Korean J Radiol.  2016 Dec;17(6):912-918. 10.3348/kjr.2016.17.6.912.

Comparison of T1rho and T2 Mapping of Knee Articular Cartilage in an Asymptomatic Population

• Yoon MA
• Hong SJ
• Im AL
• Kang CH
• Kim BH
• Kim IS

• KMID: 2466288
• DOI: http://doi.org/10.3348/kjr.2016.17.6.912

Abstract

OBJECTIVE
To analyze subregional differences in T1rho (T1ρ) and T2 values and their correlation in asymptomatic knee cartilage, and to evaluate angular dependence with magic angles.
MATERIALS AND METHODS
Six asymptomatic volunteers underwent knee MRI with T1ρ and T2 mapping. T1ρ and T2 values were measured by two radiologists independently, at nine subregions in the medial femoral condyle (MFC) cartilage, at angles of ± 0°, 15°, 35°, 55°, 75° respective to a vertical line (B0) bisecting the width of the distal femur, and at two locations in the patella. Subregional values of T1ρ and T2 were analyzed and significant differences in three divided portions of the MFC (anterior, central, and posterior) were statistically evaluated. Correlation between T1ρ and T2 and angular dependence with magic angles were also assessed for statistical significance.
RESULTS
T1ρ values were lowest at +15° and highest at -55°. T2 values were lowest at +75° and highest at +35°. Both T1ρ and T2 were higher in superior patella than inferior patella. T1ρ showed significant differences in the three divided portions of the MFC, while T2 showed significant differences only between central and posterior portions. There was a weak correlation between T1ρ and T2 (r = 0.217, p = 0.127). T1ρ showed more angular dependence than T2.
CONCLUSION
T1ρ and T2 showed different subregional values and angular dependence in asymptomatic knee cartilage with a weak correlation. Awareness of these differences will aid in assessment of cartilage in a specific subregion of the knee.

Keyword

MRI; Cartilage; Knee; T1rho; T2 mapping; Magic angle

MeSH Terms

Adult
Cartilage, Articular/*diagnostic imaging
Female
Humans
Knee Joint/*diagnostic imaging
*Magnetic Resonance Imaging
Male
Middle Aged
Osteoarthritis, Knee/diagnosis/diagnostic imaging/pathology
Prospective Studies

Figure

• 

  Fig. 1 T2 (A) and T1ρ (B) maps with ROIs in nine subregions in MFC. Dashed white line indicates horizontal line crossing posterior margin of MFC cartilage. ROIs were drawn at angles of ± 0°, 15°, 35°, 55°, 75° degrees respective to vertical line (B0) bisecting width of distal femur, which was perpendicular to dashed white line. MFC = medial femoral condyle, ROIs = regions of interest, T1ρ = T1rho

• 

  Fig. 2 Line graphs of mean value overlaid on scatter plots of T1ρ (A) and T2 (B) values (ms) at each angle (degrees) of medial femoral condyle and patella. IP = inferior patella, SP = superior patella, T1ρ = T1rho

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