Separating Glioma Hyperintensities From White Matter by Diffusion-Weighted Imaging With Spherical Tensor Encoding

Jan Brabec; Faris Durmo; Filip Szczepankiewicz; Patrik Brynolfsson; Björn Lampinen; Anna Rydelius; Linda Knutsson; Carl-Fredrik Westin; Pia C Sundgren; Markus Nilsson

doi:10.3389/fnins.2022.842242

Separating Glioma Hyperintensities From White Matter by Diffusion-Weighted Imaging With Spherical Tensor Encoding

Front Neurosci. 2022 Apr 21:16:842242. doi: 10.3389/fnins.2022.842242. eCollection 2022.

Authors

Jan Brabec¹, Faris Durmo², Filip Szczepankiewicz^{2

3}, Patrik Brynolfsson⁴, Björn Lampinen¹, Anna Rydelius⁵, Linda Knutsson^{1

6

7}, Carl-Fredrik Westin³, Pia C Sundgren^{2

8

9}, Markus Nilsson²

Affiliations

¹ Medical Radiation Physics, Lund University, Lund, Sweden.
² Diagnostic Radiology, Lund University, Lund, Sweden.
³ Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States.
⁴ Division of Medical Radiation Physics, Department of Translational Medicine, Lund University, Lund, Sweden.
⁵ Department of Neurology, Lund University, Lund, Sweden.
⁶ Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, Baltimore, MD, United States.
⁷ F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States.
⁸ Lund University Bioimaging Center, Lund University, Lund, Sweden.
⁹ Department of Imaging and Physiology, Skåne University Hospital, Lund University, Lund, Sweden.

Abstract

Background: Tumor-related hyperintensities in high b-value diffusion-weighted imaging (DWI) are radiologically important in the workup of gliomas. However, the white matter may also appear as hyperintense, which may conflate interpretation.

Purpose: To investigate whether DWI with spherical b-tensor encoding (STE) can be used to suppress white matter and enhance the conspicuity of glioma hyperintensities unrelated to white matter.

Materials and methods: Twenty-five patients with a glioma tumor and at least one pathology-related hyperintensity on DWI underwent conventional MRI at 3 T. The DWI was performed both with linear and spherical tensor encoding (LTE-DWI and STE-DWI). The LTE-DWI here refers to the DWI obtained with conventional diffusion encoding and averaged across diffusion-encoding directions. Retrospectively, the differences in contrast between LTE-DWI and STE-DWI, obtained at a b-value of 2,000 s/mm², were evaluated by comparing hyperintensities and contralateral normal-appearing white matter (NAWM) both visually and quantitatively in terms of the signal intensity ratio (SIR) and contrast-to-noise ratio efficiency (CNR_eff).

Results: The spherical tensor encoding DWI was more effective than LTE-DWI at suppressing signals from white matter and improved conspicuity of pathology-related hyperintensities. The median SIR improved in all cases and on average by 28%. The median (interquartile range) SIR was 1.9 (1.6 - 2.1) for STE and 1.4 (1.3 - 1.7) for LTE, with a significant difference of 0.4 (0.3 -0.5) (p < 10^-4, paired U-test). In 40% of the patients, the SIR was above 2 for STE-DWI, but with LTE-DWI, the SIR was below 2 for all patients. The CNR_eff of STE-DWI was significantly higher than of LTE-DWI: 2.5 (2 - 3.5) vs. 2.3 (1.7 - 3.1), with a significant difference of 0.4 (-0.1 -0.6) (p < 10^-3, paired U-test). The STE improved CNR_eff in 70% of the cases. We illustrate the benefits of STE-DWI in three patients, where STE-DWI may facilitate an improved radiological description of tumor-related hyperintensity, including one case that could have been missed out if only LTE-DWI was inspected.

Conclusion: The contrast mechanism of high b-value STE-DWI results in a stronger suppression of white matter than conventional LTE-DWI, and may, therefore, be more sensitive and specific for assessment of glioma tumors and DWI-hyperintensities.

Keywords: conspicuity; detection; diffusion MRI; glioma; hyperintensity; isotropic encoding; spherical encoding; white matter (WM).