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Image Gently – Back to Basics: Ten steps to help manage radiation dose in pediatric digital radiography Copyright 2012 Alliance for Radiation Safety in.

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Presentation on theme: "Image Gently – Back to Basics: Ten steps to help manage radiation dose in pediatric digital radiography Copyright 2012 Alliance for Radiation Safety in."— Presentation transcript:

1 Image Gently – Back to Basics: Ten steps to help manage radiation dose in pediatric digital radiography Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

2 The Alliance for Radiation Safety in Pediatric Imaging The image gently campaign

3 What is Image Gently An education, awareness and advocacy campaign To improve radiation protection for children worldwide Alliance for Radiation Safety in Pediatric Imaging >70 health care organizations/agencies >800,000 radiologists radiology technologists medical physicists worldwide Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

4 The Alliance for Radiation Safety in Pediatric Imaging The Image Gently Alliance is a coalition of health care organizations dedicated to providing safe, high quality pediatric imaging worldwide. The primary objective of the Alliance is to raise awareness in the imaging community of the need to adjust radiation dose when imaging children. The ultimate goal of the Alliance is to change practice. Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

5 Objectives Raise awareness of opportunities to lower radiation dose while maintaining diagnostic image quality when imaging children Address methods to standardize the approach to pediatric digital radiography Highlight challenges related to the technology when used with patients of widely variable body size Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

6 Imaging Statistics Radiography is the most common type of exam in diagnostic imaging 74% of all imaging exams Represents 85% of all ionizing radiation studies in children During a three-year radiography study: 40% children had 1 study 22% had 2 14% had >3 Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

7 Changing of Technology Digital radiography has largely replaced screen-film (SF) radiography throughout the United States Imaging community is responsible for understanding technology changes Exposure creep – increase in technique factors over time Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

8 Exposure Creep Image processing compensates for underexposure and overexposure Radiologists prefer noise-free images Overexposure common 40% of adult digital radiographs overexposed 43% of pediatric digital radiographs overexposed

9 Step 1. Understand the basics of digital radiography Digital radiography encompasses both computed radiography (CR) and direct digital radiography (DR) Computed Radiography (CR) Readout process Separate laser reader from the image receptor Readout availability in seconds Image Receptors Photostimulable-phosphor plate Needle phosphor plate (CsBr) Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

10 Step 1. Understand the basics of digital radiography Direct Digital Radiography (DR) Readout process Thin-film transistor layer bonded with image receptor Readout availability in less than 10 seconds Image Receptors Two types depending on method of converting x- ray to image 1. Direct converts x-rays to electrical charge Selenium most common type of receptor 2. Indirect converts x-rays to light which then produces electrical charge CsI and Gadolinium Oxysulfide most common types Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

11 Step 1. Understand the basics of digital radiography Digital radiography advantages over traditional SF radiography Latitude of exposure ~ 100 times greater Image manipulation (processing) Electronic images can be stored and distributed anywhere Point-of-care image access Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

12 Step 1. Understand the basics of digital radiography Digital radiography performance Characterized by spatial resolution and noise Sharpness/Modulation Transfer Function (MTF) Noise Level/Noise Power Spectrum (NPS) Characteristics determine efficiency of the system in converting x-rays into an image Described as Detective Quantum Efficiency (DQE) Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

13 Step 1. Understand the basics of digital radiography Detective Quantum Efficiency (DQE) Function of spatial frequency Ideal detector has a DQE of 1.0 For lower beam energies used in pediatric radiology, experiments show that DR with CsI can achieve higher DQE than CR and SF radiography The higher the DQE, less radiation exposure is needed to achieve the same image quality Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

14 Step 1. Understand the basics of digital radiography Radiologists, technologists, and medical physicists must leverage the strengths and weaknesses of each of their detectors to optimize exposure factors and reduce doses, especially when imaging children Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

15 Step 2. Understand challenges associated with digital imaging Screen-film radiography provided immediate and direct feedback regarding overexposure or underexposure Overexposed image was too black Underexposed image was too white Optical density was directly coupled to the exposure technique Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

16 Step 2. Understand challenges associated with digital imaging Digital radiography is fundamentally different Optical density feedback is lost Image processing adjusts grayscale images to the correct brightness despite underexposure or overexposure Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

17 Step 2. Understand challenges associated with digital imaging Underexposed digital images Fewer x-rays absorbed by the detector Results in increased quantum mottle The image appears noisy or grainy Increased exposure in digital imaging Reduction in quantum mottle Overexposure may go unnoticed Results in needless overexposure and potential harm to the patient Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

