Dragana Savic^1,2, Valentina Pedoia¹, Youngho Seo¹, Matthew Bucknor¹, Benjamin Franc¹, and Sharmila Majumdar^1
1University of California San Francisco, San Francisco, CA, United States, ²University of Oxford, Oxford, United Kingdom

This first in human study evaluated cartilage biochemistry and bone function in sixteen knee osteoarthritis patients using simultaneous Time-Of-Flight (TOF) PET/MR imaging.  Bone turnover and blood flow was studied using ¹⁸F Sodium Fluoride (NaF) and quantitative voxel by voxel MR derived T_1ρ relaxation times characterizing the biochemical cartilage degeneration. Increased degeneration of cartilage, was associated with increased turnover in the adjoining bone as well as in the non-adjoining compartments. These observations highlight the complex biomechanical and biochemical interactions in the whole knee joint, alluding to a “bone-cartilage connectome”, that potentially changes during the natural history of the disease. 

Audrey P Fan¹, Feliks Kogan¹, Aleema Patel¹, Edwin HG Oei², Andrew Quon¹, and Garry E Gold^1
1Radiology, Stanford University, Stanford, CA, United States, ²Erasmus MC: University Medical Center Rotterdam, Rotterdam, Netherlands

This study investigates dynamic uptake of [18F]-fluoride in bone marrow lesions (BMLs) and osteophytes observed on MRI of patients with knee osteoarthritis. Through kinetic modeling, we characterized rate constants of bone metabolism in bone pathology relative to healthy bone. BMLs and higher-grade osteophytes showed higher total bone metabolism K_i (P < 0.01) and higher bone mineralization rate k₃ (P < 0.01) relative to grade 1 osteophytes and normal bone. While a similar trend was observed for blood flow, the differences from normal tissue were subtler suggests that rate of mineralization k₃ and not blood flow is a key driver of [¹⁸F]-fluoride accumulation in OA lesions. These new physiological parameters may help differentiate between different grades of OA lesions or identify which lesions are active parts of the disease process.

Xian Xu¹, Ningyu An¹, Panli Zuo², and Esther Raithel^3
1Department of Radiology, Chinese PLA General Hospital, Beijing, China, People's Republic of, ²Siemens Healthcare, MR Collaborations NE Asia, Beijing, China, People's Republic of, ³Siemens Healthcare GmbH, Berlin, Germany

This study combined T2 mapping and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) technique to evaluate the repair cartilage tissue after Matrix-associated autologous chondrocyte implantation (MACI). We found that the T2 and ΔR1 values of the repair tissue were significantly higher than the native tissue at 1, 3 and 6 months after MACI, but showed a downward trend and showed no difference with native tissue at 12 months, which suggested that the integrity of the collagen and GAG of repair tissue was similar to native cartilage. 

Matthew F. Koff¹, Hongsheng Wang², Suzanne Maher², Scott Rodeo³, and Hollis G Potter^1
1Department of Radiology and Imaging - MRI, Hospital for Special Surgery, New York, NY, United States, ²Department of Biomechanics, Hospital for Special Surgery, New York, NY, United States, ³Sports Medicine and Shoulder Service, Hospital for Special Surgery, New York, NY, United States

The relationship between calculated articular cartilage deformation when using an MR compatible loading device and actual contact mechanics has not been assessed. This study evaluated the accuracy of in vivo cartilage deformation as a surrogate for in vivo contact mechanics. Meniscal allograft transplantation patients underwent loaded MR pre-operatively and direct stress measurement intra-operatively. Good correlation, 0.72 (range: 0.56 to 0.85), between cartilage deformation and contact stress measurements was found. In vivo cartilage deformation may be a surrogate for in vivo contact mechanics.

Fang Liu¹, Alexey Samsonov¹, Wally Block², and Richard Kijowski^1
1Department of Radiology, University of Wisconsin-Madison, Madison, WI, United States, ²Department of Medical Physics, University of Wisconsin-Madison, Madison, WI, United States

Nuclear magnetic resonance studies have identified multiple water components within cartilage tissue. Previous studies using steady-state sequences based rapid method such as mcDESPOT and mcRISE have shown feasibility of multicomponent T2 analysis of cartilage. However, steady-state signal can be influenced by the finite pulse effect which might lead to biased parameter estimation. In this study, we incorporated the finite pulse correction in the mcRISE model and demonstrated the potential MT and finite pulse effect in-sensitive T2 parameters for multicomponent cartilage relaxometry analysis.

