Sentinel Lymph Node Biopsy in High-Risk Cutaneous Squamous Cell Carcinoma: Analysis of a Large Size Retrospective Series.

BACKGROUND: One of the most important prognostic factors for mortality in cutaneous squamous cell carcinoma (cSCC) is the development of nodal metastasis. There is no consensus regarding which patient with cSCC should be offered sentinel lymph node biopsy (SLNB). OBJECTIVE: This study aimed to establish the rate of positive SLNBs among patients with high-risk cSCCs and to identify which high-risk features are associated with a positive SLNB. METHODS: Five-year retrospective case series in an academic tertiary care center reviewing 93 SLNBs. RESULTS: Of the 93 SLNBs performed, 5 (5.4%) were positive. Three patients (3/5) had neck dissection and one (1/5) had radiation therapy, with no recurrence at the time of last follow-up. A tumor diameter ≥2 cm, a tumor depth >6 mm or below subcutaneous fat, perineural invasion of nerves with a diameter ≥0.1 mm, moderate or poor histological differentiation, lymphovascular invasion, and immunosuppression were associated with a positive SLNB. All tumors with a positive SLNB were classified as T2b according to the Brigham and Women's Hospital (BWH) tumor staging. LIMITATIONS: Retrospective study and absence of a control group. CONCLUSION: Sentinel lymph node biopsy can be considered for BWH T2b and T3 tumors. However, more randomized controlled studies are needed.

Intra-Arterial Image Guidance With Optical Frequency Domain Reflectometry Shape Sensing.

Intra-arterial liver cancer therapies, such as trans-arterial chemoembolization, are the preferred therapeutic approaches for advanced hepatocellular carcinoma. However, these palliative techniques are challenging for delivering therapeutic agents selectively in the tumor without real-time 3-D visualization of the catheter within the hepatic arteries. The objective of this paper is to develop and evaluate in pre-clinical tests an advanced interventional guidance platform using a distributed strain sensing device based on optical frequency-domain reflectometry (OFDR) to track the tip and shape of a catheter. The scattering properties of a fiber triplet are enhanced by focusing an ultraviolet beam on these fibers, producing a fully distributed strain sensor, which avoids interpolation errors observed with traditional shape tracking systems. A 3-D roadmap of the hepatic arteries is obtained from a combined fully convolutional and residual networks trained on MR angiography and combined with a 4-D flow dynamic sequence enabling to map blood flow velocities. An anisotropic curvature matching method is proposed to map the sensed data onto pre-operative MR and using 3-D ultrasound to correct for non-rigid deformations. Experiments were conducted in a controlled environment setting as well as in both synthetic phantoms and in five porcine models to assess the performance for device navigation, yielding satisfactory tracking accuracy with 3-D mean errors of 2.8 ± 0.9 mm. We present the first pilot study of MR-compatible UV-exposed OFDR optical fibers for non-ionizing device guidance in intra-arterial procedures, with the potential of avoiding multiple hospitalizations required to perform invasive selective chemoembolizations.

Enhancement of accuracy in shape sensing of surgical needles using optical frequency domain reflectometry in optical fibers.

We demonstrate a novel approach to enhance the precision of surgical needle shape tracking based on distributed strain sensing using optical frequency domain reflectometry (OFDR). The precision enhancement is provided by using optical fibers with high scattering properties. Shape tracking of surgical tools using strain sensing properties of optical fibers has seen increased attention in recent years. Most of the investigations made in this field use fiber Bragg gratings (FBG), which can be used as discrete or quasi-distributed strain sensors. By using a truly distributed sensing approach (OFDR), preliminary results show that the attainable accuracy is comparable to accuracies reported in the literature using FBG sensors for tracking applications (~1mm). We propose a technique that enhanced our accuracy by 47% using UV exposed fibers, which have higher light scattering compared to un-exposed standard single mode fibers. Improving the experimental setup will enhance the accuracy provided by shape tracking using OFDR and will contribute significantly to clinical applications.

Vessel-based registration of an optical shape sensing catheter for MR navigation.

PURPOSE: Magnetic resonance navigation (MRN), achieved with an upgraded MRI scanner, aims to guide therapeutic nanoparticles from their release in the hepatic vascular network to embolize highly vascularized liver tumors. Visualizing the catheter in real-time within the arterial network is important for selective embolization within the MR gantry. To achieve this, a new MR-compatible catheter tracking technology based on optical shape sensing is used. METHODS: This paper proposes a vessel-based registration pipeline to co-align this novel catheter tracking technology to the patient's diagnostic MR angiography (MRA) with 3D roadmapping. The method first extracts the 3D hepatic arteries from a diagnostic MRA based on concurrent deformable models, creating a detailed representation of the patient's internal anatomy. Once the optical shape sensing fibers, inserted in a double-lumen catheter, is guided into the hepatic arteries, the 3D centerline of the catheter is inferred and updated in real-time using strain measurements derived from fiber Bragg gratings sensors. Using both centerlines, a diffeomorphic registration based on a spectral representation of the high-level geometrical primitives is applied. RESULTS: Results show promise in registration accuracy in five phantom models created from stereolithography of patient-specific vascular anatomies, with maximum target registration errors below 2 mm. Furthermore, registration accuracy with the shape sensing tracking technology remains insensitive to the magnetic field of the MR magnet. CONCLUSIONS: This study demonstrates that an accurate registration procedure of a shape sensing catheter with diagnostic imaging is feasible.

Fabrication of ultrafast laser written low-loss waveguides in flexible As2S3 chalcogenide glass tape.

As2S3 glass has a unique combination of optical properties, such as wide transparency in the infrared region and a high nonlinear coefficient. Recently, intense research has been conducted to improve photonic devices using thin materials. In this Letter, highly uniform rectangular single-index and 2 dB/m loss step-index optical tapes have been drawn by the crucible technique. Low-loss (<0.15 dB/cm) single-mode waveguides in chalcogenide glass tapes have been fabricated using femtosecond laser writing. Optical backscatter reflectometry has been used to study the origin of the optical losses. A detailed study of the laser writing process in thin glass is also presented to facilitate a repeatable waveguide inscription recipe.

Toward the integration of optical sensors in smartphone screens using femtosecond laser writing.

We demonstrate a new type of sensor incorporated directly into Corning Gorilla glass, an ultraresistant glass widely used in the screen of popular devices such as smartphones, tablets, and smart watches. Although physical space is limited in portable devices, the screens have been so far neglected in regard to functionalization. Our proof-of-concept shows a new niche for photonics device development, in which the screen becomes an active component integrated into the device. The sensor itself is a near-surface waveguide, sensitive to refractive index changes, enabling the analysis of liquids directly on the screen of a smartphone, without the need for any add-ons, thus opening this part of the device to advanced functionalization. The primary function of the screen is unaffected, since the sensor and waveguide are effectively invisible to the naked eye. We fabricated a waveguide just below the glass surface, directly written without any surface preparation, in which the change in refractive index on the surface-air interface changes the light guidance, thus the transmission of light. This work reports on sensor fabrication, using a femtosecond pulsed laser, and the light-interaction model of the beam propagating at the surface is discussed and compared with experimental measurement for refractive indexes in the range 1.3-1.7. A new and improved model, including input and output reflections due to the effective mode index change, is also proposed and yields a better match with our experimental measurements and also with previous measurements reported in the literature.