Effects of the Ground Resolution and Thresholding on Crack Width Measurements.

When diagnosing the condition of a structure, it is necessary to measure the widths of any existing cracks in the structure. To ensure safety when relying on images of cracks, the selected imaging parameters and processing technology must be well understood. In this study, the effects of the ground sample distance and threshold values on the crack width measurement error are analyzed from a theoretical perspective. Here, the main source of such errors is assumed to be due to the mixed pixel phenomena in the left and right boundary pixels. Thus, a mathematical model is proposed in which the intensity changes in these pixels are computed via an equation. In addition, the relationship between the error and error probability distribution is represented with an equation based on the threshold values and mean error. Upon analysis, it was found that the threshold value that minimizes the error is at the mid-point between the background and foreground, and the probabilistic nature of the error indicates that it is theoretically possible to predict both the error and its probability distribution. The proposed model was validated using artificial images.

Cardiac and Pericardial 18F-FDG Uptake on Oncologic PET/CT: Comparison with Echocardiographic Findings.

BACKGROUND: Interpretation of cardiac uptake on 18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is often confounded by intense physiological FDG uptake and numerous benign conditions. The aim of the study was to describe the echocardiographic features in concordance with cardiac and pericardial 18F-FDG uptake on whole-body oncology PET/CT. METHODS: We enrolled 43 consecutive patients (34 solid tumors, 8 lymphomas and 1 leukemia) who were newly diagnosed with non-cardiac malignancy showing incidental cardiac or pericardial 18F-FDG uptake on PET/CT and underwent transthoracic Doppler echocardiography (TTE) within 1 month of PET/CT. The maximum standardized uptake (SUVmax) of all lesions was measured. RESULTS: Fifty-six 18F-FDG uptake lesions (32 pericardium, 7 myocardium, 9 cardiac chambers and 8 great vessels) were found, and pericardial effusion was the most common echocardiographic finding (22/43, 51.2%) among study population. Pericardial FDG uptake was shown as pericardial effusion (68.8%), intrapericardial echogenic materials (31.3%), pericardial thickening (28.1%), hyperechogenicity of myopericardium (18.8%), and restricted sliding movement or constrictive pericarditis (15.6%) on TTE. Lesions with regional wall motion abnormality (p = 0.004) or constrictive pericarditis (p = 0.021) had significantly higher mean SUVmax than those without. Myocardial FDG uptake demonstrated pericardial effusion (57.1%), regional wall motion abnormality (57.1%), and increased myocardial wall thickness (42.9%). All cardiac chamber FDG uptakes showed intracardiac mass on TTE. CONCLUSIONS: Cardiac or pericardial 18F-FDG uptake on oncology PET/CT shows characteristic echocardiographic features according to which heart sites are involved.

Analysis of Crack Image Recognition Characteristics in Concrete Structures Depending on the Illumination and Image Acquisition Distance through Outdoor Experiments.

The effects of illumination and shooting distance on crack image recognition were investigated by examining cracks in images taken with a camera. In order to examine the effects, images of cracks in a concrete structure taken while varying the illumination and shooting distance in an outdoor environment were analyzed. The images were acquired at a daytime illumination of 52,000 lx and a night illumination of 13 lx. The crack specimen images produced for the experiment were taken by increasing the shooting distance from 5 m to 100 m in each illumination. On the basis of the analysis on the modulation transfer function (MTF) and contrast sensitivity of the crack images, the effects of illumination and shooting distance on the sharpness of the crack images were investigated. The minimum crack widths that can be identified under each illumination were analyzed using MTF10 and Weber contrast 0.1, respectively. It was found that as the shooting distance increases, the effects of illumination on crack recognition become greater.

Observation of narrowband intrinsic spectra of Brillouin dynamic gratings.

We experimentally demonstrate that the reflection spectrum of a Brillouin dynamic grating in a polarization-maintaining fiber can be much narrower than the intrinsic linewidth of the stimulated Brillouin scattering, matching well with the theory of a fiber Bragg grating in terms of the linewidth and the reflectivity. A 3 dB bandwidth as narrow as 10.5 MHz is observed with the Brillouin dynamic grating generated in a 9 m uniform fiber.

High-resolution Brillouin optical time domain analysis based on Brillouin dynamic grating.

We propose and experimentally demonstrate a high-resolution distributed measurement of the Brillouin gain spectrum in a polarization-maintaining fiber (PMF) using Brillouin dynamic grating. In our approach, acoustic waves which contain the information of the local Brillouin frequency are generated by a long pump pulse in one polarization along the PMF and are read out by a short probe pulse with an orthogonal polarization at a different optical frequency from the pump. In experiments, a distributed strain measurement with a 10 cm spatial resolution is demonstrated in a 105 m PMF.