18 Step 2. Understand challenges associated with digital imaging Image acquisition process varies Depends on vendor and equipment type Techniques may be different than SF Requires technologists to adjust techniques Different detectors may require different techniques due to differences in efficiency (DQE) Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

19 Step 2. Understand challenges associated with digital imaging Need for a standard approach Differences in technique amongst digital systems may cause confusion Result in varying levels of image quality Approach must be based on: 1. Feedback provided from exposure indicator 2. Individual image quality analysis Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

20 Step 3. Learn new exposure terminology standards Proprietary Exposure Indicator Terminology Method for estimating exposure to image receptor May be linear or logarithmic Directly or inversely related to plate exposure Hospitals frequently have more than one detector type from more than one vendor Difficult to familiarize with all of the proprietary exposure terminology Causes confusion

21 Step 3. Learn new exposure terminology standards Solution to the exposure terminology problem 2004 ALARA conference in digital radiography AAPM and IEC Developed standardized terminology designed to eliminate proprietary terminology in the installed equipment in the future Medical Imaging and Technology Alliance (MITA) Publically agreed to adopt the IEC standard Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

22 Step 3. Learn new exposure terminology standards IEC standard terms to learn: Target exposure index (EI T ) Exposure index (EI) Deviation index (DI) Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

23 Step 3. Learn new exposure terminology standards Target exposure index (EI T ) Ideal exposure at the image receptor Can be set by: Manufacturer User facility Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

24 Step 3. Learn new exposure terminology standards Exposure index (EI) Image receptor radiation exposure Measured in relevant region Direct, linear with respect to mAs Doubling the mAs will double the EI Value depends on: Body part selected and body part thickness, kVp and any added filtration Type of detector EI it is NOT an individual patient dose metric Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

25 Step 3. Learn new exposure terminology standards Deviation index (DI) Indicates how much the EI deviates from the EI T The DI is defined as: DI= 10×log 10 (EI/EI T ) Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

26 Step 3. Learn new exposure terminology standards The meaning of DI An ideal situation where EI is equal to the EI T, the DI is zero (DI =0) If the exposure index is higher than the EI T (overexposed), the DI is positive, and if it is lower than the EI T (underexposed), the DI is negative A DI of -1 is 20% below the appropriate exposure, while +1 is a 26% overexposure A DI of ±3 indicates halving or doubling of the exposure relative to the EI T Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

27 Deviation Index Percentage (%) Step 3. Learn new exposure terminology standards Underexposure Overexposure Ideal { {

28 Step 3. Learn new exposure terminology standards The importance of DI Immediate feedback Indicates the adequacy of the exposure Goal Few studies DI > +3 or <-3 Standardized terminology will reduce confusion from proprietary terminology Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

29 Step 3. Learn new exposure terminology standards Deviation Index is only one factor in image quality: To assure image quality, checks should be made for : positioning, patient motion, collimation, and appropriate use of grids Image noise levels for underexposure and saturation with overexposure should also be monitored The Image Gently Campaign encourages radiologists and technologists to go “Back to BASICS” with digital radiography Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

30 Step 4. Establish technique charts using a team approach Automatic exposure control (AEC) sensors, commonly used in adults, is often problematic in children For smaller children the imaged area of anatomy may be smaller than the single central sensor Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved Goske, M. J., E. Charkot, et al.(2011). Pediatr Radiol 41(5): Reused with permission.

31 Step 4. Establish technique charts using a team approach Manual techniques may be most appropriate for small children Team approach: Physician, technologist, medical physicist, vendor Start with limited exams: Chest, abdomen, small parts May need detector-specific technique charts Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

32 Step 4. Establish technique charts using a team approach Image processing is different for pediatric patients and adults Review and adjust anatomically programmed radiography techniques Appropriate values must be included for both AEC and manual technique selection Pre-programmed adult techniques used for pediatric imaging may not result in the appropriate image quality or patient dose Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

33 Step 5. Measure body part thickness X-ray absorption/transmission depends on the composition of the body part being imaged Body part thickness is the most important technique determinant One cannot reliably use patient age as a guide for techniques The largest 3-year old’s abdomen thickness is the same as the smallest 18-year old Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

34 Step 5. Measure body part thickness Revert “Back to Basics” The goal is for reproducible, consistent images for children with a body part of the same size Use calipers to measuring patients Ensures standardized technique is selected One then selects kV, filtration, and mAs for that specific study to “child size” the examination Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

35 Step 6. Use grids only when body part thickness is > 12 cm Anti-scatter grids remove scatter from the image Grids improve the subject contrast Scatter degrades image when the body part is >12 cm of water-equivalent thickness Air containing structures greater than 12 cm thickness can be imaged without a grid Example: chest radiographs Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

