研究者詳細 - 河津　俊幸

論文 - 河津　俊幸

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Assessment of image quality in dental radiography, part 2 - Optimum exposure conditions for detection of small mass changes in 6 intraoral radiography systems 査読

K Yoshiura, T Kawazu, T Chikui, M Tatsumi, K Tokumori, T Tanaka, S Kanda

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY ORAL RADIOLOGY AND ENDODONTICS 87 ( 1 ) 123 - 129 1999年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：MOSBY-YEAR BOOK INC

Objective, The purpose of this study was to compare 2 film systems and several digital intraoral systems with regard to visual image quality through use of a test phantom developed for this purpose.
Study design. The detectors used for digital imaging were as follows: Computed Dental Radiography (CDR), Digora, Dixel, and Sens-A-Ray without scintillator layer Two types of digital images were prepared for the observer performance test: one with original gray scales and another with contrast enhancement. Images with and without enhancement from the 4 systems were displayed to 7 observers. The change in the average number of perceptible holes was plotted against exposure, and modified perceptibility curves were created and compared with curves for the film systems. The exposure level at which the maximum number of holes was perceived was defined to be optimum. The optimum exposure levels were determined for each digital system and compared with that of the film systems. At the optimum exposure, the average maximum numbers of perceptible holes in each digital system with and without contrast enhancement were compared with the maximum numbers for the film systems. The minimum exposure levels were determined to be those at which the number of perceptible holes exceeded the number for film, and the possibility of exposure reduction was evaluated.
Results. All digital systems except the Digora system showed lower optimum exposures than E-speed film. In all digital images without enhancement, however, the maximum number of perceptible holes was significantly lower than that for the film systems at that exposure. With contrast enhancement, all digital systems except the Sens-A-Ray system showed visibility superior to that of the film systems. With the CDR, Digora, and Dixel systems, exposures could be further reduced by a considerable amount, with greater retention of information than was associated with film.
Conclusions. Our results strongly suggest that digital systems, if properly used, can exceed film systems in the detection of smalt mass changes.

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Assessment of image quality in dental radiography, part 1 - Phantom validity 査読

K Yoshiura, T Kawazu, T Chikui, M Tatsumi, K Tokumori, T Tanaka, S Kanda

ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY ORAL RADIOLOGY AND ENDODONTICS 87 ( 1 ) 115 - 122 1999年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：MOSBY-YEAR BOOK INC

Objective. The purpose of this study was to describe and validate an image-quality phantom to be used in dental radiography for comparison of film and digitally acquired images.
Study design. An aluminum block of 12 steps, with 7 holes in each step, was covered by acrylic blocks. This phantom was radiographed with Kodak Ultra-speed and Ektaspeed Plus films at 70, 65, and 60 kVp with the whole exposure range available. All together, 50 dental films were randomly sequenced and presented to 7 observers. The average number of perceptible holes from all steps was plotted against exposure for each tube voltage and film type, generating a modified perceptibility curve. The tentative optimum exposure revel was determined from perceptibility curves in each experimental condition and compared with that determined by means of the standard aluminum step-wedge and the preset time of the x-ray machine. The density range of this phantom at the optimum exposure was compared with that of clinical dental radiographs. Validity of the phantom was evaluated according to the optimum exposure level from the modified perceptibility curves and the overall density range. Finally, the average maximum numbers of perceptible holes at the tentative optimum exposure level were compared for each tube voltage and film type. The statistical test used was a 2-way factorial analysis of variance.
Results, The exposure at the perceptibility curve peak approximated that obtained by means of the standard aluminum step-wedge and the time preset by the manufacturer. The overall density range at the perceptibility curve peak covered the clinical density range for each tube voltage and film type. There were no statistically significant differences between firm types or among tube voltages.
Conclusions. The x-ray attenuation range for this phantom seemed to approximate clinical conditions. In addition, differences in image quality could be quantitatively evaluated by means of the number of the holes seen in the phantom.

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Consideration for Density Optimization and Dose Reduction of Digital Dental Imaging System Using Fuzzy C-Means Clustering

Tanaka Takemasa, Kawazu Toshiyuki, Kanda Shigenobu

International Journal of Biomedical Soft Computing and Human Sciences: the official journal of the Biomedical Fuzzy Systems Association 5 ( 1 ) 33 - 38 1999年

記述言語：英語出版者・発行元：バイオメディカル・ファジィ・システム学会

Recently the digital dental imaging system (DDIS) has been developed and its use has spread widely. Although it has several advantages, the image quality is not better than that of conventional dental radiographs. Particularly, the density distributions of DDIS images are often insufficient and inadequate. Therefore, the authors considered the density optimization of DDIS images. For this aim, we applied a fuzzy c-means clustering algorithm because the pattern of DDIS images has an extensive variety. Using our method, the denstity distribution of most DDIS images can be improved appropriately. In addition, this method provides a dose reduction for the patients. Consequently, 38.3% of the absorbed dose was decreased.

