Purpose: The various commercially available treatment planning systems (TPSs) may have differing capabilities in the context of single-isocenter multiple-metastases. Plan quality was compared between Brainlab Elements Multiple Mets Software v.3.0 (Elements) and RayStation v.11A (RS).
Methods: Eight patients, originally planned for treatment with Elements, were selected for analysis with 21 total lesions (1-4 per patient, average 2.4 lesions). Organs-at-risk were auto-contoured in Elements and reviewed by physicist/physician prior to treatment planning. Gross tumor volumes (GTVs) and planning target volumes (PTVs) were developed in Elements. All structures, CT, MRI, and registration files were exported to RS for planning. Plans in Elements utilized dynamic conformal arcs (DCA) and RS plans utilized volumetric modulated arc therapy (VMAT) with couch kicks. Plan quality metrics include PTV coverage (D98%), conformity index (CI), normal brain V12Gy and V4Gy.
Results: PTV VRx (volume receiving prescription dose) coverage was comparable between Elements and RS plans, demonstrating an average of 0.37% (±0.58%, p=0.01) difference (with RS having higher average VRx). RS plans were on average cooler with D5% difference of 0.23 Gy (± 0.80 Gy, p=0.23). The greatest difference between Elements and RS was the dose to the normal brain: average V12Gy was 3.70cc (± 2.54cc) vs. 4.54cc (±2.53cc, p=0.009) and average V4 was 26.33cc (±18.77cc) vs. 32.57cc (±18.86cc, p=0.043) for Elements vs. RS, respectively. The conformity indices were also better in Elements vs RS (1.22 vs 1.47 average, p=0.001).
Conclusion: While PTV coverage, determined by the VRx is similar between the two planning systems, the plans developed in Brainlab Elements Multiple Mets Software are superior due to lower CI’s and normal brain doses. These superior parameters are important in case the patient would need to be retreated.
Stereotactic Radiosurgery, Treatment Planning