PRE Flashcards
- __________ - NUMBER PHOTONS IN BEAM
- __________ - BEAM PENETRABILITY / HOW MANY PHOTONS PENETRATE ANATOMY
- THESE TERMS DESCRIBE ___________
- QUANITY = #
- QUALITY = PENETRATING
- X-RAY BEAM
- WHAT IS X-RAY OUTPUT?
- WHAT AFFECTS QUALITY?
- WHAT AFFECTS QUANTITY?
- QUANTITY = OUTPUT, INTENSITY, EXPOSURE
- AFFECTED KVP AND FILTRATION
- MAS, KVP, DISTANCE & FILTRATION
- QUANTITY MEASURED IN:
- QUALITY MEASURED IN:
- WHAT IS INTENSITY OR EXPOSURE?
- ROENTEGENS
- HALF VALUE LAYER (HVL)
- QUANTITY
- __________ & ___________ EVALUATE QUALITY OF IMAGE RESOLUTION
- VISIBILITY OF DETAILS:
- HOW RECOGNIZABLE DETAILS ARE:
- PHOTOGRAPHIC & GEOMETRIC PROPERTIES
- PHOTOGRAPHIC
- GEOMETRIC
- PHOTOGRAPHIC PROPERTIES MEANS _____________
- PHOTOGRAPHIC REFERS TO __________ & __________*
- GEOMETRIC PROPERTIES MEANS _____________
- GEOMETRIC REFERS TO ________ & __________
- VISBILITY DETAIL
- IR EXPOSURE & CONTRAST
- HOW RECOGNIZABLE DETAILS ARE
- SPATIAL RESOLUTION & DISTORTION
- WHAT IS IR EXPOSURE?
- CONTROLLING FACTOR:
- INFLUENCING FACTORS (7)
- AMOUNT OF RADIATION REACHING IMAGE DETECTOR
- mAs
- KVP, DISTANCE, FILTRATION, ANODE HEEL EFFECT, BEAM RESTRICTION, ANATOMICAL PART & GRID
- WHEN ARE CONTROLLING FACTOR USED?
- HOW DO WE ASSES IMAGE QUALITY & IMPACT OF EXPOSURE REACHING IR?
- SPATIAL RESOLUTION IN DIGITAL CONTROLLING FACTOR:
- PRIMARY MEANS OF ADJUSTMENT
- LOOKING AT EI VALUES FOR ACCEPTANCE
- PIXEL SIZE & SMALL FOCAL SPOT SIZE
- WHAT IE EI?
- ANOTHER TERM - WHAT ARE DI VALUES?
- UNDER EXPOSURE = ___%
- OVER EXPOSURE - _____%
- AMOUNT RADIATION REACHING IR
- *NOT PATIENT DOSE **
- S NUMBER - DEVIATION INDEX
- VARIANCE BETWEEN TARGET EI VALUE - UNDER =20%
OVER = 25%
- UNDER EXPOSURE RESULTS IN
- INADEQUATE EXPOSURE TO DETECTOR RESULTS IN
- EXTREME OVEREXPOSURE CAN RESULT IN
- UNDEREXP = NOISE
- INADEQU = PHOTON STARVATION
- EXTREME = DATA DROP (INCAPABLE OF RECOGNIZING HIGH ENERGY VALUES)
- IR EXPOSURE INCREASES WHEN:
mAs -
kVp -
DISTANCE -
FILTRATION -
BEAM RESTRICTION -
ANATOMICAL PART -
INC EXPOSURE BY:
INC. MAS
INC. KVP
DECR. DISTANCE
DECR. FILTER
INC. BEAM RESTRICTION
DEC. ANATOMICAL PART
DEC. GRID / GRID RATIO
- WHAT IS MAS & HOW DOES IT CONTROL IR EXPOSURE?
- mAs & IR EXPOSURE DIRECT OR INDIRECT
- QUANTITY AKA: (3)
- DOUBLE MAS = _________
- HALVED MAS = ___________
- PRODUCT OF TUBE CURRENT (mA) & EXPOSURE TIME (s)
- NUMBER OF ELECTRONS CROSSING TUBE FROM CATHODE TO ANODE PER SECOND
- CONTROLS # OF XRAYS PRODUCED
- DIRECT : INC. MAS = INC IR EXPOSURE
- INTENSITY, OUTPUT & EXPOSURE RATE
- DBL = DBL EXP
- HALVED = HALF EXPOSURE
- EXPLAIN RECIPROCITY LAW
- DOES mAs AFFECT CONTRAST?
- 100 mA × ____s = 75 mAs
- 300 mA × ____s = 15 mAs
- ____mA × 300 ms = 60 mAs
- ____ mA × 150 ms = 75 mAs
- 100 mA × ____s = 75 mAs
- IR EXPOSURE REMAINS SAME AS LONG AS mAs VALUES CONSTANT REGARDLESS OF mA AND TIME COMBINATION
- NO !!
