Non-EPI versus Multishot EPI DWI in Cholesteatoma Detection: Correlation with Operative Findings

BACKGROUND AND PURPOSE:Although multishot EPI (readout-segmented EPI) has been touted as a robust DWI sequence for cholesteatoma evaluation, its efficacy in disease detection compared with a non-EPI (eg, HASTE) technique is unknown. This study sought to compare the accuracy of readout-segmented EPI with that of HASTE DWI in cholesteatoma detection.MATERIALS AND METHODS:A retrospective review was completed of consecutive patients who underwent MR imaging for the evaluation of suspected primary or recurrent/residual cholesteatomas. Included patients had MR imaging examinations that included both HASTE and readout-segmented EPI sequences and confirmed cholesteatomas on a subsequent operation. Two neuroradiologist reviewers assessed all images, with discrepancies resolved by consensus. The ratio of signal intensity between the cerebellum and any observed lesion was noted.RESULTS:Of 23 included patients, 12 (52.2%) were women (average age, 47.8 [SD, 25.2] years). All patients had surgically confirmed cholesteatomas: Six (26.1%) were primary and 17 (73.9%) were recidivistic. HASTE images correctly identified cholesteatomas in 100.0% of patients. On readout-segmented EPI sequences, 16 (69.6%) were positive, 5 (21.7%) were equivocal, and 2 (8.7%) were falsely negative. Excellent interobserver agreement was noted between reviews on both HASTE (κ = 1.0) and readout-segmented EPI (κ = 0.9) sequences. The average signal intensity ratio was significantly higher on HASTE than in readout-segmented EPI, facilitating enhanced detection (mean difference 0.5; 95% CI, 0.3–0.8; P = .003).CONCLUSIONS:HASTE outperforms readout-segmented EPI in the detection of primary cholesteatoma and disease recidivism.

Middle ear cholesteatomas are ectopic, keratinizing squamous epithelium, which may be acquired or, much less commonly, congenital.^1,2 Although not considered a true neoplasm, cholesteatomas are locally destructive and have a high propensity for recurrence following surgical removal. As they gradually expand, cholesteatomas erode the osseous structures within and adjacent to the middle ear cavity, including the ossicles, labyrinth, fallopian canal, and middle fossa bone plate.³ Current mainstay therapy includes microsurgical extirpation, with the chief goal of complete disease removal and prevention of intratemporal and intracranial complications.⁴ The most common microsurgical approach for cholesteatoma is an canal wall up tympanomastoidectomy, in which the posterior bony ear canal is left intact and the tympanic membrane is reconstructed. Depending on the extent of disease at surgery, a planned second-look procedure may be performed approximately 1 year after the initial operation to evaluate residual disease and potentially reconstruct the ossicular chain when indicated. Nevertheless, residual and/or recurrent (ie, recidivism) disease occurs in up to 30% of cases. Imaging is crucial in cholesteatoma management; it aids in the initial diagnosis and may obviate the need for second-look surgery.^5,6During the past decade, DWI has emerged as a powerful diagnostic tool for detection of both primary and residual or recurrent cholesteatomas.^7-9 Cholesteatomas demonstrate marked hyperintensity on DWI , likely related to either T2 shinethrough or intralesional restricted diffusion related to keratin debris.¹⁰ Across the years, there have been many iterations of DWI optimization for cholesteatoma identification. The EPI trajectory used by conventional DWI makes such sequences prone to substantial susceptibility artifacts, and single-shot EPI sequences were found to be poor at identifying lesions of <4–5 mm.^11-13 Consequently, non-EPI DWI techniques began to be favored; such algorithms minimize susceptibility artifacts and geometric distortion related to the skull base and are able to detect lesions as small as 2 mm.^14,15 BLADE (Siemens) and other such PROPELLER sequences are subtypes of non-EPI techniques that minimize susceptibility artifacts and geometric distortions by sampling k-space in a rotating fashion.^16,17More recently, HASTE DWI (Siemens) has emerged as a particularly effective sequence, which is relatively insensitive to motion and has been shown in prior studies to detect cholesteatomas with promising accuracy.^18,19 Although traditional EPI techniques have been largely abandoned in the setting of cholesteatoma detection, readout-segmented EPI (RESOLVE; Siemens) DWI is a relatively new technique that has been promoted as a possible alternative diffusion sequence. RESOLVE is a multishot (MS) EPI sequence that is able to reduce geometric distortions at the expense of longer imaging time. Recent reports have indicated that RESOLVE may be a useful sequence in cases of suspected cholesteatoma.^7,20Despite its proposed efficacy in cholesteatoma imaging, the diagnostic utility of RESOLVE sequences has yet to be robustly evaluated against non-EPI DWI, the current criterion standard. Thus, this study was conceived with the chief goal of assessing the accuracy of RESOLVE in the detection of cholesteatomas and comparing the ability of RESOLVE with that of HASTE sequences in this context.