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Ik-Kyung Jang

Publications and source records attributed to Ik-Kyung Jang.

At least 19 recordsLinked to original sources
PubMed2007

Comparison of nonuniform rotational distortion between mechanical IVUS and OCT using a phantom model.

Optical coherence tomography (OCT) is an optical analog of mechanical intravascular ultrasound (M-IVUS) with much higher spatial resolution. However, no data exist regarding the nonuniform rotational distortion (NURD) with OCT. The aim of the study was to investigate whether OCT generates less NURD relative to M-IVUS. A coronary artery phantom model was constructed with a rubber ring (3.68 mm in diameter), located at the distal end of the phantom. This model was also composed of eight equally spaced steel wires and an additional marker-wire. Two types of vascular phantoms were used, mild curve (90 degrees ) and acute curve (near 180 degrees ). Subsequent M-IVUS (n = 6) and OCT (n = 6) imaging was performed. Eight angles between eight wires, except the marker-wire, were measured from each image. These angles, measured with M-IVUS and OCT, were compared with those of high-resolution optical photography as a gold standard. The average in angle differences was significantly smaller in OCT compared with M-IVUS in the mild curve model (3.2 +/- 1.0 degrees vs, 6.9 +/- 2.1 degrees , p < 0.01). Compared with the latter model, the average in angle differences was exaggerated in the acute curve model with M-IVUS (9.1 +/- 0.9 degrees vs. 6.9 +/- 2.1 degrees , p < 0.05) but not with OCT (3.5 +/- 0.8 degrees vs. 3.2 +/- 1.0 degrees , p= not significant). OCT generates significantly less NURD compared with M-IVUS, especially in tortuous situation.

Artifacts↗
PubMed2006

Comprehensive volumetric optical microscopy in vivo.

Comprehensive volumetric microscopy of epithelial, mucosal and endothelial tissues in living human patients would have a profound impact in medicine by enabling diagnostic imaging at the cellular level over large surface areas. Considering the vast area of these tissues with respect to the desired sampling interval, achieving this goal requires rapid sampling. Although noninvasive diagnostic technologies are preferred, many applications could be served by minimally invasive instruments capable of accessing remote locations within the body. We have developed a fiber-optic imaging technique termed optical frequency-domain imaging (OFDI) that satisfies these requirements by rapidly acquiring high-resolution, cross-sectional images through flexible, narrow-diameter catheters. Using a prototype system, we show comprehensive microscopy of esophageal mucosa and of coronary arteries in vivo. Our pilot study results suggest that this technology may be a useful clinical tool for comprehensive diagnostic imaging for epithelial disease and for evaluating coronary pathology and iatrogenic effects.

Angioplasty↗
PubMed2006

Comparison of sixty-four-slice multidetector computed tomographic coronary angiography to coronary angiography with intravascular ultrasound for the detection of transplant vasculopathy.

Coronary allograft vasculopathy (CAV) is the most important limitation to long-term survival in adult heart transplant recipients and is difficult to detect without intravascular ultrasound (IVUS). We systematically evaluated the image quality of 64-slice multidetector computed tomographic (MDCT) coronary angiography in heart transplant recipients and tested the hypothesis that this modality is comparable to invasive coronary angiography with IVUS for the detection of CAV. Heart transplant recipients (n = 20) underwent invasive coronary angiography with IVUS and MDCT coronary angiography with a 64-slice scanner. Images were systematically analyzed for image quality and the presence of CAV. In addition, multidetector computed tomography and quantitative coronary angiography were used to measure lumen diameters at prespecified locations. Image quality analysis showed that, despite high mean heart rates (77 +/- 7 beats/min) and body mass index (29.5 +/- 5.3 kg/m(2)), 83% of coronary segments were graded as of excellent or good image quality. On average, 95 +/- 9% of the overall visualized length of the coronary arteries was imaged without motion artifacts, and the mean contrast-to-noise ratio was 11.3 +/- 4.6. Compared with IVUS, multidetector computed tomography had a sensitivity of 70%, specificity of 92%, positive predictive value of 89%, and negative predictive value of 77% for the detection of CAV. MDCT vessel diameter measurements correlated well with those obtained from quantitative coronary angiography (R(2) = 0.89). In conclusion, 64-slice multidetector computed tomography provides good to excellent image quality in heart transplant recipients and has moderate to excellent test characteristics for the detection of CAV. Further, MDCT measurements of lumen diameters correlated well with quantitative coronary angiography.

