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Extracting statistical characteristics from radiographic films is vital for film system classification and contrast sensitivity evaluation and serves as a basis for film noise simulation. A new method for digitising radiographic films in order to extract these characteristics is presented. The method consists of a camera-based setup and image processing procedure to digitise films. Correct optical density values and granularity can be extracted from the digitised images, which are equal to results obtained by standardised measurement procedures. Specific statistical characteristics of film noise are theoretically derived and subsequently verified by the obtained data, including characteristics such as Gaussianity and spatial spectral characteristics of the optical density fluctuations. It is shown that the presented method correctly measures the granularity of film noise and can therefore replace time-consuming microdensitometer measurements traditionally required for film system classifications. Additionally, the inherent unsharpness of film systems was investigated and compared with literature data. This comparison serves as another validation approach of the presented method.

Purpose Microbeam radiation therapy is a developing technique that promises superior tumour control and better normal tissue tolerance using spatially fractionated X-ray beams only tens of micrometres wide. Radiochromic film dosimetry at micrometric scale was performed using a microdensitometer, but this instrument presents limitations in accuracy and precision, therefore the use of a microscope is suggested as alternative. The detailed procedures developed to use the two devices are reported allowing a comparison. Methods Films were irradiated with single microbeams and with arrays of 50 µm wide microbeams spaced by a 400 µm pitch, using a polychromatic beam with mean energy of 100 keV. The film dose measurements were performed using two independent instruments: a microdensitometer (MDM) and an optical microscope (OM). Results The mean values of the absolute dose measured with the two instruments differ by less than 5% but the OM provides reproducibility with a standard deviation of 1.2% compared to up to 7% for the MDM. The resolution of the OM was determined to be ~ 1 to 2 µm in both planar directions able to resolve pencil beams irradiation, while the MDM reaches at the best 20 µm resolution along scanning direction. The uncertainties related to the data acquisition are 2.5–3% for the OM and 9–15% for the MDM. Conclusion The comparison between the two devices validates that the OM provides equivalent results to the MDM with better precision, reproducibility and resolution. In addition, the possibility to study dose distributions in two-dimensions over wider areas definitely sanctions the OM as substitute of the MDM.

Purpose: Microbeam radiation therapy (MRT) is a still preclinical tumor therapy approach that uses arrays of a few tens of micrometer wide parallel beams separated by a few 100 μm. The production, measurement, and planning of such radiation fields are a challenge up to now. Here, the authors investigate the feasibility of radiochromic film dosimetry in combination with a microscopic readout as a tool to validate peak and valley doses in MRT, which is an important requirement for a future clinical application of the therapy. Methods: Gafchromic® HD-810 and HD-V2 films are exposed to MRT fields at the biomedical beamline ID17 of the European Synchrotron Radiation Facility (ESRF) and are afterward scanned with a microscope. The measured dose is compared with Monte Carlo calculations. Image analysis tools and film handling protocols are developed that allow accurate and reproducible dosimetry. The performance of HD-810 and HD-V2 films is compared and a detailed analysis of the resolution, noise, and energy dependence is carried out. Measurement uncertainties are identified and analyzed. Results: The dose was measured with a resolution of 5 × 1000 μm2 and an accuracy of 5% in the peak and between 10% and 15% in the valley region. As main causes for dosimetry uncertainties, statistical noise, film inhomogeneities, and calibration errors were identified. Calibration errors strongly increase at low doses and exceeded 3% for doses below 50 and 70 Gy for HD-V2 and HD-810 films, respectively. While the grain size of both film types is approximately 2 μm, the statistical noise in HD-V2 is much higher than in HD-810 films. However, HD-810 films show a higher energy dependence at low photon energies. Conclusions: Both film types are appropriate for dosimetry in MRT and the microscope is superior to the microdensitometer used before at the ESRF with respect to resolution and reproducibility. However, a very careful analysis of the image data is required. Dosimetry at low photon energies should be performed with great caution due to the energy sensitivity of the films. In this respect, HD-V2 films showed to have an advantage over HD-810 films. However, HD-810 films have a lower statistical noise level. When a higher resolution is required, e.g., for the dosimetry of pencil beam irradiations, noise may render HD-V2 films inapplicable.

Objetivou-se neste trabalho determinar o perfil da densidade aparente em painel aglomerado confeccionado com partículas da madeira de Acacia mangium. Utilizou-se a técnica de microdensitometria de raios X correlacionada com a densidade gravimétrica. Foram utilizados os adesivos ureia formaldeído e tanino comercial de Acacia mearnsii aplicado na forma de pó diretamente nas partículas previamente encoladas. Os painéis foram fabricados com quatro razões de compactação (1,39; 1,55; 1,73; e, 2,00) combinadas a quatro proporções de tanino em pó (0, 10, 20 e 30%), totalizando 16 tratamentos (4 painéis por tratamento). Foram determinados, analisados e comparados o perfil da densidade aparente (densidade média, densidade máxima e densidade mínima) e a densidade gravimétrica dos aglomerados produzidos. O perfil da densidade é apresentado graficamente e interpretado por análise de variância e regressão linear múltipla. Os valores de densidade aparente média, máxima e mínima observados para os painéis aglomerados obtidos pela microdensitometria de raios X variaram de 357 a 697 kg/m3, 386 a 824 kg/m3 e 334 a 634 kg/m3, respectivamente, e pelo método gravimétrico de 369 a 742 kg/m3. A técnica mostrou-se eficiente na determinação de variações nos perfis de densidade aparente ao longo da espessura dos painéis em todos os tratamentos, bem como mostrou-se eficiente na obtenção direta da densidade aparente. Estas variações poderiam ser minimizadas se o tanino utilizado fosse anteriormente hidratado em água. Houve forte correlação entre as médias das densidades obtidas pelo método do microdensitômetro de raios X e pelo método gravimétrico.

