Abstract：
:Accurate targeting is important in intensity-modulated radiation therapy (IMRT). The positional uncertainties of structures with respect to the external beams arise in part from random organ motion and patient setup errors. While it is important to improve immobilization and reduce the influence of organ motion, the residual effects should be included in the IMRT plan design. Current inverse planning algorithms follow the conventional approach and include uncertainties by assuming population-based margins to the target and sensitive structures. Margin around a structure represents a "hard boundary" and the fact that a structure has a spatial probability distribution has been completely ignored. With increasing understanding of spatial uncertainties of structures and the technical capability of fine-tuning the dose distribution on an individual beamlet level in IMRT, it seems timely and important to fully utilize the information in the planning process. This will reduce the "effective" margins of the structures and facilitate dose escalation. Instead of specifying a "hard margin," we describe an inverse planning algorithm which takes into consideration positional uncertainty in terms of spatial probability distribution. The algorithm was demonstrated by assuming that the random organ motion can be represented by a three-dimensional Gaussian distribution function. Other probability distributions can be dealt with similarly. In particular, the commonly used "hard margin" is a special case of the current approach with a uniform probability distribution within a specified range. The algorithm was applied to plan treatment for a prostate case and a pancreatic case. The results were compared with those obtained by adding a margin to the clinical target volume. Better sparing of the sensitive structures were obtained in both cases using the proposed method for approximately the same target coverage.
journal_name
Med Physjournal_title
Medical physicsauthors
Li JG,Xing Ldoi
10.1118/1.599023subject
Has Abstractpub_date
2000-07-01 00:00:00pages
1573-8issue
7eissn
0094-2405issn
2473-4209journal_volume
27pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：PURPOSE:Over the last four decades, Ocular Proton Therapy has been successfully used to treat patients affected by intraocular lesions. For this, treatment geometry verification is routinely performed using radiographic images to align a configuration of fiducial radiopaque markers implanted on the sclera outer surface...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12841
更新日期：2018-05-01 00:00:00
abstract：:Clinical and biological evidence suggest that the success of GRID therapy in debulking large tumors depends on the high peak-to-valley contrast in the dose distribution. In this study, we show that the peaks and valleys can be significantly blurred out by respiration-induced tumor motion, possibly affecting the clinic...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2977538
更新日期：2008-10-01 00:00:00
abstract：PURPOSE:To present the results of a patient dose evaluation program in pediatric cardiology and propose local diagnostic reference levels (DRLs) for different types of procedure and age range, in addition to suggesting approaches to correlate patient dose values with patient weight. This study was the first conducted i...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4905116
更新日期：2015-02-01 00:00:00
abstract：PURPOSE:The primary feasibility steps of demonstrating the ability of microwave-induced thermoacoustic (TA) in phantoms have been previously reported. However, none were shown to target a diseased site in living subjects in thermoacoustic tomography (TAT) field so far. To determine the expressions of oncogenic surface ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3466696
更新日期：2010-08-01 00:00:00
abstract：:While simple, intravascular brachytherapy (IVB) presents a considerable potential for harm to the patient. The medical physicist maintains the responsibility to minimize the likelihood of operational problems or dosimetric errors. The principals for safe operation remain the same as with any radiotherapy treatment: to...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1524167
更新日期：2002-12-01 00:00:00
abstract：PURPOSE:To compare beam characteristics of superficial X-rays with 6 MeV Electrons for the purpose of replacing superficial treatments with electron fields for skin lesions. METHODS:Electron beam cutouts were made with 12mm thickness cerrobend in diameters 2-5 cm to match superficial X-ray machine cones. Central axis ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735294
