Dixon with view angle tilting for improved post-contrast MRI of the prostate

Silke Hey¹, Vijayasarathy Elanchezhian², and Marius van Meel²

¹Clinical Excellence & Research, Philips HealthTech, Best, Netherlands, ²MR Clinical Applications, Philips HealthTech, Best, Netherlands

Synopsis

A T1w TSE Dixon acquisition is combined with view angle tilting (VAT) in order to reduce susceptibility induced artifacts from orthopedic implants close to the prostate and at the same time improve fat suppression in the area of interest. The comparison with SPIR fat suppression shows clear improvement when using Dixon together with VAT by providing more homogeneous and complete fat suppression and reduced susceptibility artifacts thus allowing clear visualization of T1 based contrast changes in the prostate and the surrounding tissue. Those results have been proven at 1.5T and 3.0T on healthy volunteers with orthopedic hip implants.

Introduction

MRI for diagnosis and follow-up of prostate cancer relies on multi-parametric imaging including contrast enhanced studies [1]. Those are heavily affected by artifacts caused by orthopedic implants specifically in the hip. Especially for pre- and post-contrast acquisitions homogeneous fat suppression in the area of interest is critical in order to reliably track the contrast uptake. Spectral fat suppression techniques like Spectral Presaturation with Inversion Recovery (SPIR) and Spectral Attenuated Inversion Recovery (SPAIR) usually fail in areas of large magnetic field inhomogeneities. Short tau inversion recovery (STIR) is an alternative since it provides a more robust suppression of fat, but leads to signal loss in regions of reduced T1 such as enhanced tissue in post contrast studies. We thus propose a combination with View Angle Tilting (VAT) [2] with Dixon-based fat suppression [3] in order to simultaneously reduce the metal-induced susceptibility artifact and provide reliable fat suppression in and around the prostate for post contrast studies.

Methods

Two healthy male volunteers with orthopedic hip implants were scanned on a 1.5T and 3.0T Ingenia MR scanner (Philips HealthTech, The Netherlands). T1 weighted multi-shot turbo spin echo (TSE) images were acquired in coronal and transverse orientation with voxel sizes of 0.9-1.0x1.4x5mm and TR/TE of 400-500/10-20ms. The same sequences were subsequently combined with SPIR, SPIR and VAT, and 2-point TSE Dixon (1.5T: TE1/TE2 = 6/10ms; 3.0T: TE1/TE2 = 18/20ms) and VAT.

Results

Figure 1 shows transverse and coronal acquisitions on 1.5T. Images a), e) show that without fat suppression, VAT provides sufficient artifact reduction in order to visualize the prostate and adjacent structures. Images b), f) using SPIR fat suppression without VAT show inhomogeneous fat suppression especially in the proximity of the implants as well as signal voids reaching out as far as the prostate. Images c), g) show a small improvement by adding VAT to the SPIR sequence. However, the artifact due to failing fat suppression remains dominant in the prostate area. Finally, images d), h) using Dixon and VAT show homogeneous fat suppression except in the direct vicinity of the implant. The area affected by susceptibility artifacts and/or failing suppression is clearly reduced. As a result, the prostate and surrounding tissue are clearly visualized. Figure 2 shows coronal images of a second volunteer at 3.0T. T1w TSE with VAT (Figure 2a) provides good visibility of the prostate area while failing fat suppression with SPIR is affecting the implant area including the vicinity of the prostate (Figure 2b). The Dixon water image (Figure 2d) shows homogeneous fat suppression except for the FOV edges and the vicinity of the implant. In contrast to SPIR fat suppression, the area of the prostate is not affected.

Discussion and Conclusion

The combination of Dixon-based fat suppression with VAT metal artifact reduction improves the visualization of T1 based contrast changes (e.g. due to T1 based contrast agents) in the prostate and the surrounding tissue in the presence of orthopedic implants at both 1.5T and 3.0T.

Acknowledgements

No acknowledgement found.

References

[1] Hegde JV et al. Multiparametric MRI of Prostate Cancer: An Update on State-of-the-Art Techniques and Their Performance in Detecting and Localizing Prostate Cancer. J Magn Res Imaging 2013;37:1035-1054

[2] Cho ZH et al. Total inhomogeneity correction including chemical shifts and susceptibility by view angle tilting. Med. Phys. 1988;15(1):7-11

[3] Eggers H et al. Dual-Echo Dixon Imaging with Flexible Choice of Echo Times. Magn. Res. Med. 2011;65:96-107

Figures

Figure 1: Male volunteer with stainless steel cannulated screws in the left femoral bone scanned on 1.5T. a), e): T1w TSE + VAT; b), f): T1w TSE SPIR; c), g): T1w TSE SPIR + VAT; d), h): T1w TSE Dixon + VAT water image. The pale yellow outline marks the area affected by susceptibility and/or failing fat suppression. The blue shaded area indicates the prostate. The yellow arrows indicate the part of the prostate affected by the artifact.

Figure 2: Male volunteer with titanium total right hip replacement scanned on 3.0T. a): T1w TSE + VAT, b): T1w TSE SPIR + VAT, c): T1w TSE Dixon + VAT water image. The pale yellow outline marks the area affected by susceptibility and/or failing fat suppression. The blue shaded area indicates the prostate. The yellow arrows indicate the part of the prostate affected by the artifact.

Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)

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