Abstract：
PURPOSE:Radiopharmaceutical applications in nuclear medicine require a detailed dosimetry estimate of the radiation energy delivered to the human tissues. Over the past years, several publications addressed the problem of internal dose estimate in volumes of several sizes considering photon and electron sources. Most of them used Monte Carlo radiation transport codes. Despite the widespread use of these codes due to the variety of resources and potentials they offered to carry out dose calculations, several aspects like physical models, cross sections, and numerical approximations used in the simulations still remain an object of study. Accurate dose estimate depends on the correct selection of a set of simulation options that should be carefully chosen. This article presents an analysis of several simulation options provided by two of the most used codes worldwide: MCNP and GEANT4. METHODS:For this purpose, comparisons of absorbed fraction estimates obtained with different physical models, cross sections, and numerical approximations are presented for spheres of several sizes and composed as five different biological tissues. RESULTS:Considerable discrepancies have been found in some cases not only between the different codes but also between different cross sections and algorithms in the same code. Maximum differences found between the two codes are 5.0% and 10%, respectively, for photons and electrons. CONCLUSION:Even for simple problems as spheres and uniform radiation sources, the set of parameters chosen by any Monte Carlo code significantly affects the final results of a simulation, demonstrating the importance of the correct choice of parameters in the simulation.
journal_name
Med Physjournal_title
Medical physicsauthors
Yoriyaz H,Moralles M,Siqueira Pde T,Guimarães Cda C,Cintra FB,dos Santos Adoi
10.1118/1.3242304subject
Has Abstractpub_date
2009-11-01 00:00:00pages
5198-213issue
11eissn
0094-2405issn
2473-4209journal_volume
36pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：:In x-ray spectral measurement using a semiconductor detector system, accurate positioning of the detector in front of the anode is very important. This needs accurate determination of the focal spot position on the target in an x-ray tube. We present a simple technique to determine the focal spot position accurately. ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597122
更新日期：1993-07-01 00:00:00
abstract：:Positron emission tomography (PET) has shown an increase in both sensitivity and specificity over computed tomography (CT) in lung cancer. However, motion artifacts in the 18F fluorodioxydoglucose (FDG) PET images caused by respiration persists to be an important factor in degrading PET image quality and quantificatio...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1448824
更新日期：2002-03-01 00:00:00
abstract：:The purpose of this work is to investigate algorithms for the delivery of intensity-modulated fields using independent collimators (IC). Two heuristic algorithms are proposed to calculate jaw-setting sequences for arbitrary 2D intensity distributions. The first algorithm is based on searching the whole intensity matri...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598794
更新日期：1999-12-01 00:00:00
abstract：:Transthoracic electrical impedance Z consists of a constant baseline component Z0 and the time variable component delta Z such that Z = Z0 + delta Z. The first time derivative of Z has a negative peak, the magnitude of which is (dZ/dt)min. Measurements of 170 volunteers show that (dZ/dt)min is a function of the consta...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.594910
更新日期：1981-01-01 00:00:00
abstract：PURPOSE:Intensity-modulated proton therapy (IMPT) is known to be sensitive to patient setup and range uncertainty issues. Multiple robust optimization methods have been developed to mitigate the impact of these uncertainties. Here, we propose a new robust optimization method, which provides an alternative way of robust...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13276
更新日期：2019-01-01 00:00:00
abstract：:Stereotactic Body Radiation Therapy (SBRT) is being increasingly used in the radiation oncology community to treat tumors in extra-cranial sites such as spine, lung, liver, pancreas and prostate. There are well established RTOG protocols (e.g. RTOG 0631 for spine, RTOG 0813 and 0915 for lung and RTOG 0438 for liver) t...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4736142
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:To evaluate the patient positioning accuracy and reproducibility of two commercially available immobilization systems for Stereotactic Body Radiotherapy (SBRT) treatment. METHODS:Forty one patients with lung (n=21) or liver (n=20) malignancies were assigned to one of the two immobilization devices: Elekta ster...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735009
更新日期：2012-06-01 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:Measured values of ultrasound attenuation in bone represent a combination of different loss mechanisms. As a wave is transmitted from a fluid into bone, reflections occur at the interface. In the bone, mode conversion occurs between longitudinal and shear modes and the mechanical wave is scattered by its comple...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3668316
更新日期：2012-01-01 00:00:00
abstract：:Spectra, yields, average energies, and kerma rates in tissue of neutrons from 21-MeV deuteron bombardment of deuterium gas targets have been calculated for target thicknesses of 1, 3.5, and 5 MeV. A high pressure gas cell was constructed and was filled with 33 atm of D2 gas (equivalent to an energy loss of 3.5 MeV for...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.594561
更新日期：1979-05-01 00:00:00
abstract：PURPOSE:To develop a fluoroscopy imaging based approach that can determine the magnitude and phase variation in respiratory motion against the treatment planning images in order to quantify the online patient setup deviation in thoracic cancer IGRT for the real time adaptive patient positionadjustment. METHODS:A numer...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734876
更新日期：2012-06-01 00:00:00
abstract：:Ultrasound-induced blood stasis has been observed for more than 30 years. Most of the literature has been focused on the health risks associated with this phenomenon and methods employed to prevent stasis from occurring during ultrasound imaging. To date, experimental observations have been either in vitro or invasive...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2198196
更新日期：2006-06-01 00:00:00
abstract：PURPOSE:To provide results of water calorimetry and ion chamber measurements in high-energy electron beams carried out at the National Research Council Canada (NRC). There are three main aspects to this work: (a) investigation of the behavior of ionization chambers in electron beams of different energies with focus on ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12463
