徳島大学病院歯科放射線科における過去10年間のX線撮影件数・内容の分析

徳島大学病院歯科放射線科における過去10年間のX線撮影件数・内容の分析


Development of a Low Radioactivity Detection System Using a Digital Intraoral Radiography Detector (Imaging Plate)

デジタル口内法X線撮影検出器(イメージングプレート)を応用した低放射能検出システムの開発


Development of an AI-based Dental Support System for Panoramic X-ray Images

AIを用いたパノラマX線画像からのカルテ入力支援システムの開発

Research and development of AI-based diagnostic systems in the medical and dental fields is flourishing worldwide. However, there are few practical dental support systems and dental databases. Support for medical record input is needed to reduce the burden at diagnosis. We have been developing a dental database with detailed annotation information and building an AI system for automatic teeth detection, teeth numbering, teeth contour estimation, and disease diagnosis from panoramic X-ray images since 2019. Three dentists and one expert of dental radiology created our database, which includes teeth number based on FDI method, coordinates of teeth contour, and various dental conditions, using Anotee, a software developed for creating dental databases. Our system consists of multiple deep neural networks that were trained using 1,781 panoramic X-ray images and annotations, which excluded deciduous teeth and rare dental conditions. The deep neural network to classify dental conditions is based on EfficientNetV2-S and can diagnose multiple dental conditions. To verify our systems usefulness, we evaluated two dental condition classifications for 20 dental conditions and 10 dental conditions such as caries, periodontitis, root canal filling, inlay, composite resin, crown, pontic, implant, and impacted tooth. We performed 5-fold cross validation and calculated precision, sensitivity, and specificity. Experimental results were encouraging. For the diagnosis of 20 conditions, precision was 90.4%, sensitivity was 86.1%, and specificity was 99.4%; for the diagnosis of 10 conditions, precision was 92.9%, sensitivity was 90.0%, and specificity was 99.1%. The system achieved high accuracy, suggesting that AI systems are useful in assisting medical record input support.

我々は従来の診断支援に関する技術をカルテ入力支援に応用するために，詳細なアノテーションを付与した歯科データベースの構築と，パノラマ X 線画像を対象としたカルテ入力支援システムの研究開発を行ってきた．本システムは，歯検出ニューラルネットワーク，セグメンテーションニューラルネットワーク，状態診断ニューラルネットワークを用いて，パノラマ X 線画像から，歯の検出，歯式推定，歯の輪郭推定および歯の状態診断を行うことができる．本システムとパノラマ X 線画像ビューアおよび電子カルテ(レセコン)を連携することでカルテの自動入力を可能にするため，歯科医のカルテ作成に必要な労力を軽減し，診断全体 の効率化に貢献することができる．また歯科医の画像診断に AI の画像診断が加わることで画像診断における見落としを防ぐことも期待できる．ただし最終的なカルテの確定は歯科医が視診等を踏まえた診断のあとにカルテを修正して行うため，本システムは確定診断のために用いるものではなく，画像から明確に判断できうる情報を AI が事前に自動入力することを目的としている．本論文では本システムの有用性を検討するために，構築したデータベースとデータ作成のプロセスについて述べ，歯の状態診断に対する精度評価を行う．また AI システムと専門医の診断結果の比較を行う．


Knowledge and risk perception of radiation for Japanese nursing students after the Fukushima Nuclear Power Plant disaster


Changes in Image Examinations at the Department of Oral Radiology -The Number of Intraoral and Panoramic Radiographs-

