螺旋断层IMRT全骨髓照射流程可行性探讨

Feasibility of helical tomotherapy intensity-modulated radiation therapy applied in total marrow irradiation

目的探讨应用螺旋断层IMRT实施全骨髓照射（TMI）的流程可行性。方法12例患者骨髓移植前1周均实施TMI预处理，处方剂量12 Gy分3次，1次/d。按照TMI流程依次完成体位固定、CT定位、靶区勾画、计划设计及剂量验证等步骤，并实施治疗。统计靶区和正常组织的剂量参数，观察剂量验证结果与图像引导结果的相关性。结果与全身照射（TBI）相比，TMI可显著降低正常组织受量，正常组织除口腔外中位数均〈6.0 Gy，其中晶体D50（1.8±0.1） Gy，脑D50（5.7±0.2） Gy，双肺D50（5.2±0.2） Gy，肝D50（4.6±0.2） Gy。3 mm/3%标准下各部位γ通过率〉95%，头颈段x轴摆位误差小于盆腔段，而z轴摆位误差则大于盆腔段。结论应用螺旋断层IMRT可顺利实施TMI，剂量学优势明显，治疗流程合理可行。

ObjectiveTo introduce the therapeutic procedures of helical tomotherapy based total marrow irradiation（HT-TMI）, and validate the feasibility of TMI.Methods At 1 week before bone marrow transplantation, 12 patients received TMI conditioning regimen at a prescriptive dose of 12 Gy in 3 times, once daily. Patient immobilization, CT simulation, target delineation, plan design and dosimetric verification were implemented in sequence according to the TMI procedures. The dosimetric paramaters of the target and normal tissues were analysed. The correlation between the dose verification and image-guided results was observed.ResultsCompared with total body irradiation（TBI）, TMI could significantly reduce the irradiation dose to normal tissues. The median dose D50 of all normal tissues except the oral cavity were lower than 6 Gy, where The D50 of lens, brain, lung and liver are （1.8±0.1） Gy, （5.7±0.2） Gy, （5.2±0.2） Gy, and （4.6±0.2） Gy, respectively. Pass rate of γ Index was larger than 95% with 3mm/3% criterian for each section. The positioning error of head and neck was relatively lower than that of pelvis at x-axis, and was higher at z-axis. ConclusionsHelical tomotherapy based TMI is a feasible and reasonable approach, which has evident dosimetric advantage.