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Digital vs Film Screen Mammography

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Digital vs Film Screen Mammography Powered By Docstoc
					DIGITAL vs. FILM-SCREEN MAMMOGRAPHY
by EDWARD L. NICKOLOFF, D.Sc. DEPARTMENT OF RADIOLOGY COLUMBIA UNIVERSITY NEW YORK, N.Y. 10032

GOALS
• COMPARE THE VARIOUS DIGITAL SYSTEMS TO FILM-SCREEN SYSTEMS • DETERMINE SOME KEY DIFFERENCES BETWEEN THE SYSTEMS: IMAGE QUALITY, RADIATION DOSES, OPERATIONAL FEATURES & PHYSICS TESTING ISSUES • IDENTIFY ADVANTAGES & DIS-ADVANTAGES OF EACH MAMMOGRAPHY SYSTEM

THE EQUIPMENT

GE 2000-D DIGITAL

GE DMR FILMSCREEN

THE EQUIPMENT

LORAD CCD DIGITAL -SELENIA SIMILAR

LORAD M IV PLATINUM FILM-SCREEN

Fischer Imaging SenoScan FFDM System

DIGITAL MAMMOGRAPHY DETECTORS

GE 2000-D IGITAL MAMMOGRAPHY UNIT
Contact Leads For Read-Out Electronics Contact Fingers Amorphous Silicon Array

Scintillator (CsI)

Glass Substrate

FROM GE

LORAD CCD DIGITAL MAMMOGRAPHY UNIT
CARBON FIBER RECEPTOR SURFACE CsI
SCINTILLATOR

40 m LIGHT PIPE LIGHT PIPE LIGHT PIPE

10 m CCD CCD

CIRCUIT BOARD

AMORPHOUS SELENIUM DETECTORS

AMORPHOUS SELENIUM DETECTOR
READOUT

VOLTAGE

-- --

IONIZATION

DETECTOR ASSEMBLY MOVES IN AN ARC
Cesium Iodide

CsI SCINTILLATOR

Fiber Optic Plate 4 CCD’s

Fischer Imaging Corporation

WORK LOAD EFFICIENCY COMPARISON

Digital Mammography - Productivity
Conventional Exam With Film
1:30 Patient in Room First Exposure 4:45 Last Exposure 2:15 First Film Out of Processor 8% Repeat Rate :05 Last Film Out of Processor :10 QC :30 Release Patient

12:10 min

Exam Using Digital Detector
1:30 Patient in Room First Exposure & QC 1:45 Last Exposure & QC :45 Release Patient / Send Study To WS

4:00 min

Minimal Repeats

Estimated > 60% Reduction In Exam Times From GE

MY EFFICIENCY ESTIMATE
• FILM-SCREEN SYSTEMS
– TALK WITH PATIENT & POSITION FOR 4 FILMS = 6 MINUTES – MARK CASSETTES WITH I.D. & BAR CODE STUDY = 1 MINUTES – WALK TO PROCESSOR WITH CASSETTES = 2 MINUTES – INSERT CASSETTES IN DAYLIGHT LOADER COUPLED TO PROCESSOR & WAIT FOR PROCESSED FILMS = 7 MINUTES – QC FILM & PLACE IN JACKET = 1 MINUTES – TALK TO PATIENT, RADIOLOGIST AND WAIT TO DRESS & LEAVE = 2 – 4 MINUTES

• TOTAL = 20 MINUTES

MY EFFICIENY ESTIMATE
• DIGITAL MAMMOGRAPHY
– TALK WITH PATIENT & POSITION FOR 4 IMAGES = 6 MINUTES – KEY IN COMPUTER INFORMATION & I.D. & BAR CODE STUDY = 2 MINUTES – REVIEW IMAGES AND TRANSMIT TO RADIOLOGIST REVIEW STATION = 2 MINUTES – TALK TO PATIENT, RADIOLOGIST AND WAIT TO DRESS & LEAVE = 2 - 4 MINUTES

