Jerome L Ackerman1,2, Erez Nevo3, Evan J. Zucker1,4, Alec J. Poitzsch1,5, Katherine Vandenberg1,6, Andrew Zhigalin7, Barry Fetics3
1Martinos Center/Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States; 2Harvard Medical School, Boston, MA, United States; 3Robin Medical, Inc., Baltimore, MD, United States; 4Tufts Medical Center, Boston, MA; 5Massachusetts Institute of Technology, Cambridge, MA, United States; 6Florida International University, Miami, FL, United States; 7Johns Hopkins School of Medicine, Baltimore, MD, United States
An MR endoscope with deployable RF coil, integrated preamplifier, varactor remote tuning circuitry, software-controlled tuning, video system and position/orientation tracking sensor was developed. Tuning was controlled by adjusting varactor diode bias voltages via a computer program. The tuned condition was found and continuously maintained by a modified simplex algorithm. Device performance, assessed with phantoms and animal carcasses, was found to achieve 130 μm resolution in a brief scan or 47x the SNR of the body RF coil. Optimization parameters which impose limits on simplex dimensions play major roles in the agility of the algorithm in tracking changing tuning conditions.