Radiology Rounds - September 2010 - Multi-Energy Computed Tomography – New Opportunities In Imaging the Abdomen

In conventional x-ray imaging, including CT, the peak tube voltage (kVp) is a variable setting that affects image contrast, especially that due to differences in attenuation of high molecular weight substances such as iodine and calcium. For example, attenuation due to iodine at 80 kVp is approximately double that at 120-140 kVp. However, if the tube current (mA) is not adjusted appropriately to compensate for lower kVP, high noise levels can degrade CT image quality. This problem is more prevalent on old scanners with relatively low x-ray tube output and when there is increased attenuation by patients of larger body habitus. For this reason, CT has typically been performed at 120-140 kVp in order to obtain images of expected quality to enable physicians to confidently render appropriate diagnoses.