Objective performance characteristics of a new asymmetric screen-film system.

abstract：:Intrafraction organ motion can limit the advantage of highly conformal dose techniques such as intensity modulated radiation therapy (IMRT) due to target position uncertainty. To ensure high accuracy in beam targeting, real-time knowledge of the target location is highly desired throughout the beam delivery process. T...

journal_title：Medical physics

authors： Mao W,Wiersma RD,Xing L

更新日期：2008-05-01 00:00:00

abstract：PURPOSE:State of the art to access radiofrequency (RF) heating near implants is computer modeling of the devices and solving Maxwell's equations for the specific setup. For a set of input parameters, a fixed result is obtained. This work presents a theoretical approach in the alternating current (ac) limit, which can p...

journal_title：Medical physics

authors： Ballweg V,Eibofner F,Graf H

更新日期：2011-10-01 00:00:00

abstract：:Generating an optimized radiation treatment plan requires understanding the factors affecting tumour control. Mathematical models of tumour dynamics may help in future studies of factors predicting tumor sensitivity to radiotherapy. In this study, a time-dependent differential model, incorporating biological cancer ma...

journal_title：Medical physics

authors： Campbell A,Davidson M,Lock M,Wong E

更新日期：2008-07-01 00:00:00

abstract：:The same calibration grade ionization chamber and electrometer were sequentially sent to all five currently AAPM Accredited Dosimetry Calibration Laboratories (ADCL). A Cesium-137 based check device was utilized to ensure chamber and electrometer factor constancy and showed a maximum deviation of 0.32% (typically less...

journal_title：Medical physics

authors： Blackwell CR,McCullough EC

更新日期：1992-01-01 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：PURPOSE:Optoacoustic imaging enables mapping the optical absorption of biological tissue using optical excitation and acoustic detection. Although most image-reconstruction algorithms are based on the assumption of a detector with an isotropic sensitivity, the geometry of the detector often leads to a response with spa...

journal_title：Medical physics

authors： Rosenthal A,Ntziachristos V,Razansky D

更新日期：2011-07-01 00:00:00

abstract：:The purpose of the present study is to characterize electron contamination in photon beams in different clinical situations. Variations with field size, beam modifier (tray, shaping block) and source-surface distance (SSD) were studied. Percentage depth dose measurements with and without a purging magnet and replacing...

journal_title：Medical physics

authors： Lopez Medina A,Teijeiro A,Garcia J,Esperon J,Terron JA,Ruiz DP,Carrion MC

更新日期：2005-05-01 00:00:00

abstract：PURPOSE:To evaluate the dose distribution of a 120-MeV laser-plasma accelerated electron beam which may be of potential interest for high-energy electron radiation therapy. METHODS:In the interaction between an intense laser pulse and a helium gas jet, a well collimated electron beam with very high energy is produced....

journal_title：Medical physics

authors： Lundh O,Rechatin C,Faure J,Ben-Ismaïl A,Lim J,De Wagter C,De Neve W,Malka V

更新日期：2012-06-01 00:00:00

abstract：PURPOSE:As the predominant driver of respiratory motion, the diaphragm represents a key surrogate for motion management during the irradiation of thoracic cancers. Existing approaches to diaphragm tracking often produce phase-based estimates, suffer from lateral side failures or are not executable in real-time. In this...

journal_title：Medical physics

authors： Hindley N,Keall P,Booth J,Shieh CC

更新日期：2019-10-01 00:00:00

abstract：:Mammography is the most effective method for breast cancer screening available today. However, the low positive predictive value of breast biopsy resulting from mammogram interpretation leads to approximately 70% unnecessary biopsies with benign outcomes. To reduce the high number of unnecessary breast biopsies, sever...

journal_title：Medical physics

authors： Elter M,Schulz-Wendtland R,Wittenberg T

更新日期：2007-11-01 00:00:00

abstract：:Stereotactic Body Radiation Therapy (SBRT) is an important form of cancer therapy with increasingly broad application across a spectrum of tumor types in primary and metastatic settings. In this presentation the radiation biology, clinical experience from various trials, and cautionary updates on normal tissue toleran...

