Differentiation between non-enhancing tumor in glioblastoma and vasogenic edema using diffusion-weighted and dynamic susceptibility contrast MR imaging

BACKGROUND AND PURPOSE: Differentiating non-enhancing glioblastoma from vasogenic edema remains a challenge in neuroimaging. This study evaluates the utility of diffusion-weighted and dynamic susceptibility contrast MR imaging, particularly apparent diffusion coefficient (ADC) and relative cerebral blood volume (rCBV), in distinguishing these entities.

MATERIALS AND METHODS: We retrospectively analyzed 111 patients diagnosed with glioblastoma with available pretreatment MRI from January 1, 2022, to December 31, 2023, including 13 patients with 15 solid non-enhancing glioblastoma lesions and 98 patients with perilesional non-enhancing T2 FLAIR hyperintensity surrounding enhancing glioblastomas. Their ADC and rCBV values were compared with those of vasogenic edema surrounding 30 brain metastatic lesions age-and sex-matched to solid non-enhancing glioblastoma lesions. Receiver operating characteristic (ROC) analysis was performed to determine optimal ADC and rCBV thresholds for classification.

RESULTS: Solid non-enhancing glioblastomas exhibited significantly lower ADC values and higher rCBV values compared to vasogenic edema (1.08 ± 0.22 × 10^-³ vs. 1.74 ± 0.17 × 10^-³ mm²/s and 2.4 ± 0.86 vs. 0.30 ± 0.13, respectively; p < 0.001). The optimal ADC and rCBV cutoffs for differentiating solid non-enhancing glioblastoma from vasogenic edema were 1.36 × 10^-³ mm²/s and 1.04, achieving excellent sensitivity (0.93-1) and specificity (1). Perilesional non-enhancing T2 FLAIR hyperintensity around enhancing glioblastomas had similar ADC values to vasogenic edema (1.67 ± 0.33 × 10^-³ vs. 1.74 ± 0.17 × 10^-³ mm²/s, p = 0.32) but significantly higher rCBV (0.60 ± 0.61 vs. 0.30 ± 0.13, p = 0.03). An rCBV cutoff value of 0.42 distinguished perilesional tumor infiltration from pure vasogenic edema with 86% specificity.

CONCLUSIONS: Diffusion-and perfusion-weighted MR imaging, particularly ADC and rCBV measurements, provide valuable biomarkers for differentiating non-enhancing glioblastoma from vasogenic edema. The identified threshold values may enhance glioblastoma characterization, improve preoperative differentiation from metastases, and support more precise, image-guided clinical management.

ABBREVIATIONS: rCBV = relative cerebral blood volume; IDH = Isocitric Dehydrogenase; KPS = Karnofsky Performance Status Scale; MGMT = O⁶-methylguanine-DNA methyltransferase; IQR = interquartile ranges; SD = standard deviation.