Diffusivity of Intraorbital Lymphoma vs. Inflammation: Comparison of Single Shot Turbo Spin Echo and Multishot Echo Planar imaging Techniques
Akio Hiwatashi1, Osamu Togao1, Koji Yamashita1, Kazufumi Kikuchi1, and Hiroshi Honda1

1Clinical Radiology, Kyushu University, Fukuoka, Japan

Synopsis

Diffusion-weighted imaging is useful to characterize orbital lesions. Various techniques were advocated to overcome image degradation in head and neck regions. We compared single shot TSE and multishot EP DWI and concluded that the ADC derived from TSE DWI, not from multishot EP DWI, might help to differentiate orbital lymphoma from inflammation.

Purpose

Diffusion-weighted imaging is useful to characterize orbital lesions. However, it is often hard to evaluate orbital structures on single shot echo planar (EP) imaging due to susceptibility artifacts. The purpose of this study was to compare single shot turbo spin echo DWI (TSE DWI) with multishot EPI DWI (MSh DWI) to discriminate orbital lymphoma from inflammatory lesions.

Methods

Pathologically proven seven patients with lymphomas and eight with inflammations (four dacryocystitis and four nonspecific) were imaged with a 3T clinical scanner (Ingenia CX, Philips Healthcare, NL). Imaging parameters for TSE DWI are as follows: TR/TE = 6800/72 msec, b factor = 0, 800 sec/mm2, sensitivity encoding factor = 2, FOV = 150 x 100 mm, voxel size = 1.56 × 1.56 × 2 mm3, NSA = 6, and acquisition time = 4 min 47 sec. Imaging parameters for MSh DWI are as follows: TR/TE = 2337/73 msec, b factor = 0, 800 sec/mm2, number of shots = 3; FOV = 150 x 97.5 mm, voxel size = 2.17 × 1.88 × 2 mm3, NSA = 3, and acquisition time = 3 min 45 sec. ADC and signal intensities compared to normal grey matter on T1-weighted images, fat-suppressed T2-weighted images, and fat-suppressed postcontrast T1-weighted images were measured. Statistical analyses were performed with Mann-Whitney U test, paired t test and receiver operating characteristic (ROC) analysis.

Results

The ADC derived from TSE DWI of lymphoma (0.70 ± 0.23 x10-3 mm2/s; mean ± standard deviation) was significantly lower than that of inflammation (1.15 ± 0.45 x10-3 mm2/s; P < 0.05). The ADC derived from MSh DWI and conventional sequences could not separate lymphoma from inflammation (1.27 ± 0.45 x10-3 mm2/s vs. 1.58 ± 0.76 x10-3 mm2/s on ADC map, 0.91 ± 0.16 vs. 0.96 ± 0.13 on T1WI, 0.81 ± 0.18 vs. 0.89 ± 0.33 on T2WI, and 2.02 ± 0.34 vs. 1.93 ± 0.74 on postcontrast T1WI, for lymphoma and inflammation, respectively; P > 0.05). ROC analysis showed the best diagnostic performance with ADC derived from TSE DWI (AUC = 0.839), followed by ADC derived from MSh DWI (0.607), T1WI (0.607), T2WI (0.607) and postcontrast T1WI (0.554). There were statistically significant differences in AUC between the ADC derived from TSE and conventional MRI only (P < 0.05).

Discussion

Lymphoma is known to show restricted diffusion because of hypercellularity. Inflammatory processes including fibrosis and phlebitis may cause higher diffusivity than lymphoma. Therefore DWI is known to beneficial to discriminate lymphoma from inflammation. There are various results regarding ADC measurement using TSE and MSh EP DWI. The noise on EP imaging may artificially increase the signal intensity on DWI, which may result in decreased ADC.

Conclusion

The ADC derived from TSE DWI might help to differentiate orbital lymphoma from inflammation.

Acknowledgements

This work was supported by JSPS KAKENHI Grant Number 26461826.

References

1. Sakamoto J, Imaizumi A, Sasaki Y, et al. Comparison of accuracy of intravoxel incoherent motion and apparent diffusion coefficient techniques for predicting malignancy of head and neck tumors using half-Fourier single-shot turbo spin-echo diffusion-weighted imaging. Magn Reson Imaging. 2014;32(7):860-6.

2. Yamashita K, Yoshiura T, Hiwatashi A, et al. Detection of middle ear cholesteatoma by diffusion-weighted MR imaging: multishot echo-planar imaging compared with single-shot echo-planar imaging. AJNR. 2011; 32(10):1915-8.

Figures

ROC analysis showed the best diagnostic performance with ADC derived from TSE DWI (AUC = 0.839), followed by ADC derived from MSh DWI (0.607), T1WI (0.607), T2WI (0.607) and postcontrast T1WI (0.554).



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