Abstract:
PURPOSE:The purpose of this work was to investigate the use of an experimental complementary metal-oxide-semiconductor (CMOS) active pixel sensor (APS) for tracking of moving fiducial markers during radiotherapy. METHODS:The APS has an active area of 5.4 × 5.4 cm and maximum full frame read-out rate of 20 frame s(-1), with the option to read out a region-of-interest (ROI) at an increased rate. It was coupled to a 4 mm thick ZnWO4 scintillator which provided a quantum efficiency (QE) of 8% for a 6 MV x-ray treatment beam. The APS was compared with a standard iViewGT flat panel amorphous Silicon (a-Si) electronic portal imaging device (EPID), with a QE of 0.34% and a frame-rate of 2.5 frame s(-1). To investigate the ability of the two systems to image markers, four gold cylinders of length 8 mm and diameter 0.8, 1.2, 1.6, and 2 mm were placed on a motion-platform. Images of the stationary markers were acquired using the APS at a frame-rate of 20 frame s(-1), and a dose-rate of 143 MU min(-1) to avoid saturation. EPID images were acquired at the maximum frame-rate of 2.5 frame s(-1), and a reduced dose-rate of 19 MU min(-1) to provide a similar dose per frame to the APS. Signal-to-noise ratio (SNR) of the background signal and contrast-to-noise ratio (CNR) of the marker signal relative to the background were evaluated for both imagers at doses of 0.125 to 2 MU. RESULTS:Image quality and marker visibility was found to be greater in the APS with SNR ∼5 times greater than in the EPID and CNR up to an order of magnitude greater for all four markers. To investigate the ability to image and track moving markers the motion-platform was moved to simulate a breathing cycle with period 6 s, amplitude 20 mm and maximum speed 13.2 mm s(-1). At the minimum integration time of 50 ms a tracking algorithm applied to the APS data found all four markers with a success rate of ≥92% and positional error ≤90 μm. At an integration time of 400 ms the smallest marker became difficult to detect when moving. The detection of moving markers using the a-Si EPID was difficult even at the maximum dose-rate of 592 MU min(-1) due to the lower QE and longer integration time of 400 ms. CONCLUSIONS:This work demonstrates that a fast read-out, high QE APS may be useful in the tracking of moving fiducial markers during radiotherapy. Further study is required to investigate the tracking of markers moving in 3D in a treatment beam attenuated by moving patient anatomy. This will require a larger sensor with ROI read-out to maintain speed and a manageable data-rate.
journal_name
Med Physjournal_title
Medical physicsauthors
Osmond JP,Zin HM,Harris EJ,Lupica G,Allinson NM,Evans PMdoi
10.1118/1.3651632subject
Has Abstractpub_date
2011-11-01 00:00:00pages
6152-9issue
11eissn
0094-2405issn
2473-4209journal_volume
38pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract:PURPOSE:Motion is a major confound of image quality in MRI. A method of retrospectively correcting the effects of rotations and translations on the acquired k-space data is presented. METHODS:In two phantom experiments of well-controlled translation and rotation, two MRI-compatible infrared cameras recorded motion dat...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3254189
更新日期:2009-12-01 00:00:00
abstract:PURPOSE:The purpose of this study was to describe and evaluate methods for calculating a megavoltage computed tomography (MVCT)-derived MR hardware attenuation map (μ-map) and dual-energy CT (DECT) for 511 keV photons. METHODS:Phantom measurements were acquired on a whole-body hybrid PET/MRI system, using a four-chann...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12407
更新日期:2017-09-01 00:00:00
abstract::Image correlation is often required to utilize the complementary information in CT, MRI, and SPECT. A practical method for automatic image correlation in three-dimensions (3D) based on chamfer matching is described. The method starts with automatic extraction of contour points in one modality and automatic segmentatio...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.597344
更新日期:1994-07-01 00:00:00
abstract::In this work, the authors have evaluated ten different ionization chambers for the relative dosimetry of kilovoltage x-ray beams in the energy range of 50-280 kVp. Percentage depth doses in water and relative detector response (in Solid Water and in air) were measured for each of the x-ray beams studied using a number...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3183820
更新日期:2009-09-01 00:00:00
abstract::The concept of equivalent uniform dose (EUD) has been suggested as a means to quantitatively consider heterogeneous dose distributions within targets. Tumor cell density/function is typically assumed to be uniform. We herein propose to use 18F-labeled 2-deoxyglucose (FDG) positron emission tomography (PET) tumor imagi...
