Static multileaf collimator for fast-neutron therapy.

abstract：PURPOSE:The purpose of this study is to quantify the change in monthly VMAT quality assurance (QA) and determine the tests to maintain consistent delivery with a baseline. METHODS:VMAT monthly QA has been performed for over 14 months on two Elekta Synergy LINACs. A baseline was established at acceptance and the monthl...

journal_title：Medical physics

authors： Stenbeck J,Oves S,Gebreamlak W,Alkhatib H

更新日期：2012-06-01 00:00:00

abstract：:In Monte Carlo simulations of light transport in tissues, a grid system is set up to score physical quantities. This study of cylindrically symmetrical problems found that the optimized radial and angular positions for the averaged physical quantities in each grid element are off-center. The error of the extrapolated ...

journal_title：Medical physics

authors： Wang L,Jacques SL

更新日期：1994-07-01 00:00:00

abstract：:Modern linear accelerators contain multiple isocentres, defined by the mechanical motions of gantry, collimator and table. Isocentre localization for these motions has been performed using film and manual evaluations which have difficulty in relating the individual motions. To address these limitations, we have develo...

journal_title：Medical physics

authors： Heaton R,Smale J,Norrlinger B,Wang Y,van Prooijen M,Islam M

更新日期：2008-07-01 00:00:00

abstract：:When parallel-plate chambers are used for dosimetry in electron fields, the AAPM dosimetry protocol recommends a value of 1.0 for the replacement correction factor, P(repl),pp,E, until further data become available. Here, P(repl),pp,E for five commercially available parallel-plate chambers was measured as a function o...

journal_title：Medical physics

authors： Reft CS,Kuchnir FT

更新日期：1991-11-01 00:00:00

abstract：:We applied Monte Carlo methods for the simulation of x-ray scattering in water phantoms. The phantom thickness was varied from 5 to 20 cm, and the monoenergetic incident x rays were varied from 15 to 100 keV. Eight screen pairs and a total absorption system were used as x-ray receptors. We determined the angular, spec...

journal_title：Medical physics

authors： Chan HP,Doi K

更新日期：1985-03-01 00:00:00

abstract：:Many new models of 125I seeds are being introduced, mainly due to the increase in prostate seed implants. We have evaluated the SourceTech Medical (STM), model STM1251, 125I seed using thermoluminescent dosimeters (TLDs) in a solid water phantom. TLD cubes, LiF TLD-100, with dimension 1 mm on each edge, were irradiate...

journal_title：Medical physics

authors： Chiu-Tsao ST,Duckworth TL,Hsiung CY,Li Z,Williamson J,Patel NS,Harrison LB

更新日期：2003-07-01 00:00:00

abstract：:In external beam radiotherapy, electronic portal imaging becomes more and more an indispensable tool for the verification of the patient setup. For the safe clinical introduction of high dose conformal radiotherapy like intensity modulated radiation therapy, on-line patient setup verification is a prerequisite to ensu...

journal_title：Medical physics

authors： Vetterli D,Riem H,Aebersold DM,Greiner RH,Manser P,Cossmann P,Kemmerling L,Born EJ,Mini R

更新日期：2004-04-01 00:00:00

abstract：PURPOSE:Accurate segmentation of lungs with severe interstitial lung disease (ILD) in thoracic computed tomography (CT) is an important and difficult task in the development of computer-aided diagnosis (CAD) systems. Therefore, we developed in this study a texture analysis-based method for accurate segmentation of lung...

journal_title：Medical physics

authors： Wang J,Li F,Li Q

更新日期：2009-10-01 00:00:00

abstract：PURPOSE:The local depth dose gradient and the displacement correction factor for Farmer-type ionization chambers are quantified for reference dosimetry at shallow depth in single-layer scanned proton fields. METHOD:Integrated radial profiles as a function of depth (IRPDs) measured at three proton therapy centers were ...

journal_title：Medical physics

authors： Palmans H,Medin J,Trnková P,Vatnitsky S

更新日期：2020-12-01 00:00:00

abstract：:Nuclear Magnetic Resonance (NMR) permits the noninvasive measurement of blood flow signals unimpaired by clothes, bandages, casts, etc. The cylindrical crossed-coil NMR blood flowmeter was used to measure blood flow through a cross-section of the human forearm. Two calibration procedures are described: one for pulsati...

