Acoustic Targeted Drug Delivery
Encyclopedia
Acoustic targeted drug delivery (ATDD) is a method that uses ultrasound energy to enhance the transport of molecule
s into and/or across specific tissue
s. Generally this class of ultrasound energy falls under the class of therapeutic ultrasound
, and ranges in ultrasonic frequencies of 1-20MHz and Sound intensity
s of 0-30 watts/cm2
The use of ATDD in conjunction with local drug delivery by injection
, topical application and convection enhanced delivery shows promise to significantly enhance the treatment of various diseases in the human body by specifically targeting the drug into the tissue.
, but at much lower powers is applied to tissues in conjunction with the local application of pharmological agent. The ultrasound source (or transducer) is pulsed on and off, and moved in a defined pattern to sonicate the tissue of interest. The pulsing of the ultrasound serves two purposes 1. to agitate the tissue matrix by extending and compressing it, and 2. to keep the tissue from absorbing to much energy and ablating it (or causing necrosis). The manual movement of the transducer allows for control of the sonicated volume of tissue and where the drug may penetrate more readily.
ATDD may be applied:
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s into and/or across specific tissue
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
s. Generally this class of ultrasound energy falls under the class of therapeutic ultrasound
Therapeutic ultrasound
Therapeutic ultrasound refers generally to any type of procedure that uses ultrasound for therapeutic benefit. This includes HIFU, lithotripsy, targeted ultrasounddrug delivery, trans-dermal ultrasound drug delivery, ultrasound hemostasis, and ultrasound assisted thrombolysis.-Physical...
, and ranges in ultrasonic frequencies of 1-20MHz and Sound intensity
Sound intensity
Sound intensity or acoustic intensity is defined as the sound power Pac per unit area A. The usual context is the noise measurement of sound intensity in the air at a listener's location.-Acoustic intensity:...
s of 0-30 watts/cm2
The use of ATDD in conjunction with local drug delivery by injection
Injection (medicine)
An injection is an infusion method of putting fluid into the body, usually with a hollow needle and a syringe which is pierced through the skin to a sufficient depth for the material to be forced into the body...
, topical application and convection enhanced delivery shows promise to significantly enhance the treatment of various diseases in the human body by specifically targeting the drug into the tissue.
How ATDD works
Focused ultrasound similar to High intensity focused ultrasoundHigh intensity focused ultrasound
High-Intensity Focused Ultrasound is a highly precise medical procedure using high-intensity focused ultrasound to heat and destroy pathogenic tissue rapidly through ablation...
, but at much lower powers is applied to tissues in conjunction with the local application of pharmological agent. The ultrasound source (or transducer) is pulsed on and off, and moved in a defined pattern to sonicate the tissue of interest. The pulsing of the ultrasound serves two purposes 1. to agitate the tissue matrix by extending and compressing it, and 2. to keep the tissue from absorbing to much energy and ablating it (or causing necrosis). The manual movement of the transducer allows for control of the sonicated volume of tissue and where the drug may penetrate more readily.
ATDD may be applied:
- Geometrically, for example with a lensLens (optics)A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. A simple lens consists of a single optical element...
or with a spherically curved transducerTransducerA transducer is a device that converts one type of energy to another. Energy types include electrical, mechanical, electromagnetic , chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a...
. - Electronically, by adjusting the relative phases of elements in an array of transducers (a "phased arrayPhased arrayIn wave theory, a phased array is an array of antennas in which the relative phases of the respective signals feeding the antennas are varied in such a way that the effective radiation pattern of the array is reinforced in a desired direction and suppressed in undesired directions.An antenna array...
"). By dynamically adjusting the electronic signals to the elements of a phased array, the beam can be steered to different locations, and aberrations due to tissue structures can be corrected.