An adaptive technique for digital noise suppression in on-line portal imaging.

abstract：:The development of alpha-emitting radiopharmaceuticals using 211At requires quantitative determination of the time-dependent nature of the 211At biodistribution. However, imaging-based methods for acquiring this information with 211At have not found wide-spread use because of its low abundance of decay emissions suita...

journal_title：Physics in medicine and biology

authors： Crawford JR,Robertson AKH,Yang H,Rodríguez-Rodríguez C,Esquinas PL,Kunz P,Blinder S,Sossi V,Schaffer P,Ruth TJ

更新日期：2018-02-21 00:00:00

abstract：:Technical advances towards high resolution PET imaging try to overcome the inherent physical limitations to spatial resolution. Positrons travel in tissue until they annihilate into the two gamma photons detected. This range is the main detector-independent contribution to PET imaging blurring. To a large extent, it c...

journal_title：Physics in medicine and biology

authors： Cal-González J,Herraiz JL,España S,Corzo PM,Vaquero JJ,Desco M,Udias JM

更新日期：2013-08-07 00:00:00

abstract：:Coronary flow rate remains complex to assess in clinical practice using non-invasive, non-ionizing imaging tools. In this study, we introduce 3D ultrafast Doppler coronary angiography (3D UDCA), an ultrasound-based method to assess coronary blood flows in three-dimensions at high volume-rate and in one single heartbea...

journal_title：Physics in medicine and biology

authors： Correia M,Maresca D,Goudot G,Villemain O,Bizé A,Sambin L,Tanter M,Ghaleh B,Pernot M

更新日期：2020-06-05 00:00:00

abstract：:A post-processing noise suppression technique for biomedical MRI images is presented. The described procedure recovers both sharp edges and smooth surfaces from a given noisy MRI image; it does not blur the edges and does not introduce spikes or other artefacts. The fine details of the image are also preserved. The pr...

journal_title：Physics in medicine and biology

authors： Placidi G,Alecci M,Sotgiu A

更新日期：2003-07-07 00:00:00

abstract：:Approximately 70% of acute coronary artery disease is caused by unstable (vulnerable) plaques with an inflammation of the overlying cap and high lipid content. A rupturing of the inflamed cap of the plaque results in propagation of the thrombus into the lumen, blockage of the artery and acute ischaemic syndrome or sud...

journal_title：Physics in medicine and biology

authors： Shikhaliev PM,Xu T,Ducote JL,Easwaramoorthy B,Mukherjee J,Molloi S

更新日期：2006-02-21 00:00:00

abstract：:The class of non-rigid registration methods proposed in the framework of PDE-constrained large deformation diffeomorphic metric mapping is a particularly interesting family of physically meaningful diffeomorphic registration methods. Inexact Gauss-Newton-Krylov optimization has shown an excellent numerical accuracy an...

journal_title：Physics in medicine and biology

authors： Hernandez M

更新日期：2019-01-07 00:00:00

abstract：:The dosimetric impact of intrafraction prostate motion was investigated for helical tomotherapy treatments. Measured motion tracks were used to calculate the dosimetric impact on delivered target dose distributions. A dynamic dose calculation engine was developed to facilitate this evaluation. It was found that the D9...

journal_title：Physics in medicine and biology

authors： Langen KM,Lu W,Ngwa W,Willoughby TR,Chauhan B,Meeks SL,Kupelian PA,Olivera G

更新日期：2008-12-21 00:00:00

abstract：:A new multiplicative correction factor for tissue heterogeneities based on an exact expression for homogeneous non-unit-density media is proposed. O'Connor's density scaling theorem is invoked to evaluate the medium-specific tissue-maximum ratios used in the exact formulation. Monte Carlo calculations were performed a...

journal_title：Physics in medicine and biology

authors： Petti PL,Siddon RL,Bjärngard BE

更新日期：1986-10-01 00:00:00

abstract：:Voxel phantoms are human models based on computed tomographic or magnetic resonance images obtained from high-resolution scans of a single individual. They consist of a huge number of volume elements (voxels) and are at the moment the most precise representation of the human anatomy. The purpose of this paper is to in...

journal_title：Physics in medicine and biology

authors： Petoussi-Henss N,Zanki M,Fill U,Regulla D

更新日期：2002-01-07 00:00:00

abstract：:A system is described in which large superficial areas of tissue may be heated using a single plane ultrasonic transducer scanned in a raster fashion. The shape of the heated area is determined by the movement of a microswitch which is activated when it strikes the rigid edge of a hole of the required shape cut in a p...

