Medical X-ray Films Research Articles

Control of Medical X-Ray Film Processing by Light Sensitometry: the Influence of Reciprocity Law Failure and Intermittency Effect

In medical X-ray imaging, film processing is one of the main parameters determining image quality, An important method for controlling film processing is sensitometry. Light sensitometers in which electroluminescent foils serve as light sources are widely used for this purpose. These sensitometers emit light pulse trains of different pulse repetition frequency and different total length, which may cause intermittency effects or give rise to reciprocity law failure. These effects may increase the uncertainty of this sensitometric method to an extent which is no longer tolerable for the intended purpose. The effects were measured for a great number of films of five leading film manufacturers. The results are presented and steps proposed which should be taken to make this kind of sensitometry more reliable.

277 A measurment of medical X-ray film with a screen-film method

277 A measurment of medical X-ray film with a screen-film method

(1) 高画質間接X-レイフィルムの開発

(1) 高画質間接X-レイフィルムの開発

Method of simulated screen sensitometry for asymmetric, low crossover medical x‐ray films

Recognition of the importance of performing simulated screen-light sensitometry of medical x-ray films for the purpose of processor quality control has increased over the past several years. As a result there is a greater need to provide new techniques for performing simulated screen-light sensitometry. Medical films with reduced intensifying screen-light crossover intended to achieve reduced blur and higher spatial resolution pose particular problems in doing simulated screen-light sensitometry if care is not taken to choose a proper simulated light sensitometer with the capability of simultaneous double-sided exposures. Misleading and incorrect sensitometric data can be obtained for film contrast evaluation if a single side exposure is used. Asymmetric, near-zero crossover films pose even greater problems as proper orientation of the film and proper degree of light output asymmetry need be achieved in order to obtain correct sensitometry. The films used in this study were three double emulsion films varying in crossover from 3% to 24%. Of the two very-low-crossover films, one had symmetric emulsion layers while the second featured emulsion layers which were asymmetric in terms of contrast and speed. Sensitometric data show several curve shapes with significant distortions, depending on orientation, for the asymmetric, low-crossover film when exposed using a single-sided exposure. Only by using a double-sided exposure and an appropriate neutral density filter to simulate the degree of screen-light asymmetry in this system could one achieve a characteristic curve comparable to that achieved by inverse square sensitometry.

1 高画質間接 X-レイフィルムの開発(第 12 回放射線機器技術発表会予稿)

1 高画質間接 X-レイフィルムの開発(第 12 回放射線機器技術発表会予稿)

Radiation-induced polymerization of acrylamide in ethanol and its application in medical x-ray film as a covering agent

The radiation-induced polymerization of acrylamide in ethanol has been studied. By this method, the aqueous solution of PAM at certain concentration and pH value has been successfully applied into the medical x-ray film emulsion as a covering agent. The utilization of product mentioned above can maintain the same quality of medical x-ray film, but also remarkably decreases the consumption of silver in the production of them.

Frequency Dependence of Minimum Perceptible Contrasts and Optimum Film Densities of Radiographs

The frequency dependence of minimum perceptible contrasts (differences in diffuse density units) for various viewer brightnesses was obtained by observing noiseless sinusoidal patterns made on fine-grain photographic films. For each frequency, the contrast is more easily perceptible zvith an increase in the viewer brightness and a decrease in the average density. Under the best conditions a contrast of 0.0043 is perceptible. The best perceptibility was attainned at 0.8 to 1.0 mm-1.The optimum densities, at which the detectability and resolution became best, were obtained from the maxima of the psychophysically modified gradient as defined by Kanamori in 1964. The optimum density decreases as the viewer brightness decreases and the frequency increases. For a typical medical x-ray film OG, the optimum densities are less than 1.3, while those of industrial x-ray film Industrial- 100 are less than 2.4.

