Radiation Protection in Digital Radiology

1. Radiation Protection in Digital Radiology Optimisation in CR & DR L03

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. Optimisation includes … • All activities that ensure consistent, maximum performance from physician and imaging facility1 • “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 1National 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. 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. “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. Factors that affect image quality and patient dose X: very important connection x: sometimes significant (x): sometimes noticeable Wolbarst (1993) Table 19-1 Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

7. 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 Quantifiable Consequences of Degraded Performance Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

8. Inherent limitations of human operators • Every process that depends on a human is a source of randomerrors • 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. 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. 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. 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. 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 Conventional Reason for Repeated Exam Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

13. 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 CR/DR Reason for Repeated Exam Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

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 trainingas indicated • Share results with vendors Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

15. 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 How can electronic system accommodate reject analysis? Some vendors implement reject analysis Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

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. 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. Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

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

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. START 1. Patient arrives in imaging department 2. Is exam scheduled? N 3. Verify exam with physician Y 5."Arrive" patient in RIS 4. Schedule exam in RIS 6. Escort patient to exam room END 7. Explain exam to patient QC? 18. Release patient 8. Select and ID cassettes QC? 17. Complete exam in RIS 9. Position patient, cassette, x-ray tube QC? 16. Release images to PACS 10. Perform exam QC? QC? N 11. Scan cassette QC? 15. Repeat necessary? 12. Preview images Y QC? QC? 13. Repeat necessary? 14. Review images at QC Y N 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. 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. 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. 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 The best image, improperly identified, is useless. Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

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

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. 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. 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. 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. 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. 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. Task Allocation Matrix Radiation Protection in Digital Radiology L03 Optimisation in CR and DR

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

37. Value of automated self-tests • Some manufacturers provide automated self-tests • Should provide operatorwith 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. 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. 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. 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. 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. 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. References: Comprehensive QC Plan for CR Radiation Protection in Digital Radiology L03 Optimisation in CR and DR