An X-ray machine is a device that is mainly used for the purpose of imaging. As the name itself suggests, an X-ray machine makes use of the properties of x-rays for a number of real-life applications including medical radiology, radiation therapy, research and development purposes, and various engineering applications. An X-ray machine is one of the most common medical equipment used in hospitals and laboratories to diagnose infections and locate fractures. Also, the security systems installed on the airports, railway stations, or other related places make use of x-ray machines to scan and detect the presence of dangerous substances in the luggage bags.
Working Principle of X-Ray Machine
An X-ray machine mainly utilizes the basic properties of the X-rays for its operation. The natural tendency of X-rays is to penetrate soft areas with ease and get absorbed by dense areas. This ability of the X-rays serves to be the working principle of the X-ray machines and helps the user obtain detailed images of the internal structure of the body organs or the objects with ease. The use of X-rays for the purpose of imaging significantly eliminates the need to cut open the object or the body part to obtain the image of the internal structure of the target object or body organ. The X-rays used by the X-ray machines are produced by accelerating electrons at a relatively higher velocity and then directing them towards a target. On hitting the target, the electrons tend to decelerate and lose energy. During the process, a major portion of the kinetic energy possessed by them gets converted into heat energy and the rest portion into x-rays.
X-rays are electromagnetic radiations that fall within the frequency range of 30 EHz – 30 PHz. The wavelength range of X-rays lies between 0.01 nanometres to 10 nanometres. In the electromagnetic spectrum, X-rays are located between ultraviolet light and gamma rays. X-rays can be broadly classified into two types, namely, soft X-rays and hard X-rays. The value of the wavelength of hard X-rays is approximately equal to 100 picometers, while soft X-rays have a relatively shorter wavelength of about 10 nanometers. X-rays were discovered in 1895 by Wilhelm Conrad Röentgen, a professor at Würzburg University in Germany. The X-rays are usually produced with the help of an x-ray tube.
Block Diagram of an X-Ray Machine
The working of an x-ray machine can be easily explained with the help of a functional block diagram. Generally, an x-ray machine consists of 10 blocks. The working of each block is given below:
1. High Voltage Source
The main purpose of using a high voltage source control to power an x-ray machine is to allow the proper operation of the x-ray tube. The voltage value typically ranges from 30 to 150 kilovolts (kV).
2. High Voltage Transformer
The high voltage produced by the high voltage source on the input side of the machine is coupled to a step-up transformer. The transformer tends to uplift the voltage and produce a signal at its output whose magnitude usually lies between the voltage range of 20-200 kV.
3. High Voltage Rectifier
The AC supply cannot be used to operate the x-ray machine, hence a high voltage rectifier is attached to the circuit that mainly performs the task of converting AC supply into DC supply.
4. X-ray Tube
The DC supply voltage produced by the rectifier circuit is coupled to the anode terminal of the x-ray tube, while the cathode terminal of the x-ray tube is connected to the filament current control. The input signal received by the x-ray tube is then used to generate multiple beams of high power x-rays that can be used for imaging and detection purposes.
The x-rays produced by the x-ray tube are desired to be highly directional in nature as the excessive exposure of the healthy body cells to the high power x-rays may encounter serious side effects. This measured exposure of the radiations is mainly controlled with the help of a collimator. The collimator is generally placed between the patient and the filter.
6. Aluminium Filter
The frequency band of the X-rays is quite broad. A large portion of the X-rays fall within the too high or too low-frequency band and can not be used for medicinal applications. The unwanted frequencies contained by the X-rays tend to cause side effects and serious health problems. Also, these frequencies tend to disrupt the image quality by lowering down the contrast value. To minimize these effects to a certain level, aluminium filters are attached to the internal circuitry of the device.
7. Rotor Control
A rotor control present in the x-ray machine is used to limit the beam power according to the usage and helps to cool down the anode. Also, an induction motor is attached to the machine that is used to control the rotation of the anode terminal of the x-ray tube via the rotor control mechanism.
8. Pulse Control Mechanism
The main purpose of the pulse control mechanism is to protect the patient and the surroundings from uncontrollable heat. The excessive heat produced by the machine may cause health problems, improper diagnosis, and the production of a distorted image. To avoid such problems, a pulse control timer is employed to limit the exposure time of the radiations.
8. Thermal Overload Detection
The main purpose of a thermal overload detection mechanism attached to the X-ray machine is to turn off the machine in case the heat level surpasses a certain threshold value.
When the x-rays produced by the x-ray tube cross the patient’s body completely or partially, they get scattered. The scattered radiations tend to disrupt the detection and may cause the burning of the output image. To reduce the negative effects caused due to the scattering of x-rays, a diaphragm is used. The material that is usually preferred for the construction of the diaphragm of an x-ray machine is the lead grid. The scattered radiations falling on the surface of the diaphragm get absorbed up to a significantly high level.
10. Film and Lead Shield
After passing through the diaphragm, the radiations tend to fall on the surface of the film and the lead shield. The main purpose of the film is to translate the signal and information contained by the radiations into an image; whereas, the main purpose of the lead shield is to collect the x-rays after they strike the film. The image so formed can now be processed and analysed by the person in charge.
Working of X-Ray Machine
An X-ray machine typically makes use of a stream of high power electromagnetic radiations to get information about the internal structure of a body organ or an object. The working of an X-ray machine can be summarized as a three-step procedure, i.e., exposing the object to the X-rays, absorption and scattering of the radiations, and formation of the image on the film. Initially, the object whose internal image is required to be formed is placed in direct exposure to the x-rays produced by the X-ray tube of the X-ray machine. The radiations are directed towards the body part that is required to be examined. The basic property of the X-rays enables the radiations to pass through the soft surfaces of the object and get absorbed by the rigid and dense portions. The radiations passing through the soft surfaces tend to get scattered, while the radiations falling on the dense surfaces get absorbed. The partial and complete passing of radiations through the object tends to form an impression of the internal structure of the object on the film. For instance, in medical diagnosis when the X-rays come in contact with the bones and tissues of a human being, a corresponding black and white image gets reflected on the surface of the metal film. Finally, the hard copy of the image is developed and processed to enhance the information contained by it. The image developed by the X-ray machine is generally black and white in nature. The black area of the film represents the soft portion or the soft tissues of the body, while the white area corresponds to the dense regions or the bones present in the body.