Using Active Breathing Control (ABC) To Evaluate The Effect Of Respiratory Motion To Lung Tumor Within The Treatment Of Radiation Oncology

Purpose:For tumors in the thorax,reducing the treatment margin for organ motion due to breathing reduces the volume of normal tissue that will be irradiated.A higher dose can be delivered to the target,provide that the risk of marginal misses is not increased.To evaluate the effect of applying the active breathing control(ABC)devices for 3-dimentional conformal radiation therapy(3DCRT)of the treatment of radiation oncology in lung tumor,and to compare paramaters to normal beathing plans.Methods:After received training adapted on the use of active breathing control(ABC)devices,patients chose with non-small-cell lung tumor and metastatic tumors underwent CT simulation of the radiotherapy had CT scans of their thorax with and without ABC devices inspiration breath hold during the 3-dimentional conformal radiation therapy(3DCRT).We measured the variation of lung position using with and without ABC devices during the breathing cycle regularity under simulation fluoroscopes.Patients were asked to inhale deeply and holding breath repeatedly for 5 times under the simulation fluoroscope,the variation was obtained.Two treatment plans were generated,and one with ABC devices was actually implemented and the other was for dosimetric study.Set-up errors of patient postion were evaluated by comparisons of electronic portal image(EPI)and digital reconstructive graph(DRR).The dosimetric parameters which were compared between ABC plans and without ABC plans included planning target volume(PTV):the percentage of whole lung volume which received radiation dose no less than 20Gy(V_{20-total lung}),and the percentage of normal lung volume which received radiation dose no less than 20Gy(V_{20-normal lung}),lung mass within a stanard 1.0-cm PTV margin around the CTV(M_CTV-PTV),set-up errors.Results:Sixteen patients with non-small-cell lung tumor and metastatic tumors were eligible for this study.All patients of this group could adapted to the use of ABC devices to the deep inspiration breath hold.There were lung motion using ABC devices at the the deep inspiration breathing hold.The mean of PTV decreased from308.83cm³(Q=522.43cm³)in without ABC situation to 285.41 cm³(Q=401.65 cm³)using ABC(P=0.044).AT the same time,whole lung(V_{20-total lung})and normal lung volume(W_{20-normal lung})which received radiation dose no less than 20Gy,respectively for without ABC and ABC patients.V₂₀were from 21.79%,17.95%to 18.99%,14.95% respectively.This resulted in an average decrease in lung mass of 1.18% within a standard 1.0-cm PTV margin around the CTV,but the absolute maximum to 18.32%.Conclusions:Using active breathing control(ABC)devices for reduce the effect of respiratory motion to lung tumor within the treatment of radiation oncology in evidence.There were reduced lung volume which received radiation dose no less than 20Gy(V₂₀),and thereby decreased the mass of normal lung within a standard margin of CTV- PTV.Using of ABC devices could decrease irradiated lung volume and normal tissue complication probability of lung(NTCP)and make for using precision radiotion therapy for tumor in the thorax.