Application of High B-Value High-Resolution Diffusion-Weighted Imaging in Differentiating Malignant from Benign Thyroid Nodules
Qingjun Wang1, Yong Guo1, Jing Zhang1, Minghua Huang1, Qinglei Shi2, and Tianyi Qian2

1Radiology, Chinese Navy General Hospital, Beijing, China, People's Republic of, 2Scientific Marketing, Siemens Healthcare, Beijing, China, People's Republic of

Synopsis

In this study, we evaluated the advantages of using high b-value high-resolution diffusion-weighted MR imaging (DWI) to differentiate between malignant and benign thyroid nodules. This prospective study included 28 consecutive patients with thyroid nodules (14 malignant nodules in 10 patients and 24 benign nodules in 20 patients). Three b-values including b-values of 0, 800 and 2000 sec/mm2 and a Readout Segmentation Of Long Variable Echo-trains (RESOLVE) imaging technique were used in the high b-value high-resolution DWI. The results showed that the high b-value high-resolution DWI can further increase the diagnostic accuracy for thyroid nodules with the best sensitivity, specificity and area under receiver operating characteristic curve (AUC) than low b-value or single high b-value.

PURPOSE

High b-value diffusion-weighted MR imaging (b-value > 1000 sec/mm2) has proven to be powerful in diagnosing prostate cancers and breast cancers, etc.1,2. However, the use of high b-value DWI to differentiate between malignant and benign thyroid nodules has never been investigated before. The purpose of our study was to evaluate the advantages of multi b-value (b = 0, 800, 2000 sec/mm2) with a commercially available high-resolution DWI imaging technique to differentiate thyroid nodules.

METHODS

The prospective study included 28 consecutive patients with thyroid nodules (14 malignant nodules in 10 patients and 24 benign nodules in 20 patients). All MRI examinations were performed using a 3T MRI scanner (MAGNETOM Skyra; Siemens Healthcare, Erlangen, Germany) and a bilateral 8-channel phased-array surface coil. Images were acquired in axial orientation and in the following order: T2-weighted fast spin echo sequence with fat suppression, T1-weighted fast spin echo sequence with fat suppression, high-resolution DWI with frequency-selective fat saturation. The high b-value high-resolution DWI images were collected using the RESOLVE technique1 with the following parameters: iPAT factor = 2 (GRAPPA), repetition time / echo time = 7700 / 67 msec, field of view = 175 mm, average = 1, matrix = 120 × 120, slice thickness = 3.0 mm, gap = 0.3 mm. Diffusion gradients were applied sequentially with b-values of 0, 800 and 2000 sec/mm2, and ADC maps were automatically generated online based on the three b-values. The scan time of the high-resolution DWI was 5 minutes and 45 seconds. The ADC value, signal intensity of each nodule (SInodule) and signal intensity of normal thyroid tissue (SINTT) were measured on ADC maps and DWI images independently by 2 experienced radiologists. All images including the T1- and T2-weighted images and nodular signals in the DWI maps were qualitatively reviewed first, and region of interest (ROI) for each nodule was drawn manually. Then the mean ADC value of each nodule was calculated based on the radiologists’ measurements. The diagnostic accuracy of ADC values was evaluated in terms of sensitivity, speci´Čücity and area under receiver operating characteristic (ROC) curve (AUC). All the nodules were proven by postoperative pathology.

RESULTS

Benign thyroid nodules included nodular goiter (n = 19), adenoma (n = 3) and thyroiditis (n = 2). Malignant thyroid nodules included papillary carcinoma (n = 12) and follicular adenocarcinoma (n = 2). On DWI images with b-value = 0 sec/mm2, the malignant thyroid nodules presented a lower ratio of SInodule/SINTT than that of benign nodules (1.37 ± 0.64 vs. 2.14 ± 0.91, P = 0.009). If ≤ 1.56 is adopted as the cutoff value, the sensitivity, specificity and AUC were 78.75%, 70.83% and 0.75. On DWI images with b-value = 800 sec/mm2, however, the malignant thyroid nodules showed a higher ratio of SInodule/SINTT than that of benign nodules (2.76 ± 1.23 vs. 1.37 ± 0.66, P < 0.001). If > 1.60 is selected as the cutoff value, the sensitivity, specificity and AUC were 85.71%, 75.00% and 0.84. On DWI images with b-value = 2000 sec/mm2, the malignant thyroid nodules showed a much higher ratio of SInodule/SINTT than that of benign nodules (3.35 ± 1.98 vs. 0.89±0.47, P < 0.001, Fig. 1 and 2). If > 1.55 is applied as the cutoff value, the sensitivity, specificity and AUC were 85.71%, 87.50% and 0.90. Furthermore, on the ADC maps obtained by combining the 3 b-values, the malignant thyroid nodules presented a lower mean ADC value than that of benign nodules (0.89 ± 0.14 × 10-3 mm2/sec vs. 1.55 ± 0.23 × 10-3 mm2/sec, P < 0.001, Fig. 3). If ≤ 1.105 × 10-3 mm2/sec is adopted as the cutoff value, the sensitivity, specificity and AUC were 100.00% (95% CI, 76.80%-100.00%), 100.00% (95% CI, 85.80%-100.00%) and 1.00.

DISCUSSION

High-resolution and high b-value DWI imaging pose a significant challenge for gradient hardware. Increasing the matrix and b-value will lead to longer TE and lower SNR. RESOLVE is a multi-shot EPI sequence with low susceptibility based image distortion which allows the reduction of TE for each individually-acquired segment and can thus obtain high-quality DWI images with both high resolution and high b-value.3 From the figures shown in this study, we can see that distortion was reduced and SNR was increased by using RESOLVE in comparison with single-shot EPI.

CONCLUSION

Compared with the conventional b-value DWI (b-value ≤ 1000 sec/mm2), high b-value high-resolution DWI using RESOLVE can increase the diagnostic accuracy for thyroid nodules. And the ADC value obtained by combining DWI images with three b-values (0, 800, 2000 sec/mm2) shows the best performance.

Acknowledgements

No acknowledgement found.

References

1. Wisner D. J., Rogers N., Deshpande V. S., et al. High-resolution diffusion-weighted imaging for the separation of benign from malignant BI-RADS 4/5 lesions found on breast MRI at 3T. Journal of Magnetic Resonance Imaging. 2014;40(3):674-681.

2. Liney G. P., Holloway L., Al Harthi T. M., et al. Quantitative evaluation of diffusion-weighted imaging techniques for the purposes of radiotherapy planning in the prostate. The British journal of radiology. 2015;88(1049):20150034.

3. Porter, D. A., Heidemann, R. M. High Resolution Diffusion Weighted Imaging Using Readout Segmented Echo Planar Imaging, Parallel Imaging and Two Dimensional Navigator based Reacquisition. Magnetic Resonance in Medicine. 2009;62(2):468-475.

Figures

Fig. 1 A thyroid adenoma in isthmus and left lobe of a 41-year-old man. The SInodule/SINTT of the nodule decreases with increasing b-values (white arrows).

Fig. 2 A thyroid papillary carcinoma in right lobe of a 26-year-old woman. The SInodule/SINTT of the nodule increases with increasing b-values (white triangles).

Fig. 3 A nodular goiter in right thyroid lobe and a papillary carcinoma in left thyroid lobe on MR images of a 52-year-old woman. The nodular goiter is marked as white triangle, and the papillary carcinoma is marked as white arrow-head.



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