歯科放射線科の撮影件数の推移 -口内法枚数と口外法件数-

After the computed radiography (CR) system was developed in 1986, it became possible to acquire, view and save digital images for medical diagnosis. Around that time, panoramic radiography was digitized by the CR system, but it was limited to large hospitals. From 1994, it has been digitized at large hospitals and dental clinics. We examined the changes in the number of intraoral and panoramic radiographs in dentistry, and based on the relationships among the numbers of radiographs, patients and dental operations, we discussed the clinical significance of digitization.
We extracted intraoral and panoramic radiography data, the number of dental operations and the number of patients from the database of Tokushima University Hospital from 2002 to 2017. Then, we extracted nationwide data from Statistics of Medical Care Activities in Public Health by the Ministry of Health, Labour and Welfare from 2002 to 2017.
As a result, although the numbers of patients and dental operations at Tokushima UniversityHospital have remained constant, the number of intraoral radiographs has decreased (72%), whereas the number of panoramic radiographs has increased annually since 2011 (131%). In addition, although the number of patients and nationwide insurance points increased in a different manner than that at Tokushima University Hospital, a decrease in the number of intraoral radiographs and an increase in the number of panoramic radiographs were noted across Japan. As panoramic imaging has been improved and adapted to different settings, panoramic radiography has been used instead of intraoral radiography, and it has been widely used in screening applications such as for perioperative patients. Although digitization is progressing, the analog images are still used (intraoral radiography analog rate, 29.7%, panoramic radiography analog rate, 12.4% in 2017).


Comparison of radiation risk perception and knowledge of radiation between Indonesian and Japanese dental students.

The purpose of the study was to obtain basic data to identify problems in radiation education in a situation where confidence in nuclear power has fluctuated over time and fear of nuclear power has increased globally due to nuclear power plant disasters at Chernobyl and Fukushima. We conducted a questionnaire survey on understanding and risk perception of radiation and atomic power, before and after lectures, for 107 Japanese and 137 Indonesian dental students. Thirty-six phrases were extracted from two supplementary texts about radiation created by the Japanese Ministry of Education, Culture, Sports, Science and Technology, and 30 events commonly used in research on risk perception were used. The students were asked to rate their level of understanding of 36 phrases and risk perception of 30 events. Moreover, the students were asked to answer 6 general questions about radiation. For Japanese students, understanding of radiation increased and risk perception for both nuclear power and X-rays decreased after lectures (p < 0.05). Concerning nuclear power, the risk-value declined as the level of understanding increased (p < 0.01). However, for Indonesian students, who had lectures on only radiation excluding nuclear power in dental radiology, risk perception increased for X-ray after lectures (p < 0.05). This indicates that thought and custom, in the absence of knowledge, are influenced by lectures. In general, it is said that increase in knowledge will lower risk perception, but even if radiation education is imparted, risk perception may rise if the lectures are not understood properly. It was concluded that educators need to incorporate sufficient knowledge in their teachings, and correct thinking, to mitigate the risk of future radiation education giving the opposite of the intended effect.


多波長植物専用LED照射装置を用いた完全制御型水耕栽培システム

多波長植物専用LED照射装置を用いた完全制御型水耕栽培システム

LED総合フォーラム2019 in 徳島 論文集

LED総合フォーラム2019 in 徳島 論文集


Trends in CT Examinations and Diagnostic Reference Level (DRL)


New application of dynamic magnetic resonance imaging for the assessment of deglutitive tongue movement.

Segmented cine-MR imaging combined with static MR images is useful for assessing soft tissue motion during deglutition. This method is particularly useful in dentistry to evaluate the relationship between tongue function and maxillofacial morphology in terms of orthodontic treatment and orofacial myofunctional therapy, and for improving tongue movement during speech therapy.


放射線教育の歴史と現状ー福島第1原子力発電所事故を踏まえて

放射線教育の歴史と現状ー福島第1原子力発電所事故を踏まえて


Principles of the magnetic resonance imaging movie method for articulatory movement.

Magnetic resonance imaging (MRI) has become a critical tool for dental examination. MRI has many advantages over radiographic examination methods, including the lack of a requirement for patient exposure and the ability to capture high-contrast images of various tissue and organ types. However, MRI also has several limitations, including long examination times and the existence of metallic or motion artifacts. A cardiac imaging method using cine sequences was developed in the 1990s. This technique allows for analysis of heart movement and functional blood flow. Moreover, this method has been applied in dentistry. Recent research involving 3 T MRI has led to the achievement of a temporal resolution of < 10 ms, surpassing the frame rate of typical video recording. The current review introduces the history and principles of the cine sequence method and its application to the oral and maxillofacial regions.


