Abstract:
PURPOSE:Currently, only iodine- and barium-based contrast media (CM) are used in clinical contrast-enhanced computed tomography (CE-CT). High-Z metals would produce a higher contrast at equal mass density for the x-ray spectra used in clinical CT. Using such materials might allow for significant dose reductions in CE-CT. The purpose of this study was to quantify the potential for dose reduction when using CM based on heavy metals. METHODS:The contrast-to-noise ratio weighted by dose (CNRD) was determined as a function of scan protocol by means of measurements and simulations on a clinical CT scanner. For simulations, water cylinders with diameters 160, 320, 480, and 640 mm were used to cover a broad range of patient sizes. Measurements were conducted with 160 and 320 mm water-equivalent plastic cylinders. A central bore of 13 mm diameter was present in all phantoms. The tube voltage was varied from 80 to 140 kV for measurements and from 60 to 180 kV for simulations. Additional tin filtration of thicknesses 0.4, 0.8, and 1.2 mm was applied in the simulation to evaluate a range of spectral hardness. The bore was filled with a mixture of water and 10 mg/ml of pure iodine, holmium, gadolinium, ytterbium, osmium, tungsten, gold, and bismuth for the simulations and with aqueous solutions of ytterbium, tungsten, gold, and bismuth salts as well as Iopromid containing 10 mg/ml of the pure materials for the measurements. CNRDs were compared to iodine at phantom size-dependent reference voltages for all high-Z materials and the resulting dose reduction was calculated for equal contrast-to-noise ratio. RESULTS:Dose reduction potentials strongly depended on phantom size, spectral hardness, and tube voltage. Depending on the added filtration, a dose reduction of 19%-60% could be reached at 80 kV with gadolinium for the 160 mm phantom, 52%-69% at 100 kV with holmium for the 320 mm phantom, 62%-78% with 120 kV for hafnium and the 480 mm phantom and 74%-86% with 140 kV for gold and the 640 mm phantom. While gadolinium might be considered at 160 mm diameter, hafnium showed the best overall performance for phantom sizes of 320 mm and above. The measurements conducted on the clinical CT scanner showed very good agreement with simulations with deviations in the order of 5 to 10%. CONCLUSIONS:The results of this study encourage the development and use of CM based on high-Z materials, especially for adipose patients, where high tube voltages are necessary to reach sufficiently short scan times. Hafnium proved to be the best compromise for average-size and for adipose patients. Even higher-Z materials such as gold and bismuth showed a good overall performance in conjunction with high tube voltage, large patients or strong added filtration and may be recommended for scans under these conditions.
journal_name
Med Physjournal_title
Medical physicsauthors
Nowak T,Hupfer M,Brauweiler R,Eisa F,Kalender WAdoi
10.1118/1.3658738subject
Has Abstractpub_date
2011-12-01 00:00:00pages
6469-82issue
12eissn
0094-2405issn
2473-4209journal_volume
38pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract:PURPOSE:In the practice code of dosimetry, humidity effect is assumed to be constant as far as the measurements are performed in the relative humidity (RH) range of (20-80)%; thus, the humidity effect can be ignored with a dose uncertainty of 0.15%. This assumption is based on the previous experimental results by Niate...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13665
更新日期:2019-09-01 00:00:00
abstract:PURPOSE:Previous studies have shown atlas-based segmentation using a single best matched (SBM) atlas subject can significantly reduce contouring time. A new multi-atlas approach has been shown to provide greater accuracy than SBM for cancer of the head and neck. The goal of this study was to evaluate the multi-atlas te...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4734942
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:The purpose of this technical note is to introduce variance component analysis to the estimation of systematic and random components in setup error of radiotherapy. METHODS:Balanced data according to the one-factor random effect model were assumed. RESULTS:Analysis-of-variance (anova)-based computation was ap...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4961397
更新日期:2016-09-01 00:00:00
abstract::The authors report on the imaging capabilities of a mammographic system demonstrator based on GaAs pixel detectors operating in single photon counting (SPC) mode. The system imaging performances have been assessed by means of the transfer functions: The modulation transfer function (MTF), the normalized noise power sp...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3097284
更新日期:2009-04-01 00:00:00
abstract:PURPOSE:Melanoma is the most lethal of the three primary skin cancers, including also basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), which are less lethal. The accepted diagnosis process involves manually observing a suspicious lesion through a Dermascope (i.e., a magnifying glass), followed by a biopsy....