- 0.75 s
- 0.05 s
- 200 mA
- 500 mA
- kVp MEASURES:
- HOW DOES IT AFFECT IR EXPOSURE?
- WHAT ELSE DOES kVp CONTROL?
- MAXIMUM ELECTRICAL POTENTIAL ACROSS X-RAY TUBE
- CONTROLS ENERGY THEREFORE SPEED/FORCE OF ELECTRONS STRIKING TARGET
- PENETRABILITY (QUALITY) OF BEAM, SUBJECT CONTRAST & SCATTER
- INCREASING kVp = _______ IR EXPOSURE
- IS kVp EVER DOUBLED?
- HOW TO USE kVp TO CHANGE IR EXPOSURE?
- INC = INC EXP
- NO, USE 15% RULE
- 15% RULE
- INCREASE 15% = DBL EXPOSURE
- DECREASE 15% = HALVES EXPOSURE
- 15% RULE AFFECTS _________ (ALWAYS) & _________ (ONLY IF NO CHANGE TO mAs TO COMPENSATE)
- DECREASING KVP = _______ PATIENT DOSE
- _________ MAS = INCREASED PT DOSE - Calculate 15% increase in kVp, if original exposure was 75kVp @ 10mAs.
- A. HOW IS IR EXPOSURE CHANGED?
- B. SUBJECT CONTRAST?
- SUBJECT CONTRAST
- IR EXPOSURE - DECR. KVP = INC PT DOSE
- INCR. MAS = INCR PT DOSE - 86 KVP
75 x 15% (.15) = 11.25
75 + 11.25 = 86
-A. IR EXP DOUBLED
- B. CONTRAST DECREASED
- HOW CAN MAINTAIN EXPOSURE LEVEL WHEN INCREASING KVP 15%
- A radiograph of the elbow is produced using 4 mAs at 60 kVp. What kVp would be required to halve the exposure to the IR?
- mAs ADJUSTED
- DEC. 15% = DOUBLE mAs
- INCR. 15% = HALF mAs - 15% of 60 kVp = 60 x 0.15 = 9 kVp
60 kVp – 9 kVp = 51 kVp
- REDUCING FROM 60 TO 51 WILL HALF EXPOSURE TO IR
- WHAT HAPPENS WITH EXPOSURE WHEN SID INCREASES?
- RELATION? - WHAT HAPPENS TO EXPOSURE / INTENSITY WHEN DISTANCE DOUBLED?
- EXPLAIN INVERSE SQUARE LAW & FORMULA
- EXPLAIN EXPOSURE MAINTENANCE & FORMULA
- EXPOSURE DECREASES
- INVERSE / INDIRECT - EXPOSURE DECREASES 4X
- QUANTITY OF XRAY PHOTONS INVERSELY PROPORTIONAL TO SQUARE OF DISTANCE
- WHEN mAs NEED BE ADJUSTED TO MAINTAIN IR EXPOSURE WHEN SID CHANGES
- An acceptable chest image results from an exposure taken using 8 mAs at 110 kVp at 72-inch SID. A second image must be taken supine at 36-inch SID. What new mAs will be required to maintain the same exposure at 36” SID?
- When changing your SID from 72” to 56”
a. decrease your kVp by 15 percent.
b. decrease your mAs by 50 percent.
c. increase the mAs by a factor of 4.
d. increase the kVp by 15 percent.
3.In the event of making a single exposure that is critical to the exam success,
most experienced technologists will
a. use slightly less mAs than necessary to prevent overexposure.
b. overexpose the IR slightly.
c. provide enough exposure to create an adequate histogram.
d. both b and c.
- Distance decreased by half – mAs must decrease 4 times (1/4 ORIGINAL)
Answer: 2 mAs will be required to use at 36” SID
- b. decrease your mAs by 50 percent.
- ANYTIME 40 TO 56 = INCREASE MAS 50% OR 72 TO 56 = DECREASE MAS 50% - B. & C
- OVEREXPOSURE BETTER IN DIGITAL & PROVIDE ENOUGH EXPOSURE FOR ADEQUATE HISTOGRAM
- FILTRATION ELIMINATES ________
- RELATION WITH IR EXPOSURE: - ANODE HEEL EFFECT IR EXPOSURE GREATER AT ________ END
- A. SIGNIFICANT WITH _______ ANODE - HOW DOES BEAM COLLIMATION EFFECT IR EXPOSURE?
- EXPLAIN!!
