Question 2822
{"accessible":false,"alternatives":[{"id":13774,"text":"beam divergence"},{"id":13775,"text":"frequency shift"},{"id":13776,"text":"gating"},{"id":13777,"text":"power Doppler"},{"id":13778,"text":"time gain compensation"}],"archived":false,"correctAlternativeId":13778,"explanation":"\u003cp\u003eTime gain compensation amplifies the receiver gain for echo pulses that have returned from deeper tissues. Depth of tissue is determined by using the 'round trip' time taken by the received echo. Those returning from deeper tissues have been attenuated more than those arising from shallower tissues.\u003c/p\u003e\u003cp\u003eAmplification of the receiver gain serves to account for these differences in attenuation and better represent the true reflected intensity at a tissue boundary, irrespective of depth.\u003c/p\u003e\u003cp\u003eBeam divergence is the spreading out of the ultrasound beam after the focal point. Frequency shift describes the change in ultrasound frequency as a wave interacts with a moving structure. Gating is used in spectral Doppler to define the sampling region to calculate spectral waveforms (velocity). Power Doppler is a Doppler mode that is sensitive to small changes in frequency shift independent of direction.\u003c/p\u003e","id":2822,"imageUrl":null,"imageAttribution":null,"imageAttributionCaseInfo":null,"firstQuestionPath":"/questions/2830","nextQuestionPath":null,"relatedArticles":[{"id":30427,"title":"Time gain compensation","link":"/articles/time-gain-compensation?lang=us"},{"id":8664,"title":"Ultrasound frequencies","link":"/articles/ultrasound-frequencies?lang=us"},{"id":30430,"title":"Power Doppler","link":"/articles/power-doppler-1?lang=us"},{"id":68369,"title":"Beam focusing","link":"/articles/beam-focusing?lang=us"},{"id":67204,"title":"Spectral Doppler (ultrasound)","link":"/articles/spectral-doppler-ultrasound?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\u003eAmplification of signal generated from ultrasound echoes returning from deeper tissues is known as what?\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/2822"}],"attemptsPercentages":[{"alternativeId":"13774","percentage":2},{"alternativeId":"13776","percentage":1},{"alternativeId":"13778","percentage":92},{"alternativeId":"13777","percentage":3},{"alternativeId":"13775","percentage":2}],"promptToLogin":false,"questionManager":false,"articleId":"doppler-shift"}