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Long Duration Ultrasound (LDU) is a method that uses ultrasound energy to enhance the transport of molecules into and/or across specific tissues. Generally this class of ultrasound energy falls under the class of therapeutic ultrasound, and ranges in ultrasonic frequencies of 1-20 MHz and Sound intensitys of 0-30 watts/cm2[1] 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.[2]
How ATDD works[edit]
Focused ultrasound similar to High intensity focused ultrasound, 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 too 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.[3]
ATDD may be applied:
- 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 due to tissue structures can be corrected.
ATDD and topical drug delivery[edit]
