Hexbyte Glen Cove Detector advance could lead to cheaper, easier medical scans

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New ultrafast photon detectors allow for rapid processing of data from positron emission or X-ray scans without the need for tomography to reconstruct images. This image shows a brain phantom (model) scanned by positron emission using the new technology. Credit: Simon Cherry, UC Davis

Researchers in the U.S. and Japan have demonstrated the first experimental cross-sectional medical image that doesn’t require tomography, a mathematical process used to reconstruct images in CT and PET scans . The work, published Oct. 14 in Nature Photonics, could lead to cheaper, easier and more accurate medical imaging.

The advance was made possible by development of new, ultrafast photon detectors, said Simon Cherry, professor of biomedical engineering and of radiology at the University of California, Davis and senior author on the paper.

“We’re literally imaging at the speed of light, which is something of a holy grail in our field,” Cherry said.

Experimental work was led by Sun Il Kwon, project scientist in the UC Davis Department of Biomedical Engineering and Ryosuke Ota at Hamamatsu Photonics, Japan, where the new detector technology was developed. Other collaborators included research groups led by Professor Yoichi Tamagawa at the University of Fukui, and by Professor Tomoyuki Hasegawa at Kitasato University.

The process of tomography is required to mathematically reconstruct cross-sectional images from the data in imaging that uses X-rays or gamma rays. In PET scans, molecules tagged with trace amounts of a radioactive isotope are injected and taken up by organs and tissues in the body. The isotope, such as fluorine-18, is unstable and emits positrons as it decays.

Ultrafast photon detection

Whenever one of these positrons encounters an electron in the body, they annihilate each other and simultaneously give off two annihilation photons. Tracking the origin and trajectory of these photons theoretically creates an image of the tissues tagged with isotopes. But until now, researchers were unable to do that without the extra step of tomographic reconstruction, because detectors were too slow to precisely determine the arrival times of two photons and thus pinpoint their location based on their .

When the annihilation photons strike the detector, they generate Cherenkov photons that produce the signal. Cherry and his fellow researchers figured out how to detect these Cherenkov photonså with an average timing precision of 32 picoseconds. This meant they could determine where the annihilation photons arose with a spatial precision of 4.8 millimeters. This level of speed and accuracy enabled the research team to produce cross-sectional images of a radioactive isotope directly from the annihilation photons without having to use tomography.

In their paper, the researchers describe various tests they conducted with their new technique, including on a test object that mimics the human brain. They feel confident that this procedure is ultimately scalable to the level needed for clinical diagnostics and has the potential to create higher quality images using a lower radiation dose. Images can also be created more quickly with this method, potentially even in real time during the PET scan, as no after-the-fact reconstruction is needed.

PET scans are currently expensive and are technically limited in some ways, as the full information present in the travel time of the annihilation photons is not captured by current clinical scanners. This new discovery involves a compact equipment setup and could lead to inexpensive, easy and accurate scans of the human body using radioactive isotopes.

Additional coauthors are: Eric Berg at UC Davis; Fumio Hashimoto and Tomohide Omura, Hamamatsu Photonics; Kyohei Nakajima and Izumi Ogawa, University of Fukui.

More information:
Sun Il Kwon et al, Ultrafast timing enables reconstruction-free positron emission imaging, Nature Photonics (2021). DOI: 10.1038/s41566-021-00871-2

Detector advance could lead to cheaper, easier medical scans (2021, October 29)
retrieved 30 October 2021
from https://phys.org/news/2021-10-detector-advance-cheaper-easier-medical.html

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Hexbyte Glen Cove Nature-inspired coatings could power tiny chemistry labs for medical testing and more

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A newly developed coating that allows for certain liquids to move across surfaces without fluid loss could usher in new advances in a range of fields, including medical testing.

This new coating—created in the DREAM (Durable Repellent Engineered Advanced Materials) Laboratory, led by University of Toronto Engineering Professor Kevin Golovin—was inspired by the natural world.

“Nature has already developed strategies to transport liquids across surfaces in order to survive,” says Mohammad Soltani, researcher in the DREAM Laboratory and lead author of a new paper recently published in Advanced Functional Materials.

“We were inspired by the structural model of natural materials such as cactus leaves or spider silk. Our can directionally transport not only , but also low tension liquids that easily spread on most surfaces.”

The innovation has important implications for microfluidics, a field where small quantities of liquids are transported within tiny channels, often less than a millimetre wide. This technique has many applications, one of them being to miniaturize the standard analytical tests that are currently preformed in chemical laboratories.

New polymer coatings, developed by Professor Kevin Golovin and his team at the University of Toronto, show the precision with which liquids can move across surfaces. Credit: Mohammad Soltani / University of Toronto Engineering

By reducing the quantity of sample and reagents required, and automating protocols for working with them, microfluidics can power lab-on-a-chip devices that offer fast, inexpensive medical tests. Proponents hope this could lead to diagnosing multiple conditions in minutes using only a drop or two of blood.

But current microfluidic devices have a key limitation: they can only effectively handle liquids with high surface tension, such as water. This property, also known as cohesion, means that the has a greater tendency to stick to itself than to the sides of the channel it is being transported through.

High surface tension liquids form discrete droplets that can be moved around independently, like raindrops on window glass. Cohesion can even be exploited to pull the liquid droplets along the channel through a process known as .

By contrast, low surface tension liquids, such as alcohols and other solvents, tend to stick to the sides of the channels, and can currently be transported for only about 10 millimetres before the droplet disintegrates. Capillary action no longer applies, so this transport requires an external force, such as magnetism or heat, to move the droplets.

The new coating enables low surface tension liquids to be transported over distances of over 150 millimetres without losing any of the liquid, about 15 times longer than currently possible.

Credit: University of Toronto

The technology uses two newly developed polymer coatings, one of which is more liquid-repellent than the other. Both are composed of liquid-like polymer brushes. The more repellent coating acts as a background, surrounding the less repellent and creating tiny channels along the surface. The channels allow for the liquids to move in a desired pattern or direction without losing any of the liquid during transport or requiring additional energy input.

“Polymer brush coatings reduce the fluid friction and allow the droplets to be transported passively,” says Soltani, “Less friction means more energy is available to transport the liquid. We then create a driving force by designing the channels with specific patterns.”

The ability to transport low surface tension liquids without loss will allow for advancements in lab-on-a-chip devices. Using these unique coatings, researchers have the ability to transport liquids over a longer range, move multiple liquids at the same time along a precise pathway and even merge and split droplets—all without losing any volume or experiencing cross-contamination.

This technology will also help limit waste in research labs. With no residue left behind on the surface of the device and therefore no risk of cross-contamination, researchers can use the same devices over and over again.

“We’re looking at using this technology for microfluidics bioassays, as this is an area where every drop of liquid is precious,” says Golovin. “Our findings also have great potential to advance point-of-care diagnostics, such as liver or kidney disease, where biological marker screening is often performed in non-aqueous media.”

More information:
Mohammad Soltani et al, Lossless, Passive Transportation of Low Surface Tension Liquids Induced by Patterned Omniphobic Liquidlike Polymer Brushes, Advanced Functional Materials (2021). DOI: 10.1002/adfm.202107465

Nature-inspired coatings could power tiny chemistry labs for medical testing and more (2021, October 22)
retrieved 24 October 2021
from https://phys.org/news/2021-10-nature-inspired-coatings-power-tiny-chemistry.html

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