Monte Carlo simulations of the imaging performance of metal plate/phosphor screens used in radiotherapy

Kausch, C.; Schreiber, B.; Kreuder, F.; Schmidt, Rainer; Dössel, Olaf

doi:10.1118/1.598727

Cited by 59 publications

(69 citation statements)

References 27 publications

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“…(The performance of MV imaging systems operated in the absence of an overlying metal plate has been previously examined.) 35,36 Also note that a reflector with negligible radiation attenuation was introduced to provide desirable optical properties and was modeled in the simulation with a zero mass attenuation coefficient for traversing x rays. Two extreme cases for the reflector were examined: one with 100% absorptivity and 0% reflectivity (referred to as "black"), and the other with 0% absorptivity and 100% reflectivity (referred to as "mirror").…”

Section: A Converter Designs Examined In the Studymentioning

confidence: 99%

Theoretical investigation of the design and performance of a dual energy (kV and MV) radiotherapy imager

et al. 2015

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Purpose: In modern radiotherapy treatment rooms, megavoltage (MV) portal imaging and kilovoltage (kV) cone-beam CT (CBCT) imaging are performed using various active matrix flat-panel imager (AMFPI) designs. To expand the clinical utility of MV and kV imaging, MV AMFPIs incorporating thick, segmented scintillators and, separately, kV imaging using a beam's eye view geometry have been investigated by a number of groups. Motivated by these previous studies, it is of interest to explore to what extent it is possible to preserve the benefits of kV and MV imaging using a single AMFPI design, given the considerably different x ray energy spectra used for kV and MV imaging. In this paper, considerations for the design of such a dual energy imager are explored through examination of the performance of a variety of hypothetical AMFPIs based on x ray converters employing segmented scintillators. Methods: Contrast, noise, and contrast-to-noise ratio performances were characterized through simulation modeling of CBCT imaging, while modulation transfer function, Swank factor, and signal performance were characterized through simulation modeling of planar imaging. The simulations were based on a previously reported hybrid modeling technique (accounting for both radiation and optical effects), augmented through modeling of electronic additive noise. All designs employed BGO scintillator material with thicknesses ranging from 0.25 to 4 cm and element-to-element pitches ranging from 0.508 to 1.016 mm. A series of studies were performed under both kV and MV imaging conditions to determine the most advantageous imager configuration (involving front or rear x ray illumination and use of a mirror or black reflector), converter design (pitch and thickness), and operating mode (pitch-binning combination). Results: Under the assumptions of the present study, the most advantageous imager design was found to employ rear illumination of the converter in combination with a black reflector, incorporate a BGO converter with a 0.508 mm pitch and a 2 cm thickness, and operate at full resolution for kV imaging and 2 × 2 binning mode for MV imaging. Such a dual energy imager design should provide soft tissue visualization at low, clinically practical doses under MV conditions, while helping to preserve the high spatial resolution and high contrast offered by kV imaging. Conclusions: The authors' theoretical investigation suggests that a dual energy imager capable of largely preserving the desirable characteristics of both kV and MV imaging is feasible. Such an imager, when coupled to a dual energy radiation source, could facilitate simplification of current treatment room imaging systems (as well as their associated quality assurance), and facilitate more precise integration of kV and MV imaging information by virtue of reduced geometric uncertainties. C 2015 American Association of Physicists in Medicine. [http://dx

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Section: A Converter Designs Examined In the Studymentioning

confidence: 99%

Theoretical investigation of the design and performance of a dual energy (kV and MV) radiotherapy imager

et al. 2015

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“…Kihlén et al ( 16 ) reported that a metal with an atomic number around 26–29 would be an optimal material for a metal screen with regard to quality after measuring the scattered to primary dose ratio. On the other hand, Kausch et al ( 17 ) reported that metals with a high atomic number perform better than lighter metals in maximizing the detective quantum efficiency using Monte Carlo simulation. In the future, investigation of the optimal thickness or material of a filter to be used would further improve the image quality of both standard and bone‐enhanced portal images.…”

Section: Discussionmentioning

confidence: 99%

Effectiveness of the single‐shot dual‐energy subtraction technique for portal images

Fujita

Morimi

Yamaguchi

et al. 2011

J Applied Clin Med Phys

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The aim of the present study was to evaluate the clinical efficacy of the single‐shot dual‐energy subtraction technique for obtaining portal images. We prepared two storage phosphor plates for this study. A 1 mm thick tungsten sheet was placed between the two storage phosphor plates. A single use of the double‐exposure technique provides two portal images simultaneously (i.e., a standard image and a low‐contrast image), using the same patient position and with no additional radiation delivered to the patient. A bone‐enhanced image is created by image subtraction between these two images. For evaluation of clinical efficacy, three treatment sites — the brain, lung, and pelvis — were imaged. Ten sets of images were obtained for each site, and five landmarks were selected for each treatment site. The visibility of each landmark and the ease of overall verification for the selected treatment sites were assessed separately for the standard and bone‐enhanced images. Four observers consisting of one radiation oncologist and three radiation therapists participated in the present study. For most of the landmarks studied, the bone‐enhanced images were significantly superior to the standard images. Regarding the ease of overall verification, the bone‐enhanced images were significantly superior to the standard images at all sites. The p‐values of mean rating for the brain, lung, and pelvis were 0.002, 0.012, and 0.003, respectively. The bone‐enhanced images obtained using our technique increased the image quality in terms of bone visibility, and are considered useful for routine clinical practice.PACS number: 87.56.Da

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“…To simulate stages 1-3, a Monte-Carlo model is used, similar to that used by Kausch et al [7]. X-ray absorption probabilities are generated using the EGSnrc software [8].…”

Section: Modeling Methodsmentioning

confidence: 99%

Organic semiconductor devices for X-ray imaging

Blakesley

Keivanidis

Campoy‐Quiles

et al. 2007

Nuclear Instruments and Methods in Physics Research Section A:

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Monte Carlo simulations of the imaging performance of metal plate/phosphor screens used in radiotherapy

Cited by 59 publications

References 27 publications

Theoretical investigation of the design and performance of a dual energy (kV and MV) radiotherapy imager

Theoretical investigation of the design and performance of a dual energy (kV and MV) radiotherapy imager

Effectiveness of the single‐shot dual‐energy subtraction technique for portal images

Organic semiconductor devices for X-ray imaging

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