Unwanted radiation produced by leakage neutrons from medical electron accelerators.

abstract：PURPOSE:To automatically and efficiently segment the lesion area of the colonoscopy polyp image, a polyp segmentation method has been presented. METHODS:An ensemble model of pretrained convolutional neural networks was proposed, using Unet-VGG, SegNet-VGG, and PSPNet. Firstly, the Unet-VGG is obtained by the first 10 ...

journal_title：Medical physics

authors： Guo X,Zhang N,Guo J,Zhang H,Hao Y,Hang J

更新日期：2019-12-01 00:00:00

abstract：:Due to practical limitations such as inter- and intraleaf transmission, nondivergent leaf end design, and leaf scatter, multileaf collimators (MLCs) are unable to accurately produce the ideal fluence patterns generated by inverse planning systems. Consequently, low dose regions receive substantially more radiation tha...

journal_title：Medical physics

authors： Popple RA,Fiveash JB,Brezovich IA

更新日期：2007-10-01 00:00:00

abstract：PURPOSE:The aim of this study is to understand the characteristics of secondary electrons generated from the interaction of gold nanoparticles (GNPs) with x-rays as a function of nanoparticle size and beam energy and thereby further the understanding of GNP-enhanced radiotherapy. METHODS:The effective range, deflectio...

journal_title：Medical physics

authors： Leung MK,Chow JC,Chithrani BD,Lee MJ,Oms B,Jaffray DA

更新日期：2011-02-01 00:00:00

abstract：:Assessment of clinic and site specific margins are essential for the effective use of three-dimensional and intensity modulated radiation therapy. An electronic portal imaging device (EPID) based methodology is introduced which allows individual and population based CTV-to-PTV margins to be determined and compared wit...

journal_title：Medical physics

authors： Prisciandaro JI,Frechette CM,Herman MG,Brown PD,Garces YI,Foote RL

更新日期：2004-11-01 00:00:00

abstract：:A method for optimizing MR imaging pulse sequence parameters in a statistical framework is presented. Parameters are defined to be optimal when the resulting scalar images yield optimal image segmentations using Bayesian pixel classification. Thus, Bayes risk is used as the objective function to minimize. Approximatio...

journal_title：Medical physics

authors： Prince JL,Pham D,Tan O

更新日期：1995-10-01 00:00:00

abstract：:A method for finding optimal primary fluence profiles for multiple field external beam radiation therapy techniques has been developed using a radiobiologically based objective function that quantifies the probability of achieving complication-free tumor control, P+. The objective function P+ has the valuable property...

journal_title：Medical physics

authors： Södertröm S,Brahme A

更新日期：1993-07-01 00:00:00

abstract：:The aim of the work was to investigate in advance the dosimetric properties of a new multileaf collimator (MLC) concept with the help of Monte Carlo (MC) simulations prior to the production of a prototype. The geometrical design of the MLC was implemented in the MC code GEANT4. For the simulation of a 6 MV treatment b...

journal_title：Medical physics

authors： Tacke MB,Szymanowski H,Oelfke U,Schulze C,Nuss S,Wehrwein E,Leidenberger S

更新日期：2006-04-01 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

authors： Vernekohl D,Tzoumas S,Zhao W,Xing L

更新日期：2018-05-25 00:00:00

abstract：:The accuracy of interpolation or averaging procedures for obtaining the calibration coefficient N(K) for 192Ir high-dose-rate brachytherapy sources has been investigated using the EGSnrc Monte Carlo simulation system. It is shown that the widely used two-point averaging procedure of Goetsch et al. [Med. Phys. 18, 462 ...

journal_title：Medical physics

authors： Mainegra-Hing E,Rogers DW

更新日期：2006-09-01 00:00:00

abstract：PURPOSE:Theoretical reasoning suggests that direct conversion digital x-ray detectors based upon photoconductive amorphous-selenium (a-Se) could attain very high values of the MTF (modulation transfer function) at spatial frequencies well beyond 20 cycles mm(-1). One of the fundamental factors affecting resolution loss...

