Comparison of conventional lateral cephalograms with corresponding CBCT radiographs

PURPOSE: This study was performed to assess the compatibility of cone beam computed tomography (CBCT) synthesized cephalograms with conventional cephalograms, and to find a method for obtaining normative values for three-dimensional (3D) assessments. MATERIALS AND METHODS: The sample group consisted of 10 adults with normal occlusion and well-balanced faces. They were imaged using conventional and CBCT cephalograms. The CBCT cephalograms were synthesized from the CBCT data using OnDemand 3D software. Twenty-one angular and 12 linear measurements from each imaging modality were compared and analyzed using paired-t test. RESULTS: The linear measurements between the two imaging modalities were not statistically different (p>0.05) except for the U1 to facial plane distance. The angular measurements between the two imaging modalities were not statistically different (p>0.05) with the exception of the gonial angle, ANB difference, and facial convexity. CONCLUSION: Two-dimensional cephalometric norms could be readily used for 3D quantitative assessment, if corrected for lateral cephalogram distortion.

Impacted supernumerary tooth in coronoid process: a case report / 대한구강악안면방사선학회지

Impaction of tooth is a situation in which an unerupted tooth is wedged against another tooth or teeth or otherwise located so that it cannot erupt normally. The supernumerary tooth is also called as hyperdontia and defined as the condition of having additional tooth to the regular number of teeth. The most common supernumerary tooth is a mesiodens, which is a mal-formed, peg-like tooth that occurs between the maxillary incisors. The supernumerary tooth is commonly impacted but they are frequently impacted on maxilla. Ectopic impaction of supernumerary tooth on mandibular condyle, coronoid process, ascending ramus, and pterygomandibular space is very rare condition. In this case, we report a case of impacted supernumerary tooth on mandibular sigmoid notch without definite pathologic change.

Comparative evaluation of computed tomography for dental implants on the mandibular edentulous area / 대한구강악안면방사선학회지

PURPOSE: The purpose of this study was to evaluate the clinical usefulness of the recently developed multi-detector computed tomography and cone beam computed tomography in pre-operative implant evaluation, by comparing them with the single detector computed tomography, already confirmed for accuracy in this area. MATERIALS AND METHODS: Five partially edentulous dry human mandibles, with 1x1 mm gutta percha cones, placed in 5 mm intervals posterior to the mental foramen on each side of the buccal part of the mandible, were used in this study. They were scanned as follows: 1) Single detector computed tomography: slice thickness 1 mm, 200 mA, 120 kV 2) Multi-detector computed tomography: slice thickness 0.75 mm, 250 mA, 120 kV 3) Cone beam computed tomography: 15 mAs, 120 kV Axial images acquired from three computed tomographies were transferred to personal computer, and then reformatted cross-sectional images were generated using V-Implant 2.0(R) (CyberMed Inc., Seoul, Korea) software. Among the cross-sectional images of the gutta percha cone, placed in the buccal body of the mandible, the most precise cross section was selected as the measuring point and the distance from the most superior border of the mandibular canal to the alveolar crest was measured and analyzed 10 times by a dentist. RESULTS: There were no significant intraobserver differences in the distance from the most superior border of the mandibular canal to the alveolar crest (p>0.05). There were no significant differences among single detector computed tomography, multi-detector computed tomography and cone beam computed tomography in the distance from the most superior border of the mandibular canal to the alveolar crest (p>0.05). CONCLUSION: Multi-detector computed tomography and cone beam computed tomography are clinically useful in the evaluation of pre-operative site for mandibular dental implants, with consideration for radiation exposure dose and scanning time.

Characteristics of a new cone beam computed tomography / 대한구강악안면방사선학회지

PURPOSE: To determine the physical properties of a newly developed cone beam computed tomography (CBCT). MATERIALS AND METHODS: We measured and compared the imaging properties for the indirect-type flat panel detector (FPD) of a new CBCT and the single detector array (SDA) of conventional helical CT (CHCT). RESULTS: First, the modulation transfer function (MTF) of the CBCT were superior to those of the CHCT. Second, the noise power spectrum (NPS) of the CBCT were worse than those of the CHCT. Third, detective quantum efficiency (DQE) of the indirect-type CBCT were worse than those of the CHCT at lower spatial frequencies, but were better at higher spatial frequencies. Although the comparison of contrast-to-noise ratio (CNR) was estimated in the limited range of tube current, CNR of CBCT were worse than those of CHCT. CONCLUSION: This study shows that the indirect-type FPD system may be useful as a CBCT detector because of high resolution.

