[11C]-Methionine PET: dysembryoplastic neuroepithelial tumours compared with other epileptogenic brain neoplasms

EANM practice guidelines for an appropriate use of PET and SPECT for patients with epilepsy

Epilepsy is one of the most frequent neurological conditions with an estimated prevalence of more than 50 million people worldwide and an annual incidence of two million. Although pharmacotherapy with anti-seizure medication (ASM) is the treatment of choice, ~30% of patients with epilepsy do not respond to ASM and become drug resistant. Focal epilepsy is the most frequent form of epilepsy. In patients with drug-resistant focal epilepsy, epilepsy surgery is a treatment option depending on the localisation of the seizure focus for seizure relief or seizure freedom with consecutive improvement in quality of life. Beside examinations such as scalp video/electroencephalography (EEG) telemetry, structural, and functional magnetic resonance imaging (MRI), which are primary standard tools for the diagnostic work-up and therapy management of epilepsy patients, molecular neuroimaging using different radiopharmaceuticals with single-photon emission computed tomography (SPECT) and positron emission tomography (PET) influences and impacts on therapy decisions. To date, there are no literature-based praxis recommendations for the use of Nuclear Medicine (NM) imaging procedures in epilepsy. The aims of these guidelines are to assist in understanding the role and challenges of radiotracer imaging for epilepsy; to provide practical information for performing different molecular imaging procedures for epilepsy; and to provide an algorithm for selecting the most appropriate imaging procedures in specific clinical situations based on current literature. These guidelines are written and authorized by the European Association of Nuclear Medicine (EANM) to promote optimal epilepsy imaging, especially in the presurgical setting in children, adolescents, and adults with focal epilepsy. They will assist NM healthcare professionals and also specialists such as Neurologists, Neurophysiologists, Neurosurgeons, Psychiatrists, Psychologists, and others involved in epilepsy management in the detection and interpretation of epileptic seizure onset zone (SOZ) for further treatment decision. The information provided should be applied according to local laws and regulations as well as the availability of various radiopharmaceuticals and imaging modalities.

[11C]-methionine positron emission tomography in the evaluation of pediatric low-grade gliomas

Background

[11C]-Methionine positron emission tomography (PET; [11C]-MET-PET) is principally used for the evaluation of brain tumors in adults. Although amino acid PET tracers are more commonly used in the evaluation of pediatric brain tumors, data on [11C]-MET-PET imaging of pediatric low-grade gliomas (pLGG) is scarce. This study aimed to investigate the roles of [11C]-MET-PET in the evaluation of pLGGs.

Methods

Eighteen patients with newly diagnosed pLGG and 26 previously treated pLGG patients underwent [11C]-MET-PET met the inclusion and exclusion criteria. Tumor-to-brain uptake ratio (TBR) and metabolic tumor volumes were assessed for diagnostic performances (newly diagnosed, 15; previously treated 26), change with therapy (newly diagnosed, 9; previously treated 7), and variability among different histology (n = 12) and molecular markers (n = 7) of pLGGs.

Results

The sensitivity of [11C]-MET-PET for diagnosing pLGG, newly diagnosed, and previously treated combined was 93% for both TBRmax and TBRpeak, 76% for TBRmean, and 95% for qualitative evaluation. TBRmax showed a statistically significant reduction after treatment, while other PET parameters showed a tendency to decrease. Median TBRmax, TBRpeak, and TBRmean values were slightly higher in the BRAFV600E mutated tumors compared to the BRAF fused tumors. Median TBRmax, and TBRpeak in diffuse astrocytomas were higher compared to pilocytic astrocytomas, but median TBRmean, was slightly higher in pilocytic astrocytomas. However, formal statistical analysis was not done due to the small sample size.

Conclusions

Our study shows that [11C]-MET-PET reliably characterizes new and previously treated pLGGs. Our study also shows that quantitative parameters tend to decrease with treatment, and differences may exist between various pLGG types.

Pediatric Imaging Using PET/MR Imaging

PET/MR imaging is a one-stop shop technique for pediatric diseases allowing not only an accurate clinical assessment of tumors at staging and restaging but also the diagnosis of neurologic, inflammatory, and infectious diseases in complex cases. Moreover, applying PET kinetic analyses and sequences such as diffusion-weighted imaging as well as quantitative analysis investigating the relationship between disease metabolic activity and cellularity can be applied. Complex radiomics analysis can also be performed.

