SU-E-J-160: 4D Dynamic Arc of Non-Modulated Variable-Dose-Rate Fields for Lung SBRT: A Feasibility Study.

abstract：:Automatic exposure control (AEC) systems have been developed by computed tomography (CT) manufacturers to improve the consistency of image quality among patients and to control the absorbed dose. Since a multichannel helical CT scan may easily increase individual radiation doses, this technical improvement is of speci...

journal_title：Medical physics

authors： Brisse HJ,Madec L,Gaboriaud G,Lemoine T,Savignoni A,Neuenschwander S,Aubert B,Rosenwald JC

更新日期：2007-07-01 00:00:00

abstract：:In this paper, we present a unified framework to reconstruct images for both fan beam and cone beam projections. The important feature of our theoretical framework is that it does not depend on the classical concept of the Radon transform at all. This property allows us to directly generalize the ideas and techniques ...

journal_title：Medical physics

authors： Chen GH

更新日期：2003-06-01 00:00:00

abstract：PURPOSE:Material-specific imaging and virtual monochromatic imaging/analysis are the two forms of spectral imaging in CT implemented via either energy-integration or photon-counting data acquisition. Aimed at further understanding the fundamentals and providing guidelines on its design and implementation, we quantitati...

journal_title：Medical physics

authors： Tang X,Ren Y

更新日期：2021-01-07 00:00:00

abstract：PURPOSE:A 3-year project called LABSYNC has been recently funded by the European Commission, with the aim of designing a radiation facility based on a compact light source, i.e., a laboratory-sized commercial synchrotron, capable of accelerating electrons up to 6 or 20 MeV. An accurate spectral description of hard x ra...

journal_title：Medical physics

authors： Marziani M,Taibi A,Di Domenico G,Gambaccini M

更新日期：2009-10-01 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

abstract：:Total body photon irradiation (TBI) may be delivered with a number of standard techniques, typically using extended SSD geometries to obtain large field sizes. Since 1982 we have treated over 620 patients (adult and pediatric) mostly in the floor-located prone/supine treatment position with AP/PA beams using a column ...

journal_title：Medical physics

authors： Evans M,Ruo R,Seuntjens J,Freeman CR,Parker W

更新日期：2012-07-01 00:00:00

abstract：:The ability to control thermal drifts is essential in operating a calorimeter. We investigated a thermal enclosure, which envelops the calorimeter with temperature-regulated air, thus thermally isolating the calorimeter from the room. The desired temperature in the enclosure is controlled by a control circuit and a th...

journal_title：Medical physics

authors： Kubo H,Brown DE,Russell MD

更新日期：1985-05-01 00:00:00

abstract：PURPOSE:The response of alanine solid state dosimeters to ionizing radiation strongly depends on particle type and energy. Due to nuclear interactions, neutron fields usually also consist of secondary particles such as photons and protons of diverse energies. Various experiments have been carried out in three different...

journal_title：Medical physics

authors： Schmitz T,Bassler N,Blaickner M,Ziegner M,Hsiao MC,Liu YH,Koivunoro H,Auterinen I,Serén T,Kotiluoto P,Palmans H,Sharpe P,Langguth P,Hampel G

更新日期：2015-01-01 00:00:00

abstract：PURPOSE:To compare and evaluate intensity-based registration methods for computation of serial x-ray mammogram correspondence. METHODS:X-ray mammograms were simulated from MRIs of 20 women using finite element methods for modeling breast compressions and employing a MRI/x-ray appearance change model. The parameter con...

journal_title：Medical physics

authors： Pinto Pereira SM,Hipwell JH,McCormack VA,Tanner C,Moss SM,Wilkinson LS,Khoo LA,Pagliari C,Skippage PL,Kliger CJ,Hawkes DJ,Silva IM

更新日期：2010-09-01 00:00:00

abstract：:DICOM format is the de facto standard for communications between therapeutic and diagnostic modalities. A plan generated by a treatment planning system (TPS) is often exported to DICOM format. BEAMnrc/DOSXYZnrc is a widely used Monte Carlo (MC) package for beam and dose simulations in radiotherapy. It has its own defi...

