Evaluation of carbon nanotube x-ray source array for stationary head computed tomography.

abstract：:Rotational angiography (RA) gantries are used routinely to acquire sequences of projection images of patients from which 3D renderings of vascular structures are generated using Feldkamp cone-beam reconstruction algorithms. However, these systems have limited resolution (<4 lp/mm). Micro-computed tomography (micro-CT)...

journal_title：Medical physics

authors： Patel V,Hoffmann KR,Ionita CN,Keleshis C,Bednarek DR,Rudin S

更新日期：2008-10-01 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：:Two side-by-side energy windows, one at the photopeak and one at lower energy, are sometimes employed in quantitative SPECT studies. We measured the count-rate losses at moderately high activities of 131I for two multihead Anger cameras in such a dual-window-acquisition mode by imaging a decaying source composed of tw...

journal_title：Medical physics

authors： Koral KF,Zasadny KR,Ackermann RJ,Ficaro EP

更新日期：1998-01-01 00:00:00

abstract：PURPOSE/OBJECTIVE:Couch and MLC tracking are two novel techniques to mitigate intrafractional tumor motion on a conventional linear accelerator, but both techniques still have residual dosimetric errors. Here, we first propose and experimentally validate a software tool to simulate couch and MLC tracking, and then use ...

journal_title：Medical physics

authors： Toftegaard J,Hansen R,Ravkilde T,Macek K,Poulsen PR

更新日期：2017-03-01 00:00:00

abstract：:Transmission data for 4-MV bremsstrahlung beams have been measured with a combination of lead and aluminum attenuators. From these data, the original energy spectra have been reconstructed using an iterative least-squares technique, previously evaluated by simulation studies. The spectra on the central axis for three ...

journal_title：Medical physics

authors： Huang PH,Kase KR,Bjärngard BE

更新日期：1983-11-01 00:00:00

abstract：PURPOSE:The collimator monitoring fill factor (CM-FF) introduced by Stelljes et al. (2017) and the FWHM fill factor (FWHM-FF) introduced by Gago-Arias et al. (2012) were determined using the measured photon fluence response functions of various 2D-arrays. The error detection capabilities of 2D-arrays were studied by co...

journal_title：Medical physics

authors： Stelljes TS,Poppinga D,Kretschmer J,Brodbek L,Looe HK,Poppe B

更新日期：2019-04-01 00:00:00

abstract：PURPOSE:Formation of new blood vessels (angiogenesis) in response to hypoxia is a fundamental event in the process of tumor growth and metastatic dissemination. However, abnormalities in tumor neovasculature often induce increased interstitial pressure (IP) and further reduce oxygenation (pO2) of tumor cells. In radiot...

journal_title：Medical physics

authors： Lagerlöf JH,Kindblom J,Bernhardt P

更新日期：2011-08-01 00:00:00

abstract：PURPOSE:The previously described 2D standardized vessel-wall-plus-plaque thickness (VWT) maps constructed from 3D ultrasound vessel wall measurements using an arc-length (AL) scaling approach adjusted the geometric variability of carotid arteries and has allowed for the comparisons of VWT distributions in longitudinal ...

journal_title：Medical physics

authors： Chen Y,Chiu B

更新日期：2016-12-01 00:00:00

abstract：:Results of an 18-alternative forced-choice experiment have shown that observers were capable of detecting a signal with a contrast of 1 in terms of 10-bit data which were displayed on a CRT monitor with an 8-bit video generator and a window width setting of 1024. We investigated the conditions under which 10-bit signa...

journal_title：Medical physics

authors： Giger ML,Ohara K,Doi K

更新日期：1986-05-01 00:00:00

abstract：PURPOSE:In previous work, the authors developed and demonstrated the concept of an image reconstruction procedure aimed to unify gated and dynamic nuclear cardiac imaging, which the authors have termed five-dimensional (5D) SPECT. Gated imaging permits the clinician to evaluate wall motion and, through the use of stres...

journal_title：Medical physics

authors： Niu X,Yang Y,King MA,Wernick MN

更新日期：2010-09-01 00:00:00

abstract：:One of the key components in modern LINAC room shielding design is the amount of 90 degrees head leakage radiation levels. With the general clinical acceptance of intensity-modulated radiation therapy (IMRT) technique, accurate knowledge of this quantity has become even more important. Measurement of 90 degrees head l...

