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Overall, this work may be used as a practical guidance for nuclear medicine professionals, hospital mortuary staff, funeral service providers and other stakeholders involved in the management of deceased nuclear medicine patients, if they face this rare situation.
2 Material and methods
2.1 Assumptions, scenarios, and radionuclides considered
The initial IRSN study conducted over the period 2008 – 2016 was carried out within the framework of an ASN’ s working group on deceased patients. Based on the contribution of funeral service professionals participating in this group, dose assessments were performed for two key post-mortem procedures: – Transport of deceased patients: the considered transport corresponds to the first transfer of the patient directly after death and before placing the body into the coffin;
– Embalming, including body cleansing, dressing, and thanatopraxy when required.
According to the recommendations of the funeral service professionals involved, the following conservative assumptions were applied for the post-mortem procedures: – The distance from professional to patient body was set at
50 cm for both procedures;
– Contact duration was estimated at 1 h for body transport and 2 h for embalming.
The following therapeutic radionuclides were considered:
– Beta emitters: phosphorus-32, strontium-89, yttrium-90, indium-111, iodine-131, samarium-153, holmium-166, erbium-169, lutetium-177, and rhenium-186;
– Alpha emitters: radium-223 and actinium-225.
Conversely, diagnostic radionuclides were excluded from this assessment, as their external dose rates are significantly lower than those of therapeutic radionuclides due to their shorter half-lives and lower administered activities.
Table 1 summarizes the key characteristics of the considered radionuclides, including half-life, physical or pharmaceutical form, medical application, and administered activities based on clinical practice.
Although some radiopharmaceuticals are no longer in use in France, i. e., phosphorus-32, therapeutic indium-111 pentetreotide, and iodine-131 Lipiodol ®, they were included in the analysis given their continued or potential future use in other countries or their possible reintroduction in France.
In this study, external and internal contamination were not considered, assuming that the professionals handling deceased patients use the standard personal protective equipment( e. g., gloves). the literature( Abuqbeitah et al., 2018; BIR, 1999; CSHPF, 2006; Dauer et al., 2014; European Commission, 1998; Gardin, 2002; Parlak et al., 2015; Prince et al., 2014; Serencsits et al., 2022).
When measurements were not available, the coefficients were taken from the French technical leaflets“ Radioprotection: Radionucléides” jointly published by INRS( French National Institute for Research and Safety) and IRSN( INRS- IRSN, 2013).
The equivalent dose rate coefficients for radionuclides in this case are summarized in Table 2.
2.2.2 Specific case: beta emitters( pure or with high beta energy)
For pure beta emitters or radionuclides with a high beta energy, defined here as a maximum beta energy exceeding 1 MeV, the equivalent dose rates from bremsstrahlung radiation were estimated using an envelope approach as described in this section. The yttrium-90 was selected as reference radionuclide because of the extensive data available. For other radionuclides, the coefficients were estimated by applying a linear scaling based on the maximum beta energy.
In a first step, a literature review was conducted for yttrium-90 to identify the highest reported equivalent dose rate coefficient among its three forms: liquid solution, TheraSphere ® and SIR-Sphere ®( Aubert et al., 2002; McCann et al., 2012).
In a second step, due to lack of data for the other radionuclides and no validated method exists for assessing bremsstrahlung-related equivalent dose rates, values were extrapolated from yttrium-90, by applying a linear scaling with maximum energy of beta. This approach is recognized to overestimate the equivalent dose rate.
In a third step, a distinction was made between radiopharmaceuticals fixed to soft tissues and those fixed to bones. Since bremsstrahlung yield is proportional to the medium’ s atomic number, a factor of 21 / 7.9, representing the ratio of the effective atomic numbers of bone to soft tissue, was applied to the soft-tissue equivalent dose rate to obtain the corresponding value for bone.
The equivalent dose rate coefficients for radionuclides in this case are summarized in Table 3.
2.3 Effective half-lives
Effective half-life values were obtained from the literature( see references in Tab. 4). When the data were not available, the physical half-life was used. This choice is conservative, because the biological half-life of radionuclides used in nuclear medicine is generally shorter than the physical half-life. The effective half-lives are summarized in Table 4.
2.2 Equivalent dose rate coefficients 2.2.1 General case for the radionuclides
In general, equivalent dose rate coefficients were measured from living or deceased individuals, reported in
2.4 Calculation method
To estimate the effective dose E, the equivalent dose H *( 10) at a distance d from the deceased patient over a time interval Dt was calculated using the following formula: