TR_002 Technical Reports Knee Articular Cartilage in an Asymptomatic Population : Comparison of T1rho and T2 Mapping Min A Yoon 1,*, Suk-Joo Hong 1, Chang Ho Kang 2, Baek Hyun Kim 3 1 Korea University Guro Hospital, Republic of Korea 2 Korea University Anam Hospital 3 Korea University Ansan Hospital * Corresponding author : mina11360@gmail.com
Nothing to disclose
Introduction Hyaline articular cartilage Chondrocyte 4% Water (65-85%) Extracellular matrix type II collagen (15-20%) proteoglycan (3-10%) MAGNETOM Flash 2/2012 www.siemens.com/magnetom-world
Biochemical MRI T1rho (T1ρ) T2 spin-lattice relaxation time in the rotating frame a time constant for transverse magnetization decay in a very weak B1 field strength produced by spin-lock RF pulse positive association with the severity of knee osteoarthritis sensitive to changes in proteoglycan content in in articular cartilage spin-spin relaxation related to dipolar interaction of water proton in ECM sensitive for collagen and water content and orientation elevated in knee osteoarthritis
Introduction Magic angle effect regions of tightly bound collagen at 54.74 of the main magnetic field (Bo) maximal at relatively short TE
Introduction Inconsistent results on magic angle effects on T2 and T1ρ in knee cartilage strong orientation dependence of T2 Grunder et al, Magn Reson Med 1998;39:376-382, Mlynárik et al, Magn Reson Imaging 1996;14:435-442 substantially less orientation effect in vivo knee cartilage T2 Mosher et al, AJR Am J Roentgenol 2001;177:665-669 elimination of laminar appearance at magic angle due to reduced dipolar interaction with spin-lock technique Akella et al, Magn Reson Med 2004;52:1103-1109 magic angle may be cause of higher T1ρ in the patella Buck et al, AJR Am J Roentgenol 2011;196:W174-179
Purpose Analyze subregional differences in T1ρ and T2 values in the medical femoral condyle and patella Correlation of T1ρ and T2 in asymptomatic knee cartilage Evaluate angular dependence with magic angles on cartilage T1ρ and T2 mapping
Material and Methods Six healthy adult volunteers 4M and 2F; mean, 32.3 yrs; range, 26-45 yrs 3.0T MR scanner (Magnetom Trio, A Tim, Siemens Medical Solutions) T1ρ mapping truefisp-based 2D T1ρ pulse sequence time of spin lock (TSL) = 0, 10, 20, 30, 40 ms, spin lock frequency = 500 Hz, TR/TE = 8/4 ms T2 mapping multi-echo spin echo sequence TR = 2000 ms, TE = 10, 20, 30, 40, 50, 59, 69, 79 ms
Material and Methods Image Analysis T1ρ and T2 quantification Two independent review by musculoskeletal radiologists Manually drawn ROIs (2-3mm 2 ) Nine anatomical subregions in the medial femoral condyle Two locations in the center of the patella
Nine anatomical subregions in the medial femoral condyle, At angles of ± 0 o, 15 o, 35 o, 55 o, 75 o respective to a vertical line (B0) bisecting the width of the distal femur Perpendicular to a horizontal line crossing the posterior margin of MFC cartilage -75 +75-55 +55-35 -15 +15 +35 B0 T2 map T1rho map
Material and Methods Statistical Analysis Intraclass correlation coefficients (ICC) Inter-reader agreement Kruskal-Wallis test and post-hoc Tukey s test significant differences between T1ρ and T2 values in three divided MFC portions (anterior: -75 o, 55 o, 35 o, central: -15 o, 0 o, 15 o, and posterior: 35 o, 55 o, 75 o ) and patella Pearson s rank correlation correlation between T1ρ and T2 values Wilcoxon signed-rank test evaluation of angular dependence with magic angle influence between values of anatomical subregions in the MFC and values at ±55 o
Results T1ρ lowest at +15 o, highest at -55 o superior patella>inferior patella lowest in the central portion of the MFC highest in the anterior portion of the MFC
Results T2 lowest at +75 o, highest at +35 o superior patella>inferior patella lowest in the posterior portion highest in the central portion of the MFC
Results Significant differences in the three divided portions of the MFC for both T1ρ (p<0.05) No significant differences in three portions of the MFC for T2 (p=0.767) Weak correlation (r=0.217, p=0.127) between T1ρ and T2 values of the MFC and the patellar cartilage
Results - Magic angle effects T2 minimal angular dependence with the magic angle effect significant differences between -55 o and (-35 o, +75 o ) T1ρ more angular dependence -55 o and (-35 o, -15 o, 0 o, +15 o, +35 o, +55 o, 75 o ), +55 o and (0 o, +15 o ) (p<0.05) T1ρ T2 Location p(1) p(2) p(1) p(2) -75 o 0.119 0.109 0.109 0.109-55 o 0.028 * 0.463-35 o 0.028 * 0.173 0.046 * 0.917-15 o 0.028 * 0.463 0.249 0.600 0 o 0.028 * 0.028 * 0.463 0.753 15 o 0.028 * 0.028 * 0.917 0.345 35 o 0.028 * 0.173 0.600 0.075 55 o 0.028 * 0.463 75 o 0.028 * 0.249 0.028 * 0.166 p(1) = p-values in comparison to 55 o p(2) = p-values in comparison to 135 o
Conclusion Significant subregional variations in T1ρ and T2 values of the MFC and patella cartilage Only T1ρ showed significant differences in the three divided portions of the MFC Lowest in the central and highest in the anterior portion A weak correlation between T1ρ and T2 in the knee articular cartilage T1rho showed more angular dependence than T2
Conclusion T1ρ and T2 mappings differences between T1ρ and T2 in asymptomatic knee will aid in assessment of cartilage in a specific subregion of the knee
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