Question 2952
{"accessible":false,"alternatives":[{"id":14376,"text":"3.5 Hz"},{"id":14377,"text":"3.5 MHz"},{"id":14378,"text":"42.6 Hz"},{"id":14379,"text":"42.6 MHz"},{"id":14380,"text":"150 Hz"}],"archived":false,"correctAlternativeId":14380,"explanation":"\u003cp\u003eChemical shift between water and fat is 3.5 parts per million (ppm).\u003c/p\u003e\u003cp\u003eThis means for every million hertz protons in water precess, protons in fat will precess 3.5 hertz less.\u003c/p\u003e\u003cp\u003eLarmor frequency = gyromagnetic ratio x field strength\u003c/p\u003e\u003cp\u003eLarmor frequency = 42.6 MHz / T x 1T\u003c/p\u003e\u003cp\u003eLarmor frequency = 42.6 MHz (42.6 million Hertz)\u003c/p\u003e\u003cp\u003eTherefore, fat precesses at 42.6 x 3.5 Hz less than water ≈ 150 Hz\u003c/p\u003e","id":2952,"imageUrl":null,"imageAttribution":null,"imageAttributionCaseInfo":null,"firstQuestionPath":"/questions/2952","nextQuestionPath":"/articles/chemical-shift-artifact-1/questions/2951","relatedArticles":[{"id":60743,"title":"Chemical shift","link":"/articles/chemical-shift?lang=us"},{"id":5855,"title":"Larmor frequency","link":"/articles/larmor-frequency?lang=us"},{"id":5855,"title":"Larmor frequency","link":"/articles/larmor-frequency?lang=us"}],"alsoUsedIn":[{"id":1927,"kind":"Course","title":"Imaging Physics: MRI - page 1927","link":"https://radiopaedia.org/courses/imaging-physics-mri/pages/1927"}],"stem":"\u003cp\u003eIn a 1T magnetic field, what is the approximate difference in hydrogen precession frequency between water and fat? (The gyromagnetic ratio of hydrogen is 42.6 MHz/T)\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/2952"}],"attemptsPercentages":[{"alternativeId":"14378","percentage":9},{"alternativeId":"14380","percentage":33},{"alternativeId":"14377","percentage":20},{"alternativeId":"14379","percentage":15},{"alternativeId":"14376","percentage":23}],"promptToLogin":false,"questionManager":false,"articleId":"chemical-shift-artifact"}