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14471
更新日期:2020-11-01 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::Current dosimetry protocols for clinical protons do not take into account any secondary electron fluence perturbation in ion chambers. In this work, we performed a systematic study of secondary electron fluence perturbation factors for spherical and cylindrical ion chambers in proton beams (70-250 MeV). The electron f...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1406519
更新日期:2001-10-01 00:00:00
abstract:PURPOSE:Detailed characterization of changes in vessel size is crucial for the diagnosis and management of a variety of vascular diseases. Because clinical measurement of vessel size is typically dependent on the radiologist's subjective interpretation of the vessel borders, it is often prone to high inter- and intra-u...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12580
更新日期:2017-12-01 00:00:00
abstract:PURPOSE:Respiratory gating in PET is an approach used to minimize the negative effects of respiratory motion on spatial resolution. It is based on an initial determination of a patient's respiratory movements during a scan, typically using hardware based systems. In recent years, several fully automated databased algor...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3483784
更新日期:2010-10-01 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:Water equivalent diameter (WED) is the preferred surrogate for patient size in CT. It is better than geometric size surrogates and patient weight/height/BMI/age because it correlates the best with x-ray attenuation. The administration of oral/IV contrast agents increases a patient's attenuation and should there...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14721
更新日期:2021-01-13 00:00:00
abstract:PURPOSE:In this study the Octavius detector 729 ionization chamber (IC) array with the Octavius 4D phantom was characterized for flattening filter (FF) and flattening filter free (FFF) static and rotational beams. The device was assessed for verification with FF and FFF RapidArc treatment plans. METHODS:The response o...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4817482
更新日期:2013-09-01 00:00:00
abstract::An applicator system for intraoperative radiation therapy has been fabricated which does not require physical docking with the accelerator. A dosimetric study has been completed which documents the properties of this system for a variety of electron beam energies, applicator sizes, collimator settings, both primary an...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596338
更新日期:1989-09-01 00:00:00
abstract::Two acrylic cube phantoms have been constructed for BNCT applications that allow the depth distribution of neutrons to be measured with miniature 10BF3 detectors in 0.5-cm steps beginning at 1-cm depth. Sizes and weights of the cubes are 14 cm, 3.230 kg, and 11 cm, 1.567 kg. Tests were made with the epithermal neutron...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598354
更新日期:1998-09-01 00:00:00
abstract:PURPOSE:To demonstrate an objective approach to determining if a negative report from the Radiological Physics Center (RPC) of greater than 10% error is valid or has clinical significance. METHODS:The discrepancy involved the clinical activity (mgRaEq) of Cs-137 sources, some manufactured by 3M and some by Amersham. M...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735271
更新日期:2012-06-01 00:00:00
abstract::The scattered-photon part of pencil-beam dose kernels for high-energy x-ray beams can be derived experimentally by differentiating the broad-beam scatter-to-primary dose ratio as a function of radius. Formally, this requires a uniform and parallel beam, and the procedure is complicated by the nonideal, actual beam con...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597884
更新日期:1996-09-01 00:00:00
abstract::Electron-beam characteristics of a Philips SL25 linear accelerator have been studied. Central-axis percentage depth doses, cross-beam profiles and beam output factors of 6-, 10-, and 20-MeV beams, selected from the available energy range of 4 to 22 MeV, are reported in this paper. The main thrust of this work is to de...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596471
更新日期:1990-07-01 00:00:00
abstract::Significant advances have been made in recent years to improve photon dose calculation. However, accurate prediction of dose perturbation effects near the interfaces of different media, where charged particle equilibrium is not established, remain unsolved. Furthermore, changes in atomic number, which affect the multi...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597611
更新日期:1995-07-01 00:00:00
