Abnormal metabolism of tryptophan has been implicated in modulation of tumor cell proliferation and immunoresistance. a-[ 11 C]Methyl-L-tryptophan (AMT) is a PET tracer to measure cerebral tryptophan metabolism in vivo. In the present study, we have measured tumor tryptophan uptake in 40 patients with primary brain tumors using AMT PET and standard uptake values (SUV). Tryptophan metabolism was further quantified in 23 patients using blood input data. Estimates of the volume of distribution (VD 0 ) and the metabolic rate constant (k 3 0 ) were calculated and related to magnetic resonance imaging (MRI) and histology findings. All grade II to IV gliomas and glioneuronal tumors showed increased AMT SUV, including all recurrent/residual tumors. Gadolinium enhancement on MRI was associated with high VD 0 values, suggesting impaired blood-brain barrier, while k 3 0 values were not related to contrast enhancement. Low-grade astrocytic gliomas showed increased tryptophan metabolism, as measured by k 3 0 . In contrast, oligodendrogliomas showed high VD 0 values but lower k 3 0 as compared with normal cortex. In astrocytic tumors, low grade was associated with high k 3 0 and lower VD 0 , while high-grade tumors showed the reverse pattern. The findings show high AMT uptake in primary and residual/recurrent gliomas and glioneuronal tumors. Increased AMT uptake can be due to increased metabolism of tryptophan and/ or high volume of distribution, depending on tumor type and grade. High tryptophan metabolic rates in low-grade tumors may indicate activation of the kynurenine pathway, a mechanism regulating tumor cell growth. AMT PET might be a useful molecular imaging method to guide therapeutic approaches aimed at controlling tumor cell proliferation by acting on tryptophan metabolism.

Summary: Purpose:We studied the relation between quantitative interictal subdural EEG data and visually defined ictal subdural EEG findings in children with intractable neocortical epilepsy, and determined whether interictal EEG data are predictive of ictal EEG onset zones.Methods: Thirteen children (aged 1.2-15.4 years) underwent prolonged intracranial EEG recording, using 48-to 120-channel subdural electrodes. Three distinct 10-min segments of the continuous interictal EEG recording were selected for each patient, and the spike frequency for each channel was determined by using an automatic spike-detection program. Subsequently the average spike frequency of each electrode was compared with ictal assessment (onset, spread, and no early ictal involvement). In addition, 50 distinct interictal spikes were averaged for each patient, and the amplitude and latency after the leading spike (averaged spike showing the earliest peak) were measured for each electrode and analyzed with respect to ictal EEG findings.Results: Reproducibility of the spike-frequency pattern derived from three 10-min segments was high (Kendall's W, 0.85 ± 0.08). Electrodes showing the highest spike frequency, the highest spike amplitude, and the leading spike were found to be a part of the seizure onset in 13 of 13, 12 of 13, and 10 of 13 cases, respectively. There was significant correlation between ictal assessment and spike frequency as well as spike amplitude. A receiver operating characteristics analysis showed that a cutoff threshold at 14% of the maximal spike frequency resulted in a specificity of 0.90 and a sensitivity of 0.77 for the detection of seizure-onset electrodes.Conclusions: Quantitative interictal subdural EEG may predict ictal-onset zones in children with intractable neocortical epilepsy. Key Words: Clinical neurophysiology-Pediatric epilepsy surgery-Quantitative interictal intracranial electroencephalography-Focal cortical dysplasia-Tuberous sclerosis complex.Cortical resection is an effective treatment for selected children with medically intractable partial epilepsy of neocortical origin (1). To delineate the exact resection margin in patients with neocortical epilepsy, prolonged subdural EEG recordings are frequently used in most epilepsy surgery centers (2). It is generally assumed that epileptogenic cortex includes seizure-onset zones, regions consistently receiving early ictal propagation, regions showing independent frequent interictal epileptiform activity, and structural lesions delineated on neuroimaging (1). Complete resection of seizure-onset zones after prolonged intracranial EEG recording does not necessarily result in a good surgical outcome (3-6).In addition, previous studies reported that >70% of patients with developmental cortical malformations showed interictal epileptiform activity beyond structural lesions and involving several lobes (4,7). Thus the assessment of intracranial interictal epileptiform activity in addition to ictal-onset zones is currently considered important in the presurgical evaluat...

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The authors describe the incidence and various uptake patterns of Tc-99m sestamibi (MIBI) in the extracardiac area due to unusual causes on myocardial perfusion single photon emission computed tomography (SPECT) studies. Seven patients are presented in whom incidental extracardiac findings were observed during the interpretation of the raw data besides the routine evaluation of myocardial reconstructed SPECT slices. These 7 patients were detected out of 582 consecutive patients (1.2%) who had myocardial perfusion SPECT with Tc-99m MIBI. The findings on the raw data led to additional reconstruction of thoracic SPECT images and eventually detailed examination of the extracardiac area. Two of the patients underwent surgery because of incidental extracardiac findings (thymoma and multinodular goiter) on cardiac scintigraphy. Other causes of increased extracardiac activity were the intestine protruded through the left hemithorax, uptake in the pulmonary arterial wall, and pulmonary interstitial fibrosis due to sarcoidosis. The reasons for decreased Tc-99m MIBI accumulation in the extracardiac area in the 2 other patients were significantly dilated pulmonary arteries and hydatic cyst, which were not defined before to our knowledge. Familiarity with the normal biodistribution and variable uptake patterns in the raw images becomes necessary during the interpretation of myocardial SPECT in order not to miss very unusual incidental extracardiac uptake or information that could lead to alteration in patient management. Potential underlying mechanisms of extracardiac Tc-99m MIBI accumulation are discussed, and the literature about noncardiac Tc-99m MIBI findings detected on myocardial perfusion SPECT studies was reviewed.

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(99m)Tc-MDP uptake can be observed in the intestines in 1% of bone scans with a prominent localization in the ascending colon and rarely all over the intestines or in thorax due to Chilaiditi's syndrome, as well. The mechanism of intestinal uptake is still unclear in some of the patients. Delayed imaging, additional spot views and SPECT studies help in the differentiation of this finding from possible misinterpretation. Intestinal (99m)Tc-MDP uptake on bone scan could be an intermittent process and should be included among other well-known reasons of soft-tissue uptake.