Determination of the quality index (Q) for photon beams at arbitrary field sizes.

abstract：PURPOSE:Recent recommendations of the International Commission on Radiological Protection state that the use of effective dose (E) for assessing patient exposure has severe limitations, though it can be kept for dose comparisons. In cardiology procedures, the equivalent dose (H(T)) is one of the most appropriate dose q...

journal_title：Medical physics

authors： Compagnone G,Ortolani P,Domenichelli S,Ovi V,Califano G,Dall'Ara G,Marzocchi A

更新日期：2011-04-01 00:00:00

abstract：:Due to practical limitations such as inter- and intraleaf transmission, nondivergent leaf end design, and leaf scatter, multileaf collimators (MLCs) are unable to accurately produce the ideal fluence patterns generated by inverse planning systems. Consequently, low dose regions receive substantially more radiation tha...

journal_title：Medical physics

authors： Popple RA,Fiveash JB,Brezovich IA

更新日期：2007-10-01 00:00:00

abstract：:The photon spectra in vacuum around four types of 192Ir HDR brachytherapy sources are calculated using the Monte Carlo code EGS4 and the most recent spectral information on 192Ir decay. The air-kerma strengths per unit activity are calculated based on the photon fluence around a bare 192Ir source and around each of fo...

journal_title：Medical physics

authors： Borg J,Rogers DW

更新日期：1999-11-01 00:00:00

abstract：PURPOSE:The limited-angle intrafractional verification (LIVE) system was developed to track tumor movement during stereotactic body radiation therapy (SBRT). However, the four-dimensional (4D) MV/kV imaging procedure results in additional radiation dose to patients. This study is to quantify imaging radiation dose from...

journal_title：Medical physics

authors： Ding GX,Zhang Y,Ren L

更新日期：2019-06-01 00:00:00

abstract：:Direct comparisons of the National Institute of Standards and Technology's (NIST) Ritz 20 kV to 100 kV standard free-air ionization chamber and a portable variable-length free-air ionization chamber designed by the University of Wisconsin-Madison Accredited Dosimetry Calibration Laboratory (UW-ADCL) were made on NISTs...

journal_title：Medical physics

authors： Coletti JG,Pearson DW,DeWerd LA,O'Brien CM,Lamperti PJ

更新日期：1997-08-01 00:00:00

abstract：PURPOSE:Arterial distensibility is a marker that can measure vessel wall functional and structural changes resulting from atherosclerosis with applications including estimation of mechanical properties of the wall. We sought to assess the feasibility of using magnetic resonance imaging (MRI) to include wall distensibil...

journal_title：Medical physics

authors： Canton G,Hippe DS,Sun J,Underhill HR,Kerwin WS,Tang D,Yuan C

更新日期：2012-10-01 00:00:00

abstract：PURPOSE:Wide-angle free-air chambers (WAFACs) are used as primary standard measurement devices for establishing the air-kerma strength of low-energy, low-dose rate brachytherapy seeds. The National Research Council of Canada (NRC) is commissioning a primary standard wide-angle free-air chamber (NRC WAFAC) to serve the ...

journal_title：Medical physics

authors： Shen H,Culberson WS,Ross CK

更新日期：2016-07-01 00:00:00

abstract：PURPOSE:To use the Monte Carlo code PENELOPE to study attenuation and tissue equivalence properties of a-Al2O3:C for OSL dosimetry. METHODS:Mass attenuation coefficients of α-Al2O3 and α-Al2O3:C with carbon percent weight concentrations from 1% to 150% were simulated with PENELOPE Monte Carlo code and compared to mass...

journal_title：Medical physics

authors： Nicolucci P,Schuch F

更新日期：2012-06-01 00:00:00

abstract：PURPOSE:To develop a real time dose monitoring and dose reconstruction tool to identify and quantify sources of errors during patient specific volumetric modulated arc therapy (VMAT) delivery and quality assurance. METHODS:The authors develop a VMAT delivery monitor tool called linac data monitor that connects to the ...

journal_title：Medical physics

authors： Tyagi N,Yang K,Gersten D,Yan D

更新日期：2012-12-01 00:00:00

abstract：:This paper proposes a new respiratory gated radiation treatment system that allows real-time tumor localization while avoiding invasive operation to a patient. The proposed system employs a three-dimensional (3D) ultrasound device, a 3D digital localizer, and a real-time image processing system. At the planning time, ...