Matthew F. Koff¹, Parina H. Shah¹, Mauro Miranda¹, Christina Esposito², Elexis Baral², Kara Fields³, Thomas Bauer⁴, HSS Adult Reconstruction & Joint Replacement Division⁵, Douglass Padgett⁵, Timothy Wright², and Hollis G. Potter^1
1Department of Radiology and Imaging - MRI, Hospital for Special Surgery, New York, NY, United States, ²Department of Biomechanics, Hospital for Special Surgery, New York, NY, United States, ³Healthcare Research Institute, Hospital for Special Surgery, New York, NY, United States, ⁴Cleveland Clinic Foundation, Cleveland, OH, United States, ⁵Adult Reconstruction and Joint Replacement Division, Hospital for Special Surgery, New York, NY, United States

A majority of primary total hip arthroplasty (THA) function well but implant failure may occur. We propose MRI to evaluate adverse local tissue reactions (ALTRs) in patients with THA. In this study, we correlate indirect measures of ALTRs with direct measurements of implant wear. Greater volumetric wear and visual damage was found in subjects with ALTR on MR images. MR also correlated with histologic metrics of implant wear. The results indicate that MRI allows for accurate diagnosis of different synovial patterns in THA, which correlate to wear analysis at retrieval.

Stefan Zbyn^1,2, Vladimir Mlynarik¹, Vladimir Juras¹, Markus Schreiner^1,3, Didier Laurent⁴, Joerg Goldhahn⁴, Nicole Getzmann⁴, Stefan Marlovits⁵, and Siegfried Trattnig^1
1Department of Biomedical Imaging and Image-Guided Therapy, Medical University Vienna, Vienna, Austria, ²CD Laboratory for Clinical Molecular MR Imaging, Vienna, Austria, ³Department of Orthopaedics, Medical University Vienna, Vienna, Austria, ⁴Novartis Institutes for Biomedical Research, Basel, Switzerland, ⁵Department of Trauma Surgery, Medical University Vienna, Vienna, Austria

To our best knowledge, this is the first report on employing sodium (23Na) MRI for the in vivo evaluation of low-grade cartilage defects in the knee joint. In this 7T study, regions with chondral defect, weight-bearing, and non-weight-bearing femoral cartilage were evaluated in 23Na-images of patients after knee injury. Test-retest comparison showed high robustness and repeatability of sodium data. 23Na-MRI allowed differentiation between normal-appearing cartilage and low-grade chondral defects. 23Na-MRI can be used for noninvasive follow-up of changes in GAG content associated with cartilage degeneration. This method might be particularly useful for the evaluation of cartilage regenerating therapies.

Colin Russell¹, Valentina Pedoia¹, Keiko Amano¹, and Sharmila Majumdar^1
1Radiology and Biomedical Imaging, University of California, San Francsico, San Francisco, CA, United States

This multicenter study employs VBR as a novel technique to analyze patients with ACL tears at the time of injury and 6 months after ACL reconstruction. T_1ρ and T₂ analysis, correlation, and dispersion difference (R₂–R_1ρ) are three methods employed to highlight significant cartilage changes. The most posterior region of the posterior lateral tibia and the patella indicated partial cartilage recovery 6 months after reconstruction, demonstrated by decreasing T_1ρ and T₂, decreased T_1ρ T₂ correlation baseline to 6 months, and dispersion differences (R₂–R_1ρ). The trochlea displayed symptoms of cartilage degeneration, such as elevated T_1ρ and T₂ and dispersion differences.

Vladimir Juras^1,2, Lenka Hornakova³, Petr Kubovy³, Daniel Hadraba^3,4, Pavel Stursa⁵, David Gerych³, Pavol Szomolanyi¹, Karel Jelen³, and Siegfried Trattnig^1,6
1Department of Biomedical Imaging and Image-Guided Therapy, High Field MR Centre, Medical University of Vienna, Vienna, Austria, ²Department of Imaging Methods, Institute for Measurement Science, Bratislava, Slovakia, ³Department of Anatomy and Biomechanics, Faculty Of Physical Education and Sport, Prague, Czech Republic, ⁴Department of Radiology, Hospital na Homolce, Prague, Czech Republic,⁵Academy of Sciences of the Czech Republic, Prague, Czech Republic, ⁶Christian Doppler Laboratory for Clinical Molecular MR Imaging, Vienna, Austria

Meniscus behavior under loading in vivo has been studied using parametric MR imaging. T2* has been acquired with vTE using very short first TE = 0.8 ms to secure the precise estimation. The knees of the subjects were loaded in situ with custom made compression device and T2* mapping was performed in 5 time points (without loading, and 4 consequent scans under the loading 7 min apart). The increase in T2* was observed in all compartments, significance was found in medial meniscus only. vTE T2* mapping might be a prospective marker for detecting the dynamic response of the meniscal tissue. 

Qun He^1,2, Michael Carl³, Graeme Bydder¹, and Jiang Du^1
1University of California, San Diego, San Diego, CA, United States, ²Ningbo Jansen NMR Technology Co., Ltd., Cixi, Zhejiang, China, People's Republic of, ³Global MR Applications & Workflow, General Electric, San Diego, CA, United States

UTE sequences combined with IDEAL processing produces high contrast images of short T₂ tissues or tissue components such as menisci, ligaments, and tendons. In this work, we report the use of 3D UTE Cones imaging and IDEAL processing (3D Cones-IDEAL) for volumetric imaging of short T₂ tissues in the knee and ankle joints at 3T. High resolution volumetric imaging of the knee and ankle joints, together with robust fat/water separation, field map estimation, R₂*/T₂* mapping and fat fraction mapping are demonstrated.