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 sequences. It was implemented and demonstrated for simulated and clinical intensity modulated cases. The simulated cases included intensity distributions from 3 x 3 to 30 x 30 in dimension with 1,000 intensity levels. The clinical examples included four treatments sites: prostate, head and neck, lung, and esophagus cancers. In particular, we studied the relationships between the intensity levels, segment numbers and their influence on the dose-volume histograms of the inversely optimized IMRT treatment plans. It was found that a significant reduction in the leaf segment numbers was achieved by applying the smoothing approach. The effects were found to be more significant for the unconstrained delivery than for the constrained delivery. The effects were also found to be more sensitive for the complex intensity distributions such as the head-and-neck cases than for the less complex ones such as the prostate cases. These results demonstrated the feasibility of maintaining inversely optimized treatment plans under acceptable tolerance levels while smoothing IMRT treatments with hardware constraints.
journal_name
Med Physjournal_title
Medical physicsauthors
Ma Ldoi
10.1118/1.1521121subject
Has Abstractpub_date
2002-12-01 00:00:00pages
2937-45issue
12eissn
0094-2405issn
2473-4209journal_volume
29pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全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：:The authors describe a method for directly digitizing optical images with a photostimulable phosphor (PSP) system. A PSP plate is initially charged with an exposure to a uniform x-ray field, and is then exposed to an optical image which discharges the plate in relation to the amount of incident light. Two applications...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596917
更新日期：1992-07-01 00:00:00
abstract：PURPOSE:To develop a probabilistic treatment planning (PTP) method which is robust to systematic patient setup errors and to compare PTP plans with plans generated using a planning target volume (PTV) margin optimized to give the same target coverage probability as the PTP plan. METHODS:Plans adhering to the RTOG-0126...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3679856
更新日期：2012-02-01 00:00:00
abstract：:An energy discriminating detector for dual-energy radiography can be configured as a two-layer sandwich, where the mean energy of photons detected by the two layers differs. To characterize the quantum noise of such a detector, the noise covariance between the two layers must be known in addition to the noise variance...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596311
更新日期：1989-11-01 00:00:00
abstract：:Electronic portal imaging devices (EPIDs) are mainly used for patient setup verification during treatment but other geometric properties like block shape and leaf positions are also determined. Electronic portal dosimetry allows dosimetric treatment verification. By combining geometric and dosimetric information, the ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1640972
更新日期：2004-02-01 00:00:00
abstract：PURPOSE:To quantitatively characterize the interfractional anatomic variations in post-operative radiation therapy (RT) for prostate bed, so that appropriate strategy that can fully address these variations can be developed. METHODS:A total of 102 daily pre-treatment CT acquired using an in-room CT (CTVision, Siemens)...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4734844
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:The hematopoietically active tissues of skeletal bone marrow are a prime target for computational dosimetry given potential risks of leukemia and, at higher dose levels, acute marrow toxicity. The complex three-dimensional geometry of trabecular spongiosa, however, complicates schema for dose assessment in such...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12002
更新日期：2017-01-01 00:00:00
abstract：PURPOSE:In breast radiotherapy with intensity modulation, it is a well established practice to extend the dose fluence outside the limit of the body contour to account for small changes in size and position of the target and the rest of the tissues due to respiration or to possible oedema. A simple approach is not appl...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3598442
更新日期：2011-07-01 00:00:00
abstract：:Delivery verification is the process in which the energy fluence delivered during a treatment is verified. This verified energy fluence can be used in conjunction with an image in the treatment position to reconstruct the full three-dimensional dose deposited. A method for delivery verification that utilizes a measure...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1352579
更新日期：2001-04-01 00:00:00
abstract：PURPOSE:The purpose of this work is twofold: First, to characterize the artifacts occurring in helical 4D-CT imaging; second, to propose a method that can automatically identify the artifacts in 4D-CT images. The authors have designed a process that can automatically identify the artifacts in 4D-CT images, which may be...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3553556
更新日期：2011-04-01 00:00:00
abstract：:The output factor for a therapy photon beam is defined as the dose per monitor unit relative to the dose per monitor unit in a reference field. Convolution models for photon dose calculations yield the dose in units normalized to the incident energy fluence with phantom scatter intrinsically modeled. Output factors ca...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596859
更新日期：1992-03-01 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:Hypoxia is one of the most important factors influencing clinical outcome after radiotherapy. Improved knowledge of factors affecting the levels and distribution of oxygen within a tumor is needed. The authors constructed a theoretical 3D model based on histological images to analyze the influence of vessel den...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4773886
更新日期：2013-02-01 00:00:00
abstract：:Modern linear accelerators contain multiple isocentres, defined by the mechanical motions of gantry, collimator and table. Isocentre localization for these motions has been performed using film and manual evaluations which have difficulty in relating the individual motions. To address these limitations, we have develo...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2965950
更新日期：2008-07-01 00:00:00
