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Dive into the research topics where Kyongtae T. Bae is active.

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Featured researches published by Kyongtae T. Bae.


Radiology | 2010

Intravenous Contrast Medium Administration and Scan Timing at CT: Considerations and Approaches

Kyongtae T. Bae

The continuing advances in computed tomographic (CT) technology in the past decades have provided ongoing opportunities to improve CT image quality and clinical practice and discover new clinical CT imaging applications. New CT technology, however, has introduced new challenges in clinical radiology practice. One of the challenges is with intravenous contrast medium administration and scan timing. In this article, contrast medium pharmacokinetics and patient, contrast medium, and CT scanning factors associated with contrast enhancement and scan timing are presented and discussed. Published data from clinical studies of contrast medium and physiology are reviewed and interpreted. Computer simulation data are analyzed to provide an in-depth analysis of various factors associated with contrast enhancement and scan timing. On the basis of basic principles and analysis of the factors, clinical considerations and modifications to protocol design that are necessary to optimize contrast enhancement for common clinical CT applications are proposed.


Journal of The American Society of Nephrology | 2007

Comprehensive Molecular Diagnostics in Autosomal Dominant Polycystic Kidney Disease

Sandro Rossetti; Mark B. Consugar; Arlene B. Chapman; Vicente E. Torres; Lisa M. Guay-Woodford; Jared J. Grantham; William M. Bennett; Catherine M. Meyers; Denise L. Walker; Kyongtae T. Bae; Qin Zhang; Paul A. Thompson; J. Philip Miller; Peter C. Harris

Mutation-based molecular diagnostics of autosomal dominant polycystic kidney disease (ADPKD) is complicated by genetic and allelic heterogeneity, large multi-exon genes, duplication of PKD1, and a high level of unclassified variants (UCV). Present mutation detection levels are 60 to 70%, and PKD1 and PKD2 UCV have not been systematically classified. This study analyzed the uniquely characterized Consortium for Radiologic Imaging Study of PKD (CRISP) ADPKD population by molecular analysis. A cohort of 202 probands was screened by denaturing HPLC, followed by direct sequencing using a clinical test of 121 with no definite mutation (plus controls). A subset was also screened for larger deletions, and reverse transcription-PCR was used to test abnormal splicing. Definite mutations were identified in 127 (62.9%) probands, and all UCV were assessed for their potential pathogenicity. The Grantham Matrix Score was used to score the significance of the substitution and the conservation of the residue in orthologs and defined domains. The likelihood for aberrant splicing and contextual information about the UCV within the patient (including segregation analysis) was used in combination to define a variant score. From this analysis, 44 missense plus two atypical splicing and seven small in-frame changes were defined as probably pathogenic and assigned to a mutation group. Mutations were thus defined in 180 (89.1%) probands: 153 (85.0%) PKD1 and 27 (15.0%) PKD2. The majority were unique to a single family, but recurrent mutations accounted for 30.0% of the total. A total of 190 polymorphic variants were identified in PKD1 (average of 10.1 per patient) and eight in PKD2. Although nondefinite mutation data must be treated with care in the clinical setting, this study shows the potential for molecular diagnostics in ADPKD that is likely to become increasingly important as therapies become available.


Circulation | 2002

Novel, Magnetically Guided Catheter for Endocardial Mapping and Radiofrequency Catheter Ablation

Mitchell N. Faddis; Walter M. Blume; Jennifer R Finney; Andrew F. Hall; John Rauch; Jon Sell; Kyongtae T. Bae; Michael Talcott; Bruce D. Lindsay

Background—Ablation of complex arrhythmias would be greatly facilitated by more precise control of ablation catheters. A feasibility study was performed in animals to evaluate a novel magnetic guidance system (MGS) that generates a magnetic field to control the movement and position of a magnetic ablation catheter. Methods and Results—The MGS is composed of a digital biplanar fluoroscope within an array of superconducting electromagnets that surround the torso of the experimental animal and a computer control system that generates a composite magnetic field for directional catheter deflection. Magnetic catheter navigation was performed in dogs and pigs (20 to 30 kg). A 7F magnetic ablation catheter was used for intracardiac navigation and radiofrequency ablation. The performance of a standard 7F deflectable catheter was not affected by the MGS. The magnetic catheter was navigated successfully to 51 predefined targets throughout the heart in 6 animals. In 5 animals, the magnetic catheter, guided by a 3D computed tomogram, was successfully navigated to all pulmonary veins. Navigation accuracy was estimated as <1 mm displacement from the target. The magnetic catheter was used to ablate the atrioventricular node in 4 animals and to perform linear ablations across the endocardial surface underlying an epicardial multielectrode recording plaque in 4 animals. Conclusions—These results demonstrate that the MGS can navigate and stabilize an ablation catheter at endocardial targets. Linear or focal radiofrequency ablation with the magnetic catheter is not compromised by the magnetic field. This technology provides precise control of endocardial catheters.