DOI： 10.24466/ijbschs.5.1_33

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ファジィ理論による超音波診断支援システム : 確定法(非ファジィ化)に関する検討

田中武昌, 河津俊幸, 神田重信

バイオメディカル・ファジィ・システム学会誌 1 ( 1 ) 1 - 6 1999年

記述言語：日本語出版者・発行元：バイオメディカル・ファジィ・システム学会

著者らはファジィ推論を用いた超音波診断支援システムを開発してきた。このシステムではファジィ推論の確定法、すなわち非(脱)ファジィ化の方法として重心法を用いてきた。しかしながら、非ファジィ化には他にも方法があり、ファジィ推論を用いた診断支援システムでは確定法による影響が考えられるが、この点に言及した報告はほとんどない。そこで著者らは他の非ファジィ化についても検討した。この目的のため著者らは従来から採用してきた重心法以外に二分法、最大中心法、最大最大法、最大最小法を選択して比較検討した。その結果、重心法、二分法、最大中心法が適切な確定法であることが示唆され、最大最大法と最大最小法によって得られたaccuracyは他の確定法より有意に劣っていた。しかし、最大最大法によるsensitivity、及び最大最小法によるspecificityは他の方法よりも優れ、臨床的にsensitivity、或いはspecificityを重視する場合にはこれらの確定法も利用可能であることが示唆された。

DOI： 10.24466/jbfsa.1.1_1_2

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口腔癌の頚部リンパ節転移に対するＣＴおよび超音波断層法の診断手順および診断能

湯浅賢治, 河津俊幸, 神田重信

日本口腔腫瘍学会誌 10 ( 4 ) 288 - 296 1998年

記述言語：日本語出版者・発行元：Japanese Society of Oral Oncology

〔目的〕口腔癌の頸部リンパ節転移に対するCTおよび超音波断層法による画像診断の手順を示すとともに, 画像診断では判定不能である場合も考慮した診断基準とその診断能について検討することを目的とした。 対象および方法: 手術所見・病理組織所見と画像との対応ができた腫大リンパ節を有する口腔扁平上皮癌147例 (173側) を対象とした。 CTについては, リンパ節の検出能および転移・非転移リンパ節の各造影所見の出現頻度および短径の分析を行った。超音波断層法については, 各内部エコー所見の出現頻度および長径, 短径, 長短径比の分析を行った。 結果: 摘出された転移リンパ節のうち約10%は, CT検査では腫大リンパ節としての存在すら見逃されていた。不均一な造影所見またはrim-enhancementを呈したリンパ節の割合は, 転移リンパ節では, 50.9%, 非転移リンパ節では4.5%であった。 超音波所見においては, 転移リンパ節では, 強いparenchymal echoeを有する場合が最も多く, 56.9%に認められた。非転移リンパ節では, 強いparenchymal echoを持たず, hilusを有する場合が最も多く, 66.5%に認められた.強いparenchymal echoおよびhilusを有しないが短径1.0cm以上または長短比3.5以上であったリンパ節の割合は, 転移リンパ節ではそれぞれ27.4%, 1.5%であり, 非転移リンパでは3.0%, 13.5%であった。 〔結語〕「転移である」または「転移でない」のどちらかを選択する二者択一的な診断基準ではなく, 画像上では判定不能とする基準も設けた本研究の診断基準は限界はあるものの, これまでの診断基準に比べより臨床的であろうと考える。

DOI： 10.5843/jsot.10.288

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ニューラルネットワークを用いた歯原性良性腫瘍と嚢胞の画像診断(一般講演2)

河津俊幸, 田中武昌, 神田重信

バイオメディカル・ファジィ・システム学会大会講演論文集 11 27 - 28 1998年

記述言語：日本語出版者・発行元：バイオメディカル・ファジィ・システム学会

Aim of this study is to consider the accuracy in differentiating between benign odontogenic tumor (ameloblastoma) and cyst (odontogenic keratocyst) on CT image using neural network. In order to determine the weights and the biases of our neural network system, 53 cases (29 ameloblastomas, and 24 odontogenic keratocysts) were used for the learning mode. Another 20 cases (6 ameloblastomas, and 14 odontogenic keratocysts) were evaluated for determining the accuracy in the test mode. The result showed that the diagnostic accuracy was 85 %. It was suggested that the neural network is useful for differentiating these lesions.

