Experimental study of the relationship between the base impedance and its time derivative in impedance plethysmography.

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 high sensitivity (HS) model of radiochromic film is receiving increasing use. The film's linear sensitometric response in the range of 0.5-40 Gy would make this film an ideal candidate for complex dosimetry applications that require tissue equivalence. This study investigates the potential use for clinical dosimetry...

journal_title：Medical physics

authors： Hirata EY,Cunningham C,Micka JA,Keller H,Kissick MW,DeWerd LA

更新日期：2005-04-01 00:00:00

abstract：:In the last 30 years, thousands of basic or clinical studies have been devoted to atherosclerosis or to the problem of restenosis after angioplasty. In these studies, axial stresses in the vessel wall have received practically no attention, contrary to circumferential stress and purely biological aspects. Based on a r...

journal_title：Medical physics

authors： Doriot PA,Dorsaz PA

更新日期：2005-02-01 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：:In order to use negative pions for the treatment of large deep-seated tumors in radiotherapy, it is necessary to produce depth-dose distributions tailored to specific shapes. We present here a method of beam shaping which utilizes a fluid-filled piston having a programmable, computer-controlled, time-dependent thickne...

journal_title：Medical physics

authors： Amols HI,Liska DJ,Halbig J

更新日期：1977-09-01 00:00:00

abstract：:The purpose of this study was to investigate the effect of z overscanning on eye lens dose and effective dose received by pediatric patients undergoing head CT examinations. A pediatric patient study was carried out to obtain the exposure parameters and data regarding the eye lens position with respect to imaged volum...

journal_title：Medical physics

authors： Tzedakis A,Perisinakis K,Raissaki M,Damilakis J

更新日期：2006-07-01 00:00:00

abstract：PURPOSE:Helical tomotherapy is a complex delivery technique, integrating CT image guidance and intensity modulated radiotherapy in a single system. The integration of the CT detector ring on the gantry not only allows patient position verification but is also often used to perform various QA procedures. This convenienc...

journal_title：Medical physics

authors： Wong JH,Hardcastle N,Tomé WA,Bayliss A,Tolakanahalli R,Lerch ML,Petasecca M,Carolan M,Metcalfe P,Rosenfeld AB

更新日期：2011-04-01 00:00:00

abstract：:The noise power spectrum (NPS) is a useful metric for understanding the noise content in images. To examine some unique properties of the NPS of fan beam CT, the authors derived an analytical expression for the NPS of fan beam CT and validated it with computer simulations. The nonstationary noise behavior of fan beam ...

journal_title：Medical physics

authors： Baek J,Pelc NJ

更新日期：2010-05-01 00:00:00

abstract：PURPOSE:To evaluate dosimetric variations of planning target volume (PTV) on critical organs such as rectal wall, bladder and femoral head, when the patient size changes due to weight loss in prostate volumetric modulated arc therapy (VMAT). METHODS:Three patients with small (32.0 cm3 ), medium (48.4 cm3 ) and large (...

journal_title：Medical physics

authors： Chow J,Jiang R

更新日期：2012-06-01 00:00:00

abstract：:Multielectrode cochlear implantation is the most effective treatment for profound sensorineural hearing loss. In vivo three-dimensional 3-D localization of cochlear implant electrodes is important for modeling of the electrical field in the cochlea, design of electrode arrays, and may improve speech processor programm...

journal_title：Medical physics

authors： Yang S,Wang G,Skinner MW,Rubinstein JT,Vannier MW

更新日期：2000-04-01 00:00:00

abstract：PURPOSE:Couch and MLC tracking are two promising methods for real-time motion compensation during radiation therapy. So far, couch and MLC tracking experiments have mainly been performed by different research groups, and no direct comparison of couch and MLC tracking of volumetric modulated arc therapy (VMAT) plans has...

journal_title：Medical physics

authors： Hansen R,Ravkilde T,Worm ES,Toftegaard J,Grau C,Macek K,Poulsen PR

更新日期：2016-05-01 00:00:00

abstract：PURPOSE:The quality of tomographic images is directly affected by the system model being used in image reconstruction. An accurate system matrix is desirable for high-resolution image reconstruction, but it often leads to high computation cost. In this work the authors present a maximum a posteriori reconstruction algo...

