Abstract：
:The purpose of this paper is to develop a method that reduces the number of segments for intensity modulated arc therapy (IMAT) and intensity modulated radiotherapy (IMRT) for concave target volumes (TV). The aim was to utilize no more than two intensity levels per organ at risk (OAR) and to derive both optimal segment widths and weights from geometric considerations. Brahme's model of an annular target surrounding a circular OAR was used as test model. Brahme's solution was substituted by a single segment added to a simple field blocking the OAR. Width and weight of the segment were the free parameters to optimize. The objective function to minimize was the root mean square (rms) error of the dose in the target volume. One boundary condition was--neglecting scatter--"zero-dose" to the OAR. The resulting rules for width and weight of the additive segment are referred to as "optimized 2-Step IMAT" and "2-Step IMRT." The recommendations were applied to some simplified plans representing clinical cases using a commercial planning system. Optimized 2-Step IMAT improved the rms by a factor of 4 with respect to techniques simply blocking the OAR. The additional segment reduced the rms below 3% for cases with gaps between OAR and TV larger than 8% of the TV diameter. The results for 2-Step IMAT are applicable to IMRT and aperture modulated arc therapy (AMAT). 2-Step IMAT can be utilized for noncylindrical cases and for more than one OAR. A geometrical and topological approach to IMAT and IMRT can be useful to understand fluence profiles. The results could be applied to ameliorate other topology-based procedures used in some planning systems. Basic mechanisms of 2-Step IMAT can assist with the creation of rules for adaptive IMRT to compensate for patient motion.
journal_name
Med Physjournal_title
Medical physicsauthors
Bratengeier Kdoi
10.1118/1.1861161subject
Has Abstractpub_date
2005-03-01 00:00:00pages
777-85issue
3eissn
0094-2405issn
2473-4209journal_volume
32pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：:We have recently installed a linear accelerator, modified to allow computer control of several machine parameters during irradiation of the patient. As an initial feasibility study of computer-controlled radiation therapy, its application to produce wedge-shaped dose distributions by moving the collimator jaws has bee...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.594440
更新日期：1978-09-01 00:00:00
abstract：:The American Association of Physicists in Medicine recommends that the reference dose-rate distribution, used for treatment planning for low-energy photon brachytherapy sources in routine clinical use, must be based on at least two independent determinations: one using experimentally measured dose rates and one using ...
journal_title：Medical physics
pub_type： 指南,杂志文章
doi：10.1118/1.1690712
更新日期：2004-05-01 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：:In this paper, a unified framework of iterative algebraic reconstruction for emission computed tomography (ECT) and its application to positron emission tomography (PET) is presented. The unified framework is based on an algebraic image restoration model and contains conventional iterative algebraic reconstruction alg...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596954
更新日期：1993-11-01 00:00:00
abstract：:An analytic representation proposed for the relative intensity distribution of the extra-focal source in a two-component x-ray source model serves as the basis for calculation. From this representation, a closed-form expression for head scatter factors defined on the central beam axis is derived by integrating over th...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597494
更新日期：1995-12-01 00:00:00
abstract：:We have developed two prototypes of portable gamma cameras for medical applications based on a previous prototype designed and tested by our group. These cameras use a CsI(Na) continuous scintillation crystal coupled to the new flat-panel-type multianode position-sensitive photomultiplier tube, H8500 from Hamamatsu Ph...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2358199
更新日期：2006-11-01 00:00:00
abstract：PURPOSE:The most common metric for comparing measured to calculated dose, such as for pretreatment quality assurance of intensity-modulated photon fields, is a pass rate (%) generated using percent difference (%Diff), distance-to-agreement (DTA), or some combination of the two (e.g., gamma evaluation). For many dosimet...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3651695
更新日期：2011-11-01 00:00:00
abstract：:The purpose of this study is to develop a 4D inverse planning strategy capable of controlling the appearance of the implanted fiducial(s) in segmented IMRT fields for cine MV or combined MV/kV image-guided IMRT. This work is focused on enhancing the visibility of the implanted fiducial(s) in 4D IMRT inverse planning, ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3121425
更新日期：2009-06-01 00:00:00
abstract：:The purpose of this work is to demonstrate a proof of feasibility of the application of a commercial prototype deformable model algorithm to the problem of delineation of anatomic structures on four-dimensional (4D) computed tomography (CT) image data sets. We acquired a 4D CT image data set of a patient's thorax that...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1929207
更新日期：2005-07-01 00:00:00
abstract：:Effects of changes in the physics of EGSnrc compared to EGS4/PRESTA on energy deposition kernels for monoenergetic photons and on dose point kernels for beta sources in water are investigated. In the diagnostic energy range, Compton binding corrections were found to increase the primary energy fraction up to 4.5% at 3...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1861412
更新日期：2005-03-01 00:00:00
abstract：PURPOSE:To examine the response properties of cylindrical cavity ionization chambers (ICs) in the depth-ionization buildup region so as to obtain a robust chamber-signal - based method for definitive water surface identification, hence absolute ionization chamber depth localization. METHOD & MATERIALS:An analytical mo...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12319
更新日期：2017-07-01 00:00:00
abstract：PURPOSE:For the past two decades, high-Z nanoparticles have been of high interest to improve the therapeutic outcomes of radiation therapy, especially for low-energy X-rays. Monte Carlo (MC) simulations have been used to evaluate the boost of dose deposition induced by Auger electrons near the nanoparticle surface, by ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14576
更新日期：2020-11-04 00:00:00
abstract：PURPOSE:The authors investigate performance of thin-film cadmium telluride (CdTe) in detecting high-energy (6 MV) x rays. The utilization of this material has become technologically feasible only in recent years due to significant development in large area photovoltaic applications. METHODS:The CdTe film is combined w...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3438082
更新日期：2010-08-01 00:00:00
