Cone-beam CT (CBCT) systems specifically designed for hard-tissue imaging of the maxillofacial region have recently become commercially available. The newly-developed CBCT system, CB Throne ® (Hitachi Medical Corp., Tokyo), is characterized by a number of features such as low dose, sub-millimeter spatial resolution, and a small footprint. This system has been clinically applied at Chiba Hospital, Tokyo Dental College, since April 2005. This article reports the characteristics of this system, and its diagnostic power for maxillofacial lesions and the pre-operative planning dental implants.

The purpose of this study was to investigate the accuracy of distance measurements of implant length based on periapical radiographs compared with that of other modalities. We carried out an experimental trial to compare precision in distance measurement. Dental implant fixtures were buried in the canine and first molar regions. These were then subjected to periapical (PE) radiography, panoramic (PA) radiography, conventional (CV) and medical computed (CT) tomography. The length of the implant fixture on each film was measured by nine observers and degree of precision was statistically analyzed. The precision of both PE radiographs and CT tomograms was closest at the highest level. Standardized PE radiography, in particular, was superior to CT tomography in the first molar region. This suggests that standardized PE radiographs should be utilized as a reliable modality for longitudinal and linear distance measurement, depending on implant length at local implantation site.

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High-resolution PDW- and T2W MR images could be processed by tissue segmentation and 3D-reconstruction procedures, and the resultant images showed the anatomical details in an easily recognizable way. By the simultaneous visualization of both bony surfaces and soft tissues, disc displacement and deformity can be recognized in a 3D context. The additional superposition of the 3D visualization with the original 2D MR slices allows for a combination with conventional diagnostics.

We report two cases of schwannoma displaying marked cystic changes; one in the temporalis muscle and one in the submandibular space. The first patient, a 44-year-old male, presented after complaining of a swelling rapidly increasing in size in the left temporal region. Computed tomography (CT) indicated a low-density area surrounded by soft tissue. Magnetic resonance imaging (MRI) revealed signal hypointensity on T1 weighted imaging and strong signal hyperintensity on T2 weighted imaging. The extirpated tumour specimen measured 58 mm x 58 mm x 30 mm. Histopathological examination identified schwannoma, comprising spindle cell proliferation in a palisading pattern with obvious cystic changes. The second case involved a 46-year-old female who presented with swelling of the right submandibular region. Panoramic radiography and lateral oblique mandible projection, which were used together with conventional sialography of the submandibular gland, revealed the so-called "ball in hand" appearance of the submandibular gland, and contrast-enhanced CT identified a lesion of 30 mm diameter with a well-defined annular margin and homogeneous low-density near the tumour centre. Benign pleomorphic adenoma was suspected, but histopathological examination identified schwannoma, predominantly comprising Antoni B type tissue.