Computer aided design and verification of megavoltage tissue compensators for oblique beams

Faddegon, Bruce A.; Pfalzner, Paul M.

doi:10.1118/1.596190

Cited by 12 publications

(4 citation statements)

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“…This has traditionally been achieved by using blocks to shape the radiation field 1 or physical compensators to modify the beam profile, [2][3][4] and hence to generate an intensity-modulated beam ͑IMB͒. The multileaf collimator ͑MLC͒ has been developed [5][6][7][8] and has the potential to replace both blocks for beam shaping [9][10][11][12][13][14][15] and compensators for generating IMBs.…”

Section: Introductionmentioning

confidence: 99%

The optimum intensities for multiple static multileaf collimator field compensation

1997

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A method of determining the optimum beam intensities for compensation using multiple static multileaf collimator fields is presented. In this method a histogram of the number of beam pixels against beam intensity is generated for the intensity-modulated beam (IMB). The intensity of each beam to be used is chosen to minimize the mean square deviation between each bin in the histogram and the closest beam intensity. This method has been applied to sample IMBs possessing one maximum and two maxima. For both cases, the use of uniform beam intensity increments is shown to be close to optimal. In the case with two maxima, the efficacy of irradiating both peaks simultaneously, rather than separately, has been studied and shown to be of potential benefit. The optimum intensities for an IMB for breast radiotherapy are also presented.

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Section: Introductionmentioning

confidence: 99%

The optimum intensities for multiple static multileaf collimator field compensation

1997

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“…We are using compensator for IMRT (cIMRT) treatment delivery. Initially, compensators were used to deliver homogenous dose within the body by compensating the effect of missing tissues, internal tissue inhomogeneities and beam obliquity [8]. Designs of variable compensators in the multibeam situation have been discussed by Djordievich et al [5].…”

Section: Introductionmentioning

confidence: 99%

Quality assurance and dosimetric analysis of intensity modulation radiotherapy using compensators for head and neck cancers

Tyagi¹,

Nangia

Chufal

et al. 2009

Polish Journal of Medical Physics and Engineering

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In this study we describe our experience in implementing compensator based intensity modulated radiotherapy (cIMRT) for head and neck cancer with regard to pre treatment quality assurance (QA), dosimetric parameters and other technical detail.This study represents the analysis of initial 48 patients who underwent cIMRT for head and neck cancers. All patients were treated with pre treatment QA in terms of point dose with ion chamber and spatial dose comparison with film dosimetry.In our study for all 48 patients, compensators revealed a deviation in central axis dose of 2% ± 1.8% in terms of cumulative calculated versus measured dose. Target coverage for high dose volume (70 Gy) was adequate in terms of volume receiving 93% and 95% of the prescription dose, which was 98.5% and 97.5% respectively. Parotid and other critical organs were spared adequately. Contralateral parotid (CLP) was spared. V30 Gy and V35 Gy was 55.9% and 36.8% for CLP and average dose was 31.7 Gy. Median variation in cumulative measured dose versus cumulative calculated dose was 1.8% (SD + 1.8) and mean variation was 2.5% (95%CI 1.5, 2.6). Range was 0 to 7%.cIMRT is practically feasible. Our QA tests revealed high degree of concordance between cumulative measured doses versus cumulative calculated doses. All dosimetric parameters were within acceptable limits. The manufacturing of compensator is cumbersome but it is a one time job followed by easy treatment delivery and simple QA procedure, high monitor unit (MU) efficiency and less treatment time. cIMRT is easy to implement and now can be applied to larger number of patients with different type of tumor.

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“…In breast radiotherapy, dose heterogeneity is believed to be one of the main contributing factors to poor cosmesis and other complications (Moody et al 1994). The use of intensitymodulated radiotherapy has been shown to be beneficial in the reduction of dose inhomogeneity within the breast (Bagne et al 1990, Carruthers et al 1999, Dixon et al 1979, Faddegon and Pfalzner 1988, Hong et al 1999, Mayles et al 1991, Kestin et al 2000, Valdagni et al 1992. There are a large number of studies that have quantified the magnitude of set-up errors within the breast (Fein et al 1996, Lirette et al 1995, Valdagni and Italia 1991, Van Tienhoven et al 1991, Westbrook et al 1991.…”

Section: Introductionmentioning

confidence: 99%

A simulation of the effects of set-up error and changes in breast volume on conventional and intensity-modulated treatments in breast radiotherapy

2001

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The effect of interfractional patient movement on dosimetry has been investigated for breast radiotherapy. Errors in patient set-up and changes in breast volume were simulated individually to determine how each contributes to the total dosimetric error. Two treatment techniques were investigated: a conventional treatment and an intensity-modulated treatment delivered using compensators. Six patients were investigated and anterior-posterior (AP) and superior-inferior (SI) displacements were simulated by displacing the isocentre in both directions by 2, 5 and 10 mm. A model of the breast was developed from the six patients to simulate changes in breast volume. In this model, the breast was described as a set of semi-ellipses. The volume of the breast was changed by varying the magnitude of the semi-major and semi-minor axes. Anisotropic changes in breast volume were also investigated. The dosimetric error was evaluated for each dose plan by calculating the volume outside the 95-105% dose range resulting from the simulations. A number of parameters describing the size and shape of the breast were also investigated to determine whether a susceptibility of outline sets to interfractional patient movement could be predicted. A parameter describing the increase in the breast volume outside the 95-105% dose range was calculated for AP a

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Computer aided design and verification of megavoltage tissue compensators for oblique beams

Cited by 12 publications

References 0 publications

The optimum intensities for multiple static multileaf collimator field compensation

The optimum intensities for multiple static multileaf collimator field compensation

Quality assurance and dosimetric analysis of intensity modulation radiotherapy using compensators for head and neck cancers

A simulation of the effects of set-up error and changes in breast volume on conventional and intensity-modulated treatments in breast radiotherapy

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