Quantitative evaluation of flow in the portal vein. Comparison of bolus tracking magnetic resonance and Doppler color ultrasound

PURPOSE: Magnetic resonance angiography (MRA) can be used to measure flow velocity in the portal vein noninvasively. Our study was aimed at measuring mean flow velocity in the portal vein and section area and overall portal flow with bolus tracking MRA versus color Doppler US. MATERIAL AND METHODS: Twenty healthy volunteers were submitted to presaturation bolus tracking MRA and color Doppler US before and after a 1500 Kcal meal. The images were acquired during breath-holding and analyzed prospectively for the following parameters: mean flow velocity, portal vein caliber and flow, before and after a meal. MRA measurements were made on both baseline images and MIP reconstructions. RESULTS: Before the meal, mean portal flow velocity was 17.07 +/- 3.01 cm/s with MRA versus 17.46 +/- 3.12 cm/s with color Doppler US (r = .85). After the meal, mean velocity was 24.52 +/- 3.8 cm/s with MRA and 24.8 +/- 4.0 cm/s with color Doppler US (r = .85). After the meal, portal velocity increased by 44% with MRA and by 42% with color Doppler US. Before the meal, the portal vein section area was 1.27 +/- .32 cm2 with MRA and 1.17 +/- .29 cm2 with color Doppler US (r = .86), versus 1.52 +/- .30 cm2 with MRA and 1.44 +/- .27 cm2 with color Doppler US (r = .85) after the meal. Portal vein flow was 1248.4 +/- 302.46 mL/min with MRA and 1202.85 +/- 316.12 mL/min with color Doppler US before the meal, versus 2252.45 +/- 523.90 mL/min with MRA and 2202 +/- 576.74 mL/min with color Doppler US (r = .91) after the meal. Portal vein flow increased by 78% with MRA versus 83% with color Doppler US after the meal. DISCUSSION AND CONCLUSIONS: Bolus tracking MRA is an accurate method to quantitate mean velocity, section area and blood flow in the portal vein.