collecting data to facilitate change

2/17/2020

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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

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Large amounts are bad for you

What We DON’T KnowWhat We Know

• Cancer

• Cataracts

• Skin effects

• Genetic effects (in some species)

• Fetal malformations


Radiation Risks

• Effects at low doses (< 100

mSv)

• Effects of low dose rates


Radiation & Cancer Risk Image Credit: NIH, Dr. Cecil Fox

Increased Cancer Risk?

Evidence for increased cancer risk at doses below 100 mSv…

“not statistically different from zero”

“inconclusive”

“lacks statistical power to directly reveal cancer risks”


Radiation & Cancer Risk

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Teratogenic effects do not occur at doses used in diagnostic imaging.

Risks of developing cancer is controversial and unresolved.


Radiation & in utero exposure risks

LNT

1. Established in 1950s

• unable to establish whether a threshold exists

• linear model is simple

• ALARA – for radiation workers

2. Ignores repair mechanisms

• “priming dose”

• fractionation in radiotherapy

3. Many data contradict LNT


Linear No-Threshold

Historical Perspective

• 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

Food and Drug Administration [21 CFR Part 1000]


Why do we shield patients?

2019

X

New Paradigm

AJR January 2019December 2017 pp 1635-6

JACR 212 April 2019

Are Accurately Placed Shields Effective?

• Male

• Flat lead shield reduced dose to the region of the testes of an adult anthropomorphic phantom by 36%.1

• Reasonable measurement of performance of flat shield.

• Poorer performance than claims from the 1950s.

1Fauber TL. Gonadal shielding in radiography: a best practice? Radiol Tech 88(2) Nov/Dec 2016, 127 – 35.

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• Simplistic model for males

• 1/32” or 1/16” (0.58 mm) of Lead:

• 90% or more of primary x-rays attenuated

• Location of Testes

• Centered bilaterally and close together

• Near surface close to shield

• Testes located within protected region below the shield

10%


• Realistic model

• 1/32” or 1/16” of Lead:

• 90% or more of primary attenuated

• Scatter Radiation

• Scatter/Primary Ratio = 7

• 10 or more scattered x-rays irradiate testes for every stopped primary x-ray.

• Some scatter still reach testes and delivers 64% of the original dose.

• Contact shield improves its performance64%

Effectiveness of Gonadal Contact Shields

• Female

• 0 - 20% reduction

• Scatter x-rays reach gonads and deliver 80 – 90% of the

original dose.

• Varied location of ovaries more

than 50% of the time places

ovary outside region of primary

shielding1Bardo DME, Black M, Schenk K. Location of the ovaries

in girls from newborn to 18 years of age: reconsidering

Ovarian shielding. Pediatric Radiology (2009)39:253-59

Typical1

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Effectiveness of Gonadal Contact Shields

• Female - Suggested Improvements in Shielding Locations

Regional Protection

1Bardo DME, Black M, Schenk K. Location of the ovaries

in girls from newborn to 18 years of age: reconsidering

Ovarian shielding. Pediatric Radiology (2009)39:253-59

Complete Protection1


• Realistic model for females

• 1/32” or 1/16” of Lead:

• 90% or more of primary attenuated

• Scatter Radiation

• Shielding may provide < 10% reduction

• Ovaries at a depth below the surface

• Ovaries are typically not centrally located: exposed by primary x-rays

• Scatter/Primary Ratio = 7 90%

Impact of Automatic Exposure Control

• AEC terminates exposure when target dose received by AEC sensor

• Gonadal shield shadowing sensor elevates patient dose

• Increase dependent on degree of shadowing

• DAP increased 63% and 147% in 5 yr old and adult anthropomorphic phantoms1

• Colon and stomach organ dose increased21 – 51% and 17 – 100% in 5 yr old and adult1

1Kaplan SL, Magill D, Felice MA, Xiao R, Ali S, Zhu X. Female gonadal shielding withautomatic exposure control increases radiation risks. Pediatric Radiology (2018) 48:227-34

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Fetal and Gonadal Shielding: TL;DR

obscured anatomy

CONS (Risks)

makes us feel better

PROS (Benefits)

negative affect on AEC

degraded image quality

Reconsidering the Value of Gonadal Shielding

• Radiosensitivity of organs

• ICRP Report 103:

• 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?


• 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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“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.


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.

• Are changes to existing regulations needed?


Effects of Patient Shielding

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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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• 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.


• 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.


• 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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• 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.


CARES –Communicating Advances in Radiation Education for Shielding

Professional Organizations in Support of the AAPM Position Statement

• American College of Radiology (ACR)

• Australasian College of Physical Scientists & Engineers in Medicine (ACPSEM)

• Canadian Organization of Medical Physicists (COMP)

• Health Physics Society (HPS)

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https://www.acr.org/Advocacy-and-Economics/Advocacy-News/Advocacy-News-Issues/In-the-June-8-2019-Issue/ACR-Endorses-AAPM-Position-on-Patient-Gonadal-and-Fetal-Shielding

https://www.acpsem.org.au/whatacpsemdoes/standards-position-papers

https://www.comp-ocpm.ca/english/news/comp-endorses-aapm-position-statement-on-the-use-of-patient-gonadal-and-fetal-shielding.htm

http://hps.org/newsandevents/societynews.html#1527

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“If there was one thing I could ask of these physicists is that they include scientific

data to back up these statements.”

The data exist.


Summary

Clinical practice should be based on current scientific knowledge.

Gonadal and fetal shielding are not ALARA.

“If there was one thing I could ask of these physicists is that they include scientific

data to back up these statements.”

The data exist.


Summary

Clinical practice should be based on current scientific knowledge.

Gonadal and fetal shielding are not ALARA.

“My grandmother told me that every person she knew in

radiology prematurely aged.”

We need to understand what the risks are

…and what the risks are [email protected] @aapmCARESRebecca Marsh, Ph.D.

Summary

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“Shield the patient because of the perception they have about radiation.”

“There are lots of ‘safety measures’ in place that aren’t exactly helpful so I will continue to shield my patients – whether or not it’s helpful – the

public views it as concern for their safety.”

Misinformation is poor patient [email protected] @aapmCARESRebecca Marsh, Ph.D.

Summary

PatientUs

[email protected] @aapmCARESRebecca Marsh, Ph.D.

Summary

The Cycle of Radiophobia

Consistency is important.

[email protected] @aapmCARESRebecca Marsh, Ph.D.

Summary

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Thank you

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collecting data to facilitate change

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