Home Roses Development of X-ray film in tanks. Method of recording an x-ray image. Dichroic veil and milky plaque in the picture. The effectiveness of nitrous oxide. Patient status. Safety of using nitrous oxide. Effect on the body

Roses

Development of X-ray film in tanks. Method of recording an x-ray image. Dichroic veil and milky plaque in the picture. The effectiveness of nitrous oxide. Patient status. Safety of using nitrous oxide. Effect on the body

Once vision has adjusted to the darkroom light, remove the wrapping from the x-ray film and carefully attach the film to the film holder with the patient's name pre-signed. At this stage the film appears empty. Then set the timer for the required development time and place the film in the developing tank.

After the timer sounds, remove the film holder with the developed film and hold it over the rinse bath to prevent the developer from dripping onto the work surface. Next, close the developing tank and rinse in the rinsing bath. film under clean running water for 30 s. This is done so as not to contaminate the fixing tank with developer. After washing the film, you need to wait for the water drops to drain. Now the first outlines of the image are visible on the film.

Dry the work surface and set the timer for the required time. Place the developed film in the fixing 6ak and do not remove it until the timer sounds. Then, just as when developing, hold the film over the rinsing bath so as not to contaminate the working surface, and rinse the floor with a stream of water. Now the x-ray is ready, you can turn off the photographic laboratory lamp and turn on normal lighting.

After the film has been processed and an image of the area under study is visible on it, it must be rinsed under running cold water for 10 minutes (5 minutes for extraoral films) to remove any remaining fixative before drying. To prevent subsequent contamination of solutions and films, used film holders are also washed and dried.

Manifestation

During the development process, an image is formed in the photosensitive layer due to the reduction of metallic silver from bromide in those places where it was affected by radiant energy. In this case, unlit or poorly illuminated grains of silver bromide should remain unaffected by the reducing agent and unaltered.

Developer composition. The developing solution includes: 1) water as a solvent, 2) a developing agent, 3) a preserving agent, 4) an accelerating agent and 5) an anti-veiling agent, which is also a retardant.

Developing substances. The most commonly used are hydroquinone, metol and phenidone. Metol develops quickly, but predominantly only the surface layers of AgBr grains. Hydroquinone acts more slowly, but throughout the entire grain depth and therefore helps to increase image contrast. Fenidon by itself is little active, but in combination with other developing substances, such as hydroquinone, it forms very effective developers. As a rule, mixtures of developing substances are used. Most Popular methol-hydroquinone And phenidone-hydroquinone developers. The compositions used for processing X-ray photographic materials differ from the compositions used in photography in that, in order to increase image contrast, they contain an increased amount hydroquinone . In terms of sensitometric characteristics, phenidone-hydroquinone developers are superior to methol-hydroquinone ones. In addition, they deplete more slowly.

Preservatives. The developing substance in an aqueous solution is quickly oxidized by atmospheric oxygen and becomes unusable. To prevent this, it is introduced into the developer as a preservative substance. sodium sulfite , which binds oxidation products in it and thereby contributes to the constancy of the properties of the developing substance. Sulfite also has the ability to dissolve silver halide, which is almost insoluble in water, during the development process, thereby supporting the development process. It also restores the developing ability of the solution during the development process, turning it into a more stable compound with developing properties.

Accelerating substances. Almost all developing substances act only in an alkaline environment, and the speed of action of the developing solution depends on the degree of alkalinity. The alkali neutralizes the hydrobromic acid formed during the development process, in the presence of which the activity of the developing substance decreases, and thereby accelerates the development process. To create an alkaline environment in developing solutions, use caustic alkalis : caustic sodium and caustic potassium Andcarbonic alkalis - sodium carbonate, potassium carbonate and borax.

Anti-fouling agents. Any developing substance has the ability to produce a chemical veil. To reduce the density of this veil, add potassium bromide as an antifogging agent and as a substance that retards the reduction of unexposed silver bromide. It is also used as an anti-veiling additive in phenidone-hydroquinone developers. benzotriazole , increasing the selectivity of the action of developing substances.

Preparation of developing solutions. The developer recommended by X-ray film manufacturers is called standard. Each company tries to recommend its own recipes. In order for the development process to proceed normally, the correct composition of the developing solution is required, therefore the recipe for the developing solution always indicates the order of dissolution of the substances

Main solvent The substance in all photographic solutions is water. It should not contain any dissolved mineral salts or traces of organic substances. It is best to use distilled water to prepare solutions, or, if it is unavailable, boiled water.