• TOTAL = 13 MINUTES

COMMENTS ON RELATIVE EFFICIENCY
• ONE DIGITAL MAMMO CAN EASILY REPLACE TWO FILM-SCREEN MAMMO UNITS • ROUTINE RT QC IS BETTER … IN COMPUTER • FEW DRIFTS WITH DIGITAL UNIT • FEWER REPEATS WITH DIGITAL UNIT

RADIATION DOSES FOR MAMMOGRAPHY UNITS

COMPARISON OF RADIATION DOSES (GE DMR FILM-SCREEN vs. GE 2000-D DIGITAL)
400

AVERAGE GLANDUALAR DOSE (mRADS)

350 300 250 200 150 100 50 0 2 3 4 5 6 THICKNESS OF BR-12 (cm)
DIGITAL AOP STANDARD FILM AoP STANDARD

7

DIGITAL AoP CONTRAST FILM AoP CONTRAST

DIGITAL AoP DOSE FILM AoP DOSE

COMPARISON OF RADIATION DOSES (LORAD FILM-SCREEN WITH DIGITAL)
600
AVERAGE GLANDUALAR DOSE (mRADS)

500 400 300 200 100 0 2 3 4 5 6 THICKNESS OF BR-12 (cm) 7 8

CCD DIGITAL AT 28 kVp FILM AUTO-FILTER 200 mAs LIMIT FILM AUTO-TIME

CCD DIGITAL WITH kVp ADJUST FILM AUTO-kVp AUTO-mAs LORAD SELENIA DIGITAL

SUMMARY OF MAMMO DOSES
• IN GENERAL, THE RADIATION DOSE FOR FILM-SCREEN & DIGITAL MODES WERE SIMILAR • HOWEVER, DIGITAL DETECTORS ARE VERY EFFICIENT EVEN WITH HIGH ENERGY XRAYS... SO HIGHER KVP’s AND FILTRATION WERE USED.... RESULTING IN SLIGHTLY LOWER RAD DOSES • FILM CONTRAST MODES DELIVERED MORE RAD DOSE BECAUSE IT USED LOWER KVP’S

SUMMARY OF RADIATION DOSES
• BEWARE, UNLIKE FILM-SCREEN, DIGITAL DETECTORS CAN OPERATE OVER A WIDE RANGE OF RAD DOSES & NOISE IMPROVES AT HIGHER DOSES • DIGITAL IMAGES WITH HIGHER RADIATION DOSES LOOK BETTER • PHYSICISTS MUST GUARD AGAINST ABUSE !!

GOALS OF AUTO AEC SYSTEMS
• UTILIZE EXPOSURE TIMES <2.5 SEC • UTILIZE Dg < 300 mrads FOR < 4.2 cm COMPRESSED BREAST THICKNESS • INCREASE Dg < 150 mrads @ +1 cm • USE HIGHER kVp’S FOR THICKER / DENSE BREASTS • MAINTAIN “ESE” < 10,000 mR • IF AVAILABLE, USE Rh ANODE AND/OR FILTER FOR THICKER / DENSE BREASTS

AUTOMATED AEC SYSTEMS
• USE DYNAMIC MEASUREMENTS DURING AN EXPOSURE TO SET PARAMETERS
– ANODE – FILTER – kVp – mAs

• INVOLVES LOOK-UP TABLES (LUT) BASED UPON PATIENT BREAST

TECHNIQUES BASED UPON AVERAGE GLANDULAR DOSE MEASUREMENTS IN BR-12
CO M PR ES SED BR E AS T THIC K NES S (C M ) X -R AY TU B E P O TEN TIAL (kV p)

