An Introduction

Abstract

When an object vibrates between 20 and 20,000 Hz, it produces an audible sound. In simple terms, sound is a vibration that can be picked up by our ears. Ultrasound is a sound wave with a frequency higher than 20,000 Hz (Fig. 1.1), which is higher than the upper audible limit of hearing. Thus, it cannot be heard by the human ear. Focused ultrasound is a noninvasive treatment procedure that uses ultrasound waves emitted from a transducer outside the body using its penetration and focusing ability to form a focus inside the body. When ultrasound waves fire, a combination of thermal, cavitation, and mechanical effects of the ultrasonic wave produce instantaneous high temperature at the focal point to cause coagulation necrosis of the target tissue. Focused ultrasound is used for the treatment of benign gynecologic diseases including uterine fibroids [1], adenomyosis [2], cesarean scar pregnancy [3] and placenta accreta [4] as well as liver cancer [5], breast cancer [6], pancreatic cancer [7], bone cancer [8], retroperitoneal sarcoma [9], and other solid tumors [10].