journal_title：Medical physics

authors： Read P

更新日期：2012-06-01 00:00:00

abstract：PURPOSE:Accurate detection of pulmonary nodules remains a technical challenge in computer-aided diagnosis systems because some nodules may adhere to the blood vessels or the lung wall, which have low contrast compared to the surrounding tissues. In this paper, the analysis of typical shape features of candidate nodules...

journal_title：Medical physics

authors： Wang B,Tian X,Wang Q,Yang Y,Xie H,Zhang S,Gu L

更新日期：2015-03-01 00:00:00

abstract：PURPOSE:Since the first publications on intensity modulated radiation therapy (IMRT) in the early 1980s almost all efforts have been focused on fairly time consuming dynamic or segmental multileaf collimation. With narrow fast scanned photon beams, the flexibility and accuracy in beam shaping increases, not least in co...

journal_title：Medical physics

authors： Andreassen B,Strååt SJ,Holmberg R,Näfstadius P,Brahme A

更新日期：2011-08-01 00:00:00

abstract：:A spread-out Bragg peak (SOBP) is used in proton beam therapy to create a longitudinal conformality of the required dose to the target. In order to create this effect in a passive beam scattering system, a variety of components must operate in conjunction to produce the desired beam parameters. We will describe how th...

journal_title：Medical physics

authors： Lu HM,Brett R,Engelsman M,Slopsema R,Kooy H,Flanz J

更新日期：2007-10-01 00:00:00

abstract：PURPOSE:Imaging the knee under realistic load-bearing conditions can be carried out in a horizontal plane using a C-arm CT scanner. Human subjects can be scanned in a standing position and acquired data successfully reconstructed. However, reconstructing this data is a challenge due to significant artifacts that are in...

journal_title：Medical physics

authors： Choi JH,Keil A,Maier A,Pal S,McWalter EJ,Fahrig R

更新日期：2012-06-01 00:00:00

abstract：:In this paper, a unified framework of iterative algebraic reconstruction for emission computed tomography (ECT) and its application to positron emission tomography (PET) is presented. The unified framework is based on an algebraic image restoration model and contains conventional iterative algebraic reconstruction alg...

journal_title：Medical physics

authors： Xu XL,Liow JS,Strother SC

更新日期：1993-11-01 00:00:00

abstract：:Skin entrance doses of patients undergoing interventional x-ray procedures are capable of causing skin damage and should be monitored routinely. Single TLD chips are not suitable because the location of maximum skin exposure cannot be predicted. Most photographic films are too sensitive at diagnostic x-ray energies fo...

journal_title：Medical physics

authors： Geise RA,Schueler BA,Lien W,Jones SC

更新日期：1997-10-01 00:00:00

abstract：:A method for the in vivo determination of the isocenter dose, Diso, and mid-plane dose, Dm, using the transmitted signal St measured by 25 central pixels of an aSi-based EPID is here reported. The method has been applied to check the conformal radiotherapy of pelvic tumors and supplies accurate in vivo dosimetry avoid...

journal_title：Medical physics

authors： Piermattei A,Fidanzio A,Stimato G,Azario L,Grimaldi L,D'Onofrio G,Cilla S,Balducci M,Gambacorta MA,Di Napoli N,Cellini N

更新日期：2006-11-01 00:00:00

abstract：:A detailed Monte Carlo study of the PTW-diamond solid state detector response in megavoltage photon beams (60Co gamma rays to 25 MV x rays) has been performed with the EGS4 Monte Carlo Code. The sensitive volume of the diamond detector is a disk of diameter 4.4 mm and thickness 0.40 mm. The phantom material was water ...

journal_title：Medical physics

authors： Mobit PN,Sandison GA

更新日期：1999-11-01 00:00:00

abstract：:A new rubber band straightening transform (RBST) is introduced for characterization of mammographic masses as malignant or benign. The RBST transforms a band of pixels surrounding a segmented mass onto the Cartesian plane (the RBST image). The border of a mammographic mass appears approximately as a horizontal line, a...

