Poststenotic signal loss in MR angiography: effects of echo time, flow compensation, and fractional echo.

Overview

PURPOSE: To evaluate with steady and pulsatile flow the influence of echo time, gradient strength and duration, and flow compensation on the degree of turbulent signal loss, factors that have been implicated in MR angiography's overestimation of the degree of stenosis. METHODS: We examined poststenotic turbulent flow in two models, one that created a turbulent jet and another that simulated a plaque-like stenosis. The pulse sequence used in these experiments allowed for a single variable (flow compensation, echo time, or gradient strength) to be varied without changing the others. RESULTS: Poststenotic signal loss can lead to overestimation of the degree of a stenosis. The area of signal loss in the turbulent jet was influenced by fractional echo and flow compensation, but not by echo time. We found that the dominant mechanism in poststenotic signal loss is related to the strength and duration of the imaging gradients. CONCLUSIONS: Flow-compensated sequences with reduced gradient strength and duration will reduce poststenotic signal loss and may lead to more accurate estimations of the extent of stenotic lesions.