Dental students' levels of understanding normal panoramic anatomy

In dentistry, panoramic radiography is an important examination technique. The Faculty of Dentistry at Tokushima University educates students about panoramic radiographic anatomical landmarks. The purpose of this study was to investigate differences in the understanding of each panoramic anatomical landmark among students. This study analyzed the results of 40 fifth- and 79 sixth-year faculty students who had taken a written examination to clarify their knowledge of anatomical landmarks in 28 panoramic radiographic regions. Anatomical landmarks were classified into 3 categories: <bone structure>, <soft tissue/air layer>, and <ghost images > to compare correct answer rates. The mean overall correct answer rate by the 119 students for the 28 regions was 53%. The rate did not vary between the 2 academic years. On comparison of the 3 categories, significant differences were only observed between <bone structure> and <soft tissue/air layer>, as the values for the latter were lower. Among the anatomical landmarks, the rates for the condylar head, hyoid bone, panoramic innominate line, styloid process, and nasopalatine line were higher, and those for ghost images of the contralateral nasopalatine line, the cervical vertebrae, mandibular foramen, mastoid air cell, and posterior pharyngeal wall were lower. The values for <soft tissue/air layer>, such as the dorsum of tongue, middle and inferior nasal conche, and middle and inferior nasal meatuses, were also lower. These results indicate the necessity of improving educational approaches for regions with lower rates of correct answers.


Time-course observation of patients with arthrosis of the temporomandibular joint on MRI

Patients with arthrosis of the temporomandibular joint are examined by MRI, but fewer cases are followed over time by performing MRI several times. The objective of this study was to investigate the presence or absence and types of changes in the structure of the mandibular condyle and articular disc on MR images over time in patients examined by MRI for the diagnosis of arthritis of the temporomandibular joint in order to clarify the usefulness of performing MRI several times.
 MR images for patients who underwent MRI several times based on the clinical diagnosis of arthrosis of the temporomandibular joint were analyzed.
 Twenty-three patients were examined by MRI twice or more. The shortest and longest intervals between the first and final examinations were 75 and 2,588 days, respectively, and the mean was 735 days. Changes in the bone structure of the mandibular condyle were noted on the first MRI in approximately 63 % and new changes were noted on the final examination in approximately 24 %. In addition, the articular disc position in the closed or open mouth had changed on the later examinationin approximately 15 %.
 Performing MRI several times along the clinical course was found to be useful to diagnose the disease stage, judge the treatment effects, and help predict the outcome in patients with arthrosis of the temporomandibular joint.


Influence of orthodontic appliance-derived artifacts on 3-T MRI movies.

Orthodontic appliances, including metallic materials, sometimes produce significant measurement error in speech evaluation using MRI movies, which often become invisible or distorted by metallic orthodontic appliances. When the distorted image is measured, caution should be exercised, as the measurement may be affected. Based on the study, it is concluded that orthodontists should not necessarily remove all metallic appliances before MRI examination because the influence varies among the appliances and should also know that a significant measurement error in speech evaluation using MRI movie may occur by image distortion caused by metallic artifacts.

A large artifact was observed over the entire oral region around orthodontic appliances, altering regional visibility. The velopharyngeal height was measured as significantly longer in the presence of metal brackets. The maximum artifact size due to a metallic bracket was > 8 cm. Our results show that even if it is possible to obtain the measurements of palate length, nasion to sella, and nasion to basion in individuals wearing metal brackets for molars, the measurements might be affected due to the presence of artifacts.


History of Digital Detectors in Intraoral Radiography


Influence of Radiation Education on Risk Perception in Japanese Dental Students


Numerical Evaluation of Image Contrast for Thicker and Thinner Objects among Current Intraoral Digital Imaging Systems.

