| 摘要 |
Subtraction images formed by digital subtraction angiography contain artefacts due to the motions of the patient. This motion disturbs the condition imposed for subtraction imaging that only the introduced contrast medium is displaced and that the remainder must remain stationary. For example, when ribs of the patient have moved, due to respiration, between the formation of the first image and the second image, this motion will appear as undesirable information (the extent of the motion of the ribs) in the subtraction image. It is proposed to deform one of the images locally so that the motion of the parts which should remain stationary is compensated for. By subtracting the locally deformed image from the other image, a subtraction image will be obtained which is substantially free from motion artefacts and which contains only the information of the moving contrast medium. To achieve this, a shift vector is determined for various pixels and a reliability criterion is calculated for each direction component of said shift vector. |
