Calculation of T2 values versus phase imaging for the distinction between flow and thrombus in MR imaging

In magnetic resonance (MR) imaging the distinction between vascular signal from flowing blood and thrombus of any nature is often difficult. Even though there are qualitative criteria to identify intravascular signal as coming from flowing blood, these can fail, and no definitive statement can be made on the nature of intravascular MR signal. In this study, the authors compared the effectiveness of T2 calculations with that of phase images in distinguishing thrombus from flow. In 13 patients with 21 regions of questionable flow or thrombus, T2 calculations were found to have a sensitivity of 69% and a specificity of 88%. Phase images correctly identified thrombus or flow in all but one case with thrombus. Whenever a thrombus is suspected on the basis of MR magnitude images, reconstruction of phase images is the method of choice. However, for the positive identification of flow, T2 value calculations are often sufficient.