{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,23]],"date-time":"2026-10-23T19:05:48Z","timestamp":1792782348640,"version":"4.5.0"},"reference-count":32,"publisher":"Wiley","issue":"3","license":[{"start":{"date-parts":[[2017,2,21]],"date-time":"2017-02-21T00:00:00Z","timestamp":1487635200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"name":"RSNA QIBA Concept Award"},{"name":"NIH\/NIBIB","award":["HHSN268201300071C"],"award-info":[{"award-number":["HHSN268201300071C"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Medical Physics"],"published-print":{"date-parts":[[2017,3]]},"abstract":"\n Purpose<\/jats:title>\n \n Computed Tomography (\n CT<\/jats:styled-content>\n ) imaging of the lung, reported in Hounsfield Units (\n HU<\/jats:styled-content>\n ), can be parameterized as a quantitative image biomarker for the diagnosis and monitoring of lung density changes due to emphysema, a type of chronic obstructive pulmonary disease (\n COPD<\/jats:styled-content>\n ).\n CT<\/jats:styled-content>\n lung density metrics are global measurements based on lung\n CT<\/jats:styled-content>\n number histograms, and are typically a quantity specifying either the percentage of voxels with\n CT<\/jats:styled-content>\n numbers below a threshold, or a single\n CT<\/jats:styled-content>\n number below which a fixed relative lung volume,\n n<\/jats:italic>\n th percentile, falls. To reduce variability in the density metrics specified by\n CT<\/jats:styled-content>\n attenuation, the Quantitative Imaging Biomarkers Alliance (\n QIBA<\/jats:styled-content>\n ) Lung Density Committee has organized efforts to conduct phantom studies in a variety of scanner models to establish a baseline for assessing the variations in patient studies that can be attributed to scanner calibration and measurement uncertainty.\n <\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n \n Data were obtained from a phantom study on\n CT<\/jats:styled-content>\n scanners from four manufacturers with several protocols at various tube potential voltage (\n kV<\/jats:styled-content>\n p) and exposure settings. Free from biological variation, these phantom studies provide an assessment of the accuracy and precision of the density metrics across platforms solely due to machine calibration and uncertainty of the reference materials. The phantom used in this study has three foam density references in the lung density region, which, after calibration against a suite of Standard Reference Materials (\n SRM<\/jats:styled-content>\n ) foams with certified physical density, establishes a\n HU<\/jats:styled-content>\n \u2010electron density relationship for each machine\u2010protocol. We devised a 5\u2010step calibration procedure combined with a simplified physical model that enabled the standardization of the\n CT<\/jats:styled-content>\n numbers reported across a total of 22 scanner\u2010protocol settings to a single energy (chosen at 80 keV). A standard deviation was calculated for overall\n CT<\/jats:styled-content>\n numbers for each density, as well as by scanner and other variables, as a measure of the variability, before and after the standardization. In addition, a linear mixed\u2010effects model was used to assess the heterogeneity across scanners, and the 95% confidence interval of the mean\n CT<\/jats:styled-content>\n number was evaluated before and after the standardization.\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n We show that after applying the standardization procedures to the phantom data, the instrumental reproducibility of the\n CT<\/jats:styled-content>\n density measurement of the reference foams improved by more than 65%, as measured by the standard deviation of the overall mean\n CT<\/jats:styled-content>\n number. Using the lung foam that did not participate in the calibration as a test case, a mixed effects model analysis shows that the 95% confidence intervals are [\u2212862.0\n HU<\/jats:styled-content>\n , \u2212851.3\n HU<\/jats:styled-content>\n ] before standardization, and [\u2010859.0\n HU<\/jats:styled-content>\n , \u2212853.7\n HU<\/jats:styled-content>\n ] after standardization to 80 keV. This is in general agreement with the expected\n CT<\/jats:styled-content>\n number value at 80 keV of \u2212855.9\n HU<\/jats:styled-content>\n with 95%\n CI<\/jats:styled-content>\n of [\u2212857.4\n HU<\/jats:styled-content>\n , \u2212854.5\n HU<\/jats:styled-content>\n ] based on the calibration and the uncertainty in the\n SRM<\/jats:styled-content>\n certified density.