As a part of the Musculoskeletal and Quantitative Imaging Research Group (MQIR) at UCSF, my group is focusing on MR based assessment of trabecular and cortical bone, bone marrow and muscle fat composition using novel MR chemical-shift based imaging techniques. Our research has a particular focus on orthopedic applications. In particular, we are interested in imaging and analyzing the trabecular and cortical bone structure, the quantification of bone water content as well as bone marrow and muscle fat composition using high (3 Tesla) and ultra-high (7 Tesla) magnetic field strengths. To this end, we develop new pulse sequence techniques and advanced digital image processing algorithms. Our clinical focus is to improve early detection and to monitor treatment of related diseases such as osteoporosis, osteoarthritis and bone and bone marrow tumors. Another current focus is the improvement of MR imaging in the presence of metal implants.

Our research effort is currently funded by NIH R01AR057336 (PI: R. Krug).

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Research Projects

Bone Marrow Fat Fraction Mapping in the Proximal Femur in vivo using IDEAL

(D. Karampinos, R. Krug)

There is some evidence that osteoporosis is associated with increased marrow fat content as well as a conversion from red marrow to yellow (fatty) marrow with age. In this project, we investigate the marrow fat composition in the proximal femur in vivo using a method based on Iterative Decomposition of water and fat with Echo Asymmetry and Least-Squares Estimation (IDEAL). Three-point IDEAL FGRE hip images of six healthy subjects were acquired and water-fat separation was performed using multi-peak IDEAL. The average fat fraction and standard deviation were determined in three different regions of interest (femoral head, trochanter and neck). Significant differences in marrow fat content were identified between the three regions for all subjects.  

Figure:  Clockwise from top lef: Water only image, Fat only image, Fat Fraction Image and In-Phase image

Figure:  Comparison of single-voxel PRESS MR spectra from the trochanteric region (left) and the neck region (right). Note the enhanced water peak on the right spectrum.

Advanced Image Analysis Techniques of New High-resolution Images of the Proximal Femur in the Presence of Red and Yellow Bone Marrow using Local Bone Enhancement Fuzzy Clustering

(J. Folkesson, R. Krug)

Using advanced MR hardware and pulse sequences technique we have achieved to image the small trabecular structure of deeper sited seated regions like the proximal femur with very high spatial resolution in a clinically feasible scan time. We have developed and employed a novel partial membership bone segmentation technique (BE-FCM) that enhances bone segmentation compared to an established dual thresholding method in the presence of signal variations due to different marrow types. The new image acquisition and analysis framework enables trabecular bone analysis in the deeply situated femoral head, something which has been previously unfeasible in vivo.

Figure:  High-resolution in vivo image of the proximal femur. Hemopoietic or red marrow is composed of ~40% water (longer T1) and appears dark (femoral head, neck and shaft). The more prevalent yellow marrow is more fatty and yields a brighter MR signal.

Figure:  Top images: ROI defined in the femoral head.
Buttom image left:Trabecular bone segmentation of the ROI using the advanced BE-FCM technique.
Buttom image right:The same ROI segmented using an established dual thresholding technique.

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Selected Publications

 (of more than 30 peer reviewed papers and over 50 conference abstracts)
 2012

1. L. Nardo, D. Karampinos, J. Carballido-Gamio, S. Majumdar, B. Ma, T.M. Link, R. Krug. Quantitative Assessment of Fat Infiltration in the Rotator Cuff Muscles using MRI. ECR 2012, Vienna, Austria (Oral Presentation).
2. H. Alizai, L. Nardo, D. C. Karampinos, G. B. Joseph, S. P. Yap, T. Baum,R. Krug, S. Majumdar, T. M. Link. Validation of clinical semi-quantitative assessment of muscle fat infiltration using quantitative assessment with chemical shift-based water/fat separation in MR studies of the calf of post-menopausal women. European Radiology (2012 in print).

