Diffusion-weighted MRI for detection and differentiation of musculoskeletal tumorous and tumor-like lesions in pediatric patients

Background: MRI is the diagnostic mainstay for detection and differentiation of musculoskeletal tumors. However, a projection regarding the biological dignity of lesions based on standard MRI sequences remains difficult and uncertain. This study was undertaken to analyse whether diffusion-weighted MRI (DWI) can distinguish between benign and malignant musculoskeletal tumorous and tumor-like lesions in pediatric patients. Methods: MR examinations of 44 consecutive pediatric patients (26 girls, mean age 11+/-6 years) including standard sequences and DWI (b=50/800 s/mm(2)) at 1.5 or 3 Tesla were retrospectively evaluated. The study group contained 10 patients with non-treated malignant tumors and 34 patients with benign lesions. Size, relative signal intensity and apparent diffusion coefficient (ADC, unit x 10(-3) mm(2)/s) were determined in one lesion per patient. Results: Mean ADC was 0.78+/-0.45 x 10(-3) mm(2)/s in patients with malignant tumors and 1.71+/-10.75 x 10(-3) mm(2)/s in patients with benign lesions (P<0.001). Relative operating characteristics (ROC) analysis showed a sensitivity of 90% and a specificity of 91% for malignancy, based on an ADC cut-off value of <= 1.03. On logistic regression, mean ADC and lesion size accounted for 62% of variability in benign vs. malignant tumors. For malignant tumors, the signal intensity ratio was higher on DWI than on T1w post-contrast images (P<0.002). Two cases of local tumor recurrence were diagnosed by DWI only. Conclusions: DWI shows promising results for determination of biological dignity in musculoskeletal tumors. Mean ADC <= 1.03 x 10(-3) mm(2)/s is a strong indicator of malignancy at the first diagnosis. The use of DWI for early diagnosis of tumor recurrence in comparison with standard MRI sequences should be evaluated in prospective studies. World J Pediatr 2012;8(4):342-349