Surgical Video Motion Magnification with Suppression of Instrument Artefacts

Video motion magnification could directly highlight subsurface blood vessels in endoscopic video in order to prevent inadvertent damage and bleeding. Applying motion filters to the full surgical image is however sensitive to residual motion from the surgical instruments and can impede practical application due to aberration motion artefacts. By storing the temporal filter response from local spatial frequency information for a single cardiovascular cycle prior to tool introduction to the scene, a filter can be used to determine if motion magnification should be active for a spatial region of the surgical image. In this paper, we propose a strategy to reduce aberration due to non-physiological motion for surgical video motion magnification. We present promising results on endoscopic transnasal transsphenoidal pituitary surgery with a quantitative comparison to recent methods using Structural Similarity (SSIM), as well as qualitative analysis by comparing spatio-temporal cross sections of the videos and individual frames.Comment: Early accept to the Internation Conference on Medical Imaging Computing and Computer Assisted Intervention (MICCAI) 2020 Presentation available here: https://www.youtube.com/watch?v=kKI_Ygny76Q Supplementary video available here: https://www.youtube.com/watch?v=8DUkcHI149

Surgical Video Motion Magnification with Suppression of Instrument Artefacts

Video motion magnification can make blood vessels in surgical video more apparent by exaggerating their pulsatile motion and could prevent inadvertent damage and bleeding due to their increased prominence. It could also indicate the success of restricting blood supply to an organ when using a vessel clamp. However, the direct application to surgical video could result in aberration artefacts caused by its sensitivity to residual motion from the surgical instruments and would impede its practical usage in the operating theatre. By storing the previously obtained jerk filter response of each spatial component of each image frame - both prior to surgical instrument introduction and adhering to a Eulerian frame of reference - it is possible to prevent such aberrations from occurring. The comparison of the current readings to the prior readings of a single cardiac cycle at the corresponding cycle point, are used to determine if motion magnification should be active for each spatial component of the surgical video at that given point in time. In this paper, we demonstrate this technique and incorporate a scaling variable to loosen the effect which accounts for variabilities and misalignments in the temporal domain. We present promising results on endoscopic transnasal transsphenoidal pituitary surgery with a quantitative comparison to recent methods using Structural Similarity (SSIM), as well as qualitative analysis by comparing spatio-temporal cross sections of the videos and individual frames

Engineering data compendium. Human perception and performance. User's guide

The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use

The Fourier analysis of saccadic eye movements

This thesis examines saccadic eye movements in the frequency domain and develops sensitive tools for characterising their dynamics. It tests a variety of saccade models and provides the first strong empirical evidence that saccades are time-optimal. By enabling inferences on the neural command, it also allows for better clinical differentiation of abnormalities and the evaluation of putative mechanisms for the development of congenital nystagmus. Chapters 3 and 4 show how Fourier transforms reveal sharp minima in saccade frequency spectra, which are robust to instrument noise. The minima allow models based purely on the output trajectory, purely on the neural input, or both, to be directly compared and distinguished. The standard, most commonly accepted model based on bang-bang control theory is discounted. Chapter 5 provides the first empirical evidence that saccades are time-optimal by demonstrating that saccade bandwidths overlap across amplitude onto a single slope at high frequencies. In Chapter 6, the overlap also allows optimal (Wiener) filtering in the frequency domain without a priori assumptions. Deconvolution of the aggregate neural driving signal is then possible for current models of the oculomotor plant. The final two chapters apply these Fourier techniques to the quick phases of physiological (optokinetic) nystagmus and of pathological (congenital) nystagmus. These quick phases are commonly assumed to be saccadic in origin. This assumption is thoroughly tested and found to hold, but with subtle differences implying that the smooth pursuit system interacts with the saccade system during the movement. This interaction is taken into account in Chapter 8 in the assessment of congenital nystagmus quick phases, which are found to be essentially normal. Congenital nystagmus models based on saccadic abnormalities are appraised

Analysis and Correction of Corneal Astigmatism in Modern Pseudophakia

Toric intraocular lenses (IOLs) are designed to reduce spectacle dependency by correcting corneal astigmatism at the time of surgery. However, these IOLs are reliant on the accurate prediction of post-operative corneal astigmatism through reliable ocular biometry and the accurate calculation of surgically induced astigmatism. In the thesis the repeatability of assessing corneal curvature was assessed using six commercially available keratometers. The results question the validity of corneal biometry and infer that much of the apparent change in corneal shape usually associated with surgically induced astigmatism may be due to measurement error. The use of the oblique cross cylinder formulae for the calculation of post-operative corneal curvature was also investigated. This formula is incorporated into all commercially available toric IOL calculators and is utilised in every toric IOL implantation. The results from this thesis indicate that the formula is not applicable to the human cornea and that the use of the calculator does not increase the effectivity of the toric correction. Furthermore, the thesis queries the assumption that post-operative corneal astigmatism is directly proportional to post-operative refractive error. The disparity between both the magnitude and axis of astigmatism measured by keratometry and manifest refraction in a pseudophakic population was investigated. The axis measurements in particular showed very poor agreement; far outside an acceptable level of misalignment, significantly decreasing the effective correction provided if the lens was aligned with the keratometry readings. Inclusion of the posterior corneal curvature and thickness, along with a smaller chord length may lead to a more accurate assessment of corneal power. Despite the difficulty in providing an effective toric IOL correction, it was found that the correction of corneal astigmatism at the time of cataract surgery might decrease the risks of falls. Uncorrected astigmatism and cataract both cause a reduction in stability when stepping oven an obstacle, which is one of the most common causes of trips and falls in the elderly population.Plymouth Universit

Wearable fusion system for assessment of motor function in lesion-symptom mapping studies

Lesion-symptom mapping studies are a critical component of addressing the relationship between brain and behaviour. Recent developments have yielded significant improvements in the imaging and detection of lesion profiles, but the quantification of motor outcomes is still largely performed by subjective and low-resolution standard clinical rating scales. This mismatch means than lesion-symptom mapping studies are limited in scope by scores which lack the necessary accuracy to fully quantify the subcomponents of motor function. The first study conducted aimed to develop a new automated system of motor function which addressed the limitations inherent in the clinical rating scales. A wearable fusion system was designed that included the attachment of inertial sensors to record the kinematics of upper extremity. This was combined with the novel application of mechanomyographic sensors in this field, to enable the quantification of hand/wrist function. Novel outputs were developed for this system which aimed to combine the validity of the clinical rating scales with the high accuracy of measurements possible with a wearable sensor system. This was achieved by the development of a sophisticated classification model which was trained on series of kinematic and myographic measures to classify the clinical rating scale. These classified scores were combined with a series of fine-grained clinical features derived from higher-order sensor metrics. The developed automated system graded the upper-extremity tasks of the Fugl-Meyer Assessment with a mean accuracy of 75\% for gross motor tasks and 66\% for the wrist/hand tasks. This accuracy increased to 85\% and 74\% when distinguishing between healthy and impaired function for each of these tasks. Several clinical features were computed to describe the subcomponents of upper extremity motor function. This fine-grained clinical feature set offers a novel means to complement the low resolution but well-validated standardised clinical rating scales. A second study was performed to utilise the fine-grained clinical feature set calculated in the previous study in a large-scale region-of-interest lesion-symptom mapping study. Statistically significant regions of motor dysfunction were found in the corticospinal tract and the internal capsule, which are consistent with other motor-based lesion-symptom mapping studies. In addition, the cortico-ponto-cerebellar tract was found to be statistically significant when testing with a clinical feature of hand/wrist motor function. This is a novel finding, potentially due to prior studies being limited to quantifying this subcomponent of motor function using standard clinical rating scales. These results indicate the validity and potential of the clinical feature set to provide a more detailed picture of motor dysfunction in lesion-symptom mapping studies.Open Acces

Characteristics and impact of nystagmus on visual acuity and eye movements in children with and without Down’s syndrome

Nystagmus, an involuntary oscillation of the eye, is one of the most common visual impairments occurring in individuals with Down’s syndrome, affecting between 15-30% of that population. In the typical population, nystagmus affects 0.02% of children. Due to the frequent occurrence of nystagmus in Down’s syndrome, nystagmus often appears to be assumed to be part of the condition and overlooked in this population of children. This study was designed to determine whether nystagmus is, in fact, the same or a different condition in children with and without Down’s syndrome. First, we investigated the visual characteristics of children with Down’s syndrome with and without nystagmus, by retrospectively reviewing clinical records of 198 children in the Down’s Syndrome Vision Research Unit cohort between 1992 and 2016. To compare the characteristics of nystagmus waveforms and the visual characteristics, we then conducted optometric assessments and recorded eye movements on 28 children with Down’s syndrome and 17 typically developing children with nystagmus. Further to this, we recorded the eye movements of both groups of children with nystagmus along with 20 children with Down’s syndrome and 20 typical children with no nystagmus while fixating on a stationary and a moving target. The aim was to characterize and compare the accuracy and precision of eye movements during fixation and when following a moving target for each group of children. The findings from this study suggest that nystagmus in children with Down’s syndrome is not a different condition from nystagmus in typically developing children. In addition, nystagmus has similar effects on visual acuity and eye movement performance in both groups of children with nystagmus. Therefore, children with Down’s syndrome and nystagmus should receive the same level of attention from health and education services that typical children with nystagmus do

Shear-promoted drug encapsulation into red blood cells: a CFD model and μ-PIV analysis

The present work focuses on the main parameters that influence shear-promoted encapsulation of drugs into erythrocytes. A CFD model was built to investigate the fluid dynamics of a suspension of particles flowing in a commercial micro channel. Micro Particle Image Velocimetry (μ-PIV) allowed to take into account for the real properties of the red blood cell (RBC), thus having a deeper understanding of the process. Coupling these results with an analytical diffusion model, suitable working conditions were defined for different values of haematocrit