Photon-Counting CT Allows for Comprehensive Lung Imaging

Chest CT scans are the preferred imaging method for analyzing lung disease and monitoring its progression. However, CT studies assessing lung function and blood flow require specific protocols that cannot be integrated. Now, a study has discovered that a new CT technology facilitates a comprehensive, simultaneous analysis of lung structure and function, an achievement beyond the capabilities of standard CT.

Researchers at Hannover Medical School (Hannover, Germany) have developed a chest imaging protocol that provides information about the structure and function of the lungs. This protocol employs the recently introduced photon-counting CT technology, which allows for high-quality images at a radiation dose lower than that of a standard chest CT. It also delivers improved spatial resolution and spectral imaging capabilities, which leverage the energy information from X-rays to determine tissue composition. The novel protocol requires advanced software, but no additional hardware. It was tested on 197 patients with varying known and unknown lung function impairments who had clinically indicated CT scans. After an intravenous contrast agent was administered, a photon-counting CT scan was conducted during inhalation, followed by another scan during exhalation. All CT-derived parameters were acquired successfully in 166 patients, reflecting an 85% success rate.

The protocol enabled simultaneous assessment of lung structure, ventilation, vasculature, and perfusion of the parenchyma, the region containing gas-exchanging alveoli, the tiny air sacs involved in the exchange of oxygen and carbon dioxide during respiration. This protocol demonstrated benefits over standard CT. The photon-counting CT protocol has the potential for further applications in lung imaging. It can be crucial for preoperative identification of emphysema areas and perfusion defects in patients with chronic thromboembolic pulmonary hypertension, a progressive disease caused by unresolved blood clots in the lungs. Postoperatively, it facilitated the evaluation of surgical success and was useful in assessing the lungs after lung or stem cell transplant procedures. It may also be valuable in the follow-up of chronic obstructive pulmonary disease and in examining pathological findings in lung tissue. Currently, the researchers are focused on enhancing processing time and bolstering the technique's robustness.

"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 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."

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