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：:Modern radiotherapy linacs often use carbon fibre for their couch tops due to its radio translucent properties. Beam attenuation by the couches is often ignored during planning and MU calculation. This work examines beam attenuation and loss of "skin sparing" (dose build up region) when various photon beams transit ei...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2965951
更新日期：2008-07-01 00:00:00
abstract：:Angioplasty balloons inflated with a solution of the beta-emitter Re-188 have been used for intravascular brachytherapy to prevent restenosis. Coronary stents are in extensive clinical use for the treatment of de novo atherosclerotic stenoses. In this study, the effect of an interposed stent on the dose distribution h...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1533749
更新日期：2003-02-01 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：PURPOSE:Megavoltage grid therapy is currently delivered with step-and-shoot multisegment techniques or using a high attenuation block with divergent holes. However, the commercial availability of grid blocks is limited, their construction is difficult, and step-and-shoot techniques require longer treatment times and ar...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4801902
更新日期：2013-05-01 00:00:00
abstract：PURPOSE:Real-time adaptive planning and treatment has been infeasible due in part to its high computational complexity. There have been many recent efforts to utilize graphics processing units (GPUs) to accelerate the computational performance and dose accuracy in radiation therapy. Data structure and memory access pat...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4895822
更新日期：2014-10-01 00:00:00
abstract：:Attention is given to means of sensing ultrasonic energy distributions over an area. Under the restraints appropiate to real-time imaging of deep body organs, piezoelectric arrays offer the most promising method. Adaptation of integrated circuit techniques to array assembly permits very large arrays of small elements ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.594247
更新日期：1976-09-01 00:00:00
abstract：:We are investigating computerized methods to ultimately characterize bone trabecular pattern from clinical skeletal radiographs. In this paper, we present a "phantom" for potential use in the development and evaluation of computerized methods for characterizing radiographic trabecular patterns and ultimately bone stre...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598743
更新日期：1999-11-01 00:00:00
abstract：PURPOSE:Intraoperative electron radiation therapy (IOERT) involves the delivery of a high radiation dose during tumor resection in a shorter time than other radiation techniques, thus improving local control of tumors. However, a linear accelerator device is needed to produce the beam safely. Mobile linear accelerators...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12482
更新日期：2017-10-01 00:00:00
abstract：:The mixed-field dosimetry for 252Cf Applicator Tube (AT) type medical sources available from Oak Ridge National Laboratory (ORNL) has been characterized using ionization chambers, a GM counter, and Monte Carlo methods. Unlike the AAPM Task Group No. 43 (TG-43), specification of dose to muscle instead of water is recom...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598646
更新日期：1999-08-01 00:00:00
abstract：PURPOSE:We have developed a robust tool for performing volumetric and temporal analysis of nodules from respiratory gated four-dimensional (4D) CT. The method could prove useful in IMRT of lung cancer. METHODS:We modified the conventional graph-cuts method by adding an adaptive shape prior as well as motion informatio...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12690
更新日期：2018-01-01 00:00:00
abstract：PURPOSE:Scatter contamination in cone-beam computed tomography (CBCT) degrades the image quality by introducing shading artifacts. A moving-blocker-based approach has been proposed to simultaneously estimate scatter and reconstruct the complete volume within field of view (FOV) from a single CBCT scan. Promising result...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4811086
更新日期：2013-07-01 00:00:00
abstract：PURPOSE:Accurately predicting outcome (i.e., overall survival (OS) time) for higher grade glioma (HGG) has great clinical value and would provide optimized guidelines for treatment planning. Radiomics focuses on revealing underlying pathophysiological information in biomedical images for disease analysis and demonstrat...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13288
更新日期：2019-01-01 00:00:00
abstract：:Adaptive histogram equalization techniques are known to be effective for the enhancement of contrast in portal images acquired during radiotherapy treatments. A significant drawback is the loss of definition on the edges of the treatment field. Analysis of this problem shows that it can be remedied by separating the t...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596807
更新日期：1992-05-01 00:00:00
abstract：:Intensity Modulated Arc Therapy (IMAT) is a rotational variant of Intensity Modulated Radiation Therapy (IMRT) that can be implemented with or without angular dose rate optimization. The purpose of this study is to determine the inter-relationship among arc range, Multi-Leaf Collimator (MLC) leaf positions and angular...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2965975
更新日期：2008-07-01 00:00:00
abstract：PURPOSE:Fluence field modulated computed tomography (FFMCT) presents a novel approach for acquiring CT images, whereby a patient model guides dynamically changing fluence patterns in an attempt to achieve task-based, user-prescribed, regional variations in image quality, while also controlling dose to the patient. This...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4829513
更新日期：2013-12-01 00:00:00
abstract：:Direct comparisons of the National Institute of Standards and Technology's (NIST) Ritz 20 kV to 100 kV standard free-air ionization chamber and a portable variable-length free-air ionization chamber designed by the University of Wisconsin-Madison Accredited Dosimetry Calibration Laboratory (UW-ADCL) were made on NISTs...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598148
更新日期：1997-08-01 00:00:00
abstract：:For Monte Carlo linac simulations and patient dose calculations, it is important to accurately determine the phase space parameters of the initial electron beam incident on the target. These parameters, such as mean energy and radial intensity distribution, have traditionally been determined by matching the calculated...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2168433
更新日期：2006-04-01 00:00:00
abstract：:Luminance scatter fractions were measured for patients and phantoms in various regions of the chest film. Scatter fractions were found to be highly variable, being quite high in the regions of the chest with a large equivalent tissue thickness (e.g. mediastinum, chest wall, and subdiaphragmatic areas). For example, ap...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595027
更新日期：1981-09-01 00:00:00
abstract：PURPOSE:The accuracy and precision of computed tomography (CT) pulmonary ventilation imaging with conventional CT scanners are limited by breathing variations. We propose a method to correct for the effect of breathing variations in CT ventilation imaging based on external respiratory signals acquired throughout a scan...
