HBOT BRAIN SPECT
Brain SPECT – Relationship to HBOT
Quantitative Imaging of Brain Function
J. Michael Uszler, M.D.
Santa Monica – UCLA Medical Center
In the last few years Hyperbaric Oxygen Therapy (HBOT) has begun to have a new therapeutic endpoint – the improvement of long-term brain disorders. Brain SPECT imaging has begun to be utilized in evaluating the effects of that therapy.
Imaging of the brain is divided into two classes: anatomic and functional. The two types of anatomic imaging are CT and MRI – "Cat" scanning and magnetic resonance imaging. The question these address is " does the brain’s physical structure look normal or abnormal. But of greater importance is: however the structure appears, is it functioning? If so is the observed function normal or different than normal.
Functional imaging is known as SPECT and PET – single photon emission computed tomography and positron emission tomography. These show brain function because the distribution of an injected radioactive tracer is directly related to functions such as brain blood flow and/or cellular activity. Both of these technologies have been well developed and used routinely over the last fifteen years. (Another form of functional imaging that is being studied for possible future use is fMRI – "functional" MRI. There is presently no experience of using fMRI with HBOT.)
Brain SPECT imaging is the only routinely used imaging evaluation of HBOT. This is because it is the only one that is widely available outside of medical university settings, and because shows blood flow and function in both normal and abnormal functional states. Its basic decision factor is to differentiate normal from abnormal tracer distribution on the scan pictures. This work adequately with localized abnormality such as a stroke, but much less well with what we understand to be more diffuse and variable abnormalities such as near-drowning episodes, toxic substance exposure and long-term neurologic conditions such as cerebral palsy and autism.
Thus the need exists for a quantitative method in which computer-aided analysis can categorize the variability of abnormality and develop standards and databases for normality and specific abnormalities. This makes possible an international registration and database comparison mechanism. I have been using such a method for the last six years to assist in differentiating subtle, true abnormalities, to express brain functional finding in quantitative color-coded images that are easier for other to understand, and compare brain SPECT changes with HBOT.