Verification of absorbed dose determined with plane-parallel chambers in clinical electron beams following AAPM Task Group 39 protocol using ferrous sulphate dosimetry.

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：:In this paper, we describe an algorithm to segment a needle from a three-dimensional (3D) ultrasound image by using two orthogonal two-dimensional (2D) image projections. Not only is the needle more conspicuous in a projected (volume-rendered) image, but its direction in 3D lies in the plane defined by the projection ...

journal_title：Medical physics

authors： Ding M,Cardinal HN,Fenster A

更新日期：2003-02-01 00:00:00

abstract：PURPOSE:The authors have developed a system that monitors intrafractional target motion perpendicular to the treatment beam with the aid of radioopaque markers by means of separating kV image and megavoltage (MV) treatment field on a single flat-panel detector. METHODS:They equipped a research Siemens Artiste linear a...

journal_title：Medical physics

authors： Fast MF,Krauss A,Oelfke U,Nill S

更新日期：2012-01-01 00:00:00

abstract：:Depth dose distributions for a d(14)Be neutron beam, measured separately for total and gamma absorbed dose, are presented for nine tissue substitutes and for two field sizes. These data are used to examine methods to transform depth dose curves from one material to another. Best results are found when the local depths...

journal_title：Medical physics

authors： Hensley FW,Rassow J,Temme A

更新日期：1985-05-01 00:00:00

abstract：PURPOSE:Image guidance is crucial for percutaneous tumor ablations, enabling accurate needle-like applicator placement into target tumors while avoiding tissues that are sensitive to injury and/or correcting needle deflection. Although ultrasound (US) is widely used for image guidance, magnetic resonance (MR) is prefer...

journal_title：Medical physics

authors： Yamada A,Tokuda J,Naka S,Murakami K,Tani T,Morikawa S

更新日期：2020-03-01 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：:AAPM Magnetic Resonance Task Group #9 on proton magnetic resonance spectroscopy (MRS) in the brain was formed to provide a reference document for acquiring and processing proton (1H) MRS acquired from brain tissue. MRS is becoming a common adjunct to magnetic resonance imaging (MRI), especially for the differential di...

journal_title：Medical physics

authors： Drost DJ,Riddle WR,Clarke GD,AAPM MR Task Group #9.

更新日期：2002-09-01 00:00:00

abstract：:In order to determine accurately the relative x-ray intensities transmitted through the different steps of an aluminum stepwedge and incident on an image intensifier (II)-TV digital system, we used a 100-mm camera which was attached to the II output. The characteristic curves of an II-TV digital system, which relate t...

journal_title：Medical physics

authors： Fujita H,Doi K

更新日期：1986-11-01 00:00:00

abstract：:We propose a new method based on statistical analysis technique to determine the minimum setup distance of a well chamber used in the calibration of 192Ir high dose rate (HDR). The chamber should be placed at least this distance away from any wall or from the floor in order to mitigate the effect of scatter. Three dif...

journal_title：Medical physics

authors： Chang L,Ho SY,Chui CS,Lee JH,Du YC,Chen T

更新日期：2008-06-01 00:00:00

abstract：PURPOSE:To use EGSnrc Monte Carlo simulations for magnetic field dosimetry to determine optimal measurement orientations, calculate beam quality conversion factors for 32 cylindrical and three parallel-plate (PP) ion chambers, evaluate the beam quality and angular dependence of these factors, and examine the magnetic f...

journal_title：Medical physics

authors： Malkov VN,Rogers DWO

更新日期：2018-02-01 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：:Use of dynamic multileaf collimation (DMLC) for intensity modulated radiation therapy (IMRT) is accelerating. Delivery systems have the ailment of interleaf leakage (IL). This is compounded by the inefficiency of IMRT delivery, estimated to be a factor of 5 for DMLC. With IL on the order of 4%, it is possible to deliv...

journal_title：Medical physics

authors： Klein EE,Low DA

更新日期：2001-08-01 00:00:00

abstract：PURPOSE:Periodic MV∕KV radiographs taken during volumetric modulated arc therapy (VMAT) for hypofractionated treatment provide guidance in intrafractional motion management. The choice of imaging frequency and timing are key components in delivering the desired dose while reducing associated overhead such as imaging do...

journal_title：Medical physics

authors： Zhang P,Hunt M,Happersett L,Cox B,Mageras G

更新日期：2012-09-01 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：:An experiment to determine the peak of the energy spectrum of the photon beam from a Toshiba LMR-15 medical linear accelerator is described. It is found that the flattening filters removed much of the bremsstrahlung spectrum below approximately 1 MeV, resulting in a photon spectrum which peaks around 1.2 MeV. ...

journal_title：Medical physics

authors： Brownridge J,Samnick S,Stiles P,Tipton P,Veselka J,Yeh N

更新日期：1984-11-01 00:00:00

abstract：:The wall of an ionization chamber is commonly assumed to have a negligible effect on chamber response in electron beams. For cylindrical chambers with thin walls this assumption is valid. However, parallel-plate chambers commonly possess large mechanical supports which may affect chamber response in a manner not accou...

journal_title：Medical physics

authors： Hunt MA,Kutcher GJ,Buffa A

更新日期：1988-01-01 00:00:00

abstract：:The calibration (in rad/nC) of an air-filled tissue-equivalent ionization chamber for neutrons of 15-MeV average energy was determined by measuring absolute fluences and calculating the kerma per unit fluence. The neutron calibration determined from the gamma-ray calibration and application of the Bragg-Gray relation ...

