Radiation Protection in Digital Radiology

IAEAInternational Atomic Energy Agency

Radiation Protection in Digital Radiology

Picture Archival and Communication System (PACS)

L09

IAEA 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)

IAEA 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


IAEA 4

• 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)

Picture Archiving and Communication System (PACS)


IAEA 5

• 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/

Digital Imaging and Communications in Medicine

(DICOM)


IAEA 6

(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

Radiation Protection in Digital Radiology L06 Avoiding Artefacts in Computed Radiography

• DICOM headers store information for all images.• A rich source of information for prospective or retrospective

patient exposure monitoring.

IAEA 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

IAEA 8

• 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)

Hospital Information System (HIS)


IAEA 9

• 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.

Health Level Seven (HL7)


IAEA 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/


IAEA 11

Four Major PACS Components

1. Acquisition 2. Network

3. Archive

4. Display

Image DatabaseRIS

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

-CRT-LCD-Laser Film

Status ofExams

Status ofImages


IAEA 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


IAEA 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


IAEA 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


IAEA 15

Acquisition: Image deleted

• Radiographer may delete image at acquisition station without transmitting to PACS

• It may not be possible to restore deleted image



IAEA 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



IAEA 17

Network: Image corrupted

• Interruption in network service may degrade image

• It may not be possible to retransmit image from acquisition station



IAEA 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


IAEA 19

Archive: storage media corrupted

• Storage media failure can prevent images from being retrieved

• May require repeated examinations and unnecessary radiation exposure to patients


IAEA 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


IAEA 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


IAEA 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.


IAEA 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


IAEA 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?


IAEA 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


IAEA 26

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


IAEA 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

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

IAEA 28

Discrepancies between PACS and hospital processes => 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.


IAEA 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


IAEA 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?


IAEA 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.


IAEA 32

“Weather never cooperates”

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!


IAEA 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.


IAEA 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


IAEA 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


Documents

Radiation Protection in Digital Radiology