Knee in early juvenile rheumatoid arthritis: MR imaging findings.

PURPOSE: To determine the magnetic resonance (MR) imaging findings in the knee in early juvenile rheumatoid arthritis. MATERIALS AND METHODS: MR imaging (1.5 T) was performed in the more symptomatic knee in 30 children with juvenile rheumatoid arthritis with a symptom duration 1 year or less. Conventional, fast spin-echo, three-dimensional gradient-echo, and gadolinium-enhanced T1-weighted images were assessed. Two radiologists independently read the images, and a third resolved disagreements. These images were compared with knee radiographs in 27 children. RESULTS: Mean maximal synovial thickness was 4.8 mm +/- 2.4 (SD). Mean synovial volume was 15.4 mL +/- 10.8. Suprapatellar joint effusions were seen in 26 (87%) of 30 knees, meniscal hypoplasia in 11 (37%) of 30 knees, and abnormal epiphyseal marrow in eight (27%) of 30 knees. Three knees had articular cartilage contour irregularity, fissures, and/or thinning. One knee had a bone erosion. Knee radiographs showed suprapatellar fullness in 78% of the knees, joint space narrowing in one knee, and no bone abnormalities. CONCLUSION: Synovial hypertrophy and joint effusions are the most frequent MR imaging findings of knees in early juvenile rheumatoid arthritis. Early in the disease, radiographically occult cartilage and bone erosions are uncommonly seen at MR imaging. The potential relationship of synovitis to cartilage abnormalities deserves further study.

Minimizing radiation dose for pediatric body applications of single-detector helical CT: strategies at a large Children's Hospital.

Adjustments of the standard helical CT protocols for adults can result in reduced radiation dose when imaging children. It is the radiologist's responsibility to critically evaluate the CT techniques used at their institution. Adjustments to CT protocols should be made to choose the appropriate mA and pitch when imaging children.

Magnetic resonance imaging of the dysplastic renal moiety and ectopic ureter.

PURPOSE: We determined the role of magnetic resonance imaging (MRI) in symptomatic children with clinically suspected and radiologically occult dysplastic renal moieties and ectopic ureters. MATERIALS AND METHODS: We reviewed clinical, imaging, cystoscopic, surgical and histological findings in 6 symptomatic children 1 to 15 years old with dysplastic renal moieties. RESULTS: After multiple conventional imaging studies failed to delineate urinary tract anatomy MRI provided detailed multiplanar images of dysplastic renal moieties that were diagnostic and predictive of subsequent intraoperative findings. Dysplastic upper pole moieties identified in 4 children were associated with ectopic ureters inserting into the vagina, prostatic urethra, bladder neck and bladder neck ureterocele in each. A solitary kidney with contralateral blind-ending ectopic ureters inserted into the bladder base in 2 cases. Pelvic cystic structures visualized by ultrasound in 3 patients were tortuous distal ureters on MRI. MRI specifically identified ureteral insertion sites that were not evident in 3 of the 5 patients who underwent cystoscopy. CONCLUSIONS: MRI may facilitate diagnosis, guide cystoscopy and aid in preoperative planning in children with poorly functioning renal moieties and ectopic ureters.

Cyclic cystography: diagnostic yield in selected pediatric populations.

PURPOSE: To test the hypothesis that the diagnostic yield of cyclic cystography is related to the prevalence of vesicoureteral reflux (VUR) in the population being evaluated. MATERIALS AND METHODS: Two groups of children were examined prospectively: 124 with severe urinary tract infection, defined as patient hospitalization or a maximum temperature greater than 39.5 degrees C, and 135 with previously diagnosed VUR. Nuclear cystography was performed in 249 patients, and fluoroscopic cystography was performed in 10. If VUR was not seen during the first cycle of bladder filling and voiding, a second cycle was performed. RESULTS: VUR was present during cycle 1 in 40 (32%) of 124 patients with severe urinary tract infection and 90 (67%) of 135 children in the VUR follow-up group (P < .001). VUR was demonstrated during cycle 2 in seven (9%) of 76 of the severe urinary tract infection group and eight (24%) of 34 of the VUR follow-up group (P = .045). Of 15 patients with VUR during cycle 2, two had grade III VUR and 13 had grade I or II VUR. CONCLUSION: The second cycle of cyclic cystography has a higher diagnostic yield in patients undergoing VUR follow-up than in patients with severe urinary tract infection. The decision to perform a second cycle of bladder filling and voiding should take into account the pretest probability of VUR in the child being examined.