- RELATION:
- ELIMINATES LOW ENERGY PHOTONS
- INC FILTER = DECR. IR EXPOSURE - GREATER AT CATHODE
- A. SMALL ANODE ANGLE ( SMALL ANGLE = MORE ANODE HEEL EFFECT) - COLLIMATING REDUCES SIZE OF PRIME BEAM & REDUCING SCATTER
- REDUCING TOTAL # PHOTONS REACHING IR = LESS IR EXPOSURE
- INC COLLIMATION = DECR. IR EXPOSURE
- HOW DO GRIDS AFFECT IR EXPOSURE?
- EXPLAIN & RELATION - ANATOMICAL PART REFERS TO: (5)
- HOW DO ANATOMICAL PARTS AFFECT IR EXPOSURE?
- EXPLAIN & RELATION
- GRIDS ABSORB SCATTER & PHOTONS
- DECREASING PHOTONS TO IR
INCR. GRID RATIO = INCR. LEAD CONTENT = DECR. IR EXPOSURE - TISSUE THICKNESS/DENSITY, ANATOMIC #, PATHOLOGICAL CONDITION, CASTS & CONTRAST
- INCREASE THICKNESS - INCREASES ATTENUATION DEPENDING ON THICKNESS / TYPE OF TISSUE BEING IMAGED
- THIS WILL DECREASE IR EXPOSURE
- INC. THICKNESS = DECR. EXPOSURE
- ATTENUATION FROM LEAST TO MOST:
MUSCLE, AIR, BONE & FAT - ADDITIVE DISEASES REQUIRE:
- DESTRUCTIVE DISEASES REQUIRE:
- AIR - FAT - MUSCLE - BONE
- INCREASE TECHNIQUE
- DECREASE TECHNIQUE
ADDITIVE CONDITIONS:
Ascites
Paget’s disease
Pneumonia
Atelectasis
Congestive heart failure
Edema
Tumors
Pleural effusion
Tuberculosis
EXAMPLES OF DESTRUCTIVE CONDITIONS
Osteoporosis
Osteomalacia (rickets)
Pneumothorax
Bowel obstruction
Emphysema
Degenerative arthritis
Atrophy
- CONTRAST REFERS TO ________
- WHAT IS RADIOGRAPHIC CONTRAST?
- WHAT IS CONTRAST RESOLUTION?
- DEPENDENT ON:
- GRAYSCALE
- DIFFERENCE BETWEEN ADJACENT IR EXPOSURES (DENSITIES)
- ABILITY OF DIGITAL SYSTEM TO DISPLAY SUBTLE CHANGES IN SHADES OF GRAY
- RELATED TO PIXEL DEPTH
- WHEN DIFFERENCE BETWEEN ADJACENT IR EXPOSURES ARE GREAT, IMAGE HAS _____ CONTRAST = ______ GRAYSCALE & _____ SHADES OF GRAY
- WHEN DIFFERENCE BETWEEN ADJACENT IR EXPOSURES ARE MINIMAL, IMAGE HAS _____ CONTRAST = ______ GRAYSCALE & _____ SHADES OF GRAY
- CONTROLLING FACTOR OF CONTRAST RESOLUTION:
- A. POSTPROCESSING ADJUSTMENT:
- GREAT = HIGH CONTRAST = SHORT SCALE = FEW SHADES
- MINIMAL = LOW CONTRAST = LONG GRAYSCALE = MANY GRAYS
- BIT DEPTH
- WIDTH (INC WIDTH =
- CONTRAST/GRAYSCALE IS CONTROLLED BY _____
- ______ DETERMINES CONTRAST RESOLUTION/GRAYSCALE
- WHAT IS SUBJECT CONTRAST?
- WHAT CONTROLS SUBJECT CONTRAST?
- LUT & POST PROCESSING WINDOW
- BIT DEPTH
- RANGE OF DIFFERENCE INTENSITIES OF X-RAY BEAM AFTER ATTENUATED BY PATIENT
- kVp & TISSUE THICKNESS/TYPE
- ATTENUATION IS:
- HOW DOES kVp CONTROL SUBJECT CONTRAST
- HIGH KVP = ______ CONTRAST = ______ SCALE (____ SHADES)
- LOW KVP = ______ CONTRAST = ______ SCALE (____ SHADES)
- REDUCTION IN XXRAY INTENSITY AS RESULT OF ABSORPTION & SCATTER
- KVP CONTROLS ENERGY & PENETRATING POWER OF BEAM
- KVP ALSO CONTROLS SCATTER
INC. KVP = INC COMPTON INTERACTION = INC. SCATTER = LONGER GRAYSCALE = LOWER CONTRAST
- HIGH KVP = LOW CONTRAST = LONG SCALE / LOTS GRAYS
- LOW KVP = HIGH CONTRAST = SHORT SCALE / LESS GRAYS
- HIGH CONTRAST DIRECTLY RELATED TO ________ INTERACTION
- LOW CONTRAST DIRECTLY RELATED TO ________ INTERACTION
- SUBJECT CONTRAST ALSO AFFECTED BY ________, ______ & _________
- HIGH = PHOTOELECTRIC
- LOW = COMPTON INTERACTION
- THICKNESS, TISSUE DENSITY & ATOMIC NUMBER
- THICKNESS OF BODY PART = ______ SUBJECT CONTRAST
- HIGHER ATOMIC # = _______ SUBJECT CONTRAST
- When there is great difference in the atomic numbers of adjacent material:
- When there is little difference in the atomic numbers of adjacent materials:
- THICK = DECREASED
- HIGHER = INCREASED
- When there is great difference in the atomic numbers of adjacent materials 🡪
subject contrast increases (bone vs soft tissue) - When there is little difference in the atomic numbers of adjacent materials 🡪
subject contrast decreases (ex: soft tissue in abdomen)
- WE USE HIGH KVP IN DR BECAUSE:
- CONTRAST RESOLUTION IN DR GREAT AFFECTED BY:
- WHY IS TIGHT COLLIMATION IMPORTANT
- IS THERE A NUMERICAL INDICATOR TO QUANTIFY CONTRAST?
