Matrix-associated autologous chondrocyte implantation (MACI) is one of the most important treatment options in cartilage repair. Biochemical MR imaging has been used as a noninvasive method to evaluate the repair tissues’ cartilage component. The purpose of this study is to use T2 mapping and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) to evaluate the maturation process of the cartilage repair tissue in patients in a 1-year follow-up after MACI.13 knees of 9 patients (4 females and 5 males; mean age, 46.9±8.4 years; age range: 40-57 years) were recruited in this study and examined four times at 1, 3, 6 and 12 months after MACI. 16 cartilage defects were treated, including 4 in the medial femoral condyle, 5 in the femoral trochlea, and 7 in the patella. The mean size of the treated lesions were 1.09±0.27 cm2, and ranged from 0.6 to 5.0 cm2. All MR imaging was performed on a 3T MR scanner (MAGNETOM Skyra, Siemens Healthcare, Erlangen, Germany) with a 15-channel Tx/Rx knee coil. Axial and sagittal PD-weighted images with fat saturation, and T1-weighted 3D VIBE images were acquired for morphological analysis. T2 mapping was performed using a multi-echo TSE sequence with 5 TEs of 13.8, 27.6, 41.4, 55.2, and 69.0 ms, TR of 1921 ms, FOV of 160´160 mm2, matrix size of 384´384, slice thickness of 3 mm. T1 mapping was acquired using a 3D VIBE sequence with 2 flip angles of 5° and 26°, TE/TR of 2.7/15 ms, FOV of 160´160 mm2, matrix of 384´384, and slice thickness of 3 mm. The second T1 mapping was performed 2 hours later after intravenous administration of Gd-DTPA (0.2 mM/kg, Magnevist, Germany). T2 and T1 maps were calculated in-line using MapIt software (Siemens Healthcare, Erlangen, Germany) on a pixel-by-pixel basis. T2 and T1 maps were registered to T1-weighted VIBE images and then automated cartilage segmentation was performed using the prototype software KneeCap (Siemens Healthcare, Erlangen, Germany) based on the segmentation algorithm including: 1) automated segmentation of the bones using a 3D active shape model; 2) extraction of the bone-cartilage interface; 3) cartilage segmentation using a deformable model. ROIs were placed in the native and repair cartilage to measure the T2 and T1 values. A paired t-test was used to compare the values between native and repair cartilage, and ANOVA analysis was used to compare the values from 1, 3, 6 and 12 months. Figure 1 shows an example case of T2 maps, T1 maps before and after contrast injection of automatically segmented cartilage in a patient at 1, 3, 6 and 12 months after MACI. The T2 and DR1 values (ΔR1 = 1/T1post － 1/T1pre) of the repair tissue were significantly higher than the native tissue at 1, 3 and 6 months after MACI (P <0.01), but showed a downward trend and showed no difference with native tissue at 12 months (P >0.05; Figure 2). T2 mapping is sensitive to changes in water and collagen content, while dGEMRIC is sensitive to the changes in GAG component. The increased T2 values in repair tissue could be caused by a greater hydration and unorganized collagen network of the newly built cartilage repair tissue, and also caused by chondral edema by the surgery. The increased DR1 values in the repair tissue could be caused by a lower GAG content. However, there was no difference in T2 and DR1 between native and repair tissues at 12 months after MACI, which suggested that the integrity of the collagen and GAG of repair tissue was similar to native cartilage. Biochemical MR imaging can provide information about the cartilage component changes in repair tissues after MRCI.