Application of particle filter for vertebral body extraction: a simulation study

Lumbar vertebra motion analysis provides objective measurement of lumbar disorder. The automatic tracking algorithm has been applied to Digitalized Video Fluoroscopy (DVF) sequence. This paper proposes a new Auto-Tracking System (ATS) with a guide device and a motion analysis to automatically measure human lumbar motion. Digitalized Video Fluoroscopy (DVF) sequence was obtained during flexion-extension lumbar movement under guide device. An extraction of human vertebral body and its motion tracking were developed by particle filter. The results showed a good repeatability, reliability and robustness. In model test, the maximum fiducial error is 3.7% and the repeatability error is 1.2% in translation and the maximal repeatability error is 2.6% in rotation angle. In this simulation study, we employed a lumbar model to simulate the motion of lumber flexion- extension with the stepping translation of 1.3 mm and rotation angle of 1?. Results showed that the fiducial error was measured as 1.0%, while the repeatability error was 0.7%. The sequence can be detected even noise contamination as more as 0.5 of the density. The result demonstrates that the data from the auto-tracking algorithm shows a strong correlation with the actual measurement and that the Vertebral Auto-Tracking System (VATS) is highly repetitive. In the human lumbar spine evaluation, the study not only shows the reliability of Auto-Tracking Analysis System (ATAS), but also reveals that it is robust and variable in vivo. The VATS is evaluated by the model, the simulated sequence and the human subject. It could be concluded that the developed system could provide a reliable and robust system to detect spinal motion in future medical application.published_or_final_versio

Auto-tracking system for human lumbar motion analysis

Previous lumbar motion analyses suggest the usefulness of quantitatively characterizing spine motion. However, the application of such measurements is still limited by the lack of user-friendly automatic spine motion analysis systems. This paper describes an automatic analysis system to measure lumbar spine disorders that consists of a spine motion guidance device, an X-ray imaging modality to acquire digitized video fluoroscopy (DVF) sequences and an automated tracking module with a graphical user interface (GUI). DVF sequences of the lumbar spine are recorded during flexion-extension under a guidance device. The automatic tracking software utilizing a particle filter locates the vertebra-of-interest in every frame of the sequence, and the tracking result is displayed on the GUI. Kinematic parameters are also extracted from the tracking results for motion analysis. We observed that, in a bone model test, the maximum fiducial error was 3.7%, and the maximum repeatability error in translation and rotation was 1.2% and 2.6%, respectively. In our simulated DVF sequence study, the automatic tracking was not successful when the noise intensity was greater than 0.50. In a noisy situation, the maximal difference was 1.3 mm in translation and 1° in the rotation angle. The errors were calculated in translation (fiducial error: 2.4%, repeatability error: 0.5%) and in the rotation angle (fiducial error: 1.0%, repeatability error: 0.7%). However, the automatic tracking software could successfully track simulated sequences contaminated by noise at a density ≤ 0.5 with very high accuracy, providing good reliability and robustness. A clinical trial with 10 healthy subjects and 2 lumbar spondylolisthesis patients were enrolled in this study. The measurement with auto-tacking of DVF provided some information not seen in the conventional X-ray. The results proposed the potential use of the proposed system for clinical applications. © 2011 - IOS Press and the authors. All rights reserved.postprin

Automatic lumbar motion analysis based on particle filtering

Spinal motion is produced by complex coordination of nerves and muscles and is constrained by vertebral structure. The observation and measurement of lumbar motion is of great value for clinical diagnosis and surgical plan of lumbar disorders. Digitalized Video Fluoroscopy (DVF) is the most suitable one to image the spine motion but it is quite time consuming. This paper proposes an automatic lumbar motion analysis system (ALMAS) with particle filtering technology. The automatically vertebral tracking for motion analysis was utilized with a friendly-interface, which provides a window for users to process the acquired DVF sequence and to analyze the tracking results. A set of simulation vertebra image were used to evaluate the performance and accuracy of this system. In simulated sequence, the maximal difference is 1.3 mm in translation and 1ͦ in rotation angle. The error is small in x- and y- translation (fiducial error: 2.4%, repeatability error: 0.5%) and in rotation angle (fiducial error: 1.0%, repeatability error: 0.7%). The ALMAS can still track the sequence contaminated by noise with the density ≤ 0.5. Besides, the results demonstrate that the data from the auto-tracking algorithm shows a strong correlation with the actual measurement and that the ALMAS is highly repetitive. Results from this study showed that ALMAS based on particle filtering are relatively robust and accurate for automatic lumbar motion analysis.published_or_final_versio

