Asynchronous calibration of quantitative computed tomography bone mineral density assessment for opportunistic osteoporosis screening: phantom-based validation and parameter influence evaluation.

Asynchronous calibration could allow opportunistic screening based on routine CT for early osteoporosis detection. In this phantom study, a bone mineral density (BMD) calibration phantom and multi-energy CT (MECT) phantom were imaged on eight different CT scanners with multiple tube voltages (80-150 kVp) and image reconstruction settings (e.g. soft/hard kernel). Reference values for asynchronous BMD estimation were calculated from the BMD-phantom and validated with six calcium composite inserts of the MECT-phantom with known ground truth. Relative errors/changes in estimated BMD were calculated and investigated for influence of tube voltage, CT scanner and reconstruction setting. Reference values for 282 acquisitions were determined, resulting in an average relative error between calculated BMD and ground truth of - 9.2% ± 14.0% with a strong correlation (R2 = 0.99; p < 0.0001). Tube voltage and CT scanner had a significant effect on calculated BMD (p < 0.0001), with relative differences in BMD of 3.8% ± 28.2% when adapting reference values for tube voltage, - 5.6% ± 9.2% for CT scanner and 0.2% ± 0.2% for reconstruction setting, respectively. Differences in BMD were small when using reference values from a different CT scanner of the same model (0.0% ± 1.4%). Asynchronous phantom-based calibration is feasible for opportunistic BMD assessment based on CT images with reference values adapted for tube voltage and CT scanner model.

Predictors of clinical outcome in emphysema patients with atelectasis following endoscopic valve therapy: A retrospective study.

BACKGROUND AND OBJECTIVE: The aim of endoscopic valve therapy in patients with emphysema is complete lobar atelectasis of the most emphysematous lobe. However, even after the radiological advent of atelectasis, great variability in clinical outcomes can be observed. METHODS: The baseline clinical measures (vital capacity (VC), forced expiratory flow in 1 s (FEV1 ), residual volume (RV) and 6-min walk test (6-MWT)) and computed tomography variables (low attenuation volume (LAV) of the target lobe, LAV% of the target and the ipsilateral untreated lobe and LAV of the target lobe to LAV of the target lung and to LAV of the total lung) of 77 patients with complete atelectasis following valve therapy were retrospectively examined to determine their impact on patient´s outcome (changes in VC, FEV1 , RV and 6-MWT from baseline to the time of atelectasis). RESULTS: Low attenuation volume of the target lobe to LAV of the target lung predicts a significant FEV1 improvement in patients with complete lobar atelectasis following valve therapy. A 10% difference in that computed tomography predictor was associated with a 82-mL improvement in FEV1 (P = 0.006). Lower 6-MWT scores, low VC and high RV at baseline were significantly associated with greater improvement in the respective parameter (all P < 0.001). CONCLUSION: Low attenuation volume of the target lobe to LAV of the target lung and baseline clinical measures seem to significantly predict clinical outcomes in patients with complete lobar atelectasis following valve treatment.