Monte Carlo study of backscatter in a flattening filter free clinical accelerator

Journal Article · Fri Sep 15 04:00:00 EDT 2006 · Medical Physics

DOI:https://doi.org/10.1118/1.2229430· OSTI ID:20853445

Titt, U; Vassiliev, O N; Poenisch, F; Kry, S F; Mohan, R ^[1]

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

In conventional linear accelerators, the flattening filter provides a uniform lateral dose profile. In intensity modulated radiation therapy applications, however, the flatness of the photon field and hence the presence of a flattening filter, is not necessary. Removing the filter may provide some advantages, such as faster treatments and smaller out-of-field doses to the patients. In clinical accelerators the backscattered radiation dose from the collimators must be taken into account when the dose to the target volume in the patient is being determined. In the case of a conventional machine, this backscatter is known to great precision. In a flattening filter free accelerator, however, the amount of backscatter may be different. In this study we determined the backscatter contribution to the monitor chamber signal in a flattening filter free clinical accelerator (Varian Clinac 21EX) with Monte Carlo simulations. We found that with the exception of very small fields in the 18-MV photon mode, the contribution of backscattered radiation to the monitor signal did not differ from that of conventional machines with a flattening filter. Hence, a flattening filter free clinical accelerator would not necessitate a different backscatter correction.

• OSTI ID: 20853445
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 9 Vol. 33; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ACCURACY
COLLIMATORS
COMPUTERIZED SIMULATION
CORRECTIONS
DOSIMETRY
EXCEPTIONS
LINEAR ACCELERATORS
MONTE CARLO METHOD
PATIENTS
PHOTONS
RADIATION DOSES
RADIOTHERAPY