Deterministic photon kerma distribution based on the Boltzmann equation for external beam radiation therapy.

abstract：PURPOSE:The aim of this study was to evaluate a surrogate-driven motion model based on four-dimensional computed tomography that is able to predict CT volumes corresponding to arbitrary respiratory phases. Furthermore, the comparison of three different driving surrogates is examined and the feasibility of using the mod...

journal_title：Medical physics

authors： Wölfelschneider J,Seregni M,Fassi A,Ziegler M,Baroni G,Fietkau R,Riboldi M,Bert C

更新日期：2017-06-01 00:00:00

abstract：:A new calibration algorithm (GLAaS) to derive absolute dose maps from images acquired with the Varian PV-aS500 electronic portal imager (based on amorphous silicon detectors) has been developed incorporating the dependence of detector response on primary and transmitted radiation and on field size. Detector calibratio...

journal_title：Medical physics

authors： Nicolini G,Fogliata A,Vanetti E,Clivio A,Cozzi L

更新日期：2006-08-01 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

abstract：:The EGS4 Monte Carlo code has been used to investigate the response of a PTW/diamond detector irradiated in both clinical and monoenergetic megavoltage electron beams ranging in energy from 5 to 20 MeV. The sensitive volume of the PTW/diamond detector simulated has a thickness of 0.4 mm and a diameter of 4.4 mm. Irrad...

journal_title：Medical physics

authors： Mobit PN,Sandison GA

更新日期：1999-05-01 00:00:00

abstract：:Recent working groups of the AAPM [Almond et al., Med. Phys. 26, 1847 (1999)] and the IAEA (Andreo et al., Draft V.7 of "An International Code of Practice for Dosimetry based on Standards of Absorbed Dose to Water," IAEA, 2000) have described guidelines to base reference dosimetry of high energy photon beams on absorb...

journal_title：Medical physics

authors： Seuntjens JP,Ross CK,Shortt KR,Rogers DW

更新日期：2000-12-01 00:00:00

abstract：:The method of images is employed to insert the effects of the presence of a single lateral boundary on contrast functions previously derived for an infinite slab using a random walk model of photon transport. The predictions of the model for zero and extrapolated boundary conditions are compared with Monte Carlo (MC) ...

journal_title：Medical physics

authors： Chernomordik V,Gandjbakhche AH,Hebden JC,Zaccanti G

更新日期：1999-09-01 00:00:00

abstract：:A comparison of two methods of scatter compensation in single photon emission computed tomography (SPECT) imaging is made on the basis of improvements in quantification. The methods, scatter-window subtraction and constrained deconvolution of an average point source response function (PSRF), are described; the theoret...

journal_title：Medical physics

authors： Yanch JC,Flower MA,Webb S

更新日期：1990-11-01 00:00:00

abstract：:A method to significantly reduce the exposure area product in fluoroscopy using a pre-patient region-of-interest (ROI) attenuator is presented. The attenuator has a thin central region and a gradually increasing thickness away from the center. It is shown that the unwanted brightening artifact caused by the attenuator...

journal_title：Medical physics

authors： Robert N,Komljenovic PT,Rowlands JA

更新日期：2002-05-01 00:00:00

abstract：PURPOSE:A commonly used beam quality index (Q) for high-energy photon beams is the tissue phantom ratio (TPR20,10) for a square field of 10 x 10 cm2 and SDD of 100 cm. On some specialized radiotherapy treatment equipment such a reference collimator setting is not achievable. Likewise a flat beam profile, not explicitly...

journal_title：Medical physics

authors： Sauer OA

更新日期：2009-09-01 00:00:00

abstract：:Permanent implants of 125I seeds at Memorial Sloan-Kettering Cancer Center are performed by the method of "dimension averaging" to determine the total activity to be implanted; that is, the activity (in mCi) is taken to be five times the average dimension (in cm) of the target region. A nomograph has recently been dev...

journal_title：Medical physics

authors： Anderson LL

更新日期：1976-01-01 00:00:00

abstract：PURPOSE:Breast magnetic resonance imaging is highly sensitive but not very specific for the detection of breast cancer. Opportunities exist to supplement the image acquisition with a more specific modality provided the technical challenges of meeting space limitations inside the bore, restricted breast access, and elec...