journal_title：Medical physics

authors： Hunter DM,Belev G,Kasap S,Yaffe MJ

更新日期：2012-02-01 00:00:00

abstract：:In this article, we report on the development of a simple and accurate method for quality assurance of electron beam output and energy. Aluminum disks of thicknesses d(max) or d50 of the particular electron energy are positioned sequentially over a parallel-plate ion chamber and the ratio of the two signals is compare...

journal_title：Medical physics

authors： Woo MK,Videla NG

更新日期：2004-05-01 00:00:00

abstract：:The immediate goal of clinically based x-ray-transmission computed tomography (CT) is to provide a measurement of the x-ray linear attenuation coefficient in cross section with the ultimate goal of impacting on patient management and care. To do this with the accuracy needed for clinical goals requires the careful int...

journal_title：Medical physics

authors： McCullough EC,Payne JT

更新日期：1977-03-01 00:00:00

abstract：:In previous work it has been shown that a standard backpropagation neural network can be trained to reconstruct sections of single photon emission computed tomography (SPECT) images based on the planar image projections as inputs. In this study, it is demonstrated that an artificial neural network (ANN) trained on a s...

journal_title：Medical physics

authors： Kerr JP,Bartlett EB

更新日期：1995-05-01 00:00:00

abstract：PURPOSE:The cardiovascular system (CVS) regulation can be studied from a central viewpoint, through heart rate variability (HRV) data, and from a peripheral viewpoint, through laser Doppler flowmetry (LDF) signals. Both the central and peripheral CVSs are regulated by several interacting mechanisms, each having its own...

journal_title：Medical physics

authors： Humeau A,Buard B,Mahé G,Rousseau D,Chapeau-Blondeau F,Abraham P

更新日期：2010-12-01 00:00:00

abstract：PURPOSE:Hypoxia is one of the most important factors influencing clinical outcome after radiotherapy. Improved knowledge of factors affecting the levels and distribution of oxygen within a tumor is needed. The authors constructed a theoretical 3D model based on histological images to analyze the influence of vessel den...

journal_title：Medical physics

authors： Lagerlöf JH,Kindblom J,Cortez E,Pietras K,Bernhardt P

更新日期：2013-02-01 00:00:00

abstract：:An adaptive linear element (Adaline) was developed to estimate the two-dimensional scatter exposure distribution in digital portable chest radiographs (DPCXR). DPCXRs and quantitative scatter exposure measurements at 64 locations throughout the chest were acquired for ten radiographically normal patients. The Adaline ...

journal_title：Medical physics

authors： Lo JY,Floyd CE Jr,Baker JA,Ravin CE

更新日期：1993-07-01 00:00:00

abstract：:The dose-rate dependence of commercially available diode detectors was measured under both high instantaneous dose-rate (pulsed) and low dose rate (continuous, Co-60) radiation. The dose-rate dependence was measured in an acrylic miniphantom at a 5-cm depth in a 10 x 10 cm2 collimator setting, by varying source-to-det...

journal_title：Medical physics

authors： Saini AS,Zhu TC

更新日期：2004-04-01 00:00:00

abstract：PURPOSE:To design an efficient method for utilizing phase-space source models in the GPU-based Monte Carlo (MC) dose calculation engine gDPM. METHODS:In GPU-based MC algorithms, particles are transported in parallel on different threads. Particles of different types and energies can require significantly different exe...

journal_title：Medical physics

authors： Townson R,Jia X,Zavgorodni S,Jiang S

更新日期：2012-06-01 00:00:00

abstract：PURPOSE:Respiratory motion in the chest region during single photon emission computed tomography (SPECT) is a major degrading factor that reduces the accuracy of image quantification. This effect is more notable when the tumor is very small, or the spatial resolution of the imaging system is less than the respiratory m...

journal_title：Medical physics

authors： Naseri M,Rajabi H,Wang J,Abbasi M,Kalantari F

更新日期：2019-11-01 00:00:00

abstract：PURPOSE:Stray neutron radiation is of concern after radiation therapy, especially in children, because of the high risk it might carry for secondary cancers. Several previous studies predicted the stray neutron exposure from proton therapy, mostly using Monte Carlo simulations. Promising attempts to develop analytical ...

