Sang-Hoon Kim

Bio: Sang-Hoon Kim is an academic researcher from Kyungpook National University. The author has contributed to research in topics: Ultimate tensile strength & Dynamic recrystallization. The author has an hindex of 20, co-authored 48 publications receiving 951 citations. Previous affiliations of Sang-Hoon Kim include Korea University of Science and Technology.

Observation of the Lenticulostriate Arteries in the Human Brain In Vivo Using 7.0T MR Angiography

Abstract: Background and Purpose— We sought to examine the feasibility of observing the lenticulostriate arteries (LSAs) noninvasively by ultrahigh-field MRI with 7.0T. Methods— We used 3-dimensional time-of-flight MR angiography with a radiofrequency coil optimized for 7.0T MRI. We examined the LSAs of 6 healthy subjects and compared 7.0T MR angiography images with 1.5T ones to examine the potentials of ultrahigh-field MRI for angiography. Results— The results show clear details of LSAs and their distribution in the normal healthy subjects with large variations in the shapes, the number of branches and the sites of origin. We also observed substantial differences between the left and right sides within each subject. Although we studied only 6 subjects, we found no age- or gender-related differences in the LSAs. Conclusions— The visualization of microvasculature of the brain, such as LSAs, using 7.0T MR angiography, is possible in in vivo human studies noninvasively. We, therefore, believe that it could play a majo...

Hypertension Correlates With Lenticulostriate Arteries Visualized by 7T Magnetic Resonance Angiography

Abstract: Hypertension, a major risk factor for stroke, is associated with altered arterial anatomy and function; however, the limited resolution of current imaging techniques has restricted the in vivo study of microvascular changes in the brain. In this report, we quantitatively examined the lenticulostriate arteries in hypertensive patients using ultrahigh-field 7T MRI. We compared the number of stems and branches, curvature, and tortuosity of the lenticulostriate arteries by 3D time-of-flight magnetic resonance angiography among 20 hypertensive patients (mean age: 46.6+/-9.1 years) and 20 age-matched healthy subjects (mean age: 47.7+/-8.1 years). The average numbers of stems and branches in hypertensive patients were significantly less than those of healthy subjects (P 45 years old), whereas the difference between young hypertensive patients (< or = 45 years old) and age-matched healthy controls was augmented by 55% for stems and 91% for branches (P=0.001). In comparison, there were no differences in the average curvature and tortuosity of the lenticulostriate arteries and no significant difference when corrected for smoking (P=0.064). In conclusion, our results showed that there was a substantial difference in the lenticulostriate arteries of hypertensive patients compared with healthy individuals when observed in vivo by ultrahigh-resolution 7T magnetic resonance angiography, and the difference was considerable in young subjects.

Novel Zn-based alloys for biodegradable stent applications: Design, development and in vitro degradation.

Abstract: The search for a degradable metal simultaneously showing mechanical properties equal or higher to that of stainless steel and uniform degradation is still an open challenge. Several magnesium-based alloys have been studied, but their degradation rate has proved to be too fast and rarely homogeneous. Fe-based alloys show appropriate mechanical properties but very low degradation rate. In the present work, four novel Zn-Mg and two Zn-Al binary alloys were investigated as potential biodegradable materials for stent applications. The alloys were developed by casting process and homogenized at 350°C for 48h followed by hot extrusion at 250°C. Tube extrusion was performed at 300°C to produce tubes with outer/inner diameter of 4/1.5mm as precursors for biodegradable stents. Corrosion tests were performed using Hanks׳ modified solution. Extruded alloys exhibited slightly superior corrosion resistance and slower degradation rate than those of their cast counterparts, but all had corrosion rates roughly half that of a standard purity Mg control. Hot extrusion of Zn-Mg alloys shifted the corrosion regime from localized pitting to more uniform erosion, mainly due to the refinement of second phase particles. Zn-0.5Mg is the most promising material for stent applications with a good combination of strength, ductility, strain hardening exponent and an appropriate rate of loss of mechanical integrity during degradation. An EBSD analysis in the vicinity of the laser cut Zn-0.5Mg tube found no grain coarsening or texture modification confirming that, after laser cutting, the grain size and texture orientation of the final stent remains unchanged. This work shows the potential for Zn alloys to be considered for stent applications.

Magnesium extrusion alloys: a review of developments and prospects

Abstract: Magnesium (Mg) alloys have received a significant interest in the past 20 years, owing to a nonlinearly increasing demand for lightweight structural materials. Magnesium extrusions alloys to date h...