更新日期：2017-10-01 00:00:00
abstract：:Scanning film densitometry routinely used for obtaining dosimetric information about therapy treatment beams is subject to several sources of inaccuracies. The most significant of these are described and appropriate methods of testing are presented. This establishes the need for adequate acceptance testing followed by...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595407
更新日期：1983-09-01 00:00:00
abstract：PURPOSE:A three-dimensional finite element analysis based canine heart model is introduced that would enable the assessment of cardiac function. METHODS:The three-dimensional canine heart model is based on the cardiac deformation and motion model obtained from the Cardiac Mechanics Research Group at UCSD. The canine h...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3496326
更新日期：2010-11-01 00:00:00
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:Cone-beam computed tomography (CBCT) is an increasingly utilized imaging modality for the diagnosis and treatment planning of the patients with craniomaxillofacial (CMF) deformities. Accurate segmentation of CBCT image is an essential step to generate three-dimensional (3D) models for the diagnosis and treatmen...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4868455
更新日期：2014-04-01 00:00:00
abstract：PURPOSE:To determine the accuracy of VMAT treatment planning and delivery for patients undergoing radiotherapy in the head and neck. METHOD AND MATERIALS:A dosimetric study of a typical head and neck treatment plan has been carried out using Chamber, film and TLD's placed inside an anthropomorphic phantom. Lateral and...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735478
更新日期：2012-06-01 00:00:00
abstract：:Many problems in physics involve imaging objects with high spatial frequency content in a limited amount of time. The limitation of available experimental data leads to the infamous problem of diffraction limited data which manifests itself by causing ringing in the image. This ringing is due to the interference pheno...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596427
更新日期：1989-05-01 00:00:00
abstract：:The ability of Leksell GammaPlan to perform stereotactic space localizations with image sets where there is misalignment of the patient's head (stereotactic frame and fiducial apparatus) relative to the computed tomography (CT) scanner coordinate system was studied. Misalignment is sometimes necessary for patient comf...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2179751
更新日期：2006-04-01 00:00:00
abstract：PURPOSE:An improved method of image guidance for lung tumor biopsies could help reduce the high rate of false negatives. The aim of this work is to optimize the geometry of the scanning-beam digital tomography system (SBDX) for providing real-time 3D tomographic reconstructions for target verification. The unique geome...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4826159
更新日期：2013-11-01 00:00:00
abstract：PURPOSE:To achieve more translatable preclinical research results, small animal irradiation needs to more closely simulate human radiotherapy. Although the clinical gold standard is intensity-modulated radiation therapy (IMRT), the direct translation of this method for small animals is impractical. In this study we des...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13872
更新日期：2019-12-01 00:00:00
abstract：:Gd2O2S phosphor screens between 250 and 1000 mg/cm2 thick were evaluated for use in megavoltage imaging systems. The phosphor layers were placed on brass plates ranging from 1 to 5 mm thick, each with and without an optical back reflector (white paint). Light output and spatial resolution were measured at 6- and 23-MV...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597209
更新日期：1994-08-01 00:00:00
abstract：PURPOSE:To study the impact of target geometrical and linac operational parameters, such as target material and thickness, electron beam size, repetition rate, and mean current on the ability of the radiotherapy treatment head to deliver high-dose-rate x-ray irradiation in the context of novel linear accelerators capab...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12615
更新日期：2017-12-01 00:00:00
abstract：PURPOSE:To develop a novel three-dimensional (3D) hybrid-encoding framework using compressed sensing (CS) and Toeplitz encoding with variable phase-scrambled radio-frequency (RF) excitation, which has the following advantages: low power deposition of RF pulses, reduction of the signal dynamic range, no additional hardw...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13987
更新日期：2020-04-01 00:00:00
abstract：PURPOSE:The availability of accurate and simple models for the estimation of x-ray spectra is of great importance for system simulation, optimization, or inclusion of photon energy information into data processing. There is a variety of publicly available tools for estimation of x-ray spectra in radiology and mammograp...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4837220
更新日期：2014-01-01 00:00:00
abstract：PURPOSE:The feasibility of intensity modulated brachytherapy (IMBT) to improve dose conformity for irregularly shaped targets has been previously investigated by researchers by means of using partially shielded sources. However, partial shielding does not fully explore the potential of IMBT. The goal of this study is t...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3456598
更新日期：2010-07-01 00:00:00
abstract：PURPOSE:Electronic portal imagers (EPIDs) with high detective quantum efficiencies (DQEs) are sought to facilitate the use of the megavoltage (MV) radiotherapy treatment beam for image guidance. Potential advantages include high quality (treatment) beam's eye view imaging, and improved cone-beam computed tomography (CB...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4927786
更新日期：2015-09-01 00:00:00
abstract：:The Radiological Physics Center (RPC) developed two heterogeneous anthropomorphic quality assurance phantoms for use in verifying the accuracy of radiation delivery: one for intensity-modulated radiation therapy (IMRT) to the pelvis and the other for stereotactic body radiation therapy (SBRT) to the thorax. The purpos...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2737158
更新日期：2007-06-01 00:00:00
abstract：:Noise, partial volume (PV) effect, and image-intensity inhomogeneity render a challenging task for segmentation of brain magnetic resonance (MR) images. Most of the current MR image segmentation methods focus on only one or two of the above-mentioned effects. The objective of this paper is to propose a unified framewo...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1944912
更新日期：2005-07-01 00:00:00