Diverse Patterns and Clinical Significance of 11C-Methionine PET in Dysembryoplastic Neuroepithelial Tumors

PURPOSE

Dysembryoplastic neuroepithelial tumors (DNETs) are slow-growing epilepsy-associated tumors. Low or normal 11C-methionine (MET) PET uptake helps to differentiate DNETs from other low-grade gliomas. However, diverse MET-PET uptake in DNETs has been observed. The aim of this study is to measure the clinical significance and prognostic value of MET-PET in DNET management.

PATIENTS AND METHODS

Retrospective review of 26 DNET patients was done. Clinical characteristics, radiologic findings, and visual and quantitative MET-PET results were analyzed. PET uptake was calculated as the tumor-to-homotopic mirror ratio (TNRm) and tumor-to-contralateral cortex ratio (TNRc). The clinical activity of the tumors at the time of PET was classified into active and quiescent groups. The surgical outcome was defined as a composite of 2 different aspects: tumor progression and/or clinical events such as seizure recurrence or tumor bleeding.

RESULTS

Twenty-seven MET-PET examinations (20 initial MET-PET and 7 MET-PET during follow-up) were included. Clinically active tumors at the time of PET presented significantly higher values of TNRm and TNRc than quiescent tumors. High MET-PET uptake by visual grading, TNRm ≥ 1.90, and TNRc ≥ 1.85 exhibited poor prognosis for event-free survival.

CONCLUSIONS

MET-PET uptake correlates well with the clinical behavior of DNETs at the time of PET examination. Moreover, High MET-PET uptake is closely related to seizure recurrence if tumors are not entirely resected. Efforts to achieve gross total resection should be made for DNETs with high MET-PET uptake.

BRAF V600E mutation mediates FDG-methionine uptake mismatch in polymorphous low-grade neuroepithelial tumor of the young

We present a case of a 14-year old boy with tumor-associated refractory epilepsy. Positron emission tomography imaging demonstrated a region with heterogeneous high ¹¹C-methionine uptake and a region with homogenous low ¹⁸F-fluorodeoxyglucose uptake within the tumor. Histopathological and genomic analyses confirmed the tumor as BRAF V600E-mutated polymorphous low-grade neuroepithelial tumor of the young (PLNTY). Within the high-methionine-uptake region, we observed increased protein levels of L-type amino acid transporter 1 (LAT1), a major transporter of methionine; c-Myc; and constituents of the mitogen-activated protein kinase (MAPK) pathway. We also found that LAT1 expression was linked to the BRAF V600E mutation and subsequent activation of MAPK signaling and c-Myc. Pharmacological and genetic inhibition of the MAPK pathway suppressed c-Myc and LAT1 expression in BRAF V600E-mutated PLNTY and glioblastoma cells. The BRAF inhibitor dabrafenib moderately suppressed cell viability in PLNTY. Collectively, our results indicate that BRAF V600E mutation-activated MAPK signaling and downstream c-Myc induces specific metabolic alterations in PLNTY, and may represent an attractive target in the treatment of the disease.

BRAF V600E mutation mediates FDG-methionine uptake mismatch in polymorphous low-grade neuroepithelial tumor of the young

We present a case of a 14-year old boy with tumor-associated refractory epilepsy. Positron emission tomography imaging demonstrated a region with heterogeneous high ¹¹C-methionine uptake and a region with homogenous low ¹⁸F-fluorodeoxyglucose uptake within the tumor. Histopathological and genomic analyses confirmed the tumor as BRAF V600E-mutated polymorphous low-grade neuroepithelial tumor of the young (PLNTY). Within the high-methionine-uptake region, we observed increased protein levels of L-type amino acid transporter 1 (LAT1), a major transporter of methionine; c-Myc; and constituents of the mitogen-activated protein kinase (MAPK) pathway. We also found that LAT1 expression was linked to the BRAF V600E mutation and subsequent activation of MAPK signaling and c-Myc. Pharmacological and genetic inhibition of the MAPK pathway suppressed c-Myc and LAT1 expression in BRAF V600E-mutated PLNTY and glioblastoma cells. The BRAF inhibitor dabrafenib moderately suppressed cell viability in PLNTY. Collectively, our results indicate that BRAF V600E mutation-activated MAPK signaling and downstream c-Myc induces specific metabolic alterations in PLNTY, and may represent an attractive target in the treatment of the disease.