journal_title：Medical physics

authors： Fu L,Qi J

更新日期：2010-02-01 00:00:00

abstract：:The image artifacts characteristic of a scanning chest radiographic system are reviewed. The technique employs a pulsed beam of radiation swept in an overlapping raster pattern that can result in severe ripple and scan line artifacts with improper scanning parameters. A one-dimensional treatment of the scanner geometr...

journal_title：Medical physics

authors： Plewes DB,Vogelstein E

更新日期：1984-03-01 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：PURPOSE:Anomalous pixels may be defined as those pixels whose exposure response relationship is deviant from the typical, expected or calibrated response. A group of anomalous pixels may Result in visible correlated artifacts. Here we demonstrate an approach to identify anomalous pixels and correlated artifacts using f...

journal_title：Medical physics

authors： Dave J,Gingold E,Yorkston J,Bercha I,Goldman L,Walz-Flannigan A,Willis C

更新日期：2012-06-01 00:00:00

abstract：:The dose distribution for an ovoid with a new tungsten shielding design was determined using Monte Carlo simulation. Standard Cesium-137 tube sources, tungsten shielding, and aluminum ovoid applicator were each modeled as a collection of solid objects. Dose was calculated in planes above, below, in front of, and on th...

journal_title：Medical physics

authors： Weeks KJ

更新日期：1998-12-01 00:00:00

abstract：PURPOSE:Hip fracture is a serious health problem and textural methods are being developed to assess bone quality. The authors aimed to perform textural analysis at femur on high-resolution digital radiographs compared to three-dimensional (3D) microarchitecture comparatively to bone mineral density. METHODS:Sixteen ca...

journal_title：Medical physics

authors： Ranjanomennahary P,Ghalila SS,Malouche D,Marchadier A,Rachidi M,Benhamou C,Chappard C

更新日期：2011-01-01 00:00:00

abstract：PURPOSE:The Alvarez-Macovski method extracts the x-ray energy-dependent information by expanding the attenuation coefficient as a linear combination of functions of energy multiplied by basis set coefficients. Since the basis functions are known a priori, the coefficients represent all the energy-dependent information....

journal_title：Medical physics

authors： Alvarez RE

更新日期：2019-01-01 00:00:00

abstract：:Projected light fields are used on treatment simulators and teletherapy treatment units to delineate the size and position of the radiation beam. Any discrepancy between these fields will lead to a systematic field placement error, with possibly serious implications with regard to the accuracy of the delivered dose di...

journal_title：Medical physics

authors： Luchka K,Chen D,Shalev S,Gluhchev G,Rajapakshe R

更新日期：1996-07-01 00:00:00

abstract：:It is known that motion of an object imaged by magnetic resonance imaging leads to errors and artifacts in the image. This effect is especially important when a pulse sequence with long echo time (TE) and long TR is used to provide T2-weighted images. We have modified the usual spin warp imaging pulse sequence in a wa...

journal_title：Medical physics

authors： Joseph PM,Shetty A,Bonaroti EA

更新日期：1987-07-01 00:00:00

abstract：:This paper deals with methods of reducing the total time required to acquire the projection data for a set of contiguous computed tomography (CT) images. Normally during the acquisition of a set of slices, the patient is held stationary during data collection and translated to the next axial location during an intersc...

journal_title：Medical physics

authors： Crawford CR,King KF

更新日期：1990-11-01 00:00:00

abstract：PURPOSE:To investigate the use of local noise power spectrum (NPS) to characterize image noise and wavelet analysis to isolate defective pixels and inter-subpanel flat-fielding artifacts for quantitative quality assurance (QA) of electronic portal imaging devices (EPIDs). METHODS:A total of 93 image sets including cus...

