## 1 Introduction  
Skin cancer arises from the skin due to the development of abnormal cells in the tissue. These cells invade or spread to other regions of the skin or to other human organs. There are three major types of skin cancers. Cutaneous melanoma (CM) is considered the most dangerous among all forms of human skin cancers. On the other hand, nodular basal cell carcinoma (NBCC) and squamous cell carcinoma (SCC) are grouped together as non-melanoma skin cancers. Melanoma and carcinoma are two different types of cancer. They originate from the melanocytes and epithelial tissue, respectively [1; 2]. Skin cancers can be effectively treated if they are detected early. However, they can be fatal if left untreated, thus it is important to develop methods for an early optical detection of skin abnormalities. One of the most applicable methods is to subject human skin to an ultrafast-laser pulse to analyze the temporal variation. The obtained modifications of the optical properties and conditions lead an early detection of skin cancer. Thus, ultrafast-laser propagation through scattering and participating media has received significant attention in literature, principally due to its importance to several biomedical diagnoses [1]. Some studies of the bio-heat transfer phenomenon are expensive and can become dangerous to living body under testing, especially in cases where an ultrafast laser is used. Further, during irradiation of the tissue by laser, diverse types of interaction may occur, among which thermal effects have a large presence. To study the effects of radiation on biomedical tissues, it is necessary to use the transient radiative transfer equation (TRTE) [2]. A detailed understanding and analysis of bio-heat transfer is required to design a new method that can ensure accurate solutions. Recently, several numerical techniques have been used to model laser light transport in participating media. The Monte Carlo method [3; 4; 5], integral equation (IE) formulation [6] and discrete ordinates method [7; 8; 9] have been used to solve the TRTE. In the past few decades, the finite volume method (FVM) has become as one of the most attractive methods for solving radiation transport [10; 11; 12; 13; 14; 15; 16; 17; 18; 19]. It has been formulated, tested and applied in several steady and transient radiative transfer problems. However, the standard FVM form suffers from ray effects and false scattering due to the angular and spatial discretization of the TRTE, respectively [10; 11; 12; 13; 14; 15; 16; 17; 18; 19]. High-order spatial differencing schemes such as minimal model (MINMOD), Curved-Line Advection Method (CLAM), Monotone Upstream-centered Scheme for Conservation Laws (MUSCL) and sharp and Monotonic Algorithm for Realistic Transport (SMART) may be able to decrease numerical smearing and increase TRTE solution accuracy [9; 14]. On the other hand, several schemes have recently been proposed to decrease ray effects, including the combined Monte Carlo and finite volume method (MCFVM) [17] and the angular-multiblock procedure [18]. The new non-uniform angular discretization scheme is called the FTn FVM [10; 11; 12; 13; 14; 19], and three-dimensional FTn FVM results have shown a decrease in ray effects and an increase in TRTE solution accuracy. [PERSON] et al. [12] recently analyzed the effects of a short-pulse laser on normal skin and malignant human skin. In that study, human skin was modeled as one-dimensional tissue; however, in the present work, a three-dimensional human skin is considered. Additionally, [PERSON] et al. [12] applied the modified discrete ordinate method, whereas in this study a high-order spatial differencing scheme (the CLAM) and the FTn angular scheme of the finite volume method have been combined to study ultrafast-laser transport through normal and malignant human skins. All these improvements have been introduced to reduce numerical smearing and ray effect errors while increasing the solution accuracy of the numerical model.