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:Several new technologies for single photon emission computed tomography (SPECT) instrumentation with parallel-hole collimation have been proposed to improve detector sensitivity and signal collection efficiency. Benefits from improved signal efficiency include shorter acquisition times and lower dose requiremen...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4897567
更新日期：2014-11-01 00:00:00
abstract：PURPOSE:In medical imaging, data scaling is sometimes desired to handle the system complexity, such as uniformity calibration. Since the data are usually saved in short integer, conventional data scaling will first scale the data in floating point format and then truncate or round the floating point data to short integ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3431573
更新日期：2010-06-01 00:00:00
abstract：:Highly focused dose distributions for radiosurgery applications are successfully achieved using either multiple static high-energy particle beams or multiple-arc circular x-ray beams from a linac. It has been suggested that conformal x-ray techniques using dynamically shaped beams with a moving radiation source would ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597654
更新日期：1995-12-01 00:00:00
abstract：PURPOSE:Quantification of body composition plays an important role in many clinical and research applications. Radiologic imaging techniques such as Dual-energy X-ray absorptiometry (DXA), magnetic resonance imaging (MRI), and computed tomography (CT) imaging make accurate quantification of the body composition possibl...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13373
更新日期：2019-03-01 00:00:00
abstract：:A doorless entry system has been designed for use in high-energy radiation therapy rooms. The doorless entry improves patient access, safety and throughput, increases the physical safety for the radiation therapists, and avoids the significant cost of heavy shielding doors. The design meets concerns relating to radiat...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598181
更新日期：1998-02-01 00:00:00
abstract：:The modulation transfer function (MTF) and the noise power spectrum (NPS) are widely recognized as the most relevant metrics of resolution and noise performance in radiographic imaging. These quantities have commonly been measured using various techniques, the specifics of which can have a bearing on the accuracy of t...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2188816
更新日期：2006-05-01 00:00:00
abstract：PURPOSE:Tumor grading is an important part of breast cancer diagnosis and currently requires biopsy as its standard. Here, the authors investigate quantitative ultrasound parameters in locally advanced breast cancers that can potentially separate tumors from normal breast tissue and differentiate tumor grades. METHODS...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4852875
更新日期：2014-01-01 00:00:00
abstract：:This study concerns the accuracy and precision of the IAEA/WHO LiF TLD system used in intercomparison by mail of absorbed doses from 60Co gamma-radiation and 4-25 MV x rays. The system employs 160 mg LiF powder in polystyrene capsules, which are placed at 5 or 7 cm depth in water and irradiated to doses close to 200 r...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.594746
更新日期：1980-09-01 00:00:00
abstract：PURPOSE:Upgrade and benchmarking of a research 4D treatment planning system (4DTPS) suitable for realistic patient treatment planning and treatment simulations taking into account specific requirements for scanned ion beam therapy, i.e., modeling of dose heterogeneities due to interplay effects and range changes caused...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4800802
更新日期：2013-05-01 00:00:00
abstract：:Convolution/superposition software has been used to produce a library of photon pencil beam dose matrices. This library of pencil beams is designed to serve as a tool for both education and investigation in the field of radiotherapy optimization. The elegance of this pencil beam model stems from its cylindrical symmet...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598615
更新日期：1999-07-01 00:00:00
abstract：PURPOSE:We have developed a robust tool for performing volumetric and temporal analysis of nodules from respiratory gated four-dimensional (4D) CT. The method could prove useful in IMRT of lung cancer. METHODS:We modified the conventional graph-cuts method by adding an adaptive shape prior as well as motion informatio...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12690
更新日期：2018-01-01 00:00:00
abstract：PURPOSE:The management of thoracic malignancies with radiation therapy is complicated by continuous target motion. In this study, a real time motion analysis approach is proposed to improve the accuracy of patient setup. METHODS:For 11 lung cancer patients a long training fluoroscopy was acquired before the first trea...
