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IAEA International Atomic Energy Agency Radiation Protection in Digital Radiology Optimisation in CR & DR L03.

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Presentation on theme: "IAEA International Atomic Energy Agency Radiation Protection in Digital Radiology Optimisation in CR & DR L03."— Presentation transcript:

1 IAEA International Atomic Energy Agency Radiation Protection in Digital Radiology Optimisation in CR & DR L03

2 IAEA 2 Educational Objectives Provide rationale for optimisation in Computed Radiography (CR) and Digital Radiography (DR) Describe components of optimisation and specific methods to detect, correct, and avert errors in CR and DR Identify standards and references for optimisation in CR and DR Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

3 IAEA 3 Optimisation includes … All activities that ensure consistent, maximum performance from physician and imaging facility 1 “A distinct series of technical procedures which ensure the production of a satisfactory product” Four steps … Acceptance Testing (AT) Establishment of baseline performance Diagnosis of changes in performance Verification of correction of deterioration 1 National Council on Radiation Protection and Measurements. (1988) Quality Assurance for Diagnostic Imaging, NCRP Report No. 99, Bethesda, MD; Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

4 IAEA 4 Optimisation includes both personnel and equipment Identifying aspects of facility operation that require decisions or actions Establishing policies with respect to these Encouraging compliance through education and recognition Analyzing records at regular intervals Dose optimisation Image quality optimisation Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

5 IAEA 5 “What’s my motivation?” Regulatory Compliance International BSS National Regulations Standards of Care Standards established by professional societies Providing the highest quality medical care MANAGING RADIATION DOSE!!! Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

6 IAEA 6 Factors that affect image quality and patient dose FactorContrastResolutionNoisePatient Dose Focal spot sizeX Off-focus radiation x(x)x Beam filtrationxX Voltage waveform (x)xx kVpX(x)X mA(x) SX mAs(x)XX SIDXX Field sizeXX Scatter rejectionXX Wolbarst (1993) Table 19-1 Radiation Protection in Digital Radiology L03 Optimisation in CR and DR X: very important connection x: sometimes significant (x): sometimes noticeable

7 IAEA 7 Quantifiable Consequences of Degraded Performance Loss of Contrast Sensitivity Loss of Sharpness/Spatial Resolution Loss of Dynamic Range Increase in Noise Decrease in System Speed Geometric Distortion artefacts Decrease in diagnostic accuracy Increase in observer time/fatigue Delay of diagnosis Increase in patient radiation dose Decrease in efficiency of imaging operation Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

8 IAEA 8 Inherent limitations of human operators Every process that depends on a human is a source of random errors Every process that automation performs independently is source of systematic errors. Human errors increase exponentially with the complexity of the system and operator interface. It is not a question of whether, but when errors will occur. ? Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

9 IAEA 9 Someone has to reconcile the checking account The technologist/supervisor must accept responsibility for appropriate delivery of all images to the physician. Processes must be in place to verify that all exams performed and all images acquired reach their intended destinations (note: an image count of two does not necessarily mean both the PA and LAT views!). Processes must be in place to correct errors when detected. Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

10 IAEA 10 Some traditional components of optimisation QA Committee Policies and Procedures Reject Analysis Radiologist Film Critique Operator QC Activities Service Events Technologist In-service training Medical Physicist QC Activities Incident investigation/troubleshooting Error log maintenance Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

11 IAEA 11 Reject Analysis once considered unnecessary with CR/DR Low repeat rates initially reported with DR DR is tolerant of incorrect exposure factor selection Criteria for improper exposure lacking Most DR systems include QC Workstations Capacity to modify non-diagnostic images before release Bad electronic DR images can disappear without a trace Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

12 IAEA 12 Conventional Reason for Repeated Exam Artefacts Mispositioning Over-collimation Patient motion Double exposure Inadequate inspiration Overexposed - too dark Underexposed - too light Marker missing or wrong Wrong exam Wrong patient Film lost in processor Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

13 IAEA 13 CR/DR Reason for Repeated Exam Artefacts Mispositioning Over-collimation Patient motion Double exposure Inadequate inspiration Overexposed - high exposure index Underexposed - low exposure index Marker missing or wrong Wrong exam Wrong patient Lost image corrupt data, cannot transfer deleted by operator (waste bin) Auto-pilot Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

14 IAEA 14 How does one perform reject analysis? Develop method for capturing rejects Collect data 3% vs. 12%? Analyze data Report results to management and staff Implement training as indicated Share results with vendors Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

15 IAEA 15 How can electronic system accommodate reject analysis? Develop codes for Radiologist exam critique QC Techs append critique code to patient name and modify Accession number, and Exam Description (Procedure) Fields “None” files archived as usual Modified exam routing tables prevent widespread dissemination of rejected images “None” files available for review Some vendors implement reject analysis Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