journal_title：Medical physics

authors： Sawada A,Yoda K,Kokubo M,Kunieda T,Nagata Y,Hiraoka M

更新日期：2004-02-01 00:00:00

abstract：:A realistic photon beam model based on Monte Carlo simulation of clinical linear accelerators was implemented in a convolution/superposition dose calculation algorithm. A primary and an extra-focal sources were used in this beam model to represent the direct photons from the target and the scattered photons from other...

journal_title：Medical physics

authors： Liu HH,Mackie TR,McCullough EC

更新日期：1997-12-01 00:00:00

abstract：PURPOSE:This study developed and validated a Motion Artifact Quantification algorithm to automatically quantify the severity of motion artifacts on coronary computed tomography angiography (CCTA) images. The algorithm was then used to develop a Motion IQ Decision method to automatically identify whether a CCTA dataset ...

journal_title：Medical physics

authors： Ma H,Gros E,Baginski SG,Laste ZR,Kulkarni NM,Okerlund D,Schmidt TG

更新日期：2018-12-01 00:00:00

abstract：PURPOSE:Cone-beam CT (CBCT) images contain severe shading artifacts mostly due to scatter. Many algorithms have been proposed to alleviate this problem by data correction on projections. Sophisticated methods have also been designed to further improve the image quality when prior patient information is available. In th...

journal_title：Medical physics

authors： Fan Q,Niu T,Zhu L

更新日期：2012-06-01 00:00:00

abstract：:The performance of an indirect-detection, active matrix flat-panel imager (FPI) at diagnostic energies is reported in terms of measured and theoretical signal size, noise power spectrum (NPS), and detective quantum efficiency (DQE). Based upon a 1536 x 1920 pixel, 127 microns pitch array of a-Si:H thin-film transistor...

journal_title：Medical physics

authors： Siewerdsen JH,Antonuk LE,el-Mohri Y,Yorkston J,Huang W,Cunningham IA

更新日期：1998-05-01 00:00:00

abstract：PURPOSE:Radiation therapy is often delivered by multiple sequential treatment plans. For an accurate radiobiological evaluation of the overall treatment, fractionation corrections to each dose distribution must be applied before summing the three-dimensional dose matrix of each plan since the simpler approach of perfor...

journal_title：Medical physics

authors： Mavroidis P,Ferreira BC,Papanikolaou N,Lopes Mdo C

更新日期：2013-03-01 00:00:00

abstract：:The American Association of Physicists in Medicine recommends that the reference dose-rate distribution, used for treatment planning for low-energy photon brachytherapy sources in routine clinical use, must be based on at least two independent determinations: one using experimentally measured dose rates and one using ...

journal_title：Medical physics

authors： Chan GH,Nath R,Williamson JF,American Association of Physicists in Medicine.

更新日期：2004-05-01 00:00:00

abstract：:Neutron cross sections for nonelastic and elastic reactions on a range of elements have been evaluated for incident energies up to 150 MeV. These cross sections agree well with experimental cross section data for charged-particle production as well as neutron and photon production. Therefore they can be used to determ...

journal_title：Medical physics

authors： Chadwick MB,Barschall HH,Caswell RS,DeLuca PM,Hale GM,Jones DT,MacFarlane RE,Meulders JP,Schuhmacher H,Schrewe UJ,Wambersie A,Young PG

更新日期：1999-06-01 00:00:00

abstract：PURPOSE:The segmentation accuracy of medical images was improved by increasing the number of training samples using a local image warping technique. The performance of the proposed method was evaluated in the segmentation of breast masses, prostate and brain tumors, and lung nodules. METHODS:We propose a simple data a...

journal_title：Medical physics

authors： Liu H,Cao H,Song E,Ma G,Xu X,Jin R,Liu T,Liu L,Liu D,Hung CC

更新日期：2020-12-10 00:00:00

abstract：:Teletherapy with high linear energy transfer radiations (LET), perhaps more than with low LET types, requires careful beam collimation to limit effects to normal structures. Intensity modulated techniques may also hold promise in this regard. Accordingly, a remote computer-controlled, high-resolution multileaf collima...

journal_title：Medical physics

authors： Farr JB,Maughan RL,Yudelev M,Blosser E,Brandon J,Horste T,Forman JD

更新日期：2007-09-01 00:00:00

abstract：:When a beam-modifying filter such as a wedge or a compensator is placed in an x-ray beam, scattered photons are generated in the filter material. The magnitude of the dose contribution from these photons for a 4-MV x-ray beam was measured. At a distance of 30 cm from the filter, a copper sheet of 1-cm thickness produc...

