2/17/2020 1 Gonadal Shielding Changes Melissa C. Martin, M.S., FAAPM, FACR AAPM Past President - 2017 [email protected]Signal Hill, CA 90755 No Conflicts of Interest to Declare Introduction: Gonadal Shielding • Is gonadal shielding really a best practice? • Effectiveness of gonadal shielding • Impact of Automatic Exposure Control • Radiosensitivity • Psychological benefit • Next steps • Atomic bomb survivors (70+ years of data) • Animal experiments • Radiation workers • Individuals who received medical radiation as children • Epidemiology • Cellular studies [email protected]@aapmCARES Radiation Risks – Available Data 1 2 3
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• Radiation doses from diagnostic x-ray examinations are ~20 - 25 times less radiation today: 1951 vs 2019
• Adult KUB: 1951 ~ 11 – 12 mGy1
2019 ~ 0.5 mGy air Kerma
• Newborn KUB: 1951 ~ 1.4 mGy2
2019 ~ 0.07 mGy air Kerma
1Handloser JS, Love RA. Radiation Doses from Diagnostic Studies. Radiology 57: 1951, pp. 252-254.2Billings MS, Norman A, Greenfield MA. Gonad Dose During Routine Roentgenography 69: 1957, pp. 37-41.
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Historical Perspective
• Gonadal shielding reduces gonadal doses to less than 10% of original dose!1 – 3
• Best information in mid 1950 was in error.
1Stanford RW, Vance J. The quantity of radiation received by the reproductive organs of patients during routine diagnostic x-ray examinations. Br J Radiol 1955 May;28(329):266-273.2Ardran GM, Crooks HE. Gonad radiation dose from diagnostic procedures. Br J Radiol 1957 Jun; 30(354):295-7.3Feldman A, Babcock GC, Lanier RR, Morkovin D. Gonadal exposure dose from diagnostic x-ray procedures. Radiology 71; 1958; 197-207.
Historical/Current Perspective
• Failure to perform gonadal shielding resulted/s in severe disciplinary action against technologists.
• Very real today!
Current Perspective
• Current CA State Regulation (Title 17):
• 30308(b) (4)
Gonadal shielding of not less than 0.5 millimeter Lead equivalent shall be used for patients who have not passed the reproductive age during radiologic procedures in which the gonads are in the direct beam, except for cases in which this would interfere with the diagnostic procedure.
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1953 1976 2018
Drosophila: This image is licensed under public domain. http://www.freestockphotos.biz/stockphoto/15433FDA: http://cdn.loc.gov/service/ll/fedreg/fr040/fr040180/fr040180.pdf
• Gonad tissue weighting factor reduced: 0.2 to 0.08
• Colon, stomach, liver, and bone marrow = 0.12.
• Why are we shielding a less sensitive organ at the expense of more sensitive organs?
Reconsidering the Value of Gonadal Shielding
• Psychological benefit?
• Initially, Yes.
• Psychological comfort is provided despite a negligible radiationprotection benefit.
• Long term, No.
• Education needed for care givers to help patients and/or their parents work through transition of change.
• Secondary shielding provides a false sense of security.
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Reconsidering the Value of Gonadal Shielding
“Changing a ‘tradition’ is not easy. . .Our patients expect, as they should, the best care we can provide. Just as we need to educate ourselves about the true merits of gonadal shielding, we need to help our patients understand that their imaging experience should evolve to allow us to continue to deliver the best care possible.”1
1Strauss KJ, Gingold EL, Frush DP. Reconsidering the value of gonadal shielding during abdominal/pelvic radiography. J Am Coll Radiol. 2017 Dec; 14(12) pp 1635-6.
Reconsidering the Value of Gonadal Shielding
NCRP Statement from Scientific Committee (SC-4.11):
• Gonadal Shielding During Abdominal and Pelvic Radiology• Purpose: To provide recommendations and guidance,
through an authoritative statement, that addresses newer information and current understanding on possible health effects of gonadal exposures of both adult and pediatric patients.
