The effects of renal variation upon measurements of perfusion and leakage volume in breast tumours.

abstract：:An algorithm for dynamic multileaf-collimator (dMLC) tracking of a target performing a known a priori, rigid-body motion during volumetric modulated arc therapy (VMAT), has been experimentally validated and applied to investigate the potential of the Agility (Elekta AB, Stockholm, Sweden) multileaf-collimator (MLC) fo...

journal_title：Physics in medicine and biology

authors： Davies GA,Clowes P,Bedford JL,Evans PM,Webb S,Poludniowski G

更新日期：2013-07-07 00:00:00

abstract：:Infrared measurements have been used to profile or image biological tissue, including human skin. Usually, analysis of such measurements has assumed that infrared absorption is due to water and collagen. Such an assumption may be reasonable for soft tissue, but introduction of exogenous agents into skin or the measure...

journal_title：Physics in medicine and biology

authors： Viator JA,Choi B,Peavy GM,Kimel S,Nelson JS

更新日期：2003-01-21 00:00:00

abstract：:Respiratory gating can reduce the apparent respiratory motion during imaging and treatment; however, residual motion within the gating window remains. Respiratory training can improve respiratory reproducibility and, therefore, the efficacy of respiratory-gated radiotherapy. This study was conducted to determine wheth...

journal_title：Physics in medicine and biology

authors： George R,Ramakrishnan V,Siebers JV,Chung TD,Keall PJ

更新日期：2006-10-21 00:00:00

abstract：:Computational simulations, such as Monte Carlo track structure simulations, offer a powerful tool for quantitatively investigating radiation interactions within cells. The modelling of the spatial distribution of energy deposition events as well as diffusion of chemical free radical species, within realistic biologica...

journal_title：Physics in medicine and biology

authors： McNamara AL,Ramos-Méndez J,Perl J,Held K,Dominguez N,Moreno E,Henthorn NT,Kirkby KJ,Meylan S,Villagrasa C,Incerti S,Faddegon B,Paganetti H,Schuemann J

更新日期：2018-09-06 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：:In this paper we present a novel method of reducing the dosimetric effects of the finite leaf width of a multileaf collimator (MLC) in conformal and intensity modulated radiotherapy (IMRT). This is achieved by decomposing the required high-resolution fluence distribution into two orthogonal components, which are deliv...

journal_title：Physics in medicine and biology

authors： Evans PM,Partridge M

更新日期：2000-03-01 00:00:00

abstract：:In order to enable a detailed analysis of radio frequency (RF) absorption in the human middle and inner ear organs, a numerical model of these organs was developed at a spatial resolution of 0.1 mm, based on a real human tissue sample. The dielectric properties of the liquids (perilymph and endolymph) inside the bony ...

journal_title：Physics in medicine and biology

authors： Schmid G,Uberbacher R,Samaras T,Jappel A,Baumgartner WD,Tschabitscher M,Mazal PR

更新日期：2007-04-07 00:00:00

abstract：:This paper concerns the robustness of discrete wavelet transform (DWT) compression in terahertz pulsed imaging (TPI). TPI datasets consist of terahertz time-domain series which are sampled at each 'pixel' of the image, leading to file sizes which are typically of the order of several megabytes (MB) per image. This mak...

journal_title：Physics in medicine and biology

authors： Handley JW,Fitzgerald AJ,Berry E,Boyle RD

更新日期：2002-11-07 00:00:00

abstract：:The clinical value of multiple b-value diffusion-weighted (DW) magnetic resonance imaging (MRI) has been shown in many studies. However, DW-MRI often suffers from low signal-to-noise ratio, especially at high b-values. To address this limitation, we present an image denoising method based on the concept of deep image ...

journal_title：Physics in medicine and biology

authors： Lin YC,Huang HM

更新日期：2020-05-11 00:00:00

abstract：:In this paper, Novikov's inversion formula of the attenuated two-dimensional (2D) Radon transform is applied to the reconstruction of attenuated fan-beam projections acquired with equal detector spacing and of attenuated cone-beam projections acquired with a flat planar detector and circular trajectory. The derivation...

