MR images of transplanted fat in the mastoidectomy cavity of the left middle ear. On the transverse spin-echo T1-weighted image ( A ) and on the transverse turbo spin-echo T2-weighted image ( B ), a lesion with high signal intensity and multiple strands is shown. C , This could be correlated to the location of hyperintense signal intensity on the transverse non-EPI DWI sequence. The high signal intensity on the DWI was caused by the use of fat from the abdominal wall placed in the mastoidectomy cavity during surgery. 

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... canal-wall-down approach is reported to have lower recurrence rates. 5 If recurrence is suspected clinically, on the basis of otoscopy and audiometry, until now second-look surgery was indicated. Because of the invasive character of second-look surgery and the risk of complications, the need for less invasive methods for diagnosing residual and/or recurrent cholesteatoma is needed. A cholesteatoma has specific signal-intensity charac- teristics on MR imaging. The lesion causes high signal intensity on T2-weighted images, low signal intensity on unen- hanced and postcontrast T1-weighted images with a thin rim enhancement on the late gadolinium-enhanced images, and a very high signal intensity on non-EPI DWI. In previous studies, delayed contrast-enhanced MR imaging could discriminate between the nonenhancing cholesteatoma and other postoperative findings, which all will show enhancement, such as mucosal edema, inflammation, and scar or granu- lation tissue. 10-13 At the present time, non-EPI DWI is becoming an alternative to invasive second-look surgery. Recent studies showed that residual and/or recurrent cholesteatomas after primary cholesteatoma surgery are very accurately detected by increased DW signal intensity on non-EPI DWI. 14-18 Middle ear cholesteatomas as small as 2 mm can be detected by using this technique. 14,16 The non-EPI DWI sequence is particularly important in diagnosing cholesteatomas because the use of this technique is reported to hardly ever produce false-positive results. 14-18 The signal intensity of postoperative findings other than cholesteatoma is demonstrated to be much lower than that of residual and/or recurrent cholesteatoma on non-EPI DWI. 14,15,17 Because using increased DW signal intensity in non-EPI DWI sequences as a diagnostic criterion for cholesteatoma produces practically no false-positive results, non-EPI DWI is a very promising technique to be used in screening for residual and/or recurrent cholesteatoma. 14-21 Recent reports even discussed the use of a non-EPI DWI sequence as the only sequence in screening for pre-second-look residual and/or recurrent cholesteatomas. 14-16,19,20 In 2005, we introduced MR imaging with non-EPI DWI sequences for the detection of residual and/or recurrent cholesteatoma after primary cholesteatoma surgery. The aim of this study was to evaluate the diagnostic accuracy, expressed as a positive predictive value, of non-EPI DWI in our hospital as an alternative for second-look surgery in detecting residual and/or recurrent cholesteatoma. Furthermore, we investigated whether the use of only a non-EPI DWI sequence without additional conventional sequences is accurate enough in screening for residual and/or recurrent cholesteatoma. Figure 2 gives a schematic overview of the results of our patient group. A total of 56 MR imaging examinations was included in our study. The non-EPI DWI sequence showed increased DW signal intensity in 36 cases. The mean calculated ADC value was 1.041 ϫ 10 Ϫ 3 mm 2 /s (range: 1.368 – 0.743 ϫ 10 Ϫ 3 mm 2 /s). In 27 of the cases showing increased DW signal intensity, second-look surgery was performed. Two patients who had not undergone surgery with increased DW signal intensity on the non-EPI DWI sequences did not show evidence of cholesteatoma on the conventional T1- and T2-weighted images, as will be discussed later in this section. Seven patients with increased DW signal intensity on non-EPI DWI studies were under close clinical and MR imaging follow-up because of comorbidity or stable clinical, otoscopic, and audiometric findings. Non-EPI DWI sequences detected and located 25 cholesteatomas, confirmed by second-look surgery. In 2 patients, MR imaging findings were shown to be false-positive after corre- lation with the intraoperative second-look surgery findings. One patient was diagnosed with an empyema in the postoperative cavity (which was suggested in the differential diagnosis of the MR imaging report). The corresponding calculated ADC value in this case was 0.932 ϫ 10 Ϫ 3 mm 2 /s; therefore, the empyema could not definitely be differentiated from a cholesteatoma by imaging findings alone (Fig 3). The second patient had increased DW signal intensity located very anteriorly in the middle ear cavity on MR imaging (Fig 4); no evidence of cholesteatoma was detected at second- look surgery in this surgically unclear area. This patient is cur- rently under close clinical and imaging follow-up. As described in the beginning of this section, in the sub- group of patients with increased DW signal intensity on non- EPI DWI sequences (36 patients), 2 patients who had not undergone surgery showed suggestion of cholesteatoma on