A team of researchers are developing what they call a “virtual biopsy,” a digital imaging technique that they believe can non-invasively distinguish between Post Traumatic Stress Disorder (PTSD) and Traumatic Brain Injury (TBI) in the brain. The biopsy, if effective, could help focus treatment protocols for scores of veterans returning from tours of duty—many of whom aren’t getting correct diagnoses today.

Nearly 8 percent of Americans will experience PTSD during their lifetimes, but that frequency is much higher among members of the military—an estimated 11 to 20 percent of veterans returning from Iraq have PTSD. To diagnose it, clinicians rely on patients’ self reports of symptoms—things like insomnia, anxiety, and depression—that can sometimes be spotty or unreliable. And especially among veterans, symptoms of PTSD can often look like those for TBI. If the clinician gets the diagnosis wrong, it can delay the patient from getting the right treatment, making it crucial that doctors have diagnostic tools that really work.

Though sufferers of both TBI and PTSD often receive similar drugs to lessen their symptoms, different processes are typically used to treat the two underlying conditions. For example, people with PTSD tend to do best with psychotherapy or other techniques to address the trauma they have experienced.

The team of scientists from nonprofit research company Draper, Harvard Medical School and Brigham and Women’s Hospital in Boston, with funding from the Pentagon’s Congressionally Directed Medical Research Programs office are using a digital imaging technique that detects concentrations of certain chemicals in the brain. And they believe this will allow correct diagnosis of PTSD and TBI based on physical, rather than psychological symptoms.

Previous research has indicated that brains that have undergone PTSD synthesize certain neurotransmitters, such asglycerophosphoethanolamines (found in the membranes of cells) and a fatty acid called PEA, in different concentrations than do healthy brains. That’s likely tied to the neurological mechanism of developing PTSD in the first place, which has to do with the brain’s stress response.

To perform the virtual biopsy, the researchers take a scan of the patient’s brain using a technique called magnetic resonance spectroscopy (MRS). This forms a crude image of the brain, but that’s not the researchers’ primary goal. “We’re really interested in the spectrum, the peaks that identify the chemicals in the brain,” John Irvine, the chief data scientist at Draper, told Vocativ. The researchers have been looking at concentrations of chemicals such as glutamate-glutamine, GABA, creatine, and N-acetylaspartate (NAA), which are involved in essential processes such as the rate of cell metabolism and the synthesis of other neurotransmitters (the role of NAA is still a mystery).

They’re not looking for the presence of any one of these neurochemicals in particular—they’re on the hunt for a signature, a particular combination of biomarkers that can indicate disease.

So far, the researchers have tested their technique on 70 people, some of whom have been diagnosed with PTSD or TBI, and some who have not. Though the researchers are starting to see a trend in their biosignatures that come from the MRS reading, they plan to get data on up to 200 participants before the end of the study.

But the path to a useful diagnostic tool might be more complex than the researchers had hoped. By comparing the MRS results between undiagnosed civilians and veterans, the researchers have already discovered a few factors that confound the biosignature, such as a patient’s physical condition (veterans are usually in better shape) and repeated brain trauma less mild than a concussion (that likely happens to military personnel both during training and combat). Those other factors might make it more difficult to distinguish PTSD and TBI based on MRS results.

At the end of this current study, the researchers hope to have discovered a biosignature that can act as a strong enough diagnostic signal to drown out the noise of those confounding factors. If this technique works the way the researchers hope, it could be used not only to better treat patients with PTSD and TBI—other clinicians could someday use MRS to treat chronic pain or to diagnose other conditions centered in the brain, such as chronic traumatic encephalopathy (CTE), thought to be caused by repeated physical trauma, or even brain tumors.

After this study concludes, the researchers would hope to verify their results in a larger trial. If it holds up, the technique would then need to be approved by the Food and Drug Administration (FDA) before it can be used as a diagnostic tool by clinicians everywhere.