Patient-specific dosimetry of conventional and intensity modulated radiation therapy using a novel full Monte Carlo phase space reconstruction method from electronic portal images

Jarry, G; Verhaegen, Frank

doi:10.1088/0031-9155/52/8/016

Cited by 27 publications

(17 citation statements)

References 49 publications

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“…38͒ and even by the patient/phantom placed in the beam. 39 A further development for improving MC-based kernel generation is to take the variation of the incident energy spectra into consideration. Kernels are created in terms of the energy spectra of open and blocked MLC fields and depend on the radial distance from the central axis.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo-based adaptive EPID dose kernel accounting for different field size responses of imagers

et al. 2009

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The aim of this study is to present an efficient method to generate imager-specific Monte Carlo ͑MC͒-based dose kernels for amorphous silicon-based electronic portal image device dose prediction and determine the effective backscattering thicknesses for such imagers. EPID field sizedependent responses were measured for five matched Varian accelerators from three institutions with 6 MV beams at the source to detector distance ͑SDD͒ of 105 cm. For two imagers, measurements were made with and without the imager mounted on the robotic supporting arm. Monoenergetic energy deposition kernels with 0-2.5 cm of water backscattering thicknesses were simultaneously computed by MC to a high precision. For each imager, the backscattering thickness required to match measured field size responses was determined. The monoenergetic kernel method was validated by comparing measured and predicted field size responses at 150 cm SDD, 10ϫ 10 cm 2 multileaf collimator ͑MLC͒ sliding window fields created with 5, 10, 20, and 50 mm gaps, and a head-and-neck ͑H&N͒ intensity modulated radiation therapy ͑IMRT͒ patient field. Field size responses for the five different imagers deviated by up to 1.3%. When imagers were removed from the robotic arms, response deviations were reduced to 0.2%. All imager field size responses were captured by using between 1.0 and 1.6 cm backscatter. The predicted field size responses by the imager-specific kernels matched measurements for all involved imagers with the maximal deviation of 0.34%. The maximal deviation between the predicted and measured field size responses at 150 cm SDD is 0.39%. The maximal deviation between the predicted and measured MLC sliding window fields is 0.39%. For the patient field, gamma analysis yielded that 99.0% of the pixels have ␥ Ͻ 1 by the 2%, 2 mm criteria with a 3% dose threshold. Tunable imager-specific kernels can be generated rapidly and accurately in a single MC simulation. The resultant kernels are imager position independent and are able to predict fields with varied incident energy spectra and a H&N IMRT patient field. The proposed adaptive EPID dose kernel method provides the necessary infrastructure to build reliable and accurate portal dosimetry systems.

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Section: Introductionmentioning

confidence: 99%

Monte Carlo-based adaptive EPID dose kernel accounting for different field size responses of imagers

et al. 2009

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“…The dose calculated within the patient model was then compared to the treatment plan 95,96 . A 3D dose calculation but using comprehensive Monte Carlo simulations has also been reported 97 . Another algorithm requires both non-transit and transit EPID images to determine the transmission through the patient.…”

Section: Transit Dosimetrymentioning

confidence: 99%

Epid Dosimetry

Greer

Vial

Rosenfeld³

et al. 2011

AIP Conference Proceedings

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“…However an increased interest is nowadays in using EPIDs for dosimetric applications such as: pre-treatment fluence verification for intensity modulated radiation therapy (IMRT) [33][34][35], transit dosimetry [26,28,30], portal dose verification during treatment [6,7,9,14,38] and 3D dose reconstruction [18,22].…”

Section: Introductionmentioning

confidence: 99%

“…Several different EPID systems have been utilized, including scanning liquid ion chambers, CCD-based camera systems and amorphous silicon (a-Si) flat-panel detectors [5,10,14,16,18,22,27,35,38]. The a-Si EPID has shown good characteristics for dosimetric purpose, it has a linear response to dose and dose rate and it is stable with time [15], it can acquire images in real-time at a high frame rate and it was also demonstrated that the a-Si EPID signal can be calibrated in terms of absolute absorbed dose [16].…”

Section: Introductionmentioning

confidence: 99%

In patient dose reconstruction using a cine acquisition for dynamic arc radiation therapy

Piermattei

Fidanzio

Azario

et al. 2009

Med Biol Eng Comput

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An amorphous silicon (a-Si) electronic portal imaging device (EPID) was implemented to perform transit in vivo dosimetry for dynamic conformal arc therapy (DCAT). A set of images was acquired for each arc irradiation using the EPID cine acquisition mode, that supplies a frame acquisition rate of one image every 1.66 s, with a monitor unit rate equal to 100 UM/min. In these conditions good signal stability, +/-1% (2SD) evaluated during 3 months, signal reproducibility within +/-0.8% (2SD) and linearity with dose and dose rate within +/-1% (2SD) were obtained. The transit signal, S (t), due to the transmitted radiotherapy beam below a solid phantom, measured by the EPID cine acquisition mode was used to determine, (1) a set of correlation functions, F(w, L), defined as the ratio between S (t) and the dose at half thickness, D (m), measured in solid water phantoms of different thicknesses, w and with square fields of side L, (2) a set of factors, f(d, L), that take into account the different x-ray scatter contribution from the phantom to the S (t) signal as a function of the variation, d, of the air gap between the phantom and the EPID. The reconstruction of the isocenter dose, D (iso), for DCAT was obtained convolving the transit signal values, obtained at different gantry angles, with the respective reconstruction factors determined by a house-made software. The method was applied to a first patient and the results show that the reconstructed D (iso) values can be obtained with an accuracy within +/-5%. In conclusion, it was assessed that an a-Si EPID with the cine acquisition mode is suitable to perform transit in vivo dosimetry for the DCAT therapy.

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Patient-specific dosimetry of conventional and intensity modulated radiation therapy using a novel full Monte Carlo phase space reconstruction method from electronic portal images

Cited by 27 publications

References 49 publications

Monte Carlo-based adaptive EPID dose kernel accounting for different field size responses of imagers

Monte Carlo-based adaptive EPID dose kernel accounting for different field size responses of imagers

Epid Dosimetry

In patient dose reconstruction using a cine acquisition for dynamic arc radiation therapy

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