Purpose: Stereotactic radiosurgery SRS is indicated technique for multiple brain metastases treatment. SRS metastases doses are depending basically on metastases volume size. Variations in metastases doses and short distance between metastases make a plan is more complicated than normal.
Methods: Three retrospective cases are selected with 2 nearly metastases PTV18 and PTV22 that have prescribed doses 18Gy and 22Gy respectively in single fraction. Three planning strategies are applied in this study using Truebeam machine and Eclipse planning system with same optimization constrains. SIB method (SIB): Single plan with 22Gy to PTV22 and 18Gy to PTV18 in same plan. Sequential method (SEQ): Two plans are generated, 18Gy for all PTVs then plan boost 4Gy to PTV22 using base dose plan option. Separated method (SEP): Two plans are generated one with 18Gy for PTV18 then creating plan with 22Gy for PTV22 using base dose plan option.
Results: Study Dose statistics comparison between (SIB), (SEQ) and (SEP) show that the average of PTV18 and PTV22 are (0.86, 0.89 and 0.88), (0.89, 0.9 and 0.86) for PI, (1.09, 1.11 AND 1.15), (0.94, 0.93 and 0.94) for CI, (0.88, 0.88 and 0.9) (0.93, 0.94 and 0.93) for QI, (1.15, 1.19 and 1.24), (1.13, 1.14 and 1.15) for HI. Furthermore the GI average are (2.48, 2.42 AND 2.72) for (SIB), (SEQ) and (SEP) respectively, while the average volumes of 12Gy for (Brain – PTV) are (8.9, 8.4 and 10cc) for (SIB), (SEQ) and (SEP) respectively, while (SIB) and (SEP) failed to achieve the criteria in one case. There is no noticeable difference between methods in other OARs. Otherwise the MU result data were (7634±740, 7444±724 and 11368±156) for (SIB), (SEQ) and (SEP) respectively.
Conclusion: The study proved that Sequential is the superior strategy in most of evaluation parameters while the separated strategy is least one.