246. Analysis of signal-to-noise ratio for a 2-channels coil developed to enable transcranial Magnetic Resonance-guided Focused Ultrasound Surgery (tcMRgFUS) with 1.5 T MRI scanners

Abstract

PurposeIn recent years trans-cranial Magnetic Resonance-guided Focused Ultrasound Surgery (tcMRgFUS) treatments have aroused large scientific and medical interest [1]. Usually, tcMRgFUS systems are integrated with 3 T systems which allow the use of the body RF coil for both real time imaging and MR-thermometry. At University Hospital of Palermo there is the world-first installation of a tcMRgFUS system integrated with a 1.5 T scanner. Here we present the characterization in terms of signal-to-noise ratio (SNR) of a dedicated RF coils suitably developed (by InSightec) to enable tcMRgFUS treatments with 1.5 T MR units. Methods and materialsThe focused ultrasound equipment (ExAblate 4000, InSightec) integrates with an MRI unit operating at 1.5 T (Signa HDxt, GE) and consists of a hemispheric 1024-element phased-array transducer. T2w-FRFSE images were obtained from a dedicated Dose Quality Assurance phantom using the same MRI protocol used for real treatments. ResultsThe dedicated flexible coil resulted in larger SNR values with respect to that achieved using MRI’s body RF coil. In particular, we obtained for the axial plane a SNR equal to 27.5 using dedicated coil whereas it was equal to 2.5 with RF body coil (SNR gain more than 10 times higher). ConclusionWe can conclude that, even though the SNR linearly increases with magnetic field strength, the use of a dedicated coil on a 1.5 T scanner enabled us to obtain images with a SNR roughly 5 times larger than those acquired on 3T scanners using MRI’s body RF coil. This could facilitate the spread of this cutting-edge technology worldwide [2].