Shoulder MR arthrography: In vitro determination of optimal gadolinium dilution as a function of field strength

PURPOSE: To find the optimal contrast agent dilution to maximize signal intensity (SI), signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in shoulder MR arthrography using MR systems operating at different magnetic field strengths. MATERIALS AND METHODS: Autoptic human glenohumeral ligaments were inserted in eight egg-shaped 20-mL phantoms filled with saline and gadolinium diethylenetriaminepentaacetic acid bismethylamide (Gd-DTPA-BMA) in different dilutions of 0.5, 1, 2, 2.5, 5, 12.5, 50 mmol/liter, to simulate the shoulder articular capsule. These phantoms were inserted inside two plastic 240-mL phantoms filled with water. MRI was performed on 0.2-, 0.5-, 1.0-, 1.5-, and 3.0-T MR systems using a three-dimensional gradient echo (GRE)-T1-weighted pulse sequence. SI, SNR, and CNR were determined. RESULTS: Peak SI and SNR were found at 5 mmol/liter, with the exception of the 0.2-T scanner, where the maximum was at 2 mmol/liter. Peak CNR was observed at 1 mmol/liter for the 3-T scanner, at 2 mmol/liter for the 0.2- and 0.5-T scanners, and at 5 mmol/liter for the remaining scanners. CONCLUSION: The optimal SI and SNR are provided by 5 mmol/liter contrast agent dilution. Peak CNR was found in a range between 1 and 5 mmol/liter dilutions, depending on the strength of the magnetic field.