General procedure for preparing developing solutions next. Usually, dissolves first a preserving substance, i.e. sulfite, and only then a developing substance. The exception to this rule is metol and glycine. Metol does not dissolve in a sulfite solution, but precipitates in it in the form of a white precipitate; therefore it always dissolves separately. In the combined metholhydroquinone developer, the hydroquinone dissolves after the sulfite has dissolved. The third one is dissolved accelerating agent - alkali. In this case, caustic potassium and caustic sodium are pre-dissolved only in cold water and carefully poured into the solution of sulfite and developing substance. Last to dissolve anti-fog agent . To accelerate the dissolution of substances, water can be heated, but not above 50 ° C, since a higher water temperature causes rapid decomposition of developing substances and loss of developer activity. The prepared developing solution must sit for at least 24 hours. The debris that floats to the surface is carefully removed, and the solution is drained from the sediment that has settled to the bottom and filtered through cotton wool to remove possible mechanical impurities. Developing solutions must be prepared only in glass, porcelain, earthenware, ceramic or enamel dishes, but not in metal, with the exception of stainless steel. Prepared developer solutions should be stored in glass jars, tightly closed with a good stopper, over which a rubber fingertip is placed.

Storability of developing solutions. A developing solution prepared with distilled or freshly boiled water can be stored for several months in bottles that are well sealed and filled to the top. Used solutions are preserved less well; in baths they oxidize faster than in bottles, since the surface of their contact with air in this case increases significantly. The developing solution should be colorless. As it deteriorates, it darkens or decomposes, releasing sediment. As the developing solution is used, it becomes depleted. In order not to use highly depleted solutions, one should take into account amount of photographic material processed . According to the standards, in 1 l developer can be processed 1 m 2 films, which is approximately: 50 films measuring 13x18 cm, or 25 films 18x24 cm, or 17 films 24x30 cm, or 10 films 30x40 cm.

The process of manifestation. In the process of development, the developer, as it were, completes the work begun by the radiation energy and completes the transformation of silver bromide crystals into particles of metallic silver. Thus, the process of manifestation is reduction reaction of silver halide into metal . In general terms, the process of manifestation is as follows. Developing solution , penetrating into the gelatin layer of the exposed film immersed in it, causing it to swell. Swollen gelatin is a complex of cells, inside of which there are microcrystals of silver halide. As soon as the developing solution has penetrated the gelatin cell and reached silver crystal , its manifestation begins, but not from the entire surface of the crystal, but only from those points that formed the latent image; it continues until the entire silver bromide crystal and other crystals in contact with it are completely restored. These individual points from which manifestation begins are called centers of manifestation .

Received after development difference in density of deposited silver in individual areas of the developed film depends not on the degree of development of each crystal separately, but on number of crystals developed . So, if in one area of the film the amount of radiation energy was absorbed more than in another, then it will contain a larger number of silver halide microcrystals capable of development, and therefore the degree of its blackening will be greater compared to the other area. In addition to black and white areas on the developed film, intermediate transitions are also obtained. These different densities create the contrast observed in the image.

Along with the restoration of silver halide microcrystals exposed to radiation, the development process also occurs silver halide reduction , not exposed to radiation . In the first case, a visible image is formed, and in the second - a veil. The later unirradiated silver bromide crystals are developed, the better the image quality will be. In irradiated silver halide crystals, the reduction of metallic silver is completed in a short time; in non-irradiated crystals it lasts a long time. Therefore, all silver bromide crystals, in which development centers managed to appear during shooting, manage to appear much earlier than the development of non-irradiated crystals begins.

Methods of manifestation. There are two ways of manifestation: a) visual , allowing you to observe the progress of development with your eye; it is produced in cuvettes and is used primarily in the processing of plates and flat films; b) manifestation over time , does not require visual control; it allows simultaneous development of a large number of films in light in light-proof tanks. The nature of the stages in the darkroom process depends on how the film is processed. They are different: cuvette development, tank development, machine automatic film processing.

Cuvette development. When the number of films being processed is small (10 - 15 pieces per shift), a manual development method with time and temperature control is used. When starting development in cuvettes, first arrange them in the most convenient order for work. cuvettes for developer, water and fixer ; then pour the developing solution into the cuvette - at least 1 cm above the surface of the photographic material being developed, for which purpose in a 30x40 cuvette cm must be poured at least 1 l solution, into a 24x30 cuvette cm - not less than 600 cm 3 . The solution temperature is first brought to the set temperature (18 - 20° C). At a low developer temperature, a low-contrast, transparent image is obtained, which can be mistaken for underexposure. Developing at temperatures above 20°C is also not recommended to avoid excessive swelling of the gelatin.