The purpose is to evaluate the performance of current intraoral digital detectors in detail using a precise phantom and new method. Two aluminum step wedges in 0.5 mm steps were exposed by two photostimulable phosphor plate (PSP) systems-one with automatic exposure compensation (AEC) and the other without AEC-and a CCD sensor. Images were obtained with 3 doses at 60 kV. The effect of metallic material also was evaluated. The contrast-to-noise ratio (CNR) for thinner steps and the low contrast value (LCV) for thicker steps were obtained. The CCD system was the best under all conditions (P < 0.001), although the Gray value was sensitive to the dose, and the Gray value-dose relation varied greatly. The PSP system with AEC was superior to that without AEC for the LCV (P < 0.001) but was inferior to it regarding the CNR (P < 0.001). CNR and LCV in the PSP system without AEC were not affected by the metallic plate. Intraoral digital imaging systems should be chosen according to their diagnostic purpose. PSP system with AEC may be the best for detecting molar proximal caries, whereas the PSP system without AEC may be better for evaluating small bone regeneration in periodontal disease. The CCD system provided the best performance.


MR撮影における画像形成の原理

MR撮影における画像形成の原理


Characterization of Swallowing Sound: Preliminary Investigation of Normal Subjects

The purpose of this study was to characterize the swallowing sound and identify the process of sound generation during swallowing in young healthy adults. Thirty-three healthy volunteers were enrolled and allocated into three experimental groups. In experiment 1, a microphone was attached to one of eight cervical sites in 20 subjects, participants swallowed 5 ml water, and the sound waveform was recorded. In experiment 2, 10 subjects swallowed either 0, 5, 10, or 15 ml water during audio recording. In addition, participants consumed the 5 ml bolus in two different cervical postures. In experiment 3, the sound waveform and videofluoroscopy were simultaneously recorded while the three participants consumed 5 ml iopamidol solution. The duration and peak intensity ratio of the waveform were analyzed in all experimental groups. The acoustic analysis of the waveforms and videofluoroscopy suggested that the swallowing sound could be divided into three periods, each associated with a stage of the swallowing movement: the oral phase comprising posterior tongue and hyoid bone movement; the pharyngeal phase comprising larynx movement, hyoid bone elevation, epiglottis closure, and passage of the bolus through the esophagus orifice; and the repositioning phase comprising the return of the hyoid bone and larynx to their resting positions, and reopening of the epiglottis. Acoustic analysis of swallowing sounds and videofluoroscopy suggests that the swallowing sound could be divided into three periods associated with each process of the swallowing movement: the oral phase comprising the posterior movement of the tongue and hyoid bone; the pharyngeal phase comprising the laryngeal movement, hyoid bone elevation, epiglottis closure, and the bolus passage to the esophagus orifice; and the repositioning phase comprising the repositioning of the hyoid bone and larynx, and reopening of the epiglottis.


Availability of Japanese Government's supplemental texts on radiation reflecting the Fukushima Daiichi Nuclear Power Plant accident for elementary and secondary education from dental students' understanding

Following the Fukushima Nuclear Power Plant accident, the Japanese government created two supplemental texts about radiation reflecting the accident for elementary, middle school, and high school students. These texts were made to explain radiation and consequently to obtain public consent for the continuation of the nuclear program. The present study aimed to evaluate the appropriateness of the content of the texts and to collect the basic data on the level of understanding necessary to improve radiation education. Lectures on radiology including nuclear energy and the Fukushima accident were given to 44 fourth-year dental students in 2013. The questionnaire was administered in 2014 when these students were in their sixth-year. The survey was also administered to 40 first-year students and 41 fourth-year students who hadn't any radiology lectures. Students rated their level of understanding of 50 phrases used in the texts on a four-point scale (understanding = 3, a little knowledge = 2, having heard = 1, no knowledge = 0). Questions on taking an advanced physics course in high school and means of learning about radiation in daily life were also asked. The level of understanding of phrases in the supplemental text for middle and high school students was significantly higher among sixth-year students (mean = 1.43) than among first-year (mean = 1.12) or fourth-year (mean = 0.93) students (p < 0.05). Overall, the level of understanding was low, with scores indicating that most students knew only a little. First-year students learning about radiation from television but four-year and six-year students learning about radiation from newspaper scored significantly higher (p < 0.05). It was concluded that radiation education should be improved by using visual material and preparing educators to teach the material for improving the public's understanding of radiation use-especially nuclear power generation because the phrases used in the supplementary texts are very difficult for students to understand.


