Abstract：
PURPOSE:To present a noninvasive technique for directly measuring the CT bow-tie filter attenuation with a linear array x-ray detector. METHODS:A scintillator based x-ray detector of 384 pixels, 307 mm active length, and fast data acquisition (model X-Scan 0.8c4-307, Detection Technology, FI-91100 Ii, Finland) was used to simultaneously detect radiation levels across a scan field-of-view. The sampling time was as short as 0.24 ms. To measure the body bow-tie attenuation on a GE Lightspeed Pro 16 CT scanner, the x-ray tube was parked at the 12 o'clock position, and the detector was centered in the scan field at the isocenter height. Two radiation exposures were made with and without the bow-tie in the beam path. Each readout signal was corrected for the detector background offset and signal-level related nonlinear gain, and the ratio of the two exposures gave the bow-tie attenuation. The results were used in the geant4 based simulations of the point doses measured using six thimble chambers placed in a human cadaver with abdomen/pelvis CT scans at 100 or 120 kV, helical pitch at 1.375, constant or variable tube current, and distinct x-ray tube starting angles. RESULTS:Absolute attenuation was measured with the body bow-tie scanned at 80-140 kV. For 24 doses measured in six organs of the cadaver, the median or maximum difference between the simulation results and the measurements on the CT scanner was 8.9% or 25.9%, respectively. CONCLUSIONS:The described method allows fast and accurate bow-tie filter characterization.
journal_name
Med Physjournal_title
Medical physicsauthors
Li X,Shi JQ,Zhang D,Singh S,Padole A,Otrakji A,Kalra MK,Xu XG,Liu Bdoi
10.1118/1.4932364subject
Has Abstractpub_date
2015-11-01 00:00:00pages
6274-82issue
11eissn
0094-2405issn
2473-4209journal_volume
42pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：PURPOSE:Intensity-Modulated Radiation Therapy (IMRT), including its variations (including IMRT, Volumetric Arc Therapy (VMAT), and Tomotherapy), is a widely used and critically important technology for cancer treatment. It is a knowledge-intensive technology due not only to its own technical complexity, but also to the...
journal_title：Medical physics
pub_type： 杂志文章,评审
doi：10.1002/mp.13526
更新日期：2019-06-01 00:00:00
abstract：:In computer simulations of x-ray CT systems one can either use continuous geometrical descriptions for phantoms or a voxelized representation. The voxelized approach allows arbitrary phantoms to be defined without being confined to geometrical shapes. The disadvantage of the voxelized approach is that inherent errors ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1461841
更新日期：2002-04-01 00:00:00
abstract：:The physical factors that govern 2D and 3D imaging performance may be understood from quantitative analysis of the spatial-frequency-dependent signal and noise transfer characteristics [e.g., modulation transfer function (MTF), noise-power spectrum (NPS), detective quantum efficiency (DQE), and noise-equivalent quanta...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3002414
更新日期：2008-12-01 00:00:00
abstract：PURPOSE:In order to build up a reliable dose monitoring system for boron neutron capture therapy (BNCT) applications at the TRIGA reactor in Mainz, a computer model for the entire reactor was established, simulating the radiation field by means of the Monte Carlo method. The impact of different source definition techni...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4897242
更新日期：2014-11-01 00:00:00
abstract：PURPOSE:The hematopoietically active tissues of skeletal bone marrow are a prime target for computational dosimetry given potential risks of leukemia and, at higher dose levels, acute marrow toxicity. The complex three-dimensional geometry of trabecular spongiosa, however, complicates schema for dose assessment in such...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12002
更新日期：2017-01-01 00:00:00
abstract：PURPOSE:The purpose of this study is to investigate whether the microvascular pseudodiffusion effects resulting with non-monoexponential behavior are present in breast cancer, taking into account tumor spatial heterogeneity. Additionally, methodological factors affecting the signal in low and high diffusion-sensitizing...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4927255
更新日期：2015-08-01 00:00:00
abstract：PURPOSE:To implement the DMAIC (Define-Measure-Analyze-Improve-Control) can be used for customizing the patient-specific QA by designing site-specific range tolerances. METHODS:The DMAIC framework (process flow diagram, cause and effect, Pareto chart, control chart, and capability analysis) were utilized to determine ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12721
更新日期：2018-02-01 00:00:00
