hey everyone ryan here and welcome back to our oral radiology series this video will be about film and digital imaging so those are our two main methods of taking x-rays traditional film and digital so a little bit of history dental x-rays were discovered in the early 1900s by a company named kodak which might sound familiar and x-rays provided the dentist with a whole new world of information with which to diagnose disease film which came first required chemicals to process whereas digital which came out much later in the late 1980s does not need chemical processing film also requires time to develop while some digital modalities allow for near instant viewing so already we have some benefits there's less time and less waste and cost associated with using all of those processing chemicals a benefit for film though is that practitioners will generally agree that the traditional film produces higher quality images especially in terms of resolution however digital technology allows you to manually adjust things like contrast brightness and other settings through image enhancement that's not possible with film film also needs more radiation to obtain a diagnostic image digital does not need as much and i want to mention ahead of time that digital has two subcategories that will talk more about psp and ccd or cmos so that'll come a little bit later in the video so where do we stand now well depending on where you are about 50 of dentists still use film the other 50 percent use some form of digital imaging and the number of practitioners that use digital imaging is to is continuing to grow with each day so a physical x-ray film consists of several different layers the base is a clear flexible cellulose acetate material which is a plastic and it supports the rest of the film the film emulsion consists of silver halide crystals these are mostly silver bromide although they could be iodide or chloride and these are sensitive to both x-rays and visible light so this is where all the magic happens it's what actually captures the image now sometimes there's a single emulsion layer and sometimes like in this diagram there is a double emulsion layer there are two separate film emulsions for panoramic and cephalometric films an intensifying screen is used and it's coated with fluorescent phosphor that converts x-ray photon energy into light and thereby reduces the amount of exposure needed but it also decreases the image resolution due to the dispersion of the light from the phosphor so now let's talk about film speed the basic rule here is that the faster the film is the less exposure it needs which is very beneficial because this is just another way that we can limit radiation dose to the patient so a is the slowest film requiring the longest exposure time and that goes all the way up to f which is the fastest requiring the shortest exposure time you do get some loss of image clarity and resolution as you get to a faster film speed so and this is actually this correlates to some of the other things we've talked about how radiation dose and image quality are often inversely related and when we decrease radiation dose somehow we're off we're often losing some image quality along with that of the ones listed here d and f are currently the most popularly used film speeds and the film speed is determined by several different factors so crystal size is one of them the larger the crystal the faster the film will be how many emulsion layers there are if there's a double emulsion that means the film will be faster and adding some radio sensitive dyes those will also increase the speed of the film so how does this stuff actually work well the x-ray photons will chemically change those silver halide or silver bromide particles and crystals in that emulsion layer into neutral silver atoms to create what's called a latent image and the latent image is an invisible image has all these ionized silver atoms that are focused into certain areas and then all of the metallic silver is later converted to a visible image through the chemical processing so we have some terms to talk about here radiolucent refers to darkness in the image where photons are able to pass through tissue and reach the film radio opaque refers to lightness in the image where photons are attenuated or blocked and do not reach the film so these two terms are true for digital imaging as well but either way a really helpful way to look at this is using art as an analogy so the original film packet starts out as a blank canvas and if you scanned an empty canvas like this it would just come out white it's only when the photons reach the film does it become painted with all of these different shades of gray and that's how we get our image so chemical processing is conducted in a special dark room setting under safe lighting without any light leaks and there are generally four steps to consider here developing which is where we make the metallic silver atoms turn black we turn that invisible latent image into a visible image fixing where we wash away any unexposed and undeveloped silver grains washing where we wash away the residual chemicals from the previous two steps and then drying so we can actually read the finished film so what's in that developing solution for the first step well this is the part again that's going to give electrons to convert those exposed silver halide grains into black metallic silver phenodone is the first electron donor and this is what's responsible for reducing those silver ions to metallic silver at the latent image and then hydroquinone steps in and provides an electron to reduce the oxidized phenotone to its original active state so basically what's going on here is that we have phenodone which is giving an electron to our silver and then we have hydroquinone that is essentially replenishing the missing electron to the phenodone so that it can continue to do its job and i keep repeating this but