Regional Pulmonary Morphology and Function: Photon-counting CT Assessment.

Background Experience with functional CT in the lungs without additional equipment in clinical routine is limited. Purpose To report initial experience and evaluate the robustness of a modified chest CT protocol and photon-counting CT (PCCT) for comprehensive analysis of pulmonary vasculature, perfusion, ventilation, and morphologic structure in a single examination. Materials and Methods In this retrospective study, consecutive patients with clinically indicated CT for various known and unknown pulmonary function impairment (six subgroups) were included between November 2021 and June 2022. After administration of an intravenous contrast agent, inspiratory PCCT was followed by expiratory PCCT after a delay of 5 minutes. Advanced automated postprocessing was performed, and CT-derived functional parameters were calculated (regional ventilation, perfusion, late contrast enhancement, and CT angiography). Mean intravascular contrast enhancement in the mediastinal vessels and radiation dose were determined. Using analysis of variance, the mean values of lung volumes, attenuation, ventilation, perfusion, and late contrast enhancement were tested for differences between subgroups of patients. Results In 166 patients (mean age, 63.2 years ± 14.2 [SD]; 106 male patients), all CT-derived parameters could be acquired (84.7% success rate; 166 of 196 patients). At the inspiratory examination, mean density was 325 HU in the pulmonary trunk, 260 HU in the left atrium, and 252 HU in the ascending aorta. The mean dose-length product for inspiration and expiration was 110.32 mGy · cm and 109.47 mGy · cm, respectively; the mean CT dose index for inspiration and expiration was 3.22 mGy and 3.09 mGy, respectively (less than the mean total radiation dose of 8-12 mGy, which is diagnostic reference level). Significant differences (P < .05) between the subgroups were found for all assessed parameters. Visual inspection allowed for voxelwise assessment of morphologic structure and function. Conclusion The proposed PCCT protocol allowed for a dose-efficient and robust simultaneous evaluation of pulmonary morphologic structure, ventilation, vasculature, and parenchymal perfusion in a procedure requiring advanced software but no additional hardware. © RSNA, 2023.

Increased regional ventilation as early imaging marker for future disease progression of interstitial lung disease: a feasibility study.

OBJECTIVES: Idiopathic pulmonary fibrosis (IPF) is a disease with a poor prognosis and a highly variable course. Pathologically increased ventilation-accessible by functional CT-is discussed as a potential predecessor of lung fibrosis. The purpose of this feasibility study was to investigate whether increased regional ventilation at baseline CT and morphological changes in the follow-up CT suggestive for fibrosis indeed occur in spatial correspondence. METHODS: In this retrospective study, CT scans were performed at two time points between September 2016 and November 2020. Baseline ventilation was divided into four categories ranging from low, normal to moderately, and severely increased (C1-C4). Correlation between baseline ventilation and volume and density change at follow-up was investigated in corresponding voxels. The significance of the difference of density and volume change per ventilation category was assessed using paired t-tests with a significance level of p ≤ 0.05. The analysis was performed separately for normal (NAA) and high attenuation areas (HAA). RESULTS: The study group consisted of 41 patients (73 ± 10 years, 36 men). In both NAA and HAA, significant increases of density and loss of volume were seen in areas of severely increased ventilation (C4) at baseline compared to areas of normal ventilation (C2, p < 0.001). In HAA, morphological changes were more heterogeneous compared to NAA. CONCLUSION: Functional CT assessing the extent and distribution of lung parenchyma with pathologically increased ventilation may serve as an imaging marker to prospectively identify lung parenchyma at risk for developing fibrosis. KEY POINTS: • Voxelwise correlation of serial CT scans suggests spatial correspondence between increased ventilation at baseline and structural changes at follow-up. • Regional assessment of pathologically increased ventilation at baseline has the potential to prospectively identify tissue at risk for developing fibrosis. • Presence and extent of pathologically increased ventilation may serve as an early imaging marker of disease activity.

[Diseases of the pleura, thoracic wall and diaphragm]. / Erkrankungen der Pleura, der Thoraxwand und des Zwerchfells.

In the case of lesions of the pleura, the thoracic wall and the diaphragm, chest x­ray is of great relevance in everyday clinical practice. In many clinical situations, it is already sufficient for the initial diagnosis or for monitoring the course of the disease; these include, for example, pleural effusion and pneumothorax. In some cases, however, supplementary cross-sectional imaging may be necessary, e.g., if there is a possible pleural empyema or if the soft tissues of the mediastinum and pleural wall are also affected. Further diagnostic workup is also necessary for more advanced questions such as staging or surgical planning. This article is intended to provide an overview of the most common diseases of the pleura, thoracic wall, and diaphragm with their typical appearances on radiographs and, at the same time, to demonstrate the importance and limitations of conventional diagnostics.

Quantification of dual-energy CT-derived functional parameters as potential imaging markers for progression of idiopathic pulmonary fibrosis.

OBJECTIVES: The individual course of disease in idiopathic pulmonary fibrosis (IPF) is highly variable. Assessment of disease activity and prospective estimation of disease progression might have the potential to improve therapy management and indicate the onset of treatment at an earlier stage. The aim of this study was to evaluate whether regional ventilation, lung perfusion, and late enhancement can serve as early imaging markers for disease progression in patients with IPF. METHODS: In this retrospective study, contrast-enhanced dual-energy CT scans of 32 patients in inspiration and delayed expiration were performed at two time points with a mean interval of 15.4 months. The pulmonary blood volume (PBV) images obtained in the arterial and delayed perfusion phase served as a surrogate for arterial lung perfusion and parenchymal late enhancement. The virtual non-contrast (VNC) images in inspiration and expiration were non-linearly registered to provide regional ventilation images. Image-derived parameters were correlated with longitudinal changes of lung function (FVC%, DLCO%), mean lung density in CT, and CT-derived lung volume. RESULTS: Regional ventilation and late enhancement at baseline preceded future change in lung volume (R - 0.474, p 0.006/R - 0.422, p 0.016, respectively) and mean lung density (R - 0.469, p 0.007/R - 0.402, p 0.022, respectively). Regional ventilation also correlated with a future change in FVC% (R - 0.398, p 0.024). CONCLUSION: CT-derived functional parameters of regional ventilation and parenchymal late enhancement are potential early imaging markers for idiopathic pulmonary fibrosis progression. KEY POINTS: • Functional CT parameters at baseline (regional ventilation and late enhancement) correlate with future structural changes of the lung as measured with loss of lung volume and increase in lung density in serial CT scans of patients with idiopathic pulmonary fibrosis. • Functional CT parameter measurements in high-attenuation areas (- 600 to - 250 HU) are significantly different from normal-attenuation areas (- 950 to - 600 HU) of the lung. • Mean regional ventilation in functional CT correlates with a future change in forced vital capacity (FVC) in pulmonary function tests.