3D Dynamic Visualization of Swallowing from Multi-Slice Computed Tomography

Human swallowing and its disorders (dysphagia) are still poorly understood, and yet many speech-language pathologists (SLPs) need to be trained to recognize correct, incorrect, and potentially dangerous swallows. The anatomy of the head and neck region is notoriously complex and difficult to visualize and study. Currently, training programs that teach SLPs to recognize swallowing disorders use artistically derived animations of swallowing, rendered at fixed viewpoints, to help students visualize the anatomy of the head and neck region. This work improves on these animations by using state-of-the-art medical images to create a dynamic, interactive, 3D simulation of human swallowing. Images of a male subject during swallow were captured in a single shot using a 320-slice CT scanner [Inamoto et al. 2011]. The images have very high spatial resolution (0:5 x 0:5 x 0:5 mm3), but low temporal resolution (10 Hz). The low temporal resolution resulted in blurring of the fluid being swallowed, making automatic segmentation and visualizations of the fluid difficult to generate

Carotid Artery Wall Imaging: Perspective and Guidelines from the ASNR Vessel Wall Imaging Study Group and Expert Consensus Recommendations of the American Society of Neuroradiology

SUMMARY: Identification of carotid artery atherosclerosis is conventionally based on measurements of luminal stenosis and surface irregularities using in vivo imaging techniques including sonography, CT and MR angiography, and digital subtraction angiography. However, histopathologic studies demonstrate considerable differences between plaques with identical degrees of stenosis and indicate that certain plaque features are associated with increased risk for ischemic events. The ability to look beyond the lumen using highly developed vessel wall imaging methods to identify plaque vulnerable to disruption has prompted an active debate as to whether a paradigm shift is needed to move away from relying on measurements of luminal stenosis for gauging the risk of ischemic injury. Further evaluation in randomized clinical trials will help to better define the exact role of plaque imaging in clinical decision-making. However, current carotid vessel wall imaging techniques can be informative. The goal of this article is to present the perspective of the ASNR Vessel Wall Imaging Study Group as it relates to the current status of arterial wall imaging in carotid artery disease

Fast upper airway magnetic resonance imaging for assessment of speech production and sleep apnea

The human upper airway is involved in various functions, including speech, swallowing, and respiration. Magnetic resonance imaging (MRI) can visualize the motion of the upper airway and has been used in scientific studies to understand the dynamics of vocal tract shaping during speech and for assessment of upper airway abnormalities related to obstructive sleep apnea and swallowing disorders. Acceleration technologies in MRI are crucial in improving spatiotemporal resolution or spatial coverage. Recent trends in technical aspects of upper airway MRI are to develop state-of-the-art image acquisition methods for improved dynamic imaging of the upper airway and develop automatic image analysis methods for efficient and accurate quantification of upper airway parameters of interest. This review covers the fast upper airway magnetic resonance (MR) acquisition and reconstruction, MR experimental issues, image analysis techniques, and applications, mainly with respect to studies of speech production and sleep apnea

Computed tomographic assessment of canine arytenoid lateralization

Unilateral arytenoid lateralization is a commonly performed surgical treatment for laryngeal paralysis in dogs. It involves fixing the moveable arytenoid cartilage to the thyroid (TAL) or cricoid (CAL) cartilage or both (CTAL). This increases the area of the rima glottidis (RGA), to allow reduced airway pressure and laryngeal resistance in vitro and ameliorates clinical signs in vivo. It may also increase the patient’s predisposition for aspiration pneumonia, which occurs in around 20% of clinical patients. No surgical technique has been correlated with clinical outcome or risk of aspiration pneumonia. Objective analysis of the effects of surgery on the three dimensional structure of the larynx has not been performed. Non-invasive assessment and standardization or classification of arytenoid lateralization techniques would allow more effective prospective clinical trials to identify prognostic factors for outcome and complications. Eight cadaver larynges were secured to radiolucent materials for Computed Tomography (CT) before and after TAL, CAL and CTAL with sutures tensioned to 100g or 500g. Multiple measurements were taken from CT 3D reconstructions of the larynx to assess arytenoid displacement in three separate planes. No significant changes were found for any CT measure except the distance between the arytenoid and thyroid wing (ATW). CTAL at 500g and TAL at 500g showed significantly smaller ATW compared to CAL at 100g suggesting that a high tension TAL or CTAL causes the most lateralization of the arytenoid. CAL may allow reduction in airway pressure without excessive lateralization of the arytenoid. ATW is a candidate for a marker of lateralization of UAL procedures, which could be implemented in future prospective clinical studies. Sequential tensioning and loosening of the suture had no significant effect on any measured parameter validating the use of larynges in sequential measurements

