S.Y. Kang

Biomechanical effect of electromechanical knee–ankle–foot-orthosis on knee joint control in patients with poliomyelitis

In this study, an ideal electromechanical KAFO, satisfying stability in the stance and knee flexion in the swing phase during walking, was developed. Biomechanical evaluations were performed on four polio patients by means of three-dimensional gait analyses and energy consumption studies. From the three-dimensional gait analysis on poliomyelitis patients, a considerable amount of knee flexion during the swing phase was observed in controlled-knee gait, which resulted in approximately 33% less energy consumption than in locked-knee gait. The developed electromechanical KAFO in this study was helpful in poliomyelitis patients having partial or complete paralysis of the lower extremity, providing both stability in the stance and free swinging of the knee. This unit was efficient in the transfer of energy.

A new software scheme for scatter correction based on a simple radiographic scattering model

AbstractIn common radiography, image contrast is often limited due mainly to scattered x-rays and noise, decreasing the quantitative usefulness of x-ray images. Several scatter reduction methods based on software correction schemes have been extensively investigated in an attempt to overcome these difficulties, most of which are based on measurement, mathematical-physical modeling, or a combination of both. However, those methods require special equipment, system geometry, and extra manual work to measure scatter characteristics. In this study, we investigated a new software scheme for scatter correction based on a simple radiographic scattering model where the intensity of the scattered x-rays was directly estimated from a single x-ray image using a weighted l1-norm contextual regularization framework. We implemented the proposed algorithm and performed a systematic simulation and experiment to demonstrate its viability. We also conducted some clinical image studies using patient’s image data of breast and L-spine to verify the clinical effectiveness of the proposed scheme. Our results indicate that the degradation of image characteristics by scattered x-rays and noise was effectively recovered by using the proposed software scheme, thus improving radiographic visibility considerably. Graphical abstractThe schematic illustrations of scatter suppression methods by using a an antiscatter grid and b a scatter estimation algorithm.

Eliminating artifacts in single-grid phase-contrast x-ray imaging for improving image quality.

In this study, we propose a modification to a single-grid phase-contrast x-ray imaging (PCXI) system using a Fourier domain analysis technique to extract absorption, scattering, and differential phase-contrast images. The proposed modification is to rotate the x-ray grid in the image plane to achieve spectral separation between the desired information and the moiré artifact, which is introduced by the superposition of the periodic image of the grid shadow and the periodic sampling by the detector. In addition, we performed some system optimization by adjusting distances between source, object, grid, and detector to further improve image quality. This optimization aimed to increase the spectral spacing between the primary spectrum (lower frequency) and the harmonics of the spectrum (higher frequency) used to extract the various image contrasts. The table-top setup used in the experiment consisted of a focused-linear grid with a 200-lines/inch strip density, a microfocus x-ray tube with a 55-μm focal spot size, and a CMOS flat-panel detector with a 49.5-μm pixel size. The x-ray grid was rotated at 27.8° with respect to the detector and the sample was placed as close as possible to the x-ray tube. Our results indicated that the proposed method effectively eliminated the PCXI artifacts, thus improving image quality.