FLAT PANEL FLUOROSCOPY
ACCEPTANCE TESTING AND
QUALITY CONTROL
by
EDWARD L. NICKOLOFF
DEPARTMENT OF RADIOLOGY
COLUMBIA UNIVERSITY &
NEW YORK –PRESBYTERIAN HOSPITAL
NEW YORK, NEW YORK
Dr. Ed Nickoloff, Columbia
University
ACCEPTANCE TESTING GOALS
•
•
•
•
•
•
•
•
PRIOR TO 1st CLINICAL USAGE
VERIFY PURCHASE ORDER
CHECK ARCHITECTURAL DESIGN & FLOW
EVALUATE RADIATION SHIELDING,
SCATTER LEVELS & RADIATION
PROTECTION
MOST COMPREHENSIVE TESTING
MAKE REPAIRS & ADJUSTMENTS
UNDERSTAND ABC OPERATION
ESTABLISH BASELINE VALUES FOR QC
Dr. Ed Nickoloff, Columbia
University
ACCEPTANCE TESTING GOALS
• COMPARISON OF MEASURED IMAGE
QUALITY TO MANUFACTURER’S SPEC’S
• ITEMS NOT ROUTINELY TESTED
–
–
–
–
MECHANICAL SYSTEMS
LASER CAMERAS
ARCHIVEAL STORAGE DEVICES
ELECTRICAL SAFETY
• REGULATORY COMPLIANCE
• RECOMMENDATIONS TO STAFF
• RADIATION DOSE CHARTS
Dr. Ed Nickoloff, Columbia
University
ROUTINE QC TESTING
• LIMITED NUMBER SPOT CHECKS
• INTENDED TO IDENTIFY DEGRADATIONS
OR CHANGES
• ENSURE PATIENT & STAFF RADIATION
SAFETY
• FOLLOW-UP TO REPAIRS & UPGRADES
• NEEDED FOR REGULATORY COMPLIANCE
• SOME TEST SIMILAR TO ACCEPTANCE
– FEWER PARAMETERS EVALUATED
– COMPARED TO BASELINE VALUES
Dr. Ed Nickoloff, Columbia
University
1
THE FIELD – of – VIEW
(FoV) GAME?
GE
FoV (cm)
SIEMENS
FoV (cm)
25
20
20
17
16
15
12
GE measures horizontal & vertical.
Siemens measures diagonal.
Dr. Ed Nickoloff, Columbia
University
Dr. Ed Nickoloff, Columbia
University
NON-UNIFORMITIES
• IMAGE INTENSIFIERS + TV
ARTIFACTS & IMAGE
UNIFORMITY
– VIGNETTING, DISTORTION, PHOSPHOR
BURNS, DIRT, SATURATION, GRID
PROBLEMS
• FLAT PANEL DETECTORS
– BAD DETECTORS, NON-UNIFORM GAIN,
CALIBRATION ERRORS, DIRT,
SATURATION, GRID PROBLEMS,
PHYSICAL DAMAGE, SOFTWARE
PROBLEMS, IMAGE PERSISTENCE
Dr. Ed Nickoloff, Columbia
University
Dr. Ed Nickoloff, Columbia
University
2
SYSTEM SPATIAL RESOLUTION
• DEPENDS UPON GEOMETRICAL MAG
( M ), FOCAL SPOT ( f )& INHERENT IMAGE
SPATIAL RESOLUTION
ASSESSMENTS
RECEPTOR RESOLUTION ( ir )
• LESS THAN THE LOWEST OF:
–
Mx
ir
– M / [ (M - 1) x f ]
ir DOMINATES
• AT HIGH “M”, FOCAL SPOT BLUR
DOMINATES
• AT LOW “M”,
Dr. Ed Nickoloff, Columbia
University
Dr. Ed Nickoloff, Columbia
University
SUMMARY OF BAR
PATTERN PLACEMENT
CAVEATS OF SPATIAL
RESOLUTION
MEASUREMENTS
• 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
– PARTIAL PIXEL SHIFT STILL A PROBLEM
Dr. Ed Nickoloff, Columbia
University
Dr. Ed Nickoloff, Columbia