After preparing the necessary solutions , turn off the white light and, before starting development, adapt your vision for a few minutes. When developing, the cuvette with the solution must be rocked all the time to mix the solution so that the development process occurs evenly over the entire surface of the photosensitive layer. If the cuvette is not shaken, then oxidation products are formed at the surface of the photosensitive layer, inhibiting the development process. To monitor the progress of development the film is removed from the cuvette and examined in front of the flashlight, but only for a very short time, since this may cause air and light veil . You can only remove the film from the cuvette using tweezers, since when removing it with your fingers, the emulsion layer may slip and fingerprints may appear on it.

It is recommended to carry out photo processing of films in standard frame holders , which reduces the risk of damage to the photosensitive layer. From the moment the film is immersed in the developing solution, its development begins, and during normal shooting first traces of the image usually appear after 30 - 40 seconds, and the entire manifestation process should finish within 6 - 7 minutes. The development time is controlled by a clock; it must be completed at the moment when the non-irradiated grains of silver bromide begin to decompose noticeably from the action of the developing solution. The manifestation should be considered finished , when the blackened areas become almost opaque, and all the details appear in the light areas, i.e., the image of the photographed object has been developed in all details, with all the transitions from lighter to darker areas. In general, it is recommended to use the rule that it is better to overdevelop the film than to underdevelop it.

Duration of manifestation largely determines the quality of the image. At shortened time development, the sensitivity and contrast of the film being developed are not fully used. As increasing duration development, at a constant temperature of the developing solution and its composition, the contrast, sensitivity and veil of the photographic layer increases. Typically, insufficient image density is caused not by underexposure, but by underdevelopment, and vice versa, increased density is often a consequence of overexposure, rather than overdevelopment. After finishing work, the developer must be poured into a bottle, otherwise it is decomposed by atmospheric oxygen and loses its activity.

Tank manifestation. If 20 films or more are processed per shift, it is recommended to use tank development. Tank - this is a metal tank on legs, inside of which there are 3 narrow tanks with a capacity of 15 liters for developer, water (intermediate rinsing) and fixing solution. Inner space The common tank is filled with water, the temperature of which is automatically regulated by an electric thermostat device. Each tank is equipped with a tightly closing lid. The tanks can simultaneously process up to 5 films of any standard size, suspended on special frames. An indispensable addition to the tank should be photo clock , on which development times for several films can be noted.

When photochemically processing films in tanks, one should observe the following rules: - films in tanks should not touch each other - the distance between them should be at least 2 cm; - to remove air bubbles from the surface of the film, as well as to ensure uniformity of the solution and uniform development, the frame with the film is periodically raised and lowered. It is necessary to observe the optimal temperature and time regime for development, which is indicated on the packages with the film and in the instructions for its processing, as well as for the use of reagents for preparing the developer. When the photochemical process is carried out correctly, the processing of 1 m 2 of X-ray film requires from 0.4 l to 1 l of developer and from 0.6 l to 1 l of fixer. To quickly determine the area of the developed film, depending on its size, it is necessary to use special tables

Refreshing solution. The amount of developing solution in the tank, as more and more films are developed in it, gradually decreases due to the entrainment of a certain amount of solution by the swollen gelatin layer. The composition of the developing solution also changes, its activity decreases mainly due to an increase in the concentration of bromide salts formed during the decomposition of silver bromide, and due to a decrease in the alkali spent on neutralizing the hydrobromic acid formed during the development process. To extend the life of the developing solution, replenish its quantity and restore the disturbed balance of its constituent parts, the so-called refreshing solution. The composition of this solution differs from the main developer recipe in that it does not contain bromine , and the concentration of its other constituent substances is increased approximately 1.5 times compared to the main recipe. Composition of the refreshing solution: Metol - 4 g; Hydroquinone - 16 g; Anhydrous sodium sulfate - 72 g; Anhydrous sodium carbonate - 48 g; Caustic sodium - 7.5 g; Water - up to 1 liter.

Replenishing the developing solution in the tank with a refreshing solution is done as follows. The level of the freshly prepared solution is noted in the tank and, as it decreases, it is replenished with a refreshing solution to the original volume, i.e., to the mark made. This addition of a refreshing solution to the initial one can be repeated until a liter of refreshing solution is consumed for each liter of the initial solution. Further addition of a refreshing solution is impractical, and the used developing solution must be replaced with a fresh one.

21.10.2017

X-ray artifacts can arise from improper handling of X-ray film during image production, storage, and film processing.

