Hybrid Sparsity Model for Fast Terahertz Imaging

In order to shorten the long-term image acquisition time of the terahertz time domain spectroscopy imaging system while ensuring the imaging quality, a hybrid sparsity model (HSM) is proposed for fast terahertz imaging in this paper, which incorporates both intrinsic sparsity prior and nonlocal self-similarity constraints in a unified statistical model. In HSM, a weighted exponentiation shift-invariant wavelet transform is introduced to enhance the sparsity of the terahertz image. Simultaneously, the nonlocal self-similarity by means of the three-dimensional sparsity in the transform domain is exploited to ensure high-quality terahertz image reconstruction. Finally, a new split Bregman-based iteration algorithm is developed to solve the terahertz imaging model more efficiently. Experiments are presented to verify the effectiveness of the proposed approach.

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Fast Terahertz Imaging Model Based on Group Sparsity and Nonlocal Self-Similarity

Micromachines ◽

10.3390/mi13010094 ◽

2022 ◽

Vol 13 (1) ◽

pp. 94

Author(s):

Xiaozhen Ren ◽

Yanwen Bai ◽

Yingying Niu ◽

Yuying Jiang

Keyword(s):

Imaging System ◽

Dimensional Space ◽

Terahertz Imaging ◽

Acquisition Time ◽

Group Sparsity ◽

Self Similarity ◽

Split Bregman ◽

Edge Preservation ◽

Imaging Model ◽

Reconstruction Performance

In order to solve the problems of long-term image acquisition time and massive data processing in a terahertz time domain spectroscopy imaging system, a novel fast terahertz imaging model, combined with group sparsity and nonlocal self-similarity (GSNS), is proposed in this paper. In GSNS, the structure similarity and sparsity of image patches in both two-dimensional and three-dimensional space are utilized to obtain high-quality terahertz images. It has the advantages of detail clarity and edge preservation. Furthermore, to overcome the high computational costs of matrix inversion in traditional split Bregman iteration, an acceleration scheme based on conjugate gradient method is proposed to solve the terahertz imaging model more efficiently. Experiments results demonstrate that the proposed approach can lead to better terahertz image reconstruction performance at low sampling rates.

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Characterizing the Layer Structures of the Lacquerware From the Palace Museum by Terahertz Imaging in Reflection Geometry

Frontiers in Physics ◽

10.3389/fphy.2021.751205 ◽

2021 ◽

Vol 9 ◽

Author(s):

Hongfei Zhang ◽

Yuanmeng Zhao ◽

Chenyu Li ◽

Cunlin Zhang

Keyword(s):

Time Domain ◽

Imaging System ◽

Structural Information ◽

Three Dimensional ◽

Terahertz Imaging ◽

Universal Method ◽

Wood Panel ◽

Non Invasive ◽

Reflection Geometry ◽

Buried Layers

Chinese lacquerware is an important invention of arts and crafts in China. In this study, Chinese lacquerware is characterized using terahertz reflectometric imaging. The lacquerware studied herein comprises an ornamental wood panel covered by multiple layers of lacquers to portray motifs. For characterizing lacquerware, a terahertz time-domain spectroscopic reflectometric imaging system is proposed. The role of the proposed terahertz imaging system in highlighting the interface between layers during stratigraphic buildup in reflection geometry is proved. The proposed system provides a universal method for assessing the structural information of lacquered objects in a contactless and non-invasive manner; moreover, it provides two-dimensional images, subsurface three-dimensional images, and stratigraphic images (b-scans) in a contactless and non-invasive manner. Using the proposed system, we examine the buried layers of the lacquerware, including faults in the wooden layer and damages in the lacquerware. Research shows the promising prospects of terahertz time-domain spectroscopic reflectometric imaging as a non-destructive detection technique suited to lacquerware.

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Terahertz Imaging: A New Technique for Inspection of Dielectric Materials

ISTFA 1999: Conference Proceedings from the 25th International Symposium for Testing and Failure Analysis ◽

10.31399/asm.cp.istfa1999p0003 ◽

1999 ◽

Author(s):

Daniel M. Mittleman

Keyword(s):

