Focussed ultrasound takes aim at chronic lower back pain

Patients with collapsed intervertebral discs could be one day be treated without the need for invasive surgery, thanks to a system that focuses high intensity ultrasound onto the spine.

The technology, developed by Prof Constantin Coussios and colleagues at the Institute of Biomedical Engineering at Oxford University, allows the ultrasound to be focused at a precise point on the spine.

Chronic lower back pain is one of the most common musculoskeletal conditions worldwide. Patients can require spinal surgery, which can lead to complications.

Partial disc replacement, in which the degenerated gelatinous core of the disc is replaced by an implant, is a less invasive procedure, but leaves a hole in the wall of the disc, through which the implant can leak out.

High-intensity focussed ultrasound (HIFU) is being considered as a potential new approach to treat the condition, in which the technology would be used to liquefy the core of the disc.

But the treatment site is deep within the body, beneath bone and layers of tissue, making it difficult to generate a focused ultrasound beam, according to Coussios.

So the researchers – including Prof Robin Cleveland – have developed a system in which an ultrasound transducer and receiver on the tip of a needle communicate with an external ultrasound array fitted around the patient’s body, he said.

The system consists of three components; a “lego style” modular ultrasound device that can be fitted together and arranged in different shapes and positions around the patient’s body; an implantable ultrasound device at the tip of a needle; and a control system.

“Once the array is configured and positioned over the skin, the next challenge is to figure out how to best drive the individual elements so as to achieve optimal focusing at the intended target,” said Coussios.

This can be done by firing each element of the array in turn and recording the signals as they reach the sensor on the needle, or by firing the transmitter on the needle and recording it as it is received by all of the array elements, he said.

“Either of these techniques can then be used to determine the relative phase between array elements to achieve optimal focussing in the intended tissue target,” said Coussios.