Multisource modeling of flattening filter free (FFF) beam and the optimization of model parameters

Cho, Woong; Kielar, K; Mok, E; Li, Xing; Park, Jeong Hoon; Jung, Woo-Hwan; Suh, Tae-Suk

doi:10.1118/1.3560426

Cited by 32 publications

(48 citation statements)

References 31 publications

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“…The MLC‐defined collimation in one axis could lead to higher penumbra and alternate head leakage spectrum 9. Second, the high dose rate FFF beams have a lower out‐of‐field dose, different electron contamination spectra, and possibly lower mean energy 10, 11, 12…”

Section: Introductionmentioning

confidence: 99%

Dosimetric validation of Monaco treatment planning system on an Elekta VersaHD linear accelerator

Narayanasamy

Saenz²,

Defoor³

et al. 2017

J Applied Clin Med Phys

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The purpose of this study is to perform dosimetric validation of Monaco treatment planning system version 5.1. The Elekta VersaHD linear accelerator with high dose rate flattening filter‐free photon modes and electron energies was used in this study. The dosimetric output of the new Agility head combined with the FFF photon modes warranted this investigation into the dosimetric accuracy prior to clinical usage. A model of the VersaHD linac was created in Monaco TPS by Elekta using commissioned beam data including percent depth dose curves, beam profiles, and output factors. A variety of 3D conformal fields were created in Monaco TPS on a combined Plastic water/Styrofoam phantom and validated against measurements with a calibrated ion chamber. Some of the parameters varied including source to surface distance, field size, wedges, gantry angle, and depth for all photon and electron energies. In addition, a series of step and shoot IMRT, VMAT test plans, and patient plans on various anatomical sites were verified against measurements on a Delta4 diode array. The agreement in point dose measurements was within 2% for all photon and electron energies in the homogeneous phantom and within 3% for photon energies in the heterogeneous phantom. The mean ± SD gamma passing rates of IMRT test fields yielded 93.8 ± 4.7% based on 2% dose difference and 2 mm distance‐to‐agreement criteria. Eight previously treated IMRT patient plans were replanned in Monaco TPS and five measurements on each yielded an average gamma passing rate of 95% with 6.7% confidence limit based on 3%, 3 mm gamma criteria. This investigation on dosimetric validation ensures accuracy of modeling VersaHD linac in Monaco TPS thereby improving patient safety.

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Section: Introductionmentioning

confidence: 99%

Dosimetric validation of Monaco treatment planning system on an Elekta VersaHD linear accelerator

Narayanasamy

Saenz²,

Defoor³

et al. 2017

J Applied Clin Med Phys

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“…A TrueBeam medical linac, equipped with high-definition multileaf collimator (HDMLC-120), is used in this work (Cho et al , 2011; Mok et al , 2010). In addition to conventional 6 MV and 15 MV beams with flattening filter, a TrueBeam system offers flattening-filter-free (FFF) beams with much higher than previously available dose rate (for 6 MV, up to 1400 MU/min; for 10 MV, up to 2400 MU/min).…”

Section: Methodsmentioning

confidence: 99%

Dose verification for respiratory-gated volumetric modulated arc therapy

Qian

Liu³

et al. 2011

Phys. Med. Biol.

