ABSTRACT

Purpose:

To determine the value of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) measurements in the diagnosis of epidermoid tumors.

Methods:

Six patients with intracranial epidermoid tumors were imaged prospectively in a 1.5 Tesla magnetic resonance (MR) unit. Five lesions were located in the cerebrospinal fluid (CSF) cisterns and one lesion was located in the vermis. Two patients had postoperative residual tumors. T2- and T1-weighted, fluid-attenuated inversion recovery (FLAIR) and echo-planar (EPI) DWI sequences were used. ADC values were obtained from all lesions, normal white matter (WM) and the left lateral ventricle. The qualitative and quantitative assessments were performed by three ra-diologists in consensus.

Results:

All epidermoids were isointense or slightly hyperintense relative to CSF on T2- and T1-weighted and FLAIR sequences. It was difficult to estimate the borders and extensions of the cisternal lesions on FLAIR and conventional MR sequences. FLAIR images revealed CSF flow artifacts that made it difficult to delineate the tumors in two patients. All lesions appeared bright on DWI and could be demarcated clearly from dark CSF. ADC values were slightly higher than CSF values, and ranged from 731 to 931 x 10-6 mm2/s within the lesion.

Conclusion:

DWI is the most valuable method in the differential diagno-sis of epidermoid tumors from cystic lesions in the preoperative assessment of lesion extensions, and in postoperative follow-up for the detection of residual or recurrent lesions.