We describe the new, fast, high-precision microdensitometer SuperCOSMOS. Some aspects of hardware and software design that enable high-precision astrometry from photographic plates are explained. We show that the positioning repeatability of the measuring machine is less than 0.1 μ μ m standard error in either coordinate, and the absolute positional accuracy is about 0.15 μ m standard error. Furthermore, measurements of the same plate in different orientations show that the sampling errors are small (e.g. ∼ 0.2 μ m, rising to ∼ 1.0 μ m at the plate limit, for stellar images in a IIIaJ emulsion), thus allowing the extraction of relative positional information from Schmidt plates at accuracies less than 1 μ m. We demonstrate that SuperCOSMOS is capable of measuring the positions of bright stars (i.e. those more than ∼ 4 mag above the plate limit) to a precision ∼ 0.5 μ m with survey–grade photographic plates employing fine–grained emulsions.

A system for reading and interpreting photographically recorded spark source mass spectra using a computer coupled microdensitometer is discussed. Its essential features are: (1) correction for line width, (2) correction for background, (3) possibility of converting the measured transmissions into optical densities, Seidel values or transmission factors, (4) possibility of choosing two calculation methods (the least-squares method and the “averaging slope” method), (5) improvement of the precision of the measurements by simultaneous processing of the data relative to all the available isotopes of a single element, and (6) a continuous interaction between operator and computer allowing erroneous data to be eliminated at various stages of the processing. A description of the commercially available program is given. The precision of the system is evaluated by repeated analyses of the same photoplate, which was obtained by the measurement of a very homogeneous standard reference sample (NBS - low alloy steel). Its internal reproducibility is assessed using the known isotopic ratios of multi-isotopic elements.

Various optical properties of the fundus camera may have important implications regarding the use of photographs for image size measurements. By scanning across retinal vessels with a microdensitometer the width and the intensity characteristics of both the central light reflex and the streaming blood column may be measured. To establish a reliable basis for future measurements, we analysed the retina-to-film magnification, possible aberrations and the resolving power of our Zeiss camera. Furthermore, fundus photography was performed in 100 young men, and the necessary level of accuracy in focusing the camera was established. We also investigated the effects of various amounts of defocusing on width and intensity readings from densitometric scans across retinal vessels.

Radiochromic film dosimetry has been extensively used for intravascular brachytherapy applications for near field within 1 cm from the sources. With the recent introduction of new model of radiochromic films, GAFCHROMIC EBT, with higher sensitivity than earlier models, it is promising to extend the distances out to 5 cm for low dose rate (LDR) source dosimetry. In this study, the use of new model GAFCHROMIC EBT film for {sup 125}I seed dosimetry in Solid Water was evaluated for radial distances from 0.06 cm out to 5 cm. A multiple film technique was employed for four {sup 125}I seeds (Implant Sciences model 3500) with NIST traceable air kerma strengths. Each experimental film was positioned in contact with a {sup 125}I seed in a Solid Water phantom. The products of the air kerma strength and exposure time ranged from 8 to 3158 U-h, with the initial air kerma strength of 6 U in a series of 25 experiments. A set of 25 calibration films each was sequentially exposed to one {sup 125}I seed at about 0.58 cm distance for doses from 0.1 to 33 Gy. A CCD camera based microdensitometer, with interchangeable green (520 nm) and red (665 nm) light boxes, wasmore » used to scan all the films with 0.2 mm pixel resolution. The dose to each {sup 125}I calibration film center was calculated using the air kerma strength of the seed (incorporating decay), exposure time, distance from seed center to film center, and TG43U1S1 recommended dosimetric parameters. Based on the established calibration curve, dose conversion from net optical density was achieved for each light source. The dose rate constant was determined as 0.991 cGy U{sup -1} h{sup -1} ({+-}6.9%) and 1.014 cGy U{sup -1} h{sup -1} ({+-}6.8%) from films scanned using green and red light sources, respectively. The difference between these two values was within the uncertainty of the measurement. Radial dose function and 2D anisotropy function were also determined. The results obtained using the two light sources corroborated each other. We found good agreement with the TG43U1S1 recommended values of radial dose function and 2D anisotropy function, to within the uncertainty of the measurement. We also verified the dosimetric parameters in the near field calculated by Rivard using Monte Carlo method. The radial dose function values in Solid Water were lower than those in water recommended by TG43U1S1, by about 2%, 3%, 7%, and 14% at 2, 3, 4, and 5 cm, respectively, partially due to the difference in the phantom material composition. Radiochromic film dosimetry using GAFCHROMIC EBT model is feasible in determining 2D dose distributions around low dose rate {sup 125}I seed. It is a viable alternative to TLD dosimetry for {sup 125}I seed dose characterization.« less

