FLUOROSCOPIC ACCEPTANCE TESTING: TEST PROCEDURES & PERFORMANCE CRITERIA

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ACCEPTANCE TESTING GOALS
FLUOROSCOPIC
ACCEPTANCE TESTING:
TEST PROCEDURES &
PERFORMANCE CRITERIA
EDWARD L. NICKOLOFF
DEPARTMENT OF RADIOLOGY
COLUMBIA UNIVERSITY
NEW YORK, NY
FLUOROSCOPIC EQUIPMENT
HAS CHANGED
•
•
•
•
FLAT PANEL IMAGE RECEPTORS
MORE X-RAY BEAM FILTRATION
SELECTABLE PULSED FLUOROSCOPY
MULTIPLE “ABC” PROGRAMS
•
•
•
•
PRIOR TO 1st CLINICAL USAGE
VERIFY PURCHASE ORDER
CHECK ARCHITECTURAL DESIGN & FLOW
MOST COMPREHENSIVE TESTING!
–
–
–
–
–
X-RAY GENERATOR & TUBE
IMAGE RECEPTOR & IMAGE QUALITY
RADIATION MEASUREMENTS
MECHANICAL SYSTEMS
SOFTWARE
• MAKE REPAIRS & ADJUSTMENTS
• UNDERSTAND ABC OPERATION
• ESTABLISH BASELINE VALUES FOR QC
I. PERFORMANCE OF
X-RAY PRODUCTION
COMPONENTS
– ANATOMICAL or STUDY SELECTIONS
– DOSE BASED
– PEDIATRIC vs ADULT
• DIFFERENT VIDEO MONITORS
• MORE SOFTWARE IMAGE PROCESSING
• 3-D ROTATING FLUOROSCOPY
1
X-RAY BEAM QUALITY (HVL)
I. PHYSICS TESTS
•
•
•
•
•
•
•
•
RADIATION OUTPUT
HALF VALUE LAYER (HVL)
kVp ACCURACY
mA or mAs REPRODUCABILITY &
LINEARITY
PULSE WIDTH & RATE ACCURACY
FOCAL SPOT SIZE MEASUREMENT
WAVEFORM DISPLAY
ABC PERFORMANCE
EFFECTS OF INCREASE
X-RAY FILTRATION
HVL ISSUES
• OFTEN CAN NOT USE METHOD OF
KEEPING TOTAL FILTRATION CONSTANT
WHILE MOVING FILTERS FROM BEHIND
DETECTOR TO IN FRONT OF DETECTOR
80 kVp X-RAY SPECTRA WITH DIFFERENT
COPPER FILTRATION
7.00E+04
6.00E+04
#X-RAYS / keV
• kVp & FILTER MAY
BE AUTOMATIC
• FILTER RANGE:
0.0 – 0.9 mm Cu
• HVL DEPENDS UPON
kVp, CONTOUR & XRAY FILTER
• FILTER MAY BE
DIFFERENT IN
FLUORO & RECORD
• TYP. HVL= 3.5 - 9.0
mm @ 80 kVp & CAN
BE HIGHER
5.00E+04
Al FILTERS
4.00E+04
3.00E+04
DETECTOR
2.00E+04
1.00E+04
Al FILTERS
0.00E+00
0
10
20
30
40
50
60
70
X-RAY ENERGY (keV)
0 mm Cu
0.3 mm Cu
0.6 mm Cu
80
X-RAYS
0.9 mm Cu
2
COMPARISON OF HVL vs. ADDED
FILTRATION
HVL MINIMUM REGULATORY
MEASURED HVL ( mm Al EQ. )
9
HVLmin > 3.5 (kVp/100) + 0.08
in mm aluminum
8
7
6
IEC Standards (new regulations ??)
for interventional labs.
5
4
3
@ 80 kVp
HVL MAXIMUM EMPIRICAL
2
1
HVL max < 4.0 to 9.0 mm Al @ 80 kVp
0
0
0.2
0.4
0.6
0.8
1
ADDED FILTRATION ( mm COPPER )
SIEMENS
GE
COMMENTS ABOUT FOCAL SPOTS
MEASURMENTS
FILTER & kVp ACCURACY
• DIFFERENT
METHODS:
INVASIVE, NONINVASIVE, TEST
POINT
• AUTOMATIC
CONTROLS ARE
METER
DEPENDENT
• FILTER & WAVE
DEPENDENT
• +/- 3 to 5% + 1 kVp
correction
factors for
filtration
kVp
meter
reflection
of meter
patient table
x-ray
tube
• COMBINED
SPATIAL
RESOLUTION MAY
BE BETTER TEST
• FILM MAY NOT BE
AVAILABLE
• GEOMETRY & #
DEG. IMPORTANT
• INTENSITY
DISTRIBUTION?
STAR PATTERN IMAGE OF
X-RAY TUBE FOCAL SPOT
D =blur diameter
3
II. PHYSICS TESTS
II. IMAGE QUALITY
ASSESSMENTS
• SPATIAL RESOLUTION
– LINE PAIRS OR MESH?
