Abstract:
:The most advanced delivery technique for proton radiotherapy is active spot scanning. So far, predominantly static targets have been treated with active spot scanning, since mobile targets in combination with dynamic treatment delivery can lead to interplay effects, causing inhomogeneous dose distributions. One way to mitigate motion effects is re-scanning. In this study we investigate the effectiveness of re-scanning in relation to different plan parameters (number of fields, field directions, number of re-scans) as well as in respect to different motion parameters (motion amplitude, motion starting phase). A systematic study was performed for three liver patients, for which ten different plans have been calculated, respectively. The treatment plans were evaluated for three different scenarios (static, motion/single-scan-delivery, motion/re-scanned-delivery). The choice of motion parameters was based on an evaluation of the 4D CT data sets of the three patients. It is shown that the effect of motion/re-scanning per fraction is largest the fewer fields per plan are used and the more the field direction differs from the main motion direction. For amplitudes up to 6 mm, re-scanning may not be required if multiple fields are used, since only dose blurring effects appear that cannot be compensated by re-scanning. For larger motion amplitudes two planning strategies are proposed.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Knopf AC,Hong TS,Lomax Adoi
10.1088/0031-9155/56/22/016subject
Has Abstractpub_date
2011-11-21 00:00:00pages
7257-71issue
22eissn
0031-9155issn
1361-6560pii
S0031-9155(11)00040-6journal_volume
56pub_type
杂志文章abstract::All available imaging devices in nuclear medicine have finite energy resolution. This leads to inclusion of scattered radiation, which in turn degrades the image quality. Different scatter correction schemes therefore try to eliminate the effect of scattered radiation. On the other hand, improvement of the camera's in...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/34/1/008
更新日期:1989-01-01 00:00:00
abstract::Commercial TPSs typically model the tongue-and-groove (TG) by extending the projections of the leaf sides by a certain constant width. However, this model may produce discrepancies of as much as 7%-10% in the calculated average doses, especially for the High Definition multi-leaf collimator (MLC) (Hernandez et al 2017...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aaf098
更新日期:2018-12-10 00:00:00
abstract::A reader study was conducted to tune the parameters of an observer model used to predict the detectability index (dʹ ) of test objects as a task-based quality control (QC) metric for digital mammography. A simple test phantom was imaged to measure the model parameters, namely, noise power spectrum,modulation transfer ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/59/21/6621
更新日期:2014-11-07 00:00:00
abstract::Generally, the inverse planning of radiation therapy consists mainly of the fluence optimization. The beam angle optimization (BAO) in intensity-modulated radiation therapy (IMRT) consists of selecting appropriate radiation incidence directions and may influence the quality of the IMRT plans, both to enhance better or...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/58/9/2939
更新日期:2013-05-07 00:00:00
abstract::Although x-ray mammography is widely developed for breast tumour detection, it suffers from spatial superposition in its two-dimensional (2D) representation of a three-dimensional (3D) breast structure. Accordingly, 3D breast imaging, such as cone-beam computed tomography (CT), arises at the historic moment. In this p...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/48/14/312
更新日期:2003-07-21 00:00:00
abstract::Although physical metrics can objectively characterize computed tomography (CT) image quality, quantitative approaches to predict human observer performance are more accurate and clinically relevant. This study compared a modified channelized Hotelling model observer (CHO) with human observers in a shape discriminatio...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/59/13/3389
更新日期:2014-07-07 00:00:00
abstract::By analyzing the radiobiological model, and the equations derived from the model, it is shown that the main results of the article 'The influence of dose heterogeneity on tumor control probability in fractionated radiation therapy' by Wiklund et al (2011 Phys. Med. Biol. 56 7585-600) are valid only under the condition...
