Abstract:
PURPOSE:Adequate evaluation of the results from multi-institutional trials involving light ion beam treatments requires consideration of the planning margins applied to both targets and organs at risk. A major uncertainty that affects the size of these margins is the conversion of x ray computed tomography numbers (XCTNs) to relative linear stopping powers (RLSPs). Various facilities engaged in multi-institutional clinical trials involving proton beams have been applying significantly different margins in their patient planning. This study was performed to determine the variance in the conversion functions used at proton facilities in the U.S.A. wishing to participate in National Cancer Institute sponsored clinical trials. METHODS:A simplified method of determining the conversion function was developed using a standard phantom containing only water and aluminum. The new method was based on the premise that all scanners have their XCTNs for air and water calibrated daily to constant values but that the XCTNs for high density/high atomic number materials are variable with different scanning conditions. The standard phantom was taken to 10 different proton facilities and scanned with the local protocols resulting in 14 derived conversion functions which were compared to the conversion functions used at the local facilities. RESULTS:For tissues within ±300 XCTN of water, all facility functions produced converted RLSP values within ±6% of the values produced by the standard function and within 8% of the values from any other facility's function. For XCTNs corresponding to lung tissue, converted RLSP values differed by as great as ±8% from the standard and up to 16% from the values of other facilities. For XCTNs corresponding to low-density immobilization foam, the maximum to minimum values differed by as much as 40%. CONCLUSIONS:The new method greatly simplifies determination of the conversion function, reduces ambiguity, and in the future could promote standardization between facilities. Although it was not possible from these experiments to determine which conversion function is most appropriate, the variation between facilities suggests that the margins used in some facilities to account for the uncertainty in converting XCTNs to RLSPs may be too small.
journal_name
Med Physjournal_title
Medical physicsauthors
Moyers MFdoi
10.1118/1.4870956subject
Has Abstractpub_date
2014-06-01 00:00:00pages
061705issue
6eissn
0094-2405issn
2473-4209journal_volume
41pub_type
杂志文章,多中心研究相关文献
MEDICAL PHYSICS文献大全abstract::The relatively precise placement of brachytherapy sources afforded by stereotactic frames for brain implants is not generally achievable for other sites, which lack the fixed geometry of the cranium and its contents. An exception is a source-containing rigid mold that delivers brachytherapy when inserted securely in a...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597454
更新日期:1995-03-01 00:00:00
abstract::In external beam radiotherapy, electronic portal imaging becomes more and more an indispensable tool for the verification of the patient setup. For the safe clinical introduction of high dose conformal radiotherapy like intensity modulated radiation therapy, on-line patient setup verification is a prerequisite to ensu...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1668391
更新日期:2004-04-01 00:00:00
abstract::The computational aspects of the design of an optical distance indicator (ODI) for use with a radiation therapy accelerator are discussed. The specifics of the optical and mechanical design of an ODI for use with a superconducting cyclotron used for fast neutron therapy are presented. ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598510
更新日期:1999-02-01 00:00:00
abstract::The goal of this study was to develop a technique to distinguish benign and malignant breast lesions in secondarily digitized mammograms. A set of 51 mammograms (two views/patient) containing lesions of known pathology were evaluated using six different morphological descriptors: circularity, mu R/sigma R (where mu R ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597707
更新日期:1996-08-01 00:00:00
abstract:PURPOSE:X-ray fluorescence (XRF) is a promising technique with sufficient specificity and sensitivity for identifying and quantifying features in small samples containing high atomic number (Z) materials such as iodine, gadolinium, and gold. In this study, the feasibility of applying XRF to early breast cancer diagnosi...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4863510
更新日期:2014-03-01 00:00:00
abstract::A discussion of the thermodynamic aspects of a relatively new treatment method for giant cell tumors of the bone is presented in this paper. The advantages of implanting methylmethacrylate acrylic bone cement into a curetted tumor site are briefly discussed and placed in perspective relative to more prevalent surgical...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595902
更新日期:1986-03-01 00:00:00
abstract::The use of electronic portal imaging devices (EPIDs) is a promising method for the dosimetric verification of external beam, megavoltage radiation therapy-both pretreatment and in vivo. In this study, a previously developed EPID back-projection algorithm was modified for IMRT techniques and applied to an amorphous sil...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2147744
更新日期:2006-02-01 00:00:00
abstract:PURPOSE:As radiation therapy evolves toward more adaptive techniques, image guidance plays an increasingly important role, not only in patient setup but also in monitoring the delivered dose and adapting the treatment to patient changes. This study aimed to validate a method for evaluation of delivered intensity modula...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4903292
更新日期:2015-01-01 00:00:00
abstract::Optimal visualization of moving structures such as the heart and coronary arteries using digital radiographic imaging systems is a difficult problem that can involve tradeoffs between temporal, spatial, and density resolution. The motion dependence of four angiographic measures of vessel dimensions is given and demons...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595651
更新日期:1985-11-01 00:00:00
abstract::One of the key components in modern LINAC room shielding design is the amount of 90 degrees head leakage radiation levels. With the general clinical acceptance of intensity-modulated radiation therapy (IMRT) technique, accurate knowledge of this quantity has become even more important. Measurement of 90 degrees head l...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2335489
更新日期:2006-09-01 00:00:00
abstract:PURPOSE:To describe Acuros® CTS, a new software tool for rapidly and accurately estimating scatter in x-ray projection images by deterministically solving the linear Boltzmann transport equation (LBTE). METHODS:The LBTE describes the behavior of particles as they interact with an object across spatial, energy, and dir...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12850
更新日期:2018-05-01 00:00:00