< 3 3 - 4 4 - 5 5 - 6 6 - 7 7 - 8

25 26 27 28 29 31

-

26 27 28 29 30 32

COMPARISON OF kVp & ANODE / FILTER FOR FILM-SCREEN vs. DIGITAL GE MAMMO IN AoP CONTRAST MODE
35

kVp UTILIZED

30

25

20 0 1 2 3 4 5 6 7 8 THICKNESS OF BR-12 (cm)
FILM Mo/Mo DIGITAL Mo/Mo FILM Mo/Rh DIGITAL Mo/Rh FILM Rh/Rh DIGITAL Rh/Rh

COMPARISON OF RADIATION DOSES (GE DMR FILM-SCREEN vs. GE 2000-D DIGITAL )
500 450

AVERAGE GRANDULAR DOSE (mRADS)

400 350 300 250 200 150 100 50 0
2 3 4 5 6 THICKNESS OF BR-12 (cm)
DIGITAL AoP CONTRAST FILM AoP CONTRAST

7

8

COMPARISON OF kVp & ANODE / FILTER FOR FILM vs. DIGITAL GE IN AoP STANDARD
34 32

kVp UTILIZED

30 28 26 24 22 20 0 1 2 3 4 5 THICKNESS BR-12 (cm)
FILM Mo/Rh DIGITAL Mo/Rh

6

7

8

FILM Mo/Mo DIGITAL Mo/Mo

FILM Rh/Rh DIGITAL Rh/Rh

COMPARISON OF RADIATION DOSE (GE DMR FILM-SCREEN vs. GE 2000-D DIGITAL)
450

AVERAGE GLANDULAR DOSE (mrads)

400 350 300 250 200 150 100 50 0 2 3 4 5 6 PHANTOM THICKNESS (cm) 7 8

DIGITAL AOP STANDARD

FILM AoP STANDARD

AutoCell:

Breast w/Photo Cells

DDD

Digital vs FilmScreen

SUMMARY OF AEC SYSTEMS
• DIGITAL SYSTEMS USE HIGHER kVp’S THAN FILM-SCREEN SYSTEMS • DIGITAL SYSTEMS USE ANODE / FILTERS WHICH PROVIDE HIGHER ENERGY XRAYS • DIGITAL SYSTEM ARE MORE FLEXIBLE WITH AEC SENSOR AREA • DIGITAL SYSTEM ARE EXPECTED TO BE SLIGHTLY LESS DOSE • DIGTIAL SYSTEMS CAN BE ADJUSTED FOR A RANGE OF DOSES

HIGH CONTRAST SPATIAL RESOLUTION

WHAT AFFECTS HIGH CONTRAST SPATIAL RESOLUTION?
•

X-RAY TUBE FOCAL SPOT SIZE – DIMENSION – GEOMETRY … MAGNIFICATION, SID – L = M / [ (M -1) x f ] – INTENSITY DISTRIBUTION • IMAGE RECEPTOR INHERENT LIMITS – FILM-SCREEN – DIGITAL SYSTEM

CONTACT FILM-SCREEN MAMMOGRAPHY SPATIAL RESOLUTION AS A FUNCTION OF BREAST THICKNESS & FOCAL SPOT SIZE
25
OVERALL SPATIAL RESOLUTION (LP/mm)

20 15 10 5 0 0 1 2 3 4 5 6 7 8 9 10 BREAST THICKNESS (CM)
F=0.3 mmf=0.6mm f=0.6 mm f=1.2 mm

1.5x MAG FILM-SCREEN MAMMOGRAPHY SPATIAL RESOLUTION AS A FUNCTION OF BREAST THICKNESS & FOCAL SPOT SIZE
18 16 14 12 10 8 6 4 2 0 0 1 2 3 4 5 6 7 8 9 10 BREAST THICKNESS (CM)
F=0.1 mm f=0.3 mm f=0.6 mm

OVERALL SPATIAL RESOLUTION (LP/mm)

6

CONTACT DIGITAL MAMMOGRAPHY SPATIAL RESOLUTION AS A FUNCTION OF BREAST THICKNESS & FOCAL SPOT SIZE

OVERALL SPATIAL RESOLUTION (LP/mm)

