Add to Calendar 2024-04-29T10:00:00 2024-04-29T12:00:00 An analysis of imaging and biological effects impacting theranostic dosimetry using radiopharmaceutical pairs Event Information: Abstract:   Radiopharmaceutical therapy (RPT) is a safe and effective cancer treatment using alpha or beta emitting radiopharmaceuticals that specifically target cancer cells to selectively destroy cancer tissue while sparing healthy cells. Treatment can be personalized on a patient-by-patient basis using dosimetry to determine suitable administered activities for subsequent treatment cycles. Dosimetry requires obtaining quantitative single photon emission computed tomography (SPECT) images which can only be done using gamma emitting radioisotopes.   Not all therapeutic radioisotopes are suitable for SPECT imaging. In such cases, it may be necessary to use an imaging surrogate to predict the radiation dose from the therapeutic isotope, either pre-therapy or during combination RPT. However, these methods may introduce inaccuracies into the dosimetry estimate. This dissertation aims to investigate some “theranostic pair” radiopharmaceuticals and determine if these pairs may be suitable for theranostic dosimetry.   In addition to a comprehensive literature review of theranostic dosimetry and the validity of multiple theranostic pairs used clinically and pre-clinically, three Monte Carlo based simulation studies are performed:     - First, an investigation into the theranostic pair 177Lu (a beta/gamma emitter) and 90Y (a beta emitter) to determine if Bremstrahhlung photons emitted by 90Y reduce the accuracy of quantitative SPECT imaging of 177Lu   - Then, simulations of 225Ac (an alpha emitter) and 177Lu within prostate cancer cells were performed and used to create nucleus absorbed dose kernels which were convolved with multicellular tumour maps of varying morphologies (i.e. hypoxic, necrotic, and normoxic tumour phenotypes) to assess the absorbed dose distribution differences between particulate radiation from 225Ac and 177Lu on a microscopic scale   - Finally, the proposition of a novel method using 99mTc (a gamma emitter) to improve bone marrow dosimetry is discussed and tested. Bone marrow dosimetry during RPT for prostate cancer with 177Lu labelled pharmaceuticals is extremely challenging, and we propose using 99mTc-sulfur colloids to assist in the determination of bone marrow location during imaging and subsequently use 177Lu for bone marrow dosimetry, which requires simultaneous SPECT imaging of 177Lu and 99mTc.  We test the feasibility of this and suggest additions to clinical scatter correction methods to reduce the impact of photon contamination from 177Lu on 99mTc images.   Event Location: 14th floor meeting room, BC Cancer Research Institute

Add to Calendar 2024-05-03T10:00:00 2024-05-03T12:00:00 Emergent optical and electronic properties in atomically thin rhombohedral-stacked transition metal dichalcogenides Event Information: Abstract: Rhombohedral(R)-stacked TMD means the neighbouring layers are oriented in the same direction, which can be obtained through either chemical synthesis or artificial stack with a small twist. The investigation into how the stacking order determines the properties of TMD homobilayers is crucial for understanding the exotic physics observed in two-dimensional semiconductors. Here we use various optical spectroscopy techniques to explore the emergent excitonic and correlated phenomena in both homogeneous and twisted TMD homobilayers of rhombohedral stacking. Specifically, we observe a spontaneous electrical polarization arising from the asymmetric interlayer-coupling-induced Berry phase in R-stacked MoS2 bilayer. Utilizing this polarization, we achieve an efficient and scalable photovoltaic effect in a Gr/R-MoS2/Gr heterostructure. By employing non-degenerate pump-probe photocurrent spectroscopy, we disentangle the competition between thermal and electronic effects, extracting a 2ps intrinsic photocurrent speed. More importantly, the out-of-plane electrical polarization in R-stacked MoS2 can be switched through in-plane sliding motion, which is referred to as sliding ferroelectricity. By harnessing the coupling between electronic polarization and excitonic effects, we demonstrate an optical method to probe the domain wall motion in both R-stacked MoS2 homo-bilayer and tri-layer.  Finally, we report the discovery of a series of correlated insulating states at both integer and fractional fillings, arising from Γ-valley flat bands, in a small-angle twisted MoSe2 homo-bilayer. We observe a Mott-insulator state instead of a semi-metal on the half-filled honeycomb lattice, in contrast to the theoretical prediction based on continuum model. The observed phenomenon is consistent with the picture of semi-metal to insulator transition at large U/t limit. Our exploration on the moire homo-bilayer in rhombohedral stacking offers a new opportunity to simulate the Mott-Hubbard physics with spin SU (2) symmetry. Event Location: QMI 188 (2355 East Mall)