Biomedical subjects

Kee-Hyun Chang

Publications and source records attributed to Kee-Hyun Chang.

At least 19 recordsLinked to original sources

PubMed2006

Cervical lymph node metastases: MR imaging of gadofluorine M and monocrystalline iron oxide nanoparticle-47 in a rabbit model of head and neck cancer.

PURPOSE: To prospectively compare the accuracy of gadofluorine M with that of monocrystalline iron oxide nanoparticle (MION)-47 for the depiction of cervical lymph node metastases at magnetic resonance (MR) imaging in a rabbit model of head and neck cancer by using histologic analysis as the reference standard. MATERIALS AND METHODS: Experiments were approved by the animal care committee. VX2 carcinomas were implanted in both ears of 11 rabbits 4 weeks before MR imaging. T2-weighted, T2*-weighted, and T1-weighted MR images were acquired, and sequential T1-weighted MR imaging was performed immediately and 30 minutes after administration of gadofluorine M (0.05 mmol gadolinium per kilogram body weight). T2-weighted and T2*-weighted MR imaging were performed 24 hours after administration of MION-47 (2.6 mg iron per kilogram body weight). Gadofluorine M- and MION-47-enhanced MR imaging were performed separately and independently by two radiologists who had no knowledge of histopathologic results, and the presence of metastases in lymph nodes was evaluated. A receiver operating characteristic analysis was conducted to compare the diagnostic value of gadofluorine M- and MION-47-enhanced MR imaging. RESULTS: Metastases were confirmed in 20 of 77 lymph nodes at histopathologic analysis. The area under the curve was significantly greater for gadofluorine M-enhanced MR imaging (0.997 and 0.981 for readers 1 and 2, respectively) than for MION-47-enhanced MR imaging (0.889 and 0.846 for readers 1 and 2, respectively). For gadofluorine M-enhanced MR imaging, sensitivity was 100% for both readers and specificity was 89.5% for reader 1 and 87.7% for reader 2. For MION-47-enhanced MR imaging, sensitivity was 80.0% for both readers and specificity was 75.4% for reader 1 and 71.9% for reader 2. CONCLUSION: Gadofluorine M-enhanced MR imaging has higher accuracy for depicting lymph node metastases than does MION-47-enhanced MR imaging.

Animals↗

PubMed2006

An MRI study of structural variations in schizophrenia using deformation field morphometry.

Magnetic resonance imaging (MRI) has an important role in investigating the changes in brain structure that are associated with schizophrenia. In this study, MRI scans of patients diagnosed with schizophrenia (37 males; 19 females; 17-42 years of age) were compared with those of an age- and sex-matched group of normal subjects (37 males; 19 females; 18-40 years of age). Based on the images of the healthy control subjects, we constructed a representative average brain template. Automated image analysis techniques were used to measure differences in the regional nonlinear deformation fields between the two groups. A deformation field, which measures the spatial transformation to deform a template of brain anatomy to each individual data, was obtained as a three-dimensional displacement vector in each voxel. There was a significantly greater magnitude of the deformation fields in the superior frontal and parietal lobes as well as in the cingulate gyrus connecting both lobes of the patients with schizophrenia than in those of healthy controls, suggesting that these cerebral regions have a significantly higher structural variability in schizophrenia.

Adolescent↗

PubMed2005

Local tumor invasiveness is more predictive of survival than International Prognostic Index in stage I(E)/II(E) extranodal NK/T-cell lymphoma, nasal type.

