On the effective point of measurement in megavoltage photon beams.

abstract：PURPOSE:The cone beam computed tomography (CBCT) guided small animal radiation research platform (SARRP) has been developed for focal tumor irradiation, allowing laboratory researchers to test basic biological hypotheses that can modify radiotherapy outcomes in ways that were not feasible previously. CBCT provides exce...

journal_title：Medical physics

authors： Yang Y,Wang KK,Eslami S,Iordachita II,Patterson MS,Wong JW

更新日期：2015-04-01 00:00:00

abstract：:Proton NMR spectroscopy was applied to quantitate the measurement of total body water/fat distributions in vivo. A special MR protocol was developed to excite a thick slab of tissue and display the magnitude NMR spectrum of the collected response signal. Very short echo time TE (8 ms) and long repetition time TR (4000...

journal_title：Medical physics

authors： Sobol WT,Elster AD,Hinson WH,Chwals WJ

更新日期：1992-01-01 00:00:00

abstract：PURPOSE:When designing a collimation system for pencil beam spot scanning proton therapy, a decision must be made whether or not to rotate, or focus, the collimator to match beamlet deflection as a function of off-axis distance. If the collimator is not focused, the beamlet shape and fluence will vary as a function of ...

journal_title：Medical physics

authors： Geoghegan TJ,Nelson NP,Flynn RT,Hill PM,Rana S,Hyer DE

更新日期：2020-07-01 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：:This paper is concerned with the proposed Birmingham accelerator-based epithermal neutron beam for boron neutron capture therapy (BNCT). In particular, the option of producing a therapy beam at an orthogonal direction to the incoming protons is considered. Monte Carlo radiation transport simulations, both with and wit...

journal_title：Medical physics

authors： Allen DA,Beynon TD,Green S

更新日期：1999-01-01 00:00:00

abstract：PURPOSE:Digital breast tomosynthesis (DBT) is becoming an important part of breast cancer screening and diagnosis. Compared to two-dimensional mammography, tomosynthesis introduces limited three-dimensional (3D) resolution, but maintains high in-plane resolution, low dose, and allows for similar clinical protocols. The...

journal_title：Medical physics

authors： Berggren K,Cederström B,Lundqvist M,Fredenberg E

更新日期：2018-10-01 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

abstract：PURPOSE:The segmentation accuracy of medical images was improved by increasing the number of training samples using a local image warping technique. The performance of the proposed method was evaluated in the segmentation of breast masses, prostate and brain tumors, and lung nodules. METHODS:We propose a simple data a...

journal_title：Medical physics

authors： Liu H,Cao H,Song E,Ma G,Xu X,Jin R,Liu T,Liu L,Liu D,Hung CC

更新日期：2020-12-10 00:00:00

abstract：PURPOSE:Liver segmentation is an important prerequisite for the assessment of liver cancer treatment options like tumor resection, image-guided radiation therapy (IGRT), radiofrequency ablation, etc. The purpose of this work was to evaluate a new approach for liver segmentation. METHODS:A graph cuts segmentation metho...

journal_title：Medical physics

authors： Beichel R,Bornik A,Bauer C,Sorantin E

更新日期：2012-03-01 00:00:00

abstract：PURPOSE:The purpose of this work was to examine the suitability of VIPARnd polymer gel-9.4 T magnetic resonance microimaging system for high spatial resolution dose distribution measurements. METHODS:The VIPARnd samples (3 cm in outside diameter and 12 cm in height) were exposed to ionizing radiation by using a linear...

journal_title：Medical physics

authors： Skorupa A,Woźnica A,Ciszek M,Staniszewski M,Kijonka M,Kozicki M,Woźniak B,Orlef A,Polański A,Boguszewicz Ł,Sokół M

更新日期：2020-08-01 00:00:00

abstract：PURPOSE:Positron emission tomography (PET) is an important tool for nuclear medical imaging. It has been widely used in clinical diagnosis, scientific research, and drug testing. PET is a kind of emission computed tomography. Its basic imaging principle is to use the positron annihilation radiation generated by radionu...