Measurement of facial soft tissues thickness using 3D computed tomographic images / 대한구강악안면방사선학회지

PURPOSE: To evaluate accuracy and reliability of program to measure facial soft tissue thickness using 3D computed tomographic images by comparing with direct measurement. MATERIALS AND METHODS: One cadaver was scanned with a Helical CT with 3 mm slice thickness and 3 mm/sec table speed. The acquired data was reconstructed with 1.5 mm reconstruction interval and the images were transferred to a personal computer. The facial soft tissue thickness were measured using a program developed newly in 3D image. For direct measurement, the cadaver was cut with a bone cutter and then a ruler was placed above the cut side, The procedure was followed by taking pictures of the facial soft tissues with a high-resolution digital camera. Then the measurements were done in the photographic images and repeated for ten times. A repeated measure analysis of variance was adopted to compare and analyze the measurements resulting from the two different methods. Comparison according to the areas was analyzed by Mann-Whitney test. RESULTS: There were no statistically significant differences between the direct measurements and those using the 3D images (p>0.05). There were statistical differences in the measurements on 17 points but all the points except 2 points showed a mean difference of 0.5 mm or less. CONCLUSION: The developed software program to measure the facial soft tissue thickness using 3D images was so accurate that it allows to measure facial soft tissues thickness more easily in forensic science and anthropology.

Clinical usefulness of facial soft tissues thickness measurement using 3D computed tomographic images / 대한구강악안면방사선학회지

PURPOSE: To evaluate clinical usefulness of facial soft tissue thickness measurement using 3D computed tomographic images. MATERIALS AND METHODS: One cadaver that had sound facial soft tissues was chosen for the study. The cadaver was scanned with a Helical CT under following scanning protocols about slice thickness and table speed; 3 mm and 3 mm/sec, 5 mm and 5 mm/sec, 7 mm and 7 mm/sec. The acquired data were reconstructed 1.5, 2.5, 3.5 mm reconstruction interval respectively and the images were transferred to a personal computer. Using a program developed to measure facial soft tissue thickness in 3D image, the facial soft tissue thickness was measured. After the ten-time repeation of the measurement for ten times, repeated measure analysis of variance (ANOVA) was adopted to compare and analyze the measurements using the three scanning protocols. Comparison according to the areas was analyzed by Mann-Whitney test. RESULTS: There were no statistically significant intraobserver differences in the measurements of the facial soft tissue thickness using the three scanning protocols (p>0.05). There were no statistically significant differences between measurements in the 3 mm slice thickness and those in the 5 mm, 7 mm slice thickness (p>0.05). There were statistical differences in the 14 of the total 30 measured points in the 5 mm slice thickness and 22 in the 7mm slice thickness. CONCLUSION: The facial soft tissue thickness measurement using 3D images of 7 mm slice thickness is acceptable clinically, but those of 5 mm slice thickness is recommended for the more accurate measurement.

Inflammatory myofibroblastic tumor: A case report / 대한구강악안면방사선학회지

The inflammatory myofibroblastic tumor (inflammatory pseudotumor) is a rarely occurring soft tissue lesion of unknown etiology. It can be of any location, but commonly it is found in lungs. It has been considered as a nonneoplastic reactive inflammatory lesion, but nowadays, confusion and dispute about its character is increasing due to its high recurrence rate and metastasis. We present a patient who had been diagnosed with an inflammatory pseudotumor in the right maxilla area, 1 year before visiting our hospital. After that, her pain and swelling did not resolved and she visit our hospital. On radiographic examination, aggressively infiltrative growth of the lesion with destruction of adjacent bony structure was noted. We found unusual aggressiveness of the inflammatory myofibroblastic tumor of the head and neck region. Because the typical behavior of the inflammatory myofibroblastic tumor is not defined yet, we recommend the surgical excision of the lesion and close follow-up.

Benefits and problems in implementation for integrated medical information system / 대한구강악안면방사선학회지

PURPOSE: Once the decision has been made to adopt an integrated medical information system (IMIS), there are a number of issues to overcome. Users need to be aware of the impact the change will make on end users and be prepared to address issues that arise before they become problems. The purpose of this study is to investigate the benefits and unexpected problems encountered in the implementation of IMIS and to determine a useful framework for IMIS. MATERIALS AND METHODS: The Yonsei University Dental Hospital is steadily constructing an IMIS. The vendor's PACS software, Piview STAR, supports transactions between workstations that are approved to integrating the healthcare enterprise (IHE) with security function. It is necessary to develop an excellent framework that is good for the patient, healthcare provider and information system vendors, in an expert, efficient, and cost-effective manner. RESULTS: The problems encountered with IMIS implementation were high initial investments, delay of EMR enforcement, underdevelopment of digital radiographic appliances and software and insufficient educational training for users. CONCLUSIONS: The clinical environments of dental IMIS is some different from the medical situation. The best way to overcome these differences is to establish a gold standard of dental IMIS integration, which estimates the cost payback. The IHE and its technical framework are good for the patient, the healthcare provider and all information systems vendors.

