A new technique could enable clinicians to use X-ray imaging to create images of fast moving organs such as the heart while reducing radiation exposure.
Researchers use X-ray to capture fast moving organs in high resolution
August 12, 2020
by John R. Fischer
, Senior Reporter
A new technique could enable providers to capture the motion of fast moving objects and study biological processes not previously able to be observed with medical X-ray imaging.
Israeli researchers at Bar-Ilan University developed a low-cost approach that takes the form of a movie made up of high-resolution X-ray images to show the motion of objects moving at fast imaging speeds. The inspiration behind the technique is a non-traditional method known as ghost imaging, which not only improves imaging speeds but reduces radiation exposure to patients.
“The high frame rate that the ghost imaging technique has demonstrated in the present work should be beneficial for medical procedures that require information on moving organs, the most prominent one being the heart,” lead researcher, professor Sharon Shwartz, and Ph.D. student Mr. Or Sefi told HCB News. “Imagine that you can get a high-resolution high-frame movie of the moving heart. This way you get not only the information on its anatomy but also on its function.”
X-ray imaging relies on a pixelated camera with each pixel measuring the intensity level of the X-ray beam at a specific position. Capturing higher resolution X-rays images, however, is difficult due to the amount of pixels required and the huge amounts of data that need time to transfer, even when using the faster, single-pixelated detectors instead of pixelated ones. And while there are specialized techniques that use extremely powerful X-rays to overcome this limitation, the X-ray sources required are only available at large synchrotrons found in a few facilities worldwide.
Ghost imaging uses single-pixel detectors that can improve imaging speed and works by correlating two X-ray beams that do not individually carry any meaningful information about an object. One beam encodes a random pattern that acts as a reference and never directly comes into contact with the sample, while the other passes through the object. As little X-ray power comes into contact with the object as it is scanned, the amount of radiation exposure is reduced.
The researchers used the approach to create a movie of a blade rotating at 100,000 frames per second. They first used standard sandpaper mounted on motorized stages to create the reference beam and form a random pattern that was recorded with a high-resolution, slow frame rate pixelated X-ray camera. The stage was moved to each position to enable the X-ray beam to hit a different area of the sandpaper and create random X-ray transmissions, or intensity fluctuations. The pixelated camera from the X-ray beam was then removed and the razor and a single-pixel detector were inserted.
The team moved the motorized stage to irradiate the razor with intensity fluctuation patterns introduced at various positions of the sandpaper. They then measured the total intensity after the beam hit the object by using the single-pixel detector.
By synchronizing the measurements with the blade’s movements, the researchers correlated the reference pattern with intensity measured by the single-pixel detector for each position of the blade to create a final image. This, in effect, created a movie of the moving blade by performing image reconstruction frame-by-frame to capture the blade at different positions. The movie clearly showed the motion with a spatial resolution of about 40 microns, which is nearly an order of magnitude better than the resolution of currently available medical imaging systems.
Shwartz and Sefi say the technique can be used with any X-ray source and can enable clinicians to use X-rays to measure fast dynamics outside the lab. They are continuing to make improvements to the overall system and the image reconstruction algorithm for greater resolution and shorter measurement times.
“We are seeking to improve the reconstruction algorithm to reduce the number of diffuser scans,” they said. “This, in effect, will reduce overall imaging time while improving spatial resolution by fabricating diffusers with smaller features.
The findings were published in Optics Express.