journal_title:Physics in medicine and biology
pub_type: 评论,信件
doi:10.1088/0031-9155/58/18/6585
更新日期:2013-09-21 00:00:00
abstract::Computer aided detection (CADe) for breast lesion can provide an important reference for radiologists in breast cancer screening. Architectural distortion (AD) is a type of breast lesion that is difficult to detect. A majority of CADe methods focus on detecting the radial pattern, which is a main characteristic of typ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab98d0
更新日期:2020-06-02 00:00:00
abstract::Prompt γ-ray imaging with a knife-edge shaped slit camera provides the possibility of verifying proton beam range in tumor therapy. Dedicated experiments regarding the characterization of the camera system have been performed previously. Now, we aim at implementing the prototype into clinical application of monitoring...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/61/22/7881
更新日期:2016-11-21 00:00:00
abstract::Today, new single photon emission computed tomography (SPECT) reconstruction techniques rely on accurate Monte Carlo (MC) simulations to optimize reconstructed images. However, existing MC scintillation camera models which usually include an accurate description of the collimator and crystal, lack correct implementati...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/56/1/006
更新日期:2011-01-07 00:00:00
abstract::This study aims to develop a computer-aided diagnosis (CADx) scheme for classification between malignant and benign lung nodules, and also assess whether CADx performance changes in detecting nodules associated with early and advanced stage lung cancer. The study involves 243 biopsy-confirmed pulmonary nodules. Among ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aaa610
更新日期:2018-02-05 00:00:00
abstract::Using MRI for radiotherapy treatment planning and image guidance is appealing as it provides superior soft tissue information over CT scans and avoids possible systematic errors introduced by aligning MR to CT images. This study presents a method that generates Synthetic CT (MRCT) volumes by performing probabilistic t...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/62/8/2935
更新日期:2017-04-21 00:00:00
abstract::Compressed sensing (CS) aims to recover images from fewer measurements than that governed by the Nyquist sampling theorem. Most CS methods use analytical predefined sparsifying domains such as total variation, wavelets, curvelets, and finite transforms to perform this task. In this study, we evaluated the use of dicti...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/60/15/5853
更新日期:2015-08-07 00:00:00
abstract::This study investigates the dosimetric impact of using population-based Hounsfield units (HUs) and ICRU-based HUs as a function of the number of tissue segments for bulk density assignment toward MRI-based treatment planning in the abdomen. To avoid potential geometric differences between CT and MR images, CT images r...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aacfb1
更新日期:2018-07-24 00:00:00
abstract::The National Physical Laboratory (NPL) provides a high-energy photon calibration service using 4-19 MV x-rays and 60Co gamma-radiation for secondary standard dosemeters in terms of absorbed dose to water. The primary standard used for this service is a graphite calorimeter and so absorbed dose calibrations must be con...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/47/3/306
更新日期:2002-02-07 00:00:00
abstract::Technical advances towards high resolution PET imaging try to overcome the inherent physical limitations to spatial resolution. Positrons travel in tissue until they annihilate into the two gamma photons detected. This range is the main detector-independent contribution to PET imaging blurring. To a large extent, it c...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/58/15/5127
更新日期:2013-08-07 00:00:00
abstract::For proton therapy, an accurate conversion of CT HU to relative stopping power (RSP) is essential. Validation of the conversion based on real tissue samples is more direct than the current practice solely based on tissue substitutes and can potentially address variations over the population. Based on a novel dose exti...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aa782c
更新日期:2017-06-23 00:00:00
abstract::Multileaf collimators (MLCs) have been in clinical use for many years and meanwhile are commonly used to deliver intensity-modulated radiotherapy (IMRT) beams. For this purpose it is important to know their dosimetric properties precisely, one of them being inter- and intraleaf leakage. The Siemens 160 MLC features a ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/56/2/N02
更新日期:2011-01-21 00:00:00
