InterNAV3D: A Navigation Tool for Robot-Assisted Needle-Based Intervention for the Lung

Lung cancer is one of the leading causes of cancer deaths in North America. There are recent advances in cancer treatment techniques that can treat cancerous tumors, but require a real-time imaging modality to provide intraoperative assistive feedback. Ultrasound (US) imaging is one such modality. However, while its application to the lungs has been limited because of the deterioration of US image quality (due to the presence of air in the lungs); recent work has shown that appropriate lung deflation can help to improve the quality sufficiently to enable intraoperative, US-guided robotics-assisted techniques to be used. The work described in this thesis focuses on this approach. The thesis describes a project undertaken at Canadian Surgical Technologies and Advanced Robotics (CSTAR) that utilizes the image processing techniques to further enhance US images and implements an advanced 3D virtual visualization software approach. The application considered is that for minimally invasive lung cancer treatment using procedures such as brachytherapy and microwave ablation while taking advantage of the accuracy and teleoperation capabilities of surgical robots, to gain higher dexterity and precise control over the therapy tools (needles and probes). A number of modules and widgets are developed and explained which improve the visibility of the physical features of interest in the treatment and help the clinician to have more reliable and accurate control of the treatment. Finally the developed tools are validated with extensive experimental evaluations and future developments are suggested to enhance the scope of the applications

Analytical ultrasonics for evaluation of composite materials response. Part 2: Generation and detection

To evaluate the response of composite materials, it is imperative that the input excitation as well as the observed output be well characterized. This characterization ideally should be in terms of displacements as a function of time with high spatial resolution. Additionally, the ability to prescribe these features for the excitation is highly desirable. Various methods for generating and detecting ultrasound in advanced composite materials are examined. Characterization and tailoring of input excitation is considered for contact and noncontact, mechanical, and electromechanical devices. Type of response as well as temporal and spatial resolution of detection methods are discussed as well. Results of investigations at Virginia Tech in application of these techniques to characterizing the response of advanced composites are presented

Freehand Three-Dimensional Ultrasound to Evaluate Scapular Movement

Altered scapular kinematics have been linked to increases in shoulder pain and pathology. As such, identifying normal scapular movement is integral to preventing pathology and maintaining health of the joint. Existing methods to evaluate scapular movement are invasive, expensive, require exposure to radiation, suffer skin based motion artifacts, or allow for examination only in static postures. Freehand three-dimensional ultrasound offers the unique ability to image bone while being non-invasive, relatively low cost, and free of radiation. This is a novel application of a technology that in the past has been used for needle guided injections and determining changes in organ volumes, but never for evaluating bone movement. We have developed a custom freehand-ultrasound system that shows high repeatability across trials (SEM < 2°) in evaluating scapular kinematics in static postures with the arm at rest and elevated in the sagittal, frontal and scapular planes. Among manual wheelchair users and able-bodied controls we found scapular kinematics with the arm in an elevated position were predicted by scapular and trunk position at rest. We also found BMI ≥ 25, presence of pathology on a physical exam, shoulder abnormalities on a clinical ultrasound exam, and greater than 10 years of wheelchair use resulted in scapular postures associated with shoulder pathology in previous studies. We found no significant differences between wheelchair users and age-matched controls but attribute this to a lack of difference in pathology between the groups. A learning curve was identified over time for capturing quality ultrasound images and it is suggested future studies incorporate ample training time and require raters to meet minimum performance measures set forth by this study. In a subsample of subjects we found increases in external rotation, upward rotation and posterior tilting at incremental angles of humeral elevation during dynamic trials indicating that it is feasible to apply our methods to evaluate dynamic scapular movement. Application of these methods may help to identify shoulder pathology and evaluate the efficacy of interventions to correct altered scapular kinematics

Coded Signals for High Frequency Ultrasound Imaging

Degeneration of articular cartilage is known as a serious and painful knee disease seriously affecting people in all ages. The disease also marks the presence of osteoarthritis which is a complex musculoskeletal disorder. A successful assessment of the degeneration status is of great importance for estimating osteoarthritis progression, and thereby beneficial for implementing clinical treatments. Ultrasound has played a vital role in imaging the articular cartilage since it is capable of providing distinct information of important cartilage structures. However, various types of noise in ultrasound signals (e.g. clutter noise) are known to limit the quality of ultrasound images, especially at high frequencies where wave attenuation becomes severe. The possibility for improving the signal to noise ratio (SNR) by using coded signals is therefore the motivation behind this thesis, with the main objective is to investigate suitable codes and compression methods for cartilage imaging. The main focus of this thesis has been put on coded ultrasound signals and related signal processing methods. Transducers made from two different piezoelectric materials (PZT and PVDF) are used to image a thick cartilage sample. For each transducer, three different waveforms (Ricker wavelet, Gaussian chirped, and a 13-bit Barker) are used to excite the ultrasonic transducers. Two different wave compression methods (Matched filtering and Wiener filtering) are also explored to decode the signals received by transducers. Ahead of processing the received signals, a time calibration was used to compensate for sample tilting, yielding an improved precision in the phase/time delay. A maximum method and a center of mass method were used for calibration. The results from the experimental work show that both Chirp coded signals and Barker coded signals work well in improving the SNR, and that both transducers are able to produce high quality images of the cartilage sample. For the situations using coded excitation signals, however, the PZT transducer has high requirement for excitation repetition frequency because of its built-in delay line. Different time calibration methods have their own applicable conditions. Matched filter and Wiener filter both perform well for decoding, but the “noise” parameter in the Wiener filter has to be adjusted carefully to produce reasonable results

