In vivo imaging of mouse cochlea by optical coherence tomography.

HYPOTHESIS: Cochlear pathology can be evaluated in living animals using optical coherence tomography (OCT). BACKGROUND: The current imaging methods available for the detailed analysis of cochlear pathology in a clinical setting provide only limited information. Thus, a cochlear imaging modality with high definition is needed for improving the diagnosis of cochlear pathology. OCT has been used in other fields for obtaining high-resolution subsurface images, and its use could potentially be extended to the analysis of cochlear pathogenesis. METHODS: Slc26a4(-/-) mice, which generate endolymphatic hydrops, and their littermates were used in this study. Auditory function was monitored by the auditory brainstem responses (ABR). After the mice were placed under general anesthesia, OCT images of the cochlea were captured. The cochlea was subsequently dissected out and histologically evaluated. Three or 7 days later, the wild-type mice cochleae were visualized again. RESULTS: In ABR assessments, Slc26a4(-/-) mice showed severe hearing loss, while no significant hearing loss was found in Slc26a4(+/-) or Slc26a4(+/+) mice. OCT demonstrated normal morphology in the cochlea of both Slc26a4(+/-) and Slc26a4(+/+) mice, including the location of Reissner's membrane. Meanwhile, in Slc26a4(-/-) mice, obvious dislocation of Reissner's membrane was observed, indicating severe endolymphatic hydrops. These findings in the OCT images were consistent with the histologic results for the cochlear morphology, as observed with hematoxylin and eosin staining. Three or 7 days later, wild-type cochleae were successfully visualized using OCT, and no otitis media or labyrinthitis was observed. CONCLUSION: OCT can be applied in the detection of endolymphatic hydrops in living mice, indicating the potential of OCT for cochlear imaging analyses for clinical use in the near future.

Preattentive processing of horizontal motion, radial motion, and intensity changes of sounds.

Localization of sound sources is critical for an appropriate behavioral response. This is not only true for localization in the horizontal plane but also for localization in depth. Depth ranging of sound sources implicates various distance cues, among others sound intensity. In this study, we measured human electroencephalography and compared mismatch negativity (MMN) amplitudes and latencies for horizontal motion, radial motion, and pure intensity changes in the free field. We observed similar MMN latencies for horizontal and radial motion, whereas MMN responses to pure intensity changes were comparably delayed. MMN amplitudes and latencies were not different for approaching and receding sounds. Our data suggest similar fast processing for horizontal and radial motion, whereas pure intensity changes are possibly processed with less priority.

Sequential FDG-PET/CT after neoadjuvant chemotherapy is a predictor of histopathologic response in patients with head and neck squamous cell carcinoma.

PURPOSE: To evaluate whether 2-deoxy-2-[(18)F]fluoro-D-glucose positron emission tomography/computed tomography (FDG-PET/CT) more accurately predicts the histopathologic response to neoadjuvant chemotherapy (NAC) than magnetic resonance imaging (MRI) in patients with head and neck squamous cell carcinoma (HNSCC). PROCEDURES: Sixteen patients with HNSCC underwent FDG-PET/CT and MRI scans before and after one cycle of NAC, followed by surgical resection. The 26 surgically resected specimens of the 16 patients were analyzed. Decreases in maximum standardized uptake value (SUV(max)) or in tumor maximum size (diameter(max)) were calculated, and their accuracies for the prediction of histopathologic response were evaluated. RESULTS: In histopathologic responders (n = 7), percent decreases in SUV(max) were significantly higher (P < 0.001) than in non-responders (n = 19). Applying a cut-off point of 55.5%, the histopathologic response could be predicted with a sensitivity and specificity of 86% and 95%, respectively. CONCLUSION: FDG-PET/CT can predict histopathologic NAC responses with higher accuracy than MRI in HNSCC patients.