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Determination of oxygen relaxivity in oxygen nanobubbles at 3 and 7 Tesla |
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| Authors: | Bluemke Emma Young Liam A J Owen Joshua Smart Sean Kinchesh Paul Bulte Daniel P Stride Eleanor |
| Affiliation: | 1.Department of Engineering Sciences, Institute of Biomedical Engineering, University of Oxford, Oxford, UK ;2.Radcliffe Department of Medicine, Oxford Centre for Clinical Magnetic Resonance Research, University of Oxford, Oxford, UK ;3.Clinical Center, National Institutes of Health, Bethesda, MD, USA ;4.Department of Oncology, Radiobiology Research Institute, University of Oxford, Oxford, UK ; |
| Abstract: | Objective Oxygen-loaded nanobubbles have shown potential for reducing tumour hypoxia and improving treatment outcomes, however, it remains difficult to noninvasively measure the changes in partial pressure of oxygen (PO2) in vivo. The linear relationship between PO2 and longitudinal relaxation rate (R1) has been used to noninvasively infer PO2 in vitreous and cerebrospinal fluid, and therefore, this experiment aimed to investigate whether R1 is a suitable measurement to study oxygen delivery from such oxygen carriers. MethodsT1 mapping was used to measure R1 in phantoms containing nanobubbles with varied PO2 to measure the relaxivity of oxygen (r1Ox) in the phantoms at 7 and 3 T. These measurements were used to estimate the limit of detection (LOD) in two experimental settings: preclinical 7 T and clinical 3 T MRI. ResultsThe r1Ox in the nanobubble solution was 0.00057 and 0.000235 s?1/mmHg, corresponding to a LOD of 111 and 103 mmHg with 95% confidence at 7 and 3 T, respectively. ConclusionThis suggests that T1 mapping could provide a noninvasive method of measuring a?>?100 mmHg oxygen delivery from therapeutic nanobubbles. |
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