Quantitative evaluation of efficacy of photodynamic therapy for port-wine stains using erythema index image analysis

SummaryBackgroundMethods for quantitatively evaluate the efficacy of photodynamic therapy (PDT) for port-wine stains (PWS) are still needed for clinical practice and studies.Methods50 pairs of pictures before and after PDT of 40 PWS patients were selected. Each PWS lesion was labeled with a marker of red color graded 0–9. These pictures were taken without assistance of instruments to keep same position or distance and were referred to as ‘experimental’ images. 70 labels were photographed at a fixed position and distance with the assistance of a bracket and the images obtained were referred to as ‘standardized’ ones. An independent group of three experts viewed the photos and assessed the efficacy. The images were processed and measured for erythema index (EI) with the ImageJ freeware. The EI difference (ΔEI) and the percent change of ΔEI (ratioΔEI(%)) of the labels and the PWS lesions was computed separately.ResultsSignificant differences of EI, ΔEI and ratioΔEI(%) were found between each two grades of the color markers in both standardized and experimental images. ΔEI of lesions achieved ‘almost cured’ and ‘great improvement’ after PDT was significantly reduced than before PDT. Significantly greater percentages of lesions were assessed as ‘response’ and ‘significant response’ in those of beforeΔEI ≥ 35 compared to those of beforeΔEI < 35. The ratioΔEI(%) decrease of lesions assessed as ‘almost cured’, ‘great improvement’ and ‘some improvement’ was significantly reduced sequentially.ConclusionThe EI image analysis is a valid method for quantitatively evaluating efficacy of PDT for PWS.