Abstract:
:A modified neutron production target assembly has been developed to provide improved performance of the proton-cyclotron-based neutron radiotherapy facility at the University of Washington for applications involving neutron capture enhanced fast-neutron therapy. The new target produces a neutron beam that yields essentially the same fast-neutron physical depth-dose distribution as is produced by the current UW clinical system, but that also has an increased fraction of BNCT enhancement relative to the total therapeutic dose. The modified target is composed of a 5-millimeter layer of beryllium, followed by a 2.5-millimeter layer of tungsten, with a water-cooled copper backing. Measurements of the free-field neutron spectrum of the beam produced by the new target were performed using activation foils with a direct spectral unfolding technique. Water phantom measurements were performed using a tissue-equivalent ion chamber to characterize the fast-neutron depth-dose curve and sodium activation in soda-lime glass beads to characterize the thermal-neutron flux (and thus the expected neutron capture dose enhancement) as a function of depth. The results of the various measurements were quite consistent with expectations based on the design calculations for the modified target. The spectrum of the neutron beam produced by the new target features an enhanced low-energy flux component relative to the spectrum of the beam produced by the standard UW target. However, it has essentially the same high-energy neutron flux, with a reduced flux component in the mid-range of the energy spectrum. As a result, the measured physical depth-dose curve in a large water phantom has the same shape compared to the case of the standard UW clinical beam, but approximately twice the level of BNCT enhancement per unit background neutron dose at depths of clinical interest. In-vivo clinical testing of BNCT-enhanced fast-neutron therapy for canine lung tumors using the new beam was recently initiated.
journal_name
Med Physjournal_title
Medical physicsauthors
Nigg DW,Wemple CA,Risler R,Hartwell JK,Harker YD,Laramore GEdoi
10.1118/1.598839subject
Has Abstractpub_date
2000-02-01 00:00:00pages
359-67issue
2eissn
0094-2405issn
2473-4209journal_volume
27pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract::Calcium concentration may be a useful feature for distinguishing benign from malignant lung nodules in computer-aided diagnosis. The calcium concentration can be estimated from the measured CT number of the nodule and a CT number vs calcium concentration calibration line that is derived from CT scans of two or more ca...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3148536
更新日期:2009-07-01 00:00:00
abstract::A clamp-on current probe utilizing the Hall effect was used to determine x-ray tube current. This noninvasive technique was compared to two other methods of mA measurement: the Machlett Dynalyzer and the mR/mAs linearity method. Three diagnostic x-ray units were used in the comparison; two modern three-phase rooms and...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596080
更新日期:1987-03-01 00:00:00
abstract::The analysis and understanding of results of computed tomography (CT) require an understanding of photon attenuation in matter. The high sensitivity and resolution of these devices coupled with the use of a polychromatic photon source require a level and breadth of understanding about photon attenuation not usually re...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594199
更新日期:1975-11-01 00:00:00
abstract::A general expression is derived for the NMR signal from a fluid undergoing random directional flow such as encountered within the microcirculation. The dependence of the echo amplitude on flow velocity, sample morphology, and experimental parameters are described in terms of a temporal velocity autocorrelation functio...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597170
更新日期:1994-04-01 00:00:00
abstract:PURPOSE:To perform a comprehensive and systematic comparison of fixed-beam IMRT and volumetric modulated arc therapy (VMAT) patient-specific QA measurements for a common set of geometries using typical measurement methods. METHODS:Fixed-beam IMRT and VMAT plans were constructed for structure set geometries provided by...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4729738
更新日期:2012-07-01 00:00:00
abstract::In this paper, the consistency of kilovoltage (tube potentials between 40 and 300 kV) x-ray beam dosimetry using the "in-air" method and the in-phantom measurement has been studied. The procedures for the measurement of the central-axis depth-dose curve, which serve as a link between the dose at the reference depth to...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598448
更新日期:1998-12-01 00:00:00