– FOV & GEOMETRY
– SOFTWARE
• LOW CONTRAST VISIBILITY
• CONTRAST RATIO & VEILING
GLARE
• UNIFORMITY & DISTORTION
• FOV ACCURACY
• DISPLAY MONITOR
• TEMPORAL RESOLUTION
• 3-D ROTATIONAL FLUORO IMAGING
SPATIAL RESOLUTION WITH
BAR PATTERN
SUBJECT CONTRAST OF BAR PATTERN
WITH DIFFERENT FILTRATION AT 80 kVp
27 CM
FoV
14 CM
FoV
CALCULATED % SUBJECT
CONTRAST OF BARS
70
• FLUORO & RECORD
MODES DIFFERENCES
• FoV DEPENDENCE
• FILTRATION
DEPENDENCE
• BAR PATTERN or
MESH
• TV or DEL DEPENDENT
• GEOMETRICAL
MAGNIFICATION &
FOCAL SPOT
DEPENDENT
60
50
40
30
20
10
0
0
0.2
0.4
0.6
0.8
1
THICKNESS OF COPPER X-RAY FILTER (mm)
0.05 mm Pb
0.10 mm Pb
4
FLAT PANEL MATRIX
BAR PATTERN (1/2) PIXEL SHIFT
BAR PATTERN ALIGNED WITH PIXELS
BARS AT 45 DEGREES TO PIXELS
5
SUMMARY OF BAR
PATTERN PLACEMENT
• PARTIAL PIXEL SHIFT EITHER VERTICAL
OR HORIZONTAL CAN ALTER MEASURED
RESOLUTION
– RESOLUTION BEST = 1 / [ 2 x PIXEL SIZE]
– OR, ZERO FOR 50% PIXEL SHIFT
– OR, ANYWHERE IN BETWEEN
• 45 DEGREE ALIGNMENT OF BAR PATTERN
INCREASES SPACING BY 1.41 x’s
GE INNOVA SOFTWARE EFFECTS
MINIMUM
SOFTWARE
SETTINGS
STANDARD
SOFTWARE
SETTINGS
– INCREASES RESOLUTION FOR BOTH FLAT
PANEL & I.I. + TV
MAXIMUM
SOFTWARE
SETTINGS
COMPARISON RESOLUTION:
MESH# vs LP/mm
MESH PATTERN FOR RESOLUTION
80
MESH# VISIBLE
70
MESH # / 25.4 mm
60
50
40
30
y = 18.602x + 5.9194
2
R = 0.8273
20
10
0
MESH # / INCH
0
1
2
#LP/mm VISIBLE
3
4
6
5 % NOISE
SPATIAL RESOLUTION AT
INPUT SURFACE OF IMAGE
RECEPTOR
NO NOISE
MAGE NOISE
I
0
0.5
1
1.5
2
2.5
3
SPATIAL FREQUENCY (LP/mm)
COMPARISON OF INHERENT DETECTOR
SPATIAL RESOLUTION
SPATIAL RESOLUTION (LP/mm)
M TF VALUE
MTF GRAPH & SPATIAL RESOLUTION LIMIT
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
SPATIAL RESOLUTION AT
DISTANCES AWAY FOR INPUT
SURFACE OF IMAGE
RECEPTOR
3.8
3.6
3.4
3.2
3
2.8
2.6
2.4
2.2
2
10
12
14
16
18
20
22
24
FIELD-of-VIEW (LP/mm)
Axiom Artis I.I.
Axiom Artis Flat Panel
Innova Flat Panel
7
SYSTEM SPATIAL RESOLUTION
SPATIAL RESOLUTION (LP/mm)
• DEPENDS UPON GEOMETRICAL MAG
( M ), FOCAL SPOT ( f ) & INHERENT
IMAGE RECEPTOR RESOLUTION ( νir )
• LESS THAN THE LOWEST OF:
–
Mx
νir
– M / [ (M - 1) x f ]
• AT LOW “M”, νir DOMINATES
3.8
3.6
3.4
3.2
3
2.8
2.6
2.4
2.2
2
0
• AT HIGH “M”, FOCAL SPOT BLUR
DOMINATES
5
10
15
20
25
30
35
40
45
DISTANCE FROM ENTRANCE SURFACE (cm)
Axiom Artis I.I.
Calc
Axiom Artis Flat Panel
Calc
Innova Flat Panel
Calc
EFFECTS OF DISTANCE
ON SPATIAL RESOLUTION
COMPARISON OF SPATIAL RESOLUTION FOR SMALL
Fov (I.I. = 13 cm, SFPD = 16 cm & GEFPD = 13 cm)
4
SPATIAL RESOLUTION (LP/mm)
COMPARISON FLUORO SPATIAL RESOLUTION IN
LARGE Fov (I.I.= 23 cm, SFPD=25 cm & GEFPD=20cm)
4
3.8
• DISPLACING THE PATTERN AWAY FROM
ENTRANCE SURFACE IMPROVES
RESOLUTION UP TO 20 – 25 cm
3.6
3.4
3.2
– SID=100 cm USED
MAG FACTOR ~ 1.30
– FLUORO FOCAL SPOTS
3
2.8
2.6
2.4
2.2
2
0
5
Axiom Artis I.I.
