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. 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. 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. 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. 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