Neuroimaging for “Solutions”
Modern brain function SPECT imaging opens a new door to the clinical management of psychiatric conditions. We look directly at the brain in action and learn what is working and not working properly. This allows us to better understand the difficulties that your brain problems are causing you. In other words, a better diagnosis. Rather, than matching your list of symptoms to a list of symptoms found in a diagnostic manual (DSM), we look at your brain. We use this functional information to choose “targeted therapies,” rather than trial and error “experiments” with medications.
Brain Imaging Methods and Their Roles
Medical brain imaging falls into two primary categories: Anatomy and Function.
This diagram gives an overview of their relationships.
MRI: Magnetic Resonance Imaging
CT: X-ray Computed Tomography
fMRI: “functional” MRI – requires cooperative patient
PET: Positron Emission Tomography
SPECT – Perfusion (blood flow) does not req. cooperation-patient can be sedated
SPECT brain imaging is objective functional information – about how the various brain regions are working. We can see this information in both a resting state, that is when the brain is quiet (not cognitively challenged) in a calm semi-darkened room. This quiet, baseline state still shows a lot of brain activity because the brain is routinely performing many important tasks even when we are consciously in a “quiet” state. A scan also can be performed during a cognitively challenging task to demonstrate how the brain changes its performance when concentrating.
A major advantage of SPECT function imaging is that the scan truly represents the fundamental “tracer” principle. Namely, that we are using a non-pharmacological dose of a substance whose dosage is so minimal that it does not disturb the brain regional function that we want to measure.
This tracer substance was designed to enter the brain in relation to the level of blood flow and function in any given part of the brain. Once the tracer molecule enters the brain cells, they change it chemically so that the molecule stays inside the cell. As a result, we can capture an image of how the brain was working in the few seconds after the tracer is injected. Subsequently, when the patient is scanned, the camera is really only “developing the film” – that is, recording the 3D image of the entire brain’s function which was captured by the tracer.
This advantage allows us to performing scanning on individuals within the autism spectrum, because we inject the test tracer when they are alert, and then they can be sedated so they can lie still in the camera and provide a motion-free scan. The sedating pharmaceutical does not alter the tracer distribution pattern, because it was “fixed” in the brain cells when the person was initially injected.
Therefore the scan represents what the brain is doing when it is injected, rather than when the head is in the scanner.
Using SPECT information for improved brain function “solutions”
We use this injection state factor for performing a “stress test” of the brain. That is, we inject the person while they are performing a cognitive challenge test, rather than in the resting state. Then, by comparing the two different states of function imaging we can tell if brain regions are able to respond to the challenge.
A key example: frontal lobes are able to increase their function in a person with depression, but not in a person who has significant frontal lobe executive dysfunction, whether from ADHD, dementia, or from traumatic or toxic substance injury.
Another example: distinguishing between anxiety, PTSD and depression, or seeing that they are simultaneously present in one person as co-morbidities.
Another example: scanning a person to see the effectiveness of their present medications. If a person with an anxiety state disorder has certain brain regions associated with anxiety still in an overactive state, then one could surmise that either the correct medication is at an inadequate dosage, or that the “wrong” medication is being used.
In this way we use functional information to decide targeted therapies that result in “solutions” of improved brain function.