 Welcome to another session of Dentistry Unmove. Today's topic is about the parts of an x-ray machine. So we expose our intraoral radiographs as well as our extraoral radiographs with the help of this machine and then x-ray tube head plays an important role in this machine. So the machine consists of a control panel, then we have an extension arm and a tube head. The control panel consists of an on and off switch and indicator as well as indicator light and then we have an exposure button wherein once you press this exposure button you can hear a noise and then once the noise fades off it indicates that the exposure cycle is being completed. Then we have certain control devices which regulate the x-ray beams such as that of a timer. So the timer indicates the exposure time period. Then we have an extension arm. The extension arm it helps us suspend the x-ray tube head and also it houses the electrical wires that extend from the control panel to that of your x-ray tube head. Then in the tube head consists of a metal shielding or a metal housing. You can see this blue outline that is your metal shielding and then we have surrounding this metal shielding we have an insulating oil that is placed within this x-ray tube head and then we have the glass tube or the glass envelope which surrounds the cathode and the anode. So I will be explaining what are the functions for each of these materials that have been used in your x-ray machine. So in the metal housing there is a blue outline that you are seeing that is enclosing the x-ray tube. It helps to surround the x-ray tube and as well as a transformer and it also protects the x-ray tube and grounds the high voltage component. Then we have an insulating oil as the name such as the insulation is the property that is seen in this. So the surrounding oil helps to maintain the insulation properties of the glass envelope and also it insulates the tube from the metal shield. Then we have our negative cathode as we have already studied during our school days there. Cathode is negatively charged and the anode is a positively charged. So we have a negatively charged cathode wherein it contains the filament as well as the focusing cup. The filament is that source of electrons which is found within the x-ray tube and the material of choice is tungsten. So a coil of tungsten wire with a higher which has a higher atomic number that is 74 and melting point of 3380 degree Celsius is being used where it is been mounted onto two strong stiff wires which support it and also carry the electric current. So these mounted wires lead through the glass envelope and serve as a connection to the low as well as the high voltage electrical source. And how these electrons are being lost from the filament is by the process called as the thermionic emission. So the filament is being heated to incandescent through a range of temperature by varying voltage wherein it helps this at this hot filament emits the electrons from the tungsten wire. And it is also said that it is found to be the rate of how much the electrons are being produced is a variety proportional to the temperature that is being used. So that is why this process is called as that of thermionic emission. And there is also another material that we use is the thorium that is one person thorium. So one person thorium is used because for this material the filament to last longer and also to prevent this property called as sun tanning. What it means is that sun tanning is that once over a long period of time there is a vaporization of the filament that can occur. So there will be particles that will vaporize and then solidify onto the glass envelope of the x-ray tube which can lead to this condition called as sun tanning. Once the sun tanning occurs what happens is that it decreases the output of your x-rays as well as it causes destruction to the back tube and also causes ultimately a tube failure. So that is why we use 1% of thorium to the filament material. Next we have a focusing cup. So in the focusing cup the material of choice is the molybdenum. So it is nothing other than a negatively charged concave reflector cup of molybdenum that houses this filament. And the focusing cup what it does is that it electrostatically focuses the electrons emitted by the incandescent filament into a narrow beam which has been directed towards the rectangular area in the anode called as a focal spot. So what happens is that it helps to facilitate the movement of this electron cloud and it helps to move these electrons towards the anode that is towards the target. And one more reason for why we have a vacuum glass envelope within the x-ray tube is that it helps to like once this x-rays are being produced these electrons will not collide with these gas molecules. If any air is being present there will be an interaction between these gas molecules with that of the electrons. So this can lead to a burnout condition called as a burnout or a oxidation of the filament. So this can be prevented by vacuuming the glass envelope. We have the positively charged anode. So earlier we mentioned that the negatively charged electrons that have been ejected from the filament it hits against the target that is the anode. So the target it contains a thin tungsten plate which is embedded within the solid copper stem. So tungsten is the material of choice because it has a higher atomic number that is 74. And in this higher atomic number it indicates that there is a high charge on the nucleus as well as there are more photons. And also there is higher binding energy of the orbital electrons. So what happens is that it gives rise to the increased interaction between the electrons and the atoms. Thereby there is an increase in the x-ray photon production. So next property is that it has a higher melting point that is around 3380 degrees Celsius. So what it states that if there is any temperature rise the target will not get minted. And then next we have the next property is the low vapor pressure. So once there's a again there's a higher temperature the target does not get vaporized or it does not get evaporated. Then we have a higher thermal conductivity. It is stated that when comparing tungsten to that of copper stem tungsten is found to be a poorer conductor of heat. So that is why we embed this tungsten target within the copper stem because copper is a good thermal conductor. So there is a higher thermal conductivity occurring in this target. Then what this target does is that it helps to convert this kinetic energy of this electrons that are generated from the filament to x-ray photon. So we have earlier mentioned that those electrons it hits against a target or an area or within the target which is called as a focal spot. So this focal it is stated that the size of the focal spot decreases the image sharpness increases. So we what we have to in order to do that in order to succeed in having a size of the focal spot decreased or smaller we have to we follow this principle called as the line focus principle. Line focus principles or the Benson line focus principle states that we need to