RecruitingClinical trialStudy of Low-intensity Focused Ultrasound Effects on Heat Evoked fMRI SignalsStudy of LIFU on fMRI pain signals. Participants receive low-intensity focused ultrasound (LIFU) and fMRI scans to measure changes in both resting and heat pain signals. Physiology may also be measured. Questionnaires and symptom monitoring will take place. The study takes place over 4 study visits.