Abstract：
:Fluoroscopy is a low dose imaging technique. As such, a very sensitive detector is required to create images of good quality. Present day flat panel active matrix read out systems introduce an amount of noise that inhibits present direct and indirect methods from producing optimal quality images at fluoroscopic exposure rates (0.1-10 microR per frame). The gain of the direct conversion approach using amorphous selenium (a-Se) was investigated to determine whether by increasing the applied electric field, a gain sufficient to overcome the noise limitations of the active matrix could be achieved. Conversion gain and avalanche multiplication in a-Se were investigated as a function of electric field from 10 to 100 V/microm. Our results show a factor of 4 increase in conversion gain is available by increasing electric field from the current standard of 10 V/microm to 100 V/microm. Furthermore, we show that avalanche multiplication can provide an additional gain of up to 25. This increase in signal is sufficient to overcome the noise level encountered in flat panel detectors and permit fully quantum noise limited operation across the whole fluoroscopic range of exposure.
journal_name
Med Physjournal_title
Medical physicsauthors
Hunt DC,Kirby SS,Rowlands JAdoi
10.1118/1.1513157subject
Has Abstractpub_date
2002-11-01 00:00:00pages
2464-71issue
11eissn
0094-2405issn
2473-4209journal_volume
29pub_type
杂志文章相关文献
MEDICAL PHYSICS文献大全abstract：:This study concerns the accuracy and precision of the IAEA/WHO LiF TLD system used in intercomparison by mail of absorbed doses from 60Co gamma-radiation and 4-25 MV x rays. The system employs 160 mg LiF powder in polystyrene capsules, which are placed at 5 or 7 cm depth in water and irradiated to doses close to 200 r...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.594746
更新日期：1980-09-01 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
pub_type： 杂志文章
doi：10.1118/1.4918321
更新日期：2015-05-01 00:00:00
abstract：PURPOSE:Respiratory motion in the chest region during single photon emission computed tomography (SPECT) is a major degrading factor that reduces the accuracy of image quantification. This effect is more notable when the tumor is very small, or the spatial resolution of the imaging system is less than the respiratory m...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.13807
更新日期：2019-11-01 00:00:00
abstract：PURPOSE:A detailed analysis of 2728 intensity modulated proton therapy (IMPT) fields that were clinically delivered to patients between 2007 and 2013 at Paul Scherrer Institute (PSI) was performed. The aim of this study was to analyze the results of patient specific dosimetric verifications and to assess possible corre...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4964449
更新日期：2016-11-01 00:00:00
abstract：:In a practical classifier design problem, the true population is generally unknown and the available sample is finite-sized. A common approach is to use a resampling technique to estimate the performance of the classifier that will be trained with the available sample. We conducted a Monte Carlo simulation study to co...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.2868757
更新日期：2008-04-01 00:00:00
abstract：:A detailed Monte Carlo study of the PTW-diamond solid state detector response in megavoltage photon beams (60Co gamma rays to 25 MV x rays) has been performed with the EGS4 Monte Carlo Code. The sensitive volume of the diamond detector is a disk of diameter 4.4 mm and thickness 0.40 mm. The phantom material was water ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598771
更新日期：1999-11-01 00:00:00
abstract：PURPOSE:To design and quantify the shielding efficacy of an inner Borated Polyethylene (BPE)wall for a 15 MV linac in a low energy vault. METHODS:A Varian TrueBeam linac with a maximum photon energy of 15 MV was installed in asmaller, preexisting vault. This vault originally housed a low-energy machine and did not hav...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735334
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:Design and optimization of medical imaging systems benefit from accurate theoretical modeling that identifies the physical factors governing image quality, particularly in the early stages of system development. This work extends Fourier metrics of imaging performance and detectability index (d') to tomosynthes...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3560428
更新日期：2011-04-01 00:00:00
abstract：PURPOSE:Monte Carlo (MC) simulation can be used for accurate electron beam treatment planning and modeling. Measurement of large electron fields, with the applicator removed and secondary collimator wide open, has been shown to provide accurate simulation parameters, including asymmetry in the measured dose, for the fu...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3592640
更新日期：2011-06-01 00:00:00
abstract：PURPOSE:The purpose of this study was to investigate the potential of MR-guided pulsed focused ultrasound (pFUS) for the enhancement of drug uptake in prostate tumors in vivo using doxorubicin (Dox). METHODS:An antitumor drug Dox, an orthotopic animal prostate tumor model using human prostate cancer, LNCaP cell line, ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4705346
更新日期：2012-05-01 00:00:00
abstract：:A method is described for calibration of 192Ir high-dose-rate (HDR) brachytherapy afterloading systems. Since NIST does not offer calibration of ionization chambers with the gamma-ray spectrum of iridium-192, an interpolation procedure is employed, using calibrations above (137Cs, 662 keV) and below (250 kVcp, 146-keV...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596649
更新日期：1991-05-01 00:00:00
abstract：:In this investigation, five experimental data sets are used to evaluate the ability of the EGSnrc Monte Carlo code to calculate the change in chamber response associated with changes in wall material and cavity dimension at 60Co energies. Calculations of the ratios of response per unit mass of air as a function of cav...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3013701
更新日期：2008-12-01 00:00:00
abstract：PURPOSE:The objective of this study is to develop a computational model for simulating 915 MHz microwave ablation (MWA), and verify the simulation predictions of transient temperature profiles against experimental measurements. Due to the limited experimental data characterizing temperature-dependent changes of tissue ...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12359
更新日期：2017-09-01 00:00:00
abstract：:Up to the present, the majority of low contrast object evaluations performed on phantom images have been accomplished in a subjective fashion. This is mainly due to the time and effort required to manually measure each radiograph with a densitometer to obtain quantitative results. However, with the development of digi...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1543153
更新日期：2003-03-01 00:00:00
abstract：:The purpose of this work is to investigate algorithms for the delivery of intensity-modulated fields using independent collimators (IC). Two heuristic algorithms are proposed to calculate jaw-setting sequences for arbitrary 2D intensity distributions. The first algorithm is based on searching the whole intensity matri...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598794
更新日期：1999-12-01 00:00:00
abstract：PURPOSE:To determine the accuracy and test-retest repeatability of fast radiofrequency (RF) transmit measurement approaches used in Dynamic Contrast Enhanced Magnetic Resonance Imaging (DCE-MRI). Spatial variation in the transmitted RF field introduces bias and increased variance in quantitative DCE-MRI metrics includi...
