Development and Initial Evaluation of an MR Compatible Preclinical SPECT Insert for Simultaneous SPECT/MR Imaging

Multi-modality medical imaging systems have become increasingly important in research and clinical applications of biomedical imaging. Two complementary imaging modalities that have not yet been fully integrated into a multimodality system are Single Photon Emission Computed Tomography (SPECT) and Magnetic Resonance Imaging (MRI). To this end, our team has developed an MR compatible SPECT insert for simultaneous preclinical SPECT/MR imaging. The SPECT insert’s detector is composed of five rings Cadmium Zinc Telluride (CZT) detector modules and an interchangeable cylindrical multi-pinhole (MPH) collimator. This dissertation discusses several new and significant contributions made towards the development of our SPECT insert. We developed methods to determine optimized design parameters for MPH collimators for the SPECT insert. These methods were used to design two MPH collimators with different imaging resolutions. Simulation results demonstrated that both collimators can be used to obtain artifact-free SPECT images with the designed resolutions. We then developed novel techniques to fabricate the collimators using MR compatible materials. Without proper system calibration and data correction, SPECT images reconstructed from data acquired with our insert exhibit poor image quality. We developed a novel energy calibration method to identify the photopeak of the gamma photons from a Tc-99m source at all 24,320 detector pixels simultaneously and a two-stage detector uniformity correction method to identify and correct for non-uniformities and malfunctioning pixels in the detector modules. Additionally, a method was developed to correct for the drift of electron-hole pairs within the detector modules due to the Lorentz force when operating the SPECT insert inside a magnetic field. After applying the system calibration and correction methods to the acquired data, reconstructed SPECT images showed significant improvement in terms of resolution, uniformity, contrast, and artifact reduction. Finally the SPECT insert was evaluated experimentally as a standalone SPECT system and as an insert inside an MRI system for simultaneous SPECT/MR imaging through phantom and small animal studies. The experimental results demonstrated that the SPECT insert met design specifications. Most importantly, results demonstrate that the insert can be used to obtain high quality SPECT images during simultaneous SPECT/MR image acquisition

Preclinical single photon emission computed tomography of alpha particle-emitting radium-223

Objective: Dose optimization and pharmacokinetic evaluation of α-particle emitting radium-223 dichloride (223RaCl2) by planar γ-camera or single photon emission computed tomography (SPECT) imaging are hampered by the low photon abundance and injected activities. In this study, we demonstrate SPECT of 223Ra using phantoms and small animal in vivo models. Methods: Line phantoms and mice bearing 223Ra were imaged using a dedicated small animal SPECT by detecting the low-energy photon emissions from 223Ra. Localization of the therapeutic agent was verified by whole-body and whole-limb autoradiography and its radiobiological effect confirmed by immunofluorescence. Results: A state-of-the-art commercial small animal SPECT system equipped with a highly sensitive collimator enables collection of sufficient counts for three-dimensional reconstruction at reasonable administered activities and acquisition times. Line sources of 223Ra in both air and in a water scattering phantom gave a line spread function with a full-width-at-half-maximum of 1.45 mm. Early and late-phase imaging of the pharmacokinetics of the radiopharmaceutical were captured. Uptake at sites of active bone remodeling was correlated with DNA damage from the α particle emissions. Conclusions: This work demonstrates the capability to noninvasively define the distribution of 223RaCl2, a recently approved α-particle-emitting radionuclide. This approach allows quantitative assessment of 223Ra distribution and may assist radiation-dose optimization strategies to improve therapeutic response and ultimately to enable personalized treatment planning

Development and Initial Evaluation of an MR Compatible Preclinical SPECT Insert for Simultaneous SPECT/MR Imaging

Multi-modality medical imaging systems have become increasingly important in research and clinical applications of biomedical imaging. Two complementary imaging modalities that have not yet been fully integrated into a multimodality system are Single Photon Emission Computed Tomography (SPECT) and Magnetic Resonance Imaging (MRI). To this end, our team has developed an MR compatible SPECT insert for simultaneous preclinical SPECT/MR imaging. The SPECT insert’s detector is composed of five rings Cadmium Zinc Telluride (CZT) detector modules and an interchangeable cylindrical multi-pinhole (MPH) collimator. This dissertation discusses several new and significant contributions made towards the development of our SPECT insert. We developed methods to determine optimized design parameters for MPH collimators for the SPECT insert. These methods were used to design two MPH collimators with different imaging resolutions. Simulation results demonstrated that both collimators can be used to obtain artifact-free SPECT images with the designed resolutions. We then developed novel techniques to fabricate the collimators using MR compatible materials. Without proper system calibration and data correction, SPECT images reconstructed from data acquired with our insert exhibit poor image quality. We developed a novel energy calibration method to identify the photopeak of the gamma photons from a Tc-99m source at all 24,320 detector pixels simultaneously and a two-stage detector uniformity correction method to identify and correct for non-uniformities and malfunctioning pixels in the detector modules. Additionally, a method was developed to correct for the drift of electron-hole pairs within the detector modules due to the Lorentz force when operating the SPECT insert inside a magnetic field. After applying the system calibration and correction methods to the acquired data, reconstructed SPECT images showed significant improvement in terms of resolution, uniformity, contrast, and artifact reduction. Finally the SPECT insert was evaluated experimentally as a standalone SPECT system and as an insert inside an MRI system for simultaneous SPECT/MR imaging through phantom and small animal studies. The experimental results demonstrated that the SPECT insert met design specifications. Most importantly, results demonstrate that the insert can be used to obtain high quality SPECT images during simultaneous SPECT/MR image acquisition

Timely Wildfire Perimeter Mapping for Unmanned Aerial Platforms

Wildfire perimeter mapping currently relies on deferred processing of data from manned and orbital platforms using hand-tuned physics-based models. We demonstrate real-time on-board multispectral data processing on cost-efficient unmanned aerial platforms using ML-based semantic segmentation

Associations between recreational cannabis legalization and cannabis-related emergency department visits by age, gender, and geographic status in Ontario, Canada: An interrupted time series study.

