Assessment of internal auditory canal tumors: A comparison of contrast-enhanced T1-weighted and steady-state T2-weighted gradient-echo MR imaging

BACKGROUND AND PURPOSE: Although contrast-enhanced T1-weighted MR imaging i s the standard of reference for diagnosing tumor in the cerebellopontine an gle, high-resolution T2-weighted imaging may show more details of the seven th and eighth cranial nerve branches, resulting in more accurate tumor volu me measurements. The purpose of this study was to compare two MR sequences for their ability to delineate internal auditory canal tumors. METHODS: Twenty-seven ears in 21 patients with 16 confirmed schwannomas wer e studied with the 3D T2-weighted prototype segment-interleaved motion-comp ensated acquisition in steady state (SIMCAST) and the T1-weighted contrast- enhanced spoiled gradient-echo (SPGR) techniques. Twenty-eight axial sectio ns were acquired using parameters of 17/3.3 (TR/TE), a 40 degrees flip angl e, a 20 x 15-cm or 22 x 16-cm field of view (FOV), a 512 x 256 matrix, and a 0.4- or 1.2-mm section thickness for the SIMCAST technique, and 30/4.2, a 30 degrees hip angle, a 20 x 20-cm FOV, a 512 x 288 matrix, and a 1.5-mm s ection thickness for the SPGR technique. Tumor appearance and depiction of surrounding anatomy, including the cranial nerves, were evaluated, Tumor vo lumes were measured by manual tracing, RESULTS: Both sequences clearly identified tumors that ranged in size from 0.06 to 3.0 cm(3). Measurements on both sequences agreed, on average, withi n 14%, The information from both sequences was complementary. SIMCAST usual ly delineated the CSF spaces better, whereas SPGR more clearly showed the t umor/brain boundary. CONCLUSION: SIMCAST and SPGR are suitable for tumor detection and volume me asurements. SPGR has somewhat better contrast, but SIMCAST excels at depict ing the surrounding anatomy and tumor involvement of the seventh and eighth cranial nerves.