Functional Imaging in the Neurosciences
The Role of Positron Emission Tomography (PET),Magnetic Resonance Emission Imaging (MRI) and
Single Positron Emission Computed Tomography (SPECT)
A/Prof. M.J. Fulham
Director of the Department of Positron Emission Tomography (PET) and Nuclear
Medicine,
Royal Prince Alfred Hospital, Camperdown
Sydney, Australia.
Date: May 6, 1998
Location: Australian Museum
ABSTRACT
Functional imaging describes techniques that provide data about the aspects of tissue metabolism, such as glucose and protein metabolism when compared with images of anatomy obtained with Computed Tomography (CT) and clinical Magnetic Resonance (MR). A mathematical model can be derived to describe the biochemical process under study, making it possible to covert the raw counts of radioactivity detected by the scanner into units of physiological function in-vivo, eg. the cerebral metabolic rate of glucose and receptor density. However, unlike for PET and SPECT, CT and MR data are obtained without using ionising radiations. Instead, signals are obtained from constituents of selected molecules in the region of interest. This presentation will focus on the emerging role of functional imaging in providing insights into brain function in both research and clinical settings.
Report on the Lecture
by Dr Michael Lake,Hon.Sec., RSNSW
In a profusely illustrated lecture marked by admirable clarity of explanation Prof. Fulham first traced the separate development and distinctive features of PET, Magnetic Resonance Imaging (MRI), and Single Positron Emission Computed Tomography (SPECT).
He went on to compare in detail the particular strengths of the contemporary versions of these three procedures. PET gains by imaging anatomical volumes as low as 5uL and can detect lesions and heterogeneity that MRI cannot. PET can show cerebral sites of epilepsy and help decide whether it is operable, and also has a valuable role in assessment of neurodegenerative disorders including dementia and Parkinson's disease. SPECT traces blood flow and easily sees the local acceleration of flow during seizures, but is less quantitative than PET.
As regards the future, Prof. Fulham referred to the superior sensitivity and microresolution associated with the use of lutetium orthosilicate. At UCLA, he said, PET and MRI have been combined, and at Hammersmith (London) development of a 3-D scanner is proceeding. It was most desirable, he added, to work towards simultaneous superior image resolution and reaction specificity.
Dr Edmund Potter
Vice-President