Study on scan timing for dual phase nephrogram

Helical CT scan protocol for dual phase nephrogram (corticomedullary and usual nephrogram) was studied at the different rate of injection of contrast media (2 ml/sec, 3 ml/sec, 4 ml/sec) in 60 patients. Consequently, corticomedullary nephrogram with great difference of CT number between the cortex and the medulla of the kidney was obtained at injection of 3 ml/sec or 4 ml/sec. Usual nephrogram with minimal difference of CT number between the cortex and the medulla was obtained at injection of 2 ml/sec. In conclusion, a scan protocol, which included intravenous injection of contrast media at 3 ml/sec, scan delay of 30 to 35 seconds after injection and scan time of 20 seconds with breath hold, was suitable for having an excellent corticomedullary distinction. The kidneys were re-scanned at 90 seconds after injection of contrast media for usual nephrogram. (author)