Radial-Biased Tracking Method to Assess Tissue Displacement in Intravascular Ultrasound Sequences: A Phantom Framework Evaluation.

OBJECTIVES: We created and evaluated a pixel-tracking method capable of accurately identify the displacement of tissue in intravascular ultrasound (IVUS) images. METHODS: Our proposed pixel-tracking method assessed the horizontal and vertical displacement of tissue from a numerical phantom of IVUS sequences. The proposed tracking method is based on a block-matching framework, comparing 2 distinct frames within a selected region by normalized cross-correlation. Our method, specialized for IVUS applications, reduced the tracking area by implementing a limiting radius and a radial bias during the search. RESULTS: The method was evaluated by using 54 numerical phantom image sequences from 9 distinct arterial models, resulting in different arteries with atherosclerotic plaques under a range of pressures. The ground truth reference coordinates of the tracked tissue were extracted from each numerical phantom sequence. Our results were compared to 8 other methods present in the literature. The mean absolute tracking errors ± SD for our method were 15.56 ± 19.46 and 13.04 ± 13.82 µm for the horizontal and vertical directions, respectively, between 2 subsequent frames, and 162.58 ± 305.93 and 102.22 ± 130.61 µm from lower to higher pressures in the range of 6 frames (n = 42,036). CONCLUSIONS: Our application-specific pixel-tracking method showed promising results and no statistically significant tracking error (P = .954), comparable to state-of-the-art methods present in the literature. Application-specific tracking methods have advantages over general methods by turning tissue-specific behavior into a directional bias in the tracking algorithm.

Rotary jet-spun porous microfibers as scaffolds for stem cells delivery to central nervous system injury.

Stem cell transplantation is a promising strategy to treat brain injuries. However, cell-based therapies are limited because poor local cell engraftment. Here, we present a polylactic acid (PLA) scaffold to support mesenchymal stem cells (MSCs) delivery in stroke. We isolated bone marrow MSCs from adult C57/Bl6 mice, cultured them on PLA polymeric rough microfibrous (PRM) scaffolds obtained by rotary jet spinning, and transplanted over the brains of adult C57/Bl6 mice, carrying thermocoagulation-induced cortical stroke. No inflammatory response to PRM was found. MSCs transplantation significantly reduced the area of the lesion and PRM delivery increased MSCs retention at the injury site. In addition, PRM upregulated α6-integrin and CXCL12 production, which may be the cause for greater cell retention at the lesion site and may provide additional benefit to MSCs transplantation procedures. We conclude that PRM scaffolds offer a promising new system to deliver stem cells to injured areas of the brain.

Bioactivity behaviour of nano-hydroxyapatite/freestanding aligned carbon nanotube oxide composite.

Bioactive and low cytotoxic three dimensional nano-hydroxyapatite (nHAp) and aligned carbon nanotube oxide (a-CNTO) composite has been investigated. First, freestanding aligned carbon nanotubes porous scaffold was prepared by large-scale thermal chemical vapour deposition and functionalized by oxygen plasma treatment, forming a-CNTO. The a-CNTO was covered with plate-like nHAp crystals prepared by in situ electrodeposition techniques, forming nHAp/a-CNTO composite. After that nHAp/a-CNTO composite was immersed in simulated body fluid for composite consolidation. This novel nanobiomaterial promotes mesenchymal stem cell adhesion with the active formation of membrane projections, cell monolayer formation and high cell viability.

Fast preparation of free-standing nanohydroxyapatite-vertically aligned carbon nanotube scaffolds.

We present a simple, low cost, and fast method to produce free-standing nanohydroxyapatite/carbon-based scaffolds. We electrodeposited nanohydroxyapatite onto vertically aligned carbon nanotube flakes and reticulated vitreous carbon bars. We prepared a highly crystalline and homogeneous thin film without any post-thermal treatment, and our results evidence that we can control the nanohydroxyapatite crystal formation according to the substrate employed. Immersion tests using simulated body fluid showed that these new nanobiomaterials had in vitro bioactivity. The free-standing nanohydroxyapatite/carbon-based scaffolds have been shown to be a suitable surface for mesenchymal stem cell adhesion with active formation of membrane projections and cell monolayer formation.