Byoung-Yong Kim

Clinical and angiographic follow-up of stent-only therapy for acute intracranial vertebrobasilar dissecting aneurysms.

BACKGROUND AND PURPOSE: Little has been known about the clinical and angiographic follow-up results of stent-only therapy for intracranial vertebrobasilar dissecting aneurysms (VBDA). The purpose of this study was to evaluate the feasibility, safety, clinical, and angiographic follow-up of stent-only therapy for VBDA. MATERIALS AND METHODS: Twenty-seven patients with 29 VBDAs (11 ruptured, 18 unruptured), not suitable for deconstructive treatment, underwent stent-only therapy. Feasibility, safety, clinical, and angiographic follow-up were retrospectively evaluated. Angiographic outcomes were compared between single-stent and multiple-stent groups. RESULTS: All attempted stent placements were successfully accomplished without any treatment-related complication. Of the 11 ruptured VBDAs, 4 were treated by single stents, 6 by double overlapping stents, and 1 by triple overlapping stents. Of the 18 unruptured VBDAs, 6 were treated by stents, and 12 by double overlapping stents. One patient with a ruptured VBDA, treated by single stent, had rebleeding and died. None of the remaining patients had posttreatment bleeding during follow-up (mean, 28 months; range, 7–50 months). Eight patients with ruptured VBDA and all patients with unruptured VBDA had excellent outcomes (modified Rankin Scale, 0–1). The remaining 2 patients with ruptured VBDA were moderately disabled because of the initial damage. Angiographic follow-up was available in 27 VBDAs, 4 to 42 months (mean, 12 months) after treatment. Follow-up angiograms revealed complete obliteration of the dissecting aneurysm in 12, partial obliteration in 12, stable in 1, enlargement in 1, and in-stent occlusion in 1. Angiographic improvement (complete or partial obliteration) was more frequent in the multiple-stent group (17/17) than in the single-stent group (7/9; P < .05). CONCLUSIONS: In this small series, stent-only therapy was safe and effective in the treatment of VBDAs that were not deemed suitable for treatment with parent-artery occlusion.

Compositional investigation of liquid crystal alignment on tantalum oxide via ion beam irradiation

The homogeneously aligned liquid crystal display on Ta2O5 via ion beam (IB) irradiation was first embodied with controllability of pretilt angle depending on incident angle of the IB. As a result of x-ray photoelectron spectroscopic analysis, the intensity of Ta–O and O–Ta bondings as a function of incident angle behaved reversely with the pretilt angle and the lowest amplitude was observed at 45°. It revealed that the creation of pretilt angle was attributed to the irradiation of the IB by breaking Ta–O and O–Ta bonding so orientational order was generated by directional IB. Comparable electro-optical characteristics to rubbed polyimide were also achieved.

Vertically aligned liquid crystals on a γ-Al2O3 alignment film using ion-beam irradiation

Using ion-beam (IB) irradiation, liquid crystals (LCs) were vertically aligned (VA) on a γ-Al2O3 alignment film. Atomic-layer deposition was used to orient the LCs on high-quality γ-Al2O3 alignment films. The LC molecule orientation indicates the vertical direction of the atomic-layer-deposited γ-Al2O3 alignment films. X-ray photoelectron spectroscopy showed that IB irradiation changed the chemical structure, shifting the Al–O binding energy and altering the Al–O bonding intensity. The low-voltage transmittance characteristics of the VA LC displays on the γ-Al2O3 alignment films were also measured, showing reduced voltage and power requirements.