An Image-Based Tool to Examine Joint Congruency at the Elbow

Post-traumatic osteoarthritis commonly occurs as a result of a traumatic event to the articulation. Although the majority of this type of arthritis is preventable, the sequence and mechanism of the interaction between joint injury and the development of osteoarthritis (OA) is not well understood. It is hypothesized that alterations to the joint alignment can cause excessive and damaging wear to the cartilage surfaces resulting in OA. The lack of understanding of both the cause and progression of OA has contributed to the slow development of interventions which can modify the course of the disease. Currently, there have been no reported techniques that have been developed to examine the relationship between joint injury and joint alignment. Therefore, the objective of this thesis was to develop a non-invasive image-based technique that can be used to assess joint congruency and alignment of joints undergoing physiologic motion. An inter-bone distance algorithm was developed and validated to measure joint congruency at the ulnohumeral joint of the elbow. Subsequently, a registration algorithm was created and its accuracy was assessed. This registration algorithm registered 3D reconstructed bone models obtained using x-ray CT to motion capture data of cadaveric upper extremities undergoing simulated elbow flexion. In this way, the relative position and orientation of the 3D bone models could be visualized for any frame of motion. The effect of radial head arthroplasty was used to illustrate the utility of this technique. Once this registration was refined, the inter-bone distance algorithm was integrated to be able to visualize the joint congruency of the ulnohumeral joint undergoing simulated elbow flexion. The effect of collateral ligament repair was examined. This technique proved to be sensitive enough to detect large changes in joint congruency in spite of only small changes in the motion pathways of the ulnohumeral joint following simulated ligament repair. Efforts were also made in this thesis to translate this research into a clinical environment by examining CT scanning protocols that could reduce the amount of radiation exposure required to image patient’s joints. For this study, the glenohumeral joint of the shoulder was examined as this joint is particularly sensitive to potential harmful effects of radiation due to its proximity to highly radiosensitive organs. Using the CT scanning techniques examined in this thesis, the effective dose applied to the shoulder was reduced by almost 90% compared to standard clinical CT imaging. In summary, these studies introduced a technique that can be used to non-invasively and three-dimensionally examine joint congruency. The accuracy of this technique was assessed and its ability to predict regions of joint surface interactions was validated against a gold standard casting approach. Using the techniques developed in this thesis the complex relationship between injury, loading and mal-alignment as contributors to the development and progression of osteoarthritis in the upper extremity can be examined

Neural Deformable Cone Beam CT

In oral and maxillofacial cone beam computed tomography (CBCT), patient motion is frequently observed and, if not accounted for, can severely affect the usability of the acquired images. We propose a highly flexible, data driven motion correction and reconstruction method which combines neural inverse rendering in a CBCT setting with a neural deformation field. We jointly optimize a lightweight coordinate based representation of the 3D volume together with a deformation network. This allows our method to generate high quality results while accurately representing occurring patient movements, such as head movements, separate jaw movements or swallowing. We evaluate our method in synthetic and clinical scenarios and are able to produce artefact-free reconstructions even in the presence of severe motion. While our approach is primarily developed for maxillofacial applications, we do not restrict the deformation field to certain kinds of motion. We demonstrate its flexibility by applying it to other scenarios, such as 4D lung scans or industrial tomography settings, achieving state-of-the art results within minutes with only minimal adjustments