Imaging System ◽

New Technology ◽

Three Dimensional ◽

Depth Resolution ◽

Far Infrared ◽

Dielectric Materials ◽

Terahertz Time Domain Spectroscopy ◽

Dielectric Interfaces ◽

A New Technique ◽

Transverse Resolution

Abstract Terahertz time-domain spectroscopy (THz-TDS) is a promising new technology which provides a relatively simple means of generating and detecting single-cycle pulses of far-infrared (or terahertz) radiation. One of the most interesting aspects of this system is its insensitivity to the thermal background. This obviates the need for cryogenic apparatus; as a result, this may be the first portable far-infrared spectrometer. Recent work has demonstrated the possibility of tomographic imaging using THz-TDS. In this imaging mode, a reflected pulse train is used to construct a three-dimensional representation of a composite material, using the timing between reflected pulses to determine the spacing between adjacent dielectric interfaces. Here, the transverse resolution is determined by the diffraction-limited focus of the THz beam, and is typically ~300 microns. The longitudinal (depth) resolution of ~100 microns is determined by the coherence length of the radiation, although the location of isolated surfaces can be determined with far higher precision. Since many common packaging materials have high transparency in the THz range, this suggests the possibility of exploiting this new imaging system for non-invasive testing and on-line monitoring. The operation of the THz “T-ray” imaging system will be described, and several examples will be provided which illustrate its capabilities and limitations.

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Some Quantification Problems in Parallel EELS Images

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133771 ◽

1990 ◽

Vol 48 (2) ◽

pp. 36-37

Author(s):

G. Botton ◽

G. L’Espérance ◽

M.D. Ball ◽

C.E. Gallerneault

Keyword(s):

Electron Microscope ◽

Imaging System ◽

Signal To Noise Ratio ◽

Scanning Transmission Electron Microscope ◽

Acquisition Time ◽

Thickness Variation ◽

Transmission Electron ◽

Distribution Of Elements ◽

Scanning Transmission ◽

Present Distribution

The recently developed parallel electron energy loss spectrometers (PEELS) have led to a significant reduction in spectrum acquisition time making EELS more useful in many applications in material science. Dwell times as short as 50 msec per spectrum with a PEELS coupled to a scanning transmission electron microscope (STEM), can make quantitative EEL images accessible. These images would present distribution of elements with the high spatial resolution inherent to EELS. The aim of this paper is to briefly investigate the effect of acquisition time per pixel on the signal to noise ratio (SNR), the effect of thickness variation and crystallography and finally the energy stability of spectra when acquired in the scanning mode during long periods of time.The configuration of the imaging system is the following: a Gatan PEELS is coupled to a CM30 (TEM/STEM) electron microscope, the control of the spectrometer and microscope is performed through a LINK AN10-85S MCA which is interfaced to a IBM RT 125 (running under AIX) via a DR11W line.

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Image Restoration Model under Poisson Noise Using Sparse Representations and Split Bregman Iteration Algorithm

ACTA AUTOMATICA SINICA ◽

10.3724/sp.j.1004.2010.01512 ◽

2010 ◽

Vol 36 (11) ◽

pp. 1512-1519 ◽

Cited By ~ 2

Author(s):

Yu-Bao SUN ◽

Xuan FEI ◽

Zhi-Hui WEI ◽

Liang XIAO

Keyword(s):

Image Restoration ◽

Poisson Noise ◽

Sparse Representations ◽

Iteration Algorithm ◽

Bregman Iteration ◽

Split Bregman ◽

Split Bregman Iteration ◽

Restoration Model

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DURIP: A Confocal Imaging System for Ultra-Fast Three-Dimensional Transport Studies in Thermal Management Applications

10.21236/ada553729 ◽

2011 ◽

Author(s):

Evelyn N. Wang

Keyword(s):

Thermal Management ◽

Imaging System ◽

Three Dimensional ◽

Confocal Imaging ◽

Transport Studies

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Estimating intrafraction tumor motion during fiducial-based liver stereotactic radiotherapy via an iterative closest point (ICP) algorithm

Radiation Oncology ◽

10.1186/s13014-019-1401-2 ◽

2019 ◽

Vol 14 (1) ◽

Cited By ~ 3

Author(s):

Wu-zhou Li ◽

Zhi-wen Liang ◽

Yi Cao ◽

Ting-ting Cao ◽

Hong Quan ◽

...

