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Improvement of 2D-multi-slice, multi-shot Cartesian T2-weighted TSE using golden angle shot reordering
Yuki Furukawa1, Takashige Yoshida1,2, Masami Yoneyama3, Kouhei Yuda1, Mariko Okura1, and Nobuo Kawauchi1

1Radiology, Tokyo Metropolitan Police Hospital, Tokyo, Nakano-ku, Japan, 2Graduate School of medicine Health Sciences, Images Analysis, Tohoku University, Sendai, Miyagi, Japan, 3IS Business Group, Philips Japan, Minato-ku, Tokyo, Japan

Synopsis

2D multi-slice, multi-shot Cartesian TSE sequence is frequently used for routine MRI but it is sensitive to motion. We evaluated the feasibility of golden angle shot reordering for 2D-multi-shot TSE with 60 patients. Golden angle shot reordering reduced effectively ghost artifacts by randomly filling in each segment of Cartesian k-space. We demonstrated that golden angle shot reordering intrinsically has a motion robustness without penalty for image quality and scan time. This technique might be useful for all anatomies in routine clinical examination..

Purpose

Two-dimensional multi-slice, multi-shot Cartesian TSE (2D-MS TSE) sequence is frequently used for routine magnetic resonance imaging (MRI). In 2D-MS TSE, various motion-compensation techniques, such as single-shot sequence, faster sequences with breath-hold acquisition, and signal averaging with multiple NSA, correspond to the motion of the body1,2, but such techniques potentially deteriorates image quality. With the aim of addressing this issue, recent studies have reported the utility of golden angle radial sampling3-4. To apply motion-compensation effects of golden angle sampling for Cartesian TSE, a new k-space shot reordering, called golden angle shot reordering, is developed. In this study, we investigate the effects of golden angle shot reordering in 2D-MS TSE.

Theory

In Cartesian TSE, k-space is basically divided segments into number of echo train length, and actual order in each segment (shot order) is filed sequentially from the lower end to the upper end (linear shot reordering) [Fig.1,2]. On the other hand, golden angle shot reordering performs unique filling-up method based on calculated golden angle step in each segment [Fig.1, 2]. Theoretically, this technique does not adversely affect for the image quality and scan time.

Experiments:

The protocol was approved by the local ethics committee, and a total of 60 patients (42 men, mean age 57.9 ± 16.0 years) provided written informed consent. Images were acquired on a clinical MR scanner (Achieva 1.5T and 3.0T, Philips Healthcare). 2D-MS TSE with linear and golden angle shot reordering were perfumed at the abdomen (N=20), pelvis (N=20), and spine (N=20). We visually compared golden angle shot reordering with conventional linear shot reordering. Visual evaluation (VE) was performed by four radiologists to assess overall image quality, ghost artifacts, and blurring artifacts. Actual evaluation manner is shown in Table.1. All comparisons were performed with a Wilcoxon t-test and P value of < 0.05 was considered to be statistically significant.Imaging parameters for abdomen were: transverse, TR/TE=1500/100ms; FOV = 350×350×74 mm3, resolution=1.04×1.68×4mm3; ETL=21; SENSE=2.0; navigator triggering and scan duration-1min2sec. Imaging parameters for pelvis were: sagittal, TR/TE=3200/100ms; FOV=250×200×70 mm3; ETL=20; resolution=0.72×0.92×5mm3; SENSE=1.8 and scan duration-1min30sec. Imaging parameters for pelvis were: sagittal, TR/TE=2000/100ms; FOV=150×300×40 mm3; ETL=25; resolution=0.65×1.33×4mm3 and scan duration-1min28sec.

Results

Golden angle shot reordering provided good image quality with reduced motion artifacts. Table.2 summarizes the VE scores. Compared to conventional linear shot reordering, golden angle shot reordering was superior in any items, only except with regard to blurring artifacts in the pelvis. Overall image quality of golden angle shot reordering was significantly better than that of linear reordering in all anatomies. Ghost artifacts of golden angle shot reordering was significantly better than that of linear reordering in the pelvis and spine. Blurring artifacts of golden angle shot reordering was significantly better than that of linear reordering in the spine.

Discussion and Conclusion

Golden angle shot reordering reduced effectively ghost artifacts by randomly filling in each segment and thus the influence of motion was distributed entire the k-space like a noise. We demonstrated that golden angle shot reordering intrinsically has a motion robustness without penalty for image quality and scan time. This technique might be useful for all anatomies in routine clinical examination.

Acknowledgements

No acknowledgement found.

References

[1] Chavhan GB et al; Radiographics 2013(33):703–719

[2] Yang RK et al; RadioGraphics 2010;30(1):185–199.

[3] Winkelmann S et al; IEEE Trans Med Imaging. 2007 Jan;26(1):68-76.

[4] Chandarana H et al; Proceedings of the 20th Annual Meeting of the ISMRM; Melbourne, Australia. 2012;

Figures

Fig. 1 Differences of shot reordering

Fig. 2　Comparison of actual shot reordering

Fig. 3 Representative images of conventional linear shot reordering and golden angle shot reordering.

Table 1. Clinical reader scores for comparison of linear and golden angle shot reordering

Table 2. Results of visual evaluation

Proc. Intl. Soc. Mag. Reson. Med. 26 (2018)
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