abstract:PURPOSE:The aim of this study was to implement a Dirichlet process mixture (DPM) model for automatic tumor edge identification on (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) images by optimizing the parameters on which the algorithm depends, to validate it experimentally, and to test its robus...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4947123
更新日期:2016-05-01 00:00:00
abstract:PURPOSE:At our institution, all proton patient plans undergo patient-specific quality assurance (PSQA) prior to treatment delivery. For intensity-modulated proton beam therapy, quality assurance is complex and time consuming, and it may involve multiple measurements per field. We reviewed our PSQA workflow and identifi...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13246
更新日期:2019-01-01 00:00:00
abstract:PURPOSE:Planning for the delivery of intensity-modulated radiation therapy (IMRT) to a moving target, referred to as four-dimensional (4D) IMRT planning, is a crucial step for achieving the treatment objectives for sites that move during treatment delivery. The authors proposed a simplistic method that accounts for bot...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3319498
更新日期:2010-05-01 00:00:00
abstract::We have developed an analytic solution for spatially resolved diffuse reflectance within the deltaP1 approximation to the radiative transport equation for a semi-infinite homogeneous turbid medium. We evaluate the performance of this solution by comparing its predictions with those provided by Monte Carlo simulations ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2828184
更新日期:2008-02-01 00:00:00
abstract::Monte Carlo calculations have been made to determine the energy delivered to a phantom by neutrons escaping from the head of a Varian Clinac 35 medical accelerator at an SSD of 1 m. The energy was sorted into two regions: inside and outside a volume defined by a circular beam of area 100 and 600 cm2. For the two beam ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595067
更新日期:1982-01-01 00:00:00
abstract::A restricted angular scattering model for electron penetration in dense media is presented. In the model, the Fermi-Eyges transport equation is modified through the addition of an extra term which may be interpreted as representing an apparent force opposing the scattering of electrons into wider angles. The introduct...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596747
更新日期:1991-01-01 00:00:00
abstract::Statistical image reconstruction (SIR) methods have shown potential to substantially improve the image quality of low-dose x-ray computed tomography (CT) as compared to the conventional filtered back-projection (FBP) method. According to the maximum a posteriori (MAP) estimation, the SIR methods are typically formulat...
journal_title:Medical physics
pub_type: 杂志文章,评审
doi:10.1002/mp.13123
更新日期:2018-10-01 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::Francis Bacon, who with Rene Decartes laid the intellectual foundations for Western science in the seventeenth century, asserted that the purpose of all knowledge is "action in the production of works for ... the relief of man's estate." We assess briefly several aspects of a few of the current efforts directed to the...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1555493
更新日期:2003-04-01 00:00:00
abstract:PURPOSE:Silicon photodetectors are of significant interest for use in positron emission tomography (PET) systems due to their compact size, insensitivity to magnetic fields, and high quantum efficiency. However, one of their main disadvantages is fluctuations in temperature cause strong shifts in gain of the devices. P...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4903889
更新日期:2015-01-01 00:00:00
abstract:PURPOSE:The spatial resolution of iterative reconstruction (IR) in computed tomography (CT) is contrast- and noise-dependent because of the nonlinear regularization. Due to the severe noise contamination, it is challenging to perform precise spatial-resolution measurements at very low-contrast levels. The purpose of th...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4916802
更新日期:2015-05-01 00:00:00
abstract::The dissemination of scientific advances has changed little since the first peer-reviewed journal was published in 1665 - that is, until this past decade. The print journal, delivered by mail and stored on office shelves and in library reading rooms around the world, has been transformed by immediate, on-demand access...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4736173
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:Cardiac motion is typically not accounted for during pretreatment imaging for central lung and mediastinal tumors. However, cardiac induced tumor motion averages 5.8 mm for esophageal tumors and 3-5 mm for some lung tumors, which can result in positioning errors. Our aim is to reduce both cardiac- and respirato...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13670