journal_title：Medical physics

authors： Salles-Cunha SX,Halbach RE,Battocletti JH,Sances A Jr

更新日期：1981-07-01 00:00:00

abstract：:A method is described for calibration of 192Ir high-dose-rate (HDR) brachytherapy afterloading systems. Since NIST does not offer calibration of ionization chambers with the gamma-ray spectrum of iridium-192, an interpolation procedure is employed, using calibrations above (137Cs, 662 keV) and below (250 kVcp, 146-keV...

journal_title：Medical physics

authors： Goetsch SJ,Attix FH,Pearson DW,Thomadsen BR

更新日期：1991-05-01 00:00:00

abstract：PURPOSE:Currently, in clinical practice of intensity-modulated proton therapy (IMPT), the influence of the minimum monitor unit (MU) constraint is taken into account through postprocessing after the optimization is completed. This may degrade the plan quality and plan robustness. This study aims to mitigate the impact ...

journal_title：Medical physics

authors： Shan J,An Y,Bues M,Schild SE,Liu W

更新日期：2018-01-01 00:00:00

abstract：:Variation of the photoactivation rate across radiation fields of three different bremsstrahlung beams of two medical accelerators has been measured, making use of the photonuclear reactions in natural indium probes: 115In(y,y')115mIn and 115In(y,n)114mIn. The third nuclear reaction, 115In(n,y)116mIn, was used to detec...

journal_title：Medical physics

authors： Krmar M,Slivka J,Bikit I,Conkić L,Rudić A

更新日期：1999-04-01 00:00:00

abstract：PURPOSE:To assess the temporal and spatial accuracy of the GateCT™ system (VisionRT, London, UK), a recently released respiratory tracking system for 4DCT, under both ideal and nonideal respiratory conditions. METHODS:Three experiments were performed by benchmarking and comparing its results with the ground-truth inpu...

journal_title：Medical physics

authors： Kauweloa KI,Ruan D,Park JC,Sandhu A,Kim GY,Pawlicki T,Watkins WT,Song B,Song WY

更新日期：2012-01-01 00:00:00

abstract：:Treatment simulation is usually performed with a conventional simulator using kV X-rays or with a computed tomography (CT) simulator before the treatment course begins. The purpose is to verify patient setup under the same conditions as for treatment planning. Systematic (preparation) setup errors can be introduced by...

journal_title：Medical physics

authors： Wu Q,Lockman D,Wong J,Yan D

更新日期：2007-05-01 00:00:00

abstract：:We attempt to select an optimal value of regularization parameter in the optimization problems for intensity-modulated radiotherapy which are solved using a variational regularization technique. We apply to inverse treatment planning the L-curve method which was developed to determine the regularization parameter in t...

journal_title：Medical physics

authors： Chvetsov AV

更新日期：2005-08-01 00:00:00

abstract：:A computer program was implemented to predict mammography x-ray beam parameters in the range 20-40 kV for Mo/Mo, Mo/Rh, Rh/Rh, and W/Al target/filter combinations. The computation method used to simulate mammography x-ray spectra is based on the Boone et al. model. The beam quality parameters such as the half-value la...

journal_title：Medical physics

authors： Kharrati H,Zarrad B

更新日期：2003-10-01 00:00:00

abstract：:The performance of a diode array (Profiler) was evaluated by comparing its enhanced dynamic wedge (EDW) profiles measured at various depths with point measurements using a 0.03 cm3 ionization chamber on a commercial linear accelerator. The Profiler, which covers a 22.5 cm width, was used to measure larger field widths...

journal_title：Medical physics

authors： Zhu TC,Ding L,Liu CR,Palta JR,Simon WE,Shi J

更新日期：1997-07-01 00:00:00

abstract：PURPOSE:Although robot-assisted coronary artery bypass grafting (RA-CABG) has gained more acceptance worldwide, its success still depends on the surgeon's experience and expertise, and the conversion rate to full sternotomy is in the order of 15%-25%. One of the reasons for conversion is poor pre-operative planning, wh...

journal_title：Medical physics

authors： Cho DS,Linte C,Chen EC,Bainbridge D,Wedlake C,Moore J,Barron J,Patel R,Peters T

更新日期：2012-03-01 00:00:00

abstract：PURPOSE:Periprocedural assessment of tissue perfusion by imaging methods could improve outcome control during treatment of peripheral vascular disease. Currently, endovascular revascularization treatments are assessed by planar angiography which only allows for qualitative inspection of blood flow in vessels. In this p...