The random variation in gloss often observed in images produced in electrophotographic printers has been examined by an analytical technique that combines the capabilities of a microdensitometer with a goniophotometer. The technique is called microgoniophotometry and measures both the spatial and the angular distribution of the specular component of reflected light. The analysis provides information about the spatial variation of specularly reflected light at all angles through which the specular light is reflected, not just at the equal/opposite angle at which gloss is traditionally measured. The results of this analysis have lead to an optical model of the random spatial variation in gloss. The results indicate that dry toner is typically not completely fused and can be described as a surface composed of two distinct regions. These two regions differ in the extent of fusing that has occurred, as manifested by their differences in specular reflectance characteristics. The difference in reflectance is manifested primarily in their different angular distributions of specular light and also in their spatial frequency.

The x-ray patterns of solid phase polymers are widely used to characterize the structures. They can be used, among others things, to calculate the degree of crystallinity, the crystalline particle size, and the lattice distortions. However, it is not perfectly clear how the characteristics of the structure effect the obtained diffractograms. The main aim of the present work is to explain what kind of diffraction patterns can be obtained from a hypothetical structure of a polymer. The effect of the following structural parameters were investigated: degree of crystallinity, crystalline particle size, lattice distortions of the first and second kind, and amorphous background. The changes of the diffraction patterns depending on these varied factors were followed. The light diffraction patterns were produced by a modified Schlieren 80 apparatus. The polymer segments were modelled by point-like scattering centers. From these, the models of an ideal crystal and the lattice distortion of the first and second kind were prepared. The crystalline particle size was varied by cutting the original mask. In the amorphous background the minimum distances of two scattering centers were altered. The light diffraction patterns were produced also by rotating the mask, and the x-ray diagram of the unoriented polycrystalline samples could be reproduced. The intensities of the obtained patterns were measured by a microdensitometer. With the help of the diagrams, both qualitative and quantitative conclusions can be obtained about the relation between the mask and its diffraction pattern.

The modulation transfer function (MTF) is a standard method used for estimating the image quality of a component for detail recording in an image forming system and for printing quality of the final products. This study focused on the measurement of MTF of nonprinted and printed silk fabrics and a correlation of the MTF data to sharpness of the printed silk fabric using the in-house formulated ink jet ink. The MTF of the surface was measured using the sinusoidal test pattern in contact with the fabric using spatial frequencies from 0.375 to 3.0 cycles/mm. The sinusoidal test target scanned by a microdensitometer in the reflection density mode. These data comprise two frequencies; the high frequency is the characteristic of the fabric while the low frequency is the light scattering of the yarns in contact with the sinusoidal target. The sinusoidal curves at the low frequency were used for further calculation of the MTF values. The result indicated that the measurement of MTF of silk fabric using the contact sinusoidal method can find the point spread function of silk fabrics. This research investigated the relationships of weave style and direction, wicking properties, and the MTF of four different silk fabrics with plain weave (silk A, C, and D) or twill weave (silk B). Dot gain by -the Yule-Nielsen model was investigated. The coefficient d calculated by the MTF empirical model was 0.0604 and the coefficient n by the Yule-Nielsen model was 1.636 for silk D which had the lowest d and n coefficients compared with other silk fabrics, indicating good quality in terms of image sharpness.

A PC-based control software and data acquisition system is developed for an existing commercial microdensitometer (Biomed make model No. SL-2D/1D UV/VIS) to facilitate scanning and analysis of X-ray films. The software is developed in Labview, which includes operation of the microdensitometer in 1D and 2D scans and analysis of spatial or spectral data on X-ray films, such as optical density, intensity and wavelength. It provides a user-friendly Graphical User Interface (GUI) to analyse the scanned data and also store the analysed data/image in popular formats like data in Excel and images in jpeg. It has also on-line calibration facility with standard optical density tablets. The control software and data acquisition system is simple, inexpensive and versatile.

Radiochromic film (RCF) dosimetry is usually based on densitometric methods which use an analyzing light source of a fixed or a broad spectrum of wavelengths. These methods have not exploited the sensitivity of the dose response of the RCF otherwise attainable by using a light source with wavelengths peaked at the two absorption peaks in the absorption spectrum of the RCF. A new algorithm of dual-peak dose measurement for the RCF has been proposed in this paper to make use of these dual absorption peaks to achieve the maximum attainable sensitivity. This technique relies on the measurement of the transmittance of the RCF at the wavelength of the major and minor absorption peaks, respectively. The dual-peak dose measurement is accomplished with the aid of a novel spectral microdensitometer developed in our Institute. The microdensitometer utilizes a monochromator to provide a light source of which the wavelength can be matched precisely to the wavelength of the absorption peaks of the RCF. The doses obtained at these wavelengths are fed into a weighted objective function and an optimum dose is searched by minimizing the objective function to give the best estimate of the dose deposited on the film. An initial test shows that there is a good agreement between the estimated and actual dose deposited; and the maximum discrepancy was found to be less than 1%.

