Diffusion-weighted imaging in the follow-up of treated high-grade gliomas: tumor recurrence versus radiation injury.

TLDR

Diffusion‑weighted MRI measures apparent diffusion coefficient differences to distinguish edema, necrosis, and tumor tissue. The study tests whether DW imaging can separate recurrent or progressive high‑grade glioma from radiation‑induced brain injury. Retrospective analysis of 18 patients’ follow‑up MR scans starting one month post‑radiation calculated mean ADC and ADC ratios of enhancing lesions versus contralateral white matter and compared them to final diagnoses. Lower ADC ratios (1.43 ± 0.11) in recurrent lesions versus higher ratios (1.82 ± 0.07) in non‑recurrent lesions proved that ADC ratios effectively differentiate recurrence from radiation damage.

Abstract

BACKGROUND AND PURPOSE: Diffusion-weighted (DW) MR imaging is a means to characterize and differentiate morphologic features, including edema, necrosis, and tumor tissue, by measuring differences in apparent diffusion coefficient (ADC). We hypothesized that DW imaging has the potential to differentiate recurrent or progressive tumor growth from treatment-induced damage to brain parenchyma in high-grade gliomas after radiation therapy. METHODS: We retrospectively reviewed follow-up conventional and DW MR images obtained starting 1 month after completion of radiation treatment with or without chemotherapy for histologically proved high-grade gliomas. Eighteen patients with areas of abnormal enhancing tissue were identified. ADC maps were calculated from echo-planar DW images, and mean ADC values and ADC ratios (ADC of enhancing lesion to ADC of contralateral white matter) were compared with final diagnosis. Recurrence was established by histologic examination or by clinical course and a combination of imaging studies. RESULTS: Recurrence and nonrecurrence could be differentiated by using mean ADC values and ADC ratios. ADC ratios in the recurrence group showed significantly lower values (mean ± SD, 1.43 ± 0.11) than those of the nonrecurrence group (1.82 ± 0.07, P CONCLUSION: Assessment of ADC ratios of enhancing regions in the follow-up of treated high-grade gliomas is useful in differentiating radiation effects from tumor recurrence or progression.