Optimization of Direct-coronal Diffusion-weighted Whole Body Imaging with Background Suppression (DWIBS) Using Single-shot Turbo Spin-echo (TSE) at 3T MRI.

Makoto Suzuki¹, Tatsuya Kuramoto¹, Yuki Hachiman¹, Yu Nishina², Satoru Morita², Kayoko Abe², and Masami Yoneyama³

¹Department of radiological servece, Tokyo Women's Medical University Hospital, Tokyo, Japan, ²Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University Hospital, Tokyo, Japan, ³IS Business Group, Philips electronics japan, Tokyo, Japan

Synopsis

Direct-coronal diffusion-weighted whole body imaging with background body signal suppression using single-shot turbo spin-echo (TSE-DWIBS) with b-values of 400, 600, 800, and 1000 mm2/s, and DWIBS using echo-planner imaging (EPI-DWIBS) with b-value of 1000mm2/s were obtained using 3T MR scanner in 5 healthy volunteers. We investigated optimal b-value of TSE-DWIBS and compared image distortions, contrast, signal-to-noise ratio (SNR), and artifacts between TSE-DWIBS and EPI-DWIBS. Image contrast and SNR of TSE-DWIBS with b-value of 800 mm2/s were equivalent to those of EPI-DWIBS with b-value of 1000 mm2/s. TSE-DWIBS had less image distortions and artifacts than EPI-DWIBS. Direct-coronal TSE-DWIBS using 3T MRI can be applied for clinical cases.

Introduction

Diffusion-weighted whole body imaging with background body signal suppression (DWIBS) can visualize malignant tumors, abscesses, and abnormal lymph nodes [1]. Single-shot echo-planner imaging (EPI) is commonly used for DWIBS (EPI-DWIBS) at 1.5T MRI. However, at 3T MRI EPI-DWIBS has problem of image distortions and various artifacts [2]. Currently, development of MR devices, including the coils and application software, brought about DWI using single-shot turbo spin-echo (TSE-DWI) at 3T MRI and TSE-DWI is reported to show less image distortions and artifacts in comparison with EPI technique [3] . Therefore, we expect that direct- coronal TSE-DWIBS is capable of creating higher image quality with shorter acquisition time than EPI-DWIBS.

Purpose

We investigated optimal b-value of TSE-DWIBS and compared image distortions, contrast, signal-to-noise ratio (SNR), and artifacts between TSE-DWIBS and EPI-DWIBS.

Methods

All examinations were performed using 3T MR scanner (Inenia, Phillips) in 5 healthy volunteers (4 males, 1 female; mean age: 28.4 years; range: 26-32 years) and included direct-coronal TSE-DWIBS, EPI-DWIBS and T2WI from neck to pelvis. Imaging parameters of TSE-DWIBS was based on those of EPI-DWIBS with b-value of 1000 mm2/s [4] (Table 1).

This study consists of three parts:

(1) Image distortions

We measured image distortions at each spinal cord level (C5, Th3, Th8, L1) using fusion images of T2WI and TSE-DWIBS (b-value: 600 mm2/s) or EPI-DWIBS (Fig. 1).

(2) Contrasts and SNR

We calculated the latissimus dorsi-to-spinal cord signal intensity ratio (referring to lesion-to spinal cord ratio (LSR) [5] ) of EPI-DWIBS and TSE-DWIBS (b-value: 400, 600, 800, 1000 mm2/s) to evaluate contrast of each images. SNRs were calculated by dividing the average signal intensity in the region of interest (ROI), which was set in the latissimus dorsi, with the standard deviation of signal intensity in the ROI.

(3) Image quality assessment

Two independent readers estimated the overall image quality including artifacts and SNR (Fig. 2).

Results

(1) Image distortions

✓EPI-DWIBS C5: 7.4 ± 1.7mm, Th3: 3.6 ± 2.2mm, Th8: 0.75 ± 1.3mm, L1: 4.2 ± 2.5mm. Some points were unmeasurable (especially Th3) .

✓TSE-DWIBS (b-value: 600 mm2/s) All points were measurable and no image distortion was noted at all levels.

