Abstract:
PURPOSE:A 3-year project called LABSYNC has been recently funded by the European Commission, with the aim of designing a radiation facility based on a compact light source, i.e., a laboratory-sized commercial synchrotron, capable of accelerating electrons up to 6 or 20 MeV. An accurate spectral description of hard x rays emitted from thin targets, irradiated by electron beams circulating in the storage ring, is of primary interest for the design and the characterization of a beamline. This article, Part I, aims at optimizing some of the parameters which are critical for the design of medical applications based on the above compact light source. The goal was to evaluate the dependence of photon fluence and beam monochromaticity on electron-beam energy, target material, and thickness. METHODS:The transport of 6 and 20 MeV electrons in a thin molybdenum, rhodium, and tungsten target is studied by means of Monte Carlo simulations using MCNPX. Configurations of the x-ray output port, different from the default forward-directed emission of the beam, are also investigated. A comparison with reference spectra for general diagnostic radiology and mammography is carried out. RESULTS:It is shown that the emitted x-ray beams can be far more intense than those generated by conventional x-ray tubes for radiography applications. The profiles of the calculated polychromatic spectra resemble those generated by conventional x-ray tubes, with x-ray energies up to the energy of the incident-electron beam. An appreciable improvement in the monochromaticity of the beams can be obtained by viewing the x-ray emission from an output port antiparallel to the direction of the incident-electron beam. CONCLUSIONS:The optimum target thickness for tungsten target spectra is practically constrained by a trade-off between bremsstrahlung efficiency and focal-spot size requirements. A larger margin for optimization of target thickness is probably available for mammographic spectra. The constraint of a backward-directed (or, to a lesser extent, orthogonal) output port is to be considered mandatory for minimizing the high-energy tail of the spectral distribution and keeping the radiation dose to a reasonable level. It is also fundamental to evaluate the impact of the high-energy tail of the emitted spectra in x-ray imaging applications, since the energy range involved is significantly beyond the diagnostic range. This topic will be dealt with in Part II of the article.
journal_name
Med Physjournal_title
Medical physicsauthors
Marziani M,Taibi A,Di Domenico G,Gambaccini Mdoi
10.1118/1.3223357subject
Has Abstractpub_date
2009-10-01 00:00:00pages
4683-701issue
10eissn
0094-2405issn
2473-4209journal_volume
36pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract::In order to use negative pions for the treatment of large deep-seated tumors in radiotherapy, it is necessary to produce depth-dose distributions tailored to specific shapes. We present here a method of beam shaping which utilizes a fluid-filled piston having a programmable, computer-controlled, time-dependent thickne...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594313
更新日期:1977-09-01 00:00:00
abstract:PURPOSE:Flattening filters (FFs) have been considered as an integral part of the treatment head of a medical accelerator for more than 50 years. The reasons for the longstanding use are, however, historical ones. Advanced treatment techniques, such as stereotactic radiotherapy or intensity modulated radiotherapy have s...
journal_title:Medical physics
pub_type: 杂志文章,评审
doi:10.1118/1.3554643
更新日期:2011-03-01 00:00:00
abstract::A prototype Emission-Transmission Computed Tomography (ETCT) system is being developed that will acquire single-slice x-ray transmission CT images simultaneously with single photon emission computed tomography (SPECT) images. This system will permit the correlation of anatomical information from x-ray CT with function...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596643
更新日期:1991-09-01 00:00:00
abstract::Heat therapies such as hyperthermia and thermoablation are very promising approaches in the treatment of cancer. Compared with available hyperthermia modalities, magnetic fluid hyperthermia (MFH) yields better results in uniform heating of the deeply situated tumors. In this approach, fluid consisting of superparamagn...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3106343
更新日期:2009-05-01 00:00:00
abstract::90Y-labeled SIR-Spheres are currently used to treat patients with hepatic metastases secondary to colorectal adenocarcinoma. In general, the prescribed activity is based on empirical data collected during clinical trials. The activity of the source vial is labeled by the manufacturer as 3.0 GBq +/- 10% and is not inde...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2889621
更新日期:2008-04-01 00:00:00
abstract:PURPOSE:Liver segmentation is an important prerequisite for the assessment of liver cancer treatment options like tumor resection, image-guided radiation therapy (IGRT), radiofrequency ablation, etc. The purpose of this work was to evaluate a new approach for liver segmentation. METHODS:A graph cuts segmentation metho...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3682171