A description of how we presently use a commercial scanner to obtain electron diffraction data from photographic plates is given. Compared to data previously obtained from a microdensitometer the R -factors and the derived standard deviations for the structure parameters were reduced with approximately 50%. Quantum chemical calculations have been made using HF, DFT and MP2 and the basis sets 6-311++G** and Aug-cc-pVTZ. The calculations are not entirely consistent in their predictions. A syn -like conformation is determined experimentally. The dihedral angle H–C–CO is about 18 degrees, i.e. the C–H bond is pointing towards the CO bond. The most important structure parameters referred to a planar structure with C s symmetry are: R (CO)=1.223(4), R (C–N)=1.358(5), R (C–C)=1.538(6), R (C–Cl)=1.776(5), ∠OCN=125.1(5), ∠CCCl=110.8(3), ∠CCN=116.3(5) where distances are in A and angles in degrees. Estimated error limits are three standard deviations from the least-squares refinement. The experimental results are essentially in agreement with the quantum chemical calculations.

Intravascular brachytherapy treatments of in-stent restenosis have been performed extensively using Ir-192 ribbon. Task Group 60 of the American Association of Physicists in Medicine (AAPM) recommends a dose reference point at 2 mm from the source center for these treatments. However, it is known that the source can be as close as 0.5 mm to the arterial wall if not centered in the lumen. Therefore, the source dosimetry needs to be characterized at these close distances to accurately determine the amount of dose delivered for noncentered cases. In this paper, we report the verification of the dose distributions around Ir-192 seed sources at radial distances from 0.5 mm to 6 mm using GAFCHROMIC film. We evaluated an Ir-192 single seed source and a train of 6 seeds spaced 1 mm apart enclosed in a nylon ribbon. Each source was placed in a homogeneous solid water phantom directly below a stack of GAFCHROMIC films (MD-55-2). The calibration curve of the lot of films used in the experiment was established for Ir-192 by exposing a set of calibration films, one at a time, to an Ir-192 high dose rate (HDR) source. All films were scanned 5 or more days after exposure with a Lumisys Model 150 microdensitometer. The data were acquired and evaluated using RIT113 (Radiological Imaging Technology) software and analyzed using Excel and IDL (Interactive Data Language) software. Isodose curve plots in the plane containing the source's longitudinal axis and dose rate plots in the radial direction were obtained. For both configurations, the dose rates along the transverse axes agree to within the margin of error with previous Monte Carlo results. The isodose curve plots display hot spots near the seed ends, which is consistent with the leakage of beta particles and electrons from the unsealed seed ends as predicted with Monte Carlo calculations.

We present an evaluation of the precision and accuracy of image-based radiochromic film dosimetry. A stack of radiochromic film FWT-60 was used to map a radiation field produced by an electron pulse from a Febetron 707 accelerator (dose rate around 5?1011Gy/s; maximum dose around 160 kGy). The three-dimensional dose distribution was obtained by a He-Nescanning-laser microdensitometer and using image segmentation and correction for non-linear response of films. Calorimetry and electron paramagnetic resonance dosimetry were used to verify the results obtained with a FWT-60 film.

A data acquisition and analysis system has been set up for on-line measurements of spatial variation of optical density using a microdensitometer. The entire processing and control of analog and digital signals as well as data analysis and plotting is carried out using a Window 95/98 based software ‘DEPICT’ developed for the purpose. Any possible errors due to variations in the scanning motor speed, intensity of the light source, and the amplifier gain are avoided by adding a shaft encoder, a photo-detector, and an on-line calibration set up. Optical density scans with a spatial accuracy better than 25 micron over large scan lengths are obtained upto an optical density of 2.5. The data acquisition and analysis system is simple, inexpensive, and is easily adaptable to various other instruments.

Purpose To measure the 2D dose distributions with submillimeter resolution for 131Cs (model CS-1 Rev2) and 125I (model 6711) seeds in a Solid Water phantom using radiochromic EBT film for radial distances from 0.06 cm to 5 cm. To determine the TG-43 dosimetry parameters in water by applying Solid Water to liquid water correction factors generated from Monte Carlo simulations. Methods Each film piece was positioned horizontally above and in close contact with a 131Cs or 125I seed oriented horizontally in a machined groove at the center of a Solid Water phantom, one film at a time. A total of 74 and 50 films were exposed to the 131Cs and 125I seeds, respectively. Different film sizes were utilized to gather data in different distance ranges. The exposure time varied according to the seed air-kerma strength and film size in order to deliver doses in the range covered by the film calibration curve. Small films were exposed for shorter times to assess the near field, while larger films were exposed for longer times in order to assess the far field. For calibration, films were exposed to either 40 kV (M40) or 50 kV (M50) x-rays in air at 100.0 cm SSD with doses ranging from 0.2 Gy to 40 Gy. All experimental, calibration and background films were scanned at a 0.02 cm pixel resolution using a CCD camera-based microdensitometer with a green light source. Data acquisition and scanner uniformity correction were achieved with Microd3 software. Data analysis was performed using ImageJ, FV, IDL and Excel software packages. 2D dose distributions were based on the calibration curve established for 50 kV x-rays. The Solid Water to liquid water medium correction was calculated using the MCNP5 Monte Carlo code. Subsequently, the TG-43 dosimetry parameters in liquid water medium were determined. Results Values for the dose-rate constants using EBT film were 1.069±0.036 and 0.923±0.031 cGy U−1 h−1 for 131Cs and 125I seed, respectively. The corresponding values determined using the Monte Carlo method were 1.053±0.014 and 0.924±0.016 cGy U−1 h−1 for 131Cs and 125I seed, respectively. The radial dose functions obtained with EBT film measurements and Monte Carlo simulations were plotted for radial distances up to 5 cm, and agreed within the uncertainty of the two methods. The 2D anisotropy functions obtained with both methods also agreed within their uncertainties. Conclusion EBT film dosimetry in a Solid Water phantom is a viable method for measuring 131Cs (model CS-1 Rev2) and 125I (model 6711) brachytherapy seed dose distributions with submillimeter resolution. With the Solid Water to liquid water correction factors generated from Monte Carlo simulations, the measured TG-43 dosimetry parameters in liquid water for these two seed models were found to be in good agreement with those in the literature.

