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Kee-Hyun Chang

Publications and source records attributed to Kee-Hyun Chang.

30 records · Page 2Linked to original sources
PubMed2003

Embolization with autologous fibroblast-attached platinum coils in canine carotid artery aneurysms: histopathological differences from plain coil embolization.

PURPOSE: This study was designed to evaluate the effect of autologous fibroblast-attached platinum coils on the promotion of intra-aneurysmal thrombus organization. MATERIALS AND METHODS: Sidewall aneurysms were surgically created at common carotid arteries bilaterally in 5 dogs. Fibroblasts were obtained from the skins of the dogs and cultured and attached to unmodified platinum coils in a 5-day coculture. In each animal, one aneurysm was embolized with fibroblast-attached platinum coils (study group) and the other with plain platinum coils of the same size (control group). RESULTS: All aneurysms were partially occluded; the mean occlusion rate was 67%. The histologic analyses performed 2 weeks after the embolization showed more advanced organization of intra-aneurysmal thrombus in the study group than in the control group (80% versus 53%, P = 0.02). Overgrowth of the organizing tissue and parent artery stenosis did not occur. CONCLUSION: Our results suggest that autologous fibroblasts delivered with platinum coils could promote the organization of intra-aneurysmal thrombus. Although further research is needed, especially on the potential complications, endovascular treatment using autologous fibroblasts may be applied to aneurysm treatment.

Aneurysm↗
PubMed2003

Dynamic contrast-enhanced MR imaging of VX2 carcinomas after X-irradiation in rabbits: comparison of gadopentetate dimeglumine and a macromolecular contrast agent.

RATIONALE AND OBJECTIVES: To compare enhancement patterns of gadomer-17 with those of gadopentetate dimeglumine in VX2 carcinomas after irradiation on rabbits. METHODS: Twelve rabbits with VX2 carcinoma in the thigh underwent dynamic contrast-enhanced magnetic resonance (MR) imaging with gadopentetate dimeglumine and gadomer-17 at 24-hour intervals before (n = 12), 3 days (group 1, n = 12), 1 month (group 2, n = 8) and 2 months (group 3, n = 4) after 30 Gy irradiation. After taking postirradiation MR images, 4 rabbits were killed for histopathologic examination at each time interval. The enhancement characteristics in MR imaging and morphology of tumor vessels in histopathologic specimen were assessed. RESULTS: After gadopentetate dimeglumine injection, the enhancement characteristics were not different among tumors before and after irradiation (P > 0.05). For gadomer-17, the enhancement ratios decreased after irradiation. The shape of the curves for tumor enhancement before irradiation was significantly different from curves of group 1(P < 0.05). The specimens from group 3 showed sclerosis and wall thickening in arterioles. CONCLUSIONS: Dynamic contrast-enhanced MR imaging with a gadomer-17 reveals increased capillary permeability at an early phase after irradiation and chronic obliterating vasculopathy at delayed phase.

Animals↗
PubMed2003

Gas generation and clot formation during electrolytic detachment of Guglielmi detachable coils: in vitro observations and animal experiment.

BACKGROUND AND PURPOSE: Recent reports describe a high rate of thromboembolic events related to Guglielmi detachable coil (GDC) use in the treatment of cerebral aneurysms. The purpose of this study was to investigate electrolysis-related changes of blood as a potential cause of thromboembolic complications associated with GDC use. METHODS: For in vitro observations, 15 GDCs (10 conventional coils and five insulated coils) were experimentally detached under microscopic observation. Three coils were detached in normal saline, five in human serum, and seven in heparinized human blood. For animal experiments, two coils were detached in two canine normal common carotid arteries with systemic heparinization. Immediately after detachment, the arteries were exposed, and clot formations were observed. RESULTS: Significant amounts of gas bubbles were observed in all in vitro observations; more were seen in conventional coils, which required longer detachment times, than in insulated coils. Gas generation started with the growth of tiny bubbles into larger ones. In insulated coils, gas was generated only at the detachment zone, and no difference between saline, serum, and blood environments was observed. During detachment within heparinized blood, clot formations of 2-3-mm diameter were observed at the detachment zones of insulated coils. Animal experiments showed clot formation at the detachment zone, and bubble entrapments around the clots were also found. CONCLUSION: The electrolytic detachment mechanism of the platinum coil can generate gas bubbles during the application of electric current. In association with electrothrombosis, this phenomenon may be a potential cause of thromboembolic complications during the treatment of cerebral aneurysms by use of GDCs.

