Biomedical Physics Seminars - Feb 13
Please join us for the Biomedical Physics Seminar Series.
TITLE: OPTICAL STUDY OF HEMOGLOBIN FORM CONVERSIONS OF BIOTISSUE OPTICAL AND OPTOACOUSTIC PHANTOMS
Student: Xiao Juan Zheng
Supervisor: Dr. Alexandre Douplik
ABSTRACT: Hemoglobin (Hb) molecules present in red blood cells have several critical roles in addition oxygen transportation to tissue. Hb carries photosensitizer substances in photodynamic therapy, though the interaction of the heme group with the light and the substrate resulting in oxygen reactive species. Optical and optoacoustic imaging (OA) are sensitive to different forms of Hb due to the relative strong absorption of Hb. . Light propagation can have significant impact in optical and OA specially in using multi wavelengths approach to detect different forms of Hb. Monitoring hemoglobin (Hb) remains challenging specially in the presence of the reactive oxygen species as it reacts with oxyhemoglobin (oxy-Hb) to form methemoglobin (Met-Hb), another form of hemoglobin. This study will focus on Hb forms conversion in liquid and silicon based phantom. Human Met-Hb sample was obtained by dissolving the lyophilized powder in phosphate buffered saline (PBS), later converted to deoxyhemoglobin (deoxy-Hb) and oxy-Hb. The different Hb forms were validated by measuring its optical absorption (from 300-1000 nm), then compared and confirmed with absorption spectra from Oregon Medical Laser Center (OMLC). Blood containing silicon phantoms with photosensitizer additive were created to conduct photochemical reaction of reducing oxy-Hb to deoxy-Hb. This involved irradiating the phantoms to active the photochemical reaction. The efficiency of various photosensitizer concentrations and irradiation time was determined by measuring the optical absorption (from 300-1000 nm) in each phantom.
TITLE: IN VIVO DETECTION OF LANTHANUM VIA X-RAY FLUORESCENCE
Student: Joanna Nguyen
Supervisor: Dr. James Grafe
ABSTRACT: Lanthanum (La) is a rare-earth metal used in phosphate binders in the form of a chewable tablet called lanthanum carbonate (LaC), commercially known as Fosrenol®. The daily high intake of LaC in patients with end-stage kidney disease is needed to reduce serum phosphate concentrations within normal range. Past studies have employed invasive bone biopsy sampling to show La accumulation in bone after long-term administration of LaC. However, the potential risks associated with long-term bone retention of La are unknown. In this work, we investigate the feasibility of using a K X-ray Fluorescence (K-XRF) spectroscopy system to quantitatively and non-invasively measure in vivo bone La. A series of hydroxyapatite (HAp) bone mineral phantoms doped with various concentrations of La were created to represent human bone. The HAp phantoms were placed in a 90° geometry relative to a bulky 1.11 GBq 241Am excitation source and high-purity germanium detector. For a live-time measurement of 2000 s, the initial minimum detection limit (MDL) was calculated to be 2.32 μg La/g Ca or 0.93 μg La/g HAp. However, for a newly acquired lead-collimated 241Am source, the MDL improved to 1.9 μg La/g Ca or 0.75 μg La/g HAp. This improvement in the MDL shows promising results and demonstrates the capabilities of this system as a non-invasive technique to monitor the long-term accumulation of La in bone. To the best of our knowledge, this is the first reported work that seeks to non-invasively measure bone La via in vivo XRF.