Question 654
{"accessible":false,"alternatives":[{"id":3274,"text":"anode rotation speed"},{"id":3286,"text":"kilovoltage"},{"id":3275,"text":" filament current and kilovoltage"},{"id":3276,"text":"filament current"},{"id":3277,"text":"focal spot size"}],"archived":false,"correctAlternativeId":3275,"explanation":"\u003cp\u003eThe energy of the x-ray photon is defined by the voltage in the tube multiplied by the electron charge. For example, 100 kV will only create x-ray photons with a maximum energy 100 KeV.\u003c/p\u003e\u003cp\u003eThe filament supply current is quite large (e.g. 5 A), but the current generated in the electron beam (the so-called X-ray tube current) is much lower (e.g. 1 mA in fluoroscopy to over 1,000 mA in angiography), depending on the efficiency of the thermionic emission. This current is one of the factors used to control x-ray exposure and its value is generally displayed on an ammeter.\u003c/p\u003e\u003cp\u003eAdapted from\u0026nbsp;\u003ca href=\"https://en.wikibooks.org/wiki/Basic_Physics_of_Digital_Radiography\"\u003eBasic Physics of Digital Radiography\u003c/a\u003e\u0026nbsp;by\u0026nbsp;Kieran Maher,\u0026nbsp;with author's permission (License:\u0026nbsp;\u003ca href=\"https://creativecommons.org/licenses/by-sa/3.0/\"\u003eCreative Commons\u0026nbsp;BY-SA 3.0\u003c/a\u003e).\u003c/p\u003e","id":654,"imageUrl":null,"imageAttribution":null,"imageAttributionCaseInfo":null,"firstQuestionPath":"/questions/654","nextQuestionPath":null,"relatedArticles":[{"id":29650,"title":"Kilovoltage peak","link":"/articles/kilovoltage-peak?lang=us"},{"id":52512,"title":"Milliampere-seconds (mAs)","link":"/articles/milliampere-seconds-mas?lang=us"}],"alsoUsedIn":[],"stem":"\u003cp\u003eThe x-ray tube current is dictated by the...\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/654"}],"attemptsPercentages":[{"alternativeId":"3277","percentage":3},{"alternativeId":"3274","percentage":6},{"alternativeId":"3275","percentage":47},{"alternativeId":"3286","percentage":16},{"alternativeId":"3276","percentage":27}],"promptToLogin":false,"questionManager":false,"articleId":"photon"}