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目的:对3例儿童颅咽管瘤进行剂量学比较,以探讨质子在儿童颅咽管瘤放疗中的潜在优越性。方法:靶区肿瘤照射剂量为55 Gy。每例患者分别作单纯光子、光子和质子混合射线以及单纯质子的治疗计划,治疗方法均为三维适形治疗;应用适形指数以量化地比较3种治疗计划对靶区的剂量覆盖和正常组织的照射容积和剂量。结果:3种治疗计划均达到满意的靶区剂量覆盖,92％～100％的PTV在处方剂量95％的范围内。质子治疗的运用使得正常脑组织、脑干、大脑颞叶和内耳的剂量显著下降。当肿瘤与视交叉有少许间隙时,质子治疗可以降低视交叉的平均剂量和最低剂量。单纯质子体现出较混合射线更强的优越性。单纯光子、混合射线和单纯质子的适形指数分别为0.631、0.784和0.848,即质子治疗提供的高剂量区曲线分布更符合PTV的形状。结论:在保证靶区剂量的基础上,质子的应用普遍减少了颅内正常组织的照射,并在部分患者中提供了剂量提升的可能性。
Objective: To compare the dosimetry of three children with craniopharyngioma to explore the potential advantages of proton in radiotherapy of children with craniopharyngioma. Methods: The targeted tumor radiation dose was 55 Gy. Each patient was treated as a simple photon, photon and proton mixed rays and simple proton treatment plan, the treatment methods are three-dimensional conformal treatment; application of conformal index to quantify the three treatment plans on the target dose coverage and normal tissue The irradiation volume and dose. RESULTS: Satisfactory target dose coverage was achieved in all three treatment plans, with PTV ranging from 92% to 100% within 95% of the prescribed dose. Proton therapy makes use of normal brain tissue, brain stem, brain temporal lobe and the inner ear dose was significantly decreased. When the tumor and the optic chiasm a little gap, proton therapy can reduce the average dose of optic chiasm and the lowest dose. Simple proton reflects more superior than mixed rays. The conformal indices of pure photons, mixed rays and pure protons were 0.631, 0.784 and 0.848, respectively. That is to say, the curve distribution of high dose region provided by proton therapy more conformed to the shape of PTV. CONCLUSIONS: The use of protons generally reduces the irradiation of normal intracranial tissues while ensuring target dose and offers the possibility of dose escalation in some patients.