Bio

Bio


I joined Vascular Surgery at Stanford School of Medicine in 2011 as a postdoctoral researcher after six years of MS-PhD program in Department of Mechanical Engineering, Stanford University in California. With Dr. Charles A. Taylor, a former professor in Bioengineering, Stanford, and founder/CTO of Heartflow Inc, I studied hemodynamics of human abdominal aortic aneurysm using medical image-based modeling and computational flow simulation. I quantified complex aneurysm hemodynamics not only during the baseline resting state, but also during the graded levels of low-limb exercise states. Currently, my research is focused on quantification of dynamic vascular geometry under cardiac pulsation and respiration of patients with native or repaired dissection or aneurysm in their thoracic or abdominal aorta. My aim is to contribute to further understanding of diseased arterial dynamics before and after the implantation of endovascular devices, and helping artery implant development.

Academic Appointments


Honors & Awards


  • Top 12 posters award, Society of Interventional Radiology (March 2012)
  • 3rd place at podium presentation, ASME Summer Bioengineering Conference (June 2009)
  • 3rd place at poster presentation, ASME Summer Bioengineering Conference (June 2007)
  • Graduate Fellowship, Kwanjeong Foundation, South Korea (Sept 2005 - Aug 2007)

Professional Education


  • B.S., Department of Mechanical Engineering, Yonsei University, Seoul, Korea (2005)
  • M.S., Department of Mechanical Engineering, Stanford University (2007)
  • Ph.D., Department of Mechanical Engineering, Stanford University (2011)

Research & Scholarship

Current Research and Scholarly Interests


Quantitative analysis of human arterial and venous geometry and in vivo deformation using MRI / CT angiography and 3D modeling techniques

Publications

All Publications


  • Comparative geometric analysis of renal artery anatomy before and after fenestrated or snorkel/chimney endovascular aneurysm repair JOURNAL OF VASCULAR SURGERY Ullery, B. W., Suh, G., Lee, J. T., Liu, B., Stineman, R., Daman, R. L., Cheng, C. P. 2016; 63 (4): 922-929
  • Geometry and respiratory-induced deformation of abdominal branch vessels and stents after complex endovascular aneurysm repair JOURNAL OF VASCULAR SURGERY Ullery, B. W., Suh, G., Lee, J. T., Liu, B., Stineman, R., Dalman, R. L., Cheng, C. P. 2015; 61 (4): 875-884

    Abstract

    This study quantified the geometry and respiration-induced deformation of abdominal branch vessels and stents after fenestrated (F-) and snorkel (Sn-) endovascular aneurysm repair (EVAR).Twenty patients (80% male; mean age, 75.2 ± 7.4 years; mean aneurysm diameter, 6.2 ± 1.8 cm) underwent computed tomography angiography during inspiratory and expiratory breath hold protocols after F-EVAR (n = 11) or Sn-EVAR (n = 9). Centerlines for the aorta and visceral vessels were extracted from three-dimensional models. Branch angles were computed relative to the orthogonal plane at the branch ostia, and end-stent angles of the left renal artery (LRA) and right renal artery (RRA) were computed relative to the distal stent orientation. The radius of peak curvature was defined by the circumscribed circle at the highest curvature.Sn-renal branches were more downward-angled than F-renal branches (P < .04). At the distal ends of the RRA stents, Sn-RRAs were angled greater than F-RRAs (P < .03) and had a smaller radius of peak curvature (P < .03). With expiration, the end-stent angle of Sn-LRAs increased by 4° ± 4° (P < .02) and exhibited a significant reduction of radius of curvature (P < .04). The unstented celiac arteries were more downward-angled (P < .02, inspiration), with a smaller radius of curvature (P < .00001), than the unstented superior mesenteric arteries. With expiration, the celiac arteries angled upwards by 9° ± 9° (P < .0005), which was greater than the superior mesenteric arteries (P < .03). At a median postoperative follow-up of 12.6 months (range, 1.0-37.1 months), branch vessel patency was 100%, serum creatinine levels remained stable, and one reintervention was required for a type III endoleak at the main body-LRA stent interface.Sn-renals were angled more inferiorly at the branch and more angulated at the stent end than F-renals due to stent placement strategies. Sn-LRAs exhibited a significant change in end-stent angle and curvature during respiration, a finding that may compromise long-term durability for parallel stent graft configurations. Further investigation is warranted to better optimize anatomic, patient, and branch vessel stent selection between fenestrated and snorkel strategies and their relationship to long-term patency.