Infiltration of trace metal ions in the oral mucosa of a rat analyzed using SRXRF, XAFS, and ICP-MS

Although the accumulation and distribution of metals from metallic orthodontic appliances in the oral mucosa have been studied extensively, they remain unclear because their concentration is quite low. In this study, metal specimens (Ni, Ni-Ti, and Co-Cr) were sutured in the unilateral oral mucosa of rats, and the distribution of the eluted elements in the mucosal tissue was estimated using inductively coupled plasma mass spectrometry (ICP-MS) and synchrotron radiation X-ray fluorescence analysis (SR-XRF). While the infiltrations of Ni, Co, and Cr into the oral mucosal connective tissue were observed with SR-XRF, significant increases were only found in Ni from the pure Ni group and Cr from the Co-Cr group. Furthermore, Ni and Co were estimated as hydrated ions while Cr was estimated in oxide form through X-ray absorption fine structure (XAFS) analysis.


Trends in Magnetic Resonance Imaging Research in Dentistry


Creation of a dental X-ray unit with a contactless exposure control switch

A new dental radiographic unit (DXRU) with a contactless switch for adjusting exposure conditions and a foot-pedal exposure switch was developed to prevent bacterial or viral contamination from patients and was compared with a conventional DXRU with a panel push-button switch with respect to user friendliness. 45 fourth-year dental school students carried out intraoral radiography using both types of DXRU. Errors regarding dose shortages of X-rays were compared and a questionnaire completed. 22 (49%) of the 45 students failed to provide the correct radiographic exposure and the number of errors was 32 for the conventional DXRU, and 4 (9%) students failed to provide the correct radiographic exposure and the number of errors was 4 for our new DXRU, at the first stage (p < 0.001). At the second stage, the number of students who failed to provide the correct radiographic exposure and the number of errors decreased to 12 and 16, respectively, for the conventional DXRU (p < 0.05). 37 (82%) of the 45 students preferred our DXRU because of its contactless switch and the push-pedal exposure switch. These data suggested that our new contactless mechanism should be used for other DXRUs for contamination control.


MRI対応生体内金属の開発

MRI対応生体内金属の開発

The Journal of the Japanese Society of Magnetic Applications in Dentistry


Magnetic susceptibility and hardness of Au-xPt-yNb alloys for biomedical applications


Preoperative evaluation of patients with squamous cell carcinoma of the oral cavity: fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography and ultrasonography versus histopathology.

PET/CT and US are complementary tools to evaluate preoperative patients.

Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology


口内法X線画像のための新しいDICOMファントムの実用化

口内法X線画像のための新しいDICOMファントムの実用化


Shielding Effect of a Customized Intraoral Mold Including Lead Material in High-dose-rate 192-Ir Brachytherapy for Oral Cavity Cancer.

A high-dose-rate (HDR) 192-Ir brachytherapy using a customized intraoral mold is effective for superficial oral cavity cancer, and the surrounding normal tissue is kept away from the radioactive source with gauze pads and/or mouth piece for reducing the dose on the normal tissues. In the Tokushima university hospital, the mold has a lead shield which utilizes the space prepared with sufficient border-molding by a specific dental technique using modeling compound. In HDR 192-Ir brachytherapy using a lead shielded customized intraoral mold, there are no reports measuring the absorbed dose. The purpose of the present study is to measure the absorbed dose and discuss the optimum thickness of lead in HDR 192-Ir brachytherapy using a customized intraoral mold with lead shield using a 1 cm thickness mimic mold. The thickness of lead in the mold could be changed by varying the arrangement of 0.1 cm thickness sheet of the acrylic resin plate and lead. The measured doses at the lateral surface of the mold with thermo-luminescence dosimeter were reduced to 1.12, 0.79, 0.57, 0.41, 0.31, 0.24 and 0.19 Gy and the ratios to the prescription dose were reduced to 56, 40, 29, 21, 16, 12 and 10 percent as lead thickness increased from 0 to 0.6 cm in 0.1 cm increments, respectively. A 0.3 cm thickness lead was considered to be required for a 1 cm thickness mold, and it was necessary to thicken the lead as much as possible with the constraint of limited space in the oral cavity, especially at the fornix vestibule.


