title: T2 quantification from only proton density and T2-weighted MRI by modelling actual refocusing angles.
abstract: Proton density and transverse relaxation (T2)-weighted fast spin echo images are frequently acquired. T2 quantification is commonly performed by applying an exponential fit to these two images, despite recent evidence that an exponential fit is insufficient to correctly quantify T2 in the presence of imperfect RF refocusing due to standard 2D slice selection or use of reduced refocusing angles. Here we examine the feasibility of accurate two echo fitting using standard proton density and T2-weighted images by utilizing Bloch equation simulations and prior knowledge of refocusing angles. This method is demonstrated in simulation, phantom, and human brain experiments, in comparison to the exponential approach, and to a 32 echo multiple-echo spin echo approach. Comparison to single spin echo is also performed in phantom experiments. The two echo method, which compensates for indirect and stimulated echoes, enables accurate quantitative T2 over a wide range of flip angle and T2 values using standard MRI methods, provided there is adequate SNR and flip angle knowledge.
authors.affiliation: Department of Physics, University of Alberta, 4-181 CCIS, Edmonton, Alberta T6G 2E1, Canada. Electronic address: kcmcphee@gmail.com.
authors.forename: Kelly C
authors.initials: KC
authors.lastname: McPhee
authors.affiliation: Department of Physics, University of Alberta, 4-181 CCIS, Edmonton, Alberta T6G 2E1, Canada; Department of Biomedical Engineering, University of Alberta, 1098 RTF, Edmonton, Alberta T6G 2V2, Canada. Electronic address: wilman@ualberta.ca.
authors.forename: Alan H
authors.initials: AH
authors.lastname: Wilman
mesh_terms: D001921:Brain; D001931:Brain Mapping; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008959:Models, Neurological; D019047:Phantoms, Imaging
keywords: Fast spin echo; ISEC; Proton density; R2 quantification; Stimulated echoes; T2-weighting