Endovascular Coil Embolization of Aneurysms with a Branch Incorporated into the Sac

BACKGROUND AND PURPOSE: Because of the concern for occlusion of the incorporated branch artery, an aneurysm with a branch incorporated into the sac has been regarded as a contraindication for coiling. The aim of this study is to evaluate the feasibility, techniques, and clinical and angiographic outcomes of coiling for aneurysms with a branch incorporated into the sac. MATERIALS AND METHODS: The medical records and radiologic studies of 69 patients with 79 aneurysms having a branch incorporated into the sac (26 ruptured, 53 unruptured) were retrospectively reviewed and evaluated. RESULTS: Coiling was accomplished in 78 aneurysms in 68 patients but was suspended in 1 due to incorporated branch occlusion. The aneurysms were treated by using the following techniques: single-catheter (n = 37), multicatheter (n = 22), balloon-remodeling (n = 7), stent-assisted coiling (n = 6), and combined (n = 7). Postembolization angiography revealed the following: near-complete occlusion in 71 (89.8%), remnant neck in 4 (5.1%), and incomplete occlusion in 4 (5.1%) aneurysms. Procedure-related permanent morbidity and mortality rates were 5.8% (4/69) and 0%, respectively. All patients with unruptured aneurysms had a modified Rankin Scale (mRS) score of 0, except for 1 patient who had an mRS score of 3. Of the 26 patients with ruptured aneurysms, 18 had favorable outcome (mRS 0–2) but 8 had poor outcome (mRS 3–6). Follow-up angiography was available at least once at 6–50 months (mean, 15 months) in 55 aneurysms (69.6%), of which 45 showed stable or improved occlusion; 4, minor recurrences; and 6, major recurrences. All 6 major recurrent aneurysms were retreated without complication by using a single-catheter (n = 1), multicatheter (n = 2), or balloon-assisted technique (n = 3). CONCLUSIONS: With appropriate techniques, most aneurysms with a branch incorporated into the sac could be safely treated by coiling, with acceptable outcomes.

Surface reformation and electro-optical characteristics of liquid crystal alignment layers using ion beam irradiation

The surface modification characteristics of liquid crystal (LC) alignment layers irradiated with various argon (Ar) ion beam (IB) energies were investigated as a substitute for rubbing technology. Various pretilt angles were created on the IB-irradiated polyimide (PI) surfaces after IB irradiation, but the Ar ions did not alter the morphology on the PI surface, indicating that the pretilt angle was not due to microgrooves. The chemical bonding states of the IB-irradiated PI surfaces were analyzed in detail by x-ray photoelectron spectroscopy to verify the compositional behavior for the LC alignment. Chemical structure analysis showed that the alignment ability of LCs was due to the preferential reorientation of the carbon network due to the breaking of C=O double bonds in the imide ring parallel to the incident IB direction. The potential of applying nonrubbing technology to display devices was further supported by the superior electro-optical characteristics compared to rubbed PI.

Vertical alignment of liquid crystals on a fully oxidized HfO2 surface by ion bombardment

High-performance liquid crystals (LCs) driven at a 0.9 V threshold were demonstrated on very thin HfO2 films with vertical (homeotropic) alignment by ion bombardment. Atomic layer deposition was used to obtain LC orientation on ultrathin high-quality films of double-layer HfO2/Al2O3. X-ray photoelectron spectroscopy indicated that full oxidization of HfO2 film surfaces was induced by ion bombardment, shifting the Hf 4f spectra to lower binding energies. The increased intensities of the Hf 4f peaks after ion bombardment confirmed that nonstoichiometric HfOx was converted to the fully oxidized HfO2 surfaces.

High-performance ZnO thin-film transistor fabricated by atomic layer deposition

We report the fabrication and characteristics of a ZnO thin-film transistor (TFT) using a 50 nm thick ZnO film as an active layer on an Al2O3 gate dielectric film deposited by atomic layer deposition. Lowering the deposition temperature allowed the control of the carrier concentration of the active channel layer (ZnO film) in the TFT device. The ZnO TFT fabricated at 110 °C exhibited high-performance TFT characteristics including a saturation field-effect mobility of 11.86 cm2 V−1 s−1, an on-to-off current ratio of 3.09 × 107 and a sub-threshold gate-voltage swing of 0.72 V decade−1.

