Fukiko Kobayashi

Detectability of anterior displacement of the articular disk in the temporomandibular joint on helical computed tomographyThe value of open mouth position

OBJECTIVE The purpose of this study was to establish the diagnostic reliability of anterior displacement of the articular disk in the temporomandibular joint on helical computed tomography. STUDY DESIGN Ninety-four consecutive patients were examined through use of both computed tomography and magnetic resonance imaging. On axial computed tomography, anterior disk displacement was defined as the presence of an area of soft tissue density that was semilunar in shape and located in front of the mandibular condyle. RESULTS With magnetic resonance imaging taken as the diagnostic gold standard in evaluation of articular disk position, the sensitivity, specificity, and accuracy for computed tomography were 91%, 100%, and 97%, respectively, in the closed mouth position and 96%, 99%, and 98%, respectively, in the open mouth position. CONCLUSIONS The detectability on axial helical computed tomography of anterior displacement of the articular disk in the temporomandibular joint in the open mouth position was almost equal to that on magnetic resonance imaging. It is recommended that the open mouth position be added when helical computed tomography is used to evaluate patients with temporomandibular joint disease.

Simple bone cyst: investigation on the presence of gas in the cavity using computed tomography: Review of 52 cases

OBJECTIVE The purpose of this study was to evaluate whether gas is present in the cavities of simple bone cysts. STUDY DESIGN Computed tomographic images of 52 simple bone cyst cases were reviewed and compared with the findings at surgery. RESULTS Whereas gas was confirmed at the time of surgery in 28 cases, no computed tomographic images indicated the presence of gas in the cavity. Bone expansion was noted in 13 of these 28 cases. CONCLUSIONS From these findings, we concluded that the presence of gas in the simple bone cyst cavity at surgery has been erroneously interpreted.

Measurement of Layer Thickness Using Spread Width of Longitudinal Image in Helical CT

We propose a new method to measure the thickness of very thin single layers in helical computed tomography images. This method involves using the density profile of a longitudinal image to obtain the image width. First, we examined the images of the step density distribution of block phantoms to clarify the step spread function and to decide the spread width (L) of longitudinal images. It was found that the spread width is half of a sum of the X-ray beam collimation and the table feed distance when 180 degrees linear interpolation is used. Next, we derived the density profile of a single layer by taking the density distributions of a single layer to be the composite of step density distributions of different step heights. An important relation is made clear that the image width of the longitudinal image for a single layer of thickness (D) is equal to D+2L whether the shape is symmetrical or not. From this relation the thickness can be measured by detecting the image width with a known value of the spread width of longitudinal images. In conditions of beam collimation of 1.0 mm, table feed distance of 1.0 mm, and reconstruction interval 0.5 mm, measurement accuracy of this method using the density profile of a longitudinal image is estimated to be within 0.05 mm. This method is much more effective than the conventional method using a gray level image for measuring thicknesses less than 0.6 mm. In addition, this method appears to be more consistent than the conventional method, as indicated by a lower standard deviation for figures obtained with this method than for those obtained with the conventional method. We applied this method to the measurement of the thickness of thin cortical bones.

The prevalence of erosive osseous changes of the articular eminence in the temporomandibular joint in patients with mandibular prognathism without internal derangement; MR and helical CT findings

The aim of this study was to assess the prevalence of erosive osseous changes of the articular eminence in the temporomandibular joint without internal derangement. Sixty joints of 30 consecutive patients with mandibular prognathism were evaluated with both MR imaging and helical CT. On MPR images obtained with helical CT, erosive osseous changes of the articular eminence were observed in 18 joints (30%) of 13 patients. None of the joints studied demonstrated an osseous change in the mandibular condyle. MR imaging failed to detect erosive osseous changes of the articular eminence in all of the joints studied. In conclusion, MPR images obtained with helical CT were of value to detect erosive osseous changes of the articular eminence.

The articular disc position relative to the mandibular condyle in patients with skeletal class III malocclusion on MRI

ObjectivesTo investigate the status of the articular disc of the temporomandibular joint (TMJ) in patients with skeletal Class III malocclusion by means of magnetic resonance (MR) imaging.MethodsThe position of the articular disc of the TMJ in closed-and opened-mouth positions was investigated in 50 adult patients with untreated skeletal Class III malocclusion by means of proton-density weighted MR imaging.ResultsOf 100 joints of 50 patients, the lack of positional change of the articular disc relative to the mandibular condyle in both closed- and opened-mouth positions was observed in 62 joints.ConclusionsAlthough the cause of the lack of positional change of the disc relative to the condyle was unclear, this peculiar relationship of the disc and the condyle might possibly be associated with the function of the temporomandibular joint in skeletal Class III malocclusion.

Results of interstitial radiotherapy for carcinoma of the buccal mucosa

Nine carcinomas of the buccal mucosa treated by interstitial radiotherapy are reported. Histopathologically, 8 were squamous cell carcinomas and one was a muco-epidermoid carcinoma. Six patients were male and three were female. Five patients were more than 60 years old. Seven tumors (77%) were stage III or stage IV according to the UICC classification (1987). All cases were followed for more than 20 months. Only two patients died and seven patients are alive at the last follow up. The cumulative 3-year survival rate was 77%.Although this study was very limited in number, it was concluded that carcinomas of the buccal mucosa without bone involvement is not difficult to control if interstitial radiotherapy is appropriately utilized for the primary lesion.