abstract：:Permanent implantation of 125I (iodine) or 103Pd (palladium) sources is a popular treatment option in the management of early stage prostate cancer. New sources are being developed, some of which are being marketed for different clinical applications. A new technique of adjuvant stereotactic permanent seed breast impl...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3006151
更新日期：2008-12-01 00:00:00
abstract：:Energy imparted is a measure of the total ionizing energy deposited in the patient during a radiologic examination and may be used to quantify the patient dose in diagnostic radiology. Values of the energy imparted per unit exposure-area product, omega (z), absorbed by a semi-infinite water phantom with a thickness z,...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.597939
更新日期：1997-04-01 00:00:00
abstract：:The bremsstrahlung spectrum from an 8-MeV linear accelerator has been measured using a NaI(T1) spectrometer system. The spectrum shows a low-energy cutoff at 0.4 MeV and the maximum photon energy to be approximately 6% greater than the nominal energy. The maximum emission of energy fluence was 1.6 and 1.8 MeV for meas...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.594221
更新日期：1976-05-01 00:00:00
abstract：:This paper presents a numerical investigation of the effective point of measurement of thimble ionization chambers in megavoltage photon beams using Monte Carlo simulations with the EGSNRC system. It is shown that the effective point of measurement for relative photon beam dosimetry depends on every detail of the cham...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2201147
更新日期：2006-06-01 00:00:00
abstract：PURPOSE:Automated 3D breast ultrasound (ABUS) has gained interest in breast imaging. Especially for screening women with dense breasts, ABUS appears to be beneficial. However, since the amount of data generated is large, the risk of oversight errors is substantial. Computer aided detection (CADe) may be used as a secon...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4914162
更新日期：2015-04-01 00:00:00
abstract：:The number of intensity modulated radiation therapy (IMRT) procedures is continuously growing worldwide and it is necessary to develop tools for patient specific quality assurance (QA) that avoid using machine time that could be employed in treating additional patients. One way of achieving this goal is to perform a m...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2815359
更新日期：2008-01-01 00:00:00
abstract：PURPOSE:Urinary particles are particularly important parameters in clinical urinalysis, especially for the diagnosis of nephropathy. Therefore, it is highly important to precisely detect urinary particles in the clinical setting. However, artificial microscopy is subjective and time consuming, and various previous dete...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14118
更新日期：2020-07-01 00:00:00
abstract：PURPOSE:X-ray fluorescence computer tomography (XFCT) is a new molecular imaging modality which uses x-ray excitation to stimulate the emission of fluorescent photons in high atomic number contrast agents. Scatter contamination is one of the main challenges in XFCT imaging which limits the molecular sensitivity. When p...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12997
更新日期：2018-05-25 00:00:00
abstract：:Heating rate (HR) patterns in cylindrical structures were studied with inhomogeneous limb phantoms. These phantoms, arm and thigh models consisting of fat, bone, and muscle material, were heated with Clini-Therm L, M, and MS applicators at 915 MHz. The thigh model is 18 cm in diameter with 2.65-cm-thick fat on the out...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596627
更新日期：1991-11-01 00:00:00
abstract：PURPOSE:This article aims to introduce a novel algorithm for fast beam angle selection in intensity modulated radiotherapy (IMRT). METHODS:The algorithm models the optimization problem as a beam angle ranking problem and chooses suitable beam angles according to their rank. A new parameter called "beam intensity profi...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3517866
更新日期：2010-12-01 00:00:00
abstract：PURPOSE:Radiotherapy is an effective treatment for many types of cancer in clinical settings. Gel dosimetry has the potential to record three-dimensional (3D) dose distribution compared to a conventional ion chamber. As the elasticity of the gel is altered after irradiation due to gel polymerization, we aim to measure ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.14020
更新日期：2020-03-01 00:00:00
abstract：PURPOSE:Deformable image registration (DIR) is often validated based on a distance-to-agreement (DTA) criterion of automatically propagated anatomical landmarks that were manually identified. Due to human observer variability, however, the performance of the registration method is diluted. The purpose of this study was...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4760990
更新日期：2012-11-01 00:00:00
abstract：:The GEANT4 application for tomographic emission (GATE) is one of the most detailed Monte Carlo simulation tools for SPECT and PET. It allows for realistic phantoms, complex decay schemes, and a large variety of detector geometries. However, only a fraction of the information in each particle history is available for p...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3078045
更新日期：2009-04-01 00:00:00
abstract：PURPOSE:Using a new linear accelerator with high dose rate (800 MU/min), fast MLC motions (5.0 cm/s), fast gantry rotation (15 s/rotation), and 1 cm wide MLCs, we aimed to quantify the effects of complexity, arc number, and fractionation on interplay for breast and lung treatments under target motion. METHODS:To study...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12899
更新日期：2018-06-01 00:00:00
abstract：:The nuclear magnetic resonance phenomenon has given rise to both magnetic resonance imaging, which yields morphologic data, and magnetic resonance spectroscopy (MRS), which yields chemical data. In humans these data are derived principally from the resonances of the hydrogen nucleus in the low molecular weight compoun...
journal_title：Medical physics
pub_type： 杂志文章,评审
doi：10.1118/1.2975225
更新日期：2008-10-01 00:00:00
abstract：:Approximately 70-85% of breast biopsies are performed on benign lesions. To reduce this high number of biopsies performed on benign lesions, a case-based reasoning (CBR) classifier was developed to predict biopsy results from BI-RADS findings. We used 1433 (931 benign) biopsy-proven mammographic cases. CBR similarity ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1501140
更新日期：2002-09-01 00:00:00
