Showing posts with label film. Show all posts
Showing posts with label film. Show all posts

Characteristics Of X-Ray Film

darkroom , film
Characteristics Of X-Ray Film

 Characteristics Of X-Ray Film

1. Density-: 

Density refers to the darkness above the film, the greater the darkness of the film, the greater the density of the film. The density depends on the exposure, the higher the density received by the radiation film in the amount, the higher the density will be on the film. Measuring the blackness of a film is called optical density.
Which is defined by the following figure.0.25–2.0 optical density is commonly used inside radiology. 
Characteristics Of X-Ray Film


The density of the film depends on the following.
A. Quantity of x-ray beam-: 
Quantity of a beam is the number of xray photons. Increasing the value of current / current inside the x ray tube will also increase the production of electrons, which will also increase the number of xray photons. And the density of the film will also increase. Due to which the patient dose will also be more. Therefore, the density will also increase as the beam's volume increases. 
B. The quality of x-ray beam
expresses the penetrating power of the X-ray beam. If you increase the Kv, a greater amount of tissue will penetrate the xrays and reach the film, which will make the film darker. And the density of the film will also increase. Hence, the density will also increase with increasing the quality of the xray beam.

2. Object density

If the density of the object is high, then the density of the film will be less. Because the density or thickness of the patient will be higher, the absorption of xray will be higher, which will lead to fewer xrays reaching the film. Due to which the blackness on the film will also be reduced. 

3. Film fog

Density is reduced due to film fog. Which can be produced due to improper safe light. 

4. Exposure 

Density also increases along with exposure.
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Types of x-ray film

darkroom , film
Types of x-ray film

 Types of x-ray film

 Xray films are transparent films made of emulsions that are active against light photons and also sensitive to radiation. xray films are classified in many ways. Which is as follows

1. dental film - :  

 It is of two types -

A. Intra oral dental film -:

 This type of film is exposed by placing it inside the patient's mouth. And it is a double emulsion film. And it is exposed without screen. In this type of films, only a maximum of 3-4 teeth at a time is possible for xray. This type of film is wrapped in the backing of lead (pb) coated so that the patient feels less radiation dose.

B. extra oral dental film(panoramic)

This type of film is exposed in the patient by keeping it out of the mouth. And it is a single emulsion film. These types of films are also called panoramic films. Because in this one time exposure, the entire 32 teeth xray is done. And has long exposure or penaromic exposure. exa- OPG (orthopantomagram)

2. Mammography film

It is a single emulsion film on the principle of fine grain, ie this type of film has only one layer of emulsion. Also known as a single-coated film. This type of film is used with single intensifying screen.

3.duplicating film 

 It is a single emulsion film. In this, any type of film is copied by ultraviolet light or by normal light. The size of the duplicating  film should be equal to the one being copied.

4. substraction film 

This type of film is used in angiography. It is a single emulsion film, high quality contrast is achieved in these types of films.

5. Medical imaging film 

This type of film is used in CT scan (computerized demography scan), MRI (magnetic resonance imaging), digital radiography, PET screen (positron emission tomography) etc.
Medical imaging films are single layer coated films of five layers

A. Base -: 

 It is made of polyester with blue tinge. And it is transparent. And it is non-folding and non-breaking, with long-term safeguarding properties. This property of the base is called dimensional stability.

B. Substratum :-

 This layer serves to affix the base to the emulsion. Meaning it performs the function of adhasive.

C. emulsion :-

 It is located on the front side of the medical imaging film. Which contains a mixture of gelatin and particles of silver halide. Which makes the film light sensitive.

D. Top coat -:

   It is made of gelatin and hardener material which provides protection to the emulsion from scratches or external shocks.

E. Anti halo layer: - 

 In this medical imaging film, it is the back layer that protects the film from halation. And provides a blur-less sharp image. In the absence of this layer, the radiation exposure may reflect off the emulsion layer, causing the film to double expose, which is called halation.


