Isotropic three-dimensional T₂ mapping of knee cartilage: Development and validation

Area of Science:

• Biomedical Engineering
• Radiology
• Medical Imaging

Background:

• Knee cartilage evaluation is crucial for diagnosing osteoarthritis.
• Existing T2 mapping techniques may lack sufficient resolution or accuracy.
• Higher resolution imaging can improve the characterization of cartilage degeneration.

Purpose of the Study:

• To develop and validate a high-resolution isotropic 3D T2 mapping technique (Iso3DGRE) for knee cartilage.
• To assess the accuracy, repeatability, and precision of the Iso3DGRE sequence in vitro and in vivo.
• To compare the Iso3DGRE technique with a standard clinical 2D multislice multiecho (MSME) T2 mapping sequence.

Main Methods:

• Developed an isotropic 0.6 mm spatial resolution Iso3DGRE sequence on a 3T MR scanner.
• Optimized pulse sequence parameters using numerical simulations and validated accuracy with phantom studies.
• Assessed repeatability in healthy volunteers and compared T2 values with MSME in healthy volunteers and knee osteoarthritis (OA) patients.

Main Results:

• Numerical simulations optimized sequence parameters (100 excitations, 15° RF angle).
• Phantom studies showed high correlation (R² ≥ 0.99) with reference standards.
• Iso3DGRE demonstrated good repeatability (5.6% CV) and identified significantly higher T2 values in OA patients, with superior precision in OA cases compared to MSME.

Conclusions:

• High-resolution isotropic 3D T2 mapping for knee cartilage is feasible, accurate, repeatable, and precise.
• The Iso3DGRE technique enables multiplanar reformatting for T2 quantification in any desired plane.
• This advanced imaging method holds promise for improved knee cartilage characterization and OA assessment.