A convenient and fast method for assessing the image quality of hepatic triphasic CT scan

The image quality is paramount in interpreting the hepatic dynamic CT scan. A poor quality image results in repeating the procedure, which is very time-consuming for the patient and staff, and besides, it is not cost-efficient. This study intended to determine the correlation between image quality and the Hounsfield unit (HU) of the liver and its vessels in the arterial and venous phase to define the acceptable range of HUs for hepatic CT images.

The image quality of 146 dynamic CT scans was assessed by qualitative and quantitative methods at Namazi Hospital of Shiraz University of Medical Sciences from September 2019 to August 2021. Two radiologists performed the qualitative evaluation. They categorized the image qualities into three groups; poor, acceptable, and high quality. For quantitative assessment of image quality, the Hounsfield unit of the aorta, hepatic vein, main portal vein, right anterior, right posterior, and left lateral lobe of the liver were evaluated in both arterial and venous phases.

According to the results of the qualitative evaluation of image quality, 59.6%, 17.8%, and 22.6% of triphasic CT scans had good, acceptable, and poor quality, respectively. There was a significant relationship between image quality and Hounsfield units of all ROIs in the arterial phase (P<0.005). Also, a significant relationship was observed between the Hounsfield units of the portal vein right on the anterior and posterior segments of the liver (P<0.03) in the venous phase.

In a high quality triphasic CT scan, the Hounsfield unit of different parts in the arterial phase should be as follows: aorta 310±78, portal vein 150±40, hepatic vein 44±7, right posterior and anterior and left lateral segments of liver 77±11, 77±7 and 78±12. Hounsfield units of the portal vein, hepatic vein, and right posterior and anterior segments of the liver in the venous phase should be 155±27, 167±30, 111±19, and 112±16, respectively.