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93 Cards in this Set
- Front
- Back
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Pyramid problem |
Technical factor Subject density Contrast Film processing pathology |
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Interrelationship of these factors can result in endless potential problems? |
Pyramid Problem |
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Analytical Process |
Diagnosing and treating image Diagnostic Process Narrowing search field Hypostases activation Information seeking Hypothesis evaluation |
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Diagnosing process |
Careful breakdown of whole into parts 4 parts |
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Goodness and greatness Diagnostic process |
Matter of attention to detail |
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Problem Solving Diagnostic process |
Analysis, Syntheses, evaluation |
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Narrowing the search field 1 Diagnostic process |
Begin with overview Note difference Seek patterns within cues |
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Hypothesis Activation 2 Diagnostic process |
Seek Hypotheses Hold cues that do not fit hypothesis in reserve |
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Information Seeking 3 Diagnostic Process |
*Questions to validate hypothesis *Shift focus to all possible explanations when cues discovered |
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Hypothesis Evaluation 4
Diagnostic Process ` |
*Must resolve most cues *Predict solution |
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Diagnostic process improvement |
1) Remember that cues are not diagnosis 2) Be careful to separate observations from inferences 3) Avoid jumping to conclusions at first cue 4) look for competing hypothesis 5) Try each cue with each hypothesis 6) Validate hypothesis w questioning when possible 7) Rule out each hypothesis one by one 8) Be Cautious of premature closure 9) Be tentative in diagnosis until experienced 10) Be confident in your expert knowledge- Important |
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Acceptable Limits |
*Graphing acceptable limits *Striving for perfection *Factors affecting acceptance limit curves *Practical considerations |
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Graphing acceptance Limits |
*Fix limits of acceptable versus not acceptable radiographs *Parties responsible for evaluation acceptance levels, rads, supervisors, radiologists, physicians |
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Striving for perfection |
*Corrections should strive for perfect image not just acceptable * Competency questioned when unable to correct repeated mistake. |
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Acceptance limit curves |
Extremely narrow, high repeat rate |
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Wide acceptance limits |
*may result in high repeat rates *technologists can become careless |
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Narrow acceptance limits |
*May result in production of near perfect center radiographs |
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Ideal acceptance limits |
Right in the middle, small but perfect image |
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Practical Considerations |
*If repeat, make changes large enough to cause visible difference *Be confident |
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Density IR/Exposure |
*Comprise visibility of detail *1 of 2 photographic properties, detail to eye * |
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New term for density is called? |
*IR exposure DR & CR |
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Brightness |
monitor control function Light VS Dark *not the same as density |
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Window level |
Post processing, changes in Brightness *Not the same as density |
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Brightness and Density |
Are not interchangeable |
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Assessing Density/ IR exposure Film |
*Assure proper densities present in anatomy of interest *Keep room dark for the film, bright light can eliminate excess information |
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Film: OD= Optical density Our range of seeing things B&W |
Typical OD range .25-2.5 (Human Visibility range ) |
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Assessing Density/ IR Exposure=Digital Systems Underexposed |
*Detail not recorded *like polar bear in a snow storm, two few photons |
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Assessing Density/ IR Exposure=Digital Systems Overexposed |
*Digital post processing can eliminate excess info on overexposed *Can save image like burnt toast *Over better than under |
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Effects on Image Appearance |
*Digital follow linear IR response curve *for mistakes=Histogram kicks in *Film follows D-Log-E Curve * Toe=underexposed * Shoulder= Overexposed Min 30% difference for eyes to see |
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Factors affecting Density/ IR exposure |
Density IR exposure *Controlling MAS *Influencing KVP Other influencing factors, -Focal spot -anode heel effect -distance -filtration -beam restriction-anatomic part( tissue type, thickness, CM, and pathology) -Grid Construction (ratio, frequency) -Image receptor ( digital, film) |
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Physical part of the image -Recorded detail (Geometric properties) What can effect detail |
*Geometry -Focal spot -Distance (OID, SID) *Image Receptor (Film Screen, Digital) *Motion (Involuntary, voluntary, equipment) |
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Physical part of the image -Distortion (Geometric properties) What can effect detail |
*Size -OID and -SID (Centering ray, Part, IR) *Shape -Alignment, angulation (Direction, Degree) |
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MAS Reciprocity Rule |
*film Only *Fails for extremely short exposure .01 (100ma x .1seconds= 10MAS) but if you need to up MA to 500 and keep 10 MAS (500MA X .02seconds= 10MAS) Same density different factors |
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Changes in mAS |
*Changes made in doubles or halves *Repeats, change 30% or higher go big or go home *as mAS increases x-ray exposure increases proportionately |
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Changes in mAs 2 |
