For many patients we can discover – or discount – physical causes of neurological problems ‘in real time’ with a range of imaging and other measurement techniques. Neuroimaging techniques are mainly children of the 20th century, and their development is ongoing in the 21st, but their roots stretch back through the 19th century. For example, photography and its ability to reproduce an enduring ‘objective’ image had a major impact when it was introduced and that extends to the study of the brain.
But a ‘normal’ camera operating in the visible (to us) spectrum of light can only see what is directly in front of it. Exposing a brain so you can see what is going on inside it carries risk. This means that – outside of an autopsy – doing so is only ever going to be justified in a small number of people. A way to investigate the structure and operation of the brain in a non-invasive way was needed.
Like MRI in general, functional MRI depends on differences in magnetic properties that are linked to physiology. The functional bit refers to the fact that MRI can be sensitive to something other than brain structure, like the types of scans covered in the posts linked above. fMRI is sensitive to brain activity. By ‘activity’ in this case we mean something different than the electrical or magnetic fields produced by neurons as measured, via fewer intermediary steps, by EEG or MEG. Activity in fMRI is not directly about neural activity, but about blood.
For many patients we can discover – or discount – physical causes of neurological problems ‘in real time’ with a range of imaging and other measurement techniques. Neuroimaging techniques are mainly children of the 20th century, and their development is ongoing in the 21st, but their roots stretch back through 19th century. For example, photography and its ability to reproduce an enduring ‘objective’ image had a major impact when it was introduced and that extends to the study of the brain.
But a ‘normal’ camera operating in the visible spectrum of light can – like us – only see what is directly in front of it. Exposing a brain so you can see what is going on inside it carries risk. This means that – outside of an autopsy – doing so is only ever going to be justified in a small number of people. A way to investigate the structure and operation of the brain in a non-invasive way was needed.
EEG, and more recently MEG, permitted this by sensing (respectively) electrical and magnetic fields produced by the brain’s operation. MRI, by manipulating atomic nuclei by way of powerful magnets, stimulates and then senses the emission of radiofrequency energy to probe the brain’s structure. CT uses very many x-ray images to construct its 3D data. This time we are going to look at method that make use of even higher energy forms of electromagnetic energy – gamma rays.
The use of gamma rays in medical imaging, especially where it concerns the brain, comes in two principal forms: positron emission tomography (PET) and single-photon emission computed tomography (SPECT). As PET was the first to be described, lets start there by picking apart that acronym:
I’m really nothing more than a photographer. I record what I see.
Jean-Marie Charcot, 7 February 1888
Hi Francesco, tell us a bit about yourself
Hi Ben, thank you for inviting me to your blog! I was born and raised in Udine, a small town in the north-eastern part of Italy, but I currently live in Modena and work in Bologna, at the IRCCS Istituto delle Scienze Neurologiche (Institute of Neurological Sciences). I started off my medical career as a full-time clinician, working my way up through many locums around Italy. It was a hard training but it gave me a chance to strengthen my competences in neurology by applying them to many other medical fields, from rehabilitation to ER, and to experience relationships with patients in diverse settings. I have been interested in epidemiology since my graduation in medical school, and about twenty years ago I made a big change in my career, devoting myself to epidemiology and the methodology of medical research while narrowing the time of spent on clinical practice (though I still do one day a week, since I think that even in a research setting it is important to see patients and listen to them).
My other great interest is in photography, that I have pursued since I was a teenager. I started taking pictures and building my own darkroom in the 1970’s, when photography was entirely analogue. I am self-taught, although I read many books and have attended workshops on various technical and historical topics about photography. My artistic production is often influenced by the relationships between photography and science. I am particularly fascinated by taxonomy, the effort of finding a name for each manifestation of nature, often based on its shape, which photography allows the representation of so accurately.
My interest in Cochrane came in the 1990’s when I was lucky enough to meet and work with Alessandro Liberati. He was an extraordinary person. His energy and enthusiasm were contagious and ten years after he passed I still feel every day his strong legacy. Currently I am co-ordinating editor of the Cochrane Review Group on Multiple Sclerosis and Rare Diseases of the CNS.
You work in neurology and have a passion for photography, as well an interest in the history of both. Is there overlap between these areas of interest?
Definitely. In the second half of the 19th century photography, among other effects, opened up unprecedented documentary possibilities in the scientific world. In fact, photography was announced as a new invention on January 6, 1839, at the French Academy of Sciences. For the first time it was possible to capture a detailed, reproducible image. It made it possible to compare images of the same individual over time or between individuals with similar features. Also, because it was carried out by a machine and produced a direct trace on a physical medium it was considered to be much more ‘objective’ and reliable than, for example, hand-drawn sketches.
Can you tell us about some of the ways photography influenced science and medicine?
The first to systematically use photography in the medical field was a neurologist, Guillaume Duchenne de Boulogne (1806-1875). Duchenne published ‘Mécanisme de la physionomie humaine’, including a series of photographs (taken by Adrien Tournachon, better known as the brother of Nadar, 19th Century photography pioneer) that document Duchenne’s studies of the mimic or facial muscles which are responsible for making expressions. They feature a patient suffering from a peculiar insensitivity of the face, allowing Duchenne to apply metal electrodes to the patient’s skin and electrically stimulate specific muscles. Duchenne’s work aroused great interest among scientists of the time, including Charles Darwin. In 1872 Darwin published ‘The Expression of the Emotions in Man and Animals‘ in which the expressions of humans and primates are analysed and compared, in the context of his evolutionary theories. It included photographs by Duchenne and others.
NeurOnToSomething 