主动呼吸控制和四维CT技术在肺部肿瘤立体定向放射治疗中的应用

目的 探讨深吸气屏气-主动呼吸控制（ABC）和四维CT（4D-CT）技术在肺部肿瘤立体定向放疗（SBRT）中的肺、靶体积差异和剂量学特征。方法 选取10例肺部肿瘤患者，分别行自由呼吸状态下CT扫描（FB-CT），4D-CT和ABC状态下CT扫描（ABC-CT）。采用SBRT技术在同等条件下，分别设计4组计划，FB-CT、ABC-CT、4D-CT和4D-CT时相中吸气末CT0（4D-CT0）计划，统计分析双肺体积（V）、计划靶区体积（PTV）、双肺接受5 Gy的体积（V₅）、双肺接受20 Gy的体积（V₂₀）、平均肺剂量（MLD）和正常组织并发症概率（NTCP）等指标。结果 与FB-CT计划相比，ABC-CT计划的V、PTV、V₅、V₂₀、MLD和NTCP增减分别为51.48%、-65.34%、-42.64%、-56.62%、-40.22%和-98.53%（t=-7.14~6.16，P<0.05）；4D-CT计划的PTV、V₅、V₂₀、MLD和NTCP增减分别为-40.14%、-16.90%、-37.16%、-17.85%和-90.96%（t=0.54~3.22，P<0.05）；4D-CT0计划的PTV、V₅、V₂₀、MLD和NTCP增减分别为-68.98%、-30.21%、-48.49%、-37.45%和-95.82%（t=1.32~5.46，P<0.05）；4D-CT和4D-CT0与FB-CT计划相比，两者的双肺体积差异均无统计学意义（P>0.05）。结论 ABC-CT方式与其他方式相比，其双肺绝对体积更大，影像伪影小，靶区匹配精度高，显著降低正常肺组织照射剂量。

Application of active breathing control (ABC) and four dimensional CT technology in stereotactic radiotherapy of lung tumor

Objective To investigate the difference of lung and target volume and dosimetry characteristics features of deep inhalation breathing holding-active breathing control (ABC) and the four dimensional CT (4D-CT) free breathing in stereotactic body radiation therapy (SBRT) technology for patients with lung cancer. Methods 10 patients with pulmonary malignant tumor who were proposed SBRT treatment were selected, and received CT under free breath (FB-CT), 4D-CT scan under quiet respiration (4D-CT) and active breathing control CT scan (ABC-CT), respectively. With SBRT technology under the same condition designed four corresponding plans, FB-CT, ABC-CT, 4D-CT and 4D-CT0 which was the end inspiratory phase of 4D-CT respectively. The lung volume(V), PTV, V₅, V₂₀, mean lung dose(MLD) and normal tissue complication probability(NTCP) of four treatment programs were counted and compared. Results Compared with FB-CT, V, PTV, V₅, V₂₀, MLD and NTCP of ABC-CT were 51.48%, -65.34%, -42.64%, -56.62%, -40.22% and -98.53% (t=-7.14 to 6.16, P<0.05); PTV, V₅, V₂₀, MLD and NTCP of 4D-CT were -40.14%, -16.90%, -37.16%, -17.85% and -90.96% (t=0.54 to 3.22, P<0.05); PTV, V₅, V₂₀, MLD and NTCP of 4D-CT0 were -68.98%, -30.21%, -48.49%, -37.45% and -95.82% (t=1.32 to 5.46, P<0.05), respectively. Compared with FB-CT, the lung volume of 4D-CT and 4D-CT0 had no statistical difference (P>0.05). Conclusions ABC-CT methods have ideal clinical characteristics, with larger double lung volume, smaller artifacts of image, and higher target matching precision. ABC-CT methods reduce the dose of normal lung tissues significantly.