BACKGROUND AND PURPOSE:Cerebral perfusion assessment is important in the preoperative evaluation and postoperative follow-up of patients with Moyamoya disease. The objective of this study was to evaluate the correlation of quantitative CBF measurements performed with arterial spin-labeling-MR imaging and H 2 [15 O]-PET in children and young adults with Moyamoya disease.

The gamma aminobutyric acid (GABA) neurotransmission system has been implicated in autism spectrum disorder (ASD). Molecular neuroimaging studies incorporating simultaneous acquisitions of GABA concentrations and GABA A receptor densities can identify objective molecular markers in ASD. We measured both total GABA A receptor densities by using [ 18 F]flumazenil positron emission tomography ([ 18 F]FMZ-PET) and GABA concentrations by using proton magnetic resonance spectroscopy ( 1 H-MRS) in 28 adults with ASD and in 29 age-matched typically developing (TD) individuals. Focusing on the bilateral thalami and the left dorsolateral prefrontal cortex (DLPFC) as our regions of interest, we found no differences in GABA A receptor densities between ASD and TD groups. However, 1 H-MRS measurements revealed significantly higher GABA/Water (GABA normalized by water signal) in the left DLPFC of individuals with ASD than that of TD controls. Furthermore, a significant gender effect was observed in the thalami, with higher GABA/Water in males than in females. Hypothesizing that thalamic GABA correlates with ASD symptom severity in gender-specific ways, we stratified by diagnosis and investigated the interaction between gender and thalamic GABA/Water in predicting Autism Quotient (AQ) and Ritvo Autism Asperger’s Diagnostic Scale – Revised (RAADS-R) total scores. We found that gender is a significant effect modifier of thalamic GABA/Water’s relationship with AQ and RAADS-R scores for individuals with ASD, but not for TD controls. When we separated the ASD participants by gender, a negative correlation between thalamic GABA/Water and AQ was observed in male ASD participants. Remarkably, in female ASD participants, a positive correlation between thalamic GABA/Water and AQ was found.

For many years the laboratory mouse has been used as the standard model for in vivo oncology research, particularly in the development of novel PET tracers, but the growth of tumors on chicken chorioallantoic membrane (CAM) provides a more rapid, low cost, and ethically sustainable alternative. For the first time, to our knowledge, we demonstrate the feasibility of in vivo PET and CT imaging in a U87 glioblastoma tumor model on chicken CAM, with the aim of applying this model for screening of novel PET tracers. Methods: U87 glioblastoma cells were implanted on the CAM at day 11 after fertilization and imaged at day 18. A small-animal imaging cell was used to maintain incubation and allow anesthesia using isoflurane. Radiotracers were injected directly into the exposed CAM vasculature. Sodium 18 F-fluoride was used to validate the imaging protocol, demonstrating that image-degrading motion can be removed with anesthesia. Tumor glucose metabolism was imaged using 18 F-FDG, and tumor protein synthesis was imaged using 2-18 F-fluoro-L-tyrosine. Anatomic images were obtained by contrast-enhanced CT, facilitating clear delineation of the tumor, delineation of tracer uptake in tumor versus embryo, and accurate volume measurements. Results: PET imaging of tumor glucose metabolism and protein synthesis was successfully demonstrated in the CAM U87 glioblastoma model. Catheterization of CAM blood vessels facilitated dynamic imaging of glucose metabolism with 18 F-FDG and demonstrated the ability to study PET tracer uptake over time in individual tumors, and CT imaging improved the accuracy of tumor volume measurements. Conclusion: We describe the novel application of PET/CT in the CAM tumor model, with optimization of typical imaging protocols. PET imaging in this valuable tumor model could prove particularly useful for rapid, high-throughput screening of novel radiotracers. PETi maging has proved an indispensable tool in oncology research and in clinical oncology (1). 18 F-FDG has been widely used to study tumor proliferation and metastasis in vivo, and radiotracers targeting specific proteins expressed on tumor cells are constantly under development (2). In recent years, there has been a substantial growth in the use of combined PET and CT imaging, both in the clinic and for small-animal research. This combination yields functional imaging data with useful anatomic information.For many years the laboratory mouse has been used as the standard model for in vivo oncology research, particularly in the development of novel PET tracers. However, despite their wide use in oncology research, mouse models obviously require all usual aspects of animal husbandry, necessitating cost and taking up valuable lab space. In particular, rodent models can be limited in their usefulness by difficulty in obtaining exact measures of tumor progression (such as volume) (3). Ethical issues relating to animal suffering and public opinion are also of increasing concern (4). Clearly, an alternative could be useful.The chicken chorioallantoic membra...

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• ILT occurrence in AAA is associated with increasing FDG uptake and growth. • MRI signalling changes in ILT reflect activities such as haemorrhage and RBC trapping. • Monitoring ILT activities using MRI may require no exogenous contrast agent.