心肌灌注显像中位移伪影的辨析

目的 探讨心肌灌注显像时位移伪影的影像学特征、不同轴向、发生位移起始点和帧数与伪影的相关性。方法 在心肌显像过程中依次沿x,y和z轴方向，分别在不同起始点，对不同帧数作一定距离的位移。其图像与正常对照比较判断有无伪影。结果作多因素分析。结果 轻度位移伪影的特征为：x轴位移表现为下壁突出的结节状热区；y轴位移表现为间隔和侧壁呈对称分布的热区；z轴位移表现为前壁的局部热区；这些表现仅见于短轴像上。重度伪影表现为“三角形”分布的壁内热区以及典型的“双三角形”改变。位移距离相同，方向相反，伪影的“冷”“热”分布的壁内热区以及典型的“双三角形”改变。位移距离相同，方向相反，伪影的“冷”“热”区位置相反。伪影与位移帧数和轴向有关，与起始点无关。结论 不同轴向位移伪影各有特征。移动帧数和y轴位移对伪影产生的影响最大。

A discrimination of myocardial tomography artifacts caused by motion

Objective　To detect the image characteristics of the motion artifacts, to determine the relationship among the axis, position and frames of the motion and the resultant image artifacts. Methods　A myocardial phantom was filled with the 99TcmO-4 solution. During imaging, the phantom was moved ±5 mm, ±10 mm, ±15 mm, ±20 mm, ±25 mm, ±30 mm and ±50 mm along the x、y and z axis respectively beginning at the different positions covering different ranges sequentially. Every image was compared with normal image and assessed by three experienced observers without knowledge of the phantom motion. The results were analyzed by logistic regression. Results　Motion artifact showed a radioactive nodule projecting from inferior wall while moved along x axis, symmetrical “hot" areas showed on septal and lateral wall images while moved along y axis, and nodular hot areas showed in anterior wall while moved along z axis. At last, all the motion artifacts became “double triangular". The “lumpy" and “defect" areas showed oppositely in position while the motion covered the same distance but in the opposite directions along the axis. Motion artifacts had something to do with the axis, distance and range of the frames affected, but had nothing to do with the beginning position of the motion. Conclusions　Motion artifacts had specific images when the phantom moved along different axes. Frames of motion and motion along y axis contributed more to the motion artifacts than other factors.