Comparison of (18)F-FET PET and 5-ALA fluorescence in cerebral gliomas.

PURPOSE: The aim of the study was to compare presurgical (18)F-fluoroethyl-L: -tyrosine ((18)F-FET) uptake and Gd-diethylenetriaminepentaacetic acid (DTPA) enhancement on MRI (Gd) with intraoperative 5-aminolevulinic acid (5-ALA) fluorescence in cerebral gliomas. METHODS: (18)F-FET positron emission tomography (PET) was performed in 30 patients with brain lesions suggestive of diffuse WHO grade II or III gliomas on MRI. PET and MRI data were coregistered to guide neuronavigated biopsies before resection. After oral application of 5-ALA, 38 neuronavigated biopsies were taken from predefined tumour areas that were positive or negative for (18)F-FET or Gd and checked for 5-ALA fluorescence. (18)F-FET uptake with a mean tumour to brain ratio ≥1.6 was rated as positive. RESULTS: Of 38 biopsies, 21 corresponded to high-grade glioma tissue (HGG) of WHO grade III (n = 19) or IV (n = 2) and 17 biopsies to low-grade glioma tissue (LGG) of WHO grade II. In biopsies corresponding to HGG, (18)F-FET PET was positive in 86% (18/21), but 5-ALA and Gd in only 57% (12/21). A mismatch between Gd and 5-ALA was observed in 6 of 21 cases of HGG biopsy samples (3 Gd-positive/5-ALA-negative and 3 Gd-negative/5-ALA-positive). In biopsies corresponding to LGG, (18)F-FET was positive in 41% (7/17), while 5-ALA and Gd were negative in all but one instance. All tumour areas with 5-ALA fluorescence were positive on (18)F-FET PET. CONCLUSION: There are differences between (18)F-FET and 5-ALA uptake in cerebral gliomas owing to a limited sensitivity of 5-ALA to detect tumour tissue especially in LGG. (18)F-FET PET is more sensitive to detect glioma tissue than 5-ALA fluorescence and should be considered as an additional tool in resection planning.

Regional impairment of 18F-FDG uptake in the cervical spinal cord in patients with monosegmental chronic cervical myelopathy.

OBJECTIVE: The aim of this preliminary report was to assess glucose metabolism in the cervical spine of patients with chronic compressive myelopathy by using FDG PET. METHODS: Ten patients with monosegmental chronic degenerative stenosis and local cord compression of the upper/middle cervical spine with signs of myelopathy on MRI and 10 control patients without known cervical abnormalities were investigated by FDG PET. Maximum standardised uptake values (SUV(max)) were measured at all levels of the cervical spine (C1-C7). RESULTS: While the controls showed the typical pattern of homogeneous linear FDG uptake along the entire cervical cord, the patients with chronic compressive myelopathy had a normal glucose utilisation only above the level of stenosis and a significant decrease in FDG uptake below their individual level of cord compression. This may be caused by atrophy of anterior grey horn cells and the loss of glucose-consuming neurons below the level of cord compression. CONCLUSION: FDG PET of the spine of patients with chronic compressive myelopathy may be helpful to determine the stage and severity of cervical myelopathy.

Prognostic value of 18F-fluoroethyl-L-tyrosine PET and MRI in small nonspecific incidental brain lesions.

UNLABELLED: Nonspecific incidental brain lesions (NILs) are being detected more frequently because of an increasing number of screening or research MRI scans of the brain, and their natural course is uncertain. METHODS: In a prospective cohort study starting in 1999, we determined the outcomes of patients with incidental, nonenhancing, supratentorial, lobar, and small-volume (<10 mL) lesions, depending on the findings of MRI and PET with the (18)F-labeled amino acid fluoroethyl-l-tyrosine ((18)F-FET). Patients with seizures, focal neurologic deficits, signs of local or systemic infection or inflammation, known brain disease, or any kind of previous cerebral treatment were excluded. Finally, 21 patients were eligible. MRI was performed in 19 of these patients because of nonspecific symptoms (such as headaches, dizziness, or sudden deafness), whereas 2 patients were healthy volunteers in MRI studies. Clinical follow-up and MRI scans were obtained at 4- to 6-mo intervals, and follow-up ranged from 3 to 8.5 y. Mean lesion-to-brain (L/B) ratios of >or=1.6 on (18)F-FET PET were rated as positive. RESULTS: Four different outcome groups were identified. In group A, 5 NILs regressed or vanished completely. All of these lesions were circumscribed on MRI, and (18)F-FET uptake was negative, with an L/B ratio of 1.2+/-0.2 (mean +/- SD). In group B, 10 NILs were stable, without growth. All of these lesions were circumscribed on MRI, and (18)F-FET uptake was negative (L/B ratio: 1.0+/-0.1). In group C, 2 NILs grew slowly over years, and an astrocytoma of World Health Organization (WHO) grade II was diagnosed after resection in each case. The lesions were circumscribed on MRI, and (18)F-FET uptake was negative (L/B ratios: 0.7 and 1.0). In group D, 4 NILs showed sudden and rapid growth, with clinical deterioration, and a high-grade glioma of WHO grade III or IV was diagnosed after resection in all cases. The lesions were diffuse on MRI, and (18)F-FET uptake was significantly increased (L/B ratio: 2.0+/-0.4) (P<0.01 for group D vs. group A or group B). CONCLUSION: For NILs, a circumscribed growth pattern on MRI and normal or low (18)F-FET uptake on PET are strong predictors for a benign course, with the eventual development of a low-grade glioma. In contrast, NILs with a diffuse growth pattern on MRI and increased (18)F-FET uptake indicate a high risk for the development of a high-grade glioma.

Multimodal metabolic imaging of cerebral gliomas: positron emission tomography with [18F]fluoroethyl-L-tyrosine and magnetic resonance spectroscopy.

OBJECT: The purpose of this study was to determine the predictive value of [18F]fluoroethyl-L-tyrosine (FET)-positron emission tomography (PET) and magnetic resonance (MR) spectroscopy for tumor diagnosis in patients with suspected gliomas. METHODS: Both FET-PET and MR spectroscopy analyses were performed in 50 consecutive patients with newly diagnosed intracerebral lesions supposed to be diffuse gliomas on contrast-enhanced MR imaging. Lesion/brain ratios of FET uptake greater than 1.6 were considered positive, that is, indicative of tumor. Results of MR spectroscopy were considered positive when N-acetylaspartate (NAA) was decreased in conjunction with an absolute increase of choline (Cho) and an NAA/Cho ratio of 0.7 or less. An FET lesion/brain ratio, an NAA/Cho ratio, and signal abnormalities on MR images were compared with histological findings in neuronavigated biopsy specimens. The FET lesion/brain ratio and the NAA/Cho ratio were identified as significant independent predictors for the histological identification of tumor tissue. The accuracy in distinguishing neoplastic from nonneoplastic tissue could be increased from 68% with the use of MR imaging alone to 97% with MR imaging in conjunction with FET-PET and MR spectroscopy. Sensitivity and specificity for tumor detection were 100 and 81% for MR spectroscopy and 88 and 88% for FET-PET, respectively. Results of histological studies did not reveal tumor tissue in any of the lesions that were negative on FET-PET and MR spectroscopy. In contrast, a tumor diagnosis was made in 97% of the lesions that were positive with both methods. CONCLUSIONS: In patients with intracerebral lesions supposed to be diffuse gliomas on MR imaging, FET-PET and MR spectroscopy analyses markedly improved the diagnostic efficacy of targeted biopsies.