Dynamic MR digital subtraction angiography using contrast enhancement, fast data acquisition, and complex subtraction.

A dynamic MR angiography technique, MR digital subtraction angiography (MR DSA), is proposed using fast acquisition, contrast enhancement, and complex subtraction. When a bolus of contrast is injected into a patient, data acquisition begins, dynamically acquiring a thick slab using a fast gradient echo sequence for 10-100 s. Similar to x-ray DSA, a mask is selected from the images without contrast enhancement, and later images are subtracted from the mask to generate angiograms. Complex subtraction is used to overcome the partial volume effects related to the phase difference between the flowing and stationary magnetization in a voxel. Vessel signal is the enhancement of flow magnetization resulting from the contrast bolus. MR DSA was performed in 28 patients, including vessels in the lungs, brains, legs, abdomen, and pelvis. All targeted vessels were well depicted with MR DSA. Corresponding dynamic information (contrast arrival time ta and duration of the arterial phase tav) was measured: ta/tav = 3.4/4.7 s for the lung, 10.3/4.9 s for the brain, 12.8/19.3 for the aorta, 15.2/12.6 s for the leg. MR DSA can provide dynamic angiographic images using a very short acquisition time.