Diffusion Weighted Magnetic Resonance Imaging in Diffuse and Focal Vertebral Bone Marrow Lesions Using Apparent Diffusion Coefficient (ADC) Mapping as a Quantitative Assessment Tool

Abstract
Background: Routine magnetic resonance imaging MRI is highly sensitive in detecting bone marrow alterations; however, it is of limited specificity in the evaluation of the causes of these alterations. Diffusion Weighted Imaging (DWI) is an imaging technique which probes the structure of a biologic tissue. The contrast achieved with this technique together with measurement of the apparent diffusion coefficient ADC values are useful complementary MRI tools and can be used for non-invasive tissue characterization and therefore reaching a more specific diagnosis.
Aim of Work: The aim of this study is to determine the value of both qualitative and quantitative assessment of DWI in differentiation between different vertebral lesions and to determine cut off ADC value between benign and malignant lesions.
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 or suspected to have vertebral lesion of any etiology. A total number of 40 patients (22 males and 18 females) with age range 2-88 (average 49).
The MRI sequences obtained were sagittal T1WI, T2WI, STIR and axial T1WI, T2WI & DWI (± post contrast images in some patients). Bone marrow signal intensity was qualita-tively analyzed by visually comparing its signal intensity with the signal intensity of the intervertebral disc, fat and muscle tissue on T1-weighted images. Hyperintense lesions on the DWI were identified and 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: 1 0–3mm2/s.
Results: Our study included 40 patients who were diag-nosed with or suspected to have vertebral lesion of any etiology. 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 benign from malignant high signal intensity on DWI.
In our study, infiltrated neoplastic marrow as well as hypercellular red marrow had higher ADC values than normal marrow while inflammatory lesions and hemangiomas had the highest ADC values.
Conclusion: Diffusion weighted MRI is a reliable tool in characterization of different vertebral bone marrow abnormal-ities. The routine MRI protocol of spine examinations could be modified to include DWI as a cost effective substitute for the gadolinium enhanced scan especially in patients with contraindication for contrast administration.