医用画像情報学会雑誌

ROC解析によるMR画像信号の検出能の評価

荒尾信一, 天野貴司, 北山彰, 板谷道信, 山下一也, 古城剛, 浮田智子

1997 年 14 巻 3 号 p. 128-138
発行日: 1997/09/05
公開日: 2012/08/27

DOIhttps://doi.org/10.11318/mii1984.14.128

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We evaluated signal detectability in magnetic resonance(MR) images by using receiver operating characteristic (ROC) analysis with the continuously - distributed scale method. MR imaging sysytem adopted was RESONA(GE - YMS), which has the operating field of 0.5T. The phantom of MR images was NiCl₂ solution varying by 0.25m mol/l in concentration, which allowed longitudinal relaxation time (T1) to change. We employed T1- weighted image of spin - echo pulse sequence for MR imaging. We performed ROC analysis by using signal intensity data from MR images. As a result, in regard to the variation of thickness, the thicker the slice was, the more improvement in signal detectability. On the variation of time of repeat (TR), signal detectability increased with the length of TR, but its variation was less than that produced by slice thickness. It was considered that there was a limitation in improvement in signal detectability by extension of TR. It was concluded that ROC analysis made possible evaluation of signal detectability in consideration of effect of signal - to - noise (SNR) for MR images and difference in Ti. We think that this method is useful in the evaluation of performance, the check of equipment, and the determination of the best image sequence.

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共通規格を用いた画像保存

島西聡, 古賀佑彦

1997 年 14 巻 3 号 p. 139-147
発行日: 1997/09/05
公開日: 2012/08/27

DOIhttps://doi.org/10.11318/mii1984.14.139

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As a Japanese standard for medical imaging storage, IS&C specifications were introduced at the beginning of 1990s. In the period between 1994 and 1995, “Common Standard for Electronic Storage of Medical Imaging Information” was established. This was in response to the Announcement, “Storage of Medical Image Information such as Radiographs onto Magnetooptical Disk(1994)”, which was published by the Ministry of Health and Welfare of Japan. This standard is based on IS&C, and consists of Type 1 and Type 2. Type 1 is a modified version of IS&C. Type 2 adopts IS&C storage media and DICOM infomation object.
Especially in case of Type 2, many issues remain to be solved at present, because DICOM and IS&C coexist in this type.
One of these issues concerns how to make DICOMDIR which is essential to Type 2. This issue was addressed by the authors, and the result of the relevant experiments is reported in this paper.

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乳房超音波断層像における腫瘤像の自動検出法

福岡大輔, 原武史, 藤田広志, 遠藤登喜子, 加藤保之

1997 年 14 巻 3 号 p. 148-154
発行日: 1997/09/05
公開日: 2012/08/27

DOIhttps://doi.org/10.11318/mii1984.14.148

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We have developed a computer-aided detection scheme of breast tumors on cross-sectional ultrasonograms. The scheme proposed in this study consists of the following three steps: (1)region segmentation by using a newly devised erosion and dilation processing with distance transformation, (2) feature analysis by using shape of tumor, and (3) three-dimensional (3D) display for detection output. Our method was found to be effective for the detection of tumors examined by 9 cases including 459 images. The sensitivity of our scheme was 78% with 4.2 false-positive (FP) findings per case. The reducation of the FP candidates is required for future works.

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