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FIG 4. Patient 16.
A and B, Surface-coil contrast-enhanced gradient-echo images (26/6/1) and PRESS spectra (1000/144/1; voxel resolution, 0.34 cm3) acquired 2 weeks before (A) and 1 month after (B) gamma knife radiosurgery and aligned retrospectively. Before radiosurgery, several voxels with Cho above that of normal-appearing tissue are present beyond the 15-Gy isodose line (shown in red) of the prescribed treatment plan. One month later, the Cho/NAA ratio in eight of the nine voxels shown has increased to greater than 1. Also conspicuous are the strong lactate/lipid resonances after treatment. One month after the last examination shown here, the patient underwent resection. Histologic analysis of biopsy samples taken during surgery showed residual/recurrent anaplastic astrocytoma.
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