Abstract:
:Elastography, which uses ultrasound to image the tissue strain that results from an applied displacement, can display tumours and heat-ablated tissue with high contrast. However, its application to liver in vivo may be problematic due to the presence of respiratory and cardiovascular sources of displacement. The aim of this study was to measure the cardiovascular-induced component of natural liver motion for the purpose of planning future work that will either use the motion to produce elasticity images or will compensate for it when employing an external source of displacement. A total of 36 sequences of 7 s real-time radio frequency (RF) echo images of the liver were acquired from six healthy volunteers during breath-hold using a stationary 3.5 MHz transducer. For each image sequence, the axial and lateral components of displacement were measured for each pair of consecutive RF images using 2D-echo tracking. The spatio-temporal character of these displacements was then analysed using a novel approach, employing proper orthogonal decomposition, whereby the dominant motion patterns are described by eigenvectors with the highest eigenvalues. The motion patterns of different liver segments were complex, but they were also found to be cyclic, highly repeatable and capable of producing measurable displacements in the liver. These observations provide good evidence to suggest that it may be possible to correct for natural liver motion when using an externally applied displacement for elasticity imaging. It was also found that about 65%-70% of all liver motion could be described using the first eigenvector. Use of only this component of the motion will greatly simplify the design of a mechanical system to be used in an objective study of elasticity imaging of phantoms and excised tissues in the presence of simulated cardiovascular-induced liver motion.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Kolen AF,Miller NR,Ahmed EE,Bamber JCdoi
10.1088/0031-9155/49/18/001subject
Has Abstractpub_date
2004-09-21 00:00:00pages
4187-206issue
18eissn
0031-9155issn
1361-6560journal_volume
49pub_type
临床试验,杂志文章abstract::The purpose of this work is to develop and test a method to estimate the relative and absolute absorbed radiation dose from axial and spiral CT scans using a Monte Carlo approach. Initial testing was done in phantoms and preliminary results were obtained from a standard mathematical anthropomorphic model (MIRD V) and ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/48/16/306
更新日期:2003-08-21 00:00:00
abstract::A non-contact approach for diffuse optical tomography (DOT) has been developed for on-demand image updates using surgical navigation technology. A stereoscopic optical tracker provides real-time localization of reflective spheres mounted to a laser diode and near-infrared camera. Standard camera calibration is combine...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab1f33
更新日期:2019-07-05 00:00:00
abstract::The in vivo electric conductivity (σ) values of tissue are essential for accurate electromagnetic simulations and specific absorption rate (SAR) assessment for applications such as thermal dose computations in hyperthermia. Currently used σ-values are mostly based on ex vivo measurements. In this study the conductivit...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/61/4/1596
更新日期:2016-02-21 00:00:00
abstract::This is a review of the relatively recently developed field of intravascular brachytherapy of coronary arteries. It presents a brief overview of the discipline of coronary angioplasty describing the problem of restenosis and discusses the potential for ionizing radiation to overcome this problem. It examines the vario...
journal_title:Physics in medicine and biology
pub_type: 杂志文章,评审
doi:10.1088/0031-9155/47/4/201
更新日期:2002-02-21 00:00:00
abstract::The purpose of this study was to determine the performance of a single lutetium oxy-orthosilicate (LSO) crystal layer High Resolution Research Tomograph (HRRT) positron emission tomography (PET) scanner. The HRRT is a high resolution PET scanner designed for human brain and small animal imaging. The scanner consists o...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/48/4/302
更新日期:2003-02-21 00:00:00
abstract::Optically stimulated luminescent dosimeters (OSLDs) are becoming increasingly popular for measuring an absorbed dose in clinical radiotherapy. OSLDs have known energy dependence, and this is accounted for by either calibrating the OSLD with a specific nominal energy, or using a standard energy correction factor to acc...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/57/9/2505
更新日期:2012-05-07 00:00:00
abstract::Peripheral neural stimulation is a major problem in current gradient coil designs. Induced current problems in patients relate directly to gradient strength and modulation frequency. Present designs of gradient coil tend to limit ultra-high-speed imaging methods such as echo-planar imaging (EPI) and echo-volumar imagi...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/53/7/001
更新日期:2008-04-07 00:00:00
abstract::The effect of the physical state (phase) of the absorbing medium and the energy straggling of the alpha particles on the calculation of the radiation dose due to the daughter products of radon deposited in the lung have been studied in detail. The stopping power data for alpha particles in water and water vapour have ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/32/8/004
更新日期:1987-08-01 00:00:00
abstract::Lung 4D computed tomography (4D-CT), which is a time-resolved CT data acquisition, performs an important role in explicitly including respiratory motion in treatment planning and delivery. However, the radiation dose is usually reduced at the expense of inter-slice spatial resolution to minimize radiation-related heal...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aa8a48
更新日期:2017-10-03 00:00:00
abstract::The purpose of this work was to determine noise levels in HMPAO RCBF SPECT images. Eight simulated images of a uniform sphere of activity were made at each of three different count levels. Three images of the Amersham brain phantom were obtained at each of three count levels, roughly corresponding to the simulation le...