NCRP Statement from Scientific Committee (SC-411):
• Gonadal Shielding During Abdominal and Pelvic Radiology• Scientific Committee Members• Donald Frush, M.D Donald Miller, M.D.• Keith Strauss, M.S. Eric Gingold, M.S.• Louis Wagner, Ph.D. Sarah McKenney, Ph.D.• Rebecca Marsh, Ph.D. Mary Ann Spohrer, B.S.• Angela Shogren, M.D John Winston, B.S.
AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding 4/2/2019 Professional Policy 32-A
Rationale for policy:
Gonadal and fetal shielding in X-ray imaging has for decades been considered consistent with the ALARA principle and therefore good practice.
Given advances in technology and current evidence of radiation exposure risks, the AAPM has reconsidered the effectiveness of gonadal and fetal shielding.
Gonadal and Fetal Shielding provide Negligible, or No, Benefit to Patients’ Health
1) Radiation doses used in diagnostic imaging are not associated with measurable harm to the gonads or fetus. ICRP Report 103 (2007) states “no human studies provide direct evidence of a radiation -associated excess of heritable disease.”
ACOG with ACR endorsement states that “with few exceptions, radiation exposure through radiography, computed tomography scan, or nuclear medicine imaging techniques is at a dose much lower than the exposure associated with fetal harm.”
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Gonadal and Fetal Shielding provide Negligible, or No, Benefit to Patients’ Health
2) Patient shielding is ineffective in reducing internal scatter.
In medical x-ray imaging, the main source of radiation dose to internal organs that are outside the imaging field of view is x-rays that scatter inside the body. However, surface shielding covering these organs has no impact on this scatter.
Use of Gonadal and Fetal Shielding can Negatively Affect the Efficacy of the Exam
1) Shielding can obscure anatomy, resulting in a repeated exam or compromised diagnostic information. Shielding placed inside the imaging field of view, or shielding that is moved into the imaging field of view, can obscure important anatomy or pathology, or introduce artifacts.
If the procedure is not repeated, the interpreting physician may lack important diagnostic information. If it is repeated, there will be a substantial increase in dose.
Use of Gonadal and Fetal Shielding can Negatively Affect the Efficacy of the Exam
2) Shielding can negatively affect automatic exposure control (AEC) and image quality.
All modern X-ray imaging systems use AEC and the presence of shielding in the imaging field of view can drastically increase X-ray output, increasing patient radiation dose and degrading image quality.
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AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding 4/2/2019 Professional Policy 32-A
• Patient gonadal and fetal shielding during X-ray based diagnostic imaging should be discontinued as routine practice.
• Patient shielding may jeopardize the benefits of undergoing radiological imaging.
• Use of these shields during X-ray based diagnostic imagingmay obscure anatomic information or interfere with the automatic exposure control of the imaging system.
AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding 4/2/2019 Professional Policy 32-A
• These effects can compromise the diagnostic efficacy of the exam, or actually result in an increase in the patient’s radiation dose.
• Because of these risks and the minimal to nonexistant benefit associated with fetal and gonadal shielding, AAPMrecommends that the use of such shielding should be discontinued.
AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding 4/2/2019 Professional Policy 32-A
• For patients or guardians experiencing fear and anxiety about radiation exposure, the use of gonadal or fetal shielding may calm and comfort the patient enough to improve the exam outcome.
• This may be considered when developing shielding policies and procedures. However, blanket statements requiring the use of such shielding are not supported by current evidence.
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AAPM Position Statement on the Use of Patient Gonadal and Fetal Shielding 4/2/2019 Professional Policy 32-A
• Additionally, the AAPM recommends that radiologic technologist educational programs (including patient outreach efforts) provide information about the limited utility and potential drawbacks of gonadal and fetal shielding.