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A novel commercial medical linac system (TrueBeam™, Varian Medical Systems, Palo Alto, CA) allows respiratory-gated volumetric modulated arc therapy (VMAT), a new modality for treating moving tumors with high precision and improved accuracy by allowing for regular motion associated with a patient's breathing during VMAT delivery. The purpose of this work is to adapt a previously-developed dose reconstruction technique to evaluate the fidelity of VMAT treatment during gated delivery under clinic-relevant periodic motion related to patient breathing. A Varian TrueBeam system was used in this study. VMAT plans were created for three patients with lung or pancreas tumors. Conventional 6 MV and 15 MV beams with flattening filter and high dose-rate 10 MV beams with no flattening filter were used in these plans. Each patient plan was delivered to a phantom first without gating and then with gating for three simulated respiratory periods (3, 4.5 and 6 seconds). Using the adapted log file-based dose reconstruction procedure supplemented with ion chamber array (Seven29™, PTW, Freiburg, Germany) measurements, the delivered dose was used to evaluate the fidelity of gated VMAT delivery. Comparison of Seven29 measurements with and without gating showed good agreement with gamma-index passing rates above 99% for 1%/1mm dose accuracy/distance-to-agreement criteria. With original plans as reference, gamma-index passing rates were 100% for the reconstituted plans (1%/1 mm criteria) and 93.5–100% for gated Seven29 measurements (3%/3 mm criteria). In the presence of leaf error deliberately introduced into the gated delivery of a pancreas patient plan, both dose reconstruction and Seven29 measurement consistently indicated substantial dosimetric differences from the original plan. In summary, a dose reconstruction procedure was demonstrated for evaluating the accuracy of respiratory-gated VMAT delivery. This technique showed that under clinical operation, the TrueBeam system faithfully realized treatment plans with gated delivery. This methodology affords a useful tool for machine and patient-specific quality assurance of the newly available respiratory-gated VMAT.

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“…Intuitively, one may consider that SPORT is a scheme with increased angular beam sampling while eliminating dispensable segments of the incident fields. In digital linacs, SPORT delivery is made efficient by (1) removing the redundant segments in the incident beams; (2) concatenating the stations so that they can be delivered in sequence automatically (i.e., auto-field sequencing); and (3) using high dose-rate beams 5,6,14 . The technique, which we termed as DASSIM-RT (dense angularly sampled and sparse intensity modulated radiation therapy) (Fig.…”

Section: Fixed-station Deliverymentioning

confidence: 99%

“…Digital linac with a few other important features has emerged for clinical use [1][2][3][4][5][6] . A distinct feature of digital linac is that parameters characterizing radiation delivery such as the gantry angle, collimator angle, couch angle, and dose rate are discretized and can be controlled easily in a programmable fashion.…”

Section: Introductionmentioning

confidence: 99%

Inverse planning in the age of digital LINACs: station parameter optimized radiation therapy (SPORT)

Li¹,

Li²

2014

J. Phys.: Conf. Ser.

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Beam's-eye-view dosimetrics (BEVD) guided rotational station parameter optimized radiation therapy (SPORT) planning based on reweighted totalvariation minimization Hojin Kim, Ruijiang Li, Rena Lee et al. Abstract. The last few years have seen a number of technical and clinical advances which give rise to a need for innovations in dose optimization and delivery strategies. Technically, a new generation of digital linac has become available which offers features such as programmable motion between station parameters and high dose-rate Flattening Filter Free (FFF) beams. Current inverse planning methods are designed for traditional machines and cannot accommodate these features of new generation linacs without compromising either dose conformality and/or delivery efficiency. Furthermore, SBRT is becoming increasingly important, which elevates the need for more efficient delivery, improved dose distribution. Here we will give an overview of our recent work in SPORT designed to harness the digital linacs and highlight the essential components of SPORT. We will summarize the pros and cons of traditional beamlet-based optimization (BBO) and direct aperture optimization (DAO) and introduce a new type of algorithm, compressed sensing (CS)-based inverse planning, that is capable of automatically removing the redundant segments during optimization and providing a plan with high deliverability in the presence of a large number of station control points (potentially non-coplanar, non-isocentric, and even multi-isocenters). We show that CS-approach takes the interplay between planning and delivery into account and allows us to balance the dose optimality and delivery efficiency in a controlled way and, providing a viable framework to address various unmet demands of the new generation linacs. A few specific implementation strategies of SPORT in the forms of fixed-gantry and rotational arc delivery are also presented.

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Multisource modeling of flattening filter free (FFF) beam and the optimization of model parameters

Cited by 32 publications

References 31 publications

Dosimetric validation of Monaco treatment planning system on an Elekta VersaHD linear accelerator

Dosimetric validation of Monaco treatment planning system on an Elekta VersaHD linear accelerator

Dose verification for respiratory-gated volumetric modulated arc therapy

Inverse planning in the age of digital LINACs: station parameter optimized radiation therapy (SPORT)

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