更新日期:2012-03-01 00:00:00
abstract:PURPOSE:This paper describes the clinical implementation and medical commissioning of the MedAustron Particle Therapy Accelerator (MAPTA) for non-isocentric scanned proton beam treatments. METHODS:Medical physics involvement during technical commissioning work is presented. Acceptance testing procedures, including adv...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13928
更新日期:2020-02-01 00:00:00
abstract:PURPOSE:The present study was conducted to investigate salivary iodine kinetics and dosimetry during repeated courses of radioiodine ((131)I) therapy for differentiated thyroid cancer (DTC). Such data could provide a better understanding of the mechanisms of (131)I induced salivary toxicity and help to develop appropri...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3602459
更新日期:2011-10-01 00:00:00
abstract:PURPOSE:Experimental dosimetry of high-dose-rate (HDR) 192 Ir brachytherapy (BT) sources is complicated due to high dose and dose-rate gradients, and softening of photon energy spectrum with depth. A single crystal synthetic diamond detector microDiamond (PTW 60019, Freiburg, Germany) has a small active volume, high se...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12694
更新日期:2018-01-01 00:00:00
abstract:PURPOSE:Temporal subtraction is used to detect the interval change in chest radiographs and aid radiologists in patient diagnosis. This method registers two temporally different images by geometrically warping the lung region, or "lung mask," of a previous radiographic image to align with the current image. The gray le...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3259712
更新日期:2009-12-01 00:00:00
abstract::The aim of the work was to investigate in advance the dosimetric properties of a new multileaf collimator (MLC) concept with the help of Monte Carlo (MC) simulations prior to the production of a prototype. The geometrical design of the MLC was implemented in the MC code GEANT4. For the simulation of a 6 MV treatment b...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2181298
更新日期:2006-04-01 00:00:00
abstract::To more accurately and precisely delineate a tumor in a 3D PET image, we proposed a novel, semi-automatic, two-stage method by utilizing an adaptive region-growing algorithm and a dual-front active contour model. First, a rough region of interest (ROI) is manually drawn by a radiation oncologist that encloses a tumor....
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2956713
更新日期:2008-08-01 00:00:00
abstract::Measurements of a 670-MeV/amu 20Ne beam at the Lawrence Berkeley Laboratory Bevalac heavy-ion accelerator with various thicknesses of water absorber were obtained with the BERKLET. The BERKLET, a simple three-stage solid-state telescope detector, has been described previously. This instrument measures the linear energ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596536
更新日期:1990-03-01 00:00:00
abstract:PURPOSE:To study if malfunction of a receiver can be detected robustly using the simple ACR SNR measurement approach on a 32-channel head coil. METHODS:Standard ACR T1W images (11slice) were acquired with a commercial 32 channel head coil on a 3T Philips Achieva MR scanner following the ACR recommended setup. Raw data...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4736227
更新日期:2012-06-01 00:00:00
abstract::Depth dose distributions for a d(14)Be neutron beam, measured separately for total and gamma absorbed dose, are presented for nine tissue substitutes and for two field sizes. These data are used to examine methods to transform depth dose curves from one material to another. Best results are found when the local depths...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595695
更新日期:1985-05-01 00:00:00
abstract:PURPOSE:To describe Acuros® CTS, a new software tool for rapidly and accurately estimating scatter in x-ray projection images by deterministically solving the linear Boltzmann transport equation (LBTE). METHODS:The LBTE describes the behavior of particles as they interact with an object across spatial, energy, and dir...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12850
更新日期:2018-05-01 00:00:00
abstract:PURPOSE:There is interest in developing linac-MR systems for MRI-guided radiation therapy. To date, the designs for such linac-MR devices have been restricted to a transverse geometry where the static magnetic field is oriented perpendicular to the direction of the incident photon beam. This work extends possibilities ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3475942
更新日期:2010-09-01 00:00:00
abstract::A method to determine the bone mineral density of the calcaneum has been reported earlier by our laboratory. In this method, the calcaneum is irradiated by a 60-keV photon beam from 241Am source and both the coherent and Compton scattered photons are detected by a high-purity Ge detector. The bone mineral density is d...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595669
