Clinical Tools
Neuroimaging in TBI Diagnosis
CT and MRI are the gold standard for detecting structural brain injury — but in mTBI, they are almost always normal. Understanding what imaging can and cannot tell us is essential to understanding why objective biomarker diagnostics are needed.
The Role of Imaging in TBI Assessment
Neuroimaging — principally computed tomography (CT) and magnetic resonance imaging (MRI) — plays a central role in the acute assessment of TBI. CT is the first-line modality in emergency settings due to its speed, availability, and sensitivity to haemorrhage, contusion, and skull fracture. MRI provides superior soft-tissue contrast and is used for subacute and chronic assessment, detecting diffuse axonal injury, white matter changes, and microstructural damage not visible on CT.
For moderate and severe TBI, imaging is diagnostically decisive — it identifies life-threatening lesions, guides neurosurgical intervention, and informs prognosis. However, the vast majority of TBI presentations are mild, and in this population, CT and MRI are frequently normal. The absence of imaging findings does not mean the absence of injury: it means that the injury may have occurred at a cellular and molecular level that current imaging technology cannot resolve.
Imaging and Mild TBI: The Evidence
~90–95%
of patients scanned following mild TBI show no intracranial injury on CT — imaging rules out haemorrhage but cannot confirm or exclude neurological injury at the cellular level
Normal
conventional MRI findings in the majority of mTBI/concussion cases, even when cognitive impairment and prolonged symptoms are present
Minutes
is the time available for sideline and field TBI assessment — advanced imaging modalities require hours and specialist facilities
Cellular
level is where mTBI injury often occurs — below the resolution threshold of standard clinical imaging technology
The Diagnostic Gap
Why Imaging Misses mTBI
mTBI/concussion — is fundamentally a neurometabolic injury. The primary pathophysiology involves ionic flux, glutamate excitotoxicity, mitochondrial dysfunction, and axonal stretching at the cellular level. These processes do not produce the macrostructural changes — haemorrhage, oedema, contusion — that CT and conventional MRI are designed to detect. The result is a diagnostic gap: a patient can have significant neurological injury, measurable cognitive impairment, and prolonged recovery, while every imaging study returns as normal.
Advanced MRI techniques — including diffusion tensor imaging (DTI), susceptibility-weighted imaging (SWI), and functional MRI (fMRI) — can detect microstructural and functional changes following mTBI that are invisible on conventional sequences. However, these modalities require specialised equipment, expert interpretation, and significant time and cost. They are not available at the PoC, are not practical for sideline or field assessment, and are not yet validated for routine clinical use in mTBI. GLIA's biomarker platform is designed to provide the objective injury signal that imaging cannot — rapidly, at the point of need, and without specialist infrastructure.
Imaging Modalities
Current and Emerging Neuroimaging Approaches
CT (Computed Tomography)
First-line emergency imaging for TBI. Fast, widely available, and sensitive to haemorrhage, contusion, and skull fracture. Normal in the vast majority of mTBI cases. Exposes patients to ionising radiation — use is guided by clinical decision rules and risk-benefit assessment, particularly in paediatric populations.
Conventional MRI
Superior soft-tissue contrast compared to CT. Detects diffuse axonal injury, white matter changes, and subacute haemorrhage. Requires specialist equipment and substantially more time and infrastructure than point-of-care assessment. Normal in most mTBI cases on standard sequences.
Diffusion Tensor Imaging (DTI)
Advanced MRI technique that maps white matter tract integrity by measuring water diffusion anisotropy. Can detect microstructural axonal injury invisible on conventional MRI. Requires specialised acquisition and post-processing — not available at point of care.
Susceptibility-Weighted Imaging (SWI)
Highly sensitive to blood products and microhaemorrhages. Detects small haemorrhagic lesions missed by conventional MRI. Useful in subacute assessment but requires specialist MRI equipment and is not practical for acute or field settings.
Functional MRI (fMRI)
Measures blood-oxygen-level-dependent (BOLD) signal as a proxy for neural activity. Can detect functional connectivity changes following mTBI. A research tool — not validated for routine clinical use and not available outside specialist centres.
PET (Positron Emission Tomography)
Detects metabolic and molecular changes in brain tissue using radiolabelled tracers. Can identify neuroinflammation, tau deposition, and metabolic dysfunction following TBI. Highly specialised, expensive, and not applicable to acute or field assessment.
The Objective Signal Imaging Cannot Provide
When imaging is normal and symptoms are the only evidence of injury, clinicians need a better tool. GLIA is being developed to complement clinical assessment and imaging rather than replace CT or MRI where imaging is clinically indicated.