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.
Highlights
Transcranial Magnetic Resonance Imaging-guided Focused Ultrasoundis an emerging incisionless stereotactic procedure based on the thermal ablation of a brain area using a high-intensity focused ultrasound (HI-FU) beam
We hypothesize that dedicated head coil significantly increases the image quality and intraoperative lesions detection in patients undergoing tcMRgFUS on 1.5-T Magnetic Resonance (MR), compared to the images acquired using the standard body radiofrequency coil
The dedicated two-channel focused ultrasound (FUS)-Head coil significantly increases the signal-to-noise ratio (SNR) on intraoperative anatomical images when the tcMRgFUS treatment is performed on 1.5-T MR scanner
Summary
Transcranial Magnetic Resonance Imaging-guided Focused Ultrasound (tcMRgFUS)is an emerging incisionless stereotactic procedure based on the thermal ablation of a brain area using a high-intensity focused ultrasound (HI-FU) beam. MR allows to acquire detailed anatomical images to calculate the optimal target coordinates and MR thermometry for real-time thermal monitoring during sonications [7]. On 3.0-T MR scanners, the anatomical images and MR thermometry are typically acquired using standard body radiofrequency coil built in the MR system because the 30-cm-diameter hemispherical FUS helmet, stereotactic frame, and supporting equipment almost fill the whole scanner space and do not allow the placement of specific head coil [9]. High-quality intraoperative imaging is needed for optimal monitoring of patients undergoing transcranial MR-guided Focused Ultrasound (tcMRgFUS) thalamotomy. 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. 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.
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