Distance Measurement Accuracy of a Digital CCD Sensor Cephalometric System Comparison with a Conventional-type Computed Radiography Photostimulable Phosphor Cephalometric System

CCDセンサー方式セファロシステムによる距離測定精度 ーCRシステムを用いた従来型セファロシステムとの比較ー


The Distribution of Thermal Neutron Flux into the Self-shielded Wall Equipped with a Medical Self-shielded PET Cyclotron

The Journal of the Korean Physical Society


High-dose-rate brachytherapy for patients with maxillary gingival carcinoma using a novel customized intraoral mold technique.

OBJECTIVE: The purpose of this study was to introduce a novel customized intraoral mold treatment for maxillary gingival carcinoma (UGC). STUDY DESIGN: Two patients with UGC were treated as salvage therapy using this technique. The mold was designed to keep normal soft tissues adjacent to the tumor away from the radioactive source as much as possible, and it was shielded by lead. The radiation dose on the buccal mucosa and tongue was measured at the inner and outer surfaces of the intraoral mold before starting high-dose-rate brachytherapy by the remote afterloading system, and was reduced to almost one tenth. RESULTS: The patient had no recurrence and no severe adverse effects on the normal soft tissue adjacent to the tumor until the end of the follow-up period. CONCLUSION: High-dose-rate brachytherapy using the novel customized intraoral mold might be a treatment option of not only salvage therapy, but definitive therapy of UGC.

Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics


Evaluation of Measurement Accuracy in Imaging Using a Cone-beam CT

小照射野歯科用CT撮影における画像測定精度の検討

Journal of Japanese Society of Oral Implantology

日本口腔インプラント学会誌


医療用自己遮蔽型PETサイクロトロン及び電子リニアックにおける中性子束の箔放射化法による測定

Japanese Journal of Radiation Safety Management

日本放射線安全管理学会誌


小照射野歯科用CT装置での患者被曝線量の検討．被曝測定用X線フィルムを用いた解析．

日本口腔インプラント学会誌


Hanging protocol and viewers for a dental full picture [corrected] archiving and communication system (PACS) [corrected].

The new system using a dental DICOM viewer and a dental Web viewer is the most advanced for examining oral and maxillofacial regions compared with medical viewers. Our local but clinically operational hanging protocol should be a good model for DICOM Working Group 22.


Evaluation of Patient Dose in Imaging Using a Cone-beam CT for Dental Use.

小照射野歯科用CT装置での患者被曝線量の検討

日本口腔インプラント学会誌


歯科インプラント治療計画の画像診断のための高速らせんCT撮影条件の画質に与える影響評価


日本の歯科学生とインドネシアの歯科学生・歯科衛生士学生における放射線に対する理解度とリスク認識との関係


一般照明および植物育成照明に応用できる新しいLED照明方法の開発

一般照明および植物育成照明に応用できる新しいLED照明方法の開発

LED総合フォーラム2018 in 徳島 論文集

LED総合フォーラム2018 in 徳島 論文集


口内法X線画像用DICOMファイルの規格化および歯科用Viewerの実用化

口内法X線画像用DICOMファイルの規格化および歯科用Viewerの実用化


2種類のデジタル口内法イメージングシステムによるコントラストの比較

2種類のデジタル口内法イメージングシステムによるコントラストの比較


デジタル画像の特徴と最新の放射線関連画像

デジタル画像の特徴と最新の放射線関連画像

日本歯科CAD/CAM学会雑誌

日本歯科CAD/CAM学会雑誌


福島原子力発電所の事故からみた放射性同位元素と放射線

福島原子力発電所の事故からみた放射性同位元素と放射線