Room: AAPM ePoster Library
Purpose: To evaluate if a standard treatment planning system without a specialty module for radiosurgery or multiple brain metastases can be used to effectively meet the CCTG CE.7 protocol constraints. Treatment planning systems are not only expensive, but also require resources for commissioning and maintaining, and for staff training. An annual service contract and maintenance can be financially significant. If a single commercially available planning system were able to effectively plan single isocenter multiple metastases cases as well as all other clinical cases, it would significantly reduce maintenance expenditures and staff training time. Furthermore, this might improve productivity measures such as simulation to treatment time.
Methods: Ten consecutive patients having between 5 and 13 brain lesions that received SRS in our center were planned with RayStation using a single isocenter for multiple lesions. The following dosimetric quantities were computed and evaluated: conformality index (CI), V12Gy, and PTV dose coverage for each lesion; V4Gy, V5Gy, V8Gy, V10Gy, and V12Gy for the entire brain; and maximum doses to optical structures and brainstem. These quantities include all of those from the CE.7 protocol as well as additions requested by our medical director. Plans meeting all CE.7 dosimetric measures were scored pass otherwise fail.
Results: Plans had one or two isocenters with one to seven lesions per isocenter. VMAT was used for all but one isocenter. CE.7 constraints of PTV coverage and optic structure doses were met for all patients. The brainstem dose constraint was missed for three patients with lesions near the brainstem. The whole brain V12Gy < 30cc constraint was missed for the patient having 13 lesions.
Conclusion: To our knowledge this is the first report showing that a comprehensive planning system permits construction of single isocenter multiple metastases radiosurgery plans meeting the CE.7 protocol.