Focusing through dynamic tissue with millisecond digital optical phase conjugation

Digital optical phase conjugation (DOPC) is a new technique employed in wavefront shaping and phase conjugation for focusing light through or within scattering media such as biological tissues. DOPC is particularly attractive as it intrinsically achieves a high fluence reflectivity in comparison to nonlinear optical approaches. However, the slow refresh rate of liquid crystal spatial light modulators and limitations imposed by computer data transfer speeds have thus far made it difficult for DOPC to achieve a playback latency of shorter than ∼200  ms and, therefore, prevented DOPC from being practically applied to thick living samples. In this paper, we report a novel DOPC system that is capable of 5.3 ms playback latency. This speed improvement of almost 2 orders of magnitude is achieved by using a digital micromirror device, field programmable gate array (FPGA) processing, and a single-shot binary phase retrieval technique. With this system, we are able to focus through 2.3 mm living mouse skin with blood flowing through it (decorrelation time ∼30  ms) and demonstrate that the focus can be maintained indefinitely—an important technological milestone that has not been previously reported, to the best of our knowledge

The Mutual Beneficial Effect between Medical Imaging and Nanomedicine

The reports on medical imaging and nanomedicine are getting more and more prevalent. Many nanoparticles entering into the body act as contrast agents, or probes in medical imaging, which are parts of nanomedicines. The application extent and the quality of imaging have been improved by nanotechnique. On one hand, nanomedicines advance the sensitivity and specificity of molecular imaging. On the other hand, the biodistribution of nanomedicine can also be studied in vivo by medical imaging, which is necessary in the toxicological research. The toxicity of nanomedicine is a concern which may slow down the application of nanomedical. The quantitative description of the kinetic process is significant. Based on metabolic study on radioactivity tracer, a scheme of pharmacokinetic research of nanomedicine is proposed. In this review, we will discuss the potential advantage of medical imaging in toxicology of nanomedicine, as well as the advancement of medical imaging prompted by nanomedicine

The Transport and Deposition of Nanoparticles in Respiratory System by Inhalation

The inhaled nanoparticles have attracted more and more attention, since they are more easily to enter the deep part of respiratory system. Some nanoparticles were reported to cause pulmonary inflammation. The toxicity of nanoparticles depends not only on its chemical component but also on the quantity and position of the deposition. The deposition of nanoparticles is not uniform and is influenced by airflow transport. The high deposition mainly occurs at the carinal ridges and the inside walls around the carinal ridges. Many factors could affect the transport and deposition of nanoparticles, such as particle size, flow rate, structure of airway, pulmonary function, and age. In this review, we discussed the methods and technique involved in particle transport and deposition studies. The features of particles deposition could be observed in clinic experiments and animal experiments. The mechanism of transport could be studied by numerical simulation. Numerical model and experiment study supplement each other. Some techniques such as medical imaging may support the study of nanoparticles transport and deposition. The knowledge of particles transport and deposition may be helpful both to defend the toxicity of inhaled particles and to direct inhaled drug delivery

High-performance fluorescence molecular tomography through shape-based reconstruction using spherical harmonics parameterization.

Fluorescence molecular tomography in the near-infrared region is becoming a powerful modality for mapping the three-dimensional quantitative distributions of fluorochromes in live small animals. However, wider application of fluorescence molecular tomography still requires more accurate and stable reconstruction tools. We propose a shape-based reconstruction method that uses spherical harmonics parameterization, where fluorophores are assumed to be distributed as piecewise constants inside disjointed subdomains and the remaining background. The inverse problem is then formulated as a constrained nonlinear least-squares problem with respect to shape parameters, which decreases ill-posedness because of the significantly reduced number of unknowns. Since different shape parameters contribute differently to the boundary measurements, a two-step and modified block coordinate descent optimization algorithm is introduced to stabilize the reconstruction. We first evaluated our method using numerical simulations under various conditions for the noise level and fluorescent background; it showed significant superiority over conventional voxel-based methods in terms of the spatial resolution, reconstruction accuracy with regard to the morphology and intensity, and robustness against the initial estimated distribution. In our phantom experiment, our method again showed better spatial resolution and more accurate intensity reconstruction. Finally, the results of an in vivo experiment demonstrated its applicability to the imaging of mice

Reconstruction results of different noise levels.

<p>The red circle denotes the boundary of the imaged object, and the white lines denote the boundaries of the real inclusions. The slice images are of 3.0 cm height.</p

Simulation experiment sketch.

<p>A full-angle CCD camera–based imaging system configuration was used for the data simulation. The imaged object was a cylinder phantom with two embedded cylinder heterogeneities (different absorption coefficients). For each projection, five different excitation sources were scanned (red dots), and the detectors, which corresponded to selected detection points on the image plane, were within 1.8 cm of the detector horizontal FOV (HFOV) and 2.2 cm of the detector vertical FOV (VFOV) with a detector spacing of 0.2 cm.</p

Visualization 1: Focusing through dynamic tissue with millisecond digital optical phase conjugation

Movie: continuous conjugate foci. Originally published in Optica on 20 August 2015 (optica-2-8-728

Reconstruction results of different fluorescence contrasts.

<p>The red circle denotes the boundary of the imaged object, and the white lines denote the boundaries of the real inclusions. The slice images are of 3.0 cm height.</p