Jianghong Zhong

Whole-Body Cerenkov Luminescence Tomography with the Finite Element SP 3 Method

Generation of an accurate Cerenkov luminescence imaging model is a current issue of nuclear tomography with optical techniques. The article takes a pro-active approach toward whole-body Cerenkov luminescence tomography. The finite element framework employs the equation of radiative transfer via the third-order simplified spherical harmonics approximation to model Cerenkov photon propagation in a small animal. After this forward model is performed on a digital mouse with optical property heterogeneity and compared with the Monte Carlo method, we investigated the whole body reconstruction algorithm along a regularization path via coordinate descent. The endpoint of the follow-up study is the in vivo application, which provides three-dimensional biodistribution of the radiotracer uptake in the mouse from measured partial boundary currents. The combination of the forward and inverse model with elastic-net penalties is not only validated by numerical simulation, but it also effectively demonstrates in vivo imaging in small animals. Our exact reconstruction method enables optical molecular imaging to best utilize Cerenkov radiation emission from the decay of medical isotopes in tissues.

Cerenkov luminescence tomography for in vivo radiopharmaceutical imaging

Cerenkov luminescence imaging (CLI) is a cost-effective molecular imaging tool for biomedical applications of radiotracers. The introduction of Cerenkov luminescence tomography (CLT) relative to planar CLI can be compared to the development of X-ray CT based on radiography. With CLT, quantitative and localized analysis of a radiopharmaceutical distribution becomes feasible. In this contribution, a feasibility study of in vivo radiopharmaceutical imaging in heterogeneous medium is presented. Coupled with a multimodal in vivo imaging system, this CLT reconstruction method allows precise anatomical registration of the positron probe in heterogeneous tissues and facilitates the more widespread application of radiotracers. Source distribution inside the small animal is obtained from CLT reconstruction. The experimental results demonstrated that CLT can be employed as an available in vivo tomographic imaging of charged particle emitters in a heterogeneous medium.

A trust region method in adaptive finite element framework for bioluminescence tomography

Bioluminescence tomography (BLT) is an effective molecular imaging (MI) modality. Because of the ill-posedness, the inverse problem of BLT is still open. We present a trust region method (TRM) for BLT source reconstruction. The TRM is applied in the source reconstruction procedure of BLT for the first time. The results of both numerical simulations and the experiments of cube phantom and nude mouse draw us to the conclusion that based on the adaptive finite element (AFE) framework, the TRM works in the source reconstruction procedure of BLT. To make our conclusion more reliable, we also compare the performance of the TRM and that of the famous Tikhonov regularization method after only one step of mesh refinement of the AFE framework. The conclusion is that the TRM can get faster and better results after only one mesh refinement step of AFE framework than the Tikhonov regularization method when handling large scale data. In the TRM, all the parameters are fixed, while in the Tikhonov method the regularization parameter needs to be well selected.

Fast-specific tomography imaging via Cerenkov emission.

PurposeDevelopment of more tumor-specific radiopharmaceuticals is not enough; to understand the disease, we must study data modeling. Although fluoro-18-deoxyglucose positron emission tomography can map a multi-peak distribution of trace radioisotopes, optical tomography should also be able to redirect the distribution.ProceduresMulti-view image acquisition of small animals injected with 2-deoxy-2-[18F]fluoro-d-glucose began with X-ray computed tomography scanning and Cerenkov luminescence imaging. After fusion processing, utilization of the geometric row scaling and L1/2 regularization operator effectively generates in vivo Cerenkov luminescence tomography images with the SP3 forward model.ResultsThe identification is confirmed by the comparison between tumor-specific tomography from Cerenkov emission and the radioactivity measured in vitro.ConclusionThe proposed technique can quickly localize the mobility of radionuclides and uptake by organs, which provides an imaging methodology in oncology.

Comparison of permissible source region and multispectral data using efficient bioluminescence tomography method

As a novel molecular imaging technology, bioluminescence tomography (BLT) has become an important tool for biomedical research in recent years, which can perform a quantitative reconstruction of an internal light source distribution with the scattered and transmitted bioluminescent signals measured on the external surface of a small animal. However, BLT is severely ill-posed because of complex photon propagation in the biological tissue and limited boundary measured data with noise. Therefore, sufficient a priori knowledge should be fused for the uniqueness and stability of BLT solution. Permissible source region strategy and spectrally resolved measurements are two kinds of a priori knowledge commonly used in BLT reconstruction. This paper compares their performance with simulation and in vivo heterogeneous mouse experiments. In order to improve the efficiency of large-scale source restoration, this paper introduces an efficient iterative shrinkage thresholding method that not only has faster convergence rate but also has better reconstruction accuracy than the modified Newton-type optimization approach. Finally, a discussion of these two kinds of a priori knowledge is given based on the comparison results.

