Abstract:
:The class of non-rigid registration methods proposed in the framework of PDE-constrained large deformation diffeomorphic metric mapping is a particularly interesting family of physically meaningful diffeomorphic registration methods. Inexact Gauss-Newton-Krylov optimization has shown an excellent numerical accuracy and an extraordinarily fast convergence rate in this framework. However, the Galerkin representation of the non-stationary velocity fields does not provide proper geodesic paths. In this work, we propose a method for PDE-constrained LDDMM parameterized in the space of initial velocity fields under the EPDiff equation. The derivation of the gradient and the Hessian-vector products are performed on the final velocity field and transported backward using the adjoint and the incremental adjoint Jacobi equations. This way, we avoid the complex dependence on the initial velocity field in the computations. We also avoid the computation of the adjoint equation and its incremental counterpart that has been recently identified as a subtle problem in PDE-constrained LDDMM. The proposed method provides geodesics in the framework of PDE-constrained LDDMM, and it shows performance competing with benchmark PDE-constrained LDDMM and EPDiff-LDDMM methods.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Hernandez Mdoi
10.1088/1361-6560/aaf598subject
Has Abstractpub_date
2019-01-07 00:00:00pages
025002issue
2eissn
0031-9155issn
1361-6560journal_volume
64pub_type
杂志文章abstract::Most commonly in radiation therapy, treatments are delivered in a co-planar geometry. Numerous advantages have been reported of adding non-coplanar beams to the treatment plan. The aim of this study was to compare current state-of-the-art VMAT and CyberKnife treatment plans to that of a novel linac design developed at...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab246f
更新日期:2019-06-20 00:00:00
abstract::The function of the placenta is challenging to characterize and as a result is understudied, despite the growing awareness of the impact of the placental environment on human health and development. Medical imaging has the potential to improve our ability to screen for diseases associated with placental insufficiency,...
journal_title:Physics in medicine and biology
pub_type: 杂志文章,评审
doi:10.1088/1361-6560/aaccd9
更新日期:2018-07-09 00:00:00
abstract::Numerous studies have reported the measurements of the dielectric properties of the skin. Clarifying the manner in which the human body interacts with electromagnetic waves is essential for medical research and development, as well as for the safety assessment of electromagnetic wave exposure. The skin comprises sever...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/59/16/4739
更新日期:2014-08-21 00:00:00
abstract::In nonlinear optimisation, using exact Hessian computations (full-Newton) hold superior convergence properties over quasi-Newton methods or gradient-based methods. However, for medium-scale problems, computing the Hessian can be computationally expensive and thus time-consuming. For solvers dedicated to a specific pro...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/ab1e17
更新日期:2019-08-14 00:00:00
abstract::Spectral x-ray imaging using novel photon counting x-ray detectors (PCDs) with energy resolving abilities is capable of providing energy-selective images. PCDs have energy thresholds, enabling the classification of photons into multiple energy bins. The extra energy information provided may allow materials such as iod...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/56/18/012
更新日期:2011-09-21 00:00:00
abstract::Energy and angular distributions of electron beams with different energies were simulated by Monte Carlo calculations. These beams were generated by the NOVAC7 system (Hitesys, Italy), a mobile electron accelerator specifically dedicated to intra-operative radiation therapy (IORT). The electron beam simulations were v...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/52/20/008
更新日期:2007-10-21 00:00:00
abstract::Treatment plans optimized for intensity modulated proton therapy (IMPT) may be sensitive to range variations. The dose distribution may deteriorate substantially when the actual range of a pencil beam does not match the assumed range. We present two treatment planning concepts for IMPT which incorporate range uncertai...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/52/10/009
更新日期:2007-05-21 00:00:00
abstract::The dependence of boron-dose enhancer (BDE) characteristics on dose protocol and 10B concentration was evaluated for BNCT using near-threshold 7Li(p,n)7Be direct neutrons. The treatable protocol depth (TPD) was utilized as an evaluation index. MCNP calculations were performed for near-threshold 7Li(p,n)7Be at a proton...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/50/1/013
