ANLS 2620 X-Ray Physics Review

ANLS 2620 X-Ray Physics Review - X-Ray Physics Review X-Ray...

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Unformatted text preview: X-Ray Physics Review X-Ray RADD 2303 Dr. Deb Roche An X-Ray Trick!!!! An X­Ray trick.mpeg Three main characteristics Three Density – Mass per unit volume of black Density metallic silver. (In Deb talk – blackness on the film the Contrast – the shades of gray Detail and distortion Detail RADIOGRAPHIC DENSITY RADIOGRAPHIC The controlling factor – mAs – The milliampere seconds milliampere mAs controls the number of x-rays mAs produced in the tube produced Radiographic Density Radiographic Primary Influencing Factors Patient Size in centimeters -Prior to taking the radiograph, -Prior it is advisable to measure the patient so that accurate technical factors may be selected. factors Radiographic Density Radiographic Primary Influencing Factors - continued kVp- Controls penetrating ability of the xray photons produced in the tube. It has ray an effect on radiographic density but should be used to control radiographic contrast in conjunction with mAs. contrast More Density Factors More Source to Image Distance (SID) – Also known as Focal Film Distance (FFD) or Also Target Film Distance (TFD) Target – Each radiographic projection has a Each recommended SID based on the anatomy in question and the level of detail required for adequate visualization of the structures. adequate Radiographic Density Radiographic Even more factors Film/Screen System Speed. – A system speed must be chosen based on the system level of radiation protection desired and the necessity for certain level of radiographic detail. detail. Radiographic Density Radiographic even more factors PROCESSING – Approximately 50% of the problems that you Approximately will experience in your x-ray area will be the result of processing areas. This may have a great effect on radiographic density. great – Are you warming up the processor? – Are you having the chemistry changed at least once per Are month depending upon workload? month – Are you performing preventative maintenance? Radiographic Density Radiographic Secondary Influencing Factors Radiographic Fog – A radiographic grid Radiographic will help to reduce the amount of fog on your films – the key is to choose the correct one for your needs. correct There are other factors that will decrease There the amount of fog on your films that will be addressed later . . . addressed Radiographic Density Radiographic Secondary Influencing Factors Collimation – necessary (and required Collimation by law) on all radiographs – should be as close as possible to your area of interest. Decreases radiation dose to patient and increases contrast. patient Radiographic Density Radiographic Bucky grid type and grid cut off – What type of chiropractic that is practiced in What your office will determine which type of grid will be necessary without OVERKILL! will – How much scatter do you create? Radiographic Density Radiographic More secondary Factors Anode Heel Effect – Anode – If your machine is installed correctly, the If anode heel effect can be used to your advantage for quality radiographs. If not, there are ways to work around it. there Density Secondary Factors Secondary Compensating Filtration – The goal is to achieve uniform radiographic The density. It compensates for variables in body part thickness as well as variables in the intensity of the primary beam. intensity – Anode heel effect – using a compensating Anode filter is the way you work around it! filter Radiographic Contrast Radiographic The goal is to choose the The technical factors that will give you the contrast level you need and provide radiation protection to the patient. patient. Radiographic Contrast Radiographic Controlling factor – Controlling The kVp/mAs relationship The kVp controls penetrating ability of the xray photons produced in the tube. It has ray an effect on radiographic density but should be used to control radiographic contrast in conjunction with the appropriate mAs. appropriate More contrast factors More Patient Tissue Quality Muscle atrophy, additive or Muscle destructive pathologies can alter the kVp selection. alter Radiographic Contrast Radiographic Primary Influencing Factors Radiographic Fog – there are a number of Radiographic ways to reduce radiographic fog on your films. films. – Using relatively low kVp techniques – Compression – Collimation – Grids Radiographic Contrast Radiographic more primary influences Radiographic grid – A radiographic grid will help to reduce radiographic the amount of fog on your films – the key is to use the correct one for your needs. You only have to choose this one time. . . one Radiographic Contrast Radiographic Primary influencing factors Collimation Collimation – Close collimation serves two main Close purposes; purposes; It reduces the radiation dose to It the patient the It decreases the amount of fog on It the film. the Radiographic Contrast Radiographic Secondary influencing factors mAs – The mAs/kVp relationship as well as the The quality of the tissue to be radiographed determines the contrast on the film. determines – This is easily achieved by the utilization of a This fixed kVp, variable mAs technique chart. fixed Radiographic Contrast Radiographic Secondary Influencing Factors Processing – Many factors in the darkroom will affect Many radiographic contrast including proper chemical replenishment and temperature as well as the elimination of light leaks. light Radiographic Contrast Radiographic More secondary factors COMPRESSION – There are devices as well as procedures that There will compress the tissue to decrease the number of atoms in the path of travel of the primary beam and decreases the probability of scatter interactions. of Detail Sharpness Detail Motion – The selection of the highest mA and The a corresponding short exposure time will help to eliminate motion unsharpness. unsharpness. Detail Sharpness Detail Influencing Factors SID – Source to Image Distance – Due to the use of photons that are Due perpendicular to the plane of the film, a longer SID will provide sharper detail with less magnification. magnification. Detail Sharpness Detail Influencing Factors Focal Spot/Filament Size – There are advantages and There disadvantages to each of the two filaments. Focal spot or filament selection will depend upon the type of radiograph and the desired detail level. This is determined by the mA selection. selection. Focal Spot Size Focal Small Filament – Provides sharper detail however, due to Provides the lower heat capacity of the small filament, higher mA settings cannot be utilized. – Exposure times will have to be longer Exposure and that increases the possibility of patient motion. patient Focal Spot Size Focal Large Filament – This filament can handle higher heat This loads which allows for shorter exposure times. times. – Decreases the possibility of patient Decreases motion. motion. – A sacrifice of radiographic detail occurs. Detail Sharpness Detail Influencing Factors Film/Screen System Speed – A higher system speed will provide radiation higher protection to the patient but due to quantum mottle, the faster the speed, the greater distortion on the resulting film distortion – The key is to find a system speed that will The provide radiation protection as well as providing the level of detail necessary for your use. use. Detail Sharpness Detail More influencing factors Intensifying screen/Film Contact – It is important to make sure that the It intensifying screens and the film maintain close contact. If not, areas of the film will exhibit blur. – The screens should be tested using a The film/screen contact test tool when they are new and then once per year new ...
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This note was uploaded on 11/23/2011 for the course ANLS 2620 taught by Professor R.brucefox during the Winter '11 term at Life Chiropractic College West.

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