A simplified model of the source channel of the Leksell Gamma Knife®: testing multisource configurations with PENELOPE

Aldweri, Feras M.; Lallena, A. M.

doi:10.1088/0031-9155/49/15/009

Cited by 21 publications

(16 citation statements)

References 10 publications

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“…1 and 17. PENELOPE has been applied to many different problems [18][19][20][21][22][23][24][25] and has been validated extensively. [26][27][28] PENE-LOPE was adapted to the specific requirements of the MANTIS simulation using PENEASY, a generic main program and accessory routines that allow easy configuration of PENELOPE.…”

Section: Iia Physics Modelsmentioning

confidence: 99%

Anisotropic imaging performance in breast tomosynthesis

et al. 2007

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We describe the anisotropy in imaging performance caused by oblique x-ray incidence in indirect detectors for breast tomosynthesis based on columnar scintillator screens. We use MANTIS, a freely available combined x-ray, electron, and optical Monte Carlo transport package which models the indirect detection processes in columnar screens, interaction by interaction. The code has been previously validated against published optical distributions. In this article, initial validation results are provided concerning the blur for particular designs of phosphor screens for which some details with respect to the columnar geometry are available from scanning electron microscopy. The polyenergetic x-ray spectrum utilized comes from a database of experimental data for three different anode/filter/kVp combinations: Mo/Mo at 28 kVp, Rh/Rh at 28 kVp, and W/Al at 42 kVp. The x-ray spectra were then filtered with breast tissue (3, 4, and 6 cm thickness), compression paddle, and support base, according to the oblique paths determined by the incidence angle. The composition of the breast tissue was 50%/50% adipose/glandular tissue mass ratio. Results are reported on the pulse-height statistics of the light output and on spatial blur, expressed as the response of the detector to a pencil beam with a certain incidence angle. Results suggest that the response is nonsymmetrical and that the resolution properties of a tomosynthesis system vary significantly with the angle of x-ray incidence. In contrast, it is found that the noise due to the variability in the number of light photons detected per primary x-ray interaction changes only a few percent. The anisotropy in the response is not less in screens with absorptive backings while the noise introduced by variations in the depth-dependent light output and optical transport is larger. The results suggest that anisotropic imaging performance across the detector area can be incorporated into reconstruction algorithms for improving the image quality of breast tomosynthesis. This study also demonstrates that the assessment of image quality of breast tomosynthesis systems requires a more complete description of the detector response beyond local, center measurements of resolution and noise that assume some degree of symmetry in the detector performance.

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Section: Iia Physics Modelsmentioning

confidence: 99%

Anisotropic imaging performance in breast tomosynthesis

et al. 2007

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“…2 that is published and freely distributed with the PENELOPE code by the Nuclear Energy Agency ͑NEA͒. PENELOPE has been applied to many problems [5][6][7][8][9][10][11][12] and has been validated extensively. [13][14][15] PENELOPE was adapted to the specific requirements of the MANTIS simulation using PENEASY, 42 a generic main program and accessory routines that allow easy configuration of PENELOPE.…”

Section: A Physics Modelsmentioning

confidence: 99%

Anisotropic imaging performance in indirect x-ray imaging detectors

Badano¹,

Kyprianou²,

Sempau³

2006

Med. Phys.

