关于菲尼酮在医用X线胶片高温快速冲洗显影药液中作用的探讨

本文总结了菲尼酮在医用X线胶片在90秒干至干,高温快速冲洗工艺中的作用和特征,如:超加和性、易接近潜影核、显影诱导期极短,对溴离子变化敏感程度低,显影结果重复性好等等。作者据此成功地配制了适用于90秒冲洗医用X线胶片的套药。     

Patient exposure in medical X-ray imaging in Europe

Patients are exposed to X rays when undergoing medical examinations in diagnostic radiology. Exposure data acquired and assessed in Germany for the year 1997 resulted in a mean annual effective dose of 2 +/- 0.5 mSv per head of the population, thereby reaching or exceeding the average level of environmental radiation in many cases. The underlying frequency of medical X-ray examinations was approximately 136 million, i.e. approximately 1.7 examinations annually per head of the population. For comparison, corresponding data of other countries were extracted from the UNSCEAR 2000 report or originate from the literature. Data analysis shows significant differences in national radiological practices and a very uneven distribution of patient doses amongst the world population. The mean annual effective dose per head of the population varies by up to a factor of 60 between health care level I and IV countries, and still by a factor of approximately 6 within health care level I countries. While projection radiography has succeeded in reducing dose consumption, computed tomography and radiological interventions have given rise to a significant growth of patient exposure, and interventional radiology can even exceed thresholds for deterministic radiation effects. Patient exposure is further shown to result from misadministration and retakes of X-ray examinations, usually not registered, as well as from technical failures of X-ray facilities, which can cause significantly enhanced exposure times. Corresponding data are presented and comments are made on the international situation of non-harmonised data collection on patient exposure as well as of parameters affecting the assessment of exposure and risk.     

Modeling quantum noise of phosphors used in medical X-ray imaging detectors

The noise properties of the granular phosphor screens, which are utilized in X-ray imaging detectors, are studied in terms of the quantum noise transfer function (QNTF). An analytical model, taking into account the effect of K-characteristic X-rays reabsorption within the phosphor material and the optical properties of the phosphor, was developed. The optical properties of the phosphor material required by the model were obtained from literature, except for the optical diffusion length (σ) that was determined by data fitting and was found to be 26 cm²/g. The deviation between theoretical and experimental data is σ depended. Specifically for σ=26 cm²/g and σ=25 cm²/g the respective deviations between experimental and predicted results were 0.698% and −1.597%. However for relative differences in σ more than 15% from the value 26 cm²/g, the corresponding deviations exceed by 6 times the value of 0.698%. The model was tested via comparison to experimental results obtained by a set of Y₂O₃:Eu³⁺ phosphor screens prepared by sedimentation. The model may be used to evaluate the effect of screen thickness and irradiation geometry on quantum noise of phosphor materials for transmission and reflection mode.     

Polyurea thin film ultrasonic transducers for nondestructive testing and medical imaging

Ultrasonic transducers using polyurea piezoelectric thin film are studied in this paper. Aromatic polyurea thin films, prepared by vapor deposition polymerization, have useful characteristics for use as an ultrasonic transducer. This paper presents the fabrication and experimental evaluation of ultrasonic transducers formed using polyurea films. First, the vapor deposition polymerization process using two monomers is briefly reviewed, and the temperature conditions for higher piezoelectric constants are explored. Second, in order to test the fundamental characteristics of this material as a high-frequency, ultrasonic transducer, a polyurea film of 2.5 microm thickness was deposited on a silicon substrate. In the pulse/echo experiment results, a resonant frequency of about 100 MHz was observed. Third, we fabricated a concave point focus transducer and a cylindrical line focus transducer. To examine the performances of the focus transducers, two-dimensional images of a coin and V(z) curve measurements for an aluminum surface were demonstrated.     

Optimisation of X-ray examinations in Lithuania: start of implementation in mammography

Optimisation of medical X-ray examinations is very important for the enhancement of the reliability of the examination and for the reduction of the radiation dose to patients. Results of investigations of doses to patients during mammography using thermoluminescence dosemeters at different hospitals are presented together with a brief overview of the situation for mammography in Lithuania. It is shown that the entrance surface air kerma varies in a broad range and differed from hospital to hospital. Nevertheless the calculated values of average glandular dose (AGD) for a 'standard' breast being relatively high were comparable with those (3.2 mGy per exposure at net optical density 1.4) currently accepted by international authorities. Differences in AGD values evaluated at different hospitals demonstrate the existing potential for optimisation of the mammography screening procedures. The results of this investigation will be included in a database for patient doses in Lithuania and used for establishing a national reference dose level for mammography. Currently, reference levels recommended by international authorities are used in Lithuania.     

