Bashir U, Vadera S, Foster T, et al. Free induction decay. Reference article, Radiopaedia.org (Accessed on 24 Mar 2025) https://doi.org/10.53347/rID-16493
Free induction decay (FID) refers to a short-lived sinusoidal electromagnetic signal which appears immediately following the 90° pulse. It is induced in the receiver coil by the rotating component of the magnetisation vector in the x-y plane which crosses the coil loops perpendicularly. It does not contribute to MR image but is used for single voxel MR spectroscopy.This sinusoidal signal decays exponentially with a time constant of T2*.
A spin echo produced by a 180° pulse following a 90° pulse appears as a back-to-back FID where the signal increases exponentially to the middle of the signal then decreases exponentially like the FID.
2. Bydder GM, Steiner RE. NMR imaging of the brain. Neuroradiology. 1982;23 (5): 231-40. Pubmed citation
3. Curry TS, Dowdey JE, Murry RE. Christensen ́s physics of diagnostic radiology 4 Ed. Lippincott Williams & Wilkins. (1990) ISBN:0812113101. Read it at Google Books - Find it at Amazon
Unable to process the form. Check for errors and try again.