Comparison of Blue and White Lamp Light with Sunlight for Daylight‐Mediated, 5‐ALA Photodynamic Therapy, in vivo

Abstract

Daylight-mediated photodynamic therapy (d-PDT) as a treatment for actinic keratosis (AK) is an increasingly common technique due to a significant reduction in pain, leading to better patient tolerability. While past studies have looked at different light sources and delivery methods, this study strives to provide equivalent PpIX-weighted light doses with the hypothesis that artificial light sources could be equally as effective as natural sunlight if their PpIX-weighted fluences were equalized. Normal mouse skin was used as the model to compare blue LED light, metal halide white light and natural sunlight, with minimal incubation time between topical ALA application and the onset of light delivery. A total PpIX-weighted fluence of 20 J cm was delivered over 2 h, and the efficacy of response was quantified using three acute bioassays for PDT damage: PpIX photobleaching, Stat3 crosslinking and quantitative histopathology. These bioassays indicated blue light was slightly inferior to both sunlight and white light, but that the latter two were not significantly different. The results suggest that metal halide white light could be a reasonable alternative to daylight PDT, which should allow a more controlled treatment that is independent of weather and yet should have similar response rates with limited pain during treatment.

Weather‐informed Light–tissue Model–Based Dose Planning for Indoor Daylight Photodynamic Therapy

“…Most investigations of daylight PDT report light dose as the effective fluence, which is the fluence weighted by the PpIX absorption spectrum (4,6,14,(16)(17)(18). So, even though the total irradiance of indoor daylight is 75% of its outdoor counterpart, the PpIX-weighted effective irradiance indoors is 60% of the outdoor complement because more UV light is blocked by the window (Fig.…”

Measuring Daylight: A Review of Dosimetry in Daylight Photodynamic Therapy

“…Different PpIX absorption spectra exist, and these vary depending on the method by which they are measured. As shown by Marra et al, using different PpIX absorption spectra in calculations on the same spectral irradiance can lead to different PpIX-effective doses [26]. Therefore, it is important to maintain traceability of both the light source and PpIX absorption spectra used in dose assessment.…”

Theoretical evaluation of the light distribution and PDT dose for a multi-wavelength light source

“…35 Some of the advantages are optimization in the time because several people could be treated simultaneously, a greater area of light exposure and a significant reduction of pain during PDT. 36 Despite these advantages, exist an important consideration for an effective PDT, the threshold dose. 37 On the assumption that the dominant mechanism in the PDT is type II, 25 it will exist a threshold of singlet oxygen.…”

“…(2018). 36 In this case, the light sources were blue LED, white lamp and sunlight. The 5-ALA and normal mouse skin were used.…”

“…This light dose can be estimated by multiplication of the normalized spectrum of PpIX with emitted spectrum of the light source, with units (J ef f .cm −2 ). 36,40 These values were located in the last column in of Table 8. Source: By the author.…”