36 Step 6. Use grids only when body part thickness is > 12 cm Grids may double or triple the exposure factors necessary to obtain an adequate image Removing the grid when it is not necessary greatly reduces patient exposure Guidelines for digital radiography have stated that grids should be used sparingly in pediatrics Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

37 Step 7. Collimate prior to the exposure It is unacceptable to open the collimators, then manipulate and electronically crop the image after the exposure ASRT survey: 50% of the technologists use electronic cropping of the image after the exposure 75% of the time Radiologists may not be aware that cropping is occurring, yet radiologists are responsible for the image before cropping occurs Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

38 Step 7. Collimate prior to the exposure The cropped portions of the body are exposed to unnecessary radiation It is better to properly immobilize patient and collimate appropriately before the exposure Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

39 Step 7. Collimate prior to the exposure Benefits of collimation: Reduces the area exposed and lowers the dose-area product (DAP) Reduces scatter radiation, which will improve image quality Improves the accuracy of the image processing Provides more accurate exposure indicator Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

40 Step 8. Display technique factors for each image Require that the kVp, mAs, EI and, especially, DI are present on the displayed image Ideally DAP meter results and image processing program should also be displayed These displayed values provide important feedback to the radiologist and technologists Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

41 Image Courtesy of Ann & Robert H. Lurie Children’s Hospital of Chicago

42 Step 9. Accept noise level appropriate to clinical question Radiologists prefer images that have little noise However, noise intolerance can lead to exposure creep Must work to understand the relationship between exposure indicators and the visual appearance of noise in an image Routinely monitoring the appropriateness of the technique based on the level of image noise along with the DI, exposure creep be avoided Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

43 Step 10. Develop a quality assurance program It is critical that radiologists, radiographers, and physicists develop standards for their institution, utilizing a team approach to assure diagnostic image quality at a properly managed dose for pediatric patients. Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

44 Step 10. Develop a quality assurance program Importance of QA program 40% of the digital radiographs obtained from one adult center are overexposed 43% of radiographs in a pediatric center were reported as overexposed By recording and monitoring exposure indicators, an individual hospital can control and reverse exposure creep Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

45 Step 10. Develop a quality assurance program Analyzing the percentage of images that fall within and outside of an acceptable range can be used to educate technologists and decrease the variation while improving image quality goals of the department Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

46 Step 10. Develop a quality assurance program Utilizing digital imaging resources DICOM headers contain information that can be exported and used in QA programs IHE REM profiles make additional information available Common IEC standard terminology can also be used Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

47 Step 10. Develop a quality assurance program Likely in the future: National diagnostic reference levels to compare digital radiographic techniques ACR Dose Index Registry program for Pediatric Digital Radiography registry has been approved Diagnostic reference levels likely will be developed from this data based on detector type and body part Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

48 Conclusion Knowledge in digital radiography will provide radiologists and technologists the basis for standardizing their approach to imaging pediatric patients Education will reduce the tendency for exposure creep The “Back to Basics” Image Gently® campaign is a reminder to standardize procedures to improve image quality while properly managing radiation dose during pediatric imaging Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

49 References 1.Ionizing Radiation Exposure of the Population of the United States. Bethesda, MD: National Council on Radiation Protection and Measurements, Dorfman AL, Fazel R, Einstein AJ, et al. Use of medical imaging procedures with ionizing radiation in children: a population-based study. Archives of pediatrics & adolescent medicine 2011;165: Willis CE, Slovis TL. The ALARA concept in pediatric CR and DR: dose reduction in pediatric radiographic exams – A white paper conference Executive Summary. Pediatric Radiology 2004;34:S162-S164 4.Korner M, Weber CH, Wirth S, Pfeifer KJ, Reiser MF, Treitl M. Advances in digital radiography: physical principles and system overview. Radiographics 2007;27: Cohen M, Corea D, Wanner M, et al. Evaluation of a New Phosphor Plate Technology for Neonatal Portable Chest Radiographs. Academic Radiology 2011;18: Willis C. Computed radiography: a higher dose? Pediatric Radiology 2002;32: Hillman BJ, Fajardo LL. Clinical assessment of phosphor-plate computed radiography: equipment, strategy, and methods. J Dig Imag 1989;2: Medical electrical equipment – Characteristics of digital X-ray imaging devices – Part 1: Determination of the detective quantum efficiency International Electrotechnical Commission (IEC), international standard IEC , Geneva, Switzerland Monnin P, Gutierrez D, Bulling S, Lepori D, Valley J-F, Verdun FR. Performance comparison of an active matrix flat panel imager, computed radiography system, and a screen-film system at four standard radiation qualities. Medical Physics 2005;32: Bertolini M, Nitrosi A, Rivetti S, et al. A comparison of digital radiography systems in terms of effective detective quantum efficiency. Medical Physics 2012;39: Seibert JA, Morin RL. The standardized exposure index for digital radiography: an opportunity for optimization of radiation dose to the pediatric population. Pediatr Radiol 2011;41: Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

