Figure 1.
Single shot pulse sequence diagram of T1ρ MRI.
T1ρ pulse sequence consist of a B1 and B0 compensated T1ρ preparation pulse cluster, crusher gradients, chemical shift selective fat saturation pulse, a gradient echo readout acquisition with centric phase encoding order and T1 recovery delay.
Figure 2.
Off-resonance effect on T1ρ mapping.
Top row contains anatomical image (A), goodness of fit (R2) map (B) and T1ρ map (C) corresponding to global volume reference frequency and voltage. Bottom row contains anatomical image (D), R2 map (E) and T1ρ map (F) corresponding to local volume (rectangular box on anatomical image) around patellar cartilage based reference frequency and voltage. Note that pixels on cartilage with R2<0.8 are not displayed on final map.
Figure 3.
High resolution T1ρ maps of articular cartilage.
First column images show patellar cartilage in axial orientation and 2nd column images show femoral and tibial cartilage in coronal orientation of a healthy volunteer at 7T. First row (A&B) contain high resolution anatomical images (TSL = 0), 2nd row (C&D) contain high resolution T1ρ-weighted images corresponding to TSL = 40 ms and 3rd row contain high resolution T1ρ (ms) maps of cartilage overlaid on anatomical images. Arrow indicates the medial side femoral cartilage with reduced contrast among different layers due to magic angle effect. Note that these are cropped images.
Figure 4.
Scatter plots of test-retest data of T1ρ values in different cartilage facets for 8 subjects at 7T.
Table 1.
Intra class correlation (ICC) coefficient values for test-retest reliability experiment along with 95% CI in open brackets.
Table 2.
Pearson correlation coefficient values for test-retest reliability experiment for medial and lateral sides of different cartilage facets.
Table 3.
Coefficient variation (mean ± s.d.) values (%) for test-retest reliability experiment for medial and lateral sides of different cartilage facets.
Figure 5.
Bar plots represents T1ρ analysis of knee cartilage at 7T.
T1ρ values from deep, middle and superficial zones of patellar, femoral and tibial cartilage are shown in Fig (A, B, C). T1ρ values from medial and lateral side of cartilage are shown in Fig. D.
Table 4.
Analysis of T1ρ values (ms) for human knee cartilage (n = 6) at 3T and 7T.
Figure 6.
High resolution data from volunteer with meniscal tear and femoral cartilage pathology in medial side.
Fig A represents anatomical image, Fig B represents T1ρ-weighted image corresponding to TSL = 40 ms and Fig C contain T1ρ (ms) map of femoral and tibial cartilages overlaid on anatomical image. The red arrow on anatomical image points to meniscal tear, the solid white arrow points to edema in femur and the dotted white arrow points to an unidentified pathology in cartilage. In the focal ROI (on anatomical image), mean T1ρ value is = 113 ms. T1ρ values >300 ms are threshold to zero. Color scale was adjusted to highlight focal region on femoral cartilage with high T1ρ values. Note that only cropped images are shown.
Figure 7.
High resolution images from volunteer with abnormal patellar cartilage.
Fig A represents anatomical image, Fig B represents T1ρ-weighted image corresponding to TSL = 40 ms and Fig C contain T1ρ (ms) map of patellar cartilages overlaid on anatomical image. Circular ROI on Fig.B encircles edema in bone. White arrows on Fig.C point to abnormal cartilage regions. Color scale was adjusted to highlight abnormal region on cartilage with high T1ρ values. Note that only cropped images are shown.