Comparison of Chemical Shift MR Imaging Findings between Vertebral Benign and Metastatic Lesions

Abstract

Objectives: To establish a cut-off value for signal intensity ratio (SIR) in dual-phase chemical shift MRI and also to evaluate the sensitivity and specificity of this method in order to differentiate benign from malignant focal vertebral lesions. Methods: Totally 51 patients (28 men and 23 women) with a mean (± SD) age of 52.61 ± 13.52 years (range, 27 - 81 years) with 116 vertebral focal lesions were studied. MR imagining was performed using a 1.5-Tesla superconducting system. Chemical shift sequences for sagittal in-phase (IP) were obtained at RT/ET 100 - 165/4.2 and out-phase (OP) 100 - 165/2.4. All images were sent to a picture archiving and communication system (PACS) work station and areas with abnormal SI on the T1 and T2 sequences were identified on the IP/OP. An elliptical cursor to define region of interest was used to describe the area with abnormality on the IP and OP images. We calculated the signal intensity ratio or SIR (SI of OP/SI of IP) to compare the OP with the IP images. Air was selected as the reference contrast as not influenced by fatty infiltration. Results: SIR of 0.73 (OP images compared with IP images) can be used as the best cut-off value to identify benign (SIR < 0.73) vs. malignant (SIR ≥ 0.73) lesions with 100% sensitivity and 89.7% specificity. Conclusions: SIR values from out-phase and in-phase images (chemical shift MR imaging) may be useful for quantitatively differentiating benign from malignant focal vertebral lesions with high specificity and sensitivity. SIR values in neoplastic focal lesions were greater than benign lesion and a value of 0.73 can be used as a cut off to differentiate between benign and malignant focal lesions.