Converting the Radiology
Department from Film-Screen
to Digital:
Making the Transition
S. Jeff Shepard, MS, DABR
University of Texas M. D. Anderson Cancer Center
Houston, Texas
jshepard@di.mdacc.tmc.edu
jshepard@di.mdacc.tmc.edu
AAPM 2005 Continuing Education Course
Radiographic and Fluoroscopy Physics and Technology
Learning Objectives
Understand the issues that a Medical
Physicist is likely to face when
supporting a clinical operation that is
undergoing (or is about to undergo) a
conversion from filmfilm-screen based
radiography to digitally acquired
images.
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Outline
Image Acquisition
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Getting started with CR
Introducing direct digital radiography
Digital Mammography
Getting Started with CR
Replace F/S receptors with CR
• StraightStraight-forward
• Cost effective
Start in Portable XX-Ray
• Traditional challenge in image quality
Quality control
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– F/S is unforgiving
– Over and under exposures are common
Acquisition device QC
Display device QC
Operational QC
Patient Identification
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• Wider dynamic range of CR yields quick
improvements
– Speed adjusts to technique automatically
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Getting Started with CR
Different detector sensitivity and
energy dependence
• New technique charts
Wide dynamic range
• Consistent image quality over a wide
range of exposures
• Very beneficial (image consistency)
• Potential downsides
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Getting Started with CR
UnderUnder- and OverOver- exposure
• Image consistency (contrast and brightness) is
maintained
Fewer photons = More noise
• Obscures lowlow-contrast details
More photons = More signal strength
• SignalSignal-toto-noise ratio improves
• Beautiful images
• High patient dose!
Flexibility in technique selection can lead to
higher patient doses (“
(“Exposure Creep”
Creep”)
Image Quality:
Image Quality:
0.1
Range of Exit
Exposure Data
(VOI)
1.0
Unused
Dynamic Range
10
Exposure Data Recognition
Signal Strength
Signal Strength
Exposure Data Recognition
Unused
Dynamic Range
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100
Incorrect VOI
0.1
Exposure (mR)
System Dynamic Range
1.0
10
100
Exposure (mR)
System Dynamic Range
VOI recognition failure
• Body habitus (Pediatrics and postpost-surgery)
• Patient mis-position – air peak
• Over-collimation, gonadal shields and
prosthetics
– Special processing algorithms
– Fixed speed techniques
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Getting Started with CR
Technologist Feedback –
Detector Exposure Indicators (E.I.)
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Agfa CR - Lgm value (Logs available)
Fuji CR - S Number (Logs available)
Konica CR – S Number
Kodak CR – EI (Exposure Index)
Canon DR - REX Number
Philips & Siemens DR - Speed value
GE DR - ?????
Getting Started with CR
Technologist Feedback –
Detector Exposure Indicators (E.I.)
• Exposure to the detector
• Accurate and consistent (reproducible)
• Patient exposure index (DAP or ESE) –
not the same!
• Not editable!!!
Proprietary algorithms – confusion
AAPM (TG116), IEC and DIN are evaluating
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Getting Started with CR
Tuning the image quality
• Verify QC console calibration conforms
to DICOM PS3.14 first
Getting Started with CR
Tuning the image quality
Convert each step to a %JND of the entire
range of JND’
JND’s from Lmin to Lmax
– Compare JND intervals in a test pattern to
those on a PACS monitor
% JND (step) = 100% x
Set post processing to drive display to Lmin and Lmax
Measure steps on the QC monitor with a
photometer (OR(OR-3)
Calculate JND at each step (DICOM 3.14, Table
B1)
DICOM is the registered trademark of the National Electrical Manufacturers Association
for its standards publications relating to digital communications of medical information.
