Radiation Protection in Digital Radiology
Picture Archival and Communication
System (PACS)
L09
IAEA
International Atomic Energy Agency
Educational Objectives
• Understand how digital radiology depends on
Picture Archiving and Communications Systems
(PACS)
• List the four components of PACS
• Explain how errors in each of the four components
of PACS can contribute to unnecessary radiation
exposure to patients
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Digital Radiology
• The application of modern information
technology to the practice of radiology
• Depends on automated systems for
acquiring, transmitting, storing, and
displaying digital images and associated
data
• Broader than just systems, includes how the
systems are used
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Picture Archiving and Communication
System (PACS)
• A system capable of acquiring, transmitting,
storing, retrieving, and displaying digital images
and relevant patient data from various imaging
sources, and capable of communicating the
information over a network
• Depends on interfaces to other medical information
systems, such as the Radiology Information
System (RIS)
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Digital Imaging and Communications in
Medicine (DICOM)
• An international standard (ISO) describing
how radiology images are identified and
formatted and how imaging devices
communicate with each other
• Jointly developed by the American College
of Radiology and the National Electronic
Manufacturers Association
• Based on the ISO Open Standards
Intercommunications (OSI) model
• http://dicom.nema.org/
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
(0008,0020) : Study Date
: 04/12/2003
(0008,0022) : Acquisition Date
: 04/12/2003
(0008,0060) : Modality
: CR
(0008,0070) : Manufacturer
: AGFA
(0008,0080) : Institution Name
: HCSC
(0008,1010) : Station Name
: ADCC2
(0008,103E) : Series Description
: lumbar AP
(0010,1010) : Patient's Age
: 020Y
(0018,0015) : Body Part Examined
: LSPINE
(0018,1004) : Plate ID
: U13-35
(0018,1401) : Acquisition Device Processing : 60025Ia712Ra
(0018,1403) : Cassette Size
: 35CMX43CM
(0018,1404) : Exposures on Plate
: 342
(0018,5101) : View Position
: AP
(0018,6000) : Sensitivity
: 4.00000000E+02
(0019,1010) : Image processing parameters :
MENU=60025 CC=0 MC=3.00 EC=0.00 LR=2.00 NR=4.00
(0019,1013) : Sensitometry name
: NK5
(0019,1015) : Dose monitoring list
: 1.54
(0020,0013) : Image Number
:1
(0020,1002) : Images in Acquisition
:1
(0028,0010) : Rows
: 3730
(0028,0011) : Columns
: 3062
(0028,0100) : Bits Allocated
: 16
(0028,0101) : Bits Stored
: 12
(0028,0102) : High Bit
: 11
Example of some of the DICOM tags in
the header
• DICOM headers store information for all images.
• A rich source of information for prospective or retrospective patient
exposure monitoring.
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Radiation Protection in Digital Radiology
L06 Avoiding Artefacts in Computed Radiography
Some key points:
• Images stored in some PACS cannot be
(sometimes) post-processed.
• This will be known in advance and appropriate post
processing should be applied before the image is
archived.
• Allowing easy access to PACS and teleradiology to
look at previous images can save exposures.
• Except of the “for presentation” images, PACS save
also images “for processing”. These may
retrospectively be processed to recover information
preventing re-exposures
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Radiation Protection in Digital Radiology
L06 Avoiding Artefacts in Computed Radiography
Hospital Information System (HIS)
• A system used to store and retrieve patient
information.
• An integrated computer system that may
include or be linked to a radiology
information system (RIS)
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Health Level Seven (HL7)
• An American National Standards Institute (ANSI) •
•
•
•
accredited Standards Developing Organization (SDO)
operating in the healthcare arena.
A messaging standard that enables healthcare applications
to exchange key sets of clinical and administrative data
Defines data to be exchanged, timing of the interchange,
and communication of certain errors to the application.
Supports functions such as security checks, participant
identification, availability checks, exchange mechanism
negotiations and, most importantly, data exchange
structuring.
