I see what you did there…a (very) brief history of imaging the brain: blood, BOLD and fMRI

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 20^th century, and their development is ongoing in the 21^st, 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.

Origins of ‘neuro’ imaging in 19th Century photography: discussing pioneers and pitfalls with Francesco Nonino (M.D, Neurology)

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.

I see what you did there…a (very) brief history of imaging and the brain: EEG and MEG

I see what you did there…a (very) brief history of imaging the brain: X-rays to CT scans

I see what you did there…a (very) brief history of imaging the brain: MRI

I see what you did there…a (very) brief history of imaging the brain: PET and SPECT

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.

I see what you did there…a (very) brief history of imaging the brain: PET and SPECT

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 20^th century, and their development is ongoing in the 21^st, 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.

Origins of ‘neuro’ imaging in 19th Century photography: discussing pioneers and pitfalls with Francesco Nonino (M.D, Neurology)

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.

I see what you did there…a (very) brief history of imaging and the brain: EEG and MEG

I see what you did there…a (very) brief history of imaging the brain: X-rays to CT scans

I see what you did there…a (very) brief history of imaging the brain: MRI

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.

From here.

PET

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 see what you did there…a (very) brief history of imaging the brain: MRI

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. Though these techniques are mainly children of the 20^th Century, and their development is ongoing in the 21^st, 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.

Origins of ‘neuro’ imaging in 19th Century photography: discussing pioneers and pitfalls with Francesco Nonino (M.D, Neurology)

In the second half of the 19th century, photography made it possible to capture and reproduce ‘objective’ records. I discuss some of the documentary possibilities this opened up in neurology with Francesco Nonino, neurologist and student of both history and photography.

But even a camera can only see what is directly in front of it. Exposing a brain so you can see what is going on within 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.

I see what you did there…a (very) brief history of imaging and the brain: EEG and MEG

Passive measurement of neuronal bio-electromagnetism goes brrr

EEG permitted this for the electrical fields produced by brain functioning and has good temporal resolution: indicating the ‘when?’ of an event with high precision. However, EEG is weaker on the ‘where?’ of spatial resolution and doesn’t provide information on structure, or metabolism. The X-ray based CT represented a major step forward, but has the drawback of exposing the scanned person to a dose of ionising radiation.

I see what you did there…a (very) brief history of imaging the brain: X-rays to CT scans

MRI: Magnetic Resonance Imaging

Overview of milestones in the history of neuroscience. Imaging, including MRI, is on the right column. From [1]

The phenomenon known as nuclear magnetic resonance spectroscopy – as elucidated by the likes of Otto Stern, I. Estermann, Isidor Isaac Rabi, Felix Bloch and Edward Purcell – would evolve into what we know as magnetic resonance imaging only in the 70s, earning Paul Lauterbur and Peter Mansfield Nobel prizes [2,3]. By then it had lost the ‘nuclear’ part of the name as a concession to a perceived PR need: even if nuclear means ‘relating to atomic nuclei’, not just to nukes, nuclear energy or radiation, those associations quite understandably loom large in the public eye.