A thermoregulated enclosure for controlling thermal drift in a radiation calorimeter.

abstract：:Modulation of the activity of the subthalamic nucleus (STN) using deep brain stimulation (DBS) in patients with advanced Parkinson's disease is the most common procedure performed today by functional neurosurgeons. The STN contours cannot be entirely identified on common 1.5 T images; in particular, the ventromedial b...

journal_title：Medical physics

authors： Stancanello J,Muacevic A,Sebastiano F,Modugno N,Cerveri P,Ferrigno G,Uggeri F,Romanelli P

更新日期：2008-07-01 00:00:00

abstract：:Variation of the photoactivation rate across radiation fields of three different bremsstrahlung beams of two medical accelerators has been measured, making use of the photonuclear reactions in natural indium probes: 115In(y,y')115mIn and 115In(y,n)114mIn. The third nuclear reaction, 115In(n,y)116mIn, was used to detec...

journal_title：Medical physics

authors： Krmar M,Slivka J,Bikit I,Conkić L,Rudić A

更新日期：1999-04-01 00:00:00

abstract：PURPOSE:The presence of respiratory motion during radiation treatment leads to degradation of the expected dose distribution, both for target coverage and healthy tissue sparing, particularly for techniques like pencil beam scanning proton therapy which have dynamic delivery systems. While tools exist to estimate this ...

journal_title：Medical physics

authors： Pepin MD,Tryggestad E,Wan Chan Tseung HS,Johnson JE,Herman MG,Beltran C

更新日期：2018-11-01 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：PURPOSE:Transcranial focused ultrasound is an emerging therapeutic modality that can be used to perform noninvasive neurosurgical procedures. The current clinical transcranial phased array operates at 650 kHz, however the development of a higher frequency array would enable more precision, while reducing the risk of st...

journal_title：Medical physics

authors： Pajek D,Hynynen K

更新日期：2013-12-01 00:00:00

abstract：:An instrument for daily beam checks of medical accelerators is described. Using three silicon diodes, the instrument provides information about calibration, beam symmetry, flatness, and energy variation for both photon and electron beams. Operating characteristics of the instrument and the electronic circuit design pe...

journal_title：Medical physics

authors： Lutz WR,Maddox BJ,Kase KR

更新日期：1985-07-01 00:00:00

abstract：:Cardiac arrhythmias are a major health burden, associated with reduced quality of life and substantial morbidity and mortality. Current therapy includes moderately effective medication and catheter-based ablation of arrhythmogenic substrates in the heart. Catheter interventions frequently have to be repeated due to re...

journal_title：Medical physics

authors： Graeff C,Bert C

更新日期：2018-11-01 00:00:00

abstract：:Intraoperative three-dimensional reconstruction of seed locations during prostate brachytherapy for purposes of immediate computation of radiation dosimetry is an active area of current investigation, including methods which use multiple fluoroscopic projections. A simulation study using seed locations extracted from ...

journal_title：Medical physics

authors： Su Y,Davis BJ,Herman MG,Robb RA

更新日期：2004-05-01 00:00:00

abstract：PURPOSE:The recent introduction of digital tomosynthesis imaging into routine clinical use has enabled the acquisition of volumetric patient data within a standard radiographic examination. Tomosynthesis requires the acquisition of multiple projection views, requiring additional dose compared to a standard projection e...

journal_title：Medical physics

authors： Sabol JM

更新日期：2009-12-01 00:00:00

abstract：PURPOSE:The purpose of this study was to develop a dual-modality positron emission tomography (PET)/magnetic resonance imaging (MRI) with insertable PET for simultaneous PET and MR imaging of the human brain. METHODS:The PET detector block was composed of a 4 × 4 matrix of detector modules, each consisting of a 4 × 4 ...

journal_title：Medical physics

authors： Jung JH,Choi Y,Jung J,Kim S,Lim HK,Im KC,Oh CH,Park HW,Kim KM,Kim JG

更新日期：2015-05-01 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：PURPOSE:To formulate convex planning objectives of treatment plan multicriteria optimization with explicit relationships to the dose-volume histogram (DVH) statistics used in plan quality evaluation. METHODS:Conventional planning objectives are designed to minimize the violation of DVH statistics thresholds using pena...

journal_title：Medical physics

authors： Engberg L,Forsgren A,Eriksson K,Hårdemark B

更新日期：2017-06-01 00:00:00

abstract：PURPOSE:To evaluate the feasibility of using an objective computer-aided system to assess bladder cancer stage in CT Urography (CTU). MATERIALS AND METHODS:A dataset consisting of 84 bladder cancer lesions from 76 CTU cases was used to develop the computerized system for bladder cancer staging based on machine learnin...

journal_title：Medical physics

authors： Garapati SS,Hadjiiski L,Cha KH,Chan HP,Caoili EM,Cohan RH,Weizer A,Alva A,Paramagul C,Wei J,Zhou C

更新日期：2017-11-01 00:00:00

abstract：PURPOSE:Squamous cell carcinoma (SCC) is commonly treated by electron beam radiotherapy (EBRT) followed by a boost via brachytherapy. Considering the limitations associated with brachytherapy, in this study, a novel boosting technique in EBRT of lip carcinoma using an internal shield as an internal dose enhancer tool (...

journal_title：Medical physics

authors： Shokrani P,Baradaran-Ghahfarokhi M,Zadeh MK

更新日期：2013-04-01 00:00:00

abstract：PURPOSE:A number of techniques are available to determine the dosimetric impact of intrafraction motion during intensity modulated radiation therapy (IMRT). Motion-induced dose perturbations can be determined both computationally and experimentally using a number of different dosimetric metrics. However, these measures...

