New approach for dose reconstruction: application to one case of localized irradiation with radiological burns

Surgical management of focal ionising radiation burns

The management of focal radiation burns after prolonged exposure to ionising radiation remains a relatively rare but significant therapeutic challenge. This narrative aims to highlight certain aspects of management that can be overlooked and mitigation strategies in the management of these potentially fatal injuries.

Advances in the management of localized radiation injuries

Localized radiation injuries account for the vast majority of accidental radiation exposures and mainly occur due to direct handling of highly intense radioactive sources. Their clinical course and severity mainly depend on the type of radiation, radiation source, dose and dose rate, duration of exposure, dose distribution, and location and size of the area exposed. Local injuries appear as skin injuries; however, they may involve radiation damage to other organs and tissues. Local injuries evolve slowly over time and clinical signs and symptoms usually take days to weeks to manifest. Although in most cases not life threatening, their delayed effects may result in serious impairments. Standardized therapeutic protocols and evidence-based approaches for the management of local injuries do not exist yet. Local injuries should therefore be treated symptomatically. The two main approaches comprise conservative and surgical treatment. Conservative methods focus on pain control, reduction of inflammation, prevention of infection and of further vasculature insult, improvement of circulation, healing acceleration, wound cleaning, and minimizing fibrosis. Surgical treatment and plastic remodeling of anatomic structures may be required. During recent years, significant progress has been made in the management of local injuries. There is increasing evidence that injections of human mesenchymal stem cells may be a promising therapeutic approach in the treatment of cutaneous radiation reactions. A consistent follow-up of radiation patients keeping in mind the possible onset of late radiation effects will contribute to the comprehensive understanding of the pathophysiology of the radiation reaction which is crucial to establish evidence-based diagnostic and therapeutic strategies.

SESAME: a software tool for the numerical dosimetric reconstruction of radiological accidents involving external sources and its application to the accident in Chile in December 2005

Estimating the dose distribution in a victim's body is a relevant indicator in assessing biological damage from exposure in the event of a radiological accident caused by an external source. This dose distribution can be assessed by physical dosimetric reconstruction methods. Physical dosimetric reconstruction can be achieved using experimental or numerical techniques. This article presents the laboratory-developed SESAME--Simulation of External Source Accident with MEdical images--tool specific to dosimetric reconstruction of radiological accidents through numerical simulations which combine voxel geometry and the radiation-material interaction MCNP(X) Monte Carlo computer code. The experimental validation of the tool using a photon field and its application to a radiological accident in Chile in December 2005 are also described.

New approach to radiation burn treatment by dosimetry-guided surgery combined with autologous mesenchymal stem cell therapy

The therapeutic management of severe radiation burns remains a challenging issue. Conventional surgical treatment (excision and skin autograft or rotation flap) often fails to prevent unpredictable and uncontrolled extension of the radiation necrotic process. We report here an innovative therapeutic strategy applied to the victim of a radiation accident (December 15, 2005) with an iridium gammagraphy radioactive source (192Ir, 3.3 TBq). The approach combined numerical dosimetry-guided surgery with cellular therapy using mesenchymal stem cells. A very severe buttock radiation burn (2000 Gy at the center of the skin surface lesion) of a 27-year-old Chilean victim was widely excised (10 cm in diameter) using a physical and anatomical dose reconstruction in order to better define the limit of the surgical excision in apparently healthy tissues. A secondary extension of the radiation necrosis led to a new excision of fibronecrotic tissues associated with a local cellular therapy using autologous expanded mesenchymal stem cells as a source of trophic factors to promote tissue regeneration. Bone marrow-derived mesenchymal stem cells were expanded according to a clinical-grade technique using closed culture devices and serum-free medium enriched in human platelet lysate. The clinical evolution (radiation pain and healing progression) was favorable and no recurrence of radiation inflammatory waves was observed during the 11 month patient's follow-up. This novel multidisciplinary therapeutic approach combining physical techniques, surgical procedures and cellular therapy with adult stem cells may be of clinical relevance for improving the medical management of severe localized irradiations. It may open new prospects in the field of radiotherapy complications.

EX vivo ESR measurements associated with Monte Carlo calculations for accident dosimetry: application to the 2001 Georgian accident

Electron spin resonance (ESR) spectroscopy and the Monte Carlo (MC) technique were jointly applied to the physical dose reconstruction of the accident that occurred on 2 December 2001 in Georgia. Three people were exposed to two very-high-activity (2.6 x 10(15) Bq) 90Sr sources. Following this exposure, the two most seriously affected victims exhibited severe radiological injuries localised in the back as well as a haematopoietic syndrome. The information concerning the circumstances of the accident in terms of sequences of irradiation and the exposure time was not clearly established. The physical dose reconstruction of the accident was performed for one victim, treated in France, using both MC simulations and ESR measurements made on one vertebra and two rib samples removed from the victim for medical reasons. The complementary nature of the two tools made it possible to estimate the dose distribution within the body with reasonable accuracy and helped to develop the treatment strategy.

