Faculty Profiles - ODA, Masahiro

Papers - ODA, Masahiro

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Automated Ulcer Detection Method From CT Images for Computer Aided Diagnosis of Crohn's Disease Reviewed

Masahiro Oda, Takayuki Kitasaka, Kazuhiro Furukawa, Osamu Watanabe, Takafumi Ando, Hidemi Goto, and Kensaku Mori

IEICE Transactions on Information and Systems Vol. E96-D ( 4 ) page： 808 - 818 2013.4

Digital Bowel Cleansing Free Colonic Polyp Detection Method for Fecal Tagging CT Colonography Reviewed

Masahiro ODA, Takayuki KITASAKA, Kensaku MORI, Yasuhito SUENAGA, Tetsuji TAKAYAMA, Hirotsugu TAKABATAKE, Masaki MORI, Hiroshi NATORI, and Shigeru NAWANO

Academic Radiology Vol. 16 ( 4 ) page： 486 - 494 2009.4

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

Rationale and Objectives:
Fecal tagging CT colonography (ftCTC) reduces the discomfort and the inconvenience of patients associated with bowel cleansing procedures prior to CT scanning. In conventional colonic polyp detection techniques for ftCTC, a digital bowel cleansing (DBC) technique is applied to detect polyps in tagged fecal materials (TFM). However, DBC removes the surface of soft tissues and hampers polyp detection. We developed a colonic polyp detection method for CT colonographic examination that enables the detection of polyps surrounded by air and polyps surrounded by TFM without DBC.

Materials and Methods:
CT values inside the polyps surrounded by air and polyps surrounded by TFM tend to gradually increase (blob structure) and decrease (inverse-blob structure) from outward to inward, respectively. We developed blob and inverse-blob structure enhancement filters based on the eigenvalues of a Hessian matrix to detect polyps using their intensity characteristic. False positive elimination is performed using three feature values: volume, maximum value of filter outputs, and standard deviation of CT values inside the polyp candidates.

Results:
The proposed method is applied to 104 cases of ftCTC images that include 57 polyps larger than 6 mm in diameter. The sensitivity of the method was 91.2% (52/57) with 11.4 false positives per case.

Conclusion:
The proposed method detects polyps with high sensitivity and 11.4 false positives per case without adverse effects on the DBC.

DOI： 10.1016/j.acra.2008.10.011

Digital bowel cleansing free colonic polyp detection method from fecal tagging CT images Reviewed

Masahiro ODA, Takayuki KITASAKA, Kensaku MORI, Yasuhito SUENAGA, Tetsuji TAKAYAMA, Hirotsugu TAKABATAKE, Masaki MORI, Hiroshi NATORI, and Shigeru NAWANO

Vol. J91-D ( 7 ) page： 1904 - 1913 2008.7

Authorship：Lead author,　Corresponding author Language：Japanese Publishing type：Research paper (scientific journal)

This paper proposes a method for the detection of colonic polyps from fecal tagging CT images without digital bowel cleansing (DBC). Previous polyp detection methods needed DBC to detect polyps which are surrounded by tagged fecal materials (TFM). However, DBC may changes shapes of polyps
while removing TFM. Our method can detect polyps which are surrounded by air or TFM without any DBC processes. We employ blob and inverse-blob structure enhancement filters based on the eigenvalues of the Hessian matrix. As the results of experiments using 104 cases of abdominal CT images, sensitivity for polyps >= 6mm was 91.2% with 11.4 FPs/case.

A Study on Method of Distortion Reduction of Virtual Unfolded Views of the Colon Reviewed

Masahiro ODA, Yuichiro HAYASHI, Takayuki KITASAKA, Kensaku MORI, and Yasuhito SUENAGA

Medical Imaging Technology Vol. 24 ( 5 ) page： 419 - 428 2006.11

Authorship：Lead author,　Corresponding author Language：Japanese Publishing type：Research paper (scientific journal)

This paper proposes a method for reducing distortions of virtual unfolded (VU) views of the colon. VU views enable physicians to observe a large area of the colonic wall efficiently. A VU view is generated by flattening the colon to a plane on computer. In a previous method, VU views are generated by casting rays of volume rendering perpendicular to the centerline of the colon. However, rays intersected at curved areas of the colon and it caused spurious holes in the VU views. Our previous system generated VU views of a constant height regardless of the perimeter of the colon. Therefore, thin areas of the colon were stretched in the VU views, which caused distortions. In this paper, we propose two methods to improve the quality of VU views. We reduce ray intersections by employing a spring model. This method allocates springs between planes perpendicular to the centerline. Then plane directions are modified by spring forces, which lead to reduce the intersections of the planes. We also reduce distortions by changing the height of VU views according to the perimeter of the colon. We applied the method to eighteen cases of abdominal CT images. Experimental results showed that the method could generate VU views satisfactorily.

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Papers - ODA, Masahiro