Measurement of fat content in vertebral marrow using a modified dixon sequence to differentiate benign from malignant processes.

PURPOSE

To determine whether fat-signal-fraction (FF) map using a modified Dixon sequence could help differentiate benign from malignant bone lesions.

MATERIALS AND METHODS

Spine magnetic resonance images (MRIs) of 120 consecutive patients were studied by using a 3T MRI with standard T -weighted image (T WI) and modified-Dixon sequence for FF measurement. There were three groups: a control group (n = 51) with normal vertebrae; a benign group (n = 40) with focal red marrow deposition, Schmorl's nodes, benign compression fracture, or Modic type 1 endplate degeneration; a malignant group (n = 29) with spinal malignancies. The following three parameters were measured on T WI and FF map by two radiologists independently: T signal intensity (SI), FF and T1 SI of normal disc (SI). Then, Lesion-to-disc ratio (LDR = SI of the lesion/SI ) and FF ratio of lesion and normal marrow were calculated. The mean values of the parameters were compared among the groups and Receiver Operating Characteristic (ROC) curves were analyzed. Then a logistic regression was performed.

RESULTS

The FF (2.8%) and FF ratio (0.082) of malignancy were lower than benign lesions (P < 0.001). There was no difference in the LDR between malignancy and Schmorl's nodes (P = 0.795) or a benign compression fracture (P = 0.866). The areas under the ROC curves of FF and FF ratio were 93% and 87%, respectively, which were higher than those of the other parameters used for differentiation (P < 0.001). In logistic regression analyses, FF remained a significant variable that could be used to independently differentiate benign from malignant lesions, with an odds ratio of 1.9 (P < 0.001).

CONCLUSION

The FF and FF ratio obtained from FF maps using modified-Dixon sequence could be used to distinguish between benign and malignant causes of focal bone marrow abnormalities when difficulty in the qualitative interpretation of conventional MR images arises.

LEVEL OF EVIDENCE

3 J. MAGN. RESON. IMAGING 2017;45:1534-1544.