Abstract：
:Simulation of small-angle x-ray scattering from collagen in healthy and cancerous breast tissue may reveal detailed information on the structural changes in collagen. Collagen fibril is modelled as a cylinder with axially periodic step-function electron density, and packing is approximated by placing the cylinders in small hexagonal bundles. The intensity from a bundle is calculated by summing analytical scattering amplitudes from the cylinders, and intensities from several bundles with varying lattice constants are averaged. Comparisons with more complex models are made to estimate the robustness of the model. The oscillations in the equatorial direction are not significantly affected by added complexity. The relative intensities of the Bragg peaks in the meridional direction can be tuned by modifying the axial electron density distribution. Tests with different fibril radius distributions show that the average radius can be determined with an accuracy of +/-0.5 nm but that the shape of the radius distribution cannot be accurately determined from the scattering patterns. The effect of multiple scattering and the detector point-spread function (PSF) is considered, and the PSF may make a significant contribution to the final slope of the scattering pattern. Comparisons with observed scattering indicate that the model is basically correct at the supra-molecular level.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Suhonen H,Fernández M,Serimaa R,Suortti Pdoi
10.1088/0031-9155/50/22/012subject
Has Abstractpub_date
2005-11-21 00:00:00pages
5401-16issue
22eissn
0031-9155issn
1361-6560pii
S0031-9155(05)95488-2journal_volume
50pub_type
杂志文章abstract：:In modern radiotherapy the verification of complex treatments plans is often performed in inhomogeneous or even anthropomorphic phantoms. For dose verification small detectors are necessary and therefore alanine detectors are most suitable. Though the response of alanine for a wide range of clinical photon energies in...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/61/3/N70
更新日期：2016-02-07 00:00:00
abstract：:A new system has been designed and built to validate the concept of 3D computerized angiography (CA). This system can acquire a set of 2D digital subtracted angiography images while rotating around a patient and then, using these images, reconstruct a 3D representation of the opacified vasculature. The design principl...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/39/3/020
更新日期：1994-03-01 00:00:00
abstract：:In proton therapy, the relative biological effectiveness (RBE) depends on various types of parameters such as linear energy transfer (LET). An analytical model for LET calculation exists (Wilkens' model), but secondary particles are not included in this model. In the present study, we propose a correction factor, L se...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/61/2/740
更新日期：2016-01-21 00:00:00
abstract：:The objective of this study was the determination of the thermal regulatory and the thermal breakdown thresholds for in-tube restrained B6C3F1 and NMRI mice exposed to radiofrequency electromagnetic fields at 905 MHz. Different levels of the whole-body averaged specific absorption rate (SAR = 0, 2, 5, 7.2, 10, 12.6 an...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/50/21/017
更新日期：2005-11-07 00:00:00
abstract：:A number of radiation-therapy-related uses based on a commercially available spreadsheet program have been developed at our facility. The graphics and display capabilities inherent in these spreadsheet programs allow for concise visual results. The spreadsheets are used as an independent check for several types of rad...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/40/6/007
更新日期：1995-06-01 00:00:00
abstract：:Monte Carlo methods have been applied to the study of the performance of antiscatter grids in radiography. Photon histories for imaging with a 20 cm thick water phantom irradiated with an 80 kV x-ray spectrum were generated by Monte Carlo simulation. The scattering and absorption of the photons transmitted from the ph...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/27/6/002
更新日期：1982-06-01 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
pub_type： 杂志文章
doi：10.1088/0031-9155/61/12/4346
更新日期：2016-06-21 00:00:00
abstract：:Measurement of total body nitrogen is assuming increasing importance in the nutritional evaluation of seriously ill patients. Nitrogen has been previously measured either by counting (i) the annihilation radiation from 13N immediately after neutron irradiation with 14 MeV neutrons or (ii) the 'prompt' gamma rays from ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/29/4/008
更新日期：1984-04-01 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
pub_type： 杂志文章
doi：10.1088/0031-9155/54/8/004
更新日期：2009-04-21 00:00:00
abstract：:In the real-time tumor-tracking radiotherapy system, fluoroscopy is used to determine the real-time position of internal fiducial markers. The pattern recognition score (PRS) ranging from 0 to 100 is computed by a template pattern matching technique in order to determine the marker position on the fluoroscopic image. ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/56/15/011
更新日期：2011-08-07 00:00:00
abstract：:The beam orientation optimization (BOO) problem in intensity modulated radiation therapy (IMRT) treatment planning is a nonlinear problem, and existing methods to obtain solutions to the BOO problem are time consuming due to the complex nature of the objective function and size of the solution space. These issues beco...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/56/17/014
更新日期：2011-09-07 00:00:00
abstract：:Contrast enhanced ultrasound (CEUS) and dynamic contrast enhanced ultrasound (DCE-US) can be used to provide information about the vasculature aiding diagnosis and monitoring of a number of pathologies including cancer. In the development of a CEUS imaging system, there are many choices to be made, such as whether to ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/1361-6560/ab13f2
更新日期：2019-04-23 00:00:00
abstract：:Treatment planning for proton tumor therapy requires a fast and accurate dose-calculation method. We have implemented a simplified Monte Carlo (SMC) method in the treatment planning system of the National Cancer Center Hospital East for the double-scattering beam delivery scheme. The SMC method takes into account the ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/55/12/018
更新日期：2010-06-21 00:00:00
