An outlook on x-ray CT research and development.

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：:One limitation to the widespread implementation of Monte Carlo (MC) patient dose-calculation algorithms for radiotherapy is the lack of a general and accurate source model of the accelerator radiation source. Our aim in this work is to investigate the sensitivity of the photon-beam subsource distributions in a MC sour...

journal_title：Medical physics

authors： Fix MK,Keall PJ,Siebers JV

更新日期：2005-04-01 00:00:00

abstract：:Patient-specific intensity-modulated radiotherapy (IMRT) verifications require an accurate two-dimensional dosimeter that is not labor-intensive. We assessed the precision and reproducibility of film calibrations over time, measured the elemental composition of the film, measured the intermittency effect, and measured...

journal_title：Medical physics

authors： Childress NL,Salehpour M,Dong L,Bloch C,White RA,Rosen II

更新日期：2005-02-01 00:00:00

abstract：:A test device which can indirectly measure the performance of an automatic exposure control system and which offers the potential to reduce the time and film requirements for such tests has been evaluated. Evaluation results demonstrate that the device can successfully predict image optical density to within +/- 0.10 ...

journal_title：Medical physics

authors： Rossi RP

更新日期：1994-01-01 00:00:00

abstract：:A computationally efficient pseudodynamical filtering setup is established for elasticity imaging (i.e., reconstruction of shear modulus distribution) in soft-tissue organs given statically recorded and partially measured displacement data. Unlike a regularized quasi-Newton method (QNM) that needs inversion of ill-con...

journal_title：Medical physics

authors： Banerjee B,Roy D,Vasu RM

更新日期：2009-08-01 00:00:00

abstract：PURPOSE:Plastic scintillation detectors are used for dosimetry in small radiation fields with high dose gradients, e.g., provided by β-emitting sources like 106 Ru/106 Rh eye plaques. A drawback is a background signal caused by Cerenkov radiation generated by electrons passing the optical fibers (light guides) of this ...

journal_title：Medical physics

authors： Eichmann M,Thomann B

更新日期：2017-09-01 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:Dynamic 18 F-FDG PET allows quantitative estimation of cerebral glucose metabolism both at the regional and local (voxel) level. Although sensitive to noise and highly computationally expensive, nonlinear least-squares (NLS) optimization stands as the reference approach for the estimation of the kinetic model p...

journal_title：Medical physics

authors： Ben Bouallègue F,Vauchot F,Mariano-Goulart D

更新日期：2019-03-01 00:00:00

abstract：PURPOSE:Water equivalent diameter (WED) is the preferred surrogate for patient size in CT. It is better than geometric size surrogates and patient weight/height/BMI/age because it correlates the best with x-ray attenuation. The administration of oral/IV contrast agents increases a patient's attenuation and should there...

journal_title：Medical physics

authors： Viggiano B,Rose S,Szczykutowicz TP

更新日期：2021-01-13 00:00:00

abstract：:Computed tomography colonography (CTC) is a minimally invasive method that allows the evaluation of the colon wall from CT sections of the abdomen/pelvis. The primary goal of CTC is to detect colonic polyps, precursors to colorectal cancer. Because imperfect cleansing and distension can cause portions of the colon wal...

journal_title：Medical physics

authors： Li P,Napel S,Acar B,Paik DS,Jeffrey RB Jr,Beaulieu CF

更新日期：2004-10-01 00:00:00

abstract：:We are developing computerized methods for characterizing the bone texture pattern from digitized skeletal radiographs. For this method to be useful clinically, it must be able to distinguish between weak and strong bone under the range of exposure conditions potentially encountered in the clinical setting. In this st...

journal_title：Medical physics

authors： Chinander MR,Giger ML,Martell JM,Favus MJ

更新日期：2000-01-01 00:00:00

abstract：:A novel iterative penalized likelihood algorithm with evolutionary components for the optimization of beamlet fluences for intensity modulated radiation therapy (IMRT) is presented. This algorithm is designed to be flexible in terms of the objective function and automatically escalates dose, as long as the objective f...

journal_title：Medical physics

authors： Baydush AH,Marks LB,Das SK

更新日期：2004-08-01 00:00:00

abstract：:A systems analysis of reduced dose mammography with scatter removal has quantitatively specified the relationships between the several parameters in mammography systems. While the results are only preliminary in the sense that they need to be proven experimentally, they do seem to provide a good feel for the nature of...

journal_title：Medical physics

authors： Muntz EP

更新日期：1979-03-01 00:00:00

abstract：PURPOSE:Transrectal ultrasound (TRUS)-guided needle biopsy is the current gold standard for prostate cancer diagnosis. However, up to 40% of prostate cancer lesions appears isoechoic on TRUS. Hence, TRUS-guided biopsy has a high false negative rate for prostate cancer diagnosis. Magnetic resonance imaging (MRI) is bett...

journal_title：Medical physics

authors： Sparks R,Bloch BN,Feleppa E,Barratt D,Moses D,Ponsky L,Madabhushi A

更新日期：2015-03-01 00:00:00

abstract：:In this study, BrachyDose, a recently developed EGSnrc Monte Carlo code for rapid brachytherapy dose calculations, has been benchmarked by reproducing previously published dosimetry parameters for three brachytherapy seeds with varied internal structure and encapsulation. Calculations are performed for two 125I seeds ...