Tin dioxide inorganic nanolevel films with different liquid crystal molecular orientations for application in liquid crystal displays (LCDs)

We generated SnO2 alignment films with one of two liquid crystal (LC) molecular orientations: a stable, vertical orientation or a homogeneous orientation. We changed the molecular orientations by altering the growth temperature of radio-frequency (RF) magnetron sputtering. An ion-beam (IB) advanced system was used to achieve uniform alignment. We obtained two LC molecular orientations as demonstrated by the shift of the Sn 3d peaks and the altered-sub peaks of Sn2+, Sn4+ intensity on X-ray photoelectron spectroscopy (XPS) images of the various films. The electro-optical (EO) characteristics of the TN-LC and VA-LC displays on the high-k SnO2/HfO2 double films were measured; a reduction in threshold voltage, response time, and low power consumption were observed.

Stenting from the vertebral artery to the posterior inferior cerebellar artery.

BACKGROUND AND PURPOSE: There are only a few reports on the feasibility and safety of stents used in the PICA, and clinical and angiographic follow-up results have not been fully addressed. We report our experiences of treating PICA origin or vertebral artery−PICA lesions by using self-expanding stents as adjuvant or rescue therapy with angiographic and clinical follow-up results. MATERIALS AND METHODS: Six patients were treated with self-expanding stent placements from the vertebral artery to the PICA. Two patients had a vertebral artery dissecting aneurysm involving the PICA origin, 3 had vertebral artery−PICA aneurysms, and 1 had segmental stenosis of the vertebral artery harboring the origin of the PICA. The safety, feasibility, and follow-up angiographic results were retrospectively evaluated. RESULTS: All procedures were successfully performed without any procedure-related complications. None of the patients showed PICA territorial infarction on DWI posttreatment. All patients were neurologically intact during the clinical follow-up of 3–24 months following the procedure. Follow-up angiography was performed at between 6 and 12 months in 5 of the 6 patients and was scheduled for the sixth patient but was not performed. The PICA showed good patency without in-stent stenosis in all 5 patients. CONCLUSIONS: In patients with lesions of the PICA origin or vertebral artery−PICA lesions, vertebral artery-to-PICA stent placement may be an option for preserving PICA patency in selected cases.

Reconstructive Endovascular Treatment of Fusiform or Ultrawide-Neck Circumferential Aneurysms with Multiple Overlapping Enterprise Stents and Coiling

BACKGROUND AND PURPOSE: Fusiform aneurysms and ultrawide-neck circumferential aneurysms are still some of the most challenging lesions. The aim of this study was to investigate the efficacy and feasibility of the use of multiple overlapping Enterprise stents with coiling for the treatment of fusiform or ultrawide-neck circumferential aneurysms. MATERIALS AND METHODS: Twelve consecutive patients (9 men and 3 women; mean age, 56 years) with fusiform (n = 5) or ultrawide-neck circumferential (n = 7) aneurysms were treated with 2–3 overlapping Enterprise stents and coiling. The feasibility of this procedure and the clinical and angiographic outcomes of this technique were retrospectively evaluated. RESULTS: All patients were successfully treated by using this technique without any complications. Posttreatment angiographic results revealed grade 4 occlusion of the aneurysm in 6, grade 3 in 4, and grade 2 in 2 patients. Clinical follow-up was performed in all patients (mean, 16 months; range, 5–24 months). Nine patients had an mRS score of 0. Two had an mRS score of 1, one of whom had an initial mRS score of 2 due to the mass effect of a giant aneurysm; the other had a recurrent aneurysm presenting with SAH 5 years after clipping. Angiographic follow-up was performed in 10 patients at 6–20 months posttreatment. Nine had stable or improved occlusion, while 1 had a minor recurrence. CONCLUSIONS: In this small series, multiple overlapping Enterprise stents with coiling were a feasible and effective option for the treatment of fusiform and ultrawide-neck circumferential aneurysms. Further experience and follow-up are required to document the long-term efficacy of this treatment.