Nanoparticle-based technologies offer exciting new approaches to disease diagnostics and therapeutics. To take advantage of unique properties of nanoscale materials and structures, the size, shape and/or surface chemistry of nanoparticles need to be optimized, allowing their functionalities to be tailored for different biomedical applications. Here we review the effects of nanoparticle size on cellular interaction and in vivo pharmacokinetics, including cellular uptake, biodistribution and circulation half-life of nanoparticles. Important features of nanoparticle probes for molecular imaging and modeling of nanoparticle size effects are also discussed.

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patients (15 catheters in total). The shift of the catheters related to the clips is visualized in Figure 1, sorted by the day of the additional CT scan. Only shifts within the CTV are considered. On the second day, the maximum shift was 5 mm, while the shifts were much larger on the third and fourth day. On 6 occasions we decided to make a new plan: once due to 200% isodose bridges, four times due to large shifts of the catheters, and once due to both. Conclusions: Position verification of the catheters was found to be necessary to achieve sufficient quality control. The decision was therefore made to extend the length of active dwell positions in the original plan by 4 mm at both sides, in order to compensate for shifts of the catheters on the second day. As a consequence, we decided to omit the second day CT evaluation as we are convinced that the treatment can safely be continued. However, on the third day, a CT scan has to be performed followed by a new plan if necessary. This procedure is now a regular part of each treatment.