Radiation and the Pregnant Nurse

In this case, the pregnant worker is a nurse. She had recently come to Lenox Hill Hospital from Indianapolis to gain additional experience as an angioplasty assistant. Her preference is to continue doing this for as long as possible. An angioplasty assistant is required to be at table-side during the entire fluoroscopic procedure. Thus an estimate of fetal exposure and an understanding of the associated risks are paramount. Initially, the nurse informed the lab manager that she was pregnant. This notification is actually a regulatory requirement. From an administrative standpoint, an individual is pregnant only when a ‘declaration of pregnancy’ form is signed. According to the radiation protection regulations, a woman is not pregnant unless the form is signed. Completion of this form triggers a consultation with radiation safety, a decision regarding work assignments during pregnancy, and the assignment of a fetal dose monitor if required. The regulatory limit for fetal exposure is 500 millirem for the entire pregnancy. Customarily, this limit is apportioned at a rate of 50 millirem per month. After declaring pregnancy, the prospective mother was given a second radiation badge for use as a fetal dose monitor. This badge is worn at waist level under the lead apron. In our institution, angiographic assistants routinely wear under-lead badges. Typically, the monthly readings on these badges are less than 10 millirem. Given our circumstances, the exposure to our nurse’s fetus is therefore expected to be less than 10 millirem per month. (The actual readings on our nurse’s fetal badge for the first two months of monitoring were 3 and 5 millirem respectively.) What are the Risks of Radiation Exposure in Pregnancy? This is a routine question that should be answered during the counseling session. A great deal of written material is available from institutional radiation safety services or on the internet. Briefly, the answer starts with a discussion of the incidence of abnormalities in the absence of occupational radiation (approximately 5%). It goes on to mention natural background radiation and its geographical variation. With regard to this point, New York City is favorably located and has essentially the lowest natural background radiation level in the United States. Natural background levels in Denver are approximately 10 millirem per month higher than in New York City. Thus, the expected fetal exposure for one of our angioplasty assistants is less than that of a non-radiation worker living in Denver. We therefore presume that there is minimal additional risk at less than 10 millirem per month as read on the fetal dose monitor. The basic principles of radiation safety, time, distance, and shielding were reviewed. The nature of an angioplasty assistant’s duties precludes any realistic radiation time management. She was encouraged to position herself as far from the beam as practicable during the procedure. In this case, she was able to manage an additional step or two away from the beam by moving toward the patient’s feet. Our normal personal shielding consists of wrap-around garments with 0.5 mm Pb (Figure 1). In some instances, she was able to adjust her position such that an additional individual was between her and the beam. This increased both distance and shielding. Reading Exposure in Real-Time Our nurse was immediately assigned a fetal dose monitor. She wore it for a day and came back to radiation safety for a reading. There was a problem when she was informed that the badges were collected and read on a monthly schedule. The lack of immediate feedback was uncomfortable for her. Real-time personal monitors are available in a variety of types and sensitivities. We selected a Model 06-105 device (Nuclear Associates, 120 Andrews Road, Hicksville, NY 11801). This unit provides cumulative readouts in units of 0.1 mR. Once the audible output was reduced, this device was satisfactory to the nurse, and the rest of the lab staff. The instrument was positioned under the lead at waist level as shown in Figure 2. This position is typically closer to the beam than midline. Thus, the readings are expected to be slightly on the high side. At the end of the first day of use, the device had a reading of 0.1 millirem. The next questions included: ‘What does this mean’ and ˜is this a dangerous level of radiation?’ A simple calculation demonstrates that this was more or less a day’s natural background. As part of the educational process, the nurse was encouraged to take the device home and keep monitoring it outside of the cath lab. After two months, the cumulative reading was 18 millirem. This reading is largely attributable to natural background. Actual fetal badge readings for the first two months were 3 and 5 millirem respectively. (Normal processing of personnel monitors uses readings of a control badge to subtract natural background levels.) We therefore conclude that this angioplasty assistant’s fetus received little more than background exposures as a result of the mother’s occupational duties.