Abdominal CT with low tube voltage: preliminary observations about radiation dose, contrast enhancement, image quality, and noise.
OBJECTIVE
To prospectively investigate the effect of low tube voltage on radiation dose, contrast enhancement, image quality, and image noise at abdominal dynamic computed tomography (CT).


METHODS
The institutional review board approved this study. Prior informed consent was obtained from all patients. Forty patients (24 women, 16 men; mean age, 62 years) underwent initial abdominal CT at 120 kV with 100 mL of contrast material (protocol A). Then all patients were randomly assigned to one of two protocols (protocol B, CT at 90 kV with 100 mL contrast material; protocol C, CT at 90 kV with 80 mL contrast material). The CT numbers of their abdominal organs were assessed quantitatively and qualitatively. Statistical analysis was performed by using the two-tailed paired t test, Kruskal-Wallis test, and kappa test of interobserver agreement. The radiation dose was measured with a phantom that consisted of glass-rod dosimeters.


RESULTS
Quantitative analysis revealed that protocols B and C yielded significantly better enhancement of the aorta, liver, pancreas, spleen, and kidney than did protocol A (P < .05). With qualitative analysis, the difference among the three protocols in regard to image quality was not significant. At 90 kV versus 120 kV, the radiation dose reduction in the center of the phantom was 56.8% (6.3 vs 14.6 mGy); in the periphery, it was 46.2% (13.6 vs 25.3 mGy).


CONCLUSIONS
By decreasing the tube voltage, the amount of contrast material can be reduced without image quality degradation. In scans obtained with a low tube voltage, the radiation dose can be reduced as much as 56.8%, and higher contrast material enhancement can be achieved.
Nakayama
Yoshiharu
Y
Department of Diagnostic Radiology, Graduate School of Medical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto 860-8556, Japan.
Awai
Kazuo
K
Funama
Yoshinori
Y
Hatemura
Masahiro
M
Imuta
Masanori
M
Nakaura
Takeshi
T
Ryu
Da
D
Morishita
Shoji
S
Sultana
Shamima
S
Sato
Natsuko
N
Yamashita
Yasuyuki
Y
D000328:Adult; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011446:Prospective Studies; D011829:Radiation Dosage; D011860:Radiography, Abdominal; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media