Radiation-induced effects in polytetrafluoroethylene (PTFE): Dose-response linearity and low-dose skin dosimetry

It is well known that at kGy levels polytetrafluoroethylene (PTFE) is radiation-sensitive, manifesting in changes to material properties, in particular mechanical degradation. Whilst industrial radiation processing focuses on damage thresholds, recent investigations by Bradley et al. have demonstrated quantifiable molecular sensitivity at considerably lower doses, from sub-mGy through to some 10 Gy, including medical radiation levels. Initial studies using Raman spectroscopy revealed dose-dependent alterations in the CF₂ symmetric stretching mode, albeit with non-linear, oscillatory characteristics proving a technique of limited dosimetric utility. Subsequent photoluminescence investigations have shown this medium to exhibit linear dose-response arising from defect-induced emission. Review is made of the molecular mechanisms, specifically bond scission and polyene formation, with dose-response observed in both vibrational (Raman/FTIR) and photoluminescence (PL) spectra, linear in the latter case. Evidence points to the dominance of the C–F group over the backbone C–C as the primary metric for low-dose sensitivity. The 75 μm tape thickness, near tissue-equivalence (Z_eff ≈ 7.7), low cost, and demonstrated sensitivity to alpha particles position PL-interrogated PTFE as a promising candidate for the specific unmet need of passive skin dosimetry at the ICRU-recommended 70 μm reference depth.