Low-dose 90Y PET/CT imaging optimized for lesion detectability and quantitative accuracy: a phantom study to assess the feasibility of pretherapy imaging to plan the therapeutic dose.

OBJECTIVE: The overall aim of this work is to optimize the reconstruction parameters for low-dose yttrium-90 (Y) PET/CT imaging, and to determine Y minimum detectable activity, in an endeavor to investigate the feasibility of performing low-dose Y imaging in-vivo to plan the therapeutic dose in radioembolization. MATERIALS AND METHODS: This study was carried out using a Siemens Biograph 6 True Point PET/CT scanner. A Jaszczak phantom containing five hot syringes was imaged serially over 15 days. For 128 reconstruction parameters/algorithms, detectability performance and quantitative accuracy were evaluated using the contrast-to-noise ratio and the recovery coefficient, respectively. RESULTS: For activity concentrations greater than 2.5 MBq/ml, the linearity of the scanner was confirmed while the corresponding relative error was below 10%. Reconstructions with smaller numbers of iterations and smoother filters led to higher detectability performance, irrespective of the activity concentration and lesion size. In this study, the minimum detectable activity was found to be 3.28±10% MBq/ml using the optimized reconstruction parameters. Although the recovered activities were generally underestimated, for lesions with activity concentration greater than 4 MBq/ml, the amount of underestimation is limited to -15% for optimized reconstructions. CONCLUSION: Y PET/CT imaging, even with a low activity concentration, is feasible for depicting the distribution of Y implanted microspheres using optimized reconstruction parameters. As such, in-vivo PET/CT imaging of low-dose Y in the pretherapeutic stage may be feasible and fruitful to optimally plan the therapeutic activity delivered to patients undergoing radioembolization.

Dispersibility of vapor phase oxygen and nitrogen functionalized multi-walled carbon nanotubes in various organic solvents.

The synthesis and characterization of gas phase oxygen- and nitrogen-functionalized multi-walled carbon nanotubes (OMWCNTs and NMWCNTs) and the dispersibility of these tubes in organic solvents were investigated. Recently, carbon nanotubes have shown supreme capacity to effectively enhance the efficiency of organic solar cells (OSCs). A critical challenge is to individualize tubes from their bundles in order to provide homogenous nano-domains in the active layer of OSCs. OMWCNTs and NMWCNTs were synthesized via HNO3 vapor and NH3 treatments, respectively. Surface functional groups and the structure of the tubes were analyzed by temperature-programmed desorption, Fourier transform infrared spectroscopy, transmission electron microscopy, and Raman spectroscopy which confirmed the formation of functional groups on the tube surface and the enhancement of surface defects. Elemental analysis demonstrated that the oxygen and nitrogen content increased with increasing treatment time of the multi-walled carbon nanotube (MWCNT) in HNO3 vapor. According to ultra-violet visible spectroscopy, modification of the MWCNT increased the extinction coefficients of the tubes owing to enhanced compatibility of the functionalized tubes with organic matrices.

Bio-functionalization of multi-walled carbon nanotubes.

Here we present a hybrid approach to functionalize multi-walled carbon nanotubes in aqueous solution, exploring a non-covalent binding strategy. We focus on formation of hybrid complexes consisting of carbon nanotubes decorated by single stranded DNA, non-covalently attached using surfactants as intermediate layers. Unlike single walled carbon nanotubes, revealing easy side wall wrapping of DNA, we observe that wrapping of nucleic acids around multi-walled carbon nanotubes is diameter dependent.