Fast time-domain diffuse correlation spectroscopy with superconducting nanowire single-photon detector: system validation and in vivo results.

Time-domain diffuse correlation spectroscopy (TD-DCS) has been introduced as an advancement of the "classical" continuous wave DCS (CW-DCS) allowing one to not only to measure depth-resolved blood flow index (BFI) but also to extract optical properties of the measured medium without using any additional diffuse optics technique. However, this method is a photon-starved technique, specially when considering only the late photons that are of primary interest which has limited its in vivo application. In this work, we present a TD-DCS system based on a superconducting nanowire single-photon detector (SNSPD) with a high quantum efficiency, a narrow timing response, and a negligibly low dark count noise. We compared it to the typically used single-photon avalanche diode (SPAD) detector. In addition, this system allowed us to conduct fast in vivo measurements and obtain gated pulsatile BFI on the adult human forehead.

Interstitial null-distance time-domain diffuse optical spectroscopy using a superconducting nanowire detector.

Significance: Interstitial fiber-based spectroscopy is gaining interest for real-time in vivo optical biopsies, endoscopic interventions, and local monitoring of therapy. Different from other photonics approaches, time-domain diffuse optical spectroscopy (TD-DOS) can probe the tissue at a few cm distance from the fiber tip and disentangle absorption from the scattering properties. Nevertheless, the signal detected at a short distance from the source is strongly dominated by the photons arriving early at the detector, thus hampering the possibility of resolving late photons, which are rich in information about depth and absorption. Aim: To fully benefit from the null-distance approach, a detector with an extremely high dynamic range is required to effectively collect the late photons; the goal of our paper is to test its feasibility to perform TD-DOS measurements at null source-detector separations (NSDS). Approach: In particular, we demonstrate the use of a superconducting nanowire single photon detector (SNSPD) to perform TD-DOS at almost NSDS ( ≈ 150 µ m ) by exploiting the high dynamic range and temporal resolution of the SNSPD to extract late arriving, deep-traveling photons from the burst of early photons. Results: This approach was demonstrated both on Monte Carlo simulations and on phantom measurements, achieving an accuracy in the retrieval of the water spectrum of better than 15%, spanning almost two decades of absorption change in the 700- to 1100-nm range. Additionally, we show that, for interstitial measurements at null source-detector distance, the scattering coefficient has a negligible effect on late photons, easing the retrieval of the absorption coefficient. Conclusions: Utilizing the SNSPD, broadband TD-DOS measurements were performed to successfully retrieve the absorption spectra of the liquid phantoms. Although the SNSPD has certain drawbacks for use in a clinical system, it is an emerging field with research progressing rapidly, and this makes the SNSPD a viable option and a good solution for future research in needle guided time-domain interstitial fiber spectroscopy.

Plastic Surgery Training across Seven Continents: Results from the First Global Trainee Survey.

Little is known about the demographics and ambitions of plastic surgery trainees and if these differ between regions. This study sought opinion from current and recently graduated plastic surgery trainees to map demographics, training structure, and ambitions of plastic surgery trainees worldwide. Methods: A cross-sectional study was designed and administered by the international trainee organization International Confederation of Societies of Plastic Surgery Trainees. A questionnaire of 45 questions was distributed digitally through several international channels using the REDCap platform. Results: A total of 290 junior plastic surgeons, of whom 124 (42.8%) were women, from all seven International Confederation of Societies of Plastic Surgery regions, participated in this study. Of the trainees, 21% have emigrated, and 75% expressed a desire to undertake a part of their training abroad. The most common length of training in plastic surgery is 5 years. There is a difference in working hours between regions, where more than 80-hour work weeks are most common in Asia (24.1%), and work weeks of less than 40 hours are most common in Middle East (30.8%). A majority of trainees (85%) reported a research interest, and we found a negative correlation between the extent of research ambition and reported clinical workload. Conclusions: We present here the first international investigation of trainee experiences of plastic surgery training. We show that training structure and organization vary between institutions, and that plastic surgery trainees report a strong interest in international training as well as in research.

Whole specimen intraoperative frozen section analysis. Experience with 1082 basal cell carcinomas.