abstract：:A technique is described for examining the mode of operation of radiation detectors and estimating the losses and gains caused by random summing effects in spectra acquired at high counting rates. The technique is applied to estimating the errors caused by random summing when measuring the amounts of carbon and nitrog...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/34/8/010
更新日期：1989-08-01 00:00:00
abstract：:The infrasonic part of the spectrum of the carotid artery wall vibration in the neck was obtained. Differences between the spectral content and vibrational amplitude in normal and occluded carotids were found. The application of this technique in clinical practice could be useful in the detection of the carotid insuff...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/21/1/011
更新日期：1976-01-01 00:00:00
abstract：:Photon quality correction factors (kQy) for ionization chamber photon dosimetry in an epithermal neutron beam were determined according to a modified absorbed dose to water formalism which was extended to mixed radiation fields. We have studied two commercially available ionization chambers in the epithermal neutron b...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/47/14/303
更新日期：2002-07-21 00:00:00
abstract：:Automatic tube current modulation (TCM) is used in modern CT devices. This is implemented in the numerical calculation of dose conversion coefficients for CT examinations. For four models of adults, the female and male reference models of ICRP and ICRU and a lighter and a heavier female model, dose conversion coeffici...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/55/20/013
更新日期：2010-10-21 00:00:00
abstract：:This work presents an improvement of the VIPARnd ('nd' stands for 'normoxic, double', or VIP) polymer gel dosimeter. The gel composition was altered by increasing the concentration of the monomeric components, N-vinylpyrrolidone (NVP) and N,N'-methylenebisacrylamide (MBA), in co-solvent solutions. The optimal composit...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/1361-6560/aa5089
更新日期：2017-02-07 00:00:00
abstract：:In this paper, a coupled radiative transfer equation and diffusion approximation model is extended for light propagation in turbid medium with low-scattering and non-scattering regions. The light propagation is modelled with the radiative transfer equation in sub-domains in which the assumptions of the diffusion appro...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/50/20/011
更新日期：2005-10-21 00:00:00
abstract：:Kilo-voltage (KV) cone-beam computed tomography (CBCT) unit mounted onto a linear accelerator treatment system, often referred to as on-board imager (OBI), plays an increasingly important role in image-guided radiation therapy. While the FDK algorithm is currently used for reconstructing images from clinical OBI data,...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/60/12/4601
更新日期：2015-06-21 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
pub_type： 杂志文章
doi：10.1088/1361-6560/aa6b45
更新日期：2017-06-21 00:00:00
abstract：:Polymer gel dosimetry aims to provide three-dimensional images of radiation therapy dose distributions in irradiated aqueous gels. The first gels required manufacture in an oxygen-free environment, but later the MAGIC formulation was introduced, which could be made in normal atmospheric conditions. Here we report our ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/52/10/N03
更新日期：2007-05-21 00:00:00
abstract：:Three-dimensional reconstruction of cardiac vasculature from angiographic C-arm CT (rotational angiography) data is a major challenge. Motion artefacts corrupt image quality, reducing usability for diagnosis and guidance. Many state-of-the-art approaches depend on retrospective ECG-gating of projection data for image ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/58/11/3717
更新日期：2013-06-07 00:00:00
abstract：:The dynamic collimation system (DCS) can be combined with pencil beam scanning proton therapy to deliver highly conformal treatment plans with unique collimation at each energy layer. This energy layer-specific collimation is accomplished through the synchronized motion of four trimmer blades that intercept the proton...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/1361-6560/ab416d
更新日期：2019-10-21 00:00:00
abstract：:This work studies the effect of age on lung dose commitments arising from the inhalation of an atmosphere containing radionuclides of varying half-lives and physical sizes. This dependence is significant in many cases, approaching a ratio of 2 in several instances when the maximum dose at a given age is compared with ...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/27/4/005
更新日期：1982-04-01 00:00:00
abstract：:Proton therapy with active scanning beam delivery has significant advantages compared to conventional radiotherapy. However, so far only static targets have been treated in this way, since moving targets potentially lead to interplay effects. For 4D treatment planning, information on the target motion is needed to cal...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/57/7/1779
更新日期：2012-04-07 00:00:00
abstract：:This study evaluates the dosimetric performance of the polymer gel dosimeter 'Methacrylic and Ascorbic acid in Gelatin, initiated by Copper' and its suitability for quality assurance and analysis of I-131-targeted radionuclide therapy dosimetry. Four batches of gel were manufactured in-house and sets of calibration vi...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/56/22/017
更新日期：2011-11-21 00:00:00
abstract：:For the treatment planning during intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT), beam fluence maps can be first optimized via fluence map optimization (FMO) under the given dose prescriptions and constraints to conformally deliver the radiation dose to the targets while sparin...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/61/7/2838
更新日期：2016-04-07 00:00:00
abstract：:A method of measuring the image quality of medical imaging equipment is considered within the framework of statistical decision theory. In this approach, images are regarded as random vectors and image quality is defined in the context of the image information available for performing a specified detection or discrimi...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/0031-9155/38/1/006
更新日期：1993-01-01 00:00:00
abstract：:Margins are employed in radiotherapy treatment planning to mitigate the dosimetric effects of geometric uncertainties for the clinical target volume (CTV). Unfortunately, whilst the use of margins can increase the probability that sufficient dose is delivered to the CTV, it can also result in delivering high dose of r...
journal_title：Physics in medicine and biology
pub_type： 杂志文章
doi：10.1088/1361-6560/aae658
更新日期：2018-10-29 00:00:00
