Artifacts caused by head motion are a substantial source of error in fMRI that limits its use in neuroscience research and clinical settings. Real-time scan-plane correction by optical tracking has been shown to correct slice misalignment and non-linear spin-history artifacts, however residual artifacts due to dynamic magnetic field non-uniformity may remain in the data. A recently developed correction technique, PLACE, can correct for absolute geometric distortion using the complex image data from two EPI images, with slightly shifted k-space trajectories. We present a correction approach that integrates PLACE into a real-time scan-plane update system by optical tracking, applied to a tissue-equivalent phantom undergoing complex motion and an fMRI finger tapping experiment with overt head motion to induce dynamic field non-uniformity. Experiments suggest that including volume by volume geometric distortion correction by PLACE can suppress dynamic geometric distortion artifacts in a phantom and in vivo and provide more robust activation maps.

Artifacts caused by regional anesthesia can influence image interpretation of ultrasound and nuclear scintigraphy. Perineural and intrasynovial anesthesia is commonly performed prior to magnetic resonance imaging (MRI); and the effects on MR images, if any, is unknown. The objectives of this prospective, randomized, blinded experiment were to determine if perineural and intrasynovial anesthesia of structures in the equine foot cause iatrogenic changes detectable with MRI. A baseline MRI of both front feet was performed on 15 horses 2 to 6 days prior to mepivacaine injection adjacent to the lateral and medial palmar digital nerves (PDN), and into the podotrochlear bursa (PB), digital flexor tendon sheath (DFTS), and distal interphalangeal joint (DIPJ) of one randomly assigned forelimb. MRI was repeated at 24 and 72 hours post-injection; then qualitative and quantitative assessments of MRI findings were performed. The results of this study showed MRI findings associated with the PDN, PB and DIPJ at 24 and 72 hours after mepivacaine injection did not alter significantly from those at baseline. Compared to baseline, a significant increase in synovial fluid volume of the DFTS was detected with MRI at 24 and 72 hours post-injection. Therefore, perineural anesthesia of the PDN and intrasynovial anesthesia of the PB or DIPJ did not interfere with the interpretation of MRI examinations performed at 24 or 72 hours after injection. However, intrasynovial anesthesia of the DFTS caused an iatrogenic increase in synovial fluid, which was detectable on MRI for at least 72 hours. Although a definite time frame for resolution of DFTS distension was not determined, we recommend waiting greater than 3 days between intrasynovial anesthesia of the DFTS and evaluation with MRI. / Equine Guelph

Multiple-mouse MRI (MMMRI) accelerates biomedical research by imaging multiple mice simultaneously. To date, MMMRI has been explored in three ways: shielded transmit-receive coils, shielded transmits coil with separate unshielded receive coils; and finally shielded transmit-receive coils with independent gradient coils. However alternative transmit coil configurations and possible benefits of eliminating shielding have not yet been explored. The goal of this thesis is to test possible radiofrequency configurations with and without shielding for the purpose of improving image quality for MMMRI. Results demonstrate that using an unshielded transmit-receive coil array provided a 20% improvement over an identical shielded coil. A new unshielded 7-coil MMMRI array is presented, minimizing the ghosting between image overlap using mutual inductance minimization and a sensitivity encoding (SENSE) reconstruction. The final array provided high resolution images (90µm) of up to seven live mice simultaneously with appropriate signal-to-noise for automated analysis.

Functional magnetic resonance imaging (fMRI) has become a widely used technique for non-invasive brain mapping, and methods have now evolved to allow fMRI of the spinal cord (spinal fMRI) as well. With the goal of improving spinal fMRI, the studies presented herein have investigated potential sources of noise that might limit its sensitivity and reliability. For example, multiple studies had previously suggested that the majority of structured physiological noise, such as spinal cord motion and cerebrospinal fluid (CSF) flow, appeared to be synchronous with cardiac pulsations. Therefore, we measured cardiac-related spinal cord motion at various levels along the cord, finding that peak anterior-posterior spinal cord displacements often exceeded 0.5 mm throughout the cervical and upper-thoracic regions. On the other hand, we found that cord motion throughout the lower-thoracic, lumbar and sacral levels was consistently small. Based on these findings, we concluded that cord motion is likely to be a significant source of error in spinal fMRI throughout superior, but not inferior, cord regions. Since all motion measurements were acquired at 24 phases of the cardiac cycle, this also allowed us to determine, and subsequently model, the main components of cardiac-related spinal cord motion. By then including these terms in a general linear model (GLM) analysis and reanalyzing 100 previously acquired cervical spinal fMRI datasets, we showed that the sensitivity and specificity were improved by 15-20 % and 5-6 %, respectively, over previous spinal fMRI methods. To push the limits of these improvements, we then carried out the first event-related spinal fMRI study, consistently observing spinal cord responses to 1 s applications of 22 °C thermal stimulation. By measuring these responses at many different phases, we were also able, for the first time, to characterize the impulse response function of SEEP (signal enhancement by extravascular water protons) contrast in the human cervical spinal cord. / Thesis (Ph.D, Neuroscience Studies) -- Queen's University, 2010-08-23 13:35:36.534

