^(18)F-FDG PET/CT延迟显像数据采集参数推算方法的探讨

Technical aspect on calculating the acquisition parameters for delayed ^(18)F-FDG PET/CT imaging

目的探讨 PET/CT 延迟显像需采集的总计数、计数率和采集时间的推算方法。方法对39例体格检查者行^(18)F-脱氧葡萄糖(FDG)PET/CT 全身显像,并将其全身图像分为8个区段,估算各区段总计数占全身总计数的百分比。对另25例患者分别进行早期和延迟显像,并求出其早期显像平均计数率、相应区段延迟显像每床位需采集的总计数(C_(dc))、理论推算计数率,然后启动 PET数据采集程序,记录延迟显像的实测计数率。分别以 C_(dc)除以理论推算和实测计数率,获得延迟显像理论推算和实际需要的采集时间。结果早期与延迟显像对应区段理论推算的每床位总计数、计数率和采集时间与对应的实测值间差异无统计学意义(t 值分别为-0.273、1.609和-1.692,P 值分别为0.788、0.120和0.103);3～4 h 后延迟显像采集时间较早期显像延长约2.2倍。结论该方法可避免延迟显像数据采集的随意性,提高早期与延迟显像图像质量和定量指标的可比性。

Objective The aim of the study was to verify calculation methods for the total counts, count rates and acquisition time for ^18F-fluorodeoxyglucose （FDG） PET/CT delay imaging. Methods Thirty-nine （male 26 and female 13 ） healthy subjects were scanned on Gemini PET/CT scanner after ^18F- FDG injection. Their whole body ^18F-FDG images were divided into 8 segments, from which the percentage of contribution from each segment to the total counts was calculated. Twenty-five patients （ male 15, female 10） were scanned twice, at 60 rain after ^18F-FDG injection as early phase imaging （3 min per hed） and at 3 to 4 h later as delay phase imaging. The total counts of early phase imaging were summed up and divided into each bed to calculate the average count rate per bed. Relevant regions of interest （ ROIs ） on delay phase imaging were determined by comparing the early and the delay fusion images. The theoretical total counts of the delay imaging were calculated by applying the contribution percentage of each segment from early phase imaging. Results There was no significant difference between the calculated and measured total counts, count rates and total acquisition time for the delay phase imaging （t = -0.273, P =0.788;t = 1. 609, P =0.120 ;t = - 1. 692, P =0.103, respectively）. For delay phase ^18F-FDG imaging, more than 2.2 time acquisition time may be needed to achieve equivalent counts as early phase imaging. Conclusion The calculation methods could help improving the image quality and making data comparable between early phase imaging and delay phase imaging.