The most widely implemented standard for healthcare
information in the world.
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Integrating the Healthcare Enterprise
(IHE)
• IHE is an initiative to improve the way computer
systems in healthcare share information
• IHE promotes use of established standards such
as DICOM and HL7
• Systems developed in accordance with IHE
• communicate with one another better
• are easier to implement
• enable care providers to use information more effectively
• http://www.ihe.net/
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Four Major PACS Components
1. Acquisition
-CR
-DX
-CT
-MR
-US
-DF
-OT
4. Display
2. Network
-CRT
-LCD
-Laser Film
RIS
Image Database
Status of
Exams
Status of
Images
3. Archive
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Examples of errors within and between
PACS components
• Acquisition errors
• Archive errors
• Improper technique
• Storage media
selection
• Wrong exam performed
• Image deleted
• Network errors
corrupted
• Storage failure
• Sequestered exams
• Display errors
• Image lost
• Image corrupted
• Unable to transmit
• Mis-calibration
• Associated data not
displayed
• Artificial shutters
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Acquisition: Improper Technique Selection
• Digital detectors are more tolerant of overexposure than conventional detectors
• Excess digital signal is scaled to provide
consistent appearance
• Consequence: is unnecessary radiation
exposure to patient
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Acquisition: Wrong exam performed
• Radiographer may image thorax using digital
examination intended for abdomen
• Digital signal is rendered inappropriately for
review
• Consequence: may be repeated
examination and unnecessary radiation
exposure to patient
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Acquisition: Image deleted
• Radiographer may delete image at
acquisition station without transmitting to
PACS
• It may not be possible to restore deleted
image
• Consequence: may be repeated
examination and unnecessary radiation
exposure to patient
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Network: Image lost
• Interruption in network service may result in losing
the image
• It may not be possible to retransmit image from
acquisition station
• Consequence: may be repeated examination and
unnecessary radiation exposure to patient
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Network: Image corrupted
• Interruption in network service may
degrade image
• It may not be possible to retransmit
image from acquisition station
• Consequence: may be repeated
examination and unnecessary
radiation exposure to patient
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Network: unable to transmit
• Interruption in network services prevents
transmission of images from acquisition
station
• Local storage capacity of acquisition station
is limited
• If acquisition continues, images can be lost,
causing repeated examinations and
unnecessary radiation exposure to patients
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Archive: storage media corrupted
• Storage media failure can prevent images from
being retrieved
• May require repeated examinations and
unnecessary radiation exposure to patients
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Archive: storage failure
• Storage failure can prevent images from being
archived
• If images have already been deleted from
acquisition station, may require repeated
examinations and unnecessary radiation exposure
to patients
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Archive: images sequestered
• When demographic and examination information
on images does not match information from RIS,
images may be hidden from view
• Unless reconciliation is performed, radiographer
may repeat examination with unnecessary
radiation exposure to patients
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Display: mis-calibration
• Improperly calibrated display can make digital
images appear under-exposed
• Radiologist may instruct radiographer to repeat
examinations or increase radiologic technique
causing unnecessary radiation exposure to
patients.
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Display: associated data not displayed
• Data accompanying the image may not be
displayed for the radiologist
• If missing data includes information on the
radiographic technique or patient exposure,
the radiologist cannot oversee radiographer
practice
• Without radiologist oversight, radiographers
may perform examinations with unnecessary
radiation exposure to patients
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Display: artificial shutters
• To improve contrast,
radiographer may add artificial
collimation
• When artificial shutters are nontransparent, radiologist cannot
oversee radiographer practice
• Without radiologist oversight,
radiographers may perform
examinations without
appropriate collimation,
resulting in unnecessary
radiation exposure to patients
Where was the actual radiation field?
