Spatial resolution properties in 3D fast spin-echo using variable refocusing flip angles

A new 3-dimensional fast spin-echo (3D FSE) method that uses a variable refocusing flip angle technique has recently been applied to imaging. The imaging pulse sequence can inhibit T2 decay by varying the refocusing flip angle. Use of a long echo train length allows acquisition of 3D T2-weighted images with less blurring in a short scan time. The smaller refocusing flip angle in the new 3D FSE method than in the conventional method can reduce the specific absorption rate. However, T2 decay differs between the new and conventional 3D FSE methods, so the resolution properties of the 2 methods may differ. We investigated the resolution properties of the new 3D FSE method using a variable refocusing flip angle technique. Varying the refocusing flip angle resulted in different resolution properties for the new 3D FSE method compared to the conventional method, a difference particularly noticeable when the imaging parameters were set for obtaining proton density weighted images. (author)