Contrast-enhanced MR cholangiography: comparison of Gd-EOB-DTPA and Mn-DPDP in healthy volunteers.

OBJECTIVE: The purpose of this study was to compare the biliary enhancement dynamics of gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic-acid (Gd-EOB-DTPA) and mangafodipir trisodium (Mn-DPDP) for contrast-enhanced MR cholangiography (MRC) in healthy subjects. METHODS: 15 healthy volunteers underwent MRI at 1.5 T with volumetric interpolated breath-hold examination sequence. Each volunteer was scanned once for each contrast agent. The signal-to-noise ratio (SNR) of the liver parenchyma and common hepatic duct (CHD) and the contrast-to-noise ratio (CNR) of CHD to liver parenchyma were evaluated and compared before and at several time points (5, 15, 30, 45, 60, 90, and 120 min) after injection of each agent. RESULTS: SNR was significantly higher for Gd-EOB-DTPA than for Mn-DPDP in liver parenchyma after 5 min and in CHD after 15 min (p<0.05). CNR of CHD to liver parenchyma using Gd-EOB-DTPA showed an initial decrease at 5 min post-injection followed by a steep increase to a peak at 15 min post-injection. CNR using Mn-DPDP showed a steady increase to a peak at 15 min post-injection without an initial decrease. At 15 min, the value of CNR was significantly higher for Gd-EOB-DTPA than for Mn-DPDP (p<0.05). CONCLUSION: For both contrast agents, CNR reached a peak at 15 min after contrast injection. At this time point, CNR of Gd-EOB-DTPA was significantly higher than that of Mn-DPDP. Therefore, Gd-EOB-DTPA may provide better contrast-enhanced MRC than Mn-DPDP at 15 min after contrast administration.

[Distribution of MICA microsatellite in 13 population groups of China].

The genetic data of MICA microsatellite were obtained by genotyping 577 samples in 13 population groups of China, which are Han-YN, Han-GD, Han-SD, Bai, Dai, Lahu, Li, Naxi, Sala, She, Tu, Wa and Zang-YN, with genescan. Five alleles have been observed in the population groups, which are A4, A5, A5.1, A6 and A9. A5 allele is the most frequent in all population groups except Lahu and Li, while the most frequent allele for Lahu and Li is A5. 1 and A4 respectively. The second most frequent allele is the A5.1 in Han-YN, Han-SD, Dai, Naxi, Sala, She, and Wa. The lest frequent allele for Han-YN, Han-GD, Lahu, Naxi, She, Wa is the A6 which is not observed in Li. A4 allele is the lest frequent in Han-SD, Bai, Dai, Sala, Tu, Zang-YN. The results show that the distribution of MICA microsatellite is different in these population groups, and the polymorphism information contents (PIC) of this microsatellite is high. It is a potential useful marker in the study of human origin and migration, personal identification, gene mapping and location, and disease diagnosis.

Classification of metaphyseal change with magnetic resonance imaging in Legg-Calvé-Perthes disease.

Seventy-eight patients (85 affected hips and 71 unaffected hips) with Legg-Calvé-Perthes disease were included in this study to evaluate the metaphyseal change in radiographs and magnetic resonance imaging (MRI) and to define the type of the metaphyseal cyst according to presence or absence of the epiphyseal involvement. The content of the metaphyseal cyst was evaluated by using T1,T2, proton, and gadolinium-enhanced T1-weighted MRI scans. Among 85 hips, there were no changes in 32 hips, marrow edema in 13 hips, false cyst with epiphyseal involvement in 28 hips, and true cyst without epiphyseal involvement in 12 hips. Granulation tissue was found in the false cysts and water-rich fibrotic tissue was found in the true cysts based on the MRI scans. The metaphyseal change in MRI scans was shown in 71% of groups 3 and 4 and in 35% of groups 1 and 2 according to the Catterall classification, and 52% of group A, 56% of group B, and 86% of group C according to the Herring classification. Of the 30 hips at the avascular stage, 33% showed metaphyseal cyst in MRI scans. Of the 53 hips at the fragmentation stage, 60% showed the metaphyseal cyst.

Bone marrow edema and associated pain in early stage osteonecrosis of the femoral head: prospective study with serial MR images.