FDOPA PET-CT of Nonenhancing Brain Tumors

BACKGROUND

Primary brain tumor grading is crucial to rapidly determine the therapeutic impact and prognosis of a brain tumor as well as the tumors' aggressiveness profile. On magnetic resonance imaging, high-grade tumors are usually responsible for blood -brain barrier breakdowns, which result in tumor enhancement. However, this is not always the case. The main objective of this study was to evaluate the diagnostic value of FDOPA PET in the assessment of primary brain tumor aggressiveness with no contrast enhancement on MRI.

METHODS

Fifty-three patients were prospectively included: 35 low-grade and 18 high-grade histologically proven gliomas, with no contrast enhancement. Each patient underwent static PET acquisitions at 30 minutes. All patients had MRSI with measurements of different metabolites ratio.

RESULTS

FDOPA was useful in the subgroup of low-grade gliomas, discriminating between dysembryoplastic neuroepithelial tumor and grade II oligodendroglioma (P < 0.01). An optimal threshold of the maximum standardized uptake value at 30 minutes (SUVmax (T/N)30) = 2.16 to discriminated low- from high-grade gliomas with a sensitivity of 60%, specificity of 100%, PPV of 100%, and NPV of 83.33% (P < 0.01). The nCho/Cr and nCho/NAA ratios were significantly higher in high- than in low-grade gliomas (P < 0.03 and P < 0.04, respectively). A significant positive correlation between MRSI ratios and SUVmax was found.

CONCLUSION

Including data from amino acid metabolism used alone or in association with MRSI allows us to discriminate between dysembryoplastic neuroepithelial tumor and grade II oligodendroglioma and between low- and high-grade gliomas with no contrast enhancement on MRI.

PET and SPECT studies in children with hemispheric low-grade gliomas

Molecular imaging is playing an increasing role in the pretreatment evaluation of low-grade gliomas. While glucose positron emission tomography (PET) can be helpful to differentiate low-grade from high-grade tumors, PET imaging with amino acid radiotracers has several advantages, such as better differentiation between tumors and non-tumorous lesions, optimized biopsy targeting, and improved detection of tumor recurrence. This review provides a brief overview of single-photon emission computed tomography (SPECT) studies followed by a more detailed review of the clinical applications of glucose and amino acid PET imaging in low-grade hemispheric gliomas. We discuss key differences in the performance of the most commonly utilized PET radiotracers and highlight the advantage of PET/MRI fusion to obtain optimal information about tumor extent, heterogeneity, and metabolism. Recent data also suggest that simultaneous acquisition of PET/MR images and the combination of advanced MRI techniques with quantitative PET can further improve the pretreatment and post-treatment evaluation of pediatric brain tumors.

Accuracy of distinguishing between dysembryoplastic neuroepithelial tumors and other epileptogenic brain neoplasms with [¹¹C]methionine PET

BACKGROUND

Dysembryoplastic neuroepithelial tumors (DNTs) represent a prevalent cause of epileptogenic brain tumors, the natural evolution of which is much more benign than that of most gliomas. Previous studies have suggested that [(11)C]methionine positron emission tomography (MET-PET) could help to distinguish DNTs from other epileptogenic brain tumors, and hence optimize the management of patients. Here, we reassessed the diagnostic accuracy of MET-PET for the differentiation between DNT and other epileptogenic brain neoplasms in a larger population.

METHODS

We conducted a retrospective study of 77 patients with focal epilepsy related to a nonrapidly progressing brain tumor on MRI who underwent MET-PET, including 52 with a definite histopathology. MET-PET data were assessed by a structured visual analysis that distinguished normal, moderately abnormal, and markedly abnormal tumor methionine uptake and by semiquantitative ratio measurements.

RESULTS

Pathology showed 21 DNTs (40%), 10 gangliogliomas (19%), 19 low-grade gliomas (37%), and 2 high-grade gliomas (4%). MET-PET visual findings significantly differed among the various tumor types (P < .001), as confirmed by semiquantitative analyses (P < .001 for all calculated ratios), regardless of gadolinium enhancement on MRI. All gliomas and gangliogliomas were associated with moderately or markedly increased tumor methionine uptake, whereas 9/21 DNTs had normal methionine uptake. Receiver operating characteristics analysis of the semiquantitative ratios showed an optimal cutoff threshold that distinguished DNTs from other tumor types with 90% specificity and 89% sensitivity.