X-ray artifacts can arise from improper handling of X-ray film during image production, storage, and film processing. The X-ray film emulsion is sensitive not only to external X-ray radiation, but also to pressure, friction or other mechanical stress, dampness, and sudden changes in temperature. During photochemical processing of X-ray photographs, defects of various origins may also appear on the film, interfering with the viewing of the image of the structures under study. In some cases, such defects (artifacts) can lead to erroneous diagnostic conclusions. This requires that you work with X-ray film and chemical reagents with a certain amount of caution and attention.

Total or partial veil.	The film was stored incorrectly or for a long time, partially or completely exposed to ionizing radiation or light. Oxidation of wet or wet film in air in the developer. Development in an old or unevenly heated developer.
Scratches.	Careless handling of film. Faulty development frames.
Fingerprints.	Working with film with wet hands.
Smudges and blurring of the image.	High temperature of solutions, water.
Yellow (yellow-brown) veil.	Manifestation in exhausted developer.
A rainbow veil, similar to gasoline in water, covering the entire film or in the form of spots.	Fixer gets into the developer.
Dark and light spots with dark edges in the form of a veil.	Solution tanks are contaminated with bacteria.
Well-defined light spots.	The developer did not react with the entire surface of the film. The film was lowered into the developer without prior wetting or did not move during the development process.
Small bubbles.	Poor washing of the image after developing the photo and fixing it in a strong fixer at high temperature.
There are white-gray spots on the wet film, after drying there is a coating in the form of white dust.	Rinse water contains a significant concentration of calcium salts (hard water).
Wrinkling of the emulsion or a crack in the emulsion layer.	Large temperature difference between developer and intermediate rinse water, fixer and final rinse water.
Dark or light spots with dark edges.	Developer or fixer has splashed onto dry film. The film was handled with hands dipped in developer or fixer. Poor quality water for rinsing.
Light spots or stripes are always of the same configuration.	The imaging table is contaminated with contrast agents. Contamination of intensifying screens.
Dark, randomly located spots of a round or tree-like shape.	Static discharges on film or screen do not occur when indoor humidity is low. Poor grounding is installed on the developing machine. Rough handling of film.
Areas of altered density in the form of flames.	The recirculation rate of solutions in the developing machine is too high or low.
Wavy stripes of varying density at the lower end of the film (swelling).	Incomplete removal of the developer from the film before it becomes a fixer.
Spotting or graininess over the entire surface of the film.	Crumbs getting under the intensifying screen. Corrosion of the metal lining of the cassette wall. Plaque on the rollers of the developing machine. Using abrasive cleaning materials when maintaining rollers. Incorrect reducing agent feed rate.
Winding lines running across the film.	Film vibrations in the developing unit of the developing machine. Depletion or insufficient recovery of developer.
Longitudinal light or dark thin stripes at a distance of approximately 2.5 cm from each other.	Traces from dirty or deformed transport guides of the developing machine
Light (undeveloped) areas.	The adhesion of two films while developing them simultaneously.
After drying, large yellow-brown spots are visible on the photograph, or the entire film is colored with this color.	The film was fixed for insufficient time or in an exhausted fixer.

Tags: lecture on radiology
Start of activity (date): 10/21/2017 21:06:00
Created by (ID): 1
Keywords: radiographs, artifacts

The successive stages of the photographic process on silver halide gelatin layers are fundamentally common to both the negative and positive processes. Therefore, almost everything stated below for a negative process also applies to a positive one. The photochemical process consists of the following stages: development, intermediate wash, fixing, intermediate wash (to be collected for silver recovery), final wash. It is known that under the influence of light a photochemical reaction occurs in a photosensitive emulsion, as a result of which a latent image is formed in the centers of photosensitivity.

