Dosimetry for the MRI accelerator: the impact of a magnetic field on the response of a Farmer NE2571 ionization chamber.

abstract：:A method of computing optimized intensity-modulated beam profiles has been further developed and used to generate highly conformal radiotherapy dose distributions. The features of these distributions are shown to be strongly dependent on the tuning built into the algorithm. The optimization aims to achieve a specified...

journal_title：Physics in medicine and biology

authors： Webb S

更新日期：1994-12-01 00:00:00

abstract：:This study examines the effectiveness of a single, first-order Arrhenius process in accurately modelling the thermally induced changes in the optical properties, particularly the reduced scattering coefficient, mu(s)', and the absorption coefficient, mu(a), of ex vivo rat prostate. Recent work has shown that mu(s)' ca...

journal_title：Physics in medicine and biology

authors： Skinner MG,Everts S,Reid AD,Vitkin IA,Lilge L,Sherar MD

更新日期：2000-05-01 00:00:00

abstract：:The design and performance of a dosimetric system for the irradiation of thin biological samples with therapeutic proton beams is reported. Protons with initial energies between 40 MeV and 250 MeV are degraded with polystyrene blocks of variable thickness in order to place the sample, an aqueous layer of 10 microm thi...

journal_title：Physics in medicine and biology

authors： Bashkirov V,Schulte RW

更新日期：2002-02-07 00:00:00

abstract：:This paper explores fast reconstruction strategies for 3D time-of-flight (TOF) positron emission tomography (PET), based on 2D data rebinning. Starting from pre-corrected 3D TOF data, a rebinning algorithm estimates for each transaxial slice the 2D TOF sinogram that would have been acquired by a single-ring scanner. T...

journal_title：Physics in medicine and biology

authors： Defrise M,Casey ME,Michel C,Conti M

更新日期：2005-06-21 00:00:00

abstract：:This study presents a combined small animal holding fixture system, termed a 'bridge capsule', which provides for small animal re-fixation with positional reproducibility. This system comprises separate holding fixtures for the head and lower body and a connecting part to a gas anesthesia system. A mouse is fixed in p...

journal_title：Physics in medicine and biology

authors： Kokuryo D,Kimura Y,Obata T,Yamaya T,Kawamura K,Zhang MR,Kanno I,Aoki I

更新日期：2010-07-21 00:00:00

abstract：:All available imaging devices in nuclear medicine have finite energy resolution. This leads to inclusion of scattered radiation, which in turn degrades the image quality. Different scatter correction schemes therefore try to eliminate the effect of scattered radiation. On the other hand, improvement of the camera's in...

journal_title：Physics in medicine and biology

authors： Wirth V

更新日期：1989-01-01 00:00:00

abstract：:RapidArc, recently released by Varian Medical Systems, is a novel extension of IMRT in which an optimized 3D dose distribution may be delivered in a single gantry rotation of 360 degrees or less. The purpose of this study was to investigate the accuracy of the analytical anisotropic algorithm (AAA), the sole algorithm...

journal_title：Physics in medicine and biology

authors： Gagne IM,Ansbacher W,Zavgorodni S,Popescu C,Beckham WA

更新日期：2008-12-21 00:00:00

abstract：:We are developing a three-dimensional (3D) position-sensitive detector with isotropic spatial resolution, the X'tal cube. Originally, our design consisted of a crystal block for which all six surfaces were covered with arrays of multi-pixel photon counters (MPPCs). In this paper, we examined the feasibility of reducin...

journal_title：Physics in medicine and biology

authors： Hirano Y,Inadama N,Yoshida E,Nishikido F,Murayama H,Watanabe M,Yamaya T

更新日期：2013-03-07 00:00:00

abstract：:Although it is known that obesity has a profound effect on x-ray computed tomography (CT) image quality and patient organ dose, quantitative data describing this relationship are not currently available. This study examines the effect of obesity on the calculated radiation dose to organs and tissues from CT using newl...

journal_title：Physics in medicine and biology

authors： Ding A,Mille MM,Liu T,Caracappa PF,Xu XG

更新日期：2012-05-07 00:00:00

abstract：:Radiochromic films are useful as dosimeters in high-precision radiotherapy owing to their high spatial resolution. However, when a particle beam is measured using a radiochromic film, the dose cannot be estimated accurately because the film darkness varies with variations in linear energy transfer (LET). This paper pr...