journal_title：Medical physics

authors： Zhang W,Gao J,Yang Y,Liang D,Liu X,Zheng H,Hu Z

更新日期：2019-11-01 00:00:00

abstract：PURPOSE:Patient motion is a common problem during dynamic positron emission tomography (PET) scans for quantification of myocardial blood flow (MBF). The purpose of this study was to quantify the prevalence of body motion in a clinical setting and evaluate with realistic phantoms the effects of motion on blood flow qua...

journal_title：Medical physics

authors： Hunter CR,Klein R,Beanlands RS,deKemp RA

更新日期：2016-04-01 00:00:00

abstract：PURPOSE:To evaluate the availability and performance of pencil beam algorithm for fast neutrons radiotherapy dose calculations and to achieve improvements in universality, speed and inhomogeneities corrections. METHODS:Pencil beam (PB) method uses integration of dose kernel cross field size to estimate dose distributi...

journal_title：Medical physics

authors： Moiseev A,Klimanov V

更新日期：2012-06-01 00:00:00

abstract：:The variance in the number of x-ray photons absorbed by a detector is derived from theoretical considerations. The distributions in the number of x-ray photons produced by the x-ray tube, transmitted through the patient, and absorbed by the detector are described. These distributions are compounded to yield a distribu...

journal_title：Medical physics

authors： Rimkus D,Baily NA

更新日期：1983-07-01 00:00:00

abstract：:The EGS4 Monte Carlo code has been used to investigate the response of a PTW/diamond detector irradiated in both clinical and monoenergetic megavoltage electron beams ranging in energy from 5 to 20 MeV. The sensitive volume of the PTW/diamond detector simulated has a thickness of 0.4 mm and a diameter of 4.4 mm. Irrad...

journal_title：Medical physics

authors： Mobit PN,Sandison GA

更新日期：1999-05-01 00:00:00

abstract：:A prototype Emission-Transmission Computed Tomography (ETCT) system is being developed that will acquire single-slice x-ray transmission CT images simultaneously with single photon emission computed tomography (SPECT) images. This system will permit the correlation of anatomical information from x-ray CT with function...

journal_title：Medical physics

authors： Liew SC,Hasegawa BH

更新日期：1991-09-01 00:00:00

abstract：:Treatment simulation is usually performed with a conventional simulator using kV X-rays or with a computed tomography (CT) simulator before the treatment course begins. The purpose is to verify patient setup under the same conditions as for treatment planning. Systematic (preparation) setup errors can be introduced by...

journal_title：Medical physics

authors： Wu Q,Lockman D,Wong J,Yan D

更新日期：2007-05-01 00:00:00

abstract：:Purpose To investigate narrow, elongated magnetically focused proton beams and compare their properties with passively collimated beams using Monte Carlo simulation. METHODS:We performed Geant4 Monte Carlo simulations involving a single quadrapole focusing magnet, thereby creating a flattened beam with an elongated e...

journal_title：Medical physics

authors： McAuley G,Barnes S,Wroe A,Slater J

更新日期：2012-06-01 00:00:00

abstract：PURPOSE:To develop an automatic knot placement algorithm to enable the use of NonUniform Rational B-Splines (NURBS) in deformable image registration. METHODS:The authors developed a two-step approach to fit a known displacement vector field (DVF). An initial fit was made with uniform knot spacing. The error generated ...

journal_title：Medical physics

authors： Jacobson TJ,Murphy MJ

更新日期：2011-08-01 00:00:00

abstract：PURPOSE:Material-specific imaging and virtual monochromatic imaging/analysis are the two forms of spectral imaging in CT implemented via either energy-integration or photon-counting data acquisition. Aimed at further understanding the fundamentals and providing guidelines on its design and implementation, we quantitati...

journal_title：Medical physics

authors： Tang X,Ren Y

更新日期：2021-01-07 00:00:00

abstract：PURPOSE:Most radiation therapy optimization problems can be formulated as an unconstrained problem and solved efficiently by quasi-Newton methods such as the Limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm. However, several next generation planning techniques such as total variation regularization- b...