This study was launched to determine the prognostic significance of local tumor invasiveness (LTI) in 114 patients diagnosed with stage I(E)/II(E) extranodal natural killer (NK)/T-cell lymphoma, nasal type (NTCL). LTI was defined as bony invasion or destruction or tumor invasion of the skin. Complete remission (CR), overall survival (OS), and disease-free survival (DFS) were compared between each group according to LTI, Ann Arbor stage, and International Prognostic Index (IPI). LTI was observed in 23 patients. Using multivariate analysis, factors associated with low probability of CR were the presence of LTI (P < .001), the presence of B symptoms (P = .003), and single-modality chemotherapy (P = .045). The presence of LTI (relative risk [RR] = 8.4, 95% confidence interval [CI] 3.9-17.9; P < .001) and high IPI score (RR = 2.8, 95% CI 1.2-6.8; P = .019) were also predictive of OS. The presence of LTI (RR = 7.3, 95% CI 3.2-16.5; P < .001) was an independently significant factor for reduced DFS. Ann Arbor staging system did not predict CR, OS, or DFS but IPI did have predictive power with regard to survival outcome. LTI is the most important prognostic factor in predicting low probability of CR and reduced OS and DFS in nasal stage I(E)/II(E) NTCL.

Adolescent↗

PubMed2005

CT sign of brain swelling without concomitant parenchymal hypoattenuation: comparison with diffusion- and perfusion-weighted MR imaging.

PURPOSE: To retrospectively evaluate the apparent diffusion coefficient (ADC) on magnetic resonance (MR) images and the perfusion parameters of lesions that show brain swelling without concomitant parenchymal hypoattenuation on computed tomographic (CT) scans. MATERIALS AND METHODS: Review board approval was obtained, and informed consent was waived. A total of 14 patients (seven men and seven women; mean age, 64 years +/- 11) were retrospectively selected from the consecutive 172 patients with acute cerebral ischemia who underwent CT within 6 hours of symptom onset. All patients had brain swelling without parenchymal hypoattenuation, including loss of gray-white matter distinction on CT scans, and they underwent diffusion- and perfusion-weighted MR imaging shortly after CT. CT attenuation, ADC, and perfusion parameters of relative cerebral blood volume (CBV), time to peak (TTP), and relative cerebral blood flow (CBF) were calculated for gray and white matter of the lesion. The measured values were compared with those of the contralateral hemisphere by using the paired t test; comparison of values of perfusion parameters among three subgroups was performed with the Kruskal-Wallis test. Arterial occlusions were determined with MR angiography or conventional angiography. RESULTS: The mean interval between initial CT and MR imaging was 2.4 hours +/- 0.9 (range, 0.4-3.4 hours). The ADC of lesions was similar to that of contralateral normal tissue (mean ADC ratio for gray matter and white matter, 0.99 and 0.97, respectively) (P > .05). Lesions had an increased relative CBV (P < .001), a mild to moderate TTP delay (P < .001), and a variable but not statistically significant reduction of relative CBF. The mean relative CBF of gray matter was less in patients who had complete infarction (0.81 +/- 0.16) than that in patients with partial infarction (0.99 +/- 0.16) or those with a normal radiologic outcome (1.12 +/- 0.22), but this difference was not statistically significant (P > .05). Proximal cerebral artery occlusions were found in all patients. In five (36%) patients, the lesion did not progress to infarction at follow-up. CONCLUSION: The CT sign of brain swelling without concomitant parenchymal hypoattenuation in patients with acute cerebral ischemia does not represent severe ischemic damage and may suggest ischemic penumbral or oligemic tissue.

Aged↗

PubMed2005

Endovascular occlusion of direct carotid cavernous fistula with detachable balloons: usefulness of 3D angiography.