- DECREASE PT DOSE
- AMOUNT SCTATER
- DR MORE SENSITIVE TO DR - CONTROL SCATTER
- NO
CONTRAST/LUT
1. CONTROLLED BY:
2. DETERMINED BY:
SUBJECT CONTRAST
3. CONTROLLING FACTOR
4. ALSO INFLUENCED BY:
- LUT
- BIT DEPTH
- KVP
PART THICKNESS, DENSITY & ATOMIC #
- Which of the following groups of exposure factors will produce the
longest grayscale?
(A) 200 mA, 1/20 second, 70 kV, 12:1 grid
(B) 500 mA, 0.02 second, 80 kV, 16:1 grid
(C) 300 mA, 30 msec, 90 kV, 8:1 grid
(D) 600 mA, 15 msec, 70 kV, 8:1 grid
- (C) 300 mA, 30 msec, 90 kV, 8:1 grid
- Long scale = lots of shades of gray = low contrast => more scatter => high kV
- Lower grid ratio = Lower contrast
- HIGH KVP & LOW GRID RATIO = LONG GRAYSCALE
- IGNORE MAS B/C DOESNT AFFECT CONTRAST
- DEFINE SPATIAL RESOLUTION:
- OTHER TERMS FOR SPATIAL RESOLUTION (5)
- FIDELITY REFERS TO ________
- XRAY FIDELTIY:
- ABILITY PERCEIVE SMALL STRUCTURES ON IMAGE AS SEPARATE AND DISTINCT
- GEOMETRIC SHARPNESS OR ACCURACY OF STRUCTURAL LINES - RECORDED DETAIL, DETAIL , DEFINITION, SHARPNESS & RESOLUTION
- TRUENESS OF IMAGE
- XRAY ALWAY HAVE LESS RECORDED DETAIL THAN OBJECT ITSELF
- POOR SPATIAL RESOLUTION IS CAUSED BY:
- GEOMETRIC UNSHARPNESS IS CALLED _____
- SHARPNESS CALLED _____ - FACTORS OF SPATIAL RESOLUTION:
- UNACCEPTABLE LEVEL OF PENUMBRA
- PENUMBRA (GEOMETRIC UNSHARPNESS)
- UMBRA - PIXEL/MATRIX SIZE
- FOCAL SPOT SIZE, OID, SID, MOTION, PATIENT THICKNESS & MAGNIFCATION
SPATIAL RESOLUTION INCREASED BY:
- PIXEL/MATRIX SIZE:
- FOCAL SPOT SIZE:
- OID:
- SID:
- MOTION:
- PATIENT THICKNESS:
- MAGNIFICATION:
- PIXEL/MATRIX SIZE: DECR. PIXEL / INCR. MATRIX
- FOCAL SPOT SIZE: DECR. FSS (SMALL FSS)
- OID: DECR. OID
- SID: INCR. SID
- MOTION: NO MOTION
- PATIENT THICKNESS: DECR. THICKNESS
- MAGNIFICATION: DECR. MAG
- HOW DOES FOCAL SPOT SIZE AFFECT SPATIAL RESOLUTION?
- HOW DOES OID AFFECT SPATIAL RESOLUTION?
- HOW DOES SID AFFECT SPATIAL RESOLUTION?
- DESIRED FOR EACH:
- DECREASE FOCAL SPOT SIZE = DECREASES PENUMBRA = INCREASES SPATIAL RESOLUTION
- DECR. OID = DECR. PENUMBRA (BC MAGNIFICATION DECREASEED) = INCR. SPATIAL RES.
- INCR. SID = DECR PENUMBRA / MAGNIFICATION = INCR. SPATIAL RES.
- SMALL FOCAL SPOT, LARGE MATRIX
- SMALL OID
- LARGE SIDE