journal_title:Medical physics
pub_type: 临床试验,杂志文章
doi:10.1118/1.1779372
更新日期:2004-09-01 00:00:00
abstract::A measurement technique previously proposed for determining dose from primary radiation has been tested using 60Co gamma rays. It is shown that the dose from primary radiation is reliably determined for field sizes of 10 X 10 and 20 X 20 cm2 at depths of 0.5, 5, and 10 cm in water. With further development this techni...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596534
更新日期:1990-01-01 00:00:00
abstract:PURPOSE:To develop a real time dose monitoring and dose reconstruction tool to identify and quantify sources of errors during patient specific volumetric modulated arc therapy (VMAT) delivery and quality assurance. METHODS:The authors develop a VMAT delivery monitor tool called linac data monitor that connects to the ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4764482
更新日期:2012-12-01 00:00:00
abstract::CEA TVS film is a therapy verification film that has been recently introduced in the North American market. This film features linear characteristic curves for photon energies from 137Cs to 18 MV as reported by Cheng and Das [Med. Phys. 23, 1225 (1996)]. In Saskatoon, TVS film was investigated for its application in t...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.598316
更新日期:1998-08-01 00:00:00
abstract::The surface radio frequency (rf) power absorption in human head and torso nuclear magnetic resonance (NMR) imaging experiments is estimated. The results are expressed as a function of the NMR frequency, the rf pulse length, and the pulse duty cycle, which are varied over six orders of magnitude for general applicabili...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595000
更新日期:1981-07-01 00:00:00
abstract:UNLABELLED:The following question is investigated: How narrow do the leaves of a multileaf collimator have to be such that further reduction of the leaf width does not lead to physical improvements of the dose distribution. Because of the physical principles of interaction between radiation and matter, dose distributio...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1319524
更新日期:2000-11-01 00:00:00
abstract:PURPOSE:Although small animal image-guided radiotherapy (SA-IGRT) systems are used increasingly in preclinical research, tools for performing routine quality assurance (QA) have not been optimized and are not readily available. Robust, efficient, and reliable QA tools are needed to ensure the accuracy and reproducibili...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1002/mp.12939
更新日期:2018-07-01 00:00:00
abstract::Heating rate (HR) patterns in cylindrical structures were studied with inhomogeneous limb phantoms. These phantoms, arm and thigh models consisting of fat, bone, and muscle material, were heated with Clini-Therm L, M, and MS applicators at 915 MHz. The thigh model is 18 cm in diameter with 2.65-cm-thick fat on the out...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596627
更新日期:1991-11-01 00:00:00
abstract::Deformable image registration is an important tool for image-guided radiotherapy. Physics-model-based deformable image registration using finite element analysis is one of the methods currently being investigated. The calculation accuracy of finite element analysis is dependent on given boundary conditions, which are ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1774131
更新日期:2004-09-01 00:00:00
abstract:PURPOSE:To determine the feasibility and potential utility of cone beam CT on breast biopsies. METHODS:CBCT simulations were done with a setup which emulates an MX-20 digital specimen radiography system (Faxitron X-Ray Corporation, Chicago, IL), albeit a DQE = 1 was assumed. The phantom consisted of a 5mm diameter cyl...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4740191
更新日期:2012-07-01 00:00:00
abstract::With the increasing complexity of dose patterns external beam radiotherapy, there is a great need for new types of dosimeters. We studied the first prototype of a new dosimeter array consisting of water-equivalent plastic scintillating fibers for dose measurement in external beam radiotherapy. We found that this array...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.2719363
更新日期:2007-05-01 00:00:00
abstract:PURPOSE:Bone strength is the key factor impacting fracture risk. Assessment of bone strength from high-resolution (HR) images have largely relied on linear micro-finite element analysis (μFEA) even though failure always occurs beyond the yield point, which is outside the linear regime. Nonlinear μFEA may therefore be m...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4802085
更新日期:2013-05-01 00:00:00
