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

Abstract

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 z50%.

Prostate SBRT using O‐Ring Halcyon Linac — Plan quality, delivery efficiency, and accuracy

“…All parameters were deemed acceptable for treating prostate SBRT patients on Halcyon with overall faster treatment time of less than 10 minutes, potentially benefiting patients who cannot lie flat in the treatment position for longer treatment time, minimizing intrafraction motion error and improving clinic efficiency. Based on this research and other previous studies, we are planning to expand our Halcyon Linac to treat other disease sites such as fractionated stereotactic treatment of brain tumors 36,37 any abdominal and pelvic nodes SBRT and selected liver, pancreas or adrenal glands SBRT patients. Due to lower total MU per treatment and relatively smaller beam‐on time, deep inspiration breath‐hold to liver or pancreatic SBRT treatments on Halcyon Linac warrant future investigation.…”

“…In a hypofractionated study, Knutson et al. reported a retrospective dosimetric analysis of intracranial stereotactic radiation therapy (SRT) treatments using the Halcyon Linac 36 . In a 20‐patient study with a fractionation scheme of 30 Gy in five fractions, they demonstrated that acceptable plan quality for brain SRT is achievable using Halcyon coplanar geometry.…”

“…[32][33][34][35] In a hypofractionated study, Knutson et al reported a retrospective dosimetric analysis of intracranial stereotactic radiation therapy (SRT) treatments using the Halcyon Linac. 36 In a 20patient study with a fractionation scheme of 30…”

Clinical validation of ring‐mounted halcyon linac for lung SBRT: comparison to SBRT‐dedicated C‐arm linac treatments

“…[24][25][26] For hypofractionation schemes, Knutson et al reported a retrospective dosimetric study of fractionated intracranial stereotactic radiation therapy (SRT) using the Halcyon. 27 In a 20-patient study (30 Gy in five fractions), they demonstrated acceptable plan quality for brain SRT using Halcyon coplanar geometry. Another study by Li et al demonstrated the Halcyon V2.0 can generate plan quality comparable to a C-arm Linac for 6-10 brain tumors (diameter >1.0 cm), with a single-isocenter VMAT approach for intracranial radiosurgery.…”

“…For hypofractionation schemes, Knutson et al. reported a retrospective dosimetric study of fractionated intracranial stereotactic radiation therapy (SRT) using the Halcyon 27 . In a 20‐patient study (30 Gy in five fractions), they demonstrated acceptable plan quality for brain SRT using Halcyon coplanar geometry.…”