Improving wedged field dose distributions

Keall, P.; Zavgorodni, Sergei; Schmidt, LeEtta; Haskard, D. L.

doi:10.1088/0031-9155/42/11/013

Cited by 11 publications

(6 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Physical wedges attenuate beam in both the gradient and nongradient directions of the wedge. For large fields data should also be taken in the nongradient direction to examine the impact of rounding off, as shown by various authors, 123,124 due to oblique incidence of the beam and selectively higher attenuation at off axis. IV.A.4.d.…”

Section: Iva4 Beam Profilesmentioning

confidence: 99%

Accelerator beam data commissioning equipment and procedures: Report of the TG‐106 of the Therapy Physics Committee of the AAPM

Das

Cheng

Watts³

et al. 2008

Medical Physics

409

424

View full text Add to dashboard Cite

For commissioning a linear accelerator for clinical use, medical physicists are faced with many challenges including the need for precision, a variety of testing methods, data validation, the lack of standards, and time constraints. Since commissioning beam data are treated as a reference and ultimately used by treatment planning systems, it is vitally important that the collected data are of the highest quality to avoid dosimetric and patient treatment errors that may subsequently lead to a poor radiation outcome. Beam data commissioning should be performed with appropriate knowledge and proper tools and should be independent of the person collecting the data. To achieve this goal, Task Group 106 (TG-106) of the Therapy Physics Committee of the American Association of Physicists in Medicine was formed to review the practical aspects as well as the physics of linear accelerator commissioning. The report provides guidelines and recommendations on the proper selection of phantoms and detectors, setting up of a phantom for data acquisition (both scanning and no-scanning data), procedures for acquiring specific photon and electron beam parameters and methods to reduce measurement errors (<1%), beam data processing and detector size convolution for accurate profiles. The TG-106 also provides a brief.discussion on the emerging trend in Monte Carlo simulation techniques in photon and electron beam commissioning. The procedures described in this report should assist a qualified medical physicist in either measuring a complete set of beam data, or in verifying a subset of data before initial use or for periodic quality assurance measurements. By combining practical experience with theoretical discussion, this document sets a new standard for beam data commissioning.

show abstract

Section: Iva4 Beam Profilesmentioning

confidence: 99%

Accelerator beam data commissioning equipment and procedures: Report of the TG‐106 of the Therapy Physics Committee of the AAPM

Das

Cheng

Watts³

et al. 2008

Medical Physics

409

424

View full text Add to dashboard Cite

show abstract

“…which reproduces the open beam profile shape in the non-wedge axis was proposed by Keall et al (1997).…”

Section: One-dimensional Beam Intensity Modifying Devices-wedgessupporting

confidence: 62%

“…Although wedge primarily modify beam intensity in one dimension (along the wedge), dose profiles produced by wedge filters in the non-wedged direction can exhibit a 7% or greater dose reduction at the outer ends of the field compared with open beam profiles (Keall et al 1997). This discrepancy increases with off-axis distance and wedge angle.…”

Section: One-dimensional Beam Intensity Modifying Devices-wedgesmentioning

confidence: 99%

Modeling and simulation of filters and devices for conformal radiotherapy

Ivanova¹

View full text Add to dashboard Cite

Modeling and simulations of filters and devices for conformal radiotherapy 3.3. Similarity of inverse problem in radiation therapy with image reconstruction in CT…………………………………………………..….40 3.4. Going beyond the direct inverse problem ………………………………..45 3.5. Conclusions………………………………………………………………48 CHAPTER 4: Rotational conformal radiotherapy with beam modifying devices 51 4.1. Introduction………………………………………………………………51 4.2. Principles of the beam modifying devices……………………………….53 4.3. Mathematical modeling of the beam modifying devices…...……………57 4.3.1. Protectors…………………………………………………57 4.3.2. Beam shapers……………………………………………..59 4.4. Discussion and conclusions………………………………………………64 CHAPTER 5: Simulations studies on use of the beam modifying devices for spinal cord protection 67 5.1.

show abstract

“…The calculated changes in beam profile in the unwedged direction were also found to be in good agreement with experiments, as shown in figure 8 for a (10 × 10) cm 2 6 MV photon beam. This is not accounted for in most TPSs (Keall et al 1997). These results show that phase space files constructed using the technique described in this paper could be efficiently used for building accurate wedge source models (Ma and Rogers 1995b).…”

Section: Mlc and Standard Physical Wedgesmentioning

confidence: 94%

Monte Carlo simulation and dosimetric verification of radiotherapy beam modifiers

2001

View full text Add to dashboard Cite

Monte Carlo simulation of beam modifiers such as physical wedges and compensating filters has been performed with a rectilinear voxel geometry module. A modified version of the EGS4/DOSXYZ code has been developed for this purpose. The new implementations have been validated against the BEAM Monte Carlo code using its standard component modules (CMs) in several geometrical conditions. No significant disagreements were found within the statistical errors of 0.5% for photons and 2% for electrons. The clinical applicability and flexibility of the new version of the code has been assessed through an extensive verification versus dosimetric data. Both Varian multi-leaf collimator (MLC) wedges and standard wedges have been simulated and compared against experiments for 6MV photon beams and different field sizes. Good agreement was found between calculated and measured depth doses and lateral dose profiles along both wedged and unwedged directions for different depths and focus-to-surface distances. Furthermore, Monte Carlo-generated output factors for both open and wedged fields agreed with linac commissioning beam data within statistical uncertainties of the calculations (<3% at largest depths). Compensating filters of both low-density and high-density materials have also been successfully simulated. As a demonstration, a wax compensating filter with a complex three-dimensional concave and convex geometry has been modelled through a CT scan import. Calculated depth doses and lateral dose profiles for different field sizes agreed well with experiments. The code was used to investigate the performance of a commercial treatment planning system in designing compensators. Dose distributions in a heterogeneous water phantom emulating the head and neck region were calculated with the convolution-superposition method (pencil beam and collapsed cone implementations) and compared against those from the MC code developed herein. The new technique presented in this work is versatile, DICOM-RT compliant and accurate in the simulation of beam modulators. This paper addresses the need to reduce the sources of error in the modelling of beam modifiers since they remain a viable alternative to the MLC technique in the delivery of IMRT beams.

show abstract

Improving wedged field dose distributions

Cited by 11 publications

References 7 publications

Accelerator beam data commissioning equipment and procedures: Report of the TG‐106 of the Therapy Physics Committee of the AAPM

Accelerator beam data commissioning equipment and procedures: Report of the TG‐106 of the Therapy Physics Committee of the AAPM

Modeling and simulation of filters and devices for conformal radiotherapy

Monte Carlo simulation and dosimetric verification of radiotherapy beam modifiers

Contact Info

Product

Resources

About