Body Mass Index↗
PubMed2006

Predictors for the development of elevated anti-heparin/platelet factor 4 antibody titers in patients undergoing cardiac catheterization.

A substantial proportion of patients who undergo cardiac catheterization develop antibodies directed against the heparin/platelet factor 4 (PF4) complex after the procedure, which have been implicated in the pathogenesis of heparin-induced thrombocytopenia. This study attempted to identify factors that predicted the development of these antibodies in a prospective cohort study. Antiheparin/PF4 antibody titers were measured at baseline and again 5 +/- 2 days after cardiac catheterization by enzyme-linked immunosorbent assay. A total of 311 patients who underwent cardiac catheterization were included in the analysis. Of these, 25 (8.0%) developed positive antibody levels after catheterization. Patients who had positive antibody test results after catheterization had significantly greater baseline antiheparin/PF4 antibody titers compared with those whose titers remained low (optical density 0.227 vs 0.158, p < 0.001). In a logistic regression model, greater baseline antibody titers, a history of heparin exposure, and a lower platelet count at enrollment were the strongest predictors of conversion to positive antiheparin/PF4 antibody titers after cardiac catheterization. It is possible to identify patients at high risk for developing elevated titers of antiheparin/PF4 antibodies on the basis of their baseline clinical characteristics.

Antibodies↗
PubMed2006

Diagnostic accuracy of optical coherence tomography and integrated backscatter intravascular ultrasound images for tissue characterization of human coronary plaques.

OBJECTIVES: The purpose of the present study was to validate the diagnostic accuracy of optical coherence tomography (OCT), integrated backscatter intravascular ultrasound (IB-IVUS), and conventional intravascular ultrasound (C-IVUS) for tissue characterization of coronary plaques and to evaluate the advantages and limitations of each of these modalities. BACKGROUND: The diagnostic accuracy of OCT for characterizing tissue types is well established. However, comparisons among OCT, C-IVUS, and IB-IVUS have not been done. METHODS: We examined 128 coronary arterial sites (42 coronary arteries) from 17 cadavers; IVUS and OCT images were acquired on the same slice as histology. Ultrasound signals were obtained using an IVUS system with a 40-MHz catheter and digitized at 1 GHz with 8-bit resolution. The IB values of the ultrasound signals were calculated with a fast Fourier transform. RESULTS: Using histological images as a gold standard, the sensitivity of OCT for characterizing calcification, fibrosis, and lipid pool was 100%, 98%, and 95%, respectively. The specificity of OCT was 100%, 94%, and 98%, respectively (Cohen's kappa = 0.92). The sensitivity of IB-IVUS was 100%, 94%, and 84%, respectively. The specificity of IB-IVUS was 99%, 84%, and 97%, respectively (Cohen's kappa = 0.80). The sensitivity of C-IVUS was 100%, 93%, and 67%, respectively. The specificity of C-IVUS was 99%, 61%, and 95%, respectively (Cohen's kappa = 0.59). CONCLUSIONS: Within the penetration depth of OCT, OCT has a best potential for tissue characterization of coronary plaques. Integrated backscatter IVUS has a better potential for characterizing fibrous lesions and lipid pools than C-IVUS.

Calcinosis↗
PubMed2006

Differentiation of recent and chronic myocardial infarction by cardiac computed tomography.

Clinical use of cardiac computed tomography is rapidly expanding, and its purpose may reach beyond noninvasive coronary angiography. We investigated the ability of 64-slice multidetector computed tomography to differentiate between recent and long-standing myocardial infarction (MI). Contrast-enhanced coronary computed tomographic (CT) scans (Siemens Sensation 64) of patients with a recent MI (< 7 days, n = 16), long-standing MI (> 12 months, n = 13), and no MI (n = 13) were retrospectively evaluated. To anticipate transmural variation of myocardial perfusion and to neutralize image noise, a series of thin, overlapping slices was created in parallel alignment to the myocardial wall. Within each of these slices, a small region of interest was placed at a constant in-plane position to measure the CT attenuation (Hounsfield units [HU]) at consecutive transmural locations of injured and normal remote myocardium. In addition, wall thickness and the myocardial cavity were measured. Significantly lower CT attenuation values were found in patients with long-standing MI (-13 +/- 37 HU) than in those with acute MI (26 +/- 26 HU) and normal controls (73 +/- 14 HU, p < 0.001). The attenuation difference between infarcted and remote myocardia was larger in patients with long-standing MI than in patients with recent MI (89 +/- 41 and 55 +/- 33 HU, respectively, p < 0.001). In addition, long-standing MI was associated with wall thinning (p < 0.01), and ventricular dilation (p < 0.05), whereas recent MI was not (p > 0.05). In conclusion, recent and long-standing MIs may be differentiated by computed tomography based on myocardial CT attenuation values and ventricular dimensions.

