4D Monte Carlo simulation of proton beam scanning: modelling of variations in time and space to study the interplay between scanning pattern and time-dependent patient geometry.

abstract：:In situ and in vivo treatment plan verification and beam monitoring as well as dose control during heavy-ion tumour therapy can be performed in principle by measurements of range distributions of beta(+)-emitting nuclei by means of PET techniques. For this purpose the performance of different types of positron camera ...

journal_title：Physics in medicine and biology

authors： Pawelke J,Byars L,Enghardt W,Fromm WD,Geissel H,Hasch BG,Lauckner K,Manfrass P,Schardt D,Sobiella M

更新日期：1996-02-01 00:00:00

abstract：:This work presents a Monte Carlo model of Leksell Gamma Knife Perfexion as well as the main parameters of the dose distribution in the standard phantom obtained using this model. The model is developed in the Geant4 simulation toolkit in a modular way which enables its reuse in other Perfexion studies. Large phase spa...

journal_title：Physics in medicine and biology

authors： Pipek J,Novotný J,Novotný J,Kozubíková P

更新日期：2014-12-21 00:00:00

abstract：:Three-dimensional reconstruction of coronary arteries can be performed during x-ray-guided interventions by gated reconstruction from a rotational coronary angiography sequence. Due to imperfect gating and cardiac or breathing motion, the heart's motion state might not be the same in all projections used for the recon...

journal_title：Physics in medicine and biology

authors： Hansis E,Schäfer D,Dössel O,Grass M

更新日期：2008-07-21 00:00:00

abstract：:A theoretical analysis is presented of the biologically effective dose of the solar long wave ultraviolet radiation (UVA) received by patients who are being treated for psoriasis by oral psoralen photochemotherapy. It is shown that patients treated during the summer months in the UK may well receive a UV dose which is...

journal_title：Physics in medicine and biology

authors： Diffey BL

更新日期：1981-11-01 00:00:00

abstract：:This work investigates the attenuation of a proton beam to reconstruct the map of the linear attenuation coefficient of a material which is mainly caused by the inelastic interactions of protons with matter. Attenuation proton computed tomography (pCT) suffers from a poor spatial resolution due to multiple Coulomb sca...

journal_title：Physics in medicine and biology

authors： Quiñones CT,Létang JM,Rit S

更新日期：2016-05-07 00:00:00

abstract：:The purpose of this work was to create a computational platform for studying motion in intensity modulated radiotherapy (IMRT). Specifically, the non-uniform rational B-spline (NURB) cardiac and torso (NCAT) phantom was modified for use in a four-dimensional Monte Carlo (4D-MC) simulation system to investigate the eff...

journal_title：Physics in medicine and biology

authors： McGurk R,Seco J,Riboldi M,Wolfgang J,Segars P,Paganetti H

更新日期：2010-03-07 00:00:00

abstract：:In magnetic drug targeting a chemotherapeutic agent is bound to coated magnetic nanoparticles, which are administered to the blood vessel system and subsequently focused by an external applied magnetic field. The optimization of intra-arterial magnetic drug targeting (MDT) requires detailed knowledge about the biodist...

journal_title：Physics in medicine and biology

authors： Richter H,Wiekhorst F,Schwarz K,Lyer S,Tietze R,Alexiou Ch,Trahms L

更新日期：2009-09-21 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 iterative algorithm has been developed to reduce blur artefacts in images obtained from the Pho/Con multiplane tomographic scanner. In this technique estimates of the activity distribution are convolved with the detector response function and compared with the original blurred image planes. Successive estimates of ...

journal_title：Physics in medicine and biology

authors： Zenari A,Hooper RH,Osborne N,Scrimger JW

更新日期：1985-07-01 00:00:00

abstract：:Compact gamma cameras with a square-shaped monolithic scintillator crystal and an array of silicon photomultipliers (SiPMs) are actively being developed for applications in areas such as small animal imaging, cancer diagnostics and radiotracer guided surgery. Statistical methods of position reconstruction, which are p...