Animals↗
PubMed2003

Delayed encephalopathy of acute carbon monoxide intoxication: diffusivity of cerebral white matter lesions.

BACKGROUND AND PURPOSE: Carbon monoxide intoxication has delayed effects on the cerebral white matter characterized by bilateral, confluent lesions that reflect diffuse demyelination. To increase our understanding of this process, we assessed the diffusion characteristics of these lesions. METHODS: Five consecutive patients with delayed encephalopathy of CO intoxication were examined with diffusion MR imaging. Diffusion-weighted images (DWIs) were obtained 25-95 days after their exposure to CO and during a relapse of neuropsychiatric symptoms, which occurred after an initial recovery. Imaging was performed at 1.5 T by using a spin-echo echo-planar sequence with diffusion gradients of 0, 500, and 1000 s/mm(2). DWIs and apparent diffusion coefficient (ADC) maps were visually evaluated, and mean ADCs were calculated from the periventricular white matter and the centrum semiovale, where confluent hyperintensity was seen on T2-weighted images. Findings were compared with those of normal-looking white matter. RESULTS: In all five patients, both T2-weighted images and DWIs showed the white matter lesions as bilateral, diffuse, confluent areas of hyperintensity in the periventricular white matter and centrum semiovale. On ADC maps, these lesions were isointense, with focal areas of hypointensity (n = 4) or diffuse hypointensity (n = 1). Mean ADC values of the white matter lesions were significantly lower than those of normal-looking white matter, regardless of their isointensity or hypointensity on ADC maps (P <.05). CONCLUSION: Bilateral, confluent, white matter lesions in patients with delayed encephalopathy of CO intoxication show decreased diffusivity.

Aged↗
PubMed2002

Craniofacial cavernous venous malformations: percutaneous sclerotherapy with use of ethanolamine oleate.

PURPOSE: To assess the efficacy of percutaneous sclerotherapy with use of ethanolamine oleate for craniofacial cavernous venous malformations. MATERIALS AND METHODS: From 1991 to 2001, sclerotherapy (average of two procedures per patient) was performed in 29 patients (mean age, 22 y; 10 male) with craniofacial venous malformations. Direct puncture venography was performed with use of water-soluble contrast media to delineate the extent of the lesions. CO(2) gas was used as contrast medium in addition to water-soluble contrast media in five patients in whom lesions had large nondependent areas. Coil embolization with a transvenous approach was performed in two patients when the lesions had large draining veins. Then, a mixture of 5% ethanolamine oleate and iodized oil (ratio, 5:1-5:2) was injected manually into the lesions under fluoroscopic guidance to monitor the process. A total of 59 procedures were performed. Clinical follow-up was obtained in 25 of 29 patients. The duration of follow-up ranged from 10 days to 6 years (mean, 8.5 mo). The effectiveness of sclerotherapy was assessed on the basis of clinical, surgical, and radiologic findings. RESULTS: The procedures were effective in 14 of 16 patients who underwent sclerotherapy only. The procedures were beneficial for all nine patients who underwent sclerotherapy and surgery. There was no skin injury or nerve damage. The trismus that appeared in two patients with lesions in the masticator space was treated well by conservative therapy. CONCLUSION: Percutaneous sclerotherapy with use of ethanolamine oleate is a safe and effective treatment of craniofacial cavernous venous malformations. However, renal function was not specifically evaluated after treatment, and therefore occult renal dysfunction cannot be excluded.

