Adaptive finite element method (AFEM) is broadly adopted to recover the internal source in biological tissues. In this letter, a novel dual-mesh alternation strategy (dual-mesh AFEM) is developed for bioluminescence tomography. By comprehensively considering the error estimation of the finite element method solution on each mesh, two different adaptive strategies based on the error indicator of the reconstructed source and the photon flux density are used alternately in the process. Combined with the constantly adjusted permissible region in the adaptive process, the new algorithm can achieve a more accurate source location compared with the AFEM in the previous experiments.

Monte Carlo (MC) method is a statistical method for simulating photon propagation in media in the optical molecular imaging field. However, obtaining an accurate result using the method is quite time-consuming, especially because the boundary of the media is complex. A voxel classification method is proposed to reduce the computation cost. All the voxels generated by dividing the media are classified into three types (outside, boundary, and inside) according to the position of the voxel. The classified information is used to determine the relative position of the photon and the intersection between photon path and media boundary in the MC method. The influencing factors and effectiveness of the proposed method are analyzed and validated by simulation experiments.

The irradiation of cells combined with the immunoconjugate of gold nanoparticles by the short pulse laser can make the plasma membrane be transiently permeabilized, which can be used to transfer exogenous molecules into the cells. We explore this technique as a novel gene transfection method for floating cells. Three different floating cells exposed to the laser are selectively transfected with fluorescein isothiocyanatedextran, antibody, and green fluorescent protein (GFP) coding plasmids, and the viability of cells are determined by propidium iodide. For fluorescein isothiocyanate-dextran, the best transfection efficiency of 65% is obtained; for the antibody, it is 74%; whereas for the green fluorescent protein coding plasmids, a very small transfection efficiency is gained. If the transfection efficiency is improved, gold nanoparticles will be very useful as mediator for gene transfection in living cells.

To avoid the ill-posedness in the inverse problem of bioluminescence tomography, a moment searching algorithm fusing the finite element method (FEM) with the moment concept in theoretical mechanics is developed. In the algorithm, the source's information is mapped to the surface photon flux density by FEM, and the source's position is modified with the feedback through the algorithm of barycenter searching, which makes full use of the position information of the photon flux density on surface. The position is modified in every iterative step and will finally converge to the real source's value theoretically.

Gold nanoparticles (NPs) have highly efficient multi-photon-induced luminescence. In this paper, we record the two-photon images of gold NPs, lymphoma cell line Karpas 299, and Karpas 299 incubated with 30-nm-diameter gold NPs and ACT-1 antibody conjugates (Au30-ACT-1 conjugates) by using a multi-photon microscopy system. Due to the specific conjugation of ACT-1 antibody and cell membrane receptor CD25, gold NPs are only bound to the surface of cell membrane of Karpas 299. The luminescence intensity of gold NPs is higher than that of cells at 750-nm laser excitation. By comparing the images of Karpas 299 cells incubated with and without gold NPs, it is found that by means of gold NPs, we can get clear cell images with lower excitation power. Their excellent optical and chemical properties make gold NPs an attractive contrast agent for cellular imaging.