A flattening filter free photon treatment concept evaluation with Monte Carlo

Journal Article · Thu Jun 15 04:00:00 EDT 2006 · Medical Physics

DOI:https://doi.org/10.1118/1.2198327· OSTI ID:20853175

Titt, U; Vassiliev, O N; Poenisch, F; Dong, L; Liu, H; Mohan, R ^[1]

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1. M. D. Anderson Cancer Center, University of Texas, 1515 Holcombe Boulevard, Houston, Texas 77030 (United States)

In principle, the concept of flat initial radiation-dose distribution across the beam is unnecessary for intensity modulated radiation therapy. Dynamic leaf positioning during irradiation could appropriately adjust the fluence distribution of an unflattened beam that is peaked in the center and deliver the desired uniform or nonuniform dose distribution. Removing the flattening filter could lead to reduced treatment time through higher dose rates and reduced scatter, because there would be substantially less material in the beam; and possibly other dosimetric and clinical advantages. This work aims to evaluate the properties of a flattening filter free clinical accelerator and to investigate its possible advantages in clinical intensity modulated radiation therapy applications by simulating a Varian 2100-based treatment delivery system with Monte Carlo techniques. Several depth-dose curves and lateral dose distribution profiles have been created for various field sizes, with and without the flattening filter. Data computed with this model were used to evaluate the overall quality of such a system in terms of changes in dose rate, photon and electron fluence, and reduction in out-of-field stray dose from the scattered components and were compared to the corresponding data for a standard treatment head with a flattening filter. The results of the simulations of the flattening filter free system show that a substantial increase in dose rate can be achieved, which would reduce the beam on time and decrease the out-of-field dose for patients due to reduced head-leakage dose. Also close to the treatment field edge, a significant improvement in out-of-field dose could be observed for small fields, which can be attributed to the change in the photon spectra, when the flattening filter is removed from the beamline.

• OSTI ID: 20853175
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 6 Vol. 33; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
COMPUTERIZED SIMULATION
DEPTH DOSE DISTRIBUTIONS
DOSE RATES
DOSIMETRY
LINEAR ACCELERATORS
MONTE CARLO METHOD
PATIENTS
PHOTONS
RADIATION DOSES
RADIOTHERAPY