Helical CT during arterial portography: optimization of contrast enhancement and scanning parameters

To determine the optimal scanning parameters for helical computed tomography during arterial portography (CTAP) of the liver.

Single- and double-helix CTAP were performed in 11 and 20 adult patients, respectively, with 200 mL of contrast material (300 mg of iodine per milliliter) injected at a rate of 3 mL/sec via the superior mesenteric artery. Scanning delays were adjusted for single-helix CTAP so the last scan was obtained at 66 seconds. Delays were adjusted for double-helix CTAP so the last scan during the first helix (CTAP-1) was obtained 10 seconds before the end of the injection at 56 seconds and the first scan during the second helix (CTAP-2) was obtained at the end of the injection at 66 seconds.

Single-helix CTAP scans were of poor quality owing to multiple perfusion abnormalities. Lesion detection for double-helix CTAP-1 was 93.2% and was 100% for CTAP-2, and CTAP-2 scans had significantly fewer perfusion abnormalities.

A scanning delay of 60-66 seconds appears to be optimal. The CTAP-1 scans showed no useful information and need not be acquired.