L 1 -regularized Cerenkov luminescence tomography with a SP 3 method and CT fusion

Imaging modality of radionuclides has been enriched by an optical approach, Cerenkov luminescence tomography (CLT). Referred to the traditional radionuclide imaging, such as positron emission tomography (PET) or single photon emission computed tomography (SPECT), any incremental improvement of CLT imaging is consistent with the application to information needs. In this contribution, the paper presents an l1-regularized imaging method for CLT problem. After utilizing the Vavilov-Cerenkov effect via third-order simplified spherical harmonics (SP3) approximation, we establish the large-scale linear equations in the CLT framework. The derived linear problem is seriously ill-posed, and transformed into an l1-regularized least squares program. The inverse solution to these equations is the three-dimensional radioisotope recovery data by an interior-point method. In the physical phantom and the in vivo mouse experiment, results demonstrate that the proposed technique produces better imaging quality and improves the reconstruction efficacy, compared with those from diffusion approximation with the Tikhonov regularization.

Recent Advances in Cerenkov Luminescence and Tomography Imaging

Molecular imaging can provide qualitative or quantitative physiological and pathological knowledge at the cellular and molecular levels for biomedical research, which has experienced a remarkable growth in recent years. Among molecular imaging techniques, optical molecular imaging has attracted considerable attention in view of its excellent performance and high cost-effectiveness. However, heretofore the experimental objects of optical imaging technique are mainly small animals like rats and mice, and optical imaging can hardly be used for clinical research not only because of the limited tissue penetration, but also due to the scarcity of appropriate imaging probes. As a newly emerging and very promising imaging modality, Cerenkov luminescence employs light signals emitting from radionuclides used in nuclear imaging based on Cerenkov radiation, which can provide more potential optical imaging probes for clinical application and facilitate the realization of multimodality imaging. In this paper, the fundamentals of Cerenkov luminescence are first introduced, and then Cerenkov luminescence imaging and tomography as well as the corresponding biomedical applications are represented. Finally, limitations of Cerenkov luminescence and the discussion of this contribution are covered.

Forward model of Cerenkov luminescence tomography with the third-order simplified spherical harmonics approximation

Applying Cerenkov luminescence tomography (CLT) to localizing Cerenkov light sources in situ is still in its nascent stage. One of the obstacles hindering the development of the CLT is the lack of dedicated imaging mode. In this contribution, the paper presented a Cerenkov optical imaging mode, in which the propagation of optical photons inside tissues generated by the Vavilov-Cerenkov effect is modeled based on simplified spherical harmonics approximation. As a significantly more transport-like and computational-efficient approximation theory, the performance of the third-order simplified spherical harmonics approximation (SP3) in the CLT forward is investigated in stages. Finally, the performance of the proposed forward model is validated using numerical phantoms and compared with the simulation data based on the Monte Carlo method.

Global solution of the finite element shape-from-shading model with a bioluminescent molecular imaging application

Only a planar bioluminescence image acquired from an ordinary cooled charge-coupled device (CCD) array every time, how to re-establish the three-dimensional small animal shape and light intensity distribution on the surface has become urgent to be solved as a bottleneck of bioluminescence tomography (BLT) reconstruction. In this paper, a finite element algorithm to solve the Dirichlet type problem for the first order Hamilton-Jacobi equation related to the shape-fromshading model is adopted. The algorithm outputting the globally maximal solution of the above problem avoids cumbersome boundary conditions on the interfaces between light and shadows and the use of additional information on the surface. The results of the optimization method are satisfied. It demonstrates the feasibility and potential of the finite element shape-fromshading (FE-SFS) model for reconstructing the small animal surface that lays one of key foundations for a fast low-cost application of the BLT in the next future.

New in vivo optical molecular imaging modalities

Recent advances in optical molecular imaging technology have led to great improvements in image resolution, and are increasingly being applied to non-invasively delineate in vivo physiological and pathological processes at cellular and molecular levels. It provides the potential for the understanding of integrative biology, earlier detection and characterization of disease and the evaluation of treatment. This paper focuses on the typical in vivo optical molecular imaging modalities as well as their potential clinical applications and future development.