Clinical use of 11C-methionine and 18F-FDG-PET for germinoma in central nervous system

Abstract

ObjectiveThe purpose of this study was to examine the 11C-methionine (MET) and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) findings of central nervous system (CNS) germinoma and the diagnostic utility of these findings.MethodsWe retrospectively evaluated the cases of 10 patients who were diagnosed with CNS germinoma according to their histopathological or clinical findings. All the patients underwent pretreatment MET and/or FDG-PET scans, and the resultant images were assessed qualitatively and quantitatively. In the qualitative assessments, we used 3- and 5-grade visual scoring systems for the MET- and FDG-PET images, respectively. In the quantitative assessments, the maximal standardized uptake value (SUVmax) and the ratio of the SUVmax of the tumor (T) divided by the mean SUV for the normal white or gray matter [T/N (WM), T/N (GM)], was calculated.ResultsThe mean and SD values of SUVmax, T/N (WM), and T/N (GM) were 1.9 ± 1.4, 2.5 ± 1.3, and 1.7 ± 0.9 on MET-PET and 5.8 ± 2.2, 1.6 ± 0.5, and 0.8 ± 0.2 on FDG-PET, respectively. On MET-PET, only one lesion was not detected. On the other hand, on FDG-PET all of the lesions exhibited uptake values that were intermediate between those of the normal white matter and gray matter.ConclusionIn terms of its tumor-contouring ability, MET is a good tracer for diagnosing CNS germinomas; therefore, MET-PET is considered to be useful for planning biopsies or surgery. Although FDG-PET is capable of detecting CNS germinomas, it produced insufficient image contrast in the present study. Further studies are needed before FDG-PET can be used in clinical examinations of CNS germinoma.

A clinical approach to parasellar lesions in the transition age

“…High lipid peaks detected on MRS appear to be a characteristic of germinomas based either on lymphocyte infiltration or apoptosis of tumour cells, such as has been reported in malignant lymphomas. There are few case reports regarding the use of 18 F‐fluorodeoxyglucose (FDG)‐positron emission tomography (PET) in intracranial germinomas, and some reports about the utility of 11 C‐methionine (MET)‐PET in the setting of basal ganglia location 69 . In a study by Okochi et al, 69 including 10 patients with 2 SGs in transition age (2 mol L ‐1 and 19 and 20 years old), MET‐PET visualised almost all of the lesions, and thus 11 C‐MET is considered to be a good tracer for diagnosing intracranial germinomas, especially for tumour contouring.…”

Imaging Spectrum and Pitfalls of 11C-Methionine Positron Emission Tomography in a Series of Patients with Intracranial Lesions

“…On the other hand, lesions at the basal ganglia show higher asymmetrical uptakes ( Fig. 8 ) ( 9 ). The 11 C-Met uptake of several rare low-grade brain tumors has a confusing appearance similar to the images of high-grade gliomas.…”

Radiographic occult cerebellar germinoma presenting with progressive ataxia and cranial nerve palsy

“…Interestingly, low-signal lesions on T2*WI and SWI were found to concomitantly expand with tumor progression. Although having not been performed in our case, 11 C-methionine positron emission topography provides valuable information for making the diagnosis of germinoma, and it is useful also for evaluating treatment effects and monitoring for tumor recurrence [ 4 , 15 ].…”