Bioluminescence tomography (BLT) has been successfully applied to the detection and therapeutic evaluation of solid cancers. However, the existing BLT reconstruction algorithms are not accurate enough for cavity cancer detection because of neglecting the void problem. Motivated by the ability of the hybrid radiosity-diffusion model (HRDM) in describing the light propagation in cavity organs, an HRDM-based BLT reconstruction algorithm was provided for the specific problem of cavity cancer detection. HRDM has been applied to optical tomography but is limited to simple and regular geometries because of the complexity in coupling the boundary between the scattering and void region. In the provided algorithm, HRDM was first applied to three-dimensional complicated and irregular geometries and then employed as the forward light transport model to describe the bioluminescent light propagation in tissues. Combining HRDM with the sparse reconstruction strategy, the cavity cancer cells labeled with bioluminescent probes can be more accurately reconstructed. Compared with the diffusion equation based reconstruction algorithm, the essentiality and superiority of the HRDM-based algorithm were demonstrated with simulation, phantom and animal studies. An in vivo gastric cancer-bearing nude mouse experiment was conducted, whose results revealed the ability and feasibility of the HRDM-based algorithm in the biomedical application of gastric cancer detection.
As one of molecular imaging, bioluminescence tomography (BLT) aims to recover internal source from surface
measurement. Being an ill-posed inverse problem, BLT source reconstruction is usually converted to an optimization
problem through regularization. In this contribution, we build a bimodal hybrid imaging system consisting of BLT and
micro-CT, and then propose an improved source reconstruction method based on adjoint diffusion equations (ADEs).
Compared with conventional methods based on constrained minimization problem (CMP), ADEs-based method replaces
expensive iterative computation with solving a group of linear ADEs. Given surface flux density, internal source power
density and photon fluence rate can be efficiently determined in one step. Both numerical and physical experiments are
performed to evaluate the bimodal BLT/micro-CT imaging system and this novel reconstruction method. The relevant
results demonstrate the feasibility and potential of this source reconstruction method.
Gastric cancer is the second cause of cancer-related death in the world, and it remains difficult to cure because it has
been in late-stage once that is found. Early gastric cancer detection becomes an effective approach to decrease the gastric
cancer mortality. Bioluminescence tomography (BLT) has been applied to detect early liver cancer and prostate cancer
metastasis. However, the gastric cancer commonly originates from the gastric mucosa and grows outwards. The
bioluminescent light will pass through a non-scattering region constructed by gastric pouch when it transports in tissues.
Thus, the current BLT reconstruction algorithms based on the approximation model of radiative transfer equation are not
optimal to handle this problem. To address the gastric cancer specific problem, this paper presents a novel reconstruction
algorithm that uses a hybrid light transport model to describe the bioluminescent light propagation in tissues. The
radiosity theory integrated with the diffusion equation to form the hybrid light transport model is utilized to describe
light propagation in the non-scattering region. After the finite element discretization, the hybrid light transport model is
converted into a minimization problem which fuses an l1 norm based regularization term to reveal the sparsity of
bioluminescent source distribution. The performance of the reconstruction algorithm is first demonstrated with a digital
mouse based simulation with the reconstruction error less than 1mm. An in situ gastric cancer-bearing nude mouse based
experiment is then conducted. The primary result reveals the ability of the novel BLT reconstruction algorithm in early
gastric cancer detection.
The optical imaging takes advantage of coherent optics and has promoted the development of visualization of biological
application. Based on the temporal coherence, optical coherence tomography can deliver three-dimensional optical
images with superior resolutions, but the axial and lateral scanning is a time-consuming process. Optical scanning
holography (OSH) is a spatial coherence technique which integrates three-dimensional object into a two-dimensional
hologram through a two-dimensional optical scanning raster. The advantages of high lateral resolution and fast image
acquisition offer it a great potential application in three-dimensional optical imaging, but the prerequisite is the accurate
and practical reconstruction algorithm. Conventional method was first adopted to reconstruct sectional images and
obtained fine results, but some drawbacks restricted its practicality. An optimization method based on 2 l norm obtained
more accurate results than that of the conventional methods, but the intrinsic smooth of 2 l norm blurs the reconstruction
results. In this paper, a hard-threshold based sparse inverse imaging algorithm is proposed to improve the sectional image
reconstruction. The proposed method is characterized by hard-threshold based iterating with shrinkage threshold strategy,
which only involves lightweight vector operations and matrix-vector multiplication. The performance of the proposed
method has been validated by real experiment, which demonstrated great improvement on reconstruction accuracy at
appropriate computational cost.
