Diffusion-weighted whole-body MRI (virtual PET) in screening for osseous metastases

Objective. To present our preliminary experience in whole-body MRI with an added diffusion-weighted sequence in screening for osseous metastases. Material and methods. 24 patients with malignant neoplasms underwent bone scintigraphy and whole-body MRI with the addition of a diffusion-weighted sequence. Whole-body MRI was performed on a 1.5 T unit using a three-station protocol; coronal T1-weighted FSE and STIR sequences and sagittal T1-weighted FSE of the spine were acquired. A diffusion-weighted sequence (b: 600 s/mm(2)) was added in the axial plane at five different stations and iconographic presentation in coronal-plane reconstructions with contrast inversion was used to obtain an image similar to that provided by PET (virtual PET). The findings at bone scintigraphy (BS) and MRI were compared for the presence of osseous metastases, evaluating the results for each patient both globally and for different osseous regions. Metastatic lesions were confirmed by biopsy or by six to eight months' follow-up. Results. Globally, whole-body MRI with diffusion-weighted sequences was superior to bone scintigraphy, with a sensitivity of 100% (BS 71%), specificity 90% (BS 80%), and reliability 96% (BS 75%). In the evaluation by osseous region, the results of MRI were also better than those of bone scintigraphy: sensitivity 96% (BS 52%). In the diffusion- weighted sequence, lytic metastases were hyperintense in all cases, with an apparent diffusion coefficient (ADC) value higher than normal bone but lower than lesions with acute edema of benign etiology. Whole-body MRI also revealed unknown extraosseous findings related to the tumors and extraosseous metastases in 42% of the patients. Conclusions. Whole-body MRI with an added diffusion-weighted sequence is an efficacious method of detecting osseous metastases and is more reliable than bone scintigraphy. Moreover, whole-body MRI provides information about extraosseous lesions. Lytic metastases are hyperintense in diffusion-weighted sequences and have a lower ADC than benign edema.