更新日期:2005-01-07 00:00:00
abstract::Breast-conserving surgery is a standard option for the treatment of patients with early-stage breast cancer. This form of surgery may result in incomplete excision of the tumor. Iodine-125 labeled titanium seeds are currently used in clinical practice to reduce the number of incomplete excisions. It seems likely that ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/60/19/7655
更新日期:2015-10-07 00:00:00
abstract::Scatter correction is a prerequisite for quantitative SPECT, but potentially increases noise. Monte Carlo simulations (EGS4) and physical phantom measurements were used to compare accuracy and noise properties of two scatter correction techniques: the triple-energy window (TEW), and the transmission dependent convolut...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/41/11/017
更新日期:1996-11-01 00:00:00
abstract::The electrostimulation excitation threshold of a nerve depends on temporal and frequency parameters of the stimulus. These dependences were investigated in terms of: (1) strength-duration (SD) curve for a single monophasic rectangular pulse, and (2) frequency dependence of the excitation threshold for a continuous sin...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/61/12/4364
更新日期:2016-06-21 00:00:00
abstract::This work presents a Monte Carlo model of Leksell Gamma Knife Perfexion as well as the main parameters of the dose distribution in the standard phantom obtained using this model. The model is developed in the Geant4 simulation toolkit in a modular way which enables its reuse in other Perfexion studies. Large phase spa...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/59/24/7609
更新日期:2014-12-21 00:00:00
abstract::We report the first experimental soft-tissue phase-contrast tomography results using a conventional x-ray tube source, with a millimeter-sized focal spot. The setup is based on a Talbot-Lau grating interferometer operated at a mean energy of 28 keV. We present three-dimensional ex vivo images of a chicken heart sample...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/54/9/010
更新日期:2009-05-07 00:00:00
abstract::In clinical computed tomography (CT) images, cortical bone features with sub-millimeter (sub-mm) thickness are substantially blurred, such that their thickness is overestimated and their intensity appears underestimated. Therefore, any inquiry of the geometry or the density of such bones based on these images is sever...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/57/23/8099
更新日期:2012-12-07 00:00:00
abstract::In recent years, the Monte Carlo method has been used in a large number of research studies in radiation therapy. For applications such as treatment planning, it is essential to validate the dosimetric accuracy of the Monte Carlo simulations in heterogeneous media. The AAPM Report no 105 addresses issues concerning cl...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/53/16/016
更新日期:2008-08-21 00:00:00
abstract::A comparative study was performed to reveal differences and relative figures of merit of seven different calculation algorithms for photon beams when applied to inhomogeneous media. The following algorithms were investigated: Varian Eclipse: the anisotropic analytical algorithm, and the pencil beam with modified Batho...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/52/5/011
更新日期:2007-03-07 00:00:00
abstract::Electron depth-dose curves and spectra have been measured from an experimental accelerator on which both energy and spectral shape could be varied independently. The measurements were made at nominal energies of 6 and 12 MeV, with the energy spread (FWHM) varied from 1.7% to over 10% of average energy. Changes in dept...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/28/12/005
更新日期:1983-12-01 00:00:00
abstract::Pinhole SPECT is rapidly gaining popularity for imaging laboratory animals using gamma-emitting molecules. Penetration and scattering of gamma radiation in the pinhole edge material can account for a significant fraction of the total number of photons detected, particularly if the pinholes have small diameters. This s...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/49/8/001
更新日期:2004-04-21 00:00:00
abstract::The degradation of low energy electrons in a methane based, tissue equivalent gas was studied experimentally by ionization chamber experiments and theoretically by Monte Carlo electron transport simulation in the energy range between 25 eV and 5 keV. From measured ionization yields and calculated ionization and energy...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/37/5/008
