Errors in cerebral blood flow determinations by xenon-enhanced computed tomography due to estimation of arterial xenon concentrations.

abstract：PURPOSE:In intensity-modulated proton therapy (IMPT), protons are used to deliver highly conformal dose distributions, targeting tumors, and sparing organs-at-risk. However, due to uncertainties in both patient setup and relative stopping power (RSP) calculation, margins are added to the treatment volume during treatme...

journal_title：Medical physics

authors： Harms J,Lei Y,Wang T,McDonald M,Ghavidel B,Stokes W,Curran WJ,Zhou J,Liu T,Yang X

更新日期：2020-09-01 00:00:00

abstract：:We report on some extensions and further developments of a well-known microcalcification detection algorithm based on adaptive noise equalization. Tissue equivalent phantom images with and without labeled microcalcifications were subjected to this algorithm, and analyses of results revealed some shortcomings in the ap...

journal_title：Medical physics

authors： Gürün OO,Fatouros PP,Kuhn GM,de Paredes ES

更新日期：2001-04-01 00:00:00

abstract：:The same calibration grade ionization chamber and electrometer were sequentially sent to all five currently AAPM Accredited Dosimetry Calibration Laboratories (ADCL). A Cesium-137 based check device was utilized to ensure chamber and electrometer factor constancy and showed a maximum deviation of 0.32% (typically less...

journal_title：Medical physics

authors： Blackwell CR,McCullough EC

更新日期：1992-01-01 00:00:00

abstract：PURPOSE:New technology has been developed to treat age-related macular degeneration (AMD) using 100 kVp pencil-beams that enter the patient through the radio-resistant sclera with a depth of interest between 1.6 and 2.6 cm. Measurement of reference and relative dose in a kilovoltage x-ray beam with a 0.42 cm diameter f...

journal_title：Medical physics

authors： Hanlon J,Chell E,Firpo M,Koruga I

更新日期：2014-02-01 00:00:00

abstract：:A new scheme, called direct aperture deformation (DAD), for online correction of interfraction geometric uncertainties under volumetric imaging guidance is presented. Using deformable image registration, the three-dimensional geometric transformation matrix can be derived that associates the planning image set and the...

journal_title：Medical physics

authors： Feng Y,Castro-Pareja C,Shekhar R,Yu C

更新日期：2006-12-01 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：:Monte Carlo calculations have been performed for the purpose of characterizing the dosimetric properties of three brachytherapy sources. The three sources are manufactured by Syncor Pharmaceuticals Inc. and consist of two 125I seeds (BT-125-1 and BT-125-2) and one 103Pd seed (BT-103-3). The BT-125-1 and BT-125-2 seed ...

journal_title：Medical physics

authors： DeMarco JJ,Hugo G,Solberg TD

更新日期：2002-05-01 00:00:00

abstract：PURPOSE:To reduce the potential of late toxicity (tissue necrosis and cognitive function loss) from brain radiotherapy, we studied a novel planning technique for MLC-equipped linear accelerators (LINACS) that reduces the high doses delivered outside the PTV, enhancing radiation dose conformity. METHODS:The feasibility...

journal_title：Medical physics

authors： Yang W,Sandler H,Fraass B

更新日期：2012-06-01 00:00:00

abstract：PURPOSE:Brachytherapy with 106 Ru/106 Rh plaques offers good outcomes for small-to-medium choroidal melanomas and retinoblastomas. The dose measurement of the plaques is challenging, due to the small range of the emitted beta particles and steep dose gradients involved. The scarce publications on film dosimetry of 106 ...

journal_title：Medical physics

authors： Hermida-López M,Brualla L

更新日期：2018-04-01 00:00:00

abstract：PURPOSE:Design and optimization of medical imaging systems benefit from accurate theoretical modeling that identifies the physical factors governing image quality, particularly in the early stages of system development. This work extends Fourier metrics of imaging performance and detectability index (d') to tomosynthes...

journal_title：Medical physics

authors： Gang GJ,Lee J,Stayman JW,Tward DJ,Zbijewski W,Prince JL,Siewerdsen JH

更新日期：2011-04-01 00:00:00

abstract：PURPOSE:Two types of tumor hypoxia most likely exist in human cancers: Chronic hypoxia due to the paucity of blood capillaries and acute hypoxia due to temporary shutdoWn of microvasculatures or fluctuation in the red cell flux. In a recent hypoxia imaging study using 18F-FMISO PET, the authors observed variation in tr...

journal_title：Medical physics

authors： Wang K,Yorke E,Nehmeh SA,Humm JL,Ling CC

更新日期：2009-10-01 00:00:00

abstract：PURPOSE:This study developed and validated a Motion Artifact Quantification algorithm to automatically quantify the severity of motion artifacts on coronary computed tomography angiography (CCTA) images. The algorithm was then used to develop a Motion IQ Decision method to automatically identify whether a CCTA dataset ...

journal_title：Medical physics

authors： Ma H,Gros E,Baginski SG,Laste ZR,Kulkarni NM,Okerlund D,Schmidt TG

更新日期：2018-12-01 00:00:00

abstract：:The ratio between scatter dose and scatter kerma for points on the central axis of 15-MV x-ray beams has been examined by Monte Carlo calculations. This ratio, beta'S, behaves differently from that between the primary dose and kerma, beta'p. Both the primary and scatter components of beta' undergo an initial rapid bui...

journal_title：Medical physics

authors： Hannallah D,Zhu TC,Bjärngard BE

更新日期：1996-11-01 00:00:00

abstract：:In this paper, we describe an algorithm to segment a needle from a three-dimensional (3D) ultrasound image by using two orthogonal two-dimensional (2D) image projections. Not only is the needle more conspicuous in a projected (volume-rendered) image, but its direction in 3D lies in the plane defined by the projection ...

