title: Outer volume suppression in steady state sequences (OVSuSS) for percutaneous interventions.
abstract: Magnetic resonance-guided percutaneous interventions with needles require fast pulse sequences with acquisition times less than 1 s to image the needle trajectory within moving organs. To guide the movement of a rigid instrument with high sampling rate, an magnetic resonance imaging method was developed that reduces the acquisition time down to a few hundred milliseconds by restricting the field of view to a small stripe around the instrument trajectory. To maintain the dynamic steady state, saturation pulses for outer volume suppression were inserted into additional repetition time-intervals. These saturation intervals were combined with three sequence variants: a spoiled gradient echo sequence, an echo-shifted steady state free precession and a balanced steady state free precession sequence. The magnetization dynamics were analyzed by means of numerical optimized simulations. Results were compared with phantom experiments and an average signal-to-suppression-ratio of 15.5 could be achieved. With a field of view reduction of up to 12.5% an update rate of six images per second could be achieved. Finally, animal experiments demonstrated the fast and reliable needle tip visualization during percutaneous magnetic resonance-guided interventions with the help of a robotic assistance system.
authors.affiliation: Department of Medical Physics in Radiology, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Jaane
authors.initials: J
authors.lastname: Rauschenberg
authors.forename: Axel J
authors.initials: AJ
authors.lastname: Krafft
authors.forename: Florian
authors.initials: F
authors.lastname: Maier
authors.forename: Patrik
authors.initials: P
authors.lastname: Zamecnik
authors.forename: Wolfhard
authors.initials: W
authors.lastname: Semmler
authors.forename: Michael
authors.initials: M
authors.lastname: Bock
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D003198:Computer Simulation; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods; D009929:Organ Size; D019047:Phantoms, Imaging; D034421:Sus scrofa