Analysis and correction of imperfections in the image intensifier-TV-digitizer imaging chain.

abstract：PURPOSE:Megavoltage grid therapy is currently delivered with step-and-shoot multisegment techniques or using a high attenuation block with divergent holes. However, the commercial availability of grid blocks is limited, their construction is difficult, and step-and-shoot techniques require longer treatment times and ar...

journal_title：Medical physics

authors： Almendral P,Mancha PJ,Roberto D

更新日期：2013-05-01 00:00:00

abstract：PURPOSE:Particle therapy is becoming increasingly available world-wide for precise tumor targeting, its favorable depth dose deposition, and increased biological damage to tumor tissue compared to conventional photon therapy. As demand increases for improved robustness and conformality, next-generation secondary dose c...

journal_title：Medical physics

authors： Kopp B,Fuglsang Jensen M,Mein S,Hoffmann L,Nyström H,Falk M,Haberer T,Abdollahi A,Debus J,Mairani A

更新日期：2020-10-01 00:00:00

abstract：PURPOSE:There is an increasing interest in calculating linear energy transfer (LET) distributions for proton therapy treatments in order to assess the influence of this quantity in biological terms. Microdosimetric Monte Carlo (MC) simulations are useful tools to calculate dose-averaged LET, as this has been broadly pr...

journal_title：Medical physics

authors： Bertolet A,Baratto-Roldán A,Barbieri S,Baiocco G,Carabe A,Cortés-Giraldo MA

更新日期：2019-09-01 00:00:00

abstract：PURPOSE:Tissue textures have been recognized as biomarkers for various clinical tasks. In computed tomography (CT) image reconstruction, it is important but challenging to preserve the texture when lowering x-ray exposure from full- toward low-/ultra-low dose level. Therefore, this paper aims to explore the texture-dos...

journal_title：Medical physics

authors： Gao Y,Liang Z,Xing Y,Zhang H,Pomeroy M,Lu S,Ma J,Lu H,Moore W

更新日期：2020-10-01 00:00:00

abstract：:Current edge detection methods used to determine coronary artery dimensions from digital (DSA) images suffer a strong dependence on the system's modulation transfer function (MTF). The videodensitometric algorithms are less sensitive to MTF blurring, yet still result in an overestimation of the vessel size of 10% to 2...

journal_title：Medical physics

authors： Weber DM

更新日期：1989-03-01 00:00:00

abstract：PURPOSE:The objective of this study is to develop a computational model for simulating 915 MHz microwave ablation (MWA), and verify the simulation predictions of transient temperature profiles against experimental measurements. Due to the limited experimental data characterizing temperature-dependent changes of tissue ...

journal_title：Medical physics

authors： Deshazer G,Hagmann M,Merck D,Sebek J,Moore KB,Prakash P

更新日期：2017-09-01 00:00:00

abstract：:Using stable materials capable of mimicking any soft tissues of the human body--quantitatively with respect to speed of sound, density, and attenuation coefficient and semiquantitatively with respect to scatter--we have constructed a torso section phantom containing simulated bowel gas, kidney, kidney fat pad, liver, ...

journal_title：Medical physics

authors： Madsen EL,Zagzebski JA,Ghilardi-Netto T

更新日期：1980-01-01 00:00:00

abstract：PURPOSE:Researchers write many computer programs with unique implementations, usually requiring a great amount of effort for other researchers to learn how to install, configure, and use. Some programs require specialized hardware platforms such as GPU workstation or CPU cluster, which may not readily available for man...

journal_title：Medical physics

authors： Folkerts M,Graves Y,Gautier Q,Kim G,Jia X,Jiang S

更新日期：2012-06-01 00:00:00

abstract：:Radiographic image guidance has emerged as the new paradigm for patient positioning, target localization, and external beam alignment in radiotherapy. Although widely varied in modality and method, all radiographic guidance techniques have one thing in common--they can give a significant radiation dose to the patient....

journal_title：Medical physics

authors： Murphy MJ,Balter J,Balter S,BenComo JA Jr,Das IJ,Jiang SB,Ma CM,Olivera GH,Rodebaugh RF,Ruchala KJ,Shirato H,Yin FF

