Abstract:
PURPOSE:Flattening filter free (FFF) beams generated by medical linear accelerators have recently started to be used in radiotherapy clinical practice. Such beams present fundamental differences with respect to the standard filter flattened (FF) beams, making the generally used dosimetric parameters and definitions not always viable. The present study will propose possible definitions and suggestions for some dosimetric parameters for use in quality assurance of FFF beams generated by medical linacs in radiotherapy. METHODS:The main characteristics of the photon beams have been analyzed using specific data generated by a Varian TrueBeam linac having both FFF and FF beams of 6 and 10 MV energy, respectively. RESULTS:Definitions for dose profile parameters are suggested starting from the renormalization of the FFF with respect to the corresponding FF beam. From this point the flatness concept has been translated into one of "unflatness" and other definitions have been proposed, maintaining a strict parallelism between FFF and FF parameter concepts. CONCLUSIONS:Ideas for quality controls used in establishing a quality assurance program when introducing FFF beams into the clinical environment are given here, keeping them similar to those used for standard FF beams. By following the suggestions in this report, the authors foresee that the introduction of FFF beams into a clinical radiotherapy environment will be as safe and well controlled as standard beam modalities using the existing guidelines.
journal_name
Med Physjournal_title
Medical physicsauthors
Fogliata A,Garcia R,Knoos T,Nicolini G,Clivio A,Vanetti E,Khamphan C,Cozzi Ldoi
10.1118/1.4754799subject
Has Abstractpub_date
2012-10-01 00:00:00pages
6455-64issue
10eissn
0094-2405issn
2473-4209journal_volume
39pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract:PURPOSE:Computerized liver extraction from hepatic CT images is challenging because the liver often abuts other organs of a similar density. The purpose of this study was to develop a computer-aided measurement of liver volumes in hepatic CT. METHODS:The authors developed a computerized liver extraction scheme based o...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3395579
更新日期:2010-05-01 00:00:00
abstract:PURPOSE:Motion compensated positron emission tomography (PET) imaging requires detecting and monitoring of patient body motion. We developed a semiautomatic list-mode method to track the three-dimensional (3D) motion of fiducial positron-emitting markers during PET imaging. METHODS:A previously developed motion tracki...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14206
更新日期:2020-08-01 00:00:00
abstract::We have reexamined the problem of estimating the luminal area of an elliptically shaped coronary artery cross section from two or more radiographic diameter measurements. The expected error is found to be much smaller than the maximum potential error. In the cases of two orthogonal views, closed form expressions have ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596296
更新日期:1988-07-01 00:00:00
abstract::Coherent scattering of x-ray photons leads to the phenomenon of x-ray diffraction, which is widely used for determining atomic structure in materials science. A technique [x-ray diffraction computed tomography (CT)] is described, analogous to conventional CT, in which the x-ray diffraction properties of a stack of two...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596063
更新日期:1987-07-01 00:00:00
abstract:PURPOSE:The authors have recently developed a cine-mode T2*/T1-weighted 4D-MRI technique and a sequential-mode T2-weighted 4D-MRI technique for imaging respiratory motion. This study aims at investigating which 4D-MRI image acquisition mode, cine or sequential, provides more accurate measurement of organ motion during ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4938066
更新日期:2016-01-01 00:00:00
abstract::An important point to consider in a brachytherapy dosimetry study is the phantom size involved in calculations or experimental measurements. As pointed out by Williamson [Med. Phys. 18, 776-786 (1991)] this topic has a relevant influence on final dosimetric results. Presently, one-dimensional (1-D) algorithms and newl...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1759826
更新日期:2004-07-01 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::A comprehensive performance testing program is an essential ingredient of high-quality single-photon emission computed tomography (SPECT). Many of the procedures previously published are complicated, time consuming, or require a special testing environment. This Task Group developed a protocol for evaluating SPECT ima...
journal_title:Medical physics
pub_type: 指南,杂志文章
doi:10.1118/1.597605
更新日期:1995-04-01 00:00:00
abstract::In patients with lymphoma, identification and quantification of the tumor extent on serial CT examinations is critical for assessing tumor response to therapy. In this paper, we present a computer method to automatically match and segment lymphomas in follow-up CT images. The method requires that target lymph nodes in...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2404617
更新日期:2007-01-01 00:00:00
abstract::Noise characterization through estimation of the noise power spectrum (NPS) is a central component of the evaluation of digital x-ray systems. We begin with a brief review of the fundamentals of NPS theory and measurement, derive explicit expressions for calculation of the one- and two-dimensional (1D and 2D) NPS, and...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598623
更新日期:1999-07-01 00:00:00
abstract::With intensity-modulated radiotherapy (IMRT), a variety of user-defined dose distribution can be produced using inverse planning. The generalized equivalent uniform dose (gEUD) has been used in IMRT optimization as an alternative objective function to the conventional dose-volume-based criteria. The purpose of this st...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1897464
更新日期:2005-05-01 00:00:00
abstract:PURPOSE:To evaluate both the Calypso Systems' (Calypso Medical Technologies, Inc., Seattle, WA) localization accuracy in the presence of wireless metal-oxide-semiconductor field-effect transistor (MOSFET) dosimeters of dose verification system (DVS, Sicel Technologies, Inc., Morrisville, NC) and the dosimeters' reading...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3578602
更新日期:2011-05-01 00:00:00
abstract:PURPOSE:The purpose of this study is to evaluate the feasibility of kilovoltage cone-beam CT (CBCT) images that are obtained with the Varian On-Board Imager in dose calculation at each radiation therapy. METHODS:CBCT images are commonly degraded by scattered radiations originating in the patient's body, and so the CT ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4734936
更新日期:2012-06-01 00:00:00
abstract::Previous ultrasound tomography work conducted by our group showed a direct correlation between measured sound speed and physical density in vitro, and increased in vivo sound speed with increasing mammographic density, a known risk factor for breast cancer. Building on these empirical results, the purpose of this work...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2964092
更新日期:2008-09-01 00:00:00
abstract:PURPOSE:To investigate image-registration errors when using fiducial markers with a manual method and the point-based rigid-body registration (PRBR) algorithm in accelerated partial breast irradiation (APBI) patients, with accompanying fiducial deviations. METHODS:Twenty-two consecutive patients were enrolled in a pro...
