Role Of Diffusion Weighted Imaging And Reliability Of ‘T2-Flair’ Mismatch Sign In Grading And Characterization Of Astrocytomas

Abstract

Background:-

Brain tumors may show various degrees of diffusion changes related to tumor cellularity and the nucleus-cytoplasmic ratio. High-cellularity of tumors results in reduced intercellular space, which in turn results in water diffusion restriction thus causing low Apparent Diffusion Coefficient (ADC) values. Diffuse and anaplastic lower-grade astrocytomas harbour specific molecular features, such as isocitrate dehydrogenase (IDH) 1 and 2 gene mutation

Objective:-

The objective of this study is to evaluate the role of diffusion weighted imaging in grading of astrocytomas. This study also puts some light on the reliability on ‘T2-FLAIR’ mismatch sign in characterizing the IDH mutant and wild counterparts of anaplastic and diffuse astrocytomas.

Results:-

Out of 36 patients , 31 patients with high grade astrocytomas proven by histopathological analysis showed diffusion restriction with reduced ADC values, with a mean ADC value of 0.885 × 10−3 mm2 /s. Almost all patients who had low grade astrocytomas proven by histopathological analysis N= 5 showed no diffusion restriction with a mean ADC value of 1.157 × 10−3 mm2 /s. There is a significant decrease (p value – 0.034) in mean ADC values  of high grade astrocytomas compared to low grade astrocytomas. Out of the 5 patients who were reported to have microcysts in their pathological specimens , MRI images of 4 patients showed , ‘T2-FLAIR’ mismatch sign.

Conclusion:

Lower ADC values suggest a malignant high-grade astrocytoma, whereas higher ADCs suggest low-grade astrocytoma. T2-FLAIR mismatch sign may reflect microcyst formation in pathological specimens , and  is a useful sign in categorizing anaplastic and diffuse astrocytomas into their IDH-mutant and wild counterparts.