MAGNETIC RESONANCE IMAGING (MRI) AND MAGNETIC RESONANCE SPECTROSCOPY (MRS) OF INTRACRANIAL LIPOMAS

R. Fründ, A. Geissler, M. Gliese, J. Seitz, S. Feuerbach

Rüdiger Fründ Institut für Röntgendiagnostik Klinikum der Universität Regensburg, D-93042 Regensburg Germany

Received 6/3/97 Accepted 9/16/97

3. MATERIALS AND METHODS

3.1. Patients:

Patient A was an 18 year old woman with headache. No biopsy was performed. Patient B was a 50 year old man. The only clinical symptom was a non stable heel to toe gait. Surgical biopsy was performed. Both patients had no abnormal cerebral liquor circulation. Four patients (1 female, 3 males, ages 58 to 73 years) with histologically verified glioblastomas grade IV (WHO) and high levels of fat signals, detected by MRS, were evaluated for the glioblastoma group. Subcutaneous fat was measured in the neck of a healthy, 35 year old man. Intraoperatively collected biopsy specimens were immediately frozen in liquid nitrogen. Normal subcutaneous fat sample was collected from the back of a person with no known disturbance in the metabolism during intervertebral disc surgery.

3.2. Methods:

For all in vivo examinations, a 1.5 T Magnetom SP 63 (Siemens, Erlangen, Germany) with a CP-headcoil was used.

3.3. Imaging:

T1 weighted MR-images were aquired with spinecho technique (TR = 570 ms, TE = 15 ms) in axial or sagital orientation. Slice thickness was 6 mm with a 20 % gap. 19 slices were aquired. Fat suppression was performed by a spectral saturation pre-pulse.

3.4. MR Spectroscopy:

3.4.1. In vivo measurements:

A stimulated echo sequence (STEAM) with 20 ms echotime, 30 ms mixing time and 1.5 s repetition time was used. Voxel size was 15x15x15 mm. 256 aquisitions with 1k points were accumulated. FIDs were eddy-current compensated with a commercialy available software using a reference scan without water suppression (8). Data were transferred to an external PC, zerofilled to 16 k points, fourier transformed, phase and baseline corrected. The resonances were Gauss fitted and integrated. T1 and T2 relaxation times were not considered.

3.4.2. Ex vivo measurement:

Biopsy samples were analyzed in D₂O at 7 Tesla with a Bruker (Karlsruhe, Germany) MSL 300 spectrometer in a 5 mm ¹H-probehead at room temperature. A simple 90 degree pulse aquisition program with pre-irradiation of the residual water peak was used. Repetition time was set to 10 s. 128 aquisitions with 8 k points were accumulated. Postprocessing was made in the same manner as the in vivo data.