abstract:PURPOSE:To present a system for robotic 4D ultrasound (US) imaging concurrent with radiotherapy beam delivery and estimate the proportion of liver stereotactic ablative body radiotherapy (SABR) cases in which robotic US image guidance can be deployed without interfering with clinically used VMAT beam configurations. M...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4964454
更新日期:2016-11-01 00:00:00
abstract::We applied Monte Carlo methods for the simulation of x-ray scattering in water phantoms. The phantom thickness was varied from 5 to 20 cm, and the monoenergetic incident x rays were varied from 15 to 100 keV. Eight screen pairs and a total absorption system were used as x-ray receptors. We determined the angular, spec...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595771
更新日期:1985-03-01 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::Quantitation of planar radionuclide images is hampered by structures containing radioactivity which overlie or underlie the organ of interest. The introduction of single photon emission computerized tomography (SPECT) overcame this problem to a large extent and enhanced the contrast of the images. Attenuation of photo...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.596684
更新日期:1991-05-01 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::For diagnostic ultrasound imaging, as in computed tomography, a feature of prime importance is the detection of focal lesions of varying size and contrast (echo amplitude) from surrounding tissue. This study describes a new tissue-stimulating phantom which has been used to measure the threshold detection of varying co...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.595218
更新日期:1982-01-01 00:00:00
abstract:PURPOSE:In this study the Octavius detector 729 ionization chamber (IC) array with the Octavius 4D phantom was characterized for flattening filter (FF) and flattening filter free (FFF) static and rotational beams. The device was assessed for verification with FF and FFF RapidArc treatment plans. METHODS:The response o...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4817482
更新日期:2013-09-01 00:00:00
abstract:PURPOSE:In a recent paper by Bouchard et al. [Med. Phys. 36(10), 4654-4663 (2009)], a theoretical model of quality correction factors for idealistic so-called plan-class specific reference (PCSR) fields was proposed. The reasoning was founded on the definition of PCSR fields made earlier by Alfonso et al. [Med. Phys. 3...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3684952
更新日期:2012-03-01 00:00:00
abstract::Angioplasty balloons inflated with a solution of the beta-emitter Re-188 have been used for intravascular brachytherapy to prevent restenosis. Coronary stents are in extensive clinical use for the treatment of de novo atherosclerotic stenoses. In this study, the effect of an interposed stent on the dose distribution h...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1533749
更新日期:2003-02-01 00:00:00
abstract:PURPOSE:Liver segmentation is an important prerequisite for the assessment of liver cancer treatment options like tumor resection, image-guided radiation therapy (IGRT), radiofrequency ablation, etc. The purpose of this work was to evaluate a new approach for liver segmentation. METHODS:A graph cuts segmentation metho...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3682171
更新日期:2012-03-01 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::We investigated protection strategies of organs at risk (OARs) in intensity modulated radiation therapy (IMRT). These strategies apply to delivery of IMRT to moving body anatomies that show relative displacement of OAR in close proximity to a tumor target. We formulated an efficient genetic algorithm which makes it po...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.3132305
更新日期:2009-07-01 00:00:00
abstract::Intensity modulated radiotherapy (IMRT) requires extensive knowledge of multileaf collimator (MLC) leaf positioning accuracy, precision, and long-term reproducibility. We have developed a technique to efficiently measure the absolute position of each MLC leaf, over the range of leaf positions utilized in IMRT, based o...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.1564091
更新日期:2003-05-01 00:00:00
abstract:PURPOSE:In Stereotactic body radiation therapy (SBRT) higher dose per fraction is delivered to patients and thus the need for an accurate dose computation is further elevated. However under such conditions of small field geometries, the electronic equilibrium can be lost, making it challenging for the dose-calculation ...
journal_title:Medical physics
pub_type: 杂志文章
doi:10.1118/1.4735539
更新日期:2012-06-01 00:00:00