Determining efficient helical IMRT modulation factor from the MLC leaf-open time distribution on precision treatment planning system

Robert Boyd, Kyoungkeun Jeong, Wolfgang A. Tome

Research output: Contribution to journalArticle

Abstract

Purpose: Since the modulation factor (MF) impacts both plan quality and delivery efficiency in tomotherapy Intensity Modulated Radiation Therapy (IMRT) treatment planning, the purpose of this study was to demonstrate a technique in determining an efficient MF from the Multileaf Collimator (MLC) leaf-open time (LOT) distribution of a tomotherapy treatment delivery plan. Methods: Eight clinical plans of varying complexity were optimized with the highest allowed MF on the Accuracy Precision treatment planning system. Using a central limit theorem argument a range of reduced MFs were then determined from the first two moments of the LOT distribution. A step down approach was used to calculate the reduced-MF plans and plan comparison tools available on the Precision treatment planning system were used to evaluate dose differences with the reference plan. Results: A reduced-MF plan that balanced delivery time and dosimetric quality was found from the set of five MFs determined from the LOT distribution of the reference plan. The reduced-MF plan showed good agreement with the reference plan (target and critical organ dose-volume region of interest dose differences were within 1% and 2% of prescription dose, respectively). Discussion: Plan evaluation and acceptance criteria can vary depending on individual clinical expectations and dosimetric quality trade-offs. With the scheme presented in this paper a planner should be able to efficiently generate a high-quality plan with efficient delivery time without knowing a good MF beforehand. Conclusion: A methodology for deriving a reduced MF from the LOT distribution of a high MF treatment plan using the central limit theorem has been presented. A scheme for finding a reduced MF from a set of MFs that results in a plan balanced in both dosimetric quality and treatment delivery efficiency has also been presented.

Original languageEnglish (US)
Pages (from-to)64-74
Number of pages11
JournalJournal of Applied Clinical Medical Physics
Volume20
Issue number5
DOIs
StatePublished - May 1 2019

Fingerprint

Radiotherapy
collimators
leaves
planning
radiation therapy
Modulation
modulation
Planning
delivery
Therapeutics
Organ Size
dosage
Prescriptions
theorems
organs
acceptability

Keywords

  • leaf-open time
  • modulation factor
  • tomotherapy
  • treatment planning

ASJC Scopus subject areas

  • Radiation
  • Instrumentation
  • Radiology Nuclear Medicine and imaging

Cite this

Determining efficient helical IMRT modulation factor from the MLC leaf-open time distribution on precision treatment planning system. / Boyd, Robert; Jeong, Kyoungkeun; Tome, Wolfgang A.

In: Journal of Applied Clinical Medical Physics, Vol. 20, No. 5, 01.05.2019, p. 64-74.

Research output: Contribution to journalArticle

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