Radiation Protection in Digital Radiology

1
Radiation Protection in Digital Radiology

• Picture Archival and Communication System (PACS)
• L09

2
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
3
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
4
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)

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
5
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/

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
6
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.

Radiation Protection in Digital Radiology
L06 Avoiding Artefacts in Computed
Radiography
7
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

Radiation Protection in Digital Radiology
L06 Avoiding Artefacts in Computed
Radiography
8
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)

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
9
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.

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
10
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/

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
11
Four Major PACS Components
4. Display
1. Acquisition
2. Network

• CR
• -DX
• -CT
• -MR
• -US
• -DF
• -OT

-CRT -LCD -Laser Film
RIS
Image Database
Status of Exams
Status of Images
3. Archive
Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
12
Examples of errors within and between PACS
components

• Acquisition errors
• Improper technique selection
• Wrong exam performed
• Image deleted
• Network errors
• Image lost
• Image corrupted
• Unable to transmit

• Archive errors
• Storage media corrupted
• Storage failure
• Sequestered exams
• Display errors
• Mis-calibration
• Associated data not displayed
• Artificial shutters

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
13
Acquisition Improper Technique Selection

• Digital detectors are more tolerant of
  over-exposure than conventional detectors
• Excess digital signal is scaled to provide
  consistent appearance
• Consequence is unnecessary radiation exposure to
  patient

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
14
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
15
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
16
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
17
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
18
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
19
Archive storage media corrupted

• Storage media failure can prevent images from
  being retrieved
• May require repeated examinations and unnecessary
  radiation exposure to patients

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
20
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
21
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
22
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.

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
23
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
24
Display artificial shutters

• To improve contrast, radiographer may add
  artificial collimation
• When artificial shutters are non-transparent,
  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?
Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
25
Sources of Errors in PACS

• 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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
26
Mistakes in configuration of PACS

• Inappropriate software settings and values
• Outdated or inconsistent versions of software
• Incompatible combinations of software and hardware

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
27
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
28
Discrepancies between PACS and hospital processes
gt false assumptions

• 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.

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
29
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
30
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?

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
31
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 re-verification of proper function.

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
32
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
Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
33
Conclusions

• Unfortunately, errors will always occur in PACS.
• Some of these errors cause unnecessary radiation
  dose to 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.

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
34
Answer True or False

• 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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)
35
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

Radiation Protection in Digital Radiology
L09 Picture Archival and Communication
System (PACS)