A radiologic study of ameloblastoma using computed tomography / 대한구강악안면방사선학회지

PURPOSE: To reveal what is the distinct differential diagnostic differences between unicystic ameloblastoma and solid or multicystic ameloblastoma. MATERIALS AND METHODS: 56 cases of ameloblastoma were retrospectively reviewed and evaluated among the patients who had taken CT scans at the department of Oral and Maxillofacial Radiology in Yonsei University Dental Hospital from January 1996 to December 2003. RESULTS: In 56 cases, 21 cases (37.5%) were unicystic ameloblastoma, 35 cases (62.5%) were solid or multicystic ameloblastoma. Only 1 case (4.8%) of unicystic ameloblastoma and 4 cases (11.4%) of solid or multicystic ameloblastoma were occurred in maxilla. 13 cases (61.9%) of unicystic ameloblastoma were observed as unilocular, and 8 cases (38.1%) as lobulated. 5 cases (14.3%) of solid or multicystic ameloblastoma were observed as unilocular, 13 cases (37.1%) as lobulated, and 17 cases (48.6%) as multilocular. In the results from the measurements after correction of the buccolingual widths and heights to the mesiodistal lengths, there is a statistically significant difference between unicystic ameloblastoma and solid or multicystic ameloblastoma in ANCOVA test (p 0.05). CONCLUSION: Characteristic differences between unicystic ameloblastoma and solid or multicystic ameloblastoma is that there is higher prevalence of solid or multicystic ameloblastoma that have lobulated or multilocular patterns. To measure the Hounsfield units in the lesion is helpful, but it is not a differential diagnostic point between unicystic ameloblastoma and solid or multicystic ameloblastoma.

Bony change of apical lesion healing process using fractal analysis / 대한구강악안면방사선학회지

PURPOSE: To investigate the change of bone healing process after endodontic treatment of the tooth with an apical lesion by fractal analysis. MATERIALS AND METHODS: Radiographic images of 35 teeth from 33 patients taken on first diagnosis, 6 months, and 1 year after endodontic treatment were selected. Radiographic images were taken by JUPITER Computerized Dental X-ray System (R). Fractal dimensions were calculated three times at each area by Scion Image PC (R) program. Rectangular region of interest (30 x 30) were selected at apical lesion and normal apex of each image. RESULTS: The fractal dimension at apical lesion of first diagnosis (L0) is 0.940+/-0.361 and that of normal area (N0) is 1.186+/-0.727 (p< 0.05). Fractal dimension at apical lesion of 6 months after endodontic treatment (L1) is 1.076+/-0.069 and that of normal area (N1) is 1.192+/-0.055 (p< 0.05). Fractal dimension at apical lesion of 1 year after endodontic treatment (L2) is 1.163+/-0.074 and that of normal area (N2) is 1.225+/-0.079 (p< 0.05). After endodontic treatment, the fractal dimensions at each apical lesions depending on time showed statistically significant difference. And there are statistically significant different between normal area and apical lesion on first diagnosis, 6 months after, 1 year after. But the differences were grow smaller as time flows. CONCLUSION: The evaluation of the prognosis after the endodontic treatment of the apical lesion was estimated by bone regeneration in apical region. Fractal analysis was attempted to overcome the limit of subjective reading, and as a result the change of the bone during the healing process was able to be detected objectively and quantitatively.

Current status and installation standard of dental PACS / 대한구강악안면방사선학회지

PURPOSE: Picture Archiving and Communication System (PACS) is difficult to implement in the best of situations, but evidence is growing that the benefits are significant. The aims of this study are to analyze the current status of full PACS and establish successful installation standard of dental PACS. MATERIALS AND METHODS: Materials and methods were based on the investigation of current working status and installation standard of PACS, and observation of variable issues to installation of dental PACS. RESULTS: By September 30, 2004, full PACS implementations in their facilities were 88.1% in specialized general hospitals (37 installations out of total 42 hospitals), 59.8% in general hospitals (144 installations out of total 241 hospitals), 12.3% in medical hospitals (116 installations out of total 941 hospitals) and 3.6% in dental hospitals (4 installations out of total 110 hospitals) Only 4 university dental hospitals currently have installed and are operating full PACS. Major obstacle to wide spread of dental PACS is initial high investments. CONCLUSIONS: Clinical environments of dental PACS differed from medical situation. Because of characteristic dental practice, the initial investments for dental PACS are generally much greater than those of medical PACS. Also new economic crisis makes users scruple. The best way to overcome these limitations is to establish an economic installation standard for dental PACS. Also the clear technical communication between the customer and the supplier before both sides are committed to the obstacles are critical to its success.

