![]() The purpose of this study was to compare the prototype SIMCAST sequence with routine contrast-enhanced T1-weighted 3D spoiled gradient-echo (SPGR) imaging for the evaluation of tumors of the internal auditory canal (IAC). ![]() Therefore, it is desirable to further increase spatial resolution in particular, slice resolution with T2-weighted MR imaging. While large lesions have been clearly depicted with fast spin-echo (FSE) (7, 8) and constructive interference in steady state (CISS) (9, 10) imaging, some small lesions (<5 mm) were missed in previous work (8). Finally, T2-weighted imaging without the need for expensive contrast agents (4–10) has been discussed as a lower cost MR imaging alternative to the cheaper but less sensitive auditory brain stem response (ABR) testing (11, 12). Thus, an assessment of very high-resolution T2-weighted MR imaging, which results in high fluid signal and high fluid/tumor and fluid/nerve contrast, as well as a comparison of T2-weighted with standard contrast-enhanced T1-weighted imaging is of interest. The monitoring and characterizing of tumors are also of interest for follow-up studies in patients who have had surgery or who have been treated with stereotactic radiosurgery.Īlthough contrast-enhanced T1-weighted MR imaging is the standard of reference for tumor detection, the relatively large section thickness (1.5 to 3 mm) and the low signal of nonenhancing structures (nerves, fluid) limit its capability for detailed tumor characterization and for allowing accurate measurements of tumor volume, especially in very small tumors. Furthermore, it is common clinical practice not to treat older patients surgically but rather to monitor their tumor growth. For example, for patients with small tumors, knowledge of the involvement of individual nerve branches may better aid surgical procedures aimed at hearing preservation. However, a more detailed characterization of the lesions, beyond mere detection, would be of significant clinical interest. SPGR has somewhat better contrast, but SIMCAST excels at depicting the surrounding anatomy and tumor involvement of the seventh and eighth cranial nerves.īecause lesions in the inner ear and cerebellopontine angle (CPA) are readily detected with contrast-enhanced T1-weighted MR imaging, this is the preferred method for screening patients with suspected CPA tumors (1–3). SIMCAST usually delineated the CSF spaces better, whereas SPGR more clearly showed the tumor/brain boundary.ĬONCLUSION: SIMCAST and SPGR are suitable for tumor detection and volume measurements. The information from both sequences was complementary. Measurements on both sequences agreed, on average, within 14%. RESULTS: Both sequences clearly identified tumors that ranged in size from 0.06 to 3.0 cm 3. Tumor volumes were measured by manual tracing. Tumor appearance and depiction of surrounding anatomy, including the cranial nerves, were evaluated. Twenty-eight axial sections were acquired using parameters of 17/3.3 (TR/TE), a 40° flip angle, a 20 × 15-cm or 22 × 16-cm field of view (FOV), a 512 × 256 matrix, and a 0.4- or 1.2-mm section thickness for the SIMCAST technique, and 30/4.2, a 30° flip angle, a 20 × 20-cm FOV, a 512 × 288 matrix, and a 1.5-mm section thickness for the SPGR technique. METHODS: Twenty-seven ears in 21 patients with 16 confirmed schwannomas were studied with the 3D T2-weighted prototype segment-interleaved motion-compensated acquisition in steady state (SIMCAST) and the T1-weighted contrast-enhanced spoiled gradient-echo (SPGR) techniques. ![]() The purpose of this study was to compare two MR sequences for their ability to delineate internal auditory canal tumors. BACKGROUND AND PURPOSE: Although contrast-enhanced T1-weighted MR imaging is the standard of reference for diagnosing tumor in the cerebellopontine angle, high-resolution T2-weighted imaging may show more details of the seventh and eighth cranial nerve branches, resulting in more accurate tumor volume measurements. ![]()
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