journal_title：Medical physics
pub_type： 杂志文章,多中心研究
doi：10.1002/mp.13518
更新日期：2019-06-01 00:00:00
abstract：:A new type of radiographic film, EDR (extended dose range) film, has been recently become available for film dosimetry. It is particularly attractive for composite isodose verification of intensity modulated radiation therapy because of its low sensitivity relative to the more common Kodak XV film. For XV film, the re...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1568979
更新日期：2003-05-01 00:00:00
abstract：:A quality assurance protocol has been developed to assess the relative accuracy of computerized monitor unit calculations. Results from this testing reveal that errors (defined as the difference between the computer results and those obtained using a standard formula with manual calculation) in monitor unit calculator...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.596539
更新日期：1990-01-01 00:00:00
abstract：:The purpose of this study is to understand the effect of pitch on raw data interpolation in multislice spiral/helical computed tomography (CT) and provide guidelines for scanner design and protocol optimization. Multislice spiral CT is mainly characterized by the three parameters: the number of detector arrays, the de...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.598804
更新日期：1999-12-01 00:00:00
abstract：:In external beam radiotherapy, electronic portal imaging becomes more and more an indispensable tool for the verification of the patient setup. For the safe clinical introduction of high dose conformal radiotherapy like intensity modulated radiation therapy, on-line patient setup verification is a prerequisite to ensu...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1668391
更新日期：2004-04-01 00:00:00
abstract：PURPOSE:Theoretical models of the detective quantum efficiency (DQE) of x-ray detectors are an important step in new detector development by providing an understanding of performance limitations and benchmarks. Previous cascaded-systems analysis (CSA) models accounted for photoelectric interactions only. This paper des...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4794495
更新日期：2013-04-01 00:00:00
abstract：:The analysis and understanding of results of computed tomography (CT) require an understanding of photon attenuation in matter. The high sensitivity and resolution of these devices coupled with the use of a polychromatic photon source require a level and breadth of understanding about photon attenuation not usually re...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.594199
更新日期：1975-11-01 00:00:00
abstract：:While simple, intravascular brachytherapy (IVB) presents a considerable potential for harm to the patient. The medical physicist maintains the responsibility to minimize the likelihood of operational problems or dosimetric errors. The principals for safe operation remain the same as with any radiotherapy treatment: to...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1524167
更新日期：2002-12-01 00:00:00
abstract：PURPOSE:There is significant current interest in the use of biological image guidance in radiotherapy planning. In lung-cancer treatment, tumor motion due to respiration is known to be a limitation. This is particularly true in PET, where image data are collected over a number of minutes. An in-house-developed 4D PET a...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.3276776
更新日期：2010-02-01 00:00:00
abstract：:The hybrid algorithms developed recently for the reconstruction of fan-beam images possess computational and noise properties superior to those of the fan-beam filtered backprojection (FFBP) algorithm. However, the hybrid algorithms cannot be applied directly to a halfscan fan-beam sinogram because they require knowle...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.1288239
更新日期：2000-09-01 00:00:00
abstract：PURPOSE:Adding magnetic resonance (MR)-derived information to standard transrectal ultrasound (TRUS) images for guiding prostate biopsy is of substantial clinical interest. A tumor visible on MR images can be projected on ultrasound (US) by using MR-US registration. A common approach is to use surface-based registratio...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4917481
更新日期：2015-05-01 00:00:00
abstract：PURPOSE:The lateral edge of a proton therapy beam is commonly used to achieve conformality to the treatment volume where critical structures reside close to the target. However, when treating shallow depths, the lateral edge of a pencil beam scanning (PBS) system may be broader than that of a double scattered (DS) syst...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4941957
更新日期：2016-03-01 00:00:00
abstract：PURPOSE:The Small Animal Radiation Research Platform (SARRP) has been developed for conformal microirradiation with on-board cone beam CT (CBCT) guidance. The graphics processing unit (GPU)-accelerated Superposition-Convolution (SC) method for dose computation has been integrated into the treatment planning system (TPS...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1002/mp.12862
更新日期：2018-05-01 00:00:00
abstract：PURPOSE:To measure the calibration curves of EBT3 dosimetry films in photon and proton beams and to quantify the related uncertainties from one beam type to another. METHODS:EBT3 Gafchromic films have similar properties than EBT2 with a symmetric construction and a matte polyester substrate to prevent Newton's ring ar...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4735176
更新日期：2012-06-01 00:00:00
abstract：PURPOSE:To evaluate a three-equation three-unknown dual-energy quantitative CT (DEQCT) technique for determining region specific variations in bone spongiosa composition for improved red marrow dose estimation in radionuclide therapy. METHODS:The DEQCT method was applied to 80/140 kVp images of patient-simulating lumb...
journal_title：Medical physics
pub_type： 杂志文章
doi：10.1118/1.4870378
更新日期：2014-05-01 00:00:00