journal_title：Medical physics
pub_type： 临床试验,杂志文章
doi：10.1002/mp.12634
更新日期：2018-01-01 00:00:00
abstract：PURPOSE:In photon radiotherapy, respiratory-induced target motion can be accounted for by internal target volumes (ITV) or mid-ventilation target volumes (midV) defined on the basis of four-dimensional computed tomography (4D-CT). Intrinsic limitations of these approaches can result in target volumes that are not repre...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14023
更新日期：2020-04-01 00:00:00
abstract：PURPOSE:Computational models are widely used during the design and characterization of microwave ablation (MWA) devices, and have been proposed for pretreatment planning. Our objective was to assess three-dimensional (3D) transient temperature and ablation profiles predicted by MWA computational models with temperature...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14318
更新日期：2020-09-01 00:00:00
abstract：PURPOSE:In this abstract, we discuss a biomechanical head and neck model that will be able to represent patient setup variations as well as physiologic changes and subsequently enable dose calculations on the deformed anatomy. METHODS:We selected Multi Pose MRI as the imaging modality to aid in model development and v...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734893
更新日期：2012-06-01 00:00:00
abstract：:An indirect flat panel imager (FPI) with programmable avalanche gain and field emitter array (FEA) readout is being investigated for low-dose and high resolution x-ray imaging. It is made by optically coupling a structured x-ray scintillator, e.g., thallium (Tl) doped cesium iodide (CsI), to an amorphous selenium (a-S...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2937652
更新日期：2008-07-01 00:00:00
abstract：PURPOSE:Imaging the knee under realistic load-bearing conditions can be carried out in a horizontal plane using a C-arm CT scanner. Human subjects can be scanned in a standing position and acquired data successfully reconstructed. However, reconstructing this data is a challenge due to significant artifacts that are in...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4736213
更新日期：2012-06-01 00:00:00
abstract：:Several updated Monte Carlo (MC) codes are available to perform calculations of voxel S values for radionuclide targeted therapy. The aim of this work is to analyze the differences in the calculations obtained by different MC codes and their impact on absorbed dose evaluations performed by voxel dosimetry. Voxel S val...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3103401
更新日期：2009-05-01 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：PURPOSE:A number of techniques are available to determine the dosimetric impact of intrafraction motion during intensity modulated radiation therapy (IMRT). Motion-induced dose perturbations can be determined both computationally and experimentally using a number of different dosimetric metrics. However, these measures...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3605633
更新日期：2011-08-01 00:00:00
abstract：:A doorless entry system has been designed for use in high-energy radiation therapy rooms. The doorless entry improves patient access, safety and throughput, increases the physical safety for the radiation therapists, and avoids the significant cost of heavy shielding doors. The design meets concerns relating to radiat...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598181
更新日期：1998-02-01 00:00:00
abstract：:A systems analysis of reduced dose mammography with scatter removal has quantitatively specified the relationships between the several parameters in mammography systems. While the results are only preliminary in the sense that they need to be proven experimentally, they do seem to provide a good feel for the nature of...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.594540
更新日期：1979-03-01 00:00:00
abstract：PURPOSE:Mammographic density of glandular breast tissue has a masking effect that can reduce lesion detection accuracy and is also a strong risk factor for breast cancer. Therefore, accurate quantitative estimation of breast density is clinically important. In this study, we investigate experimentally the feasibility o...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13031
更新日期：2018-06-03 00:00:00
