Müller-Bierl Bernd M, Martirosian Petros, Graf Hansjörg, Boss Andreas, König Claudius, Pereira Philippe L, Schick Fritz
Max-Planck Institute for Biological Cybernetics, Spemannstrasse 41, D-72076 Tübingen, Germany.
Med Phys. 2008 Jun;35(6):2273-8. doi: 10.1118/1.2919082.
Needle tip visualization is of high importance in magnetic resonance imaging (MRI) guided interventional procedures, for example for taking biopsies from suspicious lesions in the liver or kidney. The exact position of the needle tip is often obscured by image artifacts arising from the magnetic properties of the needle. The authors investigated two special biopsy needle tip designs using diamagnetic coatings. For common interventional MR sequences, the needle tip can be identified in the MR image by several equidistant dark spots arranged along a straight line. A dotted instead of a solid line allows for an improved control of the movement of the needle, not only if the needle is tilted toward the imaging plane, but also if the needle leaves an empty canal with signal extinction, which cannot be distinguished from the needle material itself. With the proposed design the position of the needle tip can be estimated with a precision of approximately 1 mm using conventional FLASH, FISP, and TSE sequences, as used for interventional MR. Furthermore, the size of the biopsy probe can be estimated from the artifact. In using needles with a properly designed tip coating, taking biopsies under MR control is beginning to be greatly simplified. The approach to design artifacts using diamagnetic material in combination with paramagnetic material paves the way toward new instruments and implants, suitably tailored to the needs of the interventional radiologist.
在磁共振成像（MRI）引导的介入手术中，例如从肝脏或肾脏的可疑病变处获取活检组织时，针尖可视化非常重要。针尖的确切位置常常被针的磁性所产生的图像伪影遮挡。作者研究了两种采用抗磁涂层的特殊活检针尖设计。对于常见的介入性MR序列，在MR图像中，针尖可通过沿直线排列的几个等距黑点来识别。采用虚线而非实线，不仅在针向成像平面倾斜时，而且在针留下信号消失的空通道（这与针材料本身无法区分）时，都能更好地控制针的移动。使用所提出的设计，利用用于介入性MR的传统FLASH、FISP和TSE序列，针尖位置的估计精度可达约1毫米。此外，活检探头的尺寸可从伪影中估算出来。使用具有适当设计的针尖涂层的针，在MR控制下进行活检正开始变得大为简化。利用抗磁材料与顺磁材料相结合来设计伪影的方法，为适合介入放射科医生需求的新型器械和植入物铺平了道路。