This paper describes the evaluation of an inexpensive, commercially available 35 mm transparency slide scanner as a potential alternative scanning device for GafChromicTM HD-810 radiochromic dye film. Besides its low cost, the principal advantages of this type of scanner are high spatial resolution and high speed (a typical scan taking less than 1 min). With broad-band illumination the useful dose range using grey-scale imaging of GafChromicTM HD-810 is limited to about 50-800 Gy. By using the colour-scale imaging capability of the scanner we have been able to achieve a significant extension covering a similar range (15-2000 Gy) to that attainable using monochromatic illumination. The short-term reproducibility of the system is good, with a coefficient of variation of doses estimated from repeat scanning of uniformly exposed calibration films of less than 2%. Long-term stability is ensured by the scanning of a manufacturer-supplied test slide. The slide scanner system has been used in the determination of depth dose distributions from a model `hot particle' source containing 106Ru/Rh. GafChromicTM dye film stacks irradiated by the source were read out on both the slide scanner and a conventional Joyce Loebl MDM6 scanning stage microdensitometer. The overall agreement between the dose estimates provided by the two systems was within 10%.

we present the discovery of a previously unknown member of the immediate solar neighbourhood, DENIS-P J104814.7 395606.1 (hereafter DENIS 1048 39), identified while mining the DENIS database for new nearby stars. A HIRES echelle spectrum obtained with the 10-m Keck telescope shows that it is an M9 dwarf. DENIS 1048 39 has a very bright apparent magnitude (I = 12.67) for its spectral type and colour (I J = 3.07), and is therefore very nearby. If it is single its distance is only 4.1±0.6 pc, ranking it as between our 12 th and 40 th closest neighbour. It is also the closest star or brown dwarf with a spectral type later than M7V. Its proper motion was determined through comparison of Sky atlas Schmidt plates, scanned by the MAMA microdensitometer, with the DENIS images. At 1.52" yr 1 it primarily attests the closeness of DENIS 1048 39 and hence its dwarf status. These characteristics make it an obvious target for further detailed studies.

To investigate normal light scattering and cataract formation, the anterior eye segments of farmed Atlantic salmon (Salmo salar) reared in fresh water and sea water were documented in vivo for the first time with a Topcon SL-45 Scheimpflug camera. A total of 40 fish from the fresh-water-rearing period, obtained from 2 groups of identical age but showing a different growth rate, and 24 fish from the sea-water-rearing period, sampled from 2 groups with identical age but being fed different food brands, were included in this study. The fish were anaesthetized before examination. Due to the naturally wide pupil, no mydriatic compound was applied. All fish were removed from the water for photography, which was performed for each eye in 0° = vertical slit position. Images were recorded on Kodak Tmax 400 black-and-white film. Microdensitometric image analysis of all negatives was performed using a Joyce-Loebl online microdensitometer. In spite of the virtual absence of an anterior chamber gap between cornea and lens and very little light scattering in the normal fish lens, a small number of distinct layers could be reproducibly identified in the lens. While there was little abnormal light scattering which could point to cataract development in young fish from the fresh water period, the evaluation of the lenses from the 2 sea water groups showed the presence of specific forms of cataract especially in the cortical and supranuclear layers. There were significant differences between the groups fed different food brands at the sea water site. In conclusion, Scheimpflug photography proved to be applicable to eye research in fish in vivo. It is suggested that this method should be employed for reproducible documentation as an extension to slit lamp monitoring in experimental research to reveal causative factors for cataracts in farmed fish.

Series of Hα spectra and slit-jaw Hα filtergrams of a quiescent prominence taken at Pic du Midi Observatory on 7 November 1977 are studied. The observations have been digitized by means of an automated Joyce Loebl microdensitometer. The image processing of the Hα filtergrams reveals an internal structure of the prominence consisting of several arches. Series of high-resolution Hα spectra obtained with the slit position located on a selected part of one of the prominence arches have been chosen for Doppler-shift analysis. The obtained time series of the line-of-sight velocity reveal large velocity variations near the periphery of the arch and a strong dependence of the velocity (in sign and magnitude) on the position along the slit. The prominence arch shows also cyclic displacements along the line-of-sight direction implying Alfven string-mode oscillations.

