Tracking voluntary motion with tagging snapshot MR imaging

An imaging technique for rapid assessment of tissue motion was developed by combining spatially selective RF tagging pulses with T1 weighted snapshot MRI. This sequence allows labeling and tracking of skeletal muscle motion during an interval between tagging and the start of image acquisition. Image acquisition is less than 2 seconds without the need for gated acquisition. The basis for this technique is magnetization-prepared gradient echo imaging. The magnetization in a selected imaging section is initially inverted. Subsequently, several RF tags orthogonal to the imaging section are superimposed. Prior to start of a GRASS acquisition using centric phase encoding, voluntary motion begins and is maintained approximately one second until end of image acquisition. Coronal and sagittal tagging images of the thighs in four healthy volunteers were obtained. The displacement of the quadriceps muscles was clearly visible. Peripheral muscular tissues just beneath the quadriceps fascia demonstrated greater displacement compared to the central muscular tissues. With less than 2 second acquisition, this technique is easily performed and has potential for kinematic studies of many mobile parts, including muscles, joints, and viscera.