PET and SPECT Imaging of the Brain: History, Technical Considerations, Applications, and Radiotracers

Advances in nuclear medicine have revolutionized our ability to accurately diagnose patients with a wide array of neurologic pathologies and provide appropriate therapy. The development of new radiopharmaceuticals has made possible the identification of regional differences in brain tissue composition and metabolism. In addition, the evolution of 3-dimensional molecular imaging followed by fusion with computed tomography and magnetic resonance imaging have allowed for more precise localization of pathologies. This review will introduce single photon emission computed tomography and positron emission tomographic imaging of the brain, including the history of their development, technical considerations, and a brief overview of pertinent radiopharmaceuticals and their applications

Advanced imaging techniques for neuro-oncologic tumor diagnosis, with an emphasis on PET-MRI imaging of malignant brain tumors

Purpose of review: This review will explore the latest in advanced imaging techniques, with a focus on the complementary nature of multiparametric, multimodality imaging using magnetic resonance imaging (MRI) and positron emission tomography (PET). Recent findings: Advanced MRI techniques including perfusion-weighted imaging (PWI), MR spectroscopy (MRS), diffusion-weighted imaging (DWI), and MR chemical exchange saturation transfer (CEST) offer significant advantages over conventional MR imaging when evaluating tumor extent, predicting grade, and assessing treatment response. PET performed in addition to advanced MRI provides complementary information regarding tumor metabolic properties, particularly when performed simultaneously. 18F-fluoroethyltyrosine (FET) PET improves the specificity of tumor diagnosis and evaluation of post-treatment changes. Incorporation of radiogenomics and machine learning methods further improve advanced imaging. The complementary nature of combining advanced imaging techniques across modalities for brain tumor imaging and incorporating technologies such as radiogenomics has the potential to reshape the landscape in neuro-oncology. Keywords: Advanced MRI; Amino acid PET; Brain tumor; Chemical exchange saturation transfer; Diffusion-weighted imaging; FET; Glioblastoma; Glioma; High-grade malignancy; Hybrid PET/MRI; MR spectroscopy; Metastasis; Perfusion-weighted imaging; Progression; Pseudoprogression; Pseudoresponse; Radiation necrosis; Radiogenomics; Radiomics; Treatment-related change; Tumor grading

Osteomacs interact with megakaryocytes and osteoblasts to regulate murine hematopoietic stem cell function

Networking between hematopoietic stem cells (HSCs) and cells of the hematopoietic niche is critical for stem cell function and maintenance of the stem cell pool. We characterized calvariae-resident osteomacs (OMs) and their interaction with megakaryocytes to sustain HSC function and identified distinguishing properties between OMs and bone marrow (BM)–derived macrophages. OMs, identified as CD45+F4/80+ cells, were easily detectable (3%-5%) in neonatal calvarial cells. Coculture of neonatal calvarial cells with megakaryocytes for 7 days increased OM three- to sixfold, demonstrating that megakaryocytes regulate OM proliferation. OMs were required for the hematopoiesis-enhancing activity of osteoblasts, and this activity was augmented by megakaryocytes. Serial transplantation demonstrated that HSC repopulating potential was best maintained by in vitro cultures containing osteoblasts, OMs, and megakaryocytes. With or without megakaryocytes, BM-derived macrophages were unable to functionally substitute for neonatal calvarial cell–associated OMs. In addition, OMs differentiated into multinucleated, tartrate resistant acid phosphatase–positive osteoclasts capable of bone resorption. Nine-color flow cytometric analysis revealed that although BM-derived macrophages and OMs share many cell surface phenotypic similarities (CD45, F4/80, CD68, CD11b, Mac2, and Gr-1), only a subgroup of OMs coexpressed M-CSFR and CD166, thus providing a unique profile for OMs. CD169 was expressed by both OMs and BM-derived macrophages and therefore was not a distinguishing marker between these 2 cell types. These results demonstrate that OMs support HSC function and illustrate that megakaryocytes significantly augment the synergistic activity of osteoblasts and OMs. Furthermore, this report establishes for the first time that the crosstalk between OMs, osteoblasts, and megakaryocytes is a novel network supporting HSC function

Simple Sequence Repeat Marker Development and Mapping Targeted to Previously Unmapped Regions of the Strawberry Genome Sequence.

The genome sequence of the woodland strawberry (Fragaria vesca L.) is an important resource providing a reference for comparative genomics studies and future sequenced rosaceous species and has great utility as a model for the development of markers for mapping in the cultivated strawberry Fragaria ×ananassa Duchesne ex Rozier. A set of 152 microsatellite simple sequence repeat (SSR) primer pairs was developed and mapped, along with 42 previously published but unmapped SSRs, permitting the precise assignment of 28.2 Mbp of previously unanchored genome sequence scaffolds (13% of the F. vesca genome sequence). The original ordering of F. vesca sequence scaffolds was performed without a physical map, using predominantly SSR markers to order scaffolds via anchoring to a comprehensive linkage map. This report complements and expands resolution of the Fragaria spp. reference map and refines the scaffold ordering of the F. vesca genome sequence using newly devised tools. The results of this study provide two significant resources: (i) the concurrent validation of a substantial set of SSRs associated with these previously unmapped regions of the Fragaria spp. genome and (ii) the precise placement of previously orphaned genomic sequence. Together, these resources improve the resolution and completeness of the strawberry genome sequence, making it a better resource for downstream studies in Fragaria spp. and the family Rosaceae

ORIGINAL RESEARCH Simple Sequence Repeat Marker Development and Mapping Targeted to Previously Unmapped Regions of the Strawberry Genome Sequence

The genome sequence of the woodland strawberry (Fragaria vesca L.) is an important resource providing a reference for comparative genomics studies and future sequenced rosaceous species and has great utility as a model for the development of markers for mapping in the cultivated strawberry Fragaria ×ananassa Duchesne ex Rozier. A set of 152 microsatellite simple sequence repeat (SSR) primer pairs was developed and mapped, along with 42 previously published but unmapped SSRs, permitting the precise assignment of 28.2 Mbp of previously unanchored genome sequence scaffolds (13 % of the F. vesca genome sequence). The original ordering of F. vesca sequence scaffolds was performed without a physical map, using predominantly SSR markers to order scaffolds via anchoring to a comprehensive linkage map. This report complements and expands resolution of the Fragaria spp. reference map and refi nes the scaffold ordering of the F. vesca genome sequence using newly devised tools. The results of this study provide two signifi cant resources: (i) the concurrent validation of a substantial set of SSRs associated with these previously unmapped regions of the Fragaria spp. genome and (ii) the precise placement of previously orphaned genomic sequence. Together, these resources improve the resolution and completeness of the strawberry genome sequence, making it a better resource for downstream studies in Fragaria spp. and the family Rosaceae