The Short of It
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Thursday May 12th
Room 520B-F  10:30 - 12:30 Moderators: Garry Gold and Matthew Koff

10:30 561.   Introduction
Won C. Bae


10:42 562.   Clinical ultra-short TE-enhanced T2* mapping of meniscus 
Ashley Williams1, Yongxian Qian2, and Constance R Chu1
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.

10:54 563.   Direct Depiction of Bone Microstructure Using ZTE Imaging 
Markus Weiger1,2, Marco Stampanoni3,4, and Klaas Paul Pruessmann3
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.

11:06 564.   SWIFT Imaging of Osteochondral Repair in Equine Model with correlation to lower case Greek muCT  -permission withheld
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 Nieminen7,8
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.

11:18 565.   Free and bound water evaluation of articular cartilage 
Jiang Du1, Chantal Pauli2, Eric Diaz1, Won Bae1, Sheronda Statum1, Darryl DLima2, and Christine Chung1
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.

11:30 566.   Investigations of The Origin of Phase Differences Seen with Ultrashort TE Imaging of Short T2 Meniscal Tissue 
Michael Carl1
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.

11:42 567.   High Resolution 3D Ultrashort TE (UTE) Imaging: In Vivo Applications 
Jiang Du1, Michael Carl2, Mark Bydder1, Jing-Tzyh Chiang1, Richard Znamirowski1, Christine Chung1, and Graeme Bydder1
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.

11:54 568.   Temporal and Regional Changes of T2* in the Repaired Meniscus 
Matthew F. Koff1, Lisa A Fortier2, Scott A Rodeo3, Atsushi Takahashi4, Suzanne Maher5, Demetris Delos3, Parina Shah1, and Hollis G. Potter1
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.

12:06 569.   Sensitivity of Quantitative UTE MRI to Degradation of Human Temporomandibular Discs 
Won C Bae1, Sheronda Statum1, Reni Biswas2, Koichi Masuda3, Jiang Du1, Terry Tanaka4, and Christine B Chung1
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 Anthony1
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.