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/mm
2, sensitivity encoding factor = 2, FOV = 150 x 100 mm, voxel
size = 1.56 × 1.56 × 2 mm
3, 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/mm
2, number of shots = 3; FOV = 150 x 97.5 mm,
voxel size = 2.17 × 1.88 × 2 mm
3, 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 mm
2/s; mean ± standard deviation) was
significantly lower than that of inflammation (1.15 ± 0.45 x10-3 mm
2/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 mm
2/s
vs. 1.58 ± 0.76 x10
-3 mm
2/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.