Detour factors in water and plastic phantoms and their use for range and depth scaling in electron-beam dosimetry.

abstract：:Positron range impairs resolution in PET imaging, especially for high-energy emitters and for small-animal PET. De-blurring in image reconstruction is possible if the blurring distribution is known. Furthermore, the percentage of annihilation events within a given distance from the point of positron emission is releva...

journal_title：Physics in medicine and biology

authors： Jødal L,Le Loirec C,Champion C

更新日期：2012-06-21 00:00:00

abstract：:Beam tracking with scanned carbon ion radiotherapy achieves highly conformal target dose by steering carbon pencil beams to follow moving tumors using real-time magnetic deflection and range modulation. The purpose of this study was to evaluate the robustness of target dose coverage from beam tracking in light of posi...

journal_title：Physics in medicine and biology

authors： Eley JG,Newhauser WD,Richter D,Lüchtenborg R,Saito N,Bert C

更新日期：2015-02-21 00:00:00

abstract：:Effects of different scatter compensation methods incorporated in fully 3D iterative reconstruction are investigated. The methods are: (i) the inclusion of an 'ideal scatter estimate' (ISE); (ii) like (i) but with a noiseless scatter estimate (ISE-NF); (iii) incorporation of scatter in the point spread function during...

journal_title：Physics in medicine and biology

authors： Beekman FJ,Kamphuis C,Frey EC

更新日期：1997-08-01 00:00:00

abstract：:The aim of this study was to evaluate angiogenic compositions and tumour response in the course of neoadjuvant chemotherapy in patients with locally advanced breast cancer (LABC) using dynamic contrast-enhanced (DCE) MRI. Thirteen patients with LABC underwent serial DCE MRI during the course of chemotherapy. DCE MRI w...

journal_title：Physics in medicine and biology

authors： Chang YC,Huang CS,Liu YJ,Chen JH,Lu YS,Tseng WY

更新日期：2004-08-21 00:00:00

abstract：:Breast-conserving surgery is a standard option for the treatment of patients with early-stage breast cancer. This form of surgery may result in incomplete excision of the tumor. Iodine-125 labeled titanium seeds are currently used in clinical practice to reduce the number of incomplete excisions. It seems likely that ...

journal_title：Physics in medicine and biology

authors： Arsenali B,de Jong HW,Viergever MA,Dickerscheid DB,Beijst C,Gilhuijs KG

更新日期：2015-10-07 00:00:00

abstract：:During minimally invasive surgery (MIS) for lung tumor resection, the localization of tumors or nodules relies on visual inspection of the deflated lung on intra-procedural video. For patients with tumors or nodules located deeper in the lung, this localization is not possible without prior invasive marking techniques...

journal_title：Physics in medicine and biology

authors： Lesage AJ,Rajaram R,Tam AL,Rigaud BS,Brock KK,Rice DC,Cazoulat G

更新日期：2020-09-09 00:00:00

abstract：:The aim of this paper is to determine the dosimetric impact of trace elements in human tissues for low-energy photon sources used in brachytherapy. Monte Carlo dose calculations were used to investigate the dosimetric effect of trace elements present in normal or cancerous human tissues. The effect of individual trace...

journal_title：Physics in medicine and biology

authors： White SA,Landry G,van Gils F,Verhaegen F,Reniers B

更新日期：2012-06-07 00:00:00

abstract：:We propose a regularized least-squares method for reconstructing 2D velocity vector fields within the left ventricular cavity from single-view color Doppler echocardiographic images. Vector flow mapping is formulated as a quadratic optimization problem based on an [Formula: see text]-norm minimization of a cost functi...

journal_title：Physics in medicine and biology

authors： Assi KC,Gay E,Chnafa C,Mendez S,Nicoud F,Abascal JFPJ,Lantelme P,Tournoux F,Garcia D

更新日期：2017-08-11 00:00:00

abstract：:This work modified the commonly used Monte Carlo tool package GATE by developing a new 'multiPatchPET' system so that GATE users can easily simulate PET systems with irregular geometries. The motivation was to design a brain PET scanner with high sensitivity. It is known that compact PET scanners with a large solid co...

journal_title：Physics in medicine and biology

authors： Chen G,Weng F,Hong X,Tao W,Zhao Z,Peng Q,Huang Q

更新日期：2018-09-06 00:00:00

abstract：:Megavoltage (MV) cone-beam computed tomography (CBCT) using an electronic portal imaging (EPID) offers advantageous features, including 3D mapping, treatment beam registration, high-z artifact suppression, and direct radiation dose calculation. Adoption has been slowed by image quality limitations and concerns about i...