journal_title：Medical physics

authors： Barschall HH,Goldberg E

更新日期：1977-03-01 00:00:00

abstract：PURPOSE:By means of Monte Carlo (MC) simulations and indirect measurements, we have evaluated the maximum dose rates achievable with conventional x-ray tubes and related them to FLASH therapy dose rates of >40 Gy/s. METHODS:Monte Carlo models of two 160 kV x-ray tubes, the 3-kW MXR-160/22 and the 6-kW MXR-165, were bu...

journal_title：Medical physics

authors： Bazalova-Carter M,Esplen N

更新日期：2019-12-01 00:00:00

abstract：:Spectrally resolved bioluminescence optical tomography is an approach to recover images of, for example, Luciferase activity within a volume using multiwavelength emission data from internal bioluminescence sources. The underlying problem of uniqueness associated with nonspectrally resolved intensity-based bioluminesc...

journal_title：Medical physics

authors： Dehghani H,Davis SC,Pogue BW

更新日期：2008-11-01 00:00:00

abstract：PURPOSE:One technical barrier to patient-specific computed tomography (CT) dosimetry has been the lack of computational tools for the automatic patient-specific multi-organ segmentation of CT images and rapid organ dose quantification. When previous CT images are available for the same body region of the patient, the a...

journal_title：Medical physics

authors： Peng Z,Fang X,Yan P,Shan H,Liu T,Pei X,Wang G,Liu B,Kalra MK,Xu XG

更新日期：2020-06-01 00:00:00

abstract：PURPOSE:Osteoporosis is a common bone disease associated with increased risk of low-trauma fractures leading to substantial morbidity, mortality, and financial costs. Clinically, osteoporosis is defined by low bone mineral density (BMD); however, increasing evidence suggests that trabecular bone (TB) microarchitectural...

journal_title：Medical physics

authors： Saha PK,Liu Y,Chen C,Jin D,Letuchy EM,Xu Z,Amelon RE,Burns TL,Torner JC,Levy SM,Calarge CA

更新日期：2015-09-01 00:00:00

abstract：:The relative sensitivity of the half-value layer (HVL) method as a quality index for megavoltage x-ray beams is examined by theoretical calculation and experimental measurements for 4-, 6-, 10-, and 25-MV x-ray beams. It is shown that lower atomic number materials are more sensitive to beam quality changes than higher...

journal_title：Medical physics

authors： Meli JA,Nath R

更新日期：1985-01-01 00:00:00

abstract：:A method to correct for geometric image distortion in the x-ray imaging chain, so-called dewarping, has been developed. A global two-dimensional polynomial model of which the degree is optimized is used. The performance of the method has been tested in a number of experiments using images of a plate with a 1 cm spaced...

journal_title：Medical physics

authors： Gronenschild E

更新日期：1997-12-01 00:00:00

abstract：:The optimum x-ray spectra for acquisition of digital mammographic images using an amorphous selenium (a-Se) photoconductor are investigated. The recorded images consist of latent charge distributions on the surface of an a-Se plate, which are then read out using two methods, laser discharge, or flat panel recharge. Th...

journal_title：Medical physics

authors： Fahrig R,Rowlands JA,Yaffe MJ

更新日期：1996-04-01 00:00:00

abstract：PURPOSE:Mammography is known to be one of the most difficult radiographic exams to interpret. Mammography has important limitations, including the superposition of normal tissue that can obscure a mass, chance alignment of normal tissue to mimic a true lesion and the inability to derive volumetric information. It has b...

journal_title：Medical physics

authors： Webb LJ,Samei E,Lo JY,Baker JA,Ghate SV,Kim C,Soo MS,Walsh R

更新日期：2011-04-01 00:00:00

abstract：PURPOSE:It is very important for calculation of clinical indices and diagnosis to detect thyroid nodules from ultrasound images. However, this task is a challenge mainly due to heterogeneous thyroid nodules with distinct components are similar to background in ultrasound images. In this study, we employ cascade deep co...

journal_title：Medical physics

authors： Ma J,Wu F,Jiang T,Zhu J,Kong D

更新日期：2017-05-01 00:00:00

abstract：PURPOSE:A radiophotoluminescent glass rod dosimeter (RGD) has recently become commercially available. It is being increasingly used for dosimetry in radiotherapy to measure the absorbed dose including scattered low-energy photons on the body surface of a patient and for postal dosimetry audit. In this article, the dosi...

journal_title：Medical physics

authors： Kadoya N,Shimomura K,Kitou S,Shiota Y,Fujita Y,Dobashi S,Takeda K,Jingu K,Matsushita H,Namito Y,Ban S,Koyama S,Tabushi K

更新日期：2012-10-01 00:00:00

abstract：PURPOSE:The depth dose of a monoenergetic broad parallel proton beam has been modeled in a number of ways, but evidently not yet for oblique incidence. The purpose of this investigation is to find an accurate analytic formula for this case, which can then be used to model the depth dose of a broad beam with an initial ...

journal_title：Medical physics

authors： Jette D,Yuan J,Chen W

更新日期：2010-11-01 00:00:00

abstract：:Modern computed tomography (CT) scanners use cone-beam configurations for increasing volume coverage, improving x-ray-tube utilization, and yielding isotropic spatial resolution. Recently, there have been significant developments in theory and algorithms for exact image reconstruction from cone-beam projections. In pa...

journal_title：Medical physics

authors： Zuo N,Xia D,Zou Y,Jiang T,Pan XC

更新日期：2006-10-01 00:00:00

abstract：:The contribution of a commercially available diode matrix (MapCHECK, provided by Sun Nuclear, Melbourne, FL) for the commissioning procedures of the voxel based Monte Carlo (VMC++) algorithm for electron beams of MasterPlan treatment planning system was investigated. The attention is mainly focused on the calculation ...

journal_title：Medical physics

authors： Borca VC,Pasquino M,Ozzello F,Tofani S

更新日期：2009-04-01 00:00:00