• 대한전자공학회논문지TE
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• 제42권1호
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• pp.21-28
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• 2005

본 논문은 토모그라픽 영상시스템에 적합한 FBP 토모그라픽 영상복원 알고리즘의 분해능에 관하여 연구하였다. 고정좌표계를 이용하는 개선된 FBP 토모그라픽 영상복원 알고리즘으로부터 분해능을 분석할 수 있는 모호함수를 유도하였고, 이를 이용한 모의실험을 통하여 얻은 진폭분포로부터 측방향 및 축방향 분해능을 정량적으로 결정하였다. 개선된 FBP 토모그라픽 영상복원 알고리즘을 통해 기존의 SAM(Scanning Acoustic Microscope)시스템으로부터 얻을 수 있는 3dB와 6dB 축방향 분해능에 대해서도 각각 0.70 파장과 0.96 파장으로 SAM 영상의 3dB 축방향 분해능인 7 파장에 비하여 매우 개선된 분해능을 얻을 수 있음을 확인하였다. 평면 입사파의 회절 토모그라픽 영상복원을 위한 개선된 FBP 토모그라픽 영상복원 알고리즘은 미세하고 복잡한 다층 박막구조를 갖는 시료에 대하여 좋은 분해능을 갖는 토모그라픽 영상시스템을 개발하는데 유용하게 활용할 수 있도록 하였다.

• 한국분무공학회지
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• 제7권4호
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• pp.9-15
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• 2002

Convolution Fourier transformation tomographically reconstructs the spatially resolved spray injection rate from direct measuring cells. Asymmetric sprays generated from a twin-hole air shroud injector are tested with 12 equiangular projections of measurements. For each projection angle, line of sight integrated injection rate was measured at 35 positions with equal spacing measuring cells of 3 mm in width, 100 mm in length, 55 mm in depth and 0.5 mm thickness of separating wall. Interpolated data between the projection angles effectively increase the number of projections, which significantly enhances the signal-to-noise level in the reconstructed data. This modified convolution Fourier transformation scheme predicts well the structure of asymmetric sprays. Comparative study has been made between sprays with and without air shrouding. Tomograhpic reconstruction of injection rate from direct measuring cells obtained can be used to estimate the accuracy of volume fraction of spray from the LDPA tomographic reconstruction.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 Proceedings of The 6th korea-china joint workshop on nuclear waste management
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• pp.126-140
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• 2005

The tomographic gamma scanner (TGS) method, a further of extension of segmented gamma scanner (SGS), is most accurate and precise for assaying heterogeneous drummed nuclear radioactive waste; it is widely used in nuclear power plants and radioactive waste storages and disposal sites. The transmission and emission images are reconstructed by image reconstruction techniques. In the paper, the principle of TGS is introduced; image reconstruction techniques are discussed as well; finally, it is demonstrated that TGS method performance.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1999년도 제19회 KOSCO SYMPOSIUM 논문집
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• pp.55-61
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• 1999

A convolution algorithm combined with Fourier transformation is applied to the tomographic reconstruction of the asymmetric soot structure to identify the local soot volume fraction distribution. The line of sight integrated data from light extinction measurement with multi-angular scanning form basic information for the deconvolution. Multi-peak following interpolation technique is applied to obtain the effect of increasing number of scanning angles. Measurement of LII signal for the same flame shows the validity of this reconstruction technigue.

• The Journal of the Acoustical Society of Korea
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• 제15권1E호
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• pp.70-76
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• 1996

We proposed to use shear waves instead of longitudinal waves in a STAM (scanning tomographic acoustic microscope system) in which the specimens are solid. For any specimen with a shear modulus, mode conversion will take place at the water-solid interface. Some of the energy of the insonifying longitudinal waves in the water will convert to shear wave energy within the specimen. The shear wave energy is detectable and can be used for tomographic reconstruction. The resolution limitation of STAM depends on the available angular view and the acoustic wavelength. While wave transmission in most solid specimens is limited to about 20°for longitudinal waves, we show that it is about twice that high for shear waves. Since the wavelength of the shear wave is shorter than that of the longitudinal wave, we are able to achieve the high resolution. In order to compare the operation of a shear-wave STAM with that of the conventional longitudinal-wave STAM we have simulated tomographic reconstruction for each. Our simulation results with aluminum specimen and back-and-forth propagation algorithm showed resolution of a shear-wave STAM is better than that of a longitudinal-wave STAM.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 춘계학술대회
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• pp.279-282
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• 1997