journal_title:Medical physics
pub_type: 临床试验,杂志文章
doi:10.1118/1.4915534
更新日期:2015-04-01 00:00:00
abstract::A photon transport algorithm for fully three-dimensional radiotherapy treatment planning has been developed based on the discrete ordinates (SN) solution of the Boltzmann equation. The algorithm is characterized by orthogonal adaptive meshes, which place additional points where large gradients occur and a procedure to...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2960247
更新日期:2008-09-01 00:00:00
abstract::Cone beam computed tomography (CBCT) is a relatively new patient imaging technique that has proved invaluable for treatment target verification and patient positioning during image-guided radiotherapy (IGRT). It has been shown that CBCT results in additional dose to bone that may amount to 10% of the prescribed dose. ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3147143
更新日期:2009-07-01 00:00:00
abstract:PURPOSE:Intraoperative electron radiation therapy (IOERT) involves the delivery of a high radiation dose during tumor resection in a shorter time than other radiation techniques, thus improving local control of tumors. However, a linear accelerator device is needed to produce the beam safely. Mobile linear accelerators...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12482
更新日期:2017-10-01 00:00:00
abstract:PURPOSE:In fractionated radiation therapy, image guidance with daily tomographic imaging becomes more and more clinical routine. In principle, this allows for daily computation of the delivered dose and for accumulation of these daily dose distributions to determine the actually delivered total dose to the patient. How...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3697524
更新日期:2012-04-01 00:00:00
abstract::In this x-ray/MR hybrid system an x-ray flat panel detector is placed under the patient cradle, close to the MR volume of interest (VOI), where the magnetic field strength is approximately 0.5 T. Immersed in this strong field, several electronic components inside the detector become magnetized and create an additional...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2963994
更新日期:2008-09-01 00:00:00
abstract::A suitable was phantom was designed for evaluating various film techniques used in subtraction radiography. Holes are drilled in a slab of wax and filled with various concentrations of iodinated wax, producing disk-shaped regions with diffuse borders. The technical details of construction and a representative applicat...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594371
更新日期:1977-05-01 00:00:00
abstract::Complementary metal-oxide-semiconductors (CMOS) active pixel sensors can be optically coupled to CsI:Tl phosphors forming a indirect active pixel flat panel imager (APFPI) for high performance medical imaging. The aim of this work is to determine the x-ray imaging capabilities of CMOS-based APFPI and study the signal ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3036117
更新日期:2009-01-01 00:00:00
abstract::We studied a recently proposed aggregated CT reconstruction technique which combines the complementary advantages of kilovoltage (kV) and megavoltage (MV) x-ray imaging. Various phantoms were imaged to study the effects of beam orientations and geometry of the imaging object on image quality of reconstructed CT. It wa...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2768862
更新日期:2007-09-01 00:00:00
abstract:PURPOSE:Commercially available fillable plastic inserts used in positron emission tomography phantoms usually have thick plastic walls, separating their content from the background activity. These "cold" walls can modify the intensity values of neighboring active regions due to the partial volume effect, resulting in e...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4813302
更新日期:2013-08-01 00:00:00
abstract:PURPOSE:Signal encoding in magnetic particle imaging (MPI) is achieved by moving a field-free point (FFP) through the region of interest. One way to increase the sensitivity of the method is to scan the region of interest with a field-free line (FFL) instead of the FFP. Recently, the first feasible FFL coil setup was i...
journal_title:Medical physics
pub_type: 信件
doi:10.1118/1.3447726
更新日期:2010-07-01 00:00:00
abstract:PURPOSE:To compare and evaluate intensity-based registration methods for computation of serial x-ray mammogram correspondence. METHODS:X-ray mammograms were simulated from MRIs of 20 women using finite element methods for modeling breast compressions and employing a MRI/x-ray appearance change model. The parameter con...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3457470
更新日期:2010-09-01 00:00:00
abstract::Analytic microdosimetry using Fourier transform techniques has been applied to internal alpha emitters. These techniques need revision and simplification for use with short-lived radionuclides such as those which may be useful for radioimmunotherapy. Analytic methods may have advantages over Monte Carlo methods in som...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596770
更新日期:1992-11-01 00:00:00
abstract::Postoperative beta-irradiation after pterygium excision has been considered a valuable therapeutic procedure to reduce the recurrence rate. Recently, it was reported that beta-irradiation also substantially reduced the risk of surgical failure after glaucoma surgery. Pure beta-irradiation using a 90Sr/Y applicator has...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2896076
更新日期:2008-05-01 00:00:00
abstract::In computer simulations of x-ray CT systems one can either use continuous geometrical descriptions for phantoms or a voxelized representation. The voxelized approach allows arbitrary phantoms to be defined without being confined to geometrical shapes. The disadvantage of the voxelized approach is that inherent errors ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1461841
更新日期:2002-04-01 00:00:00
abstract::Accurate segmentation of microcalcifications in mammography is crucial for the quantification of morphologic properties by features incorporated in computer-aided diagnosis schemes. A novel segmentation method is proposed implementing active rays (polar-transformed active contours) on B-spline wavelet representation t...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2991286
更新日期:2008-11-01 00:00:00