CONCLUSIONS

Normal MET-PET findings in patients with an epileptogenic nonrapidly progressing brain tumor are highly suggestive of DNT, whereas a markedly increased tumor methionine uptake makes this diagnosis unlikely.

Choosing the tumoral epilepsy surgery candidate

The management of epilepsy is an essential clinical issue in many patients with brain tumors. Tumoral epilepsy is often drug resistant and is associated with poor quality of life. Surgery represents a key therapeutic option in the management of patients with refractory tumoral epilepsy, with high rates of postoperative seizure freedom, especially when gross total resection can be performed. The selection of surgical candidates first requires extrapolation of the presumed underlying pathology and its potential for malignant transformation from clinical and imaging data, especially MRI characteristics. These data determine the decision for surgery, as well as its timing and technical aspects in relation to the risk of postoperative deficit. In glioneuronal tumors, where seizures are often drug-resistant and risk of malignant transformation is very low, epilepsy surgery is usually recommended to alleviate disabling seizures and side effects of antiepileptic drugs. However, the risk of postoperative deficit may outweigh potential benefits of surgery in tumors located within eloquent cortex. This issue is particularly relevant for glioneuronal tumors located within the dominant mesial temporal structures in patients in whom seizure control might require additional hippocampectomy, associated with a high risk of memory decline. In contrast, in patients with low-grade gliomas or aggressive brain neoplasms, both the decision to perform surgery and selection of the best surgical approach primarily rely on the oncologic imperative rather than epileptologic considerations. In these patients, the extent of tumor resection correlates with improved survival, progression-free survival, as well as with the chances of postoperative seizure control.

Epilepsy surgery of dysembryoplastic neuroepithelial tumors using advanced multitechnologies with combined neuroimaging and electrophysiological examinations

Purpose

We report three cases of dysembryoplastic neuroepithelial tumor (DNT) with intractable epilepsy which were successfully treated with surgery.

Methods

In all cases, technology beyond the routine workup was critical to success. Preoperative magnetic resonance imaging, ¹⁸F-fluorodeoxyglucose positron emission tomography (PET), ¹¹C-methionine-PET, interictal electroencephalography, and intraoperative electrocorticography were utilized in all patients. In individual cases, however, additional procedures such as preoperative magnetoencephalography (Case 1), diffusion tensor fiber tractography, a neuronavigation system, and intraoperative somatosensory-evoked potential (Case 2), and fiber tractography and the neuronavigation-guided fence-post tube technique (Case 3) were instrumental.

Results

In all the cases, the objectives of total tumor resection, resection of the epileptogenic zone, and complete postoperative seizure control and the avoidance of surgical complications were achieved.

Conclusions

Dysembryoplastic neuroepithelial tumor is commonly associated with medically intractable epilepsy, and surgery is frequently utilized. As DNT may arise in any supratentorial and intracortical locations within or near the critical area of the brain, meticulous surgical strategies are necessary to avoid neurological deficits. We demonstrate in the following three cases how adjunct procedures using advanced multitechnologies with neuroimaging and electrophysiological examinations may be utilized to ensure success in DNT surgery.

Increased tryptophan transport in epileptogenic dysembryoplastic neuroepithelial tumors

Dysembryoplastic neuroepithelial tumors (DNTs) are typically hypometabolic but can show increased amino acid uptake on positron emission tomography (PET). To better understand mechanisms of amino acid accumulation in epileptogenic DNTs, we combined quantitative α-[(11)C]methyl-L: -tryptophan (AMT) PET with tumor immunohistochemistry. Standardized uptake values (SUVs) of AMT and glucose were measured in 11 children with temporal lobe DNT. Additional quantification for AMT transport and metabolism was performed in 9 DNTs. Tumor specimens were immunostained for the L: -type amino acid transporter 1 (LAT1) and indoleamine 2,3-dioxygenase (IDO), a key enzyme of the immunomodulatory kynurenine pathway. All 11 tumors showed glucose hypometabolism, while mean AMT SUVs were higher than normal cortex in eight DNTs. Further quantification showed increased AMT transport in seven and high AMT metabolic rates in three DNTs. Two patients showing extratumoral cortical increases of AMT SUV had persistent seizures despite complete tumor resection. Resected DNTs showed moderate to strong LAT1 and mild to moderate IDO immunoreactivity, with the strongest expression in tumor vessels. These results indicate that accumulation of tryptophan in DNTs is driven by high amino acid transport, mediated by LAT1, which can provide the substrate for tumoral tryptophan metabolism through the kynurenine pathway, that can produce epileptogenic metabolites. Increased AMT uptake can extend to extratumoral cortex, and presence of such cortical regions may increase the likelihood of recurrent seizures following surgical excision of DNTs.