DOI： 10.24466/pacbfsa.11.0_27

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ファジィc-meansクラスタリングによる歯科用デジタル画像診断システムの濃度の最適化と被曝線量軽減の検討(一般講演2)

田中武昌, 河津俊幸, 神田重信

バイオメディカル・ファジィ・システム学会大会講演論文集 11 29 - 30 1998年

記述言語：日本語出版者・発行元：バイオメディカル・ファジィ・システム学会

Recently the digital dental imaging system (DDIS) has been developed and spread widely. The density distribution of DDIS images, however, are insufficient or inadequate. Therefore, the authors considered the density optimization of DDIS images, and applied the fuzzy reasoning and fuzzy c-means clustering algorithm for this purpose. According to our method, density distribution of most DDIS images could be improved appropriately. Moreover, this method could be applied to the dose reduction of the patients. Consequently, it was suggested that the absorbed dose could be decreased 38.3%.

DOI： 10.24466/pacbfsa.11.0_29

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ファジィ推論とc-meansクラスタリングによる歯科用デジタル画像診断システムの濃度の最適化(一般講演-画像2-)

田中武昌, 河津俊幸, 神田重信

バイオメディカル・ファジィ・システム学会大会講演論文集 10 75 - 76 1997年

記述言語：日本語出版者・発行元：バイオメディカル・ファジィ・システム学会

The digital dental imaging system (DDIS) has been developed and spread widely in recent years. The images of DDIS, however, aren't always so good, because of insufficient density distribution. Therefore, it seems that DDIS requires density optimization in an appropriate way. The authors applied the fuzzy reasoning and fuzzy c-means clustering algorithm for this purpose. According to our method, density distribution of most DDIS images could be improved better than the conventional histogram equalization method.

DOI： 10.24466/pacbfsa.10.0_75

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Morphologic analysis of odontogenic cysts with computed tomography 査読

Kazunori Yoshiura, Yoshinori Higuchi, Kazuyuki Araki, Masanori Shinohara, Toshiyuki Kawazu, Kenji Yuasa, Osamu Tabata, Shigenobu Kanda

Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics 83 ( 6 ) 712 - 718 1997年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Mosby Inc.

Purpose. The purpose of this study was to analyze the effects of lesion site and epithelial keratinization on the morphologic characteristics of odontogenic cysts and clarify determinate factors for cyst morphology. Material and methods. Computed tomographic images of 92 odontogenic cysts were analyzed: 31 primordial, 31 dentigerous and 30 radicular. Thirty-four cysts were located in the maxilla (6 primordial, 10 dentigerous, and 18 radicular) and 58 in the mandible (25 primordial, 21 dentigerous, and 12 radicular). Histologically, 31 cysts showed epithelial keratinization (18 primordial and 13 dentigerous). No keratinization was seen in radicular cysts. The morphologic features of cysts were assessed by measuring long length parallel to dental arch and short length vertical to it and calculating the long/short ratio. In addition, the computed tomography pattern of the cyst was classified into unilocular, lobulated, and multilocular patterns. Appearance of the sclerotic rim and surrounding cortex were classified into three and four patterns respectively to evaluate the developmental features of the cyst. Results. As a whole, the long length of the primordial cysts was statistically larger than the other two cyst groups and resulted in a larger long/short ratio. Statistical differences of CT pattern were also seen among cyst groups. There was no preference in any cyst group for the appearance of the sclerotic rim and cortex. There were statistical differences between maxilla and mandible in short axis and long/short ratio. The maxillary cysts generally showed round shapes irrespective of their histologic characteristics. A multilocular pattern was more frequent in the keratinized group of mandibular primordial cysts. In dentigerous cysts, a multilocular pattern was seen only in the keratinized group and the long/short ratio was statistically larger
cyst shape was elliptical along the long axis. Conclusion. Our results demonstrated morphologic differences of odontogenic cysts caused by lesion site and keratinization. The dentigerous cyst with predominant keratinization should be included in the primordial cyst (odontogenic keratocyst) group.

DOI： 10.1016/S1079-2104(97)90325-5

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