In this paper we present complete two-dimensional measurements of the observed brightness of the 9th November 1990Hαflare, using a PDS microdensitometer scanner and image processing software MIDAS. The resulting isophotal contour maps, were used to describe morphological-cum-temporal behaviour of the flare and also the kernels of the flare. Correlation of theHαflare with SXR and MW radiations were also studied.

ABSTRA C T We present a new sample of brown dwarf (BD) candidates from a survey covering 68 · 68 centred on the Pleiades. The survey was constructed using I- and R-band photographic plates, from the United Kingdom Schmidt Telescope, measured using the new high-precision microdensitometer SuperCOSMOS at the Royal Observatory, Edinburgh. Objects as faint as or up to ,0:5 mag fainter than the Pleiades lithium boundary are selected on the basis of having extremely red photographic colours and proper motions consistent with cluster membership; follow-up near-infrared and infrared photoelectric photometry yields nine candidate BD Pleiads. Coordinates, magnitudes and finders are presented for these objects. We use these data and information on higher mass stars to construct a mass function having an increasingly shallow gradient towards and across the stellar/substellar boundary; a few of the candidates are found at distances of more than 28 from the nominal cluster centre. We discuss the implications of these results for future surveys.

Photographic Schmidt plates are among the most effective tools in wide-field astronomy. One of the principal difficulties of photographic plates when compared to modern detectors is lack of image depth. We present a technique for stacking plates digitized using the SuperCOSMOS microdensitometer, aimed at maximizing the signal-to-noise ratio in faint images. The efficacy of several image combination algorithms is tested by stacking plate frames in the presence of spurious images. We find that an ‘average sigma clipping’ type pixel rejection in conjunction with our weighting scheme is most effective in delivering a clean, high signal-to-noise ratio stack. The gain in limiting magnitude obtained from stacking is found to be consistent with that expected: ΔM∼1.5 for a stack of 16 good-quality plates.

Using the PDS microdensitometer at the R oyal Greenwich Observatory, we have acquired U, B, V, R and I surface photometry from UK Schmidt photographic plates for all the galaxies with measured redshifts in the Durham ‐AAT redshift survey. By comparison with CCD photometry we show that such precision photographic photometry of galaxies off IIIa emulsions is capable of an accuracy as good as a few hundredths of a magnitude. We discuss the colour-related properties of these galaxies, and derive luminosity functions in each waveband. We show that when divided by colour, the faint-end slope of the luminosity function of the bluer galaxies is significantly steeper than that for the redder ones.

The need for test objects in mammography quality control programmes to provide an objective measure of image quality pertinent to clinical problems is well documented. However, interobserver variations may be greater than the fluctuations in image quality that the quality control programme is seeking to detect. We have developed a computer algorithm to score a number of features in the Leeds TOR(MAX) mammography phantom. Threshold scoring techniques have been applied in the first instance; scoring schemes which utilize measures such as signal-to-noise ratio and modulation have also been formulated. This fully automatic algorithm has been applied to a set of 10 films which have been digitized at 25 microns resolution using a Joyce-Loebl scanning microdensitometer. The films were chosen retrospectively from quality control test films to demonstrate: (a) a range of optimized imaging systems, and (b) variation from the optimum. The performance of the algorithm has been compared with that of five experienced observers, and has been shown to be as consistent as individual observers, but more consistent than a pool of observers. Problems have been encountered with the detection of small details, indicating that a more sophisticated localization technique is desirable. The computer performs more successfully with the scoring scheme which utilizes the full imaging information available, rather than with the threshold-determined one. However, both the observers and the computer algorithm failed to identify the non-optimum films, suggesting that the sensitivity of the TOR(MAX) test object may not be adequate for modern mammography imaging systems.

Circular disks (280 mm diameter, 2 mm thickness) were injection molded from two grades of isotactic polypropylene under systematic variation of processing parameters (melt temperature, mold temperature, flow rate, packing pressure, and packing time) according to a two-level fractional factorial design. The disks showed ring-shaped zones (“halos”) of enhanced turbidity. The wide-angle X-ray scattering of the disks was measured as a function of the distance from the gate at 13 positions along the radius, using a diffractometer and reflection geometry. These measurements yielded radial profiles of the orientation of α-PP and of the distribution of β-PP crystallites. Both kinds of profiles revealed clear correlations with the polymer grade and with the melt and/or mold temperature. Radial profiles of optical turbidity of the disks were obtained by means of a microdensitometer. Pronounced maxima of turbidity were found to coincide with the maxima observed in the radial distribution of β-PP. An analysis of variance (ANOVA) of the experiments showed that the mass temperature has the greatest influence on the radial distances of the maxima of turbidity. Increasing mass temperature led to decreasing radial distances of the turbidity maxima, whereas the mold temperature as well as the flow rate only had a small influence on the radial positions of the turbidity maxima. The investigation of cross-sections, which were taken from some disks at selected distances from gate, by means of optical microscopy using polarized light revealed significant changes in the morphology with increasing distance from gate, e.g., changes in the size and distribution of β-PP spherulites.

