New Imaging Allows Doctors to Watch Spinal Cord During Surgery

By Pat Anson, PNN Editor

A new type of imaging technology could improve the effectiveness of spinal surgeries by allowing doctors to view high resolution images of the spinal cord during surgery.

The technology, known as fUSI or functional ultrasound imaging, is currently used to track neural activity in the brain. Researchers at the University of California Riverside (UCR) and University of Southern California say fUSI could also be used during back surgery to help doctors “see” the spinal cord in real time and how it responds to electrical stimulation. That could improve the success rate of spinal cord stimulators and other devices that use neuromodulation to dull pain signals.

“The fUSI scanner is freely mobile across various settings and eliminates the requirement for the extensive infrastructure associated with classical neuroimaging techniques, such as functional magnetic resonance imaging (fMRI),” lead author Vasileios Christopoulos, PhD, an assistant professor of bioengineering at UCR, said in a press release. “Additionally, it offers ten times the sensitivity for detecting neuroactivation compared to fMRI.”

Christopoulos and his colleagues reported in the journal Neuron that fUSI imaging was used on six people with chronic back pain who had partial laminectomies, a surgery that eases pressure on spinal nerves through the removal of bone or tissue. During the surgeries, clinicians also stimulated the patients’ spinal cords with mild electric signals to test the viability of fUSI.

Until now, it’s been difficult to assess whether a surgery for back pain is working because patients are asleep under anesthesia and cannot provide feedback on their pain levels. The motion caused by a patient’s heart and breathing may also interfere with MRIs and other imaging methods.

“These movements introduce unwanted noise into the signal, making the spinal cord an unfavorable target for traditional neuroimaging techniques,” Christopoulos explained. “With ultrasound, we can monitor blood flow changes in the spinal cord induced by the electrical stimulation. This can be an indication that the treatment is working.”

Images produced by fUSI are clearer and less sensitive to motion. It uses ultrasound waves to track the flow of blood in specific areas. Christopoulos likens it to a submarine that uses sonar to detect objects in the water.

“We have big arteries and smaller branches, the capillaries. They are extremely thin, penetrating your brain and spinal cord, and bringing oxygen places so they can survive,” he said. “With fUSI, we can measure these tiny but critical changes in blood flow.”

Spinal cord stimulators (SCSs) are invasive and have poor success rates. That’s why it’s customary for patients to go through a short trial period before having the devices surgically implanted. With improved monitoring of blood flow during surgery, Christopoulos hopes the success rate of SCSs will improve dramatically.

“We needed to know how fast the blood is flowing, how strong, and how long it takes for blood flow to get back to baseline after spinal stimulation. Now, we will have these answers,” Christopoulos said. “With less risk of damage than older methods, fUSI will enable more effective pain treatments that are optimized for individual patients.”

About 50,000 spinal cord stimulators are implanted annually in the U.S. The devices are often touted as an alternative to opioid pain medication, although a growing number of studies have questioned their safety and efficacy.