title: Magnetic resonance elastography using an air ball-actuator.
abstract: The purpose of this study was to develop a new technique for a powerful compact MR elastography (MRE) actuator based on a pneumatic ball-vibrator. This is a compact actuator that generates powerful centrifugal force vibrations via high speed revolutions of an internal ball using compressed air. This equipment is easy to handle due to its simple principles and structure. Vibration frequency and centrifugal force are freely adjustable via air pressure changes (air flow volume), and replacement of the internal ball. In order to achieve MRI compatibility, all parts were constructed from non-ferromagnetic materials. Vibration amplitudes (displacements) were measured optically by a laser displacement sensor. From a bench test of displacement, even though the vibration frequency increased, the amount of displacement did not decrease. An essential step in MRE is the generation of mechanical waves within tissue via an actuator, and MRE sequences are synchronized to several phase offsets of vibration. In this system, the phase offset was detected by a four-channel optical-fiber sensor, and it was used as an MRI trigger signal. In an agarose gel phantom experiment, this actuator was used to make an MR elastogram. This study shows that the use of a ball actuator for MRE is feasible.
authors.affiliation: Department of Radiological Science, Graduate School of Human Health Science, Tokyo Metropolitan University, Higashiogu, Arakawa-ku, Tokyo, Japan. t-numano@hs.tmu.ac.jp
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Numano
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Kawabata
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Mizuhara
authors.forename: Toshikatsu
authors.initials: T
authors.lastname: Washio
authors.forename: Naotaka
authors.initials: N
authors.lastname: Nitta
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Homma
mesh_terms: D000388:Air; D054459:Elasticity Imaging Techniques / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005240:Feasibility Studies; D007089:Image Enhancement / Q000295:instrumentation*; D010173:Palpation / Q000295:instrumentation*; D019047:Phantoms, Imaging; D010812:Physical Stimulation / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014732:Vibration