Evaluation of intracranial lesions with inversion recovery half-Fourier single-shot turbo spin-echo MR: initial observations.

PURPOSE To determine the value of inversion recovery half-Fourier single-shot turbo spin-echo (IR-HASTE) MR sequences in the characterization of a variety of intracranial lesions, with the focus on differentiating between epidermoids and nonneoplastic cystic lesions. METHODS We used a 1.5-T MR unit to study five epidermoids, seven arachnoid cysts, seven other nonneoplastic cysts (three neuroepithelial cysts, two interhemispheric cysts, and two Rathke's cleft cysts), and eight solid neoplasms (three meningiomas, two astrocytomas, one subependymoma, one cavernoma, and one metastatic tumor) using IR-HASTE sequences with variable inversion times (TI). Imaging time for each section was 2 seconds for the sequence. The TI nulling values were analyzed statistically. RESULTS The TI nulling values were 1200 to 2300 for the epidermoids, 2800 to 3000 for the arachnoid cysts, 300 and 800, respectively, for the Rathke's cleft cysts, 2500 to 3000 for the other nonneoplastic cysts, and 300 to 1500 for the solid neoplasms. There was no overlap of TI nulling values between the arachnoid cysts and the epidermoids; the difference was statistically significant. Both patients with interhemispheric cysts had two lesions in which the TI nulling values were different. CONCLUSION IR-HASTE sequences provide a rapid and reliable imaging method for differentiating among epidermoids, arachnoid cysts, and solid neoplasms. This technique also provides information about the continuity of the multicystic lesions in terms of the differences in their TI nulling values. For solid intraaxial masses, the use of IR-HASTE helps to differentiate intratumoral cysts and necrosis from solid components.