Legalization of recreational cannabis in Ontario included the legalization of flower and herbs (Phase 1, October 2018), and was followed by the deregulation of cannabis retailers and sales of edibles (Phase 2, February 2020). Research on the impact of cannabis legalization on acute care utilization is nascet; no research has investigated potential age, gender, and geographically vulnerable subgroup effects. Residents living in Northern Ontario not only have higher levels of substance use problems, but also have inadequate access to primary healthcare. Our study investigated the impact of Ontario's recreational cannabis policy (including Phase 1 and 2) on cannabis-attributable emergency department (ED) visits, and estimated the impact separately for different age and gender groups, with additional analyses focused on Northern Ontarians. We created a cohort of adults (18 and over) eligible for provincial universal health insurance with continuous coverage from 2015-2021 (n = 14,900,820). An interrupted time series was used to examine the immediate impact and month-to-month changes in cannabis-related ED visits associated with Phase 1 & 2 for each subgroup. While Northern Ontario has higher rates of cannabis-related ED visits, both Northern and Southern Ontario show similar patterns of changes. Phase 1 was associated with significant increases in adults 25-64, with the strongest increases seen in women 45-64. Month-to-month trends were flattened in most groups compared to pre-legalization. Phase 2 was associated with significant immediate increases for adults aged 18-44 in both genders, but the increases were larger in women than men. No significant month-to-month changes were detected in this period. While current preventive efforts are largely focused on reducing cannabis-related harms in youths and younger adults, our results show that adults 25-64, particularly women, have been significantly impacted by cannabis policies. Further research on gender-specific cannabis dosage and targeted interventions for adult women should be investigated. Legalization did not appear to have a differential impact on Northern versus Southern Ontario, but higher rates of ED visits in the North should be addressed

Preclinical Single Photon Emission Computed Tomography of Alpha Particle-Emitting Radium-223

Objective: Dose optimization and pharmacokinetic evaluation of α-particle emitting radium-223 dichloride (223RaCl2) by planar γ-camera or single photon emission computed tomography (SPECT) imaging are hampered by the low photon abundance and injected activities. In this study, we demonstrate SPECT of 223Ra using phantoms and small animal in vivo models. Methods: Line phantoms and mice bearing 223Ra were imaged using a dedicated small animal SPECT by detecting the low-energy photon emissions from 223Ra. Localization of the therapeutic agent was verified by whole-body and whole-limb autoradiography and its radiobiological effect confirmed by immunofluorescence. Results: A state-of-the-art commercial small animal SPECT system equipped with a highly sensitive collimator enables collection of sufficient counts for three-dimensional reconstruction at reasonable administered activities and acquisition times. Line sources of 223Ra in both air and in a water scattering phantom gave a line spread function with a full-width-at-half-maximum of 1.45 mm. Early and late-phase imaging of the pharmacokinetics of the radiopharmaceutical were captured. Uptake at sites of active bone remodeling was correlated with DNA damage from the α particle emissions. Conclusions: This work demonstrates the capability to noninvasively define the distribution of 223RaCl2, a recently approved α-particle-emitting radionuclide. This approach allows quantitative assessment of 223Ra distribution and may assist radiation-dose optimization strategies to improve therapeutic response and ultimately to enable personalized treatment planning

Reducing readmission rates for individuals discharged from acute psychiatric care in Alberta using peer and text message support: Protocol for an innovative supportive program

Abstract Background Individuals discharged from inpatient psychiatry units have the highest readmission rates of all hospitalized patients. These readmissions are often due to unmet need for mental health care compounded by limited human resources. Reducing the need for hospital admissions by providing alternative effective care will mitigate the strain on the healthcare system and for people with mental illnesses and their relatives. We propose implementation and evaluation of an innovative program which augments Mental Health Peer Support with an evidence-based supportive text messaging program developed using the principles of cognitive behavioral therapy. Methods A pragmatic stepped-wedge cluster-randomized trial, where daily supportive text messages (Text4Support) and mental health peer support are the interventions, will be employed. We anticipate recruiting 10,000 participants at the point of their discharge from 9 acute care psychiatry sites and day hospitals across four cities in Alberta. The primary outcome measure will be the number of psychiatric readmissions within 30 days of discharge. We will also evaluate implementation outcomes such as reach, acceptability, fidelity, and sustainability. Our study will be guided by the Consolidated Framework for Implementation Research, and the Reach-Effectiveness-Adoption-Implementation-Maintenance framework. Data will be extracted from administrative data, surveys, and qualitative methods. Quantitative data will be analysed using machine learning. Qualitative interviews will be transcribed and analyzed thematically using both inductive and deductive approaches. Conclusions To our knowledge, this will be the first large-scale clinical trial to assess the impact of a daily supportive text message program with and without mental health peer support for individuals discharged from acute psychiatric care. We anticipate that the interventions will generate significant cost-savings by reducing readmissions, while improving access to quality community mental healthcare and reducing demand for acute care. It is envisaged that the results will shed light on the effectiveness, as well as contextual barriers and facilitators to implementation of automated supportive text message and mental health peer support interventions to reduce the psychological treatment and support gap for patients who have been discharged from acute psychiatric care. Trial registration clinicaltrials.gov, NCT05133726 . Registered 24 November 202