Abstract:
PURPOSE:To develop an automatic knot placement algorithm to enable the use of NonUniform Rational B-Splines (NURBS) in deformable image registration. METHODS:The authors developed a two-step approach to fit a known displacement vector field (DVF). An initial fit was made with uniform knot spacing. The error generated by this fit was then assigned as an attractive force pulling on the knots, acting against a resistive spring force in an iterative equilibration scheme. To demonstrate the accuracy gain of knot optimization over uniform knot placement, we compared the sum of the squared errors and the frequency of large errors. RESULTS:Fits were made to a one-dimensional DVF using 1-20 free knots. Given the same number of free knots, the optimized, nonuniform B-spline fit produced a smaller error than the uniform B-spline fit. The accuracy was improved by a mean factor of 4.02. The optimized B-spline was found to greatly reduce the number of errors more than 1 standard deviation from the mean error of the uniform fit. The uniform B-spline had 15 such errors, while the optimized B-spline had only two. The algorithm was extended to fit a two-dimensional DVF using control point grid sizes ranging from 8 x 8 to 15 x 15. Compared with uniform fits, the optimized B-spline fits were again found to reduce the sum of squared errors (mean ratio = 2.61) and number of large errors (mean ratio = 4.50). CONCLUSIONS:Nonuniform B-splines offer an attractive alternative to uniform B-splines in modeling the DVF. They carry forward the mathematical compactness of B-splines while simultaneously introducing new degrees of freedom. The increased adaptability of knot placement gained from the generalization to NURBS offers increased local control as well as the ability to explicitly represent topological discontinuities.
journal_name
Med Physjournal_title
Medical physicsauthors
Jacobson TJ,Murphy MJdoi
10.1118/1.3609416subject
Has Abstractpub_date
2011-08-01 00:00:00pages
4579-82issue
8eissn
0094-2405issn
2473-4209journal_volume
38pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract:PURPOSE:Ablative hyperthermia (>55 °C) has been used as a definitive treatment for accessible solid tumors not amenable to surgery, whereas mild hyperthermia (40-45 °C) has been shown effective as an adjuvant for both radiotherapy and chemotherapy. An optimal mild hyperthermia treatment is spatially accurate, with prec...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4769116
更新日期:2013-01-01 00:00:00
abstract:PURPOSE:To validate a delivery quality assurance (DQA) protocol for tomotherapy based on the measurement of the leaf open times (LOTs). In addition, to show the correlation between the mean relative LOT discrepancy and the dose deviation in the planning target volume (PTV). MATERIALS AND METHODS:We used a LOT measurem...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14348
更新日期:2020-09-01 00:00:00
abstract:PURPOSE:To investigate how the setting of optimization parameters, fractional dose and tuning structure in tomotherapy treatment planning affects plan dosimetric quality and treatment efficiency. METHODS:A digital phantom to simulate head and neck radiotherapy was constructed for this study. Tumor was 10cm long C-shap...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735724
更新日期:2012-06-01 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:The purpose of the work is to describe a new algorithm for the automatic detection of implanted radioactive seeds within the prostate. The algorithm is based on the traditional Hough transform. A method of quality assurance is described as well as a quantitative phantom study to determine the accuracy of the al...
journal_title:Medical physics
pub_type: 临床试验,杂志文章
doi:10.1118/1.1778837
更新日期:2004-09-01 00:00:00
abstract:PURPOSE:The outcome of radiotherapy can be further improved by combining irradiation with dose enhancers such as high-Z nanoparticles. Since 2004, spectacular results have been obtained when low-energy x-ray irradiations have been combined with nanoparticles. Recently, the same combination has been explored in hadron t...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4934370
更新日期:2015-11-01 00:00:00
abstract::The trend toward conformal techniques in stereotactic radiosurgery necessitates an accurate and practical method for verification of irregular three-dimensional dose distributions. This work presents the design and evaluation of a phantom system facilitating the measurement of conformal dose distributions using one or...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598962
更新日期:2000-05-01 00:00:00
abstract:PURPOSE:To demonstrate the feasibility of a three-plenoptic camera projection, scintillation-based dosimetry system for measuring three-dimensional (3D) dose distributions of static photon radiation fields. METHODS:Static x-ray photon beams were delivered to a cubic plastic scintillator volume embedded within acrylic ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14213
更新日期:2020-08-01 00:00:00
abstract:PURPOSE:A dynamic bowtie filter can modulate flux along both fan and view angles for reduced patient dose, scatter, and required photon flux, which is especially important for photon counting detectors (PCDs). Among the proposed dynamic bowtie designs, the piecewise-linear attenuator (Hsieh and Pelc, Med Phys. 2013;40:...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13272
更新日期:2019-01-01 00:00:00
abstract::For Monte Carlo linac simulations and patient dose calculations, it is important to accurately determine the phase space parameters of the initial electron beam incident on the target. These parameters, such as mean energy and radial intensity distribution, have traditionally been determined by matching the calculated...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2168433
更新日期:2006-04-01 00:00:00
abstract:PURPOSE:This paper describes the clinical implementation and medical commissioning of the MedAustron Particle Therapy Accelerator (MAPTA) for non-isocentric scanned proton beam treatments. METHODS:Medical physics involvement during technical commissioning work is presented. Acceptance testing procedures, including adv...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13928
更新日期:2020-02-01 00:00:00
abstract::Optical-resolution photoacoustic microscopy (OR-PAM) has been validated as a valuable tool for label-free volumetric microvascular imaging. More importantly, the advantages of noninvasiveness and measurement consistency suggest the use of OR-PAM for chronic imaging of intact microcirculation. Here, such chronic imagin...