2011

1. J. Carballido-Gamio, J. Folkesson, Dimitrios C. Karampinos, T. Baum, T.M. Link, S. Majumdar, R. Krug. Generation of an Atlas of the Proximal Femur and its Application to Trabecular Bone Analysis. Magn Reson Med. (2011 in print).
2. R. Krug, P.E.Z. Larson, C. Wang, A.J. Burghardt, D.A.C. Kelley, T.M. Link, X. Zhang, D.B. Vigneron, S. Majumdar. Ultrashort Echo Time Magnetic Resonance Imaging of Cortical Bone at 7 Tesla Field Strength: A Feasibility Study. J Magn Reson Imaging. (2011 in print).
3. M. Han, B.A. Hargreaves, R. Krug. Bilateral Hip MRI using Dual-Band Excitation with Slab-Phase Modulation. ISMRM 2011, Montreal, Canada.  
4. J. Folkesson, J. Goldenstein, J. Carballido-Gamio, G. Kazakia, A.J. Burghardt, A. Rodriguez,R. Krug, A.E. de Papp, T.M. Link, S. Majumdar. Longitudinal Evaluation of the Effects of Alendronate on MRI Bone Microarchitecture in Postmenopausal Osteopenic Women. Bone Volume 48(3):611-21 (2011).
5. D.C. Karampinos, S. Banerjee, K. F. King, R. Krug, T. M. Link, S. Majumdar. Reduced FOV spinal muscle DWI with single-shot interleaved multi-slice inner volume diffusion-weighted stimulated echo EPI. ISMRM 2011, Montreal, Canada.
6. J. Carballido-Gamio, J. Folkesson, T. Baum, T. M. Link, S. Majumdar, R. Krug. 3D Geodesic Topological Analysis of Trabecular Bone Micro-Architecture of the Proximal Femur. ISMRM 2011, Montreal, Canada.
7. J. Folkesson, J. Carballido-Gamio, D.C. Karampinos, T. Baum, T.M. Link, S. Majumdar, R. Krug. Quantification of Bone Marrow Types from High-Resolution MR Images in the Proximal Femur using Three Class Clustering. ISMRM 2011, Montreal, Canada.         

 

2010

1. R. Krug, A.J. Burghardt, S.Majumdar, T.M. Link. High-resolution Imaging Techniques for the Assessment of Osteoporossis, Radiologic Clinics of North America 2010 (in press)
2.  R. Krug, T. Henning, R. Meier, B. Hargreaves. Advances in MRI of the knee for Osteoarthritis, World Scientific (in press)
   
3. J. Folkesson, J. Carballido-Gamio, D. C. Karampinos, P. Koon, S. Banerjee, E.T. Han, T. M. Link, S. Majumdar, R. Krug. Advanced Image Analysis Techniques of New High-resolution Images of the Proximal Femur in the Presence of Red and Yellow Bone Marrow using Local Bone Enhancement Fuzzy Clustering. ISMRM 2010, Stockholm, Sweden.
   
4. D. C. Karampinos, H. Yu, A. Shimakawa, E.T. Han, T. M. Link, S. Majumdar, R. Krug. Bone Marrow Fat Fraction Mapping in the Proximal Femur in vivo using IDEAL gradient echo imaging. ISMRM 2010, Stockholm, Sweden.
   
5. B. Wu, C. Wang, R. Krug, D.A.C. Kelley, D. Xu, S. Banerjee, D. Vigneron, S. Nelson, S. Majumdar, X. Zhang. 7T Human Spine Imaging Arrays with Adjustable Inductive Decoupling. IEEE Trans Biomed Eng.; Volume 57(2):397-403 (2010).
   
6.  O. Ristow, Ch. Stehling, R. Krug, L. Steinbach, G. Sabo, A. Ambekar, M. Huber, T.M. Link. Isotropic 3D Fast Spin Echo Imaging Versus Standard 2D Imaging at 3.0 T of the knee – Artificial Cartilage and Meniscal Lesions in a Porcine Model. JCAT 2010 (in press)
   
7. S. Banerjee, R. Krug, S. Prevrhal, S. Majumdar. Osteoporosis – Pathophysiology and Clinical Management, second edition, Humana Press; 51-76 (2010)
   
8. C. Stehling, H. Liebl, R. Krug, N. E. Lane, M. C. Nevitt, J. Lynch, et al. Patellar cartilage: T2 values and morphologic abnormalities at 3.0-T MR imaging in relation to physical activity in asymptomatic subjects from the osteoarthritis initiative. Radiology; Volume 254(2):509-20 (2010).

