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PET Resolution Increases by Leaps and Bounds


Three PET scans of the same heart are compared. One is normal, one at high definition, and one motion frozen HD.

PET stands for Positron Emission Tomography. It is a medical diagnosis and display technology which creates 3D images of organic tissue - such as a living human - in tens of thousands of slices imaged using gamma radiation. These can then be layered together to reconstruct the tissue, virtually.

The gamma irradiator is run down the body from multiple angles such that each slice of the body is captured from multiple vantage points, typically only a few degrees apart. In addition, imaging is performed via tracers inside the body which absorb the radiation. It is a time consuming process, with tracers injected or digested to spread throughout the system and later pass out harmlessly. However, it does create high quality images.

At least it mostly creates high quality images. PET scans suffer quite a bit when they image moving tissue, such as a beating heart. No scan is instantaneous, and as the slices move down, the beating of the heart causes distortion that is hard to remove from the result, as pieces do not line up correctly. A solution to this, that increases the resolution as a side-effect, may have been found.

Researchers at Cedars-Sinai Medical Center in Los Angeles have used in-house developed "motion-frozen" technology in combination with a Siemens high definition PET scanner to spot myocardial defects that would otherwise have been invisible.

The high-definition PET scanner uses "spatially variant detector spatial response" when the image is reconstructed, correcting for distortion and noise that can make images hard to interpret. The motion-frozen technology, originally developed by Piotr Slomka, research scientist at Cedars-Sinai Medical Center, is an image-processing technique that compensates for the motion of the beating heart.

In other words it extrapolates from known data, what the heart would look like if it was not beating, by studying the shape of the heart as the slices are taken, knowing the speed of slice collection and the deformations the heart goes through in its beat cycle.

Because all motion can effectively be eliminated from the image, even minute blurring of tissues can be processed out, effectively doubling the image resolution.

References

"Motion-Frozen" Technology Meets High-Definition PET: Helping Heart Patients

Virtual Dictionary: PET

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