A dynamic model for ALA-PDT of skin: simulation of temporal and spatial distributions of ground-state oxygen, photosensitizer and singlet oxygen
Why this work is in the frame
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Bibliographic record
Abstract
Singlet oxygen (¹O₂) direct dosimetry and photosensitizer fluorescence photobleaching are being investigated and applied as dosimetric tools during 5-aminolevulinic acid (ALA)-induced protophorphyrin IX (PpIX) photodynamic therapy (PDT) of normal skin and skin cancers. The correlations of photosensitizer fluorescence and singlet oxygen luminescence (SOL) emission signals to ¹O2 distribution and cumulative ¹O₂dose are difficult to interpret because of the temporal and spatial variations of three essential components (light fluence rate, photosensitizer concentration and oxygen concentration) in PDT. A one-dimensional model is proposed in this paper to simulate the dynamic process of ALA-PDT of normal human skin in order to investigate the time-resolved evolution of PpIX, ground-state oxygen (³O₂and ¹O₂ distributions. The model incorporates a simplified three-layer semi-infinite skin tissue, Monte Carlo simulations of excitation light fluence and both PpIX fluorescence and SOL emission signals reaching the skin surface, ¹O₂-mediated photobleaching mechanism for updating PpIX, ³O₂ and ¹O₂ distributions after the delivery of each light dose increment, ground-state oxygen supply by diffusion from the atmosphere and perfusion from blood vessels, a cumulative ¹O₂-dependent threshold vascular response, and the initial non-uniform distribution of PpIX. The PpIX fluorescence simulated using this model is compared with clinical data reported by Cottrell et al (2008 Clin. Cancer Res. 14 4475-83) for a range of irradiances (10-150 mW cm⁻²). Except for the vascular response, one set of parameters is used to fit data at all irradiances. The time-resolved depth-dependent distributions of PpIX, ³O₂ and ¹O₂ at representative irradiances are presented and discussed in this paper, as well as the PDT-induced vascular response at different depths. Tissue hypoxia and shutdown of oxygen supply occur in the upper dermis, where PpIX is also preserved at the end of treatment.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it