significant increase in radiation dose to the abdominal organs.
Schindera
Sebastian T
ST
Department of Radiology, Duke University Medical Center, Duke University Medical Center, Durham, NC 27710, USA.
Nelson
Rendon C
RC
Lee
Ellie R
ER
Delong
David M
DM
Ngyen
Giao
G
Toncheva
Greta
G
Yoshizumi
Terry T
TT
D000704:Analysis of Variance; D002138:Calibration; D005260:Female; D006801:Humans; D009765:Obesity; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011860:Radiography, Abdominal / Q000592:standards*; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000592:standards*