Investigative Radiology | 1994

Computerized detection of pulmonary nodules in computed tomography images.

Maryellen L. Giger; Kyongtae T. Bae; Heber MacMahon

RATIONALE AND OBJECTIVES.Interpretation of computed tomographic (CT) scans of the lungs is a time-consuming task that involves visual correlation of possible nodules in one section with those in contiguous sections to distinguish actual nodules from blood vessels. Thus, the authors are developing automated methods to detect nodules on CT images of the thorax. METHODS.The computerized technique uses various computer-vision techniques and a priori information of the morphologic characteristics of pulmonary nodules. In each section, the external thoracic wall and lung boundaries are detected, and the features within the lung boundaries are subjected to gray-level thresholding operations. By analyzing the relationships between features arising at different threshold levels with respect to their shape, size, and location, each feature is assigned a likelihood of being a nodule or a vessel. Features in adjacent sections are compared to resolve ambiguous features. Detected nodule candidates are displayed in three dimensions within the lung. RESULTS.The system provided a sensitivity of 94% for nodule detection and an average of 1.25 false-positive results per case. CONCLUSIONS.Continued development of an automated method for detecting pulmonary nodules in CT scans is expected to aid radiologists in the task of locating nodules in three dimensions.


Clinical Journal of The American Society of Nephrology | 2005

Magnetic Resonance Imaging Evaluation of Hepatic Cysts in Early Autosomal-Dominant Polycystic Kidney Disease: The Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease Cohort

Kyongtae T. Bae; Fang Zhu; Arlene B. Chapman; Vicente E. Torres; Jared J. Grantham; Lisa M. Guay-Woodford; Deborah A. Baumgarten; Bernard F. King; Louis H. Wetzel; Philip J. Kenney; William M. Bennett; Saulo Klahr; Catherine M. Meyers; Xiaoling Zhang; Paul A. Thompson; J. Philip Miller

The objective of this study was to investigate the prevalence of hepatic cysts by age and gender in patients with early autosomal-dominant polycystic kidney disease (ADPKD) and to determine whether hepatic cyst volume is related to renal and renal cyst volumes by using magnetic resonance imaging (MRI). A total of 230 patients with ADPKD (94 men and 136 women) who were aged 15 to 46 yr and had relatively preserved renal function were studied. MRI images of the kidney and liver were obtained to measure renal, renal cyst, and hepatic cyst volumes. These volume measurements and hepatic cyst prevalence were compared in all patients and in subgroups on the basis of gender and age (15 to 24, 25 to 34, and 35 to 46 yr). The overall prevalence of hepatic cysts was 83%; the prevalence was 58, 85, and 94% in the sequential age groups and 85% in women and 79% in men. The prevalence was related directly to renal volume (chi2 = 4.30, P = 0.04) and to renal cyst volume (chi2 = 5.59, P = 0.02). The total hepatic cyst volume was significantly greater in women than in men (a logarithmic transformation mean of 5.27 versus 1.94 ml; P = 0.003). The average hepatic cyst volume was 0.25, 5.75, and 22.78 ml in sequential age groups. Hepatic cysts are evident in 94% of patients who are older than 35 yr and in 55% of individuals who are younger than 25 yr. Hepatic cysts are more prevalent and larger in total cyst volume in women than in men. Hepatic cyst prevalence and aggregate total hepatic cyst volume increased with age.


Clinical Journal of The American Society of Nephrology | 2012

Kidney Volume and Functional Outcomes in Autosomal Dominant Polycystic Kidney Disease

Arlene B. Chapman; James E. Bost; Vicente E. Torres; Lisa M. Guay-Woodford; Kyongtae T. Bae; Douglas Landsittel; Jie Li; Bernard F. King; Diego R. Martin; Louis H. Wetzel; Mark E. Lockhart; Peter C. Harris; Marva Moxey-Mims; Mike Flessner; William M. Bennett; Jared J. Grantham

