Leaf sequencing techniques for Mlc-Based IMRT

Cheng B. Saw, R. ALFREDO C. Siochi, Komanduri M. Ayyangar, Weining Zhen, Charles A. Enke

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


The nonuniform fields required by intensity-modulation radiation therapy (IMRT) can be delivered using conventional multileaf collimators (MLC) as beam modulators. In MLC-based IMRT, the nonuniform field is initially converted into an intensity map represented as a matrix of beam intensities. The intensity map is then decomposed into a series of subfields or segments of uniform intensities. Although there are many ways of segmenting the beam intensity matrix, a resulting subfield is only deliverable if it satisfies the constraints imposed by the MLC. These constraints exist as a result of the design of the MLC. The simplest constraint of the MLC is that its pairs of leaves can only move in and out in one dimension. Additional constraints include collision of opposing leaves and the need to match the tongue-and-groove to reduce interleaf leakage. The practical aspect of MLC-based IMRT requires that an optimized algorithm decomposes the nonuniform field into the least number of segments and therefore reduces the delivery time. This paper examines the static use and the dynamic use of MLCs to perform MLC-based IMRT.

Original languageEnglish (US)
Pages (from-to)199-204
Number of pages6
JournalMedical Dosimetry
Issue number2
StatePublished - 2001


  • IMRT
  • Intensity modulation
  • Leaf sequencing
  • MLC

ASJC Scopus subject areas

  • Radiological and Ultrasound Technology
  • Oncology
  • Radiology Nuclear Medicine and imaging


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