OAK BROOK, Ill. – New CT technology allows for a comprehensive, simultaneous evaluation of lung structure and function, something not possible with standard CT, according to a study published in Radiology, a journal of the Radiological Society of North America (RSNA).
Chest CT is the imaging method of choice for analyzing lung disease and tracking changes over time. However, CT studies of lung function and perfusion, or blood flow, require dedicated protocols that cannot be combined.
Researchers in Germany and the Netherlands developed a chest imaging protocol that yields information on structure and function of the lungs as a one-stop-shop procedure. The protocol uses recently introduced photon-counting CT technology. Photon-counting CT enables high image quality at a radiation dose below that of a standard chest CT. In addition, it provides better spatial resolution and options for spectral imaging, which uses energy information from the X-rays to characterize tissue composition. The new protocol requires advanced software but no additional hardware.
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The researchers studied the protocol in 197 patients with clinically indicated CT for various known and unknown lung function impairment. After administration of an intravenous contrast agent, the photon-counting CT scan was taken when the patients inhaled. This was followed by a scan when the patients exhaled.
In 166 patients, the researchers were able to acquire all CT-derived parameters, for a success rate of 85%.
The protocol allowed for simultaneous evaluation of lung structure, ventilation, vasculature and perfusion of the parenchyma, the region of the lungs that contain the gas-exchanging alveoli. The alveoli are tiny air sacs where the lungs and the blood exchange oxygen and carbon dioxide during the process of breathing in and out. The protocol showed advantages over standard CT.
“The improvement in the contrast-to-noise ratio and spatial resolution of the pulmonary blood volume images was substantial,” said study senior author Hoen-oh Shin, M.D., professor of radiology at the Institute of Diagnostic and Interventional Radiology at Hannover Medical School in Hannover, Germany. “In my opinion, the most important advantage is the significantly improved spectral resolution, which enables new applications such as functional imaging of the lungs with CT.”
The photon-counting CT protocol has other promising applications in lung imaging. It can provide important preoperative identification of areas of emphysema and perfusion defects in patients with chronic thromboembolic pulmonary hypertension, a progressive disease caused by blood clots that do not clear from the lungs.