journal_title：Medical physics

authors： Zhan L,Jiang R,Osei EK

更新日期：2012-07-01 00:00:00

abstract：:A calculation is described that enables the rapid assessment of dose rate at various points of interest within the eye (lens, optic nerve, etc.) for the treatment of choroidal melanoma by plaque therapy. 125I seeds are used as the radiation source. The location of the plaque and its associated seeds relative to the ey...

journal_title：Medical physics

authors： Kepka AG,Johnson PM,Kline RW

更新日期：1988-05-01 00:00:00

abstract：PURPOSE:In breast radiotherapy with intensity modulation, it is a well established practice to extend the dose fluence outside the limit of the body contour to account for small changes in size and position of the target and the rest of the tissues due to respiration or to possible oedema. A simple approach is not appl...

journal_title：Medical physics

authors： Giorgia N,Antonella F,Alessandro C,Eugenio V,Luca C

更新日期：2011-07-01 00:00:00

abstract：PURPOSE:Current respiratory motion monitoring devices used for motion synchronization in medical imaging and radiotherapy provide either 1D respiratory signal over a specific region or 3D information based on few external or internal markers. On the other hand, newer technology may offer the potential to monitor the en...

journal_title：Medical physics

authors： Fayad H,Pan T,Clement JF,Visvikis D

更新日期：2011-06-01 00:00:00

abstract：:Soft-tissue detectability in cone-beam computed tomography (CBCT) was evaluated via two-alternative forced-choice (2AFC) tests. Investigations included the dependence of detectability on radiation dose, the influence of the asymmetric three-dimensional (3D) noise-power spectrum (NPS) in axial and sagittal or coronal p...

journal_title：Medical physics

authors： Tward DJ,Siewerdsen JH,Daly MJ,Richard S,Moseley DJ,Jaffray DA,Paul NS

更新日期：2007-11-01 00:00:00

abstract：:Interchange or transfer of radiographic techniques through measurement of penetration quality is discussed. The usefulness of this achievement is verified using an aluminum step wedge. Also, the procedure described provides a method for performance evaluation of kVp compensation on diagnostic x-ray installations. ...

journal_title：Medical physics

authors： Lin PJ

更新日期：1975-01-01 00:00:00

abstract：:The purpose of this work is to show the feasibility of using in vivo proton radiography of a radiotherapy patient for the patient individual optimization of the calibration from CT-Hounsfield units to relative proton stopping power. Water equivalent tissue (WET) calibrated proton radiographs of a dog patient treated f...

journal_title：Medical physics

authors： Schneider U,Pemler P,Besserer J,Pedroni E,Lomax A,Kaser-Hotz B

更新日期：2005-01-01 00:00:00

abstract：:A new approach to the calculation of the x-ray spectrum emerging from an x-ray tube is proposed. Theoretical results for the bremsstrahlung cross section appearing in the literature are summarized. Four different treatments of electron penetration, based on the work presented in Part I, are then used to generate brems...

journal_title：Medical physics

authors： Poludniowski GG

更新日期：2007-06-01 00:00:00

abstract：:Ultrasound contrast agents consist of microscopically small encapsulated bubbles that oscillate upon insonification. To enhance diagnostic ultrasound imaging techniques and to explore therapeutic applications, these medical microbubbles have been studied with the aid of high-speed photography. We filmed medical microb...

journal_title：Medical physics

authors： Postema M,van Wamel A,ten Cate FJ,de Jong N

更新日期：2005-12-01 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：PURPOSE:The purpose of this study is to investigate some characteristics of the beam delivery system and their effects on the dose distribution of intensity-modulated radiation therapy (IMRT) and the results of patient-specific IMRT quality assurance (QA). These characteristics include the accelerator source distributi...

journal_title：Medical physics

authors： Li JS,Lin T,Chen L,Price RA Jr,Ma CM

更新日期：2010-06-01 00:00:00

abstract：PURPOSE:Photon counting arrays (PCAs), capable of measuring the spectral information of individual x-ray photons and recording that information digitally, provide a number of advantages compared to conventional, energy-integrating active matrix flat-panel imagers - such as reducing the undesirable effects of electronic...

