Customized Contrast Media Dose Clinical Trial

1. To determine if a formula derived from PCA using specific patient parameters can be used to determine the individual contrast material dose and provide a more consistent level of vascular and parenchymal enhancement during MDCT scanning of the abdomen and pelvis. 2. Up to 500 adult patients referred for a "CT of the abdomen and pelvis with contrast material" will be recruited to participate in this trial. Single CT axial slices (n=2) will be obtained at the level of the L4 pedicle and the supra-acetabular pelvis using a field-of-view that includes all of the patient. From patient measurements (height, weight, body dimensions), a customized dose of contrast material will be specified according to the derived formula for 400 subjects. One hundred subjects will receive the usual fixed contrast dose. 3. Enhancement data in HU will be measured from the CT scans using manually-placed ROIs on the upper abdominal aorta, main portal vein and liver parenchyma, avoiding visible liver tumors, major blood vessels and artifacts, if present. This enhancement data will be used to determine the patient-to-patient variability.