Intracranial Stereotactic Radiation Therapy With a Jawless Ring Gantry Linear Accelerator Equipped With New Dual Layer Multileaf Collimator

doi:10.1016/j.adro.2020.01.003

Advances in Radiation Oncology

Volume 5, Issue 3, May–June 2020, Pages 482-489

https://doi.org/10.1016/j.adro.2020.01.003 Get rights and content

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Abstract

Purpose

To test the feasibility of a simplified, robust, workflow for intracranial stereotactic radiation therapy (SRT) using a ring gantry linear accelerator (RGLA) equipped with a dual-layer stacked, staggered, and interdigitating multileaf collimator.

Materials and Methods

Twenty recent clinical SRT cases treated using a radiosurgery c-arm linear accelerator were anonymized. From these data sets, a new planning workflow was developed and used to replan these cases, which then were compared to their clinical counterparts. Population-based dose-volume histograms were analyzed for target coverage and sparing of healthy brain. All plans underwent plan review and quality assurance and were delivered on an end-to-end verification phantom using image guidance to simulate treatment.

Results

The RGLA plans were able to meet departmental standards for target coverage and organ-at-risk sparing and showed plan quality similar to the clinical plans. RGLA plans showed increases in the 50% isodose in the axial plane but decreases in the sagittal and coronal planes. There were no statistically significant differences in the homogeneity index or number of monitor units between the 2 systems. There were statistically significant increases in conformity and gradient indices, with median values of 1.09 versus 1.11 and 2.82 versus 3.13, respectively, for the c-arm versus RGLA plans. These differences were not believed to be clinically significant because they met clinical goals. The population-based dose-volume histograms showed target coverage and organ-at-risk sparing similar to that of the clinical plans. All plans were able to meet the departmental quality assurance requirements and were delivered under image guidance on an end-to-end phantom with measurements agreeing within 3% of the expected value. RGLA plans showed a median reduction in delivery time of ≈50%.

Conclusions

This work describes a simplified and efficient workflow that could reduce treatment times and expand access to SRT to centers using an RGLA.

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: Sources of support: The authors of this work received financial and nonfinancial support from Varian Medical Systems in this work.

: Disclosures: Dr Cai reports nonfinancial support from Varian Medical Systems, during the conduct of the study, and grants, personal fees, and nonfinancial support from Varian Medical Systems outside the submitted work. Dr Hugo reports grants from Varian Medical Systems during the conduct of the study, as well as grants from Varian Medical Systems, Siemens, and ViewRay outside the submitted work. Dr Knutson reports nonfinancial support from Varian Medical Systems during the conduct of the study, and grants, personal fees, and nonfinancial support from Varian Medical Systems outside the submitted work. Dr Mutic reports grants from Varian Medical Systems during the conduct of the study, as well as grants, personal fees, nonfinancial support, and other from Varian Medical Systems, other from Radialogica, and other from TreatSafely outside the submitted work. Dr Henke reports grants, personal fees, and nonfinancial support from Varian Medical Systems and ViewRay, outside the submitted work.