Lamb J, Lee P, Jani S, Dahlbom M, White B, Low D
UCLA School of Medicine, Los Angeles, CA.
Med Phys. 2012 Jun;39(6Part8):3691. doi: 10.1118/1.4735008.
To examine the impact of 4D-PET on target volume delineation of upper-abdominal tumors, versus conventional un-gated PET.
Four patients with upper-abdominal tumors underwent respiratory-correlated FDG PET/CT scanning (4D-PET) as part of a continuing IRB-approved research protocol. Internal target volumes of FDG-avid tumors were contoured on the 4D-PET and conventional un-gated PET by a radiation oncologist who is a specialist in gastro-intestinal tumors. To create the 4D-PET ITV, the end-inhale and end-exhale 4D-PET phases were used. The relative volumes and volumetric overlaps of the 4D and un-gated target volumes were examined. Additionally, 4D-PET was used to measure the motion of the tumors.
Of the four patients who were imaged, one showed minimal motion (〈 3 mm in any direction) and one showed minimal FDG avidity; these were removed from further analysis. Of the two tumors which showed significant motion and FDG uptake, 4D-PET volumes were 28% and 21% larger than un-gated PET volumes. The un-gated PET volumes were almost entirely contained within the 4D-PET volumes (95% and 93% for the two tumors). Tumors appeared to deform as well as translate with breathing, although this could be due to varying intra-gate motion rather than actual physiological deformation. The superior-inferior borders of the tumors exhibited the most motion, with displacements of 5.6 mm and 6.4 mm.
4D-PET can be used to estimate the motion of FDG-avid upper-abdominal tumors. Use of 4D-PET increases the size of target volumes compared to un-gated PET in a subset of upper-abdominal cancer patients. Direct measurement of tumor motion and deformation by 4D-PET imaging could allow the use of patient-specific margins rather than population-based margins, potentially leading to increased target coverage and reduced normal tissue irradiation.
探讨与传统非门控PET相比，四维PET（4D-PET）对上腹肿瘤靶区勾画的影响。
作为一项持续的、经机构审查委员会批准的研究方案的一部分，4例上腹肿瘤患者接受了呼吸相关的FDG PET/CT扫描（4D-PET）。由一位胃肠道肿瘤专家放疗肿瘤医师在4D-PET和传统非门控PET上勾勒出FDG摄取阳性肿瘤的内部靶区。为创建4D-PET内部靶区体积（ITV），使用了吸气末和呼气末的4D-PET相位。检查了4D和非门控靶区体积的相对体积和体积重叠情况。此外，4D-PET用于测量肿瘤的运动。
在接受成像的4例患者中，1例显示运动极小（任何方向〈3 mm），1例显示FDG摄取极少；这2例被排除在进一步分析之外。在2例显示明显运动和FDG摄取的肿瘤中，4D-PET体积比非门控PET体积分别大28%和21%。非门控PET体积几乎完全包含在4D-PET体积内（2例肿瘤分别为95%和93%）。肿瘤似乎随呼吸变形并移动，尽管这可能是由于门控内运动变化而非实际生理变形所致。肿瘤的上下边界运动最大，位移分别为5.6 mm和6.4 mm。
4D-PET可用于估计FDG摄取阳性的上腹肿瘤的运动。与非门控PET相比，在一部分上腹癌症患者中，使用4D-PET会增加靶区体积。通过4D-PET成像直接测量肿瘤运动和变形，可允许使用个体化边界而非基于群体的边界，这可能会增加靶区覆盖范围并减少正常组织受照剂量。
