Abstract:
:The Akaike information criterion and the associated Akaike weights (AW) rank pharmacokinetic models on the basis of goodness-of-fit and number of parameters. The usefulness of this information for improving the haemodynamic parameter estimates from DCE-MRI was investigated through two examples. In each of these, the estimates from the two-compartment exchange model (2CXM) were combined on the basis of the AW with those of a simplified model (either the uptake model or the extended Tofts model). Data were simulated using the 2CXM for a range of experimental and tissue conditions. Two multimodel approaches exploiting the AW were investigated: the ‘bestmodel’ approach which selects the parameter estimates from the model with highest AW and the ‘weighted model’ approach in which AW-weighted averages of the estimates from the competing models are calculated. Although these approaches were shown to be beneficial in some cases, they were found to frequently lead to unexpected increases in the bias and/or uncertainty of the resulting parameter estimates. Within the limited scope of this simulation study, the use of the Akaike criterion showed no systematic benefit over a fitting strategy involving only the more complex model.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Luypaert R,Ingrisch M,Sourbron S,de Mey Jdoi
10.1088/0031-9155/57/11/3609subject
Has Abstractpub_date
2012-06-07 00:00:00pages
3609-28issue
11eissn
0031-9155issn
1361-6560journal_volume
57pub_type
杂志文章abstract::This work studies the effect of age on lung dose commitments arising from the inhalation of an atmosphere containing radionuclides of varying half-lives and physical sizes. This dependence is significant in many cases, approaching a ratio of 2 in several instances when the maximum dose at a given age is compared with ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/27/4/005
更新日期:1982-04-01 00:00:00
abstract::Delivering accurate radiation dose to blood specimens during biological irradiations is essential in quantifying damage of ionizing radiation. To estimate dose to blood samples as accurately as possible, pieces of EBT2 model GAFCHROMIC™ film were placed within an approximately 10 mm finely ground rice layer that was u...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/58/10/3177
更新日期:2013-05-21 00:00:00
abstract::Recent acute shortage of medical radioisotopes prompted investigations into alternative methods of production and the use of a cyclotron and ¹⁰⁰Mo(p,2n)(99m)Tc reaction has been considered. In this context, the production yields of (99m)Tc and various other radioactive and stable isotopes which will be created in the ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/56/17/002
更新日期:2011-09-07 00:00:00
abstract::Target motion is one of the major limitations of each high precision radiation therapy. Using advanced active beam delivery techniques, such as the magnetic raster scanning system for particle irradiation, the interplay between time-dependent beam and target position heavily distorts the applied dose distribution. Thi...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/49/14/001
更新日期:2004-07-21 00:00:00
abstract::Within an epidemiological study regarding the correlation between skin pathologies and personal ultraviolet (UV) exposure due to solar radiation, 14 field campaigns using polysulphone (PS) dosemeters were carried out at three different Italian sites (urban, semi-rural and rural) in every season of the year. A polysulp...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/51/17/019
更新日期:2006-09-07 00:00:00
abstract:BACKGROUND:During transcranial electrical stimulation (tES), including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS), current density concentration around the electrode edges that is predicted by simplistic skin models does not match experimental observations of ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/abb7c1
更新日期:2020-09-11 00:00:00
abstract::Intensity modulated proton radiotherapy (IMPT) can reduce the dose to critical structures by optimizing the distribution and intensity of individual pencil beams. The IMPT can be delivered by dynamically scanning a pencil beam with variable intensity and energy across the tumor target volume. The lateral penumbra of a...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/53/6/016
更新日期:2008-03-21 00:00:00
abstract::Precision image-guided small animal radiotherapy is rapidly advancing through the use of dedicated micro-irradiation devices. However, precise modeling of these devices in model-based dose-calculation algorithms such as Monte Carlo (MC) simulations continue to present challenges due to a combination of very small beam...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/58/10/3377
更新日期:2013-05-21 00:00:00
abstract::Segmentation of liver in abdominal computed tomography (CT) is an important step for radiation therapy planning of hepatocellular carcinoma. Practically, a fully automatic segmentation of liver remains challenging because of low soft tissue contrast between liver and its surrounding organs, and its highly deformable s...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aabd19
更新日期:2018-05-04 00:00:00
abstract::An inverse radiation treatment planning algorithm for Sensus Healthcare's SculpturaTM electronic brachytherapy system has been designed. The algorithm makes use of simulated annealing to optimize the conformation number of the treatment plan. The highly anisotropic dose distributions produced by the SculpturaTM x-ray ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/abda9a
更新日期:2021-01-11 00:00:00
abstract::Kilovoltage intratreatment monitoring (KIM) is a novel real-time localization modality where the tumor position is continuously measured during intensity modulated radiation therapy (IMRT) or intensity modulated arc therapy (IMAT) by a kilovoltage (kV) x-ray imager. Adding kV imaging during therapy adds radiation dose...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/58/17/5983
更新日期:2013-09-07 00:00:00
abstract::Measurements of patient entrance surface dose rate provide valuable data for interpreting results from dose-area product studies on fluoroscopic x-ray equipment. Methods for measurement of entrance surface dose rate with backscatter and incident dose rate without backscatter have been investigated. Entrance surface do...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/40/5/008
更新日期:1995-05-01 00:00:00
abstract::The purpose of this work is to provide an evaluation of the mean glandular dose (MGD) for breast computed tomography (CT) with synchrotron radiation in an axial scanning configuration with a partial or total organ volume irradiation, for the in vivo program of breast CT ongoing at the ELETTRA facility (Trieste, Italy)...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/61/2/569
更新日期:2016-01-21 00:00:00