Location of the hip joint centre using ultrasonic techniques

Kinematic and kinetic gait parameters are essential indicators of musculoskeletal wellbeing. In order to accurately determine these parameters, the hip joint centre (HJC) must first be located. The accuracy with which it is located directly affects the estimated magnitude of these parameters; yet current techniques still give inaccurate results.This study was therefore aimed at exploring the features of modern ultrasonography with a view to developing an accurate and convenient method of locating the HJC using medical ultrasound imaging.Five participants whose BMI were less than 26.5 took part in the study in accordance with ethical approval. Ultrasound images of their hip joint were taken. Points created on the femoral head arc projected in the ultrasound image were used to fit a circle along in the probe reference frame. Coordinate transformations were then performed to relate the centre of this circle (which ought to coincide with the HJC) in pelvic anatomical reference frame.Results obtained for one of the participants were validated with MRI technique. With respect to the position of the HJC determined from the MRI images, the ultrasound technique located the HJC to within 1mm and 3.97mm in the anterior-posterior and medio-lateral directions respectively. The inferior-superior coordinates were 41.55mm apart. Further studies are however required to refine the methodology and ascertain its accuracy limits.Kinematic and kinetic gait parameters are essential indicators of musculoskeletal wellbeing. In order to accurately determine these parameters, the hip joint centre (HJC) must first be located. The accuracy with which it is located directly affects the estimated magnitude of these parameters; yet current techniques still give inaccurate results.This study was therefore aimed at exploring the features of modern ultrasonography with a view to developing an accurate and convenient method of locating the HJC using medical ultrasound imaging.Five participants whose BMI were less than 26.5 took part in the study in accordance with ethical approval. Ultrasound images of their hip joint were taken. Points created on the femoral head arc projected in the ultrasound image were used to fit a circle along in the probe reference frame. Coordinate transformations were then performed to relate the centre of this circle (which ought to coincide with the HJC) in pelvic anatomical reference frame.Results obtained for one of the participants were validated with MRI technique. With respect to the position of the HJC determined from the MRI images, the ultrasound technique located the HJC to within 1mm and 3.97mm in the anterior-posterior and medio-lateral directions respectively. The inferior-superior coordinates were 41.55mm apart. Further studies are however required to refine the methodology and ascertain its accuracy limits

Spatial calibration of a 2D/3D ultrasound using a tracked needle

PURPOSE: Spatial calibration between a 2D/3D ultrasound and a pose tracking system requires a complex and time-consuming procedure. Simplifying this procedure without compromising the calibration accuracy is still a challenging problem. METHOD: We propose a new calibration method for both 2D and 3D ultrasound probes that involves scanning an arbitrary region of a tracked needle in different poses. This approach is easier to perform than most alternative methods that require a precise alignment between US scans and a calibration phantom. RESULTS: Our calibration method provides an average accuracy of 2.49 mm for a 2D US probe with 107 mm scanning depth, and an average accuracy of 2.39 mm for a 3D US with 107 mm scanning depth. CONCLUSION: Our method proposes a unified calibration framework for 2D and 3D probes using the same phantom object, work-flow, and algorithm. Our method significantly improves the accuracy of needle-based methods for 2D US probes as well as extends its use for 3D US probes

New Mechatronic Systems for the Diagnosis and Treatment of Cancer

Both two dimensional (2D) and three dimensional (3D) imaging modalities are useful tools for viewing the internal anatomy. Three dimensional imaging techniques are required for accurate targeting of needles. This improves the efficiency and control over the intervention as the high temporal resolution of medical images can be used to validate the location of needle and target in real time. Relying on imaging alone, however, means the intervention is still operator dependent because of the difficulty of controlling the location of the needle within the image. The objective of this thesis is to improve the accuracy and repeatability of needle-based interventions over conventional techniques: both manual and automated techniques. This includes increasing the accuracy and repeatability of these procedures in order to minimize the invasiveness of the procedure. In this thesis, I propose that by combining the remote center of motion concept using spherical linkage components into a passive or semi-automated device, the physician will have a useful tracking and guidance system at their disposal in a package, which is less threatening than a robot to both the patient and physician. This design concept offers both the manipulative transparency of a freehand system, and tremor reduction through scaling currently offered in automated systems. In addressing each objective of this thesis, a number of novel mechanical designs incorporating an remote center of motion architecture with varying degrees of freedom have been presented. Each of these designs can be deployed in a variety of imaging modalities and clinical applications, ranging from preclinical to human interventions, with an accuracy of control in the millimeter to sub-millimeter range

Development of a Three-Dimensional Image-Guided Needle Positioning System for Small Animal Interventions

Conventional needle positioning techniques for small animal microinjections are fraught with issues of repeatability and targeting accuracy. To improve the outcomes of these interventions a small animal needle positioning system guided by micro-computed tomography (micro-CT) imaging was developed. A phantom was developed to calibrate the geometric accuracy of micro-CT scanners to a traceable standard of measurement. Use of the phantom ensures the geometric fidelity of micro-CT images for use in image-guided interventions or other demanding quantitative applications. The design of a robot is described which features a remote center of motion architecture and is compact enough to operate within a micro-CT bore. Methods to calibrate the robot and register it to a micro-CT scanner are introduced. The performance of the robot is characterized and a mean targeting accuracy of 149 ± 41 µm estimated. The robot is finally demonstrated by completing an in vivo biomedical application