Adolescent↗
PubMed2002

Hypoechoic normal renal sinus and renal pelvis tumors: sonographic differentiation.

OBJECTIVE: To evaluate the sonographic findings of an unusually hypoechoic renal sinus that mimics a tumor in the renal pelvis or renal sinus. METHODS: Sonographic scans of 7 patients with an unusually hypoechoic portion in the renal sinus were reviewed retrospectively. Computed tomography, excretory urography, or both confirmed all sinuses as normal. Five consecutive cases of renal pelvis tumors, which were detected on sonography initially in same period, were also reviewed to determine the differences between the 2 conditions. All cases were transitional cell carcinomas of the renal calyces. The images were analyzed for location, shape, margin, presence of posterior sonic attenuation, and associated findings such as caliectasis. RESULTS: Sonographic findings noted in patients with hypoechoic normal renal sinuses were irregular and poorly defined margins (n = 7), a central and symmetric location in the renal sinus (n = 6), the presence of posterior sonic attenuation with nonvisualization of the posterior border of the lesion (n = 7), an unaffected peripheral hyperechoic renal sinus (n = 7), and traversing hilar vessels in the lesion on color Doppler sonography (n = 7). In contrast, renal pelvis tumors had a relatively well-defined margin (n = 4), an eccentric location in the renal sinus (n = 2), a partially or completely obliterated hyperechoic renal sinus (n = 2), a visible posterior margin (n = 5), no posterior shadowing (n = 5), vessel displacement by the mass on color Doppler sonography (n = 5), and associated caliectasis (n = 1). CONCLUSIONS: By being familiar with the sonographic characteristics of a hypoechoic renal sinus, it can be differentiated from renal pelvis tumors, and unnecessary diagnostic workups can be avoided.

Adult↗
PubMed2002

Apparent diffusion coefficient value of the hippocampus in patients with hippocampal sclerosis and in healthy volunteers.

BACKGROUND AND PURPOSE: MR diffusion-weighted (DW) imaging with apparent diffusion coefficient (ADC) has had widespread use clinically in a variety of intracranial diseases; however, only a few studies report ADC changes in patients with hippocampal sclerosis. We sought to determine the ability of ADC to lateralize the epileptogenic lesion in patients with hippocampal sclerosis. METHODS: Nineteen healthy volunteers and 18 patients with intractable temporal lobe epilepsy whose MR imaging diagnosis was unilateral hippocampal sclerosis were examined prospectively with DW imaging and ADC mapping. DW images were obtained at 1.5 T with a spin-echo echo-planar sequence (6500/103 [TR/TE]) with variable diffusion gradients. ADCs were calculated from bilateral hippocampi. The ability of DW imaging and ADC to lateralize the lesion was evaluated visually and by comparing ADC values between healthy volunteers and patients with hippocampal sclerosis. RESULTS: In all patients, visual assessment of DW images failed to lateralize the lesion. However, the mean ADC value measured at the hippocampal area was significantly higher on the lesion side than on the contralateral side (P <.001). The overall correct lateralization rate of ADC was 100% (18 of 18 patients). Mean ADC in sclerotic hippocampi was also significantly higher than that in healthy volunteers. The normal-appearing hippocampus of the contralateral side in the patients had higher ADC values compared with those of healthy volunteers (P =.045). CONCLUSION: ADC can be used as a complementary tool in lateralizing the epileptogenic lesion in patients with hippocampal sclerosis, although the practical role of ADC value is yet to be determined in patients with inconclusive MR imaging findings.

Adolescent↗
PubMedDate not supplied

Nasopharyngeal carcinoma: posttreatment changes of imaging findings.

