The accuracy of SPECT brain activation images: propagation of registration errors.

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：:A technique was developed to reduce the size and magnitude of the hot and cold spots in the abutting regions of photon and electron fields. The photon and electron fields were set up such that the photon field extended approximately 2 cm into the electron field in the abutting region. The region of the photon beam tha...

journal_title：Medical physics

authors： Li JG,Xing L,Boyer AL,Hamilton RJ,Spelbring DR,Turian JV

更新日期：1999-11-01 00:00:00

abstract：:An algorithmic solution to the biological effective dose (BED) calculation from the Lea-Catcheside formula for a piecewise defined function is presented. Data from patients treated for metastatic thyroid cancer were used to illustrate the solution. The Lea-Catcheside formula for the G-factor of the BED is integrated n...

journal_title：Medical physics

authors： Hobbs RF,Sgouros G

更新日期：2009-03-01 00:00:00

abstract：:A water beam imaging system (WBIS) has been developed and used to verify dose distributions for intensity modulated radiotherapy using dynamic multileaf collimator. This system consisted of a water container, a scintillator screen, a charge-coupled device camera, and a portable personal computer. The scintillation ima...

journal_title：Medical physics

authors： Li JS,Boyer AL,Ma CM

更新日期：2001-12-01 00:00:00

abstract：:We compare the results of absorbed dose determined at reference conditions according to the AAPM TG-21 dose calibration protocol and the new AAPM TG-51 protocol. The AAPM TG-21 protocol for absorbed dose calibration is based on ionization chambers having exposure calibration factors for 60Co gamma rays, N(x). The new ...

journal_title：Medical physics

authors： Ding GX,Cygler JE,Kwok CB

更新日期：2000-06-01 00:00:00

abstract：PURPOSE:To demonstrate the feasibility of a three-plenoptic camera projection, scintillation-based dosimetry system for measuring three-dimensional (3D) dose distributions of static photon radiation fields. METHODS:Static x-ray photon beams were delivered to a cubic plastic scintillator volume embedded within acrylic ...

journal_title：Medical physics

authors： Rilling M,Allain G,Thibault S,Archambault L

更新日期：2020-08-01 00:00:00

abstract：:Absorbed doses from main charged-particle beams and charged-particle fragments have been measured with high accuracy for particle therapy, but there are few reports for doses from neutron components produced as fragments. This study describes the measurements on neutron doses produced by carbon beams; microdosimetric ...

journal_title：Medical physics

authors： Endo S,Tanaka K,Takada M,Onizuka Y,Miyahara N,Sato T,Ishikawa M,Maeda N,Hayabuchi N,Shizuma K,Hoshi M

更新日期：2007-09-01 00:00:00

abstract：PURPOSE:Two diodes which do not require correction factors for small field relative output measurements are designed and validated using experimental methodology. This was achieved by adding an air layer above the active volume of the diode detectors, which canceled out the increase in response of the diodes in small f...

journal_title：Medical physics

authors： Charles PH,Cranmer-Sargison G,Thwaites DI,Kairn T,Crowe SB,Pedrazzini G,Aland T,Kenny J,Langton CM,Trapp JV

更新日期：2014-10-01 00:00:00

abstract：PURPOSE:In C-arm computed tomography (CT), the field of view (FOV) is often not sufficient to acquire certain anatomical structures, e.g., a full hip or thorax. Proposed methods to extend the FOV use a fixed detector displacement and a 360° scan range to double the radius of the FOV. These trajectories are designed for...

journal_title：Medical physics

authors： Herbst M,Schebesch F,Berger M,Choi JH,Fahrig R,Hornegger J,Maier A

更新日期：2015-05-01 00:00:00

abstract：:In the presence of intrafraction organ motion, target localization uncertainty can greatly hamper the advantage of highly conformal dose techniques such as intensity modulated radiation therapy (IMRT). To minimize the adverse dosimetric effect caused by tumor motion, a real-time knowledge of the tumor position is requ...

