A medical imaging device that can
create 3D renderings of the entire human body in as little as 20 seconds could
soon be used for a wide variety of research and clinical applications. The
modified positron emission tomography (PET) scanner is faster than conventional
PET scans — which can take an average of 20 minutes — and requires less
radiation exposure for the person being imaged. Researchers presented video
taken by the device last week at the US National Institutes of Health’s
High-Risk, High-Reward Research Symposium in Bethesda, Maryland. The machine
could be especially helpful for imaging children, who tend to wiggle around
inside a scanner and ruin the measurements, as well as for studies of how drugs
move through the body. Standard PET scanners detect γ-rays from radioactive
tracers that doctors inject into the person being imaged. The person’s cells
take up the molecule and break it down, releasing two γ-rays.
A ring-shaped detector positioned
around the person measures the angle and speed of the rays and reconstructs
their origin, creating a 3D map of the cells that are metabolizing the
molecule. The ring is just 25 centimetres thick, however, so physicians can
image only a small portion of the body at a time. Capturing larger areas
requires them to dose the person with more of the radioactive molecule ― it
decays quickly, which means the signal fades fast ― and move them back and
forth through the ring. Researchers solved this problem by connecting eight PET
scanner rings into a 2-metre-long tube that can image the entire body at once.
It creates a rendering in 1/40 of the time of a conventional scanner, using
1/40 of the radiation dose and so reducing the radiation risk. The researchers
can also leave someone in the scanner for longer periods and take
motion-capture images to see how a radioactive tracer spreads through the body.
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