University
3
SUMMARY OF NOISE EFFECTS
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
• AS IMAGE NOISE INCREASES THE
LIMITING HIGH CONSTRAST SPATIAL
RESOLUTION DECREASES
NO NOISE
5 % NOISE
MAGE NOISE
I
0
0.5
1
1.5
2
2.5
3
SPATIAL FREQUENCY (LP/mm)
– QUANTUM MOTTLE IS A KEY FACTOR IN
IMAGE NOISE
– RECORD MODE (CINE) WILL HAVE LESS
QUANTUM MOTTLE THAN FLUORO MODE
WHICH MIGHT IMPROVE RESOLUTION
– ABC DOSE MODES WILL INFLUENCE
RESULTS
Dr. Ed Nickoloff, Columbia
University
Dr. Ed Nickoloff, Columbia
University
80 kVp X-RAY SPECTRA WITH DIFFERENT
COPPER FILTRATION
EFFECTS OF FILTRATION AND kVp
UPON SPATIAL RESOLUTION
7.00E+04
#X-RAYS / keV
6.00E+04
5.00E+04
4.00E+04
3.00E+04
2.00E+04
1.00E+04
0.00E+00
0
10
20
30
40
50
60
70
80
X-RAY ENERGY (keV)
0 mm Cu
0.3 mm Cu
0.6 mm Cu
Dr. Ed Nickoloff, Columbia
University
0.9 mm Cu
• SOME NEW FLUORO UNITS USE
CONSIDEABLE FILTRATION IN X-RAY BEAM
• HIGH kVp AND FILTRATION REDUCE
INHERENT CONTRAST OF BAR PATTERN
• 0.10 mm LEAD BAR PATTERN OR THICKER
WOULD BE BEST FOR SPATIAL
RESOLUTION
• SCATTERED RADIATION IS MORE
PENETRATING & WILL AFFECT SHIELDING
OR ROOM & LEADED APPAREL
Dr. Ed Nickoloff, Columbia
University
4
X-RAY BEAM QUALITY (HVL)
HVL MINIMUM REGULATORY
HVLmin > 3.50 (kVp/100) + 0.08
in mm aluminum
• kVp & FILTER MAY
BE AUTOMATIC
• HVL DEPENDS UPON
kVp, CONTOUR & XRAY FILTER
• FILTER MAY BE
DIFFERENT IN
FLUORO & CINE`
• TYP. HVL=3.5 - 9.0
mm @ 80 kVp & CAN
BE HIGHER
IEC STANDARD (REGULATORY FOR IR??)
HVL MAXIMUM EMPIRICAL
HVL max < 4.0 to 9.0 mm Al @ 80 kVp
MODERN ANGIO ROOMS HAVE VARIABLE
FILTRATION WHICH CAN BE UP TO 0.9 mm Cu
Dr. Ed Nickoloff, Columbia
University
Dr. Ed Nickoloff, Columbia
University
COMPARISON OF HVL vs. ADDED FILTRATION
MEASURED HVL ( mm Al EQ. )
9
8
SPATIAL RESOLUTION AT
INPUT SURFACE OF IMAGE
RECEPTOR
7
6
5
4
3
@ 80 kVp
2
1
0
0
0.2
0.4
0.6
0.8
1
ADDED FILTRATION ( mm COPPER )
SIEMENS
Dr. Ed Nickoloff, Columbia
University
GE
Dr. Ed Nickoloff, Columbia
University
5
SUMMARY ABOUT INHERENT
SPATIAL RESOLUTION
SPATIAL RESOLUTION (LP/mm)
COMPARISON OF INHERENT DETECTOR
SPATIAL RESOLUTION
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
Dr. Ed Nickoloff, Columbia
University
• SPATIAL RESOLUTION OF IMAGE INTENSIFIER +
T.V. IMPROVES WITH SMALL FoV’S
• FLAT PANEL RESOLUTION DOES NOT INCREASE
WITH FoV CHANGES
• SPATIAL RESOLUTION OF FLAT PANEL SYSTEMS
IS LESS THAN IMAGE INTENSIFIER PLUS T.V.