DEVELOPMENT Development is the process by which a latent image captured by a photograph is magnified millions to billions of times and becomes visible. The lightest areas of a photographic object will have the most silver recovered, while the darkest areas will have the least amount of silver recovered. The transition tones (midtones) will be darker or lighter depending on the amount of light reflected by the subject being photographed and therefore recovered when the metallic silver is developed. The quality of the resulting image depends not only on the amount of light falling on the photosensitive layer, but also on the properties of the developing solution. Let us consider the basic properties of developing solutions. The selectivity of the developer lies in its ability to restore the metallic silver of the image in proportion to the light applied. The more light that hits the photosensitive layer, the faster the recovery process goes. In areas where the light has no effect, metallic silver is reduced at the end of the process in small quantities, forming a so-called veil. The greater the selective ability of the developer, the greater the gap in time between the development of the latent image and the appearance of the veil, therefore, the higher the selective ability of the developer, the smaller the veil. The speed of action of the developer is characterized by the development time during which the desired image contrast is achieved. This property depends on the components included in the solution and on the temperature of the solution. The time that elapses from the moment the exposed photographic material is immersed in the developer until the first traces of the image appear is called the induction period, the value of which depends not only on the speed of action of the developer, but also on the amount of light applied. Based on the induction period, one can judge the correct exposure time and the degree of developer depletion. The maximum image contrast created by the developer depends both on the composition of the developing solution and on the photosensitive material being processed, as well as on the development time. If we process X-ray photographs taken under the same conditions, at the same time, but in different developing solutions, we will obtain a different contrast ratio, but by changing the development time, we can obtain the same contrast ratio. Consequently, to obtain high contrast, some developers require less time, others more, i.e. contrast is a function of the speed of the developer, which allows us to talk about contrast as a property of the developer. Using a fine-grained developer with phenidon, you can increase photosensitivity by 4-6 times by changing the processing time, but at the same time the image contrast increases. The effect of the developer on the graininess of the image depends on the size of the halogen silver grains, the size of which in turn depends on the photosensitivity of the photolayer. But during processing, the size of these grains can be reduced to some extent. The main substance influencing the grain size during the development process is sodium sulfite, which has a dissolving effect on the grains of halogen silver. Hence the large amount of sodium sulfite in fine-grained developers. Fine-grained developers are also characterized by a low alkali content, as a result of which the development time increases, which has a positive effect on the leveling properties of the developer. Processing a larger amount of photographic material worsens the quality of the image, since as photographic materials are developed, the quantitative and qualitative composition of the solution changes, i.e. the pH value of the solution changes, due to a decrease in the alkali concentration, the accumulation of oxidation products, bromides, etc. occurs. To increase the stability of developing solutions and in order to save on the consumption of chemicals, so-called reinforcing additives are introduced into them, the task of which is to maintain the concentration of developing substances and the pH of the solution at the same level, which significantly increases the service life of the solutions and their ability to process a larger number of photographic materials . To do this, developing solutions that are not used should be stored in closed containers, and it is necessary that there is a minimum amount of air between the surface of the solution and the lid. For these purposes, tanks with floating lids are used, which are in contact with the surface of the solution, regardless of the volume of the solution in the tank. Knowing the basic properties of developing solutions, you can operate with them, emphasizing one or another property (strengthening it or weakening it) to obtain an image with predetermined parameters.

The rate of development depends on the temperature of the solution: it increases with increasing temperature and decreases with decreasing temperature. But it is necessary to take into account that the change in the development speed in areas of the photo layer that received different exposure values is different, and this changes the nature of the image. Therefore, one of the main conditions for the normal conduct of the process is the stability of the temperature of the solutions in compliance with the specified tolerances for a given developer. Developers of different types of action have different speeds of action to achieve the desired contrast ratio and maximum blackening density. But in all solutions the speed of their action throughout the process is different. Increasing in the first, so-called induction period, the rate of manifestation reaches a maximum in the second period - post-induction. Then the speed of manifestation gradually decreases. Consequently, with increasing development time, the maximum blackening density and contrast ratio increase up to a certain limit, after which the increase in maximum density stops, but the minimum density and veil density continue to increase, and the contrast ratio begins to decrease. There are two main methods of processing negative photographic materials: time processing and visual control.

INTERMEDIATE WASHING To increase the service life of the fixing solution, the material being processed must be subjected to intermediate washing after development to remove the developing solution from the photographic layer. The disadvantage of intermediate washing is that the development process in the processed material will continue after washing, which can increase the density when processing materials in high-speed developers. If you need to quickly stop the development process, you should sharply lower the pH in the photographic layer. To do this, the developed photographic material must be processed in a solution that has an acidic reaction.

