To explore the difference between two dosimetric verification methods by using the IBA MatrixX in the verification of dynamic and static intensity modulated plan for breast tumor.

A total of 20 breast tumor patients treated with postoperative radiotherapy in our hospital form November 2023 to October 2024 were selected. The integrated dosimetric measurement of static intensity modulation (sIMRT) and dynamic intensity modulation (dIMRT) treatment plans for each patient were measured with the gantry fixed at 0 degree for all beams and actual gantry. According to different 1mm/1%, 2mm/2%, 2 mm/3% and 3mm/3% standards, the γ passing rate of each measurement result was analyzed.

Under the 3mm/3% standard, the γ passing rate of each measurement result was greater than 95%, which meets clinical requirements. The γ passing rate with the continuous improvement of the standard, the differences in dose distribution gradually become more prominent, and the γ passing rate gradually deteriorates. Under the same intensity modulation mode, the gantry Angle zeroing group was significantly better than the actual gantry group, and the difference was statistically significant (P<0.05). There was no significant difference between sIMRT and dIMRT under 2mm/2%, 2mm/3%, 3mm/3% standard conditions with the same verification method and different intensity modulation modes (P<0.05). At the 1mm/1% standard, the BCS_sIMRT_0 was better than the BCS_dIMRT_0, and the RM_sIMRT was better than RM_dIMRT, and the difference was statistically significant (P<0.05). In the BEV direction, the average maximum vertical distances from the PTV edge to the center of the shooting field in X and Y axis directions were (9.80±1.72) cm and (7.18±1.48) cm in BCS group, and (12.89±2.13) cm and (9.48±0.98) cm in RM group, respectively. Actual gantry Angle multi-field combination verification method γ pass rate is not affected by PTV edge to X wheelbase separation (P<0.05), but the γ pass rate of RM group was negatively correlated with PTV edge to Y wheelbase departure (r<0) and were statistically significant (P<0.05).

When validating the IMRT radiotherapy plan for breast tumor in the tangent field off the center, if selecting the 3mm/3% standard, the verification method of actual rack angle multi field synthesis that is more in line with the real irradiation situation can be used, or selecting the 2mm/2% and 2mm/3% standards, the verification method of 0-angle can be chosen.