Bayesian reconstruction methods for emission computed tomography have been a topic of interest in recent years, partly because they allow for the introduction of prior information into the reconstruction problem. Early formulations incorporated priors that imposed simple spatial smoothness constraints on the underlying object using Gibbs priors in the form of four-nearest or eight-nearest neighbors. While these types of priors, known as "membrane" priors, are useful as stabilizers in otherwise unstable ML-EM reconstructions, more sophisticated prior models are needed to model underlying source distributions more accurately. In this work, we investigate whether the "thin plate" model has advantages over the simple Gibbs smoothing priors mentioned above. To test and compare quantitative performance of the reconstruction algorithms, we use Monte Carlo noise trials and calculate bias and variance images of reconstruction estimates. The conclusion is that the thin plate prior outperforms the membrane prior in terms of bias and variance.

• 한국연소학회지
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• 제8권3호
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• pp.24-30
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• 2003

A convolution algorithm combined with Fourier transformation has been applied to the tomographic reconstruction of asymmetric soot structure to identify the local soot volume fraction distribution. Line-of-sight integrated data from light extinction measurement with multi-angular scanning formed basic information for the deconvolution. Multi-peak following interpolation technique was applied to obtain the effect of increasing number of scanning angles. Height-by-height reconstructed soot volume fraction distribution was compared with laser-induced incandescence signals.

• 한국자동차공학회논문집
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• 제4권1호
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• pp.177-186
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• 1996

A convolution alogorithm combined with Fourier transformation is applied to the tomographic reconstruction of the asymmetric spray structure to identify the local drop size and volume concentration. The line of sight intergrated data from Malvern particle analyzer with multiangular scanning form a basic information for the deconvolution. Linear interpolation is tested to obtain the effect of increasing number of scanning angles. This transformation method predicts well the structure of asymmetric spray. The tehnique can be extended to other line of sight combustion diagnostics.

• 한국음향학회지
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• 제18권5호
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• pp.83-90
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• 1999

본 논문에서는 초음파 회절 토모그라피를 위한 FBP와 BFP 영상복원 알고리즘에 관한 분해능을 연구하였다. 고정좌표계를 사용한 수정된 FBP 영상복원 알고리즘과 평면구조물에 적합한 BFP 영상복원 알고리즘을 이용하여 복원할 수 있는 토모그라픽 영상에 대한 분해능을 분석할 수 있는 모호함수를 유도하고 모의실험을 통하여 얻은 측방향 및 축방향 분해능을 분석하였다. 분석결과, FBP 영상복원 알고리즘에 대한 측방향 및 축방향의 3dB분해능은 각각 0.27파장, 0.70파장을 얻었으며, 또한 BFP 영상복원 알고리즘에 대한 측방향 및 축방향 분해능도 각각 0.39파장과 0.98파장으로 정량적으로 결정하였다. 따라서 본 연구를 통하여 수정된 FBP 영상복원 알고리즘과 BFP 영상복원 알고리즘은 회절 토모그라피를 위한 영상복원에 유용하게 이용할 수 있음을 확인하였다.

• Archives of Reconstructive Microsurgery
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• 제22권2호
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• pp.43-47
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• 2013

Purpose: Un-healing and centrally located defect on back area, it is sometimes a challenge for the reconstructive surgeon. Although skin grafts are considered as the first choice for reconstruction of large skin defect on the back region, it is not always helpful but vascularized flaps provide a superior functional and aesthetic outcome. The present study was designed to investigate the clinical anatomy of the lumbar artery perforator flap to reconstruct back ulcer. Materials and Methods: Clinical anatomy study was undertaken using computed tomographic angiographic analysis. We identified the courses of lumbar arteries and its perforators, measured pedicle length by layers. The location of the perforator vessel was charted against anatomical landmarks. Results: The pedicle lengths of the third and fourth lumbar artery perforator reached a mean of 27.8 mm and 37.1 mm respectively from superficial fascia to deep fascia. The fourth perforator was more laterally located than the third perforator and less than 1 cm above the iliac crest. A case in which the fourth lumbar artery perforator was used as flap pedicle is described. Conclusion: For the reconstruction of central defect on the back area, the lumbar artery perforator flap coverage may be a good alternative option. Computed tomographic angiography can easily identify the course and location of lumbar artery perforators and can be helpful to elevate the flap successfully.