FIXING Fixing is the conversion of halogen silver, as well as Ag4 silver salts, into soluble compounds that were not reduced during the development process. The speed of diffusion of the fixing solution into the layer has a great influence on the speed of fixation. The highest diffusion rate is observed from the boundary layer, the concentration of which should be sufficient. But since the capacity of the boundary layer is small and the concentration of the fixing solution in it is quickly depleted, a constant supply of fresh solution is necessary, which is achieved by stirring the fixing solution or by moving the processed photographic material relative to the solution. In addition, the rate of diffusion increases as the temperature of the solution increases. The quality of subsequent rinsing also depends on the duration of fixation and the composition of the fixer. The end of fixation cannot be considered the clarification of the negative in the solution, since the layer still contains insoluble silver salts, which, as the process continues, react with sodium thiosulfate, forming water-soluble salts. Therefore, the duration of fixation is determined by double or triple lightening time, depending on the material being processed. The fixation reaction, like any other, occurs with a change in the concentration of the substances involved in the process. During the fixation process, the concentration of substances included in the fixer decreases and the concentration of substances formed as a result of the reaction increases. And naturally, such a qualitative change in the composition of the fixer significantly affects the speed and quality of fixation. When machine processing materials, where there are several fixing tanks and there is constant circulation of solutions, countercurrent fixing is used, the solution moves towards the moving film. Thus, the fresh solution treats the film in the last stage. Three types of fixers are used for processing photographic materials: simple, acidic and tanning. Simple fixers, which contain only sodium thiosulfate, have a pH of about 8 and require careful washing after development to prevent developer from getting into the fixing solution. Otherwise, the silver that goes into fixer may be partially restored. With vigorous developer, metallic silver forms a dichroic veil, and the oxidation products of the developing substance color the gelatin yellow. To reduce intermediate rinsing in this case, it is necessary to use an acidic intermediate bath. Acidic fixers no longer require the use of acidic and intermediate baths, since they do not form a dichroic veil and do not stain the gelatin. In an acidic environment, the pH of which ranges from 4 to 6, the manifestation immediately stops. Unlike simple fixers, acidic ones have a greater ability to dissolve metallic silver, and the rate of dissolution depends on the pH value. At pH=5, the dissolution of metallic silver becomes so significant that it is necessary to take into account the effect of this on the image density, since, along with halogen silver, metallic silver also begins to dissolve in such an environment. Acidic tanning fixers are used when it is necessary to tan the photo layer. A negative processed in such a solution becomes more resistant to elevated temperatures, the hardness of the photo layer increases, and the swelling of gelatin during washing decreases, helping to speed up the drying of the negative.

FINAL WASHING The further safety of photographic materials depends on the quality of the final washing. The washing process consists of removing sodium thiosulfate and reaction products absorbed by the photolayer during chemical-physical treatment from the photolayer. In physical terms, the washing process is the diffusion of dissolved substances from the photolayer into the washing water and takes place in two stages:

1) diffusion of matter from the photographic layer;

2) removal of diffusible substances by replacing water.

There are several ways to wash photographic materials.

1. Changing the water or transferring photographic materials from one bath to another with stagnant water, in this case it is necessary to make 5-6 water changes within an hour.

2. Cascade method, when the washing baths are arranged on a ledge and fresh running water enters the upper bath, where photographic materials undergo the last stage of washing. Water enters the lower bath with a small concentration of thiosulfate, and the first stage of washing is performed there. As washing progresses, the washed photographic material is transferred from the lower bath to the upper one. The cascade method is countercurrent, since the advancement of photographic material occurs against the movement of water. It is economical, but slower than intense. 3. Intensive method, in which fresh water is constantly supplied to the tank and removed after use.

4. Shower method, in which a high washing rate is achieved by destroying the boundary layer with jets of water.

The rate of washing of photographic materials also depends on the water temperature, which in turn determines the rate of diffusion and swelling of the gelatin of the photographic emulsion. The best washing rate for untanned or slightly tanned layers is achieved at a temperature of 14-20°C. Increasing the temperature to 20°C and above causes excessive swelling of gelatin. Although the diffusion coefficient increases with increasing temperature, it does not provide a significant gain in the washing rate, since the path of diffusing particles increases. Therefore, the above temperature range is considered the best washing mode.

The easiest way to determine the quality of washing is with an alkaline solution of potassium permanganate of the following composition: Potassium permanganate, g. - 1 Potash (or soda), g. - 1 Distilled water, l. - 1 To do this, pour 250 ml of water from the tap into two beakers, then a negative is taken from the last wash and the solution is allowed to drain from it into one of the glasses for 30 s. The second glass is used for control. Then add 1 ml of the above solution to both glasses. In the presence of sodium thiosulfate, the violet color of the wash water turns into orange within approximately 30 s, and at higher concentrations it turns yellow or becomes completely discolored. Determination accuracy: 10 mg of thiosulfate per 1 liter of water.