The objective of this study is to show rotational 3D angiography findings and their usefulness in the occlusion of carotid cavernous fistulas (CCFs) using detachable balloons. Five patients with direct CCF were retrospectively reviewed for details of interventional procedures and 2D and 3D angiography findings. Pretherapeutic 2D and 3D angiograms (n=2) were compared to evaluate the size of the fistula and the relative size of the cavernous sinus with respect to the fistula. Postinflation-predetachment (n=3) and postdetachment (n=4) 2D and 3D angiograms were compared in each stage to evaluate the relative location of the balloon to the internal carotid artery (ICA), presence of a pseudoaneurysm, and relative size of the balloon to the fistula. Pretherapeutic 2D and 3D angiograms were equally effective in showing the fistula and relative size of the cavernous sinus. But, 3D angiography with "cut images" at arbitrary viewing angles clearly visualized the 3D relations between the ICA, fistula, and cavernous sinus. Both postinflation-predetachment 2D and 3D images in two patients equally showed a contrast-filled pseudoaneurysm outside the ICA and intraluminal location of the balloon. However, only the 3D images showed no difference in size of the balloon compared with the fistula, which was relevant to traction-induced instability in the remaining one patient. Both postdetachment 2D and 3D angiograms were equal in terms of showing ICA compromise (60%) in one patient and an extraluminal balloon location with complete fistular occlusion in two patients. In the remainder, a small pseudoaneurysm was identified only on 3D images. Three-dimensional angiography is a useful imaging tool for capturing the complex perifistular anatomy in the pretherapeutic stage, and for providing detailed information about the degree of balloon inflation and its location, the presence of a pseudoaneurysm, and the expected traction-induced instability in the predetachment stage. Postinflation-predetachment 3D angiography may therefore offer a chance to correct an erroneous manipulation that would otherwise lead to an incomplete procedural outcome and disastrous balloon migration.

Adult↗

PubMed2005

Inflammatory myofibroblastic tumor of the central nervous system: clinicopathologic analysis of 10 cases.

To verify the pathologic features, anaplastic lymphoma kinase (ALK) expression and biologic behavior of inflammatory myofibroblastic tumors (IMTs) of the central nervous system (CNS), we analyzed 10 cases of IMTs-CNS (8 cranial, 1 spinal, and 1 orbital). Our series of IMTs of the CNS showed a male predominance (male:female = 6:4) and a wide age range (10-60 years; mean age, 46.7 years). Lesion location also varied, but they were basically dura-based. Radiologically, they showed two patterns: isolated mass forming (n = 6) and an en plaque-like pattern (n = 4). Histopathologically, plasma cell granuloma (PCG)-like (n = 5) or fibrohistiocytic (FHC) variant (n = 5) was present. No correlation was found between the radiologic and histopathologic patterns. Spindle-shaped mesenchymal cells of IMTs expressed smooth muscle actin (SMA) in all cases. ALK expression was not found in our IMTs of the CNS. Late recurrence was found in 2 cases in different sites (20%). Pathologically, IMT-CNS could be subclassified into PCG-like and FHC. Immunostaining for SMA was found to helpfully discriminate myofibroblastic cells and to make a differential diagnosis. Although our cases did not show ALK immunoreactivity, some IMTs-CNS can recur, which suggests the neoplastic potential of these tumors. The rearrangement of the ALK gene in IMTs-CNS should be verified by an examination of more cases.

Actins↗

PubMed2005

Cerebellopontomandibular vascular malformation: a rare type of cerebrofacial arteriovenous metameric syndrome. Case report.

The concept of a cerebrofacial arteriovenous metameric syndrome (CAMS) recently has been posited. A 22-year-old woman presented with gait ataxia. She had unilateral angiomatous lesions involving the lower face, the auricle, and the retromastoid area, as well as the tongue on the right side. Angiography revealed the presence of extensive arteriovenous malformations (AVMs) in the ipsilateral cerebellum and pons, in addition to those located in the facial region. The authors report a case of multiple AVMs of the face, cerebellum, and pons, corresponding to CAMS Type 3, and include a review of the literature.

Adult↗

PubMed2005

MR imaging findings of uveal leiomyoma: three cases.

Leiomyoma is a rare tumor arising from the uveal tract. Fundoscopically, it appears as a yellowish-white, elevated mass and cannot be readily distinguished from melanoma or other uveal tumors. Cross-sectional imaging may have an important role, particularly when the opaque ocular media or a vitreous hemorrhage precludes a clear ophthalmoscopic view. In this respect, radiologists should be aware of suggestive findings of uveal leiomyoma to avoid an incorrect diagnosis and unnecessary radical surgery. We report MR imaging findings of three cases of uveal leiomyoma.

