双探头SPECT心肌灌注显像中位移伪影的实验研究

An experimental study of motion artifacts acquired in myocardial perfusion SPECT with double-head detector

目的 探讨双探头SPECT心肌灌注显像时位移伪影的影像特征和识别方法。方法 将心脏模型置于检查床上 ,与受检患者的心脏方向一致。在图像采集过程中 ,模型依次沿相当于患者左右、头尾和前后方向分别在不同起始点、对不同帧数作一定距离的位移。结果 位移伪影的共同特点是表现为室壁放射性分布不均匀 ,“热区”与“冷区”交替出现 ,在短轴上最早出现 ,且表现最为明显 ;伪影进一步发展会在水平长轴和垂直长轴上表现为心尖附近放射性稀疏或缺损 ,出现与相邻室壁伴行且形态相近的“伴影”。结论 位移伪影主要表现为室壁放射性分布不均 ,“热区”与“冷区”交替出现 。

Objective To detect the image characteristics of the motion artifacts acquired in double- head detector SPECT, and to find the methods for discriminating it. Metho ds A myocardial phantom was filled with pertechnetate solution. During imaging, the phantom was moved ±0.5 cm, ±1.0 cm, ±1.5 cm, ±2.0 cm, ±2.5 cm and ±3.0 cm along the X (from right to left), Y (from head to c audal ) and Z (from back to ventral) axes, respectively at the different positions w ith different ranges sequentially. Myocardial perfusion SPECT images were acquir ed with and without attenuation correction (AC) simultaneously. The images were compared with normal and low (noise background was shown or not) contrast images and were assessed by three experienced observers without knowledge of the phant om motion. Results When the phantom was moved sl ightly (the amount of moved frames and the moved distance were small) no visual artifacts were found. The general characteristics of motion artifacts were that the radioactivity distribution of the ventricle turned out uneven. Both the irr egular lumpy distribution of radioactivity and perfusion defects, as well as cur vilinear extraventricular radioactivity, were shown at the same time. The radio active marker dot was shown and gradually disappeared in the anterior wall first ly in vertical short slices and then the marker dot will separated from the wall when the phantom moved along X axis; the anterior lateral wall beca me defect when moved along Y axis, and the nodular hot would show up in ante rio r wall when moved along Z axis. With the amount of moved frames and or moved distance being increased, the motion artifacts would become more obvious. Whe n the artifacts were serious, the lump and defect were very clear and the con tour of the ventricle was always distorted. At the same time the accompanying sh adow, its configuration was the same with its nearest wall, was found near the n ormal ventricular site. When the image contrast was decreased, the accompanying shadow could be discriminated easily. When the attenuation correction was used, the motion artifacts were more serious than the correction was not used. C onclusions The general characteristics of motion artifacts were that the u neven radioactivity distribution, the irregular lumps and the opposing defects, were always shown at the same time. Decreasing contrast would help discriminate slight accompanying shadow.