Patient Gonadal and Fetal Shielding in Diagnostic Imaging

Huntington-Hill Imaging Centers have adopted a policy to discontinue routine use of patient fetal and gonadal shielding. This policy will be implemented into practice on January 1, 2022.

Our decision is based on an April 2019 position statement released by the American Association of Physicists in Medicine (AAPM) outlining data driven reasons for discontinuing its use. The AAPM position statement has since been endorsed by the American College of Radiology (ACR), The Radiological Society of North American (RSNA), the Image Gently Alliance, and other national and international stakeholders in medical imaging.

Therefore, in keeping with Huntington Hill Imaging Centers’ goal to provide patients with the best and most appropriate imaging exam with as little radiation as possible, and to reduce the risk that use of gonadal and/or fetal shielding during diagnostic imaging procedures could interfere with the diagnostic imaging obtained during the procedure, it is the policy of The Hill Medical Corporation that proactive placement of lead shields on patients will be discontinued. An exception to this policy may only be made if the patient has requested shielding and the radiologist and/or radiologic technologist believes its use will calm and comfort the anxiety of a patient or patient’s guardian enough to improve the exam outcome.

FREQUENTLY ASKED QUESTIONS

Please review these Frequently Asked Questions developed by the AAPM CARES Committee which includes suggested wording that can be used when discussing patient shielding with patients and parents/caregivers.

If you have additional questions about our policy, please contact your Huntington-Hill Imaging Center Physician Relations Specialist (insert contact # here) – or refer to the provided resource and reference lists following the FAQs.

Gonadal shielding was introduced into clinical practice over 70 years ago, when it was believed that exposing the gonads to radiation could damage reproductive cells such as sperm-producing cells and eggs, causing damage to patients’ future offspring.⁸ However, these genetic effects have not been observed in humans, even 3 to 4 generations after the atomic bombings in WWII.⁹ International radiation protection organizations have lowered the risk weighting to the gonads in every successive revision of their tissue risk weighting factors since such factors were introduced in 1977.^10,11

The amount of radiation required to cause infertility is more than 100 times the dose from a medical imaging exam.¹¹ For example, the gonadal dose to an X-ray of the pelvis is less than 0.8 mGy for a teenage boy and less than 0.3 mGy for a teenage girl. Gonadal doses for newborns receiving medical imaging is about 90% lower than this.¹² In comparison, male fertility is not affected below an acute dose of 150 mGy. Permanent sterility does not occur in males below 3500 mGy. Female fertility is not affected below 2500 mGy.¹¹

Any intended decrease in radiation exposure from shielding is negligible compared to the dose from radiation that is scattered within the patient’s body. Shields do little or nothing to benefit the patient.^13-17 As with other areas of medicine, the use of patient shielding should be evaluated from a risk-benefit perspective. For example, any time a shield is used, there is a risk that it will cover and obscure anatomy that is important for an accurate diagnosis.^12,18-30 Since shielding can introduce these risks and provides little or no benefit to the patient, we should discontinue using shields as part of routine practice.

Advances in medical imaging technology, such as better detectors, have greatly reduced the amount of radiation required to create a quality image. However, some of the features of modern imaging equipment (such as automatic exposure control) do not perform as intended when lead shielding is in the path of the beam.³¹ As the medical imaging community continues to deepen its understanding about how radiation affects the body, we are recognizing that the risk for the majority of imaging exams is either too small to be determined or may even be zero. These advances have made patient shielding a practice that introduces more risk than benefit.

Fetal and gonadal shielding should not be used by default, regardless of the patient’s age, sex, or pregnancy status. While shielding should not be used routinely, in very limited circumstances, it may be in the best interest of an extremely anxious patient to use shielding. (Please see FAQ 6 for more information.)

Clinical practice should be based on the best and most recent scientific evidence. Although patients expect to be shielded because it has been common practice for many decades, we should explain to the patient the benefits from shielding are negligible and thus there is no value to continuing this practice. Further, there is a small risk of compromising the exam if the shield enters the imaging field.

There are situations, however, that may require special consideration. For example, if a pregnant patient with a suspected pulmonary embolism refuses to have imaging done without shielding, then the benefit of getting a timely diagnosis outweighs the risk posed by using shielding. Similarly, for the parent of a critically ill pediatric patient, the psychological benefit to anxious parents or caregivers may exceed the risk posed by shielding.

In most situations, it is appropriate for the technologist and/or physician to explain why shielding is not recommended. If the patient or parent continues to insist that shielding be used, shields may be used at the discretion of the technologist, provided that careful attention is given to ensuring that image quality is not compromised and overall dose is not increased. While we propose some general rules for stopping the use of gonadal or fetal shielding, it is important to recognize that there will be situations that require professional judgement based on the individual patient and circumstances.

The American College of Obstetricians and Gynecologists (ACOG) has a guideline that states: “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.”³²This is true even for a CT scan of the abdomen and pelvis. If the fetus is outside of the imaging field of view, the dose to the fetus is below 1 mGy33, which is about the same as the dose a fetus gets from background radiation during gestation. This is the case for a CT scan of the mother’s chest.

Healthy cells have repair mechanisms to help protect them against small doses of radiation.³⁴ We take advantage of these repair mechanisms in radiation therapy, where treatments are set up so that there are multiple treatment sessions. For example, radiation therapy for breast cancer may consist of 20 sessions with 2000 mGy delivered during each session, rather than a single session that delivered 40,000 mGy. This is done because delivering the dose in smaller amounts over a longer period of time, instead of all at once, allows more healthy tissue to recover, while killing cancer cells. Thus, there is evidence that the risk from multiple exams is not cumulative.

Often, a faint signal can be seen outside of the collimated field of view. This is from radiation that exposes anatomy within the collimated field of view and is then scattered within the patient, before reaching parts of the detector that are outside of the field of view. It is important to note that the dose to tissues outside of the collimated field of view is very small – hundreds to thousands of times smaller than the dose to anatomy within the field of view. We can see these regions on images only because modern X-ray detectors are very sensitive to small amounts of radiation. This very small amount of radiation outside the field of view is not justification for shielding patients.

Absolutely. If you are working in an area with potential exposure to radiation (such as in an imaging exam room) occupational safety standards and regulations require that radiation workers take appropriate action to limit their occupational exposures. These actions include minimizing the time you are exposed to a radiation source, maximizing the distance between you and the radiation source, and placing shielding between yourself and the radiation source. The shielding can be the leaded window or wall of the control area or personal protective devices such as leaded aprons. These universally accepted methods to control occupational radiation exposures are not impacted in any way by recommendations to discontinue the use of shielding on patients.