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Articular Cartilage & Onset of OA
10/8/2013 1
Molecular view of AC
Disrupted collagen fibrils and network
Proteoglycan Los...
Sodium MRI Challenges & Objective
10/8/2013 2
• Low in-vivo sodium concentration in AC
• Requires a specialised RF coil to...
Methods
10/8/2013 3
Sodium reference Marker
Scanning Protocols
Sodium Imaging: 3D Gradient Echo sequence
(TR/TE = 11.4/4.0...
Results
10/8/2013 4
Mean sodium signal intensities are used to measure
absolute sodium content in AC using equation
Region...
Conclusions
10/8/2013 5
• Sodium concentration in AC region measured from sodium images correspond
to values reported earl...
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Articular Cartilage & Onset of OA

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Articular Cartilage & Onset of OA

  1. 1. Articular Cartilage & Onset of OA 10/8/2013 1 Molecular view of AC Disrupted collagen fibrils and network Proteoglycan Loss Tibial AC Femoral AC Fine collagen orientation ProteoglycanOnset of Osteoarthritis Provided by: Dileep KumarProvided by: Dileep Kumar
  2. 2. Sodium MRI Challenges & Objective 10/8/2013 2 • Low in-vivo sodium concentration in AC • Requires a specialised RF coil to excite sodium nuclei & high field magnetic strength • So far, sodium concentration of AC has been measured significantly on high field magnetic strength (>4Tesla) • Availability of MRI Scanner with >3Tesla in most of the clinics is rare that limits the clinical aspects of sodium imaging Challenges Objective • To investigate the possibility of imaging and quantification of local sodium content of articular cartilage using sodium MRI at 1.5Tesla clinical MR system. Provided by: Dileep Kumar
  3. 3. Methods 10/8/2013 3 Sodium reference Marker Scanning Protocols Sodium Imaging: 3D Gradient Echo sequence (TR/TE = 11.4/4.0 ms, flip angle = 62 , isotropic resolution = 2.81 x 2.81 x 8 mm3, and total acquisition time ~30 min) Proton Imaging: MEDIC 3D sequence (TR/TE = 37/20 ms, flip angle = 8 , isotropic resolution = 0.47 x 0.51 x 1.5mm3, and total acquisition time ~5 min) ref refNa Na AC Na S S Na ][][ Sodium concentration was determined in the AC ([Na]AC) region of 23Na MRI images as ratio of the mean 23Na signal intensities (SNa) in cartilage region to the sodium signal from reference marker (SNa,ref) of 300mmol/L sodium concentration ([Na]ref) using the Equation below: Provided by: Dileep Kumar
  4. 4. Results 10/8/2013 4 Mean sodium signal intensities are used to measure absolute sodium content in AC using equation Region No. of Pixels Mean Signal Intensity Reference 22 199.24 Articular Cartilage 81 168.42 Estimated sodium concentration in AC region from sodium image is 253mmol/L LmmolNa S S Na ref refNa Na AC /59.253300. 24.199 42.168 ][][ Provided by: Dileep Kumar
  5. 5. Conclusions 10/8/2013 5 • Sodium concentration in AC region measured from sodium images correspond to values reported earlier at higher field strength • Study shows the feasibility of imaging and quantification of local sodium content of AC using sodium MRI at 1.5 Tesla • Estimation of changes in sodium concentration of normal and degenerative AC can be done using acquired images. For diagnostic purposes, more sample scans will be required with known diagnostic conditions • Since no contrast agent is required, this technique is suitable for non-invasive in vivo physiological measurement of articular cartilage Provided by: Dileep Kumar

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