DRYING NEGATIVES To remove excess moisture from the photographic layer and substrate, the negative is dried in a dry, clean room at the temperature and humidity of the air in this room or in drying cabinets, where purified air is supplied at a certain temperature and humidity. In the first case, the drying time depends on the temperature and humidity of the environment (from 5 to 14 hours), in the second - on the temperature and humidity of the supplied air. During natural drying, various particles can get onto the negative, reducing its quality; When drying in cabinets, this is excluded, since the supplied air first passes through special filters. Drying conditions affect the condition of the substrate and image quality. At a high temperature of the drying air, the contrast and density of the negative image may increase, and the emulsion layer, when overdried, acquires a structure that is mistaken for graininess. In addition, overdrying the film can cause warping and significant shrinkage of the substrate. The residual moisture content of the substrate must be at least 15%, since at 10% residual moisture the film becomes brittle. Automatic method of photo processing In addition to the undoubted convenience in work, the automatic method of photo processing of medical X-ray films ensures high stability of the results obtained. In developing machines, basically the same processes occur as in the manual method of photo processing, however, at significantly higher temperatures of the developer and fixer (not lower than 25 ° C) and shorter processing times. The time for a complete cycle from the moment the film enters the developing machine until a dry radiograph is obtained (“from dry to dry”) does not exceed several minutes. Roll-type developing machines are the most widely used in medicine.

When processing radiographic films for general purposes, the first two processes are usually used, and the modern one is the express process, in which a finished radiograph is obtained in 1.5-2 minutes. In the third process, the film is subjected to the most severe processing, resulting in the high image contrast necessary, for example, for mammography. The fourth process requires special reagents and is not yet widespread. When processing fluorographic films in roll-type developing machines, one should take into account the fact that roll films are made on a thinner basis than sheet films. To ensure their reliable passage through the developing machine, it is necessary to attach a so-called “leader” with a format of at least 13x13 cm to the beginning of the roll. A sheet of radiographic film intended for automatic processing can be used as a leader. All roll-type developing machines are designed, in principle, the same. To ensure the stability of the photoprocessing process, developer and fixer regenerators are automatically added to the working tanks of developing machines (in proportion to the amount of film being processed). The regeneration rate of the fixer is usually higher due to the fact that it is difficult to carry out effective intermediate washing in the machine, and a certain amount of developer regularly gets into the fixer along with the film. Thanks to the regular addition of regenerators, developing machines can operate for a long time without completely replacing the working solutions. However, in no case should waste solutions fall into containers for fresh developer and fixer regenerators. Only in this case is the required quality of radiographs ensured. Due to high temperatures and humidity, a very aggressive environment is created in developing machines, so machine parts are subject to increased wear. To extend the service life of developing machines, it is necessary to regularly (at least once a month) carry out preventive measures in accordance with the operating instructions for a specific machine. Equipment for a darkroom The darkroom must be equipped with water supply, sewerage, general and special (working) lighting and have a device for chemical and photographic processing of films. Manual processing of radiographic films is usually carried out in tanks using special frames for securing the films, allowing them to be processed in a vertical position. Modern devices for manual photographic processing of radiographic films are made of plastic materials that are not subject to corrosion, and are equipped with a block for thermostatting the developer solution and a timer. It should be emphasized that processing sheet film in cuvettes is not recommended due to the instability of the results obtained. For manual processing of fluorographic films, it is best to use cylindrical light-proof tanks, inside of which there are reels for securing the film rolls in a fixed position in the form of a spiral. Fluorographic film can also be processed in conventional tanks by first wrapping it around a frame designed for processing sheet radiographic film. In this case, the film emulsion should face outward. Otherwise, light stripes may form at the points where the film emulsion contacts the frame, leading to loss of information in the image. A modern method of photographic processing of medical X-ray films is the use of roll-type developing machines. In addition to undoubted ease of use, developing machines provide high stability of the photo processing process. For working lighting in darkrooms, flashlights with various filters are used. When working with blue-sensitive films, it is recommended to use (from among those produced in Russia) yellow-green filter No. 117 or red filters No. 104 and 107; with orthochromatic films - only red filters. Films sensitive to red light must be processed in complete darkness. In the darkroom lamp it is allowed to use incandescent lamps with a power of no more than 25 watts. In this case, the distance from the flashlight to the surface of the desktop must be at least 50 cm for yellow-green filter No. 117 and at least 75 cm for red filters No. 104 and 107. If it is necessary to use a lamp with a power of 40 Watts, this distance should either be increased, or somehow increase the filter density. However, in this case, it is better to use the flashlight for indirect illumination of the darkroom, for example, by directing the light of the flashlight to the ceiling. Installation of lamps with higher power in a darkroom lamp is not allowed. Before working with each type of X-ray film, it is necessary to check that the darkroom lighting is non-actinic. To do this, in complete darkness, take a sheet of unexposed film out of the box and place it on the workbench, covering about half with a light-proof material, for example, a piece of cardboard. Then turn on the flashlight and expose the film under it for 3 minutes, after which it is photographed in complete darkness in the mode that will be used in further work. If there is clearly noticeable blackening on the exposed portion of the film, then the darkroom lighting is not suitable for working with this film. According to the current standard, lighting is considered non-actinic if the increase in veil density does not exceed 0.1 B.