Three-dimensional image analysis of the skull using variable CT scanning protocols-effect of slice thickness on measurement in the three-dimensional CT images / 대한구강악안면방사선학회지

PURPOSE: To evaluate the quantitative accuracy of three-dimensional (3D) images by means of comparing distance measurements on the 3D images with direct measurements of dry human skull according to slice thickness and scanning modes. MATERIALS AND METHODS: An observer directly measured the distance of 21 line items between 12 orthodontic landmarks on the skull surface using a digital vernier caliper and each was repeated five times. The dry human skull was scanned with a Helical CT with various slice thickness (3, 5, 7 mm) and acquisition modes (Conventional and Helical). The same observer measured corresponding distance of the same items on reconstructed 3D images with the internal program of V-works 4.0 TM (Cybermed Inc., Seoul, Korea). The quantitative accuracy of distance measurements were statistically evaluated with Wilcoxons' two-sample test. RESULTS: 11 line items in Conventional 3 mm, 8 in Helical 3 mm, 11 in Conventional 5 mm, 10 in Helical 5 mm, 5 in Conventional 7 mm and 9 in Helical 7 mm showed no statistically significant difference. Average difference between direct measurements and measurements on 3D CT images was within 2 mm in 19 line items of Conventional 3 mm, 20 of Helical 3 mm, 15 of Conventional 5 mm, 18 of Helical 5 mm, 11 of Conventional 7 mm and 16 of Helical 7 mm. CONCLUSION: Considering image quality and patient's exposure time, scanning protocol of Helical 5 mm is recommended for 3D image analysis of the skull in CT.

The elimination of the linear artifacts by the metal restorations in the three dimensional computed tomographic images using the personal computer and software / 대한구강악안면방사선학회지

PURPOSE: The purpose of this study is to evaluate the effectiveness and usefulness of newly developed personal computer-based software to eliminate the linear artifacts by the metal restorations. MATERIALS AND METHODS: A 3D CT image was conventionally reconstructed using ADVANTAGE WINDOWS 2.0 3D Analysis software (GE Medical System, Milwaukee, USA) and eliminated the linear artifacts manually. Next, a 3D CT image was reconstructed using V-works 4.0 TM (Cybermed Inc., Seoul, Korea) and the linear artifacts eliminated manually in the axial images by a skillful operator using a personal computer. A 3D CT image was reconstructed using V-works 4.0 TM (Cybermed Inc., Seoul, Korea) and the linear artifacts were removed using a simplified algorithm program to eliminate the linear artifacts automatically in the axial images using a personal computer, abbreviating the manual editing procedure. Finally, the automatically edited reconstructed 3D images were compared to the manually edited images. RESULTS AND CONCLUSION: We effectively eliminated the linear artifacts automatically by this algorithm, not by the manual editing procedures, in some degree. But programs based on more complicated and accurate algorithms may lead to a nearly flawless elimination of these linear artifacts automatically.

Reproducibilities of cephalometric measurements of three-dimensional CT images reconstructed in the personal computer / 대한구강악안면방사선학회지

PURPOSE: The purpose of this study was to report the reproducibility of intra-observer and inter-observer consistency of cephalometric measurements using three-dimensional (3D) computed tomography (CT), and the degree of difference of the cephalometric measurements. MATERIALS AND METHODS: CT images of 16 adult patients with normal class I occlusion were sent to personal computer and reconstructed into 3D images using V-Works 3.5 TM (Cybermed Inc., Seoul, Korea). With the internal program of V-Works 3.5 TM, 12 landmarks on regular cephalograms were transformed into 21 analytic categories and measured by 2 observers and in addition, one of the observers repeated their measurements. Intra-observer difference was calculated using paired t-test, and inter-observer by two sample test. RESULTS: There were significant differences in the intra-observer measurements (p< 0.05) in four of the categories which included ANS-Me, ANS-PNS, Cdl-Go (Lt), GoL-GoR, but with the exception of Cdl-Go (Lt), ZmL-ZmR, Zyo-Zyo, the average differences were within 2 mm of each other. The inter-observer observations also showed significant differences in the measurements of the ZmL-ZmR and Zyo-Zyo categories (p< 0.05). With the exception of the Cdl-Me (Rt), ZmL-ZmR, Zyo-Zyo categories, the average differences between the two observers were within 2 mm, but the ZmL-ZmR and Zyo-Zyo values differed greatly with values of 8.10 and 19.8 mm respectively. CONCLUSION: In general, 3D CT images showed greater accuracy and reproducibility, with the exception of suture areas such as Zm and Zyo, than regular cephalograms in orthodontic measurements, showing differences of less than 2 mm, therefore 3D CT images can be useful in cephalometric measurements and treatment planning.