The commissioning data indicated good consistency among the three TB-LINAC units. The commissioning data provided us valuable insights and reliable evaluations on the characteristics of the new treatment system. The systematically measured data might be useful for future reference.

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Brain metastasis (BM), the most common adult brain tumor, develops in 20% to 40% of patients with late‐stage cancer and traditionally are associated with a poor prognosis. The management of patients with BM has become increasingly complex because of new and emerging systemic therapies and advancements in radiation oncology and neurosurgery. Current therapies include stereotactic radiosurgery, whole‐brain radiation therapy, surgical resection, laser‐interstitial thermal therapy, systemic cytotoxic chemotherapy, targeted agents, and immune‐checkpoint inhibitors. Determining the optimal treatment for a specific patient has become increasingly individualized, emphasizing the need for multidisciplinary discussions of patients with BM. Recognizing and addressing the sequelae of BMs and their treatment while maintaining quality of life and neurocognition is especially important because survival for patients with BMs has improved. The authors present current and emerging treatment options for patients with BM and suggest approaches for managing sequelae and disease recurrence.

Purpose Multileaf collimator (MLC) delivery discrepancy between planned and actual (delivered) positions have detrimental effect on the accuracy of dose distributions for both IMRT and VMAT. In this study, we evaluated the consistency of MLC delivery discrepancies over the course of treatment and over time to verify that a predictive machine learning model would be applicable throughout the course of treatment. Next, the MLC and gantry positions recorded in prior trajectory log files were analyzed to build a machine learning algorithm to predict MLC positional discrepancies during delivery for a new treatment plan. An open source tool was developed and released to predict the MLC positional discrepancies at treatment delivery for any given plan. Methods Trajectory log files of 142 IMRT plans and 125 VMAT plans from 9 Varian TrueBeam linear accelerators were collected and analyzed. The consistency of delivery discrepancy over patient‐specific quality assurance (QA) and patient treatment deliveries was evaluated. Data were binned by treatment site and machine type to determine their relationship with MLC and gantry angle discrepancies. Motion‐related parameters including MLC velocity, MLC acceleration, control point, dose rate, and gravity vector, gantry velocity and gantry acceleration, where applicable, were analyzed to evaluate correlations with MLC and gantry discrepancies. Several regression models, such as simple/multiple linear regression, decision tree, and ensemble method (boosted tree and bagged tree model) were used to develop a machine learning algorithm to predict MLC discrepancy based on MLC motion parameters. Results MLC discrepancies at patient‐specific QA differed from those at patient treatment deliveries by a small (mean = 0.0021 ± 0.0036 mm, P = 0.0089 for IMRT; mean = 0.0010 ± 0.0016 mm, P = 0.0003 for VMAT) but statistically significant amount, likely due to setting the gantry angle to zero for QA in IMRT. MLC motion parameters, MLC velocity and gravity vector, showed significant correlation (P < 0.001) with MLC discrepancy, especially MLC velocity, which had an approximately linear relationship (slope = −0.0027, P < 0.001, R2 = 0.79). Incorporating MLC motion parameters, the final generalized model trained by data from all linear accelerators can predict MLC discrepancy to a high degree of accuracy with high correlation (R2 = 0.86) between predicted and actual MLC discrepancies. The same prediction results were found across different treatment sites and linear accelerators. Conclusion We have developed a machine learning model using trajectory log files to predict the MLC discrepancies during delivery. This model has been a released as a research tool in which a DICOM‐RT with predicted MLC positions can be generated using the original DICOM‐RT file as input. This tool can be used to simulate radiotherapy treatment delivery and may be useful for studies evaluating plan robustness and dosimetric uncertainties from treatment delivery.

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