journal_title：Physics in medicine and biology

authors： Morozov A,Alves F,Marcos J,Martins R,Pereira L,Solovov V,Chepel V

更新日期：2017-05-07 00:00:00

abstract：:A full-field speckle interferometry method for non-contact and prospectively high speed Photoacoustic Tomography is introduced and evaluated as proof of concept. Thermoelastic pressure induced changes of the objects topography are acquired in a repetitive mode without any physical contact to the object. In order to ob...

journal_title：Physics in medicine and biology

authors： Horstmann J,Spahr H,Buj C,Münter M,Brinkmann R

更新日期：2015-05-21 00:00:00

abstract：:The characteristics of an Elekta Precise treatment machine with a gating interface were investigated. Three detectors were used: a Farmer ionization chamber, a MatriXX ionization chamber array and an in-house, single pulse-measurement ionization chamber (IVC). Measurements were made of dosimetric accuracy, flatness an...

journal_title：Physics in medicine and biology

authors： Evans PM,Symonds-Tayler JR,Colgan R,Hugo GD,Letts N,Sandin C

更新日期：2010-04-21 00:00:00

abstract：:Time- and space-resolved diffuse reflectance measurements were used to identify the optical parameters, the reduced scattering and absorption coefficients, of bulk living tissue in the region from 1.15 to 1.52 microm. Although in this region the detector was limited in its temporal resolution, we applied a peak-time s...

journal_title：Physics in medicine and biology

authors： Nishimura G,Kida I,Tamura M

更新日期：2006-06-07 00:00:00

abstract：:The least known parameters in a Monte Carlo simulation of a linear accelerator treatment head are often the properties of the initial electron beam directed onto the exit vacuum window. Several initial beams with different spatial fluence distributions, angular divergences and energy spectra have been transported thro...

journal_title：Physics in medicine and biology

authors： Björk P,Knöös T,Nilsson P

更新日期：2002-11-21 00:00:00

abstract：:A theoretical analysis and numerical solutions are presented for viscosity-dominated flow through a uniform, highly distensible tube with a slit-shaped cross section undergoing peristalsis. At flow rates below an intrinsic upper limit to the peristaltic carrying capacity of the tube, provided that there is always at l...

journal_title：Physics in medicine and biology

authors： Griffiths DJ

更新日期：1987-07-01 00:00:00

abstract：:To monitor and strategically control energy deposition in magnetic resonance imaging (MRI), measured as a specific absorption rate (SAR), numerical methods using generic human models have been employed to estimate worst-case values. Radiofrequency (RF) sequences are therefore often designed conservatively with large s...

journal_title：Physics in medicine and biology

authors： Jin J,Liu F,Weber E,Crozier S

更新日期：2012-12-21 00:00:00

abstract：:The transverse magnetic field of an MRI-linac sweeps contaminant electrons away from the radiation beam. Films oriented perpendicular to the magnetic field and 5 cm from the radiation beam edge show a projection of the divergent beam, indicating that contaminant electrons spiral along magnetic field lines and deposit ...

journal_title：Physics in medicine and biology

authors： Hackett SL,van Asselen B,Wolthaus JWH,Bluemink JJ,Ishakoglu K,Kok J,Lagendijk JJW,Raaymakers BW

更新日期：2018-05-01 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：: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：:Segmentation of liver in abdominal computed tomography (CT) is an important step for radiation therapy planning of hepatocellular carcinoma. Practically, a fully automatic segmentation of liver remains challenging because of low soft tissue contrast between liver and its surrounding organs, and its highly deformable s...