journal_title：Physics in medicine and biology

authors： ter Haar G,Hopewell JW

更新日期：1985-12-01 00:00:00

abstract：:The purpose of this work was to determine noise levels in HMPAO RCBF SPECT images. Eight simulated images of a uniform sphere of activity were made at each of three different count levels. Three images of the Amersham brain phantom were obtained at each of three count levels, roughly corresponding to the simulation le...

journal_title：Physics in medicine and biology

authors： Houston AS,Kemp PM,Griffiths PT,MacLeod MA

更新日期：1994-05-01 00:00:00

abstract：:Multileaf collimators (MLCs) have been in clinical use for many years and meanwhile are commonly used to deliver intensity-modulated radiotherapy (IMRT) beams. For this purpose it is important to know their dosimetric properties precisely, one of them being inter- and intraleaf leakage. The Siemens 160 MLC features a ...

journal_title：Physics in medicine and biology

authors： Klüter S,Sroka-Perez G,Schubert K,Debus J

更新日期：2011-01-21 00:00:00

abstract：:Energy-resolved attenuation data in spectral x-ray imaging enables material decomposition, in which the different materials inside an object can be identified and separated virtually. Material decomposition has the drawback of increased noise in the resulting material images relative to the measured images. Recently, ...

journal_title：Physics in medicine and biology

authors： Schaff F,Morgan KS,Paganin DM,Kitchen MJ

更新日期：2020-10-07 00:00:00

abstract：:The aim of this study is to determine the impact of longitudinal micro-CT imaging on the growth of B16F1 tumours in C57BL/6 mice. Sixty mice received 2 × 10(5) B16F1 cells subcutaneously in the hind flank and were divided into control (no scan), 'low-dose' (80 kVp, 70 mA, 8 s, 0.07 Gy), 'medium-dose' (80 kVp, 50 mA, 3...

journal_title：Physics in medicine and biology

authors： Foster WK,Ford NL

更新日期：2011-01-21 00:00:00

abstract：:Mean glandular dose (MGD) is the figure of merit to assess breast dose after a mammographic acquisition. The use of normalized MGD obtained from Monte Carlo computations with measured incident air kerma determines the MGD delivered to patients. The Geant4 Application for Tomographic Emission (GATE) toolkit is a modern...

journal_title：Physics in medicine and biology

authors： Myronakis ME,Zvelebil M,Darambara DG

更新日期：2013-04-07 00:00:00

abstract：:Light propagation in a turbid medium is considered using the linear transport equation. The existence of a diffusion length is proved for the Henyey-Greenstein scattering kernel for all absorption ratios. Numerical methods are given that allow accurate computation of the diffusion coefficient quite easily. ...

journal_title：Physics in medicine and biology

authors： Sahni DC,Dahl EB,Sjöstrand NG

更新日期：2003-12-07 00:00:00

abstract：:The purpose of this study was the characterization of local magnetic susceptibility deviations by spectral analysis of their induced magnetic field inhomogeneities. Magnetic resonance spectra and related signal decay curves of local susceptibility deviations were simulated for different volume fractions and compositio...

journal_title：Physics in medicine and biology

authors： Seppenwoolde JH,van Zijtveld M,Bakker CJ

更新日期：2005-01-21 00:00:00

abstract：:We describe an improved algorithm for localising equivalent sources of biomagnetic fields in the human brain. The algorithm is an improvement over the sphere model in that it considers two distinct surfaces: an ellipsoid, to model the region of the skull on which the sensors are placed, and a sphere as the medium in w...

journal_title：Physics in medicine and biology

authors： Pistella F,Barone P,Narici L,Ocello N,Pizzella V,Romani GL

更新日期：1987-01-01 00:00:00

abstract：:Magnetic resonance imaging (MRI) may be used to image three-dimensional dose distributions of ionizing radiation in tissue equivalent gels infused with ferrous sulphate solutions, commonly known as Fricke gels. In this technique, ferrous (Fe2+) ions are oxidized to ferric (Fe3+) ions by free radicals produced by ioniz...

journal_title：Physics in medicine and biology

authors： Harris PJ,Piercy A,Baldock C

更新日期：1996-09-01 00:00:00

abstract：:This paper evaluates results of a survey of electrostimulation models of myelinated nerve. Participants were asked to determine thresholds of excitation for 18 cases involving different characteristics of the neuron, the stimulation waveform, and the electrode arrangement. Responses were received from 7 investigators ...

