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TUTORIAL: Clinical PET - Oncology
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Topics:
Brain Tumors
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The above images depict a normal FDG-PET scan of the brain. Note that the cortex and basal ganglia normally have a relatively high glucose utilization and should not be confused with a tumor. In addition, cortical metabolism has a heterogeneous metabolic intensity, with more prominent metabolism at the motor, visual, and auditory cortices.
Astrocytoma
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The first step in image interpretation for FDG-PET brain tumor studies is the identification of a region or focus of relatively intense (hypermetabolic) tissue in relation to surrounding white or gray matter. Careful visual examination of all slices, and correlations with CT or MRI scans also can be helpful in determining the area of tumor involvement.
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The preferred treatment of brain tumors is surgical removal. FDG-PET scans are useful for evaluating the efficacy of surgical procedures. In the above case, PET confirmed that the contrast enhancement observed with CT prior to surgery (A, green arrow) represented a region of hypermetabolism (A, red arrow). Such a hypermetabolic region suggests the presence of a high-grade tumor. Postoperatively, the primary indication for FDG-PET studies is to identify foci of tumor recurrence. Contrast enhancing lesions on CT scans (e.g., B, green arrow) may represent tumor recurrence or radiation necrosis. The lack of a corresponding hypermetabolic region in the FDG-PET image suggests that the contrast enhancement observed in the CT scan (B) is due to post-surgical trauma, and that no residual tumor was present at that time. However, several months later (C), a hypermetabolic rim reappears in the FDG-PET image (C, red arrow), indicating a recurrence of the tumor.
Credits
Material for this section was kindly provided by:
Carl Hoh, M.D.
Dept. of Molecular and Medical Pharmacology
UCLA School of Medicine
Yong Choi, Ph.D.
Dept. of Radiology
University of Pittsburgh School of Medicine
Randall Hawkins, M.D., Ph.D.
Nuclear Medicine Division
UCSF School of Medicine
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