Several new image-guidance tools and devices are being prototyped, investigated, and compared. These tools are introduced and include prototype software for image registration and fusion, thermal modeling, electromagnetic tracking, semiautomated robotic needle guidance, and multimodality imaging. The integration of treatment planning with computed tomography robot systems or electromagnetic needle-tip tracking allows for seamless, iterative, "see-and-treat," patient-specific tumor ablation. Such automation, navigation, and visualization tools could eventually optimize radiofrequency ablation and other needle-based ablation procedures and decrease variability among operators, thus facilitating the translation of novel image-guided therapies. Much of this new technology is in use or will be available to the interventional radiologist in the near future, and this brief introduction will hopefully encourage research in this emerging area.

Currently, several challenges prevent poly(lactic-co-glycolic acid) (PLGA) particles from reaching clinical settings. Among these is a lack of understanding of the molecular mechanisms involved in the formation of these particles. We have been studying in depth the formation of patchy polymeric particles. These particles are made of PLGA and lipid-polymer functional groups. They have unique patch-core-shell structural features: hollow or solid hydrophobic cores and a patchy surface. Previously, we identified the shear stress as the most important parameter in a patchy particle's formation. Here, we investigated in detail the role of shear stress in the patchy particle's internal and external structure using an integrative experimental and computational approach. By cross-sectioning the multipatch particles, we found lipid-based structures embedded in the entire PLGA matrix, which represents a unique finding in the PLGA field. By developing novel computational fluid dynamics and molecular dynamics simulations, we found that the shear stress determines the internal structure of the patchy particles. Equally important, we discovered that these particles emit a photoacoustic (PA) signal in the optical clinical imaging window. Our results show that particles with multiple patches emit a higher PA signal than single-patch particles. This phenomenon most likely is due to the fact that multipatchy particles absorb more heat than single-patchy particles as shown by differential scanning calorimetry analysis. Furthermore, we demonstrated the use of patchy polymeric particles as photoacoustic molecular probes both in vitro and in vivo studies. The fundamental studies described here will help us to design more effective PLGA carriers for a number of medical applications as well as to accelerate their medical translation.

The objective of this paper is to develop an implicit, monolithic, nite element (FE) scheme for the solution of the incompressible Navier-Stokes (NS) equations. The design of the method is based on the pressure stability properties of an implicit second order in time fractional step (FS) method, which is conditionally stable. The nal monolithic scheme preserves the second order accuracy of the FS method, and it is unconditionally stable (i.e. stable for all timestep sizes). In addition, it is shown that the nal pressure stabilizing term is practically the same fourth order pressure term added by some authors, but following di erent arguments, to obtain high order accurate results. It is also shown that the nal stabilized convective term is a formally second order discretization of the advective operator. Finally, a non-linear numerical switch was designed to lower the discretization order in ow regions where the solution could present o ver or undershoots, which can inhibit the algorithm convergence. Some numerical examples are presented. 1 Introduction Among the schemes developed over the last decade for the solution of the incompressible NS equations (monolithic schemes 16, 1 3 ], projection or fractional step (FS) schemes 8, 1 9 , 3 , 2 2 , 2 5 , 2 0 , 2 1 ], arti cial compressibility (AC) 7, 2 6 , 24, 2 3 , 1 4 , 1 8 ], preconditioning of the compressible NS equations 27, 6, 28], etc,) the FS schemes yields highly accurate pressure-stable results by i n tegrating in an explicit manner the advective terms of the NS