Journal ArticleDOI
Relative dosimetry using active matrix flat‐panel imager (AMFPI) technology
Youcef El-Mohri,Larry E. Antonuk,John Yorkston,K Jee,Manat Maolinbay,Kwok L. Lam,Jeffrey H. Siewerdsen +6 more
TLDR
In this article, the first examination of the use of active matrix flat-panel arrays for dosimetry in radiotherapy is reported, where an array consisting of 512 x 512 pixels with a pixel pitch of 508 microm giving an area of 26 x 26 cm2 is used.Abstract:
The first examination of the use of active matrix flat-panel arrays for dosimetry in radiotherapy is reported. Such arrays are under widespread development for diagnostic and radiotherapy imaging. In the current study, an array consisting of 512 x 512 pixels with a pixel pitch of 508 microm giving an area of 26 x 26 cm2 has been used. Each pixel consists of a light sensitive amorphous silicon (a-Si:H) photodiode coupled to an a-Si:H thin-film transistor. Data was obtained from the array using a dedicated electronics system allowing real-time data acquisition. In order to examine the potential of such arrays as quality assurance devices for radiotherapy beams, field profile data at photon energies of 6 and 15 MV were obtained as a function of field size and thickness of overlying absorbing material (solid water). Two detection configurations using the array were considered: a configuration (similar to the imaging configuration) in which an overlying phosphor screen is used to convert incident radiation to visible light photons which are detected by the photodiodes; and a configuration without the screen where radiation is directly sensed by the photodiodes. Compared to relative dosimetry data obtained with an ion chamber, data taken using the former configuration exhibited significant differences whereas data obtained using the latter configuration was generally found to be in close agreement. Basic signal properties, which are pertinent to dosimetry, have been investigated through measurements of individual pixel response for fluoroscopic and radiographic array operation. For signal levels acquired within the first 25% of pixel charge capacity, the degree of linear response with dose was found to be better than 99%. The independence of signal on dose rate was demonstrated by means of stability of pixel response over the range of dose rates allowed by the radiation source (80-400 MU/min). Finally, excellent long-term stability in pixel response, extending over a 2 month period, was observed.read more
Citations
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Journal ArticleDOI
A literature review of electronic portal imaging for radiotherapy dosimetry.
Wouter van Elmpt,L. N. McDermott,Sebastiaan M. J. J. G. Nijsten,M. Wendling,Philippe Lambin,Ben J. Mijnheer +5 more
TL;DR: As strategies evolve and commercial products become available, EPID dosimetry has the potential to become an accurate and efficient means of large-scale patient-specific IMRT dose verification for any radiotherapy department.
Journal ArticleDOI
Dosimetry tools and techniques for IMRT
TL;DR: The overall goal of this task group report is to provided a document that aids the physicist in the proper selection and use of the dosimetry tools available for IMRT QA and to provide a resource for physicists that describes Dosimetry measurement techniques for purposes of IMRT commissioning and measurement-based characterization or verification of IM RT treatment plans.
Journal ArticleDOI
The use of an aSi-based EPID for routine absolute dosimetric pre-treatment verification of dynamic IMRT fields.
TL;DR: The basic dosimetric characteristics of an aSi portal imager investigated are reproducible and self-consistent, lending itself to quality assurance measurements, and the acquisition mode is accurate in integrating all PD over a wide range of monitor units, provided detector saturation is avoided.
Patent
Cone-beam computed tomography with a flat-panel imager
TL;DR: In this paper, a cone-beam computer tomography system was proposed, where a computer is connected to a radiation source and the cone beam computerized tomography, wherein the computer receives the image of the object and based on the image sends a signal to the radiation source that controls the path of the radiation.
Journal ArticleDOI
Clinical use of electronic portal imaging: Report of AAPM Radiation Therapy Committee Task Group 58
Michael G. Herman,James M. Balter,David A. Jaffray,Kiarin P. McGee,Peter Munro,Shlomo Shalev,Marcel van Herk,John Wong +7 more
TL;DR: This report provides comprehensive information about the physics and technology of currently available EPID systems; a detailed discussion of the steps required for successful clinical implementation, based on accumulated experience; a review of software tools available and clinical use protocols to enhance EPID utilization; and specific quality assurance requirements for initial and continuing clinical use of the systems.
References
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Journal ArticleDOI
Water-equivalent plastic scintillation detectors for high-energy beam dosimetry: I. Physical characteristics and theoretical considerations
TL;DR: Application of Burlin cavity theory shows that the energy dependence of such detectors is expected to be better than the commonly used systems (ionization chambers, LiF thermoluminescent dosimeters, film and Si diodes).
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Water-equivalent plastic scintillation detectors for high-energy beam dosimetry: II. Properties and measurements.
TL;DR: Dose distributions in water, using miniature plastic scintillation detectors, have been measured for different high-energy photon and electron beams, showing that they have better spatial resolution than ionization chambers and have much less energy or depth dependence in electron fields due to the removal of the influence of the polarization effect.
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The generation of intensity-modulated fields for conformal radiotherapy by dynamic collimation
David J Convery,M E Rosenbloom +1 more
TL;DR: In this article, an algorithm was developed to calculate the collimator jaw motions required to generate intensity-modulated fields for use in conformal radiotherapy, which can be extended to 3D treatment plans and fields through the use of computer-controlled multileaf collimators.
Journal ArticleDOI
Empirical and theoretical investigation of the noise performance of indirect detection, active matrix flat-panel imagers (AMFPIs) for diagnostic radiology
Jeffrey H. Siewerdsen,Larry E. Antonuk,Youcef El-Mohri,John Yorkston,Weidong Huang,J. Boudry,Ian A. Cunningham +6 more
TL;DR: These theoretical predictions suggest that imagers of this general design incorporating a CsI: Tl intensifying screen can be optimized to provide detective quantum efficiency (DQE) superior to existing screen-film and storage phosphor systems for general radiography and mammography.
Journal ArticleDOI
Demonstration of megavoltage and diagnostic x-ray imaging with hydrogenated amorphous silicon arrays
Larry E. Antonuk,J. Boudry,Weidong Huang,Daniel L. McShan,E.J. Morton,John Yorkston,Michael J. Longo,Robert A. Street +7 more
TL;DR: Initial megavoltage and diagnostic-quality x-ray images taken with several arrays made with hydrogenated amorphous silicon, including the first examples of anatomical-phantom images are presented.
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