Adult↗

PubMed2005

Evaluation of the lenticulostriate arteries with rotational angiography and 3D reconstruction.

BACKGROUND AND PURPOSE: Anatomic evaluation of the lenticulostriate arteries (LSAs) is important, especially in cases of surgical or endovascular treatment, but biplanar angiography provides limited information. We analyzed the LSAs with rotational angiography (RA) and 3D reconstruction and compared the findings with those of previous autopsy studies. METHODS: We retrospectively reviewed the LSAs on 3D reconstructed RA images (200 sides in 159 cases) to analyze their origin, course, and supplying territories. The angiographic configurations of the LSAs were classified by using the scheme devised by Yasargil. RESULTS: LSAs from the anterior cerebral artery were demonstrated on 140 sides (70%). They originated from the A1 segment in 59 sides, from the A1-A2 junction on 41 sides, and from the A2 segment on 35 sides. They arose as a single trunk and ended as the most medial and anterior perforators in most cases. Arteries from the middle cerebral artery (MCA) were demonstrated on 190 sides (95%). They originated from the M1 segment on 131 sides, from the MCA bifurcation on 26 sides, and from the M2 segment on 33 sides; notably, all LSAs arising from the M2 segment originated from the superior division. In terms of configuration, we identified four major and 11 minor types. The most frequent LSA type was the combination of medial and lateral distal striate arteries, which comprised 53 sides (28%). CONCLUSION: Analysis of LSAs with RA and 3D reconstructed images may provide useful information in patients with cerebrovascular diseases, especially before surgical and endovascular treatment.

Adolescent↗

PubMed2005

Short-term outcome of intracranial aneurysms treated with polyglycolic acid/lactide copolymer-coated coils compared to historical controls treated with bare platinum coils: a single-center experience.

BACKGROUND AND PURPOSE: Aneurysm recanalization is an innate problem in endovascular treatment of aneurysms with coils. A coated coil system, covered with a bioabsorbable polymeric material (polyglycolic acid/lactide copolymer, PGLA), was developed to accelerate intra-aneurysmal clot organization and fibrosis. The purpose of this study was to evaluate the efficacy and safety of the PGLA-coated coils in patients with intracranial aneurysms and to compare the outcome with that of bare platinum coils. PATIENTS AND TECHNIQUES: Fifty-one patients harboring 56 intracranial aneurysms underwent endovascular embolization with the PGLA-coated coils. In the control group were 78 consecutive patients, harboring 87 aneurysms, who underwent coil embolization with bare platinum coils. The authors compared coil volume, packing attenuation, degree of occlusion of aneurysms, procedure-related complications, and follow-up results between the 2 groups. RESULTS: The PGLA-coil group showed comparable data regarding rate of total or near-total occlusion of the aneurysm, incidence procedure-related thromboembolism, and management outcome. Mean coil volume deployed and packing attenuation of the PGLA-coil group were significantly higher than those of the bare-coil group (P = .0026 and P < .0001, respectively). Radiologic follow-up evaluation revealed recanalization in 14 of 39 aneurysms (major recanalization in 5 [13%] and minor recanalization in 9 [23%]) among the PGLA-coil group and in 29 of 64 aneurysms (major recanalization in 9 [14%] and minor recanalization in 20 [31%]) among the bare-coil group. CONCLUSION: In this study, the incidence of recanalization was not different in aneurysms treated with PGLA-coated coils compared with historical controls treated with bare platinum coils.

Adult↗

PubMed2005

Serial MR imaging findings of acute hemorrhagic leukoencephalitis: a case report.

