THE ROLE OF THE STIR SEQUENCE IN MAGNETIC-RESONANCE-IMAGING EXAMINATION OF BONE-TUMORS

Sixty patients with primary bone tumours were evaluated with magnetic resonance imaging (MRI) at 0.5 T with both conventional spin-echo (SE) and short inversion time inversion recovery (STIR) sequences. The results have been reviewed in order to evaluate the accuracy of STIR and conventional SE sequences in the detection of tumours, the definition of intramedullary extent and soft-tissue involvement. The intraosseous neoplastic extent has been compared with macroslides of surgical specimens in 24 cases. The role of the STIR sequence in detection of recurrences in the post-surgical follow-up was also evaluated. The STIR sequence, designed to suppress signal from fat, also enhances the signal from tissue with long T1 and T2 relaxation times, such as neoplastic and inflammatory tissue. The STIR sequence with T1 of 120-130 ms in all cases suppressed the high signal from fatty bone marrow, giving a clear depiction of tumour extent, in both its intramedullary and soft-tissue components, and is superior to conventional SE images. The high sensitivity (100% of our cases) of this technique is counterbalanced by its lack of specificity: on STIR sequences both tumour and peritumorous oedema give an increase of signal intensity, limiting assessment of tumour extent. Peritumoral oedema, only present in our series in malignant neoplasms, may however be differentiated on the basis of the configuration of the abnormal areas, and by comparing STIR images with short repetition time/echo time sequence results.