A patient with a dysembryoplastic neuroepithelial tumor who underwent epilepsy surgery after initial seizure

BACKGROUND

Since dysembryoplastic neuroepithelial tumors (DNTs) are benign tumors that are frequently associated with long-standing medically intractable epilepsy, it is well known that the surgical strategy is resection of the associated epileptogenic zone as well as the tumor. However, the surgical strategy for DNT with a single seizure has not been fully discussed.

METHODS

We report an 8-year-old boy with DNT in the nondominant frontal lobe who underwent epilepsy surgery at 3 months after his initial seizure.

RESULTS

An intraoperative electrocorticogram revealed frequent paroxysmal cortical activity lateral to the tumor. Since resection of the tumor resulted in persistent paroxysmal activity in this cortex, additional resection was performed. The histological findings in the cortex revealed the presence of cortical dysplasia (CD) (Palmini type IIA). Lesionectomy alone might have left the epileptogenic CD.

CONCLUSION

It is thought that epilepsy surgery should be recommended in patients with typical neuroimaging findings of DNT, even if the patients had only one episode of seizure.

18Fluoroethyl-L-tyrosine-PET in long-term epilepsy associated glioneuronal tumors

PURPOSE

Long-term epilepsy associated tumors (LEATs) are a frequent cause of drug-resistant partial epilepsy. A reliable tumor diagnosis has an important impact on therapeutic strategies and prognosis in patients with epilepsy, but often is difficult by magnetic resonance imaging (MRI) only. Herein we analyzed a large LEAT cohort investigated by 18fluoroethyl-L-tyrosine-positron emission tomography (FET-PET).

METHODS

Thirty-six patients with chronic partial epilepsy and a LEAT-suspect MRI lesion were analyzed by FET-PET using visual inspection and quantitative analysis of standard uptake values (SUV). PET results were correlated with clinical and histopathologic data.

RESULTS

FET-PET study was positive in 22 of 36 analyzed lesions and in 14 of 22 histologically verified LEAT lesions. The precise World Health Organization (WHO) tumoral entity was not predicted by FET-PET. Notably, FET uptake correlated strikingly with age at epilepsy onset (p = 0.001). Further correlations were seen for age at surgery (p = 0.007) and gadolinium-contrast enhancement on MRI (p < 0.05).

DISCUSSION

FET-PET is a helpful tool for LEAT diagnosis, particularly when MRI readings are ambiguous. FET uptake, which is likely mediated by the l-amino acid transporter (LAT) family, might indicate a principally important biologic property of certain LEATs, since LAT molecules also are involved in cell growth regulation.

Differential kinetics of α-[¹¹C]methyl-L-tryptophan on PET in low-grade brain tumors

Increased tryptophan metabolism via the kynurenine pathway is a major mechanism of tumor immuno-resistance. α-[(11)C]Methyl-L: -tryptophan (AMT) is a positron emission tomography (PET) tracer for tryptophan catabolism, and increased AMT uptake has been demonstrated in brain tumors. In this study we evaluated the use of AMT PET for detection of low-grade gliomas and glioneuronal tumors, and determined if kinetic parameters of AMT uptake can differentiate among tumor types. AMT PET images were obtained in 23 patients with newly diagnosed low-grade brain tumors (WHO grade II gliomas and WHO grade I dysembryoplastic neuroepithelial tumors [DNETs]). Kinetic variables, including the unidirectional uptake rate (K-complex) and volume of distribution (VD; which characterizes tracer transport), were measured using a graphical approach from tumor dynamic PET and blood-input data, and metabolic rates ([Formula: see text]) were also calculated. These values as well as tumor/cortex ratios were compared across tumor types. AMT PET showed increased tumor/cortex K-complex (n = 16) and/or VD ratios (n = 15) in 21/23 patients (91%), including 11/13 tumors with no gadolinium enhancement on MRI. No increases in AMT were seen in an oligodendroglioma and a DNET. Astrocytomas and oligoastrocytomas showed higher [Formula: see text] tumor/cortex ratios (1.66 ± 0.46) than oligodendrogliomas (0.96 ± 0.21; P = 0.001) and DNETs (0.75 ± 0.39; P < 0.001). These results demonstrate that AMT PET identifies most low-grade gliomas and DNETs by high uptake, even if these tumors are not contrast-enhancing on MRI. Kinetic analysis of AMT uptake shows significantly higher tumor/cortex tryptophan metabolic ratios in astrocytomas and oligoastrocytomas in comparison with oligodendrogliomas and DNETs.