    View details for DOI 10.1016/j.jvs.2014.11.075

    View details for Web of Science ID 000351776100005

    View details for PubMedID 25601499

  • A longitudinal comparison of hemodynamics and intraluminal thrombus deposition in abdominal aortic aneurysms. American journal of physiology. Heart and circulatory physiology Arzani, A., Suh, G., Dalman, R. L., Shadden, S. C. 2014; 307 (12): H1786-95

    Abstract

    Abdominal aortic aneurysm (AAA) is often accompanied by in traluminal thrombus (ILT), which complicates AAA progression and risk of rupture. Patient-specific computational fluid dynamics modeling of 10 small human AAA was performed to investigate relations between hemodynamics and ILT progression. The patients were imaged using magnetic resonance twice in a 2- to 3-yr interval. Wall content data were obtained by a planar T1-weighted fast spin echo black-blood scan, which enabled quantification of thrombus thickness at midaneurysm location during baseline and followup. Computational simulations with patient-specific geometry and boundary conditions were performed to quantify the hemodynamic parameters of time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and mean exposure time at baseline. Spatially resolved quantifications of the change in ILT thickness were compared with the different hemodynamic parameters. Regions of low OSI had the strongest correlation with ILT growth and demonstrated a statistically significant correlation coefficient. Prominent regions of high OSI (>0.4) and low TAWSS (<1 dyn/cm(2)) did not appear to coincide with locations of thrombus deposition.

    View details for DOI 10.1152/ajpheart.00461.2014

    View details for PubMedID 25326533

  • Aortic Arch Vessel Geometries and Deformations in Patients with Thoracic Aortic Aneurysms and Dissections JOURNAL OF VASCULAR AND INTERVENTIONAL RADIOLOGY Suh, G., Beygui, R. E., Fleischmann, D., Cheng, C. P. 2014; 25 (12): 1903-1911

    Abstract

    To quantify aortic arch geometry and in vivo cardiac-induced and respiratory-induced arch translations and arch branch angulations using three-dimensional geometric modeling techniques.Scanning with electrocardiogram-gated computed tomography angiography during inspiratory and expiratory breath holds was performed in 15 patients (age, 64 y ± 14) with thoracic aortic aneurysms or dissections. From the lumen models, centerlines of the thoracic aorta, brachiocephalic artery, left common carotid artery, and left subclavian artery and their branching ostia positions were quantified. Three-dimensional translation of vessel ostia, branching angles, and their changes secondary to cardiac pulsation and respiration were computed.During expiration, all ostia translated rightward from systole to diastole (P < .035). Regardless of cardiac phase, all ostia translated posteriorly and superiorly from inspiration to expiration (P < .05). Respiration induced greater posterior and superior translations than cardiac pulsation (P < .03). The left common carotid artery branch angled significantly more toward the aortic arch compared with the brachiocephalic artery and left subclavian artery (P < .03). No significant changes in branching angle were found from systole to diastole or inspiration to expiration.In patients with thoracic aortic aneurysms or dissections, the thoracic aortic arch translated significantly secondary to inspiration and expiration and to a lesser extent secondary to cardiac pulsation. Insignificant branching angle changes suggest that the aortic arch and its branch origins move predominantly in unison.

