High-intensity focused ultrasound, or HIFU, is an innovative, noninvasive treatment for prostate cancer as well as for pain caused by cancer that has spread to bones. The ultrasound transducer used for HIFU is similar to those used for diagnostic imaging but it emits sound waves of much higher intensity. Much as a magnifying glass can focus sunbeams to burn a hole in a piece of paper, the HIFU transducer focuses sound waves onto a tiny area of abnormal tissue, generating enough heat to destroy the cells. This treatment is also known as MRgFUS (MRI-guided focused ultrasound) and FUS (focused ultrasound surgery). The technique’s precision makes it possible to destroy cancerous cells without damaging healthy tissue and allows for safely repeating the process as many times as needed. The ultrasound waves can pass through layers of tissue without causing harm until they reach their target. MRI imaging is used both to plan the treatment and to monitor the target’s heat level during the procedure. Depending on the condition being treated, patients may be under general anesthesia (completely asleep) or awake but sedated.