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Rad exposures 1
radiograhic exposures and processing
| Question | Answer |
|---|---|
| what is body habitus? | common variations in the shape of the human body |
| radiopaque | light can not get through ex. additive = harder to penetrate ascites, fluid in chest/pleural effusion, fluid in lungs |
| radiolucent | light can get through it ex. destructive = easier to penetrate bowel obstr./emphysema-COPD/pneumothorax |
| radiographic density | the blackening of the image receptor |
| film density formula | only used on film log=Io incident light It transmitted light |
| what is brightness? | the degree of blackening to the image receptor |
| exposure index in mR/S# | CR 100-200 |
| exposure index in mR/EXI# | DR 125-500 |
| density is the same as? | contrast which is density differences ex. black/white/gray scale |
| amperage | the measurement of current |
| what two factors control density? | MA & SID |
| what factor has a significant influence? | kVp = penetration or energy. also controls how fast the kinetic energy is |
| volt = | potential difference |
| OID | object to image receptor distance |
| ISL | inverse square law |
| scatter | unwanted imaging |
| what other types of influencing factors are there? | filtration, beam restriction, part, pathology, grids, film/screen combo, and automatic processing |
| radiographic contrast | visible density differences between two selected areas of density |
| density | blackening to the image receptor black, white, gray scale |
| contrast | density differences (control kvp) |
| image contrast | display of contrast determined by primarily the processing defualt algorithm dr=100-200 cr=125-500 |
| long scale contrast | many shades of grey without contrast ex. low contrast is always a long scale |
| short scale contrast | few shades of gray with great variation ex. short scale will always be high contrast |
| bit depth/electric imaging | number of shades of gray |
| what is used to control contrast? | kvp |
| 15% change in kvp would change? | contrast |
| what are some influencing factors? | subject- pt. size,age, shape,kvp, tissue type, film receptor, scatter, grid, collimation and over/under-exp |
| what influences over or under exposure? | mAs and SID |
| what influences air gap? | OID |
| filtration influencing factor | over filtration can cut out penetration |
| grid | device put between pt. and IR that helps prevent scatter ex. more than 60 kVp use grid |
| collimation | beam restriction which reduces the amount of scatter and radiation |
| recorded detail | ability to see small structures |
| spatial resolution | sharpness of structural edges recorded in the image |
| edge ehancement | enhances detail between bone and soft tissue |
| smoothing | applied if there is to much grain |
| evaluation of contrast | verify appropriate range of densities are visible. no amount of mas can accommodate for insufficient kvp. must have sufficient density. kvp used depends on pt., pathology and scale of contrast |
| factors affecting recorded detail/spatial resolution | 1. motion (blur) 2. OID - short as possible 3. SID - long as practical 4. FSS - depends on mA (focal spot size) 5. IR - smaller pictures gives you better resolution |
| visibility of detail | anything that affect contrast (contrast resolution) or density on an image |
| umbra | distinctly sharp area of a shadow; normally the center of an image |
| penumbra | imperfect, unsharp shadow surrounding the umbra; outer area of image/peripheral |
| FSS | focal spot size |
| attenuation (absorption unsharpness) | weakening of the beam |
| distortion | deviation from the norm ex. anatomy closer to IR/ SID as long as possible |
| size distortion | magnified, not true to size |
| shape distortion | elongation, foreshortening ex. angling of the part or angling of the tube affects elogation or foreshadowing |
| magnification | deviation from true size |
| magnification size distortion is controlled by what? | SID and OID ex. OID issue use SID to correct ex. elbow injury, increase SID |
| shape distortion | deviation from true shape |
| factors of shape distortion | angle of part/ angle of CR |
| rule of thumb for distortion | keep part as close to the IR as possible and parallel to IR, kkep SID as long as practical 40"/48"/72" |
| data | collected facts |
| image acquisition or capture station | where radiographer capture or acquire images |
| analog | radiographic film |
| A-D converter | called a digitizer which places radiographic film onto a computer/matrix. the image can not be changed |
| how do you view analogy? | via a viewbox or light box |
| what are the digitization steps? | 1. scan- which divides analog image into array of pixels. 2. sampling- measures brightness level of each pixel 3. quantization- brightness levels are assigned a number gray scale value |
| digital | consists of definite quantities of current |