Coronary Angiography↗
PubMed2006

Noninvasive assessment of plaque morphology and composition in culprit and stable lesions in acute coronary syndrome and stable lesions in stable angina by multidetector computed tomography.

OBJECTIVES: The purpose of this study was to assess morphology and composition of culprit and stable coronary lesions by multidetector computed tomography (MDCT). BACKGROUND: Noninvasive identification of culprit lesions has the potential to improve noninvasive risk stratification in patients with acute chest pain. METHODS: Thirty-seven patients with acute coronary syndrome (ACS) or stable angina underwent coronary 16-slice MDCT and invasive selective angiography. In all significant coronary lesions two observers measured the degree of stenosis, plaque area at stenosis, and remodeling index and assessed plaque composition. Differences between culprit lesions in patients with ACS and stable lesions in patients with ACS or stable angina were determined. RESULTS: We analyzed 40 lesions with excellent image quality in 14 patients with ACS and 9 patients with stable angina. Culprit lesions in patients with ACS (n = 14) had significantly greater plaque area and a higher remodeling index than both stable lesions in patients with ACS (n = 13) and in patients with stable angina (n = 13) (17.5 +/- 5.9 mm2 vs. 9.1 +/- 4.8 mm2 vs. 13.5 +/- 10.7 mm2, p = 0.02; and 1.4 +/- 0.3 vs. 1.0 +/- 0.4 vs. 1.2 +/- 0.3, p = 0.04, respectively). The prevalence of non-calcified plaque was 100%, 62%, and 77%, respectively, and the prevalence of calcified plaque was 71%, 92%, and 85%, respectively, in culprit lesions in patients with ACS and in stable lesions in patients with ACS or stable angina. CONCLUSIONS: We introduce the concept of noninvasive detection and characterization of coronary atherosclerotic lesions in patients with ACS by MDCT. We identified differences in lesion morphology and plaque composition between culprit lesions in ACS and stable lesions in ACS or stable angina, consistent with previous intravascular ultrasound studies.

Acute Disease↗
PubMed2006

Characterization of non-calcified coronary atherosclerotic plaque by multi-detector row CT: comparison to IVUS.

UNLABELLED: Multi-detector row Computed Tomography (MDCT) permits non-invasive visualization of the coronary arteries. The ability to visualize and, with limitations, to characterize non-calcified coronary atherosclerotic plaque has been described. We investigated the CT attenuation of non-calcified plaques as determined by 16-slice MDCT in comparison to intravascular ultrasound (IVUS). METHODS AND RESULTS: Thirty-two patients were investigated by contrast-enhanced 16-slice CT. In addition, IVUS of one coronary artery (motorized pullback) was performed (LM+LAD: 22, LM+LCX: 4, RCA: 6). At 252 sites within the coronary system, in which non-calcified atherosclerotic plaque could be identified both in MDCT and IVUS, the CT attenuation within the plaque was measured using a centrally placed region of interest and correlated to the appearance of the plaque in IVUS at the corresponding location. The mean CT attenuation within plaque that corresponded to hyper-echogenic appearance in IVUS was 121+/-34HU (n=76). The mean CT attenuation within plaque that corresponded to hypo-echogenic appearance was 58+/-43HU (n=176, p<0.001). However, there was substantial overlap of the density values measured by MDCT in the two groups. CONCLUSIONS: A significant difference of the mean CT attenuation within atherosclerotic lesions of hypo-echogenic and hyper-echogenic appearance in IVUS could be observed. However, we observed substantial overlap of attenuation values between plaque types so that the differentiation of "vulnerable" and "stable" plaques based on their CT attenuation is doubtful.

Aged↗
PubMed2006

Accuracy of 16-slice multi-detector CT to quantify the degree of coronary artery stenosis: assessment of cross-sectional and longitudinal vessel reconstructions.

