Evaluation of Acute Radiation Syndrome and Radiation Accident Dosimetry Knowledge and Awareness Levels of Turkish Radiation Oncology Professionals for Radiation Accident Emergencies, TROD 11-011 Study

Even if radiation protection precautions are taken, radiation emergencies may occur caused by artificial radiation sources during medical procedures or in other ways. Alongside the radiation exposure of the Japanese population due to atomic bombs (1945, Japan), the Radiation Emergency Response Center/Training Site Radiation Accident Records reported 420 nuclear incidents between 1944 and 2011, the most important of which are Goiânia (1985, Brazil), Chernobyl (1986, Ukraine), and Fukushima (2011, Japan).[]

A radiation accident could be defined as an incident involving an unplanned or unforeseen radiation emission, misuse of radiation devices, or misapplication or mislay of radioactive substances. During a radiation accident, it is possible to be exposed to various types of radiation and different magnitudes of radiation dose.

Ionizing radiation has early and late-term adverse side effects on living organisms, which can vary depending on the amount of dose and duration of exposure.[,] Acute radiation syndrome (ARS) is a high-risk, low-frequency diagnosis that can be fatal and is difficult to diagnose without a history of significant ionizing radiation exposure.[] Acute radiation syndrome is a group of dose-dependent signs and symptoms that occur after short-term exposure to high levels of ionizing radiation.[,] The first multinational and multidisciplinary guideline for ARS, specifically for radiation-related emergencies, was published in 1997 by the European Commission, called MEDICAL TREATMENT PROTOCOLs for Radiation Accident Victims (METREPOL).[]

Classically, it has been stated that for ARS to develop, whole body or partial body exposure must be at least 1.0 Gy, and ARS is not expected for exposures below 0.5 Gy.[] Due to its dose-dependent effects, ARS has been divided into four different subsyndromes named after the system affected at each dose threshold: Hematopoietic (≥1.0 Gy), cutaneous (≥3.0 Gy), gastrointestinal (≥6.0 Gy), and neurovascular (≥8.0 Gy).[,]

In the hematopoietic subsyndrome, ionizing radiation damages radiosensitive lymphocytes and stem cells in the bone marrow, causing pancytopenia and predisposing the patient to opportunistic infections. [,-] Clinically, monitoring the decline in absolute lymphocyte count (ALC) is the most practical method of assessing radiation dose after exposure. A 50% decrease in ALC within the first 24 hours after exposure followed by a more severe decrease within 48 hours indicates a potentially lethal exposure in the range of 5.0- 10.0 Gy radiation dose. The post-exposure lymphocyte nadir typically occurs 8-30 days.[,]

In the cutaneous subsyndrome, ionizing radiation can cause epilation, erythema, scaling, and even radionecrosis because the skin contains differentiated and rapidly dividing cells, like those in the bone marrow and gastrointestinal tract.[,,,] Following exposure to doses of ≥3.0 Gy, the cutaneous syndrome manifests itself and overlaps with other sub-syndromes.

In the gastrointestinal (GI) subsyndrome, damage in the intestine track can cause a wide range of problems, including bleeding, electrolyte abnormalities, and infection.[] This subsyndrome usually develops within 5 days after exposure. Radiation Dose <1.5 Gy: Prodromal symptoms: Nausea and vomiting. Radiation Dose >5.0 Gy: Destruction of intestinal crypt cells and loss of mucosal barrier. Death is related to dehydration, electrolyte imbalances, bacterial translocation, GI wall necrosis and subsequent perforation.[,]

Neurovascular sub-syndrome is associated with brain edema along with loss of consciousness, fever and hypotension, among other findings.[] When the radiation exposure dose is >10.0 Gy, localized changes in the cerebrovascular system include: Impaired capillary circulation, damage to the blood-brain barrier, acute inflammation of the meninges, petechial hemorrhages. Patients may present with headache, nausea, altered mental status or seizures. [,]

Regardless of subsyndromes, ARS progresses through four stages: Prodromal, latent, overt disease, and recovery/death. The higher the dose, the faster the patient progresses through these stages. Prodromal Stage: Begins 0-2 days after exposure, Latent Stage: Begins 2-20 days after exposure, Overt Disease: Begins 21-60 days after exposure.[]

Unfortunately, historically, ARS has been diagnosed late in its course.[] The METREPOL guideline has determined the first step of treatment as taking a good anamnesis regarding the type, duration and dose of exposure, removing external contamination and fluidelectrolyte replacement. Individuals exposed to a dose of 2.0-3.0 Gy should be isolated due to the risk of infection.[] Early symptoms that manifest themselves in the prodromal phase include nausea, vomiting, anorexia, apathy, diarrhea, fever, headache, and tachycardia. If these symptoms begin within approximately 2 hours, the guideline states that the patient is most likely exposed to a dose exceeding 2.0-4.0 Gy, and if they begin within minutes, to doses exceeding 10 Gy.[]

It is critical that first responders be able to diagnose and provide initial treatment for patients presenting with ARS. This critical requirement makes it essential to identify competent and educated professionals of healthcare institutions, keep relevant training up to date, and increase their awareness. In advanced healthcare institutions, the contributions of radiation oncology professionals, as well as emergency physicians, to the first response team in radiation accidents or emergencies have been recognized. First of all, radiotherapy is a practice that develops errors or near misses as termed "incidents", or accidents, despite the precautions taken during the use of highradiation doses and complex treatment process. Managing these rare events makes radiation oncology professionals who may encounter them daily, prepared to respond and evaluate radiation accidents quickly compared to many other teams.

