Ultrasound is a favorable tool for intra-operative surgical guidance due to its fast imaging speed and non-invasive nature. However, deformations of the anatomy caused by breathing, heartbeat, and movement of the patient make it difficult to track the location of anatomical landmarks during intra-operative ultrasound-guided interventions. While elastic registration can be used to compensate for image misalignment, its adaptation for clinical use has only been gradual due to the lack of standardized guidelines to quantify the performance of different registration techniques. Evaluation of elastic registration algorithms is a difficult task since the point to point correspondence between images is usually unknown. This poses a major challenge in the validation of non-rigid registration techniques for performance comparisons. Current validation guidelines for non-rigid registration algorithms exist for the comparison of techniques for magnetic resonance images of the brain. These frameworks provide users with standardized brain datasets and performance measures based on brain region alignment, intensity differences between images, and inverse consistency of transformations. These metrics may not all be suitable for ultrasound registration algorithms due to the different properties of the imaging modalities. Furthermore, other metrics are required for validating the registration performance on different anatomical images with large deformations such as the liver. This work presents a validation framework dedicated for ultrasound elastic registration algorithms. Quantitative validation metrics are evaluated for ultrasound images. These include a simulation technique to measure registration accuracy, a segmentation algorithm to extract anatomical landmarks to measure feature overlap, and a technique to measure the alignment of images using similarity metrics. An extensive study of an ultrasound temporal registration algorithm is conducted using the proposed validation framework. Experiments are performed on a large database of 2D and 3D US images of the carotid artery and the liver to assess the performance of this algorithm. In addition, two graphical user interfaces which integrate the image registration and segmentation techniques have been developed to visualize the performance of these algorithms on ultrasound images captured in real time. In the future, these interfaces may be used to enhance ultrasound examination. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2007-10-24 22:35:20.875

Spinal injections for back-pain management are frequently carried out in hospitals and radiological clinics. Currently, these procedures are performed under fluoroscopy or CT guidance in specialized interventional radiology facilities, and thus incur a major financial burden on the healthcare system. Additionally, the current practice exposes patients and surgeons to X-ray radiation. The use of US for image guided navigation of the spine would greatly reduce the exposure of both the patient and the physician to ionizing radiation and allow the procedure to be performed outside of a specialized facility. However, US as the sole guidance modality has its own challenges. In particular, due to the significant level of occlusion in spinal US images, it can be difficult to accurately identify the appropriate injection site. Here, a groupwise US to CT registration algorithm for guiding percutaneous spinal interventions is presented. In our registration methodology, each vertebra in CT is treated as a sub-volume and transformed individually. A biomechanical model is used to constrain the displacement of the vertebrae relative to one another. The sub-volumes are then reconstructed into a single volume. In each iteration of registration, an US image is simulated from the reconstructed CT volume and an intensity-based similarity metric with the real US image is calculated. Validation studies are performed on datasets from a lamb cadaver, five patient-based phantoms designed to preserve realistic curvatures of the spine and a sixth patient-based phantom where the curvature of the spine is changed between preoperative and intraoperative imaging. For datasets where the spine curve between two imaging modalities was artificially perturbed, the proposed methodology was able to register initial misalignments of up to 20 mm with a success rate of 95%. For the phantom with a physical change in the curvature of the spine introduced between the US and CT datasets, the registration success rate was 98.5%. Finally, the registration success rate for the lamb cadaver with soft tissue information was 87%. The results demonstrate that our algorithm robustly registers US and CT datasets of the spine, regardless of a change in the patients pose between preoperative and intraoperative image acquisitions. / Thesis (Master, Computing) -- Queen's University, 2009-11-27 13:48:33.288

