Departments of Radiation Oncology, University Hospital Freiburg, Freiburg, Germany.
Clin Nucl Med. 2012 Feb;37(2):e24-9. doi: 10.1097/RLU.0b013e318238f550.
To define the appropriate scan time for fluorine-18-labeled dihydroxyphenylalanine (F-18 DOPA) PET in oncological imaging of pheochromocytomas and paragangliomas.
F-18 DOPA PET examinations were performed in 9 patients with 7 pheochromocytomas and 4 head and neck paragangliomas using a dedicated PET scanner. The acquisition started with a dynamic single-bed scan in the tumor region over the first 60 minutes after tracer injection followed by a late time whole-body scan at approximately 130 minutes. Standard uptake values (SUVs) were calculated in tumors, surrounding background, and adjacent normal tissues of relevance. Furthermore, kinetic analysis was performed using a 2-compartment model with rate constants for uptake (K1'), release (k2'), metabolism (k3'), and reverse reaction (k4') for region of interest and pixel-wise analysis.
All tumors show a marked increased F-18 DOPA uptake, which was visually detectable and distinguishable from the surrounding tissue. The SUV is significantly lower in neck paraganglioma compared with abdominal pheochromocytomas. Mean time-activity curves of F-18 DOPA in tumors show a rapid uptake of the tracer. Already 2 minutes after the injection, the activity in the tumor is beyond that of the blood pool. The average maximum value (SUVmean = 8.2) has already been reached after 20 minutes. Afterward, a very slight decrease of the tumor SUV starts, which still amounts to 80% of the maximum value after 132 minutes. Due to the continuous decrease of activity in the background tissue, the tumor-to-background ratio of SUVs shows a constant increase within the entire period of examination. The mean values of apparent kinetic constants obtained by region of interest analysis averaged over all tumors are as follows: K1' = 2.89 ± 2.56 min(-1), k2' = 2.59 ± 2.81 min(-1), k3' = 0.301 ± 0.395 min(-1), and k4' = 0.044 ± 0.043 min(-1).
Pheochromocytoma and paraganglioma take up F-18 DOPA very quickly. At best, the acquisition for static clinical PET imaging of paraganglioma with F-18 DOPA can start at 20 minutes postinjection for maximum uptake in tumors. Separation of tumor, background, and adjacent normal tissues is feasible due to their differences in SUV values and kinetics. The kinetic analysis demonstrates an F-18 DOPA accumulation within the tumor due to considerable differences between the rate constants of uptake and metabolism. Second, in contradiction to healthy brain, paraganglionic tumors show a reversible F-18 DOPA metabolism.
确定氟-18 标记的二羟苯丙氨酸（F-18 DOPA）正电子发射断层扫描（PET）在嗜铬细胞瘤和副神经节瘤肿瘤学成像中的适当扫描时间。
使用专用 PET 扫描仪对 9 例 7 例嗜铬细胞瘤和 4 例头颈部副神经节瘤患者进行了 F-18 DOPA PET 检查。在注射示踪剂后最初的 60 分钟内，在肿瘤区域进行动态单床位扫描，随后在大约 130 分钟时进行晚期全身扫描。在肿瘤、周围背景和相关的相邻正常组织中计算标准摄取值（SUVs）。此外，使用 2 室模型进行了动力学分析，该模型具有感兴趣区域和像素分析的摄取率常数（K1'）、释放率常数（k2'）、代谢率常数（k3'）和反向反应率常数（k4'）。
所有肿瘤均显示出明显的 F-18 DOPA 摄取增加，这在视觉上是可检测到的，并且与周围组织区分开来。与腹部嗜铬细胞瘤相比，颈部副神经节瘤的 SUV 明显较低。肿瘤的平均时间-活性曲线显示 F-18 DOPA 快速摄取示踪剂。在注射后仅 2 分钟，肿瘤中的活性就超过了血池。平均最大值（SUVmean=8.2）在 20 分钟后已经达到。此后，肿瘤 SUV 值开始轻微下降，但在 132 分钟后仍达到最大值的 80%。由于背景组织中的活性持续下降，肿瘤与背景 SUV 比值在整个检查期间呈持续增加。通过感兴趣区域分析获得的表观动力学常数的平均值在所有肿瘤中的平均值如下：K1'=2.89±2.56min(-1)，k2'=2.59±2.81min(-1)，k3'=0.301±0.395min(-1)，k4'=0.044±0.043min(-1)。
嗜铬细胞瘤和副神经节瘤非常快地摄取 F-18 DOPA。对于使用 F-18 DOPA 进行副神经节瘤的静态临床 PET 成像，最佳的采集时间是在注射后 20 分钟，此时肿瘤摄取达到最大值。由于 SUV 值和动力学的差异，肿瘤、背景和相邻正常组织之间的分离是可行的。动力学分析表明，由于摄取和代谢之间的速率常数存在明显差异，肿瘤内存在 F-18 DOPA 积聚。其次，与健康大脑相反，副神经节瘤显示出可逆的 F-18 DOPA 代谢。
