Bi-exponential diffusion-weighted imaging for differentiating high-grade gliomas from solitary brain metastases: a VOI-based histogram analysis

Abstract

This study investigated the use of bi-exponential diffusion-weighted imaging (DWI) combined with structural features to differentiate high-grade glioma (HGG) from solitary brain metastasis (SBM). A total of 57 patients (31 HGG, 26 SBM) who underwent pre-surgical multi-b DWI and structural MRI (T1W, T2W, T1W + C) were included. Volumes of interest (VOI) in the peritumoral edema area (PTEA) and enhanced tumor area (ETA) were selected for analysis. Histogram features of slow diffusion coefficient (D_slow), fast diffusion coefficient (D_fast), and perfusion fraction (frac) were extracted. Results showed that HGG patients had higher skewness of D_fast (P = 0.022) and frac (P = 0.077), higher kurtosis of D_slow (P = 0.019) and frac (P = 0.025), and lower entropy of D_slow (P = 0.005) and frac (P = 0.001) within the ETA. Additionally, HGG exhibited lower mean frac in both ETA (P = 0.007) and PTEA (P = 0.017). Combining skewness of frac in ETA with clear tumor margin enhanced diagnostic performance, achieving an optimal AUC of 0.79. These findings suggest that histogram analysis of diffusion and perfusion characteristics in ETA and structural features can effectively differentiate HGG from SBM.

Keywords: Diffusion; Diffusion-weighted imaging; High-grade glioma; Perfusion; Solitary brain metastasis.

Fig. 1

Study flow chart.

Fig. 2

A 63-year-old male diagnosed with glioblastoma. (A) T2W imaging. (B) T1W imaging. (C) Contrast-enhanced T1W imaging. (D) D_fast (×10-4mm²/s). (E) D_slow (×10-4mm²/s). (F) frac (%). (G-I) Histogram plot of Dfast, Dslow, and frac of the enhanced tumor area. The MRI examination revealed an irregular lesion in the sub-cortex of the right frontal lobe, characterized by a blurred margin. The lesion exhibited diffuse enhancement, marked in red, along with hyper-intensity on T2-weighted imaging and hypo-intensity on T1-weighted imaging. Peritumoral edema was also observed. Parametric values obtained from histogram analysis of the enhanced tumor area are as follows: D_fast: mean: 37.98, entropy: 3.19, skewness: 1.15, kurtosis: 6.60. D_slow: mean: 8.52, entropy: 3.68. skewness: 0.33, kurtosis: 3.60, frac: mean: 18.46, entropy: 3.07, skewness: 0.68, kurtosis: 5.06.

Fig. 3

A 34-year-old female diagnosed with brain metastasis originating from breast cancer. (A) T2W imaging. (B) T1W imaging. (C) Contrast-enhanced T1W imaging. (D) D_fast (×10-4mm²/s). (E) D_slow (×10-4mm²/s). (F) frac (%). (G-I) Histogram plot of Dfast, Dslow, and frac of the enhanced tumor area. The MRI examination revealed an irregular lesion with a well-defined margin in the sub-cortex of the right occipital lobe. The lesion exhibited diffuse enhancement, marked in red, and appeared hyper-intense on T2-weighted imaging, hypo-intense on T1-weighted imaging, and was accompanied by peritumoral edema. Additionally, central necrosis was observed within the lesion. Parametric values obtained from histogram analysis of the enhanced tumor area are as follows: D_fast: mean: 45.38, entropy: 3.80, skewness: 0.70, kurtosis: 4.42; D_slow: mean: 8.55, entropy: 4.09, skewness: 0.47, kurtosis: 2.85; frac: mean: 25.15, entropy: 3.76, skewness: 0.49, kurtosis: 3.31.

Fig. 4

The ROC curves for univariate (A) and binary (B) logistic regression analysis.