journal_title：Physics in medicine and biology

authors： Hu YH,Fueglistaller R,Myronakis M,Rottmann J,Wang A,Shedlock D,Morf D,Baturin P,Huber P,Star-Lack J,Berbeco R

更新日期：2018-06-20 00:00:00

abstract：:Backscatter factors for orthovoltage x-ray beams are fitted with the expression BSF = 1 + ms/(s + n), where s is field size and m and n are adjustable parameters. The accuracy is better than 0.5%. Good results were also obtained for Cs-137 gamma rays at depth 0.12 cm and Co-60 gamma rays at depth 0.5 cm using the same...

journal_title：Physics in medicine and biology

authors： Xiao Y,Bjärngard B

更新日期：1998-05-01 00:00:00

abstract：:Evidence that some lung tumors change shape during respiration is derived from respiratory gated CT data by statistical shape modeling and image manipulation. Some tumors behave as rigid objects while others show systematic shape changes. Two views of lung motion are presented to allow analysis of the results. In the ...

journal_title：Physics in medicine and biology

authors： Kyriakou E,McKenzie DR

更新日期：2012-02-21 00:00:00

abstract：:Target motion is one of the major limitations of each high precision radiation therapy. Using advanced active beam delivery techniques, such as the magnetic raster scanning system for particle irradiation, the interplay between time-dependent beam and target position heavily distorts the applied dose distribution. Thi...

journal_title：Physics in medicine and biology

authors： Li Q,Groezinger SO,Haberer T,Rietzel E,Kraft G

更新日期：2004-07-21 00:00:00

abstract：:Calculations indicate that an assembly consisting of an antimony-beryllium source at the centre of a 4 cm radius water sphere surrounded by a 1 mm thick shell of boron-10 will emit neutrons with a broad spectrum at intermediate energies. A device based on this design was constructed using a water-filled, boron-carbide...

journal_title：Physics in medicine and biology

authors： Harvey JR,Bending RC

更新日期：1976-01-01 00:00:00

abstract：:In clinical computed tomography (CT) images, cortical bone features with sub-millimeter (sub-mm) thickness are substantially blurred, such that their thickness is overestimated and their intensity appears underestimated. Therefore, any inquiry of the geometry or the density of such bones based on these images is sever...

journal_title：Physics in medicine and biology

authors： Pakdel A,Robert N,Fialkov J,Maloul A,Whyne C

更新日期：2012-12-07 00:00:00

abstract：:Although the calculation of the surface average of the low-frequency current density distribution over a cross-section of 1 cm2 is required by ICNIRP guidelines, no reference averaging algorithm is indicated, neither in the ICNIRP guidelines nor in the Directive 2004/40/EC that is based on them. The lack of a general ...

journal_title：Physics in medicine and biology

authors： Zoppetti N,Andreuccetti D

更新日期：2009-08-07 00:00:00

abstract：:The 'monoenergetic' electron loss model was derived in a previous work to account for pathlength straggling in the Fermi-Eyges pencil beam problem. In this paper, we extend this model to account for energy-loss straggling and secondary knock-on electron transport in order to adequately predict a depth dose curve. To m...

journal_title：Physics in medicine and biology

authors： Chvetsov AV,Sandison GA,Yeboah C

更新日期：2000-10-01 00:00:00

abstract：:The process of organ motion correction in scintigraphy is analysed in the frequency domain. The sequence of the chi- and gamma- coordinates registered during scintigraphic recording is converted to a frequency spectrum by a discrete Fourier transform. In the frequency domain motion correction is performed by linear fi...

journal_title：Physics in medicine and biology

authors： Schmidlin P

更新日期：1975-05-01 00:00:00

abstract：:An important aspect of robotic radiation therapy is active compensation of target motion. Recently, ultrasound has been proposed to obtain real-time volumetric images of abdominal organ motion. One approach to realize flexible probe placement throughout the treatment fraction is based on a robotic arm holding the ultr...

journal_title：Physics in medicine and biology

authors： Schlüter M,Fürweger C,Schlaefer A

更新日期：2019-10-04 00:00:00

abstract：:The exponential edge-gradient effect must arise in any x-ray transmission CT scanner whenever long sharp edges of high contrast are encountered. The effect is non-linear and is due to the interaction of the exponential law of x-ray attenuation and the finite width of the scanning beam in the x-y plane. The error induc...

