Ashley Williams¹, Yongxian Qian², and Constance R Chu^1
1Cartilage Restoration Center, University of Pittsburgh, Pittsburgh, PA, United States, ²Department of Radiology, University of Pittsburgh

UTE-T2* images of menisci were acquired from 32 human subjects: 10 asymptomatic patients, 9 patients with an ACL tear but no meniscal tear, and 13 subjects with medial meniscal tears. UTE-T2* repeatability among asymptomatics was <10%. UTE-T2* values of menisci in subjects with clinically diagnosed medial tears were 42% higher (P=0.005) than asymptomatics. Interestingly, UTE-T2* values of subjects with an ACL injury but no meniscal tear were 32% higher (P=0.028) than asymptomatics, suggesting that UTE-T2* mapping may be sensitive to sub-clinical meniscus degeneration. Longitudinal evaluation is needed to assess whether UTE-T2* mapping of meniscus is predictive of progressive meniscal degeneration.

Markus Weiger^1,2, Marco Stampanoni^3,4, and Klaas Paul Pruessmann^3
1Bruker BioSpin AG, Faellanden, Switzerland, ²Bruker BioSpin MRI GmbH, Faellanden, Germany, ³Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, ⁴Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland

Direct depiction of the microstructure of trabecular bone is enabled by MRI with zero echo time (ZTE). The immediate signal acquisition, the maximum encoding speed in the k-space centre, and the high acquisition duty cycle of ZTE enable to achieve the required high resolution, robustness, and SNR efficiency under the rapid T2 relaxation of bone. A comparison with high-quality x-ray images shows an excellent agreement of the two modalities.

Mikko Johannes Nissi¹, Jari Rautiainen¹, Lauri Juhani Lehto¹, Virpi Tiitu¹, Outi Kiviranta¹, Hertta Pulkkinen¹, Anne Brunott², Rene van Weeren³, Pieter Brama⁴, Ilkka Kiviranta⁵, Jutta Ellermann⁶, and Miika Tapio Nieminen^7,8
1University of Eastern Finland, Kuopio, Finland, ²Brünott Equine Surgery and Ortopedics, Netherlands, ³University of Utrecht, Netherlands, ⁴University College Dublin, Ireland, ⁵University of Helsinki, Finland, ⁶University of Minnesota, United States, ⁷University of Oulu, Finland, ⁸Oulu University Hospital, Finland

Characterization of osteochondral repair using conventional MRI techniques is limited due to lack of signal from important tissues such as calcified cartilage and the bone matrix. SWIFT is capable of capturing signal from extremely short T2 species and is thus a very appealing method for the evaluation of osteochondral repair. In this study, spontaneous repair of chondral and osteochondral defects was investigated in an equine model using SWIFT and findings were correlated with micro -computed tomography. Results demonstrate, for the first time, the ability of SWIFT to reveal a high level of detail in repair tissue, particularly from calcified structures.

Jiang Du¹, Chantal Pauli², Eric Diaz¹, Won Bae¹, Sheronda Statum¹, Darryl DLima², and Christine Chung^1
1Radiology, University of California, San Diego, San Diego, California, United States, ²Scripps Reseach Institution

Multi-component analysis of CPMG spin echo images has been performed by several groups to identify and characterize different water compartments in articular cartilage. However, CPMG sequences on clinical MR scanners typically operated in a TE range (>10 ms) that does not allow detection of short T2 water components, or water bound to collagen and/or PG. Here we propose a bi-component T2* analysis of images from ultrashort TE (UTE) or UTE spectroscopic imaging (UTESI) to quantify T2* and fractions of the free and bound water components in cartilage.

Michael Carl^1
1Global Applied Science Laboratory, GE Healthcare, San Diego, CA, United States

We present UTE phase images of the meniscus that show surprisingly high contrast in spite of the very short TEs used. We investigated the source of this contrast using the Bloch equations, simulations, phantom experiments, and tissue studies. Phase evolution was shown to occur in UTE sequences primarily during the finite RF pulse and readout periods, and previously unrecognized susceptibility differences between fiber groups were observed in the meniscus.

