Figure 15

fast-SENC and sf-fast-SENC. (a) fast-SENC pulse sequence. The tagging part has two slice-selective RF pulses applied in the x- and y-directions, respectively, to restrict tagging to a small square region, which allows for reducing FOV without much compromising spatial resolution. The second modification in fast-SENC is the implementation of alternating LT and HT tunings in consecutive heart phases to reduce scan time in half. The third modification is the application of spiral acquisition to reduce the imaging time. sf-fast-SENC pulse sequence (not shown) is similar to fast-SENC, except that it replaces the first tagging RF pulse by 2-D cylindrical excitation in the x-y direction and the second RF pulse by a slice-selective pulse in the z-direction to restrict the tagged region to a small disc-shaped region of the intersection of the two excited regions. (b) Shapes showing the tagged and imaged regions in SENC, fast-SENC, and sf-fast-SENC. In SENC, all the body is tagged; thus large FOV imaging is required. In fast-SENC, tagging is restricted to the intersection of the two orthogonal slabs. This allows for using small imaging FOV. In sf-fast-SENC, tagging is restricted to a disc-shaped thin region, which is the intersection of the 2-D cylindrical region and the orthogonal slice. This allows for applying slice following by imaging with a thicker slice that has reduced FOV. (c) In SENC, two scans are required to capture LT and HT images at different heart phases. In fast-SENC and sf-fast-SENC, the tunings are applied alternatively in one scan only.