New brain scan combines best of both

ScienceDaily reports that the first images from a new type of brain scanner that combines both magnetic and radiation-based imaging have been shown at a recent medical conference.

The new technology is called MR/PET because it allows magnetic resonance and positron emission tomography scans to be conducted at the same time.

MRI uses very strong magnets that align the spin of the atoms in your body. It then sends a radio pulse which knocks the atoms out of alignment.

After the knock, the atoms return to their previous alignment but the time taken will differ, depending on the body tissue. As they return, they send off their own pulse, and this can be picked up and turned into an MR image of the tissue by computer software.

PET involves adding a small amount of oxygen or glucose into the body that the brain uses to do its work. Crucially, the substance has been altered so it is slightly radioactive.

As the brain works, the areas that are most active will be slightly more radioactive, and this can be measured to generate a map of brain activity.

You can create similar maps using functional MRI, but one advantage of PET is that it is especially good at ‘resting PET’, meaning you’re not asked to do any tasks. It just gives a general picture of which brain areas are most active.

This is particularly useful if the medical team think your brain might be structurally intact but may have areas which are under or overactive, or want to know the effects of structural damage in one area on function in the rest of the brain.

PET can also be used to track the effects of specific chemicals in the brain (by making them slightly radioactive and injecting them), which is something that fMRI currently can’t do very well.

Previously, to combine the two scans, someone would have to go into a MR scanner to get a structural image, and then go into a PET scanner to get a measure of activity, and computer software would impose the PET image onto the MR image.

This causes problems because the two images aren’t perfectly aligned and so information gets lost.

Imagine you are trying to fit a photo you took from an airplane onto a street map. You might need to stretch or edit the photo to make it fit properly, and in doing so, you might miss bits out or blur important details.

The reason the combined MR/PET will be useful is that the two scans are taken at exactly the same time, so no information is lost.

It also means patients with fragile brains won’t need to be moved between scanners.

One of the difficulties with combining the types of scanning before is that PET normally uses photomultiplier tubes to detect the effects of radiation, which don’t work in magnetic fields, but now new sensors have been developed which are MR safe.

Unfortunately, I can’t seem to find any images of the new scans online (please let me know if you find or have any!).

However, if you want to know more, Radiology Today magazine has a more in-depth article and Siemens, the creator of the technology, has some information as a webpage and pdf.

Also there’s an image of the scanner from a Cambridge University team also working on the technology.

Link to ScienceDaily on new MR/PET images.
Link to Radiology Today article on the technology.

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