To Study Cholesteatomas And Cholesterol Granulomas Of The Temporal Bone With PROPELLER Diffusion-Weighted MR Imaging

PURPOSE:To prospectively evaluate the diagnostic value of multishot fast spin-echo periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion-weighted MR imaging (DWI) in the detection of cholesteatomas and cholesterol granulomas of temporal bone, and observe the corresponding images of conventional sequences and array spatial sensitivity encoding technique (ASSET) single-shot echo-planar DWI.MATERIALS AND METHODS:Sixty-eight patients with chronic otitis media, two patients with atresia of external auditory canal, and four suggested external auditory canal cholesteatomas underwent3.OT MR imaging unit (Signa HDx; GE Healthcare) with conventional MR imaging, PROPELLER DWI, ASSET single-shot echo-planar DWI by using a standard head coil with8elements. Overall sensitivity, specificity, and negative predictive value (NPV), and positive predictive value (PPV) were assessed by evaluating the images produced by these sequences. Single-shot echo-planar DWI takes two b factors which are0and1000s/mm2. PROPELLER DWI takes three b factors which are0,750and1000s/mm2The apparent diffusion coefficient (ADC) values of lesions, brain gray matter and cerebrospinal fluid (CSF) were measured and compared by analysis of variance.RESULTS:Forty-one cholesteatomas of the middle ear and mastoid and four external auditory canal cholesteatomas were found at surgery. Overall specificity, PPV, NPV were different with the PROPELLER DW images between2readers, but the sensitivity was same. There were statistical differences between ADC values of cholesteatoma, cerebell ar gray matter, chronic inflammatory tissue and CSF. The distortion and susceptibility artifacts of SE EP DWI are very severe. One false-positive case with increased signal intensities in the DWI turned out to be cholesterol granuloma, however its ADC value was in the range of cholesteatomas’ but lower than the mean. The cholesterol granuloma can be hyperintense or hypointense on T1-weighted images. CONCLUSIONS:PROPELLER DWI allows an easier detection of cholesteatomas than ASSET EP DWI by reducing artifacts and improving the signal to noise ratio. Cholesteatomas appear to have high signal intensity on DWI, attributed predominantly to the T2shine through effect. It is difficult to differentiate cholesteatoma and cholesterol granuloma on images.