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Tomography is published by MDPI from Volume 7 Issue 1 (2021). Previous articles were published by another publisher in Open Access under a CC-BY (or CC-BY-NC-ND) licence, and they are hosted by MDPI on mdpi.com as a courtesy and upon agreement with Grapho, LLC.

Tomography, Volume 5, Issue 4 (December 2019) – 5 articles

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2920 KiB

Open AccessArticle

Trimodal Cell Tracking In Vivo: Combining Iron- and Fluorine-Based Magnetic Resonance Imaging with Magnetic Particle Imaging to Monitor the Delivery of Mesenchymal Stem Cells and the Ensuing Inflammation

by Olivia C. Sehl, Ashley V. Makela, Amanda M. Hamilton and Paula J. Foster

Tomography 2019, 5(4), 367-376; https://doi.org/10.18383/j.tom.2019.00020 - 1 Dec 2019

Cited by 25 | Viewed by 1752

Abstract

The therapeutic potential of mesenchymal stem cells (MSCs) is limited, as many cells undergo apoptosis following administration. In addition, the attraction of immune cells (predominately macrophages) to the site of implantation can lead to MSC rejection. We implemented a trimodal imaging technique to monitor the fate of transplanted MSCs and infiltrating macrophages in vivo. MSCs were labeled with an iron oxide nanoparticle (ferumoxytol) and then implanted within the hind limb muscle of 10 C57BI/6 mice. Controls received unlabeled MSCs (n = 5). A perfluorocarbon agent was administered intravenously for uptake by phagocytic macrophages in situ; 1 and 12 days later, the ferumoxytol-labeled MSCs were detected by proton (1H) magnetic resonance imaging (MRI) and magnetic particle imaging (MPI). Perfluorocarbon-labeled macrophages were detected by fluorine-19 (19F) MRI. 1H/19F MRI was acquired on a clinical scanner (3 T) using a dual-tuned surface coil and balanced steady-state free precession (bSSFP) sequence. The measured volume of signal loss and MPI signal declined over 12 days, which is consistent with the death and clearance of iron-labeled MSCs. 19F signal persisted over 12 days, suggesting the continuous infiltration of perfluorocarbon-labeled macrophages. Because MPI and 19F MRI signals are directly quantitative, we calculated estimates of the number of MSCs and macrophages present over time. The presence of MSCs and macrophages was validated with histology following the last imaging session. This is the first study to combine the use of iron- and fluorine-based MRI with MPI cell tracking. Full article

1754 KiB

Open AccessArticle

Quantification of Human Central Adipose Tissue Depots: An Anatomically Matched Comparison Between DXA and MRI

by Christopher D. Crabtree, Richard A. LaFountain, Parker N. Hyde, Chong Chen, Yue Pan, Nathan Lamba, Teryn N. Sapper, Jay A. Short, Madison L. Kackley, Alex Buga, Vincent J. Miller, Debbie Scandling, Irma Andersson, Samantha Barker, Houchun H. Hu, Jeff S. Volek and Orlando P. Simonetti

Tomography 2019, 5(4), 358-366; https://doi.org/10.18383/j.tom.2019.00018 - 1 Dec 2019

Cited by 9 | Viewed by 1095

Abstract

Excess visceral adipose tissue (VAT) and VAT volume relative to subcutaneous adipose tissue (SAT) are associated with elevated health risks. This study compares fat measurements by dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI). In total, 21 control subjects (Control) and 16 individuals with metabolic syndrome (MetSyn) were scanned by DXA and MRI. The region measured by MRI was matched to the android region defined by DXA, and MRI reproducibility was also evaluated. In addition, liver fat fraction was quantified via MRI and whole-body fat by DXA. VAT measurements are interchangeable between DXA and MRI in the Control (R = 0.946), MetSyn (R = 0.968), and combined cohort (R = 0.983). VAT/SAT ratio did not differ in the Control group (P = .10), but VAT/SAT ratio measured by DXA was significantly higher in the MetSyn group (P < .01) and the combined (P = .03) cohort. Intraobserver (ICC = 0.998) and interobserver (ICC = 0.977) reproducibility of MRI VAT measurements was excellent. Liver fat fraction by MRI was higher (P = .001) in MetSyn (12.4% ± 7.6%) than in controls (2.6% ± 2.2%), as was whole-body fat percentage by DXA (P = .001) between the MetSyn (42.0% ± 8.1%) and Control groups (26.7% ± 6.9%). DXA and MRI VAT are interchangeable when measured over an anatomically matched region of the abdomen, while SAT and VAT/SAT ratio differ between the 2 modalities. Full article

2713 KiB

Open AccessArticle

Short-Term Environmental Conditioning Enhances Tumorigenic Potential of Triple-Negative Breast Cancer Cells

by Samantha S. Eckley, Johanna M. Buschhaus, Brock A. Humphries, Tanner H. Robison, Kathryn E. Luker and Gary D. Luker

Tomography 2019, 5(4), 346-357; https://doi.org/10.18383/j.tom.2019.00019 - 1 Dec 2019

