H Διπλωματική Εργασία αυτή επικεντρώνεται στο θέμα της Υπερηχητικής Απεικόνισης του ανθρώπινού σώματος με την παρατήρηση της δεύτερης αρμονικής που πηγάζει από την μη-γραμμική αλληλεπίδραση των υπερήχων με τους ιστούς που φωτίζονται από ένα παλμικό σήμα με φέρουσα συχνότητα εκπομπής f0. Η επεξεργασία των σημάτων λήψης στην ζώνη γύρω από την συχνότητα 2f0 και η απεικόνισή τους με συμβατικό τρόπο (b-mode) επιτρέπει την επίτευξη καλλίτερης χωρητικής διακριτικής ικανότητας. Η μελέτη ακολουθεί δύο παράλληλες μεθόδους: α) την κυματική ανάλυση του φαινομένου σκέδασης από μια μη γραμμική σφαίρα των υπερηχητικών κυμάτων και β) την εκτέλεση πειραματικών μετρήσεων με χρήση συστήματος υπερηχογράφου που έχει "ανοικτή" αρχιτεκτονική. Τόσο τα θεωρητικά όσο και τα πειραματικά αποτελέσματα επιβεβαιώνουν την χρησιμότητα της μεθόδου σαν μια εναλλακτική ιατρική απεικονιστική τεχνική. / The present Diploma Thesis is focused on the study of using 2nd harmonic ultrasound imaging of tissues as an alternate imaging technology in biomedical engineering.The principle of using of 2nd harmonic imaging is based on the illumination of a tissue medium with a frequency of f0 and then receive and prosess the signals with the same transducer at 2fo frequency. In order to derive specific conclusions this imaging problem is treated both theoreticaly and experimentally in the framework of the present Diploma Thesis.

Recent clinical studies have demonstrated that photoacoustic imaging (PAI) provides important diagnostic information for breast cancer staging. Despite these promising studies, PAI remains an unfeasible option for clinics due to the cost to implement, the required large modification in user conduct and the inflexibility of the hardware to accommodate other applications for the incremental enhancement in diagnostic information. The research described in this dissertation addresses these issues by designing attachments to clinical ultrasound probes and incorporating custom detectors into commercial ultrasound scanners. The ultimate benefit of these handheld devices is to expand the capability of current ultrasound systems and facilitate the translation of PAI to enhance cancer diagnostics and neurosurgical outcomes. Photoacoustic enabling devices (PEDs) were designed as attachments to two clinical ultrasound probes optimized for breast cancer diagnostics. PAI uses pulsed laser excitation to create transient heating (<1°C) and thermoelastic expansion that is detected as an ultrasonic emission. These ultrasonic emissions are remotely sensed to construct noninvasive images with optical contrast at depths much greater than other optical modalities. The PEDs are feasible in terms of cost, user familiarity and flexibility for various applications. Another possible application for PAI is in assisting neurosurgeons treating aneurysms. Aneurysms are often treated by placing a clip to prevent blood flow into the aneurysm. However, this procedure has risks associated with damaging nearby vessels. One of the developed PEDs demonstrated the feasibility to three-dimensionally image tiny microvasculature (<0.3mm) beyond large blood occlusions (>2.4mm) in a phantom model. The capability to use this during surgery would suggest decreasing the risks associated with these treatments. However, clinical ultrasound arrays are not clinically feasible for microsurgical applications due to their bulky size and linear scanning requirements for 3D. Therefore, capacitive micromachined ultrasound transducer (CMUT) two-dimensional arrays compatible with standard ultrasound scanners were used to generate real-time 3D photoacoustic images. Future probes, designed incorporating CMUT arrays, would be relatively simple to fabricate and a convenient upgrade to existing clinical ultrasound equipment. Eventually, a handheld tool with the ability to visualize, in real-time 3D, the desired microvasculature, would assist surgical procedures. The potential implications of PAI devices compatible with standard ultrasound equipment would be a streamlined cost efficient solution for translating photoacoustics into clinical practice. The practitioner could then explore the benefits of the enhanced contrast adjunctive to current ultrasound applications. Clinical availability of PAI could enhance breast cancer diagnostics and cerebrovascular surgical outcomes.

