Abstract:
PURPOSE:To demonstrate, via Monte Carlo simulation, that an image obtained from the patient-generated scattered radiation forced to impinge on the detector from a known direction by means of parallel-focused grids, can be used to complement the information conveyed by the primary image, such that accurate stereoscopic three-dimensional localization of fiducial markers can be achieved in a single kV x-ray exposure. METHODS:A voxelized Zubal phantom was used to model the process of fiducial marker localization. The markers were represented as made of gold and cylindrical in shape with dimensions of 5 mm in length and 1 mm in diameter. Three such markers were placed in the Zubal phantom at the prostate level. Two gantry-mounted image acquisition geometries were modeled: a single kV imaging system and a dual kV-MV imaging system. The detector was modeled as a 30 cm × 40 cm Gd2 O2 S screen with a thickness of 0.2 cm and a resolution of 768 × 1024 pixels. The PENELOPE Monte Carlo code was used to calculate the absorbed dose in this detector imparted by the transmitted primary and directional scatter radiation. A grayscale conversion was then applied to obtain an image from which the positions of the markers were determined. Two parallel-focused grid geometries were modeled, one based on the standard lead-carbon fiber grids and a proposed modification using tungsten as the shielding material. Absorbed dose in the patient model was also calculated. RESULTS:It is shown that the combination of primary and directional scatter images provides the means for an accurate stereoscopic fiducial marker 3D localization in a single x-ray exposure, provided the antiscatter grids are made thick enough to allow radiation traveling only in a particular direction to reach the detector. For the proposed tungsten grid and the x-ray spectrum used in this work, grid ratios of 20 and thickness of 0.2 cm, provide the necessary shielding while for the standard lead grids, a ratio of at least 166 and a thickness of 2 cm are needed to obtain discernible directional scatter images. CONCLUSIONS:We have shown that it is in principle possible to determine the 3D position of fiducial markers in a single exposure by making use of the radiation scattered by the patient to form an image that complements the information obtained with the primary beam. The method here proposed requires minimal modification of existing clinical hardware.
journal_name
Med Physjournal_title
Medical physicsauthors
Garnica-Garza HMdoi
10.1002/mp.12712subject
Has Abstractpub_date
2018-02-01 00:00:00pages
703-713issue
2eissn
0094-2405issn
2473-4209journal_volume
45pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract:PURPOSE:To investigate the use of local noise power spectrum (NPS) to characterize image noise and wavelet analysis to isolate defective pixels and inter-subpanel flat-fielding artifacts for quantitative quality assurance (QA) of electronic portal imaging devices (EPIDs). METHODS:A total of 93 image sets including cus...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4959541
更新日期:2016-09-01 00:00:00
abstract:PURPOSE:In MRI-guided needle interventions, such as biopsies and brachytherapy, tissue deformation caused by needle movement may result in localization errors and thus hamper the outcome of the procedure. Monitoring the local tissue deformation provides the ability to compensate for it, e.g., by increasing the needle i...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3633906
更新日期:2011-10-01 00:00:00
abstract::Multislice helical computed tomography (CT) is a promising noninvasive technique for coronary artery imaging. Various factors can cause inconsistencies in cardiac CT data, which can result in degraded image quality. These inconsistencies may be the result of the patient physiology (e.g., heart rate variations), the na...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2163247
更新日期:2006-02-01 00:00:00
abstract::Charge coupled devices (CCDs) are being increasingly used in radiation therapy for dosimetric purposes. However, CCDs are sensitive to stray radiation. This effect induces transient noise. Radiation-induced noise strongly alters the image and therefore limits its quantitative analysis. The purpose of this work is to c...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2975147
更新日期:2008-10-01 00:00:00
abstract::The aim of the present study is to examine the validity of using silicon semiconductor detectors in degraded electron beams with a broad energy spectrum and a wide angular distribution. A comparison is made with diamond detector measurements, which is the dosimeter considered to give the best results provided that dos...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1315317
更新日期:2000-11-01 00:00:00
abstract:PURPOSE:Computer-aided diagnosis (CAD) systems assist in solving subjective diagnosis problems that typically rely on personal experience. A CAD system has been developed to differentiate malignant thyroid nodules from benign thyroid nodules in ultrasound images based on deep learning methods. The diagnostic performanc...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.14301
更新日期:2020-09-01 00:00:00
abstract:PURPOSE:To model X-ray coherent scatter diffraction patterns in GEANT4 for simulating experiments involving material detection through diffraction pattern measurement. Although coherent scatter cross-sections are modeled accurately in GEANT4, diffraction patterns for crystalline materials are not yet included. Here we ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4734794
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:Hybrid Photon Counting (HPC) detectors profoundly improved x-ray diffraction experiments at third generation synchrotron facilities. Enabling the simultaneous measurement of x-ray intensities in multiple energy bins, they also have many potential applications in the field of medical imaging. A prerequisite for ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12323
更新日期:2017-09-01 00:00:00
abstract::A method for the in vivo determination of the isocenter dose, Diso, and mid-plane dose, Dm, using the transmitted signal St measured by 25 central pixels of an aSi-based EPID is here reported. The method has been applied to check the conformal radiotherapy of pelvic tumors and supplies accurate in vivo dosimetry avoid...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2360014