更新日期：2007-10-01 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

authors： Williams MB,Mangiafico PA,Simoni PU

更新日期：1999-07-01 00:00:00

abstract：:Most detectors in current positron emission tomography (PET) scanners and prototypes use lutetium oxyorthosilicate (LSO) or lutetium yttrium oxyorthosilicate (LYSO) scintillators. The aim of this work is to provide a complete set of background energy spectra, due to the scintillator intrinsic radioactivity, for a wide...

journal_title：Medical physics

authors： Domínguez-Jiménez DY,Alva-Sánchez H

更新日期：2021-01-21 00:00:00

abstract：:Ionization chambers of varying inside diameter have been used to investigate the penumbral region of 60Co, 6-MV, and 31-MV x-ray beams. Measurements were made in water at varying depths up to 25 cm for a square field of side length 10 cm. The dependence of the penumbral widths on both the inside diameter of the ioniza...

journal_title：Medical physics

authors： Dawson DJ,Schroeder NJ,Hoya JD

更新日期：1986-01-01 00:00:00

abstract：:A new beam line for radiotherapy and radiosurgery with accelerated helium-ion beams has been set up at the Bevalac. The new treatment room has been equipped with a very precise patient positioner in order to utilize the superior dose localization properties of light-ion beams. The beam spreading and shaping system is ...

journal_title：Medical physics

authors： Ludewigt BA,Chu WT,Phillips MH,Renner TR

更新日期：1991-01-01 00:00:00

abstract：PURPOSE:To determine the accuracy of VMAT treatment planning and delivery for patients undergoing radiotherapy in the head and neck. METHOD AND MATERIALS:A dosimetric study of a typical head and neck treatment plan has been carried out using Chamber, film and TLD's placed inside an anthropomorphic phantom. Lateral and...

journal_title：Medical physics

authors： Aldaais E,Tedeschi D,Gebreamlak W,Shieder T,Alkhatib H

更新日期：2012-06-01 00:00:00

abstract：PURPOSE:To find an upper bound on the maximum dose reduction possible for any reconstruction algorithm, analytic or iterative, that result from the inclusion of the data statistics. The authors do not analyze noise reduction possible from prior knowledge or assumptions about the object. METHODS:The authors examined th...

journal_title：Medical physics

authors： Hsieh SS,Chesler DA,Fleischmann D,Pelc NJ

更新日期：2016-03-01 00:00:00

abstract：PURPOSE:The aim of this study was to assess the suitability of Gafchromic EBT3 films for reference dose measurements in the beam of a prototype high dose-per-pulse linear accelerator (linac), capable of delivering electron beams with a mean dose-rate (Ḋm ) ranging from 0.07 to 3000 Gy/s and a dose-rate in pulse (Ḋp ) o...

journal_title：Medical physics

authors： Jaccard M,Petersson K,Buchillier T,Germond JF,Durán MT,Vozenin MC,Bourhis J,Bochud FO,Bailat C

更新日期：2017-02-01 00:00:00

abstract：PURPOSE:In breast radiotherapy with intensity modulation, it is a well established practice to extend the dose fluence outside the limit of the body contour to account for small changes in size and position of the target and the rest of the tissues due to respiration or to possible oedema. A simple approach is not appl...

journal_title：Medical physics

authors： Giorgia N,Antonella F,Alessandro C,Eugenio V,Luca C

更新日期：2011-07-01 00:00:00

abstract：PURPOSE:Cherenkov light during MV radiotherapy has recently found imaging and therapeutic applications but is challenged by relatively low fluence. Our purpose is to investigate the feasibility of increasing Cherenkov light production during MV radiotherapy by increasing photon energy and applying specialized beam-hard...

journal_title：Medical physics

authors： Shrock Z,Yoon SW,Gunasingha R,Oldham M,Adamson J

更新日期：2018-07-01 00:00:00

abstract：:An algorithm, which combines the scanning beam with dynamic collimation to generate any arbitrary intensity profile, is presented. The desired intensity profile is assumed to be piecewise linear. The dynamic collimation method used is the "sliding window." The algorithm can be used either for a given scanning beam pro...

journal_title：Medical physics

authors： Spirou SV,Chui CS

更新日期：1996-01-01 00:00:00

abstract：:Routine electron beam quality assurance requires an accurate, yet practical, method of energy characterization. Subtle shifts in beam energy may be produced by the linac bending magnet assembly, and the sensitivity of a commercially available electron beam energy-monitoring device for monitoring these small energy dri...

