Clinical History
This is a 23 year-old female with pleomorphic xanthoastrocytoma, status post craniotomy and resection times two and status post radiation therapy to the right parietal lobe. Now with recent MR demonstrating recurrent tumor.
Technique
The patient was administered 10.5 mCi of 18F-FDG and 45 minutes later brain imaging was performed from the vertex to the base of the skull. Comparison is made to the MRI exam of the head obtained 5 days earlier.
Findings
1. There is evidence of encephalomalacia within the right hemisphere, corresponding to abnormality noted on outside MR of the brain. Specifically, this is located within the right hemisphere in the frontal parietal temporal regions. This is consistent with post therapeutic changes of craniotomy and radiation.
2. Directly adjacent to the region of encephalomalacia, within the area of the deep white matter tracts, there are two foci of abnormally increased activity, corresponding to the abnormal masses identified on previous MR exam. While these are located within the regions of the deep white matter tracts, they demonstrate marked intensity (as intense as normal gray matter). The largest and most intense focus is located adjacent to the superior apical margin of the region of encephalomalacia and extends superiorly, along the anteromedial margin of the area of encephalomalacia to near the level of the high parietal lobe. When isocontoured using an SUV of 2.5, as measured on image plane 8 this region demonstrates a cross sectional area of 3.05 square cm, a maximum SUV of 3.8 and an average SUV of 2.8. The threshold for malignancy is an SUV of greater than 2.5. There is a second nodular appearing focus of abnormally increased metabolic activity which is located near the base of the region of encephalomalacia, within the posterior frontal, medial temporal, and inferior parietal white matter tracts. These findings are consistent with recurrent malignant neoplasm and correspond to the two lesions seen on recent outside MR examination and described on that report.
Impression
FINDINGS SUGGEST METABOLICALLY ACTIVE, HIGH GRADE (GRADE 3 OR GRADE 4) ASTROCYTOMA SURROUNDING THE CYSTIC LESION IN THE WHITE MATTER TRACTS IN THE REGION OF THE CENTRUM SEMIOVALE.