# Wavelia Breast Imaging: The Optical Breast Contour Detection Subsystem
## 1 Introduction
With no access to such level of detail, the annotation of the breast quadrant and clock-position at which an abnormality has been detected with MBI cannot be very accurate, when using the MBI system stand-alone, thus inhibiting the comparison and ultimate validation of the microwave breast imaging modality against conventional reference breast imaging data (X-Ray mammography and Ultrasound breast scan). For the third purpose to be achieved at the maximal possible level with the actual prototype #1 implementation of the Wavelia system, which involves operation of the OBCD and MBI scans on two separate identical examination tables, it is important that the patient lies in the same position for both scans. A standardized position for the arms and the overall body posture of the patient has been established and respected on both scanners during the ongoing first-in-human clinical investigation, such that rigid registration of the two breast surface reconstructions (OBCD and MBI) of each patient's breast is feasible. Two indicative results of OBCD reconstructions of patient breast surfaces, after rigid registration with the MBI scan, are presented in Section 3.4 of the paper. The importance of retrieving the external breast envelope with high accuracy as a priori information for efficient microwave breast imaging has been extensively highlighted by the microwave breast imaging research community so far [8; 9; 10; 11; 12]. The significant added-value of the use of an auxiliary (laser) system to further enhance the maximal achievable accuracy of the estimated breast envelope has been analyzed in [13; 14]. Such a laser system has been incorporated in the TSAR microwave breast imaging system and has been clinically trialed on a small group of patients in Calgary, Canada [13; 14]. For the Wavelia system, an infrared 3D stereoscopic camera has been integrated, after appropriate selection and configuration, to perform optimally in the interior of the Wavelia examination table and for the case of the human skin texture. To the authors' knowledge, this is the first time that such an optical system is incorporated in the setting of clinical breast imaging. The relevant state-of-the-art methods from which the Wavelia OBCD design could have been inspired are the existing 3D Surface Imaging methods, mainly designed for post-surgical and/or aesthetic breast reconstruction. An overview of these methods, the set of commercial devices in which they are used, as well the achievable accuracy of the volume computation can be found in [15; 16; 17; 18]. Due to their application to aesthetic breast reconstruction, most of those systems and methods are designed to image the patient's torso, while at regular standing or sitting position. To the authors' knowledge, other than the MRI and CT scanners, there are no well-known systems and methods for surface reconstruction and volume computation of the pendulum breast (patient lying at prone position). Other particularities of the Wavelia OBCD system, which justify the need for a new, system-tailored development, are:  
* the requirement for integration of the OBCD system in a specific examination table, the layout of which is driven by the architecture of the MBI subsystem; this is the main reason why system-specific algorithms for denoising and extraction of the useful portion of the recorded 3D point clouds are required to be designed;
* the need to operate in an obscure, closed environment, which justifies the specific choice of a stereoscopic 3D camera to scan the breast. The procedure that led to the selection of the specific 3D camera is presented in Appendix A. This paper will focus on the presentation of the Wavelia OBCD subsystem. An overview of the Wavelia system architecture is presented in Section 2.1.