abstract：:Inherent in the line-spread function approach in modulation transfer function (MTF) determinations is the use of a microdensitometer to scan the density pattern resulting from the line exposure. In such a procedure, loss of fidelity in the distribution being scanned is expected. This loss is due in part to the use of ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.594187
更新日期：1975-09-01 00:00:00
abstract：PURPOSE:To develop an automated technique for evaluating lung stereotactic body radiotherapy (SBRT) plan quality and predicting achievable lung dose constraints. METHODS:We examined the workflow scripting capabilities of a radiation oncology software package (MIM Software Inc) for automatically generating mean dose gr...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735279
更新日期：2012-06-01 00:00:00
abstract：:Total scalp irradiation is a treatment technique used for a variety of superficial malignancies. Helical tomotherapy is an effective technique used for total scalp irradiation. Recent published work has shown the TomoTherapy planning system to overestimate the superficial dose. In this study, the superficial doses for...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2996288
更新日期：2008-11-01 00:00:00
abstract：PURPOSE:The aims of this work were to evaluate the performance of several deformable image registration (DIR) algorithms implemented in our in-house software (NiftyReg) and the uncertainties inherent to using different algorithms for dose warping. METHODS:The authors describe a DIR based adaptive radiotherapy workflow...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4905050
更新日期：2015-02-01 00:00:00
abstract：PURPOSE:Stringent quality assurance is required in MRI breast screening to ensure that different scanners and imaging protocols reach similar diagnostic performance. The authors propose a methodology, based on power spectrum analysis (PSA), to evaluate spatial resolution in clinical images. To demonstrate this approach...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4966704
更新日期：2016-12-01 00:00:00
abstract：PURPOSE:Task Group 119 (TG-119) has been adopted for evaluating the adequacy of intensity-modulated radiation therapy (IMRT) commissioning and for establishing patient-specific IMRT quality assurance (QA) passing criteria in clinical practice. TG-119 establishes 95% confidence limits (CLs), which help clinics identify ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12759
更新日期：2018-03-01 00:00:00
abstract：:Modern computed tomography (CT) scanners use cone-beam configurations for increasing volume coverage, improving x-ray-tube utilization, and yielding isotropic spatial resolution. Recently, there have been significant developments in theory and algorithms for exact image reconstruction from cone-beam projections. In pa...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2337270
更新日期：2006-10-01 00:00:00
abstract：:The method of images is employed to insert the effects of the presence of a single lateral boundary on contrast functions previously derived for an infinite slab using a random walk model of photon transport. The predictions of the model for zero and extrapolated boundary conditions are compared with Monte Carlo (MC) ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598687
更新日期：1999-09-01 00:00:00
abstract：PURPOSE:To develop and validate a multivariate statistical method to optimize scanning parameters for material quantification in spectral x-rayimaging. METHODS:An optimization metric was constructed by extensively sampling the thickness space for the expected number of counts for m (two or three) materials. This resul...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734708
更新日期：2012-06-01 00:00:00
abstract：:A method to determine the bone mineral density of the calcaneum has been reported earlier by our laboratory. In this method, the calcaneum is irradiated by a 60-keV photon beam from 241Am source and both the coherent and Compton scattered photons are detected by a high-purity Ge detector. The bone mineral density is d...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.595669
更新日期：1985-07-01 00:00:00
abstract：:Flat-panel (FP) based digital radiography systems have recently been introduced as a new and improved digital radiography technology; it is important to evaluate and compare this new technology with currently widely used conventional screen/film (SF) and computed radiography (CR) techniques. In this study, the low-con...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1408620
更新日期：2001-11-01 00:00:00
abstract：:A new type of radiographic film, EDR (extended dose range) film, has been recently become available for film dosimetry. It is particularly attractive for composite isodose verification of intensity modulated radiation therapy because of its low sensitivity relative to the more common Kodak XV film. For XV film, the re...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1568979
更新日期：2003-05-01 00:00:00
abstract：BACKGROUND AND PURPOSE:The purpose of this study is to develop a deep learning-based approach to simultaneously segment five pelvic organs including prostate, bladder, rectum, left and right femoral heads on cone-beam CT (CBCT), as required elements for prostate adaptive radiotherapy planning. MATERIALS AND METHODS:We...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14196
更新日期：2020-08-01 00:00:00
abstract：:An artificial neural network using input data derived from attenuation measurements was trained to generate spectral profiles (relative number of photons versus energy). Once the relative spectral distribution is reconstructed, absolute spectra (number of photons per unit exposure spectral distribution is reconstructe...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596495
更新日期：1990-07-01 00:00:00
abstract：PURPOSE:To investigate the inconsistency of recent literature on the effect of magnetic field on the response of radiochromic films, we studied the influence of 0.35 T magnetic field on dosimetric response of EBT3 and EBT-XD GafchromicTM films. METHODS:Two different models of radiochromic films, EBT3 and EBT-XD, were ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14313
更新日期：2020-09-01 00:00:00
abstract：:Studies suggest that clinical outcomes are improved in repeat trigeminal neuralgia (TN) Gamma Knife radiosurgery if a different part of the nerve from the previous radiosurgery is treated. The MR images taken in the first and repeat radiosurgery need to be coregistered to map the first radiosurgery volume onto the sec...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1944287
更新日期：2005-07-01 00:00:00
abstract：:New radiation therapy techniques such as IMRT present significant efficiency due to their highly conformal dose distributions. A consequence of the complexity of their dose distributions (high gradients, small irradiation fields, low dose distribution, ...) is the requirement for better precision quality assurance tha...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2897966
更新日期：2008-05-01 00:00:00
