Types Of Diagnostic Tests
Imaging techniques are becoming more sophisticated each year. The goal is to visualize brain activity and function on the cellular level. Newer techniques routinely used by neuroscientists are becoming more common to prove traumatic brain injury (TBI) claims. A lawyer representing TBI victims must have an intimate knowledge of imaging to effectively bring the strongest case.
For more than 30 years, the San Francisco attorneys at Abramson Smith Waldsmith LLP have obtained results for those who have suffered traumatic brain injuries. We will explain advantages and disadvantages of each imaging test. We’ll ensure an appropriate diagnosis to increase the chance of full compensation for the brain injury.
Learn more about how we can help by calling our office at 415-421-7995 or sending a message to set up an appointment. We offer free initial consultations to address your concerns.
Standard Diagnostic Tests
Three diagnostic tests have been around for many years and are commonly admitted into evidence at trial with proper expert foundation. They include:
- X-rays — These are excellent at showing skull fractures and other bony injuries. They are of no assistance in visualizing or differentiating soft tissues like the brain.
- CT scans — Computed tomography scans reveal much more detail than a regular X-ray. They allow anatomical slices to be reviewed individually or stacked to create a 3D model. Pixel intensities are mapped to allow reliable discrimination between different densities — the more dense the material (e.g., metal or bone), the brighter it appears while less dense tissue (e.g., fat and water) appears darker. CT scans are the gold standard for showing brain swelling, brain bleeds, enlarged ventricles (containing cerebrospinal fluid) and encephalomalacia.
- MRI scans — Magnetic resonance imaging (MRI) interprets signals derived from water molecules. A computer uses this information to produce high-resolution images. An MRI can distinguish between fat, air, blood and water of a given structure in the brain. The latest technology allows the slices to be lined up to create a full 3D model of the brain. MRI scans are particularly useful for visualizing tissues with many hydrogen nuclei or protons and little density, like the brain. MRI scanners come in different magnetic powers. It is preferable to obtain at least a 3.0 Tesla if possible.
CT and MRI are complementary techniques, each with its own strengths and weaknesses. The choice of which examination is appropriate depends upon how quickly it is necessary to obtain the scan, what part of the head is being examined and the age of the patient, among other considerations.
Studies That Focus On Brain Function
These diagnostic imaging studies for traumatic brain injury show the effects without having to rely solely on the testimony of experts. Admissibility in court can become a challenge for some of the structural imaging studies.
Mild and moderate TBIs sometimes have no positive or visible “structural” defects, so one has to rely on the oral testimony of neurologists and neuropsychologists to prove injury. Although psychometric testing performed by these experts can be “objective,” it is not as objective and convincing as seeing the actual injury on a brain imaging study. It is always best to try to correlate psychometric testing with imaging whenever possible.
- PET scans — Positron Emission Tomography has greatly advanced since the 1970s. A small amount of radionuclide (a tracer or isotope) substance is injected into the body. The goal is to wait and see how the brain absorbs and metabolizes the glucose. If the brain does not absorb or metabolize the glucose at all or does so poorly, there is abnormal metabolism (hypometabolism). PET scans provide dynamic information (that can be missed in a CT or MRI) about the working brain and deficits in areas of the brain responsible for attention, memory, mood regulation, etc. The highest resolution available is HRRT (high resolution research tomography), which is available at the University of California, Irvine Brain Imaging Center.
- fMRI — functional MRI measures brain activity and is based on the same technology as the MRI. Both techniques use a strong magnetic field and radio waves (signals) to create detailed images. Whereas traditional MRI creates images only, fMRI looks at blood flow in the brain to detect affected areas. Increased blood flow translates to increased brain activity and vice versa. While its advantages include that it does not use radiation, produces very high resolution images and records signals from all regions of the brain, it continues to be very expensive. As with any test, it has limitations and may not be admissible at trial.
- Single-Photon Emission Computed Tomography (SPECT) scans — provide information regarding blood flow to the brain. A tracer is injected and absorbed as it circulates through the bloodstream. The study shows how blood flows through the brain. SPECT scans are similar to PET scans, but with lower resolution. fMRI is a similar measurement that is safer because no isotopes are used.
Mild and moderate TBI sometimes have no positive or visible “structural” defects, so one has to rely on the oral testimony of neurologists and neuropsychologists to prove injury.
Diffusion Tensor Imaging (DTI)
The newest study, DTI, visually tracks nerve fibers to see if there are disruptions from an injury. It allows one to estimate the damage to nerve fibers that connect the white matter of the brain.
DTI measures the restricted diffusion of water through brain tissue. DTI can be used to track a nerve fiber or path through which information travels in the brain. Tractography shows the path of neural information from the brain, down the spinal cord and to the peripheral nerves. This concept can be imaged and measured.