Tateishi Ukihide, Daisaki Hiromitsu, Tsuchiya Junichi, Kojima Yuji, Takino Keisuke, Shimada Naoki, Yokoyama Kota
Department of Diagnostic Radiology, Graduate School of Medicine, Tokyo Medical and Dental University, Tokyo, Japan.
Department of Radiological Technology, Gunma Prefectural College of Health Sciences, Gunma, Japan.
EJNMMI Phys. 2021 Oct 30;8(1):72. doi: 10.1186/s40658-021-00420-4.
This study was conducted to clarify how patient body mass affects the image quality and quantification accuracy of images obtained using Zr PET/CT. Zr PET/CT images from time-of-flight (TOF) PET/CT and semiconductor (SC) PET/CT were obtained using three types (M, L, LL; corresponding to increasing patient body weight) of custom-made body phantoms designed similarly to the National Electrical Manufacturers Association (NEMA) IEC body phantom. The phantom data were analyzed visually and quantitatively to derive image quality metrics, namely detectability of the 10-mm-diameter hot sphere, percent contrast for the 10-mm-diameter hot sphere (Q), percent background variability (N), contrast-to-noise ratio (Q/N), and coefficient of variation of the background area (CV).
Visual assessment revealed that all the 10-mm-diameter hot spheres of the three types of phantoms were identifiable on both SC and TOF PET/CT images. The N and CV values were within the proposed reference levels, and decreased with acquisition duration for both PET/CT types. At 10-min acquisition, the Q/N of SC PET/CT was greater than the proposed reference level in all phantoms. However, the Q/N of TOF PET/CT was greater than the proposed reference level in M-type phantom alone. All the SUV values were within 1.00 ± 0.05 for both PET/CT types.
This study showed that the image quality and quantification accuracy depend on the patient's body mass, suggesting that acquisition time on Zr PET/CT should be changed according to the patient's body mass.
本研究旨在阐明患者体重如何影响使用锆（Zr）正电子发射断层扫描/计算机断层扫描（PET/CT）获得的图像的质量和定量准确性。使用三种类型（M、L、LL；对应患者体重增加）的定制人体模型获得了来自飞行时间（TOF）PET/CT和半导体（SC）PET/CT的Zr PET/CT图像，这些人体模型的设计与美国国家电气制造商协会（NEMA）IEC人体模型相似。对模型数据进行了视觉和定量分析，以得出图像质量指标，即直径10毫米热球体的可检测性、直径10毫米热球体的对比度百分比（Q）、背景变异性百分比（N）、对比度噪声比（Q/N）以及背景区域的变异系数（CV）。
视觉评估显示，在SC和TOF PET/CT图像上均可识别三种类型模型中所有直径10毫米的热球体。N和CV值均在建议的参考水平范围内，并且两种PET/CT类型的这些值均随采集持续时间而降低。在采集10分钟时，SC PET/CT的Q/N在所有模型中均大于建议的参考水平。然而，TOF PET/CT的Q/N仅在M型模型中大于建议的参考水平。两种PET/CT类型的所有标准化摄取值（SUV）均在1.00±0.05范围内。
本研究表明，图像质量和定量准确性取决于患者体重，这表明Zr PET/CT的采集时间应根据患者体重进行调整。