Digital tracking algorithm reveals the influence of structural irregularities on joint movements in the human cervical spine

The final publication is available at Elsevier via https://dx.doi.org/10.1016/j.clinbiomech.2018.04.015 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Background Disc height loss and osteophytes change the local mechanical environment in the spine; while previous research has examined kinematic dysfunction under degenerative change, none has looked at the influence of disc height loss and osteophytes throughout movement. Methods Twenty patients with pain related to the head, neck or shoulders were imaged via videofluoroscopy as they underwent sagittal-plane flexion and extension. A clinician graded disc height loss and osteophytes as “severe/moderate”, “mild”, or “none”. A novel tracking algorithm quantified motions of each vertebra. This information was used to calculate intervertebral angular and shear displacements. The digital algorithm made it practical to track individual vertebrae in multiple patients through hundreds of images without bias. Findings Cases without height loss/osteophytes had a consistent increase in intervertebral angular displacement from C2/C3 to C5/C6, like that of healthy individuals, and mild height losses did not produce aberrations that were systematic or necessarily discernable. However, joints with moderate to severe disc height loss and osteophytes exhibited reduced range of motion compared to adjacent unaffected joints in that patient and corresponding joints in patients without structural irregularities. Interpretation Digitally-obtained motion histories of individual joints allowed anatomical joint changes to be linked with changes in joint movement patterns. Specifically, disc height loss and osteophytes were found to influence cervical spine movement in the sagittal plane, reducing angular motions at affected joints by approximately 10% between those with and without height loss and osteophytes. Further, these joint changes were associated with perturbed intervertebral angular and shear movements.Natural Sciences and Engineering Research Council (NSERC) Discovery Grant

RAJKIRAN NATARAJAN

Many research questions in dysphagia research require frame-by-frame annotation of anatomical landmarks visible in videofluorographs as part of the research workflow, which can be a tedious and error prone process. Such annotation is done manually using image analysis tools, is error prone, and characterized by poor rater reliability. In this thesis, a computer-assisted workflow that uses a point tracking technique based on the Kanade-Lucas-Tomasi tracker to semi-automate the annotation process, is developed and evaluated. Techniques to semi-automate the annotation process have been explored but none have had their research value demonstrated. To demonstrate the research value of a workflow based on point tracking in enhancing the annotation process, the developed workflow was used to perform an enhanced version of the recently published Coordinate Mapping swallowing study annotation technique to determine several swallowing parameters. Evaluation was done on eight swallow studies obtained from a variety of clinical sources and showed that the workflow produced annotation results with clinically insignificant spatial errors. The workflow has the potential to significantly enhance research processes that require frame-by-frame annotation of anatomical landmarks in videofluorographs as part of their data preparation steps, by reducing the total time required to annotate clinical case

The reliability of video fluoroscopy, ultrasound imaging, magnetic resonance imaging and radiography for measurements of lumbar spine segmental range of motion in-vivo: A review.

BACKGROUND: Lower back pain (LBP) is a principal cause of disability worldwide and is associated with a variety of spinal conditions. Individuals presenting with LBP may display changes in spinal motion. Despite this, the ability to measure lumbar segmental range of motion (ROM) non-invasively remains a challenge. OBJECTIVE: To review the reliability of four non-invasive modalities: Video Fluoroscopy (VF), Ultrasound imaging (US), Magnetic Resonance Imaging (MRI) and Radiography used for measuring segmental ROM in the lumbar spine in-vivo. METHODS: The methodological quality of seventeen eligible studies, identified through a systematic literature search, were appraised. RESULTS: The intra-rater reliability for VF is excellent in recumbent and upright positions but errors are larger for intra-rater repeated movements and inter-rater reliability shows larger variation. Excellent results for intra- and inter-rater reliability are seen in US studies and there is good reliability within- and between-day. There is a large degree of heterogeneity in MRI and radiography methodologies but reliable results are seen. CONCLUSIONS: Excellent reliability is seen across all modalities. However, VF and radiography are limited by radiation exposure and MRI is expensive. US offers a non-invasive, risk free method but further research must determine whether it yields truly consistent measurements

A two-sling mechanism of hyolaryngeal elevation in the pharyngeal phase of swallowing

Thesis (Ph.D.)--Boston UniversityThe pharyngeal phase of swallowing is a complex function that transfers a bolus from the oral cavity through the hypopharynx into the esophagus. A critical event in this process is the elevation of the hyolaryngeal complex, which opens the upper esophageal sphincter and relocates the airway away from an oncoming bolus. The suprahyoid group of muscles (mylohyoid, geniohyoid, digastric, and stylohyoid) and thyrohyoid are thought to underlie this function. The role of a deeper posterior sling of muscles that is comprised of stylopharyngeus, salpingopharyngeus and palatopharyngeus has not been determined. This project aims to investigate a hypothesized two-sling mechanism for hyolaryngeal elevation in the pharyngeal phase of swallowing. The thesis begins with background information of the functional anatomy thought to underlie hyolaryngeal elevation followed by an outline of studies that validate the structure, function, and clinical relevance of the two-sling mechanism. A cadaver model is first used to calculate potential force vectors of the muscular slings. The function of the two-sling apparatus is then investigated in vivo by using muscle functional MRI to evaluate muscles active in swallowing and dynamic MRI to perform kinematic analysis on key anatomical landmarks that represent attachment sites of the two-sling mechanism. Finally, the clinical significance of the two-sling mechanism is demonstrated by comparing spatial and temporal measurements collected from fluoroscopic imaging studies of patients with normal swallowing ability and swallowing difficulty

Time-varying changes in the lumbar spine from exposure to sedentary tasks and their potential effects on injury mechanics and pain generation

General body discomfort increases over time during prolonged sitting and it is typically accepted that no single posture can be comfortably maintained for long periods. Despite this knowledge, workplace exposure to prolonged sitting is very common. Sedentary occupations that expose workers to prolonged sitting are associated with an increased risk of developing low back pain (LBP), disc degeneration and lumbar disc herniation. Given the prevalence of occupations with a large amount of seated work and the propensity for a dose-response relationship between sitting and LBP, refining our understanding of the biomechanics of the lumbar spine during sitting is important. Sitting imposes a flexed posture that, when held for a prolonged period of time, may cause detrimental effects on the tissues of the spine. While sitting is typically viewed as a sedentary and constrained task, several researchers have identified the importance of investigating movement during prolonged sitting. The studies in this thesis were designed to address the following two global questions: (1) How do the lumbar spine and pelvis move during sitting? (2) Can lumbar spine movement and postures explain LBP and injury associated with prolonged sitting? The first study (Study 1) examined static X-ray images of the lower lumbo-sacral spine in a range of standing and seated postures to measure the intervertebral joint angles that contribute to spine flexion. The main finding was that the lower lumbo-sacral joints approach their total range of motion in seated postures. This suggests that there could be increased loading of the passive tissues surrounding the lower lumbo-sacral intervertebral joints, contributing to low back pain and/or injury from prolonged sitting. Study 2 compared external spine angles measured using accelerometers from L3 to the sacrum with corresponding angles measured from X-ray images. While the external and internal angles did not match, the accelerometers were sensitive to changes in seated lumbar posture and were consistent with measurements made using similar technology in other studies. This study also provided an in-depth analysis of the current methods for data treatment and how these methods affect the outcomes. A further study (Study 3) employed videofluoroscopy to investigate the dynamic rotational kinematics of the intervertebral joints of the lumbo-sacral spine in a seated slouching motion in order to determine a sequence of vertebral motion. The pelvis did not initiate the slouching motion and a disordered sequence of vertebral rotation was observed at the initiation of the movement. Individuals performed the slouching movement using a number of different motion strategies that influenced the IVJ angles attained during the slouching motion. From the results of Study 1, it would appear as though the lowest lumbar intervertebral joint (L5/S1) contribute the most to lumbo-sacral flexion in upright sitting, as it is at approximately 60% of its end range in this posture. However, the results from Study 3 suggest that there is no consistent sequence of intervertebral joint rotation when flexing the spine from upright to slouched sitting. When moving from standing to sitting, lumbar spine flexion primarily occurs at the lowest joint (i.e. L5/S1); however, a disordered sequence of vertebral motion the different motion patterns observed may indicate that different joints approach their end range before the completion of the slouching movement. In order to understand the biomechanical factors associated with sitting induced low back pain, Study 4 examined the postural responses and pain scores of low back pain sufferers compared with asymptomatic individuals during prolonged seated work. The distinguishing factor between these two groups was their respective time-varying seated lumbar spine movement patterns. Low back pain sufferers moved more than asymptomatic individuals did during 90 minutes of seated work and they reported increased low back pain over time. Frequent shifts in lumbar spine posture could be a mechanism for redistributing the load to different tissues of the spine, particularly if some tissues are more vulnerable than others. However, increased movement did not completely eliminate pain in individuals with pre-existing LBP. The LBP sufferers’ seated spine movements increased in frequency and amplitude as time passed. It is likely that these movements became more difficult to properly control because LBP patients may lack proper lumbar spine postural control. The results of this study highlight the fact that short duration investigations of seated postures do not accurately represent the biological responses to prolonged exposure. Individuals with sitting-induced low back pain and those without pain differ in how they move during seated work and this will have different impacts on the tissues of the lumbar spine. A tissue-based rational for the detrimental effects on the spinal joint of prolonged sitting was examined in Study 5 using an in vitro spine model and simulated spine motion patterns documented in vivo from Study 4. The static protocol simulated 2 hours of sitting in one posture. The shift protocol simulated infrequent but large changes in posture, similar to the seated movements observed in a group of LBP sufferers. The fidget protocol replicated small, frequent movements about one posture, demonstrated by a group of asymptomatic individuals. Regardless of the amount of spine movement around one posture, all specimens lost a substantial amount of disc height. Furthermore, the passive range of motion of a joint changed substantially after 2 hours of simulated sitting. Specifically, there were step-like regions of reduced stiffness throughout the passive range of motion particularly around the adopted “seated flexion” angle. However, small movements around a posture (i.e. fidgeting) may mitigate the changes in the passive stiffness in around the seated flexion angle. The load transferred through the joint during the 2-hour test was varied either by changing postures (i.e. shifting) or by a potential creep mechanism (i.e. maintaining one static posture). Fidgeting appeared to reduce the variation of load carriage through the joint and may lead to a more uniform increase in stiffness across the entire passive range of motion. These changes in passive joint mechanics could have greater consequences for a low back pain population who may be more susceptible to abnormal muscular control and clinical instability. Nevertheless, the observed disc height loss and changes in joint mechanics may help explain the increased risk of developing disc herniation and degeneration if exposure to sitting is cumulative over many days, months and years. In summary, this work has highlighted that seated postures place the joints of the lumbar spine towards their end range of motion, which is considered to be risky for pain/injury in a number of tissue sources. In-depth analyses of both internal and external measurements of spine postures identified different seated motion patterns and self-selected seated postures that may increase the risk for developing LBP. The model of seated LBP/discomfort development used in this thesis provided evidence that large lumbar spine movements do not reduce pain in individuals with pre-existing LBP. Tissue-based evidence demonstrated that 2 hours of sitting substantially affects IVJ mechanics and may help explain the increased risk of developing disc herniation and degeneration if exposure to sitting is cumulative over many days, months and years. The information obtained from this thesis will help develop and refine interventions in the workplace to help reduce low back pain during seated work

