Virtual chest X-ray with phase-contrast imaging detects small-airway obstruction
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Small-airway obstruction, which cannot be seen with conventional X-rays, was observed in a virtual chest X-ray enhanced by phase-contrast imaging, according to study results published in Proceedings of the National Academy of Sciences.
With this detection ability, asthma and COPD could be more clearly displayed to clinicians during screening, according to a press release from KTH Royal Institute of Technology.
“The chest radiography that clinics and hospitals use today plays an important role in detecting respiratory disease, but it is fundamentally limited by the way in which it generates images,” Ilian Häggmark, PhD, postdoctoral researcher at The University Museum of The University of Tokyo and at KTH Royal Institute of Technology, said in the release.
By employing a model that virtually simulates a human chest, Häggmark and colleagues assessed phase-contrast imaging, which the release said is typically used in research labs for small soft tissue samples, to see if this technology could detect solitary pulmonary nodules (6 mm-20 mm) and small-airways better than the conventional X-ray technology in preprocessed virtual patients.
To test for pulmonary nodules, researchers evaluated 80 different regions of interest from the virtual radiographs, each measuring 8 x 8 cm2 and including 0 to 3 nodules. Researchers then assessed each region of interest in a conventional X-ray, phase-contrast X-ray and a control group to determine if one X-ray performed better than the other.
In terms of detection sensitivity and size estimates of nodules, no statistically significant improvement was observed based on the results from both types of X-rays, according to researchers.
On the other hand, edge enhancement of bronchial walls in the phase-contrast X-ray allowed researchers to virtually see airways less than 2 mm in size, as well as their disease-related obstructions, both of which researchers noted cannot be seen with standard clinical X-rays in place because their “measurement accuracy is insufficient” in determining this type of obstruction.
With this technology, pulmonary diseases such as asthma or early-stage COPD may possibly be seen in screening if it is created for clinical use outside of research labs, according to the release.
In terms of how phase-contrast imaging works, researchers wrote that it enhances X-ray attenuation, which plays a major role in displaying contrast in X-ray images. According to the release, this technology captures information on variations in waveforms of X-ray beams that go through a virtual body, and this allows for an image that makes subtle pathological lung changes more visible.
“Phase-contrast X-ray imaging can extract more information at higher resolution using the same amount of radiation dose as in conventional radiography,” Häggmark said in the release.
Reference:
- Early-stage lung disease could be detected with advanced imaging tech. https://www.kth.se/en/om/nyheter/centrala-nyheter/advanced-imaging-tech-could-be-used-to-detect-early-stage-lung-disease-1.1230778. Published Feb. 17, 2023. Accessed Feb. 17, 2023.
Perspective
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Since chronic lung diseases are considered by WHO to be the second leading cause of death worldwide — most recently evident during the COVID-19 pandemic — chest radiography plays a pivotal role in the early detection of lung injuries (eg, idiopathic pulmonary fibrosis).
Although the resolution of clinical chest radiography has improved over the past few decades, it is challenging to detect scant pathological injuries in soft tissue as in lung parenchyma due to poor contrast-to-noise ratio in the soft tissue regime. Propagation-based phase-contrast imaging (PBI) is based on the interference patterns between diffracted and undiffracted waves and allows for improvement in the sensitivity and spatial resolution of lung injuries invisible in conventional clinical X-rays.
In general, Häggmark and colleagues elegantly presented a virtual simulation of phase contrast radiography. They highlighted the enormous impact of phase contrast radiography to enhance the detection of solitary pulmonary nodules or the obstruction of small airways smaller than 2 millimeters. There is a lack of medical imaging-specific architecture algorithms and a high unmet medical need for improving the resolution of pulmonary chest radiography. The use of propagation-based PBI will fulfill these needs by translating “invisible” image data into the underlying subtle pathological changes of lung parenchyma.
Further studies are need to optimize the propagation distance and edge enhancement in regard to different body weights and heights.
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