    View details for DOI 10.1016/j.jvir.2014.06.012

    View details for Web of Science ID 000345676700011

    View details for PubMedID 25066591

  • Respiratory-Induced 3D Deformations of the Renal Arteries Quantified With Geometric Modeling During Inspiration and Expiration Breath-Holds of Magnetic Resonance Angiography JOURNAL OF MAGNETIC RESONANCE IMAGING Suh, G., Choi, G., Draney, M. T., Herfkens, R. J., Dalman, R. L., Cheng, C. P. 2013; 38 (6): 1325-1332

    Abstract

    PURPOSE: To quantify renal artery deformation due to respiration using magnetic resonance (MR) image-based geometric analysis. MATERIALS AND METHODS: Five males were imaged with contrast-enhanced MR angiography during inspiratory and expiratory breath-holds. From 3D models of the abdominal aorta, left and right renal arteries (LRA and RRA), we quantified branching angle, curvature, peak curve angle, axial length, and locations of branch points. RESULTS: With expiration, maximum curvature changes were 0.054 ± 0.025 mm(-1) (P < 0.01), and curve angle at the most proximal curvature peak increased by 8.0 ± 4.5° (P < 0.05) in the LRA. Changes in maximum curvature and curve angles were not significant in the RRA. The first renal bifurcation point translated superiorly and posteriorly by 9.7 ± 3.6 mm (P < 0.005) and 3.5 ± 2.1 mm (P < 0.05), respectively, in the LRA, and 10.8 ± 6.1 mm (P < 0.05) and 3.6 ± 2.5 mm (P < 0.05), respectively, in the RRA. Changes in branching angle, axial length, and renal ostia locations were not significant. CONCLUSION: The LRA and RRA deformed and translated significantly. Greater deformation of the LRA as compared to the RRA may be due to asymmetric anatomy and mechanical support by the inferior vena cava. The presented methodology can extend to quantification of deformation of diseased and stented arteries to help renal artery implant development. J. Magn. Reson. Imaging 2013;. © 2013 Wiley Periodicals, Inc.

    View details for DOI 10.1002/jmri.24101

    View details for Web of Science ID 000327756800003

  • Respiration-induced Deformations of the Superior Mesenteric and Renal Arteries in Patients with Abdominal Aortic Aneurysms JOURNAL OF VASCULAR AND INTERVENTIONAL RADIOLOGY Suh, G., Choi, G., Herfkens, R. J., Dalman, R. L., Cheng, C. P. 2013; 24 (7): 1035-1042

    Abstract

    To quantify respiration-induced deformations of the superior mesenteric artery (SMA), left renal artery (LRA), and right renal artery (RRA) in patients with small abdominal aortic aneurysms (AAAs).Sixteen men with AAAs (age 73 y ± 7) were imaged with contrast-enhanced magnetic resonance angiography during inspiratory and expiratory breath-holds. Centerline paths of the aorta and visceral arteries were acquired by geometric modeling and segmentation techniques. Vessel translations and changes in branching angle and curvature resulting from respiration were computed from centerline paths.With expiration, the SMA, LRA, and RRA bifurcation points translated superiorly by 12.4mm ± 9.5, 14.5mm ± 8.8, and 12.7mm ± 6.4 (P < .001), and posteriorly by 2.2mm ± 2.7, 4.9mm ± 4.2, and 5.6mm ± 3.9 (P < .05), respectively, and the SMA translated rightward by 3.9mm ± 4.9 (P < .01). With expiration, the SMA, LRA, and RRA angled upward by 9.7° ± 6.4, 7.5° ± 7.8, and 4.9° ± 5.3, respectively (P < .005). With expiration, mean curvature increased by 0.02mm(-1) ± 0.01, 0.01mm(-1) ± 0.01, and 0.01mm(-1) ± 0.01 in the SMA, LRA, and RRA, respectively (P < .05). For inspiration and expiration, RRA curvature was greater than in other vessels (P < .025).With expiration, the SMA, LRA, and RRA translated superiorly and posteriorly as a result of diaphragmatic motion, inducing upward angling of vessel branches and increased curvature. In addition, the SMA exhibited rightward translation with expiration. The RRA was significantly more tortuous, but deformed less than the other vessels during respiration.