BACKGROUND: Basal cell carcinomas (BCCs) excised leaving positive tumour margins, are at a higher risk of recurrence. Accordingly, complete tumour removal with preservation of healthy tissue, aiming for low recurrence rates, is the main goal in treating BCCs. OBJECTIVE: The present study aimed to identify the reliability of the Whole Specimen Intraoperative Frozen Section Analysis (WIFSA) technique by comparing intraoperative WIFSA and postoperative Formalin-Fixed Paraffin-Embedded section analysis (FFPE) results in 1082 basal cell carcinomas and by assessing the recurrence rates during a follow-up period up to 10 years. METHODS: A single-centre retrospective cohort of all patients with BCC of the face receiving surgical excision with the WIFSA method between January 2007 and December 2013 was evaluated. We compared the intraoperative frozen section results with postoperative FFPE in order to assess accuracy of the WIFSA. Recurrence rates were assessed among all BCCs with a tumour-free margin at final excision that had a minimum follow-up of 6 months. RESULTS: A total of 996 patients with 1082 BCCs were treated with the WIFSA. Overall agreement of WIFSA with conventional postoperative FFPE was 98·8%, sensitivity and specificity being 99·0% and 98·7% respectively. We excluded 23 BCCs that still had positive tumour margins at the end of the procedure and another 67 for the analysis of recurrence rate because follow-up was shorter than 6 months. A total of 992 BCCs with a tumour-free margin at final excision had a mean follow-up of 5·6 years (mean 67 ± 27·7 months (range 6-117 months)). The total recurrence rate was 2·1% (21 out of 992 BCCs). The recurrence rate among the primary tumours was 1·6% (13 out of 828 cases) and 4·9% among the recurring tumours (8 out of 164 cases). CONCLUSION: This study indicates that, in patients with primary or recurring BCCs, WIFSA provides a high accuracy for intraoperative specimen analysis and has a low recurrence rate after a mean follow-up of 5·6 years. FUNDING: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Origami lattices with free-form surface ornaments.

Lattice structures are used in the design of metamaterials to achieve unusual physical, mechanical, or biological properties. The properties of such metamaterials result from the topology of the lattice structures, which are usually three-dimensionally (3D) printed. To incorporate advanced functionalities into metamaterials, the surface of the lattice structures may need to be ornamented with functionality-inducing features, such as nanopatterns or electronic devices. Given our limited access to the internal surfaces of lattice structures, free-form ornamentation is currently impossible. We present lattice structures that are folded from initially flat states and show that they could bear arbitrarily complex surface ornaments at different scales. We identify three categories of space-filling polyhedra as the basic unit cells of the cellular structures and, for each of those, propose a folding pattern. We also demonstrate "sequential self-folding" of flat constructs to 3D lattices. Furthermore, we folded auxetic mechanical metamaterials from flat sheets and measured the deformation-driven change in their negative Poisson's ratio. Finally, we show how free-form 3D ornaments could be applied on the surface of flat sheets with nanometer resolution. Together, these folding patterns and experimental techniques present a unique platform for the fabrication of metamaterials with unprecedented combination of physical properties and surface-driven functionalities.

Incomplete Reossification After Craniosynostosis Surgery.

A patient with unicoronal craniosynostosis was treated by an open cranial vault remodeling procedure at 11 months of age. A calvarial defect persists at the site of the sagittal suture at 7 years follow-up. This unexpected outcome led us to evaluate current literature on incidence and possible causes of incomplete reossification after craniosynostosis surgery.English literature was searched from 1982 to 2013. Variables of interest were incidence, diagnose, type of surgery, age at operation, possible causes for incomplete reossification, and duration and type of follow-up.Incidence in unselected cohorts ranged from 0.5% to 18.2%. Incomplete reossification has been reported in syndromical and nonsyndromical cases, after multiple types of surgery for any type of suture. Follow-up was done by palpation, radiology or both, for a period of 6 to 264 months.Higher age at operation and a dura tear are associated with an increased risk of incomplete reossification.Type and duration of follow-up is inhomogeneous and there is a wide variety in the terminology used for incomplete reossification.To improve international communication on this topic, more long-term studies, using a consistent type and length of follow-up and uniform terminology are needed.