BACKGROUND AND OBJECTIVES Autosomal dominant polycystic kidney disease (ADPKD) is characterized by increased total kidney volume (TKV) and renal failure. This study aimed to determine if height-adjusted TKV (htTKV) predicts the onset of renal insufficiency. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS This prospective, observational, longitudinal, multicenter study included 241 adults with ADPKD and preserved renal function. Magnetic resonance imaging and iothalamate clearance were used to measure htTKV and GFR, respectively. The association between baseline htTKV and the attainment of stage 3 CKD (GFR <60 ml/min per 1.73 m(2)) during follow-up was determined. RESULTS After a mean follow-up of 7.9 years, stage 3 CKD was attained in 30.7% of the enrollees. Using baseline htTKV, negative correlations with GFR increased from -0.22 at baseline to -0.65 at year 8. In multivariable analysis, a baseline htTKV increase of 100 cc/m significantly predicted the development of CKD within 8 years with an odds ratio of 1.48 (95% confidence interval: 1.29, 1.70). In receiver operator characteristic curve analysis, baseline htTKV of 600 cc/m most accurately defined the risk of developing stage 3 CKD within 8 years with an area under the curve of 0.84 (95% confidence interval: 0.79, 0.90). htTKV was a better predictor than baseline age, serum creatinine, BUN, urinary albumin, or monocyte chemotactic protein-1 excretion (P<0.05). CONCLUSIONS Baseline htTKV ≥600 cc/m predicted the risk of developing renal insufficiency in ADPKD patients at high risk for renal disease progression within 8 years of follow-up, qualifying htTKV as a prognostic biomarker in ADPKD.


The New England Journal of Medicine | 2014

Blood Pressure in Early Autosomal Dominant Polycystic Kidney Disease

Robert W. Schrier; Kaleab Z. Abebe; Ronald D. Perrone; Vicente E. Torres; William E. Braun; Theodore I. Steinman; Franz T. Winklhofer; Godela Brosnahan; Peter G. Czarnecki; Marie C. Hogan; Dana C. Miskulin; Frederic Rahbari-Oskoui; Jared J. Grantham; Peter C. Harris; Michael F. Flessner; Kyongtae T. Bae; Charity G. Moore; Arlene B. Chapman

BACKGROUND Hypertension is common in autosomal dominant polycystic kidney disease (ADPKD) and is associated with increased total kidney volume, activation of the renin-angiotensin-aldosterone system, and progression of kidney disease. METHODS In this double-blind, placebo-controlled trial, we randomly assigned 558 hypertensive participants with ADPKD (15 to 49 years of age, with an estimated glomerular filtration rate [GFR] >60 ml per minute per 1.73 m(2) of body-surface area) to either a standard blood-pressure target (120/70 to 130/80 mm Hg) or a low blood-pressure target (95/60 to 110/75 mm Hg) and to either an angiotensin-converting-enzyme inhibitor (lisinopril) plus an angiotensin-receptor blocker (telmisartan) or lisinopril plus placebo. The primary outcome was the annual percentage change in the total kidney volume. RESULTS The annual percentage increase in total kidney volume was significantly lower in the low-blood-pressure group than in the standard-blood-pressure group (5.6% vs. 6.6%, P=0.006), without significant differences between the lisinopril-telmisartan group and the lisinopril-placebo group. The rate of change in estimated GFR was similar in the two medication groups, with a negative slope difference in the short term in the low-blood-pressure group as compared with the standard-blood-pressure group (P<0.001) and a marginally positive slope difference in the long term (P=0.05). The left-ventricular-mass index decreased more in the low-blood-pressure group than in the standard-blood-pressure group (-1.17 vs. -0.57 g per square meter per year, P<0.001); urinary albumin excretion was reduced by 3.77% with the low-pressure target and increased by 2.43% with the standard target (P<0.001). Dizziness and light-headedness were more common in the low-blood-pressure group than in the standard-blood-pressure group (80.7% vs. 69.4%, P=0.002). CONCLUSIONS In early ADPKD, the combination of lisinopril and telmisartan did not significantly alter the rate of increase in total kidney volume. As compared with standard blood-pressure control, rigorous blood-pressure control was associated with a slower increase in total kidney volume, no overall change in the estimated GFR, a greater decline in the left-ventricular-mass index, and greater reduction in urinary albumin excretion. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases and others; HALT-PKD [Study A] ClinicalTrials.gov number, NCT00283686.).