abstract::A general theory is presented for minimizing noise in linear dimension reduction of sequences of medical images when the factors and the covariance matrix and mean of the noise are given. A dimension reduction is optimal when all diagonal elements in the covariance matrix of the noise in the signal (factor) space are ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/40/11/010
更新日期:1995-11-01 00:00:00
abstract::A new function to treat tetrahedral-mesh geometry was implemented in the particle and heavy ion transport code systems. To accelerate the computational speed in the transport process, an original algorithm was introduced to initially prepare decomposition maps for the container box of the tetrahedral-mesh geometry. Th...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aa6b45
更新日期:2017-06-21 00:00:00
abstract::Task group 43 (TG43)-based dosimetry algorithms are efficient for brachytherapy dose calculation in water. However, human tissues have chemical compositions and densities different than water. Moreover, the mutual shielding effect of seeds on each other (interseed attenuation) is neglected in the TG43-based dosimetry ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/57/11/3273
更新日期:2012-06-07 00:00:00
abstract::A parametric model for the x-ray linear attenuation coefficient is used to describe the compositional dependence of Hounsfield numbers measured by medical CT scanners. Measurements with materials of known density and composition, that span and evenly sample the compositional range of tissues, are written as linear sim...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/59/23/7479
更新日期:2014-12-07 00:00:00
abstract::The electron pencil-beam redefinition algorithm (PBRA), which is used to calculate electron beam dose distributions, assumes that the virtual source of each pencil beam is identical to that of the broad beam incident on the patient. In the present work, a virtual source specific for each pencil beam is modelled by inc...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/46/11/306
更新日期:2001-11-01 00:00:00
abstract::A common dose-saving technique used in modern CT devices is automatic tube current modulation (TCM), which was originally designed to also reduce the dose in paediatric CT patients. In order to be able to deduce detailed organ doses of paediatric models, dose conversion coefficients normalized to CTDI(vol) for an eigh...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/57/20/6309
更新日期:2012-10-21 00:00:00
abstract::The aim of this study is the evaluation of on-the-fly volume of intersection computation for system's geometry modelling in 3D PET image reconstruction. For this purpose we propose a simple geometrical model in which the cubic image voxels on the given Cartesian grid are approximated with spheres and the rectangular t...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/59/3/561
更新日期:2014-02-07 00:00:00
abstract::The free space method using a pair of lens antennas was modified for the complex permittivity measurement of biological samples from 20 to 110 GHz. Two methodologies were used to obtain the complex permittivities by the free space method, which were based on the reflection and transmission coefficients. The measuremen...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/58/5/1625
更新日期:2013-03-07 00:00:00
abstract::In this study, two computational phantoms of the newborn patient were used to assess individual organ doses and effective doses delivered during head, chest, abdomen, pelvis, and torso examinations using the Siemens SOMATOM Sensation 16 helical multi-slice computed tomography (MSCT) scanner. The stylized phantom used ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/51/20/005
更新日期:2006-10-21 00:00:00
abstract::In this study, we explore the potential of compressed sensing (CS) accelerated broadband 3D phase-encoded turbo spin-echo (3D-PE-TSE) for the purpose of geometrically undistorted imaging in the presence of field inhomogeneities. To achieve this goal 3D-PE-SE and 3D-PE-TSE sequences with broadband rf pulses and dedicat...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/60/2/615
更新日期:2015-01-21 00:00:00
abstract::We present a novel linear programming (LP) based approach for efficiently solving the intensity modulated radiation therapy (IMRT) fluence-map optimization (FMO) problem to global optimality. Our model overcomes the apparent limitations of a linear-programming approach by approximating any convex objective function by...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/48/21/005
更新日期:2003-11-07 00:00:00
abstract::In the current work, EPR (electron paramagnetic resonance) dosimetry using alanine films (134 microm thick) was utilized for dose measurements in inhomogeneous phantoms irradiated with radiotherapy photon beams. The main phantom material was PMMA, while either Styrofoam or aluminium was introduced as an inhomogeneity....
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/51/24/003
更新日期:2006-12-21 00:00:00