journal_title：Medical physics

authors： Lee S,Yan G,Bassett P,Gopal A,Samant S

更新日期：2016-09-01 00:00:00

abstract：PURPOSE:Wide-angle free-air chambers (WAFACs) are used as primary standard measurement devices for establishing the air-kerma strength of low-energy, low-dose rate brachytherapy seeds. The National Research Council of Canada (NRC) is commissioning a primary standard wide-angle free-air chamber (NRC WAFAC) to serve the ...

journal_title：Medical physics

authors： Shen H,Culberson WS,Ross CK

更新日期：2016-07-01 00:00:00

abstract：PURPOSE:The purpose of this study was to describe and evaluate methods for calculating a megavoltage computed tomography (MVCT)-derived MR hardware attenuation map (μ-map) and dual-energy CT (DECT) for 511 keV photons. METHODS:Phantom measurements were acquired on a whole-body hybrid PET/MRI system, using a four-chann...

journal_title：Medical physics

authors： Patrick JC,Terry Thompson R,So A,Butler J,Faul D,Stodilka RZ,Yartsev S,Prato FS,Gaede S

更新日期：2017-09-01 00:00:00

abstract：BACKGROUND:The rapid development and complexity of new x-ray computed tomography (CT) technologies and the need for evidence-based optimization of image quality with respect to radiation and contrast media dose call for an updated approach towards CT performance evaluation. AIMS:This report offers updated testing guid...

journal_title：Medical physics

authors： Samei E,Bakalyar D,Boedeker KL,Brady S,Fan J,Leng S,Myers KJ,Popescu LM,Ramirez Giraldo JC,Ranallo F,Solomon J,Vaishnav J,Wang J

更新日期：2019-11-01 00:00:00

abstract：:The MCNP Monte Carlo radiation transport code was modified for diagnostic medical physics applications. In particular, the modified code was thoroughly benchmarked for the production of polychromatic tungsten x-ray spectra in the 30-150 kV range. Validating the modified code for coupled electron-photon transport with ...

journal_title：Medical physics

authors： Mercier JR,Kopp DT,McDavid WD,Dove SB,Lancaster JL,Tucker DM

更新日期：2000-12-01 00:00:00

abstract：PURPOSE:This study aims to measure the surface dose on an anthropomorphic phantom for intensity-modulated radiation therapy (IMRT) plans treated in a 1.5 T magnetic resonance (MR)-Linac. Previous studies have used Monte Carlo programs to simulate surface dose and have recognized high surface dose as a potential limitin...

journal_title：Medical physics

authors： Lim-Reinders S,Keller BM,Sahgal A,Chugh B,Kim A

更新日期：2020-07-01 00:00:00

abstract：:Cone-beam computed tomography systems have been developed to provide in situ imaging for the purpose of guiding radiation therapy. Clinical systems have been constructed using this approach, a clinical linear accelerator (Elekta Synergy RP) and an iso-centric C-arm. Geometric calibration involves the estimation of a s...

journal_title：Medical physics

authors： Cho Y,Moseley DJ,Siewerdsen JH,Jaffray DA

更新日期：2005-04-01 00:00:00

abstract：PURPOSE:This paper provides a comparison between a fast, commercial, in-patient Monte Carlo dose calculation algorithm (GPUMCD) and geant4. It also evaluates the dosimetric impact of the application of an external 1.5 T magnetic field. METHODS:A stand-alone version of the Elekta™ GPUMCD algorithm, to be used within th...

journal_title：Medical physics

authors： Ahmad SB,Sarfehnia A,Paudel MR,Kim A,Hissoiny S,Sahgal A,Keller B

更新日期：2016-02-01 00:00:00

abstract：PURPOSE:To show that Cherenkov emission is generated by external radiotherapy beam in tissue, and could serve as optical source to excite an oxygen sensitive phosphor, Oxyphor G4, within tissue. The intensity and lifetime of the phosphorescence was measured with a time-gated system and reveals the oxygenation levels in...

journal_title：Medical physics

authors： Zhang R,Kanick S,Vinogradov S,Esipova T,Pogue B

更新日期：2012-06-01 00:00:00