Coupling ultrasound with fine needles for better biopsies

To accurately diagnose medical conditions, needle biopsies must ensure sufficient quality and quantity in a tissue sample. However, current medical needles too often yield inadequate tissue to meet diagnostic needs.

Perra et al. induced cavitation in bovine liver samples via an ultrasonically actuated fine needle.

Longitudinal ultrasound waves were generated by a Langevin transducer and converted into flexural waves within the needle through a waveguide. This resulted in energy amplification toward the needle tip, exactly where the action is intended.

“The tip of the needle oscillates up and down, inducing pressure fluctuations,” said author Heikki Nieminen. “The nucleation sites near the needle start growing into microbubbles. The pressure fluctuations make the bubbles grow and shrink rapidly, and the liquid around the bubbles moves with them, providing localized shear forces that influence tissue.”

“Like shaking a ketchup bottle to get the liquid out, this technique releases energy into the tissue and makes it more fluid,” said author Ken Pritzker.

This process facilitates sample movement up the needle. The affected area is very small, creating little damage in the surrounding tissue.

“We’re starting to demonstrate that this cavitation technology can not only increase the yield of our sample; we can get good quality samples as well,” said author Nick Hayward.

The researchers were able to generate controllably gentle or violent cavitation, as well as apply the ultrasound without any cavitation. They aim to start clinical trials soon and believe the method could be extended from biopsy to applications like drug and gene delivery.

Source: “An ultrasonically actuated fine-needle creates cavitation in bovine liver,” by Emanuele Perra, Nick Hayward, Kenneth P. H. Pritzker, and Heikki J. Nieminen, The Journal of the Acoustical Society of America (2022). The article can be accessed at https://doi.org/10.1121/10.0010534 .