Papers - TAKESHITA Yohei

A new method to evaluate image quality of CBCT images quantitatively without observers. Reviewed International journal

Yohei Takeshita, Mayumi Shimizu, Kazutoshi Okamura, Shoko Yoshida, Warangkana Weerawanich, Kenji Tokumori, Gainer R Jasa, Kazunori Yoshiura

Dento maxillo facial radiology   46 ( 3 )   20160331 - 20160331   2017.3

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：BRITISH INST RADIOLOGY  

OBJECTIVES: To develop an observer-free method for quantitatively evaluating the image quality of CBCT images by applying just-noticeable difference (JND). METHODS: We used two test objects: (1) a Teflon (polytetrafluoroethylene) plate phantom attached to a dry human mandible; and (2) a block phantom consisting of a Teflon step phantom and an aluminium step phantom. These phantoms had holes with different depths. They were immersed in water and scanned with a CB MercuRay (Hitachi Medical Corporation, Tokyo, Japan) at tube voltages of 120 kV, 100 kV, 80 kV and 60 kV. Superimposed images of the phantoms with holes were used for evaluation. The number of detectable holes was used as an index of image quality. In detecting holes quantitatively, the threshold grey value (ΔG), which differentiated holes from the background, was calculated using a specific threshold (the JND), and we extracted the holes with grey values above ΔG. The indices obtained by this quantitative method (the extracted hole values) were compared with the observer evaluations (the observed hole values). In addition, the contrast-to-noise ratio (CNR) of the shallowest detectable holes and the deepest undetectable holes were measured to evaluate the contribution of CNR to detectability. RESULTS: The results of this evaluation method corresponded almost exactly with the evaluations made by observers. The extracted hole values reflected the influence of different tube voltages. All extracted holes had an area with a CNR of ≥1.5. CONCLUSIONS: This quantitative method of evaluating CBCT image quality may be more useful and less time-consuming than evaluation by observation.

DOI： 10.1259/dmfr.20160331

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輝度弁別閾を用いた画質評価法の開発 Reviewed

吉田祥子, 岡村和俊, 徳森謙二, 清水真弓, 竹下洋平, Warangkana Weerawanich, 吉浦一紀

歯科放射線   56 ( 1 )   27 - 32   2016

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Language：Japanese   Publisher：(NPO)日本歯科放射線学会  

平均的な観察者が識別可能な最小輝度差である輝度弁別閾(JND)を検出閾値の設定に利用した画質評価法を開発し、観察者評価に替わり得るか否かを検討した。撮影対象は厚さを1mmずつ増加させた12段のアルミニウム製ブロックで、計7個の直径1mmのホールを有していた。デジタル口内法X線画像システムはDigora、Digora Optime、YCR-21XGの3機種を使用して撮影し、解析および観察により検出されなかったホール数(ホール非検出数)を画質視標とした。開発した評価法では、JNDインデックスを用いてホール非検出数の理論値を算出した。その結果、JNDを利用した評価法は、画像処理を行った場合の機種間の比較には注意を要するものの、おおむね観察者と同様の評価が可能であることが示された。更に、観察値と解析値について回帰分析を行った結果、得られた回帰式の決定係数は0.80を超え、観察値は解析値により高い精度で推定できることが確認された。なお、解析値と観察値のばらつきを比較した結果、解析値のばらつきは著明に小さかった。

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Other Link： https://search-tp.jamas.or.jp/index.php?module=Default&action=Link&pub_year=2016&ichushi_jid=J00567&link_issn=&doc_id=20170529210006&doc_link_id=%2Fcg7dentr%2F2016%2F005601%2F006%2F0027-0032%26dl%3D0&url=https%3A%2F%2Fwww.medicalonline.jp%2Fjamas.php%3FGoodsID%3D%2Fcg7dentr%2F2016%2F005601%2F006%2F0027-0032%26dl%3D0&type=MedicalOnline&icon=https%3A%2F%2Fjk04.jamas.or.jp%2Ficon%2F00004_2.gif

Effectiveness of imaging modalities for screening IgG4-related dacryoadenitis and sialadenitis (Mikulicz's disease) and for differentiating it from Sjögren's syndrome (SS), with an emphasis on sonography. Reviewed International journal

Mayumi Shimizu, Kazutoshi Okamura, Yoshitaka Kise, Yohei Takeshita, Hiroko Furuhashi, Warangkana Weerawanich, Masafumi Moriyama, Yukiko Ohyama, Sachiko Furukawa, Seiji Nakamura, Kazunori Yoshiura

Arthritis research & therapy   17   223 - 223   2015.8

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BIOMED CENTRAL LTD  

INTRODUCTION: The aim of this study was to clarify the effectiveness of various imaging modalities and characteristic imaging features in the screening of IgG4-related dacryoadenitis and sialadenitis (IgG4-DS), and to show the differences in the imaging features between IgG4-DS and Sjögren's syndrome (SS). METHODS: Thirty-nine patients with IgG4-DS, 51 with SS and 36 with normal salivary glands were enrolled. Images of the parotid and submandibular glands obtained using sonography, 2-[(18)F]-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (FDG-PET/CT), computed tomography (CT) and magnetic resonance imaging (MRI) were retrospectively analyzed. Six oral and maxillofacial radiologists randomly reviewed the arranged image sets under blinded conditions. Each observer scored the confidence rating regarding the presence of the characteristic imaging findings using a 5-grade rating system. After scoring various findings, diagnosis was made as normal, IgG4-DS or SS, considering all findings for each case. RESULTS: On sonography, multiple hypoechoic areas and hyperechoic lines and/or spots in the parotid glands and obscuration of submandibular gland configuration were detected mainly in patients with SS (median scores 4, 4 and 3, respectively). Reticular and nodal patterns were observed primarily in patients with IgG4-DS (median score 5). FDG-PET/CT revealed a tendency for abnormal (18)F-FDG accumulation and swelling of both the parotid and submandibular glands in patients with IgG4-DS, particularly in the submandibular glands. On MRI, SS had a high score regarding the findings of a salt-and-pepper appearance and/or multiple cystic areas in the parotid glands (median score 4.5). Sonography showed the highest values among the four imaging modalities for sensitivity, specificity and accuracy. There were significant differences between sonography and CT (p = 0.0001) and between sonography and FDG-PET/CT (p = 0.0058) concerning accuracy. CONCLUSIONS: Changes in the submandibular glands affected by IgG4-DS could be easily detected using sonography (characteristic bilateral nodal/reticular change) and FDG-PET/CT (abnormal (18)F-FDG accumulation). Even inexperienced observers could detect these findings. In addition, sonography could also differentiate SS. Consequently, we recommend sonography as a modality for the screening of IgG4-DS, because it is easy to use, involves no radiation exposure and is an effective imaging modality.

DOI： 10.1186/s13075-015-0751-x

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