Magnetic resonance imaging in juvenile rheumatoid arthritis

OBJECTIVES

This study was undertaken to examine the role of magnetic resonance imaging (MRI) in the management of patients with juvenile rheumatoid arthritis (JRA).

METHODS

A Medline search was performed to identify all publications pertaining to MRI in JRA. Further searches and identification of articles from bibliographies identified articles pertaining to plain radiograph imaging in JRA and MRI in adult rheumatoid arthritis.

RESULTS

Studies in both children and adults have shown superiority of MRI to plain radiography in detecting synovial hypertrophy and articular cartilage abnormalities. Several studies in adults have shown a good correlation of MR images with gross anatomic as well as histological findings at arthroscopy. Biochemical changes that occur before structural changes within the joint may even be detectable with magnetic resonance spectroscopy.

CONCLUSIONS

MRI holds promise for the assessment of disease progression in JRA and may be useful in serial evaluation, as in clinical trials.

Wilms tumor and nephroblastomatosis: imaging characteristics at gadolinium-enhanced MR imaging

Twelve children with Wilms tumors were prospectively evaluated with 1.5-T magnetic resonance (MR) imaging. Spin-echo images were obtained before and after administration of gadopentetate dimeglumine. Nine of the 12 children had histologically proved nephroblastomatosis or nephrogenic rests involving a total of 14 kidneys. MR imaging depicted involvement in eight of these kidneys, including five of five kidneys with lesions contralateral to the primary Wilms tumor. Overall sensitivity of detection of nephrogenic rests was 43% on nonenhanced images and 58% when gadolinium-enhanced images were added. Nephrogenic rests admixed with Wilms tumors less than 4 mm in diameter were not depicted at MR imaging. On gadolinium-enhanced T1-weighted images, Wilms tumors and hyperplastic were hypointense to normal renal tissue. On T2-weighted images, Wilms tumors and hyperplastic nephrogenic rests were iso- or slightly hyperintense to renal cortex, while sclerotic nephrogenic rests were hypointense to renal cortex. On all images, including gadolinium-enhanced T1-weighted images, the signal intensity of Wilms tumors was inhomogeneous, while the signal intensity of nephrogenic rests was homogeneous.

The effect of intra-articular gadolinium-DTPA on synovial membrane and cartilage

This investigation evaluated the potential effect of gadolinium (Gd)-DTPA-dimeglumine on synovial membrane and joint cartilage, using macroscopic, microscopic, and x-ray fluorescent spectroscopic techniques. Thirteen New Zealand white rabbits (26 knees) were used in this study, ten receiving 500 micromolar injections of Gd-DTPA-dimeglumine in their right knees; the remainder of the knees served as controls. One injected knee had minimal joint effusion and one had mild hyperemia. Microscopically four knees exhibited mild focal hyperplasia of the synovium, another three minimal focal mononuclear cell infiltration. X-ray fluorescent spectroscopy demonstrated no evidence of Gd-DTPA-dimeglumine in the synovium or articular cartilage. Neither macroscopic nor microscopic evaluation detected any Gd-DTPA-dimeglumine related effects. Gd-DTPA-dimeglumine was found to be safe for intra-articular injection in this animal model.

Detection of testicular torsion by magnetic resonance imaging in a rat model

Testicular torsion is one of the most common pediatric urological emergencies. Incorrect or delayed diagnosis contributes significantly to morbidity. We previously have shown that magnetic resonance displays scrotal contents with great detail using hydrogen concentration weighted and T2 weighted images. Sprague-Dawley rats underwent either unilateral 720-degree testicular torsion or a sham procedure. Magnetic resonance images were obtained at intervals with a 3 or 5-inch surface coil. Scans after surgical torsion showed a characteristic spiral distortion of the fascial planes of the spermatic cord, not seen in the sham animals, as well as a decrease in testicular size with prolonged torsion.

A wire-sheath system for MR-guided biopsy and drainage: laboratory studies and experience in 10 patients

On the basis of laboratory experiments, we devised a wire-sheath system for MR-guided biopsy and drainage and then evaluated that system in 10 patients. The localizing system consisted of a 20-gauge plastic sheath into which a stainless-steel alloy wire had been inserted. In laboratory studies, we compared this wire-sheath assembly with other materials to determine its optimal visualization on MR images. We then used the same wire-sheath system to perform 16 procedures (in 10 patients), including six biopsies, five diagnostic fluid aspirations, and five catheter drainages of infected and noninfected fluid collections. The laboratory results showed that the wire-sheath assembly cast a 7-mm artifact, was visualized well on all pulse sequences, and was safe within the magnet (minimal attraction). The assembly was visualized well in each patient and provided adequate localization. MR-guided biopsy and drainage can be performed with high-resolution detail by using this wire-sheath system. Potential uses of this system include (1) treatment of lesions that can be seen on MR images only (or that can be seen to significantly better advantage on MR images than on sonograms or CT scans), and (2) treatment of patients in whom avoidance of the radiation delivered by CT is imperative.

Inflatable surface coil for MR imaging of the prostate

An inflatable surface coil for transrectal magnetic resonance imaging of the prostate was designed. The coil was tested during imaging of an insulated saline phantom and of the prostates of four patients. Phantom images were comparable to those obtained with commercial coils of similar size. High spatial resolution and excellent contrast were noted in coronal images of the prostates. Use of this coil could substantially improve studies of the prostate and cervix.

Magnetic resonance imaging of the cryptorchid testis

Magnetic resonance imaging was used to evaluate seven patients with undescended testes. In six patients the presence or absence of testicular tissue was predicted correctly prior to surgery. Spermatic cord structures, if present, were accurately visualized in all patients.