Multimodal Optical Diagnostics of Glycated Biological Tissues.

Diabetes mellitus is a metabolic disorder characterized by chronic hyperglycemia accompanied by the disruption of carbohydrate, lipid, and proteins metabolism and development of long-term microvascular, macrovascular, and neuropathic changes. This review presents the results of spectroscopic studies on the glycation of tissues and cell proteins in organisms with naturally developing and model diabetes and in vitro glycated samples in a wide range of electromagnetic waves, from visible light to terahertz radiation. Experiments on the refractometric measurements of glycated and oxygenated hemoglobin in broad wavelength and temperature ranges using digital holographic microscopy and diffraction tomography are discussed, as well as possible application of these methods in the diabetes diagnostics. It is shown that the development and implementation of multimodal approaches based on a combination of phase diagnostics with other methods is another promising direction in the diabetes diagnostics. The possibilities of using optical clearing agents for monitoring the diffusion of substances in the glycated tissues and blood flow dynamics in the pancreas of animals with induced diabetes have also been analyzed.

Shape-from-focus for real-time terahertz 3D imaging.

Thanks to significant advances in real-time terahertz imaging in terms of resolution and image quality, adapting and extending optical methods for 3D imaging at the millimeter scale is now promising. The shape-from-focus algorithm is a post-processing tool used in optical microscopy to reconstruct the external shape surface of a convex surface object. Images acquired at different distances from the object-side focal plane are implemented in this algorithm. We localize the best focus position in the stack of images for each pixel and then reconstruct the object in 3D due to the short depth of field. In this Letter, we propose an application of this algorithm in active and real-time terahertz imaging. We achieve the experimental reconstruction in 3D with a terahertz waves imaging system composed of a powerful source and a real-time terahertz camera.

Liquid index matching for 2D and 3D terahertz imaging.

Two-dimensional (2D) terahertz imaging and 3D visualization suffer from severe artifacts since an important part of the terahertz beam is reflected, diffracted, and refracted at each interface. These phenomena are due to refractive index mismatch and reflection in the case of non-orthogonal incidence. This paper proposes an experimental procedure that reduces these deleterious optical refraction effects for a cylinder and a prism made with polyethylene material. We inserted these samples in a low absorption liquid medium to match the sample index. We then replaced the surrounding air with a liquid with an optimized refractive index, with respect to the samples being studied. Using this approach we could more accurately recover the original sample shape by time-of-flight tomography.

Terahertz imaging and tomography as efficient instruments for testing polymer additive manufacturing objects.

Additive manufacturing (AM) technology is not only used to make 3D objects but also for rapid prototyping. In industry and laboratories, quality controls for these objects are necessary though difficult to implement compared to classical methods of fabrication because the layer-by-layer printing allows for very complex object manufacturing that is unachievable with standard tools. Furthermore, AM can induce unknown or unexpected defects. Consequently, we demonstrate terahertz (THz) imaging as an innovative method for 2D inspection of polymer materials. Moreover, THz tomography may be considered as an alternative to x-ray tomography and cheaper 3D imaging for routine control. This paper proposes an experimental study of 3D polymer objects obtained by additive manufacturing techniques. This approach allows us to characterize defects and to control dimensions by volumetric measurements on 3D data reconstructed by tomography.

Low-frequency noise effect on terahertz tomography using thermal detectors.

In this paper, the impact of low-frequency noise on terahertz-computed tomography (THz-CT) is analyzed for several measurement configurations and pyroelectric detectors. We acquire real noise data from a continuous millimeter-wave tomographic scanner in order to figure out its impact on reconstructed images. Second, noise characteristics are quantified according to two distinct acquisition methods by (i) extrapolating from experimental acquisitions a sinogram for different noise backgrounds and (ii) reconstructing the corresponding spatial distributions in a slice using a CT reconstruction algorithm. Then we describe the low-frequency noise fingerprint and its influence on reconstructed images. Thanks to the observations, we demonstrate that some experimental choices can dramatically affect the 3D rendering of reconstructions. Thus, we propose some experimental methodologies optimizing the resulting quality and accuracy of the 3D reconstructions, with respect to the low-frequency noise characteristics observed during acquisitions.

Ordered subsets convex algorithm for 3D terahertz transmission tomography.

We investigate in this paper a new reconstruction method in order to perform 3D Terahertz (THz) tomography using a continuous wave acquisition setup in transmission mode. This method is based on the Maximum Likelihood for TRansmission tomography (ML-TR) first developed for X-ray imaging. We optimize the Ordered Subsets Convex (OSC) implementation of the ML-TR by including the Gaussian propagation model of THz waves and take into account the intensity distributions of both blank calibration scan and dark-field measured on THz detectors. THz ML-TR reconstruction quality and accuracy are discussed and compared to other tomographic reconstructions.

