Introduction

Compressed sensing is one of the state-of-the-art acceleration technologies for MRI acquisition and reconstruction ^[1]. Compressed SENSE technology is built on the combination of compressed sensing and SENSE ^[2] theories by leveraging a balanced under-sampling acquisition scheme with variable density and incoherent sampling pattern ^[3]. Iterative reconstruction is used to solve an inverse problem with the priori information of coil sensitivities and a sparsity constraint. This study aimed to demonstrate the feasibility of compressed SENSE for 3D T2-weighted breast imaging.

Method

The whole-breast imaging was performed on an Ingenia Prodiva 1.5 T MR scanner (Philips Healthcare, Suzhou, China) on healthy volunteers with informed consent, study approved by a local IRB. A 7-channel phase-arrayed breast coil was used for a 3D turbo spin echo (TSE) acquisition with TSE factor 66. The imaging FOV = 360x360 mm², voxel size = 1mm isotropic, number of slices = 200, and TE/TR = 170/1300 ms. Compressed SENSE was applied with 5.3 times acceleration to enhance the imaging efficiency (hereafter CS-SENSE). To examine the image quality with comparable acceleration, scans were also performed with 1) 5 times SENSE acceleration in phase encoding direction (hereafter SENSE-1), 2) 2.6 and 2.0 times SENSE acceleration in both phase encoding and slice encoding directions (hence a total acceleration factor of 5.2, hereafter SENSE-2), and 3) 2.6 and 2.0 times SENSE acceleration in both phase encoding and slice encoding directions with oversampling in the slice encoding direction (hereafter SENSE-3). Other imaging parameters were the same as abovementioned.

Results

Imaging time for CS-SENSE, SENSE-1, SENSE-2, and SENSE-3 were 2m39s, 2m40s, 2m32s, and 5m17s, respectively. Figure 1 illustrates a comparison of CS-SENSE and SENSE-1 using the same net acceleration factor of about 5. Severe aliasing artifact was observed in the SENSE-1 image while not significant in the image from CS-SENSE. In-plane artifacts were reduced in SENSE-2 when compared to that in SENSE-1, while the through-plane artifact started to present (Figure 2).

Discussion

Our results showed that, under the same acceleration factor of about 5, 3D T2-weighted images can be obtained using compressed SENSE without observable imaging artifacts, at a relatively low field (1.5 T) with a moderate quality coil (7 channels). At the same time, it posed a challenge for traditional SENSE to achieve such a high acceleration factor, where the acceleration factor is heavily limited by the number and alignment of coil elements. When the SENSE acceleration was distributed into two directions, folding-artifacts started to appear in the slice direction, which could be removed by oversampling in the same direction at the cost of doubled imaging time. A further study should be performed to verify the clinical significance of compressed SENSE for T2-weighted breast imaging.

Conclusion

For 3D T2-weigted breast imaging, image acquisition can be highly accelerated by compressed SENSE at 1.5 T.

Acknowledgements

No acknowledgement found.