The utility of in-phase/opposed-phase imaging in differentiating malignancy from acute benign compression fractures of the spine

Benign and malignant fractures of the spine may have similar signal intensity characteristics on conventional MR imaging sequences. This study assesses whether in-phase/opposed-phase imaging of the spine can differentiate these 2 entities.

Twenty-five consecutive patients who were evaluated for suspected malignancy (lymphoma [4 patients], breast cancer [3], multiple myeloma [2], melanoma [2], prostate [2], and renal cell carcinoma [1]) or for trauma to the thoracic or lumbar spine were entered into this study. An 18-month clinical follow-up was performed. Patients underwent standard MR imaging with an additional sagittal in-phase (repetition time [TR], 90-185; echo time [TE], 2.4 or 6.5; flip angle, 90 degrees ) and opposed-phase gradient recalled-echo sequence (TR, 90-185, TE, 4.6-4.7, flip angle, 90 degrees ). Areas that were of abnormal signal intensity on the T1 and T2 sequences were identified on the in-phase/opposed-phase sequences. An elliptical region of interest measurement of the signal intensity was made on the abnormal region on the in-phase as well as on the opposed-phase images. A computation of the signal intensity ratio (SIR) in the abnormal marrow on the opposed-phase to signal intensity measured on the in-phase images was made.

Twenty-one patients had 49 vertebral lesions, consisting of 20 malignant and 29 benign fractures. There was a significant difference (P < .001, Student t test) in the mean SIR for the benign lesions (mean, 0.58; SD, 0.02) compared with the malignant lesions (mean, 0.98; SD, 0.095). If a SIR of 0.80 as a cutoff is chosen, with >0.8 defined as malignant and <0.8 defined as a benign result, in-phase/opposed-phase imaging correctly identified 19 of 20 malignant lesions and 26 of 29 benign lesions (sensitivity, 0.95; specificity, 0.89).

There is significant difference in signal intensity between benign compression fractures and malignancy on in-phase/opposed-phase MR imaging.