journal_title：Physics in medicine and biology

authors： Kawashima M,Matsumura A,Souda H,Tashiro M

更新日期：2020-06-15 00:00:00

abstract：:The development and improvement of techniques for an accurate dose assessment in medical physics is an important task. In this study, we focus on the validation of Monte Carlo calculations, by comparing organ doses assessed experimentally with thermoluminescent detectors in the Rando-Alderson phantom with doses calcul...

journal_title：Physics in medicine and biology

authors： Struelens L,Vanhavere F,Smans K

更新日期：2008-10-21 00:00:00

abstract：:In critical organ in vivo x-ray dosimetry, the relative contaminating electron contribution to the total dose and total detector response outside the field will be different to the corresponding contributions at the central axis detector calibration position, mainly due to the effects of shielding in the linear accele...

journal_title：Physics in medicine and biology

authors： Edwards CR,Mountford PJ,Moloney AJ

更新日期：2006-12-21 00:00:00

abstract：:Magnetic resonance-guided radiation therapy (MR-GRT) offers great potential to improve radiation treatment outcomes by providing more accurate and patient-tailored therapy. Despite superior soft tissue contrast in MRI, one of the challenges towards MRI-only workflows is that the process often requires some sort of 'MR...

journal_title：Physics in medicine and biology

authors： Nosrati R,Paudel M,Ravi A,Pejovic-Milic A,Morton G,Stanisz GJ

更新日期：2019-07-16 00:00:00

abstract：:Blood and blood products are irradiated with gamma rays to reduce the risk of graft versus host disease (GVHD). A simple technique using electron beams produced by a medical linear accelerator has been studied to evaluate irradiation of blood and blood products. Variations in applied doses for a single field 20 MeV el...

journal_title：Physics in medicine and biology

authors： Butson MJ,Cheung T,Yu PK,Stokes MJ

更新日期：2000-11-01 00:00:00

abstract：:In order to effectively utilize the prominent properties of heavy ions in radiotherapy, it is important to evaluate both the position of the field irradiated with incident ions and the absorbed dose distribution in a patient's body. One of the methods for this purpose is the utilization of the positron emitters produc...

journal_title：Physics in medicine and biology

authors： Inaniwa T,Kohno T,Tomitani T,Sato S

更新日期：2008-02-07 00:00:00

abstract：:Computational modeling is an important tool in ultrasound imaging research, but realistic three-dimensional (3D) simulations can exceed the capabilities of serial computers. This paper uses a 3D simulator based on a k-space method that incorporates relaxation absorption and nonreflecting boundary conditions. The simul...

journal_title：Physics in medicine and biology

authors： Daoud MI,Lacefield JC

更新日期：2009-09-07 00:00:00

abstract：:Polymer gel dosimetry aims to provide three-dimensional images of radiation therapy dose distributions in irradiated aqueous gels. The first gels required manufacture in an oxygen-free environment, but later the MAGIC formulation was introduced, which could be made in normal atmospheric conditions. Here we report our ...

journal_title：Physics in medicine and biology

authors： Luci JJ,Whitney HM,Gore JC

更新日期：2007-05-21 00:00:00

abstract：:A water calorimeter has been used for the direct measurement of absorbed dose to water in a d(15) + Be neutron beam. The absorbed dose measured with the calorimeter was compared with that measured with an Exradin ionisation chamber, constructed of A-150 plastic. The doses measured by the ionisation chamber were calcul...

journal_title：Physics in medicine and biology

authors： Galloway G,Greening JR,Williams JR

更新日期：1986-04-01 00:00:00

abstract：:The probability of a photon (x-ray, gamma-ray, bremsstrahlung, etc) of a given energy E undergoing absorption or scattering when traversing a layer of material Z can be expressed quantitatively in terms of a linear attenuation coefficient mu (cm(-1)). Since mu is dependent on the material's density, rho (g cm(-3)), wh...

journal_title：Physics in medicine and biology

authors： Hubbell JH

更新日期：1999-01-01 00:00:00

abstract：:Ultraviolet (UV) treatment dose is determined by the length of time that a patient spends in a phototherapy cabin. The output from UV fluorescent lamps declines with use and a method is needed to compensate for the change in irradiance and to identify and replace any lamps that fail. The decline in lamp output with ag...