After complete immersion in the fixative solution, during the first 10 seconds, the frame with the X-ray film is raised and lowered several times. After about 1 minute, this technique is repeated, after which the tank is covered with a lid and the x-ray remains in the fixer until the fixation process is complete.

Repeated movement of the film promotes uniform action fixer on the entire surface of the emulsion layer and, to some extent, mixing of the solution is ensured, as a result of which the fixation process is accelerated and made more complete. In addition, sticking of sheets of X-ray film is prevented.

When fixing, you must ensure that all X-ray film surface was accessible to the solution, since when the films come into contact with each other, the fixation process slows down and in some cases is completely interrupted.

Fixation process it is impossible to interrupt ahead of time, since salts remaining in the emulsion layer, even in small quantities, subsequently or immediately cause yellow-brown spots to appear on X-ray photographs.

It was stated above that the process fixing consists of two stages. Each stage takes approximately the same amount of time. the end of the first stage of fixation can be easily determined visually by the disappearance of all visible traces of the milky “color” of the X-ray film emulsion, i.e., traces of silver bromide. The end of the second stage of fixation is determined by time, by the clock. There is a rule in photography that to complete the fixing process, the negative must be fixed twice as long as it takes to develop. This rule is acceptable for fixing X-ray film if development is carried out in a standard developer, and fixation is carried out in an acidic fixer at the same temperature of the solutions.

After finishing frame fixing process with X-ray film is removed from the solution and held for some time above the open tank with an inclination to one of the corners. The frame must be held in this position until the fixing solution drains from the film and frame. The X-ray film frame can then be lowered into a tank of running water for a final rinse.

Please remember that until the process is completed fixation x-ray film it cannot be removed from the solution and examined on a X-ray viewer, otherwise purplish-red spots and stripes may appear on x-rays, especially when using an old solution.
In cases of violation of the recording rules, the following defects may appear on x-ray photographs.

In too short a time fixing or when fixed in a solution that is too warm, a dichroic or yellow veil appears. A dichroic veil also appears in cases where, during fixation, film films stick together or touch the wall of the tank, or as a result of inadequate processing of the film in a stop solution after development or exhaustion of this solution. A dichroic veil can also appear when the developer is contaminated with a fixer solution or when the fixer is insufficiently acidic or depleted (in the latter case, a yellow veil may also appear). The dichroic veil has a yellowish-green or reddish-green color when viewing the image in reflected light, and pink in transmitted light .

Milky plaque on x-ray pictures may occur with insufficiently long fixation or with fixation in an exhausted and low-concentrated solution of sodium thiosulfate.

If wrong a fixing solution has been prepared or the solution is overacidified, or contaminated with developer alkali and is severely depleted, or remained open for a long time at elevated temperatures, then a yellowish-white or whitish-gray (like calcium precipitate) coating appears on x-ray photographs.

After fixation of x-ray film a certain amount of silver remains in the fixer solution, namely from 5 to 20 g after fixing one square meter of film.

Spent fixing solution Under no circumstances should it be poured out. The remaining silver must be collected and handed over to collection points, the location of which is indicated in the relevant instructions and orders. The collection and delivery of silver and silver-containing waste should be carried out by all employees of x-ray rooms and not occasionally, but systematically.

Development of X-ray film in tanks. Method of recording an x-ray image. Dichroic veil and milky plaque in the picture. The effectiveness of nitrous oxide. Patient status. Safety of using nitrous oxide. Effect on the body

Other articles

The effectiveness of nitrous oxide. Patient status. Safety of using nitrous oxide. Effect on the body.

Intraoral bitewing radiography.

The effectiveness of nitrous oxide. Method of administration and dose. Concentration of nitrous oxide in the inhaled mixture.

Drug allergies (doctor's note). Introduction.

Typical mistakes during x-ray examination.

Panoramic tomography of the dentition. Part 2.

Manifestation

New on the site

International distance competitions and olympiads

International distance competitions and olympiads

The best English textbooks to improve your vocabulary Effectively improve your English vocabulary

The Romanov family: the history of the reigning family

Features of drawing up a manager's order on the creation of a commission to test knowledge on labor protection Order on the appointment of a commission on occupational safety

Most popular

How the Romanovs became a royal dynasty

Characteristics and permissible noise levels in workplaces

history of the "Vyborg Appeal"

Cod with vegetables in a slow cooker How to cook cod with vegetables in a slow cooker

Cooking oyster mushrooms in sour cream and onions: delicious recipes

POPULAR SECTIONS