journal_title：Medical physics

authors： Li Z,Mutic S,Low D

更新日期：2006-09-01 00:00:00

abstract：PURPOSE:State of the art to access radiofrequency (RF) heating near implants is computer modeling of the devices and solving Maxwell's equations for the specific setup. For a set of input parameters, a fixed result is obtained. This work presents a theoretical approach in the alternating current (ac) limit, which can p...

journal_title：Medical physics

authors： Ballweg V,Eibofner F,Graf H

更新日期：2011-10-01 00:00:00

abstract：PURPOSE:We investigated the feasibility of proton tomosynthesis as daily positioning of patients and compared the results with photon tomosynthesis as an alternative to conventional portal imaging or on-board cone-beam computed tomography. METHODS:Dedicated photon-like proton beam using the passively scattered proton ...

journal_title：Medical physics

authors： Min B,Kwak J,Lee J,Cho S,Park S,Yoo S,Chung K,Cho S,Lim Y,Shin D,Lee S,Kim J

更新日期：2012-06-01 00:00:00

abstract：:The calibration and quality control of compensators is conventionally performed with an ion chamber in a water-equivalent phantom. In our center, the compensator factor and four off-axis fluence ratios are measured to verify the central axis beam modulation and orientation of the compensator. Here we report the invest...

journal_title：Medical physics

authors： Menon GV,Sloboda RS

更新日期：2003-07-01 00:00:00

abstract：PURPOSE:Wide-angle free-air chambers (WAFACs) are used as primary standard measurement devices for establishing the air-kerma strength of low-energy, low-dose rate brachytherapy seeds. The National Research Council of Canada (NRC) is commissioning a primary standard wide-angle free-air chamber (NRC WAFAC) to serve the ...

journal_title：Medical physics

authors： Shen H,Culberson WS,Ross CK

更新日期：2016-07-01 00:00:00

abstract：:An indirect flat-panel imager (FPI) with avalanche gain is being investigated for low-dose x-ray imaging. It is made by optically coupling a structured x-ray scintillator CsI(Tl) to an amorphous selenium (a-Se) avalanche photoconductor called HARP (high-gain avalanche rushing photoconductor). The final electronic imag...

journal_title：Medical physics

authors： Zhao W,Li D,Reznik A,Lui BJ,Hunt DC,Rowlands JA,Ohkawa Y,Tanioka K

更新日期：2005-09-01 00:00:00

abstract：PURPOSE:To develop an accurate and efficient single-marker-based optical tracking system to enhance patient safety and quality of care in radiotherapy. METHODS:The optical tracking system consists of a Polaris camera as well as in-house software. The camera is mounted inside the treatment room and detects the location...

journal_title：Medical physics

authors： Yan G,Lu B,Mittauer K,Liu C,Li J

更新日期：2012-06-01 00:00:00

abstract：:Noise, partial volume (PV) effect, and image-intensity inhomogeneity render a challenging task for segmentation of brain magnetic resonance (MR) images. Most of the current MR image segmentation methods focus on only one or two of the above-mentioned effects. The objective of this paper is to propose a unified framewo...

journal_title：Medical physics

authors： Li X,Li L,Lu H,Liang Z

更新日期：2005-07-01 00:00:00

abstract：:It is well established that the diffusion approximation (DA) is valid for light propagation in highly scattering media, but it breaks down in nonscattering void regions. The methods that handle the void with refractive index matched boundary were previously developed. For the void with refractive index mismatched boun...

journal_title：Medical physics

authors： Lee JH,Kim S,Kim YT

更新日期：2004-08-01 00:00:00

abstract：PURPOSE:Intraventricular hemorrhage (IVH) is a major cause of brain injury in preterm neonates. Three dimensional ultrasound (US) imaging systems have been developed to visualize 3D anatomical structure of preterm neonatal intracranial ventricular system with IVH and ventricular dilation. To allow quantitative analysis...

journal_title：Medical physics

authors： Chen Y,Qiu W,Kishimoto J,Gao Y,Chan RH,de Ribaupierre S,Fenster A,Chiu B

