alright so I'm gonna go over a basics of the terms and characteristics I'm sure you'll have more detail and your other lessons here but just some terms that I want you to know and sort of have an idea of what they're talking about okay so the matrix every image is formed and displayed with a grid so similar to this one it's called a matrix it's how it's laid out it's in rows and columns image matrix so it's made up of pixels or picture elements as you might have heard it each pixel it's gonna have a number value and it determines the brightness of the cells and each box has a range of how many gray values it can have it's usually by Weitz's BY tes word spatial resolution so I know you guys I've heard this term before but it's really related to pixel size so spatial resolution how detailed is your image what can you see the smaller the pixel size the greater your resolution so this image over here with small pixels is gonna give me better resolution similar to this one here so I want smaller pixels to get me higher resolution you're also gonna have matrix size options and you always want the bigger matrix but smaller pixels for greater resolution field of view so how big of a view is being imaged right so how wide open do you have your cones did you call me collimation is automatically gonna increase your image quality right there's two terms I have down here two pixel and voxels so you might hear voxel 2 voxels your three dimensional pixels two dimensional so the computer manipulates data based on into these binary numbers which is two digits it's either a 0 or 1 okay so remember we you saw in the images on the direct and indirect situation we your x-rays are either converted to light in an indirect on a direct system we skip the scintillator part convert it into electric charge and then sent as you know the signal over in digits so it's either a 0 1 4 bits 8 bits equals 1 byte and in one bite there's 256 possible values of gray values here for each of these pixels the brightness of the phosphor its corresponding each area covered by the pixel can be assigned so your x-ray image in the background may have these numbers selected and that's what it's gonna sort of produce okay pixel bit depth is the number of bits used to define each pixel the greater the bit depth the greater the number of tones now that can be risen represented you might see the term pixel pitch it describes the distance between the pixels on the image and it's measured by the center of one pixel to the center of an adjacent pixels the smaller the distance between the pixels the better your resolution okay pixel density you might see this is the number of pixels per unit area sampling frequency is when it's being read the number of pixels sampled per millimeter as the laser scans each line of the imaging plate you might see this Nyquist frequency as well it's another term it's the relationship between the sampling frequency and the spatial resolution so how detailed is your image analog to digital converter so we know that your x-ray images are converted into this electric electrical signal right and into these binary numbers so it needs to be then converted into a digital image and that's where your ADC analog to digital converter comes in and that will produce the digital image okay if you're using a photo simular plate this image alone that the signal is an inform of analog data then converting it to digital number stored as one pixel on each image dynamic range you're gonna or exposure latitude you're gonna use her here these terms throughout your time here but dynamic range the range of x-ray intensities of detector can differentiate a high dynamic range provides the discrimination between small differences in x-ray attenuation so digital imaging provides a wide dynamic range what does that mean it means your error your range of error so how badly can I screw up on my technique and still get a radiograph well it's a lot easier with digital equipment than it was with film right so you know if your even if your techniques off the computer is still gonna try and fix it for you and still get you an image so it has a wider dynamic range right image noise the highest what is image noise from mostly is from scatter radiation and whose the principal source of your scatter radiation your patient so how can you control this using an appropriate technique and collimation want to model or quantum noise is usually due to your technique choice so you didn't use enough mass majority of the time it's gonna appear like this grainy appearance similar to this image here so we didn't give it enough juice right we didn't hit it with enough mass cuz it's grainy kind of modelled cuz not enough photons made it to our imaging plate alright signal-to-noise ratio SNR or CNR are really sort of similar terms here but it's the ratio of the signal so the x-ray is that get to your image receptor compared to the amount of noise alright histogram is your graphical display of the pixel intensities that's distributed on the image so your each each time you choose something on your control panel so you choose PHS or you choose P a hand each of those settings in your control panel has this graph for the pixel values for the values of interest where they think where they think the gray values will be within that image so that's why it's important to choose the correct settings on your control panel ma'am for that okay spatial resolution your ability to distinguish the individual parts of an object or closely adjacent am i news right so sometimes people confuse spatial resolution and contrast resolution spatial resolution is my detail so my borders of anatomy the border of the humerus can you see the border of the joint spaces within you know the metacarpals or something like that can you find a tumor due to its gray color being different than you know the color variance of the lungs that's contrast resolution right spatial frequency its how spatial resolution is measured its measured in the line pairs per millimeter okay EQE is demonstrates the detectors ability for high quality images for a given x-ray exposure so it's also measured as spatial resolution MTF or modulator transfer function tells us how well a system is able to represent the object spatial frequency and it's expressed as the modulator transfer function so your number ranges are between 0 & 1 and I believe it goes by a point system so it's like zero point one point two something like that and then but the closer you are to one the better overall resolution one is sort of an impossible number to get to but in an ideal world one is what you want right one is equal to a hundred percent of image transfer contrast resolution so these are your density differences of neighboring regions and remember contrast resolution and digital imaging is control by your lookup table subject contrast which is your patient your subject of different densities that's controlled by the different attenuations of each tissue and KDP and I gave you my elephant and penguin chart over here right remember you're short penguin who's black and white they're high contrast and your penguin likes to get high your big elephant who's big and gray and wine that's a low contrast look-up tables so the lookup table is the data that's what its gonna expect so it's gonna change the values so your raw image well by the look up table produces the image that you have and it's a prime controller so you're gonna you either use window level or window width to control that when doing an image is the ability to alter sort of your contrast of the digital image that's following the processing so this is sort of a post-processing thing that you can do as a technologist window level you can change the brightness so I think of window level as an opening or closing a window shade as I open it or increase my window level I'm getting brighter as I close my window shade or decrease in my window level it's gonna get darker window width is your contrast and the grayscale so remember window width I think an elephant is wider than a penguin and my elephant is my contrast so window width is contrast wider you're getting up if your elephant gets wider you've got more gray so that's still your low contrast and long scale if your elephant is nearer then you're going high contrast and you're going to get a shorter scale