    View details for DOI 10.1016/j.jvir.2013.04.006

    View details for Web of Science ID 000321029500020

  • Hemodynamic Changes Quantified in Abdominal Aortic Aneurysms with Increasing Exercise Intensity Using MR Exercise Imaging and Image-Based Computational Fluid Dynamics ANNALS OF BIOMEDICAL ENGINEERING Suh, G., Les, A. S., Tenforde, A. S., Shadden, S. C., Spilker, R. L., Yeung, J. J., Cheng, C. P., Herfkens, R. J., Dalman, R. L., Taylor, C. A. 2011; 39 (8): 2186-2202

    Abstract

    Abdominal aortic aneurysm (AAA) is a vascular disease resulting in a permanent, localized enlargement of the abdominal aorta. We previously hypothesized that the progression of AAA may be slowed by altering the hemodynamics in the abdominal aorta through exercise [Dalman, R. L., M. M. Tedesco, J. Myers, and C. A. Taylor. Ann. N.Y. Acad. Sci. 1085:92-109, 2006]. To quantify the effect of exercise intensity on hemodynamic conditions in 10 AAA subjects at rest and during mild and moderate intensities of lower-limb exercise (defined as 33 ± 10% and 63 ± 18% increase above resting heart rate, respectively), we used magnetic resonance imaging and computational fluid dynamics techniques. Subject-specific models were constructed from magnetic resonance angiography data and physiologic boundary conditions were derived from measurements made during dynamic exercise. We measured the abdominal aortic blood flow at rest and during exercise, and quantified mean wall shear stress (MWSS), oscillatory shear index (OSI), and particle residence time (PRT). We observed that an increase in the level of activity correlated with an increase of MWSS and a decrease of OSI at three locations in the abdominal aorta, and these changes were most significant below the renal arteries. As the level of activity increased, PRT in the aneurysm was significantly decreased: 50% of particles were cleared out of AAAs within 1.36 ± 0.43, 0.34 ± 0.10, and 0.22 ± 0.06 s at rest, mild exercise, and moderate exercise levels, respectively. Most of the reduction of PRT occurred from rest to the mild exercise level, suggesting that mild exercise may be sufficient to reduce flow stasis in AAAs.

    View details for DOI 10.1007/s10439-011-0313-6

    View details for Web of Science ID 000292268900008

    View details for PubMedID 21509633

  • Quantification of Particle Residence Time in Abdominal Aortic Aneurysms Using Magnetic Resonance Imaging and Computational Fluid Dynamics ANNALS OF BIOMEDICAL ENGINEERING Suh, G., Les, A. S., Tenforde, A. S., Shadden, S. C., Spilker, R. L., Yeung, J. J., Cheng, C. P., Herfkens, R. J., Dalman, R. L., Taylor, C. A. 2011; 39 (2): 864-883

    Abstract

    Hemodynamic conditions are hypothesized to affect the initiation, growth, and rupture of abdominal aortic aneurysms (AAAs), a vascular disease characterized by progressive wall degradation and enlargement of the abdominal aorta. This study aims to use magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) to quantify flow stagnation and recirculation in eight AAAs by computing particle residence time (PRT). Specifically, we used gadolinium-enhanced MR angiography to obtain images of the vessel lumens, which were used to generate subject-specific models. We also used phase-contrast MRI to measure blood flow at supraceliac and infrarenal locations to prescribe physiologic boundary conditions. CFD was used to simulate pulsatile flow, and PRT, particle residence index, and particle half-life of PRT in the aneurysms were computed. We observed significant regional differences of PRT in the aneurysms with localized patterns that differed depending on aneurysm geometry and infrarenal flow. A bulbous aneurysm with the lowest mean infrarenal flow demonstrated the slowest particle clearance. In addition, improvements in particle clearance were observed with increase of mean infrarenal flow. We postulate that augmentation of mean infrarenal flow during exercise may reduce chronic flow stasis that may influence mural thrombus burden, degradation of the vessel wall, and aneurysm growth.