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JND(step)JND(step)-JND(Lmin)
JND(Lmax) – JND(Lmin)
Repeat on PACS monitor and compare at each step
For DICOMDICOM-compliant PACS, calculate JND index
at each step and test for linearity from Lmin to Lmax
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Display Matching
100%
90%
Modality QC
80%
PACS
%JND
70%
60%
50%
40%
30%
20%
10%
0%
0
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100%
90%
Modality QC
80%
PACS
600
800
1000
QC console calibration is supported by
few vendors
• Use contrast and brightness settings to
get as close as possible
• Pressure vendors to add calibration
capability to QC displays
• Calibrate it yourself
70%
%JND
400
Digital
Driving Level
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Getting Started with CR
Display Matching
60%
50%
40%
30%
20%
– Add 3rd party software
– Replace display with selfself-calibrating
10%
0%
0
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200
200
400
600
Digital
Driving Level
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800
1000
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Getting Started with CR
Tuning the Image Processing
• Start with vendor default settings on
sample “raw”
raw” images
Getting Started with CR
Portable XX-Ray
• Start with chest
• Add abdomen/pelvis
• Add long bones
– VendorVendor-supplied unprocessed image data of
real patients for tweaking
– Work with key technologists and radiologist(s)
radiologist(s)
to find optimal default settings
– Change individual settings one at a time
• Phantoms first for contrast and dose,
then 5 patients
• Adjust & repeat as necessary
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Getting Started with CR
General Radiography
• Recalibrate AEC
Direct Digital Radiography
Introduction into the clinical operation:
Same strategy as with CR
• Verify AEC calibration
• Verify QC console calibration
• Start with vendor default settings on
sample “raw”
raw” images
• Phantoms first, then patients
• Adjust techniques and processing &
repeat as necessary
• Get processing established in one room
• Migrate to other rooms when stable
– Constant S/N ratio or detector exposure –
not O.D.
• Calibrate QC console
• Use same strategy as with portable
X-Ray to get techniques and postpostprocessing established in one room
• Migrate to other rooms when stable
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Image Quality
Moire patterns between the fixed grid
lines and the and detector sampling
matrix.
Digital Mammography
Acquisition Devices
• FullFull-Field Digital Mammography (FFDM)
– Scanning slot CCD with CsCs-I
– Amorphous Silicon TFT with CsCs-I
scintillator
– Amorphous Selenium
– CR (Pending FDA)
• Usually seen in CR, but can happen in DR
• Use high grid line frequency (> 4 lines/mm)
• Some systems employ low pass filters
– Decreases resolution
– Inappropriate for smaller plates
• Most DR’
DR’s use high line rate (~8 lines/mm)
stationary or standard reciprocating grids
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Digital Mammography
Introduction into the clinical operation:
• Same as DR and CR in general
radiography
• Verify AEC & QC console calibration
• Tune the techniques in one room, then
propagate to others
Digital Mammography
Connectivity
• Huge data sets (up to 300 MB/study)
require large local storage and fast
hardware
• Dedicated workstations using pointtopoint-topoint connections can impose crippling
additional transmission times
• Intermediate routing modules
– kV selection may be limited
• Image postpost-processing flexibility is
restricted by FDA
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– Bottleneck if not very robust
– Single point of failure
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Digital Mammography
Workflow – What to store?
• Unprocessed images (“
Processing”)
(“For Processing”
Digital Mammography
Workflow – What to store?
• Both?
