Screen Radiography · Screen Radiography Robert E. Dickerson Senior Research Associate Health Imaging Eastman Kodak Company ©Eastman Kodak Company, 2005 8/12/2005 AgX Photodetector

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©Eastman Kodak Company, 20058/12/2005

Advances in Film / Advances in Film / Screen RadiographyScreen Radiography

Robert E. Dickerson

Senior Research AssociateHealth Imaging

Eastman Kodak Company


AgX Photodetector

� Inorganic, digital photoconductor

� 1-4 µm pixel size


AgX Photodetectors

� Light photons produced by intensifying screens are captured by each AgX crystal to produce stable latent image

� 4-30 photons needed for stable latent image


AgX Photodetector

� Latent image formed by exposure is chemically amplified by development to yield viewable silver image

� Amplification factor >109

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Tabular vs Conventional, 3-D crystals


Cubic Grain Microcrystals


Non Commercialized Micro crystals


X-Wing Fighter

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PACMAN


Opportunities for Improved Film Design

� Higher contrast by control of grain size distribution and sensitivity

� Higher resolution film/screen systems� Improved quantum sensitivities of silver

halide microcrystals� Novel coating structures to improve film

processing rates� New display properties


KODAK MIN-R EV FilmNew asymmetric coating structure, in conjunction with novel emulsions, optimizes image quality from toe to shoulder of the response and improves physical properties.

Screen

Primary Emulsio

n

Second

ary Emulsi

on

Support (Blue)

Antihala

tion Laye

r

Orienta

tion La

yer

Total


� Novel silver halide microcrystals in the parenchymal emulsion contain shallow electron trapping dopants. In conjunction with the improved monodispersity of the grains, this allows it to achieve high contrast with a sharp toe.

� High contrast makes breast anatomy, including abnormalities, more visible

� Sharp toe might enable new optimization of imaging chain and better visualization of microcalcifications

Parenchymal Emulsion

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Min-R EV 150 system vs. Min-R 2000 system

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Log E

Den

sity

Sharp toe is due to novel emulsion technology

Higher contrast is due to monodisperse cubic grains

High D-max and shoulder contrast is due to high opacity grains and backside emulsion

Results in greater overexposure latitude, which is due to higher upper scale contrast

Better visualization of breast parenchyma

X-ray Sensitometry

KODAK MIN-R EV 150 Screen vsKODAK MIN-R 2000 Screen

KODAK MIN-R 2000/2000 Screens

KODAK MIN-R EV & EV 150Screens

Results in whiter whites, more “sparkle,” improved visibility of microcalcifications



� Images were exposed to a density of ~1.9 in the center of the image

� Images made with a GE DMR mammographic unit

� Two imaging systems: MIN-R 2000 and MIN-R EV

� Eight kVps: 25-32

� Two anode/filter combinations: Mo/Mo and Rh/Rh

� Two duplicate sets

� Total of 64 images

� All processed in KODAK X-OMAT EX II Developer and Replenisher


� CDMAM Phantom, Type 3.4, used in the study

� Gold disks range in diameter from 60 µm to2 mm, and in thickness from 30 nm to 2 µm

� Each square contains two identical disks, one in the center and one in a randomly chosen corner

� The task is to pick the corner containing the disk



� Score sheet from one observer for MIN-R 2000 Film/Screen, 26 kVp, Mo/Mo

� Blue indicates that the correct corner was identified

� Red indicates that the wrong corner was identified or that the observer said they could no longer detect the disks


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Phantom: CDMAM Phantom, Type 3.4

Results

System kVp Filtration CDMAM Exposure RelativeDetectability* Time (sec) Mid-line

Dose

MIN-R 2000 28 Mo/Mo 0 1.92 1.0MIN-R 2000 30 Rh/Rh −−−−2 0.60 0.4

MIN-R EV 28 Mo/Mo +2 1.68 0.9MIN-R EV 30 Rh/Rh 0 0.55 0.4

* Average relative column number


� Because of the improved film properties (toe contrast, mid-scale contrast, speed) and improved screen properties (improved MTF, speed)

� MIN-R EV Systems demonstrate simultaneously high sharpness and low, high-frequency noise

� At 28 kVp, Mo/Mo, the MIN-R EV System will reduce the mid-line dose by 10%, yet provide better detection of the disks in the CDMAM Phantom than the MIN-R 2000 System

� At 30 kVp, Rh/Rh, the MIN-R EV System will provide similar detection of the disks in the CDMAM Phantom as a MIN-R 2000 System but at 40% the mid-line dose

SummarySummary


Features oxidatively enhanced, high quantum efficiency AgX microcrystal that provides improved sensitivity

Support

Low Exposure RegionImaging Layer

(Provides improved resolution and visually adaptive contrast)

High Exposure Imaging Layer+ Gradient Crossover Control

KODAK Hyper Speed G Medical Film


KODAK Hyper Speed G Medical Film

Hyper Speed G 0.30 logE faster

T-MAT G/RA

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Radiographic Speed – Historical Timeline

� 1896: Paper used for media-based radiography. Calcium tungstate intensifying screens discovered. Relative speeds unknown (VERY low).

