arXiv subjects

Hicham Saylani

Publications and source records attributed to Hicham Saylani.

3 recordsLinked to original sources

arXiv2025

New methods to improve the decontamination of slitless spectra

This paper proposes four new methods to decontaminate spectra of stars and galaxies resulting from slitless spectroscopy used in many space missions such as Euclid. These methods are based on two distinct approaches and simultaneously take into account multiple dispersion directions of light. The first approach, called the local instantaneous approach, is based on an approximate linear instantaneous model. The second approach, called the local convolutive approach, is based on a more realistic convolutive model that allows simultaneous decontamination and deconvolution of spectra. For each approach, a mixing model was developed that links the observed data to the source spectra. This was done either in the spatial domain for the local instantaneous approach or in the Fourier domain for the local convolutive approach. Four methods were then developed to decontaminate these spectra from the mixtures, exploiting the direct images provided by photometers. Test results obtained using realistic, noisy, Euclid-like data confirmed the effectiveness of the proposed methods.

astro-ph.IM↗

arXiv2023

A new approach for identifying skin diseases from dermatological RGB images using source separation

In this article, we propose a new BSS approach for identifying skin diseases from RGB images that proceeds in two steps. We begin by separating the three main chromophores (oxyhemoglobin, deoxyhemoglobin and melanin) using Non-negative Matrix Factorization (NMF). For this purpose, we propose a special initialization of the solution matrices based on the sparsity of the chromophores, instead of initializing them with random matrices as is the case for basic versions of NMF. We then propose a new disease identification criterion that exploits the three contributions of each chromophore on the three spectral bands of our RGB dermatological image. To validate our approach, we used an open access database containing RGB images of melanoma and neavus. The results obtained showed good performance for our approach in terms of chromophore separation, compared to the most commonly used method in the literature, as well as disease identification compared to identification based on the most popular criterion.

physics.med-ph↗

arXiv2023

Identification of melanoma diseases from multispectral dermatological images using a novel BSS approach

In this paper we propose a new approach to identify melanoma diseases by identifying the distribution of its main skin chromophores (melanin, oxyhemoglobin and deoxyhemoglobin) from multispectral dermatological images. Based on Blind Source Separation (BSS), our approach takes into account the shading present in most of the images. Assuming that the multispectral images have at least 4 spectral bands, it allows to estimate the distribution of each chromophore in addition to the shading without any a priori information, contrary to all existing methods that use 3 bands, i.e. RGB images. Indeed, the fact of neglecting the shading degrades their performance. To validate our method, we used a database of real multispectral dermatological images of skin affected by melanoma cancer. To measure our performance, in addition to the classical criterion of visually analyzing the estimated distributions with referring to the physiological knowledge of the disease, we proposed a new criterion that is based on our independence hypothesis. Using these two criteria, we could see that our approach is very efficient for the identification of melanoma.

physics.med-ph↗