journal_title：Medical physics

authors： Meaney PM,Golnabi AH,Epstein NR,Geimer SD,Fanning MW,Weaver JB,Paulsen KD

更新日期：2013-10-01 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：PURPOSE:In Stereotactic body radiation therapy (SBRT) higher dose per fraction is delivered to patients and thus the need for an accurate dose computation is further elevated. However under such conditions of small field geometries, the electronic equilibrium can be lost, making it challenging for the dose-calculation ...

journal_title：Medical physics

authors： Shosha M,Deiab N,Eldib A,Tohamy K

更新日期：2012-06-01 00:00:00

abstract：:The fast imaging method named skipped phase encoding and edge deghosting (SPEED) has been demonstrated to reduce scan time considerably with typical magnetic resonance imaging data. In this work, SPEED is simplified with improved efficiency to accelerate the scan of sparse objects; we refer to this method as S-SPEED. ...

journal_title：Medical physics

authors： Chang Z,Xiang QS

更新日期：2007-08-01 00:00:00

abstract：PURPOSE:To improve the dose homogeneity in patch-field proton therapy using beam current modulation. METHODS:MCNPX simulations were performed for various configurations of the Mevion S250 beamline. Spread-out Bragg peak (SOBP) dose distributions were calculated, and lateral and distal dose profiles were extracted for ...

journal_title：Medical physics

authors： Hill P,Klein E,Bloch C

更新日期：2012-06-01 00:00:00

abstract：PURPOSE:Cardiac motion is typically not accounted for during pretreatment imaging for central lung and mediastinal tumors. However, cardiac induced tumor motion averages 5.8 mm for esophageal tumors and 3-5 mm for some lung tumors, which can result in positioning errors. Our aim is to reduce both cardiac- and respirato...

journal_title：Medical physics

authors： Reynolds T,Shieh CC,Keall PJ,O'Brien RT

更新日期：2019-09-01 00:00:00

abstract：:Respiratory motion can introduce significant errors in radiotherapy. Conventional CT scans as commonly used for treatment planning can include severe motion artifacts that result from interplay effects between the advancing scan plane and object motion. To explicitly include organ/target motion in treatment planning a...

journal_title：Medical physics

authors： Rietzel E,Pan T,Chen GT

更新日期：2005-04-01 00:00:00

abstract：:Monte Carlo simulations of x-ray beams typically take parameters of the electron beam in the accelerating waveguide to be free parameters. In this paper, a methodology is proposed and implemented to determine the energy, spectral width, and beam divergence of the electron source. All treatment head components were rem...

journal_title：Medical physics

authors： Sawkey DL,Faddegon BA

更新日期：2009-03-01 00:00:00

abstract：PURPOSE:The authors combine the registration of 2D beam's eye view (BEV) images and 3D planning computed tomography (CT) images, with relative, markerless tumor tracking to provide automatic absolute tracking of physician defined volumes such as the gross tumor volume (GTV). METHODS:During treatment of lung SBRT cases...

journal_title：Medical physics

authors： Bryant JH,Rottmann J,Lewis JH,Mishra P,Keall PJ,Berbeco RI

更新日期：2014-12-01 00:00:00

abstract：:Depending on the clinical application, it is frequently necessary to tilt the gantry of an x-ray CT system with respect to the patient and couch. For single-slice fan-beam systems, tilting the gantry introduces no errors or artifacts. Most current systems, however, are helical multislice systems with up to 16 slices. ...

journal_title：Medical physics

authors： Hein I,Taguchi K,Silver MD,Kazama M,Mori I

更新日期：2003-12-01 00:00:00

abstract：PURPOSE:Computed tomography (CT) and, in particular, cone beam CT (CBCT) have been increasingly used as a diagnostic tool in recent years. Patient motion during acquisition is common in CBCT due to long scan times. This results in degraded image quality and may potentially increase the number of retakes. Our aim was to...

