ABSTRACT
Objective To investigate the influence to dosimetry of the patient with rectum cancer by setup errors.Methods First an intensity modulated radiation treatment planning for a rectum cancer patient was designed,then the isocenter was moved 5 mm respectively to the left side,right side,abdomen side,back side,head side and foot side;and the isocenter was moved 5 mm to head side,back side and left side at the same time;and the isocenter was moved 5 mm to foot side,abdomen side and right side at the same time;and the isocenter was moved according to the largest set-up error for the first five Cone Beam CT scanning,thus nine new plans and a confirmed plan were got,the influence to dosimetry for targets and fermur head,bladder and intestine for these ten plans was analyzed.Results The influence to the dosimetry gained the maximum value in the planning target volume (PTV) with the isocenter moving 5 mm to three directions and normal organs.All the plans had little influence on clinical target volume (CTV),which posed few effects on small intestine and bladder while big influence to femoral head incase of high dose D2 to 2％ target volume and mean dose.Conclusion The set-up error may influence dosimetry of PTV,and the reduction of low dose D98 to 98％ target volume may affect treatment effect.For patients whose set-up errors are large,times of cone beam CT scanning have to be increased in order to ensure the precise implementation of the treatment plans.
ABSTRACT
Objective To investigate the influence to dosimetry of the patient with rectum cancer by setup errors.Methods First an intensity modulated radiation treatment planning for a rectum cancer patient was designed,then the isocenter was moved 5 mm respectively to the left side,right side,abdomen side,back side,head side and foot side;and the isocenter was moved 5 mm to head side,back side and left side at the same time;and the isocenter was moved 5 mm to foot side,abdomen side and right side at the same time;and the isocenter was moved according to the largest set-up error for the first five Cone Beam CT scanning,thus nine new plans and a confirmed plan were got,the influence to dosimetry for targets and fermur head,bladder and intestine for these ten plans was analyzed.Results The influence to the dosimetry gained the maximum value in the planning target volume (PTV) with the isocenter moving 5 mm to three directions and normal organs.All the plans had little influence on clinical target volume (CTV),which posed few effects on small intestine and bladder while big influence to femoral head incase of high dose D2 to 2％ target volume and mean dose.Conclusion The set-up error may influence dosimetry of PTV,and the reduction of low dose D98 to 98％ target volume may affect treatment effect.For patients whose set-up errors are large,times of cone beam CT scanning have to be increased in order to ensure the precise implementation of the treatment plans.
ABSTRACT
Objective To evaluate the impact of breathing motion on target volume and the factors influencing the set-up errors during tangential whole breast irradiation.Methods From Jan 2003 to Dec 2003,patients with early-stage breast cancer after breast conserving surgery,were selected to be eligible for the study.All patients were immobilized in treatment position by breast beard of Med-Tec 250.The motion of the breast treatment volume was observed on a fluoroscope in different directions under free breathing in 16 patients.The set-up errors in different dimensions during irradiation were measured by weekly portal films (PF) in comparison with digital reconstructed radiographs (DRR) in 11 patients.Results The central lung distance (CLD) variation during free breathing was (2.1?1.2) mm which is greater than the motion to- wards the other directions.By comparing the PF and DRR,the systemic error,random error and overall er- ror in the outer,inner and cranio-caudal directions was 1.9,1.6,2.5 and 2.4,1.7,3.1 and 2.6,2.3, 3.5 mm,respectively.In addition,the discrepancy of the treatment position in cranio-caudal direction and breast volume was most obvious at the beginning 2 weeks with the peak of breast volume at the second week. It decreased gradually during the following 3 weeks.Conclusions This study suggests that the mean value of the motion of the breast target volume during one breathing cycle is less than 2 mm.The set-up errors dur- ing irradiation is the greatest in cranio-caudal direction,suggesting that the fixing precision of the breast board should be further improved.The set-up error during irradiation are most obvious at the beginning two weeks,with the peak of the breast volume in the second week.
ABSTRACT
A special method of clinical tumor radiation therapy,namely 3DCRT& IMRT,is described in this paper,including its design and clinical application.