New technology developed to capture high resolution images of the human spinal cord during surgery will enable more effective treatment and hopefully bring relief for people with chronic back pain.
The technology is called functional ultrasound imaging, or fUSI, and it allows clinicians to see the spinal cord and map its response to treatment in real time.
According to a new paper in the journal Neuron, fUSI was tested on 6 patients undergoing electrical stimulation of the spinal cord for treatment of chronic lower back pain and was shown to detect blood flow changes with unprecedented detail.
“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),” says Vasileios Christopoulos, assistant professor of bioengineering at the University of California Riverside, who helped develop the technology.
“Additionally, it offers ten times the sensitivity for detecting neuroactivation compared to fMRI.
Until now, the spinal cord has been an unfavourable target for traditional imaging techniques, due “motion artifacts”, like heart pulsation and breathing, that muddy the signal.
But fUSI is less sensitive to background noise. It emits sound waves into the area of interest, which are then echoed back by red blood cells.
“It’s like submarine sonar. Based on the strength and speed of the echo, they can learn a lot about the objects nearby,” says Christopoulos.
The 6 patients enrolled in the study underwent a type of surgery in which clinicians stimulate the spinal cord with electrodes, in hopes to alleviate discomfort and improve 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,” says 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.
“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.”
The results of the study show that fUSI can detect blood flow changes at unprecedented levels of less than 1 millimetre per second. For comparison, fMRI is only able to detect changes of 2 centimetres per second.
“We have big arteries and smaller branches, the capillaries. They are extremely thin, penetrating your brain and spinal cord, and bringing oxygen so they can survive. With fUSI, we can measure these tiny but critical changes in blood flow,” says Christopoulos.
“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 says.
Generally, spinal cord stimulation surgery has a 50% success rate, but Christopolous hopes that this will increase with improved monitoring of blood flow changes.
“With less risk of damage than older methods, fUSI will enable more effective pain treatments that are optimised for individual patients. It is a very exciting development,” he says.