this is so crucial this is this can definitely appear on the board exam that the developer is what actually converts the invisible image to a visible image so if the final image is coming out really light for example the chances are that your developer solution isn't doing its job properly it's probably old and needs to be replaced the fixer solution again is what removes the undeveloped silver halide crystals from the emulsion so fixing keeps the black metallic silver that we want and removes all the other unexposed stuff that we don't want anymore and ammonium thiosulfate is really the workhorse here it's what actually does the cleaning we also have some other components aluminum salts hardens and preserves the emulsion acetic acid maintains a level of acidity and neutralizes the developer sodium sulfite is a preservative prolongs the shelf life of this stuff and water allows much like it does in other things in dentistry is the solvent that dissolves the other ingredients all right so now let's shift gears and talk about digital and like i said before we have two main categories here psp stands for photo stimulable phosphor and so we have these barium fluoro halide plates that capture and store x-ray energy from the dental exposure and then they're read by a scanner and sent to your computer so it's an extra little step here where you have to first capture the image and then get it scanned into your computer that's compared to the ccd or cmos system ccd stands for charge couple charge coupled device it's a little older and bulkier and this one stands for complementary metal oxide semiconductor this one's the newer and sleeker model but both of them are these silicone sensor chips that plug directly into your computer usually by usb so you can capture the x-ray and it instantly displays the image on your monitor so it cuts out that extra scanning step so we talked about a lot of different models film digital psp versus the more direct form of digital x-rays and what's the difference between all of these why would you use one over the other and it comes down to several key factors so contrast resolution refers to the ability to distinguish between different shades of gray and so for contrast resolution film is simply better than digital and that's because an analog system like film has a continuous grayscale whereas digital has discrete grayscale it's limited to a certain amount of gray levels so for instance an 8-bit image has 256 gray levels now that's still a lot of different gray values but it's not technically continuous so can you really can the human eye detect the difference between film and digital contrast probably not but if we're going technical here film is superior spatial resolution refers to the ability to distinguish two points that are close together here film is once again superior ccd or cmos though is better than psp then we have detector latitude so latitude is basically how forgiving a receptor is in other words even if you under expose or overexpose the receptor if you have a wide latitude it can still produce a diagnostic quality image psp is actually the best one here then ccd or cmos and film and last and finally detector sensitivity this is an important one the dose required to achieve a standard gray level and ccd or cmos is half that of the f speed film and remember f speed is one of the fastest analog films we have and that's still two times the radiation dose you'd get with a ccd or cmos sensor so just goes to show how much less radiation you're using with a digital mode so wherever technology is concerned we need to have quality assurance or the maintenance of a high level of quality so any dental office should have a program implemented to ensure optimal and consistent operation of each component in the imaging chain daily tasks talk about recording all errors that's always good practice weekly tasks to review the error log of each of the things that you've seen come up that week monthly tasks examining those psp plates for any scratches inspecting your lead aprons for any tears and then yearly tasks the machines should be calibrated by professional and to very verify digital sensors with a phantom that's some kind of template kind of looks like a human head but it's created so that you can test if the x-ray is capturing everything properly and lastly we have some troubleshooting so troubleshooting some issues that you particularly will see with film underexposing the image means that we had an inadequate exposure time we could have had an inadequate development time or the chemicals were old that developer solution was out of date or maybe the temperature was too low if we and this is an example of an underexposed film image for under for overexposure that means that the exposure time may have been too long we could have over developed the image or it could have been exposed to light this is an example of an over exposed film image creases or folds when the image was developed or scanned could create something that looks like this just a dark radiolucent sharp line going through the image static electricity is really interesting it causes these black tree kind of tree branch lines to form wherever that static electricity is generated from and finally this is very specific for film images we can get this tire track appearance called the herringbone effect and this is where the lead foil attenuation pattern from the back of the film is projected onto the actual emulsion layer because the film was placed backwards so that's something that you'd see specifically for any film packet that's placed backwards all right so that's it for this video on film and digital imaging thank you so much for watching everyone please like this video if you enjoyed it and subscribe to this channel for much 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 will be in the description thanks again for watching everyone and i'll see you in the next video