journal_title：Medical physics

authors： Wiersma RD,Mao W,Xing L

更新日期：2008-04-01 00:00:00

abstract：PURPOSE:The need for an accurate lesion segmentation tool in 18FDG PET is a prerequisite for the estimation of lesion response to therapy, for radionuclide dosimetry, and for the application of 18FDG PET to radiotherapy planning. In this work, the authors have developed an iterative method based on a mathematical fit d...

journal_title：Medical physics

authors： Nehmeh SA,El-Zeftawy H,Greco C,Schwartz J,Erdi YE,Kirov A,Schmidtlein CR,Gyau AB,Larson SM,Humm JL

更新日期：2009-10-01 00:00:00

abstract：PURPOSE:The feasibility of magnetic resonance image (MRI)-based proton therapy is based, among several other factors, on the implementation of appropriate extensions on current dose calculation methods. This work aims to develop a pencil beam algorithm (PBA) for dose calculation of proton beams within magnetic field re...

journal_title：Medical physics

authors： Padilla-Cabal F,Georg D,Fuchs H

更新日期：2018-05-01 00:00:00

abstract：:A general expression is derived for the NMR signal from a fluid undergoing random directional flow such as encountered within the microcirculation. The dependence of the echo amplitude on flow velocity, sample morphology, and experimental parameters are described in terms of a temporal velocity autocorrelation functio...

journal_title：Medical physics

authors： Kennan RP,Gao JH,Zhong J,Gore JC

更新日期：1994-04-01 00:00:00

abstract：PURPOSE:There are several options to consider in the design of a vault that will house a cyclotron for radioisotopes production with regards to the door entrance. Alternatives are a direct-shielded door, a simple maze, or a double-legged maze. In this work, the impact of the neutron and photon doses at the vault entran...

journal_title：Medical physics

authors： Facure A,França WF

更新日期：2010-12-01 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：:Double checking of the monitor units (MU) is an important step in the quality assurance (QA) process in radiosurgery. In this paper we propose the use of an independent algorithm constructed using the ellipsoid which best fits the measurements taken with the bubble head frame. The monitor units calculated by this inde...

journal_title：Medical physics

authors： Ramos LI,Monge RM,Aristu JJ,Moreno LA

更新日期：2008-01-01 00:00:00

abstract：:A method is presented for calculation of transmission functions for high energy photon beams through patients. These functions are being used in our clinic for prediction of portal dose images (PDIs) which are compared with PDIs measured with an electronic portal imaging device (EPID). The calculations are based on th...

journal_title：Medical physics

authors： Pasma KL,Heijmen BJ,Kroonwijk M,Visser AG

更新日期：1998-06-01 00:00:00

abstract：PURPOSE:The aim of this research was to explore x-ray beam parameters with intent to optimize pediatric x-ray settings in the cardiac catheterization laboratory. This study examined the effects of peak x-ray tube voltage (kVp) and of copper (Cu) x-ray beam filtration independently on the image quality to dose balance f...

journal_title：Medical physics

authors： Gislason AJ,Davies AG,Cowen AR

更新日期：2010-10-01 00:00:00

abstract：:Mammography is the most effective method for breast cancer screening available today. However, the low positive predictive value of breast biopsy resulting from mammogram interpretation leads to approximately 70% unnecessary biopsies with benign outcomes. To reduce the high number of unnecessary breast biopsies, sever...

journal_title：Medical physics

authors： Elter M,Schulz-Wendtland R,Wittenberg T

更新日期：2007-11-01 00:00:00

abstract：PURPOSE:Recent recommendations of the International Commission on Radiological Protection state that the use of effective dose (E) for assessing patient exposure has severe limitations, though it can be kept for dose comparisons. In cardiology procedures, the equivalent dose (H(T)) is one of the most appropriate dose q...

journal_title：Medical physics

authors： Compagnone G,Ortolani P,Domenichelli S,Ovi V,Califano G,Dall'Ara G,Marzocchi A