Cited by 5 | Viewed by 1419

Abstract

Tumor microenvironments expose cancer cells to heterogeneous, dynamic environments by shifting availability of nutrients, growth factors, and metabolites. Cells integrate various inputs to generate cellular memory that determines trajectories of subsequent phenotypes. Here we report that short-term exposure of triple-negative breast cancer cells to growth factors or targeted inhibitors regulates subsequent tumor initiation. Using breast cancer cells with different driver mutations, we conditioned cells lines with various stimuli for 4 hours before implanting these cells as tumor xenografts and quantifying tumor progression by means of bioluminescence imaging. In the orthotopic model, conditioning a low number of cancer cells with fetal bovine serum led to enhancement of tumor-initiating potential, tumor volume, and liver metastases. Epidermal growth factor and the mTORC1 inhibitor ridaforolimus produced similar but relatively reduced effects on tumorigenic potential. These data show that a short-term stimulus increases tumorigenic phenotypes based on cellular memory. Conditioning regimens failed to alter proliferation or adhesion of cancer cells in vitro or kinase signaling through Akt and ERK measured by multiphoton microscopy in vivo, suggesting that other mechanisms enhanced tumorigenesis. Given the dynamic nature of the tumor environment and time-varying concentrations of small-molecule drugs, this work highlights how variable conditions in tumor environments shape tumor formation, metastasis, and response to therapy. Full article

558 KiB

Open AccessArticle

Defining Characteristics of Nodal Disease on PET/CT Scans in Patients With HIV-Positive and -Negative Locally Advanced Cervical Cancer in South Africa

by Carrie Anne Minnaar, Ans Baeyens, Olusegun Akinwale Ayeni, Jeffrey Allan Kotzen and Mboyo-Di-Tamba Vangu

Tomography 2019, 5(4), 339-345; https://doi.org/10.18383/j.tom.2019.00017 - 1 Dec 2019

Cited by 2 | Viewed by 1123

Abstract

Literature reports increased FDG nodal uptake in HIV-positive patients. Our aim is to identify differences in presentation and characteristics of FDG-avid lymph nodes between HIV-positive and HIV-negative locally advanced cervical cancer (LACC) patients in our clinical setting. We evaluated 250 pre-treatment ¹⁸F-FDG PET/CT imaging studies from women screened for a phase III randomised controlled trial investigating modulated electro-hyperthermia as a radiosensitiser (Ethics approval: M120477). The number of nodes; size; maximum standardised uptake value (SUVmax); symmetry; and relationship between nodal size and SUVmax uptake, were assessed by region and by HIV status. In total, 1314 nodes with a SUVmax ≥ 2.5 were visualised. Of 128(51%) HIV-positive participants, 82% were on antiretroviral therapy (ART) and 10 had a CD4 count four nodes visualised in the neck, symmetrical inguinal lymph nodes, increased rates of supraclavicular node visualisation; FDG-avid axillary nodes were more common, but not exclusive, in HIV-positive participants. ¹⁸F-FDG PET/CT is a reliable staging method for LACC in HIV-positive patients who are not in acute stages of HIV infection, have a CD4 count >200 cells/µL, and/or are on ART and there is a potential risk of underestimating metastatic spread by attributing increased nodal metabolic activity to HIV infection in these patients. Full article

1359 KiB

Open AccessArticle

Ex Vivo Human Placenta Perfusion, Metabolic and Functional Imaging for Obstetric Research—A Feasibility Study

by Katrine Elbæk Madsen, Christian Østergaard Mariager, Christina S. Duvald, Esben Søvsø Szocska Hansen, Lotte Bonde Bertelsen, Michael Pedersen, Lars Henning Pedersen, Niels Uldbjerg and Christoffer Laustsen

Tomography 2019, 5(4), 333-338; https://doi.org/10.18383/j.tom.2019.00016 - 1 Dec 2019

Cited by 11 | Viewed by 1223

Abstract

Placenta metabolism is closely linked to pregnancy outcome, and few modalities are currently available for studying the human placenta. Here, we aimed to investigate a novel ex vivo human placenta perfusion system for metabolic imaging using hyperpolarized [1-¹³C]pyruvate. The metabolic effects of 3 different human placentas were investigated using functional and metabolic magnetic resonance imaging. The placenta glucose metabolism and hemodynamics were characterized with hyperpolarized [1-¹³C]pyruvate magnetic resonance imaging and by dynamic contrast-enhanced (DCE) imaging. Hyperpolarized [1-¹³C]pyruvate showed a decrease in the ¹³C-lactate/¹³C-pyruvate ratio from the highest to the lowest metabolic active placenta. The metabolic profile was complemented by a more homogenous distributed hemodynamic response, with a longer mean transit time and higher blood volume. This study shows different placenta metabolic and hemodynamic features associated with the placenta functional status using hyperpolarized magnetic resonance ex vivo. This study supports further studies using ex vivo metabolic imaging of the placenta alterations associated with pregnancy complications. Full article

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Tomography, Volume 5, Issue 4 (December 2019) – 5 articles

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