Skin dose rate conversion factors after contamination with radiopharmaceuticals: influence of contamination area, epidermal thickness and percutaneous absorption

Abstract

Skin contamination with radiopharmaceuticals can occur during biomedical research and daily nuclear medicine practice as a result of accidental spills, after contact with bodily fluids of patients or by inattentively touching contaminated materials. Skin dose assessment should be carried out by repeated quantification to map the course of the contamination together with the use of appropriate skin dose rate conversion factors. Contamination is generally characterised by local spots on the palmar surface of the hand and complete decontamination is difficult as a result of percutaneous absorption. This specific issue requires special consideration as to the skin dose rate conversion factors as a measure for the absorbed dose rate to the basal layer of the epidermis. In this work we used Monte Carlo simulations to study the influence of the contamination area, the epidermal thickness and the percutaneous absorption on the absorbed skin dose rate conversion factors for a set of 39 medical radionuclides. The results show that the absorbed dose to the basal layer of the epidermis can differ by up to two orders of magnitude from the operational quantity Hp(0.07) when using an appropriate epidermal thickness in combination with the effect of percutaneous absorption.

Calculation of Skin Dose Rate Conversion Factors Due to Surface Contamination from Frequently used Radionuclides in Local Nuclear and Medical Facilities

“…Similar results can be found in the literature. [ 13 ] In the rest of the radionuclides analyzed, the skin dose conversion factors values decrease smoothly because the energy deposited by electrons remains high.…”

Estimation of absorbed radiation doses to skin and S‐values for organs at risk due to nasal administration of PET agents using Monte Carlo simulations

“…Although nasal mucosa serves as a primary barrier to prevent pathogens, they can also be highly absorptive to certain molecules 28 . The effect of absorption through skin tissue has been shown to affect the absorbed dose to the basal layer of the epidermis, differing by up to two orders of magnitude of Hp(0.07) when considering percutaneous absorption 17 . Tabulated values of deterministic effects against skin dose have been derived for x‐ray procedures, with a value of 2 Gy before the onset of early transient erythema, epilation at 3 Gy, main erythema at 6 Gy, and dermal necrosis >18 Gy 29 .…”

“…28 The effect of absorption through skin tissue has been shown to affect the absorbed dose to the basal layer of the epidermis, differing by up to two orders of magnitude of Hp(0.07) when considering percutaneous absorption. 17 Tabulated values of deterministic effects against skin dose have been derived for x-ray procedures, with a value of 2 Gy before the onset of early transient erythema, epilation at 3 Gy, main erythema at 6 Gy, and dermal necrosis >18 Gy. 29 For the values determined from this work of approximately 35 mGy/MBq for 18 F and 11 C agents for 1 h of contamination, an administered activity via IN of approximately 200 MBq would be well within the region of transient FIG.…”

“…A basic analytical approach can be calculated based on a contamination scenario of a planar surface. We utilized absorbed skin beta dose rate conversion factors averaged over 1 cm 2 of skin tissue of 1.63 mGy h −1 kBq −1 and 1.61 for 11 C and 18 F, respectively, from literature 17 . Assuming 1 MBq of the radiotracer to be fixed in place for a duration of 1 h, and with the area under the time activity curve (calculated as the integral of the exponential decay curve of 11 C and 18 F) and multiplying by the conversion factors above, the total skin absorbed dose in mGy can be estimated for specific contamination areas.…”

Assessing the feasibility of intranasal radiotracer administration for in brain PET imaging

“…Previous work using Monte Carlo simulations has determined absorbed skin dose rate conversion factors for a range of radionuclides, which subsequently allow the calculation of cumulated absorbed dose to the basal layer of the skin after a contamination event [24,25]. The cumulative skin dose can be expressed as:DT=D×AD()1−e−λeffnormalΔTλeffe−λitaliceffΔTwhere D T represents total cumulated skin dose over an area of 1 cm 2 (mSv), D represents the skin dose rate of a 1 cm 2 contamination, averaged over an area of 1 cm 2 (mSv/h/kBq); A D is the mean measured activity over 1 cm 2 (kBq); λ eff is the effective decay constant (=ln(2)/ T 1/2eff approximated here as standard physical decay only) and Δ T is the total exposure time ( h ).…”