journal_title：Physics in medicine and biology

authors： Amatiello H,Martin CJ

更新日期：2006-01-21 00:00:00

abstract：:The prompt-gamma neutron activation facility at Brookhaven National Laboratory was upgraded to improve both the precision and accuracy of its in vivo determinations of total body nitrogen. The upgrade, guided by Monte Carlo simulations, involved elongating and modifying the source collimator and its shielding, reposit...

journal_title：Physics in medicine and biology

authors： Dilmanian FA,Lidofsky LJ,Stamatelatos I,Kamen Y,Yasumura S,Vartsky D,Pierson RN Jr,Weber DA,Moore RI,Ma R

更新日期：1998-02-01 00:00:00

abstract：:The electrostimulation excitation threshold of a nerve depends on temporal and frequency parameters of the stimulus. These dependences were investigated in terms of: (1) strength-duration (SD) curve for a single monophasic rectangular pulse, and (2) frequency dependence of the excitation threshold for a continuous sin...

journal_title：Physics in medicine and biology

authors： Šarolić A,Živković Z,Reilly JP

更新日期：2016-06-21 00:00:00

abstract：:Experimental radiobiological investigations of fast neutron beams involve irradiation of thin cell layers. The irradiation of cells is done either in free air or with a material such as graphite, TE plastic or bone-equivalent plastic covering the cells. This paper discusses the computed dose distributions in LET at sh...

journal_title：Physics in medicine and biology

authors： Bhatia DP,Nagarajan PS

更新日期：1979-09-01 00:00:00

abstract：:The local noise property of a 3D PET reconstructed image is investigated for a uniform-activity sphere distributed in a constantly attenuating spherical object. The positional dependence of the statistical noise is approximately derived and calculated for some special cases. It is suggested that a larger diameter of t...

journal_title：Physics in medicine and biology

authors： Murayama H,Nohara N

更新日期：1997-01-01 00:00:00

abstract：:Charge-coupled devices (CCDs) coupled to scintillation crystals can be used for high-resolution imaging with x-rays and gamma rays. When the CCD images can be read out fast enough, the energy and interaction position of individual gamma quanta can be estimated by a real-time image analysis of the scintillation light f...

journal_title：Physics in medicine and biology

authors： Heemskerk JW,Westra AH,Linotte PM,Ligtvoet KM,Zbijewski W,Beekman FJ

更新日期：2007-04-21 00:00:00

abstract：:The poor agreement in the photon calibrations of tissue-equivalent ionisation chambers between different participants in two major neutron dosimetry intercomparisons is noted. The methods of converting measurements made with a calibrated secondary standard exposure meter to the absorbed dose in the wall of a tissue-eq...

journal_title：Physics in medicine and biology

authors： Williams JR,Greening JR

更新日期：1980-03-01 00:00:00

abstract：:Electronic article surveillance (EAS) devices are widely used in most stores as anti-theft systems. In this work, the compliance with international guidelines in the human exposure to these devices is analysed by using the finite-difference time-domain (FDTD) method. Two sets of high resolution numerical phantoms of d...

journal_title：Physics in medicine and biology

authors： Martínez-Búrdalo M,Sanchis A,Martín A,Villar R

更新日期：2010-02-21 00:00:00

abstract：:We comment on a recent article (Gomà et al 2014 Phys. Med. Biol. 59 4961-71) which compares different routes of reference dosimetry for the energy dependent beam monitor calibration in scanned proton beams. In this article, a 3% discrepancy is reported between a Faraday cup and a plane-parallel ionization chamber in t...

journal_title：Physics in medicine and biology

authors： Palmans H,Vatnitsky SM

更新日期：2016-09-07 00:00:00

abstract：:The spatial resolution of 2D detector arrays equipped with ionization chambers or diodes, used for the dose verification of IMRT treatment plans, is limited by the size of the single detector and the centre-to-centre distance between the detectors. Optimization criteria with regard to these parameters have been develo...

journal_title：Physics in medicine and biology

authors： Poppe B,Djouguela A,Blechschmidt A,Willborn K,Rühmann A,Harder D

更新日期：2007-05-21 00:00:00

abstract：:A comparative study was performed to reveal differences and relative figures of merit of seven different calculation algorithms for photon beams when applied to inhomogeneous media. The following algorithms were investigated: Varian Eclipse: the anisotropic analytical algorithm, and the pencil beam with modified Batho...

journal_title：Physics in medicine and biology

authors： Fogliata A,Vanetti E,Albers D,Brink C,Clivio A,Knöös T,Nicolini G,Cozzi L

更新日期：2007-03-07 00:00:00