A surface coil on the neck causes adiabatic fast passage in blood as it flows by through a magnetic field gradient. This allows separation of blood and stationary tissue images of the head. Coronal and sagittal images of a volunteer are presented showing the vertebral and common, internal and external carotid arteries in projection views.

Multiple averaging can be a powerful tool against motional artifacts if significant motion occurs between the redundant acquisitions taken at a given gradient strength. However, if the time delay between these redundant measurements is too short, data or images depicting the patient is exactly the same position will be combined. Pooling such identical data has no effect on motional artifacts. This problem can be solved by increasing TR, increasing the number of redundant acquisitions, or changing the order in which acquisitions are taken. Usually all acquisitions at a particular value of the warp gradient are taken before proceeding to the next gradient value. This order minimizes motion between redundant acquisitions and so maximizes artifacts. The effect of other acquisition orders on both periodic and nonrepetitive motion is discussed. Human images for breathing and phantom results for single-occurrence motions are presented.

The traditional perfusion rate is based on the amount of fluid flowing longitudinally down the capillaries, often given in ml/100 g tissue/min. In principle, fluid flowing radially out of or into the capillaries can be measured as well. Radial and longitudinal perfusion have the same units but independent values. If spins leave and reenter a capillary several times during a transit, radial perfusion can exceed longitudinal perfusion and it probably does. Radial perfusion measures capillary wall function. Progressively increasing the time between two gradient pulses in a proposed radial perfusion imaging sequence allows more magnetization to move into the vasculature to be dephased or removed. Progressive decreases in gradient strength keep diffusion effects constant allowing isolation of the desired perfusion effects.