An MRI-based decision tree to distinguish lipomas and lipoma variants from well-differentiated liposarcoma of the extremity and superficial trunk: Classification and regression tree (CART) analysis.

PURPOSE: To build and validate a decision tree model using classification and regression tree (CART) analysis to distinguish lipoma and lipoma variants from well-differentiated liposarcoma of the extremities and superficial trunk. METHODS: This retrospective study included patients who underwent surgical resection and preoperative contrast-enhanced MR imaging for lipoma, lipoma variants, and well-differentiated liposarcoma in two tertiary referral centers. Six MRI findings (tumor size, anatomical location, tumor depth, shape, enhancement pattern, and presence of intermingled muscle fibers) and two demographic factors (patient age and sex) were assessed to build a classification tree using CART analysis with minimal error cross-validation pruning based on a complexity parameter. RESULTS: The model building cohort consisted of 231 patients (186 lipoma and lipoma variants and 45 well-differentiated liposarcoma) from one center, while the validation cohort consisted of 157 patients (136 lipoma and lipoma variants and 21 well-differentiated liposarcoma) from another center. In the CART analysis, the contrast enhancement pattern (no enhancement or thin septal enhancement versus thick septal, nodular, confluent hazy, or solid enhancement) was the first partitioning predictor, followed by a maximal tumor size of 12.75 cm. The tree model allowed distinction of lipoma and lipoma variants from well-differentiated liposarcoma in both the model building cohort (C-statistics, 0.955; sensitivity 80 %, specificity 94.62 %, accuracy 91.77 %) and the external validation cohort (C-statistics, 0.917; sensitivity 66.67 %, specificity 95.59 %, accuracy 91.72 %). CONCLUSION: The distinction of lipoma and lipoma variants from well-differentiated liposarcoma can be achieved with the simple classification tree model.

Quantitative assessment of synovial vascularity using contrast-enhanced power Doppler ultrasonography: correlation with histologic findings and mr imaging findings in arthritic rabbit knee model.

OBJECTIVE: To validate contrast-enhanced power Doppler ultrasonography (PD US) for the evaluation of synovial vascularity in an arthritic rabbit knee model in correlation with MR and histological findings. MATERIALS AND METHODS: Power Doppler ultrasonography was performed for carrageenin-induced arthritic left knee and control right knee of 13 rabbits, first without and then with sonic contrast agent enhancement (Levovist, Schering, Berlin Germany), followed by gadolinium-enhanced MR imaging. Synovial vascularity was quantitatively assessed by calculating the color pixel area in power Doppler sonography using a computer-aided image analysis program and by grading the enhancement on MR images: grade 1, enhancement of knee joint is less than one-third of the area; grade 2, one-third to two-thirds enhancement; and grade 3, more than two-thirds enhancement. Microvessel density (MVD) was measured on slides stained immunohistochemically for CD31 antigen for histological assessment. RESULTS: The mean area of color pixels in PD US changed from 4.37 to 16.42 mm(2) in the arthritic knee after enhancement (p < 0.05), whereas it changed from 0.77 to 2.31 mm(2) in the control knee (p < 0.05). Arthritic knees had greater power Doppler signal than control knees both before and after contrast administration (p < 0.05). The average MVD was 88 in arthritic knees and 46 in control knees. MVDs correlated with color pixel areas of contrast-enhanced power Doppler imaging in arthritic knees. In MR grading of arthritic knees, five were grade 2 and eight were grade 3. MVD and PD US revealed no significant difference between grade 2 and 3 arthritic knees (p > 0.05). CONCLUSION: Sonic contrast-enhanced PD US improves the visualization of synovial vascularity and allows quantitative measurement in experimentally induced rabbit arthritic knees.

Assessment of musculoskeletal infection in rats to determine usefulness of SPIO-enhanced MRI.

OBJECTIVE: The objective of our study was to evaluate the usefulness of superparamagnetic iron oxide (SPIO)-enhanced MRI in experimental models of infectious disease and to analyze the intracellular uptake of SPIO. MATERIALS AND METHODS: Nine rats with infectious arthritis of the knee or soft-tissue infection were imaged on an MRI unit on days 4-6 after i.v. injection of a bacterial suspension. All animals were imaged on a T2-weighted fast spin-echo sequence before and 24 hours after administration of SPIO. The nine rats were classified into two groups according to the dose of SPIO. We calculated the relative signal-to-noise ratio (SNR) change and compared the relative SNR change with the histologic findings. We analyzed iron-loaded cells and the intracellular uptake of iron particles according to the dose of SPIO. RESULTS: The SNR value decreased in proportion to the increase in the number of iron-laden macrophages or fibroblasts in the wall of the soft-tissue abscess (p < 0.01). The intracellular uptake of iron particles was shown in fibroblasts as well as in macrophages, and their uptake in the fibroblasts was greater than that in the macrophages (p < 0.05). There was no statistically significant difference in the intracellular uptake of iron particles according to the dose of SPIO (p > 0.1). CONCLUSION: SPIO-enhanced MRI can be useful in evaluating infectious disease of the joint or soft tissue and is influenced by the uptake of iron particles in fibroblasts as well as macrophages.