Calc I
10
15
20
25
30
DISTANCE FORM ENTRANCE (cm)
Axiom Artis Flat Panel
Calc S
35
40
Innova Flat Panel
Calc G
45
• LONGER DISTANCE RESULT IN FOCAL
SPOT BLUR DEGRADING RESOLUTION
• FLAT PANEL SYSTEMS BETTER AT LARGE
FoV’S & BOTH SYSTEMS TESTED SIMILAR
• IMAGE INTENSIFIER SYSTEM BETTER AT
ALL SMALL FoV’S
8
LOW CONTRAST DISCRIMINATION
PENETRAMETER LOW CONTRAST
(TOO EASY FOR ANGIO & CARDIAC)
POLAR BEAR CHASING A WHITE
SEAL IN A SNOW STORM
C-D PHANTOM DESIGN
DEPTH HOLES (INCH)
DIAMETER HOLES (INCH)
9
ACR
ACR FLUOROSCOPY
FLUOROSCOPY PHANTOM
PHANTOM
ACR FLUOROSCOPY PHANTOM
MESH
LOW
CONTRAST
CONTRASTDETAIL
19.3 cm
ACRYLIC + 4.6
mm ALUMINUM
LOW CONTRAST DEPENDS UPON:
•
•
•
•
kVp USED
X-RAY BEAM FILTRATION
THICKNESS OF ATTENUATOR
TYPE OF LOW CONTRAST
PHANTOM IS USED
• SOFTWARE: FRAME AVERAGING,
EDGE ENHANCEMENT, ETC
• DOSE (ABC) PROGRAM
• FoV USED
CONTRAST RATIO (RCC)
• MEASURES
DEGRADATION DUE
TO LIGHT &
PHOTON SCATTER
• CAN DEGRADE
VISIBILITY OF
SMALL VESSELS
• USE LIGHT ON
MONITOR
• RC > 60 : 1
10
EXCESSIVE SOFTWARE EDGE ENHANCEMENT
LOWERS CONTRAST RATIO
TEMPORAL RESOLUTION
• 6 WIRES 0.13 - 0.56
mm DIAMETER AT 30
RPM
• FLUORO & CINE`/ DSA
• STATIONARY vs.
ROTATING
• WATER PHANTOM
SIMULATES PATIENT
ATTENUATION
• 2 - 3 SPOKES VISIBLE
MOVING
ROTATING SPOKE PATTERN UNDER
PULSED FLUOROSCOPY
SMPTE PATTERN FOR VIDEO DISPLAY MONITORS
bar
pattern for
resolution
max white
gray
scale
blocks
max black
low contrast
visualiztion
11
III. RADIATION DOSES
III. PHYSICS TESTS
• TYPICAL PATIENT ENTRANCE RADIATION
LEVELS
I.I.
– PEDIATRIC, SMALL ADULT, AVERAGE ADULT &
LARGE ADULT
– FLUOROSCOPY & RECORD MODES
– DIFFERENT FoV’s & ABC PROGRAMS
FIXED 30 cm
ATTENUATION
MATERIAL
T
RADIATION
DETECTOR
TABLE
SID = 100 cm
X-RAY
TUBE
NEW YORK STATE NEW FLUORO REGULATIONS FOR
PATIENT ENTRANCE EXPOSURE
•
•
•
•
•
MAXIMUM FLUORO ENTRANCE DOSE RATE
IMAGE RECEPTOR ENTRANCE DOSE RATES
DAP METER CALIBRATION CHECK
SCATTERED RADIATION LEVELS
RADIATION PROTECTION SURVEY
NEW YORK STATE FLUORO
ENTRANCE EXPOSURE RATES
• PEDIATRIC = 0.75 inches of Al
• SMALL ADULT = 1.50 inches of Al
• AVERAGE ADULT = 1.50 inches of Al
plus 0.50 mm Cu
• LARGE ADULT = 1.50 inches of Al plus
2.10 mm Cu
• USE AT TYPICAL CLINICAL SETTINGS
IN ALL FoV’s USED CLINICALLY
12
COMPARISON OF ACRYLIC WITH ALUMINUM AND
COPPER FOR FLUORO
OTHER PHYSICS CHECKS
FLUORO ENTRANCE
EXPOSURE RATE (R/min)
12
10
GE INNOVA
– all FoV’s
8
6
4
2
0
0
5
10
15
20
25
30
35
THICKNESS OF ACRYLIC (cm)
acrylic
1.5" Al + 0.5 mm Cu
0.75" Al
1.5" Al +2.1 mm Cu
1.5" Al
Expon. (acrylic)
CHECK LIST ITEMS
• ELECTRICAL LEAKAGE &
GROUNDING TESTS
• “EMERGENCY” ELECTRICAL POWER
• ELECTRICAL RECEPTICAL POLARITY
• DATA ACHIVEAL AND RETRIEVAL
• 5 MINUTE FLUORO TIMER
• ROOM LIGHTING
• ROOM SHIELDING
• REGULATORY COMPLIANCE
13
14
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