Cranial Neuronavigation with Direct Integration of ¹¹C Methionine Positron Emission Tomography (PET) Data – Results of a Pilot Study in 32 Surgical Cases

Summary.

Summary.

 

Background:

MRI detects small intracranial lesions, but has difficulties in differentiating between tumour, gliosis and edema. ¹¹C methionine-PET may help to overcome this problem. For its appropriate intra-operative use, it must be integrated into neuronavigation. We present the results of our pilot study with this method.

 

Method:

32 patients with 34 intracranial lesions detected by MRI underwent additional ¹¹C methionine-PET, because the pathophysiological behaviour or the tumour delineation was unclear. All lesions were treated surgically. In 25 patients PET data could be integrated directly into cranial neuronavigation.

 

Findings:

¹¹C methionine uptake was observed in 27/34 lesions, 26 of them were tumours: 14 malignant and 7 benign gliomas, 3 gliomas without further histological typing, one Ewing sarcoma and one non-Hodgkin lymphoma. Only one ¹¹C methionine positive lesion was non-tumourous: it was staged as post-irradiation necrosis in a patient operated on for a malignant glioma. 3/7 ¹¹C-methionine negative lesions were classified as gliosis (n=2) and M. Whipple (n=1), but 4/7 were tumours: 2 astrocytomas WHO^°II, 1 DNT and one astrocytoma WHO^°III. The sensitivity of ¹¹C methionine-PET was 87%, the specifity 75%, the positive predictive value 96% and the negative predictive value 43%. In all tumourous cases with positive tracer uptake the borderline area of the tumour was better defined by ¹¹C methionine-PET than by MRI.

 

Interpretation:

A positive ¹¹C methionine-PET is highly suspicious of a tumour, a negative one does not exclude it. ¹¹C methionine-PET seems to be more sensitive than MRI for differentiating between tumour and edema or gliosis. Simultaneous integration MRI and ¹¹C methionine-PET into cranial neuronavigation can facilitate cross total tumour removal in glioma surgery.