journal_title：Physics in medicine and biology

authors： Huang Q,Zeng GL,You J,Gullberg GT

更新日期：2005-05-21 00:00:00

abstract：:Four dimensional cone beam computed tomography (4DCBCT) uses a constant gantry speed and imaging frequency that are independent of the patient's breathing rate. Using a technique called respiratory motion guided 4DCBCT (RMG-4DCBCT), we have previously demonstrated that by varying the gantry speed and imaging frequency...

journal_title：Physics in medicine and biology

authors： O'Brien RT,Stankovic U,Sonke JJ,Keall PJ

更新日期：2017-06-07 00:00:00

abstract：:For low-energy (up to 150 kV) x-rays, the ratio of mass-energy absorption coefficients for water to air, (mu(en)/rho)w.air, and the backscatter factor B are used in the conversion of air kerma, measured free-in-air, to water kerma on the surface of a water phantom. For clinical radiotherapy, similar conversion factors...

journal_title：Physics in medicine and biology

authors： Ma CM,Seuntjens JP

更新日期：1999-01-01 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：:The purpose of this study is to explain the unplanned longitudinal dose modulations that appear in helical tomotherapy (HT) dose distributions in the presence of irregular patient breathing. This explanation is developed by the use of longitudinal (1D) simulations of mock and surrogate data and tested with a fully 4D ...

journal_title：Physics in medicine and biology

authors： Kissick MW,Flynn RT,Westerly DC,Hoban PW,Mo X,Soisson ET,McCall KC,Mackie TR,Jeraj R

更新日期：2008-09-21 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：:Proton therapy is very sensitive to daily density changes along the pencil beam paths. The purpose of this study is to develop and evaluate an automated method for adaptation of IMPT plans to compensate for these daily tissue density variations. A two-step restoration method for 'densities-of-the-day' was created: (1)...

journal_title：Physics in medicine and biology

authors： Jagt T,Breedveld S,van de Water S,Heijmen B,Hoogeman M

更新日期：2017-06-07 00:00:00

abstract：:Computer tomographic (CT) scans are used to correct for tissue inhomogeneities in radiotherapy treatment planning. In order to guarantee a precise treatment, it is important to obtain the relationship between CT Hounsfield units and electron densities (or proton stopping powers for proton radiotherapy), which is the b...

journal_title：Physics in medicine and biology

authors： Schneider U,Pedroni E,Lomax A

更新日期：1996-01-01 00:00:00

abstract：:Single energy x-ray analysis is explored in the context of computed tomography (CT), whereby Hounsfield numbers (HN) are used to estimate electron density N(e) and parameters that describe composition. We examine measurements with tissue substitute materials and theoretical HN for a broad range of tissues. Results are...

journal_title：Physics in medicine and biology

authors： Midgley SM

更新日期：2012-12-07 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：:Irradiation of moving targets using a scanned ion beam can cause clinically intolerable under- and overdosages within the target volume due to the interplay effect. Several motion mitigation techniques such as gating, beam tracking and rescanning are currently investigated to overcome this restriction. To enable detai...

journal_title：Physics in medicine and biology

authors： Steidl P,Richter D,Schuy C,Schubert E,Haberer T,Durante M,Bert C

更新日期：2012-04-21 00:00:00

abstract：:Treatment planning based on probability distribution function (PDF) of patient geometries has been shown a potential off-line strategy to incorporate organ motion, but the application of such approach highly depends upon the reproducibility of the PDF. In this paper, we investigated the dependences of the PDF reproduc...

journal_title：Physics in medicine and biology

authors： Cai J,Read PW,Altes TA,Molloy JA,Brookeman JR,Sheng K

更新日期：2007-01-21 00:00:00

abstract：:Talbot-Lau interferometry (TLI) provides additional contrast modes for x-ray imaging that are complementary to conventional absorption radiography. TLI is particularly interesting because it is one of the few practical methods for realizing phase contrast with x-rays that is compatible with large-spot high power x-ray...

