Abstract:
PURPOSE:This paper provides a comparison between a fast, commercial, in-patient Monte Carlo dose calculation algorithm (GPUMCD) and geant4. It also evaluates the dosimetric impact of the application of an external 1.5 T magnetic field. METHODS:A stand-alone version of the Elekta™ GPUMCD algorithm, to be used within the Monaco treatment planning system to model dose for the Elekta™ magnetic resonance imaging (MRI) Linac, was compared against GEANT4 (v10.1). This was done in the presence or absence of a 1.5 T static magnetic field directed orthogonally to the radiation beam axis. Phantoms with material compositions of water, ICRU lung, ICRU compact-bone, and titanium were used for this purpose. Beams with 2 MeV monoenergetic photons as well as a 7 MV histogrammed spectrum representing the MRI Linac spectrum were emitted from a point source using a nominal source-to-surface distance of 142.5 cm. Field sizes ranged from 1.5 × 1.5 to 10 × 10 cm(2). Dose scoring was performed using a 3D grid comprising 1 mm(3) voxels. The production thresholds were equivalent for both codes. Results were analyzed based upon a voxel by voxel dose difference between the two codes and also using a volumetric gamma analysis. RESULTS:Comparisons were drawn from central axis depth doses, cross beam profiles, and isodose contours. Both in the presence and absence of a 1.5 T static magnetic field the relative differences in doses scored along the beam central axis were less than 1% for the homogeneous water phantom and all results matched within a maximum of ±2% for heterogeneous phantoms. Volumetric gamma analysis indicated that more than 99% of the examined volume passed gamma criteria of 2%-2 mm (dose difference and distance to agreement, respectively). These criteria were chosen because the minimum primary statistical uncertainty in dose scoring voxels was 0.5%. The presence of the magnetic field affects the dose at the interface depending upon the density of the material on either sides of the interface. This effect varies with the field size. For example, at the water-lung interface a 33.94% increase in dose was observed (relative to the Dmax), by both GPUMCD and GEANT4 for the field size of 2 × 2 cm(2) (compared to no B-field case), which increased to 47.83% for the field size of 5 × 5 cm(2) in the presence of the magnetic field. Similarly, at the lung-water interface, the dose decreased by 19.21% (relative to Dmax) for a field size of 2 × 2 cm(2) and by 30.01% for 5 × 5 cm(2) field size. For more complex combinations of materials the dose deposition also becomes more complex. CONCLUSIONS:The GPUMCD algorithm showed good agreement against GEANT4 both in the presence and absence of a 1.5 T external magnetic field. The application of 1.5 T magnetic field significantly alters the dose at the interfaces by either increasing or decreasing the dose depending upon the density of the material on either side of the interfaces.
journal_name
Med Physjournal_title
Medical physicsauthors
Ahmad SB,Sarfehnia A,Paudel MR,Kim A,Hissoiny S,Sahgal A,Keller Bdoi
10.1118/1.4939808subject
Has Abstractpub_date
2016-02-01 00:00:00pages
894-907issue
2eissn
0094-2405issn
2473-4209journal_volume
43pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract::Because of complex dose distributions and dose gradients that are created in three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiation therapy (IMRT), photon- and electron-energy spectra might change significantly with spatial locations and doses. This study examined variations in photon- and...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2710550
更新日期:2007-04-01 00:00:00
abstract::A new high-resolution detector has been developed for use in a slot-scanned digital mammography system. The detector is a hybrid device that consists of a CCD operating in time-delay integration mode that is bonded to a 150-microm-thick CdZnTe photoconductor array. The CCD was designed with a detector element pitch of...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1523932
更新日期:2002-12-01 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::Volumetric modulated arc therapy (VMAT) has recently been used to improve the dose distribution and efficiency of treatment delivery over the standard intensity-modulated radiotherapy (IMRT) technique. This study compares the dosimetry between RapidArc plan and standard IMRT plan for head and neck cancer. Three head a...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4740174
更新日期:2012-07-01 00:00:00
abstract::A computationally efficient pseudodynamical filtering setup is established for elasticity imaging (i.e., reconstruction of shear modulus distribution) in soft-tissue organs given statically recorded and partially measured displacement data. Unlike a regularized quasi-Newton method (QNM) that needs inversion of ill-con...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3158808
更新日期:2009-08-01 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:PURPOSE:Radiopharmaceutical applications in nuclear medicine require a detailed dosimetry estimate of the radiation energy delivered to the human tissues. Over the past years, several publications addressed the problem of internal dose estimate in volumes of several sizes considering photon and electron sources. Most o...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3242304
更新日期:2009-11-01 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:PURPOSE:Automated detection of solitary pulmonary nodules using positron emission tomography (PET) and computed tomography (CT) images shows good sensitivity; however, it is difficult to detect nodules in contact with normal organs, and additional efforts are needed so that the number of false positives (FPs) can be fu...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4948498
更新日期:2016-06-01 00:00:00
abstract::A simple method to measure the line spread function of computed tomographic scanners has been developed. The line spread function of the EMI-Scanner was measured and the MTF of the scanner was calculated. The reproducibility of the method indicated this technique could be utilized to compare the spatial resolution of ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594283
更新日期:1976-07-01 00:00:00
abstract:PURPOSE:Cone-beam CT (CBCT) images contain severe shading artifacts mostly due to scatter. Many algorithms have been proposed to alleviate this problem by data correction on projections. Sophisticated methods have also been designed to further improve the image quality when prior patient information is available. In th...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4736218
更新日期:2012-06-01 00:00:00
abstract::Noise power spectrum (NPS) and detective quantum efficiency (DQE) for metal-plate/film portal detectors are reported for the Co-60 and Linac 10 MV spectra. The detectors consist of a double-emulsion portal film secured between plates of aluminum, copper, brass, or lead. The NPS was found to be independent of the detec...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598437