journal_title：Medical physics

authors： Liu X,Pelizzari C,Belcher AH,Grelewicz Z,Wiersma RD

更新日期：2017-04-01 00:00:00

abstract：:We have developed an analytic solution for spatially resolved diffuse reflectance within the deltaP1 approximation to the radiative transport equation for a semi-infinite homogeneous turbid medium. We evaluate the performance of this solution by comparing its predictions with those provided by Monte Carlo simulations ...

journal_title：Medical physics

authors： Seo I,Hayakawa CK,Venugopalan V

更新日期：2008-02-01 00:00:00

abstract：:Reconstruction of electron spectra of medical accelerators from measured depth dose distributions is an attractive tool for commissioning of a Monte Carlo treatment planning system. However, the reconstruction method is an inverse radiation transport problem which is poorly conditioned, in the sense it may become unst...

journal_title：Medical physics

authors： Chvetsov AV,Sandison GA

更新日期：2002-04-01 00:00:00

abstract：PURPOSE:The limited-angle intrafractional verification (LIVE) system was developed to track tumor movement during stereotactic body radiation therapy (SBRT). However, the four-dimensional (4D) MV/kV imaging procedure results in additional radiation dose to patients. This study is to quantify imaging radiation dose from...

journal_title：Medical physics

authors： Ding GX,Zhang Y,Ren L

更新日期：2019-06-01 00:00:00

abstract：PURPOSE:To investigate image-registration errors when using fiducial markers with a manual method and the point-based rigid-body registration (PRBR) algorithm in accelerated partial breast irradiation (APBI) patients, with accompanying fiducial deviations. METHODS:Twenty-two consecutive patients were enrolled in a pro...

journal_title：Medical physics

authors： Inoue M,Yoshimura M,Sato S,Nakamura M,Yamada M,Hirata K,Sasaki M,Fujimoto T,Ogura M,Hiraoka M

更新日期：2015-04-01 00:00:00

abstract：:In this article, the authors present a novel real-time cancer detection technique by using needle insertion forces in conjunction with patient-specific criteria during percutaneous interventions. Needle insertion experiments and pathological analysis were performed for developing a computer-aided detection (CAD) model...

journal_title：Medical physics

authors： Yan K,Li L,Joseph J,Rubens DR,Messing EM,Liao L,Yu Y

更新日期：2009-07-01 00:00:00

abstract：:Modern radiotherapy linacs often use carbon fibre for their couch tops due to its radio translucent properties. Beam attenuation by the couches is often ignored during planning and MU calculation. This work examines beam attenuation and loss of "skin sparing" (dose build up region) when various photon beams transit ei...

journal_title：Medical physics

authors： Niedbala M,Nyiri B,Gerig L

更新日期：2008-07-01 00:00:00

abstract：PURPOSE:Although x-ray projection mammography has been very effective in early detection of breast cancer, its utility is reduced in the detection of small lesions that are occult or in dense breasts. One drawback is that the inherent superposition of parenchymal structures makes visualization of small lesions difficul...

journal_title：Medical physics

authors： Le Huy Q,Ducote JL,Molloi S

更新日期：2010-03-01 00:00:00

abstract：PURPOSE:The performance of a newly developed, high resolution, microangiographic fluoroscope (MAF) (35 μm pixel pitch and 300 μm thick CsI phosphor) was evaluated using a generalized linear system analysis and compared with that of a standard amorphous Si thin film transistor flat panel detector (FPD) (194 μm pixel pit...

journal_title：Medical physics

authors： Jain A,Bednarek DR,Rudin S

更新日期：2013-03-01 00:00:00

abstract：PURPOSE:The purpose of this study is to quantify the change in monthly VMAT quality assurance (QA) and determine the tests to maintain consistent delivery with a baseline. METHODS:VMAT monthly QA has been performed for over 14 months on two Elekta Synergy LINACs. A baseline was established at acceptance and the monthl...

journal_title：Medical physics

authors： Stenbeck J,Oves S,Gebreamlak W,Alkhatib H

更新日期：2012-06-01 00:00:00