Patient-specific technology for in vivo assessment of 3-D spinal motion

One of the most common musculoskeletal problems affecting people is neck and low back pain. Traditional clinical diagnostic techniques such as fluoroscopic imaging or CT scans are limited due to their static and/or planar measurements which may not be able to capture all neurological pathologies. More advanced diagnostics have proven successful in assessing 3-D patient-specific spinal kinematics by combining a patient-specific 3-D spine model (CT or MRI) with bi-planar fluoroscopic imaging; however, custom, not clinically available advanced imaging equipment as well as an increase in radiation exposure is required to acquire a complete patient-specific spinal kinematic description. Hence, the purpose of this research was to develop a clinically viable bi-planar fluoroscopic imaging technique which acquires a complete patient-specific kinematic description of the spine with reduced radiation exposure. Development of the proposed technique required evaluating the accuracy of 3-D kinematic interpolation techniques in reconstructing spinal kinematic data in order to reduce radiation exposure from bi-planar fluoroscopic diagnostic techniques. Several interpolation and sampling algorithms were evaluated in reconstructing cadaveric lumbar (L2-S1) flexion-extension motion data; ultimately, a new interpolation algorithm was proposed. Similarly, the success of the interpolation algorithm was evaluated in reconstructing spine-specific kinematic parameters. Next, the interpolation algorithm was combined with a CT-based bi-planar fluoroscopic method. Accuracy of the proposed diagnostic technique was evaluated against previously validated work on an ex vivo optoelectronic 3-D kinematic assessment technique. Bi-planar fluoroscopic images were acquired during both flexion-extension and lateral bending motions of cadaveric cervical (C4-T1) and lumbar (L2-S1) spine. Registration of the bi-planar fluoroscopic images to the CT-based 3-D model was optimized using a gradient derived similarity function. Additionally, a stochastic approach, covariance matrix adaptive evolution strategy, was used as the optimizing function. The newly developed interpolation algorithm was used to reduce the sample size of the bi-planar fluoroscopic images which reduces radiation exposure. Experimental results illustrate the potential success of the technique, but ultimately improvements in registration and validation methods are needed before becoming clinically viable

