Method and apparatus for registration of medical images

A medical image registration apparatus comprising:

• a memory for executing program data;
• an ultrasound probe configured to transmit ultrasound signals to a region of interest (ROI) of an object and detect reflected signals corresponding to the transmitted ultrasound signals;
• and
• at least one processor configured to:
• generate a first medical image set which includes a plurality of first medical images captured during at least two breathing states of a subject and a plurality of interpolated medical images of intermediate breathing states that are adjacent to the at least two breathing states;
• acquire a second medical image based on the reflected signals;
• perform an initial registration, comprising a first rigid registration, between at least a first one of the first medical images which is included in the generated first medical image set and the acquired second medical image;
• transform, by applying a transform function, the first medical image set by using a registration parameter which is determined based on the initial registration;
• down-sample a plurality of medical images which are included in the transformed first medical image set;
• perform a second registration, comprising a second rigid registration, between the down-sampled plurality of medical images and the acquired second medical image;
• determine, among the down-sampled plurality of medical images, a down-sampled medical image having a minimum registration cost value among registration cost values obtained by the second registration between the down-sampled plurality of medical images and the acquired second medical image;
• update the down-sampled plurality of medical images to include a plurality of additional interpolated medical images interpolated based on the determined down-sampled medical image;
• up-sample a subset of the updated down-sampled plurality of medical images, the subset including the determined down-sampled medical image;
• perform an additional registration during an intraoperative stage, comprising a third rigid registration, between the up-sampled subset of the updated down-sampled plurality of medical images and the second medical image;
• and
• display a combined image which is based on a result of the additional registration,
• wherein the plurality of interpolated medical images is generated by a first interpolation using a displacement vector which is determined by performing a non-rigid registration with respect to the plurality of first medical images,
• wherein the plurality of additional interpolated medical images is generated by a second interpolation using the displacement vector with respect to the determined down-sampled medical image, and
• wherein an interval used for segmentation of the displacement vector in the second interpolation is smaller than in the first interpolation.