FracMod: A computational tool for assessing IMRT field modulation

Texture analysis on the fluence map to evaluate the degree of modulation for volumetric modulated arc therapy

“…18 Therefore, quantification of the degree of modulation for both IMRT and VMAT plans is valuable to eliminate excessively modulated plans at the planning stage. [7][8][9][10][11][12][13][14][15][16][17][18][19] Various attempts have been made to quantify the degree of modulation for both IMRT and VMAT in association with the plan deliverability. [7][8][9][10][11][12][13][14][15][16][17][18][19] Most of the previous studies have focused on IMRT, 7,[10][11][12][13][15][16][17][18][19] while studies on VMAT 8,9,14 have been limited, as mentioned above.…”

“…2,3 Although the beam intensity modulation of IMRT and VMAT makes possible the delivery of a conformal dose to the target while sparing organs at risk (OAR), excessive modulation may result in delivery of dose distributions to the patient that are different from the intended calculated dose distributions. 2,5,[7][8][9][10][11][12][13][14][15][16][17][18] This is caused by increased uncertainties in the mechanical components of the Linac due to excessive movement and inaccurate dose calculations of small or irregular fields by treatment planning systems (TPS), the significance of which increases as the degree of modulation increases. 18 Therefore, excessive modulation of IMRT and VMAT may impair the treatment efficacy as well as potentially cause severe complications for the patient.…”

“…2,5 Studies have also been performed on the modulation index, which evaluates the degree of modulation of IMRT or VMAT plans to allow detection of excessively modulated plans at the planning level. [7][8][9][10][11][12][13][14][15][16][17][18][19][20] The modulation index is beneficial in comparison with pretreatment QA as it can lead to early detection of undeliverable plans, resulting in the sparing of resources needed to perform pretreatment QA. Various studies on the modulation index have been performed for IMRT, 7,10-13,15-20 however, such study has been more limited for VMAT.…”

Textural feature calculated from segmental fluences as a modulation index for VMAT

“…Intensity modulated radiation therapy modulates photon beam intensities by modulating multi-leaf collimator (MLC) positions, while VMAT modulates photon intensities by modulating MLC positions, gantry rotation speed and dose-rate, simultaneously [1,4,7]. Although modulation of photon beam intensity is essential for both IMRT and VMAT, excessive modulation results in differences between calculated dose, which is the dose intended to be delivered to the patient, and the dose which is actually delivered to the patient [8][9][10][11][12][13][14][15][16][17][18][19]. Excessive modulation increases uncertainties in the mechanical operation of linac components, as well as increases the use of small or irregular MLC apertures of which dose calculation with commercial treatment planning system (TPS) is currently inaccurate as compared to that of large or regular MLC apertures [14,16,17].…”

Effect of treatment planning system parameters on beam modulation complexity for treatment plans with single-layer multi-leaf collimator and dual-layer stacked multi-leaf collimator

“…The modulation complexity has been studied widely on linacs with single-layer MLC architecture, using metrics such as modulation index (MI) 16 , modulation complexity score (MCS) 17 , texture methods 18 , dimensional fractal analysis 19 , and aperture-based methods 20 . These complexity analyses have proven to be useful to compare linac performances between treatment techniques 5 , to evaluate the best plan parameters in specific planning scenarios 20,21 , to predict delivery accuracy 22 , and to establish reference values for dosimetry audits 23 The primary aim of the present study was to investigate the effect of specific TPS-parameters on modulation complexity for VMAT treatments.…”