Possibilities of Using DWIBS for Clinical Tasks with the Measurement of the Apparent Diffusion Coefficient

Abstract

Additional suppression of the background signal in diffusion-weighted images (DWIBS) allows to get more contrast images to highlight areas with restricted diffusion, for example, in many malignant primary and metastatic tumors. Due to fundamental differences in DWIBS and DWI acquisition, the apparent diffusion coefficient (ADC) values may differ, which could negatively affect attempts to compare with the available literature data or with conventional DWI studies. Purpose. Evaluation of the correctness of the calculation of the ADC values based on DWIBS images, compared to regular DWI. Material and methods. A comparative analysis of the ADC values obtained using DWIBS and conventional DWI on an MR-compatible phantom and on 20 healthy volunteers was carried out. Free breathing DWIBS as well as DWI with breath synchronization were acquired using 1.5 T MRI scanner. Results and discussion. ADC values measured with DWIBS and DWI were found to coincides well both for the phantom and for the volunteers in all the areas (vertebra, kidney, spleen), except for the liver, where the ADC values obtained from DWIBS images were 11 % lower than with standard DWI (1.06 vs 0.92 mm2/s). This may be due to the greater displacement of the liver during respiratory movements. The advantages of the DWIBS technique include a significant decrease in scan time (1.5-2 times with a 10 % decrease in signal-to-noise ratio compared to routine DWI), which allows for a quantitative analysis of ADC values in a whole-body scan in a comfortable timing for the patient. Conclusion. DWIBS can be recommended for calculating ADC values, however, a comparative analysis of ADC values in organs and tissues exposed to strong respiratory movements require additional assessments of repeatability and reproducibility directly when comparing areas with a strongly pronounced diffusion restriction.