We report a patient with acute hemorrhagic leukoencephalitis with a focus on serial MR imaging findings. Initial MR imaging of a 42-year-old woman revealed a 2.5-cm focal nonhemorrhagic lesion in the left thalamus and internal capsule. Twenty-four days later, fever and altered consciousness developed, and MR imaging showed huge masslike lesions in both frontal lobes, mainly involving the white matter and the genu of the corpus callosum, with massive edematous swelling that contained multifocal small hemorrhages. Most lesions showed high apparent diffusion coefficient value with peripheral small areas of low apparent diffusion coefficient. On follow-up MR imaging obtained 49 days after initial MR imaging, the lesions progressed with increase in extent and development of rim-enhancing necrosis, despite steroid therapy. Following stereotactic biopsy and subsequent high-dose steroid treatment, the patient recovered with some neurologic sequelae. MR imaging obtained at 72 and 126 days revealed residual necrosis and cerebromalacia in the both frontal lobes.

Adrenal Cortex Hormones↗

PubMed2004

Diffusion tensor MRI as a diagnostic tool of upper motor neuron involvement in amyotrophic lateral sclerosis.

BACKGROUND: Clinical identification of upper motor neuron (UMN) dysfunction in amyotrophic lateral sclerosis (ALS) is often difficult, particularly early in the course of the disease, or when lower motor neuron (LMN) dysfunction is prominent. Diffusion tensor MR imaging (DTI) can provide unique information on axonal organization by measuring diffusion anisotropy and the directionally independent diffusion. OBJECTIVE: The purpose of this study was to assess water diffusion changes along pyramidal tracts of the brainstem in patients with ALS and to investigate possible correlations between changes of diffusion properties and various clinical parameters. METHODS: We studied 16 patients (M:F=9:7, 50.5+/-12.4 years) with ALS as defined by clinical and electrophysiological examinations. These patients were compared with 11 healthy, age and sex-matched controls (M:F=5:6, 54.5+/-9.9 years). DTI was performed using a single shot SE-EPI with 25 noncollinear diffusion gradient directions (b=1000 s/mm(2)) and with no diffusion gradient on a 3.0-T MR system. RESULTS: By multifactorial ANOVA, the effects of group (patient versus control) and anatomical level on fractional anisotropy (FA) and mean diffusivity (MD) were significant (p<0.001 for both parameters), whereas the effect of side (left versus right) and interactions between factors (group by side and group by anatomical level) were not (p>0.05). In all subjects, FA and MD varied greatly depending on the anatomical level, and FA was highly variable even between contiguous slices in the pons and medulla, whereas relatively constant FA values were noted at the level of the midbrain. Cerebral peduncle was the only area that showed significant differences of diffusion properties between patients and controls (p<0.001 for FA, p=0.001 for MD). Correlation analysis revealed a significant inverse relationship between the FA value and the extent of UMN signs (r=-0.81, p<0.001). CONCLUSIONS: Alteration of diffusion properties in the cerebral peduncle in ALS may reflect pathological changes in structures rather than regional architectural variations of the corticospinal tracts or experimental artifacts.

Adult↗

PubMed2004

Role of immediate postictal diffusion-weighted MRI in localizing epileptogenic foci of mesial temporal lobe epilepsy and non-lesional neocortical epilepsy.