High resolution, two-dimensional thickness profiles of ArF excimer laser deposited Bi films are recorded by a microdensitometer. The azimuthal dependent cross-sectional profiles are consistently fitted by linear combinations of a cos4Θ evaporation-like component and a much more sharply peaked one with exponents ranging from 8 to 61. When keeping the laser spot dimensions fixed, no dependence on laser fluence is obtained. An increase in Ar pressure from 10-6 to 10-1 Torr leads to the sharpening of the angular distribution along both axes: the forward directed component narrows from cos23Θ to cos61Θ along the short, and from cos9Θ to cos17Θ along the long axis, respectively. Further increase in pressure results in a sudden broadening leading to circular symmetry at around 0.5 Torr. Above 10-4 Torr the deposition rate continuously decreases with increasing Ar pressure. In He atmosphere only narrowing is obtained above 10-1 Torr., This work has been carried out in the Instituto de Optica, CSIC, Madrid, Spain. One of the authors (T.S.) would like to say thanks for a NATO fellowship.

We report the serendipitous discovery of a new, very low luminosity, cool degenerate in the region of Taurus. The object was found as a very high proper-motion star (μ = 13 yr-1) on seven I-band UK Schmidt Telescope plates, dating from 1987 to 1994, via digitized scans from the new, fast, high-precision microdensitometer SuperCOSMOS. Photometry and spectrophotometry indicate that the object has a temperature comparable to those of the handful of coolest white dwarfs currently known (T~3900 K). We discuss the relevance of this discovery to current research concerning Galactic structure and evolution.

From PDS microdensitometer measurements of 10 plate pairs of the open cluster M 11 with epoch differences of 16–70 years taken with our 40 cm double astrograph, the relative proper motions of 872 stars in the cluster region are determined. 85% of these have accuracies better than 0.1 arcsec per century. The distribution parameters of stars with different magnitudes are found from a new mathematical model. The membership probabilities of the stars are calculated. 541 stars have membership probabilities higher than 0.7. The new approach of membership determination is shown to be not only theoretically rigorous, but also practically feasible, and more reasonable results can be obtained from its use. Some evidence is found for mass segregation in space and lesser evidence for mass segregation in velocity space.

The present state of the hardware and software of our Joyce-Loebl MK III CS 1970 microdensitometer is reported. The modifications to the existing software necessary for it to be applicable to the data from an Agfa Arcus II commercial scanner are described. The accuracies of the two instruments are compared by the measurement and analysis of photographic plates for two data sets of the short nozzle-to-plate distance of benzene. For about 30000 measured points on both devices, the two instruments give practically the same accuracy, except for very light plates where the Joyce-Loebl results seem to be the best ones. The ra(C–C) distance obtained from the scanner data is systematically elongated by about 0.5%. Acceptable agreement of the root-mean-square vibrational amplitudes from the two instruments is obtained. A sixfold increase in the number of points applied from the scanner does not improve the agreement very much. The conclusion is that the scanner, in connection with the applied software, can be used as a microdensitometer for gas electron-diffraction plates.

The X-ray Nova GRO J0422+32 in its low brightness has been identified with a B∼ 21m, R∼20m star on Palomar Sky Survey glass copies. The scans obtained with an automatical microdensitometer along with our special PC program were used. The resulting outburst amplitude 8m is one of similarity features for the class of the low mass X-ray Novae, black hole candidates.

The limititations to the use of data from the major Schmidt surveys, i.e. grain noise as well as practical considerations of image processing and astrometry, are discussed, together with the question of mounting films on microdensitometer platens. Next, the major scanning systems dedicated to Schmidt surveys, their accomplishments, and their future programs are considered. Finally, the archiving and distribution of the scan data is discussed, and some suggestions regarding future directions are made.

Microfocus X-ray film radiography was applied to image submillimetre gaps formed by an accurate micrometer. Optical density profiles of the images were measured by a microdensitometer. Gap widths as well as the focal spot size were determined. Measured width results were compared with true values and the agreement is of the order of 2% for gaps in the range of 0.05 mm to 0.20 mm.

Circularly symmetrical phase etched computer-generated hologram (CGH) are widely used to test aspheric surface. In CGH fabrication errors, pattern distortion errors not only strongly affect the test precision but also can’t be facilely eliminated. In order to improve the test accuracy of system, a moire fringes method is described for testing circularly symmetrical pattern distortion. Compared with the conventional method of using microdensitometer, the new method is more accurate and quicker for measuring the pattern distortion. Then, based on the accurate measurement of CGH pattern distortion, the impact on test accuracy that pattern distortion brings is eliminated with synthetic wavefront error map. Finally, through computer simulating, it is proved that the new method can effectively reduce the impact on test accuracy that pattern distortion brings.

