The Research Of Setup Errors Of CTVision And Anatomic Marks For Precise RT In BC With Postoperative

Objective：Radiation therapy is an important part of treating breastcancer patients with postoperative. The development of radiotherapypattern undergo two-dimensional conventional radiotherapy,three-Dimen-sional conformal radiotherapy, intensity modulated radiation therapy(IMRT) conformal and image guided radiotherapy. The development ofthe precise radiotherapy, have higher requirements in the fixedtechnology and setup errors of the patients. Using KV CT of CTVisionimage-guided radiotherapy system research setup error of Breast bracketand thermoplastic immobilization in breast cancer patients withpostoperative undergo precise radiotherapy. Through CTVision imageguided radiotherapy system applied to the precision radiotherapy in breastcancer patients with postoperative using osseous registration and skinmarker in tumor bed area registration in three dimensional directions ofdisplacement error, preliminary investigate the Planning Clinical TargetVolume (PTV) and Planning Risk Volume(PRV) margins of CTVisionclinical treatment planning system the target volume, surface markers in IGRT of the reference value. So as to guide clinical precise radiotherapy.materials and methods： From April2013to December2013,consecutive brest cancer patient with postoperative of48cases,38cases with conventional radiotherapy,SIEMENS CTVision guided linearaccelerator radiation treatment of10breast cancer patients withpostoperative,including7modified radical masectomy for patients,3Conservative Surgery for Patients with Breast Cancer. eligible10breastpostoperative patients for consecutive introduce breast bracket jointthermoplastic immobilization with large aperture CT scans in theCTVision image guidance system. image guide for CT scan the first3fractions and1fraction each week during treatment. Each patient acquire8times images, a total of83CT scan image. the difference in osseousregistration and skin marking registration was compared. Analysisdifference about the displacement error on the left and right (X axis),head and foot (Y axis) and dorsum and abdomen (Z axis) direction.Thestudy analyzed the set-up error and PTV,PRV margins.Result：Total of83sets of KV CT images in the CTVisionimage-guided radiotherapy system. The displacement error(mean±standard) in X,Y,Z axis directions were（0.07±0.24）cm and（-0.13±0.56）cm,（0.05±0.26）cm and（-0.03±0.44）cm,（0.07±0.11）cm and（0.19±0.20）cm in10breast cancer patients with osseous registrationand skin marking registration respectively.There was significant difference with osseous registration and skin marking registration in X（P=0.002）and Z axi（sP=0.000）respectively,but there was no statisticaldifference in Y axis（P=0.071）. there was also no statistical differencewith osseous registration in X and Y axis,X and Z axis,Y and Zrespectively（P=0.643，P=0.965，P=0.635）. displacement error statisticalis difference with skin marking registration in X and Y axis,X and Zaxis,Y and Z axis respectively（P=0.126，P=0.000，P=0.001）.The PTVmargins required to account for total error are4.79mm,5.81mm,1.46mmand13.62mm,8.52mm,3.71mm in X,Y,Z axis with osseous registrationand skin marking registration,respectively.PRV margins were2.62mmand7.28mm,3.13mm and4.50mm,0.80mm and2.04mm in X,Y,Z axiswith osseous registration and skin marking registration.any one axisdirections exceed5mm to correct the setup error with setup once again ormove couch. the setup error after correct is lower than before, only3.8%need to setup once again or move couch.Conclusion：the study of setup error is in standard permission scopeKVCT scan images in the CTVision image-guided radiotherapy systemfor breast cancer patient with postoperative. The positioning error ofosseous registration is smaller, osseous registration in IMRT for breastcancer patient with postoperative should fit clinical application.Reproducibility and stability of breast bracket and thermoplasticimmobilization in breast cancer patients with postoperative is better. Using thermoplastic immobilization can effectively reduce respiratorymotion of the chest wall and external contour. breast bracket andthermoplastic immobilization is used in clinical application.To study system error and random error of IMRT breast cancerpatients with postoperative,The PTV margin and PORV margin accountfor total error with osseous registration fit clinical application. The PTVmargin for5mm is feasible.The correlation is significant with osseous registration and skinmarking registration in X axis.Skin marking registration in CTVision IGRT system have greatdifference, That will lead to CT scan image and planning CT image ofmismatch. Research shows that it is key that breast superficial characte-ristics of breast cancer,using video-based three-dimensional opticalsurface imaging in detection of set-up may further improve the effect ofradiotherapy.