title: Automatic tuning of flexible interventional RF receiver coils.
abstract: Microcontroller-based circuitry was built and tested for automatically tuning flexible RF receiver coils at the touch of a button. This circuitry is robust to 10% changes in probe center frequency, is in line with the scanner, and requires less than 1 s to tune a simple probe. Images were acquired using this circuitry with a varactor-tunable 1-inch flexible probe in a phantom and in an in vitro porcine knee model. The phantom experiments support the use of automatic tuning by demonstrating 30% signal-to-noise ratio (SNR) losses for 5% changes in coil center frequency, in agreement with theoretical calculations. Comparisons between patellofemoral cartilage images obtained using a 3-inch surface coil and the surgically-implanted 1-inch flexible coil reveal a worst-case local SNR advantage of a factor of 4 for the smaller coil. This work confirms that surgically implanted coils can greatly improve resolution in small-field-of-view (FOV) applications, and demonstrates the importance and feasibility of automatically tuning such probes.
authors.affiliation: Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, CA 94305, USA. ross@mrsrl.stanford.edu
authors.forename: Ross D
authors.initials: RD
authors.lastname: Venook
authors.forename: Brian A
authors.initials: BA
authors.lastname: Hargreaves
authors.forename: Garry E
authors.initials: GE
authors.lastname: Gold
authors.forename: Steven M
authors.initials: SM
authors.lastname: Conolly
authors.forename: Greig C
authors.initials: GC
authors.lastname: Scott
mesh_terms: D000818:Animals; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D007719:Knee Joint / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008838:Microcomputers; D011846:Radio Waves; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D025321:Surgery, Computer-Assisted / Q000295:instrumentation* / Q000379:methods; D013552:Swine; D013686:Telemetry / Q000295:instrumentation / Q000379:methods; D014159:Transducers