Application of simplified manual intensity modulated technique in breast tangential irradiation / 中华放射医学与防护杂志

ABSTRACT

Objective To compare the planning systems of the simplified manual intensity modulated (SMIM) irradiation and standard tangential (ST) irradiation,in order to explore the application of SMIM technique in clinic.Methods In 64 cases of breast cancers after breast conserving surgery,each underwent both SMIM and ST planning systems.SMIM planning was designed by copying additional fields for shielding the high dose areas from internal or lateral tangential field.The high dose areas were reduced by adjusting the size of the additional field and open tangential field.To optimize the SMIM planning,3 high dose areas (＞ 103% ,＞ 105% and ＞ 107%) were shielded and 3 protocols carried out.The wedges were also optimized in ST plan.The target coverage and dose homogeneity and dose of organ at risk were compared between SMIM and ST planning systems.Results When the dose was normalized to cover the volume of 95% CTV,85% of the shielded areas in optimal SMIM planning were that of ＞ 103% high dose area,and 94% of target area was covered.The study on the volume of breast CTV showed that,in the large breast group,SMIM could not only significantly reduce the high dose areas,and the maximum dose as well as the dose of organ at risk,but also enhance the dose homogeneity index.However,no such effect was not significant in the small breast group.Conclusions The simplified manual intensity modulated technique can improve target dose homogeneity in the large breast cases instead of the standard tangential technique.