更新日期:2019-09-01 00:00:00
abstract:PURPOSE:Positron emission tomography (PET) is considered the gold standard for measuring myocardial blood flow in vivo but it is known that respiratory motion can lead to misalignment of the PET and computed tomography (CT) data sets and introduce artifacts in the CT-based attenuation correction (AC) of images. In addi...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4788669
更新日期:2013-02-01 00:00:00
abstract::The polarity effect was investigated for three different commercially available plane-parallel ionization chambers: the Memorial Pipe chamber, the Victoreen/Nuclear Associates model 30-329 chamber manufactured by PTW, Frieburg, and the Capintec PS-033 thin-window ionization chamber. The primary study was the polarity ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596072
更新日期:1987-03-01 00:00:00
abstract::The purpose of this paper is to examine the thermal dose distribution, to configure the optimal absorbed power deposition, and to design an appropriate heating strategy for ultrasound thermal therapy. This work employs simulation programs, which are based on the transient bio-heat transfer equation and an ideal absorb...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1406516
更新日期:2001-10-01 00:00:00
abstract:PURPOSE:In C-arm computed tomography (CT), the field of view (FOV) is often not sufficient to acquire certain anatomical structures, e.g., a full hip or thorax. Proposed methods to extend the FOV use a fixed detector displacement and a 360° scan range to double the radius of the FOV. These trajectories are designed for...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4915542
更新日期:2015-05-01 00:00:00
abstract::90Y-labeled SIR-Spheres are currently used to treat patients with hepatic metastases secondary to colorectal adenocarcinoma. In general, the prescribed activity is based on empirical data collected during clinical trials. The activity of the source vial is labeled by the manufacturer as 3.0 GBq +/- 10% and is not inde...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2889621
更新日期:2008-04-01 00:00:00
abstract::Attention is given to means of sensing ultrasonic energy distributions over an area. Under the restraints appropiate to real-time imaging of deep body organs, piezoelectric arrays offer the most promising method. Adaptation of integrated circuit techniques to array assembly permits very large arrays of small elements ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594247
更新日期:1976-09-01 00:00:00
abstract:PURPOSE:To measure patient-specific maximum skin dose (MSD) associated with CT fluoroscopy (CTF) lung biopsies and to compare measured MSD with the MSD estimated from phantom measurements, as well as with the CTDIvol of patient examinations. METHODS:Data from 50 patients with lung lesions who underwent a CT fluoroscop...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4884231
更新日期:2014-07-01 00:00:00
abstract:PURPOSE:To simplify the often complex and user-dependent manual region of interest (ROI) selection process for head motion monitoring, an automatic ROI selection method was developed. METHODS:The automatic ROI selection algorithm calculated the displacements and velocities of 3D surface points between a temporally cor...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4711805
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:One of the promising options for motion management in radiation therapy (RT) is the use of LINAC-compatible robotic-arm-mounted ultrasound imaging system due to its high soft tissue contrast, real-time capability, absence of ionizing radiation, and low cost. The purpose of this work is to develop a novel deep l...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13510
更新日期:2019-05-01 00:00:00
abstract::Several updated Monte Carlo (MC) codes are available to perform calculations of voxel S values for radionuclide targeted therapy. The aim of this work is to analyze the differences in the calculations obtained by different MC codes and their impact on absorbed dose evaluations performed by voxel dosimetry. Voxel S val...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3103401
更新日期:2009-05-01 00:00:00
abstract::The Monte Carlo (MC) method has been shown through many research studies to calculate accurate dose distributions for clinical radiotherapy, particularly in heterogeneous patient tissues where the effects of electron transport cannot be accurately handled with conventional, deterministic dose algorithms. Despite its p...
journal_title:Medical physics
pub_type: 杂志文章,评审
doi:10.1118/1.2795842
更新日期:2007-12-01 00:00:00