MR imaging of pediatric musculoskeletal inflammatory and infectious disorders.

Inflammatory and infectious disorders of the skeletally immature extraspinal musculoskeletal system affect the bones, contiguous soft tissues, muscles, and joints. MR imaging of osteomyelitis, soft tissue infection, inflammatory muscle disease, and acute and chronic joint disease are discussed in the context of underlying pathophysiology. Discussion includes imaging optimization, contribution of MR imaging to overall patient management, and differential diagnostic considerations for the pediatric patient.

Unilateral vesicoureteral reflux: association with protected renal function in patients with posterior urethral valves.

OBJECTIVE: The prognosis in patients with posterior urethral valves (PUV) is related to the degree of renal insufficiency. Urinary ascites or urinoma, congenital bladder diverticula, or severe unilateral vesicoureteral reflux has been associated with protected renal function. We present clinical and imaging findings in eight patients with PUV and unilateral reflux who have preserved renal function. Initial and follow-up sonography, voiding cystourethrography, and nuclear imaging were reviewed and compared with long-term serum creatinine levels. CONCLUSION: All eight patients had normal renal function on long-term follow-up, suggesting that unilateral reflux, which occurs in as many as 35% of boys with PUV, is associated with protected renal function. Although early nephrectomy of the refluxing unit has been advocated for patients with PUV and unilateral reflux into a dysplastic kidney (the vesicoureteral reflux and renal dysplasia syndrome), we found that significant renal function may be present in the refluxing kidney and that function may even increase with time. Most of these patients did well without nephrectomy. Therefore, a sufficient interval should elapse before nephrectomy is considered in these patients.

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.

Carpal tunnel syndrome: morphologic changes after release of the transverse carpal ligament.

We describe the morphologic changes that follow division of the transverse carpal ligament in patients with carpal tunnel syndrome. Fifteen hands in 12 patients with carpal tunnel syndrome were studied with magnetic resonance imaging before operation and for 6 weeks after operation. Eight hands were studied at 8 months after operation. Carpal arch width, anterior displacement of the carpal canal contents, and carpal canal volume were measured by use of multiplanar reformation and three-dimensional reconstruction of magnetic resonance images. There was a 24.2 +/- 11.6% increase in carpal canal volume 6 weeks after carpal tunnel release (p less than 0.001). This difference persisted at 8-month follow-up. There was an anterior displacement of carpal canal contents 3.5 +/- 1.9 mm from its original position 6 weeks after operation (p less than 0.001). This palmar displacement persisted at the 8-month follow-up. There was no statistically significant increase in carpal arch width 8 months after carpal tunnel release. We believe that division of the transverse carpal ligament restores median nerve function by increasing the volume of the carpal canal. This volumetric increase results from an anterior displacement of the newly formed transverse carpal ligament and not from a widening of the bony carpal arch.

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.

The high signal intensity meniscus of the knee. Magnetic resonance evaluation and in vivo correlation.

This study describes the different appearances of meniscal abnormalities on magnetic resonance (MR) images and correlates macroscopic and histologic findings. Twenty-three of 40 cadaveric menisci with MR signal abnormalities were examined macroscopically; five of the 23 were studied histologically. In addition, MR studies of seven patients (14 menisci) were examined and findings were correlated arthroscopically. Histologic analysis was performed on two of these menisci. The two major findings on MR images were: (1) abnormal, high, centrally located signal intensity within the meniscus and (2) disruption of the peripheral meniscal contour. Macroscopically evident meniscal degeneration correlated well with findings on MR images in all cases. Histologic abnormalities included microcyst formation and separation of collagen bundles. Four menisci with intact outer contour lines on MR images had macroscopically identifiable tears. In addition, two meniscal tears were appreciated only after intra-articular injection of gadolinium-DTPA. We conclude that MR imaging is superior to macroscopic examination as performed by arthroscopy or arthrotomy for the detection of degenerative meniscal lesions. The technique also accurately identifies meniscal tears, a capability that might be enhanced by prior intra-articular injection of MR contrast agents.