5 4 3 2 1 0 0 1 2
F=0.3 mm

3 4 5 6 7 BREAST THICKNESS (cm)
f=0.6 mm

8

9

10

f=1.2 mm

1.5x MAG DIGITAL MAMMOGRAPHY SPATIAL RESOLUTION AS A FUNCTION OF BREAST THICKNESS & FOCAL SPOT SIZE
9 8 7 6 5 4 3 2 1 0

OVERALL SPATIAL RESOLUTION (LP/mm)

0

1

2
F=0.1

3 4 5 6 7 8 BREAST THICKNESS (cm)
F=0.3

9
F=0.6

10

PIN-HOLE CAMERA OF X-RAY FOCAL SPOT

HIGH CONTRAST SPATIAL RESOLUTION (GE DMR FILM-SCREEN vs GE 2000-D DIGITAL)
18
SPATIAL RESOLUTION (LP/mm)

16 14 12 10 8 6 4 2 0 0 1 2 3 4 5 6 7 8 9 PHANTOM THICKNESS (cm)
DIGITAL MEASURED THEORY FILM-SCREEN FILM MEASURED THEORY DIGITAL

HIGH CONTRAST SPATIAL RESOLUTION (LORAD MIV PLATINUM FILM-SCREEN vs LORAD CCD & SELENIA DIGITAL)
18

SPATIAL RESOLUTION (LP/mm)

16 14 12 10 8 6 4 2 0 0 1 2 3 4 5 6 7 8 PHANTOM THICKNESS (cm)
CCD DIGITAL MEASURED THEORY FILM-SCREEN SELENIA DIGITAL MEASURED FILM MEASURED THEORY CCD DIGITAL THEORY SELENIA DIGITAL

SUMMARY OF HIGH CONTRAST SPATIAL RESOLUTION
• DIGITAL MAMMOGRAPHY UNITS HAVE LOWER SPATIAL RESOLUTION THAN THE FILM SCREEN UNITS ( 5 – 8 LP/mm) • MEASURED DIGITAL RESOLUTION WAS 30% TO 60% OF FILM-SCREEN RESOLUTION (15 – 20 LP/mm) • SPATIAL RESOLUTION DOES NOT TELL THE WHOLE STORY!

Flat Panel-Light Sensor
scan line FET

Very High Fill Factor
Fill Factor= Sensitive Area
Pitch x Pitch
data line

Pitch

FROM GE

Pitch

IMAGE RECEPTOR DEPENDENCE
• FILM-SCREEN SYSTEMS – DESIGN OF SCREEN (THICKNESS, DYES, REFLECTIVE LAYER, PHOSPHOR CRYSTALS) – TYPICALLY….. 15 TO 25 LP/mm • DIGITAL SYSTEMS – PITCH ( 25m To 100m ) – L = 1 / (2 x PITCH) – TYPICALLY …… 5 TO 10 LP/mm

LOW CONTRAST DETECTABILITY

LOW CONTRAST DETECTABILITY

RMI 180 C-D PHANTOM
• NINE HOLE DEPTHS RANGE FROM 0.062 mm TO 1.0 mm • SUBJECT CONTRAST = EXP (-m T) • TEN HOLE DIAMETERS RANGE FROM 0.312 mm TO 7.07 mm

COMPARISON OF LOW CONTRAST DETECTION OF FILM-SCREEN vs. DIGITAL MAMMO SYSTEMS ---- GE 100
% 0F LOW CONTRAST TARGET VISUALIZED (%)

90 80 70 60 50 40 30 20 10 0 0 2 4 6 8 ACRYLIC THICKNESS OF PHANTOM (cm)
GE 2000-D DIGITAL Linear (GE 2000-D DIGITAL) GE DMR+FILM Linear (GE DMR+FILM)

