Mrs braino phantom

The MRSI trajectories were tested on three phantoms using the same acquisition parameters as used for in vivo measurements. First, the trajectories and their reconstructions were tested on a cylindrical resolution phantom (General Electric Medical Systems, Milwaukee, WI, USA). Second, a phantom measurement to assess the SRF was performed on a small water containing cylinder phantom with diameter 45 mm. Finally, a phantom experiment was performed using the larger volume of interest (VOI) of the semi‐LASER localization (120 mm × 120 mm) on an MRS ‘Braino’ phantom (General Electric Medical Systems) containing 10 mmol creatine, 3 mmol choline, 5 mmol Lac, 1 mL/L Gd‐DPTA (Magnevist), 12.5 mmol Glu, 7.5 mmol myo‐Ins, 12.5 mmol NAA, 0.1% sodium azide, 56 mmol sodium hydroxide and 50 mmol potassium phosphate monobasic. Only a fully excited 15 × 15 voxel region was used for quantitative SNR analysis.

In vitro sequence validation was subsequently performed on a MRS “Braino” phantom (GE Medical Systems, Milwaukee, WI, USA⁵³) that contained NAA (12.5 mM), Cr (10 mM), choline (Cho; 3 mM), Ins (7.5 mM), L‐glutamic acid (12.5 mM), DL‐lactic acid (5 mM), sodium azide (0.1%), 50 mM of potassium phosphate monobasic [KH₂PO₄], 56 mM of sodium hydroxide [NaOH], and 1 mL/L of Gd‐DPTA solution (Magnevist). MRS data were acquired with sLASER and J‐sLASER using a range of TE values between 38 and 148 ms, TR = 5000 ms, number of signal averaged (NSA) = 8, BW = 3 kHz, and the number of time domain points (np) = 2048.

The two MRSI sequences were tested on two phantoms. First, the concentric ring k‐space trajectory and its reconstruction was tested on a cylindrical resolution phantom (General Electric Medical Systems, Milwaukee, WI, USA) using the non‐water suppressed metabolite‐cycling MRSI sequence with the following parameters: N_rings = 32, N_{p_ring} = 160, FOV = 320 mm × 320 mm, STEAM localization =160 mm × 160 mm × 10 mm, T_R = 2 s, T_E = 14 ms, T_M = 32 ms, N_avg = 2, ADC bandwidth =200 kHz, maximum gradient slew rate = 141.3 mT/m/ms. The 160 points per ring were sufficient to satisfy the requirement of avoiding azimuthal aliasing.32 Second, a phantom experiment for metabolite spectra depiction for both a water‐suppressed and the metabolite‐cycling technique was performed on an MRS ‘braino’ phantom (General Electric Medical Systems, Milwaukee, WI, USA) containing 10 mmol Cr, 3 mmol Cho, 5 mmol lactate (Lac), 1 mL/L Gd‐DPTA (Magnevist), 12.5 mmol Glu, 7.5 mmol myo‐inositol (myo‐Ins), 12.5 mmol NAA, 0.1% sodium azide, 56 mmol sodium hydroxide and 50 mmol potassium phosphate monobasic.