*f/s= a min of 30% *Digital systems= 25%-30% *use seldom, anytime changing MAS you are alternating the # of photons as MAS goes up so does density. |
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MAS |
*Only changes in MAS -Halves= Divide by 2 -Doubles= Double multiple by 2 *Beware of the plethora of changes possible -Machinery-Pathology-Pts |
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KV as an influencing factor1 |
*alters intensity in 2 ways (Strength of photons, controls ave energy of X-ray phones @anode target) |
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KV as an influencing factor 2 |
*Affects production of scatter *Change in Kvp varies quantity & quality *Increase scatter increase density, unwanted fog *Increase KVP creates density but is the overall controlling factor for CONTRAST |
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(KVP) Small changes can have profound impact on density IR exposure |
-15% increase= doubles exposure -15% decrease= halves exposure *4-5% in power kip ranges (30-50kvp) *10-12% in higher range (90-130% KVP) Will effect visibility * only use when density and contrast desired |
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Generator configuration (we use only high frequency) |
*Affects average energy of beam -only consider when changing single to high-frequency multi-phase -better to just change kip
1^2= HIGH FREQUENCY= times MAS by conversion factor of .5 High frequency= 1^2= times MAS by conversion factor of 2.0 |
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Grid conversion factor |
Mas X Conversion factor ex: 10 MAS x 0.5= 10 MAS |
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Focal spot (Only affects detail) |
Large (1.5-2) small (.5) |
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Anode Heel Effect |
*alters intensity across cathode and anode axis *Density= 45% greater at cathode side *wide open collimator *small anode angle inside machine (12 degrees or less) makes anode heel affect more pronounced with wide open collimator
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Distance SID and OID (Formula) |
*Inverse square law (new exposure) - I1/I2= (D2)sq (D1)sq *Exposure maintenance (mas maintenance) -MAS1/MAS2=D1sq/D2sq |
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Distance SID and OID |
Accuracy=only with moderate acceptance range impossible to predict with all factors of the imaging system *Direct swear law directly proportional |
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Rough "Rule of thumb" |
*Distance doubling and halving will bring IR exposure within roughly 50% OF THE ORIGINAL EXPOSURE *BETTER TO DO EXACT CONVERSION FACTORS AND PREDICT YOUR EXACT RESULT |
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FILTRATION |
*Types= Inherent, added and total (2.5 mm al 70 KVP or higher) *Inversely related to density *Increase filtration Decrease density |
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Technique adjustments |
*Large body parts *High KVP *Low Grid efficiency (Low grid ratio) *non-grid (Extremities) |
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Anatomic part 1 |
-PT prime factor -Thickness, tissue type average z#, tissue density CM |
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Anatomic 2 |
-Positive CM= increase atomic # and decrease density -Negative CM= decreased atomic # and Increased density -Pathology -Additive radiopaque ( decreased Density) - Negative radiolucent ( Increased density) |
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Part thickness variation with large tube angles |
*every 10-15% angle adds thickness to 1 inch sid and Increases tissue thickness *treat cast if thicker part |
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Grids |
- Inversely related - increase grid ratio decreases density - More efficient a grid is less IR exposure less density will be recorded only improve contrast |
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Grid conversion factor |
MAS1/MAS2=GCF1/GCF2 |
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Image Receptor |
-Exposure index number useful parameter for digital -(EI and SI #s) -Relative speed (RS#s) -Useful parameter for film screen combinations (MAS1/MAS2)=RS2/RS1 |
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Film processing |
-increases density -increase developer temp (hot oven) -increase immersion time (in oven to long burnt) -increase replenishment rate of chemicals (to much chlorine) - if these factors decrease so does density |
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Digital world |
-Manufacturers set collaboration -Uses algorithms to set histograms -exposure indicates EI and SI #s -Digital systems have much wider acceptance ranges (Fudge factors) -Limits will be set on how much post processing techs can do in the future. |
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contrast |
-Difference between adjacent densities |
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Assessing contrast |
-2 photogenic effects allow detail to be seen -allows us to see density and contrast -digital range- digital image on a monitor window width- changes brightness and contrast |
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Assessing contrast 2 |
-Image contrast - difference between adjacent densities -Dynamic range - range of brightness as displaced on screen -difficult to separate the 2 change in density will affect contrast -add or take away density inverse relationship, if density goes up contrast goes down |
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High contrast (Extremities) |
- short scale -B&W -Low Kvps -short narrow dynamic range - low frequency, low penetration -increased contrast |
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Low contrast (Abdomens) H=high E=energy L=Low contrast L= Long scale wide latitude |
-long scale -gray -high kvp -decreased contrast -high frequency -more penetration |
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Manipulating contrast |
-Depending on desired contrast the densities are compressed or expanded into a range of visible densities (Achieved by:) -Change in D log E curve film - Adjustment to kvp - Adjustment of window width -digital |
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Image contrast |
-IS the total amount of contrast from - IR= image receptor contrast - Pts= patients anatomic part=subject contast |
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IR/ Film itself contrast
low contrast |
-Film contrast= range of densities the film system is capable of recording - D log E curve *depends on 4 things 1) intensifying screens 2) film density 3) D log E curve 4) processing |
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Intensifying screens