10

COMPARISON OF LOW CONTRAST DETECTION OF FILM-SCREEN vs. DIGITAL MAMMO SYSTEMS --- LORAD 100
% OF LOW CONTRAST TARGET VISUALIZED (%)
90 80 70 60 50 40 30 20 10 0 0 2 4 6 8 ACRYLIC THICKNESSOF PHANTOM (cm)
LORAD CCD DIGITAL Linear (LORAD CCD DIGITAL) Linear (LORAD SELENIA DIGITAL)

10

LORAD MIV + FILM LORAD SELENIA DIGITAL Linear (LORAD MIV + FILM)

DIGITAL SYSTEM SIGNAL-TO-NOISE RATIO (SNR)

DIGITAL MAMMOGRAPHY SYSTEMS SNR vs. RADIATION EXPOSURE 1000
SIGNAL-TO-NOISE RATIO (SNR)

y = 12.216x 100

0.5374

y = 9.759x 10

0.5552

1 0.1 1
LORAD DIGITAL Power (LORAD DIGITAL)

10

100
GE 2000-D DIGITAL Power (GE 2000-D DIGITAL)

1000

ENTRANCE RADIATION EXPOSURE (mR)

OTHER CONSIDERATIONS

DYNAMIC RANGE CONSIDERATIONS

FILM-SCREEN CHARACTERISTIC CURVE -GE DMR WITH KODAK MIN-R 2000
4 3.5 3 2.5 2 1.5 1 0.5 0 0 0.5 1 1.5 2 2.5 LOG [EXPOSURE (mR)]
USEFUL RANGE = 78.9 mR / 8.9 mR = 8.7 28 kVp, 3 cm ACRYLIC, INTO BUCKY KODAK 270 RA PROCESSOR WITH KODAK CHEMISTRY FILM DYNAMIC RANGE

FILM DENSITY [O.D.]

FILM-SCREEN CONTRAST GRADIENT -GE DMR WITH KODAK MIN-R 2000 FILM
4.5 4

FILM CONTRAST GRADIENT

3.5 3 2.5 2 1.5 1 0.5 0 0 0.5 1 1.5 2 2.5 3 3.5 4 FILM OPTICAL DENSITY (O.D.) FILM-SCREEN DYNAMIC

DYNAMIC RANGE OF DIGITAL MAMMOGRAPHY -- GE 2000-D DIGITAL 10000
RELATIVE DIGITAL SIGNAL
DIGITAL DYNAMIC RANGE

1000

100
USEFUL RANGE = > 260 mR / 0.1 mR = > 2600

10

1

0.1

1

10

100

1000

ENTRANCE EXPOSURE ( mR)]

LORAD 2000 DIGITAL MAMMOGRAPHY: SIGNAL vs RADIATION EXPOSURE
100000
DIGITAL DYNAMIC RANGE

SIGNAL (relative units)

10000

1000

100
USEFUL RANGE = 130 mR / 0.1 mR = 1300

10

1 0.1 1 10 100 1000 10000 ENTRANCE EXPOSURE (mR)

TISSUE EQUALIZATIONS

Thickness Compensation
GOAL: EQUALIZATION OF DENSITIES TO SKIN LINE. Algorithm: 1. Estimate the thickness of the breast at all pixels 2. Add a nearly-equivalent thickness [of water] to raise gray level.
Line-Profile through Breast

Original

TC-Processed

Compensation Thickness Breast Thickness

{

{
FROM GE

Breast 3 RMLO no TE

FROM GE

Breast 3 - RMLO TISSUE EQUILIZATION

COMPUTERS IN MAMMOGRAPHY
• • • • • • Computer Aided Diagnosis (CAD) Data Compression PACS Image Enhancement Dual Energy Subtraction Tomosynthesis

COMPUTER AIDED DIAGNOSIS

FROM : L CLARKE et al., Acad. Radiol. 1997

GE C ompany Proprietary - Not for External Distribution

October 6, 1998

COMPUTER-AIDED DETECTION
Applications • Automated detection • Automated classification
TM Current ImageCheckerTM Performance • Flagged 85% of overlooked cancers • Flagged 83% of diagnosed cancers

