Understanding the Effect of Electron Beam Melting Scanning Strategies on the Aluminum Content and Materials State of Single Ti-6Al-4V Feedstock.

Research on the additive manufacturing of metals often neglects any characterization of the composition of final parts, erroneously assuming a compositional homogeneity that matches the feedstock material. Here, the composition of electron-beam-melted Ti-6Al-4V produced through three distinct scanning strategies (linear raster and two point melting strategies, random fill and Dehoff fill) is characterized both locally and globally through energy-dispersive spectroscopy and quantitative chemical analysis. As a result of the different scanning strategies used, differing levels of preferential vaporization occur across the various parts, leading to distinct final compositions, with extremes of ~5.8 wt.% Al and ~4.8 wt.% Al. In addition, energy-dispersive spectroscopy composition maps reveal specific features in both the XY and XZ planes (with Z being the build direction) as a result of local inhomogeneous preferential vaporization. The subsequent change in composition significantly modifies the materials' state of parts, wherein parts and local regions with higher aluminum contents lead to higher hardness levels (with a ~50 HV difference) and elastic property values and vice versa. While varying scan strategies and scan parameters are known to modify the microstructure and properties of a part, the effect on composition cannot, and should not, be neglected.

The value of sentinel lymph-node biopsy in women with node-positive breast cancer at diagnosis and node-negative tumour after neoadjuvant therapy: a systematic review.

PURPOSE: To conduct a systematic review to analyse the performance of the sentinel lymph-node biopsy (SLNB) in women with node-positive breast cancer at diagnosis and node-negative tumour after neoadjuvant therapy, compared to axillary lymph-node dissection. METHODS: The more relevant databases were searched. Main outcomes were false-negative rate (FNR), sentinel lymph-node identification rate (SLNIR), negative predictive value (NPV), and accuracy. We conducted meta-analyses when appropriate. RESULTS: Twenty studies were included. The pooled FNR was 0.14 (95% CI 0.11-0.17), the pooled SLNIR was 0.89 (95% CI 0.86-0.92), NPV was 0.83 (95% CI 0.79-0.87), and summary accuracy was 0.92 (95% CI 0.90-0.94). SLNB performed better when more than one node was removed and double mapping was used. CONCLUSIONS: SLNB can be performed in women with a node-negative tumour after neoadjuvant therapy. It has a better performance when used with previous marking of the affected node and with double tracer.