2015 年 53 巻 3 号 p. 168-178
Magnetic resonance-guided focused ultrasound (MRgFUS) is becoming one of the foremost treatment options for uterine fibroids and breast cancer. However, for an abdominal organ such as the liver, a target tracking technique to “lock on” to the focal area is required because the organ moves and deforms with respiratory motion. This technique, which is based on the relative displacement of the portal vein using sagittal MR images, is effective for translational motion and deformation because blood flow is visualized as high intensity in MR images using TrueFISP. The aim of this study was to develop a three-dimensional target tracking technique based on the results of an analysis of three-dimensional dynamic information about the portal vein structure. It is difficult to acquire multi-slice images quickly using MR. Therefore, in this study, we propose a method to reconstruct a three-dimensional dynamic model of the liver using multi-slice MR images acquired during slow breathing. Forty-two frames of the image set were acquired during slow breathing. The images were arranged in breathing phase order based on the motion of the diaphragm. Interpolated images were enhanced using a morphology technique and were inserted between the discontinuous frames. Finally, the images were interpolated in isotropic voxels in an out-plane direction. The experimental results demonstrate the feasibility of three-dimensional tracking based on a portal vein tree structure.