| digital is also what? | an image on computer on which acquisition processing can be performed |
| LUT | look up table, manifest or visible gray scale rendered image fixed by automatic rescaling |
| pixel | picture element |
| computer matrix | rows and columns called pixels which can use D-A converter to print laser image or cd/dvd |
| z#= | atomic number (number of protons within the nucleus) |
| pixel pitch | space from the center of a pixel to the center of the adjacent pixel |
| pixels are measured in what? | microns |
| pixel density | number of pixels per mm |
| electric or digital pixel density | gives you better image resolution with smaller pictures |
| spatial resolution | the sharpness of structural edges recorded in the image which depends on pixel/matrix, pixel pitch, or bit depth- computer screen which you buy |
| ITO | image to object |
| spatial frequency | line pair per mm direct relationship to resolution |
| modulation transfer function | ratio of image to object as a function of spatial frequency. the ability to image objects of different sizes and demonstrate detail |
| FOV | field of view = IR size |
| pixel size formula | pixel size= FOV=IR size matrix |
| voxel | 3d pixel/ 3d picture element |
| bit depth | shows more shades of gray n 2 n = number of bits 10 bit = 1024 shades of gray 12 bit = 4096 shades of gray |
| bit depth | limited by dynamic range and quantization gray scale limited to bit depth |
| dynamic range | range of exposures that may be captured by a detector. will always be better than film screen will show you a wide array of grays (scale) |
| quantization | number of bits per pixel |
| subject contrast | built into patient and depends on pathology, body habitus, and tissue etc |
| receptor contrast | fixed characteristics, linear response to exposure, and contrast resolution. smallest exp. change or signal difference detected/ affected by dynamic range and quantization |
| attenuation beam | comes out of the patient, normally the beam has lost energy |
| exit radiation | exits the patient which is an attenuated beam. also affects the contrast of your image |
| soft copy image | the image that comes up on the LUT |
| hard copy image | any images that are placed on a cd/dvd |
| algorithm/contrast | internal mathematical code built in to provide the desired image appearance (default) bone-longer dynamic range w/ more whitening soft tissue- shortened dynamic range to have more blackening |
| brightness | measurement of the luminance of a monitor |
| CR | variable FOV sizes/ cassettes which need to be processed |
| DR | not variable/fixed field of view |
| what is the difference between dynamic range and exposure latitude? | dyn. range is the range of exposure that the image receptor is exposed to. exposure lat. is, is it safe (ALARA)dose appropriate |
| exposure latitude | range or degree of error that can be made |
| CRT | cathode ray tube which is not used in radiography. ex. light emitting, curved surface, scanning e- beam, glare, spot pixel and phosphor nonunifority |
| AMLCD | active matrix liquid crystal display that is only used in radiography. ex. light modulating, flat surface, active matrix address, pixel cross distortion, square pixel and LC nonuniformity |
| LAN | local area network |
| WAN | wide area network/webAmbassador |
| ZDA | zero download ambassador |
| post processing | done on the LUT only after the image is taken |
| what can be done while using post processing? | annotation, window & level, magnification, image flip, image inversion, pixel shift and DSA/ROI |
| DSA | digital subtraction angiography |
| ROI | region of interest |
| defective pixel post/procs./prob | interpolate adjacent pixel signals |
| image lag post/procs/prob | offset correction |
| line noise post/procs/prob | correct from dark reference zone |
| archiving | electronic term used for saving info (images) ex. hard drive, dvd (cd), hologram, down-time-flash drive |
| hard drive RAID | redundant array of inexpensive discs in a single cabinet (jukebox). also optical laser discs jukebox |
| the cloud | sharing of information |
| pacs cube | DVD (CD) burner |
| archiving compression ratio | 1:1 (takes up more space) - 1:20. depends on protocols and modality, each modality has their own compression ratio. ex. average xray 15:1/ ct 7:1/ mr&nm 5:1 |
| ratio | compares on thing to another |
| SIN ratio | signal to noise ratio. signal- good pt. information noise- grainy appearance that is unwanted. happen when you underexpose to correct you increase mas. high signal less noise |
| lossless | no loss of information (images), but takes up space, very rarely used. avg. compression ratio 3:1 |
| nearly lossless | loss of alittle bit of information, not much visible to the naked eye. avg. compression ratio 5:1 |
