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In Vivo Proton MR Three-dimensional T1 Mapping of Human Articular Cartilage: Initial Experience¹

¹ From the MMRRCC, Department of Radiology, B1, Stellar-Chance Laboratories, University of Pennsylvania Medical Center, 422 Curie Blvd, Philadelphia, PA 19104-6100. Received August 26, 2002; revision requested October 18; revision received December 2; accepted February 3, 2003. Supported by NIH research resource grant RR02305, grants R0145242 and R0145404 from National Institutes of Arthritis and Musculoskeletal and Skin Diseases, and the Arthritis Foundation. Address correspondence to R.R.R. (e-mail: regatte@mail.mmrrcc.upenn.edu).

View larger version (21K): [in a new window]   Figure 1. Diagram of the pulse sequence used for 3D T1-weighted MR imaging. The first three pulses (two hard pulses at 90° and a long rectangular spin-locking pulse) prepared the spin-lock magnetization and stored it along the z axis. The strong crusher gradient (black rectangle) was applied before the pulse to destroy any residual magnetization in the transverse plane and prevent the formation of unwanted coherences. The stacked lines in the gradient region indicate phase-encoding gradient pulses. TSL = duration of spin-locking pulse.

View larger version (140K): [in a new window]   Figure 2. In vivo transverse T1-weighted images of the patellofemoral joint in a 30-year-old healthy human volunteer. A, T1-weighted image obtained with a 2D fast SE pulse sequence (3,000/17, TSL = 10 msec) with 1 of 440 Hz, field of view of 10 x 10 cm, section thickness of 3 mm, matrix of 256 x 128 pixels, bandwidth of 16 kHz, and one signal acquired. B, T1-weighted image obtained with a 3D GRE pulse sequence (140/2.2, TSL = 1 msec) with 1 of 440 Hz, field of view of 10 x 10 cm, section thickness of 3 mm, matrix of 256 x 128, bandwidth of 16 kHz, and one signal acquired.

View larger version (44K): [in a new window]   Figure 3. In vivo transverse T1 relaxation maps of the patellofemoral joint in a 30-year-old healthy human volunteer. A, 2D T1 map. B, Representative transverse section of 3D T1 map from a data set of 16 sections. The horizontal rectangular ROI (dotted arrow) and vertical rectangular ROI (solid arrow) were used to compute the average relaxation times and the profile plot, respectively. The bar scale at the right in A indicates variations in T1 relaxation time (0-100 msec).

View larger version (99K): [in a new window]   Figure 4. In vivo transverse T1-weighted image and corresponding map of the patellofemoral joint in a 40-year-old woman with knee pain. A, 3D T1-weighted image obtained by using a 3D GRE pulse sequence (140/2.2, TSL = 1 msec) with 1 of 440 Hz, field of view of 10 x 10 cm, section thickness of 3 mm, matrix of 256 x 128, bandwidth of 16 kHz, one signal acquired. B, Representative transverse section of 3D T1 map from a data set of 16 sections. The high signal intensity in the lateral patellar facet (arrow) of cartilage reflects an increase of approximately 45% in T1 relaxation time compared with baseline values. The bar scale at the right in B indicates variations in T1 relaxation time (0-100 msec).

View larger version (23K): [in a new window]   Figure 5. Profile plot of T1 relaxation times measured in the same healthy subject as in Figure 3; the vertical rectangular ROI (Fig 3, solid arrow) was used for profile plotting. Only 7 pixels were obtained within the patellar cartilage. Each point on the profile plot is an average measurement for an area of 4 x 4 pixels. The T1 relaxation times in superficial regions, at or near the articular surface, are higher than those in medial and subchondral regions.