Benjamin Schmitt, Presenter: Nothing to Disclose

Stefan Zbyn, Abstract Co-Author: Nothing to Disclose

David Stelzeneder MD, Abstract Co-Author: Nothing to Disclose

Vladimir Jellus MA, Abstract Co-Author: Developer, Siemens AG

Peter Bachert, Abstract Co-Author: Nothing to Disclose

Siegfried Trattnig MD, Abstract Co-Author: Nothing to Disclose

gagCEST as well as 23Na imaging offer the possibility to assess cartilage quality by provision of a contrast sensitive to glycosaminoglycan (GAG) content. With high magnetic fields, limiting factors such as low intrinsic signal intensities can be overcome. We present initial results of a study carried out on patients with cartilage repair surgeries (Matrix-associated autologous chondrocyte transplantation and microfracture).

Experiments were carried out on a Siemens 7-T whole-body system with a new 28-channel Tx/Rx knee coil (QED) on 6 volunteers and 3 patients. A modified 3D spoiled GRE sequence was used for gagCEST imaging. The magnetization of each slice in the 3D slab was prepared with a CEST module, i.e. a series of Gaussian RF pulses, to saturate proton pools at different offset frequencies. After normalization of saturated images to an unsaturated image set, CEST contrast was generated by subtracting an image recorded after selective saturation at a positive offset from the water resonance from a reference image recorded at the same offset with opposite sign.23Na imaging was performed with a circularly-polarized sodium knee coil (Stark) using a modified GRE sequence.

The average CEST signal intensity at offset 1.7 ppm from water (the resonance of GAG –OH groups) in healthy volunteers was determined to be 8.2 ± 0.4 % (mean ± SEM). In the transplants, significantly decreased signal intensities (-5.9 ± 3 %) compared to controls as well as significantly decreased signal intensities compared to normal appearing cartilage in the same images were found (5.3 ± 0.6 %). A good correlation between CEST and 23Na imaging was found in the delineation of repair tissue in all 3 patients.

Whole-body high-field MR systems offer the opportunity to exploit the potential of the presented techniques to a new extent. Due to improved magnetic properties compared to lower magnetic fields, it is possible to achieve reliable and reproducible results. The results obtained with different techniques suggest that cartilage repair tissue has lower GAG content than native tissue leading to consistent impaired functionality.

Cartilage quality assessment can be performed without i.v. administration of contrast agent, thus reducing compliance issues.

Schmitt, B, Zbyn, S, Stelzeneder, D, Jellus, V, Bachert, P, Trattnig, S, Cartilage Quality Assessment Using gagCEST and 23Na MRI at 7 Tesla.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9006696.html