The effect of MLC leaf width in single-isocenter multi-target radiosurgery with volumetric modulated arc therapy

Zhanerke Abisheva, Scott R. Floyd, Joseph K. Salama, John Kirkpatrick, Fang Fang Yin, Michael J. Moravan, William Giles, Justus Adamson

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Purpose: Single-isocenter multi-target (SIMT) volumetric modulated arc therapy (VMAT) is primarily limited to linear accelerators utilizing 2.5 mm leaf width MLCs. We explore feasibility of applying this technique to linear accelerators utilizing MLCs with leaf width of 5 mm. Methods: Twenty patients with 3-10 intracranial brain metastases originally treated with 2.5 mm MLCs were re-planned using 5 mm MLCs and relevant dosimetric indices were compared. We also evaluated various strategies of adding VMAT arcs to mitigate degradations of dose quality values. Results: Wider MLCs caused small changes in total MUs (5827 ± 2334 vs 5572 ± 2220, p = 0.006), and conformity index (CI) (2.22% ± 0.05%, p = 0.045), but produced more substantial increases in brain V30%[%] and V50%[%] (27.75% ± 0.16% and 20.04% ± 0.13% respectively, p < 0.001 for both), and V12Gy[cc] (16.91% ± 0.12%, p < 0.001). Conclusion: SIMT radiosurgery delivered via VMAT using 5 mm wide MLCs can achieve similar CI compared to that using 2.5 mm leaf width MLCs but with moderately increased isodose spill, which can be only partially mitigated by increasing the number of VMAT arcs.

Original languageEnglish
Pages (from-to)131-138
Number of pages8
JournalJournal of Radiosurgery and SBRT
Volume6
Issue number2
StatePublished - 2019

Keywords

  • 2.5 mm leaf width MLCs
  • 5 mm leaf width MLCs
  • Intracranial brain metastases
  • SIMT
  • SRS
  • VMAT

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