BackgroundQuantitative computer tomography (QCT) has emerged as a screening tool for opportunistic measurements of volumetric bone mineral density (vBMD) from clinical CT scans, enabling early diagnosis of osteoporosis. However, intravenous contrast media administered during clinical CT examinations, calibration methods as well as different scan phases may influence vBMD and must be considered.1 Calibration methods include synchronous and asynchronous CT phantoms as well as phantom-less

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... calibration.ObjectivesTo investigate the effect of intravenous contrast media on QCT-measured vBMD. Furthermore, to review the effects of different calibration methods and scan protocols on vBMD.MethodsIn this systematic literature review, two independent reviewers (AH and AC) conducted a blinded screening for articles involving human participants who had undergone a contrast and non-contrast CT scan to measure vBMD. A total of 1,981 studies, published between 01.01.2000 and 17.01.2021, were screened and 9 eligible studies were included. A meta-analysis was conducted and standard mean differences (SMD) with 95% confidence intervals (CI) were calculated and presented in a forest-plot. Quality of studies was rated by the preliminary ROBINS-E risk of bias tool.2ResultsIn total, the 9 studies included 515 patients. On average the vBMD SMD changed 0.45 (95% CI: 0.24-0.67, P < .0001) from non-contrast to contrast-enhanced (CE) scans at the lumbar region (Figure 1). Phantom-based QCT had a SMD of 0.64 (95% CI: 0.33-0.94, P < .0001) and phantom-less QCT had a SMD of 0.20 (95% CI: -0.00-0.40, P = 0.05). Subgroup analyses showed a mean arterial phase vBMD SMD of 0.29 (95% CI: 0.12-0.45 P < .0008) and a venous phase vBMD of 0.56 (95% CI: 0.30-0.81, P < .0001). All studies were deemed to have moderate or serious risk of bias by the ROBINS-E tool.Figure 1.Meta-analysis of standardized mean difference in lumbar spine vBMD (mg/cm3) change from non-contrast enhanced (non-CE) CT scans and contrast enhanced (CE) CT scans.ConclusionQCT-measured vBMD is higher in CE scans in both phantom-based and phantom-less scans compared to non-contrast CT. Our meta-analysis suggest that contrast has a larger impact on vBMD in phantombased vs. phantom-less and in venous phase scans vs. arterial phase scans, underlining not only the time-dependency but also the dependency of the calibration method. Arterial phase CT scans using internal calibration may be preferred when measuring vBMD in a clinical setting without an adjusting conversion factor. However, if CE scans are to be used in opportunistic vBMD screening, development of a universal calibration- and protocol specific conversion factor is of importance.References[1]Engelke, K. et al. Clinical Use of Quantitative Computed Tomography-Based Advanced Techniques in the Management of Osteoporosis in Adults: the 2015 ISCD Official Positions-Part III. J Clin Densitom18, 393-407, doi:10.1016/j.jocd.2015.06.010 (2015).[2]Preliminary risk of bias for exposures tool template [http://www.bristol.ac.uk/population-health-sciences/centres/cresyda/barr/riskofbias/robins-e/].Disclosure of InterestsAnders Hjortdal: None declared, Andia Cheneymann: None declared, Josephine Therkildsen: None declared, Ellen-Margrethe Hauge Speakers bureau: Received fees for speaking and/or consulting from AbbVie, Sanofi, Sobi, MSD, UCB;, Grant/research support from: Recieved research funding to Aarhus University Hospital from Novo Nordic Foundation, Danish Rheumatism Association, Danish Regions Medicine Grants, Roche, Novartis; travel expenses from Celgene, MSD, Pfizer, Roche, Sobi., Simon Winther: None declared, Morten Böttcher Speakers bureau: Disclose advisory board participation for NOVO Nordisk, Astra-Zeneca, Boeringer Ingelheim, Bayer, Sanofi, Novartis and Acarix outside of submitted work