Question 985
{"accessible":false,"alternatives":[{"id":4936,"text":"acute hemorrhage/clot has a density higher than the upper limit of routine CT window width and level"},{"id":4937,"text":"acute hemorrhage/clot has a density lower than the lower limit of routine CT window width and level"},{"id":4938,"text":"acute hemorrhage/clot has a density similar to bone (about 1000HU) and thus looks the same as bone"},{"id":4939,"text":"acute hemorrhage/clot has a density similar to brain parenchyma (about 30-40HU) and thus looks the same as cortex"}],"archived":false,"correctAlternativeId":4936,"explanation":"\u003cp\u003eRoutine non-contrast CT brain window width and level is typically a\u0026nbsp;width of 80 HU with a level (center) of 40 HU. As such any value higher than 80 HU (center + 1/2 x width) will be completely white and indistinguishable from other higher values. Acute blood can often be around 100 HU and bone much higher than this. Both will appear white and the hemorrhage will merely look like a thicker skull. To distinguish this a wider window (e.g. subdural window) needs to be used.\u0026nbsp;\u003c/p\u003e","id":985,"imageUrl":null,"imageAttribution":null,"imageAttributionCaseInfo":null,"firstQuestionPath":"/questions/2307","nextQuestionPath":"/articles/windowing-ct/questions/984","relatedArticles":[{"id":2121,"title":"Subdural hemorrhage","link":"/articles/subdural-haemorrhage?lang=us"},{"id":48361,"title":"CT head (subdural window)","link":"/articles/ct-head-subdural-window-1?lang=us"}],"alsoUsedIn":[{"id":123,"kind":"Course","title":"Emergency Radiology Course - Melbourne - page 123","link":"https://radiopaedia.org/courses/emergency-radiology-course-melbourne-2020/pages/123"},{"id":123,"kind":"Course","title":"Trauma Radiology Course - Sydney - page 123","link":"https://radiopaedia.org/courses/trauma-radiology-course-sydney-2020/pages/123"},{"id":123,"kind":"Course","title":"Trauma CT Brain Learning Pathway - page 123","link":"https://radiopaedia.org/courses/trauma-ct-brain-learning-pathway/pages/123"},{"id":612,"kind":"Course","title":"Radiopaedia 2020 - Lectures Only - page 612","link":"https://radiopaedia.org/courses/radiopaedia-2020-exclusive/pages/612"},{"id":612,"kind":"Course","title":"2020 Virtual Conference Private Use - page 612","link":"https://radiopaedia.org/courses/2020-virtual-conference-private-use/pages/612"},{"id":700,"kind":"Course","title":"Trauma \u0026 Emergency Radiology Course - page 700","link":"https://radiopaedia.org/courses/medical-mums/pages/700"},{"id":700,"kind":"Course","title":"Trauma Radiology Course - page 700","link":"https://radiopaedia.org/courses/trauma-radiology-course-online/pages/700"},{"id":700,"kind":"Course","title":"2020 Virtual Conference Private Use - page 700","link":"https://radiopaedia.org/courses/2020-virtual-conference-private-use/pages/700"}],"stem":"\u003cp\u003eWhy can thin acute intracranial subdural hemorrhages be difficult to identify on routine non-contrast CT of the brain?\u003c/p\u003e","menuLinks":[{"text":"Report problem with question","url":"https://docs.google.com/forms/d/e/1FAIpQLSfO3soWYhOjJ7yErSysyCe5V4A1CqW7WK3rDA7MtAkecMGqNw/viewform?entry.1624461248\u0026entry.553583435=https://radiopaedia.org/questions/985"}],"attemptsPercentages":[{"alternativeId":"4938","percentage":35},{"alternativeId":"4939","percentage":28},{"alternativeId":"4937","percentage":5},{"alternativeId":"4936","percentage":32}],"promptToLogin":false,"questionManager":false,"articleId":"windowing-ct"}