更新日期:1985-07-01 00:00:00
abstract::It is shown that predictions can be made of scatter-to-primary ratios for a variety of mammographic configurations. The different configurations can be produced by changes in source-detector distance; source-phantom distance; air gap; photon energy; phantom composition, thickness, and cross-sectional area. A detailed ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595807
更新日期:1986-11-01 00:00:00
abstract:PURPOSE:The purpose of this study is to investigate the feasibility of increasing the system spatial resolution and scanning speed of Hologic Selenia Dimensions digital breast tomosynthesis (DBT) scanner by replacing the rotating mammography x-ray tube with a specially designed carbon nanotube (CNT) x-ray source array,...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3694667
更新日期:2012-04-01 00:00:00
abstract::We present a technique for semiautomated segmentation of human prostates using suprapubic ultrasound (US) images. In this approach, a speckle reducing anisotropic diffusion (SRAD) is applied to enhance the images and the instantaneous coefficient of variation (ICOV) is utilized for edge detection. Segmentation is acco...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1809791
更新日期:2004-12-01 00:00:00
abstract::Absorbed doses from main charged-particle beams and charged-particle fragments have been measured with high accuracy for particle therapy, but there are few reports for doses from neutron components produced as fragments. This study describes the measurements on neutron doses produced by carbon beams; microdosimetric ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2767933
更新日期:2007-09-01 00:00:00
abstract::Plaque rupture with superimposed thrombosis is the main cause of the acute coronary syndromes of unstable angina, myocardial infarction, and sudden death. Endothelial disruption leading to plaque rupture may relate to mechanical fatigue associated with cyclic flexion of plaques. A novel method is proposed to assess st...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1593635
更新日期:2003-11-01 00:00:00
abstract::The computed tomography (CT) radiation dose to pediatric patients has received considerable attention recently. Moreover, it is important to be able to determine CT radiation doses for various patient sizes ranging from infants to large adults. The current AAPM protocol only measures CT radiation dose using a 16 cm ac...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1543149
更新日期:2003-03-01 00:00:00
abstract::In this investigation, five experimental data sets are used to evaluate the ability of the EGSnrc Monte Carlo code to calculate the change in chamber response associated with changes in wall material and cavity dimension at 60Co energies. Calculations of the ratios of response per unit mass of air as a function of cav...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3013701
更新日期:2008-12-01 00:00:00
abstract::Preclinical experiments are carried out with approximately 20-30 microm wide, approximately 10 mm high parallel microbeams of hard, broad-"white"-spectrum x rays (approximately 50-600 keV) to investigate microbeam radiation therapy (MRT) of brain tumors in infants for whom other kinds of radiotherapy are inadequate an...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1562169
更新日期:2003-04-01 00:00:00
abstract::Current generation electronic portal imaging devices (EPID) contain a 1.0 mm copper conversion plate to increase detection efficiency of a therapeutic megavoltage spectrum. When using these EPIDs for low-Z target imaging, the conversion plate largely attenuates the large populations of diagnostic energy photons, there...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4740105
更新日期:2012-07-01 00:00:00
abstract:PURPOSE:Patient-specific IMRT QA measurements are important components of processes designed to identify discrepancies between calculated and delivered radiation doses. Discrepancy tolerance limits are neither well defined nor consistently applied across centers. The AAPM TG-218 report provides a comprehensive review a...
journal_title:Medical physics
pub_type: 杂志文章,评审
doi:10.1002/mp.12810
更新日期:2018-04-01 00:00:00
abstract::The Monte Carlo (MC) method has been shown through many research studies to calculate accurate dose distributions for clinical radiotherapy, particularly in heterogeneous patient tissues where the effects of electron transport cannot be accurately handled with conventional, deterministic dose algorithms. Despite its p...
journal_title:Medical physics
pub_type: 杂志文章,评审
doi:10.1118/1.2795842
更新日期:2007-12-01 00:00:00
abstract::Photon point dose kernels and absorbed fractions were generated in water for the full photon emission spectrum of each radionuclide of interest in nuclear medicine, by simulating the transport of particles using Monte Carlo. The kernels were then fitted to a mathematical expression. Absorbed fractions for point source...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597670
更新日期:1996-05-01 00:00:00