journal_title：Physics in medicine and biology

authors： Reilly JP

更新日期：2016-06-21 00:00:00

abstract：:Input functions required for positron emission tomography (PET) tracer kinetic modeling are often obtained from arterial blood. In some situations, using short-lived radiotracers, e.g. [(15)O]water, rapid sample handling is required. A method used at several facilities is to pump blood through a detector system at a c...

journal_title：Physics in medicine and biology

authors： Laymon CM,Sashin D,Carney JP,Ruszkiewicz J,Altenburger D,Becker CR,Lopresti BJ,Mason NS,Mountz JM,Price JC,Schavey R,Mathis CA

更新日期：2008-01-21 00:00:00

abstract：:Monte Carlo simulation of beam modifiers such as physical wedges and compensating filters has been performed with a rectilinear voxel geometry module. A modified version of the EGS4/DOSXYZ code has been developed for this purpose. The new implementations have been validated against the BEAM Monte Carlo code using its ...

journal_title：Physics in medicine and biology

authors： Spezi E,Lewis DG,Smith CW

更新日期：2001-11-01 00:00:00

abstract：:Heating induced near deep brain stimulation (DBS) lead electrodes during magnetic resonance imaging with a 3 T transceive head coil was measured, modeled, and imaged in three cadaveric porcine heads (mean body weight = 85.47 ± 3.19 kg, mean head weight = 5.78 ± 0.32 kg). The effect of the placement of the extra-crania...

journal_title：Physics in medicine and biology

authors： Shrivastava D,Abosch A,Hughes J,Goerke U,DelaBarre L,Visaria R,Harel N,Vaughan JT

更新日期：2012-09-07 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：:The local noise property of a 3D PET reconstructed image is investigated for a uniform-activity sphere distributed in a constantly attenuating spherical object. The positional dependence of the statistical noise is approximately derived and calculated for some special cases. It is suggested that a larger diameter of t...

journal_title：Physics in medicine and biology

authors： Murayama H,Nohara N

更新日期：1997-01-01 00:00:00

abstract：:Optimization-based algorithms for image reconstruction in multispectral (or photon-counting) computed tomography (MCT) remains a topic of active research. The challenge of optimization-based image reconstruction in MCT stems from the inherently non-linear data model that can lead to a non-convex optimization program f...

journal_title：Physics in medicine and biology

authors： Chen B,Zhang Z,Sidky EY,Xia D,Pan X

更新日期：2017-11-02 00:00:00

abstract：:Reference dosimetry in the presence of a strong magnetic field is challenging. Ionisation chambers have shown to be strongly affected by magnetic fields. There is a need for robust and stable detectors in MRI-guided radiotherapy (MRIgRT). This study investigates the behaviour of the alanine dosimeter in magnetic field...

journal_title：Physics in medicine and biology

authors： Billas I,Bouchard H,Oelfke U,Shipley D,Gouldstone C,Duane S

更新日期：2020-06-03 00:00:00

abstract：:The potential of the variable-aperture collimator (VAC) in intensity-modulated radiation therapy (IMRT) has been evaluated by comparing its performance with that of the multi-leaf collimator (MLC). This comparison used a decomposition algorithm to find the series of collimator segments that would treat a given intensi...

journal_title：Physics in medicine and biology

authors： Anderson JW,Symonds-Tayler R,Hartmann G,Echner G,Lang C,Schlegel W,Webb S

更新日期：2006-04-07 00:00:00

abstract：:The behaviour of scatter dose in 4 and 8 MV wedged x-ray beams has been studied by calculating scatter-to-primary dose ratios (SPR) and comparing these with SPR for non-wedged beams. On the central axis the SPR for wedged and non-wedged beams differ only by a few per cent, a difference which increases slightly with we...

journal_title：Physics in medicine and biology

authors： Brown LH,Siddon RL,Bjärngard BE

更新日期：1987-10-01 00:00:00

abstract：:Coronary computed tomography angiography (cCTA) is a commonly used imaging modality for the evaluation of coronary artery disease. cCTA is generally reconstructed in multiple cardiac phases because different coronary arteries may be better visualized in some phases than in others due to the periodic cardiac motion. We...

journal_title：Physics in medicine and biology

authors： Hadjiiski L,Zhou C,Chan HP,Chughtai A,Agarwal P,Kuriakose J,Kazerooni E,Wei J,Patel S

更新日期：2014-08-21 00:00:00