Laminar optical tomography (LOT) is a new three-dimensional in vivo functional optical imaging technique. Adopting a microscopy-based setup and diffuse optical tomography (DOT) imaging principles, LOT can perform both absorption- and fluorescence-contrast imaging with higher resolution (100–200 μm) than DOT and deeper penetration (2–3 mm) than laser scanning microscopy. These features, as well as a large field of view and acquisition speeds up to 100 frames per second, make LOT suitable for depth-resolved imaging of stratified tissues such as retina, skin, endothelial tissues and the cortex of the brain. In this paper, we provide a detailed description of a new LOT system design capable of imaging both absorption and fluorescence contrast, and present characterization of its performance using phantom studies.

Background and Purpose To evaluate whether breath-holding (BH) BOLD fMRI can quantify differences in vascular reactivity (VR), as there is a need for improved contrast mechanisms in gliomas. Methods 16 patients (gliomas, grade II=5, III=2, IV=9) were evaluated using the BH paradigm: 4second single deep breath followed by 16seconds of BH and 40seconds of regular breathing for 5 cycles. VR was defined as the difference in BOLD signal between the minimal signal seen at the end of the deep breath and maximal signal seen at the end of BH (peak-to-trough). VR was measured for every voxel and compared for gray vs. white matter and tumor vs. normal contralateral brain. VR maps were compared to the areas of enhancement and FLAIR/T2 abnormality. Results VR was significantly lower in normal white matter than gray matter (p<0.05) and in tumors compared to the normal, contralateral brain (p<0.002). The area of abnormal VR (1103±659mm2) was significantly greater (p=0.019) than the enhancement (543±530mm2), but significantly smaller (p=0.0011) than the FLAIR abnormality (2363±1232mm2). However, the variability in the areas of gadolinium contrast enhancement versus VR abnormality indicates that the contrast mechanism elicited by BH (caused by abnormal arteriolar smooth muscles) appears to be fundamentally different from the contrast mechanism of gadolinium enhancement (caused by the presence of “leaky” gap junctions). Conclusions BH maps based on peak-to-trough can be used to characterize VR in brain tumors. VR maps in brain tumor patients appear to be caused by a different mechanism than gadolinium enhancement.

ETS-related gene (ERG) is a transcription factor that has been linked to angiogenesis. Very little research has been done to assess ERG expression in central nervous system (CNS) tumors. We evaluated 57 CNS tumors, including glioblastomas (GBMs) and hemangioblastomas (HBs), as well as two arteriovenous malformations and four samples of normal brain tissue with immunohistochemistry using a specific ERG rabbit monoclonal antibody. In addition, immunostains for CD31, CD34, and α-smooth muscle actin (α-SMA) were performed on all samples. CD31 demonstrated variable and sometimes weak immunoreactivity for endothelial cells. Furthermore, in 1 case of a GBM, CD34 stained not only endothelial cells, but also tumor cells. In contrast, we observed that ERG was only expressed in the nuclei of endothelial cells, for example, in the hyperplastic vascular complexes that comprise the glomeruloid microvascular proliferation seen in GBMs. Conversely, α-SMA immunoreactivity was identified in the abluminal cells of these hyperplastic vessels. Quantitative evaluation with automated methodology and custom Matlab 2008b software was used to calculate percent staining of ERG in each case. We observed significantly higher quantitative expression of ERG in HBs than in other CNS tumors. Our results show that ERG is a novel, reliable, and specific marker for endothelial cells within CNS tumors that can be used to better study the process of neovascularization.

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