journal_title:Physics in medicine and biology
pub_type: 临床试验,杂志文章
doi:10.1088/0031-9155/39/5/006
更新日期:1994-05-01 00:00:00
abstract::MRI-guided prostate biopsy in conventional closed-bore scanners requires transferring the patient outside the bore during needle insertion due to the constrained in-bore space, causing a safety hazard and limiting image feedback. To address this issue, we present our custom-made in-bore setup and software to support M...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/57/18/5823
更新日期:2012-09-21 00:00:00
abstract::This paper explores fast reconstruction strategies for 3D time-of-flight (TOF) positron emission tomography (PET), based on 2D data rebinning. Starting from pre-corrected 3D TOF data, a rebinning algorithm estimates for each transaxial slice the 2D TOF sinogram that would have been acquired by a single-ring scanner. T...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/50/12/002
更新日期:2005-06-21 00:00:00
abstract::At present, there exists few openly available methods for evaluation of simultaneous segmentation and registration algorithms. These methods allow for a combination of both techniques to track the tumor in complex settings such as adaptive radiotherapy. We have produced a quality assurance platform for evaluating this...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/61/19/7012
更新日期:2016-10-07 00:00:00
abstract::Over the course of radiation therapy, a patient's anatomy may change substantially. The relatively recent addition of frequent in-room imaging to assist with patient localization has provided a database of images that may be used to recalculate dose distributions for adaptive radiotherapy purposes. The TomoTherapy Hi-...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/56/24/010
更新日期:2011-12-21 00:00:00
abstract::This paper presents two 4D mathematical observer models for the detection of motion defects in 4D gated medical images. Their performance was compared with results from human observers in detecting a regional motion abnormality in simulated 4D gated myocardial perfusion (MP) SPECT images. The first 4D mathematical obs...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/60/7/2751
更新日期:2015-04-07 00:00:00
abstract::Microcalcification is one of the earliest and main indicators of breast cancer. Because dual-energy digital mammography could suppress the contrast between the adipose and glandular tissues of the breast, it is considered a promising technique that will improve the detection of microcalcification. In dual-energy digit...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/53/22/004
更新日期:2008-11-21 00:00:00
abstract::The in-phantom calibration method for radiotherapy kilovoltage x-ray beams requires ionization chamber correction factors. The overall ionization chamber correction factor accounts for changes in the chamber response due to the displacement of water by the chamber cavity and wall, the presence of the stem and the chan...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab82e7
更新日期:2020-05-11 00:00:00
abstract::In order to enable a detailed analysis of radio frequency (RF) absorption in the human middle and inner ear organs, a numerical model of these organs was developed at a spatial resolution of 0.1 mm, based on a real human tissue sample. The dielectric properties of the liquids (perilymph and endolymph) inside the bony ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/52/7/001
更新日期:2007-04-07 00:00:00
abstract::Computational simulations, such as Monte Carlo track structure simulations, offer a powerful tool for quantitatively investigating radiation interactions within cells. The modelling of the spatial distribution of energy deposition events as well as diffusion of chemical free radical species, within realistic biologica...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aad8eb
更新日期:2018-09-06 00:00:00
abstract::In this work we present the first delivery of intensity modulated arc therapy on the Elekta Unity 1.5 T MR-linac. The machine's current IMRT based control system was modified suitably to enable dynamic delivery of radiation, for the purpose of exploring MRI-guided radiation therapy adaptation modes in a research setti...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/abd66d
更新日期:2020-12-23 00:00:00
abstract::For treatments with dynamic intensity modulated radiotherapy (IMRT), the adjustment of multileaf collimator (MLC) parameters affecting both the optimization algorithm and dose distributions is crucial. The main parameters characterizing the MLC are the transmission (T) and the dosimetric leaf separation (DLS). The aim...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/50/4/001
更新日期:2005-02-21 00:00:00
abstract::In radiotherapy with photon beams, the use of dynamic wedges, which are obtained by the movement of one of the jaws, offers an increasing flexibility relative to the traditional use of metal wedges. But it is a disadvantage for the measurement of absorbed dose distributions, because the absorbed dose at each measureme...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/43/6/009
更新日期:1998-06-01 00:00:00
abstract::Imaging technologies that allow non-radiative visualization and quantification of apoptosis have a great potential for assessing therapy response, early diagnosis, and disease monitoring. Magnetic particle imaging (MPI), the direct imaging of magnetic nanoparticles as positive contrast agent and sole signal source, en...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/abad7c
更新日期:2020-09-24 00:00:00
abstract::The Compton camera is an imaging device which has been proposed to detect prompt gammas (PGs) produced by proton-nuclear interactions within tissue during proton beam irradiation. Compton-based PG imaging has been developed to verify proton ranges because PG rays, particularly characteristic ones, have strong correlat...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aab737
更新日期:2018-04-19 00:00:00
abstract::Three-dimensional reconstruction of coronary arteries can be performed during x-ray-guided interventions by gated reconstruction from a rotational coronary angiography sequence. Due to imperfect gating and cardiac or breathing motion, the heart's motion state might not be the same in all projections used for the recon...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/53/14/007
更新日期:2008-07-21 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::A photoluminescent thermometer, based on the transient emission response of a europium-activated calcium sulphide phosphor, is described in detail. This optical thermometry system has special advantages for temperature measurements in microwave and RF fields and potential application in electromagnetically induced cli...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/27/1/011
更新日期:1982-01-01 00:00:00
abstract::Determining plaque vulnerability is critical when selecting the most suitable treatment for patients with atherosclerotic plaque. Currently, clinical non-invasive ultrasound-based methods for plaque characterization are limited to visual assessment of plaque morphology and new quantitative methods are needed. In this ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/60/8/3151
更新日期:2015-04-21 00:00:00
abstract::Several recent reports agree that the potentially dangerous heating around extended wires or coaxial cables inside the bodycoil of a magnetic resonance imager is related to resonant effects. No quantitative description of this idea has been given so far. We analyse a simplified situation, where a straight metallic wir...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/47/16/312
更新日期:2002-08-21 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