Journal of The American Society of Nephrology | 2006

Cyst Number but Not the Rate of Cystic Growth Is Associated with the Mutated Gene in Autosomal Dominant Polycystic Kidney Disease

Peter C. Harris; Kyongtae T. Bae; Sandro Rossetti; Vincente E. Torres; Jared J. Grantham; Arlene B. Chapman; Lisa M. Guay-Woodford; Bernard F. King; Louis H. Wetzel; Deborah A. Baumgarten; Kenney Pj; Mark B. Consugar; Saulo Klahr; William M. Bennett; Catherine M. Meyers; Qin Zhang; Paul A. Thompson; Fang Zhu; J. P. Miller

Data from serial renal magnetic resonance imaging of the Consortium of Radiologic Imaging Study of PKD (CRISP) autosomal dominant polycystic kidney disease (PKD) population showed that cystic expansion occurs at a consistent rate per individual, although it is heterogeneous in the population, and that larger kidneys are associated with more rapid disease progression. The significance of gene type to disease progression is analyzed in this study of the CRISP cohort. Gene type was determined in 183 families (219 cases); 156 (85.2%) had PKD1, and 27 (14.8%) had PKD2. PKD1 kidneys were significantly larger, but the rate of cystic growth (PKD1 5.68%/yr; PKD2 4.82%/yr) was not different (P = 0.24). Cyst number increased with age, and more cysts were detected in PKD1 kidneys (P < 0.0001). PKD1 is more severe because more cysts develop earlier, not because they grow faster, implicating the disease gene in cyst initiation but not expansion. These insights will inform the development of targeted therapies in autosomal dominant PKD.


American Journal of Roentgenology | 2008

Contrast Enhancement in Cardiovascular MDCT: Effect of Body Weight, Height, Body Surface Area, Body Mass Index, and Obesity

Kyongtae T. Bae; Brian A. Seeck; Charles F. Hildebolt; Cheng Tao; Fang Zhu; Masayuki Kanematsu; Pamela K. Woodard

OBJECTIVE The purpose of our study was to evaluate the effect of body weight, height, body surface area (BSA), body mass index (BMI), and obesity on aortic contrast enhancement in cardiac MDCT. MATERIALS AND METHODS Seventy-three consecutive patients underwent cardiac CT angiography on a 64-MDCT scanner. Seventy-five mL of contrast medium (350 mg I/mL) was injected at 4.5 mL/s, followed by a 40-mL saline flush at 4.5 mL/s. The scanning delay of CT was determined with a bolus tracking technique. Aortic attenuation was measured over the aortic-root lumen. BMI and BSA were calculated from the patients body weight and height. The patients were divided into low-(BMI < 30) and high-(> or = 30) BMI groups. Associations of aortic attenuation with body weight, height, BMI, and BSA were evaluated with regression analysis and the Students t test. RESULTS Strong inverse correlations were seen between aortic attenuation and body weight (r = -0.73), height (r = -0.47), BMI (r = -0.63), and BSA (r = -0.74) (p < 0.001 for all). The regression formula of aortic attenuation versus body weight suggests that 1.0 mL/kg of contrast medium would yield a mean aortic attenuation of 355 H. The mean aortic attenuation was significantly higher in the low-BMI (352.6 +/- 59.1 H) than in the high-BMI (286.2 +/- 55.5 H) group. The regression formula for aortic attenuation on body weight was aortic attenuation = 586-3.1 body weight (p < 0.001) for the low-BMI group and aortic attenuation = 485-1.9 body weight (p < 0.001) for the high-BMI group, suggesting that the amount of contrast medium required with increased body weight is less in the high-BMI group. This group difference was less pronounced for the regression of aortic attenuation on BSA. CONCLUSION To achieve a consistent contrast enhancement in cardiac CT angiography (CTA), contrast-medium dose should be adjusted with the body weight or the BSA (which accounts for both the body weight and height factors) to provide adjustment of iodine dose over a wide range of body sizes.


Journal of Magnetic Resonance Imaging | 2000

Artery and vein separation using susceptibility-dependent phase in contrast-enhanced MRA.

Y. Wang; Y. Yu; Debiao Li; Kyongtae T. Bae; Jeffrey J. Brown; Weili Lin; E.M. Haacke

In magnetic resonance angiography, contrast agents are frequently used to help highlight arteries over background tissue. Unfortunately, enhancing veins hamper the visualization of arteries when data are collected over a long period of time after the arterial phase of the contrast agent. To overcome this problem, we have developed a novel imaging and postprocessing method that is capable of eliminating veins by utilizing the susceptibility difference between veins and surrounding tissue. This method was applied in the peripheral vasculature where the vessels are predominantly parallel to the main field and where the blood oxygen level‐dependent effect is most pronounced. Results are presented for both long (15.8 msec) and short echo times (7.8 msec) and for sequential and centrally reordered acquisition schemes. The short echo scan approach appears to be the most promising, making it possible to obtain good suppression of the venous signal even when the timing is not perfect or when repeat scans are necessary. J. Magn. Reson. Imaging 2000;12:661–670.

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