16 IAEA 16 DR systems must be operated properly to make good images! Select the proper examination Properly associate demographic and exam information to image Properly manipulate the detector Review the image before releasing Know how to recover from errors without repeating examination Follow exposure factor control limits Select appropriate factors for paediatrics and young adults Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

17 IAEA 17 Human operators need to know what is expected of them. Vendor applications training is never sufficient. Local policies and practice must be developed, communicated, documented, reinforced, and enforced. Clinical Competency Criteria are helpful for standardizing and documenting basic proficiency training. Training must be tailored for technologists, radiologists, clinical engineers, and PACS personnel. Radiation protection training of referring physicians should also be considered. CRITICAL ELEMENTS SU OPERATOR LEVEL 1Has knowledge of the following status changes and how to differentiate between them. a. "WARNING" b. "LOCKED" c. "ERROR" 2Demonstrates ability to differentiate between an error "CODE" message and a "Service" message 3Demonstrates the ability to properly identify the cassette and image plate location on the displayed pictogram when a jam occurs. 4Has knowledge that the [RESET] button should never be pressed by personnel other that an AGFA service engineer. 5Has knowledge of the correct extension to call the PACS Trouble call line. SUPERVISOR LEVEL 6Demonstrates ability to clear a plate jam in the Upper Section of the ADC70 by performing the proper sequence of events. a. Makes sure there are no cassettes protruding through the emergency slot. b. Properly raises the top cover. c. Locates and unlocks support rod, and secures top cover into position with support rod. d. Properly removes any jammed cassettes or image plates. Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

18 IAEA 18 So how do you go about establishing optimization? Define hospital processes from scheduling patient to reporting diagnosis (workflow analysis) Define PACS components and processes that support hospital processes (IHE references, system architecture) For each hospital process, identify operational roles and responsibilities (task allocation matrix) Identify reasonable failure scenarios. Identify single points of failure. Minimize by redundancy. (failure modes and effects analysis) Institute performance measures that indicate when processes are working and detect, correct, and document errors. Add to the task allocation matrix. Create, document, test, and train downtime and recovery procedures. Periodically review and publicize the results of measurements and adjust as needed. Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

19 IAEA 19 Reasons for differences between CR and DR optimisation CR cassette-based vs. integrated receptor DR Cleaning Physical defects Erasure Mis-identified patient, view, orientation Need adequate knowledge of radiographic technique Separation between image acquisition and development Time Geographic (PACS) Distinctions are blurring Poorly integrated DR Integrated CR Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

20 IAEA 20 Consider QC procedures to be a series of sieves … Caught by RT before exam Caught by RT after exam Caught by Supervisor Passed on to Radiologist Errors RT – Radiography Technologist Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

21 IAEA 21 Which image is worse? Reported by radiologist Subsequent image, same machine, reported by same radiologist Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

22 IAEA 22 3. Verify exam with physician 5."Arrive" patient in RIS 6. Escort patient to exam room 7. Explain exam to patient 8. Select and ID cassettes 9. Position patient, cassette, x-ray tube 10. Perform exam 11. Scan cassette 14. Review images at QC 15. Repeat necessary? 17. Complete exam in RIS END 4. Schedule exam in RIS 12. Preview images 13. Repeat necessary? 18. Release patient 1. Patient arrives in imaging department Y Y N N START 2. Is exam scheduled? N Y 16. Release images to PACS QC? Process map Flowchart of steps Identify potential QC control points actions to be taken Identify “work-arounds” Example: What if RIS is out-of-service? How to continue operations? Don’t forget actions on restoration of service Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

23 IAEA 23 Step 1. Patient reports for an examination. The technologist verifies: the patient is the person identified in the exam request the anatomy to be examined matches the exam request other information about the patient, such as Pregnancy Restricted motion Allergies Appliances QC accomplished by training or checklist Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

24 IAEA 24 Step 2. Technologist identifies the patient and exam to the imaging system Usually occurs before, but sometimes after the exam is performed Misidentification has consequences incorrect information can cause image unavailability incorrect exam info can affect image development mis-association complicates error detection proliferation of digital images complicates correction Automation of association = imperfect QC! New classes of errors Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

25 IAEA 25 The best image, improperly identified, is useless. Consequences of misidentification: Broken studies Orphans Exceptions Penalty Box Automation of association: RIS interfaces Bar code scanner augmentation DICOM Modality Worklist Management (MWL) unscheduled exams resource re-allocation Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

26 IAEA 26 Step 3. Technologist positions the patient in the radiation field and performs the examination Potential errors mispositioning patient motion incorrect radiographic technique selection poor inspiration improper collimation incorrect alignment of x-ray beam and grid wrong exam performed double exposure QC accomplished at acquisition station? Image processing inadequate to correct Correction requires repeated exam (s) Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