\n <\/jats:p>\n <\/jats:sec>\n \n Conclusions<\/jats:title>\n \n This study provides a quantitative assessment of the variations expected in\n CT<\/jats:styled-content>\n lung density measures attributed to non\u2010biological sources such as scanner calibration and scanner x\u2010ray spectrum and filtration. By removing scanner\u2010protocol dependence from the measured\n CT<\/jats:styled-content>\n numbers, higher accuracy and reproducibility of quantitative\n CT<\/jats:styled-content>\n measures were attainable. The standardization procedures developed in study may be explored for possible application in\n CT<\/jats:styled-content>\n lung density clinical data.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.1002\/mp.12087","type":"journal-article","created":{"date-parts":[[2017,1,6]],"date-time":"2017-01-06T13:12:53Z","timestamp":1483708373000},"page":"974-985","source":"Crossref","is-referenced-by-count":65,"title":["Standardizing\n CT<\/scp>\n lung density measure across scanner manufacturers"],"prefix":"10.1002","volume":"44","author":[{"given":"Huaiyu Heather","family":"Chen\u2010Mayer","sequence":"first","affiliation":[{"name":"Radiation Physics Division Physical Measurements Laboratory National Institute of Standards and Technology Gaithersburg MD 20899 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Matthew K.","family":"Fuld","sequence":"additional","affiliation":[{"name":"Siemens Medical Solutions USA Inc. Malvern PA 19355 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bernice","family":"Hoppel","sequence":"additional","affiliation":[{"name":"Toshiba Medical Research Institute USA Inc. Vernon Hills IL 60061 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Philip F.","family":"Judy","sequence":"additional","affiliation":[{"name":"Department of Radiology Brigham & Women's Hospital Boston MA 02115 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jered P.","family":"Sieren","sequence":"additional","affiliation":[{"name":"VIDA Diagnostics Inc. Coralville IA 52241 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Junfeng","family":"Guo","sequence":"additional","affiliation":[{"name":"Departments of Radiology and Biomedical Engineering University of Iowa Iowa City IA 52242 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David A.","family":"Lynch","sequence":"additional","affiliation":[{"name":"Department of Radiology National Jewish Health Denver CO 80206 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Antonio","family":"Possolo","sequence":"additional","affiliation":[{"name":"Statistical Engineering Division Information Technology Laboratory National Institute of Standards and Technology Gaithersburg MD 20899 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sean B.","family":"Fain","sequence":"additional","affiliation":[{"name":"Department of Medical Physics University of Wisconsin School of Medicine and Public Health Madison WI 53705 USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2017,2,21]]},"reference":[{"key":"e_1_2_13_2_1","doi-asserted-by":"publisher","DOI":"10.1080\/02841859709172418"},{"key":"e_1_2_13_3_1","doi-asserted-by":"publisher","DOI":"10.1148\/radiol.2015141579"},{"key":"e_1_2_13_4_1","doi-asserted-by":"publisher","DOI":"10.1164\/rccm.200912-1843CC"},{"key":"e_1_2_13_5_1","doi-asserted-by":"publisher","DOI":"10.1164\/rccm.201402-0256PP"},{"key":"e_1_2_13_6_1","doi-asserted-by":"publisher","DOI":"10.1148\/radiol.2382042196"},{"key":"e_1_2_13_7_1","doi-asserted-by":"publisher","DOI":"10.1513\/pats.200804-040QC"},{"key":"e_1_2_13_8_1","doi-asserted-by":"publisher","DOI":"10.1186\/1465-9921-11-136"},{"key":"e_1_2_13_9_1","doi-asserted-by":"publisher","DOI":"10.1118\/1.4851535"},{"key":"e_1_2_13_10_1","doi-asserted-by":"publisher","DOI":"10.1001\/jamainternmed.2015.2735"},{"key":"e_1_2_13_11_1","doi-asserted-by":"publisher","DOI":"10.1097\/RTI.0b013e31829efbe9"},{"key":"e_1_2_13_12_1","doi-asserted-by":"publisher","DOI":"10.1080\/02841850410005525"},{"key":"e_1_2_13_13_1","doi-asserted-by":"publisher","DOI":"10.15326\/jcopdf.1.1.2014.0111"},{"key":"e_1_2_13_14_1","doi-asserted-by":"publisher","DOI":"10.2214\/AJR.11.6444"},{"key":"e_1_2_13_15_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ejrad.2011.06.028"},{"key":"e_1_2_13_16_1","doi-asserted-by":"publisher","DOI":"10.1148\/radiol.2443061330"},{"key":"e_1_2_13_17_1","doi-asserted-by":"publisher","DOI":"10.1007\/s00330-011-2277-1"},{"key":"e_1_2_13_18_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.acra.2009.12.010"},{"key":"e_1_2_13_19_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.acra.2011.08.001"},{"key":"e_1_2_13_20_1","unstructured":"QIBA.Lung Density Profile Under Development and Will Appear. 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