PROBLEM TO BE SOLVED: To improve the reliability of information to be provided to an inspector about the acoustic characteristics of a subjects tissue.SOLUTION: An ultrasonic tomogram is taken at the same section of a tissue as its reference tomogram acquired by an X-ray CT system (an imaging device 34). Standard points (1, 1, 2, 2) are set up by a standard point setting means at points on the tissue to which two or more sets of reference and ultrasonic tomogram correspond. An acoustic characteristics evaluator 50 calculates the reference distance (Dct), i.e., a distance between the standard points set for the reference tomogram and the points of their projection along lines in the direction corresponding to the ultrasonic transmission direction, as a reference distance (Dct). The evaluator 50 operates physical quantities concerning the acoustic characteristics of the subjects tissue on the basis of the calculated reference distance (Dct), the ratio of the reference distance to the ultrasonic transmission distance (Dus), i.e., a distance between the standard points set for ultrasonic tomogram and the points of their projection along lines in the direction corresponding to the ultrasonic transmission direction, as well as an assumed ultrasonic sound velocity (Cnow), and displays these physical quantities on a display.COPYRIGHT: (C)2009,JPO&INPIT【課題】検者に提供する被検体の組織の音響特性に関する情報の信頼性を向上する。【解決手段】X線CT装置(画像撮像装置34)により取得された被検体のリファレンス断層像と同一断層面の超音波断層像を撮像する。基準点設定手段によりリファレンス断層像及び超音波断層像の2組以上の対応する組織部位に基準点(1,1´,2,2´)を設定する。音響特性評価部50は、リファレンス断層像の設定基準点を超音波送信方向に相当する方向の直線上に投影した投影点間の距離をリファレンス距離(Dct)として算出するとともに、このリファレンス距離と超音波断層像の設定基準点を超音波送信方向の直線上に投影した投影点間の距離である超音波距離(Dus)との比と、超音波断層像を撮像した際の超音波の設定音速(Cnow)とに基づいて、被検体の組織の音響特性に関する物理量を演算して表示手段に表示する。【選択図】図3