Prostate cancer is one of the leading causes of death by cancer for men. Focal therapy is being tested to target only the dominant cancer lesion in the prostate. However, due to the need to ensure that the laser is targeting only the cancer, a real-time treatment monitoring system is required. A combined optical-ultrasound monitoring system is in development at Princess Margaret Hospital based on different optical properties for coagulated versus normal tissue. In this project, we developed a light delivery and collection device that is compatible for use with an existing trans-rectal ultrasound-imaging probe. Computer-aided design software was used to visualize the prototype in relation to the trans-rectal ultrasound probe. This thesis describes the critical tasks necessary to assemble the final prototype, including listing of specifications, selection of device material based on safety and mechanical properties, method of prototype fabrication, positioning and fixation of optical fibers and testing.

Prostate cancer is one of the leading causes of death by cancer for men. Focal therapy is being tested to target only the dominant cancer lesion in the prostate. However, due to the need to ensure that the laser is targeting only the cancer, a real-time treatment monitoring system is required. A combined optical-ultrasound monitoring system is in development at Princess Margaret Hospital based on different optical properties for coagulated versus normal tissue. In this project, we developed a light delivery and collection device that is compatible for use with an existing trans-rectal ultrasound-imaging probe. Computer-aided design software was used to visualize the prototype in relation to the trans-rectal ultrasound probe. This thesis describes the critical tasks necessary to assemble the final prototype, including listing of specifications, selection of device material based on safety and mechanical properties, method of prototype fabrication, positioning and fixation of optical fibers and testing.

Shear wave (SW) imaging is an ultrasound elastogrpahy technique for estimating the elastic properties of biological tissues. Increasing the frequency would improve both the confinement of the radiation force generating the shear wave, and the imaging spatial resolution. The objectives of the study were to realize a simple high frequency (HF) system for the generation and detection of SW propagation and to implement this system to develop and characterize tissue-mimicking gelatin phantoms (TMGP) for HF SWI with elastic properties in the range of those encountered in biological tissue. A 5 MHz and 10 MHz focused transducer were used to induced SW’s in TMGP ranging from 4% to 12% gelatin with 3% silica for scattering and a 25 MHz single-element focused transducer recorded pulse-echo signals in order to capture the SW. The shear wave speeds in the TMGP were found to range linearly from 1.59-4.59 m/s in the 4% to 12% gelatin samples.

Shear wave (SW) imaging is an ultrasound elastogrpahy technique for estimating the elastic properties of biological tissues. Increasing the frequency would improve both the confinement of the radiation force generating the shear wave, and the imaging spatial resolution. The objectives of the study were to realize a simple high frequency (HF) system for the generation and detection of SW propagation and to implement this system to develop and characterize tissue-mimicking gelatin phantoms (TMGP) for HF SWI with elastic properties in the range of those encountered in biological tissue. A 5 MHz and 10 MHz focused transducer were used to induced SW’s in TMGP ranging from 4% to 12% gelatin with 3% silica for scattering and a 25 MHz single-element focused transducer recorded pulse-echo signals in order to capture the SW. The shear wave speeds in the TMGP were found to range linearly from 1.59-4.59 m/s in the 4% to 12% gelatin samples.

Recently among different ways of processing of materials the combined processing is applied. Applying different complex methods of processing of a surface of materials, it is possible to reduce a roughness of a processable surface, to increase thickness of a layer of the processed surface, to increase stability to wear process and microhardness. The further prospects in processing metals are opened with use of laser radiation and ultrasonic fluctuations. It is possible to notice, that complex ways of processing of metals are still not so widely investigated. This work is intended for research of a structure of steel in the field of influence of the combined laser radiation and ultrasonic fluctuations. It is established, that applying ultrasonic fluctuations at technologies of laser processing metals, it is possible to reach more uniform distribution of impurity in a surface of metal, to level a relief of the processed surface.

