Signal characteristics of normal adult bone marrow in whole-body diffusion-weighted imaging

Background: Knowledge of the signal characteristics of normal adult bone marrow in whole-body diffusion-weighted (DW) images (WB-DWI) is essential for correctly interpreting DW images in clinical practice; however, these factors have not yet been clearly determined. Purpose: To evaluate the signal characteristics of normal adult bone marrow in WB-DWI, to correlate these characteristics with age and gender, and to determine the causes of these phenomena. Material and Methods: Ninety-eight healthy volunteers underwent WB-DWI (b=0 and 800s/mm(2)). Two radiologists visually evaluated the signal characteristics of bone marrow in DW images separately. One radiologist measured the apparent diffusion coefficient (ADC) of the thoracic and lumbar vertebrae, bilateral femur (including head, neck, and proximal and distal femoral shaft), bilateral humeral head, ilium, and scapula. The signal characteristics of normal bone marrow were analyzed. Results: The visual evaluation results of DW images indicated that hyperintensity of bone marrow was more frequently seen in women aged 21-50 years (68.4%) than in men aged 21-50 years (3.3%) (P<0.001), men aged 51-81 years (5.9%) (P<0.001), and women aged 51-81 years (15.4%) (P=0.001). However, no statistically significant difference was found between men and women aged 51-81 years (P=0.565). The ADC of bone marrow was significantly higher in women than in men aged 21-50 years. Bone marrow ADC showed significant negative correlation with age in women but not in men. Conclusion: The signal intensity of bone marrow varies with age and gender in DW images. ADC and the T2 shine-through effect contributed to the bone marrow signal intensity in DW images, and the latter effect may predominate.