Analysis of Normal Anatomy of Oral Cavity in Open-mouth View with CT and MRI: Comparison with Closed-mouth View

PURPOSE: When MRI and CT of the oral cavity utilize the traditional closed-mouth approach, direct contact between the tongue and surrounding structures may give rise to difficulty in recognizing the anatomy involved and demonstrating the possible presence of pathologic features. we describe a more appropriate scan technique, involving open-mouthed imaging, which may be used to demonstrate the anatomy of the oral cavity in detail. MATERIALS AND METHODS: Axial and coronal MR imaging and axial CT scanning were performed in 14 healthy volunteers, using both the closed and open-mouth approach. For the latter, a mouth-piece was put in place prior to examination. In all volunteers, open-mouth MR and CT examinations involved the same parameters as the corresponding closed-mouth procedures. The CT and MR images obtained by each method were compared, particular attention being paid to the presence and symmetry of motion artifact of the tongue and the extent of air space in the oral cavity. Comparative imaging analysis was based on the recognition of 13 structures around the boundaries of the mouth. For statistical analysis, Student 's t test was used and a p value < 0.05 was considered significant. RESULTS: Due to symmetry of the tongue, a less severe motion artifact, and increased air space in the oral cavity, the open-mouth method produced excellent images. The axial and coronal MR images thus obtained were superior in terms of demarcation of the inferior surface and dorsum of the tongue, gingiva, buccal surface and buccal vestibule to those obtained with the mouth closed (p<0.05). In addition, axial MR images obtained with the mouth open showed better demarcation of structures at the lingual margin and anterior belly of the digastric muscle (p<0.05), while coronal MR images of the base of the tongue, surface of the hard palate, soft palate, and uvula, were also superior (p<0.05). Open-mouth CT provided better images at the lingual margin, dorsum of the tongue and buccal surface than the closed-mouth approach (p<0.05). CONCLUSION: Open-mouth MRI and CT are both practical and useful for evaluation of the structures of the oral cavity. The images thus obtained are superior to those acqhired with the month closed.

Quantitative Morphologic Assessment of Thoracolumbar Vertebrae in Korean Women by Morphometric X-rayAbsorptiometry

PURPOSE: To compare the accuracy of lateral radiography of the spine with that of morphometric X-rayabsorptiometry(MXA) in vertebral morphometry, and to evaluate normal vertebral morphometry using MXA in Koreanwomen. MATERIALS AND METHODS: A spine phantom was constructed using copper pipe. Its anterior and posteriorheights were measured directly, with lateral radiographs and with MXA, and the values thus obtained were compared.Inter -and intra -observer variations were evaluated by three radiologists. The vertebral morphometry of 30 youngwomen volunteers were imaged using thoracic and lumbar lateral radiographs and MXA, and analysis included themeasurement of anterior and posterior heights from T4 to L4. We also obtained the vertebral morphometry of 200normal Korean women who underwent MXA between March 1995 and February 1996, though those with osteoporosis andother spinal lesions were excluded from this study. Thoracolumbar vertebral indexes were statistically correlatedwith age, height and bone mineral. RESULTS: There were no statistically significant differences in the heights ofspine phantom measured by MXA compared with actual size (mean difference=0.28mm). Simple radiographs weremagnified by 23.7% at a phantom-table distance of 15cm, and distortion ranged from 0.5% to 22.5%, depending onphantom level and phantom-table distance. In the study of volunteers, the magnification rate between a simpleradiograph and MXA was about 26.6%. Anterior height increased progressively from the thoracic to the lumbar spine,though posterior height peaked at L2, and L4 was less than anterior height. In Korean women, indices of vertebralmorphometry decreased significantly with aging, with the most prominent decrease occurring during the seventhdecade. The mineral density of spinal bone decreased markedly after the sixth decade. CONCLUSION: Radiographsshowed more magnification and distortion than did MXA, though between morphometric X-ray absorptiometry (MXA) andactual size, there was no significant difference. The vertebral morphometric indices of Korean women and referredbone mineral density may provide useful data for determining and evaluating follow-up changes in spinalmorphology.

Normal Value of Mucosal Thickness of Paranasal Sinuses, as Seen on Brain

PURPOSE: To evaluate incidentally observed thickened mucosa of paranasal sinuses on brain MRI of patients without evidence of sinusitis. MATERIALS AND METHODS: We reviewed brain MRI of 82 adults aged over 20 ; 45 were males and 37 were females. Brain axial MRI was obtained from the hard palate with 8mm thickness and 2mm gap. The mucosal thickness of incidentally observed paranasal sinuses seen on brain MRI was measured at the mostly thickened portion by T2- and T1-weighted images. RESULTS: The mean mucosal thickness at the most thickened portion of paranasal sinuses, regardless of their location was 3.5mm with S.D. of 1.5mm. The mucosal thickening was observed more commonly in maxillary (79 patients, mean 3.0mm, S.D. 1.4mm) and ethmoid sinuses (80 patients,mean 2.7mm, S.D. 1.1mm) than in sphenoid (39 patients, mean 1.6mm, S.D. 1.4mm) or frontal sinuses (38 patients, mean 1.9mm, S.D. 1.4mm). CONCLUSION: Mucosal thickening of up to 6.5mm was a common finding on brain MRI of patients without evidence of sinusitis ; accuracy was 95%.

The Usefulness of Whole Body Bone Mineral Densitometry in the Osteopenia of Preterm Infants: Comparison with the Wrist Radiography and Biochemical Parameters

PURPOSE: To evaluate the usefulness of whole body bone mineral densitometry in the diagnosis of frequent osteopenia of preterm infants by comparison with the wrist radiographs and biochemical parameters. MATERIALS AND METHODS: From January 1995 to January 1996, we obtained whole body bone mineral density(BMD) studies using dual energy X-ray absorptiometry(DXA) and wrist radiographs of 39 preterm infants. They were divided into three groups according to birth weight, under 1500g, 1501g to 2000g and above 2000g, and four grades of skeletal change, as seen on wrist radiography, according to the scoring method of Koo et al. Groups of birth weight and grades of skeletal change were then correlated with whole body BMD and biochemical parameters. For comparison, normal data were obtained from 13 infants born at full term. Data were analyzed by one way analysis of variation(ANOVA) and correlation and regression analysis. A p-value of less than 0.05 was considered significant. RESUTLS: Whole body BMDs were significantly lower in the more premature and smaller birth weight infants(r=0.77, p=0.0000), and in the higher grade of skeletal change (r=-0.5276, p=0.0000). Aggravated skeletal changes were found in infants with lower birth weight(r=-0.3822, p=0.01). Interobserver variation in grading skeletal change was 42.9%, and intraobserver variation was 18.4%. Biochemical parameters such as serum calcium, phosphate, alkaline phosphatase, parathromone, calcitonin and 25-hydroxy-vitamine D did not vary significantly according to either birth weight or skeletal change (p>0.05). CONCLUSION: Premature osteopenia is more effectively diagnosed by measuring whole body BMD using DXA than by grading radiographical skeletal change or by biochemical parameters.