journal_title：Medical physics

authors： Liang AK,Koniczek M,Antonuk LE,El-Mohri Y,Zhao Q

更新日期：2018-10-01 00:00:00

abstract：:Functional single photon emission computed tomography (SPECT) images of brain activation are based on a comparison of base line and activation images. The correctness of the functional images depends, among other factors, on the accurate spatial registration (alignment) of the base line and activation image data. The ...

journal_title：Medical physics

authors： Sychra JJ,Pavel DG,Chen Y,Jani A

更新日期：1994-12-01 00:00:00

abstract：:Absorbed doses from main charged-particle beams and charged-particle fragments have been measured with high accuracy for particle therapy, but there are few reports for doses from neutron components produced as fragments. This study describes the measurements on neutron doses produced by carbon beams; microdosimetric ...

journal_title：Medical physics

authors： Endo S,Tanaka K,Takada M,Onizuka Y,Miyahara N,Sato T,Ishikawa M,Maeda N,Hayabuchi N,Shizuma K,Hoshi M

更新日期：2007-09-01 00:00:00

abstract：:Fluoroscopy is a low dose imaging technique. As such, a very sensitive detector is required to create images of good quality. Present day flat panel active matrix read out systems introduce an amount of noise that inhibits present direct and indirect methods from producing optimal quality images at fluoroscopic exposu...

journal_title：Medical physics

authors： Hunt DC,Kirby SS,Rowlands JA

更新日期：2002-11-01 00:00:00

abstract：:Monte Carlo (MC) simulations were performed to estimate brachytherapy dose distributions for Collaborative Ocular Melanoma Study (COMS) eye plaques. Brachytherapy seed models 200, 6711, and CS-1 Rev2 carrying 103Pd, 125I, and 131Cs radionuclides, respectively, were modeled and benchmarked against previously published ...

journal_title：Medical physics

authors： Melhus CS,Rivard MJ

更新日期：2008-07-01 00:00:00

abstract：PURPOSE:Scattered radiation remains to be a major cause of image quality degradation in Flat Panel Detector (FPD)-based Cone-beam computed tomography (CBCT). We have been investigating a novel two-dimensional antiscatter grid (2D-ASG) concept to reduce scatter intensity, and hence improve CBCT image quality. We present...

journal_title：Medical physics

authors： Alexeev T,Kavanagh B,Miften M,Altunbas C

更新日期：2018-02-01 00:00:00

abstract：PURPOSE:Spirometry exhibits baseline drift and frequent measurement errors so it cannot be used by itself to provide tidal volume-based image sorting or breathing motion modeling. Other breathing surrogates, in this study an abdominal bellows system, are drift free but do not measure tidal volume. Simultaneously using ...

journal_title：Medical physics

authors： Werner R,White B,Handels H,Lu W,Low DA

更新日期：2010-02-01 00:00:00

abstract：:Backscatter factors for kVps and half-value layers typical of mammographic beams have been determined as a function of beam diameter and half-value layer. The method utilized thin TLD-100 chips with the scattering medium alternately present and absent. Results indicate that the field-size dependence of the backscatter...

journal_title：Medical physics

authors： Dubuque GL,Cacak RK,Hendee WR

更新日期：1977-09-01 00:00:00

abstract：:Double checking of the monitor units (MU) is an important step in the quality assurance (QA) process in radiosurgery. In this paper we propose the use of an independent algorithm constructed using the ellipsoid which best fits the measurements taken with the bubble head frame. The monitor units calculated by this inde...

journal_title：Medical physics

authors： Ramos LI,Monge RM,Aristu JJ,Moreno LA

更新日期：2008-01-01 00:00:00

abstract：PURPOSE:The simultaneous measurement of PET and magnetic resonance imaging (MRI) is an emerging field for molecular imaging research. Although optical fiber based PET∕MRI systems have advantages on less interference between PET and MRI, there is a drawback in reducing the scintillation light due to the fiber. To reduce...

journal_title：Medical physics

authors： Yamamoto S,Watabe H,Kanai Y,Watabe T,Aoki M,Sugiyama E,Kato K,Hatazawa J

更新日期：2012-11-01 00:00:00