OBJECTIVE: To determine whether meaningful changes in signal intensity or in the apparent diffusion coefficient of water (ADC) in the ictal onset zone can be detected through immediate postictal and interictal diffusion-weighted magnetic resonance imaging (DWMRI) in patients with localization-related epilepsy. METHOD: In randomly selected 10 medial and lateral temporal lobe epilepsy (TLE) and four extratemporal epilepsy patients, DWMRI was performed immediately after a seizure and during the interictal period. All 14 patients were non-lesional except for hippocampal sclerosis detected on MRI. The mean time interval from seizure onset to postictal DWMRI was 81 min. Regions of interest (ROI) were selected in both the cortex, which was believed to be the ictal onset zone, and the corresponding anatomical region of the contralateral hemisphere in the postictal and interictal DWMRI. The mean ADC measured from all ROIs was compared. Ictal onset zones were determined by ictal electroencephalography (EEG) and seizure semiology. RESULTS: On visual inspection of postictal and interictal DWMRI, signal changes in the ictal onset zone could be identified in only one patient with medial TLE. The mean ADC values from the ictal onset zones were not significantly different from those of the corresponding contralateral regions of the cortices in both postictal and interictal DWMRI. However, the postictal ADC values of the epileptogenic foci of neocortical epilepsy or neocortical temporal portion of TLE without hippocampal sclerosis were decreased compared with interictal ones in whom both interictal and postictal DWMRIs were obtained (P = 0.028). CONCLUSION: Our results demonstrate that water diffusion can change even after a single seizure in non-lesional neocortical epilepsy.

Adolescent↗

PubMed2004

Parietal lobe epilepsy: the semiology, yield of diagnostic workup, and surgical outcome.

PURPOSE: To characterize the clinical features, the prognostic value, and diagnostic sensitivities of various presurgical evaluations and the surgical outcomes in parietal lobe epilepsy (PLE), we describe 40 patients who were diagnosed as having PLE, including 27 surgically treated patients. METHODS: The diagnosis was established by means of a standard presurgical evaluation, including magnetic resonance imaging (MRI), fluorodeoxyglucose-positron emission tomography (FDG-PET), ictal single-photon emission tomography (SPECT), and scalp video-electroencephalography (EEG) monitoring, with additional intracranial EEG monitoring in selected cases. RESULTS: Among the 40 patients, 27 experienced at least one type of aura. The most common auras were somatosensory (13 patients), followed by affective, vertiginous, and visual auras. The patients had diverse manifestations. Eighteen patients showed simple motor seizure, followed by automotor seizure, and dialeptic seizure. Two patients manifested generalized tonic-clonic seizures only, and 19 patients experienced more than one type of seizure. The surgical outcome was favorable in 22 of 26 patients including 14 who were seizure free. Patients with localized MRI abnormality had a higher probability to be seizure free, with marginal significance (p = 0.062), whereas other diagnostic modalities failed to predict the surgical outcome. In the seizure-free group, localization sensitivity was 64.3% by MRI, 50% by PET, 45.5% by ictal SPECT, and 35.7% by ictal EEG. The concordance rate of the various diagnostic modalities was higher in the seizure-free group than in the non-seizure-free group, although it did not reach statistical significance. CONCLUSIONS: Seizures, in the case of PLE, can manifest themselves in a wider variety of ways than was previously thought. Surgical outcome was favorable in most of the patients. MRI abnormality and concordance of different diagnostic modalities were associated with high seizure-free rate.

Adolescent↗

PubMed2004

Volumetric investigation of the frontal-subcortical circuitry in patients with obsessive-compulsive disorder.

The pathophysiology of obsessive-compulsive disorder (OCD) is thought to involve disturbance of the frontal-subcortical circuitry. To investigate the morphological characteristics of this circuitry, we examined the volume of the orbitofrontal cortex, anterior cingulate, thalamus, caudate, and the putamen in 36 age- and sex-matched OCD patients and normal control subjects using three-dimensional magnetic resonance (MR) brain imaging. The left orbitofrontal volumes were found to be significantly smaller in the OCD patients and showed significant negative correlations with obsessive-compulsive symptom severity. These findings suggest that a structural abnormality of this brain region is implicated in the pathophysiology of OCD.

Adult↗

PubMed2004

Postoperative 3D angiography in intracranial aneurysms.

