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Discrimination of Malignant Melanoma by Light-Tissue Interaction Model and Optical Properties Extraction using Optical Coherence Tomography”

Turani, Zahra | 2020

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 56750 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Fatemizadeh, Emadeddin; Nasiri Avanaki, Mohammad Reza
  7. Abstract:
  8. The current gold standard for clinical diagnosis of melanoma is excisional biopsy and histopathologic analysis. Approximately 15–30 benign lesions are biopsied to diagnose each melanoma. In addition, biopsies are invasive and result in pain, anxiety, scarring, and disfigurement of patients, which can add additional burden to the health care system. Among several imaging techniques developed to enhance melanoma diagnosis, optical coherence tomography (OCT), with its highresolution and intermediate penetration depth, can potentially provide required diagnostic information noninvasively.
    an image analysis algorithm, "optical radiomic melanoma detection (ORMD)" has been presented which improves the specificity and sensitivity of OCT by identifying unique optical radiomic signatures pertinent to melanoma detection. The propsed method consists of optical propertis extraction (OPE) in which scattering coefficient, absorption coefficient and anisotropy factor are extracted from an OCT image. OPE is based on 3-parameter EHF model which is proposed in this thesis as an extension to 2-parameter EHF model. In 2-parameter EHF model, just scattering evensts are distinguished while in 3-parameter EHF model, absorption coefficient is also considered in the model. It increases the performance of the model for discrimination between melanoma and non-melanoma lesions. Performance of the algorithm is evaluated using several tissue-mimicking phantoms and then the ORMD algorithm has been tested on 69 human subjects. Results show that benign nevi and melanoma can be differentiated with 97% sensitivity and 98% specificity, while these values are 83% and 78%, respectively for dermoscopy method. These results suggest that the adoption of the ORMD algorithm in the clinic can lead to improvements in melanoma diagnosis and patient experience. This study describes a noninvasive, safe, simple-to-implement, and accurate method for differentiation of malignant melanoma versus benign nevi. On the other hand, refractive index is a very important optical parameter which is different in layers of a bulk tissue and considered constant value in ordinary OCT imaging,. A robust method for refractive index correction followed by layer depth correction is also proposed. Using this method, the depth of skin layers were changed more than 15% which shows the effectiveness of this refractive index correction methodology. This method can potentially help find more presice value for Breslow’s depth which shows the severity of the melanoma
  9. Keywords:
  10. Optical Imaging ; Melanoma Cancer ; Refractive Index ; Optical Properties ; Scattering Coefficient ; Absorption Coefficent ; Anisotropy Factor ; Light-Tissue Interaction ; Image Processing ; Malignant Melanoma Cancer ; Optical Tomography ; Extended Huygens Fresnel Model

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