2009

(Peer Reviewed Manuscripts only)

1. R. Krug, C. Stehling, D.A.C. Kelley, S. Majumdar, T.M. Link. Imaging of the Musculoskeletal System In Vivo using Ultra-high Field Magnetic Resonance at 7 Tesla. Invest Radiol.; Volume 44(9):613-8 (2009)
2. J. Carballido-Gamio, R. Krug, M.B. Huber, B. Hyun, F. Eckstein, S. Majumdar, T.M. Link. Geodesic Topological Analysis Of Trabecular Bone Micro-Architecture From High-Spatial Resolution Magnetic Resonance Images. Magn Reson Med.; Volume 61(2):448-56 (2009)/li>
3. J. Zhao, R. Krug, D. Xu, Y. Lu, T.M. Link. 3T versus 1.5T MR Imaging of the Spine - Comparison of image quality and normal/neoplastic marrow contrast. AJR Am J Roentgenol.; Volume 192(4):873-80 (2009)
4. R. Krug, J. Zuo, B. Ma, S. Majumdar, T.M. Link. Assessment of cartilage dedicated sequences at Ultra High Field MRI: comparison of imaging performance and diagnostic confidence between 3.0 Tesla and 7.0 Tesla with respect to osteoarthritis-induced changes at the knee joint. Skeletal Radiol.; Volume 38(8):771-83 (2009)
5. J. Folkesson, R. Krug, A.S. Issever, C. Fang, T.M. Link, S. Majumdar. Evaluation of correction methods for coil-induced intensity inhomogeneities and their influence on trabecular bone structure parameters from MR images. Med Phys.; Volume 36(4):1267-74 (2009)
6. J.S. Bauer, R. Monetti, R. Krug, M. Matsuura, D. Müller, F. Eckstein, E.J. Rummeny, E.M. Lochmüller, C.W. Räth, T.M. Link. Advances of 3T MR imaging in visualizing trabecular bone structure of the calcaneus are partially SNR-independent – analysis using simulated noise in relation to microCT, 1.5 Tesla MRI and biomechanical strength. J Magn Reson Imaging; Volume 29(1):132-40 (2009)
7. O. Ristow, L. Steinbach, G. Sabo, R. Krug, M. Huber, I. Rauscher, B. Ma, T.M. Link. Isotropic 3D Fast Spin Echo Imaging Versus Standard 2D Imaging at 3.0T of the Knee – Image Quality and Diagnostic Performance. Eur Radiol.; Volume 19(5):1263-72 (2009)

2008

(Peer Reviewed Manuscripts only)

1. R. Krug, J. Carballido-Gamio, A.J. Burghardt, G. Kazakia, B.H. Hyun, B. Jobke, S. Banerjee, M. Huber, T.M. Link, S. Majumdar, Assessment of Trabecular Bone Structure Comparing Magnetic Resonance Imaging at 3 Tesla with High-Resolution Peripheral Quantitative Computed Tomography Ex-Vivo and In-Vivo. Osteoporos Int.; Volume 19(5):653-61 (2008)
2. R. Krug, J. Carballido-Gamio, S. Banerjee, A.J. Burghardt, T.M. Link, S. Majumdar, In-Vivo Ultra-High-Field Magnetic Resonance Imaging of Trabecular Bone Microarchitecture at 7 Tesla. J Magn Reson Imaging; Volume 27(4):854-9 (2008)
3. S. Banerjee, R. Krug, J. Carballido-Gamio, D.A.C. Kelley, D. Xu, D. Vigneron, S. Majumdar. Rapid in vivo musculoskeletal MR with parallel imaging at 7 Tesla. Magn Reson Med.; Volume 59(3):655-60 (2008)
4. R. Stahl, A Luke, C.B. Ma, R. Krug, L. Steinbach, S. Majumdar, T.M. Link. Prevalence of pathologic findings in asymptomatic knees of marathon runners before and after a competition in comparison with physically active subjects-a 3.0 T magnetic resonance imaging study. Skeletal Radiol.; Volume 37(7):627-38 (2008)
5. J. Carballido-Gamio, T.M. Link, X. Li, E.T. Han, R. Krug, M.D. Ries, S. Majumdar. Feasibility and Reproducibility of Relaxometry, Morphometric, and Geometrical Measurements of the hip joint with magnetic resonance imaging at 3T.  J Magn Reson Imaging; Volume 28(1):227-35 (2008)