journal_title：Medical physics
pub_type： 临床试验,杂志文章
doi：10.1118/1.4794489
更新日期：2013-04-01 00:00:00
abstract：:A very important issue in contemporary inverse treatment radiotherapy planning is the specification of proper dose-volume constraints limiting the treatment planning algorithm from delivering high doses to the normal tissue surrounding the tumor. Recently we have proposed a method called reverse mapping of normal tiss...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2198307
更新日期：2006-09-01 00:00:00
abstract：:The purpose of this work is to compare the efficacy of mathematical models in predicting the occurrence of radiotherapy-induced left ventricular perfusion defects assessed using single-photon emission computed tomography (SPECT). The basis of this study is data from 73 left-sided breast/ chestwall patients treated wit...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1823571
更新日期：2005-01-01 00:00:00
abstract：:Purpose To investigate narrow, elongated magnetically focused proton beams and compare their properties with passively collimated beams using Monte Carlo simulation. METHODS:We performed Geant4 Monte Carlo simulations involving a single quadrapole focusing magnet, thereby creating a flattened beam with an elongated e...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735386
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:The purpose of this study is to investigate some characteristics of the beam delivery system and their effects on the dose distribution of intensity-modulated radiation therapy (IMRT) and the results of patient-specific IMRT quality assurance (QA). These characteristics include the accelerator source distributi...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3413997
更新日期：2010-06-01 00:00:00
abstract：:The use of magnetic resonance imaging as a readout method for polymer gel dosimetry commonly involves long imaging sessions, particularly when high spatial resolution is required in all three dimensions, for the investigation of dose distributions with steep dose gradients and stringent dose delivery specifications. I...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2065367
更新日期：2005-11-01 00:00:00
abstract：:The aim of this study is to perform a statistical analysis to verify the calculated percentage depth dose (PDD) based on the tissue maximum ratio (TMR) with the PDD measurements taken in water. 6 and 15 MV photon beams produced by a Varian linear 2100 C/D accelerator were used. PDDs and TMRs were measured at various d...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4740131
更新日期：2012-07-01 00:00:00
abstract：PURPOSE:To formulate convex planning objectives of treatment plan multicriteria optimization with explicit relationships to the dose-volume histogram (DVH) statistics used in plan quality evaluation. METHODS:Conventional planning objectives are designed to minimize the violation of DVH statistics thresholds using pena...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12146
更新日期：2017-06-01 00:00:00
abstract：PURPOSE:To investigate a novel locally adaptive projection space denoising algorithm for low-dose CT data. METHODS:The denoising algorithm is based on bilateral filtering, which smooths values using a weighted average in a local neighborhood, with weights determined according to both spatial proximity and intensity si...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3232004
更新日期：2009-11-01 00:00:00
abstract：:Intraoperative three-dimensional reconstruction of seed locations during prostate brachytherapy for purposes of immediate computation of radiation dosimetry is an active area of current investigation, including methods which use multiple fluoroscopic projections. A simulation study using seed locations extracted from ...
journal_title：Medical physics
pub_type： 临床试验,杂志文章
doi：10.1118/1.1707740
更新日期：2004-05-01 00:00:00
abstract：PURPOSE:An optimized air ventilation system design for a treatment room in Heavy-ion Medical Facility is an important issue in the aspects of nuclear safety because the activated air produced in a treatment room can directly affect the medical staff and the general public in the radiation-free area. METHODS:Optimized ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12914
更新日期：2018-06-01 00:00:00
abstract：PURPOSE:A modular phantom for dosimetry and imaging performance evaluation in cone-beam computed tomography (CBCT) is reported, providing a tool for quantitative technical assessment that can be adapted to a broad variety of CBCT imaging configurations and clinical applications. METHODS:The phantom presents a set of m...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13952
更新日期：2020-02-01 00:00:00
abstract：:A method is developed to smooth intensity-modulated beam delivery while considering hardware constraints. The method uses matrix algebra to model MLC leaf motion and hardware constraints such as interleaf digitization, synchronization requirements, and intersegment field abutment to deliver intensity modulated beam se...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1521121
更新日期：2002-12-01 00:00:00