Assessment of Signal Detectability for Conventional and Reversal-Processed Medical X-Ray Films Obtained without Intensifying Screens

The detectability of the conventional and reversal-processed images obtained without intensifying screens was assessed by using the maximum information content (Imax) generated from receiver operating characteristic (ROC) curve data and the noise-equivalent number of quanta (NEQ). It was demonstrated, from the Imax values versus background density, that reversal-processed images have a very high detectability at lower density levels, but exhibit a rapid decrease in detectability at higher density levels. On the other hand, the detectability of conventional images was not as strongly affected by the density. Therefore, the detectability of both conventional and reversal-processed images varies with the density, and conventional images are superior to reversal-processed images at higher densities. This was confirmed by measureing the NEQ.

201. 医療用感材の新しい現像/定着処理液の開発(第 47 回総会学術大会一般研究発表予稿)

201. 医療用感材の新しい現像/定着処理液の開発(第 47 回総会学術大会一般研究発表予稿)

201. 医療用感材の新しい現像/定着処理液の開発(写真・画像技術-1 自動現象機)

201. 医療用感材の新しい現像/定着処理液の開発(写真・画像技術-1 自動現象機)

Problems associated with simulated light sensitometry for low‐crossover medical x‐ray films

Over the past ten years the evolution of medical x-ray films has been toward films with reduced intensifying-screen light crossover in order to reduce blur and obtain higher spatial resolution. For films with very low crossover, misleading and incorrect sensitometric data may be obtained for film contrast evaluation and processor control if a simulated light sensitometer with a single-sided, light-exposing device is used. Screen light exposures were made using an inverse square, intensity-scale sensitometer. Simulated light exposures were made using a widely used single-sided, simulated-light sensitometer commonly used for film processor quality control, and a new simulated-light sensitometer capable of producing either single- or double-sided sensitometric exposures. The films used included one single-emulsion film and three double-emulsion medical x-ray films with light-crossover values ranging from approximately 3% to 30%. Sensitometric data showed a significant distortion (bump) in the characteristic curve for the 3% light-crossover film exposed with the single-sided, simulated-light sensitometer.

Screen film processing systems for medical radiography: a historical review.

Since Roentgen first experimented with radiation to produce a radiographic image, many milestones have been reached in the design and manufacture of intensifying screens, medical x-ray films, film processors and chemicals. As a result, high-quality medical radiographs are obtainable today at very low radiation dose. This progress is the result of major contributions and the collaborative efforts of many individuals in industries, universities, and medical institutions involved in basic research, development and manufacturing. This article highlights some of the major advances in the evolution of screen-film-processor chemical systems for medical radiography. Photographs, radiographs, and scientific data are included which illustrate some of the major achievements.

Letters to the Editor Comments on ‘Necessity and Outlines of a New Theory of the Granularity of Medical and Industrial X-ray Films’1

Letters to the Editor Comments on ‘Necessity and Outlines of a New Theory of the Granularity of Medical and Industrial X-ray Films’¹

Necessity and Outlines of a New Theory of the Granularity of Medical and Industrial X-ray Films

AbstractTile analysis of film granularity of medical and industrial X-ray films is based on tile ideas of Rossmann formulated in 1963. Thsi relation seemed to be so well proved by many experiments and calculations in tile spectral range of 0-10 mm-1 , tile visible range, that no attention was paid to the invisible rest of tile Wiener spectrum. But just tile measurements of Wiener spectra in a spectral region up to 250 mm-1 (or higher) give results which contradict Rossmann’s theory. It is shown that neither the expression for quantum noise nor the assumption of a linear superposition of film noise and quantum noise is valid. The latter can only be seen as an approximation following out of the new theory, which is based on the idea that σ2, as the integral over the Wiener spectrum, corresponds to the amount of silver in the film and is constant for a given density, film and developer. The shape of the Wiener spectrum is given by the |MTF|2 of the system film +screen+X-ray-quantum under the boundary conditi...

