The Effect of Calculation Grid Size on the Quality of Intensity Modulated Radiotherapy Planning After Modified Radical Mastectomy for Breast Cancer
Objective To investigate the effect of calculation grid size(GS)on the quality of intensity modulated radiotherapy(IMRT)planning after modified radical mastectomy for breast cancer.Methods With the selection of fifteen patients who received IMRT after modified radical mastectomy for breast cancer in hospital from January 2022 to December 2023 as the study subjects,firstly,the 3 mm GS was adopted to design the IMRT plan(3 mm plan).Then,the GS was changed to 2 mm(other parameters remained unchanged),and the plan was redesigned(2 mm plan).The dosimetry indicators for planning target volume(PTV)[Including D2%,D98%,Dmean,homogeneity index(HI)and conformity index(CI)],and organ at risk(OARs)(Affected lung V5,V20,V30,Dmean,and healthy lung V5,heart Dmean,spinal cord Dmax),and monitor unit(MU)and optimization time(OT)were compared between the two plans.Results In the dosimetric indexes of PTV,the Dmean of 2 mm plan was lower than that of 3 mm plan,and the CI was higher than that of 3 mm plan,with statistical significance(P<0.05);In the dosimetric indexes of OARs,the spinal cord Dmax of 2 mm plan was lower than that of 3 mm plan,and the difference was statistically significant(P<0.05);The OT of the 2 mm plan was 2.96 times that of the 3 mm plan,and the difference was statistically significant(P<0.05).Conclusions The dosimetric indicators of the 2 mm GSIMRT plan were better than those of the 3 mm plan,and the protective effect on the spinal cord was better,but the computational efficiency was lower.Therefore,GS should be selected reasonably in the design of IMRT plan after modified radical mastectomy for breast cancer to achieve the best balance between dose calculation accuracy and calculation efficiency.
Calculation grid sizeModified radical mastectomy for breast cancerIntensity modulated radiotherapyPlan qualityPlanning target volumeOrgans at risk