AffiliationNW Medical Physics, Christie Hospital NHS Trust, Withington, Manchester, UK. firstname.lastname@example.org
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AbstractAsymmetric offset fields are an important tool for radiotherapy and their suitability for treatment should be assessed. Dose homogeneity for highly asymmetric fields has been studied for a Siemens PRIMUS clinical linear accelerator. Profiles and absolute dose have been measured in fields with two jaws at maximal position (20 cm) and the other two at maximal overtravel (10 cm), corresponding to 10 cm x 10 cm fields with extreme offset. Measured profiles have a marked decreasing gradient towards the beam edge, making these fields unsuitable for treatments. The flattening filter radius is smaller than the primary collimator aperture, and this creates beam inhomogeneities that affect large fields in areas far from the collimator axis, and asymmetric fields with large offset. The results presented assess the effect that the design of the primary collimator and flattening filter assembly has on beam homogeneity. This can have clinical consequences for treatments involving fields that include these inhomogeneous areas. Comparison with calculations from a treatment planning system, Philips Pinnacle v6.3, which computes under the hypotheses of a uniformly flattened beam, results in severe discrepancies.
CitationA study on beam homogeneity for a Siemens Primus linac. 2007, 30 (2):147-51 Australas Phys Eng Sci Med
JournalAustralasian Physical & Engineering Sciences in Medicine
- The flatness of Siemens linear accelerator x-ray fields.
- Authors: Faddegon BA, O'Brien P, Mason DL
- Issue date: 1999 Feb
- Sensitivity analysis of an asymmetric Monte Carlo beam model of a Siemens Primus accelerator.
- Authors: Schreiber EC, Sawkey DL, Faddegon BA
- Issue date: 2012 Mar 8
- A semianalytical method for the design of a linac x-ray beam flattening filter.
- Authors: Flock ST, Shragge PC
- Issue date: 1987 Mar-Apr
- Measurement of backscattered radiation from secondary collimator jaws into the beam monitor chamber from a dual energy linear accelerator.
- Authors: Ravikumar M, Ravichandran R
- Issue date: 2001 Dec
- SU-E-T-514: Implementation and Commissioning of a Micro Multileaf Collimator in Pinnacle Treatment Planning System.
- Authors: Hernández TG, González LB, González AV, Ferrando JR, Cabañero DG
- Issue date: 2012 Jun