The Children's Cancer and Leukaemia Group guidelines for the diagnosis and management of dysembryoplastic neuroepithelial tumours

Dysembryoplastic neuroepithelial tumours (DNETs) were incorporated into the new World Health Organization classification of brain tumours as part of the group of glioneuronal tumours in 1993. Large series of patients with DNETs and pharmaco-resistant epilepsy have been reported. DNETs are most often located in the temporal lobe, occurring in both mesial and lateral temporal locations. DNETs have also been reported in the insular cortex, brain stem, cerebellum, occipital lobe and striatum. Approximately 40% of DNETs are cystic, and solitary nodular, multinodular or diffuse forms have been recognized. Approximately 30% of DNETs are associated with subtle cortical dysplastic changes in the adjacent cortex. DNET nodules usually look like oligodendroglioma, whilst between the nodules it may be possible to recognize vertical columns of neurons surrounded by oligodendrocyte-like cells. Cytologically, oligodendroglial-like cells of DNETs are distinguished from oligodendroglioma by larger nuclei with frequent nuclear indentations and multiple, small nucleoli, whilst oligodendrogliomas consistently show nuclear roundness with one or two occasional nucleoli. Very rare cases of malignant transformation have been reported. DNETs are hypodense on CT and demonstrate decreased signal on the T1-weighted images and a hyper-intense signal on T2-weighted MRI. DNETs associated with pharmaco-resistant epilepsy should be removed early to achieve seizure freedom and prevent tumour progression. The surgical approach should be that of an extended lesionectomy, i.e. excision of the lesion and the abnormal dysplastic cortex around it. Use of MRI-based image guidance (neuronavigation) as a surgical tool to identify this area of abnormal cortex is very helpful to ensure that the extended lesionectomy includes any visibly dysplastic cortex. It is not advocated to use a stereotactic biopsy only, as this may generate an unrepresentative tissue sample consisting of an oligodendroglial component only and may lead to an incorrect diagnosis.

Role of neuroimaging in the presurgical evaluation of epilepsy

A significant minority of patients with focal epilepsy are candidates for resective epilepsy surgery. Structural and functional neuroimaging plays an important role in the presurgical evaluation of theses patients. The most frequent etiologies of pharmacoresistant epilepsy in the adult population are mesial temporal sclerosis, malformations of cortical development, cavernous angiomas, and low-grade neoplasms. High-resolution multiplanar magnetic resonance imaging (MRI) with sequences providing T1 and T2 contrast is the initial imaging study of choice to detect these epileptogenic lesions. The epilepsy MRI protocol can be individually tailored when considering the patient's clinical and electrophysiological data. Metabolic imaging techniques such as positron emission tomography (PET) and single photon emission tomography (SPECT) visualize metabolic alterations of the brain in the ictal and interictal states. These techniques may have localizing value in patients with a normal MRI scan. Functional MRI is helpful in non-invasively identifying areas of eloquent cortex.Developments in imaging technology and digital postprocessing may increase the yield for imaging studies to detect the epileptogenic lesion and to characterize its connectivity within the epileptic brain.

PET imaging in the surgical management of pediatric brain tumors

OBJECTIVE

The present article illustrates whether positron-emission tomography (PET) imaging may improve the surgical management of pediatric brain tumors (PBT) at different steps.