OBJECTIVE: The purpose of this study was to determine the radiologic results of nasopharyngeal carcinoma (NPC) that showed complete responses on follow-up imaging studies after radiation therapy. MATERIALS AND METHODS: This study is a retrospective review of 23 patients (18 male, 5 female, aged 15-71 years; mean age, 48.5 years) affected with NPC, from August 1995 to July 2000, who were examined with magnetic resonance imaging or computed tomography scan before and after either radical radiotherapy or chemoradiotherapy. The median follow-up was 24.7 months and ranged from 12 to 48 months. We analyzed the primary tumors by ascertaining/measuring tumor size, depth, middle ear effusion, skull base invasion, and lymphadenopathy. The treatment responses for primary tumors were classified as either atrophy, scar (asymmetric elevation without enhancement), or normalized. The tumor response and the appearance of bone regeneration in the previous destructive part of the skull base were also recorded. RESULTS: The 23 patients consisted of 12 superficial tumors, for whom treatment results were normalized in 10, atrophy in 1, and scar in 1 and 11 deep tumors for whom treatment results were scar in 6, normalized in 3, and atrophy in 2. Skull base invasion was detected in 6 patients, 5 of whom showed complete healing of skull base destruction after radiotherapy. However, the other patient exhibited an unusual hyperostotic change in the skull base mimicking fibrous dysplasia of the skull base. CONCLUSIONS: The superficial tumors tended to be radiologically normalized even when they were large. However, the deep tumors mainly changed to scar after radiation therapy. On the other hand, skull base invasion could be normalized after radiotherapy.

Adolescent↗
PubMedDate not supplied

Intracranial and spinal ependymomas: review of MR images in 61 patients.

OBJECTIVE: To compare the age distribution and characteristic MR imaging findings of ependymoma for each typical location within the neuraxis. MATERIALS AND METHODS: During a recent eleven-year period, MR images of 61 patients with histologically proven ependymomas were obtained and retrospectively reviewed in terms of incidence, peak age, location, size, signal intensity, the presence or absence of cyst and hemorrhage, enhancement pattern, and other associated findings. RESULTS: Among the 61 patients, tumor location was spinal in 35 (57%), infrartentorial in 19 (31%), and supratentorial in seven (12%). In four of these seven, the tumor was located in brain parenchyma, and in most cases developed between the third and fifth decade. Approximately half of the infratentorial tumors occurred during the first decade. The signal intensity of ependymomas was nonspecific, regardless of their location. A cystic component was seen in 71% (5/7) of supratentorial, 74% (14/19) of infratentorial, and 14% (5/35) of spinal cord tumors. Forty- nine percent (17/35) of those in the spinal cord were associated with rostral and/or caudal reactive cysts. Intratumoral hemorrhage occurred in 57% (4/7) of supratentorial, 32% (6/19) of infratentorial, and 9% (3/35) of spinal cord tumors. In 17% (6/35) of spinal ependymomas, a curvilinear low T2 signal, suggesting marginal hemorrhage, was seen at the upper and/or lower margins of the tumors. Peritumoral edema occurred in 57% (4/7) of supratentorial, 6% (3/19) of infratentorial and 23% (8/35) of spinal cord tumors. Seventy-two percent (5/7) of supratentorial and 95% (18/19) of infratentorial tumors showed heterogeneous enhancement, while in 50% (17/34) of spinal cord tumors, enhancement was homogeneous. CONCLUSION: Even though the MR imaging findings of ependymomas vary and are nonspecific, awareness of these findings, and of tumor distribution according to age, is helpful and increases the likelihood of correct preoperative clinical diagnosis.

Adult↗
PubMedDate not supplied

Comparison of 1.5T and 3T 1H MR spectroscopy for human brain tumors.

