Role of diffusion-weighted imaging in evaluation of intracranial infections

Abstract

Objective: The objective is to evaluate the role of diffusion weighted imaging (DWI) in evaluation of intracranial infections. Methods: The present study was conducted in the Department of Radiology, Jawaharlal Nehru Medical College, Sawangi, Maharashtra, India. Participants after understanding the study protocol and procedure were asked to give their written consent for the study. DWI was performed on 24 patients having ring-enhancing lesions on their post-contrast brain magnetic resonance imaging scans with infective etiology. Commonly found lesions were tuberculomas, cysticercosis, pyogenic abscess, and fungal infections. Correlation of all these findings was done with histopathology obtained in all these patients. DWI and mean apparent diffusion coefficient (ADC) value were calculated. Results: Tuberculomas showed heterogeneous areas of restricted diffusion on DWI were as pyogenic abscess showed homogenous restricted diffusion, the mean ADC values from of these lesions were 0.74 × 10−3 and 0.5 × 10−3 mm2/s, respectively. Fungal abscesses were also ring enhancing. They had restricted diffusion in the central nonenhancing portions. Mean ADC for all fungal lesions was 0.33 ± 0.06 × 10−3 mm2/s, with an average ADC ratio of 0.43. However, there was no significant difference between ADC values of pyogenic abscess and fungal abscess. The vesicular cysts of NCC showed ring enhancement but no significant restriction on DWI, the ADC values from the vesicular cysticercus cysts core measured (1.66 ± 0.29) ×10 − 3 mm2/s, which was highest among the infective intracranial infection. Conclusion: DWI is noninvasive method with high sensitivity and specificity which can help in differentiation of infective ring-enhancing lesions. Fungal cerebral abscesses may have central restricted diffusion similar to that of bacterial abscesses but with histologic features of acute or chronic inflammation and necrosis rather than suppuration. Altered water diffusion in these lesions likely reflects highly proteinaceous fluid and cellular infiltration. The tuberculoma and NCC lesions showed heterogeneous and no restriction on DWI respectively with significant change in the ADC values which helped in differentiating these lesions. This modality should be read in conjunction with conventional imaging.