journal_title：Medical physics

authors： Niebler S,Schömer E,Tjaden H,Schwanecke U,Schulze R

更新日期：2019-10-01 00:00:00

abstract：:Volumetric modulated arc therapy (VMAT) has recently been used to improve the dose distribution and efficiency of treatment delivery over the standard intensity-modulated radiotherapy (IMRT) technique. This study compares the dosimetry between RapidArc plan and standard IMRT plan for head and neck cancer. Three head a...

journal_title：Medical physics

authors： Jiang R,Fleck A,Schaly B,Charland P,Zhan L,Alliet K,Rachakonda R,Osei E

更新日期：2012-07-01 00:00:00

abstract：PURPOSE:Stationary computed tomography (s-CT) conceptually offers several advantages over existing rotating gantry-based CT. Over the last 40 yr, s-CT has been investigated using different technological approaches. We are developing a s-CT system specifically for head/brain imaging using carbon nanotube (CNT)-based fie...

journal_title：Medical physics

authors： Spronk D,Luo Y,Inscoe CR,Lee YZ,Lu J,Zhou O

更新日期：2020-12-31 00:00:00

abstract：PURPOSE:This article aims to introduce a novel algorithm for fast beam angle selection in intensity modulated radiotherapy (IMRT). METHODS:The algorithm models the optimization problem as a beam angle ranking problem and chooses suitable beam angles according to their rank. A new parameter called "beam intensity profi...

journal_title：Medical physics

authors： Vaitheeswaran R,Narayanan VK,Bhangle JR,Nirhali A,Kumar N,Basu S,Maiya V

更新日期：2010-12-01 00:00:00

abstract：:The Radiological Physics Center (RPC) developed two heterogeneous anthropomorphic quality assurance phantoms for use in verifying the accuracy of radiation delivery: one for intensity-modulated radiation therapy (IMRT) to the pelvis and the other for stereotactic body radiation therapy (SBRT) to the thorax. The purpos...

journal_title：Medical physics

authors： Followill DS,Evans DR,Cherry C,Molineu A,Fisher G,Hanson WF,Ibbott GS

更新日期：2007-06-01 00:00:00

abstract：PURPOSE:Manual delineation of head and neck (H&N) organ-at-risk (OAR) structures for radiation therapy planning is time consuming and highly variable. Therefore, we developed a dynamic multiatlas selection-based approach for fast and reproducible segmentation. METHODS:Our approach dynamically selects and weights the a...

journal_title：Medical physics

authors： Haq R,Berry SL,Deasy JO,Hunt M,Veeraraghavan H

更新日期：2019-12-01 00:00:00

abstract：PURPOSE:Radiosensitizer enhanced radiotherapy provides the possibility of improved treatment outcomes by preferentially increasing the effectiveness of radiation within the tumor. Proton therapy offers improved sparing of tissue distal of the tumor along the beam path and reduced integral dose compared to conventional ...

journal_title：Medical physics

authors： Peukert D,Kempson I,Douglass M,Bezak E

更新日期：2020-02-01 00:00:00

abstract：PURPOSE:Texture analysis (TA) has proved to be useful to distinguish different tissues and disease states using magnetic resonance imaging (MRI). TA has been successfully applied clinically to improve identification of abnormalities in the brain, liver, and bone and, more recently, has been used to enhance the specific...

journal_title：Medical physics

authors： Waugh SA,Lerski RA,Bidaut L,Thompson AM

更新日期：2011-09-01 00:00:00

abstract：:Noise power spectrum (NPS) and detective quantum efficiency (DQE) for metal-plate/film portal detectors are reported for the Co-60 and Linac 10 MV spectra. The detectors consist of a double-emulsion portal film secured between plates of aluminum, copper, brass, or lead. The NPS was found to be independent of the detec...

journal_title：Medical physics

authors： Falco T,Fallone BG

更新日期：1998-12-01 00:00:00

abstract：:Breast density, the percentage of glandular breast tissue, has been identified as an important yet underutilized risk factor in the development of breast cancer. A quantitative method to measure breast density with dual energy imaging was investigated using a computer simulation model. Two configurations to measure br...

journal_title：Medical physics

authors： Ducote JL,Molloi S

更新日期：2008-12-01 00:00:00