更新日期:2006-11-01 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:Computed tomography (CT) and, in particular, cone beam CT (CBCT) have been increasingly used as a diagnostic tool in recent years. Patient motion during acquisition is common in CBCT due to long scan times. This results in degraded image quality and may potentially increase the number of retakes. Our aim was to...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13731
更新日期:2019-10-01 00:00:00
abstract::In this article, we present a characterization of the effect of difference of Gaussians (DoG) filters in the detection of mammographic regions. DoG filters have been used previously in mammographic mass computer-aided detection (CAD) systems. As DoG filters are constructed from the subtraction of two bivariate Gaussia...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2358326
更新日期:2006-11-01 00:00:00
abstract:PURPOSE:To evaluate a commercial volumetric modulated arc therapy (VMAT), using multiple noncoplanar arcs, for linac-based cranial radiosurgery, as well as evaluate the combined accuracy of the VMAT dose calculations and delivery. METHODS:Twelve patients with cranial lesions of variable size (0.1-29 cc) and two multip...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3641874
更新日期:2011-11-01 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:Current on-board imaging systems commonly used by modern linear accelerators (LINACs) have a limited field of view (FOV) for a cone-beam CT (CBCT) scan, which is typically less than 50 cm. Consequently, truncation artifacts often occur for large patients. The goal of this work is to investigate a novel method t...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3514130
更新日期:2010-12-01 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:Patient-specific QA of highly conformal radiotherapy treatments are usually conducted using 2D or 3D dosimetry of the incident dose distribution in a water-equivalent phantom. However, dosimeters typically used for this task usually lack in either spatial resolution or dose accuracy. The purpose of this work is...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4736526
更新日期:2012-08-01 00:00:00
abstract:PURPOSE:The fundamental nature of positron emission tomography (PET), as an event detection system, provides some flexibility for data handling, including retrospective data manipulation. The reorganization of acquisition data allows the emulation of new scans arising from identical radiotracer spatial distributions, b...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13517
更新日期:2019-06-01 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:Both spatial and biological information are necessary in order to perform true optimization of a treatment plan and for predicting clinical outcome. The goal of this work is to develop an enhanced treatment plan evaluation tool which incorporates biological parameters and retains spatial dose information. METH...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3497152
更新日期:2010-11-01 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:PURPOSE:Because the small-radius photon beams shaped by cones in stereotactic radiosurgery (SRS) lack lateral electronic equilibrium and a detector's finite cross section, direct experimental measurement of dosimetric data for these beams can be subject to large uncertainties. As the dose calculation accuracy of a trea...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3488900
更新日期:2010-10-01 00:00:00
abstract::A direct data link between a CT scanner and a radiation treatment planning system has been developed. The link transmits the data serially over a coaxial cable using the pseudo-paper-tape punch and reader (serial PIO) interfaces. The data transmission rate with error-check is approximately 25,000 8-bit bytes/s. This t...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.594536
更新日期:1979-09-01 00:00:00
abstract:PURPOSE:For the purpose of size-specific dose estimation, information regarding patient attenuation is required. The purpose of this work is to describe a method for measuring patient attenuation and expressing the results in terms of a water cylinder, with cross sectional area A(w), which would absorb the same average...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4754303
更新日期:2012-11-01 00:00:00
abstract:PURPOSE:Two ultra-high-resolution (UHR) computed tomography (CT) scanners are clinically available. One is achieved by a CT system with a 0.25 mm × 160 row detector (Detector-UHR), whereas the other is with a 0.6 mm × 32 row detector with in-plane comb filtering in a dual source CT (Comb-UHR). We compared radiation dos...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.13949
更新日期:2020-02-01 00:00:00
abstract:PURPOSE:To design volume-specific breast phantoms from breast CT (bCT) data sets and estimate the associated normalized mean glandular dose coefficients for breast CT using Monte Carlo methods. METHODS:A large cohort of bCT data sets (N = 215) was used to evaluate breast volume into quintiles (plus the top 5%). The av...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12477
更新日期:2017-10-01 00:00:00
abstract:PURPOSE:A commonly used beam quality index (Q) for high-energy photon beams is the tissue phantom ratio (TPR20,10) for a square field of 10 x 10 cm2 and SDD of 100 cm. On some specialized radiotherapy treatment equipment such a reference collimator setting is not achievable. Likewise a flat beam profile, not explicitly...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3197062
更新日期:2009-09-01 00:00:00
abstract:PURPOSE:Within the European project ALLEGRO (grant agreement no. 231965), the out-of-field dose delivered to a patient when treated with different radiotherapy modalities was investigated. The study compared the dose distribution during photon and particle irradiations both in a water and an anthropomorphic phantom to ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735792
更新日期:2012-06-01 00:00:00
abstract:PURPOSE:Stringent quality assurance is required in MRI breast screening to ensure that different scanners and imaging protocols reach similar diagnostic performance. The authors propose a methodology, based on power spectrum analysis (PSA), to evaluate spatial resolution in clinical images. To demonstrate this approach...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4966704
更新日期:2016-12-01 00:00:00
abstract:PURPOSE:To develop a new biological equivalent dose (BED) formulism that includes repair, repopulation and resensitization (redistribution and reoxygenation), and can be used to calculate prescribed dose for permanent implant with Cs-131. METHODS:Because of lack of sufficient clinical data, the prescribed dose with ne...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735551
更新日期:2012-06-01 00:00:00