Patient dose and image quality from the low kilovoltage dynamic liver computed tomography examinations

Background: In cases of patients with chronic liver disease, lesions were often detected in MRI replacing in computed tomography (CT) test because of the difference in X-ray attenuation that is likely to depend on constituent nodules. Therefore, the importance of pre enhancement study at liver dynamic CT scan is being emphasized.

Objective: To find optimal protocol and to reduce radiation dose without compromising image quality while taking low kilovoltage (kVp) liver dynamic CT examination using MDCT.

Subjects and Methods: Fifty patients under follow-up who were diagnosed of liver cancer have been examined using a 16-slice MDCT scanner, CT body dose phantom, and CT performance phantom for simulation. Contrast noise ratio and noise of water using phantom have been measured and Volume Computed Tomography Dose Index has been measured according to examination methods. Three points of liver parenchyma, aorta, and subcutaneous fat has been measured for CT attenuation value and compared with magnification picture archiving and communication system in 200% and region of interest for the same size.

Results: Scanning parameters were 120 kVp-140 mAs, 120 kVp-120mAs, and 80 kVp-280 mAs. The CNR was 6.87, 3.36, and 7.66 HU, respectively. Also, the noise of water was 6.83, 7.36, and 9.04 HU respectively. The CT attenuation value for the liver parenchyma, aorta, and fat is high about 15, 217, and 19 HU, respectively. Also, CTDIvol decreased to about 47.36%.

Conclusion: Four phase liver dynamic CT examination with low CT kVp setup is a useful tactic to reduce radiation dose and also can provide necessary images for clinical diagnosis when compared to the results from three phase liver dynamic CT.