Development ofa new MR compatible biopsy needle without effects of the direction of static magnetic field

利用磁导率伪影在MRI上改变磁导兼容针的视直径，使之与静磁场方向相反。静磁场方向的影响会随着针的磁化率的变化而变化。针筒由芯轴和外柱组成。因此，通过改变针芯的药敏度，可以改变整个针的药敏效应。芯筒采用Ni-Cr- mo合金、Ni-Cr合金、不锈钢合金，外柱采用Ni-Cr- mo，直径为18 Gage。每个心柱、外柱及其组合的MRI成像顺序如下：自旋回波（TR/TE 200/17），梯度回波（TR/TE/FA 200/13/25, 200/30/25），快速衰减梯度回波（TR/TE/FA 180/5.5/90, 180/20/90）。在针芯的药敏效应中，不锈钢的药敏效应最强，镍铬的药敏效应最弱，整个针芯和柱的药敏效应与针芯的药敏效应一致。当镍铬芯针与静磁场方向垂直（90度）放置时，镍铬钼芯针和不锈钢芯针的视直径应与镍铬芯针的视直径在70度和30度角上相同。我们设计了一种新的磁共振相容性活检针，它可以改变MRI上的表观直径。

Apparent diameters ofMR compatible needles by susceptibility artifact on MRI are changed for the direction against the direction of static magnetic field. The effect by the direction of static magnetic field will be revised with the changeable susceptibility of needles. The needle is composed of the mandrel and outer column. So the susceptibility effect of the whole needle will be able to be changed by altering the susoeptibility of the mandrel.We madethe mandrelsofNi-Cr-Mo alloy, Ni-Cr alloy and stainless steel alloy, and outer columns of Ni-Cr-Mo with 18 Gage diameter. MRI of each mandrels, outer columns and those combination were obtained with the following sequence ; spin echo (TR/TE 200/17), gradient echo (TR/TE/FA 200/13/25, 200/30/25), fast spoiled gradient echo (TR/TE/FA 180/5.5/90, 180/20/90). In susceptibility effect of the mandrel, that ofstainless steel was the strongest and that of Ni-Crwas the weakest, hi susceptibility effect of the whole needle by combination of the mandrels and the column, the result was the same as the mandrels. When the needle with Ni-Cr mandrel was set up at the perpendicular (90 degree) to the direction ofstatic magnetic field, the apparent diameters of the needle with Ni-Cr-Mo mandrel and stainless steel mandrel should be the same diameters as that of the needle with Ni-Crmandrelatthe angle of 70 degree and 30 degree.We designed a new MR compatible biopsy needle of which an apparent diameter on MRI could be changed.