Classification of films by screen

1. Screen film ( indirect exposure film )

 This type of film is mostly used in radiography. Intensifying screen is used with this type of film. The intensifying screen photo on this type of film creates a latent image with an electric effect. There are many types of light sensitive film available in this category. Example - mammographic film

2. Direct exposure / non screen film -:

The emulsion of this type of film is thicker than that of a screen film. And their exposure is done by direct xray. Non-screen film is expose by placing it in a cardboard / cardboard holder. Meaning is used without an intensifying screen. And it is four times faster than normal speed film. So generally a quarter of exposures are required for good contrast and blackening. This type of film is used in factories.


Types of Films based on Light Sensitive Emulsion Coating -

 1.blue light sensitive film 

 2. Green light sensitive orthochromatic films

 3. Red light sensitive panchromatic films



Types of films based on film speed -

1. Standard or pan speed film

2.fast speed films 

3.ultra fast speed film

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xray film

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xray film

xray film

X-ray film is a medium used to record the image of an exposed body part for x ray. This film is generally similar to photographic film. The difference in radiographic film is that one side or both of it is radiosensitive or light sensitive. The emulsion material is coated or coated so that it can be used with the intensifying screen by exposing it on top of this radiographic film and creating a latent image And later, by processing it, the latent image is converted into a visible image. The structure of the radiographic film is as follows

Structure of x ray film

Often the film is produced from a lower layer or layer which is as follows -

xray film


1.base layer

It is the central or central part of the x ray film that supports the photographic emulsion layer from both sides.

This base part should be non-folding and non-breaking. It should be able to bear any type of geometric distortion (temperature, pressure) so that it can be processed.The base provides a transparent, uniform visual background to the film.

First the x ray film plate consisted of an emulsion layer on both sides of a glass base. But during the First World War, belzium shut down its supply of photographic glass. Then the demand for xray film base started coming up all over the world.

In 1914, cellulose triacetate was first used as a film base. And by 1924 completely cellulose tri acetate was used for the base.Cellulose tri acetate is a flammable material. Hence polyester base was manufactured in the 1960s and polyester base is also used at present. The dimensional stability of the polyester base is very good. The film base is a transparent material. Blue tint was given inside the film base for the first time in 1933 to reduce the fatigue of the radiographer's eyes. Blue tint is also currently used.The thickness of the CTA (cellulose tri acitate) base is 8 miles and the thickness of the polyester base is 7 miles. Which is 0.01 inch = 1 mile.

2.adhesive layer

Most emulsion layers do not attach easily to the base layer. Hence, its main function is to glue two layers together. That persist between the emulsion and the base layer.

3. Emulsion layer

This is the most active layer of the Xray film. Which are located between the protective layer and the adhesive layer. Radiographic images are produced on this layer. This layer mainly consists of two components.

A. Gelatin medium

B. Silver halide crystal (grain)

Which are found as particles in the silver halide gelatin medium. Apart from these, other chemical substances such as weighting agent, centicogluent, and hardner are also added to the emulsion.In order to obtain a good quality image on the film, 90–99% silver bromide (AgBr) and 1–10% silver iodide (AgI) are found in the silver halide crystals. The emulsion is the part of the xray film on which xray photons work and produce the image. For this, the emulsion must be cleaned so that the xray photon can easily enter the emulsion. And the processing solution can easily enter the emulsion evenly. The silver halide crystals have a thickness of 0.1 –1.5 micrometers.

Property of emulsion

 To increase the quality of the radiograph, the emulsion of the film should have the following qualities

A. Speed ​​/ sensitivity -: Speed ​​or sensitivity emulsion has the ability to react with xray, ie when the emulsion is able to provide good density and good contrast to the film at very low exposure, then this type of emulsion is called fast or high speed emulsion. is. Normal films are fast films.

B. Latitude -: Latitude has the ability to show contrast of radiographic images of emulsions over a long scale from white to black with a long range of Tons. The letitude of the emulsion should be high so that the mistakes in the exposure have the least impact on the image of the film.

4. protective layer

During the film handling, a protective layer is used to protect the emulsion part from scratching and damage. These layers are also made of gelatin.

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