The dose response of high‐sensitivity GafChromic film to photons from 125I seeds for doses up to 200 Gy was established. The optical densities were measured using two types of densitometers: (a) a Macbeth spot densitometer with broadband light spectrum, and (b) an LKB He‐Ne laser scanning microdensitometer with red light of wavelength 632.8 nm. The net optical density was found to be a power function of dose with exponents of 0.858 and 0.997, for the Macbeth and LKB densitometers, respectively. Film sensitivity with the LKB densitometer was about double of that with the Macbeth densitometer. The dose measurements were performed using the high‐sensitivity GafChromic films for 125I model 6702 seed in solid water phantom. Each film was positioned parallel to the seed’s long axis and centered at the seed’s transverse axis. Films were exposed at various distances, ranging from contact to 3 cm from the seed center. The radiation dose delivered to the film center varied from 7 to 50 Gy, depending on the distance. The optical density at the film center was measured using both types of densitometers. Dose conversion was achieved with the established dose response curves for the respective densitometers. The dose values, along the seed’s transverse axis obtained using both densitometers, were compared with each other, and also compared with published thermoluminescent dosimeter(TLD) data and Monte Carlo results. General agreement was found. It was concluded that the high‐sensitivity GafChromic film measurement is a feasible method for 125I seed dosimetry in solid water phantom. Furthermore, in order to investigate the energy dependence of the dose response of the high‐sensitivity GafChromic film, the dose responses of such film for photon energies, 660 and 1250 keV, emitted by 137Cs and 60Co, respectively, for doses up to 200 Gy were studied. The dose response curves, obtained with the LKB laser densitometer, were essentially linear for both radionuclides. However, those curves obtained with the Macbeth densitometer were fitted to power functions of dose, with an exponent of 0.839 and 0.849 for 137Cs and 60Co, respectively. The relative sensitivities for 125I and 137Cs compared to that for 60Co were found to be 0.56 and 0.93, respectively.

The measurement of absorbed dose as well as dose distributions (profiles and isodose curves) for small radiation fields (as encountered in stereotactic surgery) has been difficult due to the usual large detector size or densitometer aperture (1 mm) relative to the radiation field (as small as 4 mm). The radiochromic direct-imaging film, when read with a scanning laser microdensitometer (laser beam diameter 0.1 mm), overcomes this difficulty and has advantages over conventional film in providing improved precision, better tissue equivalence, greater dynamic range, higher spatial resolution, and room light handling. As a demonstration of suitability, the calibrated radiochromic film has been used to measure the dose characteristics for the 18-, 14-, 8-, and 4-mm fields from the gamma-ray stereotactic surgery units at Mayo Clinic and the University of Pittsburgh. Intercomparisons of radiochromic film with conventional methods of dosimetry and vendor-supplied computational dose planning system values indicate agreement to within +/- 2%. The dose, dose profiles, and isodose curves obtained with radiochromic film can provide high-spatial-resolution information of value for acceptance testing and quality control of dose measurement and/or calculation.

Very faint Hα emission in the solar corona registered on over-exposed photographs made by a coronagraph and an Hα filter is studied. The over-exposed filtergrams have been processed by a Joyce Loebl automated microdensitometer and the two-dimensional scans have been analysed by the residual image method. A classification of the faint Hα emission objects, revealed on the isodensity maps, is proposed and the latitudinal distribution, the morphology, and the location with respect to the other active phenomena are analysed. Taking into account some possible plasma effects that could be caused by coronal magnetic field changes, a hydromagnetic interpretation of the faint Hα emission is proposed.

A new dosimeter material has been developed which consists of a radiation sensitive layer on a reflective base, and utilises a portable microdensitometer for response measurement. The instrument, modified from a readily available hand-held unit, is a standard in the printing industry. The system was designed with the demands of ‘in plant’ use in mind, and is equally suitable for either gamma or electron beam irradiation. The dosimeter material develops an easily visible colour change, which is quantitative, highly reproducible and stable over the dose range of approximately 5–45 kGy. The results presented demonstrate the calibration and characteristics of the dosimetry system, and explore some of its potential.

The absolute calibration of the method of determination of the energy and spatial parameters of γ-quanta in X-ray emulsion experiments is presented. X-ray films exposed in the calibration experiment PAMIR by π 0 → 2γ decay formed the experimental material. The accuracy of γ-quantum energy determination by the method of one-point measurement is σ ( ln E ) ≅0.3. The estimation of shower parameters is solved by the method of maximum likelihood using the darkening density matrix measured with a PDS microdensitometer.

To study the potential of the computer interpretation of digital mammograms it is necessary to use digitized conventional films because at the present time insufficient resolution may be achieved using computed radiography. For example, the automatic detection of very small subtle calcifications requires digitization at 50 μm or smaller with at least 8 bits of grey level (Chan et al, 1987; Dance, 1993). In this paper we present a simple and practical method to evaluate and compare the technical performance of three film digitizers. These all cost about £20 000 and are being assessed as possible methods for obtaining digital mammograms for a national database (Astley, 1993). The digitizers investigated are a drum scanning microdensitometer, a laser scanning densitometer and a CCD camera. According to manufacturers' specifications, each has a high resolution sampling pixel size (50 μm or less) and is capable of digitizing to a grey level of at least 8 bits over the complete range of diffuse optical densitie...