MO-G-18C-08: Increasing Throughput of a Clinical MR Protocol for Prostate Cancer with a Factor of Two Using Multiband Imaging

Authors


Abstract

Purpose:

To increase throughput of a clinical, multi-parametric, prostate MRI protocol by individual scan acceleration using multiband excitation, in which multiple slices are excited simultaneously, and CAIPIRINHA.

Methods:

A healthy subject was scanned on a 3T clinical MR-system with a 16-channel torso receive array. A T2w-TSE scan from a clinical prostate MR protocol was acquired to simulate three acceleration Methods: (1) traditional in-plane parallel imaging (SENSE) (R=2), (2) multi-slice parallel imaging (MS-SENSE, R=2), in which two slices are acquired simultaneously and (3) multi-slice CAIPIRINHA (R=2), in which one of the simultaneously acquired slices is shifted with FOV/2 with respect to the other slice. The normalized expected SNR was calculated within an ROI in the center of the slice. To demonstrate the feasibility of multiband MRI for the prostate, two 2D gradient echo slices (TE/TR=2.4ms/5.0ms, FA=20°, FOV=250×405mm2, voxelsize=0.5×0.5×4mm3, slice gap=20mm) were excited simultaneously using a numerically designed multiband RF pulse. The slices were acquired either with or without shifting the second slice by FOV/2 (i.e. CAIPIRINHA).

Results:

Simulations showed an expected relative SNR of 0.67 for in-plane two-fold SENSE acceleration, 0.14 for multi-slice SENSE, and 0.94 for multi-slice CAIPIRINHA within the ROI (SNR=1 for non-accelerated acquisition). In-vivo multiband experiments demonstrated that separation of the simultaneously acquired slices was practically impossible when slices folded on top of each other. However, the multi-slice CAIPIRINHA experiment, showed low g-factors and good image quality after unfolding.

Conclusion:

We demonstrated that the twofold multiband acceleration with CAIPIRINHA technique is the most SNR beneficial compared to the other acceleration techniques with only a moderate SNR penalty compared to the non-accelerated acquisition. In-vivo experiments demonstrated the feasibility of two-fold CAIPIRINHA acceleration for pelvic MRI. This can be used to e.g. increase patient throughput, SNR or temporal resolution of the scans included in the multiparametric prostate MR protocol.

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