更新日期：2015-11-01 00:00:00

abstract：:Coherent scattering of x-ray photons leads to the phenomenon of x-ray diffraction, which is widely used for determining atomic structure in materials science. A technique [x-ray diffraction computed tomography (CT)] is described, analogous to conventional CT, in which the x-ray diffraction properties of a stack of two...

journal_title：Medical physics

authors： Harding G,Kosanetzky J,Neitzel U

更新日期：1987-07-01 00:00:00

abstract：PURPOSE:To eliminate or reduce the error to Pareto optimality that arises in Pareto surface navigation when the Pareto surface is approximated by a small number of plans. METHODS:The authors propose to project the navigated plan onto the Pareto surface as a postprocessing step to the navigation. The projection attempt...

journal_title：Medical physics

authors： Bokrantz R,Miettinen K

更新日期：2015-10-01 00:00:00

abstract：:Many papers discussed the I value for water given by the ICRU, concluding that a value of about 80 +/- 2 eV instead of 67.2 eV would reproduce measured ion depth-dose curves. A change in the I value for water would have an effect on the stopping power and, hence, on the water-to-air stopping power ratio, which is impo...

journal_title：Medical physics

authors： Henkner K,Bassler N,Sobolevsky N,Jäkel O

更新日期：2009-04-01 00:00:00

abstract：:The introduction of negative pions into cancer therapy has required the construction of large new proton accelerators together with special magnetic systems to form and direct the pion beam to a patient. A summary is presented of the fundamental properties of pions and of the methods used to study the therapeutic beam...

journal_title：Medical physics

authors： Richman C

更新日期：1981-05-01 00:00:00

abstract：:It is well-known that the edge effect produced by phase contrast imaging results in the edge enhancement of x-ray images and thereby sharpens those images. It has recently been reported that phase contrast imaging using practical x-ray tubes with small focal spots has improved image sharpness as observed in the phase ...

journal_title：Medical physics

authors： Matsuo S,Katafuchi T,Tohyama K,Morishita J,Yamada K,Fujita H

更新日期：2005-08-01 00:00:00

abstract：:Intensity modulated radiation therapy (IMRT) is used to deliver highly conformal radiation doses to tumors while sparing nearby sensitive tissues. Discrepancies between calculated and measured dose distributions have been reported for regions of high dose gradients corresponding to complex radiation fluence patterns. ...

journal_title：Medical physics

authors： Bergman AM,Otto K,Duzenli C

更新日期：2004-12-01 00:00:00

abstract：PURPOSE:The GammaPod is a novel dedicated prone breast stereotactic radiosurgery (SRS) device recently developed at the University of Maryland Medical Center. This device utilizes multiple rotating Co-60 sources to create highly conformal dose distributions for breast treatments, including boosts, partial breast irradi...

journal_title：Medical physics

authors： Becker SJ,Culberson WS,Poirier Y,Mutaf Y,Niu Y,Nichols EM,Yi B

更新日期：2020-08-01 00:00:00

abstract：PURPOSE:The purpose of this study was to characterize the Hounsfield unit (HU) distributions of mesothelioma and other tissues present in contrast-enhanced thoracic CT scans, to compare the HU distributions of mesothelioma, muscle, and liver by scanner and reconstruction filter/kernel combination, and to assess interpa...

journal_title：Medical physics

authors： Corson N,Sensakovic WF,Straus C,Starkey A,Armato SG 3rd

更新日期：2011-02-01 00:00:00

abstract：PURPOSE:The availability of accurate and simple models for the estimation of x-ray spectra is of great importance for system simulation, optimization, or inclusion of photon energy information into data processing. There is a variety of publicly available tools for estimation of x-ray spectra in radiology and mammograp...

journal_title：Medical physics

authors： Sisniega A,Desco M,Vaquero JJ

更新日期：2014-01-01 00:00:00

abstract：PURPOSE:In recent years, laser-based acceleration of charged particles has rapidly progressed and medical applications, e.g., in radiotherapy, might become feasible in the coming decade. Requirements are monoenergetic particle beams with long-term stable and reproducible properties as well as sufficient particle intens...

journal_title：Medical physics

authors： Beyreuther E,Enghardt W,Kaluza M,Karsch L,Laschinsky L,Lessmann E,Nicolai M,Pawelke J,Richter C,Sauerbrey R,Schlenvoigt HP,Baumann M

更新日期：2010-04-01 00:00:00