journal_title：Medical physics

authors： Taylor RE,Yegin G,Rogers DW

更新日期：2007-02-01 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

authors： Bortfeld T,Oelfke U,Nill S

更新日期：2000-11-01 00:00:00

abstract：:As a potentially important technology for medical x-ray computed tomography (CT), lambda tomography (LT) is to reconstruct a gradient-like image only from local projection data. Based on our recently derived exact fan-beam LT formula, [H. Y. Gu and G. Wang, Int. J. Biomed. Imaging 2006(1), 1-9 (2006)] here we propose ...

journal_title：Medical physics

authors： Yu H,Ye Y,Wang G

更新日期：2006-10-01 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：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:The authors investigated the potential of optimized noncoplanar irradiation trajectories for volumetric modulated arc therapy (VMAT) treatments of nasopharyngeal patients and studied the trade-off between treatment plan quality and delivery time in radiation therapy. METHODS:For three nasopharyngeal patients, ...

journal_title：Medical physics

authors： Wild E,Bangert M,Nill S,Oelfke U

更新日期：2015-05-01 00:00:00

abstract：:Intensity Modulated Arc Therapy (IMAT) is a rotational variant of Intensity Modulated Radiation Therapy (IMRT) that can be implemented with or without angular dose rate optimization. The purpose of this study is to determine the inter-relationship among arc range, Multi-Leaf Collimator (MLC) leaf positions and angular...

journal_title：Medical physics

authors： Oliver M,Chen J,Wong E

更新日期：2008-07-01 00:00:00

abstract：PURPOSE:For accurate tissue inhomogeneity correction in radiotherapy treatment planning, the authors had previously proposed a novel conversion of the energy-subtracted CT number to an electron density (ΔHU-ρe conversion), which provides a single linear relationship between ΔHU and ρe over a wide ρe range. The purpose ...

journal_title：Medical physics

authors： Saito M,Tsukihara M

更新日期：2014-07-01 00:00:00

abstract：:A simple approach was developed that calculates the output factors and tissue maximum ratio of an asymmetric field at any point within the open field, and specifically both at the central axis (when the jaws do not shadow it) and at the effective center of the open field, using the existing tables for symmetric fields...

journal_title：Medical physics

authors： Rosenberg I,Chu JC,Saxena V

更新日期：1995-01-01 00:00:00

abstract：PURPOSE:The purpose of this paper was to present a method of determining the dose profile of the beam bow-tie filter (BTF) without the need for fixing the x ray tube in a position or using special instruments or dosimeters other than the ordinary types of ion chambers used for CT dosimetry (e.g., Farmer chamber). METH...

journal_title：Medical physics

authors： Al-Senan R

更新日期：2018-11-01 00:00:00

abstract：:Inherent in the line-spread function approach in modulation transfer function (MTF) determinations is the use of a microdensitometer to scan the density pattern resulting from the line exposure. In such a procedure, loss of fidelity in the distribution being scanned is expected. This loss is due in part to the use of ...

journal_title：Medical physics

authors： Villafana T

更新日期：1975-09-01 00:00:00

abstract：PURPOSE:To investigate the inconsistency of recent literature on the effect of magnetic field on the response of radiochromic films, we studied the influence of 0.35 T magnetic field on dosimetric response of EBT3 and EBT-XD GafchromicTM films. METHODS:Two different models of radiochromic films, EBT3 and EBT-XD, were ...

journal_title：Medical physics

authors： Darafsheh A,Hao Y,Maraghechi B,Cammin J,Reynoso FJ,Khan R

更新日期：2020-09-01 00:00:00

abstract：:Due to practical limitations in data acquisition, 3-D computed tomography systems must attempt to provide rapid reconstructions of acceptable quality from a limited number of views. The use of convolution backprojection (CBP) for image reconstruction from an inadequate number of projections, results in view aliasing a...

journal_title：Medical physics

authors： Galigekere RR,Wiesent K,Holdsworth DW

更新日期：1999-06-01 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：:The attenuating properties of several types of lead (Pb)-based and non-Pb radiation shielding materials were studied and a correlation was made of radiation attenuation, materials properties, calculated spectra and ambient dose equivalent. Utilizing the well-characterized x-ray and gamma ray beams at the National Rese...

journal_title：Medical physics

authors： McCaffrey JP,Shen H,Downton B,Mainegra-Hing E

更新日期：2007-02-01 00:00:00

abstract：:Effective radioimmunotherapy may depend on a priori knowledge of the radiation absorbed dose distribution obtained by trace imaging activities administered to a patient before treatment. A new, fast, and effective treatment planning approach is developed to deal with a heterogeneous activity distribution. Calculation ...

journal_title：Medical physics

authors： Erdi AK,Yorke ED,Loew MH,Erdi YE,Sarfaraz M,Wessels BW

更新日期：1998-11-01 00:00:00