Types of Scans To Detect Concussion and Brain Injury
- Traditional Gradient Echo or Sequence MRI
- Susceptibility Weighted Imaging (SWI) MRI
- Diffusion Weighted Imaging (DWI) MRI
- Diffusion Tensor Imaging (DTI) MRI
MRI scans are non-invasive which means they do not involve instruments entering the body. MRI scans do not use Gamma radiation or x rays, although CT scans do. Brain injury MRI scans do not require dyes or tracers. There are no known side effects of an MRI scan.
NeuroQuant Volumetric MRI
NeuroQuant® is software used to measure brain atrophy. It processes a standard 3D Brain MRI to create a 3D volumetric image. The software measures the volumes of the structures and compares the information to a database of normal data adjusted for age, gender and cranial volume.
CorTechs Labs, makers of NeuroQuant
Susceptibility Weighted Imaging (SWI) MRI
SWI is an advanced type of MRI and can determine the existence of hemosiderin (specks of dried blood) in the brain thus confirming a previous hemorrhage. SWI imaging is more reliable than conventional MRI for detecting microbleeds. SWI should be done at least two months after the accident. (Time: 1:59 Difficulty: simple-well explained)
Diffusion Weighted Imaging (DWI)
DWI is an advanced type of MRI and measures the movement of water, salt and chemicals through brain tissue to look for areas of restriction by comparing the contrast of the acquired images. In animal models, DWI shows a positive result within 20 minutes of vascular injury. (Time: 13:29 Difficulty: moderate but well explained)
Diffusion Tensor Imaging (DTI)
DTI is an advanced type of MRI and is a modeling of DWI data which measures the direction of diffusion of water through brain tissue. Measurements showing the direction of flow as expected would indicate the lack of injury but flow in abnormal directions identify areas of brain injury.
DTI is currently the most advanced and sensitive MRI available to identify and locate brain lesions from injury. When traditional gradient echo or gradient sequence MRI does not detect a brain injury and symptoms are present to suggest the possibility of concussion or brain injury, a DTI MRI should be performed.
DTI can identify brain injury which conventional MRI cannot. See Review of Magnetic Resonance Imaging and Diffusion Tensor Imaging Findings in Mild Traumatic Brain Injury. In a widely reported study (attributed to sciencedaily.com, 4/23/2009 but which I have not been able to locate), DTI scans found tumors, hemorrhages and obstructions in 63 of 179 patients that were undiscovered using traditional MRI scans.
Interesting video of a DTI MRI scan showing connectivity in the brain (Time: 51 seconds Difficulty: not applicable)
Watch the fibers of “connectivity” in the brain, as seen through diffusion tensor imaging (DTI)
Technical discussion for medical students by Dr. Michael Lipton (chapter 50 of his MRI course), associate professor of radiology at Albert Einstein College of Medicine and associate director of its Gruss Magnetic Resonance Research Center. (Time: 28:36 Difficulty: difficult)
Computed (Axial) Tomography or CT scans
CT is still the imaging method most often used after an accident for initial evaluation of head trauma in the hospital ER because it is:
- effective in detecting intracranial hemorrhages (blood escaping from a ruptured blood vessel) which require immediate neurosurgery;
- less expensive; and
- can be used for patients with metal implants.
Hospital ERs are concerned about serious bleeding in the brain requiring immediate surgery. Very small hemorrhages, while potentially life altering, are generally not life threatening and thus not a concern for trauma doctors in the emergency room. Conventional MRI (T2 weighted gradient-echo) is not much better than CT scans, so CT remains the choice in hospital emergency rooms.
After release from a hospital when head trauma is suspected and a CT scan failed to identify a hemorrhage, SWI and/or DTI MRI should be used instead of CT for the following reasons:
- SWI and DTI MRI provide much more reliable and precise identification and location of very small hemorrhages not visible on CT or conventional MRI. Conventional CT and MRI scans …”do not adequately depict brain injury in mTBI (mild Traumatic Brain Injury) because they are not sensitive to detecting diffuse axonal injuries (DAI), also described as traumatic axonal injuries (TAI), the major brain injuries in mTBI”.
- SWI and DTI MRI can identify useful information regarding the mechanism of the injury
- SWI and DTI MRI can identify the need for treatment, type of treatment and the potential clinical outcome
- CT scans emit Gamma radiation or x rays while MRI does not
Imaging Hemorrhage on traditional MRI and CT (Time: 5:25 Difficulty: moderately difficult)
Traditional Brain MRI Scan
MR Imaging of Hemorrhage – Technical discussion for medical students by Dr. Michael Lipton (chapter 52 of his MRI course), associate professor of radiology at Albert Einstein College of Medicine and associate director of its Gruss Magnetic Resonance Research Center. (Time: 28:11 Difficulty: difficult)