A 3-D-Printed Tactile Probe Based on Fiber Bragg Grating Sensors for Noninvasive Breast Cancer Identification

Abstract

Tissue palpation is one of the most popular techniques to detect tissue abnormalities in clinical scenarios, including breast examination. However, the tactile sensation used to identify tumors by the clinician or a woman during breast palpation makes this procedure subjective. Over the past decades, tactile sensors have been developed o to quantitatively discriminate between cancerous and healthy tissues, but most of these systems still suffer from low force sensitivity, high power consumption, reduced sterilization durability, and electrical noise.This study aims at overcoming these limitations by exploiting the advantages of fiber Bragg grating (FBG) technology combined with the ones of 3D printing to develop an innovative tactile probe for breast cancer identification. FBGs have already been proposed for tissue palpation in minimally invasive surgery via tactile sensing, while their application in superficial palpation is still overlooked. To the best of our knowledge, this is the first work in which the FBG integration into 3D printed structures is proposed for breast superficial palpation. Here, we first focused on the sensing unit design optimization via finite element analysis, fabrication, and metrological characterization. Then, the final prototype of the tactile probe integrating multiple identical sensing units was fabricated, and the results of tests on silicone samples with different hardness and on a phantom mimicking breast tissue with an early-stage tumor were discussed. The promising findings will guide further optimization of the tactile probe design to improve system spatial resolution, reduce its encumbrance and provide feedback to the user for applications on patients.

Design Optimization and Characterization of a 3-D-Printed Tactile Sensor for Tissue Palpation

“…Hence, this study proposed the optimization of the structural design of the FBG-based sensing core of the tactile probe in [32] to undergo tension under F. It means that the enclosed FBG is expected to experience a positive DlB with F [33], [34]. Fig.…”

“…The structural design optimization of the sensor core in [32] was guided by a FEM analysis. To better describe the model, we introduce the coordinate system {𝑂, 𝑥, 𝑦, 𝑧}, positioned at the lowermost plane on the vertical symmetry axis (the 𝑧 axis) as shown in Fig.…”

“…To optimize the response of the sensor in [32], we proposed a change in the value of the fillet radius (𝑅 %'(()* ) of the central column [32]. In fact, results in [32] underlined how the absence of a fillet (𝑅 %'(()* = 0) induced a non-negligible effect of the central column sustaining the contact head of the tactile probe consisting in a local clamping action on the horizontal span of the U-shape under F (see Fig. 2).…”

“…To date, only a few 3D-printed sensors based on FBG technology have been used in clinical applications, including tissue palpation, but most still glue the optical fiber to the printed structures to guarantee a secure optical fiber alignment during its embedment [19], [28]- [31]. To the best of our knowledge, we were the first to develop a tactile probe for soft tissue (i.e., breast) palpation that combines FBG in 3Dprinting technology without using glue at the interface between the optical fiber and the printed layer [32]. The structural design of this previous attempt is a U-shaped beam with a vertical body named "central column" and a semispherical contact head placed above for indenting the soft tissue and localizing the mechanical response in the central part of the beam where the FBG is located.…”

“…The present study aims at proposing an optimization of the design of the sensing core of the tactile probe developed in [32] guided by a finite element model (FEM) to allow the proposed structure to experience 1D strain distribution with higher positive values where the FBG is located. This causes sensor elongation under external F with a reduction in the risk of breakage.…”