    View details for DOI 10.1007/s10439-010-0202-4

    View details for Web of Science ID 000287213300022

    View details for PubMedID 21103933

  • Quantifying In Vivo Hemodynamic Response to Exercise in Patients With Intermittent Claudication and Abdominal Aortic Aneurysms Using Cine Phase-Contrast MRI JOURNAL OF MAGNETIC RESONANCE IMAGING Tenforde, A. S., Cheng, C. P., Suh, G., Herfkens, R. J., Dalman, R. L., Taylor, C. A. 2010; 31 (2): 425-429

    Abstract

    To evaluate rest and exercise hemodynamics in patients with abdominal aortic aneurysms (AAA) and peripheral occlusive disease (claudicants) using phase-contrast MRI.Blood velocities were acquired by means of cardiac-gated cine phase-contrast in a 0.5 Tesla (T) open MRI. Volumetric flow was calculated at the supraceliac (SC), infrarenal (IR), and mid-aneurysm (MA) levels during rest and upright cycling exercise using an MR-compatible exercise cycle.Mean blood flow increased during exercise (AAA: 130%, Claudicants: 136% of resting heart rate) at the SC and IR levels for AAA participants (2.6 +/- 0.6 versus 5.8 +/- 1.6 L/min, P < 0.001 and 0.8 +/- 0.4 versus 5.1 +/- 1.7 L/min, P < 0.001) and claudicants (2.3 +/- 0.5 versus 4.5 +/- 0.9 L/min, P < 0.005 and 0.8 +/- 0.2 versus 3.3 +/- 0.9 L/min, P < 0.005). AAA participants had a significant decrease in renal and digestive blood flow from rest to exercise (1.8 +/- 0.7 to 0.7 +/- 0.6 L/min, P < 0.01). The decrease in renal and digestive blood flow during exercise correlated with daily activity level for claudicants (R = 0.81).Abdominal aortic hemodynamic changes due to lower extremity exercise can be quantified in patients with AAA and claudication using PC-MRI. The redistribution of blood flow during exercise was significant and different between the two disease states.

    View details for DOI 10.1002/jmri.22055

    View details for Web of Science ID 000274117200019

    View details for PubMedID 20099356

  • HEMODYNAMICS IN ABDOMINAL AORTIC ANEURYSMS AT REST AND GRADED LEVELS OF EXERCISE PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B Suh, G. K., Tenforde, A., Shadden, S., Spilker, R., Cheng, C. P., Herfkens, R. J., Dalman, R. L., Taylor, C. A. 2009: 383-384
  • Quantification of three-dimensional motion of the renal arteries using image-based modeling techniques PROCEEDING OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2007 Suh, G. Y., Choi, G., Blomme, M. D., Taylor, C. A. 2007: 715-716
  • Quantification of radial compression and deflection of superficial femoral artery due to musculoskeletal motion Choi, G., Cheng, C. P., Suh, G. Y., Donnovan, F. D., Herfkens, R. J., Taylor, C. A. EXCERPTA MEDICA INC-ELSEVIER SCIENCE INC. 2006: 108M-108M
  • In vivo axial and twisting deformations of the superficial femoral artery due to hip and knee flexion: The RESIStent consortium experience Cheng, C. P., Choi, G., Suh, G. Y., Donovan, F. D., Herfkens, R. J., Taylor, C. A. EXCERPTA MEDICA INC-ELSEVIER SCIENCE INC. 2006: 110M-110M