journal_title：Medical physics

authors： Ding M,Cardinal HN,Fenster A

更新日期：2003-02-01 00:00:00

abstract：:We propose a new starting point for comparing planar dose distributions using a Jacobian-based measure. The measure is normalization independent, i.e., is sensitive to dose patterns while not being biased by global dose scaling. The measure is free of tunable parameters and is bounded between zero and one. We also pro...

journal_title：Medical physics

authors： Paniak LD,Charland PM

更新日期：2008-11-01 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：:In Monte Carlo simulations of light transport in tissues, a grid system is set up to score physical quantities. This study of cylindrically symmetrical problems found that the optimized radial and angular positions for the averaged physical quantities in each grid element are off-center. The error of the extrapolated ...

journal_title：Medical physics

authors： Wang L,Jacques SL

更新日期：1994-07-01 00:00:00

abstract：:We have reported in our previous studies on the methodology, and feasibility of 4D-PET (Gated PET) acquisition, to reduce respiratory motion artifact in PET imaging of the thorax. In this study, we expand our investigation to address the problem of respiration motion in PET/CT imaging. The respiratory motion of four l...

journal_title：Medical physics

authors： Nehmeh SA,Erdi YE,Pan T,Pevsner A,Rosenzweig KE,Yorke E,Mageras GS,Schoder H,Vernon P,Squire O,Mostafavi H,Larson SM,Humm JL

更新日期：2004-12-01 00:00:00

abstract：:Two recently developed A 150 plastic-equivalent gas mixtures have been tested for suitability in proportional counter applications. Methane- and propane-based "tissue-equivalent" gases were also included for comparison purposes. Event-size weighted dose distributions were measured in a 14.8-MeV neutron beam. Resolutio...

journal_title：Medical physics

authors： DeLuca PM Jr,Schell MC,Pearson DW,Higgins PD,Attix FH

更新日期：1984-07-01 00:00:00

abstract：:The last 50 years have seen great advances in the accuracy of external beam radiation therapy. Geometrical uncertainties have been reduced from a centimeter or more in presimulation, skin-mark guided days to 1-2 mm in today's image-guided radiation therapy treatments. Medical physicists, with the support and guidance ...

journal_title：Medical physics

authors： Yorke ED,Keall P,Verhaegen F

更新日期：2008-03-01 00:00:00

abstract：PURPOSE:Current respiratory motion monitoring devices used for motion synchronization in medical imaging and radiotherapy provide either 1D respiratory signal over a specific region or 3D information based on few external or internal markers. On the other hand, newer technology may offer the potential to monitor the en...

journal_title：Medical physics

authors： Fayad H,Pan T,Clement JF,Visvikis D

更新日期：2011-06-01 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：: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

abstract：PURPOSE:Flattening filter free (FFF) beams generated by medical linear accelerators have recently started to be used in radiotherapy clinical practice. Such beams present fundamental differences with respect to the standard filter flattened (FF) beams, making the generally used dosimetric parameters and definitions not...

journal_title：Medical physics

authors： Fogliata A,Garcia R,Knoos T,Nicolini G,Clivio A,Vanetti E,Khamphan C,Cozzi L

更新日期：2012-10-01 00:00:00

abstract：PURPOSE:To develop a novel system for patient-specific combined optimization of couch, collimator, and gantry angles for use in volumetric modulated arc therapy (VMAT) treatment planning. The system was designed to produce highly compact dose distributions by extensively sampling the 4π space. Automated fixed couch tra...

journal_title：Medical physics

authors： MacDonald RL,Syme A,Little B,Ward L,Thomas CG

更新日期：2020-02-01 00:00:00

abstract：:Like Medical Physics, Imaging Informatics encompasses concepts touching every aspect of the imaging chain from image creation, acquisition, management and archival, to image processing, analysis, display and interpretation. The two disciplines are in fact quite complementary, with similar goals to improve the quality ...

journal_title：Medical physics

authors： Andriole K

更新日期：2012-06-01 00:00:00

abstract：:The half-life of two I-125 encapsulated clinical seeds was measured with a Si(Li) semiconductor detector. Two measurements of each seed yielded an average half-life of 59.56 +/- 0.17 days. The results are discussed in terms of the influence of possible I-126 contamination and leakage of I-125 activity through encapsul...

journal_title：Medical physics

authors： Kubo H

更新日期：1983-11-01 00:00:00

abstract：:Total body photon irradiation (TBI) may be delivered with a number of standard techniques, typically using extended SSD geometries to obtain large field sizes. Since 1982 we have treated over 620 patients (adult and pediatric) mostly in the floor-located prone/supine treatment position with AP/PA beams using a column ...

journal_title：Medical physics

authors： Evans M,Ruo R,Seuntjens J,Freeman CR,Parker W

更新日期：2012-07-01 00:00:00

abstract：PURPOSE:The aim of this study was to demonstrate a new model for implementing a transit dosimetry system as a means of in vivo dose verification with a water equivalent electronic portal imaging device (WE-EPID) and a conventional treatment planning system (TPS). METHOD AND MATERIALS:A standard amorphous silicon (a-Si...

journal_title：Medical physics

authors： Deshpande S,Blake SJ,Xing A,Metcalfe PE,Holloway LC,Vial P

更新日期：2018-03-01 00:00:00

abstract：PURPOSE:To develop a pharmacokinetic modelfree framework to analyze the dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) data for assessment of response of brain metastases to radiation therapy. METHODS:Twenty patients with 45 analyzable brain metastases had MRI scans prior to whole brain radiation thera...

journal_title：Medical physics

authors： Farjam R,Tsien CI,Lawrence TS,Cao Y

更新日期：2014-01-01 00:00:00