An algorithm for detection of couch-beam intersection

Buckle, A.

doi:10.1016/j.meddos.2005.01.001

Cited by 8 publications

(3 citation statements)

References 6 publications

(3 reference statements)

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“…An incident gantry angle that avoided penetration of the support rails by the beam was calculated by using a sophisticated planning protocol. However, Buckle, by using a computer program, has predicted that the treatment field is also significantly attenuated by other parts of the couch 1 . In addition, the rails on both sides and in the middle of a couch can impede beam penetration.…”

mentioning

confidence: 99%

Impact of radiation attenuation by a carbon fiber couch on patient dose verification

Chou

Liao

et al. 2017

Sci Rep

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The aim of this study was to understand the difference between the measured and calculated irradiation attenuations obtained using two algorithms and to identify the influence of couch attenuation on patient dose verification. We performed eight tests of couch attenuation with two photon energies, two longitudinal couch positions, and two rail positions. The couch attenuation was determined using a radiation treatment planning system. The measured and calculated attenuations were compared. We also performed 12 verifications of head-and-neck and rectum cases by using a Delta phantom. The dose deviation (DD), distance to agreement (DTA), and gamma index of pencil-beam convolution (PBC) verifications were nearly the same. The agreement was least consistent for the anisotropic analytical algorithm (AAA) without the couch for the head-and-neck case, in which the DD, DTA, and gamma index were 74.4%, 99.3%, and 89%, respectively; for the rectum case, the corresponding values were 56.2%, 95.1%, and 92.4%. We suggest that dose verification should be performed using the following three metrics simultaneously: DD, DTA, and the gamma index.

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confidence: 99%

Impact of radiation attenuation by a carbon fiber couch on patient dose verification

Chou

Liao

et al. 2017

Sci Rep

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“…116 More recently, software methods using a graphical user interface separate from the TPS have been developed. 117 As IMRT became more widely used with larger numbers of equally spaced coplanar beams, it became apparent that intersections with absorbing parts of the couch were common unless this was detected in advance and alterations to the treatment plan were made. In one study, either frame positions (i.e., rails) were moved or gantry angles were changed to avoid the intersection.…”

Section: A Couch Top Avoidancementioning

confidence: 99%

Dosimetric effects caused by couch tops and immobilization devices: Report of AAPM Task Group 176

et al. 2014

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The dosimetric impact from devices external to the patient is a complex combination of increased skin dose, reduced tumor dose, and altered dose distribution. Although small monitor unit or dose corrections are routinely made for blocking trays, ion chamber correction factors, e.g., accounting for temperature and pressure, or tissue inhomogeneities, the dose perturbation of the treatment couch top or immobilization devices is often overlooked. These devices also increase skin dose, an effect which is also often ignored or underestimated. These concerns have grown recently due to the increased use of monolithic carbon fiber couch tops which are optimal for imaging for patient position verification but cause attenuation and increased skin dose compared to the "tennis racket" style couch top they often replace. Also, arc delivery techniques have replaced stationary gantry techniques which cause a greater fraction of the dose to be delivered from posterior angles. A host of immobilization devices are available and used to increase patient positioning reproducibility, and these also have attenuation and skin dose implications which are often ignored. This report of Task Group 176 serves to present a survey of published data that illustrates the magnitude of the dosimetric effects of a wide range of devices external to the patient. The report also provides methods for modeling couch tops in treatment planning systems so the physicist can accurately compute the dosimetric effects for indexed patient treatments. Both photon and proton beams are considered. A discussion on avoidance of high density structures during beam planning is also provided. An important aspect of this report are the recommendations the authors make to clinical physicists, treatment planning system vendors, and device vendors on how to make measurements of surface dose and attenuation and how to report these values. For the vendors, an appeal is made to work together to provide accurate couch top models in planning systems.

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“…In general, tabletop designs can be divided into two main families: support bar tables and homogenous tables. The former consist of a thin carbon fibre or tennis racket insert which is combined with more solid (adjustable) supporting bars underneath (Gillis et al 2005, Buckle 2005). The latter consist of a thicker homogenous foam sandwiched between two carbon layers without any support bars.…”

Section: Introductionmentioning

confidence: 99%

Absorption measurements on a new cone beam CT and IMRT compatible tabletop for use in external radiotherapy

2009

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With the development of intensity-modulated radiotherapy (IMRT), intensity-modulated arc therapy (IMAT), volumetric single arc therapy (RapidArc) and cone beam CT (CBCT) in 3D conformal radiotherapy, a need for new homogeneous treatment tabletops has evolved. Therefore, a new homogenous carbon fibre rotatable treatment tabletop Contesse has been developed. The intension was to create a CT compatible treatment tabletop accommodating all the standard treatment areas without add-on devises or the need to reconfigure the tabletop in everyday practice. At the same time, the absorption was sought to be minimized. Measurements of absorption with an ionization chamber have been performed for the main treatment geometries at normal and oblique angles together with build-up measurements at normal incidence. Absorption and build-up properties were shown to be comparable to those of other treatment tabletops with similar fixation devices. No artefacts from the tabletop are seen on CBCT scans. In order to reveal the absorption characteristics of tabletops, careful measurements at oblique angles including fixation devices on all clinically used tabletops must be performed. The Contesse tabletop is CBCT compatible, has acceptable absorption and is presently being used in the clinic for all patients, including IMRT and kilovoltage CBCT.

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An algorithm for detection of couch-beam intersection

Cited by 8 publications

References 6 publications

Impact of radiation attenuation by a carbon fiber couch on patient dose verification

Impact of radiation attenuation by a carbon fiber couch on patient dose verification

Dosimetric effects caused by couch tops and immobilization devices: Report of AAPM Task Group 176

Absorption measurements on a new cone beam CT and IMRT compatible tabletop for use in external radiotherapy

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