journal_title：Medical physics

authors： Sahiner B,Chan HP,Petrick N,Helvie MA,Goodsitt MM

更新日期：1998-04-01 00:00:00

abstract：PURPOSE:A novel 3D printing method has been developed, which employs human CT images to construct patient specific phantoms by controlling the filament extrusion rate. METHODS:An in-house software was developed comprising pixel-by-pixel (PbP) reading of the Hounsfield Units (HU) values in the original patient DICOM im...

journal_title：Medical physics

authors： Okkalidis N

更新日期：2018-10-01 00:00:00

abstract：:A measurement technique previously proposed for determining dose from primary radiation has been tested using 60Co gamma rays. It is shown that the dose from primary radiation is reliably determined for field sizes of 10 X 10 and 20 X 20 cm2 at depths of 0.5, 5, and 10 cm in water. With further development this techni...

journal_title：Medical physics

authors： Nizin PS,Kase KR

更新日期：1990-01-01 00:00:00

abstract：PURPOSE:To develop a pharmacokinetic modelfree framework to analyze the dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) data for assessment of response of brain metastases to radiation therapy. METHODS:Twenty patients with 45 analyzable brain metastases had MRI scans prior to whole brain radiation thera...

journal_title：Medical physics

authors： Farjam R,Tsien CI,Lawrence TS,Cao Y

更新日期：2014-01-01 00:00:00

abstract：:Cone beam computed tomography (CBCT) is a relatively new patient imaging technique that has proved invaluable for treatment target verification and patient positioning during image-guided radiotherapy (IGRT). It has been shown that CBCT results in additional dose to bone that may amount to 10% of the prescribed dose. ...

journal_title：Medical physics

authors： Walters BR,Ding GX,Kramer R,Kawrakow I

更新日期：2009-07-01 00:00:00

abstract：:A filtered backprojection algorithm is developed for single photon emission computed tomography (SPECT) imaging with an astigmatic collimator having a displaced center of rotation. The astigmatic collimator has two perpendicular focal lines, one that is parallel to the axis of rotation of the gamma camera and one that...

journal_title：Medical physics

authors： Wang H,Smith MF,Stone CD,Jaszczak RJ

更新日期：1998-08-01 00:00:00

abstract：PURPOSE:To establish accurate experimental dosimetry techniques for reference dose measurements in nonstandard composite fields. METHODS:A cylindrical PMMA phantom filled with water was constructed, at the center of which reference absorbed dose to water for a head and neck IMRT delivery was measured. Based on the pro...

journal_title：Medical physics

authors： Chung E,Bouchard H,Seuntjens J

更新日期：2010-06-01 00:00:00

abstract：:This paper presents a numerical investigation of the effective point of measurement of thimble ionization chambers in megavoltage photon beams using Monte Carlo simulations with the EGSNRC system. It is shown that the effective point of measurement for relative photon beam dosimetry depends on every detail of the cham...

journal_title：Medical physics

authors： Kawrakow I

更新日期：2006-06-01 00:00:00

abstract：:A simple modification is presented for two commercially available hyperthermia applicators which dramatically improves the regulation and dynamic control of the temperature at the bolus/tissue interface. This alteration requires the addition of a variable speed pump, bubble trap, simple heat exchanger, and a few minor...

journal_title：Medical physics

authors： Diederich CJ,Stauffer PR,Bozzo D

更新日期：1994-09-01 00:00:00

abstract：:We have made a comparative investigation of the estimated spectra obtained by the Laplace transform analysis of the transmitted exposure data measured in an absorption study of a 4-MV x-ray beam. Four transform pair models currently used with this method have been evaluated. It has been determined that the Archer-Wagn...

journal_title：Medical physics

authors： Ahuja SD,Steward PG,Roy TS,Slessinger ED

更新日期：1986-05-01 00:00:00

abstract：PURPOSE:The efficiency of radioembolization procedures could be greatly enhanced if results of the 99m Tc-MAA pretreatment procedure were immediately available in the interventional suite, enabling 1-day procedures as a result of direct estimation of the hepatic radiation dose and lung shunt fraction. This would, howev...

journal_title：Medical physics

authors： van der Velden S,Dietze MMA,Viergever MA,de Jong HWAM

更新日期：2019-01-01 00:00:00