PET/CT imaging for treatment verification after proton therapy: A study with plastic phantoms and metallic implants
PET/CT imaging for treatment verification after proton therapy: A study with plastic phantoms and metallic implants
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DOI：
10.1118/1.2401042
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发表时间：
2007-02-01
期刊：
影响因子：
3.8
通讯作者：
Bortfeld, Thomas
中科院分区：
文献类型：
--
作者：
Parodi, Katia;Paganetti, Harald;Bortfeld, Thomas
波士顿马萨诸塞州总医院目前正在研究离线正电子发射断层扫描/计算机断层扫描 (PET/CT) 用于质子放射治疗常规三维体内治疗验证的可行性。在准备临床试验时，进行了模型实验，以研究该方法根据照射和成像参数的灵敏度和准确性。此外，他们还讨论了 PET/CT 作为金属植入物存在情况下强大验证工具的可行性。这些会产生 X 射线 CT 伪影和能量密度扰动，可能会影响治疗计划算法的准确性。分散的布拉格峰值质子场被传送到不同的模型，这些模型包括聚甲基丙烯酸甲酯（PMMA）、堆叠有肺和骨等效材料的PMMA以及带有钛棒的PMMA以模拟患者的植入物。 PET 数据是在商用基于钌氧正硅酸盐 (LSO) 的 PET/CT 扫描仪照射后 20 分钟内开始以列表模式获取的。基于 GEANT4 和 FLUKA 蒙特卡罗代码的计算可以很好地再现测量活动的数量和空间分布。尽管照射和成像之间存在延迟，但即使在 2 Gy 的低治疗剂量照射后，这项模型研究也支持毫米级精度的范围监测和横向场位置验证的潜力。它还表明了 PET 在金属植入物存在的情况下进行治疗验证的价值，表明与商业分析治疗计划系统相比，它对能量通量扰动具有更高的敏感性。最后，它讨论了基于 LSO 的 PET 探测器用于强子治疗监测的适用性。 PET 的这种非常规应用涉及的计数率比诊断示踪成像低几个数量级，即，感兴趣的信号与源自探测器本身固有放射性的噪声相当。除了单独的 PET 之外，PET/CT 成像还可以提供有关成像对象位置的准确信息，并可以评估临床应用中分割放射治疗期间可能出现的解剖变化。 (c) 2007 年美国医学物理学家协会。
The feasibility of off-line positron emission tomography/computed tomography (PET/CT) for routine three dimensional in-vivo treatment verification of proton radiation therapy is currently under investigation at Massachusetts General Hospital in Boston. In preparation for clinical trials, phantom experiments were carried out to investigate the sensitivity and accuracy of the method depending on irradiation and imaging parameters. Furthermore, they addressed the feasibility of PET/CT as a robust verification tool in the presence of metallic implants. These produce x-ray CT artifacts and fluence perturbations which may compromise the accuracy of treatment planning algorithms. Spread-out Bragg peak proton fields were delivered to different phantoms consisting of polymethylmethacrylate (PMMA), PMMA stacked with lung and bone equivalent materials, and PMMA with titanium rods to mimic implants in patients. PET data were acquired in list mode starting within 20 min after irradiation at a commercial luthetium-oxyorthosilicate (LSO)-based PET/CT scanner. The amount and spatial distribution of the measured activity could be well reproduced by calculations based on the GEANT4 and FLUKA Monte Carlo codes. This phantom study supports the potential of millimeter accuracy for range monitoring and lateral field position verification even after low therapeutic dose exposures of 2 Gy, despite the delay between irradiation and imaging. It also indicates the value of PET for treatment verification in the presence of metallic implants, demonstrating a higher sensitivity to fluence perturbations in comparison to a commercial analytical treatment planning system. Finally, it addresses the suitability of LSO-based PET detectors for hadron therapy monitoring. This unconventional application of PET involves countrates which are orders of maonitude lower than in diagnostic tracer imaging, i.e., the signal of interest is comparable to the noise originating from the intrinsic radioactivity of the detector itself. In addition to PET alone, PET/CT imaging provides accurate information on the position of the imaged object and may assess possible anatomical changes during fractionated radiotherapy in clinical applications. (c) 2007 American Association of Physicists in Medicine.