碳离子放射治疗泪囊泪腺肿瘤的剂量学研究

Dosimetric study of carbon ion radiotherapy for treating tumors at lacrimal system

目的比较碳离子治疗泪囊泪腺肿瘤相对于光子放疗的剂量学差异.方法利用上海市质子重粒子医院治疗的10例术后残留的泪囊腺肿瘤患者CT图像,重新制定碳离子计划,光子容积调强计划(VMAT)与固定野光子调强计划(IMRT),所有患者处方均为给予临床靶区54Gy相对生物学效能(RBE)/18次,并给予临床加量靶区同步加量至63Gy(RBE)/18次.在计划靶区覆盖相似情况下,比较正常组织受量.结果在计划靶区覆盖差异无统计学意义的情况下,与光子VMAT和与IMRT相比,碳离子计划患侧与健侧的眼球平均剂量、视神经近似最大剂量(D2%)与平均剂量均降低(患侧:t=7.35、3.79、4.66、8.48、2.52、2.76,P<0.05;健侧:t=3.87、10.49、9.16、4.43、6.53、5.12,P<0.05);脑组织平均剂量由(5.65±3.58)和(5.76±2.09)Gy(RBE)降至(0.81±0.90)Gy(RBE),差异具有统计学意义(t=6.76、17.33,P<0.05).结论与光子VMAT与IMRT相比,碳离子计划能有效降低泪囊泪腺肿瘤周围视觉器官受照体积与剂量,具有降低放疗不良反应的潜在优势.

Objective To evaluate the dosimetric difference between carbon ion radiotherapy and photon radiotherapy for treating tumors at lacrimal system. Methods Using the CT images of 10 patients with tumors at lacrimal system, the carbon ion plan, the photon volume intensity modulation plan (VMAT) and the fixed wild photon intensity modulation radiotherapy (IMRT) plan were generated. The prescription was 54 Gy(RBE) in 18 fractions for clinical target volume (CTV) and 63 Gy(RBE) in 18 fractions for CTV-boost. Dosimetric differences of organ at risks were compared based on the same planning target volumes (PTVs) with similar dose coverages. Results There was no statistically significant difference in the PTV coverage among three plans (P>0.05). Compared to VMAT and IMRT plans, carbon ion plans reduced the mean doses of eyeballs, mean doses and near-maximum doses of optical nerves of both ipsilateral (t=7.35, 3.79, 4.66, 8.48, 2.52, 2.76, P < 0.05) and contralateral eyes (t=3.87, 10.49, 9.16, 4.43, 6.53, 5.12, P < 0.05), while the mean dose of brain was decreased from(5.65±3.58) and (5.76±2.09)Gy(RBE) to (0.81±0.90)Gy(RBE)(t=6.76, 17.33, P < 0.05). Conclusions Compared to photon VMAT or IMRT, carbon ion could reduce the doses to optical critical organs around tumors. Thus, carbon ion radiotherapy has potential to reduce patients' radiation related side-effects.