Thermographic analysis of a porcine gel doped with the photosensitizer PpIX: A dosimetric study for Photodynamic Therapy

Photodynamic therapy (PDT) is an emerging cancer treatment in which a specific wavelength (laser) is used to activate a molecule that is sensitive to light (photosensitizer) and damages cancer cells. Prior to treating a patient with PDT, a reliable dosimetric verification method is required, since the success of the treatment depends on the accurate delivery of the photodynamic dose. The present study evaluates the response of a possible dosimeter based on porcine gel with dispersion properties (intralipid emulsion to mimic human skin) doped with the photosensitizer PpIX (absorbent property) under different radiation doses of a 635 nm laser (PpIX excitation). The porcine gel was synthesized both with and without PpIX. To determine the effect of the radiation dose on both porcine gels, the dose enhancement factor was quantified. For this, IR thermography measurements were taken on doped and non-doped gels. The radiation-induced temperature (ΔT) changes of the PpIX-loaded gel samples compared to the control samples (without PpIX) after red laser irradiation at different doses (15, 30, 45, 60, and 100 J/cm²) showed a significant dose enhancement that was greater than unity, except for 45 J/cm². Our findings show that porcine gels respond to a range of radiation doses that include the standard dose (37 J/cm²) used for skin treatments, making them attractive for use as dosimeters that are capable of being read by a thermal imaging camera.