Carpal tunnel volume determination by magnetic resonance imaging three-dimensional reconstruction.

Three-dimensional computer reconstruction of magnetic resonance images (MRI) of ten cadaveric specimens was used to determine carpal tunnel volume and carpal arch width. Magnetic resonance images-acquired data were compared with direct measurement of cadaveric carpal canal volume by means of a silicone-injection technique. Mean MRI three-dimensional reconstruction volume was 5.84 ml +/- 1.24 ml. Mean silicone-mold volume was 4.73 +/- 1.01 ml. A correction factor of 0.8161 was used to accurately calculate carpal tunnel volume from MRI-acquired data. There was no significant difference between calculated carpal tunnel volumes and silicone-mold volumes (p = 0.623), and there was a linear relationship between MRI-acquired volumes and silicone-mold volumes (correlation coefficient r = 0.97). Differences in MRI-volume determinations between observers were not significant (0.25 greater than or equal to p greater than 0.1). MRI three-dimensional reconstruction, a valid and reproducible technique for measuring carpal tunnel volume and dimensions, has considerable research potential for the evaluation of the relationship between the carpal canal and its contents before and after carpal tunnel release.

Localization grid for MR-guided biopsy.

A localization grid for use with magnetic resonance (MR)-guided biopsies was designed and evaluated. First, the signal intensities of various concentrations of Gd-DTPA in polyethylene tubes of different sizes and at various pulse sequences were evaluated. The optimal signal intensity on all pulse sequences was obtained with a concentration of 500 microM. A grid was then made with 5-mm-diameter polyethylene tubes filled with 500-microM Gd-DTPA. The grid has provided excellent localization for MR-guided biopsy and fluid aspiration.

Articular cartilage defects: detectability in cadaver knees with MR.

The capability of 1.5-T MR imaging to detect focal defects in articular cartilage was investigated with cadaveric knees with and without intraarticular injection of saline and gadolinium-DTPA (Gd-DTPA). Full-thickness cartilage lesions ranging in diameter from 1 to 5 mm were surgically created in the femoral articular surfaces. Images were acquired with a variety of pulse techniques, slice thicknesses, and interslice gaps as well as one or two signal excitations. Potential intraarticular contrast agents (saline and Gd-DTPA) were tested, and their signal behaviors compared with that of hyaline cartilage. All cartilage defects were occult on T1-weighted and balanced images without Gd-DTPA. The smallest defect identified by using intraarticular saline was 3 mm in diameter and was apparent only on T2-weighted images. Intraarticular Gd-DTPA afforded detection of defects as small as 2 mm, even with short imaging times. Signal-intensity differences between saline and articular cartilage were minimal on T1-weighted images and increased on T2-weighted images; intensity differences were high between Gd-DTPA and articular cartilage on all imaging sequences. These results indicate that intraarticular fluid and appropriate selection of imaging sequences are necessary for delineation of focal defects in articular cartilage. They also show that Gd-DTPA is the optimal contrast agent for this purpose.

Perfluorochemicals as gastrointestinal contrast agents for MR imaging: preliminary studies in rats and humans.

The ability to distinguish bowel from other intraabdominal structures is essential for the accurate diagnosis of intraabdominal disease with MR. Because perfluorochemicals have no protons, they cause no MR signal. Since they are immiscible with water, they create a signal void in bowel independent of bowel contents and thus are suitable as oral contrast agents. Furthermore, they are tasteless and odorless and have no side effects. We evaluated the use of perfluorochemicals by performing MR scans of the abdomen in rats after the oral administration of unemulsified perfluorohexylbromide or perfluoroctylbromide. Since the latter is approved as an investigational drug for oral use in humans, two volunteers were also studied. Both compounds created signal void in the bowel of both rats and human subjects allowing identification of the gastrointestinal tract. The results suggest that these compounds have potential as oral contrast agents for MR imaging.