Increase the sensitivity for cancer detection when combined with the radiologist

From GE

DISPLAY MONITORS

VDT verses VIEWBOX
• BRIGHTNESS
– VDT = 200 TO 400 LUX – VIEWBOX = 3000 - 4000 LUX

• VDT HAS WINDOWS & LEVELS FOR VARIABLE CONTRAST / BRIGHTNESS • COLOR TINT DIFFERENCES • CALIBRATION REQUIREMENTS & DRIFT

MONITOR CHARACTERISTICS

THE SMPTE TEST PATTERN WITH 13 SHADES OF GRAYSCALE PATCHES WAS UTILIZED TO MEASURE THE GRAYSCALE “LUT “.

SMPTE TEST PATTERN
VISIBILITY OF BARS EACH SHADE OF GRAY BLOCK DIFFERENT

LINES STRAIGHT

0% / 5% CONTRAST BLOCK VISIBLE

100% / 95% CONTRAST BLOCK VISIBLE

IMAGE MANIPULATION

LMLO - Full Zoom, no Invert

FROM GE

LMLO - Full Zoom, Invert
FROM GE

UNSHARP MASK ENHANCEMENT
DENSITY DENSITY

ORIGINAL

SMOOTH

DISTANCE

DISTANCE

DENSITY

ORIGINAL - SMOOTH

DENSITY

ORIGINAL + 4 DIFFERENCE
DISTANCE

DISTANCE

Tomosynthesis
Series of low-dose images used to reconstruct tomography images at any level

FROM GE

ADVANTAGES OF DIGITAL TECHNOLOGY
• LARGE DYNAMIC RANGE -- NOT TOO DARK OR TOO LIGHT • WINDOW & LEVEL CAPABILITY • IMAGE PROCESSING • FAST RETREIVAL & LAYOUT • LOWER REPEAT RATES • LESS PATIENT RADIATION DOSE • COMPUTER AIDED DIAGNOSIS (CAD) • TELERADIOLOGY CAPABILITY

ADVANTAGES OF DIGITAL TECHNOLOGY
• BETTER SENSITIVITY & EARLY DETECTION • COMBINE WITH RIS/HIS DISPLAY • COMPACT IMAGE STORAGE • BETTER PATIENT TRACKING & BILLING • SERVICES TO REMOTE LOCATIONS • LATITUDE & CONTRAST

DIS-ADVANTAGES OF DIGITAL TECHNOLOGY
• • • • • HIGH INITIAL COSTS HIGHER MAINTENANCE COSTS TECHNOLOGY OBSOLENCE ISSUES HIGH QUALITY SUPPORT PERSONNEL NEED FOR NETWORK & NETWORK SUPPORT • LOWER SPATIAL RESOLUTION • NETWORK TRANSFER SPEED LIMITS • MORE COMPLEX VIEWING PROCESS

DIS-ADVANTAGES OF DIGITAL TECHNOLOGY
• ENTERING INCORRECT ID# CAN MISPLACE STUDIES & BILLING • PACS/NEMA COMPATABLE HARDWARE MAY NOT BE INSTALLED • INTRA-VENDOR COMPATABILITY • POWER / COMPONENT FAILURES • LONG-TERM DATA RETRIEVAL DELAYS • LACK OF INSTANT FLUORO REVIEW

CONCLUSIONS
• DIGITAL IS MORE TIME EFFICIENT • RAD DOSE CAN BE SIMILAR • FILM-SCREEN HAS BETTER HIGH CONTRAST RESOLUTION & DIGITAL BETTER LOW CONTRAST SENSITIVITY • DIGITAL MAMMO SYSTEMS ARE MORE ROBUST:
– WIDER DYNAMIC RANGE – WINDOW / LEVEL ADJUSTMENT – COMPUTER IMAGE ENHANCEMENT

ARRET


				
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