Purpose: To identify the predictors of bone-marrow DWI signals from anthropometric, complete blood count (CBC), and C-reactive protein (CRP), and to evaluate the association with fat-content in patients.
Method: This retrospective study was approved by the institutional review board. A total of 113 consecutive tumor patients underwent whole-body PET/MRI. Apparent diffusion coefficient (ADC) and proton density fat fraction (PDFF) were measured and averaged in lumbar vertebrae (L3-5) and bilateral ilia. Due to respiratory motion, ribs were evaluated by 3-point visual scoring on DWI with b = 800 (1: invisible, 2: partially visible, 3: fully visible). The relationships between ADC/visual scores and anthropometric, CBC, CRP, and PDFF were examined. In females, the age-dependency was evaluated.
Results: Multi-regression analyses identified age as the strongest predictor of lumbar ADC (standardized coefficient: β = 0.45), followed by red cell distribution width (RDW) (β = -0.24), while age was the strongest predictor of iliac ADC (β = 0.43), followed by hemoglobin (Hb) (β = 0.22). RDW was the strongest predictor (β = 0.47) for rib visual score and age was the second (β = -0.39). ADC showed significant positive correlations with PDFF at L3-5 and ilium. Lumbar ADC showed a decreasing trend during middle age in females.
Conclusions: Age, anemia (lower Hb), and increased hematopoietic activity (higher RDW) are the predominant predictors of ADC and the visibility of red marrow on DWI. Fat-suppression methods and bone-marrow physiology in middle-aged females may have affected the measured correlations between ADC and PDFF inconsistent with previous studies.
Keywords: Age factors; Anemia; Bone marrow; Diffusion magnetic resonance imaging; Hematopoiesis.
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