Hisayuki Kato

Despite apparent ability of computed tomography (CT) in clinical practice, otology, which requires diagnosis and treatment of variaous diseases involve very small areas and sometimes entails a limitation on the performance of CT in depicting lesions located in such areas. Recently, ultra-high-resolution (UHR) CT, which can provide images at dramatically higher spatial resolution than ever before, has been developed and has become commercially available. UHRCT has a pixel size (0.25×0.25 mm) twice comparing dense in both vertical and horizontal directions as conventional high-resolution (CHR) CT and the maximum spatial resolution of 0.15mm or less in the axial direction. The maximum size image is 2048×2048 pixels. Here, we report our experience of the early stage development of UHRCT in the field of otology. We performed UHRCT scan in otology patients and compared the images obtained from UHRCT with those obtained from CHRCT. Spatial resolution in UHRCT images was obviously improved. Tiny structures, such as the chorda tympani and ossicles, and small pathological changes caused by the progression of otitis media, etc. were clearly depicted. Due to an increase in the partial volume effect, improvements such as the performance of UHRCT in depicting soft-tissue lesions or lesions adjacent to the bone, were considered to be difficult to depict at CHRCT. The tiny structures which had been indistinct before, became clearly visible due to UHRCT, indicating the possibility of providing important information for clinical practice. However, because the issues include the necessity of building infrastructure (including display) and a powerful computer system enough to save and handle huge volume of data, it is necessary to examine the further usage of UHRCT in the future.

Odontogenic myxoma (OM), which was classified by the WHO in 2017, as a benign mesenchymal tumor composed of stellate and spindle-shaped cells in an abundant myxoid stroma. OM is a rare tumor that accounts for only 1.6 − 2.7% of all odontogenic tumors. OM is distinguished from myxofibroma by the amount of collagen fibers in the tumors. We herein report a case of odontogenic myxofibroma of the maxilla. The patient was a 31-year-old man with right nasal obstruction that had been present for three months. It developed into a tumor that filled the right nasal cavity with painless swelling of the maxillary gingiva, hard palate and buccal region. CT demonstrated that the tumor was associated with the destruction of the right maxillary bone, and had spread to the maxillary sinus, nasal cavity, hard palate, ethmoid sinus, sphenoid sinus, temporal fossa and nasopharynx that was histopathologically diagnosed as myxoma by gingival incision biopsy. We performed subtotal maxillectomy by the Weber Ferguson approach. A pathological examination revealed that the tumor was composed of spindle-shaped mesenchymal cells without cytological atypia and with an abundance of collagenous fibers. Consequently, it was diagnosed as myxofibroma.