| lossy high quality | some loss (used more in xray)alters minute image details to reduce compressed image size. compression around 10:1 to 100:1 suitable for sending images over low bandwidth network |
| lossy medium quality | lost of more information (lost of detail). will work faster than lossy high quality and compress even more. all gray scale images will be reduced to 256 shades of gray |
| when can images be loaned? | in film images are the property of the facilty |
| CR/DR | print laser film or on paper dvd/cd patient can keep as original is archived. md offices wan web images |
| PACS | picture achiving and communication system used to acquire images from all modalities to save and share information |
| DR | dominator radiology |
| dominator | radiologist work (reading) station/ low ambient room lighting |
| dragon VR | voice recognition |
| ambassador | where you actually acquire images |
| catapult | technologists workstation (through digate images are sent to radiologist) |
| laser film printers | infrared or helium neon laser that produces transilluminated hard copy images from digital data. exposes silver halides to light |
| dicoming image | transmission from catapult to dominator |
| system requirements | digital imaging and communication in medicine (DICOM)standards for imaging systems to transfer images. health level 7 (HL7) HIS (meditech) to transmit info and populate pt. data in RIS (DR PACS) |
| RIS | radiology information system. we use dominator radiology (DR PACS) |
| HIS | hospital imaging system (meditech). health level we have to meet dicom standards |
| HIPAA | health insurance portability and accountability act of 1996 (hipaa privacy and security rules) |
| AEC | automatic exposure control/ whenever the detector is in the bucky set kvp- depends on part thickness, pathology, atomic number (high) and contrast (high) select fields- controls the amount of mas 1&3 outer fields and 2 center field. back up time |
| what are the two types of digital radiography and which one do we use? | direct capture and indirect capture which we use |
| SPR | scanned projection radiography- which is a method of making a digital image (CT) |
| element | basic unit of structure used to capture or acquire an image |
| PSP (CR)- indirect | photostimulable phosphor which gives off light twice initially when it captures energy, then it stores light |
| cesium iodide (DR silicon base) | indirect capture |
| gadiolinium oxysulfide (DR silicon base) | we use an it is an indirect capture |
| amorphous selenium (DR base) | direct capture |
| coupling | conductive layer that allows light to flow through, transfers x-ray signal to collection element |
| what are CR coupling elements? | lens or hairlike material called fiber optics |
| describe how an analog image is converted to a digital image? | the exit beam, radiation is collected by the silicon plate and then converted into light. the light is then converted into electronic data via a (TFT) on the computer matrix. indirect transfer |
| collection | analog to digital converter |
| photodiode | collects light/ diode +/- charge (terminal) CR |
| CCD | charged couple device which collects light photons and converts to electronic image for computer matrix. not stable first used in the 1970s |
| TFT | thin film transistor- electronic switch that is connected to each pixel that directly collects electronic image |
| flat panel detector | DR indirect capture that is not variable but fixed.It has charging capabilities is wireless and cassette-less |
| CMOS | complementary metal-oxide semiconductor/ detector |
| what is the difference between detectors and cassettes? | cassettes have variable sizes whereas flat panel detectors have a fixed size |
| Charged Coupled Device | uses cesium iodide phosphor to convert x-ray to light.light is transmitted to CCD by fiber optics. CCD then converts light into electronic image for computer matrix |
| CMOS | complementary metal-oxide semiconductor/ detector, similar to CCD but placed on silicon plate. converts x-rays to light. an embedded TFT converts light into an electronic image |
| HHMC uses what instead of CCD? | uses amorphous silicon and a thin film transistor (TFT) array which converts the x-ray beam to light. light is then converted to electrons to create an image (indirect capture) |
| scintillator | anything that gives off light |
| amorphous silicon (indirect capture DR) | element that is a semiconductor material which allows some floe of e- between atoms |
| scintillator photodetector | absorbs x-rays and remits part of energy as visible light |
| cesium iodide (detector/capture element) | uses charged couple device (CCD) that converts analog info into electronic signal |
| gadolinium oxysulfide (detector/capture element) | which we use, uses thin film transistor, electronic switch (TFT)that converts light into electrons/electrical image |
Created by:
eckoultd1972
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