The Value Of The Fluid-fluid Levels Pattern In The MRI Imaging Diagnosis Of Bone And Soft Tissue Lesions

Objective: To report the prevalence of fluid-fluid levels(FFLs) in the bone and soft tissue lesions as demonstrated by magnetic resonance imaging (MRI) and to analyze the features(quantity, size and proportion of the lesion occupied by FFLs)of FFLs and signal pattern on MRI of the FFLs and to further indentify the relationship between benign and malignant bone and soft tissue lesions.Material and Methods: A retrospective analysis 614 cases with bone and soft tissue tumors and tumor like conditions proved by surgically or pathologically from 2005 to 2010 in our hospital,of them 95 cases were tumor like conditions, 146 were benign neoplasms and 373 were malignant neoplasms. All cases were performed of MRI. 48 lesions in above all cases had FFLs, of them 29 lesions were benign and 19 malignant. Lesions with FFLs were sub-categorized depending upon FFLs size, quantity, the proportion of the lesion occupied by FFLs, and signal pattern on MRI. The proportion of the benign and malignant lesions were compared in all above groups using chi-squared analysis. Assumption multiple,large fluid-fluid levels being diagnostic of bone benign lesion was analyzed.Results: Forty-eight of the 614 (7.8%: 95% CI 5.8~10.2%) bone and soft tissue lesions contained FFLs. The prevalence of FFLs in benign lesions is over malignant lesions, especially giant cell tumor(15%) and aneurysmal bone cysts(20.5%) .In 25 patients with large FFLs group(diameter≥2cm), 19 (76%) of these were benign lesions(including benign tumor and tumor-like condition), 6(24%) were malignant; In 23 patients with small FFLs (diameter<2cm), 10 (43.4%) of them were benign lesions, 13(56.6%) were malignant. Compared with the population of benign and malignant lesions, large FFLs group was significantly associated with benign lesions (P=0.021). This group is 4.117 times more than small FFLs group likely to contain a benign lesion (95%CI 1.199-14.137).In 36 patients with multiple FFLs group, 23 (63.7%) of them were benign lesions, 13(36.4%) were malignant. In 12 patients with single FFL group, 6 (50%) of them were benign lesions, 6(50%) were malignant. There was no statistically significant difference between the proportion of benign and malignant lesions.In 24 patients, FFLs occupied less than 1/2 of the whole lesion volume(group A). 10 (41.7%) of them were benign, 14(58.3%) were malignant. In 24 patients, FFLs occupied over than 1/2 of the lesion volume(group B), 19 (79.2%) of them were benign, 5(20.8%) were malignant. Compared with the population of benign and malignant lesions there was statistically significant, and group B is 5.320-times more than group A likely to contain a benign lesion (95%CI 1.485-19.064).The sensitivity is 51.9% and specificity is 93.8%, ROC area 0.728(95%CI0.577,0.879)if multiple,large FFLs was taken as a benign bone lesions.All cases with FFLs demonstrated high/low signal intensity (H/L) pattern in T2WI. T1WI shown H/L, low/high(L/H), no different(ND)respectively. In 14 patients, FFLs shown L/H pattern in T1WI. 10 (71.4%) of them were benign, 4(28.6%) were malignant. In 22 patients, FFLs shown H/L pattern in T1WI. 12 (54.5%) of them were benign, 10(45.5%) were malignant. In 12 patients, FFLs ND in T1WI. 8 (66.7%) of them were benign, 4(33.3%) were malignant. Compared with each other, there was no statistically significant difference between the proportion of benign and malignant lesions. Compared with the population of benign and malignant lesions without FFLs, L/H pattern on T1W was significantly associated with benign lesions.,and other groups no statistically significant.Conclusion:The prevalence of FFLs is 7.8%(95%CI5.8-10.2%) in bone and soft-tissue tumors and tumor-like conditions. Benign lesions show FFL(s12%,95%CI8.2-16.8%)is over malignant lesions. 80% of bone and soft tissue lesions with multiple, large FFls were benign. 56.2% of bone and soft tissue lesion with multiple, small FFls were malignant. If multiple,large FFLs was taken as a benign bone lesions,the specificity is high(93.8%). However the diagnosis should be made on the basis of other radiological and clinical findings.