Jiang Du¹, Michael Carl², Mark Bydder¹, Jing-Tzyh Chiang¹, Richard Znamirowski¹, Christine Chung¹, and Graeme Bydder^1
1Radiology, University of California, San Diego, San Diego, California, United States, ²Global Applied Science Laboratory, GE Healthcare, San Diego, California, United States

There are many species or tissue components which have very short T2 relaxation times and so cannot be detected with conventional magnetic resonance imaging (MRI) sequences. These include cortical bone, meniscus, ligaments, aponeuroses, the Achilles tendon, etc. High resolution in vitro imaging has been reported, together with in vivo imaging with moderate resolution and especially limited short T2 image contrast. Here we report 3D high resolution and contrast imaging of these short T2 species in vivo on a clinical 3T MR scanner.

Matthew F. Koff¹, Lisa A Fortier², Scott A Rodeo³, Atsushi Takahashi⁴, Suzanne Maher⁵, Demetris Delos³, Parina Shah¹, and Hollis G. Potter^1
1Department of Radiology and Imaging - MRI, Hospital for Special Surgery, New York, NY, United States, ²College of Veterinary Medicine, Cornell University, Ithaca, NY, United States, ³Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY, United States, ⁴Global Applied Science Laboratory, General Electric Healthcare, Menlo Park, CA, United States, ⁵Department of Biomechanics, Hospital for Special Surgery, New York, NY, United States

The poor sensitivity and qualitative nature of clinical knee meniscus healing evaluation precludes accurate decisions about return to activities of daily living. MRI is frequently used to evaluate meniscal repairs, but visualization of the meniscus is difficult due to short transverse relaxation times (T2). Qualitative MRI Ultrashort echo imaging (UTE) allows objective and quantitative assessment of meniscal healing. This study evaluated the qMRI technique of T2* mapping using UTE imaging as a biomarker of meniscal integrity. This goal was achieved by measuring the regional and temporal variation in T2* values in an ovine meniscal repair model.

Won C Bae¹, Sheronda Statum¹, Reni Biswas², Koichi Masuda³, Jiang Du¹, Terry Tanaka⁴, and Christine B Chung^1
1Radiology, University of California, San Diego, San Diego, CA, United States, ²Bioengineering, University of California, San Diego, La Jolla, CA, United States, ³Orthopaedic Surgery, University of California, San Diego, La Jolla, CA, United States, ⁴School of Dentistry, Department of Graduate Prosthodontics, University of Southern California, Los Angeles, CA, United States

The temporomandibular joint (TMJ) facilitates jaw movement. TMJ disorders involve degeneration of the TMJ disc; early detection using MRI would be useful. TMJ tissues have inherently short T2 values and their quantitative evaluation benefits from ultrashort time-to-echo (UTE) techniques. This study evaluated sensitivity of UTE T1rho property to biochemical changes of human TMJ discs incurred by trypsin digestion. UTE T1rho values increased significantly with digestion duration, during which glycosaminoglycan loss has also occurred. Incremental increase in UTE T1rho values correlated significantly with incremental glycosaminoglycan loss. UTE T1rho may be useful for early and longitudinal assessment of TMJ disc degeneration.

Tsz Kwun Law¹, Dino Samartzis², Mina Kim¹, Queenie Chan³, Pek-Lan Khong¹, M C Kenneth Cheung², and Marina-Portia Anthony^1
1Diagnostic Radiology, The University of Hong Kong, Hong Kong, China, People's Republic of, ²Orthopaedics and Traumatology, The University of Hong Kong, Hong Kong, China, People's Republic of, ³Philips Healthcare, Hong Kong, China, People's Republic of

Early diagnosis of CEP defects by UTE technique may provide useful information for understanding the pathogenesis of each of DDD and Schmorl¡¦s nodes (SN). The objective of this study was to assess CEP integrity in normal IVD levels, levels with degenerated IVDs and levels with SNs. Based on the UTE images, CEP defects were defined as discontinuity of high signal over 4 consecutive slices. Results showed that CEP defects were found to have a 4.5 fold increased likelihood of having DDD. No association between CEP defects and SNs was established. The effects of age and CEP defects were found to be level dependent.