Differentiation of Hyperplastic from Metastatic Lymph Nodes Using a Lymph Node Specific MR Contrast Agent Gadofluorine M

PURPOSE: We wanted to evaluate the value of a lymph node specific MR contrast agent, Gadofluorine M, for the differentiation of hyperplastic and metastatic lymph nodes. MATERIALS AND METHODS: This study included thirty-one rabbits. In ten rabbits, an injection of egg yolk or feces of rat into the calf muscles induced hyperplasia of the lymph node. In sixteen rabbits, metastasis of the lymph node was induced by implantation of VX2 tumor. Five rabbits were normal control models. We acquired the T1-, T2-weighted and SPGR coronal imaging before enhancement with 1.5 T MR. After injection of Gadofluorine M (5 micromol/mL, total amount: 4 mL) interstitially into the interdigital skin fold of the hind limb, we acquired the SPGR coronal imaging at 15, 30, 60 and 90 minutes. We calculated the signal-to-noise ratios on the sequential images, and we recorded the number, size and location of the popliteal and iliac lymph nodes. Three readers assessed the state of the lymph nodes according to the pattern of enhancement: they were deemed hyperplastic nodes when totally enhanced and as metastatic nodes when there was no or partial enhancement. We also compared the imaging patterns with the histopathological results. RESULTS: Among the 26 hyperplasia- or metastasis-induced rabbits, two rabbits were excluded because of failure to be enhanced. Histopathologic evaluation of the 24 rabbits detected one hundred seventeen lymph nodes: forty-six lymph nodes in nine hyperplasia-induced rabbits and seventy-one (metastasis in twenty-eight) lymph nodes in fifteen metastasis-induced rabbits. Out of one hundred two lymph nodes that were larger than 5 mm in size, MR enabled us to detect one hundred one lymph nodes (99.1%). The means of sensitivity, specificity, and the positive and negative predictive values for the diagnosis of lymph node metastasis by three readers were 97.6% (82/84), 98.2% (215/219), 95.3% (82/86), and 99.1% (215/217), respectively (p < 0.05). CONCLUSION: Interstitial MR lymphography using Gadofluorine M showed excellent results in differentiating hyperplastic from metastatic lymph nodes.

Magnetic Resonance Appearance of Normal Popliteal Lymph Nodes: Location and Relationship of Number, Fatty change, and Size of the Lymph nodes with Aging

PURPOSE: To investigate the location of popliteal lymph nodes and the relationship between patient age and their number, size, and the occurrence of fatty chang. MATERIALS AND METHODS: We retrospectively evaluated the magnetic resonance (MR) images of 222 patients [age range, 8-79 (mean, 47.1) years]who had undergone MRI of the knee after its internal derangement. Images were obtained in the axial, coronal, and sagittal planes. A lymph node was defined as 'observed' if it was visible in at least two planes, such as axial and sagittal or axial and coronal. With regard to location, nodes were classified as anteromedial, anterolateral, posteromedial, or posterolateral, depending upon their relationship with the popliteal vein. To determine their size, the smallest diameter was measured. RESULTS: Popliteal lymph nodes were present in 116 of 222 examinations (52.3%), and their total number was 158 (mean, 1.36). Patients'age correlated negatively with their presence (R square=0.826), and positively with the occurrence of fatty change (R square=0.840). Sixty- five of 158 lymph nodes (41.1%) were located anteromedially, 58 (36.7%) posterolaterally, 27 (17.1%) anterolaterally, and eight (5.1%) posteromedially. Their distance from the most distal femoral articular surface was 4.6+/-1.4 cm (mean +/-SD), and their mean diameter was 4.96+/-2.4 mm (mean +/-SD; range, 4-8 mm). CONCLUSION: The number of popliteal lymph nodes decreased with age, while the incidence of fatty change increased. Nodes were most frequently anteromedial or posterilateral to the popliteal vein.

Magnetization Transfer Ratio in Head and Neck Lymphadenopathy

PUYPOSE: The purpose of this study was to determine whether the magnetization transfer ratio(MTR) differs between malignant and benign cervical lymphadenopathy. MATERIALS AND METHODS: Magnetization transfer ratios were obtained from 104 lymph nodes of 43 patients. Fifty-five nodes were malignant and 49 were benign. Biopsy or cervical lymph node dissection was performed in 83 nodes, while the remaining 21 were diagnosed clinically or by follow-up imaging studies. Among the 55 malignant nodes, squamous cell carcinomas accounted for 29 cases, lymphomas for 15, undifferentiated carcinomas for four, acute myelogenous leukemia for four, and melanomas for three. The 49 benign nodes comprised 21 cases of reactive hyperplasia, 12 of Kikuchi's disease, nine of acute lymphadenitis, and seven of tuberculous lymphadenitis. All scans were performed using a 1.5T Magnetom Vision(Siemens, Erlangen, Germany) with phased-array or Helmholtz-type neck coil. Scanning was performed with and without magnetization transfer pulse(MT pulse : 11.2 T, 250 Hz band-width, off-set 2.0 KHz) using FLASH 2D sequencing. The region of interest(ROI) for signal intensity(SI) measurements was sampled at the same nodes by keeping the position, shape and size of the ROI constant for the scans before and after the MT pulse was applied. SI measurements were repeated more than three times in each node and the mean value was used to calculate MTR. In this study, however, corrected MTRs(CoMTRs) were used for correction of the effect of background noise produced by magnetic field inhomogeneity. RESULTS: Mean CoMTRs of malignant and benign nodes were 0.33(SD: +/- 0.04) and 0.28(SD: +/- 0.05), respectively. This difference was statistically significant. At CoMTR 0.31, the sensitivity and specificity of malignant nodes were 83% and 75%, respectively. CONCLUSION: A CoMTR of above 0.31 suggests malignant lymphadenopathy. CoMTR is one of the MR criteria which can serve to differentiate between malignant and benign lymphadenopathy.