PURPOSE: To determine whether the marrow edema around focal osteonecrosis on magnetic resonance (MR) images is associated with clinical symptoms. MATERIALS AND METHODS: Thirty-three patients with 37 hips showing early stage osteonecrosis of the femoral head were followed up at 3-month intervals with clinical evaluation, conventional radiography, and serial MR imaging. RESULTS: Seven (50%) of 14 symptomatic hips showed marrow edema around focal osteonecrosis on initial MR images, whereas only one (4%) of 23 asymptomatic hips showed edema (P < .01). Six (86%) of seven hips that were moderately to severely painful were associated with surrounding marrow edema. All eight hips showing osteonecrosis with marrow edema at the initial MR examination had joint effusion and exhibited intense radionuclide uptake in the proximal femur, which corresponded to the extent of edema on MR images. In all eight hips, the marrow edema resolved on follow-up MR images, and the pain subsided with the resolution of edema. CONCLUSION: The results of this study suggest that the combination of marrow edema of the proximal femur and focal osteonecrosis of the femoral head are strongly associated with hip pain in early stage osteonecrosis, even prior to collapse. Pain improvement usually parallels the resolution of edema.

Variations in meniscofemoral ligaments at anatomical study and MR imaging.

PURPOSE: To demonstrate variations in the meniscofemoral ligaments (ligaments of Wrisberg and Humphrey) at anatomical study and magnetic resonance (MR) imaging. DESIGN: Twenty-eight cadaveric knees were partially dissected for the examination of the meniscofemoral ligaments. One hundred knee MR examinations were reviewed by two experienced musculoskeletal radiologists. Proximal variations in the meniscofemoral ligaments at MR imaging were classified into three types according to the attachment site: type I, medial femoral condyle; type II, proximal half of the posterior cruciate ligament (PCL); type III, distal half of the PCL. Distal variations were classified into vertical or oblique types according to the orientation of the intermediate signal at the interface of the ligament and lateral meniscus. RESULTS: At anatomical study, six cases showed variations in the proximal insertion site of the meniscofemoral ligaments. At MR imaging 93 cases had one or more meniscofemoral ligaments, giving a total of 107 ligaments: 90 ligaments of Wrisberg and 17 ligaments of Humphrey. Forty-one ligaments of Wrisberg were type I, 28 type II, 19 type III, and with two indeterminate type, while 6 ligaments of Humphrey were type I and the remaining 11 were indeterminate. Seven cases showed no meniscofemoral ligament. Of the 107 meniscofemoral ligaments, the distal insertion orientation was of vertical type in 10 ligaments, oblique type in 70 and unidentified in 27. CONCLUSION: An understanding of the high incidence of meniscofemoral ligament variations may help in the interpretation of knee MR studies.

Comparison of MRI with subchondral fracture in the evaluation of extent of epiphyseal necrosis in the early stage of Legg-Calvé-Perthes disease.

We reviewed 20 patients in the early stage of Legg-Calvé-Perthes disease who showed a subchondral fracture line in radiographs. All 20 patients underwent magnetic resonance imaging (MRI) within 2 months after the first symptoms. Follow-up MRI after treatment was performed in 10 patients. The subchondral fracture line in radiographs and serial T1-weighted image was used to measure the extent of the epiphyseal necrosis volumetrically. These extents in the early stage were compared with those in the late stage for determination of prognostic significance. The intensities of coronal MRIs under the subchondral fracture were not homogeneous. The uninvolved epiphysis also showed nonhomogeneous intensities because the posterior column revealed higher intensity compared with the anterior column. The extent of the subchondral fracture line is more accurate in predicting the amount of eventual necrosis than is the extent of necrosis in MRI, which does not have a consistent correlation.

Minimizing artifacts caused by metallic implants at MR imaging: experimental and clinical studies.

