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A brain injury can affect people differently. The San Francisco brain injury attorneys at Abramson Smith Waldsmith LLP work closely with clients to ensure they receive an accurate diagnosis and appropriate medical treatment for their injuries. Our experience handling such cases and access to medical and investigative experts have enabled us to build a track record of successful results for our clients. To learn more, contact a personal injury lawyer at our law firm to schedule a free initial consultation.
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. 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.
There are three major methods of structural imaging, each of which is commonly admitted into evidence at trial with the proper expert foundation:
Of course, X-rays have been around for a very long time (1895) and are excellent at showing skull fractures and other bony injuries. They are of no assistance in visualizing or differentiating soft tissues like the brain.
Computed tomography is based on the measurement of the amount of energy that the head absorbs from a beam of radiation that passes through it from a source to a detector. The radiation source and detector within a CT scanner are mounted opposite one another along a circular track, or gantry, allowing them to rotate rapidly in a synchronized manner around the table on which the patient lies.
A computer controls the radiation source, the rotation of the radiation tube and the detector, and the movement of the table. Measurements taken in anatomical slices, or tomograms, are then stored on a computer. The “tome” in tomography is the Greek word for “slice.”
CT scans capture density, or mass per unit volume. Pixel intensities are mapped to allow reliable discrimination between different densities of tissue such as air, water, fat, bone and various brain components. The more dense the material (e.g., metal or bone), the brighter it appears in CT images. In turn, less dense tissue (e.g., fat and water) appears darker.
CT scans reveal much more detail than a regular X-ray. Physicians have the option of studying a scanned brain one slice at a time or stacking the slices to create a full 3D model. CT scans are the gold standard for showing brain swelling, brain bleeds, enlarged ventricles (containing cerebrospinal fluid) and encephalomalacia.
Magnetic resonance imaging (MRI) interprets signals derived from water molecules. The human body is full of water molecules, each of which has two hydrogen nuclei (H2O) also known as protons. These protons line up in the direction of the imposed magnetic field and radio waves (i.e., a signal) detectable by the scanner. The computer uses this signal to produce high resolution images. MRI can distinguish between fat, air, blood and water of a given structure in the brain. No radioactive material is necessary to obtain this image so the scan is harmless. MRI produces two-dimensional images that consist of individual slices of the brain. The latest technology allows the slices to be lined up to create a full 3D model of the brain.
The MRI table or scanner does not move to cover different slices in the brain. Rather, images can be obtained in any plane through the head by electronically “steering” the plane of the scan. The switching on and off of these magnetic field gradients are the source of the loud clicking and whirring noises that are heard during an MRI scan. This process requires more time than CT scanning.
MRI scans are used to image all areas of the body but are particularly useful for visualizing tissues with many hydrogen nuclei or protons and little density like the brain, muscles, tumors etc. MRI scanners come in different magnetic powers. They vary from 1.5 Tesla, 3.0 Tesla, 4.0 Tesla to 7.0 Tesla. The rule is the higher the Tesla magnetic rating, the higher the resolution of the scan. It is preferable to at least obtain a 3.0 Tesla if possible.
CT Scan Vs. MRI
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.
Advantages of Brain CT Scans
- CT scans are much faster than MRI, thus preferred in cases of emergency and trauma
- CT scans cost less than MRI
- CT scans are less sensitive to patient motion during the examination
- CT scans are usually easier for claustrophobic patients to handle
- CT scans present no risk to patients with implantable medical devices, such as pacemakers
Advantages of Brain MRI
- MRI does not use ionizing radiation, thus is preferred in children
- MRI depicts brain anatomy and abnormalities in greater detail
- MRI does not require the patient to physically move
- MRI presents a much smaller risk of causing potentially lethal allergic reaction
- MRI can show structures that may be obscured by bone in CT images
Traumatic Brain Injury (TBI) imaging information:
An Introduction to Brain Function Imaging Studies for Traumatic Brain Injury (TBI)