Comparison of transcranial MR-guided focused ultrasound phase correction simulations to clinically measured MRTI

Essential tremor and Parkinson's disease are neurological disorders causing involuntary shaking that affects an estimated 8 million people in the United States. Transcranial Magnetic Resonance-guided Focused Ultrasound (tcMRgFUS) is a noninvasive alternative method of treating tremors to the invasive deep brain stimulation standard treatment. Phase aberration correction is an important component of tcMRgFUS that best focuses the ultrasound beams into the brain. Simulations can be used to characterize the application of phase correction before starting the clinical treatment. They can also be used to compare different methods of phase aberration correction. In this study, three different methods of phase correction and the Magnetic Resonance Thermal Imaging (MRTI) from clinical treatments are created and compared. The simulation was performed by taking the Computed Tomography (CT) scan of a patient's head from clinical treatments and transforming it into MR treatment space. The CT is segmented and run through an acoustic and thermal simulation to simulate temperature rise from tcMRgFUS treatments. We found that the hottest voxel temperatures from clinical phase correction and MRTI had no significance differences for 16 out of 20 simulated patients. The other two methods of phase correction were time reversal and no phase correction. Time reversal on average produced higher temperatures and was significantly different than the other methods. Utilizing a method with no correction was significantly worse than the other methods of phase correction. Based on these findings, we will continue to simulate all clinical treatment patients. ii