Propagation beam consideration for 3D THz computed tomography.

In this paper, a model of the beam propagation is developed according to the physical properties of THz waves used in THz computed tomography (CT) scan imaging. This model is first included in an acquisition simulator to observe and estimate the impact of the Gaussian beam intensity profile on the projection sets. Second, the model is introduced in several inversion methods as a convolution filter to perform efficient tomographic reconstructions of simulated and real acquired objects. Results obtained with three reconstruction methods (BFP, SART and OSEM) are compared to the techniques proposed in this paper. We will demonstrate an increase of the overall quality and accuracy of the 3D reconstructions.

Linear to radial polarization conversion in the THz domain using a passive system.

This paper addresses a passive system capable of converting a linearly polarized THz beam into a radially polarized one. This is obtained by extending to THz frequencies and waveguides an already proven concept based on mode selection in optical fibers. The approach is validated at 0.1 THz owing to the realization of a prototype involving a circular waveguide and two tapers that exhibits a radially polarized beam at its output. By a simple homothetic size reduction, the system can be easily adapted to higher THz frequencies.

X irradiation-induced transcription from the HIV type 1 long terminal repeat.

It has been previously shown in vitro and in vivo that the human immunodeficiency virus type 1 can be dramatically enhanced by certain heterologous viral, chemical, and physical (ultraviolet irradiation) agents. A common denominator shared by these agents is their ability to cause stress responses in cells. To analyze if a similar effect could occur by X irradiations, we tested the in vitro effect of X rays on HIV LTR-directed gene expression. The results demonstrate that the HIV-1 LTR is activated by X irradiation in a dose- and time-dependent manner, in all cell types tested, including epitheloid, fibroblast, and lymphoid cell lines. This study raises the possibility that exposure of AIDS patients to ionizing radiation (e.g., during treatment of epidemic Kaposi's sarcoma) could play a role in the activation of HIV-1 in vivo.

Fractionated total body irradiation and bone marrow transplantation in acute lymphoblastic leukemia.

From March 1982 to September 1988, 108 patients with acute lymphoblastic leukemia (ALL) were conditioned before allogeneic (57 patients of whom 16 T-depleted) or before autologous (51 patients) bone marrow transplantation (BMT). BMT was realized in 66 patients (31 allogeneic and 35 autologous) in first complete remission (CR) and in 42 patients (26 allogeneic and 16 autologous) in second CR or greater or in relapse. All patients received high doses of alkylating agents prior to a low-dose fractionated total body irradiation of 11 Gy in 5 fractions and 5 days. Rejection and relapse rate are described in relation to the three BMT types, allogeneic non T-depleted, allogeneic T-depleted, and autologous, and to the status of the patient at the time of the transplantation. Leukemic deaths are detailed according to the same parameters. Non-leukemic deaths and complications are determined. For the allogeneic population, the 4-year disease-free survival (DFS) is 47%; it is 68.5% in first CR patients, 23.5% in second or subsequent CR patients, and 50% in T-depleted BMT. For the autologous population, 4-year DFS is 35.7%; it is 52% in first CR patients and 30% in patients in second CR or greater. The conditioning regimen appears to be efficient in terms of disease control with a low rate of complications for the non T-depleted population, transplanted in first CR, but has to be improved for the other patients.

Results of fractionated TBI prior to bone marrow transplantation in standard risk leukaemia at Marseille.

One hundred and six patients with standard risk leukaemia were given fractionated TBI prior to allogeneic (72 cases, 27 of whom were T-depleted) or autologous (34 cases) bone marrow transplantation (BMT). Disease free survival at 5 years is 68% for allogeneic non T-depleted BMT and 33% for T-depleted BMT. Deaths are related to relapse, GVHD, infections, pneumonitis, encephalitis, VOD, AIDS, rejection.

Fractionated total body irradiation and allogeneic bone marrow transplantation for standard risk leukemia.

From March 1982 to December 1986, 32 patients with standard risk leukaemia were conditioned for allogeneic bone marrow transplantation (BMT) with low dose fractionated total body irradiation (TBI) after infusion of alkylating agents. This series includes six children and 26 adults. Minimal follow-up was 24 months. The total dose of 11 Gy, given in 5 daily fractions of 2.20 Gy, was given in the lateral position, following chemotherapy with either melphalan or cyclophosphamide. Lungs were shielded for 2 out of the 5 fractions. All patients had in vivo dosimetry. The death rate is 25% without relapse or rejection. Disease-free survival is 73% at 5 years. Toxic deaths are detailed: 2 from sepsis and veino-occlusive disease of the liver, 3 from severe graft versus host disease (GVHD), 2 from GVHD associated with virus pneumonitis and one from HIV infection. Fractionated low dose rate TBI is discussed regarding its decreased toxicity and its efficiency for disease control.