high contrast |
-Directly exposed film has LOW contrast than screen film (with an intensifying screen) - Dramatic change in D log E curve when screen film directly exposed |
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Changes to contact FILM |
-intensifying screens have higher contrast (increase,short scale) -the speed of the screen doesnt matter -both excessive or inadequate density /IR exposure decrease contrast (all black or all white) -Steeper the slope higher the contast |
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Changes to contrast DIGITAL |
-window with manipulation -pre set algorithms -techs post process and histograms and LUT are used to standardize the data -ALARA -Differential absorption: for detector sensitivity to tissue differences |
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Subject contrast |
-differences in intensity of beam after, it passes though pt (Attenation) -Dependent upon= kip, amount of irradiated and type of material |
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KV and subject contrast |
-kvp prime factor -as kip increase (Wider range of photon energy) - greater penetrability, wider greater range of exposure - great amount of scatter Compton-long scale-contrast grays. |
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Amount of irradiated material |
- dependent on thickness of part and field size -Affects # of photons reaching the IR - when the differences between adjacent body part thickness is great, subject contrast increases |
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Amount of irradiated material 2 |
Increase in thickness and field size - increase scatter - long scale of contrast - Decrease subject is the result |
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Types of irradiated material |
-influences by atomic # and tissue density (physical) how tightly packed the cells are *high atomic # tissue density - greater attenuation (bones, muscle) -Large difference in atomic # and tissue density of adjacent tissues - increase contrast - CM= positive= higher contrast - CM= negative= low contast |
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Evaluating contast |
-good range of densities present -anatomical structures intrest present -satisfy diagnostic quality -sufficient contrast and density -knowledge of anatomy of physiology - normal and abnormal |
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Random kip tis digital |
-Dont exceed 80 kip for non grid -PE increases as kip increases |
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Factors affecting contrast |
-KVP -increased Kvp and decreased contrast more grays (Inversely related) - controls scatter production (Direct relationship) -MAS influences |
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Influencing factors |
Mas Focal spot size anode heel effect beam restriction, collimation pbl grids f/s combos anatomical part distance SID Filtration OID |
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MAS |
changes density, alters contrast |
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Focal spot size |
nothing only detail duh |
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Anode heel effect |
little to no effect |
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Beam restriction |
collimation, PBR= direct effect |
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Grids |
primary function is contrast improvement, it removes scatter |
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F/S combos |
increase grid ratio increase contrast - d log e curve - steeper the slope greater the contrast |
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Processing contrast improvement factor |
k= ave gradient with grid ave gradient without grid -if k= 1 no improvement occurred -most grids k= 1.5-3.5 times better contrast than non grid |
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Anatomical part |
tissue type, thickness and pathology |
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Distance |
SID= alters image receptor exposure -can change contrast if change in mass OID= air gap technique increases contrast |
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Filtration |
-altering the average photon energy of the beam, measured in mm of al eq -Inversely related **increased filtration - increase average beam energy - decreases contrast, creates more scatter as in Compton
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Digital systems |
-determined by histograms and LUT - displayed as various bit depth values - post processing effects contrast and visibility of detail |
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KVP negabile effect |
increasing MAS decreasing MAS focal spot size anode heel effect increasing SID decreasing SID increasing F/S relative speed decreasing F/S relative speed |
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KVP increasing contrast |
-increasing OID -decreasing filtration -increasing beam restriction/collimation -decreasing amounts of irradiated material -increasing the differences between the atomic # and tissues -decreasing density of tissue -using CM increase or decrease atomic # -destructive pathological condition -increasing grid ratio |
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KVP decreasing contrast |
-decreasing OID -increasing filtration -decreasing beam restriction/collimation -increasing amount of irradiated tissue -decreasing the differences between the atomic number of tissues -increasing density of tissue -additive pathological conditions -decrease grid ratio |
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MAS negligible effect with density |
-focal spot size -anode heel effect |
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MAS increasing density |
-Increasing KVP -increasing number of pulses in the generator waveform -decreasing distance -decreasing filtration -decreasing anatomical part -decreasing beam restriction/ collimation -decreasing grid ratio -using radiolucent contrast media -destructive pathological conditions -increasing F/S combination relative speed -increasing film processing developer time temp and replenishment rate |
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MAS decreasing density |
-Decreasing KVP -Decreasing number of pulses in the generator waveform -increasing distance -increasing beam restriction/collimation -increasing anatomical part thickness or tissue type -using radiopaque -additive pathological conditions -increasing grid ratio -decreasing film screen combination relative speed -decreasing film processing developer time temp and or replenishment rate |