Computer assisted surgery uses a collection of different techniques including but not limited to: CT-guided, fluoroscopy-guided, and ultrasound-guided imaging which allows medical staff to view bony anatomy of a patient in relation to surgical tools on a computer screen. By providing this visual data to surgeons less invasive surgeries can be performed on a patient's fractured scaphoid. The data required for a surgeon to perform a minimally invasive surgery while looking only at a computer screen, and not directly at a patient's anatomy, will be provided by CT and ultrasound data. We will discuss how ultrasound and CT data can be used together to allow a minimally invasive surgery of the scaphoid to be performed. In this thesis we will explore two techniques of registering segmented ultrasound images to CT data; an Iterative Closest Point (ICP) approach, and an Unscented Kalman Filter-based Registration (UKF). We use two different ultrasound segmentation methods; a semi-automatic segmentation, and a Bayesian segmentation technique. The segmented ultrasound data is then registered to a CT volume. The success or failure of the registrations is measured by the error calculated in mapping the corresponding land- marks to one another and calculating the target registration error. The results show that the Unscented Kalman Filter-based registration using the Bayesian segmentation of ultrasound images has the least registration error, and has the most robustness to error in initial alignment of the two data sets. / Thesis (Master, Computing) -- Queen's University, 2010-05-28 11:17:31.934

Spinal needle injections for back pain management are frequently carried out in hospitals and radiological clinics. Currently, these procedures are performed under fluoroscopy or CT guidance in specialized interventional radiology facilities. As an alternative, the use of inexpensive ultrasound image guidance promises to improve the efficacy and safety of these procedures. We propose to eliminate or reduce the need for ionizing radiation, by creating and registering a statistical shape model of the lumbar vertebrae to 3D ultrasound volumes of patient, using a groupwise registration algorithm. From a total of 35 patient CT volumes, a statistical shape model of the L2, L3 and L4 vertebrae is built, including the mean shape, and principal modes of variation. The statistical shape model is registered to the 3D ultrasound by interchangeably optimizing the model parameters and their relative poses. We also use a biomechanical model to constrain the relative motion of the models throughout the registration process. Validation is performed on three tissue mimicking-phantoms designed to preserve realistic curvature of the spine. We compare pairwise and groupwise registration of the statistical shape model of the spine and demonstrate that clinically acceptable mean target error registration of 2.4 mm can be achieved with the proposed method. Registration results also show that the groupwise registration outperforms the pairwise in terms of success rate. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2010-09-27 20:08:01.828

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This thesis is based on observations of the physical properties of wheat flour dough using ultrasonic measurements. Three frequency ranges were used in the study, low frequencies (near 40 kHz), intermediate frequencies (1 to 5 MHz, where bubble resonance effects are apparent), and high frequencies (near 20 MHz). Doughs mixed under different head space air pressures, from vacuum to atmospheric pressure, as well as under nitrogen, were studied at low frequency to investigate their relaxation behavior. Subsamples from ambient dough and vacuum dough displayed differences in the dependence of velocity and attenuation on time after compression, but no post mixing relaxation effect was apparent. A critical headspace pressure of approximately 0.16 atmospheres determined whether vacuum-like or ambient-like relaxation was observed. A peak in attenuation and changes in ultrasonic velocity were observed around the bubble resonance frequency, and these ultrasonic parameters changed substantially as a function of time. A bubble resonance model was used to interpret the results around the bubble resonance frequency, and bubble size distributions were estimated for ambient and vacuum dough from the ultrasonic data. For the high frequency range, a molecular relaxation model was used to interpret the results. Different fast relaxation times were observed for ambient dough (5 ns) and vacuum dough (1 ns). This relaxation time may be associated with conformational rearrangements in glutenin inside the dough matrix. These experiments have enabled dough relaxation to be probed over a very wide range of time scales (from ns to hours), and will lead to a better understanding of the role of dough matrix and gas cell effects on the physical properties of wheat flour doughs.

Crude gliadins were extracted from Canada Western Red Spring (CWRS) wheat flour with 70% (v/v) aqueous ethanol solutions and then lyophilized. Lyophilized crude gliadins were dissolved in 70% (v/v) aqueous ethanol (EtOH) or 4 mM acetic acid (HAc) and the density and ultrasound properties were measured at 20 °C. Good linear relationships of density, ultrasound velocity and ultrasound attenuation with solution concentrations were found. Solvent and sonication effects on the crude gliadins were discussed in terms of the values of the partial specific volume and the partial specific adiabatic compressibility coefficient for crude gliadins. The ethanol soluble crude gliadins had a larger partial specific volume and larger partial specific adiabatic compressibility coefficient than those for acidic soluble crude gliadins. These large values for the physical properties of ethanol soluble crude gliadins were thought to be evidence for the existence of complexes formed by some proteins (ethanol soluble LMW-glutenins and gliadins) and lipids in ethanol solutions and it was also found that the protein-lipid complexes were not destroyed by sonication treatment. Besides, there was no evidence showing that gliadins change with different wheat flours and cause different volume and compressibility properties of crude gliadins.