journal_title：Medical physics

authors： Giordano M,Vonken EJ,Bertram M,Mali W,Viergever MA,Neukirchen C

更新日期：2012-03-01 00:00:00

abstract：PURPOSE:To develop an automatic segmentation algorithm integrating imaging information from computed tomography (CT), positron emission tomography (PET), and magnetic resonance imaging (MRI) to delineate target volume in head and neck cancer radiotherapy. METHODS:Eleven patients with unresectable disease at the tonsil...

journal_title：Medical physics

authors： Yang J,Beadle BM,Garden AS,Schwartz DL,Aristophanous M

更新日期：2015-09-01 00:00:00

abstract：PURPOSE:The collimator monitoring fill factor (CM-FF) introduced by Stelljes et al. (2017) and the FWHM fill factor (FWHM-FF) introduced by Gago-Arias et al. (2012) were determined using the measured photon fluence response functions of various 2D-arrays. The error detection capabilities of 2D-arrays were studied by co...

journal_title：Medical physics

authors： Stelljes TS,Poppinga D,Kretschmer J,Brodbek L,Looe HK,Poppe B

更新日期：2019-04-01 00:00:00

abstract：PURPOSE:Power spectral analysis in radiographic images is conventionally performed using a windowed overlapping averaging periodogram. This study describes an alternative approach using a multitaper technique and compares its performance with that of the standard method. This tool will be valuable in power spectrum est...

journal_title：Medical physics

authors： Wu G,Mainprize JG,Yaffe MJ

更新日期：2012-02-01 00:00:00

abstract：:Our purpose in this work was to assess the reliability of the calibration coefficient for magnetic resonance water proton chemical shift temperature mapping. Over a six month period, the calibration coefficient was measured 15 times in several different phantoms. A highly linear relationship between water proton chemi...

journal_title：Medical physics

authors： Wu T,Kendell KR,Felmlee JP,Lewis BD,Ehman RL

更新日期：2000-01-01 00:00:00

abstract：PURPOSE:To correlate the Cole relaxation frequencies obtained from measurements of the electrical properties of breast tissue to the presence or absence of cancer. METHODS:Four-lead impedance measurements were obtained on ex vivo specimens extracted during surgery from 187 volunteer patients. Data were acquired with a...

journal_title：Medical physics

authors： Gregory WD,Marx JJ,Gregory CW,Mikkelson WM,Tjoe JA,Shell J

更新日期：2012-07-01 00:00:00

abstract：:Based on direction from AAM Board of Directors, JMPLSC has redefined its scope and name. On November 4, 2011 the subcommittee renamed itself the Medical Physics Licensure and Regulatory Recognition Subcommittee. Its newly defined charge is to promote the protection of the public through the recognition of the professi...

journal_title：Medical physics

authors： Pizzutiello R

更新日期：2012-06-01 00:00:00

abstract：:Previous ultrasound tomography work conducted by our group showed a direct correlation between measured sound speed and physical density in vitro, and increased in vivo sound speed with increasing mammographic density, a known risk factor for breast cancer. Building on these empirical results, the purpose of this work...

journal_title：Medical physics

authors： Glide-Hurst CK,Duric N,Littrup P

更新日期：2008-09-01 00:00:00

abstract：:An important aspect of dual-energy (DE) x-ray image decomposition is the incorporation of noise reduction techniques to mitigate the amplification of quantum noise. This article extends cascaded systems analysis of imaging performance to DE imaging systems incorporating linear noise reduction algorithms. A general ana...

journal_title：Medical physics

authors： Richard S,Siewerdsen JH

更新日期：2008-02-01 00:00:00

abstract：:Ir-192 wires have been used in low-dose-rate brachytherapy for many years. Commercially available treatment planning systems approximate the dose rate distribution of the straight or curved wires applying the superposition principle using one of the following methods: (i) The wire is modeled as a set of point sources,...

journal_title：Medical physics

authors： van der Laarse R,Granero D,Pérez-Calatayud J,Meigooni AS,Ballester F

更新日期：2008-03-01 00:00:00

abstract：PURPOSE:High-spatial-resolution x-ray imaging in the few-ten-keV range is becoming increasingly important in several applications, such as small-animal imaging and phase-contrast imaging. The detector properties critically influence the quality of such imaging. Here the authors present a quantitative comparison of scin...

journal_title：Medical physics

authors： Larsson JC,Lundström U,Hertz HM

更新日期：2016-06-01 00:00:00