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From X-rays to phase contrast: How do scientists improve image contrast?
With the advancement of medical imaging, the application of X-ray technology is becoming more and more common. Traditional X-ray imaging relies on the attenuation of the intensity of the X-ray beam to generate images, but this method cannot effectively distinguish subtle differences in tissues. However, scientists have recently discovered phase-contrast X-ray imaging, which produces images with higher contrast by observing the phase changes of an X-ray beam after it passes through an object, especially when detecting samples of low-atomic-number elements.
The development of phase contrast imaging technology originated from the observation of interference patterns, which greatly improves the contrast of images.
The basic principle of phase contrast X-ray imaging is that when X-rays pass through matter, not only their intensity is changed, but also their phase is affected. Although this phase change is not easy to measure directly, it can be converted into a change in image intensity for recording. Therefore, phase contrast technology can not only generate projection images, but also be combined with other technologies to obtain richer three-dimensional image information.
In the history of this technology, groundbreaking work dates back to 1895, when Wilhelm Conrad Röntgen first discovered X-rays and recorded images of the human skeleton. In the following decades, scientists continued to improve X-ray technology, but it was not until the mid-20th century that Frits Zernike successfully applied the principles of phase contrast to visible light microscopy. Zernike's discovery earned him a Nobel Prize in 1953, but transferring the concept to X-ray imaging took much longer.
The success of phase contrast X-ray imaging technology fully demonstrates the complex behavior of X-ray beams when passing through matter, which is not as simple as geometric optics.
In the 1970s, with the advent of synchrotron radiation, scientists gradually realized that this radiation was more powerful and flexible than traditional X-ray tubes. This discovery promoted the further development of phase contrast X-ray imaging. In 1965, Ulrich Bangs and Michael Hart's innovations led to the development of the crystal interferometer, a device that provided the basis for subsequent biological imaging. However, conventional X-ray tubes have difficulty meeting the requirements for use of these crystals.
In 2012, Han Wen and his team’s research broke through traditional constraints, using nanoscale phase gratings instead of crystals, and successfully detected sub-nanometer refractive bends in biological samples. With the emergence of these new technologies, scientists have also begun to explore more efficient imaging methods, including imaging technology based on diffraction gratings.
Scientists are committed to promoting phase contrast imaging technology into clinical applications so that this technology can play a greater role in daily medical care.
During the study, scientists discovered several different phase contrast imaging techniques, such as propagation imaging and analyzer-based imaging. Propagation imaging technology mainly relies on the detection of Fresnel fringes and does not require any optical elements. The emergence of this method has greatly simplified the imaging process. Analyzer-based imaging uses a Bragg crystal as an angle filter, reflecting only a portion of the X-rays that meet the Bragg condition, making the image clearer.
As these innovative technologies have developed, research teams have also developed new methods such as edge lighting and grid interferometry, which have been very effective in improving image contrast, especially in medical imaging, making medical treatment more precise and detailed. Recent studies have shown that these advances are not limited to basic pathology testing, but also extend to complex tissue sample analysis, further extending to pre-clinical trials and practical applications.
It is worth noting that some of the latest research results in the scientific community have shown that phase contrast imaging technology has a bright future, especially in the biomedical field, and will be an important tool to help doctors detect diseases earlier or analyze pathological changes. In addition, as the technology gradually matures, these rigorous imaging methods will likely become standard diagnostics, not only improving the accuracy of diagnosis but also improving patient treatment outcomes.
Phase contrast X-ray imaging is gradually maturing. How will medical imaging develop further in the future to reveal details that have not yet been understood?