� 1912: Glass plate radiography. VERY low speed.

� 1918-1970s: Double-emulsion films, calcium tungstate screens improved, relative system speeds 25-200.

� 1970s – present: Rare earth screens and appropriate films commercialized, relative system speeds 100-400 (A few small niche markets use faster systems).

� 2004: Hyper-speed systems, relative system speeds 400-1600 (with greatly improved high-frequency NEQ and DQE).


Modulation Transfer Function (image blur)

MTF (cycles/mm)Screen / Film Speed 2 4 8

LANEX Regular / T-MAT G 400 100% 100% 100%

X-SIGHT / Hyper Speed G 800 175% 250% 270%LANEX Fast / Hyper Speed G 1300 90% 95% 100%


Modulation Transfer Function (image blur) MTF (cycles/mm)

Screen / Film Speed 2 4 8

LANEX Regular / T-MAT G 400 100% 100% 100%

INSIGHT Skeletal Medium / Hyper Speed G 400 250% 500% 750%LANEX Fine / Hyper Speed G 200 300% 600% 900%

GE Digital Radiography 200-400 150% 60% NAComputed Radiography 200-400 90% 60% NA


How Hyper Speed Works, cont.

MTF benefit can be utilized in two MTF benefit can be utilized in two basicbasic waysways::

1.1. Provide improved image quality (better visibility Provide improved image quality (better visibility of fine detail) at current system speeds.of fine detail) at current system speeds.

OROR2.2. Provide clinically acceptable, high image quality Provide clinically acceptable, high image quality

at 2X current system speeds, exchanging potential at 2X current system speeds, exchanging potential

image quality for radiation dose reduction.image quality for radiation dose reduction.

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What does this mean?

�� MammographicMammographic – MTF at 200200--300300 speed

�� XX--SIGHTSIGHT – MTF at 800800 speed

�� LANEX Regular/TLANEX Regular/T--MATMAT – MTF at 13001300 speed


Benefits of High-Speed Systems

�� Higher image quality from stopping motionHigher image quality from stopping motion

�� grids, body motiongrids, body motion

�� Opportunity to reduce KvOpportunity to reduce Kv

�� Smaller focal spotSmaller focal spot

�� MagnificationMagnification

�� Increased tube lifeIncreased tube life

�� Reduced radiation dose to radiology staffReduced radiation dose to radiology staff


Visually Adaptive ContrastVisually Adaptive Contrast

� The human visual system loses it’s ability to distinguish differences in density as an image gets darker.

� This means that lesion detection is less likely if the lesion appears in a darker area of the radiograph.

Lesion Detection vs Density

Film Density

Les

ion

De

tect

abili

ty

DarkLight

More

Less


Visually Adaptive Contrast

Visually Adaptive Contrast

Film Density

Les

ion

Det

ecta

bili

ty

DarkLight

More

Less

Visually adaptive contrast puts the contrast where the eyes need it.

Film

Con

tras

t

Higher

Lower

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KODAK X-SIGHT L/RA Film

X-RAY SENSITOMETRYSPEED MATCHED AT D = 1.20

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log10 Relative Exposure

Gam

ma

T-MAT L/RA &LANEX RegularX-SIGHT L/RA &X-SIGHTXLA+ & TRIMATICRegular

Visually Adaptive ContrastLocal contrast comparison with other of Kodak’s latitude systems


Summary

� New film/screen system allows for significantly reduced X-ray dose at improved MTF (image blur).

� Significant improvements in system MTF are possible at equivalent X-ray doses

� New film/screen system provide opportunities for dose reduction as result of higher system speed while maintaining high image quality


� Improved film/screen systems continue to be developed.

� Opportunities for improved image quality and processability still exist.

� New systems provide possibilities for lower-dose radiology at high image quality.

Conclusion


Documents

Screen Radiography · Screen Radiography Robert E. Dickerson Senior Research Associate Health Imaging Eastman Kodak Company ©Eastman Kodak Company, 2005 8/12/2005 AgX Photodetector