Modeling quantum and structure noise of phosphors used in medical X-ray imaging detectors

The noise properties of granular phosphors used in X-ray imaging detectors are studied in terms of a noise transfer function, NTF. This study is performed in high-exposure conditions where the contribution of structure noise to total screen noise is considerable. An analytical model, based on the cascaded linear systems methodology presented in the literature, is developed. This model takes into account the quantum noise and structure noise. Furthermore, it considers the effect of the K X-rays reabsorption on the phosphor material and the effect of screen thickness on the NTF. The model was validated against experimental results obtained by a set of Zn₂SiO₄:Mn phosphor screens prepared by sedimentation. The model may be used to evaluate the effect of screen thickness and the effect of the characteristic X-rays on NTF in high-exposure conditions where structure noise is considerable.     

Adaptive strain estimation using retrospective processing [medical US elasticity imaging

Because errors in displacement and strain estimates depend on the magnitude of the induced strain, the strain signal-to-noise ratio (SNR) will be a function of the applied deformation. If deformation is applied at the body surface, it is difficult during data acquisition to select a single surface displacement providing the highest strain SNR throughout the image. By applying continuous deformation and capturing data in real-time, the surface displacement providing the highest strain SNR can be selected retrospectively. A method to adaptively optimize strain SNR over the image plane using retrospective processing is presented and demonstrated with experimental results.     

Optimization of processing parameters for laser alloying of aluminium alloys by X-ray imaging

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

X-ray colour imaging

A prototype X-ray colour imaging system has been assembled using the principle of tomographic energy-dispersive diffraction imaging (TEDDI). The new system has been tested using samples of nylon-6, aluminium powder and deer antler bone. Non-destructive three-dimensional images of the test objects have been reconstructed on a 300 microm scale with an associated diffraction pattern at each voxel. In addition, the lattice parameters of the polycrystalline material present in the sampled voxels have been determined using full pattern refinement methods. The use of multiple diffracted parallel colour X-ray beams has allowed simultaneous spatially resolved data collection across a plane of the sample. This has simplified the sample scan motion and has improved data collection times by a factor scaling with the number of detector pixels. The TEDDI method is currently limited to thin samples (approx. 1-2mm) with light atoms owing to the very low detection efficiency of the silicon detector at X-ray energies above 25 keV. We describe how these difficulties can be removed by using semiconductor detectors made from heavier atomic material.     

X-ray imaging tubes

The important parameters of X-ray imaging tubes are considered in relation to their main components, the X-ray detection screen, the photocathode, the electron optics and the output screen. These parameters define the performance which can be achieved in terms of noise, contrast and resolution. Possible further improvements are also discussed.     

Occupational exposure of medical radiation workers in Lithuania, 1950-2003

This study presents the summary of historical exposures, measurementpractice and evolution of the recording of the individual dosesof medical radiation workers during 1950–2003 in Lithuania.The aim of this study is to present occupational exposure ofmedical radiation workers in Lithuania since the earliest appearanceperiod. Data from publications have been used for the earliesttwo periods prior to 1969; data from the archives of the largesthospitals, for the period 1970–1990 and data from LithuanianSubdivision of Individual Dosimetry of Radiation ProtectionCenter, for the period 1991–2003. The analysis of thedata obtained from personal records allows to conclude thatthe average annual effective dose of Lithuanian medical radiationworkers was greatly reduced in radiology, radiotherapy and nuclearmedicine in all occupational categories from 1950 to 2003. Duringthe last period 1991–2003 extremity doses clearly decreasedand after 1994 were no longer present in Lithuania.     