journal_title：Physics in medicine and biology

authors： Joseph PM,Spital RD

更新日期：1981-05-01 00:00:00

abstract：:At certain frequencies, when the human head becomes a resonant structure, the power absorbed by the head and neck, when the body is exposed to a vertically polarized plane wave propagating from front to back, becomes significantly larger than would ordinarily be expected from its shadow cross section. This has possibl...

journal_title：Physics in medicine and biology

authors： Tinniswood AD,Furse CM,Gandhi OP

更新日期：1998-08-01 00:00:00

abstract：:Monte Carlo simulation techniques are applied to track the annihilation photons from positron decay, and store the photon histories. Reasonably realistic models of the isotope distribution in the brain and heart during typical PET studies, as well as the traditional phantoms used for measuring PET scanner performance ...

journal_title：Physics in medicine and biology

authors： Thompson CJ,Moreno-Cantu J,Picard Y

更新日期：1992-03-01 00:00:00

abstract：:The influence of artefacts due to metal implants on the range of ion beams is investigated, using a geometrically well-defined head and pelvic phantom together with inserts from steel, titanium and tungsten. The ranges along various beam paths including artefacts were calculated from the TPS and compared to known calc...

journal_title：Physics in medicine and biology

authors： Jäkel O,Reiss P

更新日期：2007-02-07 00:00:00

abstract：:The dose-calculation accuracy of the tomotherapy Hi-Art II(R) (Tomotherapy, Inc., Madison, WI) treatment planning system (TPS) in the presence of low-density lung media was investigated. In this evaluation, a custom-designed heterogeneous phantom mimicking the mediastinum geometry was used. Gammex LN300 and balsa wood...

journal_title：Physics in medicine and biology

authors： Chaudhari SR,Pechenaya OL,Goddu SM,Mutic S,Rangaraj D,Bradley JD,Low D

更新日期：2009-04-21 00:00:00

abstract：:This paper describes the algorithm and examines the performance of an intensity-modulated radiation therapy (IMRT) beam-angle optimization (BAO) system. In this algorithm successive sets of beam angles are selected from a set of predefined directions using a fast simulated annealing (FSA) algorithm. An IMRT beam-profi...

journal_title：Physics in medicine and biology

authors： Djajaputra D,Wu Q,Wu Y,Mohan R

更新日期：2003-10-07 00:00:00

abstract：:A method is presented for extraction of intra and inter fraction motion of seeds/markers within the patient from cone beam CT (CBCT) projection images. The position of the marker is determined on each projection image and fitted to a function describing the projection of a fixed point onto the imaging panel at differe...

journal_title：Physics in medicine and biology

authors： Marchant TE,Amer AM,Moore CJ

更新日期：2008-02-21 00:00:00

abstract：:The ion recombination is examined in parallel-plate ionization chambers in scanning proton beams at the Danish Centre for Particle Therapy and the Skandion Clinic. The recombination correction factor k s is investigated for clinically relevant energies between 70 MeV and 244 MeV for dose rates below 400 Gy min-1 in ai...

journal_title：Physics in medicine and biology

authors： Christensen JB,Almhagen E,Stolarczyk L,Liszka M,Hernandez GG,Bassler N,Nørrevang O,Vestergaard A

更新日期：2020-06-05 00:00:00

abstract：:A step and shoot sequencer was developed that can be integrated into an IMRT optimization algorithm. The method uses non-uniform fluence steps and is adopted to the constraints of an MLC. It consists of a clustering, a smoothing and a segmentation routine. The performance of the algorithm is demonstrated for eight mat...

journal_title：Physics in medicine and biology

authors： Bär W,Alber M,Nüsslin F

更新日期：2001-07-01 00:00:00

abstract：:All particle beam scanning systems are subject to dose delivery errors due to errors in position, energy and intensity of the delivered beam. In addition, finite scan speeds, beam spill non-uniformities, and delays in detector, detector electronics and magnet responses will all contribute errors in delivery. In this p...

journal_title：Physics in medicine and biology

authors： Coutrakon G,Wang N,Miller DW,Yang Y

更新日期：2010-12-07 00:00:00

abstract：:Results from dielectric studies on the freshwater fish Cyprinus carpio exposed to a sublethal concentration of sodium alkyl benzene sulphonate were compared with those from untreated control fish; recovery from the test solution was also checked. The influence of the anionic detergent on the intracellular matter of fi...

journal_title：Physics in medicine and biology

authors： Bielinska I,Terlecki J

更新日期：1984-05-01 00:00:00