achieve a smaller focal spot size at the same time to and also the heat should be generated over a wide area in the target. So in order to achieve that we have to angulate the anode or the target in a 15 to 20 degree inclination. So what happens is that the electrons bombarding to this target we will get in focal spot sizes of around 1 into 1 mm in size. Whereas if in case it is found to be in a 90 degree what happens is that electrons when hit perpendicularly the focal spot size will be more as compared to that of this apparent focal spot size. So the actual focal spot size will get when placed in a 90 degrees around 1 to 3 mm in size. So that is why we need to attain a focal spot size smaller so as to get a sharper image. So this is why this called as a line focus principle. Till now we spoke about the components of the X-ray machine. Next we will be speaking about how these X-rays have been produced. So once the X-ray machine is turned on the L2 current moves towards the control panel and then it is headed towards the tube head via L2 bias in the extension arm. And then this current is directed towards the filament in the cathode with the help of your step down transformer. What is the role of the step down transformer is that it tries to convert the line voltage of 110 to 220 volts and meaning it steps down. So it reduces to 3 to 5 volts so that it can heat the tungsten filament. Once the filament is been heated up it undergoes a process called as a thermionic emission. So and that electron cloud is being formed in the focusing curve. And then this cloud is being activated where when the exposure button is being pushed on the high voltage circuit is being activated. And this electron cloud produced in the cathode is accelerated across the X-ray tube and it hits against the target on the anode. So the electron when it strikes the tungsten target the energy that is the kinetic energy is being converted to an X-ray energy and heat. So among that there is a 99% of dissipation of heat and this heat is being carried away by the help of the copper stem and also some of them are being absorbed by the insulating oil in the tube head. So it is an insulating oil plays an inherent filtration role. So it tries to filter all these unwanted heat and the X-rays. And then what happens is that the X-rays it is being produced and it hits against all the surfaces within the glass envelope. So what happens is that this the leaded glass housing it tries to prevent the X-rays from escaping from the X-ray tube head. So only a few portion that is the sum of the portion of the X-rays are being exited out with the through this vent that is the unleaded glass window that is the arrow where I am pointing out. So through this X-rays are being passed across the unleaded glass window. It is then it travels through the tube head seal then the aluminum filters which helps to filter the long wavelength X-rays from the X-ray beam. And then it moves across the collimator wherein the collimator controls the size and the shape of the X-ray beam and then this X-ray beam then travels through the lead light pair position indicating device and then it exits through the tube head at the opening of the position indicating device. So this is a schematic or a flow chart of how the X-rays are being produced. So again I will repeat it. There is an electric current that passes through the control panel and then through the control panel it reaches the filament through the help of your step down transform. So the filament gets heated up to release the process called as a thermoionic emission wherein the electron cloud is being formed. And once when you expose your button is switched on this electron cloud then j is accelerated towards the anode and it hits the target. So the electron strikes the target and the kinetic energy of this electrons are the converted to X-ray photon energy. And also along with this process there's also heat dissipation occurring. And then what happens is next is that this X-rays are found to be exited through this unleaded glass window. So the size and shape of the X-ray beam that is being directed out is found to be controlled by the lead collimators. And then this X-ray beam travels down to the lead light position indicating device which exits through the tube head at the opening of the position indicating device and which helps in the exposure of the patient. Then we have something called as a terminology called as a linear energy transfer. Sometimes in Viva they might ask what is this linear energy transfer? There's nothing other than the rate of loss of energy from a particle as it moves through the matter or a tissue. So this factors that are affecting the linear energy transfer is that the size and charge of the particle. If it is found to be greater the size and the charge of the particle then it is said that it is found to be a greater linear energy transfer. And also the velocity is found to be decreased. So it's between the when compared with the alpha particles with the beta particles it is stated that the alpha particles have a higher linear energy transfer because it is found to be densely ionizable. So they have a higher charge and also they have a lesser velocity. That is why they have a higher linear energy transfer when compared to beta particles where beta particles is found to be less densely ionizing. Next we have two types of X-rays that have been produced that is a trend sterling radiation and the characteristic radiation. Trend sterling radiation it comprises around the 70% of the X-rays that have been produced. Then characteristic radiation is found to be around 30%. Trend sterling meaning it's a German terminology meaning the breaking. What it refers to that since the sudden breaking of the high speed electrons once it hits the tungsten target in the anode. So what happens here is that the incident electrons is found to be have more attracted towards the positively charged nucleus. So once it reaches the nucleus it tries to slow down and it seizes. So it releases the X-ray photon. Next is the characteristic radiation. In characteristic radiation what happens is that and if an incident electron it reaches the innermost shell that is in the k shell it interacts with this electron in the k shell and this electron has been released and once the void is being created in this innermost shell the electron from the L shell moves in towards this void and once this it moves towards this void there is this radiation that has been produced that is called as the characteristic radiation. That is the loss of energy is the resultant of the binding energy differences between these two energy levels that is from the k shell and the L shell. So to summarize we spoke about each component of the X-ray machine and what the role that plays and then we spoke about how the X-rays have been produced and then we moved on to what are the types of the X-rays that have been produced that is the Bremstrail radiation and the characteristic radiation. So the next session I will be speaking about how is the interaction of the X-ray with the atom. Thank you.