MRI of orofacial tumors and paragangliomas with 2D GE sequences: indications and optimal sequence parameters.

The aim of this paper is to determine to what extent and in which cases 2D gradient echo (2D GE) sequences can be applied alternatively or additionally to spin echo (SE) sequences for improved diagnostic evaluation. Imaging with SE sequences is the most frequently used MR technique in the assessment of ear, nose and throat (ENT) tumors. In literature there are only a few reports on the contrast behaviour of 2D GE sequences using different sequence parameters and their application in ENT tumors. This paper set out to establish the most suitable sequence type and sequence parameters. Measurements were performed with a Magnetom SP 63 MR system (Siemens) with a field strength of 1.5 T, using head and Helmholtz coils. One-hundred twenty-eight volunteers and 369 patients were examined with 2D GE sequences. In order to find the best MR technique for the examination of orofacial tumors and paragangliomas, FLASH, FISP and PSIF sequences with different sequence parameters (TR, TE, flip angle, bandwidth) were applied. The results of these examinations confirmed the superiority of 2D GE sequences over SE sequences. In conclusion, contrast enhanced or unenhanced T1 weighted SE sequences should be replaced by 2D GE FLASH 70 degrees in the examination of orofacial tumors. In the case of paragangliomas of the jugular bulb and the parapharyngeal space T1- and T2-weighted SE sequences should be replaced by 2D GE FLASH 40 degrees.