OBJECTIVE: The purpose of this study was to investigate the effect of metallic implant positioning on MR imaging artifacts, to determine the optimal imaging conditions for minimizing artifacts, and to show the usefulness of artifact-minimizing methods in imaging of the knee. MATERIALS AND METHODS: Using MR images of experimental phantoms (titanium alloy and stainless steel screws), we compared the magnitude of metal-induced artifacts for various pulse sequences, different imaging parameters for the fast spin-echo sequence, and different imaging parameters for several incremental angles between the long axis of the screw and the direction of the main magnetic field. In clinical MR imaging of knees with metallic implants (n = 19), we assessed geometric distortion of anatomic structures to compare the influence of different pulse sequences (n = 19), frequency-encoding directions (n = 7), and knee positions (n = 15). RESULTS: Titanium alloy screws consistently produced smaller artifacts than did stainless steel screws. In experimental MR studies, artifacts were reduced with fast spin-echo sequences, with a screw orientation as closely parallel to the main magnetic field as possible, and, particularly, with smaller voxels that correlated positively with artifact size (R2 = .88, p < .01). In clinical MR studies, fast spin-echo MR imaging obscured articular structures less than did spin-echo imaging (8/19 patients). In particular, the anterior-posterior frequency-encoding direction (3/7 patients) and the flexion position of the knee (5/15 patients) were effective in reducing artifacts. CONCLUSION: MR artifacts can be minimized by optimally positioning in the magnet subjects with metallic implants and by choosing fast spin-echo sequences with an anterior-posterior frequency-encoding direction and the smallest voxel size.

Relationship between lateral subluxation and widening of medial joint space in Legg-Calvé-Perthes disease.

Fifty-five patients (61 affected hips and 49 unaffected hips) with Perthes disease were reviewed to evaluate the relationship between widening of medial joint space and lateral subluxation of the femoral head in radiographs. The components of the medial joint space were evaluated by using T1, T2, proton, and Gd-enhanced T1WI magnetic resonance images (MRI). The widened medial joint space in radiographs was filled with overgrown cartilage at the initial stage (27 hips) in MRI, with both overgrown cartilage and widened true medial joint space at the fragmentation stage (23 hips) and widened true medial joint space at the healing stage (11 hips). Between affected hips and unaffected hips, the mean difference of medial joint space in radiographs between hips at the initial stage and at the fragmentation stage was 2 and 4.5 mm, respectively; the mean difference in percentage of lack of coverage of the femoral head between hips at the initial stage and at the fragmentation stage was 3 and 15%, respectively. During the healing stage, widening of the medial joint space decreased or normalized because of ossification of overgrown cartilage despite the existence of lateral subluxation because of coxa magna. We concluded that widening of the medial joint space may be used as an index of lateral subluxation at only the fragmentation stage in Perthes disease.

Venous malformations: sclerotherapy with a mixture of ethanol and lipiodol.

PURPOSE: To evaluate the usefulness of a mixture of absolute ethanol and lipiodol in the management of venous malformations. METHODS: Percutaneous sclerotherapy was performed with a mixture of absolute ethanol and lipiodol (9:1) in 17 patients with venous malformations, once in 12 patients, twice in 5. The therapeutic efficacy was evaluated by pain reduction. Conventional radiographs (n = 15) and posttreatment magnetic resonance imaging (n = 5) were obtained for the follow-up evaluation. RESULTS: Sclerotherapy was successful in all but two patients. The therapeutic effect was excellent in two patients, good in seven, fair in five, and poor in one. Radiopacity of lipiodol was beneficial for monitoring the procedure rather than for follow-up evaluations. Areas with low signal-intensity strands were increased on T2-weighted images obtained after the sclerotherapy. CONCLUSION: Sclerotherapy with a mixture of ethanol and lipiodol is effective in treating venous malformations.

Contrast enhancement pattern and frequency of previously unoperated lumbar discs on MRI.

Enhancement frequency and patterns (linear intradiscal, nodular intradiscal, and peridiscal) of the 210 previously unoperated lumbar discs were evaluated using contrast-enhanced lumbar MRI. They also were compared with morphologic abnormalities (normal, bulging, protruded, and extruded) and signal alteration (high signal on T2-weighted images) of the disc. Image interpretation was decided by the consensus of two musculoskeletal radiologists. Enhancement was observed in 69 (32.6%) discs. The enhancement patterns were either intradiscal, linear of (79.7%) or nodular (10.2%), peridiscal (7.2%), or combined (2.9%). Thirty-five (77.8%) of the 45 herniated discs, 35 (77.8%) were enhanced, whereas 34 (20.6%) of 165 normal-appearing disc were enhanced. Enhancement was observed more frequently in discs with high signal intensity zones (P < 0.05). In the six patients with enhanced discs, surgery revealed granulation tissue in three extruded discs, two protruded discs, and one bulging disc. The authors believe that contrast enhancements are frequent in herniated discs and are not infrequent in normal-appearing discs. The understanding of various enhancement patterns may help in the interpretation of lumbar spine MRI.