SYSTEMS IN SMALL FoV’S
• SPATIAL RESOLUTION OF FLAT PANEL SYSTEMS
IS BETTER THAN IMAGE INTENSIFIER + T.V. IN
LARGE FoV’S
Dr. Ed Nickoloff, Columbia
University
SUMMARY ABOUT INHERENT
SPATIAL RESOLUTION
• FLAT PANEL RESOLUTION IS APPROX.
– 1 / [ 2 x PIXEL SIZE (mm)]
• GE PIXEL = 200 T & SIEMENS PIXEL = 185 T
• ESTIMATE SPATIAL RESOLUTION FLAT
PANELS
– 2.5 LP/mm & 2.7 LP/mm
– CORRESPONDS TO MEASUREMENTS
SPATIAL RESOLUTION AT
DISTANCES AWAY FOR INPUT
SURFACE OF IMAGE
RECEPTOR
• ABC MODES, RADIATION DOSE, SOFTWARE
AND ANGULATION HAVE AN EFFECT
Dr. Ed Nickoloff, Columbia
University
Dr. Ed Nickoloff, Columbia
University
6
COMPARISON OF SPATIAL RESOLUTION IN MEDIUM
FoV ( I.I.= 17cm, SFPD=20cm & GEFPD=17cm)
COMPARISON OF SPATIAL RESOLUTION FOR SMALL
Fov (I.I. = 13 cm, SFPD = 16 cm & GEFPD = 13 cm)
4
SPATIAL RESOLUTION (LP/mm)
SPATIAL RESOLUTION (LP/mm)
3.6
3.4
3.2
3
2.8
2.6
2.4
2.2
3.8
3.6
3.4
3.2
3
2.8
2.6
2.4
2.2
2
2
0
5
10
15
20
25
30
35
40
45
0
5
DISTANCE FROM ENTRANCE (cm)
Axiom Artis I.I.
Calc
Axiom Artis Flat Panel
Calc
Dr. Ed Nickoloff, Columbia
University
Innova Flat Panel
Calc
Axiom Artis I.I.
Calc I
10
15
20
25
30
DISTANCE FORM ENTRANCE (cm)
Axiom Artis Flat Panel
Calc S
35
40
45
Innova Flat Panel
Calc G
Dr. Ed Nickoloff, Columbia
University
EFFECTS OF DISTANCE
ON SPATIAL RESOLUTION
• DISPLACING THE PATTERN AWAY FROM
ENTRANCE SURFACE IMPROVES
RESOLUTION UP TO 20 – 25 cm
– SID=100 cm USED
MAG FACTOR ~ 1.30
– FLUORO FOCAL SPOTS ~ 0.7 mm effective
FLUORO vs. CINE (RECORD
MODE) SPATIAL RESOLUTION
• 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
Dr. Ed Nickoloff, Columbia
University
Dr. Ed Nickoloff, Columbia
University
7
SUMMARY OF FLUORO vs CINE
SPATIAL RESOLUTION
RESOLUTION COMPARISON OF FLUORO vs.
RECORD MODE FOR SIEMENS AXIOM ARTIS FLAT
PANEL
4
MEASURED SPATIAL
RESOLUTION (LP?mm)
3.8
3.6
3.4
3.2
3
2.8
2.6
2.4
2.2
2
0
5
10
15
20
25
30
35
40
DISTANCE FORM INPUT SURFACE (cm)
FLUORO 16 cm Fov
RECORD 16 cm FoV
Dr. Ed Nickoloff, Columbia
University
SUMMARY OF FLUORO vs. CINE
SPATIAL RESOLUTION
• FOR IMAGE INTENSIFIER UNITS WITH
DIGITIZED TV
– FLUORO MAY BE 1023 LINE & CINE 512 LINES
– FLUORO RESOLUTION IS MUCH BETTER THAN
CINE
• FOR IMAGE INTENSIFIER UNITS WITH CINE
FILM
– CINE IS BETTER THAN FLUORO AT I.I. BECAUSE
IT IS NOT LIMITED BY TV LINES & BANDPASS
– AT DISTANCES, FOCAL SPOT BLUR DOMINATES
– CINE FILM HAS BETTER RESOLUTION THAN
RECORD MODE ON FLAT PANEL SYSTEMS
Dr. Ed Nickoloff, Columbia
University
• FLAT PANEL UNITS AT INPUT SURFACE
– RECORD MODE (CINE) USE MORE RADIATION
– RECORD MODE HAS LESS Q.M.