Current developments at IRSN on computational tools dedicated to assessing doses for both internal and external exposure

The paper presents the OEDIPE (French acronym that stands for tool for personalised internal dose assessment) and SESAME (for simulation of external source accident with medical images) computational tools, dedicated to internal and external dose assessment, respectively, and currently being developed at the Institute for Radiological Protection and Nuclear Safety. The originality of OEDIPE and SESAME, by using voxel phantoms in association with Monte Carlo codes, lies in their ability to construct personalised voxel phantoms from medical images and automatically generate the Monte Carlo input file and visualise the expected results. OEDIPE simulates in vivo measurements to improve their calibration, and calculates the dose distribution taking both internal contamination and internal radiotherapy cases into account. SESAME enables radiological overexposure doses to be reconstructed, as also victim, source and accident environment modelling. The paper presents the principles on which these tools function and an overview of specificities and results linked to their fields of application.

PCC-FISH in Skin Fibroblasts for Local Dose Assessment: Biodosimetric Analysis of a Victim of the Georgian Radiological Accident

We propose a new method of biodosimetry that could be applied in cases of localized irradiation. The approach is based on excess chromosome segments determination by the PCC-FISH technique in fibroblasts isolated from skin biopsy. Typically, 0 to 10 Gy ex vivo gamma-irradiated human skin biopsies were dissociated and fibroblasts were isolated and grown for several days. Cells next underwent PCC-FISH painting of whole chromosome 4, and the number of excess chromosome segments per metaphase was determined. An ex vivo reference curve correlating the number of excess chromosome segments per metaphase to the radiation dose was established and used to assess the dose delivered to the skin of one of the victims of the radiological accident that occurred at Lia in Georgia in December 2001. Specifically, the victim suffering from moist desquamation underwent skin excision in Hospital Percy (France). Measurement of excess chromosome segments per metaphase was done in fibroblasts isolated and grown from removed wounded skin and subsequent conversion to radiation doses was performed. The radiation dose map obtained was shown to be in accordance with clinical data and physical dosimetry as well as with conventional biodosimetry. These results demonstrated that PCC-FISH painting applied to skin fibroblasts may be a suitable technique for dose estimation. To assess its worth, this approach needs to be extended to future accidents involving localized radiation exposure.

Burn Injuries From Radiation

Accidental exposure to radiation leading to injury and illness occurs notwithstanding safety devices and protocols used for protection. The medicalmanagement of radiation casualties is amajor concern. Radiation effects are principally thermal, similar to electrical burn injuries, but with some unique systemic expression. The pathological effects of radiation to the skin are known; it is often difficult to assess the level of severity, quickly and with accuracy, because of the delay between exposure and the appearance of lesions and obscured lesions.The severity depends mainly on the nature of the radiation.High-energy penetrating radiation causes more irreversible damage than low-energy radiation, which penetrates tissues less than the former. A thorough knowledge, high index of suspicion, and a team approach are keys to successful management.

Consequences of Radiation Accidents

Radiation injury attributable to radiotherapy is a topic that has attracted ample attention in the literature, especially in a vast number of publications in plastic surgery. However, the literature is clearly devoid of compilations regarding the effects of ionized radiation accidents. A case of a radiation accident is presented. It is nearly impossible to anticipate the extent of effects of external irradiation of the skin and subcutaneous tissues. The initially healed area should be expected to show late recurrent necrosis. Patients exposed to ionized external irradiation are no longer radioactive and can be treated as ordinary patients. However, these patients should be followed closely for years, keeping in mind the onset of late radiation effects like skin necrosis in various parts of the body, skin and other organ cancers, leukemia, infertility, hypothyroidism, and cataracts.

A computational tool based on voxel geometry for dose reconstruction of a radiological accident due to external exposure

In the case of overexposure to ionising radiation, estimation of the absorbed dose in the organism is an important indicator for evaluating the biological consequences of this exposure. The physical dosimetry approach is based either on real reconstruction of the accident, using physical phantoms, or on calculation techniques. Tools using Monte Carlo simulations associated with geometric models are very powerful since they offer the possibility to simulate faithfully the victim and the environment for dose calculations in various accidental situations. Their work presents a new computational tool, called SESAME, dedicated to dose reconstruction of radiological accidents based on anthropomorphic voxel phantoms built from real medical images of the victim in association with the MCNP Monte Carlo code. The utility was, as a first step, validated for neutrons by experimental means using a physical tissue-equivalent phantom.