Question 2787
{"accessible":false,"alternatives":[{"id":13599,"text":"0,01us"},{"id":13600,"text":"51,9us"},{"id":13601,"text":"80us"},{"id":13602,"text":"103,89us"},{"id":13603,"text":"10 380us"}],"archived":false,"correctAlternativeId":13602,"explanation":"\u003cp\u003e\u003cstrong\u003eTime (us) = 2 x Depth (cm) / Speed (cm/us)\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eTime = 2 x 8 (cm) / 0,154 (cm/us)\u003c/p\u003e\u003cp\u003eTime = 103,89us\u003c/p\u003e\u003cp\u003eA useful rule of thumb - in soft tissue, for each additional centimeter of object depth, the sound wave requires 13us of travel time. This is helpful in choosing the correct pulse repetition period/ pulse repetition frequency when trying to image to a certain depth.\u003c/p\u003e","id":2787,"imageUrl":null,"imageAttribution":null,"imageAttributionCaseInfo":null,"firstQuestionPath":"/questions/2837","nextQuestionPath":null,"relatedArticles":[{"id":46915,"title":"Propagation speed","link":"/articles/propagation-speed?lang=us"}],"alsoUsedIn":[{"id":1608,"kind":"RestrictedPage","title":"Page 1608 (in no courses)","link":"https://radiopaedia.org/admin/restricted_pages/1608"},{"id":1972,"kind":"Course","title":"Imaging Physics: Ultrasound Peer Review - page 1972","link":"https://radiopaedia.org/courses/imaging-physics-ultrasound-peer-review/pages/1972"},{"id":1972,"kind":"Course","title":"Imaging Physics: Ultrasound - page 1972","link":"https://radiopaedia.org/courses/imaging-physics-ultrasound/pages/1972"}],"stem":"\u003cp\u003eHow long from pulse generation does it take for an ultrasound echo to be received if reflecting off a mass 8cm below the surface of the skin? (Assume a transducer frequency of 5Mhz and speed in soft tissue of 1540m/s)\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/2787"}],"attemptsPercentages":[{"alternativeId":"13600","percentage":15},{"alternativeId":"13603","percentage":10},{"alternativeId":"13602","percentage":39},{"alternativeId":"13601","percentage":21},{"alternativeId":"13599","percentage":16}],"promptToLogin":false,"questionManager":false,"articleId":"pulse-repetition-frequency"}