Role of Diffusion Weighted Magnetic Resonance Imaging in Differentiation between Benign and Malignant Vertebral Body Collapse

Abstract
Background: In recent years, MRI has increasingly become the modality of choice for imaging of musculoskeletal disor-ders. Diffusion weighted MR sequences provide microscopic information to supplement the macroscopic information pro-vided by conventional sequences. It is a non invasive imaging technique which is suitable for probing the physical structure of a biologic tissue at a microscopic level and it exploits the random, translational motion of water protons in a biologic tissue, which reflects the tissue specific diffusion capacity and can be used for tissue characterization.
Aim of Work: The aim of this study is to determine the value of Diffusion Weighted Imaging (DWI) in differentiation between different causes of vertebral collapse.
Patients and Methods: This is a prospective study carried out in Radio-Diagnosis Department, Faculty of Medicine, Cairo University between August 2014 and February 2016 for patients diagnosed with vertebral body collapse. A total number of 35 patients (20 males and 15 females) with age range 18-74 (average 52).
The MRI sequences obtained were sagittal T1WI, T2WI, STIR and axial T1WI, T2WI & DWI (± post contrast images in some patients). Bone marrow signal intensity of the collapsed vertebra was analyzed by comparing its signal intensity with the signal intensity of the intervertebral disc, fat and muscle tissue on T1-weighted images, the signal intensity of the affected veteba was also inspected on DWI then ADC values were automatically calculated using the software provided by the MR scanner manufacturer (Diffusion Calculation: Philips Medical Systems) and the ADC quantitative parameter was expressed in: 10–3mm2/s.
Results: Our study included 35 patients who were diag-nosed with vertebral body collapse. Qualitative evaluation of the lesion contrast in diffusion-weighted MRI of the vertebral column has been shown to be valuable for the differentiation of lesion etiology; however, visual assessment of high signal intensity was not specific for malignancy.
On the other hand the quantitative assessment by meas-uring the ADC value was able to distinguish different types of vertebral collapse.
In our study, there was statistically Highly Significant (HS) difference between malignant and the following benign causes of vertebral collapse; acute fracture, chronic osteoporot-ic collapse and pyogenic spondylodiscitis. There is also statistically significant difference (S) between malignant and TB spondylodiscitis lesions according to ADC values.
Conclusion: Diffusion weighted MRI can be used as a reliable tool in differentiation between different causes of vertebral body collapse. DWI could be applied as a cost effective substitute for the gadolinium enhanced scan especially in patients with contraindication for contrast administration.