The Evolution of Brain Imaging
Thursday, 05 March 2015
From 7.00 to 9.00
Medico-Chirurgical Hall
Professor Alison Murray, Professor of Radiology & Dr Gordon Waiter, Senior Lecturer in MRI Physics, University of Aberdeen
We will be taken on a journey through brain imaging developments over the last 40 years - from the introduction of computed tomography through to modem structural and molecular imaging of the unconscious patient. Key methods will be introduced and their application to important disease burdens explained.
Notes
Minute of meeting held in the Society's Hall, Foresterhill on 5th March 2015.
The President, Professor Mike Greaves, presided.
He introduced the evening's speaker - Professor Alison Murray, Professor of Radiology, University of Aberdeen. Her topic was The Evolution of Brain Imaging.
Her talk was liberally illustrated with images of the various techniques which she described.
Prof Murray started by talking about Roentgen, who discovered X-rays in 1895; she then spoke of air encephalograms which were developed in Baltimore. 1927 saw the first cerebral arteriography but it was not until 1953 that catheter cerebral arteriography was developed using access via the femoral artery.
There were then three revolutions in cerebral imaging - computerised tomography (CT), molecular imaging (SPECT and PET) and magnetic resonance imaging (MRI)
Godfry Hounsfield was an electrical engineer (ex RAF who had worked on RADAR) who developed CT whilst working for EMI. He developed CT in 1975 for which he was awarded the Nobel Prize. (EMI had sufficient money to allow him free reign for his research because of the money their record division made from the sale of Beatles' records). Then came CT angiography and 3D rotation. CT perfusion scans can also be performed, for example in people with stroke.
Turning to molecular scanning, Prof Murray spoke about Professor John Mallard, who developed the Aberdeen section scanner (a form of CT) and then developed Positron Emission Tomography (PET) in Aberdeen resulting in Aberdeen having the first NHS PET scanner. A further development was Single Photon Emission CT (SPECT) which is useful for example in imaging blood flow in Alzheimer’s' Disease. Glucose or specific neurotransmitters can be imaged. Prof Murray showed a SPECT scan of somebody with Parkinson's Disease. Although PET most often uses marked glucose, other tracers are being developed.
MRI was developed in 1979 and the first whole body scan on a patient was performed in Aberdeen. It is especially good at providing excellent anatomical images and so is particularly useful at showing tumours. MRI angiograms can be done and Prof Murray also showed startling images of white matter tracks in the brain.
Functional MRI (fMRI) involves imaging the brain whist it is performing tasks, which causes slight differences in the signals from the part of the brain being used. She said that was particularly useful in conditions such as autism and disorders of consciousness, She mentioned cases of traumatic brain injury in which patients were apparently in a vegetative state but in whom fMRI showed responses to speech or touch.
She talked briefly about possible future developments such as hybrid imaging and the possibility of much quieter MRI machines.
She then handed over to one of her colleagues, Dr Roger Staff, an imaging physicist in Aberdeen. He talked about Alzheimer's disease which was initially described in 1906. In an attempt to try to identify the disease in its early stage, without having to perform lengthy memory tests, surrogate markers have been sought. This would enable clinical trials of possible drug treatments to be performed with fewer participants.
A lot of work has been done on the role of amyloid in Alzheimer's disease but no clinical trials of drugs targeting it have yet shown success. In Aberdeen, Professor Claude Wischik is interested in the role of Tau tangles in Alzheimer's and is conducting a trail of a drug which targets these tangles, rather that the amyloid protein to which all previous drug trials have been aimed - the TauRx trial.
Using various imaging techniques, the team have shown variations in blood flow which has decreased in the control group but increased or stabilised in those on the active drug. The phase lll trial uses a modification of the drug used in the phase ll trial (LMTM rather than MTC) Initially participants had to have an MRI every 3 months but after interim analysis this was reduced to six monthly. Tau tracers are being developed and correlate well with MRI images, thus showing that MRI provides a good surrogate marker.
The President invited questions which included the ethical problems surrounding scanning in vegetative states. Dr Sandy McDonald, retired consultant radiologists who specialised in neuro imaging, spoke about witnessing the initial CT brain scan and the initial MRI scans.
The President thanked the speakers.