OBJECTIVE: We wanted to estimate the practical improvements of 3T proton MR spectroscopy ((1)H MRS) as compared with 1.5T (1)H MRS for the evaluation of human brain tumors. MATERIALS AND METHODS: Single voxel (1)H MRS was performed at both 1.5T and 3T in 13 patients suffering with brain tumors. Using the same data acquisition parameters at both field strengths, the (1)H MRS spectra were obtained with a short echo time (TE) (35 msec) and an intermediate TE (144 msec) with the voxel size ranging from 2.0 cm(3) to 8.7 cm(3). The signal to noise ratios (SNRs) of the metabolites (myoinositol [MI], choline compounds [Cho], creatine /phosphocreatine [Cr], N-acetyl-aspartate [NAA], lipid and lactate [LL]) and the metabolite ratios of MI/Cr, Cho/Cr, Cho/NAA and LL/Cr were compared at both TEs between the two field strengths in each brain tumor. The degrees of spectral resolution between the Cho and Cr peaks were qualitatively compared between the two field strengths in each brain tumor. RESULTS: The SNRs of the metabolites at 3T demonstrated 49-73% increase at a short TE (p < 0.01) and only 2-12% increase at an intermediate TE (p > 0.05) compared with those of 1.5T. The SNR of inverted lactate at an intermediate TE decreased down to 49% with poorer inversion at 3T (p < 0.05). There was no significant difference in the metabolite ratios between the two field strengths. The degrees of the spectral resolution at 3T were slightly superior to those of 1.5T at a short TE. CONCLUSION: As compared with 1.5T, 3T 1H MRS demonstrated 49-73% SNR increase in the cerebral metabolites and slightly superior spectral resolution only at a short TE, but little at an intermediate TE, in the brain tumors. There was no significant difference in the metabolite ratios between the two field strengths.

Adolescent↗
PubMedDate not supplied

MR imaging findings of intracranial dural arteriovenous fistulas: relations with venous drainage patterns.

BACKGROUND AND PURPOSE: Venous drainage patterns are a major determinant of clinical outcome in intracranial dural arteriovenous fistula (DAVF) patients. In this study, we sought to identify MR imaging finding differences between DAVF types classified on the basis of venous drainage patterns. METHODS: Twenty-seven patients diagnosed as having DAVFs by conventional angiography were included. Medical records (n = 27), and MR imaging (n = 27) and MR angiography (MRA; n = 11) findings were retrospectively reviewed. MR imaging findings included flow void cluster, engorged ophthalmic vein/proptosis, white matter hyperintensity, intracranial hemorrhage, dilated leptomeningeal or medullary vessels, venous pouch, and leptomeningeal or medullary vascular enhancements. MRA findings included identifiable fistula, venous flow-related enhancement, and prominent extracranial vessels. Patients' presentations and MR imaging findings were compared among angiographic type I, II, and III cases (according to Borden's classification), and MRA findings were compared between cases with and without retrograde leptomeningeal venous drainage (RLVD). RESULTS: Patient presentations were aggressive in one (13%) of the type I cases, 5 (50%) of the type II cases, and 8 (100%) of the type III cases (P = .002). Aggressive presentations included hemorrhage, focal neurologic deficits, seizures, intracranial hypertension, and an altered mental status. MR images showed significantly higher frequencies of dilated leptomeningeal or medullary vessels in a higher type [0 in type I, 5 (42%) in type II, and 7 (100%) in type III], and of leptomeningeal or medullary vascular enhancements [0 in type I, 4 (33%) in type II, and 7 (100%) in type III]. By using MRA, fistulas were identified only in cases with RLVD (5 [83%]). Venous flow-related enhancement was present in 10 cases (91%). A sole false-negative case on MRA, as compared with conventional angiography, resulted from nonvisualization of the slow venous flow (8%). No false-positive fistula was found at the other intracranial sites in all cases. Overall, MRA assessment for DAVF was adequate for both fistula and venous flow-related enhancement in 10 cases (91%) and inadequate in a remaining case because of the fistular location out of field. CONCLUSION: MR imaging demonstration of leptomeningeal or medullary vascular dilation and enhancements may be associated with features that are considered predictors of a poor outcome and indicates a need for urgent therapy in intracranial dural AVF patients. MRA is a complementary tool for the identification of dural AVF with venous flow-related enhancement.

Adolescent↗