– RECORD MORE IS A LITTLE BETTER
• FLAT PANEL UNITS DISPLACED FROM INPUT
SURFACE
– RECORD MODE HAS LARGER FOCAL SPOT &
MORE FOCAL SPOT BLUR
– FOR FLAT PANEL UNITS FLUORO RESOLUTION
BETTER AT LARGE DISTANCES
– GE FLAT PANEL PROBABLY USED SMALL FOCAL
SPOT IN RECORD
Dr. Ed Nickoloff, Columbia
University
TEMPORAL RESOLUTION &
PERSISTANCE
• 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
Dr. Ed Nickoloff, Columbia
University
8
TYPICAL PATIENT RADIATION DOSES
MEASUREMENTS OF
PATIENT ENTRANCE
RADIATION DOSES
I.I.
FIXED 30 cm
ATTENUATION
MATERIAL
T
RADIATION
DETECTOR
TABLE
SID = 100 cm
Dr. Ed Nickoloff, Columbia
University
Dr. Ed Nickoloff, Columbia
University
CINE DOSE RATES FOR DIFFERENT FoV's &
THICKNESS--- SIEMENS AXION ARTIS dBC
SUMMARY OF PATIENT ENTRANCE
RADIATION EXPOSURE RATES
100
NORMAL,
15
FPS CINE
• EACH VENDORS HAS MULTIPLE RADIATION
DOSE PROGRAMS!!!
• GE HAS:
EXPO
SU
RE(R/M
IN
)
10
1
0
5
10
X-RAY
TUBE
15
20
25
– IQ+, IQ STAND., SMART IQ, RDL+, RDL STAND.
– RANGE OF Max / Min = 3 or 4 : 1
– “LOW” is about 50% of “NORMAL”
• SIEMENS HAS:
– MINUS = -50%; NORMAL; PLUS = +50%
0.1
ACRYLIC THICKNESS (cm)
25 cm FoV
20 cm FoV
Dr. Ed Nickoloff, Columbia
University
16 cm FoV
• FOR BOTH FLAT PANELS, EACH CINE
FRAME =
4 TO 10 FLUORO FRAMES
Dr. Ed Nickoloff, Columbia
University
9
SUMMARY OF PATIENT ENTRANCE
RADIATION EXPOSURE RATES
• USEFUL TO PLOT “LN( EXPOSURE RATE)”
VERSES THICKNESS
• HVL FOR TISSUE 3.7 TO 4.4 cm
COMPARING 17 cm FoV, IN THE 15 – 25 cm
THICKNESS ACRYLIC:
– SIEMENS FLAT PANEL = 2x’s I.I. WITH
DIGITIZED TV FOR RECORD
– GE FLAT PANEL (“RDL+,NORMAL”) ABOUT
SAME EXPOSURE RATES AS SIEMENS
FLAT PANEL IN FLUORO & LESS IN CINE
• VARIOUS MODES ALLOW A LARGE RANGE
Dr. Ed Nickoloff, Columbia
University
ABC CONTROLS
Dr. Ed Nickoloff, Columbia
University
I.I. INPUT EXPOSURE RATES (IIIER)
FLUORO ABC CONTROL OF FLAT PANEL SYSTEMS
TUBE POTENTIAL (kVp)
110
100
90
80
70
60
50
0
5
10
15
20
25
THICKNESS ACRYLIC (cm)
GE INNOVA
SIEMENS 0.3 mm Cu
SIEMENS 0.9 mm Cu
SIEMENS 0.2 mmCu
Dr. Ed Nickoloff, Columbia
University
SIEMENS 0.6 mm Cu
30
• IIIER IS HOW X-RAY
SERVICE ADJUSTS
RADIATION LEVELS
• GRID REMOVED
• FLUORO < 100 T R /
SEC*
• CINE` < 20 T R /
FRAME*
• DSA < 1000 T R /
FRAME*
• * 9 INCH (23 cm) FoV
I.I.
