Signal intensity dynamics of malignant lymphoma in diffusion-weighted magnetic resonance imaging compared to positron emission tomography

This article discusses a study performed with an aim to determine the usefulness of diffusion-weighted MRI in pre-treatment assessment and evaluation of chemotherapy response of mediastinal lesions of malignant lymphoma by analysing signal intensity, accumulation of contrast agent and changes in values of ADC. Comparing the results of PET/CT and DW-MRI was another goal of this study. We reviewed data of 21 patients that underwent treatment during years 2013-2014 at the Hospital of Lithuanian University of Health Sciences Kaunas Clinics and had DW-MRI and PET/CT scans carried out. For all patients the diagnosis of malignant lymphoma in mediastinal lymph nodes was confirmed histological. Whether the lymphoma was in active state was determined by PET/CT or histological data. In MRI scans, signal intensity and ADC values were evaluated, while in PET/CT maximum and average standardized uptake values were assessed. Patients underwent chemotherapy and follow up scans were performed to evaluate response. In total, 25 PET/CT and 50 DW-MRI scans were analysed. We found statistically significant difference of values of ADC in active and inactive states of malignant lymphoma of mediastinal lymph nodes. In follow up tests, performed during 2 years after treatment, a tendency of decreasing ADC values over time was seen when chemotherapy was successful and no relapse was observed. Among the reviewed cases, DW-MRI had slightly worse specificity than PET/CT in differentiation of malignant and benign changes in lymph nodes.