Use of Diffusion-weighted Imaging at MRI in Differentiating Enchondroma and Low-grade and High-grade Chondrosarcoma

Purpose or Learning Objective: To evaluate the potential role of diffusion-weighted imaging (DWI) at magnetic resonance imaging (MRI) to differentiate enchondroma, low-grade chondral tumors (atypical chondral tumors/grade I chondrosarcoma [CS]), and high-grade CS (grades II and III CS).

Methods or Background: Between 2013 and 2020, 23 patients (17 men and 7 women; mean age: 54 years) underwent MR examination (Aera Siemens, Erlangen, Germany) with morphological (coronal turbo spin-echo [TSE] T1, short tau inversion recovery [STIR], axial TSE T2 and STIR, sagittal TSE T1, and axial three-dimensional T1 volumetric interpolated breath-hold examination (VIBE) Dixon with 1.2 mm thickness before and after gadobutrol injection) and functional sequences (DWI with single-shot echo planar imaging b-values of 0, 50, 500, and 1,000 s/mm²). We carefully searched for signs of high-grade CS (bone expansion, active periostitis, cortical disruption and soft tissue mass, and solid areas of contrast enhancement > 1 cm).

At postprocessing if the lesion was homogeneous without signs of malignancy, we plotted a large region of interest (ROI), contouring the mass on each slice to obtain apparent diffusion coefficient (ADC) values. In contrast, if suspicious signs of malignancy were apparent, we drew ROIs only on the suspected area. Then the average number of ADCs was calculated for each mass. Within 3 months, all patients with lesions underwent surgery and pathologic examination. We correlated the results with the analysis of variance (ANOVA) test and the Kruskal-Wallis test the average ADC of each mass with its histologic grade and with the Tukey Honest Significant Difference (HSD)/Tukey-Kramer. Both considering four groups (enchondroma grades I, II, and III) and three groups (low- and high-grade enchondroma), we searched for the significant difference within groups.

Results or Findings: We found 3 enchondromas (mean ADC: 2.47 mm²/s), 6 low-grade CS (2.2 mm²/s), 14 high-grade CS (1.66 mm²/s), 6 grade II CS (1.72 mm²/s), and 8 grade II CS (1.61 mm²/s). Even if the Levene's test power was low (0.097), the ANOVA test showed a significant difference within the four groups (p = 0.041), as did Kruskal-Wallis (p = 0.047) when Levene's test power was low (0.154). The Tukey HSD/Tukey-Kramer demonstrated that largest differences are in the pairs enchondroma grade II and grade I–II.

Conclusion: Our study shows that DWI may play a role in differentiating enchondroma and low-grade and high-grade CS if the ADC ROIs are plotted on the areas suspicious for low-grade and high-grade malignancy.

Publikationsverlauf

Artikel online veröffentlicht:
02. Juni 2022