Question 2821
{"accessible":false,"alternatives":[{"id":13769,"text":"amplifies smaller echoes preferentially"},{"id":13770,"text":"compensates for the linear attenuation of ultrasound"},{"id":13771,"text":"eliminates posterior enhancement"},{"id":13772,"text":"eliminates posterior shadowing"},{"id":13773,"text":"uses timing of echoes to calculate the degree of receiver gain applied"}],"archived":false,"correctAlternativeId":13773,"explanation":"\u003cp\u003eTime gain compensation accounts for the predicted (non-linear) loss of sound intensity as ultrasound waves travel through tissue. The time taken for an ultrasound echo to return to the probe is used to estimate the depth of the tissue boundary from which it has been reflected (using the range equation).\u003c/p\u003e\u003cp\u003eTime = 2 x depth of boundary / speed of sound in soft tissue\u003c/p\u003e\u003cp\u003eEchoes returning from greater depths are amplified more than those from shallower tissues to account for the differential loss of intensity. Importantly, it is not the intensity of the returning echo that determines the degree of amplification, rather the depth from which that echo has returned from.\u003c/p\u003e\u003cp\u003eTime gain compensation can exacerbate posterior enhancement artifact and is not able to eliminate posterior shadowing (cannot amplify signals that do not exist)\u003c/p\u003e","id":2821,"imageUrl":null,"imageAttribution":null,"imageAttributionCaseInfo":null,"firstQuestionPath":"/questions/2821","nextQuestionPath":null,"relatedArticles":[{"id":67529,"title":"Attenuation (ultrasound)","link":"/articles/attenuation-ultrasound?lang=us"},{"id":24967,"title":"Acoustic shadowing","link":"/articles/acoustic-shadowing?lang=us"},{"id":30427,"title":"Time gain compensation","link":"/articles/time-gain-compensation?lang=us"},{"id":31476,"title":"Ultrasound artifacts","link":"/articles/ultrasound-artifacts-3?lang=us"}],"alsoUsedIn":[{"id":1615,"kind":"RestrictedPage","title":"Page 1615 (in no courses)","link":"https://radiopaedia.org/admin/restricted_pages/1615"},{"id":1979,"kind":"Course","title":"Imaging Physics: Ultrasound Peer Review - page 1979","link":"https://radiopaedia.org/courses/imaging-physics-ultrasound-peer-review/pages/1979"},{"id":1979,"kind":"Course","title":"Imaging Physics: Ultrasound - page 1979","link":"https://radiopaedia.org/courses/imaging-physics-ultrasound/pages/1979"}],"stem":"\u003cp\u003eWhich of the following is true regarding time gain compensation?\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/2821"}],"attemptsPercentages":[{"alternativeId":"13771","percentage":2},{"alternativeId":"13772","percentage":3},{"alternativeId":"13769","percentage":8},{"alternativeId":"13773","percentage":51},{"alternativeId":"13770","percentage":36}],"promptToLogin":false,"questionManager":false,"articleId":"acoustic-enhancement"}