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We report on the variability in imaging system performance due to oblique x-ray incidence, and the associated transport of quanta (both x rays and optical photons) through the phosphor, in columnar indirect digital detectors. The analysis uses MANTIS, a combined x-ray, electron, and optical Monte Carlo transport code freely available. We describe the main features of the simulation method and provide some validation of the phosphor screen models considered in this work. We report x-ray and electron three-dimensional energy deposition distributions and point-response functions (PRFs), including optical spread in columnar phosphor screens of thickness 100 and 500 microm, for 19, 39, 59, and 79 keV monoenergetic x-ray beams incident at 0 degrees, 10 degrees, and 15 degrees. In addition, we present pulse-height spectra for the same phosphor thickness, x-ray energies, and angles of incidence. Our results suggest that the PRF due to the phosphor blur is highly nonsymmetrical, and that the resolution properties of a columnar screen in a tomographic, or tomosynthetic imaging system varies significantly with the angle of x-ray incidence. Moreover, we find that the noise due to the variability in the number of light photons detected per primary x-ray interaction, summarized in the information or Swank factor, is somewhat independent of thickness and incidence angle of the x-ray beam. Our results also suggest that the anisotropy in the PRF is not less in screens with absorptive backings, while the noise introduced by variations in the gain and optical transport is larger. Predictions from MANTIS, after additional validation, can provide the needed understanding of the extent of such variations, and eventually, lead to the incorporation of the changes in imaging performance with incidence angle into the reconstruction algorithms for volumetric x-ray imaging systems.

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“…Previously, numerous studies were done to analyze the accuracy of plugging in Gamma Knife 7 , 8 , 9 , 10 . There are a set of Monte Carlo (MC) studies which were successfully used for simulating Gamma Knife sources and units itself, including plugging patterns 2 , 7 , 10 , 11 , 12 , 13 , 14 , 15 . Cheung et al (7) employed Monte Carlo general‐purpose code EGS4 implementing PRESTA (parameter reduced electron‐step transport algorithm) algorithm and GAFCHROMIC films (Type MD 55) 16 , 17 to verify the accuracy of LGP TPS when plugged collimators were used.…”

Section: Introductionmentioning

confidence: 99%

MAGAT gel and EBT2 film‐based dosimetry for evaluating source plugging‐based treatment plan in Gamma Knife stereotactic radiosurgery

Natanasabapathi

Subbiah

Kale

et al. 2012

J Applied Clin Med Phys

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This work illustrates a procedure to assess the overall accuracy associated with Gamma Knife treatment planning using plugging. The main role of source plugging or blocking is to create dose falloff in the junction between a target and a critical structure. We report the use of MAGAT gel dosimeter for verification of an experimental treatment plan based on plugging. The polymer gel contained in a head‐sized glass container simulated all major aspects of the treatment process of Gamma Knife radiosurgery. The 3D dose distribution recorded in the gel dosimeter was read using a 1.5T MRI scanner. Scanning protocol was: CPMG pulse sequence with 8 equidistant echoes, TR=7 s, echo step=14 ms, pixel size=0.5 mm x 0.5 mm, and slice thickness of 2 mm. Using a calibration relationship between absorbed dose and spin‐spin relaxation rate (R2), we converted R2 images to dose images. Volumetric dose comparison between treatment planning system (TPS) and gel measurement was accomplished using an in‐house MATLAB‐based program. The isodose overlay of the measured and computed dose distribution on axial planes was in close agreement. Gamma index analysis of 3D data showed more than 94% voxel pass rate for different tolerance criteria of 3%/2 mm, 3%/1 mm and 2%/2 mm. Film dosimetry with GAFCHROMIC EBT 2 film was also performed to compare the results with the calculated TPS dose. Gamma index analysis of film measurement for the same tolerance criteria used for gel measurement evaluation showed more than 95% voxel pass rate. Verification of gamma plan calculated dose on account of shield is not part of acceptance testing of Leksell Gamma Knife (LGK). Through this study we accomplished a volumetric comparison of dose distributions measured with a polymer gel dosimeter and Leksell GammaPlan (LGP) calculations for plans using plugging. We propose gel dosimeter as a quality assurance (QA) tool for verification of plug‐based planning.PACS number: 87.53.Ly, 87.55.‐x, 87.56.N‐

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A simplified model of the source channel of the Leksell Gamma Knife®: testing multisource configurations with PENELOPE

Cited by 21 publications

References 10 publications

Anisotropic imaging performance in breast tomosynthesis

Anisotropic imaging performance in breast tomosynthesis

Anisotropic imaging performance in indirect x-ray imaging detectors

MAGAT gel and EBT2 film‐based dosimetry for evaluating source plugging‐based treatment plan in Gamma Knife stereotactic radiosurgery

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