– Interpretation workstation must apply FDAFDAapproved processing
– Unprocessed images are ugly
– Processed for clinics, unprocessed for
Radiologist’
Radiologist’s workstations
– Doubles storage space on PACS
– Doubles bandwidth requirements
– Slows everything down
• Processed images (“
Presentation”)
(“For Presentation”
– Image is processed prior to archival
– Further processing is not possible (W/L only)
– Images in clinics look good
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QC - Acquisition Device
and Operation
AAPM Report #74
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Chapter 1 – The QC process
Chapter 2 – QC Instrumentation
Chapter 3 – The Physics Report
Chapter 4 – Repeat Rate Analysis
Chapter 5 – Radiographic units
Chapter 7 – Conventional Tomography
Chapter 8 – Portable XX-Ray
Chapter 14 – Photostimulable Phosphor
Systems
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Quality Control
Equipment selection
• Match performance and configuration to
clinical needs
Equipment QC
• Acquisition Devices
• Display Devices
Technical Operation
Patient Data Integrity
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Quality Control
… of the Equipment
• Acquisition Device
Quality Control
… of the Equipment
• Acquisition Device
– X-Ray generator (AAPM Report 74)
– Exposure index calibration
– Exposure index dependence on beam quality
– VOI recognition algorithms
– Noise
– Uniformity
– Artifacts
– Contrast sensitivity
kV
mA linearity
Exposure time
Collimation
Focal Spots
Grids
Beam alignment
– AEC (Constant raw SNR, or detector
exposure)
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Quality Control
… of the Equipment
• Acquisition Device
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Quality Control
… of the Equipment
• Acquisition Device
– DR systems
– DICOM calibration at the QC console
Detector sensitivity (SNR2 vs Exposure)
Verify quarterly
DR QC Workshop - J. Seibert, L. Goldman (1:15 PM
WEWE-D-W-608608-1)
Monthly
Annual if selfself-calibrating
– Mammography
MQSA - Vendors QC Program
– CR devices
Erasure thoroughness
AAPM Report #74, PSP System QC
Siebert AJ, AAPM Monograph 20, 1994
Samei E, et al, Med Phys. 2001
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QC - Primary Displays
AAPM OROR-3 Tests (Jerry Thomas and Mike
Flynn, 8:30 tomorrow)
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Luminance Uniformity
Chromaticity
Noise
Luminance Response
Diffuse and Specular
Reflection
• Pixel Defects
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Quality Control
… of the Equipment
• Film printers (AAPM Report #74)
• Veiling Glare (CRT only)
• Resolution (CRT only)
• Geometric Distortion
(CRT only)
• Angular dependence
of LR (@ +45
degrees from
normal, LCD only)
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– Density calibration (daily or as needed)
– Density uniformity (monthly)
– Geometric distortion (monthly)
– Artifacts (monthly)
– View boxes (annually)
– SMPTE or TG18TG18-QC
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QC - Operation
Repeat/Reject Rate Analysis and
Exposure Index Logs
• Expect same results as with Film/Screen
• Films no longer available for counting
• Software at console to track reasons for
rejects and repeats
– By tech
– By anatomical view
Easily accessible
Formatted to facilitate interrogation
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QC - Data Integrity
Modality Work List Management (MWLM)
• Modality queries the RIS for a list of
scheduled patients through a “Broker”
Broker”
• RIS returns the requested list (through the
broker) with patient demographics
• Automatically refreshes every 15 minutes
• Tech selects patient from the list at the
acquisition console
• Exams are uniquely identified with “Accession
Number”
Number” for later pairing with reports
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QC - Data Integrity
MWLM implementation
• Opportunity for patient mismis-ID greatly
diminished
QC -Data Integrity
Verification
• Errors are still possible
• Technologist or supervisor views EVERY
exam on web viewer or QC workstation
immediately after archival to verify
status
– Reiner B, et al, JDI, 2000
Overall patient ID failure rates decreased
from 7.6% to 2% with introduction of MWLM
in Baltimore VA’
VA’s CT operation
– Missing images
– Patient mismis-ID
• Mandatory requirement for ALL
modalities
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Summary
Conversion to DR requires:
• An inin-depth understanding of the
technology behind CR, DR, PACS, RIS,
workstations, and printers.
• Understanding the impact of DR on
workflow in exam rooms
• Understanding the impact of DR on the
QC program
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Other Considerations
• Reading room illumination
• Prior, filmfilm-based comparisons with
softsoft-copy
• Primary interpretation display devices
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Calibration
QC
Matrix size >3 MP? (Langer S, et al)
Dead pixel definition
M. Flynn - tomorrow, 8:55
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Other Considerations
• Detector latent image decay
• DualDual-Energy subtraction,
tomosynthesis,
tomosynthesis, & image stitching
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Workflow?
Optimization?
Techniques?
Latent image affects?
Other Considerations
• Film Digitizers
• Calibration
– Linear?
– Barten?
Barten?
• QC
• DICOM
• Conformance statements
• Workflow enhancements
• Detector calibration uniformity
• Uncorrected flatflat-fields
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– Storage Commitment
– Performed Procedure Step
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Other Considerations
Other Considerations
The Role of the Physicist in Planning and Design
of Digital Image Management Systems (PACS) –
D. Peck, M. Flynn (7:30 AM MOMO-A-I-609609-1)
Overview of Digital Detector Technology - J.
