A Low-Kilovolt (Peak) High-Tube Current Technique Improves Venous Enhancement and Reduces the Radiation Dose at Indirect Multidetector-Row CT Venography

Abstract

The purpose was to evaluate the image noise, contrast-to-noise ratio, and radiation dose at indirect multidetector-row computed tomographic venography (CTV) using a low-kilovolt (peak) (kV[p]) high-tube current technique. Thirty patients underwent indirect CTV of the lower extremity at 120 kV(p) with 170 mA and at 80 kV(p) with 426 mA (CT dose index volumes 11.8 and 9.0 mGy, respectively) on a 64-detector CT scanner. We assessed CT numbers, image noise, and contrast-to-noise ratio of deep (femoral and popliteal) veins. The mean (SD) CT numbers of the femoral and popliteal veins were significantly greater at 80 kV(p) than at 120 kV(p) (142.8 [24.5] and 147.0 [19.4] Hounsfield units [HU], respectively, vs 93.1 [15.5] and 105.0 [14.9] HU, respectively; P < 0.01). The mean (SD) image noise was significantly higher at 80 kV(p) than at 120 kV(p) (11.6 [2.6] and 7.4 [1.4] HU, respectively, vs 8.9 [1.6] and 6.2 [1.5] HU, respectively; P < 0.01). Contrast-to-noise ratios at the femoral and popliteal veins were significantly higher at 80 kV(p) than at 120 kV(p) (6.0 [2.2] and 9.7 [2.4], respectively vs 3.3 [1.8] and 6.9 [2.5], respectively; P < 0.01). At indirect CTV, 80 kV(p) and a high tube current setting yielded significantly improved image quality at a reduced radiation dose compared with 120 kV(p).