Importantly, embryofetal risks from low-dose diagnostic radiation appear to be minimal. Current evidence suggests that risks for malformations, growth restriction, or abortion are not increased from a radiation dose of less than 0.05 Gy (5 rad). Indeed, Brent (2009) concluded that gross congenital malformations would not be increased with exposure to less than 0.2 Gy (20 rad). Because diagnostic x-rays seldom exceed 0.1 Gy (10 rad) , Strzelczyk and associates (2007) concluded that these procedures are unlikely to cause deterministic efects. As emphasized by Groen and coworkers (2012), 0.1 Gy is the radiation equivalent to that from more than 1000 chest x-rays!
These efects refer to random, presumably unpredictable oncogenic or mutagenic efects of radiation exposure. Stochastic efects concern associations between fetal diagnostic radiation exposure and increased risk of childhood cancers or genetic diseases. According to Doll and Wakeford (1997), as well as the National Research Council (2006) BEIR VII Phase 2 report, excess cancers can result from in utero exposure to doses as low as 0.01 Svror 1 rad. Stated another way by Hurwitz and colleagues (2006), the estimated risk of childhood cancer following fetal exposure to 0.03 Gy or 3 rad doubles the background risk of 1 in 600 to that of 2 in 600.
In one report, in utero radiation exposure was determined for 10 solid cancers in adults from age 17 to 45 years. here was a dose-response relationship as previously noted at the 0.r1 Sv or 10 rem threshold. hese cancers likely are associated with a complex series of interactions between DNA and ionizing radiation. They also make it more problematic to predict cancer risk from low-dose radiation of less than 0.1 Sv or 10 rem. Importantly, below doses of 0.1 to 0.2 Sv, there is no convincing evidence of a carcinogenic efect (Brent, 2009, 2014; Preston, 2008; Strzelczyk, 2007).
Estimates of dose to the uterus and embryo for various frequently used radiographic examinations are summarized in Table 46-5. Imaging of maternal body parts farthest from the uterus results in a very small dose of radiation scatter to the embryo or fetus. The size of the woman, radiographic technique, and equipment performance are other variables (Wagner, 1997). hus, data in the table serve only as guidelines. When the radiation dose for a specific individual is required, a medical physicist should be consulted. Brent (2009) recommends consulting the Health Physics Society website (ww.hps.org) to view some examples of questions and answers posed by patients exposed to radiation.
he Radiation Therapy Committee Task Group of the American Association of Physics in Medicine (Stovall, 1995) emphasizes careful individualization of radiotherapy for the pregnant woman (Chap. 63, p. 1191). For example, in some cases, shielding of the fetus and other safeguards can be employed (Fenig, 2001; Nuyttens, 2002). In other instances, the fetus will be exposed to dangerous radiation doses, and a carefully designed plan must be improvised (Prado, 2000). Examples include models that estimate the fetal dose given during maternal brain radiotherapy or tangential breast irradiation (Mazonakis, 1999, 2003). The harmful efects of radiotherapy on future fertility and pregnancy outcomes were reviewed by Wo and Viswanathan (2009) and others and are detailed in Chapter 63 (p. 1192).
To estimate fetal risk, approximate x-ray dosimetry must be known. According to the merican College of Radiology, no single diagnostic procedure results in a radiation dose signiicant enough to threaten embryo-fetal well-being (Hall, 1991).