BACKGROUND: Sixteen-slice multi-detector computed tomography (MDCT) permits reliable noninvasive detection of significant coronary stenosis based on qualitative visual assessment. The purpose of this study was to determine the accuracy of MDCT to quantify the degree of coronary stenosis as compared to quantitative coronary angiography (QCA) using two different reconstruction methods. METHODS: We studied 69 coronary artery lesions from 38 consecutive patients that underwent 16-slice MDCT as a part of research study, which enrolled consecutive subjects scheduled for clinically indicated invasive coronary angiography. Nine coronary artery lesions with motion artifacts, heavily calcified plaques or stents were excluded from the analysis. The degree of stenosis was calculated by two independent readers non-blinded to the location of the stenosis, but blinded to the results of the QCA. MDCT luminal diameters were measured in cross-sectional multi-planar reformatted (CS-MPR) images created perpendicular to the centerline of the vessel and in 5 mm thin-slab maximum intensity projections (MIP) parallel to the long axis of the vessel. Both MDCT methods were compared against QCA. RESULTS: The mean degree of stenosis as measured by MDCT was closely correlated to QCA for both methods (CS-MPR versus QCA: 61 +/- 23% versus 64 +/- 29%; r2 = 0.83, p < 0.001 and MIP versus QCA: 64 +/- 22% versus 64 +/- 29%; r2 = 0.84, p < 0.001 for MIP. Bland-Altman analysis demonstrated a negative bias of the degree of stenosis of -2.8 +/- 12% using CS-MPR and a minimally positive bias of 0.6 +/- 12% for MIP. In stratified analysis for lesion severity (mild, 0-40%; moderate, 41-70% or severe, > 70%) the agreement between both CS-MPR and MIP was high when compared to QCA (kappa = 0.74 and 0.71, respectively). CONCLUSION: Multi-detector spiral CT permits accurate quantitative assessment of the degree of coronary stenosis in selected data sets of sufficient quality using both cross-sectional and longitudinal vessel reconstructions.

Aged↗
PubMed2006

Threshold-dependent variability of coronary artery calcification measurements -- implications for contrast-enhanced multi-detector row-computed tomography.

INTRODUCTION: The present study investigated the threshold-dependent variability of coronary artery calcification (CAC) measurements and the potential to quantify CAC in contrast-enhanced multi-detector row-computed tomography (MDCT). METHODS: We compared the mean CT attenuation of CAC to luminal contrast enhancement of the coronary arteries in 30 patients (n = 30) undergoing standard coronary contrast-enhanced spiral MDCT. The modified Agatston score [AS], calcified plaque volume [CV], and mineral mass [MM]) at four different thresholds (130, 200, 300, and 400 HU) were measured in 50 patients who underwent non-contrast-enhanced MDCT. RESULTS: Mean CT attenuation of CAC was similar to the attenuation of the contrast-enhanced coronary lumen (CAC 297.1 +/- 68.7 HU versus 295 +/- 65 HU (p < 0.0001), respectively). Above a threshold of 300 HU CAC measurements significantly varied to standard measurements obtained at a threshold of 130 HU (p < 0.0001). The threshold-dependent variation of MM measurements was significantly smaller than for AS and CV (130 HU versus 400 HU: 63, 75, and 81, respectively; p < 0.001). These differences resulted in a change of age and gender based percentile category for AS in 78% of subjects. DISCUSSION: We demonstrated that CAC measurements are threshold dependent with MM measurements having significantly less variation than AS or CV. Due to the similarity of mean CT attenuation of CAC and the contrast-enhanced coronary lumen accurate quantification of CAC may be difficult in standard coronary contrast-enhanced spiral MDCT.

Calcinosis↗
PubMed2006

Argatroban: update.

Unfractionated heparin has historically been used as the anticoagulant of choice in the management of a number of thrombotic diseases. Recognition of the limitations of heparin has led to the development of a newer class of anticoagulants, the direct thrombin inhibitors. Argatroban is a synthetic small molecule that selectively inhibits thrombin at its active site. In preclinical studies, argatroban has been shown to be more effective than heparin in preventing arterial thrombosis and in promoting vessel patency in conjunction with thrombolysis in a number of animal models. In clinical trials, argatroban has been shown to be as effective as heparin in the management of ST-segment elevation myocardial infarction in conjunction with thrombolysis. It has been shown to be an effective anticoagulant in patients undergoing percutaneous coronary interventions. In patients with heparin-induced thrombocytopenia and heparin-induced thrombocytopenia complicated by thrombosis, argatroban significantly decreases the risk of thrombotic events. Small studies have demonstrated a potential role for its use in ischemic stroke and hemodialysis. Additional studies are warranted to confirm argatroban's efficacy in a wide variety of clinical settings.

Animals↗
PubMed2006

Prevalence of heparin-induced thrombocytopenia in patients undergoing cardiac catheterization.