journal_title:Medical physics
pub_type: 信件
doi:10.1118/1.3137572
更新日期:2009-06-01 00:00:00
abstract::We attempt to select an optimal value of regularization parameter in the optimization problems for intensity-modulated radiotherapy which are solved using a variational regularization technique. We apply to inverse treatment planning the L-curve method which was developed to determine the regularization parameter in t...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1949750
更新日期:2005-08-01 00:00:00
abstract:PURPOSE:Quantitative cone-beam CT (CBCT) imaging is on increasing demand for high-performance image guided radiation therapy (IGRT). However, the current CBCT has poor image qualities mainly due to scatter contamination. Its current clinical application is therefore limited to patient setup based on only bony structure...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3693050
更新日期:2012-04-01 00:00:00
abstract:PURPOSE:Though failure mode and effects analysis (FMEA) is becoming more widely adopted for risk assessment in radiation therapy, to our knowledge, its output has never been validated against data on errors that actually occur. The objective of this study was to perform FMEA of a stereotactic body radiation therapy (SB...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4919440
更新日期:2015-06-01 00:00:00
abstract::A method is presented for calculation of transmission functions for high energy photon beams through patients. These functions are being used in our clinic for prediction of portal dose images (PDIs) which are compared with PDIs measured with an electronic portal imaging device (EPID). The calculations are based on th...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598293
更新日期:1998-06-01 00:00:00
abstract::The dose distribution for an ovoid with a new tungsten shielding design was determined using Monte Carlo simulation. Standard Cesium-137 tube sources, tungsten shielding, and aluminum ovoid applicator were each modeled as a collection of solid objects. Dose was calculated in planes above, below, in front of, and on th...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598459
更新日期:1998-12-01 00:00:00
abstract::The design and construction of a Styrofoam cutter used in the fabrication of custom shielding blocks is described. ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594206
更新日期:1975-11-01 00:00:00
abstract:PURPOSE:Air-communicating well ionization chambers are commonly used to assess air kerma strength of sources used in brachytherapy. The signal produced is supposed to be proportional to the air density within the chamber and, therefore, a density-independent air kerma strength is obtained when the measurement is correc...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4831757
更新日期:2013-12-01 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::Various techniques have been developed to localize radioactive sources in brachytherapy implants. The most common methods include the orthogonal film method, the stereo-shift film method, and recently, direct localization from a series of contiguous CT transverse images. The major advantage of the CT method is that it...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598548
更新日期:1999-04-01 00:00:00
abstract::A Monte Carlo method was developed and implemented to simulate x-ray photon transport. Simulations consisted of a pencil beam of monoenergetic photons with energies from 50 to 110 keV incident on water and aluminum slabs. The dependence of scatter fraction and multiple scattering on x-ray energy, scatterer thickness, ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596268
更新日期:1988-11-01 00:00:00
abstract::In this paper, two new boundary tracing algorithms for segmentation of breast masses are presented. These new algorithms are based on the dynamic programming-based boundary tracing (DPBT) algorithm proposed in Timp and Karssemeijer, [S. Timp and N. Karssemeijer, Med. Phys. 31, 958-971 (2004)] The DPBT algorithm contai...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2791034
更新日期:2007-11-01 00:00:00
abstract::The photon spectra in vacuum around four types of 192Ir HDR brachytherapy sources are calculated using the Monte Carlo code EGS4 and the most recent spectral information on 192Ir decay. The air-kerma strengths per unit activity are calculated based on the photon fluence around a bare 192Ir source and around each of fo...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598763
更新日期:1999-11-01 00:00:00
abstract:PURPOSE:Stereotactic ablative body radiotherapy (SABR) for lung patients can be performed with volumetric-modulated arc therapy (VMAT) plans using off-axis target geometry to allow treatment in their CBCT verified position. For patient-specific quality assurance measurements using the PTW Octavius 4D phantom (PTW, Frei...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12805
更新日期:2018-04-01 00:00:00
abstract:PURPOSE:We have investigated the dosimetric errors caused by the interplay between the motions of the LINAC and the tumor during the delivery of a volume modulated arc therapy treatment. This includes the development of an IMRT QA technique, applied here to evaluate RapidArc plans of varying complexity. METHODS:An IMR...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3263614
更新日期:2010-01-01 00:00:00
abstract::In this work, the authors have evaluated ten different ionization chambers for the relative dosimetry of kilovoltage x-ray beams in the energy range of 50-280 kVp. Percentage depth doses in water and relative detector response (in Solid Water and in air) were measured for each of the x-ray beams studied using a number...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3183820
更新日期:2009-09-01 00:00:00
abstract::In this investigation, five experimental data sets are used to evaluate the ability of the EGSnrc Monte Carlo code to calculate the change in chamber response associated with changes in wall material and cavity dimension at 60Co energies. Calculations of the ratios of response per unit mass of air as a function of cav...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3013701
更新日期:2008-12-01 00:00:00
abstract:PURPOSE:There is an increasing interest in calculating linear energy transfer (LET) distributions for proton therapy treatments in order to assess the influence of this quantity in biological terms. Microdosimetric Monte Carlo (MC) simulations are useful tools to calculate dose-averaged LET, as this has been broadly pr...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13643
更新日期:2019-09-01 00:00:00
abstract:PURPOSE:Modulated electron radiation therapy (MERT) represents an active area of interest that offers the potential to improve healthy tissue sparing in treatment of certain cancer cases. Challenges remain however in accurate beamlet dose calculation, plan optimization, collimation method, and delivery accuracy. In thi...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4876297
更新日期:2014-06-01 00:00:00