2007

(Peer Reviewed Manuscripts only)

1. R. Krug, J. Carballido-Gamio, A.J. Burghardt, S. Haase, J.W. Sedat, W.C. Moss, S. Majumdar. Wavelet-based characterization of vertebral trabecular bone structure from magnetic resonance images at 3T compared with micro-computed tomographic measurements. Magn Reson Imaging; Volume 25(3):392-398 (2007)
2. R. Krug, J. Carballido-Gamio, S. Banerjee, R. Stahl, L. Carvajal, D. Xu, D. Vigneron, D.A.C. Kelley, T.M. Link, S. Majumdar, In-Vivo Bone and Cartilage Magnetic Resonance Imaging using Fully Balanced Steady-state Free Precession at 7 Tesla. Magn Reson Med.; Volume 58(6):1294-8 (2007)
3. J.S. Bauer, S. Banerjee, T.D. Henning, R. Krug, S. Majumdar, T.M. Link: Fast, high spatial resolution MRI of the ankle with parallel imaging using GRAPPA at 3.0T. American Journal of Roentgenology; Volume 189(1): 240-5 (2007)
4. J.G. Eichhorn, R. Krissak, H.J. Rudiger, S. Ley, R. Arnold, J. Boese, R. Krug, M. Gorenflo, M. Khalil, H. Ulmer, H.U. Kauczor, C. Fink: Compliance of the Normal-Sized Aorta in Adolescents with Marfan Syndrome: Comparison of MR Measurements of Aortic Distensibility and Pulse Wave Velocity. Röfo; Volume 179(8):841-846 (2007)
5. J. Blumenfeld, J. Carballido-Gamio, R. Krug, D.J. Blezek, I. Hancu, S. Majumdar: Automatic Prospective Registration of High-Resolution Trabecular Bone Images of the Tibia. Ann Biomed Eng.; Volume 35(11):1924-31 (2007)
6. G.J. Kazakia, B. Hyun, A. Burghardt, R. Krug, D. Newitt, A. de Papp, T. Link, S. Majumdar, In Vivo Determination of Bone Structure in Post-Menopausal Women: A Comparison of HR-pQCT and High-Field MR Imaging. J Bone Miner Res.; Volume 23(4):463-74 (2007)

2006 and older

(Peer Reviewed Manuscripts only)

1. R. Krug, E.T. Han, S. Banerjee, S. Majumdar: Fully Balanced Steady State 3D-Spin-Echo (bSSSE) Imaging at 3 Tesla, Magn Reson Med; Volume 56 (5):1033-1040 (2006)
   
2. J.S. Bauer, S.J. Krause, C.J. Ross, R. Krug, J. Carballido-Gamio, E. Ozhinsky,S.Majumdar, T.M. Link: Volumetric Cartilage Measurements of Porcine Knee at 1.5-T and 3.0-T MR Imaging: Evaluation of Precision and Accuracy, Radiology; Volume 241(2):399-406 (2006)
   
3. R. Krug, S. Banerjee, E.T. Han, D.C. Newitt, T.M Link, S. Majumdar: Feasibility of In Vivo Structural Analysis of High-Resolution Magnetic Resonance Images of the Proximal Femur, Osteoporos Int; Volume 16 (11):1307-14 (2005)
   
4. S. Banerjee, E.T. Han, R. Krug, D.C. Newitt, S. Majumdar: In vivo High Resolution Magnetic Resonance Imaging of Trabecular Bone using refocused SSFP methods at 1.5T and 3T, J Magn Reson Imaging; Volume 21:818-825 (2005)
   
5. R. Krug et al.: Determination of Aortic Compliance from Magnetic Resonance Images using an Automatic Active Contour Model, Phys. Med. Biol. Volume 48 2391-2404 (2003)

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