Susceptibility weighted imaging

SWI is offered as a clinical package by Philips and Siemens but can be run on any manufacturer's machine at field strengths of 1.0 T, 1.5 T, 3.0 T and higher.

SWI uses a fully velocity compensated, RF spoiled, high-resolution, 3D gradient recalled echo (GRE) scan.

It is also common to create minimum intensity projections (mIP) over 8 to 10 mm to better visualize vein connectivity.

This increases the contrast in the magnitude image for objects with low phase values such as veins, iron, and hemorrhage.

SWI is usually run at relatively high resolution (1 mm3) and is extremely sensitive to bleeding in the gray matter/white matter boundaries making it is possible to see very small lesions increasing the ability to detect more subtle injuries.

The bright region in the gradient echo weighted image shows the area affected in this acute stroke example.

Future stroke research will involve comparisons of perfusion weighted imaging and SWI to learn more about local flow and oxygen saturation.

The abnormal venous vasculature in the left occipital lobe extending between the posterior horn of the ventricle and the cortical surface is clearly visible in the venogram.

Part of the characterization of tumors lies in understanding the angiographic behavior of lesions both from the perspective of angiogenesis and micro-hemorrhages.

This key new information may help understand the physiology of MS.[4] The magnetic resonance frequency measured with an SWI scan was shown to be sensitive to MS lesion formation.

[7] A conventional gradient echo T2*-weighted image (left, TE=20 ms) shows some low-signal foci associated with CAA.