Brain structure and brain function are rarely connected to psychological and psychiatric symptoms. SPECT scanning makes this connection obvious.
Opinions about SPECT scanning in the literature range from miracle to malpractice.
Who should we listen to?
What facts do we have to go on?
How familiar is the speaker with the technology being commenting on?
Are the opinions those of researchers or of clinicians? Clinicians must work with complex clinical presentations which cannot be simplified as is required in research.
Let us look at the facts.
Blood flow has long considered an accurate measure of brain function. The three principal Imaging technologies for measuring blood flow include Positron Emission Tomography (PET) scanning, Single Photon Emission Computerized Tomography (SPECT) scanning (both nuclear medicine techniques) and more recently functional Magnetic Resonance Imaging scanning (fMRI). SPECT takes a snapshot of blood flow while PET and fMRI make movies of blood flow.
PET and fMRI are substantially more expensive to operate than SPECT scanning.
So, practically and clinically we are left with SPECT scanning. But does it work? Is it ready for prime time? Some “experts ” say no while there is a growing group of practitioners who say yes. In cardiology SPECT stress tests have been considered invaluable for two decades For approximately the same period of time SPECT has been approved and recognized as a useful for conditions where brain blood flow is reduced, for example Alzheimer’s disease or traumatic brain injury.
The traditional approach to reading brain SPECT scans only seeks to identify areas of low blood flow and pays no heed to areas of high blood flow. In other words in circumstances where there is variation in blood flow if you don’t use all the data it’s not surprising that SPECT scans are not considered helpful.
If one considers areas of low blood flow, normal blood flow and high blood flow, a new level of clinical clarity is created.
Reading tomographic two-dimensional slices is not easy. This is the traditional data that nuclear medicine and radiology physicians interpret. Using computer-generated 3-D images of brain blood flow produces images which look like a brain. When this approach is coupled with thresholding, something similar to fine-tuning a radio, it gives a clearer picture which is easier to understand for clinicians and patients.
These technological issues are rarely addressed in the literature and if you are not using this technology it is unlikely you will understand these reading/interpretation subtleties. In a recent publication In the American Journal of Neuropsychiatry we looked at these technological differences in detail and found that the sensitivity and specificity was significantly higher and clinically useful using 3-D imaging. The traditional 2D reading techniques were not clinically useful as the sensitivity and specificity of the readings was too low (1).
Thus the confusion in the literature is explained when you understand that people who say SPECT scanning doesn’t work are probably using traditional reading techniques and people who say SPECT scanning works are almost certainly using the 3D reading techniques.
For SPECT scanning to become widely available in psychiatry two things have to happen. First psychiatrists have to learn how to read and make clinical use of SPECT scans. Second they must ask nuclear medicine/radiology for the scans they need. When these two groups begin to understand what they have to offer to each other, SPECT scan imaging will become the gold standard in psychiatry.
We have the technology now, but, we must educate each other on how to use it.
- Conventional SPECT Versus 3D Thresholded SPECT Imaging in the Diagnosis of ADHD: A Retrospective Study, Howard Schneider, John F. Thornton, Marc A. Freeman, Mary K. McLean, Muriel J. van Lierop, Jonathan Schneider Am. J. Neuropsychiatry, 2014, 26(4), pp. 335–343 http://dx.doi.org/10.1176/appi.neuropsych.12110280
John F. Thornton M.D. F.R.C.P.C. Psychiatry. Toronto
Mary K. McLean M.D. F.R.C.P.C. Psychiatry. Toronto
Muriel J. van Lierop M.D. M.G.P.P. Toronto