Photoacoustic imaging (PAI) is a non-ionizing modality that provides high spatiotemporal resolution and resolves optical absorbers at depth, allowing for potential simultaneous therapy monitoring with quantitative molecular imaging. Liposome-encapsulated J-aggregates of indocyanine green (Lipo-JICG) are a PAI agent that can be antibody-targeted and provide high-contrast imaging. Mice with ovarian tumors were injected with either targeted or untargeted Lipo-JICGs and imaged on the MSOT inVision PAI system before injection and immediately, 30-min, and 1-hour post-injection. Lipo-JICG contrast in the tumor was statistically significantly higher in the targeted mice, indicating success in molecular targeting and unmixing accuracy of Lipo-JICGs in vivo.
We present a novel method to pre-process magnetic relaxation (MRX) data. The method is used to estimates the initial magnetic field generated by Super Paramagnetic Nano Particles (SPIONs) from decay curves measured by superconducting quantum interference devices (SQUIDs). The curves are measured using a MagSense MRX Instrument (PrecisionMRX, Imagion Biosystems, Albuquerque, NM). We compare the initial field estimates to the standard method used by Imagion Biosystems. As compared to the standard method our new method results in more stable estimates in the presence of noise and allows monitoring of the long term stability of the MagSense MRX instrument. We demonstrate these findings with phantom scans conducted over the period of about one year.
Acute lymphoblastic leukemia (ALL) interacts with bone marrow cells, creating hypoxic niches that stabilize HIF-1α and promote chemotherapeutic resistance. Spectrosocopic photoacoustic (PA) imaging is a label-free, noninvasive technique that probes the in vivo oxygenation status of hemoglobin, resulting in a measurement of oxygen saturation (SO2) and providing a surrogate measure of tissue hypoxia. This work investigates multispectral PA imaging to assess the SO2 in the femoral bone marrow in mice. Preliminary work was performed to assess the capability of imaging through bone, followed by an oxygen challenge to determine the magnitude of systemic SO2 changes measurable in wild type mice. Furthermore, a pilot study to compare SO2 measured in a murine model of ALL versus in healthy controls was performed to investigate a correlation between SO2 changes in the femoral bone marrow and disease progression. Study results show that femoral SO2 can be measured with a variation less than 10% in wild type mice over multiple time-points. In the oxygen challenge, a 10% difference in systemic SO2 was observed between 100% and 21% O2 inhalation conditions. Additionally, leukemic mice demonstrate significantly more variation in femoral SO2 over the length of the femur than control mice at day 14 post-inoculation, indicating that femoral SO2 is affected by leukemic disease progression. This work demonstrates the feasibility of observing changes in leukemic disease progression through the measurement of SO2 with spectroscopic PA imaging, which could help develop a more complete understanding of the interplay of the local microenvironment with leukemogenesis.
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