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In panoramic three-dimensional (3D) shape measurement based on a turntable, the point cloud registration accuracy is greatly affected by the calibration of the rotating axis. To improve the calibration accuracy of the rotating axis, a calibration method based on an auxiliary camera is proposed. The calibration procedure uses a checkerboard and an auxiliary camera. Firstly, the checkerboard is rotated on the turntable to determine the rotation axis, and is used to calibrate the relative orientation of the auxiliary camera and the measurement camera, so that the two cameras have the same world coordinate system. Then, the origin point of the coordinate of the rotation axis is obtained by the auxiliary camera, and the Z-axis direction is taken as the direction of the rotation axis. Finally, the 3D shape of the multi-view is measured by the fringe projection system, and the rotation registration is completed according to the rotation axis vector. The proposed method does not need to reconstruct the 3D coordinates of multiple points when the rotating axis is calibrated. The experimental results show that the proposed method effectively improves the calibration accuracy of the rotation axis vector, and reduces the complexity of the calibration process. [ABSTRACT FROM AUTHOR]

Existing methods to measure 3D shape of complex object involve processing more than six captured images to obtain the absolute phase, which limit the measurement speed. This paper presents two sinusoidal fringes and two triangular wave fringes which is used to measure 3D shape of complex object. The two-step phase-shifting sinusoidal fringes and two-step phase-shifting triangular wave fringes are calculated to obtain the wrapped phase, and then the two-step phase-shifting triangular wave fringes are used to determine the fringe order. Due to decrease the number of projection fringes, the speed of measurement increases. The triangular wave fringe carries more information of the object than linear increasing/decreasing ramp fringe in the actual measurement, more noise in the base phase to be overcome, thus improving the measurement accuracy. The benefits can be widely applied in high-speed, real-time 3D measurement of complex shape. Experimental results have demonstrated that the proposed method is simple, but effective. [ABSTRACT FROM AUTHOR]

To assess the ability of dual-energy CT (DECT) to separate intravenous contrast of bowel wall from intraluminal contrast, we scanned 16 rabbits on a clinical DECT scanner: n = 3 using only iodinated intravenous contrast, and n = 13 double-contrast enhanced scans using iodinated intravenous contrast and experimental enteric non-iodinated contrast agents in the bowel lumen (five bismuth, four tungsten, and four tantalum based). Representative image pairs from conventional CT images and DECT iodine density maps of small bowel (116 pairs from 232 images) were viewed by four abdominal imaging attending radiologists to independently score each comparison pair on a visual analog scale (−100 to +100%) for (1) preference in small bowel wall visualization and (2) preference in completeness of intraluminal enteric contrast subtraction. Median small bowel wall visualization was scored 39 and 42 percentage points (95% CI 30-44% and 36-45%, both p < 0.001) higher for double-contrast DECT than for conventional CT with enteric tungsten and tantalum contrast, respectively. Median small bowel wall visualization for double-contrast DECT was scored 29 and 35 percentage points (95% CI 20-35% and 33-39%, both p < 0.001) higher with enteric tungsten and tantalum, respectively, than with bismuth contrast. Median completeness of intraluminal enteric contrast subtraction in double-contrast DECT iodine density maps was scored 28 and 29 percentage points (95% CI 15-31% and 28-33%, both p < 0.001) higher with enteric tungsten and tantalum, respectively, than with bismuth contrast. Results suggest that in vivo double-contrast DECT with iodinated intravenous and either tantalum- or tungsten-based enteric contrast provides better visualization of small bowel than conventional CT. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Gray code plus phase-shifting method embed the codeword into intensity to reconstruct complex three-dimensional shape. Owing to surface reflectivity and noise, it is less robust for measuring the surfaces of object with low contrast. In order to solve the problem, the codeword is embedded into phase to determine fringe order for obtaining the unwrapped phase. However, measurement speed is limited. Therefore, a fast three-dimensional shape measurement method based on color phase coding is proposed. As it adopts a color sinusoidal fringe to obtain wrapped phase and an additional color phase coding fringe to determine fringe order, the method can achieve fast complex three-dimensional shape measurement with different contrast. Color crosstalk and gamma nonlinearity are compensated to improve the measurement accuracy. The experiment results confirm the effectiveness and robustness of the proposed method. [ABSTRACT FROM AUTHOR]

Purpose: To compare the incidence of contrast-induced nephropathy (CIN) for intravenous vs. intra-arterial administration of iodixanol, compared to non-administration. Methods: We retrospectively identified 650 patients who had intravenous iodixanol-enhanced CT, 695 with intra-arterial iodixanol cardiac catheterization, 651 with unenhanced CT, and those who also had baseline and follow-up serum creatinine within 5 days of the exam. From the medical records, we recorded the gender, age, baseline and follow-up serum creatinine/eGFR; underlying renal injury risk factors; indication for imaging; contrast material administration volume, concentration, and route of administration; and use of pre-imaging prophylactic measures for CIN. Univariate and multivariate models were used to determine predictors of CIN. Results: Baseline eGFR was lower for patients undergoing unenhanced CT than intravenous or intra-arterial patients (68 vs. 74.6 and 72.2, respectively, p < 0.01) and not different between intravenous and intra-arterial patients ( p = 0.735). Simple logistic regression did not show a difference in the rate of CIN in patients who received intravenous vs. intra-arterial iodixanol (28 of 650, 4%, vs. 28 of 695, 4%, respectively, p = 0.798), nor a higher rate of CIN than seen with unenhanced CT (45 of 651, 7%, p = 0.99 and p = 0.98 by one-sided t test). Multivariate regression modeling showed that only elevated baseline creatinine or decreased eGFR and low hematocrit/hemoglobin were associated with CIN incidence (odds ratio 1.28 and 2.5; p < 0.023 and <0.006, respectively). Conclusions: Elevation in serum creatinine due to intravenous and intra-arterial iodixanol administration is infrequent and is not more common than after unenhanced CT scans. [ABSTRACT FROM AUTHOR]

A novel highly birefringent photonic crystal fiber (PCF) based on rectangular-hole is proposed and numerically analyzed by employing the finite-element method. The proposed PCF can achieve birefringences similar to those of the elliptical-hole PCF and rhombic-hole PCF. The properties of such PCFs are investigated for different parameters related to rectangular-holes, including the rectangular-hole pitch, length and the length and width ratio. The results show that the birefringence of rectangular-hole PCF reaches the magnitude of 10 −3 which fulfills the requirements of high precision applications in optical systems, which will find application in nonlinear optics. [ABSTRACT FROM AUTHOR]

Phase is better immune to surface contrast variations, ambient light, and camera noises, compared with intensity. A method that combines phase coding fringe with sinusoidal fringe is used to achieve 3D shape measurement of complex surface. However, because of the projection angle deviation, the captured fringe period lacks consistency and the measurement error is induced. Evident error is caused when larger object is measured. Period correction method of phase coding fringe is proposed. The corrected fringe patterns are projected by digital light processing, and then the desired uniform fringe patterns are captured by the CCD camera. Experiment results demonstrate that the proposed method can solve the broadening of fringes and improve the measurement accuracy. This method can be widely employed for measuring larger object with different contrast surfaces. [ABSTRACT FROM AUTHOR]