3202
Combination of Echo Planar Imaging Correction and Compressed SENSE Framework for enhanced Diffusion weighted imaging1Philips Healthcare, Beijing, China, 2MR Clinical Science, Philips Healthcare (Suzhou), Suzhou, China, 3MR R&D, Philips Healthcare (Suzhou), Suzhou, China
Synopsis
Diffusion-weighted imaging (DWI) using single-shot EPI (ssEPI) has suffered from distortion, blurring, and signal loss caused by B0 inhomogeneity. SENSE can be used to reduce distortion. However, it also suffers from noise breakthrough issues when the accelerator factor is high. It’s still a challenge to get DWI images with reduced distortion and high SNR without significantly increasing the scan time. We propose a framework that combines FSL top-up technique, Compressed Sensing and SENSE framework simultaneously to overcome these challenges. This framework allows a new solution for ssEPI based diffusion imaging with high resolution, low distortion, and without noise breakthrough issue.
Purpose
The goal of this work is to provide a new solution which combines the Echo Planar Imaging Correction using FSL top-up correction (EPIC)，Compressed Sensing (CS) and SENSE simultaneously (EPICS+) simultaneously to reduce distortion and overcome the noise breakthrough issue at the same time.Introduction
Diffusion weighted imaging (DWI) based on ssEPI has been widely used for oncological applications and microstructure study1. But it suffers severe geometry distortion, image blurring, and signal voids which are caused by the local B0 inhomogeneity1. To improve resolution and reduce the distortion of DWI, several methods have been used, such as Multi-shot DWI2, reduced FOV3, parallel imaging4, and Echo Planar Imaging Correction using top-up (EPIC) 5. However, the scan time will be increased for multi-shot DWI. DWI with reduced FOV can only be used for small FOV. The top-up based DWI combined with conventional parallel imaging is one promising method to reduce the distortion with high time efficiency, and has been widely used. However, it does not work well when the B0 inhomogeneity is large. In addition, for high b value diffusion image, it also often suffers from increased noise-like artifacts on the center of the images due to the high geometry factor when large reduction factors are used with respect to the coil geometry characteristics5. ssEPI utilizing CS and SENSE framework (EPICS) has been used to solve the noise breakthrough issues when large reduction factors are used6. We propose a new scheme that combines EPIC, CS and SENSE framework simultaneously with high acceleration factor to produce DWI images with low distortion and relative high SNR.Methods
CS could dramatically reduce noise-like artifacts, so it can be used for much higher accelerator combined with SENSE than conventional parallel imaging methods, which is called as CS SENSE framework. DWI with CS SENSE framework could have less distortion and higher SNR than DWI with conventional parallel imaging methods when the acceleration factor is same. We combined FSL top-up correction method, CS SENSE framework simultaneously (we called it EPICS+), the reconstruction and postprocessing pipeline as Fig 1. In this scheme the blip-up images were acquired for only b value equals 0. The blip-down images were acquired for all b value. Both blip-up and blip down acquisition were reconstructed with Compressed SENSE framework. Then the module of FSL topup7,8 was used to realize the top up correction using the images of blip-up and blip-down. Finally the corrected images were output by the pipeline. To evaluate the performance of EPICS+, conventional DWI based on ssEPI, EPIC, EPICS and our proposed EPICS+ were acquired on a Philips 3.0T Elition system (Philips Healthcare, Suzhou, China) with a 16-ch head and spine coil. The characteristics of these techniques were summarized on Table 1. For conventional DWI using ssEPI, SENSE was used, the SENSE factor is 2. For EPIC, it also uses SENSE, SENSE factor 4 was used. For EPICS, it also uses CS SENSE framework for reconstruction, acceleration factor equals 4 was use. For our proposed EPICS+, acceleration factor equals 4 was used, both for blip up and down acquisition. TSE has also been scanned. Detailed scan parameters were summarized in Table 2.Results
Fig. 2 shows the comparison between conventional DWI based on ssEPI, EPIC, EPICS and our proposed EPICS+. Compared with other techniques, our proposal EPICS+ has the best SNR and lower distortion. The image quality was dramatically improved with EPICS+, as the dashed red line and dashed yellow line showed. Compared with anatomical T2W images, conventional DWI with ssEPI has good SNR but with severe distortion, EPIC with SENSE 4 shows noise breakthrough issue with good distortion performance, EPICS with acceleration factor 4 shows good SNR but it has larger distortion than EPICS+. The results shows that our proposed EPICS+ has best performance on SNR and minimum distortion level than other methods. Although further clinical investigation is needed, EPICS+ might be clinically useful and promising in high resolution, low distortion DWI and without noise breakthrough issue.Discussion and conclusions
The proposed method EPICS+ shows lower distortion and also higher SNR for DWI imaging compared with conventional DWI, EPIC and EPICS. This strategy could enhance the applicability and offer a new solution of DWI in applications that is expected for high resolution and low distortion, such as brain, spine, prostate etc. Because this method doesn’t increase the scan time, it should also be promising for fMRI.Acknowledgements
No.References
1. Bihan DL, Poupon C, Amadon A, Artifacts and pitfalls in diffusion MRI, J. Magn. Reason., 2006; 24: 478-488.
2. Jeong HK, Gore JC, Anderson AW, High-resolution human diffusion tensor imaging using 2-D navigated multishot SENSE EPI at 7T, Magn. Reason. Med. 2013; 69: 793-802.
3. Wu ZG, Zhang J, Fang WX, Huang F, B1 insensitive zoomed FOV imaging, ISMRM., 2015; 0953.
4. Pruessmann KP, Weiger M, Scheidegger M, Boesiger P，SENSE: sensitivity encoding for fast MRI, Magn. Reason. Med., 1999;42(5):952-62.
5. Andersson JLR, Skare S, Ashburner J, How to correct susceptibility distortions in spin-echo echo-planar images: application to diffusion tensor imaging, NeuroImage, 2003; 20(2):870-888.
6. Yoneyama M, Morita K, Peeters J, Nakaura T, Cauteren MV, Noise Reduction in Prostate Single-Shot DW-EPI utilizing Compressed SENSE Framework, Proc. ISMRM. ,2019;1634. https://archive.ismrm.org/2019/1634.html.
7. De Luca M, Drobnjak I, Flitney DE, Niazy R, Saunders J, Vickers J, Zhang Y, et. al., Advances in functional and structural MR image analysis and implementation as FSL. NeuroImage, 2004; 23(S1):208-219.
8. Tournier JD, Smith R, Raffelt D, Tabbara R, et.al., MRtrix3: A fast, flexible and open software framework for medical image processing and visualization, NeuroImage, 2019; 202:116137.
Figures
