Purpose: To reduce intraoral radiographic errors in undergraduate clinical discipline.
Materials and methods: We evaluated a total of 2, 434 intraoral radiographs taken by 50 students, during undergraduate clinical discipline in 1998, with the bisecting technique at each practice stage.
Results:
1. The frequency of errors significantly decreased as the practice stage progressed.
2. Errors were most frequent in the area of the canines and premolars, followed by the molars, and least frequent in the incisors.
3. The most frequent cause of error was incorrect film placement, followed by vertical overangulation and cone cutting.
Conclusions:
1. Repeated patient practice with student participation in diagnosis and treatment was considered effective for the clinical discipline of intraoral radiography.
2. In the teaching of intraoral radiographic practice, it is important to provide the student with a sufficient understanding of the morphology of oral structures.
3. It is necessary to instruct the students sufficiently in correct patient placement, film placement and cone placement.

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A brand-new multidimensional linear array probe for medical ultrasound imaging was evaluated. This probe is composed of 192 transducers in a 40mm scanning direction and 6 in the elevational direction. Axial, lateral and elevational resolutions were evaluated. The spatial resolutions of a conventional single-array linear probe, composed of 192 transducers in 40mm directions were also evaluated and compared.
Elevational resolution was measured with a specially ordered phantom consisting of fine parallel stainless-steel wires immersed in a water bath. The wires were placed parallel to the scanning direction of the probe. Elevational resolution was defined as the maximal distance between two parallel wires when both wires were displayed in a single image. The resolution was measured at a depth of 5, 10, 15, 20 and 30mm from the surface of the probe.
Lateral and axial resolutions were measured with a ready made phantom consisting of fine nylon pins at various depths in a tissue mimicking gel. Resolution was defined as the dimensions of the pins in the image.
The multidimensional array probe provided superior elevational resolution near the surface of the probe, and gradually degraded along the probe. The elevational resolution of the single-array probe gradually improved along the probe. Between the two probes, the resolution was reversed at 30mm depth.
The multidimensional array probe consistently provided superior lateral and axial resolutions consistently.
From the point of spatial resolution, the multidimensional array probe has an advantage, especially near the probe.

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Purpose: The aim of this study was to develop scenarios and checklists of dental radiology to be suitable to multi-station Objective Structured Clinical Examination (OSCE) used as part of the students' summative in-course assessment.
Materials and Methods: An OSCE in radiology was developed and implemented by a panel, which was consisted of two faculty members of radiology. Student's clinical competency was tested along the general instruction objective of radiology for 5th-year students. The contents were 1) to obtain a patient's consent for a radiographic examination, 2) to take a intraoral radiograph of the specified tooth properly using a film-holding device, 3) to mount a full-mouth periapical and bitewing radiographs, 4) and 5) to interpret a full-mouth periapical and panoramic radiographs respectively and report to a colleague in the form of a written document. Each student was examined through a series of five 5-min stations. Two on-site examiners were posted at stations 1 and 2, an examiner at station 3, and no examiners were posted at stations 4 and 5. The written reports produced at stations 4 and 5 were checked by two examiners following the test. A checklist was developed through careful discussion by the panel, and the criteria were calibrated within and across the examiners just before the test. A simulated patient was positioned at stations 1 and 2. The examinations were performed every two weeks, at the end of each term of radiological study. Each time 7-8 students were tested, and all of 37 students participated. Following the examination, the students were given feedback on their performance by the examiners and the simulated patient. After the examination, students and examiners filled out questionnaires.
Results and Conclusion: The examiners and students agreed that the scenarios proposed in this study were relevant to clinical skills in radiology and could be used in the Dental OSCE. The feedback to faculty on the results of this trial increased his/her concern about the instruction method. The results indicated that further development of scenario and checklist would be necessary in order to improve the validity and reliability of the examination.

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Purpose: The purpose of this study was to reduce the cost and time required for the fabrication of anatomical models built by Rapid Prototyping Technologies (RPT) for maxillo-facial surgery and dental implant planning and to establish and share the responsibility for making models between our hospital and the RPT model factory.
Method: Data: Axial CT images of the complex anatomical structures of the face scan and jaw bones, which were obtained using Spiral CT, were processed by a homemade software program using Compaq Visual Fortran. The output model data were written in HP-GL formats. A dental radiologist determined the threshold of the CT value and edit segments using the CT images. The Internet was used as model data communication system between the dental hospital and the model factory.
Results: There were two major advantages in using an Internet-based system. First, the hospital did not need to purchase an expensive RPT system, so, our method helps to reduce the cost of fabrications of medical rapid prototype models. Second, the Internet was very effective for discussions on the date and structure of the model between the radiologist and the model fabrication engineer using digital images of the model. The Engineers at the model factory could concentrate and be responsible only for fabricating the anatomical structure of the models.
Conclusion: Using the Internet is a useful method in medical RPT for maintaining quality, sharing responsibility, and reducing the cost.

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Scintigraphy with ^99mTc-labeled phytate for detection of sentinel lymph nodes (SN) of the tongue was performed using two healthy volunteers as a preliminary study to determine for its clinical applicability.
^99mTc-labeled phytate was injected into the submucosa of the left border of the tongue in both cases by one operator. Accumulation that was thought to be SNs was detected on scintigrams after injection, and the accumulation had increased after two hours in the same locations, though the spots of accumulation were located at different levels of the neck in the two cases.
It is not clear whether the difference between the locations of SNs in the two cases indicates normal variation in lymph drainage of the tongue or difficulty in technical stability of injection. These results suggest the necessity for further investigation of detection of SNs using normal materials to determine its clinical application to tongue carcinomas.

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