Nov 5, 2017
In this episode we explore emerging radiology technologies and the new field of Preventative Radiology The info in this show will help you understand your risk for Alzheimer's and cognitive impairment and possibly even concussion related brain changes - and what to ask your doctor to get it ordered correctly.
Our guest, Cyrus Raji MD PhD, is a clinical fellow at the University of California - San Francisco. He completed his combined MD and PhD at the NIH-funded Medical Scientist Training Program at the University of Pittsburgh School of Medicine in 2010. He has worked with leaders in the field including Dr Bennet Omalu (the pathologist played by Will Smith from the movie, Concussion). His current research involves Diffusion Magnetic Resonance Imaging based Edge Density Connectome Mapping for Prediction of Alzheimer's Disease. He is an advisor to the NeuroReader.
Neuroradiology is the branch of radiology focusing on the brain and spinal cord. Ironically, very few radiologists actually have deep expertise in neurodegenerative conditions like Alzheimer's.
An MRI of the Brain- looks at brain structures and is readily available to most anyone through a local doctor. Typically they are simply interpreted by an individual radiologist which may or may not be useful in assessing your risk of Alzheimer's.
A better assessment may be the individual radiologist joining forces with computer programs that perform volumetric analyses of specific brain regions (explained in min 26:38). These volumetric analyses programs assist the radiologist by comparing domains of your brain to a database of normal brains and may give you a more detailed analysis and detect areas of early concern before it is obvious to the naked eye (even a trained one sometimes!). It can also identify other patterns of brain shrinkage - like vascular disease (e.g. strokes, mini-strokes, and suboptimal blood pressure issues), alcoholism, and psychiatric disorders.
The Different Types of Imaging Used for Alzheimer's
1) MRI (Magnetic Resonance Imaging). Looks at the structure of the brain alone. Does not look at function. A brain MRI contains no radiation if it is done without IV contrast.
2) fMRI (functional MRI) measures oxygen reflecting blood flow in the brain. Can identify problematic areas before structural changes are evident. It is overall a more sensitive tool than regular MRI, but for the most part is only available in research setting.
3) "Nuclear imaging" - looks at metabolism in the brain using radioactive tracers that have patterns consistent with Alzheimer's and other dementias. 2 examples of nuclear imaging a) PET-fdg assesses glucose utilization, high cost if not covered by insurance and not as available as MRI b) SPECT scans - not widely available and cost is somewhat prohibitive at this time.
What insights imaging can give you about Alzheimer's Brains
Classic brain atrophy (shrinkage) in Alzheimer's happens in the hippocampal regions in the medial temporal lobes near the middle of the brain. The hippocampi are important in the making (encoding) of new memories. The hippocampi start to shrink up to 3 years before actual symptoms of Alzheimer's begins. And in that area one can get a loss of volume in the temporal lobe.
Posterior cingulate gyrus and precuneus in the brain's parietal lobes can develop problematic changes as well. These areas are important in tracking information and cognitive integration.
What do my MRI volumetric numbers mean?
To be considered abnormal and potentially consistent with Alzheimer's diagnosis - the "magic number" for hippocampal volumes on MRI of the brain (using the Neuroreader or Neuroquant tool) is a number below the 25 percentile (this information is included in the report provided by Neuroreader or Neuroquant). Ventricular volumes, if higher than 75th percentile, may be too big and suggestive of Alzheimer's or another disorder as well.
An Introduction to the field of "Preventative Neuroradiology" (discussed at minute 23:30).
Knowing your risk for Alzheimer's with imaging. It's not the whole story but its good data.
If your MRI is read as "normal" but is noted to have some "periventricular white matter" or white matter changes suggesting "chronic ischemia" and low blood flow - this may not be exactly normal. Remember T2 FLAIR (one way the radiologist views the MRI images where fluids lights up brighter) is the easiest place to see these changes on your MRI. These changes may represent issues like hypertension, diabetes, or artery disease. When there is white matter problems then gray matter disease (or problems with brain cells like neurons) is probably not far behind.
Lifestyle changes seem to be able to impact the hippocampus in a positive direction.
Brain changes classic for CTE (Chronic Traumatic Encephalopathy) that happen as a consequence of concussion/traumatic brain injury may be found within the brain stem. Ventral diencephalon and frontal lobe may be affected as well.
How to Get a Volumetric MRI of your Brain
To get a Volumetric Brain MRI study done so that it can be computer-read by Neuroreader (by the Brainreader company) or NeuroQuant (by Cortechs labs). Make sure to have it done in a "volumetric acquisition" (ie really "thin slices"). Ask the imaging center's MRI technologist:
if the MRI Volumetric scan is done in the "sagittal" orientation with General Electric machine- "acquisition in SBGR" or if the machine is a Siemens machine-acquisition ask for it to be done in "MP-RAGE" or whatever settings the institution uses for volumetric acquisitions.