The production of highly aerated foods remains a challenge that requires skill to obtain desired appearance and texture. Since foams are fragile and inherently unstable, evaluation of structure changes with time requires a delicate approach. Non-invasive but informative evaluation of changes in aerated food properties is a desired goal to be achieved in this thesis. I studied the aging of egg white foams of different void fraction using two noninvasive techniques - ultrasonic spectroscopy and electrical resistivity - with a view to understanding aging mechanisms that would affect the quality of the final product. To help in interpretation of the results, a commercial high void fraction foam, Gillette (Sensitive), was also analyzed. As a support technique for ultrasound results I used image analysis in order quantitatively evaluate the size of bubbles in the foams. Large increases in attenuation were observed with increasing aging time and frequency. Results were modeled using an effective medium theory originated by Foldy (1945) in order to understand the factors governing foam lifetime and texture. From electrical resistance measurements, liquid fraction changes in an egg white foam column were evaluated quantitatively and qualitatively by using a generalized free drainage model. Although egg-white foams were more prone to changes due to drainage, I observed that for all foams the ultrasonic scaling parameter alfa*lambda/freq was proportional to the square of average bubble size (indicative of a diffusively driven aging process due to disproportionation of bubbles). Slopes of alfa*lambda/freq versus aging time were 6*10-8 and 11*10-8 for egg white foams of void fraction 0.65 and 0.78, respectively, indicating that disproportionation progressed approximately twice as fast in the high void fraction foam. The slopes of alfa*lambda/freq versus aging time were similar for both Gillette foam void fractions (0.93 and 0.91) at a value of 1.5*10–8 s-1, attributable to a lower solubility of isobutane compared to air. By combining ultrasound and electrical resistivity, this thesis has provided novel insights into understanding instability processes occurring in foams. Potentially, ultrasound techniques could be used instead of imaging for foam aging studies, since non-invasive and non-destructive measurements of attenuation and phase velocity permit interrogation of opaque foam structures.

The addition of pea fibre to wheat bread supports the growing trend of improving health through diet. Various evaluation tools (bread scoring, C-cell, texture profile analysis, and ultrasound) were used to monitor the sensory and mechanical quality of air bubbles in bread. Different pea fibre particle sizes (250, 125, 180, 90 μm) were added at 0, 2, 4, 6, 8 g/serving into a bread formulation. Improvements in specific loaf volume were observed when water absorption was optimized. Adequate water absorption mitigated the high dough viscosity effect of pea fibre. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay was used to measure antioxidant activity of pea fibre. All particle sizes of pea fibres had substantially greater antioxidant scavenging ability compared to wheat flour. The DPPH scavenging activity of pea fibre approached that of ascorbic acid by the end of the assay. Fibre-enriched bread had higher antioxidant activity compared to that of the control bread.

We investigated an emerging brain-computer interface (BCI) modality, namely, transcranial Doppler ultrasonography (TCD), which measures cerebral blood flow velocity. We hypothesized that a bilateral TCD-driven online BCI would be able to dichotomously classify a user’s intentions with at least 70% accuracy. To test this hypothesis, we had three objectives: (1) to develop a signal classifier that yielded high (>80%) offline accuracies; (2) to develop an online TCD-BCI system with an onscreen keyboard; and, (3) to determine the achievable online accuracy with able-bodied participants. With a weighted, forward feature selection and a Naïve Bayes classifier, sensitivity and specificity of 81.44 ± 8.35% and 82.30 ± 7.39%, respectively, were achieved in the online differentiation of two mental tasks. The average information transfer rate and throughput of the system were 0.87 bits/min and 0.35 ± 0.18 characters/min, respectively. These promising online results encourage future testing of TCD-BCI systems with the target population.