Relationship Between Contrast Media Volume and Tube Voltage in CT for Optimal Liver Enhancement, Based on Body Weight.

Computed Tomography (CT) is widely used in abdominal imaging for a variety of indications. Contrast media (CM) is used to enhance vascular structures and organ parenchyma. Attenuation of the liver makes it possible to recognize hypo- and hypervascular lesions, which are often invisible on unenhanced CT images. Lesions can only be detected in case they are large enough and the contrast with the background is high enough. Heiken et al. showed already in 1995 that a difference in Hounsfield Units (HU) of at least 50 HU is needed to be able to recognize liver lesions \[1\]. On the other hand, patients should not receive more CM than necessarily, because of possible underlying physiological effects \[2-4\]. Although there has been some controversy about this recently, there is no need to give patients more CM than needed, because of increased costs, no quality improvement and their might still be a relationship with contrast induced nephropathy (CIN) \[5\]. Recent publications suggested individualization of injection protocols that can be based on either total body weight (TBW) or lean body weight (LBW) \[6-9\]. In the investigators department an injection protocol based on TBW is currently used. Besides the CM injection parameters, scanner parameters are of influence on the attenuation as well. Because of recent technical developments it became possible to reach a good image quality (IQ) at lower tube voltages \[10\]. When the x-ray output comes closer to the 33 keV k-edge of Iodine, attenuation increases. In short, decreasing the tube voltage increases the attenuation of iodine. Scanning at a lower tube voltage therefore gives rise to even lower CM volumes. Lastly, it would be revolutionary to accomplish a liver enhancement that is homogenous, sufficient for lesion detection and comparable between patients and in the same patients, regardless of weight and scanner settings used.