BACKGROUND: Heparin is ubiquitously used in cardiac catheterization but predisposes to the development of heparin-induced thrombocytopenia. The objective was to examine prospectively the prevalence of anti-platelet factor 4 (PF4)/heparin antibodies and heparin-induced thrombocytopenia in the population undergoing cardiac catheterization. METHODS: This is a prospective study of 500 consecutive patients presenting for cardiac catheterization at our institution who were enrolled over the course of 1 year. Anti-PF4/heparin antibodies and concurrent platelet counts were measured at catheterization and 5 days thereafter. Thrombotic complications were assessed 30 days after the procedure via telephone interview. All patients presenting for cardiac catheterization at our institution were screened. Inclusion criteria were (a) males and nonpregnant females with age >18 years and (b) patients scheduled to undergo cardiac catheterization. Patients with a known history of heparin-induced thrombocytopenia, with documented bleeding or hypercoagulability, and those at high risk for bleeding were excluded. RESULTS: Of 500 patients, 15 (3%) had anti-PF4/heparin antibodies before catheterization. After catheterization, the prevalence of anti-PF4/heparin antibodies increased to 10.1% (36 of 357) of the patients. Overall rates of thrombotic complications were low (4 of 445, 0.9%) and did not correlate with anti-PF4/heparin antibody status. Patients with an initial positive test for anti-PF4/heparin antibodies were more likely to have prior coronary disease (73.3% vs 45.2%; P < .05). Patients who developed anti-PF4/heparin antibodies after catheterization were more likely to have increased length of stay (3.7 vs 2.4 days; P = .02). The platelet count at the time of catheterization was lower in the cohort of patients who developed the second positive anti-PF4/heparin antibody test versus patients without a second positive antibody test (mean values of 191,800/microL vs 222,300/microL; P = .008). CONCLUSIONS: The prevalence of antibodies to PF4/heparin is low in the population presenting for cardiac catheterization. However, a significant proportion of patients develop antibodies to PF4/heparin after a small exposure to heparin during catheterization. Clinically significant thrombotic complications were rare and did not correlate with antibody status.

Aged↗
PubMed2006

Technology Insight: optical coherence tomography--current status and future development.

The understanding of concepts in coronary artery disease, such as the vulnerable or high-risk plaque, which accounts for many acute coronary events arising from non-flow-limiting coronary lesions, has advanced remarkably. Although coronary angiography is an established imaging technique for visualizing atherosclerotic disease, it is limited by its two-dimensional imaging aspect and a low sensitivity for identifying lesions in the presence of positive remodeling and diffuse disease. Moreover, coronary atherosclerotic plaques cannot be characterized. Although intravascular ultrasound is currently the most commonly employed adjunctive method to better define lesions, it is limited by low resolution. The development of new technologies for improved coronary plaque characterization has, thus, been desired. Optical coherence tomography is a developing technique that uses near-infrared light for the cross-sectional visualization of the vessel wall at the microscopic level. It enables excellent resolution of coronary architecture and precise characterization of plaque architecture. Quantification of macrophages within the plaque is also possible. These capabilities allow precise identification of the most common type of vulnerable plaque, the thin-cap fibroatheroma. Here, we discuss results from clinical studies which indicate that optical coherence tomography is a promising imaging technique for improved characterization of the coronary atherosclerotic plaque.

Animals↗
PubMed2006

Coronary stent malapposition as a result of a post-stenotic aneurysm detected by optical coherence tomography.

Stent malapposition remains an important cause of complications following stent implantation. Stent underexpansion is a frequent cause of this. We describe a case of coronary stent malapposition as a result of a post-stenotic aneurysm. Both the malapposition and its etiology were clearly demonstrated by optical coherence tomography, a novel high-resolution imaging technology.

Aged, 80 and over↗
PubMed2005

Comparison of the degree of coronary stenoses by multidetector computed tomography versus by quantitative coronary angiography.

Sixteen-slice multidetector computed tomography (MDCT) and quantitative coronary angiography (QCA) were performed in 29 patients. Quantification of the degree of luminal narrowing and lesion length measurements were performed independently on MDCT and QCA at 42 sites with sufficient computed tomographic image quality. The correlation between MDCT and QCA for quantifying the degree of stenosis was excellent (r2 = 0.93), although a systematic overestimation was observed by MDCT (bias 4% +/- 8%). The correlation between MDCT and QCA was moderate with respect to lesion length (r2 = 0.54). In the absence of severe calcifications or motion artifacts, MDCT permits noninvasive quantification of coronary stenosis.

Aged↗