(2) Contrasts and SNR

✓LSR of EPI-DWIBS (b-value: 1000 mm2/s): 4.3 ± 0.62

✓LSR of TSE-DWIBS with b-value: 400 mm2/s: 3.4 ± 0.26, 600 mm2/s: 4.0 ± 0.41, 800 mm2/s: 4.4 ± 0.61, 1000 mm2/s: 4.7 ± 0.62

✓SNR of EPI-DWIBS (b-value: 1000 mm2/s): 10.1 ± 2.2

✓SNR of TSE-DWIBS with b-value: 400 mm2/s: 20.1 ± 5.6, 600 mm2/s: 13.3 ± 1.7, 800 mm2/s: 10.3 ± 1.8, 1000 mm2/s: 10.1 ± 2.2.

(3) Image quality assessment Compared to TSE-DWIBS, EPI-DWIBS showed insufficient signal suppression of fatty tissue in all images. TSE-DWIBS showed less image distortion; however, using higher b-value lead to lower SNR and using lower b-value showed effects of signal intensity of urinary bladder and cerebral spinal fluid.

Disscussion

In this study, EPI-DWIBS shows imaging distortions to the phase encoding direction, and no signal was noted at several regions due to susceptibility artifacts. We suspected that chemical artifacts caused insufficient signal suppression of fatty tissue on EPI-DWIBS. In contrast, TSE-DWIBS had no effect on phase encoding direction and various artifacts. As for LSR and SNR, the values of EPI-DWIBS with b-value of 1000 mm2/s was close to those of TSE-DWIBS with b-value of 800 mm2/s. Since lower b-value of DWIBS leads to less water signal suppression and higher b-value of DWIBS leads to lower SNR, we are considered that TSE-DWIBS with b-value of 800 mm2/s would be an ideal setting for yielding a detailed image in these imaging parameters.

Conclusion

Direct-coronal TSE-DWIBS displays less image distortions and less various artifacts than EPI-DWIBS. TSE-DWIBS with b-value of 800 mm2/s is comparable to EPI-DWIBS with b-value of 1000 mm2/s with regard to LSR, SNR, and image quality assessment. We suggest that direct-coronal TSE-DWIBS using 3T MRI can be applied to clinical cases.

Acknowledgements

No acknowledgement found.

References

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2. Kwee, T. C, Takahara, T. Ochiai, R. Diffusion-weighted whole-body imaging with background body signal suppression (DWIBS): features and potential applications in oncology. Eur Radiol. 2008;18:1937–1952

3. Verhappen MH, Pouwels PJ, Ljumanovic R, et al. Diffusion-weighted MR imaging in head and neck cancer: comparison between half-fourier acquired single-shot turbo spin-echo and EPI techniques. AJNR Am J Neuroradiol. 2012;33:1239-46.

4. Mürtz, P, Kaschner, M, Träber, et al. Diffusion-weighted whole-body MRI with background body signal suppression: Technical improvements at 3.0 T. J. Magn. Reson. Imaging. 2012;35:456–461.

5. Uto T, Takehara Y, Nakamura Y, et al. Higher sensitivity and specificity for diffusion-weighted imaging of malignant lung lesions without apparent diffusion coefficient quantification. Radiology. 2009;252:247–254

Figures

Imaging parameters of diffusion weighted whole body imaging with background body signal suppression using single-shot echo-planner imaging with (EPI-DWIBS), diffusion weighted whole body imaging with background body signal suppression using single-shot turbo spin-echo (TSE-DWIBS) and T2-weighted imaging.

Fusion images of T2WI and EPI-DWIBS with b-value: 1000 mm2/s (Fig.1-a, 1-c) and Fusion images of T2WI and TSE-DWIBS with b-value: 600 mm2/s (Fig.1-b, 1-d). Image distortions to the right is noted on EPI-DWIBS (➔).　In contrast, no image distortion is noted on TSE-DWIBS (▲).

EPI-DWIBS shows insufficient signal suppression of fatty tissue due to chemical shift artifacts (▲) . TSE-DWIBS with higher b-values (800 and 1000 mm2/s) showed sufficient signal suppression of the he bladder and the cerebral spinal fluid compared to TSE-DWIBS with lower b-values (400 and 600 mm2/s) (➔).

Subcutaneous and muscle hemangiomas are noted in the left side of pelvis (➔). TSE-DWIBS can visualize the lesions as well as EPI-DWIBS and fusion image of T2WI and TSE-DWIBS is helpful to clarify anatomical information of the lesions.

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

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