the basis of non-EPI DWI alone. After interpretation of the DWI in combination with the conventional T1-weighted images, hyperintense signal intensity on the conventional T1- weighted images was found, which could be correlated to the location of hyperintense signal intensity on the DWI (Fig 5). These imaging findings were suggestive of fat in the mastoidectomy cavity; at primary cholesteatoma surgery, fat of the abdominal wall had been placed in the cavity. No fat-saturation images were included in the standard imaging protocol. Twenty patients did not show hyperintense signal intensity on the non-EPI DWI sequences. Clinical follow-up (ranging from 14 to 44 months, with a mean follow-up period of 26 months), including otoscopy and audiometry, was without suspicion of residual and/or recurrent cholesteatoma. Find- ings in all of these patients were no residual and/or recurrent disease after primary cholesteatoma surgery. The positive predictive value of non-EPI DWI sequences in depicting pathologically confirmed residual and/or recurrent cholesteatomas was 93% (25/27). After primary cholesteatoma surgery by means of the canal- wall-up technique or the canal-wall-down approach as performed in our hospital, there is a risk of leaving some diseased tissue behind at first-stage surgery (residual cholesteatoma) or a new cholesteatoma can develop after surgery (recurrent cholesteatoma). Therefore, these techniques, especially the canal- wall-up technique, often require second-look surgery. In the past, all patients had to undergo routine second-look surgery several months after their primary cholesteatoma surgery to rule out residual and/or recurrent disease. The use of non-EPI DWI has been shown to be a promising alternative for invasive second-look surgery in screening for residual and/or recurrent cholesteatoma in previous studies, with very high sensitivity and specificity and high positive and negative predictive values as reported by De Foer et al 14,16,19 and Vercruysse et al. 18 There are hardly any false-positive findings reported in the literature by using non-EPI DWI sequences in screening for residual and/or recurrent disease and only sparse false-nega- tive findings. False-negative findings are almost exclusively a consequence of examinations degraded by motion artifacts or empty retraction pockets. Non-EPI DWI can detect residual and/or recurrent cholesteatomas with a size limit as small as 2 mm, because of a high imaging matrix, thin section thickness, and a complete lack of susceptibility artifacts. 14,16,21 The findings of our study concerning the predictive value of current MR imaging techniques for detecting residual and/or recurrent cholesteatoma are in agreement with recent literature; we reported a positive predictive value for the non- EPI DWI sequence of 93% in our study population. Because the learning curve of the 2 head and neck radiologists was incorporated in the final outcome of our study, the results of this study can be reliably translated to daily practice. The sensitivity and specificity of non-EPI DWI sequences combined with conventional sequences in depicting residual and/or recurrent cholesteatomas was respectively 100% and 92%. This is also in agreement with recent literature. 14-21 There are some limitations to our study. First, the study included only a small number of 56 MR imaging studies. Second, the study design was retrospective. Third, the high sensitivity reported in our study is, to some extent, a consequence of the fact that our hospital patients who did not show increased DW signal intensity on pre-second-look non-EPI DWI studies did not undergo second-look surgery. Therefore, in 22 patients with negative findings on non-DWI, we were not able to correlate the ra- diologic findings with intraoperative findings to confirm the absence of residual and/or recurrent cholesteatoma. In our study, an empty retraction pocket on imaging was considered as a true- negative. This is in agreement with very recently published studies regarding the use of non-EPI DWI in relation to second-look cholesteatoma surgery. 19,25 Finally, we used the reported diagnoses based on the initial assessment by the head and neck radiologists in the analysis of our study. No reassessment of the included imaging studies took place. Although this can be considered as a limitation of the study design, it also implies that the results of our study are adaptable to everyday practice. Recent studies investigated the possibility of screening for residual and/or recurrent cholesteatoma by use of the non-EPI DWI sequence as the only sequence in the imaging protocol. 14-16,19,20 The DWI sequence needs very little scan- ning time, and intravenous contrast injection of gadolinium can be avoided by use of a DWI-only sequence. Furthermore, the correct interpretation of non-EPI DWI is not particularly dependent on the observer’s experience. The results of these studies were positive regarding the use of non-EPI DWI alone in screening for residual and/or recurrent cholesteatoma. A very interesting finding of our study was that, in contrast to the literature, we encountered 4 patients who showed increased DW signal intensity on non-EPI DWI. Two of these patients underwent surgery and showed ...