Transcranial Magnetic Resonance Imaging-Guided Focused Ultrasound with a 1.5 Tesla Scanner: A Prospective Intraindividual Comparison Study of Intraoperative Imaging

Abstract

Background: High-quality intraoperative imaging is needed for optimal monitoring of patients undergoing transcranial MR-guided Focused Ultrasound (tcMRgFUS) thalamotomy. In this paper, we compare the intraoperative imaging obtained with dedicated FUS-Head coil and standard body radiofrequency coil in tcMRgFUS thalamotomy using 1.5-T MR scanner. Methods: This prospective study included adult patients undergoing tcMRgFUS for treatment of essential tremor. Intraoperative T2-weighted FRFSE sequences were acquired after the last high-energy sonication using a dedicated two-channel FUS-Head (2ch-FUS) coil and body radiofrequency (body-RF) coil. Postoperative follow-ups were performed at 48 h using an eight-channel phased-array (8ch-HEAD) coil. Two readers independently assessed the signal-to-noise ratio (SNR) and evaluated the presence of concentric lesional zones (zone I, II and III). Intraindividual differences in SNR and lesional findings were compared using the Wilcoxon signed rank sum test and McNemar test. Results: Eight patients underwent tcMRgFUS thalamotomy. Intraoperative T2-weighted FRFSE images acquired using the 2ch-FUS coil demonstrated significantly higher SNR (R1 median SNR: 10.54; R2: 9.52) compared to the body-RF coil (R1: 2.96, p < 0.001; R2: 2.99, p < 0.001). The SNR was lower compared to the 48-h follow-up (p < 0.001 for both readers). Intraoperative zone I and zone II were more commonly visualized using the 2ch-FUS coil (R1, p = 0.031 and p = 0.008, R2, p = 0.016, p = 0.008), without significant differences with 48-h follow-up (p ≥ 0.063). The inter-reader agreement was almost perfect for both SNR (ICC: 0.85) and lesional findings (k: 0.82–0.91). Conclusions: In the study population, the dedicated 2ch-FUS coil significantly improved the SNR and visualization of lesional zones on intraoperative imaging during tcMRgFUS performed with a 1.5-T MR scanner.

MR-guided focused ultrasound–induced blood-brain barrier opening for brain metastasis: a review

“…Currently, the most common clinical and experimental tFUS setups use an FUS system coupled with a 1.5-or 3-T MRI machine (MR-guided FUS [MRgFUS]). The use of an MRI scanner allows realtime monitoring and feedback during sonication by MR thermometry, 7 acoustic monitoring, and intraoperative imaging, [8][9][10][11] which together with real-time patient feedback results in a groundbreaking closed-loop technology. Specifically, MR thermometry can measure absolute temperature or temperature changes, allowing for noninvasive monitoring of the thermal distribution and heat deposition in real time during MR-guided procedures.…”

Comprehensive Evaluation of Factors Affecting Tremor Relapse after MRgFUS Thalamotomy: A Case-Control Study

“…Over recent years, Magnetic Resonance-guided Focused Ultrasound (MRgFUS) thalamotomy has become an attractive treatment for medically intractable tremor due to Essential Tremor (ET) or Parkinson’s Disease (PD); the technique shows clinical effectiveness with minimal invasiveness compared to other treatments [ 1 , 2 , 3 , 4 , 5 , 6 ]. With accumulating experience and research, many critical aspects of MRgFUS have significantly evolved, namely patient selection criteria, surgical targeting, and technique optimization [ 7 , 8 , 9 , 10 , 11 , 12 ].…”