abstract：:A computer program was implemented to predict mammography x-ray beam parameters in the range 20-40 kV for Mo/Mo, Mo/Rh, Rh/Rh, and W/Al target/filter combinations. The computation method used to simulate mammography x-ray spectra is based on the Boone et al. model. The beam quality parameters such as the half-value la...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1608498
更新日期：2003-10-01 00:00:00
abstract：INTRODUCTION:Ultrasound (US) guidance of the prostate has long been conducted using a transabdominal (TA) approach. More recently, a transperineal (TP) approach has been made available for image guidance. Our aim was to determine if both methods produced similar alignments within the same patients. MATERIALS AND METHO...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14522
更新日期：2020-12-01 00:00:00
abstract：:A four-parameter Laplace transform pair model, which accurately reconstructs an experimental bremsstrahlung spectrum from attenuation data, is presented. Computed spectral values with both aluminum and copper attenuators generally agree with experimental 70-kVp data to better than 2%. Reconstructed spectra at other kV...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595193
更新日期：1982-11-01 00:00:00
abstract：PURPOSE:In this study, a dedicated device for ion chamber measurements of absorbed dose-to-water for a Nucletron microSelectron-v2 HDR (192)Ir brachytherapy source is presented. The device uses two ionization chambers in a so-called sandwich assembly. Using this setup and by taking the average reading of the two chambe...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4816673
更新日期：2013-09-01 00:00:00
abstract：PURPOSE:To investigate tight-frame based iterative reconstruction (TFIR) technique for spectral breast computed tomography (CT) using fewer projections while achieving greater image quality. METHODS:The experimental data were acquired with a fan-beam breast CT system based on a cadmium zinc telluride photon-counting d...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4790468
更新日期：2013-03-01 00:00:00
abstract：:Various techniques have been developed to localize radioactive sources in brachytherapy implants. The most common methods include the orthogonal film method, the stereo-shift film method, and recently, direct localization from a series of contiguous CT transverse images. The major advantage of the CT method is that it...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598548
更新日期：1999-04-01 00:00:00
abstract：PURPOSE:Magnetic particle imaging (MPI) is a relatively new method to image the spatial distribution of magnetic nanoparticle (MNP) tracers administered to the body with high spatial and temporal resolution using an inhomogeneous magnetic field. The spatial information of the MNP's is encoded using a field free point (...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13411
更新日期：2019-04-01 00:00:00
abstract：:An automated technique for the alignment of right and left breast images has been developed for use in the computerized analysis of bilateral breast images. In this technique, the breast region is first identified in each digital mammogram by use of histogram analysis and morphological filtering operations. The anteri...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597307
更新日期：1994-03-01 00:00:00
abstract：:Multimodality NIR spectroscopy systems offer the possibility of region-based vascular and molecular characterization of tissue in vivo. However, computationally efficient 3D image reconstruction algorithms specific to these image-guided systems currently do not exist. Image reconstruction is often based on finite-elem...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2795832
更新日期：2007-11-01 00:00:00
abstract：:A detailed derivation is presented of the formulas required to determine Ngas and Dmed in the AAPM TG-21 dosimetry protocol. This protocol specifies how to determine the absorbed dose in an electron or photon beam when using exposure or absorbed dose calibrated ion chambers. It is shown that the expression given in TG...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596292
更新日期：1988-01-01 00:00:00
abstract：:A combination of Monte Carlo, convolution, and experimental techniques have been used to investigate bremsstrahlung production at 50 MeV in full-range targets to produce narrow elementary photon beams for scanning. Calculations using the ITS 3.0 Monte Carlo system for various target designs, including particle transpo...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597681
更新日期：1996-04-01 00:00:00
abstract：:The photon spectra in vacuum around four types of 192Ir HDR brachytherapy sources are calculated using the Monte Carlo code EGS4 and the most recent spectral information on 192Ir decay. The air-kerma strengths per unit activity are calculated based on the photon fluence around a bare 192Ir source and around each of fo...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598763