Seibert (8:55 AM MOMO-B-I-618618-2)
Characteristics and Performance Evaluation of
Digital Image Displays - H. Roehrig (7:30 AM TUTUA-I-609609-1)
Evaluating Digital Mammography Systems - E. Berns
(7:30 AM TUTU-A-I-618618-1)
Digital Image Processing in Radiography - D. Foos,
Foos,
X. Wang (7:30 AM WEWE-A-I-609609-1)
Recent Advances in Digital Mammography - M.
Yaffe,
Yaffe, R. Jong (7:30 AM WEWE-A-I-618618-1)
Testing Flat Panel Imaging Systems – What the
Medical Physicist Needs to Know - J. Tomlinson
(8:30 AM WEWE-B-I-618618-1)
Digital Image Displays – Resolution, Brightness
and Grayscale Calibration - M. Flynn (8:55 AM
WEWE-B-I-618618-2)
Design and Performance Characteristics of Digital
Radiographic Receptors - J. Seibert (7:30 AM
THTH-A-I-609609-1)
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Other Considerations
Display Evaluation Demonstration Workshop - E.
Samei (1:30 PM MOMO-D-W-608608-1)
DR QC Workshop - J. Seibert, L. Goldman (1:15 PM
WEWE-D-W-608608-1)
Bibliography
Digital Imaging and Communications in Medicine (DICOM),
National Electrical Manufacturer’
Manufacturer’s Association (NEMA),
Rosslyn,
Rosslyn, VA, 2000, (http://www.nema.org
(http://www.nema.org))
Freedman M, Pe E, Mun SK, Lo SCB, Nelson M. The potential
for unnecessary patient exposure from the use of storage
phosphor imaging systems. Proceedings of the International
Society for Optical Engineering. 1993;1897:4721993;1897:472-479.
Gur D, Fuhman CR, Feist JH, Slifko R, Peace B. Natural
migration to a higher dose in CR imaging. Eighth European
Congress of Radiology; September 1212-17, 1993; Vienna.
Abstract 154.
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Bibliography
Honea R, Blado ME, Ma Y. Is reject analysis necessary after
converting to computed radiography? J Digit Imaging, v15
#2, Suppl 1 (May), 2002, 4141-52.
Langer S, et al, Comparing the Efficacy of 5 MP CRT vs 3 MP
LCD in the Evaluation of Interstitial Lung Disease, J Digit
Imaging, v17 #3 (September), 2004, 149149- 157.
Reiner B, Seigel E, Kuzmak P, and Severance S, Transmission
Failure Rate for Computed Tomography Exams in a Filmless
Radiology Department, J Digit Imaging, v13 #2, Supp 1
(May), 2000, 7979-82
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Bibliography
Samei E, Seibert JA, Willis CE, Flynn MJ, Mah E, Junck KL.
Performance evaluation of computed radiography systems.
Med Phys. 2001;28:3612001;28:361-371. Samei E, et al, Assessment of
Display Performance for Medical Imaging Systems, AAPM
OnOn-Line Report #3 (OR(OR-3), AAPM, 2005.
Seibert JA. Photostimulable phosphor system acceptance
testing. In: Seibert JA, Barnes GT, Gould RG, eds.
Specification, Acceptance Testing and Quality Control of
Diagnostic XX-ray Imaging Equipment. Woodbury, NY:
American Association of Physicists in Medicine; 1994:7711994:771800. Monograph No. 20.
Shepard S J, et al, Quality Control in Diagnostic Radiology,
AAPM Report #74 AAPM, 2002.
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Bibliography
Willis CE, Mercier J, Patel M. Modification of conventional
quality assurance procedures to accommodate computed
radiography. SCAR '96 Computer Applications To Assist
Radiology. Great Falls, Va:
Va: Society for Computer Applications
in Radiology; 1996:2751996:275-281
Willis CE. Quality assurance: an overview of quality assurance
and quality control in the digital imaging department. In:
Quality Assurance: Meeting the Challenge in the Digital
Medical Enterprise. Great Falls, Va:
Va: Society for Computer
Applications in Radiology; 2002:12002:1-8.
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