journal_title：Medical physics

authors： Pérez-Andújar A,Zhang R,Newhauser W

更新日期：2013-12-01 00:00:00

abstract：PURPOSE:Pulmonary magnetic-resonance-imaging (MRI) and x-ray computed-tomography have provided strong evidence of spatially and temporally persistent lung structure-function abnormalities in asthmatics. This has generated a shift in their understanding of lung disease and supports the use of imaging biomarkers as inter...

journal_title：Medical physics

authors： Guo F,Svenningsen S,Eddy RL,Capaldi DPI,Sheikh K,Fenster A,Parraga G

更新日期：2016-06-01 00:00:00

abstract：PURPOSE:To propose a method to calculate the tissue phantom ratio (TPR) using the depth dose and to compare the proposed method with two other methods. METHODS:An analytical dose model from Bjärngard was used to describe the depth dose and the TPR. The parameters of the model were derived from depth dose measurements,...

journal_title：Medical physics

authors： Ramos Garcia LI,Almansa JF

更新日期：2011-05-01 00:00:00

abstract：PURPOSE:To demonstrate the ultra-high resolution capability of a small field-of-view (FOV) solid state x-ray imaging detector based on an EMCCD sensor. METHODS:A micro-solid state x-ray image intensifier (micro-SSXII) was developed to serve as an ultra-high resolution region-of-interest (ROI) imaging detector. It is b...

journal_title：Medical physics

authors： Singh V,Loughran B,Jain A,Sharma P,Bednarek D,Rudin S

更新日期：2012-06-01 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

authors： Archambault L,Briere TM,Beddar S

更新日期：2008-10-01 00:00:00

abstract：:The dosimetry for radiocolloid therapy of cystic craniopharyngiomas is investigated. Analytical calculations based on the Loevinger and the Berger formulas for electrons and photons, respectively, are compared with Monte Carlo simulations. The role of the material of which the colloid introduced inside the craniophary...

journal_title：Medical physics

authors： Rojas EL,Al-Dweri FM,Lallena AM,Bodineau C,Galán P

更新日期：2003-09-01 00:00:00

abstract：:Cone-beam computed tomography systems have been developed to provide in situ imaging for the purpose of guiding radiation therapy. Clinical systems have been constructed using this approach, a clinical linear accelerator (Elekta Synergy RP) and an iso-centric C-arm. Geometric calibration involves the estimation of a s...

journal_title：Medical physics

authors： Cho Y,Moseley DJ,Siewerdsen JH,Jaffray DA

更新日期：2005-04-01 00:00:00

abstract：PURPOSE:To investigate dosimetry for ocular brachytherapy for a range of eye plaque models containing(103)Pd, (125)I, or (131)Cs seeds with model-based dose calculations. METHODS:Five representative plaque models are developed based on a literature review and are compared to the standardized COMS plaque, including pla...

journal_title：Medical physics

authors： Lesperance M,Martinov M,Thomson RM

更新日期：2014-03-01 00:00:00

abstract：PURPOSE:The standardized uptake value (SUV) is a quantitative measure of FDG tumor uptake frequently used as a tool to monitor therapeutic response. This study aims to (i) assess the reproducibility and uncertainty of SUV max and SUV mean, due to purely statistical, i.e., nonbiological, effects and (ii) to establish th...

journal_title：Medical physics

authors： Schwartz J,Humm JL,Gonen M,Kalaigian H,Schoder H,Larson SM,Nehmeh SA

更新日期：2011-05-01 00:00:00

abstract：:Depth dose distributions for a d(14)Be neutron beam, measured separately for total and gamma absorbed dose, are presented for nine tissue substitutes and for two field sizes. These data are used to examine methods to transform depth dose curves from one material to another. Best results are found when the local depths...

journal_title：Medical physics

authors： Hensley FW,Rassow J,Temme A

更新日期：1985-05-01 00:00:00

abstract：PURPOSE:Currently, no 3D or 4D volumetric x-ray imaging techniques are available for intrafraction verification of target position during actual treatment delivery or in-between treatment beams, which is critical for stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) treatments. This study a...

journal_title：Medical physics

authors： Ren L,Zhang Y,Yin FF

更新日期：2014-02-01 00:00:00