Keyword(s):

Stereotactic Radiotherapy ◽

Imaging System ◽

Liver Tumors ◽

Three Dimensional ◽

Rigid Motion ◽

Iterative Closest Point ◽

Tumor Motion ◽

Tracking Accuracy ◽

Icp Algorithm ◽

Anterior Posterior

Abstract Background Tumor motion may compromise the accuracy of liver stereotactic radiotherapy. In order to carry out a precise planning, estimating liver tumor motion during radiotherapy has received a lot of attention. Previous approach may have difficult to deal with image data corrupted by noise. The iterative closest point (ICP) algorithm is widely used for estimating the rigid registration of three-dimensional point sets when these data were dense or corrupted. In the light of this, our study estimated the three-dimensional (3D) rigid motion of liver tumors during stereotactic liver radiotherapy using reconstructed 3D coordinates of fiducials based on the ICP algorithm. Methods Four hundred ninety-five pairs of orthogonal kilovoltage (KV) images from the CyberKnife stereo imaging system for 12 patients were used in this study. For each pair of images, the 3D coordinates of fiducial markers inside the liver were calculated via geometric derivations. The 3D coordinates were used to calculate the real-time translational and rotational motion of liver tumors around three axes via an ICP algorithm. The residual error was also investigated both with and without rotational correction. Results The translational shifts of liver tumors in left-right (LR), anterior-posterior (AP),and superior-inferior (SI) directions were 2.92 ± 1.98 mm, 5.54 ± 3.12 mm, and 16.22 ± 5.86 mm, respectively; the rotational angles in left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions were 3.95° ± 3.08°, 4.93° ± 2.90°, and 4.09° ± 1.99°, respectively. Rotational correction decreased 3D fiducial displacement from 1.19 ± 0.35 mm to 0.65 ± 0.24 mm (P<0.001). Conclusions The maximum translational movement occurred in the SI direction. Rotational correction decreased fiducial displacements and increased tumor tracking accuracy.

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Validation of Scolioscan Air-Portable Radiation-Free Three-Dimensional Ultrasound Imaging Assessment System for Scoliosis

Sensors ◽

10.3390/s21082858 ◽

2021 ◽

Vol 21 (8) ◽

pp. 2858

Author(s):

Kelly Ka-Lee Lai ◽

Timothy Tin-Yan Lee ◽

Michael Ka-Shing Lee ◽

Joseph Chi-Ho Hui ◽

Yong-Ping Zheng

Keyword(s):

Ultrasound Imaging ◽

Imaging System ◽

Outcome Measurement ◽

Three Dimensional ◽

3D Ultrasound ◽

Mean Difference ◽

Assessment System ◽

Absolute Difference ◽

Data Sets ◽

Low Profile

To diagnose scoliosis, the standing radiograph with Cobb’s method is the gold standard for clinical practice. Recently, three-dimensional (3D) ultrasound imaging, which is radiation-free and inexpensive, has been demonstrated to be reliable for the assessment of scoliosis and validated by several groups. A portable 3D ultrasound system for scoliosis assessment is very much demanded, as it can further extend its potential applications for scoliosis screening, diagnosis, monitoring, treatment outcome measurement, and progress prediction. The aim of this study was to investigate the reliability of a newly developed portable 3D ultrasound imaging system, Scolioscan Air, for scoliosis assessment using coronal images it generated. The system was comprised of a handheld probe and tablet PC linking with a USB cable, and the probe further included a palm-sized ultrasound module together with a low-profile optical spatial sensor. A plastic phantom with three different angle structures built-in was used to evaluate the accuracy of measurement by positioning in 10 different orientations. Then, 19 volunteers with scoliosis (13F and 6M; Age: 13.6 ± 3.2 years) with different severity of scoliosis were assessed. Each subject underwent scanning by a commercially available 3D ultrasound imaging system, Scolioscan, and the portable 3D ultrasound imaging system, with the same posture on the same date. The spinal process angles (SPA) were measured in the coronal images formed by both systems and compared with each other. The angle phantom measurement showed the measured angles well agreed with the designed values, 59.7 ± 2.9 vs. 60 degrees, 40.8 ± 1.9 vs. 40 degrees, and 20.9 ± 2.1 vs. 20 degrees. For the subject tests, results demonstrated that there was a very good agreement between the angles obtained by the two systems, with a strong correlation (R2 = 0.78) for the 29 curves measured. The absolute difference between the two data sets was 2.9 ± 1.8 degrees. In addition, there was a small mean difference of 1.2 degrees, and the differences were symmetrically distributed around the mean difference according to the Bland–Altman test. Scolioscan Air was sufficiently comparable to Scolioscan in scoliosis assessment, overcoming the space limitation of Scolioscan and thus providing wider applications. Further studies involving a larger number of subjects are worthwhile to demonstrate its potential clinical values for the management of scoliosis.

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