[Positron emission tomography with 11C-methionine in primary brain tumor diagnosis]

To investigate the variations in ¹¹C-methionine uptake in the intact brain tissue and in glial brain tumors of different types.

Forty patients (21 men, 19 women) with gliomas, Grade I-IV, underwent ¹¹C-methionine PET-CT and contrast-enhanced MRI. Standardized uptake value (SUV), tumor-to-normal (T/N) ratios and tumor volume were analyzed.

The high inter-subject variability was detected in the intact brain tissue (SUV in the frontal lobe (FL) varies from 0.47 to 1.73). Amino acid metabolism was more active in women than in men (FL SUV 1.32±0.22 and 1.05±0.24, respectively). T/N ratio better differentiates gliomas by the degree of anaplasia compared to SUV. Gliomas of Grade III (T/N=2.64±0.98) were significantly different (p<0.05) from those of Grade IV (T/N=3.83±0.75). The lowest level of methionine uptake was detected in diffuse astrocytomas (T/N=1.52±0.57), which was lower than with anaplastic astrocytomas (T/N=2.34±0.77, p<0.05).

¹¹C-methionine PET-CT was informative in the high/low degree of malignancy differentiation (T/N 1.66±0.71 for Grade I-II and 3.18±1.06 for Grade III-IV, p<0.05). The method was also useful in separating astrocytomas of Grade II and III. The considerable variation of SUV in the intact brain tissue as well as the difference in uptake between selected areas of the brain were revealed.