journal_title：Medical physics

authors： Evans MD,Moftah BA,Olivares M,Podgorsak EB

更新日期：2000-07-01 00:00:00

abstract：PURPOSE:Transurethral MR-HIFU is a minimally invasive image-guided treatment for localized prostate cancer that enables precise targeting of tissue within the gland. The treatment is performed within a clinical MRI to obtain real-time MR thermometry used as an active feedback to control the spatial heating pattern in t...

journal_title：Medical physics

authors： Schmitt A,Mougenot C,Chopra R

更新日期：2014-11-01 00:00:00

abstract：PURPOSE:Contrast-enhanced imaging of the breast is frequently used in breast MRI and has recently become more common in mammography. The purpose of this study was to make single-scan contrast-enhanced imaging feasible for photon-counting breast CT (pcBCT) and to assess the spectral performance of a pcBCT scanner by eva...

journal_title：Medical physics

authors： Ruth V,Kolditz D,Steiding C,Kalender WA

更新日期：2020-07-01 00:00:00

abstract：PURPOSE:Polymer-based gel dosimeter (MAGIC type) is a preferable phantom material for PET range verification of proton beam therapy. However, improvement in elemental tissue equivalency (specifically O/C ratio) is very desirable to ensure realistic time-activity measurements. METHODS:Glucose and urea was added to the ...

journal_title：Medical physics

authors： Zhu X,Reese TG,Crowley EM,El Fakhri G

更新日期：2010-01-01 00:00:00

abstract：:A computer program was implemented to predict mammography x-ray beam parameters in the range 20-40 kV for Mo/Mo, Mo/Rh, Rh/Rh, and W/Al target/filter combinations. The computation method used to simulate mammography x-ray spectra is based on the Boone et al. model. The beam quality parameters such as the half-value la...

journal_title：Medical physics

authors： Kharrati H,Zarrad B

更新日期：2003-10-01 00:00:00

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

authors： Suzuki K,Kohlbrenner R,Epstein ML,Obajuluwa AM,Xu J,Hori M

更新日期：2010-05-01 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

authors： Zhang N,Magland JF,Rajapakse CS,Bhagat YA,Wehrli FW

更新日期：2013-05-01 00:00:00

abstract：PURPOSE:Pulse pileup occurring at high x-ray fluxes can severely degrade the energy resolution provided by a photon counting detector, which can represent a problem in spectroscopic CT when performing quantitative material discrimination tasks. As the effects of pileup can be most easily seen as a degradation of a dete...

journal_title：Medical physics

authors： Rink K,Oelfke U,Fiederle M,Zuber M,Koenig T

更新日期：2013-10-01 00:00:00

abstract：PURPOSE:Monte Carlo (MC) dose calculation is generally superior to analytical dose calculation (ADC) used in commercial TPS to model the dose distribution especially for heterogeneous sites, such as lung and head/neck patients. The purpose of this study was to provide a validated, fast, and open-source MC code, MCsquar...

journal_title：Medical physics

authors： Huang S,Souris K,Li S,Kang M,Barragan Montero AM,Janssens G,Lin A,Garver E,Ainsley C,Taylor P,Xiao Y,Lin L

更新日期：2018-12-01 00:00:00

abstract：:Techniques have been developed for reducing motion blurring artifacts by using respiratory gated computed tomography (CT) in sinogram space and quantitatively evaluating the artifact reduction. A synthetic sinogram was built from multiple scans intercepting a respiratory gating window. A gated CT image was then recons...

journal_title：Medical physics

authors： Lu W,Parikh PJ,Hubenschmidt JP,Politte DG,Whiting BR,Bradley JD,Mutic S,Low DA

更新日期：2005-11-01 00:00:00

abstract：:A micro-angiographic detector was designed and its performance was previously tested to evaluate its feasibility as an improvement over current x-ray detectors for neuro-interventional imaging. The detector was shown to have a modulation transfer function value of about 2% at the Nyquist frequency of 10 cycles/mm and ...

journal_title：Medical physics

authors： Ganguly A,Rudin S,Bednarek DR,Hoffmann KR

更新日期：2003-11-01 00:00:00