No description available.

This thesis presents the design of a personal computer (PC) based needle insertion robotic manipulator for biopsy. The robot was designed and built using materials available in the research laboratory. The robot is intended primarily for use inside the confined area of a cylindrical magnetic resonance (MR) scanner. Selection of the robot geometry and novel locations for drive actuators allowed placement of actuators outside the MRI bore. The robot is modeled using Denavit-Hartenberg transformations. Custom developed software control is developed to test the functional aspects of the robot. The robot performs to the tolerance required for the stated clinical application. This thesis addresses only proof of concept chosen for the manipulator design and is not ready for any clinical trials. The work also addresses MRI compatible and safety issues and recommends appropriate materials for future development. Traditionally, neurosurgical navigation has relied on preoperative images and the assumption that anatomical structures of interest remain in the same position with respect to each other and the fiducial markers used for registration. However, during surgery, tissue deformation and shift disrupt the spatial relation between the patient and the preoperative image volumes. This results in localization errors. Developing a manipulator that works inside an imaging machine guided by real time images is expected to minimize the problem of “tissue shift” during the surgery.

Artifacts caused by head motion are a substantial source of error in fMRI that limits its use in neuroscience research and clinical settings. Real-time scan-plane correction by optical tracking has been shown to correct slice misalignment and non-linear spin-history artifacts, however residual artifacts due to dynamic magnetic field non-uniformity may remain in the data. A recently developed correction technique, PLACE, can correct for absolute geometric distortion using the complex image data from two EPI images, with slightly shifted k-space trajectories. We present a correction approach that integrates PLACE into a real-time scan-plane update system by optical tracking, applied to a tissue-equivalent phantom undergoing complex motion and an fMRI finger tapping experiment with overt head motion to induce dynamic field non-uniformity. Experiments suggest that including volume by volume geometric distortion correction by PLACE can suppress dynamic geometric distortion artifacts in a phantom and in vivo and provide more robust activation maps.

Multiple-mouse MRI (MMMRI) accelerates biomedical research by imaging multiple mice simultaneously. To date, MMMRI has been explored in three ways: shielded transmit-receive coils, shielded transmits coil with separate unshielded receive coils; and finally shielded transmit-receive coils with independent gradient coils. However alternative transmit coil configurations and possible benefits of eliminating shielding have not yet been explored. The goal of this thesis is to test possible radiofrequency configurations with and without shielding for the purpose of improving image quality for MMMRI. Results demonstrate that using an unshielded transmit-receive coil array provided a 20% improvement over an identical shielded coil. A new unshielded 7-coil MMMRI array is presented, minimizing the ghosting between image overlap using mutual inductance minimization and a sensitivity encoding (SENSE) reconstruction. The final array provided high resolution images (90µm) of up to seven live mice simultaneously with appropriate signal-to-noise for automated analysis.

No description available.

This study presented six typically developing children between the ages of five to eight with familiarization (baseline) in a mock scanner after which behavioural intervention ensued, in a non-concurrent multiple baseline design. The behavioural intervention included reinforcement for the contingency of lying motionless, and response cost (the removal of desirable stimuli) as a punishment contingency for movement. During baseline, all children showed a fair amount of head motion in the mock scanner. During intervention, small to large reductions in head motion were observed for five of the six participants. Therefore, use of the mock scanner and the reinforcement/punishment contingencies, may be an aid used prior to actual MRI/fMRI scans for children between the ages of five to eight: it is cost effective, may require only a session or two of intervention to be effective, and the potentially dangerous side effects and/or disabilities of sedation/anaesthesia can be avoided.