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Sources of Errors in PACS
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•
•
•
•
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Mistakes in configuration of PACS
Improper calibration of PACS devices
Discrepancies between PACS and hospital processes
PACS design flaws
Inherent limitations of human operators
Inadequate training and documentation of PACS and
hospital processes
• Insufficient planning for PACS service interruptions
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Mistakes in configuration of PACS
• Inappropriate software settings and values
• Outdated or inconsistent versions of software
• Incompatible combinations of software and
hardware
Main Department
Orthopedic Clinic
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Improper calibration of PACS devices
• Includes monitors, Digital Radiography (DR), film digitizers,
laser cameras, analogue interfaces, phototimers, etc.
• Methodology for calibrations not well-established
• Frequency of calibrations not well-established
• Consequences of mis-calibration not widely acknowledged
Before
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Discrepancies between PACS and
hospital processes => false assumptions
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Patient identification data is invariant.
Only one radiologist is associated with a report.
Only one physician is associated with a request.
Images are used in surgery in the same manner as images
are used in clinics.
The patient scheduled for an exam in Room 4 will be
examined in Room 4.
The exam started in Room 4 will be completed in Room 4.
Outpatients are only examined in the Outpatient Center.
The same supervisors of exams on 1st shift are also
present on 3rd shift.
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
PACS design flaws
• Some software and hardware features either do not
function, or act in an undesired manner (bugs)
• Some processes that are absolutely required for clinical
practice are not supported.
• Limited connectivity
• Incomplete implementation of DICOM
• Incompatible interpretations of DICOM
• Divergence from Integrating the Healthcare Enterprise (IHE)
• Lack of adherence to software design principles
• Lack of application of Reliability Engineering
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
“To err is human, but to really foul things
up requires a computer!”
• Electronic images are imperfect: they are subject to deletion,
mis-association, mis-routing, and mis-interpretation.
• Electronic devices and media are im-permanent records: the
consequence of loss is greater than one film or one film
jacket.
• A single bad electronic image can be proliferated: a single
bad film image can be controlled.
• Bad electronic images can disappear without a trace: bad
films disappear, but leave a signature. How many films were
in the box at start-of-shift?
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
The best maintenance is preventive
maintenance.
• Calibrations need to be performed on-schedule.
• Operators need to clean, inspect, and document.
Start-of-shift routines or checklists are helpful.
• Schedule PM to occur at convenience of clinical operation.
• Software upgrades are major service events that demand reverification of proper function.
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Insufficient planning for PACS service
interruptions
• How is PACS affected by loss of utility services, i.e., power, HVAC,
•
•
•
or network?
How do I maintain continuity of clinical operations during downtime
of an individual PACS component?
Can local components operate during downtime of a central PACS
component (database, archive, gateway, RIS or RIS interface)?
How does PACS recover after service is restored?
Software upgrade is a service interruption!
“Weather never cooperates”
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Conclusions
• Unfortunately, errors will always occur in PACS.
• Some of these errors cause unnecessary radiation dose to
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patients
QC is the key to detecting errors.
Training is key to averting errors.
Reliability engineering is key to continuity of clinical
operations.
Disaster recovery is key to restoring normal clinical
operations.
Optimisation includes all of the above.
Other lectures in this series concentrate on errors that
occur in acquisition and display, rather than those that
affect network quality of service and archive reliability.
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Answer True or False
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•
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PACS is a system to store and retrieve patient
information
Reason for retake of radiographic
examination could be due to network
problems
Improperly calibrated display can involve
unnecessary radiation exposure to patient
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)
Answer True or False
• False. Hospital information system (HIS) is used to
store and retrieve patient information. This can be
linked with the radiology information system (RIS)
• True. Interruption in network service may result in
losing the image, hence repeated radiographic
examination would be required.
• True. Improperly calibrated display can make
digital images appear under-exposed. The
radiologist may instruct radiographer to repeat
examinations or increase radiologic technique
causing unnecessary radiation exposure to
patients
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Radiation Protection in Digital Radiology
L09 Picture Archival and Communication System (PACS)