Because of the ability of integrating the strengths of different modalities and providing fully integrated information,
multi-modality molecular imaging techniques provide an excellent solution to detecting and diagnosing earlier cancer,
which remains difficult to achieve by using the existing techniques. In this paper, we present an overview of our research
efforts on the development of the optical imaging-centric multi-modality molecular imaging platform, including the
development of the imaging system, reconstruction algorithms and preclinical biomedical applications. Primary
biomedical results show that the developed optical imaging-centric multi-modality molecular imaging platform may
provide great potential in the preclinical biomedical applications and future clinical translation.
Light-absorbing nanoparticles that are heated by short laser pulses can transiently increase membrane permeability. We evaluate the membrane permeability by flow cytometry assaying of propidium iodide and fluorescein isothiocyanate dextran (FITC-D) using different laser sources. The dependence of the transfection efficiency on laser parameters such as pulse duration, irradiant exposure, and irradiation mode is investigated. For nano- and also picosecond irradiation, we show a parameter range where a reliable membrane permeabilization is achieved for 10-kDa FITC-D. Fluorescent labeled antibodies are able to penetrate living cells that are permeabilized using these parameters. More than 50% of the cells are stained positive for a 150-kDa IgG antibody. These results suggest that the laser-induced permeabilization approach constitutes a promising tool for targeted delivery of larger exogenous molecules into living cells.
Due to their unique optical properties, optical probes, including metal nanoparticles (NPs) and fluorescent dyes, are increasingly used as labeling tools in biological imaging. Using multiphoton microscopy and fluorescence lifetime imaging (FLIM) at 750-nm excitation, we recorded intensity and FLIM images from gold NPs (30 nm) and the fluorescent dye Alexa 488 (A488) conjugated with monoclonal ACT-1 antibodies as well as Hoechst 33258 (H258) after incubation with the lymphoma cell line (Karpas-299). From the FLIM images, we can easily discriminate the imaging difference between cells and optical probes according to their distinct fluorescence lifetimes (cellular autofluorescence: 1 to 2 ns; gold NPs: <0.02 ns; A488: 3.5 ns; H258: 2.5 ns). The NP-ACT-1 and A488-ACT-1 conjugates were bound homogeneously on the surface of cells, whereas H258 stained the cell nucleus. We demonstrate that the emission intensity of gold NPs is about ten times stronger than that of the autofluorescence of Karpas-299 cells at the same excitation power. Compared with fluorescent dyes, stronger emission is also observed from gold NPs. Together with their high photostability, these observations suggest that gold NPs are a viable alternative to fluorescent dyes for cellular imaging and cancer diagnosis.
We describe a new method for delivering macromolecules into the target cells based on light-absorbing cationic colloidal
gold nanoparticles that are irradiated by focused femtosecond laser pulses. Cationic colloidal 15nm gold particles which
were made by conjugation with poly-L-Lysine, were attached on the anionic sites, especially on the membrane, of CHO-K1
cells because of their strong positive charge at physiological pH. Target cells labeled with cationic gold nanoparticles
were imaged under two-photon fluorescence microscopy, and lifetime images of the same targets were taken by TCSPC
technique in order to verify the fluorescence of the marker and the luminescence of the gold particles.
A macromolecular 10k Dalton fluorescein isothiocyanate dextran (FITC-D), was added into the sample and the focused
femtosecond laser of two-photon fluorescence microscopy was employed to scan the target cells layer by layer. Typical
laser power level used in biological imaging is about 3-5 mW. Here the laser power of scanning was below 5 mW in
order to prevent photochemical damage of the fs-pulses alone and to localize effects to the nanoparticles on a nano-scale.
After scanning the target cells under stack mode, macromolecular fluoresceins surrounding the cells was observed to
cross the membrane and to diffuse in the cytoplasma. Comparing with the images before scanning, the two-photon
fluorescence and fluorescence lifetime images revealed the delivery of FITC-D into target cells.
Due to the unique optical properties, gold nanoparticles (NPs) can play a useful role in biological cellular imaging as
biological probes. Using multiphoton microscopy and fluorescence lifetime imaging (FLIM) system, we recorded the
images of Karpas 299 cells incubated without, or with gold NPs, and ACT1 antibodies conjugated with gold NPs. From
the FLIM, we can easily discriminate the difference among different experiment conditions due to the distinct lifetime
between cells and gold NPs. Our results present that nonconjugated gold NPs are accumulated inside cells, but
conjugated gold NPs bind homogeneously and specifically to the surface of cancer cells. For single Karpas 299 cells, the
signal is very week when the excitation power is about 10mw; while the power is approximately 28 mw, a very sharp cell
imaging can be obtained. For the Karpas 299 incubated with ACT1 conjugated gold NPs, while the excitation power is
10mw, gold NPs have clear fluorescence signal so that the profile of cells can be detected; Signal of gold NPs is very
strong when the power arrived in 20mw. These results suggest that the multiphoton lifetime imaging of antibody
conjugated gold NPs can support a useful method in diagnosis of cancer.
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