Watanabe Yuya, Hosokawa Shota, Otaka Yutaka, Takahashi Yasuyuki
Graduate School of Health Sciences, Hirosaki University.
Nishidai Clinic.
Nihon Hoshasen Gijutsu Gakkai Zasshi. 2020;76(9):955-962. doi: 10.6009/jjrt.2020_JSRT_76.9.955.
The aim of this study was to clarify the artifacts that occurred in the non-activity signal with computed tomography (CT)-based attenuation correction (CTAC) error due to image misregistration.
We used a cylindrical phantom containing a test tube with a diameter of 15 mm as the non-activity signal part. Positron emission tomography (PET) images were acquired for 30 minutes using the phantom with water in the non-activity signal part and F-fluoro-2-deoxy-d-glucose (F-FDG) (5.3 kBq/ml) in the background area. CT scanning was performed by replacing the water with contrast agents at different dilutions to obtain arbitrary CT numbers (-1000 to 1000). The PET images were attenuation-corrected individually by the CT images in which the CT number of the non-activity signal part had changed. The relationship between the CT numbers and the CTAC artifact was determined by measuring the PET value in the non-activity signal part of the PET images and comparing C.
As the CT number of the CT images increased, C of the artifact increased. The CT number and C had a correlation of y=1.48x+2.86×10 (R =0.99) when CTAC was performed in units of CT numbers above 0 for PET data of water (0 HU) and a correlation of y=3.15x+6.26×10 (R =0.97) when CTAC was performed in units of CT numbers below 0 for PET data of air (-1000 HU). Although the original CT image was air, the artifacts due to CTAC errors with different Hounsfield units showed larger changes. In particular, positive artifacts were recognized in the PET images after CTAC depending on the Hounsfield units.
When the CT number was different from the original in CTAC, the PET value was different. CTAC should be performed with caution as there may be image misregistration.
本研究旨在阐明因图像配准错误导致基于计算机断层扫描（CT）的衰减校正（CTAC）误差在非活性信号中出现的伪影。
我们使用一个包含直径为15毫米试管的圆柱形体模作为非活性信号部分。使用非活性信号部分装有水且背景区域含有F - 氟 - 2 - 脱氧 - d - 葡萄糖（F - FDG）（5.3 kBq/ml）的体模采集30分钟的正电子发射断层扫描（PET）图像。通过用不同稀释度的造影剂替换水来进行CT扫描，以获得任意CT值（-1000至1000）。PET图像分别由非活性信号部分CT值已改变的CT图像进行衰减校正。通过测量PET图像非活性信号部分的PET值并进行比较来确定CT值与CTAC伪影之间的关系。
随着CT图像的CT值增加，伪影的C值增加。对于水（0 HU）的PET数据，当以CT值大于0为单位进行CTAC时，CT值与C的相关性为y = 1.48x + 2.86×10（R = 0.99）；对于空气（-1000 HU）的PET数据，当以CT值小于0为单位进行CTAC时，相关性为y = 3.15x + 6.26×10（R = 0.97）。尽管原始CT图像为空气，但不同亨氏单位的CTAC误差导致的伪影显示出更大变化。特别是，根据亨氏单位，CTAC后的PET图像中识别出正性伪影。
当CTAC中的CT值与原始值不同时，PET值也不同。由于可能存在图像配准错误，应谨慎进行CTAC。
