| Objectives:The stady observed the influence of active breathing control (ABC) system on the motion of primary tumor of lung cancer,volumes of target and dose distribution during precise radiotherapy.Methods:Trained twenty-one patients with non-small cell lung cancer to use ABC system,nine were enrolled,whom were all male,including six peripheral lung cancer and three central type.The lung function of eight patients were too wrose to use ABC system,and four patients'dental defects due to dysraphism can not use ABC system. The patients receiving three-dimensional conformal radiotherapy controlled by ABC system beld their breath when their inspiratory.The tumor moving ranges of patients who accepted simulation when breathing freely either controlling by ABC system beld their breath were measured. CT scans were performed under FB and ABC,which transmitting to TPS system.Total volume of lung, Dmean,V20,volume of GTV,CTV,PTV were calculated by treatment planning system and compared by t-test.Ensure lung V20≤25% and spinal cord Dmax≤45Gy, raise the dose of PTVg, V20 was compared by t-test.Results :①The mean ranges when paitents free breathing in left-right (X) ,superior-inferior (Y) and cranial-caudal (Z) directions were(2.22±0.95)mm, (2.78±1.48)mm(,6.44±4.75)mm;when controlled by ABC system beld their breath, the ranges of primary tumor could not differentiate.②Total bilateral lung volume were (5980.2±1018.34)cm3,(4338.62±826.27)cm3(P <0.05),which increased 37.8% when used ABC hold breath.③V20 were(11.44±3.95)%,(14.38±5.06)%(P<0.05); Dmean were (712.9±243.2)cGy,(885.9±314.4)cGy(P<0.05);the volumes of GTV were (42.57±33.68)cm3(,43.27±36.47)cm(3P>0.05); the volumes of CTV were(42.57±33.68)cm3,(43.27±36.47)cm3(P>0.05); and the volumes of PTV were(252.89±222.75)cm3,(277.52±224.17)cm3(P<0.05)respectively under ABC and free breathing condtion.④Ensure lung V20≤25% and spinal cord Dmax≤45Gy, raise the dose of PTVg, 8 patients can surpass 100Gy when free breathing,7when used ABC system.V20 were (13.23±4.6)%,(16.8±6.07)% (P<0.05).Conclusion:When the NCLC patients receiving 3D-CRT,the motion of tumor under FB is obviously. The motion of tumor, the volume of ITV and PTV are reduced by holding the patients'breath by ABC system,which reduceds the volume of normal tissues around lung tumor during radiotherapy.Total lung volumes are enlarged when patients holding their breath while inhaling,which may reduce the lung Dmean,V20.The local dose of tumor may increase when the tolerance of normal tissues around lung tumor is accepted. |
