T1rho relaxation mapping in human osteoarthritis (OA) cartilage: comparison of T1rho with T2.

Purpose: To quantify the spin-lattice relaxation time in the rotating frame (T1rho) in various clinical grades of human osteoarthritis (OA) cartilage specimens obtained from total knee replacement surgery, and to correlate the T1rho with OA disease progression and compare it with the transverse relaxation time (T2).

Materials And Methods: Human cartilage specimens were obtained from consenting patients (N = 8) who underwent total replacement of the knee joint at the Pennsylvania Hospital, Philadelphia, PA, USA. T2- and T1rho-weighted images were obtained on a 4.

Depth-dependent proton magnetization transfer in articular cartilage.

Purpose: To measure the proton magnetization transfer ratio (MTR) maps in control and collagen-depleted bovine patellar cartilage specimens as a function of cartilage depth during mechanical compression.

Materials And Methods: One-dimensional proton projection MR images employing a spin-echo imaging sequence were obtained on a custom-built NMR spectrometer interfaced to an Oxford magnet operating at 2T. The mechanical compressions were performed with a custom-built MR-compatible pressure cell and evaluated dynamically via one-dimensional projection.

In vivo quantification of T1rho using a multislice spin-lock pulse sequence.

A multislice spin-lock (MS-SL) pulse sequence is implemented on a clinical scanner to acquire multiple images with spin-lock-generated contrast of the knee joints of six healthy human subjects. The MS-SL sequence produces images with T1rho contrast with an additional factor of intrinsic T2rho weighting, which hinders direct measurement of T1rho. A method is presented to compensate the MS-SL-generated data with regard to T2rho in an effort to accurately calculate multislice T1rho maps in a feasible experimental time.

Reduction of residual dipolar interaction in cartilage by spin-lock technique.

The influence of radiofrequency (RF) spin-lock pulse on the laminar appearance of articular cartilage in MR images was investigated. Spin-lock MRI experiments were performed on bovine cartilage plugs on a 4.7 Tesla small-bore MRI scanner, and on human knee cartilage in vivo on a 1.

3D-T1rho-relaxation mapping of articular cartilage: in vivo assessment of early degenerative changes in symptomatic osteoarthritic subjects.

Rationale And Objectives: To determine the in vivo feasibility of quantifying early degenerative changes in patellofemoral joint of symptomatic human knee using spin-lattice relaxation time in the rotating frame (T(1rho)) magnetic resonance imaging (MRI).

Materials And Methods: All the MRI experiments were performed on a 1.5 T whole-body GE Signa clinical scanner using a custom built 15-cm diameter transmit-receive quadrature birdcage radiofrequency coil.

Proteoglycan loss in human knee cartilage: quantitation with sodium MR imaging--feasibility study.

The feasibility of using sodium magnetic resonance (MR) imaging to detect proteoglycan loss in early-stage osteoarthritis is evaluated. Fixed charge density (FCD) maps were calculated from sodium MR imaging data collected in nine healthy volunteers and three individuals with symptoms of early-stage osteoarthritis by using a 4.0-T clinical MR imaging unit.

In vivo measurement of T1rho dispersion in the human brain at 1.5 tesla.

Purpose: To measure T1rho relaxation times and T1rho dispersion in the human brain in vivo.

Materials And Methods: Magnetic resonance imaging (MRI) was performed on a 1.5-T GE Signa clinical scanner using the standard GE head coil.

In vivo proton MR three-dimensional T1rho mapping of human articular cartilage: initial experience.

The purpose of this study was to demonstrate the feasibility of computing three-dimensional relaxation maps of spin-lattice relaxation time in the rotating frame (T1rho) from in vivo magnetic resonance (MR) images of the human patellofemoral joint. T1rho was measured by applying a three-dimensional gradient-echo pulse sequence in six healthy subjects and one symptomatic subject by using a 1.5-T MR imager and a 15-cm-diameter transmit-receive quadrature birdcage radiofrequency coil.

T 1 rho-relaxation mapping of human femoral-tibial cartilage in vivo.

Purpose: To demonstrate the in vivo feasibility of measuring spin-lattice relaxation time in the rotating frame (T(1rho)); and T(1rho)-dispersion in human femoral cartilage. Furthermore, we aimed to compute the baseline T(1rho)-relaxation times and spin-lock contrast (SLC) maps on healthy volunteers, and compare relaxation times and signal-to-noise ratio (SNR) with corresponding T(2)-weighted images.

Materials And Methods: All MR imaging experiments were performed on a 1.

T1rho MR imaging of the human wrist in vivo.

Rationale And Objectives: The purpose of this study was (a) to demonstrate the feasibility of computing T1rho maps of, and T1rho dispersion in, human wrist cartilage at MR imaging in vivo and (b) to compare T1rho and T2 weighting in terms of magnitude of relaxation times and signal intensity contrast.

Materials And Methods: T2 and T1rho magnetic resonance images of wrist joints in healthy volunteers (n = 5) were obtained with a spin-echo sequence and a fast spin-echo sequence pre-encoded with a spin-lock pulse cluster. A 1.

Three-dimensional T1rho-weighted MRI at 1.5 Tesla.

Purpose: To design and implement a magnetic resonance imaging (MRI) pulse sequence capable of performing three-dimensional T(1rho)-weighted MRI on a 1.5-T clinical scanner, and determine the optimal sequence parameters, both theoretically and experimentally, so that the energy deposition by the radiofrequency pulses in the sequence, measured as the specific absorption rate (SAR), does not exceed safety guidelines for imaging human subjects.

Materials And Methods: A three-pulse cluster was pre-encoded to a three-dimensional gradient-echo imaging sequence to create a three-dimensional, T(1rho)-weighted MRI pulse sequence.

Proteoglycan depletion-induced changes in transverse relaxation maps of cartilage: comparison of T2 and T1rho.

Rationale And Objectives: The authors performed this study to (a) measure changes in T2 relaxation rates, signal-to-noise ratio (SNR), and contrast with sequential depletion of proteoglycan in cartilage; (b) determine whether there is a relationship between the T2 relaxation rate and proteoglycan in cartilage; and (c) compare the T2 mapping method with the spin-lattice relaxation time in the rotating frame (T1rho) mapping method in the quantification of proteoglycan-induced changes.

Materials And Methods: T2- and T1rho-weighted magnetic resonance (MR) images were obtained in five bovine patellae. All images were obtained with a 4-T whole-body MR unit and a 10-cm-diameter transmit-receive quadrature birdcage coil tuned to 170 MHz.

Proton spin-lock ratio imaging for quantitation of glycosaminoglycans in articular cartilage.

Purpose: To quantify glycosaminoglycans (GAG) in intact bovine patellar cartilage using the proton spin-lock ratio imaging method. This approach exploits spin-lattice relaxation time in the rotating frame (T(1rho)) imaging and T(1rho) relaxivity (R(1rho)).

Materials And Methods: All the magnetic resonance imaging (MRI) experiments were performed on a 4-T whole-body GE Signa scanner (GEMS, Milwaukee, WI), and spectroscopy experiments of chondroitin sulfate (CS) phantoms were done on a 2-T custom-built spectrometer.

Quantifying sodium in the human wrist in vivo by using MR imaging.

The authors quantified sodium content in the wrist joints of six healthy volunteers with no known history of arthritis or pain. Average sodium concentrations ranged from 115 to 150 mmol/L in noncartilaginous regions and from 200 to 210 mmol/L in cartilaginous regions. The feasibility of quantifying sodium in vivo was demonstrated.