Signature of a three-dimensional photonic band gap observed on silicon inverse woodpile photonic crystals

We have studied the reflectivity of CMOS-compatible three-dimensional silicon inverse woodpile photonic crystals at near-infrared frequencies. Polarization-resolved reflectivity spectra were obtained from two orthogonal crystal surfaces corresponding to 1.88 pi sr solid angle. The spectra reveal broad peaks with high reflectivity up to 67 % that are independent of the spatial position on the crystals. The spectrally overlapping reflectivity peaks for all directions and polarizations form the signature of a broad photonic band gap with a relative bandwidth up to 16 %. This signature is supported with stopgaps in plane wave bandstructure calculations and with the frequency region of the expected band gap.Comment: 9 pages, 5 figure

Volumetric ultrasound image reconstruction from a single-element forward-looking intracardiac steerable catheter using 3D adaptive normalized convolution

In interventional cardiology catheters are routinely used to access and treat defects and diseases in the heart. Image guidance using forward-looking (FL)ultrasound transducers at the tip of the catheter could give the physician visual feedback during complex procedures such as valve replacement or transseptal puncture. In this work, we investigate FL 3D imaging by integrating a 7 MHz single-element ultrasound transducer at the tip of a novel multi-steerable intracardiac catheter together with an optical shape sensing fiber (OSS). We tested the imaging capability of the integrated device on an ex-vivo pig heart. By acquiring ultrasound A-lines at different locations while steering the catheter tip, a sparse 3D image is obtained. To reconstruct a volumetric image from the sparse data we implemented an adaptive Normalized Convolution (NC)algorithm were the dimension, orientation and angle of the 3D anisotropic kernel changes dynamically according to the scanning path. We acquired ultrasound A-lines of the tricuspid valve and we computed the 3D image using NC with both an isotropic kernel and an anisotropic kernel. We successfully interpolated the sparse data obtaining 3D volumes of the heart. By using an anisotropic kernel better 3D reconstruction is achieved with higher detail information compared to the reconstruction obtained using an isotropic kernel. This pilot experiment demonstrates the potential of FL image guidance during intracardiac procedures using a single-element transducer integrated in a steerable catheter with an OSS fiber

3D Imaging with a single-element forward-looking steerable IVUS catheter: Initial testing

In the field of vascular interventions, forward-looking intravascular ultrasound transducers (FL-IVUS) are needed for better visualization of complex lesions, such as chronic total occlusions. In this work, we propose a strategy for 3D imaging using a single-element transducer and an optical shape sensing fiber (OSS) in a steerable catheter tip. We evaluate the performance of the integrated device by imaging a six-wire phantom submerged in water. While steering the catheter tip across the wires, ultrasound and OSS data are acquired continuously. We combine the distance information obtained from the ultrasound data with the tip position and direction obtained from the OSS data to reconstruct the wires in 3D space. We quantify the accuracy of the imaging technique by the distance between the wires, and find a mean relative error of 36%. We discuss how this estimate can be further improved by modifications of the probe. This proof-of-principle test demonstrates the feasibility of FL-IVUS imaging using a single-element transducer integrated in a steerable catheter together with an OSS fiber