MR arthrography of the lower extremity

MRI has been shown to be very useful in the diagnosis of several joint disorders. MR arthrography, through its ability accurately to delineate intra-articular structures, further expands the clinical use of MRI. There are, however, some features of MR arthrography that have limited clinical use: the conversion of a noninvasive procedure into an invasive procedure, and the increased cost and time required to perform MR arthrography compared with conventional MRI. Despite these limitations, the use of MR arthrography is increasing secondary to its improved accuracy compared with conventional MRI for the diagnosis of several intra-articular disorders. MR arthrography is performed by injecting a gadolinium-diethylentriamine pentaacetic acid (GdDTPA) mixture into the joint. A Gd-DTPA mixture consisting of 0.2 mL of a standard Gd-DTPA solution (469.01 mg/mL, Magnevist, Schering AG, Germany) mixed with 50 mL of saline (2 mmol/L Gd-DTPA solution) has been observed to give an optimal contrast between the contrast medium and the intra-articular structures or abnormalities [1]. No side effects have been reported to date that are attributable to intraarticular Gd-DTPA. Imaging should be performed shortly after the intra-articular injection of contrast medium, to prevent absorption of contrast solution and guarantee the desired capsular distention, although imaging delays of up to 2 hours are tolerated in the leg joints [2]. Gd-DTPA and iodinated contrast material can be mixed before MRI without any release of free gadolinium and is safe for confirming the intra-articular placement of contrast material [3].