ABSTRACT
Psoriasis is one of the most common skin disorders. The disease appears as red scaling plaques that can spread on any body part [1]. In psoriasis, the immune system sends incorrect signals that speed up the growth of new skin cells. Psoriasis affects about 2%–3% of the world’s population [2, 3]. The Dermatological Society of Malaysia estimates the prevalence of psoriasis in Malaysia to be 3% [4]. Since the disease cannot be totally cured, a psoriasis patient needs continuous and long-term treatment. The Psoriasis Area and Severity Index (PASI) scoring method is the gold standard for severity
CONTENTS
3.1 Introduction .................................................................................................. 87 3.2 PASI Area Assessment ................................................................................88 3.3 Development of the PASI Area Assessment Method ............................. 94
3.3.1 Image Acquisition of 2D Body Surface Images ........................... 94 3.3.2 Area Segmentation of Psoriasis Lesions from 2D Body
Surface Images ................................................................................. 96 3.3.3 Correcting for Overlapped Areas in BSA Measurement ......... 101 3.3.4 Validation of Overlapping Areas in BSA Measurement .......... 106 3.3.5 Validation on a Medical Mannequin .......................................... 109 3.3.6 Fuzzy c-Means Clustering for PASI Area Classication .......... 111
3.4 Results and Analysis ................................................................................. 112 3.4.1 ROI Segmentation in the PASI Area Algorithm ........................ 112 3.4.2 Lesion Segmentation in the PASI Area Algorithm ................... 114 3.4.3 Lesion Area Classication for PASI Area Scoring..................... 114 3.4.4 Evaluation on PASI Area Agreement .......................................... 116
3.5 Conclusion .................................................................................................. 117 Appendix: Matlab Code ..................................................................................... 118 References ............................................................................................................. 121
assessment and in determining treatment efcacy [5]. Four parametersarea (ratio of lesion area to total body surface area), erythema, scaliness, and thickness-are examined to determine the PASI score. The parameter scores from each body region (head, trunk, upper limbs, and lower limbs) are weighted and totaled to provide a PASI score ranging from 0 to 72.