Eu-doped CsBr phosphor as a new optically-stimulable phosphor material for medical X-ray imaging sensor

CsBr phosphor ceramics doped with different luminescence centres such as In2O3, Eu2O3, EuCl3, SmCl3, TbCl3, GdCl3 or NdCl3 as the candidate for a new optically-stimulable phosphor for medical X-ray imaging sensor were prepared using a conventional ceramic fabrication process. It was found that X-ray-irradiated Eu-doped CsBr (CsBr:Eu) exhibited intense optically stimulated luminescence (OSL). The peak wavelength of the OSL emission and stimulation spectra of CsBr:Eu phosphor ceramic sample were 450 and 690 nm, respectively. The dependence of OSL properties on the conditions of preparation of phosphor ceramic samples, such as Eu concentration, sintering temperature and sintering time, were studied. The optimum preparation conditions were also studied. It was found that the OSL intensity of CsBr:Eu phosphor ceramics fabricated under optimum preparation conditions is higher than that of commercially available imaging plates using BaFBr:Eu.     

医用影像诊断胶片发展动态

综述了医用诊断技术的重要历程，医用影像胶片的技术动态、世界市场概况，以及Ｘ－射线胶片的种类与型号。     

T颗粒X线胶片和矽肺X线摄影

本文以实例表明用柯达T颗粒感绿X线胶片配合专用的硫氧化钆/铽稀土元素绿增感屏进行矽肺肺摄影可以取得优越的临床诊断效果:细微结构清晰、信息量增加,有利于早期病变的检出。X线投照量仅需作对比用的常规富士感蓝X线胶片和钨屏组合的五分之一至三分之一。     

X-ray fluorescent spectrometer with total X-ray reflection for studies of kinetics of thin film deposition

An X-ray fluorescent spectrometer with total X-ray reflection and minimum detection limit by zinc of n · 10⁻¹⁰ g is developed that allows performing analysis of elements from magnesium to uranium. This spectrometer is used to determine the elemental composition of Bi-Nd-Fe-O films grown on an Al₂O₃ single crystal (transparent sapphire, face 0001) in a gas-discharge sputtering chamber of a ceramic Bi_0.95Nd_0.05FeO₃ target. It is shown that the spectrometer allows registering formation and growth of films starting from the sputtering time of 15 s.     

X-ray dark-field imaging modeling

Dark-field images are formed from x-ray small-angle scattering signals. The small-angle scattering signals are particularly sensitive to structural variation and density fluctuation on a length scale of several tens to hundreds of nanometers, offering a unique contrast mechanism to reveal subtle structural features of an object. In this study, based on the principle of energy conservation, we develop a physical model to describe the relationship between x-ray small-angle scattering coefficients of an object and dark-field intensity images. This model can be used to reconstruct volumetric x-ray small-angle scattering images of an object using classical tomographic algorithms. We also establish a relationship between the small-angle scattering intensity and the visibility function measured with x-ray grating imaging. The numerical simulations and phantom experiments have demonstrated the accuracy and practicability of the proposed model.     

Two digital X-ray imaging systems for applications in X-ray diffraction

Two digital X-ray imaging systems developed at the Rutherford Appleton Laboratory are described: the Mark I and the Mark II. Both use a bidimensionally sensitive multiwire proportional counter (MWPC) as the basic X-ray image transducer coupled, in the case of the Mark I to a Digital LSI 11–23 microcomputer system via CAMAC, and in the case of the Mark II to a Digital LSI 11–73 microcomputer system via custom-built data acquisition hardware mounted directly on the Q-bus of the microcomputer. The Mark I system provides the advantages of high speed, high sensitivity digital imaging directly into the computer with the potential for software control of the sample orientation and environment. The Mark II system adds the novel features of signal averaging and multiframe exposures. The dedicated digital memories have a resolution of 512×512 pixels of 16 bits, matching well to the spatial resolution of the xenon-filled MWPC (0.5 mm fwhm over an aperture of 200 mm×200 mm). A 512×512×4 bit video graphics system displays the images in grey scales or colour.     

Multielement imaging in computerised X-ray tomography

A method by which several elements can be independently imaged in a single X-ray CT scan is described. The method is based on measurements of differential absorption across absorption edges. The images produced show the distribution of element concentration. Mass attenuation coefficients for the elements comprising the matrix are not required because corrections for matrix effects are made. The method is capable of imaging elements which are consecutive in the periodic table. Detection limits, in the apparatus described, are of the order of mg/cm³. The elements chosen for imaging were palladium, silver and cadmium.