Question 634
{"accessible":false,"alternatives":[{"id":3174,"text":"pseudolinear transformation"},{"id":3175,"text":"quantum mottle"},{"id":3176,"text":"penumbra"},{"id":3177,"text":"magnification"},{"id":3178,"text":"space charge effect"}],"archived":false,"correctAlternativeId":3176,"explanation":"\u003cp\u003eThe finite size of the focal spot leads to geometric blurring or penumbra.\u003c/p\u003e\u003cp\u003eQuantum mottle refers to the grainy appearance of medical images, due to random radiographic noise associated with acquiring an image. Magnification images require a smaller focal spot to decrease the degree of blurring. The space charge effect refers to the repulsion of electrons in a beam, leading to a diverging beam.\u0026nbsp;\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":634,"imageUrl":null,"imageAttribution":null,"imageAttributionCaseInfo":null,"firstQuestionPath":"/questions/2751","nextQuestionPath":"/articles/focal-spot/questions/619","relatedArticles":[{"id":29786,"title":"Space charge","link":"/articles/space-charge?lang=us"}],"alsoUsedIn":[],"stem":"\u003cp\u003eThe finite size of the x-ray tube focal spot gives rise to...\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/634"}],"attemptsPercentages":[{"alternativeId":"3177","percentage":13},{"alternativeId":"3175","percentage":8},{"alternativeId":"3176","percentage":50},{"alternativeId":"3174","percentage":6},{"alternativeId":"3178","percentage":24}],"promptToLogin":false,"questionManager":false,"articleId":"focal-spot"}