Piezoelectric ultrasonic transducers open up new and innovative therapeutic possibilities that improve or even substitute many established procedures: Minimally invasive and gentle treatment methods with improved therapy success and fewer side effects can be realized using piezoelectric ultrasound transducers. Therapeutic ultrasound refers to methods in which ultrasound is not only a means of diagnosis but also the core element of the therapy, e. g. tissue ablation, targeted drug delivery, ultrasound-assisted thrombolysis, and lithotripsy. Both focused and unfocused ultrasound can be used for these applications.
High Intensity Focused Ultrasound (HIFU) for Noncontact Tissue Ablation
The ultrasound-based ablation of tissue, for example for the removal of tumors in the prostate or uterus, is carried out extracorporeal and is, therefore, noninvasive. For this therapy, high-intensity focused ultrasound (HIFU) is projected into the body with the help of piezoelectric transducer elements. In order to generate a directed wave, many piezo ceramic elements are arranged on a spherical dome and excited synchronously to focus the energy in the shock wave.
These acoustic waves have various effects in the body: In histotripsy, ultrasound produces cavitation bubbles whose mechanical energy causes cells to burst. Thermal ablation using ultrasound generates heat of over 42°C by absorbing the wave energy so that the proteins of the cell structures become denaturated and entire tissue areas are coagulated in the sound focus. HIFU can also be used to treat tremor or epilepsy without medication by targeting specific brain structures with heat. Monitoring in these cases is performed simultaneously by MRT.
PI Ceramic, a global leader in PZT ceramics components and value-added standard and custom piezoelectric transducers, offers a wide range of piezo components that can be used to build HIFU transducers: Discs, plates, and focus bowls are manufactured in customer-specific geometries and electrode designs. Our extensive know-how in the manufacturing technologies of bonding and soldering enables us to assemble and contact these components. The resulting focus elements are suitable for use in strong magnetic fields, for example in MRT applications.
Learn more on How to Generate Ultrasound with Piezoelectric Transducers.
Targeted Drug Delivery: Drug Application within the Body
Targeted drug delivery using HIFU enables the release or activation of drugs at a specific site in the body. Various mechanisms are possible: The basic method is the injection of microspheres filled with medication or gas, which are distributed in the patient's bloodstream during treatment and are only used where they are in the sound field focus. An unstable cavitation caused by ultrasound causes the microspheres to burst and the medication to be released locally.
Gas-filled microspheres can be injected to increase the uptake of therapeutic substances. The stable oscillation of these microspheres produces microcurrents which, in combination with the mechanical energy of the acoustic waves, increase the permeability of the blood vessel walls for the active substance in the blood. This sonoporation mechanism is used, for example, for the reversible opening of the blood-brain barrier – a process that can improve the medicinal therapy of neurodegenerative diseases such as Parkinson's or Alzheimer's significantly.
In sonodynamic therapy, focused ultrasound waves induce the formation of reactive oxygen species (ROS) which act cytotoxically on cells, e.g. in cancer tumors. As with tissue ablation, HIFU is generated for targeted drug delivery procedures using piezoelectric discs, plates, and focus bowls.
Intravascular Lithotripsy with Miniaturized Piezo Components
Intravascular lithotripsy is used in a minimally invasive way to reduce atherosclerotic plaques in blood vessels or at the heart valves as well as life-threatening stenoses. Waves generated by ultrasonic transducers increase the permeability of the blood vessel wall through sonoporation so that the medication can penetrate better and induce the dissolution of plaques.
If a thrombus has already formed, its structure can be loosened with the help of mechanical ultrasound energy. This makes it easier for drugs to penetrate into the thrombus and dissolve it, therefore, ensuring the flow of blood to vital organs and preventing embolisms.
Miniaturized piezo tubes or tiny plates are suitable for intravascular lithotripsy and thrombectomy since they can generate ultrasound waves even when integrated into the finest catheters. PI Ceramic manufactures miniaturized PZT piezoelectric elements with dimensions of less than one millimeter and refines them for specific applications, for example by contacting them with strands or assembling them on substrates.