更新日期:1992-05-01 00:00:00
abstract::Inverse treatment planning in intensity modulated particle therapy (IMPT) with scanned carbon-ion beams is currently based on the optimization of RBE-weighted dose to satisfy requirements of target coverage and limited toxicity to organs-at-risk (OARs) and healthy tissues. There are many feasible IMPT plans that meet ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aaf400
更新日期:2019-01-04 00:00:00
abstract::In this note, we present the first experimental results of in-beam PET measurements during high energy photon phantom irradiation. An inhomogeneous phantom was irradiated with pulsed 34 MV bremsstrahlung. The measurements have been conducted with a dedicated double head positron camera. A high material contrast could ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/52/20/N01
更新日期:2007-10-21 00:00:00
abstract::A new component module (CM), designated DYNVMLC, was developed to fully model the geometry of the Varian Millennium 120 leaf collimator using the BEAMnrc Monte Carlo code. The model includes details such as the leaf driving screw hole, support railing groove and leaf tips. Further modifications also allow sampling of ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/48/24/004
更新日期:2003-12-21 00:00:00
abstract::The purpose of this work was to create a computational platform for studying motion in intensity modulated radiotherapy (IMRT). Specifically, the non-uniform rational B-spline (NURB) cardiac and torso (NCAT) phantom was modified for use in a four-dimensional Monte Carlo (4D-MC) simulation system to investigate the eff...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/55/5/014
更新日期:2010-03-07 00:00:00
abstract::In this paper, we investigate an off-line strategy to incorporate inter-fraction organ motion in IMRT treatment planning. It was suggested that inverse planning could be based on a probability distribution of patient geometries instead of a single snap shot. However, this concept is connected to two intrinsic problems...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/49/17/013
更新日期:2004-09-07 00:00:00
abstract::A Monte Carlo model of a novel electronic portal imaging device (EPID) has been developed using Geant4 and its performance for imaging and dosimetry applications in radiotherapy has been characterised. The EPID geometry is based on a physical prototype under ongoing investigation and comprises an array of plastic scin...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/59/22/6827
更新日期:2014-11-21 00:00:00
abstract::Projection and backprojection are operations that arise frequently in tomographic imaging. Recently, we proposed a new method for projection and backprojection, which we call distance-driven, and that offers low arithmetic cost and a highly sequential memory access pattern. Furthermore, distance-driven projection and ...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/49/11/024
更新日期:2004-06-07 00:00:00
abstract::Medulloblastoma treatment involves irradiation of the entire central nervous system, i.e. craniospinal irradiation (CSI). This is associated with the significant exposure of large volumes of healthy tissue and there is growing concern regarding treatment-associated side effects. The current study compares out-of-field...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/1361-6560/aa6c9e
更新日期:2017-07-07 00:00:00
abstract::For quality assurance of hyperthermia treatment planning systems, quantitative validation of the electromagnetic model of an applicator is essential. The objective of this study was to validate a finite-difference time-domain (FDTD) model implementation of the Lucite cone applicator (LCA) for superficial hyperthermia....
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/52/11/010
更新日期:2007-06-07 00:00:00
abstract::Conversion factors, which relate the kerma-area product to effective dose, have been estimated for paediatric cardiac x-ray angiography. Monte Carlo techniques have been used to calculate the conversion factors for a wide range of projection angles for children of five ages and for adults. Correction factors are provi...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/45/10/323
更新日期:2000-10-01 00:00:00
abstract::The purpose of this paper was to study the source model for a Monte Carlo simulation of electron beams from a medical linear accelerator. In a prior study, a non-divergent Gaussian source with a full-width at half-maximum (FWHM) of 0.15 cm was successful in predicting relative dose distributions for electron beams wit...
journal_title:Physics in medicine and biology
pub_type: 杂志文章
doi:10.1088/0031-9155/54/1/007
更新日期:2009-01-07 00:00:00