50 References 12.Medical electrical equipment - Exposure index of digital X-ray imaging systems - Part 1: Definitions and requirements for general radiography International Electrotechnical Commission (IEC), international standard IEC , Geneva, Switzerland Shepard SJ, Wang J, Flynn M, et al. An exposure indicator for digital radiography: AAPM Task Group 116 (Executive Summary). Medical Physics 2009;36: Don S, Goske MJ, John S, Whiting B, Willis CE. Image Gently pediatric digital radiography summit: executive summary. Pediatr Radiol 2011;41: Vastagh S. Statement by MITA on behalf of the MITA CR-DR group of the X-ray section. Pediatr Radiol 2011;41: Don S, Whiting BR, Rutz LJ, Apgar B. New Exposure Indicators for Digital Radiography Simplified for Radiologists and Technologists Am J Roentgenol 2012 (accepted for publication) 17.Goske MJ, Charkot E, Herrmann T, et al. Image Gently: challenges for radiologic technologists when performing digital radiography in children. Pediatr Radiol 2011;41: Don S, Whiting BR, Ellinwood JS, Foos DH, Kronemer KA, Kraus RA. Neonatal chest computed radiography: image processing and optimal image display. AJR American journal of roentgenology 2007;188: Kleinman PL, Strauss KJ, Zurakowski D, Buckley KS, Taylor GA. Patient Size Measured on CT Images as a Function of Age at a Tertiary Care Children's Hospital. American Journal of Roentgenology 2010;194: Kalender W. Monte Carlo calculations of x-ray scatter data for diagnostic radiology. Physics in medicine and biology 1981;26: Cartlon RR, Adler AM. The Grid. In: Principles of radiographic imaging : an art and a science Clifton Park, NY: Delmar Cengage Learning, ACR-SPR Practice Guideline for General Radiography. American College of Radiology. Reston, VA, 2008 Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

51 References 23.ACR–AAPM–SIIM Practice Guidelime for Digital Radiography. American College of Radiology. Reston, VA, Morrison G, John SD, Goske MJ, et al. Pediatric digital radiography education for radiologic technologists: current state. Pediatr Radiol 2011;41: Curry T, Dowdey J, Murry R. In: Christensen's Physics of Diagnostic Radiology. Philadelphia: Lea & Febiger, 1990: Don S. Radiosensitivity of children: potential for overexposure in CR and DR and magnitude of doses in ordinary radiographic examinations. Pediatric Radiology 2004;34:S167-S Don S, Hildebolt CF, Sharp TL, et al. Computed radiography versus screen-film radiography: detection of pulmonary edema in a rabbit model that simulates neonatal pulmonary infiltrates. Radiology 1999;213: Roehrig H, Krupinski EA, Hulett R. Reduction of patient exposure in pediatric radiology. Academic Radiology 1997;4: Gibson DJ, Davidson RA. Exposure Creep in Computed Radiography: A Longitudinal Study. Academic Radiology 2012;19: O'Donnell K. Radiation exposure monitoring: a new IHE profile. Pediatr Radiol 2011;41: Cohen MD, Cooper ML, Piersall K, Apgar BK. Quality assurance: using the exposure index and the deviation index to monitor radiation exposure for portable chest radiographs in neonates. Pediatr Radiol 2011;41: Cohen MD, Markowitz R, Hill J, Huda W, Babyn P, Apgar B. Quality assurance: a comparison study of radiographic exposure for neonatal chest radiographs at 4 academic hospitals. Pediatr Radiol 2011 Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved

52 imagegently.org

53 Thanks to Digital Radiography Committee Members: Steven Don, M.D. Robert MacDougall, MSc Keith Strauss, MSc, FAAPM, FACR Quentin Moore, MPH, R.T.(R)(T)(QM) Marilyn J. Goske, M.D., FAAP Mervyn Cohen, M.D., MBChB Tracy Herrmann, MEd, R.T.(R) Susan D. John, M.D Lauren Noble, Ed.D., R.T.(R) Greg Morrison, MA, R.T.(R), CNMT, CAE Lois Lehman, R.T.(R)(CT) Coreen Bell Ceela McElveny Loren Stacks Shawn Farley Copyright 2012 Alliance for Radiation Safety in Pediatric Imaging All Rights Reserved


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