abstract::Conventional molecular assessment of tissue through histology, if adapted to fresh thicker samples, has the potential to enhance cancer detection in surgical margins and monitoring of 3D cell culture molecular environments. However, in thicker samples, substantial background staining is common despite repeated rinsing...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aa6cf1
更新日期:2017-06-21 00:00:00
abstract::Monte Carlo methods have been applied to the study of the performance of antiscatter grids in radiography. Photon histories for imaging with a 20 cm thick water phantom irradiated with an 80 kV x-ray spectrum were generated by Monte Carlo simulation. The scattering and absorption of the photons transmitted from the ph...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/27/6/002
更新日期:1982-06-01 00:00:00
abstract::Previous treatment of cerebrospinal fluid (CSF) malignancies by intrathecal administration of (131)I-radiolabelled monoclonal antibodies has led to the assumption that more healthy tissue will be spared when a pure beta-emitter such as (90)Y replaces (131)I. The purpose of this study is to compare and quantitatively e...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/51/1/014
更新日期:2006-01-07 00:00:00
abstract::Coronary flow rate remains complex to assess in clinical practice using non-invasive, non-ionizing imaging tools. In this study, we introduce 3D ultrafast Doppler coronary angiography (3D UDCA), an ultrasound-based method to assess coronary blood flows in three-dimensions at high volume-rate and in one single heartbea...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab8d78
更新日期:2020-06-05 00:00:00
abstract::The aim of this study is to calculate realistic dose distributions that include the continuous deformation of organs and continuous motion of machine using 4D Monte Carlo methods for both volumetric modulated arc therapy and helical tomotherapy treatments. As part of a previous study, we presented a method to perform ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/58/9/2807
更新日期:2013-05-07 00:00:00
abstract::Microbeam radiation therapy (MRT) is a pre-clinical, spatially-fractionated treatment modality noted for its ability to achieve a large differential response between normal and tumoral tissues. In the present study, TOPAS Monte Carlo (MC) simulations were used to optimize the design of a compact, affordable multi-slit...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aad7e2
更新日期:2018-08-29 00:00:00
abstract::A cost-effective method employing polysulphone, nalidixic acid, 8-methoxypsoralen and phenothiazine as UV dosimeters is presented for evaluating the UV spectrum. The exposure measured by each dosimeter is a function of the source spectrum and the spectral response of the material. Each material has a different spectra...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/42/1/005
更新日期:1997-01-01 00:00:00
abstract::A method to determine the spectrum of a clinical photon beam from measured depth-dose data is described. At shallow depths, where the range of Compton-generated electrons increases rapidly with photon energy, the depth dose provides the information to discriminate the spectral contributions. To minimize the influence ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/45/1/312
更新日期:2000-01-01 00:00:00
abstract::In order to measure in vivo resistivity of tissues in the thorax, the possibility of combining anatomical data extracted from high-resolution images with multiple-electrode impedance measurements, a priori knowledge of the range of tissue resistivities, and a priori data on the instrumentation noise is assessed in thi...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/39/1/001
更新日期:1994-01-01 00:00:00
abstract::The dose distribution near a non-radioactive gold seed under a 6 MV photon beam was measured using radiographic film, water equivalent bolus and solid water slabs. This type of small seed is typically used as a marker in target positional verification using a portal imager for conformal prostate treatment such as inte...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/50/18/N02
更新日期:2005-09-21 00:00:00
abstract::A new mathematical model of the head has been constructed from a set of serial MRI slices from one subject. Finite-difference time-domain (FDTD) calculations of the specific energy absorption rate (SAR) have been performed on this model with a 2 mm resolution for a generic mobile communication transceiver represented ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/39/10/003
更新日期:1994-10-01 00:00:00
abstract::In this letter the authors highlight the presence of an error appearing in the discussion of the note 'The use of the Henyey-Greenstein phase function in Monte Carlo simulations in biomedical optics' previously published by them (Binzoni et al 2006 Phys. Med. Biol. 51 N313). In the light of this error, the discussion ...
journal_title:Physics in medicine and biology
pub_type: 评论,信件
doi:10.1088/0031-9155/51/22/L01
更新日期:2006-11-21 00:00:00
abstract::We have compared two methods of estimating the cellular radiosensitivity of a heterogeneous tumour, namely, via cell-survival and via tumour control probability (TCP) pseudo-experiments. It is assumed that there exists intra-tumour variability in radiosensitivity and that the tumour consists predominantly of radiosens...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/60/15/N293
更新日期:2015-08-07 00:00:00
abstract::The presence of motion artifacts is a typical problem in thoracic imaging. However, synchronizing the respiratory cycle with computed tomography (CT) image acquisition can reduce these artifacts. We currently employ a method of in vivo respiratory-gated micro-CT imaging for small laboratory animals (mice). This proced...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/49/17/023
更新日期:2004-09-07 00:00:00
abstract::In magnetic resonance (MR) guided radiotherapy, the magnetic field-dependent change in the dose response of ionization chambers is typically included by means of a correction factor [Formula: see text]. This factor can be determined experimentally or calculated by means of Monte Carlo (MC) simulations. To date, a smal...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab2837
更新日期:2019-07-04 00:00:00
abstract::Recent theoretical research on spatiobiologically integrated radiotherapy has focused on optimization models that adapt fluence-maps to the evolution of tumor state, for example, cell densities, as observed in quantitative functional images acquired over the treatment course. We propose an optimization model that adap...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aab4b6
更新日期:2018-03-27 00:00:00
abstract::Monitoring the spatio-temporal characteristics of microcirculation is crucial for studying the functional activities of biotissue and the mechanism of disease. However, conventional methods used to measure blood flow suffer from limited spatial resolution or the injection of exogenous substances or the need of scannin...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/49/7/020
更新日期:2004-04-07 00:00:00