PET/CT 검사 시 주사실 근무자의 주사 시간의 입력과 PET 검사실 근무자의 검사 시작 시간의 오차가 발생할 수 있으며 이러한 시간 입력의 오차는 반정량적 평가 방법으로 사용되고 있는 표준화섭취계수(이하 SUV) 값에 영향을 줄 수 있다. 이에 시간 입력 차이에 따른 SUV의 변화를 분석하고 시간 동기화의 필요성을 알아보고자 한다. $^{18}F$-FDG Fusion Whole Body PET 검사를 시행한 환자 중 성인 30명을 대상으로 연구 분석하였다. 시간 차이에 따른 SUV의 변화를 분석하기 위해 1, 2, 3, 5, 10, 20분의 시간 오차를 주어 영상을 재구성하였다. 각각의 재구성한 영상은 liver, aorta, primary lesion에서 ROI를 설정하여 SUV를 측정하였다. 환자 30명의 영상을 각각 1, 2, 3, 5, 10, 20분의 오차를 주어 재구성한 영상과 기존의 시간을 입력한 영상의 SUV를 비교 분석하였다. liver의 mean SUV는 1, 2, 3, 5, 10, 20분에서 각각 1.6, 2.5, 3.0, 4.2, 6.6, 12.8%, aorta의 mean SUV는 각각 0.3, 1.1, 1.4, 3.2, 4.7, 12.5%, lesion의 max SUV는 각각 1.0, 1.5, 2.2, 3.5, 6.6, 12.8%의 차이를 확인 할 수 있었다. SUV를 보다 정확하게 측정하기 위해서 이러한 오차를 최소화 하려는 노력을 해야 하며 그 중 시간 동기화는 정확한 검사를 하기위한 노력의 초석이 될 수 있을 것으로 사료된다.
Purpose: $^{18}F$-FDG Fusion Whole Body PET scan is performed approximately 1 hour after injecting $^{18}F$-FDG. At this point in the injection procedure, as a tool of the criteria of time input, time of clocks or computers can be used and in the scan procedure, time of workstation can be used. In case that synchronized time input is not done in the injection and scan procedures for PET scan, time error from injection to scan can occur. This time error may affect Standard Uptake Value (SUV) being used as quantitative assessment. Therefore, in this study, we analyzed the change of SUV according to time input difference and necessity of time synchronization. Materials and Methods: The analysis was performed to 30 patients ($54.8{pm}15.5$ years old) who examined $^{18}F$-FDG Fusion Whole Body PET scan in Department of nuclear medicine, Asan Medical Center from December 2009 to February 2010. To observe the change of SUV according to time input difference, the image was reconstructed and analyzed by artificially changing time difference of 1, 2, 3, 5, 10, 20 min against the same patients based on 60 minutes. Result: SUV of the image that reconstructed the images of 30 patients by giving intervals of 1, 2, 3, 5, 10, 20 min respectively and the image that entered original time was compared and analyzed through paired t-test. Based on 0 minute, mean SUV of aorta was changed by 0.3, 1.1, 1.4, 3.2, 4.7, 12.5% respectively and there was no statistically significant difference in 1, 2 minutes (p>0.05) but there was significant difference in 3, 5, 10, 20 min (p<0.05). The changes of $SUV_{avg}$ of liver were 1.6, 2.5, 3.0, 4.2, 6.6, 12.8% in 1, 2, 3, 5, 10, 20 min respectively and the changes of $SUV_{max}$ of primary lesion were 1.0, 1.5, 2.2, 3.5, 6.6, 12.8% respectively (p<0.05). Conclusion: Errors may occur in the process of measuring or recording variables affecting SUV such as height and weight of patients, $^{18}F$-FDG dose, Emission scan start time etc. and as these errors are more, the accurate assessment of SUV is interfered. Therefore, in order to assess SUV more accurately, it is thought that efforts to minimize these errors should be made. Of these efforts, time synchronization will be a cornerstone for accurate scanning.