更新日期:1998-12-01 00:00:00
abstract:PURPOSE:Dual source CT (DSCT) systems utilize two measurement systems (A) and (B) offset by about 90 degrees. A special challenge in DSCT is cross-scattered radiation, i.e., scattered radiation from x-ray tube (B) detected in detector (A) and vice versa. Cross-scattered radiation can produce artifacts and degrade the c...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3504606
更新日期:2010-11-01 00:00:00
abstract::The computed tomography (CT) radiation dose to pediatric patients has received considerable attention recently. Moreover, it is important to be able to determine CT radiation doses for various patient sizes ranging from infants to large adults. The current AAPM protocol only measures CT radiation dose using a 16 cm ac...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1543149
更新日期:2003-03-01 00:00:00
abstract:PURPOSE:To develop a pencil beam dose calculation algorithm for scanned proton beams that improves modeling of scatter events. METHODS:Our pencil beam algorithm (PBA) was developed for calculating dose from monoenergetic, parallel proton beams in homogeneous media. Fermi-Eyges theory was implemented for pencil beam tr...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735624
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:Task Group 119 (TG-119) has been adopted for evaluating the adequacy of intensity-modulated radiation therapy (IMRT) commissioning and for establishing patient-specific IMRT quality assurance (QA) passing criteria in clinical practice. TG-119 establishes 95% confidence limits (CLs), which help clinics identify ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12759
更新日期:2018-03-01 00:00:00
abstract:PURPOSE:It is very important for calculation of clinical indices and diagnosis to detect thyroid nodules from ultrasound images. However, this task is a challenge mainly due to heterogeneous thyroid nodules with distinct components are similar to background in ultrasound images. In this study, we employ cascade deep co...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12134
更新日期:2017-05-01 00:00:00
abstract::Radiographic magnification is often employed in mammography to improve detection of small anatomical details of clinical interest, such as microcalcifications. The image size depends on the conventional magnification factor, on the focal spot size, and on the x-ray angulation. In this paper magnification effects are i...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597288
更新日期:1994-02-01 00:00:00
abstract::Many problems in physics involve imaging objects with high spatial frequency content in a limited amount of time. The limitation of available experimental data leads to the infamous problem of diffraction limited data which manifests itself by causing ringing in the image. This ringing is due to the interference pheno...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596427
更新日期:1989-05-01 00:00:00
abstract::Radiation therapy treatment modalities continue to develop and have become increasingly complex. With this, dose verification and quality assurance (QA) is of great importance to ensure that a prescribed dose is accurately and precisely delivered to a patient. Radiochromic film dosimetry has been adopted as a convenie...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4740126
更新日期:2012-07-01 00:00:00
abstract:PURPOSE:In radiotherapy, it is important to predict the response of tumors to irradiation prior to the treatment. This is especially important for hypoxic tumors, which are known to be highly radioresistant. Mathematical modeling based on the dose distribution, biological parameters, and medical images may help to impr...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4903298
更新日期:2015-01-01 00:00:00
abstract::Due to practical limitations in data acquisition, 3-D computed tomography systems must attempt to provide rapid reconstructions of acceptable quality from a limited number of views. The use of convolution backprojection (CBP) for image reconstruction from an inadequate number of projections, results in view aliasing a...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598606
更新日期:1999-06-01 00:00:00
abstract:PURPOSE:The aim of this research was to explore x-ray beam parameters with intent to optimize pediatric x-ray settings in the cardiac catheterization laboratory. This study examined the effects of peak x-ray tube voltage (kVp) and of copper (Cu) x-ray beam filtration independently on the image quality to dose balance f...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3488911
更新日期:2010-10-01 00:00:00
abstract::Recently, portal imaging systems have been successfully demonstrated in dosimetric treatment verification applications, where measured and predicted images are quantitatively compared. To advance this approach to dosimetric verification, a two-step model which predicts dose deposition in arbitrary portal image detecto...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1289375
更新日期:2000-09-01 00:00:00
abstract:BACKGROUND:The rapid development and complexity of new x-ray computed tomography (CT) technologies and the need for evidence-based optimization of image quality with respect to radiation and contrast media dose call for an updated approach towards CT performance evaluation. AIMS:This report offers updated testing guid...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13763
更新日期:2019-11-01 00:00:00
abstract::Encapsulated, cylindrical sources containing 2, 5, and 8 Ci of 241Am have been designed and fabricated for intracavitary irradiation of uterine cancers. Exposure rates in air and dose rates in water around these sources have been measured using an ionization chamber and a lithium fluoride thermoluminescent dosimetry s...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596007
更新日期:1987-09-01 00:00:00
abstract:PURPOSE:Traditionally, unidirectional leaf-sweeping schemes have been employed to deliver IMRT plans using the dynamic multileaf collimator (DMLC) technique. The goal of this research is to investigate the potential impact of relaxing the leaf-motion restrictions in DMLC IMRT on the beam-modulation quality and the deli...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13158
更新日期:2018-11-01 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::A combination of Monte Carlo, convolution, and experimental techniques have been used to investigate bremsstrahlung production at 50 MeV in full-range targets to produce narrow elementary photon beams for scanning. Calculations using the ITS 3.0 Monte Carlo system for various target designs, including particle transpo...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597681
更新日期:1996-04-01 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