The impact of a high-definition multileaf collimator for spine SBRT

Kelly C. Younge, John R. Kuchta, Justin K. Mikell, Benjamin Rosen, Jeremy S. Bredfeldt, Martha M. Matuszak

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Purpose: Advanced radiotherapy delivery systems designed for high-dose, high-precision treatments often come equipped with high-definition multi-leaf collimators (HD-MLC) aimed at more finely shaping radiation dose to the target. In this work, we study the effect of a high definition MLC on spine stereotactic body radiation therapy (SBRT) treatment plan quality and plan deliverability. Methods and Materials: Seventeen spine SBRT cases were planned with VMAT using a standard definition MLC (M120), HD-MLC, and HD-MLC with an added objective to reduce monitor units (MU). M120 plans were converted into plans deliverable on an HD-MLC using in-house software. Plan quality and plan deliverability as measured by portal dosimetry were compared among the three types of plans. Results: Only minor differences were noted in plan quality between the M120 and HD-MLC plans. Plans generated with the HD-MLC tended to have better spinal cord sparing (3% reduction in maximum cord dose). HD-MLC plans on average had 12% more MU and 55% greater modulation complexity as defined by an in-house metric. HD-MLC plans also had significantly degraded deliverability. Of the VMAT arcs measured, 94% had lower gamma passing metrics when using the HD-MLC. Conclusion: Modest improvements in plan quality were noted when switching from M120 to HD-MLC at the expense of significantly less accurate deliverability in some cases.

Original languageEnglish
Pages (from-to)97-103
Number of pages7
JournalJournal of applied clinical medical physics
Issue number6
StatePublished - Nov 2017


  • Complexity
  • Deliverability
  • HD-MLC
  • Spine SBRT


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