Iodine-124 PET dosimetry in differentiated thyroid cancer:: recovery coefficient in 2D and 3D modes for PET(/CT) systems
Iodine-124 PET dosimetry in differentiated thyroid cancer:: recovery coefficient in 2D and 3D modes for PET(/CT) systems
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DOI：
10.1007/s00259-007-0554-7
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发表时间：
2008-03-01
影响因子：
9.1
通讯作者：
Bockisch, Andreas
中科院分区：
文献类型：
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作者：
Jentzen, Walter;Weise, Reiner;Bockisch, Andreas
目的 本研究评估了在 I-131 或 I-131 标记放射治疗之前使用该同位素进行剂量测定时碘 124 (I-124) 活性浓度的绝对定量。使用模型确定使用 I-124 的正电子发射断层扫描（/计算机断层扫描）PET（/CT）系统的恢复系数，然后在分化型甲状腺癌（DTC）患者中观察到的典型条件下进行验证。方法使用嵌入的含同位素线源进行以 I-124 和氟 18 (F-18) 作为参考的横向空间分辨率和恢复测量 水中和六个直径为 9.7 至 37.0 毫米的含同位素球体，放置在含水体和圆柱体模型中。圆柱体幻影球体中仅填充有 F-18。使用独立 PET (EXACT HR+) 和组合 PET/CT (BIOGRAPH EMOTION DUO) 系统进行二维 (2D) 和三维 (3D) 模式测量。另外，使用圆柱模型在 GE ADVANCE PET 系统上进行了回收率比较测量。使用感兴趣的圆形区域的活性浓度除以由剂量校准器确定的制备的活性浓度直接确定回收系数。在我们的 I-124 PET(/CT) 方案下，对 DTC 患者的体模进行连续 3 次扫描，对恢复校正方法进行了验证。 结果 与 F-18 相比，I-124 的横向空间分辨率略有下降，但具有统计学意义的显着下降（7.4 mm vs. 8.3 mm，P < 0.002）。使用人体模型，在 2D 和 3D 模式下，I-124 的恢复率均低于 F-18。最大球体的 I-124 回收系数在 2D 模式下显着高于 3D 模式（81% vs. 75%，P=0.03）。值得注意的是，对于除 GE ADVANCE 之外的所有扫描仪，最大球体的 F-18 恢复系数都显着偏离统一（范围为 87%-93%，P < 0.004）。对于直径 >= 12.6 mm 的球体，应用部分体积校正后，在体内条件下测量的 I-124 活性浓度的最大误差范围为 +/- 10%。 结论 对于 I-124 PET 定量，即使对于大型结构，回收率校正也是强制性的。为了确保准确的剂量测定，必须针对要使用的特定 PET 扫描仪和放射性核素单独建立彻底的绝对回收率测量。
Purpose This study evaluated the absolute quantification of iodine-124 (I-124) activity concentration with respect to the use of this isotope for dosimetry before therapies with I-131 or I-131-labeled radiotherapeuticals. The recovery coefficients of positron emission tomography(/computed tomography) PET(/CT) systems using I-124 were determined using phantoms and then validated under typical conditions observed in differentiated thyroid cancer (DTC) patients.Methods Transversal spatial resolution and recovery measurements with I-124 and with fluorine-18 (F-18) as the reference were performed using isotope-containing line sources embedded in water and six isotope-containing spheres 9.7 to 37.0 mm in diameter placed in water-containing body and cylinder phantoms. The cylinder phantom spheres were filled with F-18 only. Measurements in two-dimensional (2D) and three-dimensional (3D) modes were performed using both stand-alone PET (EXACT HR+) and combined PET/CT (BIOGRAPH EMOTION DUO) systems. Recovery comparison measurements were additionally performed on a GE ADVANCE PET system using the cylinder phantom. The recovery coefficients were directly determined using the activity concentration of circular regions of interest divided by the prepared activity concentration determined by the dose calibrator. The recovery correction method was validated using three consecutive scans of the body phantom under our I-124 PET(/CT) protocol for DTC patients.Results Compared with that of F-18, transversal spatial resolution of I-124 was slightly, but statistically significantly degraded (7.4 mm vs. 8.3 mm, P < 0.002). Using the body phantom, recovery was lower for I-124 than for F-18 in both 2D and 3D modes. The I-124 recovery coefficient of the largest sphere was significantly higher in 2D than in 3D mode (81% vs. 75%, P=0.03). Remarkably, the F-18 recovery coefficient for the largest sphere significantly deviated from unity (range of 87%-93%, P < 0.004) for all scanners but the GE ADVANCE. The maximum range of inaccuracy of the measured I-124 activity concentration under in vivo conditions after applying partial volume correction was +/- 10% for spheres >= 12.6 mm in diameter.Conclusion Recovery correction is mandatory for I-124 PET quantification, even for large structures. To ensure accurate dosimetry, thorough absolute recovery measurements must be individually established for the particular PET scanner and radionuclide to be used.