Spin label angiography compares two images by subtraction. The first is obtained after blood in one region is labeled by inversion and flows into a region of interest. Labeling is not used for the second image, so only labeled blood remains in the final angiogram after subtraction. This subtraction is never perfect, but with starting images containing less static tissue signal, the remaining background can be reduced. This can be achieved by observing at the zero crossing following an inversion. Multiple inversions allow one to null the signal from tissues with differing T1 simultaneously. We present equations and sample calculations for inversion times and demonstrate the resistance to subject motions (peristalsis, breathing, speaking) resulting from two inversions. Adequate suppression of static tissue signal allows one to dispense with labeling and subtraction, halving the minimum time needed to acquire an image.

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A new adiabatic inversion pulse is tested for a spin-labeling subtraction angiography method. Adiabatic nature of the pulse is achieved by ramping the gradient during the RF pulse. In addition, with cardiac triggering, any irregularity of the heartbeat would decrease cancellation of the static tissue after subtraction. A 90 degree presaturation pulse applied to prevent this suppresses the background intensity from the static tissue by a factor greater than 2. Slice angiograms of carotid arteries are presented.

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