journal_title：Physics in medicine and biology

authors： Qin W,Wu J,Han F,Yuan Y,Zhao W,Ibragimov B,Gu J,Xing L

更新日期：2018-05-04 00:00:00

abstract：:A Monte Carlo computational model of a fluoroscopic imaging chain was used for deriving optimal technique factors for paediatric fluoroscopy. The optimal technique was defined as the one that minimizes the absorbed dose (or dose rate) in the patient with a constraint of constant image quality. Image quality was assess...

journal_title：Physics in medicine and biology

authors： Tapiovaara MJ,Sandborg M,Dance DR

更新日期：1999-02-01 00:00:00

abstract：:Oxygen ([Formula: see text]) ions are a potential alternative to carbon ions in ion beam therapy. Their enhanced linear energy transfer indicates a higher relative biological effectiveness and a reduced oxygen enhancement ratio. Due to the limited availability of [Formula: see text] ion beams, Monte Carlo (MC) transpo...

journal_title：Physics in medicine and biology

authors： Resch AF,Fuchs H,Georg D

更新日期：2017-09-05 00:00:00

abstract：:A computer program was developed to calculate both integral absorbed dose in a water phantom and entrance exposure, for the imaging of iodine contrast with x-ray intensifying screens. The effect of filtration of the x-ray beam on integral absorbed dose and entrance exposure was studied for 27 different filter material...

journal_title：Physics in medicine and biology

authors： Koedooder K,Venema HW

更新日期：1986-06-01 00:00:00

abstract：:In this note a technique is described for direct aperture optimization of components deliverable by a variable aperture collimator (VAC) for intensity-modulated radiation therapy. The first key result found was that, provided a large number of VAC components were selected for optimization, the resulting fluence profil...

journal_title：Physics in medicine and biology

authors： Webb S

更新日期：2004-03-07 00:00:00

abstract：:This study presents a theoretical approach to the dosimetry for small and non-equilibrium radiation fields. We applied the newly developed VMCBC algorithm to the dosimetry for megavoltage photon beams using Monte Carlo techniques. The approach assumes that a Monte Carlo simulated beam can be calibrated per incident pa...

journal_title：Physics in medicine and biology

authors： Ding GX,Duggan DM,Coffey CW

更新日期：2008-07-07 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：:Ho-166 is a combined beta-gamma emitter of which the betas can be used therapeutically. From the 81 keV gammas of Ho-166, SPECT images can be obtained, which give opportunities to guide Ho-166 therapy. Accurate reconstruction of Ho-166 images is currently hampered by photopeak-scatter in the patient, down-scatter in t...

journal_title：Physics in medicine and biology

authors： de Wit TC,Xiao J,Nijsen JF,van het Schip FD,Staelens SG,van Rijk PP,Beekman FJ

更新日期：2006-10-07 00:00:00

abstract：:Most commonly in radiation therapy, treatments are delivered in a co-planar geometry. Numerous advantages have been reported of adding non-coplanar beams to the treatment plan. The aim of this study was to compare current state-of-the-art VMAT and CyberKnife treatment plans to that of a novel linac design developed at...

journal_title：Physics in medicine and biology

authors： Schüler E,Wang L,Loo BW,Maxim PG

更新日期：2019-06-20 00:00:00

abstract：:A new function to treat tetrahedral-mesh geometry was implemented in the particle and heavy ion transport code systems. To accelerate the computational speed in the transport process, an original algorithm was introduced to initially prepare decomposition maps for the container box of the tetrahedral-mesh geometry. Th...

journal_title：Physics in medicine and biology

authors： Furuta T,Sato T,Han MC,Yeom YS,Kim CH,Brown JL,Bolch WE

更新日期：2017-06-21 00:00:00

abstract：:This paper investigates the feasibility of a scanned cylindrical ultrasound system for producing uniform heating from the central to the superficial portions of the breast or localized heating within the breast at a specific location. The proposed system consists of plane ultrasound transducer(s) mounted on a scanned ...

journal_title：Physics in medicine and biology

authors： Ju KC,Tseng LT,Chen YY,Lin WL

更新日期：2006-02-07 00:00:00