journal_title：Medical physics

authors： Waghorn BJ,Meeks SL,Langen KM

更新日期：2011-08-01 00:00:00

abstract：:Gd2O2S phosphor screens between 250 and 1000 mg/cm2 thick were evaluated for use in megavoltage imaging systems. The phosphor layers were placed on brass plates ranging from 1 to 5 mm thick, each with and without an optical back reflector (white paint). Light output and spatial resolution were measured at 6- and 23-MV...

journal_title：Medical physics

authors： Wowk B,Shalev S

更新日期：1994-08-01 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:In computed tomography (CT), organ dose, effective dose, and risk index can be estimated from volume-weighted CT dose index (CTDI(vol)) or dose-length product (DLP) using conversion coefficients. Studies have investigated how these coefficients vary across scanner models, scan parameters, and patient size. Howe...

journal_title：Medical physics

authors： Li X,Samei E,Williams CH,Segars WP,Tward DJ,Miller MI,Ratnanather JT,Paulson EK,Frush DP

更新日期：2012-11-01 00:00:00

abstract：PURPOSE:To investigate how using different sets of decision criteria impacts the quality of intensity modulated radiation therapy (IMRT) plans obtained by multiobjective optimization. METHODS:A multiobjective optimization evolutionary algorithm (MOEA) was used to produce sets of IMRT plans. The MOEA consisted of two i...

journal_title：Medical physics

authors： Holdsworth C,Stewart RD,Kim M,Liao J,Phillips MH

更新日期：2011-06-01 00:00:00

abstract：PURPOSE:This paper describes the low-kV spectral optimization of dual-energy CT (DECT) equipped with high-kV tin filtration for the quantitative acquisition of electron density information, which is essential for treatment planning in radiotherapy. In addition, an analytical DECT image simulation was preliminarily perf...

journal_title：Medical physics

authors： Saito M

更新日期：2011-06-01 00:00:00

abstract：PURPOSE:The purpose of this study is to evaluate the feasibility of kilovoltage cone-beam CT (CBCT) images that are obtained with the Varian On-Board Imager in dose calculation at each radiation therapy. METHODS:CBCT images are commonly degraded by scattered radiations originating in the patient's body, and so the CT ...

journal_title：Medical physics

authors： Usui K,Ogawa K,Kunieda E

更新日期：2012-06-01 00:00:00

abstract：PURPOSE:To evaluate the performance and efficacy for intensity inhomogeneity correction of various sequences of the human brain in 7T MRI using the extended version of the unified segmentation algorithm. MATERIALS:Ten healthy volunteers were scanned with four different sequences (2D spin echo [SE], 3D fast SE, 2D fast...

journal_title：Medical physics

authors： Uwano I,Kudo K,Yamashita F,Goodwin J,Higuchi S,Ito K,Harada T,Ogawa A,Sasaki M

更新日期：2014-02-01 00:00:00

abstract：:Ir-192 wires have been used in low-dose-rate brachytherapy for many years. Commercially available treatment planning systems approximate the dose rate distribution of the straight or curved wires applying the superposition principle using one of the following methods: (i) The wire is modeled as a set of point sources,...

journal_title：Medical physics

authors： van der Laarse R,Granero D,Pérez-Calatayud J,Meigooni AS,Ballester F

更新日期：2008-03-01 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：PURPOSE:Over the last four decades, Ocular Proton Therapy has been successfully used to treat patients affected by intraocular lesions. For this, treatment geometry verification is routinely performed using radiographic images to align a configuration of fiducial radiopaque markers implanted on the sclera outer surface...

journal_title：Medical physics

authors： Via R,Hennings F,Fattori G,Fassi A,Pica A,Lomax A,Weber DC,Baroni G,Hrbacek J

更新日期：2018-05-01 00:00:00

abstract：PURPOSE:Micro-CT is widely used for small animal imaging in preclinical studies of cardiopulmonary disease, but further development is needed to improve spatial resolution, temporal resolution, and material contrast. We present a technique for visualizing the changing distribution of iodine in the cardiac cycle with du...

journal_title：Medical physics

authors： Johnston SM,Johnson GA,Badea CT

更新日期：2012-08-01 00:00:00

abstract：:We are developing a computer program for automated detection of clustered microcalcifications on mammograms. In this study, we investigated the effectiveness of a signal classifier based on a convolution neural network (CNN) approach for improvement of the accuracy of the detection program. Fifty-two mammograms with c...

journal_title：Medical physics

authors： Chan HP,Lo SC,Sahiner B,Lam KL,Helvie MA

更新日期：1995-10-01 00:00:00

abstract：PURPOSE:A commonly used beam quality index (Q) for high-energy photon beams is the tissue phantom ratio (TPR20,10) for a square field of 10 x 10 cm2 and SDD of 100 cm. On some specialized radiotherapy treatment equipment such a reference collimator setting is not achievable. Likewise a flat beam profile, not explicitly...

journal_title：Medical physics

authors： Sauer OA

更新日期：2009-09-01 00:00:00

abstract：PURPOSE:To evaluate the energy dependence of Gafchromic EBT3 film for establishing a quality assurance method of bolus electron conformal radiotherapy. METHODS:We irradiated electron beam to EBT3 films, which were set in the water tank. The linear accelerator used was Varian Clinac 21EX. The energy of electron beams w...

journal_title：Medical physics

authors： Inoue T,Sugimoto S,Fukata K,Kurokawa C,Ozawa S,Sasai K

更新日期：2012-06-01 00:00:00

abstract：:This study proposes an algorithm for selecting beam weight, wedge angle, and wedge orientation for three-dimensional radiation therapy treatment planning. According to dose gradient analysis, the necessary and sufficient condition for achieving a homogeneous dose over the target volume is that the total vector sum of ...

journal_title：Medical physics

authors： Dai J,Zhu Y

更新日期：2000-08-01 00:00:00