更新日期：2011-04-01 00:00:00

abstract：:Intensity modulated radiation therapy (IMRT) with a dynamic multileaf collimator (DMLC) requires synchronization of DMLC leaf motion with dose delivery. A delay in DMLC communication is known to cause leaf lag and lead to dosimetric errors. The errors may be exacerbated by gated operation. The purpose of this study wa...

journal_title：Medical physics

authors： Duan J,Shen S,Fiveash JB,Brezovich IA,Popple RA,Pareek PN

更新日期：2003-08-01 00:00:00

abstract：PURPOSE:Both spatial and biological information are necessary in order to perform true optimization of a treatment plan and for predicting clinical outcome. The goal of this work is to develop an enhanced treatment plan evaluation tool which incorporates biological parameters and retains spatial dose information. METH...

journal_title：Medical physics

authors： Zhao B,Joiner MC,Orton CG,Burmeister J

更新日期：2010-11-01 00:00:00

abstract：:Depending on the clinical application, it is frequently necessary to tilt the gantry of an x-ray CT system with respect to the patient and couch. For single-slice fan-beam systems, tilting the gantry introduces no errors or artifacts. Most current systems, however, are helical multislice systems with up to 16 slices. ...

journal_title：Medical physics

authors： Hein I,Taguchi K,Silver MD,Kazama M,Mori I

更新日期：2003-12-01 00:00:00

abstract：:We have measured the linearity, spatial resolution (MTF), noise (NPS), and signal-to-noise characteristics (DQE) of an electronic portal imaging device (EPID) based on an amorphous silicon flat-panel array. The array has a 128 x 128-pixel matrix and each pixel is 0.75 x 0.75 mm2 in dimension so the array covers an are...

journal_title：Medical physics

authors： Munro P,Bouius DC

更新日期：1998-05-01 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：PURPOSE:The thermoluminescence dosimeter (TLD) has desirable features including low cost, reusability, small size, and relatively low energy dependence. However, the commonly available poly-crystal TLDs (e.g., TLD-100) exhibit high interdetector variability that requires individual calibration for high detection accura...

journal_title：Medical physics

authors： Shang D,Gu W,Landers A,Woods K,Yu V,Neph R,Tenn S,Sheng K

更新日期：2020-01-01 00:00:00

abstract：PURPOSE:To determine if NSCLC GTV CT textures can be predictive for tumor shrinkage after proton therapy with concurrent chemotherapy. METHODS:Simulation and weekly 4DCTs were obtained from 25 patients with locally advanced NSCLC treated by proton therapy at a 74 Gy dose level with concurrent chemotherapy. In-house de...

journal_title：Medical physics

authors： Hunter L,Chen Y,Zhang L,Liao Z,Dong L,Court L

更新日期：2012-06-01 00:00:00

abstract：:In x-ray spectral measurement using a semiconductor detector system, accurate positioning of the detector in front of the anode is very important. This needs accurate determination of the focal spot position on the target in an x-ray tube. We present a simple technique to determine the focal spot position accurately. ...

journal_title：Medical physics

authors： Kubota H,Ozaki Y,Matsumoto M,Kanamori H

更新日期：1993-07-01 00:00:00

abstract：:The photon spectra in vacuum around four types of 192Ir HDR brachytherapy sources are calculated using the Monte Carlo code EGS4 and the most recent spectral information on 192Ir decay. The air-kerma strengths per unit activity are calculated based on the photon fluence around a bare 192Ir source and around each of fo...

journal_title：Medical physics

authors： Borg J,Rogers DW

更新日期：1999-11-01 00:00:00

abstract：PURPOSE:As the predominant driver of respiratory motion, the diaphragm represents a key surrogate for motion management during the irradiation of thoracic cancers. Existing approaches to diaphragm tracking often produce phase-based estimates, suffer from lateral side failures or are not executable in real-time. In this...

journal_title：Medical physics

authors： Hindley N,Keall P,Booth J,Shieh CC

更新日期：2019-10-01 00:00:00