## 1 Introduction  
Cancer is still one of the top diseases which causes death in the world [1]. In the past few decades, there has been apparent fast growth in the incidence rate of oesophageal cancer [2, 3, 4]. Due to its aggressive nature and poor survival rate [5], an early diagnosis of oesophageal cancer is important and could contribute to the treatment. The clinical diagnosis golden standard for oesophageal cancer is gastroscopy. The diagnosis and staging of oesophageal cancer can be verified with histopathological results from a target biopsy [6]. In the field of staging of oesophageal cancer, computed tomography (CT), endoscopic ultrasound (EUS) and endosymography are involved as well. Some studies reported that staging oesophageal cancer by using EUS and enosonography should be reconsidereddue to its low diagnostic accuracy [7; 8]. Histopathology analysis is time consuming; in addition, the outcome of the histopathology analysis is highly dependent on the examiner's consistency, for example, the pathologist's experience [9; 10; 11]. From a biological perspective, carcinoma causes pathological change to the tissue, not only the biological properties, but also the tissue's physical properties. In practical diagnosis, clinicians perform a general diagnosis methodology which includes palpation where the tumours can be differentiated from the healthy tissue based on the elasticity properties. For example, breast cancer and prostate cancer tissue show different elastic properties from normal tissue, which can be considered a biomarker for cancer diagnosis [12; 13]. An understanding of the quantitative mechanical characteristics of tissues constituting the human oesophagus wall is necessary to investigate its behaviour as well as the conditions of failure. It will contribute to the disease diagnosis and to developing the biomaterial for replacement, when needed.  
As a high-resolution, non-invasive technique, OCT is capable of providing a cross-section micro-structure image of tissue by measuring back-scattered light energy intensity [14]. The reflected light power intensity is subjected to the optical properties of tissue [15; 16]. The optical properties of the tissue could be applied to the characterisation and differentiation of the histopathological change of soft tissue [17; 18]. By combining external stimulation devices, OCT is integrated into OCE, in which the quantitative mechanical properties can be estimated. Our research group raised the vibrational OCE by combining OCT with an external vibration stimulator in 2013 [19]. Vibrational OCE has shown promising results in soft-tissue elastic property characterisation [20; 21]. Across the types of OCE methods, the resolution of vibrational OCE is higher than the SAW-OCE and SW-OCE [22]. The vibrational OCE has been reported to be used in detecting and characterising cancerous tissue, such as suspected prostate cancer [23; 24]. Thus, OCT and vibrational OCE could be applied to investigate both structural and elastic properties of human cadaver oesophageal tissue.  
In this research project, a Phase-sensitive OCT (PhS-OCT) with ultra-high resolution [25] and integrated vibrational OCE were applied to explore the layers' structure and elastic properties of human cadaver oesophageal tissue. This is the first study which quantitatively evaluates both the optical properties and elastic properties of human Thiel-embalmed cadavers, as well as the structural information, by employing OCT/OCE. This study reveals the feasibility of OCT and OCE in investigating both optical and elastic properties of human cadaver oesophageal tissue which could potentially contribute to the clinical diagnosis of oesophageal disease.