tomosynthesis

日

トモシンセシス

(1)

• Digital tomosynthesis combines digital image capture and processing with simple tube/detector motion as used in conventional radiographic tomography - although there are some similarities to CT, it is a separate technique. In CT, the source/detector makes a complete 360 degree rotation about the subject obtaining a complete set of data from which images may be reconstructed. In digital tomosynthesis, only a small rotation angle (e.g. 40 degrees) with a small number of discrete exposures (e.g. 10) are used. This incomplete set of data can be digitally processed to yield images similar to conventional tomography with a limited depth of field. However, because the image processing is digital, a series of slices at different depths and with different thicknesses can be reconstructed from the same acquisition, saving both time and radiation exposure.

• Because the data acquired is incomplete, tomosynthesis is unable to offer the extremely narrow slice widths that CT offers. However, higher resolution detectors can be used, allowing very-high in-plane resolution, even if the Z-axis resolution is poor. The primary interest in tomosynthesis is in breast imaging, as an extension to mammography, where it may offer better detection rates, with little extra increase in radiation exposure.

• Reconstruction algorithms for tomosynthesis are significantly different from conventional CT, as the conventional filtered back projection algorithm requires a complete set of data. Iterative algorithms based upon expectation maximization are most commonly used, but are extremely computationally intensive. Some manufacturers have produced practical systems using commercial GPUs to perform the reconstruction.

(2)

• 高速データ通信が可能なフラットパネルディテクタの出現により、幾何学的断層撮影法がトモシンセシスとして

再び脚光を浴びつつある1,2)。従来の幾何学的断層撮影法では各深さにおける断層像の取得毎にX線照射が 必要であったが、このトモシンセシスでは１度のX線照射で任意の深さでの断層像を何枚でも再構成できる。欧 米では既に Digital Breast Tomosynthesis (DBT)として吸収コントラストによる乳房撮影の分野で臨床試験が進 められ、2009年からの臨床利用が計画されている。

(3)

• The Flat Panel Detector(FPD)and digital imaging technologies have widely utilized in various clinical application with R/F diagnostic table system. Tomosynthesis is the digital imaging technique which reconstructs the tomography images of any height with one-time tomographic application. This report refers to the principle of Tomosysthesis and its clinical application with the Shimadzu Sonialvision safire digitalized X-ray diagnostic table system.

参考文献

• (1)Digital Tomosynthesis

<click2in>http://www.youtube.com/watch?v=P5n3Avqqo2c</click2in>

• (2)「屈折強調 Digital Breast Tomosynthesis に関する基礎研究」

<click2in>http://www.ipu.ac.jp/houkoku/h20/s08shimao.pdf</click2in>

• (3)トモシンセシスの原理と応用 ～FPDが生み出した新技術～

<click2in>http://www.jstage.jst.go.jp/article/mii/24/2/24_22/_article/-char/ja</click2in>

• 医用画像情報学会雑誌, Vol. 24 (2007) , No. 2 pp.22-27
• 塩見 剛1)
• 1) 株式会社島津製作所医用機器事業部

• (4)株式会社 横浜総合研究所

<click2in>http://www.yri.co.jp/me.html</click2in>