MATERIALS AND METHODS

Among 400 consecutive PBT treated between 1995 and 2005 at Erasme Hospital, Brussels, Belgium, we have studied with (18) F-2-fluoro-2-deoxy-D-glucose (FDG)-PET and/or L-(methyl-(11)C)methionine (MET)-PET and integrated PET images in the diagnostic workup of 126 selected cases. The selection criteria were mainly based on the lesion appearance on magnetic resonance (MR) sequences. Cases were selected when MR imaging showed limitations for (1) assessing the evolving nature of an incidental lesion (n = 54), (2) selecting targets for contributive and accurate biopsy (n = 32), and (3) delineating tumor tissue for maximal resection (n = 40). Whenever needed, PET images were integrated in the planning of image-guided surgical procedures (frame-based stereotactic biopsies (SB), frameless navigation-based resections, or leksell gamma knife radiosurgery).

RESULTS

Like in adults, PET imaging really helped the surgical management of the 126 children explored, which represented about 30% of all PBT, especially when the newly diagnosed brain lesion was (1) an incidental finding so that the choice between surgery and conservative MR follow-up was debated, and (2) so infiltrative or ill-defined on MR that the choice between biopsy and resection was hardly discussed. Integrating PET into the diagnostic workup of these two selected groups helped to (1) take a more appropriate decision in incidental lesions by detecting tumor/evolving tissue; (2) better understand complex cases by differentiating indolent and active components of the lesion; (3) improve target selection and diagnostic yield of stereotactic biopsies in gliomas; (4) illustrate the intratumoral histological heterogeneity in gliomas; (5) provide additional prognostic information; (6) reduce the number of trajectories in biopsies performed in eloquent areas such as the brainstem or the pineal region; (7) better delineate ill-defined PBT infiltrative along functional cortex than magnetic resonance imaging (MRI); (8) increase significantly, compared to using MRI alone, the number of total tumor resection and the amount of tumor tissue removed in PBT for which a total resection is a key-factor of survival; (9) target the resection on more active areas; (10) improve detection of tumor residues in the operative cavity at the early postoperative stage; (11) facilitate the decision of early second-look surgery for optimizing the radical resection; (12) improve the accuracy of the radiosurgical dosimetry planning.

CONCLUSIONS

PET imaging may improve the surgical management of PBT at the diagnostic, surgical, and post-operative steps. Integration of PET in the clinical workup of PBT inaugurates a new approach in which functional data can influence the therapeutic decision process. Although metabolic information from PET are valid and relevant for the clinical purposes, further studies are needed to assess whether PET-guidance may decrease surgical morbidity and increase children survival.

The use of SPECT and PET in routine clinical practice in epilepsy

PURPOSE OF REVIEW

The aim of this article is to give a subjective review of the usefulness of single photon emission computed tomography (SPECT) and positron emission tomography (PET) imaging in clinical practice in epilepsy for 2007.

RECENT FINDINGS

Both ictal perfusion SPECT and interictal fluorodeoxyglucose PET can provide new information in the presurgical evaluation of intractable partial epilepsy. These functional imaging modalities reflect dynamic seizure-related changes in cerebral cellular functions. Although asymmetry of fluorodeoxyglucose PET metabolism has been useful to localize the epileptic temporal lobe, which tends to be more hypometabolic than the contralateral one, both frontal lobes are more hypometabolic than the epileptic temporal lobe, and may represent a region of 'surround inhibition'. Due to its low temporal resolution, ictal perfusion SPECT hyperperfusion patterns often contain both the ictal onset zone and propagation pathways. These patterns often have a multilobulated 'hourglass' appearance. The largest and most intense hyperperfusion cluster often represents ictal propagation, and does not always need to be resected in order to render a patient seizure free.

SUMMARY

Optimized interictal FDG-PET and ictal perfusion SPECT as part of a multimodality imaging platform will be important tools to better understand the neurobiology of epilepsy and to better define the epileptogenic, ictal onset, functional deficit and surround inhibition zones in refractory partial epilepsy.

Positron emission tomography: clinical applications in oncology. Part 2

This review continues from a previous review on this topic, which was published in the December issue. In that review, the role of positron emission tomography in lung cancer, lymphoma, breast cancer, head and neck cancer, gastroesophageal cancer, colorectal cancer, malignant melanoma, bone tumors and ovarian cancer was discussed. In this review, the role of positron emission tomography in other malignancies, such as gynecological malignancies other than ovary, pancreatic cancer, hepatocellular cancer, gastrointestinal tumors, urological malignancies, neuroendocrine tumors, adrenocortical tumors, soft-tissue sarcomas, pituitary and brain tumors, is discussed.