Intervertebral Disc Height Loss and Restoration: Outcomes and Implications

This thesis is unified around the theme of disc height loss. Current knowledge in the area of spine research identifies mechanical overload as the culprit for the initiation of injury to the spine. While genetic predispositions may play a factor in the severity of spine degeneration or in the resiliency to applied load, ultimately, injury occurs when a load exceeds a tissue’s tolerance. Disc height loss has the potential to be a primary factor in the progression of spinal degeneration. For example, disc height has been touted as a major component for the initiation of pathological and degenerative changes to the spine. Pathologic, non-recoverable disc height loss can occur through herniation or endplate fracture and could result in a degenerative cascade of injury that eventually involves the facet joints, narrows nerve root space, and increases stress at adjacent segments. What is not known is the degree to which disc height affects the degenerative cascade; that is, there is no quantitative data outlining the progression of mechanical consequences at adjacent segments or at the injured segment itself during disc height loss. Further, the degree to which restoring disc height, if even possible, will reverse the process of degeneration is not entirely clear. There is data which suggests that nucleus replacement can restore stress distributions within an injured disc, but the extent of repair material survivability is unknown. Finally, clinical categories of measuring spinal degeneration are based on visual cues and features from medical imaging. Understanding the links between joint visual cues and aberrant movement may help to guide clinical practice; researchers will gain greater insight into the mechanical consequences of anatomical features associated with degeneration. This thesis was comprised of three studies. Study 1 examined the effect of disc height loss and subsequent restoration using an injectable hydrogel on the relative kinematics of a segment with height loss and an adjacent segment. It was found that disc height loss produced an immediate effect, where relative angular displacement was reduced in the segment with height loss and increased in the adjacent segment. Restoring disc height with an injectable hydrogel brought the relative angular displacement of both segments back to their initial values. This study is the first of its kind to examine the immediate effects of disc height loss via loss of nucleus pulposus and restoration. Whether these effects are as clear in-vivo remains to be seen. Study 2 evaluated the efficacy of a novel repair strategy to restore the mechanical profile of a spine segment with disc height loss initiated via compressive fracture. The strategy employed the use of PMMA injected into the vertebral body to attempt to seal a fracture from above the disc, and an injectable hydrogel to restore disc height. The use of PMMA was found to restore the compressive stiffness of the injured segment to within approximately 20% of its initial value, while the use of the injectable hydrogel restored the sagittal plane rotational stiffness to within approximately 50-80% of its initial value. After further repetitive compression had been applied to the spine segment however, the restorative influence of both interventions was lost in terms of rotational and compressive stiffness. It was found that large cracks in the endplate prevented the hydrogel from being contained and quickly returned the segment back to its injured profile. Future efforts at restoring the disc while maintaining its anatomical structures need better methods of creating a sufficient seal inside the disc to allow it to re-pressurize and sustain the stresses encountered on a daily basis. Study 3 employed the use of a novel spine tracking algorithm developed as part of this thesis to evaluate sagittal plane cervical spine motion of a series of patient image sequences who had experienced trauma and had a chief complaint related to their neck, head, or shoulders. Some patients had evidence of disc height loss while others did not. Clinical subgroups were created that classified disc height loss as either moderate/severe (3 cases), mild (8 cases), or non-existent (9 cases). When normalized angular displacement of the C5/C6 segment in a group with moderate to severe height loss was compared to the same level in a group with no height loss, there was a statistically significant difference in angular displacement between the two groups (p = 0.004). Angular displacement at C5/C6 was 20.2% ± 2.3% of total measured neck angular displacement in the moderate/severe height loss group compared to 30.6% ± 4.0% of total measured neck angular displacement in the group without height loss. Based on the limited sample size of this study it would appear that disc height loss creates a loss in range of motion. This work has further revealed the heterogeneous nature of individual segmental movement patterns. However, in the group without height loss, there was a systematic trend seen of an increasing angular displacement with descending segmental level. This was not observed in those with moderate to severe disc height loss. The broad implications of this work are that disc height loss influences spine kinematics, which has implications with respect to further injury propagation through the spinal linkage. Angular displacement of a spine segment appears to be governed by its local stiffness. Restoration of disc height under real injury scenarios is a difficult proposition and any attempts at repair need to sufficiently seal the disc space and prevent extrusion of nucleus pulposus or hydrogel-based implants. We now appreciate the difficulty in this objective. Further, repeating the mechanism of injury will reduce the mechanical effects of the restorative intervention, preventing this is highly important