BACKGROUND AND PURPOSE: Postsurgical evaluation of patients with intracranial aneurysms is important because there is a risk of regrowth and subarachnoid hemorrhage from residual aneurysms. We assessed the role and value of 3D angiography in this evaluation. METHODS: Images from both 3D angiography and digital subtraction angiography (DSA) were preoperatively obtained in 71 consecutive patients with 88 intracranial clipped aneurysms. We analyzed the incidence of postoperative residual aneurysms and compared the 3D angiographic and DSA images in these patients. RESULTS: With 3D angiography, 37 residual aneurysms were found among 88 clipped aneurysms. These comprised 12 large residual necks and 25 small, dog-eared remnants. DSA demonstrated 12 large, residual necks and only six small, dog-eared remnants. 3D angiography also demonstrated the clips, aneurysms, and parent arteries simultaneously, enabling us to appreciate the clip-aneurysm configuration completely. CONCLUSION: 3D angiography allowed us to detect more residual aneurysms after surgical clip placement than did conventional DSA, although none of those detected on only 3D angiography were judged to require additional treatment. 3D angiography may provide baseline data for the long-term follow-up of postsurgical aneurysms.

Adult↗

PubMed2003

Primary thyroid lymphoma: CT findings.

INTRODUCTION: To evaluate the computed tomographic (CT) findings of primary thyroid lymphoma. METHODS AND MATERIAL: The clinicopathological data and CT images of nine patients with primary thyroid lymphoma were retrospectively reviewed. The CT appearances were classified into three types: type 1, a solitary nodule surrounded by normal thyroid tissue; type 2, multiple nodules in the thyroid, and type 3, a homogeneously enlarged both thyroid glands with a reduced attenuation with or without peripheral thin hyperattenuating thyroid tissue. RESULTS: All patients had a rapidly enlarging thyroid mass and coexistent Hashimoto's thyroiditis. One patient showed type 1 pattern, three type 2, and five type 3. Six patients had homogeneous tumor isoattenuating to surrounding muscles. The tumors had a strong tendency to compress normal remnant thyroid and the surrounding structure without invasion. CONCLUSION: Primary thyroid lymphoma should be included in the differential diagnosis when old female had a homogeneous thyroidal mass isoattenuating to muscles, which does not invade surrounding structures.

Aged↗

PubMed2003

Vascular responses in normal canine carotid arteries: comparison between various self-expanding stents of the same unconstrained size.

RATIONALE AND OBJECTIVES: To compare long-term vascular responses upon the insertion of various self-expandable stents, all the same unconstrained size, in canine carotid artery models. MATERIALS AND METHODS: Twenty-two stents (5 SMARTs, 5 Wallstents, 6 Niti-Ss, 6 Niti-Ds) of the same unconstrained size (6 mm in diameter, 20 mm in length) were endovascularly placed in canine common carotid arteries. The luminal changes were measured on three occasions, on prestenting, immediate poststenting, and angiograms taken before specimens were killed. After en-bloc harvest of the stented carotid arteries at 6 months, the intraluminal surface was evaluated by gross observation and scanning electron microscopy (SEM). Neointimal thickness was measured at several points both over the wire and between the wires. RESULTS: Niti-D was excluded from analysis because of high rate of poststenting occlusion. SMART stent showed the greatest expansibility with average initial luminal gain ( < 0.05) of 21.2% (Niti-S: 16.5%, Wallstent: 12.9%). At 6 months follow-up, the dilated arterial lumen had returned almost to the prestenting caliber without any significant differences among the stent types ( > 0.05). The thickness of neointimal coverage was more prominent with SMART stent (354 microm over the wire and 258 microm between the wires) than Niti-S (228 microm and 83 microm) or Wallstent (187 microm and 78 microm). CONCLUSION: Stent types with its higher initial luminal gain appeared to be associated with thicker neointimal formation at 6 months. The acute expanding force of a self-expanding stent may be the key to the cause of neointimal hyperplasia. Regardless of the inserted stent type, the variations in neointimal response were offset by luminal gains of varying degree, thus preserving the arterial patency almost to the prestenting size.

Analysis of Variance↗