DETECTOR
NO GRID
ATTENUATION
X-RAY
TUBE
Dr. Ed Nickoloff, Columbia
University
10
SUMMARY OF INPUT
RADIATION TO DETECTORS
• ALL SYSTEM MEET < 100 µR/ sec
FLUORO & < 20 µR / frame IN RECORD
FOR 23 cm FoV
• GE HAS ABOUT SAME RAD LEVELS IN
15 pps & 30 pps FLUORO
• IN LARGE FoV’s LEVELS ABOUT SAME
FOR ALL TYPES OF FLUORO &
RECORD
• THERE ARE DIFFERENCE BETWEEN
SETTINGS AND VENDORS
Dr. Ed Nickoloff, Columbia
University
LOW CONTRAST IMAGING
• STANDARD
PENETRAMETER
WITH LOW
CONTRAST HOLES
TOO EASY
• kVp & FILTER
DEPENDENT
• C-D PHANTOMS
USEFUL FOR
RELATIVE
MEASUREMENTS
Dr. Ed Nickoloff, Columbia
University
CONTRAST RATIO (RC)
• MEASURES
DEGRADATION DUE
TO LIGHT &
PHOTON SCATTER
• CAN DEGRADE
VISIBILITY OF
SMALL VESSELS
• USE LIGHT ON
MONITOR
• RC > 60 : 1
Dr. Ed Nickoloff, Columbia
University
CONTRAST OF HOLES
C0 = EXP [ - µ ( T) ]
VISIBILITY OF HOLES
C0 * MTF ( ) = K / SNR
where (1 / 2D) <
< (1 / D)
Dr. Ed Nickoloff, Columbia
University
11
DATA FROM “C-D” PHANTOM
GE FPD
FLUOR.
55%@
20cm
60%@
17 cm
57%@
15 cm
62%@
12 cm
SIEMENS FPD
CINE
FLUOR.
55% @
62% @
20 cm
25 cm
60% @
62% @
17 cm
20 cm
63% @
62% @
15 cm
16 cm
73% @
12 cm
Dr. Ed Nickoloff, Columbia
CINE
71% @
25 cm
71.5% @
20 cm
75% @
16 cm
MONITOR CRITERIA
• MONITORS MUST HAVE A BALANCED
GRAY SCALE
• 5% CONTRAST MUST BE VISIBLE
• MINIMUM BRIGHTNESS (BLACK LEVEL)
<1 TO 2 nit (Cd / m2 )
• MAXIMUM BRIGHTNESS >400 TO 500 nit
• NO DEFECT & DISTORTIONS
• TINT OR COLOR DIFFERENCES
University
Dr. Ed Nickoloff, Columbia
University
OTHER PHYSICS TESTS
OTHER PHYSICS TEST
• X-RAY EQUIPMENT TEST
– kVp, WAVEFORM, HVL, mA LINEARITY,
FOCAL SPOT SIZE, ETC.
• REGULATORY TESTS
– MAX FLUORO EXPOSURE RATE,
COLLIMATION, SAFETY CHECKS, ETC.
• MECHANICAL CHECKS
– ISOCENTER, CENTRAL BEAM, MOTION,
ALIGNMENT, COLLISION SENSOR, ETC.
• “DAP” METER ACCURACY
• ARCHIVING & PACS TRANSMISSION
• ELECTRICAL SAFETY
– GROUNDING, POLARITY, EMERGENCY
POWER, CUT-OFF SWITCHES, ETC.
• GRID EVALUATION
• SID TRACKING
• RADIATION PROTECTION SURVEY
Dr. Ed Nickoloff, Columbia
University
Dr. Ed Nickoloff, Columbia
University
12
THE END!
Dr. Ed Nickoloff, Columbia
University
13