journal_title：Physics in medicine and biology

authors： Zan G,Vine DJ,Yun W,Lewis SJY,Wang Q,Wang G

更新日期：2020-02-04 00:00:00

abstract：:The purpose of this study was to develop a method to simulate breathing motion induced interplay effects for volumetric modulated arc therapy (VMAT), to verify the proposed method with measurements, and to use the method to investigate how interplay effects vary with different patient- and machine specific parameters....

journal_title：Physics in medicine and biology

authors： Edvardsson A,Nordström F,Ceberg C,Ceberg S

更新日期：2018-04-19 00:00:00

abstract：:Determination of the cardiorespiratory phase of the heart has numerous applications during cardiac imaging. In this article we propose a novel view-angle independent near-real time cardiorespiratory motion gating and coronary sinus (CS) catheter tracking technique for x-ray fluoroscopy images that are used to guide ca...

journal_title：Physics in medicine and biology

authors： Panayiotou M,Rhode KS,King AP,Ma Y,Cooklin M,O'Neill M,Gill J,Rinaldi CA,Housden RJ

更新日期：2015-10-21 00:00:00

abstract：:We extend the theory of three-dimensional (3D) tomographic intensity modulated radiation therapy (IMRT). The geometry consists of two-dimensional modulated beams on a sphere centred in the tumour. The theory provides an efficient algorithm for computing beam modulation patterns that approximately 'reconstruct' the pre...

journal_title：Physics in medicine and biology

authors： Levine RY,Braunstein M

更新日期：2002-03-07 00:00:00

abstract：:A motorized electron multileaf collimator (eMLC) was developed as an add-on device to the Varian linac for delivery of advanced electron beam therapy. It has previously been shown that electron beams collimated by an eMLC have very similar penumbra to those collimated by applicators and cutouts. Thus, manufacturing pa...

journal_title：Physics in medicine and biology

authors： Eldib A,Jin L,Li J,Ma CM

更新日期：2013-08-21 00:00:00

abstract：:For renal dynamic studies, the COST B2 hybrid phantom is an example of an artificially created software phantom. Although this phantom is useful, it is not possible to implement the phantom in a self-consistent fashion to produce, for example, a collection of tracer in the bladder which is related to the flow from the...

journal_title：Physics in medicine and biology

authors： Houston AS,Sampson WF,Jose RM,Boyce JF

更新日期：1999-02-01 00:00:00

abstract：:Evaluation of the radioisotopic purity of technetium-99m (99mTc) produced in GBq amounts by proton bombardment of enriched molibdenum-100 (100Mo) metallic targets at low proton energies (i.e. within 15-20 MeV) is conducted. This energy range was chosen since it is easily achievable by many conventional medical cyclotr...

journal_title：Physics in medicine and biology

authors： Uzunov NM,Melendez-Alafort L,Bello M,Cicoria G,Zagni F,De Nardo L,Selva A,Mou L,Rossi-Alvarez C,Pupillo G,Di Domenico G,Uccelli L,Boschi A,Groppi F,Salvini A,Taibi A,Duatti A,Martini P,Pasquali M,Loriggiola M,Mare

更新日期：2018-09-19 00:00:00

abstract：:Dynamic radiation therapy techniques require that the treatment head setup varies in time and space during dose delivery. Examples are leaf motion in intensity modulated x-ray therapy, modulator wheel rotation in conventional proton therapy and variable magnet settings in proton beam scanning. Consequently, for Monte ...

journal_title：Physics in medicine and biology

authors： Paganetti H

更新日期：2004-03-21 00:00:00

abstract：:This study investigated the relationship between the specific absorption rate and temperature elevation in an anatomically-based model named NORMAN for exposure to radio-frequency far fields in the ICNIRP guidelines (1998 Health Phys. 74 494-522). The finite-difference time-domain method is used for analyzing the elec...

journal_title：Physics in medicine and biology

authors： Hirata A,Asano T,Fujiwara O

更新日期：2007-08-21 00:00:00