Q. All are true regarding role of Computed Tomography in evaluation of hepatic steatosis except
a.attenuation value of hepatic parenchyma is reduced
b.usually performed using unenhanced CT scan
c.has poor sensitivity to detect mild steatosis
d.routine tool for quantification of hepatic steatosis
Ans —d
Hepatic steatosis evaluation by computed tomography (CT) scan is based on the measurement of attenuation value of liver parenchyma, using Hounsfield units (HUs). Different tissue composition will have different attenuation value in HUs, for example, it is usually − 100 HU for fat and around 30– 40 HU for soft tissue.
With hepatic steatosis, the attenuation value of the liver parenchyma is reduced .Absolute liver attenuation value is developed as a quantitative method to measure steatosis . This is generally performed using unenhanced CT scan to avoid the potential changes in attenu- ation after contrast injection despite some studies reporting similar efficacy with contrast-enhanced CT. However, the ac- curacy of the absolute attenuation value for the quantification of hepatic steatosis may be limited by intra- and inter-scanner variability Established quantitative CT techniques of measuring liver-to-spleen attenuation ratio (CT L/S) limit the variability. In these techniques, the spleen, which generally has a lower attenuation value, is used as an internal control.
CT has been reported to be reasonably accurate in diagnosing moderate to severe steatosis but lack the sensitivity to detect mild steatosis.The sensitivity of CT in de- tecting hepatic steatosis ≥ 5% has been reported to be 50.5 to 67.7% using the MRI-PDFF as reference standard
More importantly, the ionizing radiation from CT deters clinician in using it as a routine tool for quantification of hepatic steatosis. The assessment of hepatic steatosis by CT is usually limited to patients who have undergone CT scan for other reasons or to potential liver donor who will need a CT scan of the liver for pre-operative assessment.
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