Quantum Aspects of Intensification by Light

Absolute monochromatic sensitometry is used to determine the characteristic curves of a medical X-ray film under conditions of optimum exposure and development and with a series of uniform low-intensity post-exposures of long duration. The sub-image density is investigated using data from both fog-free and high-fog latensifieation. Analytical problems caused by fog growth are identified. Effective photon sensitivity distributions are derived for the most populous grains-size class for each of the exposure conditions. Conclusions are drawn concerning the size of the stable latent sub-image and the proportion of sub-image grains.

A Contribution to Interpretation of the Photographic Characteristic Curve

The problem of the photon sensitivity of emulsion crystals is reviewed and is seen to rest on interpretation of the characteristic curve. A partial-development technique for the identification of grains hearing latent image is used to determine characteristic curves for effectively mono-sized classes of grains in a fast medical X-ray film given monochromatic exposure. The characteristic curve of a pure-bromide nominally monodisperse emulsion is also shown for monochromatic exposure. Characteristic curves of the two emulsions are analyzed according to models which assume, respectively, a unique photon sensitivity and efficiency factor, and the existence of a spread of effective photon sensitivities. Conclusions are drawn concerning the success of the partial development technique and of the analytical methods, the photon sensitivities found and the minimum size of latent image.

Assessment of Image Quality of Negative- and Reversal-Processed Medical X-Ray Films with Intensifying Screens by Entropy Method

The image quality, mainly from the viewpoint of granularity, of negative- and reversal-processed X-ray films with intensifying screens was assessed by the entropy method using two types of screen-film system. It was found, from the transmitted information (TI) or the relative efficiency of transmission η versus the relative exposure and density, that optimum conditions under which TI or η is a maximum exist for both negative and reversal X-ray films. It was also shown, from the conditional entropy Hx(y) which refers to granularity, that negative and reversal systems have better and poorer regions and that reversal systems are better at higher exposures than negative systems. This was confirmed by measuring the Wiener spectra.

Modified Bootstrap Sensitometry In Radiography

A new modified bootstrap approach to sensitometry is presented which provides H and D curves that show almost exact agreement with those obtained using conventional methods. Two bootstrap techniques are described; both involve a combination of inverse-square and stepped-wedge modulation of the radiation field and provide intensity-scale sensitometric curves as appropriate for medical radiography. H and D curves obtained with these modified techniques are compared with those obtained for screen-film combinations using inverse-square sensitometry as well as with those obtained for direct x-ray film using time-scale sensitometry. The stepped wedge of the Wisconsin X-Ray Test Cassette was used in the bootstrap approach since it provides sufficient exposure latitude to encompass the useful density range of medical x-ray film. This approach makes radiographic sensitometry quick and convenient, allowing accurate characteristic curves to be obtained for any screen-film cassette using standard diagnostic x-ray equipment.

Image Quality of Reversal-Developed X-Ray Film with Reference to Density

The image quality of medical X-ray film treated by reversal development is studied. Evaluation of the image quality is performed by determining the characteristic curve, the contrast transfer function (CTF), the noise-equivalent number of quanta (NEQ), and the detective quantum efficiency (DQE), all of which depend on the density. The CTF of reversal-developed film is better than that of negative film in the low-exposure domain. There is no notable difference between the DQE of reversal-developed film and that of negative film. The S/N ratio of the output (NEQ) of reversal-developed film is almost the same or larger than that of negative film over the complete exposure range.

Reciprocity-Law Failure in Radiographic Image-Forming Systems

The Reciprocity-law failure characteristics of three brands of medical blue-sensitive X-ray films exposed with intensifying screens are studied. The variation in X-ray intensity for different points on a reciprocity failure curve is obtained by varying the focus-film distance (FFD), since it is confirmed that the X-ray intensity varies approximately as FFD to the minus 2.15th power, for FFDs from 0.40 to 5.68 meters. All of the films investigated show no high-intensity reciprocity failure effects for exposure times of 1/120 to 5 seconds. However, they show remarkably low-intensity reciprocity failure effects for exposure time longer than about 0.3 sec. It is considered that the existence of this low-intensity reciprocity failure must be taken into consideration, since it would affect the patient dose significantly according to the selection of the exposure conditions.