**4. Regulatory mechanisms and safety enforcement**

**3. Biological manifestations of HMRE**

60 Vignettes in Patient Safety - Volume 4

levels in a systematized fashion.

dose [28].

**Radiation dose** 

0–2 No effect

**(Gy)**

Two broad categories of clinical (e.g., biologic) effects of radiation, specific to the contexts of radiation therapy or accidental isotope exposure, include deterministic injuries and stochastic injuries. Deterministic injuries manifest as radiation-induced escalation of normal physiologic apoptosis resulting in increased death of essential cells with resultant tissue and organ dysfunction [27]. These types of injuries occur when large numbers of cells become damaged and, as a result, die immediately or shortly after irradiation [28]. Dermatoligic post-exposure injury can range from "local erythema" to "skin necrosis" [28]. Estimation of dosage is measured in the units of Gy, with 0–2 Gy associated with no biological effects; 2–5 Gy causing transient erythema (<2 weeks), followed by epilation (2–8 weeks) and recovery (6–52 weeks); 5–10 Gy associated with prolonged erythema (up to 8 weeks), epilation (2–8 weeks), and recovery (6–52 weeks); 10–15 Gy exposure causes transient erythema (<2 weeks), dry/moist desquamation (2–8 weeks), followed by permanent epilation (6–52 weeks) and finally atrophy (>40 weeks); and >15 Gy being associated with acute ulceration (<2 weeks), moist desquamation (2–8 weeks), dermal necrosis (6–52 weeks), and eventual surgery (>40 weeks) [28]. **Table 3** outlines the above exposure

Stochastic effects manifest as cellular carcinogenesis and result from radiation induced mutations in genetic material of cells including germ cells [27]. For stochastic injuries, postradiation damage becomes the key determinant of clinically apparent, usually long-term manifestation [28]. Such effects also depend on the type/activity of the isotope involved. More specifically, these kinds of injuries have a linear nonthreshold dose that may lead to radiation-induced malignancy and/or heritable genetic defects [28]. Estimation of dosage from radiologic studies utilizes the units of Sieverts (Sv), with procedures such as dual-isotope SPECT (24 mSv) and CT angiography (19 mSv), carrying the highest effective radiation doses [28]. Of note, victims of the Chernobyl disaster were exposed to a maximum radioactivity of 300–450 mSv/h within a 15 km radius. The individuals that had suffered from radiation are suspected to have received a minimum of 0.8–2 Gy (80–200 Rad)

**Possible adverse reaction Timeline**

10–15 Dry/moist desquamation leading to permanent epilation 2–8 weeks → 6–52 weeks

**Table 3.** Post-exposure deterministic injury shown with radiation dose in Gray units and the typical timeline associated

<2 weeks → 6–52 weeks

2–5 Transient erythema <2 weeks 5–10 Prolonged erythema <8 weeks

>15 Acute ulceration leading to desquamation and dermal

necrosis

with the appearance of adverse effects.

The first line of ensuring safety is the presence of organizational policies and procedures pertaining to HMRE as well as the handling of radioisotope-containing medical materials, both at the departmental and institutional levels [29–31]. In addition to applicable policies and procedures that are harmonized to prevailing laws and regulations, organizations also employ radiation safety experts in the role of Radiation Safety Officer (or functional equivalent thereof) to ensure the maintenance of appropriate legal and procedural compliance [31–33]. Any HMRE events that are deemed reportable to appropriate local, regional, or national authorities are handled by the Radiation Safety Officer. In addition, employees who work around radiation equipment and/or interact with medical radioisotopes must wear radiation monitoring badges that help quantify levels of healthcare worker exposure [34, 35]. Some general considerations of how appropriate policies and procedures can help protect the well-being of both patients and healthcare workers include [7, 32, 36–38]:


In the European Union and associated countries, the Euratom Treaty recommends that a patient examination and clinical justification are provided before a referral is made to a radiologist or a nuclear medicine expert. Moreover, nonionizing radiation is preferred whenever it will provide comparable information to that obtained by means of ionizing radiation [39]. For example, an ultrasound or magnetic resonance imaging (MRI) may provide the same desired information as a CT, without the need for ionizing radiation [40]. Additional safety enforcement strategies include: safety checklists to verify the patient and study being performed; radiation dose customization utilizing the patient's weight, age, medical history, and intended body segment to be scanned/imaged; and decision support systems which provide ordering physicians an opportunity to answer questions regarding their patients and consider alternatives to ionizing diagnostics [40].

The US Food and Drug Administration (FDA) has partnered with other organizations to promote education and communication regarding radiation safety to patients and medical professionals [41]. Among their resources, the FDA collaborated with the National Council on Radiation Protection and Measurement to communicate the risk of radiation exposure with patients, particularly imaging involving young children [41, 42]. The FDA advocates for patient and healthcare provider awareness via the Image Wisely and Image Gently radiation risk campaigns, as well as with the International Atomic Energy Agency's "Radiation Protection of Patients" website [41, 43, 44]. The FDA has also advocated for patient and healthcare provider tools to reduce radiation exposure. One particular innovative safety tool is the "Patient Medical Imaging Record Card", which was developed by the FDA in collaboration with Image Wisely [41, 43]. The card can be used to track patient imaging studies by date, type, and location to prevent unnecessary repeat ionizing radiation exposures [41]. Looking toward the future, this card would ideally be integrated into the patient's electronic health record and stored in a nationally accessible database for healthcare providers, such as the Federal Data service Hub, which is established by the Affordable Care Act and backed by the Health and Human Services department [45].

The US Nuclear Regulatory Commission was established with The Energy Reorganization Act of 1974 to license and regulate the civilian use of radioactive materials to protect public health and safety and the environment. It is in charge of overseeing nuclear reactors, security, and materials as well as radioactive waste. The commission sets rules and licensing, enforces those rules, evaluates facilities, and provides support and logistics for incident response. Some aspects of management and regulation of certain radioactive materials have been granted to Agreement States [46].
