DeGrado T R, Turkington T G, Williams J J, Stearns C W, Hoffman J M, Coleman R E
Duke University Medical Center, Durham, NC 27710.
J Nucl Med. 1994 Aug;35(8):1398-406.
This study characterizes the performance of a newly developed whole-body PET scanner (Advance, General Electric Medical Systems, Milwaukee, WI). The scanner consists of 12,096 bismuth germinate crystals (4.0 mm transaxial by 8.1 mm axial by 30 mm radial) in 18 rings, giving 35 two-dimensional image planes through an axial field of view of 15.2 cm. The rings are separated by retractable tungsten septa. Intrinsic spatial resolution, scatter fraction, sensitivity, high count rate performance and image quality are evaluated.
Transaxial resolution (in FWHM) is 3.8 mm at the center and increases to 5.0 mm tangential and 7.3 mm radial at R = 20 cm. Average axial resolution decreases from 4.0 mm FWHM at the center to 6.6 mm at R = 20 cm. Scatter fraction is 9.4% and 10.2% for direct and cross slices, respectively. With septa out, the average scatter fraction is 34%. Total system sensitivity for true events (in kcps/(microCi/cc)) is 223 with septa in and 1200 with septa out. Dead-time losses of 50% correspond to a radioactivity concentration of 4.9 (0.81) microCi/cc and a true event count rate of 489 (480) kcps with septa in (out). Noise-equivalent count rate (NECR) for the system as a whole shows a maximum of 261 (159) kcps at a radioactivity concentration of 4.1 (0.65) microCi/cc with septa in (out). NECR is insensitive to changes in lower gamma-energy discrimination between 250-350 keV.
The results show the performance of the newly designed PET scanner to be well suited for clinical and research applications.
本研究描述了一种新开发的全身正电子发射断层扫描仪（Advance，通用电气医疗系统公司，威斯康星州密尔沃基）的性能。该扫描仪由18个环中的12096块锗酸铋晶体（横向4.0毫米、轴向8.1毫米、径向30毫米）组成，通过15.2厘米的轴向视野提供35个二维图像平面。这些环由可伸缩的钨隔板隔开。评估了固有空间分辨率、散射分数、灵敏度、高计数率性能和图像质量。
横向分辨率（半高宽）在中心处为3.8毫米，在R = 20厘米处切向增加到5.0毫米，径向增加到7.3毫米。平均轴向分辨率从中心处的4.0毫米半高宽降至R = 20厘米处的6.6毫米。直接切片和交叉切片的散射分数分别为9.4%和10.2%。隔板移除后，平均散射分数为34%。真事件的总系统灵敏度（单位：kcps/(微居里/立方厘米)），隔板在位时为223，隔板移除后为1200。50%的死时间损失对应于放射性浓度4.9（0.81）微居里/立方厘米以及隔板在位（移除）时的真事件计数率489（480）kcps。整个系统的噪声等效计数率（NECR）在放射性浓度4.1（0.65）微居里/立方厘米时，隔板在位（移除）情况下分别显示最大值261（159）kcps。NECR对250 - 350 keV之间较低伽马能量鉴别力的变化不敏感。
结果表明新设计的正电子发射断层扫描仪的性能非常适合临床和研究应用。
