Developed at UC Riverside, fUSI (functional ultrasound imaging) enables clinicians to see the spinal cord and map the cord’s response to treatments in real time. A paper published in Neuron details how fUSI worked for six people undergoing electrical stimulation for chronic back pain treatment.
“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),” said Vasileios Christopoulos, assistant professor of bioengineering at UCR who helped develop the technology. “Additionally, it offers ten times the sensitivity for detecting neuroactivation compared to fMRI.”
According to UC Riverside , it has been difficult to evaluate whether a back pain treatment is working since patients are under anesthesia and cannot provide verbal feedback on their pain levels during treatment.
“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,” Christopoulos said in a statement.
The spinal cord is difficult to image with traditional techniques due to motion artifacts, including heart pulsation and breathing.
“These movements introduce unwanted noise into the signal, making the spinal cord an unfavourable target for traditional neuroimaging techniques,” said Christopoulos.
By contrast, fUSI emits sound waves into the area of interest, and red blood cells in that area echo the sound, producing a clear image.
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Christopoulos partnered with the USC Neurorestoration Center at Keck Hospital to test the technology on six patients with chronic low back pain who were scheduled for the pain surgery. No other treatments, including drugs, had eased their severe pain.
For this surgery, clinicians stimulated the spinal cord with electrodes in the hope that the voltage would alleviate the patient’s discomfort and improve their quality of life.
“If you bump your hand, instinctively, you rub it. Rubbing increases blood flow, stimulates sensory nerves, and sends a signal to your brain that masks the pain,” said Christopoulos. “We believe spinal cord stimulation may work the same way, but we needed a way to view the activation of the spinal cord induced by the stimulation.”
The Neuron paper details how fUSI can detect blood flow changes at levels of less than 1mm per second. For comparison, fMRI detects changes of 2cm per second.
“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,” said Christopoulos. “With fUSI, we can measure these tiny but critical changes in blood flow.”
Generally, this type of surgery has a 50 per cent success rate. With improved monitoring of the blood flow changes, Christopoulos hopes this rate will increase.
“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,” he said.
Moving forward, the researchers are also hoping to show that fUSI can help optimise treatments for patients who have lost bladder control due to spinal cord injury or age.
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