abstract::A new calibration algorithm (GLAaS) to derive absolute dose maps from images acquired with the Varian PV-aS500 electronic portal imager (based on amorphous silicon detectors) has been developed incorporating the dependence of detector response on primary and transmitted radiation and on field size. Detector calibratio...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2218314
更新日期:2006-08-01 00:00:00
abstract:PURPOSE:The aim of this study is to investigate the performance of Sentinel(™), a patient setup verification device based on a laser/camera system, when used on rigid-body phantoms. METHODS:The Sentinel system consists of a scanner unit, containing the laser and the camera, and surface-matching registration software. ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3675973
更新日期:2012-02-01 00:00:00
abstract::A modified neutron production target assembly has been developed to provide improved performance of the proton-cyclotron-based neutron radiotherapy facility at the University of Washington for applications involving neutron capture enhanced fast-neutron therapy. The new target produces a neutron beam that yields essen...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598839
更新日期:2000-02-01 00:00:00
abstract::Patient-specific intensity-modulated radiotherapy (IMRT) verifications require an accurate two-dimensional dosimeter that is not labor-intensive. We assessed the precision and reproducibility of film calibrations over time, measured the elemental composition of the film, measured the intermittency effect, and measured...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1852791
更新日期:2005-02-01 00:00:00
abstract::A spread-out Bragg peak (SOBP) is used in proton beam therapy to create a longitudinal conformality of the required dose to the target. In order to create this effect in a passive beam scattering system, a variety of components must operate in conjunction to produce the desired beam parameters. We will describe how th...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2776255
更新日期:2007-10-01 00:00:00
abstract::A study of the objective imaging characteristics of a new asymmetric screen-film system is presented herein. The system is characterized by high x-ray absorption asymmetric screens, and a low-noise, high-contrast asymmetric film having near-zero crossover. Comparisons are made with the imaging characteristics of two w...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597407
更新日期:1994-09-01 00:00:00
abstract::We describe a unique method that allows the comparison of spatially registered ultrasound (SRUS) images and computed tomography-derived contours (CTDCs) that were acquired with a minimal time lapse. As such, we have a tool that will provide validation of the spatial accuracy of the US system and that will allow compar...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1644515
更新日期:2004-03-01 00:00:00
abstract:PURPOSE:Computer-aided diagnosis (CAD) systems assist in solving subjective diagnosis problems that typically rely on personal experience. A CAD system has been developed to differentiate malignant thyroid nodules from benign thyroid nodules in ultrasound images based on deep learning methods. The diagnostic performanc...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14301
更新日期:2020-09-01 00:00:00
abstract:PURPOSE:For cone-beam computed tomography (CBCT) systems, we propose a sphere phantom based method to estimate the full three-dimensional (3D) modulation transfer function (MTF). METHODS:The FDK reconstruction of CBCT system in a local region was modeled by a triple convolution operator. Afterward, we calculated the d...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14147
更新日期:2020-07-01 00:00:00
abstract::The goal is to perform geometric studies on cone-beam CT scanning along a three-dimensional (3D) spiral of variable radius. First, the background for variable radius spiral cone-beam scanning is given in the context of electron-beam CT/micro-CT. Then, necessary and sufficient conditions are proved for existence and un...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1751251
更新日期:2004-06-01 00:00:00
abstract::Postoperative beta-irradiation after pterygium excision has been considered a valuable therapeutic procedure to reduce the recurrence rate. Recently, it was reported that beta-irradiation also substantially reduced the risk of surgical failure after glaucoma surgery. Pure beta-irradiation using a 90Sr/Y applicator has...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2896076
更新日期:2008-05-01 00:00:00
abstract:PURPOSE:The combination of nonhuman primates (NHPs) with the state-of-the-art molecular imaging technologies allows for within-subject longitudinal research aiming at gaining new insights into human normal and disease conditions and provides an ideal foundation for future translational studies of new diagnostic tools, ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14333
更新日期:2020-09-01 00:00:00