<unk>  beams are precisely<unk>  on a small region of diseased tissue to locally deposit<unk>  levels of energy. The focusing effect of the transducer allows<unk>  sound pressures to be delivered to a focal point without causing unwanted damage to other tissue. This increase in pressure can cause a number of effects including heating and cavitation. The transducers differ from ultrasonic imaging probes which many people are familiar with. In this picture, two examples of<unk>  transducers are shown on the left. They both have acoustic bowl-shaped lenses focus the sound inside the body. For comparison, on the right is an ultrasound imaging probe that might be used for cardiac imaging. *Ultrasound sources may be used to generate regional heating and mechanical changes in biological tissue, e.g. in and cancer treatment.<unk>  ultrasound may be used to generate<unk> ly localized heating to treat cysts and tumors (benign or malignant). This is known as Magnetic Resonance guided<unk>  Ultrasound (MRgFUS) or<unk>  <unk> . These procedures generally use lower frequencies than medical diagnostic ultrasound (from 0.250 to 2 MHz), but significantly<unk> er energies.<unk>  treatment is often guided by MRI.<unk>  ultrasound may be used to break up kidney stones by lithotripsy. *Ultrasound may be used for cataract treatment by phacoemulsification. In 2015 the FDA had requested the 501K Safety tests for SonaCare<unk>  device for the ablation of prostate tissue. Temperature The temperature of tissue at the focus will rise to between 65 and 85 °C, destroying the diseased tissue by coagulative necrosis. If tissue is elevated above the threshold of 60 °C for longer than 1 second this process is irreversible.<unk> er temperatures are usually avoided to prevent boiling of liquids inside the tissue. Each sonication (individual ultrasound energy deposition) treats a precisely defined portion of the targeted tissue. The entire therapeutic target is treated by using multiple sonications to create a volume of treated tissue, according to a protocol developed by the physician. Anesthesia is not required, but sedation is generally recommended. The amount of damage caused in the tissue can be modeled using Cumulative Equivalent Minutes (CEM). The treatment will be done by means of the shape of the cylinder in the tissue, therefore, the ideal formula will be adopted by the primitive Bessel's (Cylinder) function. The ideal formulations of the CEM equation have been supposed as Dewey and Sapareto: with the integral being over the treatment time, R=0.5 for temperatures over 43 °C and 0.25 for temperatures between 43 °C and 37 °C, a reference temperature of 43 °C, and time T is in minutes. The equations and methods described in this report are not intended to represent the only approach for thermal dose estimation; . As an acoustic wave propagates through the tissue, part of it is absorbed and converted to heat. With<unk>  beams, a very small region of heating can be achieved deep in tissues (usually on the order of millimeters). Tissue damage occurs as a function of both the temperature to which the tissue is heated and how long the tissue is exposed to this heat level in a metric referred to as "thermal dose". By focusing at more than one place or by scanning the focus, a volume can be thermally ablated. Thermal doses of 120-240 min at 43 °C coagulate cellular protein and leads to irreversible tissue destruction. There is some evidence that<unk>  can be applied to cancers to disrupt the tumor microenvironment and trigger an immune response, as well as possibly enhance the efficacy of immunotherapy. Mechanical Inertial cavitation At<unk>  enough acoustic<unk> es, cavitation (microbubbles forming and interacting with the ultrasound field) can occur. Microbubbles produced in the field oscillate and grow (due to factors including rectified diffusion), and can eventually implode (inertial or transient cavitation). During inertial cavitation, very<unk>  temperatures occur inside the bubbles, and the collapse during the rarefaction phase is associated with a shock wave and jets that can mechanically damage tissue. Stable cavitation Stable cavitation creates microstreaming which induces<unk>  shear forces on cells and leads to apoptosis. Elaborating, bubbles produced by the vaporization of water due to acoustic forces oscillate under a low-pressure acoustic field. Strong streaming may cause cell damage but also reduces tissue temperature via convective heat loss. Theory There are several ways to focus ultrasound—via a lens (for example, a polystyrene lens), a curved transducer, a phased array, or any combination of the three. This concentrates it into a small focal zone; it is similar in concept to focusing light through a magnifying glass. This can be determined using an exponential model of ultrasound attenuation. The ultrasound<unk>  profile is bounded by an exponentially decreasing function where the decrease in ultrasound is a function of distance traveled through tissue: is the initial<unk>  of the beam, is the attenuation coefficient (in units of inverse length), and z is distance traveled through the attenuating medium (e.g. tissue). In this model, is a measure of the power density of the heat absorbed from the ultrasound field. Sometimes, SAR is also used to express the amount of heat absorbed by a specific medium, and is obtained by dividing Q by the tissue density. This demonstrates that tissue heating is proportional to<unk> , and that<unk>  is inversely proportional to the area over which an ultrasound beam is spread—therefore, focusing the beam into a sharp point (i.e. increasing the beam<unk>  creates a rapid temperature rise at the focus. The ultrasound beam can be<unk>  in these ways: *Geometrically, for example with a lens or with a spherically curved transducer. *Electronically, by adjusting the relative phases of elements in an array of transducers (a "phased array"). By dynamically adjusting the electronic signals to the elements of a phased array, the beam can be steered to different locations, and aberrations in the ultrasound beam due to tissue structures can be corrected. *Assumpt no reflection and absorption from intermediate tissue.
High-intensity focused ultrasound
Bonney myomectomy clamp
Tubal ligation
Ultrasonic transducer
Low-intensity pulsed ultrasound
Uterine myomectomy
Sacrohysteropexy
Glomectomy