title: MRI contrast using solid-state, B1-distorting, microelectromechanical systems (MEMS) microresonant devices (MRDs).
abstract: Presently, signal generation in MRI depends on the concentration and relaxivity of protons or other MR-active nuclei, and contrast depends on local differences in signal. In this proof-of-principle study, we explore the use of nonchemical, solid-state devices for generating detectable signal and/or contrast in vitro and in vivo. We introduce the concept of microresonant devices (MRDs), which are micron-sized resonators fabricated using microelectromechanical systems (MEMS) technology. Fifteen-micrometer (15-microm)-thick, coil MRDs were designed to resonate at the 3T Larmor frequency of protons (127.7 MHz) and were fabricated using tantalum (Ta) oxide thin-film capacitors and copper-plated spiral inductors. The performance of MRDs having final diameters of 300, 500, and 1000 microm were characterized in saline using a radio frequency (RF) scanning microscope and a clinical 3T MR scanner. The measured B(1) fields of 300 microm to 1000 microm MRDs ranged from 3.25 microT to 3.98 microT, and their quality factors (Q) ranged from 3.9 to 7.2. When implanted subcutaneously in the flank of a mouse, only MRDs tuned to the resonant frequency of protons generated a measurable in vivo B(1) field. This study lays the foundation for a new class of solid-state contrast agents for MRI.
authors.affiliation: Division of Hematology/Oncology, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA.
authors.forename: Razvan
authors.initials: R
authors.lastname: Ciocan
authors.forename: Robert E
authors.initials: RE
authors.lastname: Lenkinski
authors.forename: Jonathan
authors.initials: J
authors.lastname: Bernstein
authors.forename: Mirela
authors.initials: M
authors.lastname: Bancu
authors.forename: Robert
authors.initials: R
authors.lastname: Marquis
authors.forename: Alex
authors.initials: A
authors.lastname: Ivanishev
authors.forename: Fotini
authors.initials: F
authors.lastname: Kourtelidis
authors.forename: Aya
authors.initials: A
authors.lastname: Matsui
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Borenstein
authors.forename: John V
authors.initials: JV
authors.lastname: Frangioni
mesh_terms: D000818:Animals; D003287:Contrast Media; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D051379:Mice; D055617:Micro-Electrical-Mechanical Systems / Q000295:instrumentation*; D015203:Reproducibility of Results; D012666:Semiconductors; D012680:Sensitivity and Specificity; D014159:Transducers; D014732:Vibration
chemical_list: D003287:Contrast Media