27 IAEA 27 Results: Rejects during one month Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

28 IAEA 28 Step 4. Image receptor captures the radiographic projection Potential errors Inadequate erasure, lag, ghosting Improper compensation for non-uniform gain Incorrect gain adjustment Incorrect exposure factor selection artefacts Interference with the projected beam Receptor defects Interference with converting the captured projection into a digital image Detection possible at acquisition station? Correction may require repeated exam Can be averted by active QC Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

29 IAEA 29 Active QC countermeasures: emphasize avoiding vs. correcting errors Prophylactic erasure at start of shift Periodic checks of non-uniformity corrections Periodic gain re-calibration Technique guide Periodic checks of Automatic Exposure Control (AEC) calibration Periodic cleaning of equipment and environment Thorough Acceptance Testing of new receptors Also incidental to service events and software upgrades Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

30 IAEA 30 Step 5. Image receptor renders the captured projection for viewing Potential errors Incorrect Exposure Field recognition; incorrect determination of values of interest (VOI) Incorrect histogram re-scaling Incorrect gray-scale rendition Incorrect edge restoration Inappropriate noise reduction Incorrect reorientation QC possible at acquisition station? Correction usually possible without repeated exam Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

31 IAEA 31 Functions of the QC workstation: sometimes integrated into acquisition station Modify image processing Imprint demographic overlays Add annotations Apply borders or shadow masks Flip and rotate Increase magnification Conjoin images Scoliosis Full leg Modify sequence of views Verify exposure indicator Select images for archive Delete images Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

32 IAEA 32 Step 6. Acquisition station transfers the image to the archive Potential errors Transmission failure Image deletion from local cache Information omitted from transmitted image Exposure indicator Processing parameters Shutters Annotations Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

33 IAEA 33 Step 7. Digital image is displayed for viewing by a physician Potential errors (hard or soft copy) Incorrect GSDF calibration Inadequate matrix Moire’ (interference) patterns Inadequate spatial resolution Incorrect or missing demographics or annotations Inadequate viewing conditions Errors not filtered by previous QC QC => Radiologist “Film” critique Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

34 IAEA 34 Task Allocation Matrix TaskResponsibilityFrequency Verify Patient ID and exam infoRadiographerEach exam Verify Patient PositioningRadiographerEach view Verify Image Quality – release or repeatLead RadiographerEach image Verify exam in PACSLead RadiographerEach exam Reconcile patient data/image counts in PACSMedical InformaticsIncidental Report substandard imagesRadiologistIncidental Erase cassette-based image receptorsRadiographerStart-of-shift Test image receptor uniformityRadiographerWeekly Clean cassette-based image receptorsRadiographerMonthly Compile and review reject analysis dataLead RadiographerMonthly Verify display calibrationsClinical EngineerQuarterly Review QC indicatorsQA CommitteeQuarterly Verify receptor calibrationsMedical PhysicistSemi-Annual Verify x-ray generator functionsMedical PhysicistAnnual Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

35 IAEA 35 Get the radiologists actively involved. Key element to any successful optimization program. Incidental guidance valuable. Radiologist’s Film Critique more valuable. Codes transcribed into report includes availability and quality items documents causes and frequency of substandard imaging; tracks improvement mechanism for establishing responsibility for quality of service Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

36 IAEA 36 New accommodations for testing in CR Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

37 IAEA 37 Value of automated self-tests Some manufacturers provide automated self-tests Should provide operator with assurance that unit is ready for clinical use Actions should be clearly indicated by faults Should provide longitudinal information on system performance Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

38 IAEA 38 What do you do with the QC data? Because systems are relatively new, manufacturers are uncertain about longitudinal data Lower limit for test is MTF @ 2.5 lp/mm = 17% CsI(Tl) is hygroscopic – columnar structure is degraded Both systems depicted required detector replacement Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

39 IAEA 39 Commitment to optimisation The optimisation effort is integral to how you organize and perform the work. The cost of optimisation is trivial compared to the cost of inefficiency: consider one bad patient outcome. Training for optimisation is professional development for hospital staff. Leverage local resources for optimisation expertise. Biomedical engineering Medical informatics / Information services Medical Physicists Hospital QA personnel Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

40 IAEA 40 Who is responsible for optimisation? (“It takes a village …” ) Physician responsible for clinical service is ultimately responsible Medical Physicist oversees the program Radiographer makes day-to-day measurements, verifies post-repair integrity Service engineer carries out repairs, PM, calibrations Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

41 IAEA 41 Answer True or False Random error is a source of inherent limitation of human operators It is the responsibility of the physician to ensure appropriate delivery of all images to PACS High doses can go undetected with the use of DR or CR systems Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

42 IAEA 42 Answer True or False True. Every process that depends on a human operator is a source of random errors and every process that automation performs independently is source of systematic errors. False. The technologist/supervisor is responsible for appropriate delivery of all images to the PACS True. DR and CR have wide latitude and high doses can go undetected. Optimised exposure parameters should be used in digital systems. Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

43 IAEA 43 References: Comprehensive QC Plan for CR Radiation Protection in Digital Radiology L03 Optimisation in CR and DR


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