PET采集处理方法对病灶检出能力和图像质量的影响

为明确采集模式、衰减校正方式及重建方法对正电子发射断层显像(PET)的病变检出能力和图像质量的影响,利用一桶状模型进行测试研究。模型内含9个阳性柱(直径4.3~37.8mm)、7个阴性柱(直径5.9~22.3mm)和7个阴性球(直径5.8~22.0mm)。研究发现,3D采集在轴向中心的检出能力相当于2~4倍时间的2D采集,但在轴向两端的图像质量明显降低,2D采集图像的对比度和清晰度更佳。带有约20MBq/L的放射性采集衰减校正图对相应区域的密度低估约3%。分割法处理可显著提高衰减校正图的均匀性,但会降低边界的清晰度。OSEM法和FBP法重建的图像对病灶的检出能力相当,前者条状噪音少、更均匀,而后者对比度更佳。PET检查时宜根据具体情况及实际需要权衡选择采集和处理方法。

The influences of acquisition and reconstruction methods on lesion detectability and image quality of PET: aphantom study

A phantom study was performed to investigate the influence of acquisition modes, attenuation correction methods and reconstruction methods on the lesion detectability and image quality of positron emission tomography. Compared with 2D mode, 3D acquisition could detect the same lesion with only 1/4 - 1/2 acquisition time, but the image quality worsened quickly from the center to two ends. Although segmentation process of attenuation map sacrificed the clarity and accuracy to some extent, it remarkably improved the uniformity and made the 2 - 4min transmission scan chnically ac- ceptable. A transmission acquisition with 22MBq/L radioactivity had only 3% decrease to the attenuation coefficient. Compared with FBP method, OSEM reconstruction decreased the stripe noises and increased the edge clarity, but it also worsened the contrast. No remarkable difference on lesion detectability was found between the two reconstruction methods. In conclusion, different methods held different advantages and disadvantages, and good knowledge of them would lead to better selection for diversified clinical needs.