Journal of Medical Physics (Jun 2024)

Evaluation of the Minimum Segment Width and Fluence Smoothing Tools for Intensity-modulated Techniques in Monaco Treatment Planning System

  • Sara Jiménez-Puertas,
  • Andrea González Rodríguez,
  • Sergio Lozares Cordero,
  • Tomás González González,
  • Javier Díez Chamarro,
  • Mónica Hernández Hernández,
  • Raquel Castro Moreno,
  • Marta Sánchez Casi,
  • David Carlos Villa Gazulla,
  • Almudena Gandía Martínez,
  • Arantxa Campos Bonel,
  • Maria del Mar Puertas Valiño,
  • José Antonio Font Gómez

DOI
https://doi.org/10.4103/jmp.jmp_156_23
Journal volume & issue
Vol. 49, no. 2
pp. 250 – 260

Abstract

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Purpose: This study aims to minimize monitor units (MUs) of intensity-modulated treatments in the Monaco treatment planning system while preserving plan quality by optimizing the “Minimum Segment Width” (MSW) and “Fluence Smoothing” parameters. Materials and Methods: We retrospectively analyzed 30 prostate, 30 gynecological, 15 breast cancer, 10 head and neck tumor, 11 radiosurgery, and 10 hypo-fractionated plans. Original prostate plans employed “Fluence Smoothing” = Off and were reoptimized with Low, Medium, and High settings. The remaining pathologies initially used MSW = 0.5 cm and were reoptimized with MSW = 1.0 cm. Plan quality, including total MU, delivery time, and dosimetric constraints, was statistically analyzed with a paired t-test. Results: Prostate plans exhibited the highest MU variation when changing “Fluence Smoothing” from Off to High (average ΔMU = −5.1%; P < 0.001). However, a High setting may increase overall MU when MSW = 0.5 cm. Gynecological plans changed substantially when MSW increased from 0.5 cm to 1.0 cm (average ΔMU = −29%; P < 0.001). Organs at risk sparing and planning target volumes remained within 1.2% differences. Replanning other pathologies with MSW = 1.0 cm affected breast and head and neck tumor plans (average ΔMU = −168.38, average Δt = −11.74 s, and average ΔMU = −256.56, average Δt = −15.05 s, respectively; all with P < 0.004). Radiosurgery and hypofractioned highly modulated plans did not yield statistically significant results. Conclusions: In breast, pelvis, head and neck, and prostate plans, starting with MSW = 1.0 cm optimally reduces MU and treatment time without compromising plan quality. MSW has a greater impact on MU than the “Fluence Smoothing” parameter. Plans with high modulation might present divergent behavior, requiring a case-specific analysis with MSW values higher than 0.5 cm.

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