hey everyone ryan here and welcome to this series on oral radiology we're going to cover a lot of great material in these next few videos there are 10 exam questions on part 2 from this section and this material will also appear on the integrated national board exam so that being said like all of my videos i'm going to focus on the highest yield things that you need to know for the exam and my hope is that these videos will help you prepare for the exam and also give you an overview for clinical application and general knowledge so first we're going to start with the big picture how does an x-ray machine work so we have a high voltage power supply that powers up the x-ray unit the position indicating device is just a plastic casing that allows you to line up the x-ray unit to the proper location and distance from the patient's mouth the x-ray tube or tube head is the housing in which the actual x-rays are created so let's take a look inside we have a circuit that heats up a filament which burns off electrons these electrons contact a tungsten target that produces the actual x-rays this copper rod is used to dissipate the heat and a leaded glass envelope surrounds and insulates the entire assembly so electricity becomes heat which becomes electrons which become x-rays x-rays are high frequency high energy waves they're between ultraviolet radiation and gamma rays on the electromagnetic spectrum and it's helpful to think of x-rays as similar in some respect to visible light rays because all of these waves are packaged into energy particles called photons so these x-ray photons are produced by the x-ray tube and scattered and absorbed by human tissue attenuation of the x-ray beam refers to how the x-ray beam weakens as it travels through matter the thicker and denser tissue there is the less x-ray photons will actually make it through to the other side so hard tissue is more dense than soft tissue enamel is more dense than dentin amalgam is more dense than composite etc and on the other side is what we call the receptor traditionally a sheet of film that we'd process with various chemicals now there are vinyl film packets that can be processed by a scanner and also direct digital sensors that can process the image directly to a computer we'll talk more about the different receptors in a later video so let's put it all together we have electricity which produces heat which creates these electrons which produce x-rays which are a form of electromagnetic radiation packaged into energy photons that are attenuated through patient tissues and the penetrating photons strike a receptor that is processed to create the x-ray image that we observe and analyze this is so so cool how it all works together so ionizing radiation is a form of energy that acts by removing electrons from atoms and molecules of materials that include air water and living tissue in order to create ions so this form of energy is widely considered invisible odorless and weightless there are two forms of ionizing radiation to be familiar with electromagnetic and particulate so electromagnetic radiation is the one we've already been talking about and it refers to movement of energy through space as a combination of electrical and magnetic fields hence the name electromagnetic radiation so this is all about waves of energy and they travel at the speed of light the wavelength refers to the distance between crests of a wave the shorter this distance becomes the higher energy a wave is so the order from highest energy to lowest energy would be gamma x-ray uv violet to red infrared microwave and radio waves so gamma rays x-rays and some high-energy uv radiation have significant and sufficient energy to ionize biologic molecules and are thus referred to as ionizing radiation the rest down here are called non-ionizing radiation because they don't have enough energy for that phenomenon particulate radiation refers to atomic nuclei or subatomic particles moving at very high speeds so if electromagnetic radiation was all about waves particulate radiation is all about discrete particles made up of matter so these include alpha and beta particles from radioactive decay as well as protons and neutrons so the alpha particles are helium nuclei and they're stopped by paper beta particles refer to electrons or positrons they're stopped by plywood or a thin sheet of aluminum this image also shows gamma rays which are a form of electromagnetic radiation that we just talked about and they're very high energy and require shielding by a dense material such as lead or concrete to stop them so let's talk about the two types of x-ray production so now we're zooming in on the part of the x-ray tube head where the electrons are striking the tungsten target to produce x-rays so first we have brem strolling x-ray production this is an interesting german word it's from bremston or bremsen which means to break or slow down and straw lung which refers to radiation so together it means breaking radiation or deceleration radiation so bremstrolling is the principal source of x-ray photons the high-energy incident electrons are attracted to the positive nuclei of the tungsten and strike the target as a result but this results in the deceleration or breaking of that electron where their loss of kinetic energy is converted into x-rays so this generates a continuous spectrum of energy characteristic x-ray production is the secondary source of x-rays and this involves again a high-energy electron striking the target but this time it accidentally knocks out an electron within the atom and then there's a vacancy so an electron in a higher energy state drops into a lower energy state usually the k shell and emits that energy difference between the two shells as x-rays it's called characteristic because each atom has distinct energy levels between electrons and so depending on which electron is knocked out a specific amount of energy is emitted in this case so with all of that information let's revisit the x-ray tube again and add in some important definitions so anything with a flow of current will have two electrodes a cathode and an anode in a battery the cathode is positive and the anode is negative but here it's the opposite the cathode is negative and the anode is positive we can see that on the diagram over here as well so the cathode consists of the tungsten filament that produces the electrons and so the filament is heated up by the circuitry and electrons literally boil off by thermionic emission there's also a molybdenum focusing cup which helps to focus electrons onto the target into a small focal spot the anode consists of a tungsten target that converts the electrons into x-ray photons by either brem strolling or characteristic production interestingly the electrons become about 99 heat and only one percent photons so we have a copper stem that conducts electricity and has a high melting point to help dissipate that heat there's also a glass enclosure this glass envelope helps to insulate the electricity it also has a high melting point it maintains a vacuum and helps to transmit the x-rays we also have an x-ray housing which consists of an aluminum filter the aluminum provides filtration for the x-rays and lead goes all the way around except for the opening at the tube window to help absorb the scattered x-rays and help to maintain a single x-ray beam this process is called collimation and we'll talk more about that in a later video as well so that's it for this video guys thank you so much for watching please like this video if you enjoyed it and subscribe to this channel for more on dentistry if you're interested in supporting this channel and what i do please check out my patreon page thank you to all of my patrons here for all of their support you can unlock extras like access to my video slides to take notes on and practice questions for the board exams so go check that out the link is in the description thanks again for watching everyone and i'll see you all in the next video