abstract:PURPOSE:This study introduces a new hybrid ZTE/Dixon MR-based attenuation correction (MRAC) method including bone density estimation for PET/MRI and quantifies the effects of bone attenuation on metastatic lesion uptake in the pelvis. METHODS:Six patients with pelvic lesions were scanned using fluorodeoxyglucose (18F-...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12122
更新日期:2017-03-01 00:00:00
abstract:PURPOSE:The purpose of this study was to provide updated radiation dose from diagnostic exams performed for pregnant patients suspected of pulmonary embolism (PE) using the recently developed BREP phantoms of pregnant woman and the fetus. Also to challenge the validity of current recommendations suggest that ventilatio...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12558
更新日期:2017-11-01 00:00:00
abstract:PURPOSE:Intensity Modulated Neutron Radiotherapy (IMNRT) has been commissioned for clinical use. The number of allowable segments in IMNRT plans is limited by MLC speed. Quality and deliverability of static IMNRT treatment plans using the TG-119 test suite were evaluated to establish guidelines for the number of segmen...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735662
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:To review the issues a physicist may encounter in a community hospital during the transition from film/paper charts to a paperless environment with ARIA and a TrueBeam LINAC. With a lean budget, it was necessary for the physics group to take on the project management responsibilities in order save costs. This w...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735291
更新日期:2012-06-01 00:00:00
abstract::The intensity modulated arc has been proposed as an alternative to tomotherapy. Treatment planing systems more typically model the conventional step and shoot or sliding window dynamic multileaf collimator (DMLC) deliveries, and may not support intensity modulated arc therapy (IMAT). As well, another potential drawbac...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1508110
更新日期:2002-10-01 00:00:00
abstract::Limiting spatial resolution is a key metric of the quality of magnetic resonance (MR) images, which can provide an indication of the smallest region that can effectively be imaged. In this paper a novel methodology for measuring the limiting spatial resolution of MR images is mathematically analyzed and successfully i...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3097633
更新日期:2009-05-01 00:00:00
abstract::Multielectrode cochlear implantation is the most effective treatment for profound sensorineural hearing loss. In vivo three-dimensional 3-D localization of cochlear implant electrodes is important for modeling of the electrical field in the cochlea, design of electrode arrays, and may improve speech processor programm...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598940
更新日期:2000-04-01 00:00:00
abstract::A 4-W, laser-based system for the positional readout of thermoluminescent (TL) plates was utilized to obtain dose profiles for a 60Co radiotherapy beam. Experimentally obtained glow curves for LiF resulting from the rapid heating rates characteristic of laser heating agreed well with results predicted using a first-or...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596580
更新日期:1990-05-01 00:00:00
abstract:PURPOSE:A prototype in-house program was developed to assist deriving image guidance shifts clinically using our 4DCT method for lung SBRT. METHODS:Our in-house prototype program was implemented in MATLAB. The 4D DICOM CT dataset of interest is imported by the program from AW and subsequently accepts input from the us...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735493
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:The Imaging and Radiation Oncology Core Houston (IROC-H) (formerly the Radiological Physics Center) has reported varying levels of agreement in their anthropomorphic phantom audits. There is reason to believe one source of error in this observed disagreement is the accuracy of the dose calculation algorithms an...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12426
更新日期:2017-09-01 00:00:00
abstract::Amorphous selenium (a-Se) based real-time flat-panel imagers (FPIs) are finding their way into the digital radiology department because they offer the practical advantages of digital x-ray imaging combined with an image quality that equals or outperforms that of conventional systems. The temporal imaging characteristi...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2042248
更新日期:2005-10-01 00:00:00
abstract:PURPOSE:The Monte Carlo simulation of electron transport in Linac targets using the condensed history technique is known to be problematic owing to a potential dependence of absorbed dose distributions on the electron step length. In the PENELOPE code, the step length is partially determined by the transport parameters...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4916686
更新日期:2015-06-01 00:00:00
abstract::Although x-ray computed tomography (CT) has been in clinical use for over 3 decades, spectral optimization has not been a topic of great concern; high voltages around 120 kV have been in use since the beginning of CT. It is the purpose of this study to analyze, in a rigorous manner, the energies at which the patient d...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3075901
更新日期:2009-03-01 00:00:00
abstract::An integrating solid-state dosimeter has been developed to detect ultraviolet radiation using the process of "direct" ultraviolet stimulation. This process yields a thermoluminescent signal after an exposure to ultraviolet radiation, without prior exposure to ionizing radiation. Magnesium oxide crystals were found to ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594259
更新日期:1976-11-01 00:00:00
abstract:PURPOSE:The cone beam computed tomography (CBCT) guided small animal radiation research platform (SARRP) has been developed for focal tumor irradiation, allowing laboratory researchers to test basic biological hypotheses that can modify radiotherapy outcomes in ways that were not feasible previously. CBCT provides exce...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4914860
更新日期:2015-04-01 00:00:00
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 ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3609416
更新日期:2011-08-01 00:00:00
abstract::Effective radioimmunotherapy may depend on a priori knowledge of the radiation absorbed dose distribution obtained by trace imaging activities administered to a patient before treatment. A new, fast, and effective treatment planning approach is developed to deal with a heterogeneous activity distribution. Calculation ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598422
更新日期:1998-11-01 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:Transrectal ultrasound (TRUS)-guided needle biopsy is the current gold standard for prostate cancer diagnosis. However, up to 40% of prostate cancer lesions appears isoechoic on TRUS. Hence, TRUS-guided biopsy has a high false negative rate for prostate cancer diagnosis. Magnetic resonance imaging (MRI) is bett...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4905104
更新日期:2015-03-01 00:00:00