Modelling fluorescence in clinical photodynamic therapy

Abstract

Understanding the interactions of non-ionizing radiation with living organisms has been the focus of much research over recent decades. The complex nature of these interactions warrants development of theoretical and experimental studies to gain an insight into predicting and monitoring the success of photodynamic therapy (PDT) protocols. There is a major impetus towards evidence-based recommendations for patient diagnosis, treatment and management. Knowledge of the biophysical aspects of PDT is important for improving dosimetry protocols. Fluorescence in clinical PDT may be used to detect and diagnose pre-malignant and malignant conditions, while photobleaching can monitor changes in fluorescence during treatment. Combining empirical fluorescence photobleaching clinical data with computational modelling enables clinical PDT dosimetry protocols to be investigated with a view to optimising treatment regimes. We will discuss how Monte Carlo radiation transfer (MCRT) modelling has been intercalated in the field of fluorescence detection and PDT. In this paper we highlight important aspects of basic research in PDT by reporting on the current utilisation of fluorescence in clinical PDT from both a clinical and theoretical perspective. Understanding and knowledge of light propagation in biological tissue from these perspectives should have a positive impact on treatment planning.

Development of a handheld fluorescence imaging device to investigate the characteristics of protoporphyrin IX fluorescence in healthy and diseased skin

“…Our unit has previously used an optical biopsy system (OBS) consisting of a 405 nm diode laser and fibre-coupled spectrometer to give measurements of the fluorescence spectrum of PpIX at one point on the skin. This system was used to study the photobleaching of PpIX fluorescence decay during treatment and reverse Monte Carlo modelling was used to learn about the PpIX distribution in skin 17,18,19 . Other groups have developed optical probes for quantitative measurement of real PpIX concentration and used it for studying the biosynthesis of PpIX from ALA precursor 16 .…”

New Approaches to Photodynamic Therapy from Types I, II and III to Type IV Using One or More Photons

“…Ideally clinical dosimetry protocols should be combined with computational modelling (e.g. Monte Carlo modelling) to predict the efficacy of PDT and optimise the treatment parameters based on PS fluorescence and singlet oxygen generation detection [130]. The development of precise PDT dosimetry is a major challenge because of the variety of parameters involved, but has the potential to become a useful tool in the development of patient customized treatments and the optimization of existing protocols.…”

3D Monte Carlo radiation transfer modelling of photodynamic therapy

“…The same 600 µm diameterer fiber probe is used for delivery of the excitation radiation and collection of the fluorescence signal. 13 The experimental set up was simulated using the MCRT code with appropriate optical properties and dimensions. A cube with the dimensions 10 mm × 10 mm × 10 mm was simulated to represent the 10 mm × 10 mm cuvette used in the lab.…”