更新日期：1999-11-01 00:00:00
abstract：:In intensity modulated radiation treatments (IMRT), the position of the field edges and the modulation within the beam are often achieved with a multileaf collimator (MLC). During the MLC calibration process, due to the finite accuracy of leaf position measurements, a systematic error may be introduced to leaf positio...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2335490
更新日期：2006-09-01 00:00:00
abstract：PURPOSE:The objectives of this study were (a) to devise a technique for measuring quantum noise in clinical body computed tomography (CT) images and (b) to develop a model for predicting that noise with high accuracy. METHODS:The study included 83 clinical image sets at two dose levels (clinical and 50% reduced dose l...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4938588
更新日期：2016-01-01 00:00:00
abstract：PURPOSE:The harmonic spectrum of magnetic nanoparticles contains valuable information about the quantity and environment of the particles. Harmonic amplitudes have been used to produce quantitative images and ratios of these amplitudes have been used to monitor changes in the particle environment. Harmonic phase angles...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3426294
更新日期：2010-06-01 00:00:00
abstract：PURPOSE:Currently, no 3D or 4D volumetric x-ray imaging techniques are available for intrafraction verification of target position during actual treatment delivery or in-between treatment beams, which is critical for stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) treatments. This study a...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4861820
更新日期：2014-02-01 00:00:00
abstract：:The American Association of Physicists in Medicine recommends that the reference dose-rate distribution, used for treatment planning for low-energy photon brachytherapy sources in routine clinical use, must be based on at least two independent determinations: one using experimentally measured dose rates and one using ...
journal_title：Medical physics
pub_type： 指南,杂志文章
doi：10.1118/1.1690712
更新日期：2004-05-01 00:00:00
abstract：PURPOSE:To reduce the potential of late toxicity (tissue necrosis and cognitive function loss) from brain radiotherapy, we studied a novel planning technique for MLC-equipped linear accelerators (LINACS) that reduces the high doses delivered outside the PTV, enhancing radiation dose conformity. METHODS:The feasibility...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735656
更新日期：2012-06-01 00:00:00
abstract：:Electron energy spectra and angular distributions, including angular spreads, were measured using magnetic spectrometer techniques, at isocenter, for two clinical linear accelerators: one scanning beam machine, which achieves field flatness by scanning a pencil beam over the desired field at the patient plane, and one...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597817
更新日期：1996-05-01 00:00:00
abstract：:Our purpose in this work is to demonstrate that the efficiency of dose-rate computations in 125I brachytherapy, using multigroup discrete ordinates radiation transport simulations, can be significantly enhanced using broad energy group cross sections without a loss of accuracy. To this end, the DANTSYS multigroup disc...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1429238
更新日期：2002-02-01 00:00:00
abstract：:Photoelectric-enhanced radiation therapy is a bimodal therapy, consisting of the administration of highly radiation-absorbing substances into the tumor area and localized regional irradiation with orthovoltage x-rays. Irradiation can be performed by a modified computed tomography (CT) unit equipped with an additional ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3125137
更新日期：2009-06-01 00:00:00
abstract：:Consensus has been developing over the past few decades on a number of measurements required for the laboratory assessment of medical imaging modalities. Nevertheless, understanding of the connection between these measurements and human observer performance in a broad range of tasks remains far from complete. Focusing...
journal_title：Medical physics
pub_type： 杂志文章,评审
doi：10.1118/1.597511
更新日期：1995-07-01 00:00:00
abstract：PURPOSE:To investigate the inconsistency of recent literature on the effect of magnetic field on the response of radiochromic films, we studied the influence of 0.35 T magnetic field on dosimetric response of EBT3 and EBT-XD GafchromicTM films. METHODS:Two different models of radiochromic films, EBT3 and EBT-XD, were ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14313
更新日期：2020-09-01 00:00:00
