Magic angle effect plays a major role in both T1rho and T2 relaxation in articular cartilage.
To investigate the effect of sample orientation on T1rho and T2 values of articular cartilage in histologically confirmed normal and abnormal regions using a whole-body 3T scanner.



Eight human cadaveric patellae were evaluated using a 2D CPMG sequence for T2 measurement as well as a 2D spin-locking prepared spiral sequence and a 3D magnetization-prepared angle-modulated partitioned-k-space spoiled gradient echo snapshots (3D MAPSS) sequence for T1rho measurement. Each sample was imaged at six angles from 0° to 100° relative to the B0field. T2 and T1rho values were measured for three regions (medial, apex and lateral) with three layers (10% superficial, 60% middle, 30% deep). Multiple histopathologically confirmed normal and abnormal regions were used to evaluate the angular dependence of T2 and T1rho relaxation in articular cartilage.



Our study demonstrated a strong magic angle effect for T1rho and T2 relaxation in articular cartilage, especially in the deeper layers of cartilage. On average, T2 values were increased by 231.8% (72.2% for superficial, 237.6% for middle, and 187.9% for deep layers) while T1rho values were increased by 92% (31.7% for superficial, 69% for middle, and 140% for deep layers) near the magic angle. Both normal and abnormal cartilage showed similar T1rho and T2 magic angle effect.



Changes in T1rho and T2 values due to the magic angle effect can be several times more than that caused by degeneration, and this may significantly complicate the clinical application of T1rho and T2 as an early surrogate marker for degeneration.
Department of Radiology, University of California, San Diego, CA, USA; Department of Radiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.
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H
Shao
Institute for Surgical Pathology, University Hospital Zurich, Zurich, Switzerland.
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C
Pauli
Department of Radiology, University of California, San Diego, CA, USA; Department of Radiology, Huadong Hospital, Fudan University, Shanghai, 200040, China.
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S
Li
Department of Radiology, University of California, San Diego, CA, USA.
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Y
Ma
Department of Radiology, University of California, San Diego, CA, USA.
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Tadros
Department of Medicine, University of California, San Diego, CA, USA.
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A
Kavanaugh
Department of Radiology, University of California, San Diego, CA, USA; Radiology Service, VA San Diego Healthcare System, San Diego, CA, USA.
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EY
Chang
Department of Radiology, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China.
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G
Tang
Department of Radiology, University of California, San Diego, CA, USA. Electronic address: jiangdu@ucsd.edu.
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J
Du
D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D002358:Cartilage, Articular / Q000000981:diagnostic imaging* / Q000473:pathology; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000000981:diagnostic imaging* / Q000473:pathology
Articular cartilage; Degeneration; Magic angle; T1rho; T2