The aim of this study was to evaluate the impact of contrast enhancement and different virtual monoenergetic image energies on automatized emphysema quantification with photon-counting detector computed tomography (PCD-CT). Material and Methods: Sixty patients who underwent contrast-enhanced chest CT on a first-generation, clinical dual-source PCD-CT were retrospectively included. Scans were performed in the multienergy (QuantumPlus) mode at 120 kV with weight-adjusted intravenous contrast agent. Virtual noncontrast (VNC) images as well as virtual monoenergetic images (VMIs) from 40 to 80 keV obtained in 10-keV intervals were reconstructed. Computed tomography attenuation was measured in the aorta. Noise was measured in subcutaneous fat and defined as the standard deviation of attenuation. Contrast-to-noise with region of interest in the ascending aorta and signal-to-noise ratio in the subcutaneous fat were calculated. Subjective image quality (and emphysema assessment, lung parenchyma evaluation, and vessel evaluation) was rated by 2 blinded radiologists. Emphysema quantification (with a threshold of −950 HU) was performed by a commercially available software. Virtual noncontrast images served as reference standard for emphysema quantification. Results: Noise and contrast-to-noise ratio showed a strong negative correlation (r = −0.98; P < 0.01) to VMI energies. The score of subjective assessment was highest at 70 keV for lung parenchyma and 50 keV for pulmonary vessel evaluation ( P < 0.001). The best trade-off for the assessment of emphysema while maintaining reasonable contrast for pulmonary vessel evaluation was determined between 60 and 70 keV. Overall, contrast-enhanced imaging led to significant and systematic underestimation of emphysema as compared with VNC ( P < 0.001). This underestimation decreased with increasing VMI-energy (r = 0.98; P = 0.003). Emphysema quantification showed significantly ( P < 0.05) increased emphysema volumes with increasing VMI energies, except between 60-70 keV and 70-80 keV. The least difference in emphysema quantification between contrast-enhanced scans and VNC was found at 80 keV. Conclusion: Computed tomography emphysema quantification was significantly affected by intravenous contrast administration and VMI-energy level. Virtual monoenergetic image at 80 keV yielded most comparable results to VNC. The best trade-off in qualitative as well as in quantitative image quality evaluation was determined at 60/70 keV.
Objectives: To evaluate the performance of virtual non-contrast images (VNC) compared to true non-contrast (TNC) images in photon-counting detector computed tomography (PCD-CT) for the evaluation of lung parenchyma and emphysema quantification. Methods: Sixty-five (mean age 73 years; 48 male) consecutive patients who underwent a three-phase (non-contrast, arterial and venous) chest/abdomen CT on a clinical first-generation, clinical dual-source PCD-CT were retrospectively included. Scans were performed in the multi energy (QuantumPlus) mode at 120kV with 70 ml intravenous contrast agent at an injection rate of 4 ml s−1. VNC were reconstructed from the arterial (VNCart) and venous phase (VNCven). TNC and VNC images of the lung were assessed quantitatively by calculating the global noise index (GNI) and qualitatively by two independent, blinded readers (overall image quality and emphysema assessment). Emphysema quantification was performed using a commercially available software tool at a threshold of −950 HU for all datasets. TNC images served as reference standard for emphysema quantification. Low attenuation values (LAV) were compared in a Bland-Altman plot. Results: GNI was similar in VNCart (103.0 ± 30.1) and VNCven (98.2 ± 22.2as compared to TNC (100.9 ± 19.0, p = 0.546 and p = 0.272, respectively). Subjective image quality (emphysema assessment and overall image quality) was highest for TNC (p = 0.001), followed by VNCven and VNCart. Both, VNCart and VNCven showed no significant difference in emphysema quantification as compared to TNC (p = 0.409 vs. p = 0.093; respectively). Conclusion: Emphysema evaluation is feasible using virtual non-contrast images from PCD-CT. Advances in knowledge: Emphysema quantification is feasible and accurate using virtual non-contrast enhanced (VNC) images in Photon-counting detector CT. Based on these findings, additional TNC scans could be omitted in the future for emphysema quantification.
Zusammenfassung Hintergrund Die moderne medizinische Bildgebung ist ein wichtiger Teil der effizienten ambulanten und stationären Patientenversorgung. Die konventionelle Röntgenaufnahme und die Computertomographie (CT) gehören zu den am häufigsten durchgeführten radiologischen Untersuchungen. Die Radiologie ermöglicht eine zielorientierte Präzisionsmedizin. Fragestellung Ziel dieses Beitrags ist eine Übersicht über die Anatomie und die häufigsten Pathologien am Lungenhilus (LH), einer wichtigen Schnittstelle elementarer Strukturen des Thorax. Außerdem werden wichtige Zeichen und Muster zur Bildinterpretation in verschiedenen Modalitäten betrachtet. Ergebnisse Eine genaue Kenntnis der Anatomie, der bildgebenden Zeichen pathologischer Veränderungen und Pitfalls in der konventionellen Röntgenaufnahme und in der sensitiveren Schnittbildgebung ist essenziell, um eine zielgerichtete Patientenversorgung zu unterstützen. Schlussfolgerung Das konventionelle Röntgenbild ist günstig und schnell verfügbar. Es eignet sich sehr gut zum Pathologie-Screening, u. a. am Lungenhilus. Die Schnittbildgebung präzisiert aufgrund der deutlich besseren Differenzierbarkeit anatomischer Strukturen die Diagnostik.
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