Room: Track 1
In this study, we proposed a novel simultaneous multi-slice (SMS) density weighted (DW) concentric ring trajectory (CRT) metabolite-cycling Magnetic Resonance Spectroscopy Imaging (MRSI) sequence to alleviate some conventional MRSI drawbacks, e.g. long acquisition time, eddy current artifacts, and side lobe artifacts. The sequence was tested on 5 healthy subjects, showing the feasibility of acquiring three slices of high-quality water-only and metabolite spectra simultaneously with a resolution of 5mm X 5mm X 10mm within 20 minutes.
Phantom and in-vivo scans were acquired using a Siemens Prisma 3-Tesla (Siemens, Germany) scanner and a 20-channel head array receive coil. Five healthy volunteers (2 males/3 females, aged 22.6± 1.67 year) participated. The metabolite-cycling MRSI acquisition was achieved by the inversion of the upfield and downfield spectral ranges before the STEAM so that water-only and metabolite spectra can be acquired simultaneously. Multi-slice excitation RF pulse was used in the z-direction pulse of STEAM localization (TR = 1 s, TE = 16 ms) to excite three 110 mm x 80 mm x 10 mm slices (FOV= 240 mm x 240 mm) with an inter-slice distance of 20 mm. Hanning-window density weighted acquisition was used in k-space to reduce the side lobe artifact as shown in Figure 1. A blipped z-gradient scheme is applied to facilitate SENSE unfolding.
Water images and MRSI metabolite spectra of a phantom and an in-vivo subject are shown in Figure 2. Metabolite concentration map derived from LCModel are displayed in Figure 3. Phantom results are consistent with the reality. A distinguished tissue contrast of Creatine and Glx can be seen in the in-vivo subject. Ventricle contours can be seen on NAA and Cho maps.
It is shown that the SMS DW-CRT MRSI acquisition in combination with metabolite-cycled STEAM pulse localization allows fast, robust, high-resolution 3D MRSI at 3T.