Targeted imaging with microbubbles may resolve the molecular expression within the abnormal blood vessels of tumours. Optimal imaging requires understanding the interaction between targeted microbubbles and high-frequency ultrasound. Therefore, the subharmonic signal, and backscattering cross-section of individual bound microbubbles were examined with coaligned 30 MHz pulses and optical images. The peak subharmonic signal was generated for 1.6 µm diameter microbubbles for 20% and 11% bandwidth pulses and 1.8 µm for 45% bandwidth pulses at 200 kPa, consistent with estimations of the resonant size of microbubble's at 15 MHz. In order to measure the scattering cross-section, a new method was proposed to measure the receive transfer function of a transducer. Measurements of the backscattering cross-section scaled with the square of the radius, with signi cant size-independent variability. The results of this thesis will help optimise the parameters for targeted imaging, as well as further our understanding of the behaviour of microbubbles.

Total Hip Replacement (THR) has become a common surgical procedure in recent years, due to the increase in the aging population with hip osteoarthritis. Identifying the proper orientation of the pelvis is a critical step in accurate placement of the femur prosthesis in the acetabulum in THR. The general approach to localize the orientation of the pelvic anatomical coordinate system (PaCS) is to use intra-operative X-ray fluoroscopy in a specialized interventional radiology facility to guide the procedure. Employing intra-operative ultrasound (US) imaging fused with pre-operative CT scan or fluoroscopy imaging was proposed to eliminate the ionizing radiation of intra-operative X-ray to the patient and the need for radiology facilities in the OR. However, the use of pre-operative imaging exposes patients to accumulative ionizing radiation which is desirable to be eliminated. In this thesis, I propose to replace pre-operative imaging with a statistical shape model (SSM) of the pelvis which is constructed from CT images of patients. An automatic deformable registration of a pelvis anatomical shape model to a sparse set of 2D ultrasound images of the pelvis is presented in order to localize the PaCS. In this registration technique, a set of 2D slices are extracted from the pelvic shape model, based on the approximate location and orientation of a corresponding 2D ultrasound image. The comparison of the shape model slices and ultrasound images is made possible by using an ultrasound simulation technique and a correlation-based similarity metric. During the registration, an instance of the shape model is generated that best matches the ultrasound data. I demonstrate the feasibility of our proposed approach in localizing the PaCS on four patient phantoms and on data from two male human cadavers. None of the test data sets were included in the SSM generation. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2010-08-23 17:57:24.708

Medical simulators have become commonly used to teach new procedures to medical students and clinicians. Their accessibility allows trainees to perform training whenever they desire, and their flexibility allows for various patient body types and conditions to be simulated. This is in contrast to {\it in-vivo} training, which requires direct supervision from a trained clinician, and access to a live patient or cadaver, both of which have restrictions. This thesis proposes a novel prototype system for spinal anesthesia procedures which combines the use of both a haptic device for virtual, ultrasound-guided (US) needle simulations, and a physical mannequin registered to a patient specific computed tomography (CT) volume in order to create an augmented reality (AR) overlay. The mannequin will provide the user with a greater sense of spatial awareness that is not present in a purely virtual simulation, as well as providing physical visual clues to navigate the patient. Another novel aspect is the simulation of US images from CT images deformed via a finite element model (FEM). The system is composed of a torso mannequin from Sawbones Inc., a MicronTracker2 optical tracking system from Claron Technology, a Sensable PHANToM Premium 1.5A haptic device and a graphical user interface (GUI) to display relevant visual feedback. The GUI allows the user to view the AR overlaid on the video feed, and the CT slice and simulated US image based the position/orientation of a dummy US probe. Forces during the insertion are created via the FEM and sent to the haptic device. These forces include force from needle tip insertion, friction along the length of the needle inside the body, and from displacing the needle off its original insertion axis. Input to the system consists of a patient CT volume. The system is able to create forces that closely match those reported in the literature. A user study consisting of subjects with expertise ranging from familiarity with medical imaging to clinical experience with needle insertion procedures, was performed to qualitatively analyze the performance of the system. Three experienced physicians were also consulted for input and improvements. The feedback received from the questionnaire, and comments from the subjects and physicians, showed the system is able to simulate a real needle insertion quite well, and the graphical aids added were helpful during the training procedure. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2011-11-27 00:04:32.173