Since radiation oncologists are the physicians most thoroughly trained to understand and manage the effects of radiation exposure on healthy and malignant cells, the American Society for Radiation Oncology (ASTRO) noticed it would be proper for its members to be one of the primary resources in responding to radiation accidents and disasters.[] In this context, ASTRO initiated the creation of a training document working with the American College of Radiology (ACR) and the American Association of Physicists in Medicine (AAPM) for radiation oncology and radiology professionals. Disaster Preparedness for Radiology Professionals booklet is designed to summarize information on preparing for a radiation accident or emergency, managing contaminated individuals, to collecting data on possible exposure dose assessment and radiation exposure on health.[] Also, the International Atomic Energy Agency (IAEA) has emphasised that one of the primary responsibilities of radiation oncology physicians (ROP) is to assess medically any radiation accident or incident.[]

On the other hand, the IAEA published a document for the medical physicists, the partner professionals of radiation oncology, called Guidance for Medical Physicists Responding to a Nuclear or Radiological Emergency. As mentioned, clinical medical physicists working in hospitals have in-depth knowledge of high energy radiation dosimetry, dose reconstruction and dose measurement techniques and tools. They constitute a unique group of professionals who, with the proper training, can provide effective support for the triage of radiation accidents, emergency preparedness and response activities. Using this reservoir of radiation protection experts in emergency and preparedness teams is good medical practice.[]

Determination or close estimation of patient radiation exposure dose is crucial for the accident response team to decide on urgent interventions and protective protocols. The most important parameter to be learned during anamnesis is the time until the onset of vomiting, and also determining the absolute lymphocyte decline rate and chromosomal aberration status is vital for the design of prophylactic and prospective treatments.

In particular, the time from exposure to the onset of vomiting and the absolute lymphocyte decline rate are guides for the dose of exposure and the corresponding intervention. Marx et al.[] reported that vomiting that started within 1 hour after exposure was generally associated with more than 6.5 Gy of dose exposure, and vomiting that started between 1-4 hours was associated with approximately 3.5 Gy of dose exposure. Determination of chromosomal aberrations can be done within 24 hours and after an incubation time, information is reached within 48-72 hours, and even if it is not effective in the emergency management of the patient, it is necessary for later.[,]

One of the most important factors in the management of this entire process is the calculation and reconstruction of the accident dose. In this context, the IAEA has created a series of training documents and focused on radiation dosimetry in radiation emergencies.[] It is possible to estimate the exposure dose and develop a rapid intervention scheme based on the ARS symptoms observed in the victims, but this process should be supported by the actual calculation results of post-accident dosimetry. In order to define a long-term treatment scheme, it is vital to determine the dose absorbed in the tissues of individuals with high accuracy.[]

If it is an accident that occurs in a radiation area, field monitors or personal dosimeters that are already at the scene can be used, but it should not be forgotten that in dose exposures above a certain range, these equipments can also overdose and become inadequate or show a value (saturation) lower than the actual dose. If the accident is in another location than the hospital, the whole body measurements of individuals who come to the emergency room should be recorded with provided portable survey meters.

However, in radiation emergencies that develop following a radiation accident that involves a higher dose or a radiation type other than the one designed to be measured, or in areas where there is no dosimetric equipment or field monitor retrospective dosimetric techniques are needed for radiaiton accident dose reconstruction. For this purpose, medical physicists start the process by collecting various materials to be used in radiation accident dosimetry (RAD).

Retrospective techniques are divided into two groups as Physical or Biological techniques. Physical techniques involve the analysis of collected samples using physical methods. Retrospective Physical dosimetry techniques can be performed with a range of materials such as glass, alanine, sugar, plastic, silicates and tobacco.[] Electron paramagnetic resonance (EPR), Thermoluminescence (TL) and Optically stimulated luminescence (OSL) are typical physical dosimetry techniques.

Retrospective biodosimetry is based on various cytogenetic analyses that can mostly detect radiationinduced DNA damage and incorrect repair. Blood circulates throughout the body, so data from blood samples are reported as an average of the radiation dose received from all parts of the body, therefore some blood samples should be collected several days or weeks after exposure to allow for complete circulation. Biolgicasl materials to be used in biological dosimetry are whole blood, lymphocytes, blood plasma/serum. Dicentric Chromosome Test (DCA), Premature Chromosome Condensation (PCC), Cytokinesis- block Micronucleus (CBMN) Cytome Assay, Translocation Analysis by FISH, The γ H 2 AX Assayand EmergingAssay: Omics are the main tests.[]

Retrospective dose reconstruction, assessment and management of ARS are vital and necessary in radiation accident emergencies. Therefore, it is critical that the first response team consists of professionals who are qualified these processes. Radiaiton oncology professionals have a major responsibility in the planning and assignment of that workflow. This survey study highlights the well planned updated education is a need for radiation accident emergency for the radiation oncololgy profesionals.

The main purpose of the study is to determine the knowledge levels of radiation oncology professionals, ROP and radiation oncology medical physicists (ROMP), about ARS and RAD in radiation accident emergencies through the questions in the survey.

The second aim of the study is to stimulate the awareness and the need for these informantions of radiation oncology professionals about ARS and RAD in radiation accident emergencies through the questions in the survey and to pioneer awareness development and the organization of necessary training based on the results.

This survey is a rare study conducted to determine the requirements and the levels of awareness in this area. In addition, the ROP and ROMP groups evaluated together as radiation oncology professionals. Planning trainings due to the determined issues will increase the effectiveness of Turkish radiation oncology professionals in case of a radiation accident emergencies.