# Wavelia Breast Imaging: The Optical Breast Contour Detection Subsystem
## 1 Introduction  
Wavelia is a prototype medical device which has recently been developed by MVG Industries. The purpose of Wavelia is to offer an alternative and/or complementary imaging modality to X-ray mammography for breast cancer diagnosis. As it involves microwave technology, so non-ionizing radiation, it may allow for diagnosis and follow-up of rapidly evolving pathologies by making it possible to safely schedule regular 3D scans of the breast as often as required [1, 2]. Given the incorporated radar detection technology [3], this novel imaging modality is also meant to provide the clinicians with a useful tool for automated Computer-Aided Diagnosis (CAD). The hardware modules integrated in Wavelia are partly inherited from the technical background and expertise of the company in antenna measurement systems [4, 5]. A detailed presentation of the actual R&D status of the system has been reported in [3]. Wavelia is now installed at Galway University Hospital, Ireland, for a first-in-human clinical investigation which started running in the last quarter of 2018. Prior to the initiation of the clinical investigation, on-site validation [3] has been performed using breast phantoms [6]. The pilot study holds full approval by the Local Ethics Committee, and the Health Products Regulatory Authority (HPRA), in Dublin, Ireland. Details on the clinical protocol of the pilot study can be found in the ClinicalTrials.gov repository to which the trial has been registered with identifier NCT03475992 [7]. The Wavelia prototype medical device consists of two subsystems, both performing a non-invasive examination: the Microwave Breast Imaging (MBI) subsystem, which is the main part of the system and the Optical Breast Contour Detection (OBCD) subsystem, which plays an auxiliary role. The MBI subsystem illuminates the breast with low-power electromagnetic waves in the microwave frequency range, which penetrate the breast under examination. The subsystem collects the scattered electromagnetic waves and recovers useful information on the breast tissue consistency, given the dielectric contrast of these tissues; this information can be represented as 3D volumetric. The OBCD subsystem performs an azimuthal scan of the breast using a 3D infrared stereoscopic camera. The objective of the OBCD subsystem is triple [3]:  
* compute the volume of the patient's breast, thus indirectly deriving the required volume of transition liquid such that the container of the MBI subsystem is optimally filled after immersion of the breast;
* compute the distance (vertical extent) from the lowest point of the pendulums breast to the lower plane of the examination table, in order to optimally define the vertical scan positions for the MBI scan of each breast; the number of vertical scan positions and thus the time duration of the MBI scan will vary accordingly to the size of each breast;
* reconstruct the external envelope of the breast, with millimetric precision; such information will further serve to quantify the level of deformation of the breast due to immersion in the transition liquid during the microwave imaging scan, as introduced in [8]; in the case of breasts minimally deformed when immersed in the transition liquid (younger patients with breasts not very large), the OBCD-reconstructed breast surface, after registration with the MBI scan, is also meant to improve the localization of the abnormalities detected with MBI in the breast, by means of revealing the exact orientation of the pendulums breast under scan, as well as details such as the nipple location, which cannot be defined using the MBI-derived reconstruction of the breast surface alone, due to its centimetric level of spatial resolution.