journal_title：Medical physics

authors： Huang PH,Chin LM,Bjärngard BE

更新日期：1986-01-01 00:00:00

abstract：:In nuclear magnetic resonance (NMR) imaging by the zeugmatographic methods, there is a common and unified theoretical description. All forms of two-dimensional and three-dimensional imaging involve NMR data which trace various geometric representations, in reciprocal transform space, of the subject's spatially blurred...

journal_title：Medical physics

authors： King KF,Moran PR

更新日期：1984-01-01 00:00:00

abstract：PURPOSE:The objectives are: (i) assess the development of the impedance of some arteries during the first decades of life; (ii) determine the influence of pulse rate in arterial impedance; (iii) compare the structure of some arterial segments with optimized structures with respect to blood flow; and (iv) explain the el...

journal_title：Medical physics

authors： Silva C,Reis AH

更新日期：2014-06-01 00:00:00

abstract：:A new radiographic patient positioning technique developed for radiosurgery has been analyzed to show the effect of computed tomography (CT) slice thickness on the precision of target localization during treatment. The positioning technique establishes the pose of the patient's anatomy during treatment by comparing tr...

journal_title：Medical physics

authors： Murphy MJ

更新日期：1999-02-01 00:00:00

abstract：:Luminance scatter fractions were measured for patients and phantoms in various regions of the chest film. Scatter fractions were found to be highly variable, being quite high in the regions of the chest with a large equivalent tissue thickness (e.g. mediastinum, chest wall, and subdiaphragmatic areas). For example, ap...

journal_title：Medical physics

authors： Niklason LT,Sorenson JA,Nelson JA

更新日期：1981-09-01 00:00:00

abstract：PURPOSE:The aim of this study is to investigate the performance of Sentinel(™), a patient setup verification device based on a laser/camera system, when used on rigid-body phantoms. METHODS:The Sentinel system consists of a scanner unit, containing the laser and the camera, and surface-matching registration software. ...

journal_title：Medical physics

authors： Pallotta S,Marrazzo L,Ceroti M,Silli P,Bucciolini M

更新日期：2012-02-01 00:00:00

abstract：PURPOSE:Manual delineation of head and neck (H&N) organ-at-risk (OAR) structures for radiation therapy planning is time consuming and highly variable. Therefore, we developed a dynamic multiatlas selection-based approach for fast and reproducible segmentation. METHODS:Our approach dynamically selects and weights the a...

journal_title：Medical physics

authors： Haq R,Berry SL,Deasy JO,Hunt M,Veeraraghavan H

更新日期：2019-12-01 00:00:00

abstract：PURPOSE:To determine if NSCLC GTV CT textures can be predictive for tumor shrinkage after proton therapy with concurrent chemotherapy. METHODS:Simulation and weekly 4DCTs were obtained from 25 patients with locally advanced NSCLC treated by proton therapy at a 74 Gy dose level with concurrent chemotherapy. In-house de...

journal_title：Medical physics

authors： Hunter L,Chen Y,Zhang L,Liao Z,Dong L,Court L

更新日期：2012-06-01 00:00:00

abstract：:The purpose of this work is to investigate algorithms for the delivery of intensity-modulated fields using independent collimators (IC). Two heuristic algorithms are proposed to calculate jaw-setting sequences for arbitrary 2D intensity distributions. The first algorithm is based on searching the whole intensity matri...

journal_title：Medical physics

authors： Dai JR,Hu YM

更新日期：1999-12-01 00:00:00

abstract：PURPOSE:Dosimetry with ionization chambers in clinical ion beams for radiation therapy requires correction for recombination effects. However, common radiation protocols discriminate between initial and general recombination and provide no universal correction method for the presence of both recombination types in ion ...

journal_title：Medical physics

authors： Christensen JB,Tölli H,Bassler N

更新日期：2016-10-01 00:00:00

abstract：:Atomic Energy of Canada Limited 60Co teletherapy units have adjustable collimator hinges to adapt to source diameters from 0.75 to 2.50 cm. Adjustment of the collimator hinge to the manfacturer's settings can cause a loss of radiation field flatness as high as 20% for large fields. The recommended settings appear to c...

journal_title：Medical physics

authors： Heintz PH

更新日期：1975-03-01 00:00:00