Whole-body MRI for detecting metastatic bone tumor. Diagnostic value of diffusion-weighted images

We assessed the diagnostic value of whole body magnetic resonance (MR) imaging (WB-MRI) using diffusion-weighted images (DWI) for detecting bone metastasis and compared it with that of skeletal scintigraphy (SS). Thirty patients with malignancies (breast cancer, 17 patients; prostate cancer, 9; and one patient each, thyroid cancer, liposarcoma, leiomyosarcoma, and extraskeletal Ewing sarcoma) underwent both WB-MRI and SS to detect bone metastasis. All patients were followed more than 6 months by MR imaging, SS, or computed tomographic (CT) examination. For WB-MRI, patients were placed in feet-first supine position with table-top extender and quadrature body coil. We acquired DWI (axial plane from lower neck to proximal femur) (single shot short TI inversion-recovery [STIR]: repetition time [TR] 6243/echo time [TE] 59/inversion time [TI] 180 ms; b value: 600 s/mm2; 5-mm slice thickness; 112 x 112 matrix), T1-weighted fast spin echo (T1WI), and STIR (sagittal plane of total spine images and coronal plane of whole body images) images. Four blinded readers independently and separately interpreted images of combined MR sequences of T1WI+STIR (session 1) and T1WI+STIR+DWI (session 2). In 10 of 30 patients, we detected a total of 52 metastatic bone lesions; in the other 20, follow-up examinations confirmed no metastatic bone lesions. For these 52 lesions, for session 2, the mean sensitivity was 96% and the positive predictive value (PPV) was 98%. Those values were superior to those of session 1 (sensitivity: 88%; PPV: 95%) and those of SS (sensitivity: 96%; PPV: 94%). WB-MRI that included DWI was useful for detecting bone metastasis. (author)