Question 2945
{"accessible":false,"alternatives":[{"id":14344,"text":"frequency encoding gradient"},{"id":14345,"text":"main magnetic field"},{"id":14346,"text":"radiofrequency transmit pulse"},{"id":14347,"text":"slice selection gradient"}],"archived":false,"correctAlternativeId":14345,"explanation":"\u003cp\u003ePrecession frequency = gyromagnetic ratio x magnetic field strength\u003c/p\u003e\u003cp\u003eThe\u003cstrong\u003e main magnetic field\u003c/strong\u003e is orders of magnitude stronger than the gradient fields. Gradient fields modify the main magnetic field creating slight differences in precession frequency.\u003c/p\u003e\u003cp\u003eThe radiofrequency transmit pulse is required for resonance and excitation, not precession.\u003c/p\u003e","id":2945,"imageUrl":null,"imageAttribution":null,"imageAttributionCaseInfo":null,"firstQuestionPath":"/questions/2963","nextQuestionPath":"/articles/gradient-coils-1/questions/2935","relatedArticles":[{"id":5855,"title":"Larmor frequency","link":"/articles/larmor-frequency?lang=us"},{"id":22023,"title":"Resonance and radiofrequency","link":"/articles/resonance-and-radiofrequency?lang=us"},{"id":22558,"title":"MRI physics","link":"/articles/mri-physics?lang=us"},{"id":60748,"title":"Effect of gradient strength and bandwidth on slice thickness","link":"/articles/effect-of-gradient-strength-and-bandwidth-on-slice-thickness?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 MRI imaging, which of the following contributes most to nuclear precession frequency?\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/2945"}],"attemptsPercentages":[{"alternativeId":"14346","percentage":13},{"alternativeId":"14344","percentage":7},{"alternativeId":"14345","percentage":77},{"alternativeId":"14347","percentage":3}],"promptToLogin":false,"questionManager":false,"articleId":"gradient-coils"}