Physics of Histotripsy

Christos Georgiades, MD, PhD, Johns Hopkins Hospital, Baltimore, Maryland, describes the physics behind histotripsy, how this technique works to treat hepatic tumors, and how it is different from existing interventional oncology treatments.

Transcript:

Most interventional oncologists are familiar with high intensity focused ultrasound. Histotripsy utilizes ultrasound, but in a different way. High intensity focused ultrasound, or HIFU, kills tissues by focusing high energy ultrasound pulses to increase temperature, thereby killing tissue.

Histotripsy avoids hitting the tissue. It constructs an ultrasound waveform that creates what we call microbubles or cavitations. It's the same way that submarines cause cavitations, or if you move a body in water, you'll cause bubbles in water. And that's because the sudden drop in pressure brings the gasses out of solution momentarily, because they immediately disappear. That disappearing is called an implosion. There’s a low-pressure bubble surrounded by higher-pressure water, and once that disturbance goes away, that microbubble implodes. It's a mini explosion to describe it imperfectly, but adequately, that creates mechanical forces that disrupt and kill the cells without increasing the temperature.

That theoretically has some advantages: by not hitting the tissue, it will not destroy blood vessels or extracellular structures or the matrix, and only kill the cells.

That is the theory. Preliminary results support that, but we need a lot more research and outcomes to make that part of our daily clinical practice.