Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
Int J Radiat Oncol Biol Phys. 2013 May 1;86(1):183-9. doi: 10.1016/j.ijrobp.2012.12.010. Epub 2013 Feb 4.
The purpose of this study is to evaluate the potential of using in-room positron emission tomography (PET) for treatment verification in proton therapy and for deriving suitable PET scan times.
Nine patients undergoing passive scattering proton therapy underwent scanning immediately after treatment with an in-room PET scanner. The scanner was positioned next to the treatment head after treatment. The Monte Carlo (MC) method was used to reproduce PET activities for each patient. To assess the proton beam range uncertainty, we designed a novel concept in which the measured PET activity surface distal to the target at the end of range was compared with MC predictions. The repositioning of patients for the PET scan took, on average, approximately 2 minutes. The PET images were reconstructed considering varying scan times to test the scan time dependency of the method.
The measured PET images show overall good spatial correlations with MC predictions. Some discrepancies could be attributed to uncertainties in the local elemental composition and biological washout. For 8 patients treated with a single field, the average range differences between PET measurements and computed tomography (CT) image-based MC results were <5 mm (<3 mm for 6 of 8 patients) and root-mean-square deviations were 4 to 11 mm with PET-CT image co-registration errors of approximately 2 mm. Our results also show that a short-length PET scan of 5 minutes can yield results similar to those of a 20-minute PET scan.
Our first clinical trials in 9 patients using an in-room PET system demonstrated its potential for in vivo treatment monitoring in proton therapy. For a quantitative range prediction with arbitrary shape of target volume, we suggest using the distal PET activity surface.
本研究旨在评估在质子治疗中使用室内正电子发射断层扫描（PET）进行治疗验证和得出合适的 PET 扫描时间的潜力。
九名接受被动散射质子治疗的患者在治疗后立即使用室内 PET 扫描仪进行扫描。治疗后，将扫描仪放置在治疗头旁边。使用蒙特卡罗（MC）方法为每位患者重现 PET 活性。为了评估质子束射程不确定性，我们设计了一种新的概念，即在射程末端比较目标远端测量的 PET 活性表面与 MC 预测值。患者重新定位进行 PET 扫描平均需要大约 2 分钟。考虑到不同的扫描时间，重建 PET 图像以测试方法对扫描时间的依赖性。
测量的 PET 图像与 MC 预测值具有总体良好的空间相关性。一些差异可以归因于局部元素组成和生物冲洗的不确定性。对于 8 名接受单一射野治疗的患者，PET 测量值与基于 CT 图像的 MC 结果之间的平均射程差异小于 5 毫米（8 名患者中有 6 名小于 3 毫米），均方根偏差为 4 至 11 毫米，PET-CT 图像配准误差约为 2 毫米。我们的结果还表明，5 分钟的短长度 PET 扫描可以产生与 20 分钟 PET 扫描相似的结果。
我们在 9 名患者中使用室内 PET 系统进行的首次临床试验证明了其在质子治疗中进行体内治疗监测的潜力。对于任意形状目标体积的定量射程预测，我们建议使用远端 PET 活性表面。
