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Simultaneous multi-slice echo planar imaging for accelerated diffusion-weighted imaging of malignant and benign breast lesions
Sabine Ohlmeyer1, Frederik Bernd Laun1, Theresa Palm1, Rolf Janka1, Elisabeth Weiland2, Michael Uder1, and Evelyn Wenkel1

1Institute of Radiology, University Hospital Erlangen, Erlangen, Germany, 2Application Development, Siemens Healthcare, Erlangen, Germany

Synopsis

The diagnostic accuracy of breast MRI can be increased by performing an additional diffusion sequence (EPI), however, further extending the examination time. Aim of our study was to investigate simultaneous multi-slice (SMS) accelerated EPI (TA 1:37 min) compared to the standard sequence (TA 2:57 min) in a clinical study. Image quality, artifacts and the apparent diffusion coefficient (ADC) of 72 breast lesions were determined. SMS-EPI achieved the same ADC values in benign and malignant breast lesions compared to the standard sequence, image quality did not differ. This indicates that SMS acceleration can be used for diffusion imaging in breast MRI.

Introduction:

Since low apparent diffusion coefficients (ADCs) in breast lesions are associated with malignancy1, 2, it is advantageous to acquire diffusion-weighted data in breast MRI. One approach to reduce the examination time needed for the diffusion sequence is simultaneous multi-slice (SMS) imaging 3. SMS-accelerated echo planar imaging (SMS-EPI) was shown to be similar to no-SMS-EPI in terms of image quality in other body regions such as liver 4, kidney 5 and prostate 6. For breast MRI, a study involving eight healthy volunteers suggested an equivalence of SMS-EPI to standard-EPI 7. Extending these results, the aim of our clinical study was to compare the diagnostic value of SMS-EPI in malignant and benign lesions of the breast compared to no-SMS-EPI.

Material and Methods:

The study was approved by the institutional ethics committee. 68 patients were examined with a diffusion-weighted EPI (standard-EPI, TE = 54 ms, TR = 9.000 ms, TA 2:57 min) and a prototypic diffusion-weighted SMS accelerated EPI (SMS-EPI, acceleration factor 2, TE = 58 ms, TR = 4.300 ms, TA 1:37 min) in addition to the standard MRI protocol. Further acquisition parameters were: 3T MAGNETOM Skyra (Siemens Healthcare, Erlangen, Germany), 2.5 mm isotropic resolution, field of view = 185 to 190 x 350 mm², 62 slices, b = 50 and 800 s/mm² with 1 and 4 averages. A dedicated 16-channel bilateral breast coil was used for imaging. Image quality was evaluated for the presence of artifacts, signal voids and quality of fat suppression. These parameters were rated using a 5-point Likert scale (1 = very strong to 5 = negligible). The ADC was measured in 72 focal lesions (46 breast carcinomas and 26 benign lesions) and the diagnostic value of the two data sets was evaluated and statistically compared.

Results:

Figure 1 shows representative image data. Artifacts and signal voids were negligible in both sequences (mean on Likert scale 4.68 vs. 4.65, p = 0.52 and mean on Likert scale 4.85 vs. 4.77, p = 0.14). Fat suppression was significantly better in SMS-EPI (mean on Likert scale 3.28 vs. 2.97, p <.001, r = 0.49). For benign lesions, the ADC in both EPI sequences was 1.86 ⋅ 10-3 mm2/s. For malignant lesions, a mean ADC of 0.90 ⋅ 10-3 mm2/s for standard-EPI and 0.89 ⋅ 10-3 mm2/s for the SMS-EPI was found. A significant difference was observed neither for ADC values (p = 0.75) nor for the area under the curve (AUC) (SMS 0.985, no-SMS 0.975). The cutoff for differentiation of benign and malignant lesions was at ADC = 1.42 ⋅ 10-3 mm2/s for SMS-EPI (sensitivity 0.89, specificity 1) and at 1.32 ⋅ 10-3 mm2/s for standard-EPI (sensitivity 0.92, specificity 1). An overview of results is shown in table 1.

Discussion:

We observed no difference with regard to diagnostic value and image artifacts between the two sequences with a slightly better fat signal suppression in the SMS-EPI. Our ADC threshold of 1.32 ⋅ 10-3 mm2/s in standard-EPI and 1.42 ⋅ 10-3 mm2/s in SMS-EPI for the differentiation of benign and malignant breast lesion is in line with published values (1.25 ⋅ 10-3 mm2/s) in EPI at 3.0 T 1, 8. In our setting, we achieved acceleration by a factor of two. In general, this acceleration factor may depend on the desired image parameters.

Conclusion:

Our data indicates that SMS acceleration can be used for diffusion imaging in breast MR in everyday clinical practice. Image quality and ADC values are equivalent to non-accelerated EPI, thus the SMS-EPI achieves the same diagnostic accuracy in breast MRI, but in a substantially reduced scan time.

Acknowledgements

No acknowledgement found.

References

  1. Bogner W, Gruber S, Pinker K, et al. Diffusion-weighted MR for differentiation of breast lesions at 3.0 T: how does selection of diffusion protocols affect diagnosis? Radiology. 2009;253(2):341-51.
  2. Ei Khouli RH, Jacobs MA, Mezban SD, et al. Diffusion-weighted imaging improves the diagnostic accuracy of conventional 3.0-T breast MR imaging. Radiology. 2010;256(1):64-73.
  3. Larkman DJ, Hajnal JV, Herlihy AH, Coutts GA, Young IR, Ehnholm G. Use of multicoil arrays for separation of signal from multiple slices simultaneously excited. J Magn Reson Imaging. 2001;13(2):313-7.
  4. Boss A, Barth B, Filli L, et al. Simultaneous multi-slice echo planar diffusion weighted imaging of the liver and the pancreas: Optimization of signal-to-noise ratio and acquisition time and application to intravoxel incoherent motion analysis. Eur J Radiol. 2016;85(11):1948-55.
  5. Kenkel D, Barth BK, Piccirelli M, et al. Simultaneous Multislice Diffusion-Weighted Imaging of the Kidney: A Systematic Analysis of Image Quality. Invest Radiol. 2017;52(3):163-9.
  6. Weiss J, Martirosian P, Taron J, et al. Feasibility of accelerated simultaneous multislice diffusion-weighted MRI of the prostate. J Magn Reson Imaging. 2017;46(5):1507-15.
  7. Filli L, Ghafoor S, Kenkel D, et al. Simultaneous multi-slice readout-segmented echo planar imaging for accelerated diffusion-weighted imaging of the breast. Eur J Radiol. 2016;85(1):274-8.
  8. Bogner W, Pinker-Domenig K, Bickel H, et al. Readout-segmented echo-planar imaging improves the diagnostic performance of diffusion-weighted MR breast examinations at 3.0 T. Radiology. 2012;263(1):64-76.

Figures

Fig. 1: Images of the breasts of a 38 year old patient with mass enhancing lesion (NST) in the left breast. The tumor is well visible in the diffusion-weighted images and in the ADC maps. A: T1w dixon; B: T1w DCE, subtraction; C: standard-EPI with b-value of 800 s/mm2; D: standard-EPI ADC map; E: SMS-EPI with b-value of 800 s/mm2; F: SMS-EPI ADC map.

Tab. 1: Overview of results

Proc. Intl. Soc. Mag. Reson. Med. 27 (2019)
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