Coherent Detection Imaging Method Research Articles

Transillumination Laser Computed Tomography System with Fiber-Optic-Based Coherent Detection Imaging Method - High Spatial-Resolution and Quantitative Tomographic Imaging of Highly Scattering Objects -

We recently proposed and developed a novel transillumination laser computed tomography (CT) imaging system using a fiber-optic method based on coherent detection imaging (CDI) for biomedical use. Use of optical fibers enables portability and robustness against environmental changes in a room, such as variable temperature, air-flow shifts, and unexpected vibrations. In addition, motion-artifact-free images can be obtained because measurements can be performed with the object fixed. In the present paper, we experimentally investigate in detail the fundamental imaging properties of the system, which has a spatial resolution of 500 μm, a dynamic range of approximately 120 dB, and a minimum-detectable-optical power of 10−14W as a result of the excellent properties of the heterodyne detection. Based on experimental observations, the proposed system can reconstruct tomographic images of highly scattering objects in the transillumination mode, similar to X-ray CT, at sub-millimeter spatial resolution and with quantitativeness. Finally, we demonstrate with experiments using a physical phantom that the imaging system possesses high resolution and quantitative imaging abilities for highly scattering objects.

In Vivo Laser Tomographic Imaging of Mouse Leg by Coherent Detection Imaging Method

The coherent detection imaging (CDI) technique based on the optical heterodyne detection method enables selective filtering of the directional coherent retaining emergent photons from biological tissues with a highly scattering nature. Therefore, the CDI can acquire on-axis information in the transillumination mode and use the same data-acquisition protocol and reconstruction algorithm as those in X-ray computed tomography (CT). Although the CDI-based laser CT cannot image thick subjects such as the head and chest, it can delineate subjects with a thickness up to several cm at a spatial resolution of sub-millimeters. We are planning to apply the technique to early diagnosis of rheumatoid arthritis (RA). Here, we performed an experiment using mice to confirm the feasibility. We compared in vivo CT images at the level of ankle joints of two mice, one normal and the other with collagen induced arthritis (CIA) as an RA model, and demonstrated that there occur significant discrepancies between the two distributions of image intensities, i.e., reconstructed scattering coefficients in each region of interest (ROI) prepared. We suggest that combining the morphological information with the quantitative information can be effective for early diagnosis of bone diseases and disorders such as rheumatoid arthritis.

Fundamental imaging properties of transillumination laser computed tomography based on coherent detection imaging method.

The coherent detection imaging (CDI) method uses the optical heterodyne detection technique. CW and single frequency lasers having long coherence lengths are used to exploit the maximum advantages of heterodyne detection, such as high directionality, selectivity and sensitivity. The CDI method based on optical heterodyne detection enables selective filtering of the directional coherence-retaining emergent photons, which leads to image reconstruction from projections, similar to X-ray computed tomography (CT). So far we have demonstrated the advantages and capabilities of the measurement technique for transillumination optical computed tomography in biomedicine. Here, we investigate the fundamental imaging properties of CDI method, such as its high directionality and quantitativeness, with preliminary physical phantom experiments. The results show that the CDI method satisfies the requirements for CT reconstruction under the first order approximation, and enables quantitative measurements in the sense that the relationship between estimated and actual concentration retains a satisfactory linearity.

Laser computed tomography of opaque industrial products measured by coherent detection imaging method

The coherent detection imaging method with a low-power He–Ne laser as the source is used to obtain transillumination laser computed tomographic and two-dimensional (2D) images of opaque industrial products such as fluorescent lamps and electric light bulbs. This method is principally based on the optical heterodyne detection technique that has the highest sensitivity along with excellent selectivity in terms of coherence, polarization and high directionality. Structures of the filament and electrode enclosed in the opaque glass were clearly identified with submillimeter resolution.

レーザーを用いたコヒーレント検出画像計測法による歯のコンピュータ断層（ＣＴ）画像の分光的測定

Optical computed tomography of human teeth is demonstrated by the coherent detection imaging method. The optical heterodyne detection technique with three different-wavelength lasers as the sources is used to obtain the optical tomographic images of extracted human teeth in the visible short wavelength to near IR regions. The different layers of the internal structure of tooth can be clearly reconstructed with high resolution. The image contrast is shown to be wavelength dependent and compared between the same extracted sample with and without saline in the pulp cavity.

In vivo laser computed tomographic imaging of human fingers by coherent detection imaging method using different wavelengths in near infrared region

We report in vivo laser computed tomographic images of the proximal interphalangeal joint region of a healthy human volunteer’s index finger. The laser computed tomographic (CT) images were obtained with a highly sensitive coherent detection imaging method that is based on the optical heterodyne detection method. These laser CT images are compared at the wavelengths of 715 nm and 1.064 μm and with images obtained by conventional imaging methods such as x-ray CT and magnetic resonance imaging. Internal structures of the proximal interphalangeal joint region could be clearly identified in the laser CT images.

Optical computed tomography for biomedical objects based on coherent detection imaging method

AbstractThis paper summarizes a series of studies aiming at realization of computed tomography imaging (CT) by laser beam for actual in vitro biological samples, which is the first successful trial achieved in the world. The method is realized first by image reconstruction, which detects and selects only the weak transmitted light component buried in stronger multiple scattered light, using the optical heterodyne detection with a very high directivity and sensitivity. This is called coherent detection imaging (CDI).To realize the optical CT using the laser light based on the projection theorem, the following three conditions should essentially be satisfied: (1) The direct‐transmitted light component in the biological system with multiple scattering should accurately be selected and detected. (2) The Lambert‐Beer law should be applied to the selectively detected direct‐transmitted light component. (3) There must exist a direct‐transmitted light component in the medium with complex distribution of refraction index as well as complex boundaries. The authors examined the medium in which the sample is buried and cannot be observed, not only by the naked eye but also by the traditional direct detection method. It was verified experimentally that the three conditions for the realization of the optical CT are applicable, and it was demonstrated that optical CT imaging is feasible for actual samples using the CDI method.

Coherent Detection Imaging Method Using Lasers. Achievement of Laser CT(Computed Tomography) for Biomedical Applications.

In this paper, we report and discuss the achievment of laser absorption computed tomography of actual in vivo/in vitro biological objects using the Coherent Detection Imaging (CDI) method. This CDI scheme offers the feasible and reliable means for the computer-assisted optical tomographic imaging based on the optical heterodyne technique that has excellent directionality and very high sensitivity. We have experimentally demonstrated the fulfillment of fundamental conditions for the establishment of laser absorption tomography by our novel CDI method in highly scattering and absorptive media such as actual biological tissues and objects. Thus we have realized the tomographic image reconstruction of several biological objects including plant stems, chicken tissue, whole egg, struma specimen and new-born mouse brain employing the projection slice theorem.

Laser Spectroscopic Coputed Topography Using Coherent Detection Imaging Method of Biomedical Applications

In this paper, we reprot the feasible and realible method for the laser absorption computer-assisted tomographic imaging based on the optical heterodyne technique that has very high sensitivity and excellent directivity to distinguish one direction from another. This new method is named the Coherent Detection Imaging (CDI). We have demonstrated experimentally the fulfillment of three fundamental conditions for the establishment of laser absorption computed tomography by means of the optical heterodyne method in biological tissues exhibiting severe multiple light scattering. Thus the first successful imaging by laser absorption computed tomography of In vivo/in vitro biological objects has been achieved utilizing our CDI method and the projection slice theorem.