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Papers by Daniel Leff

Research paper thumbnail of Investigation of Partial Directed Coherence for Hand-Eye Coordination in Laparoscopic Training

Lecture Notes in Computer Science, 2008

Effective hand-eye coordination is an important aspect of training in laparoscopic surgery. This ... more Effective hand-eye coordination is an important aspect of training in laparoscopic surgery. This paper investigates the interdependency of the hand and eye movement along with the variability of their temporal relationships based on Granger-causality. Partial directed coherence is used to reveal the subtle effects of improvement in hand-eye coordination, where the causal relationship between instrument and eye movement gradually reverse during simple laparoscopic tasks. For assessing the practical value of the proposed technique for minimally invasive surgery, two laparoscopic experiments have been conducted to examine the ability of the trainees in handling mental rotation tasks, as well as dissection and manipulation skills in laparoscopic surgery. Detailed experimental results highlight the value of the technique in investigating handeye coordination in laparoscopic training, particularly during early motor learning for complex bimanual procedures.

Research paper thumbnail of Is the presence of small volume disease in the sentinel node an indication for axillary clearance?

The finding of micrometastases (M(i)) and isolated tumour cells (ITC) within the axillary lymph n... more The finding of micrometastases (M(i)) and isolated tumour cells (ITC) within the axillary lymph nodes of patients with breast cancer has raised the question whether either/both have some prognostic significance. Several studies have shown that compared to node-negative patients, prognosis is significantly poorer in patients with M(i) and ITC. The fact that patients with M(i)/ITC in their sentinel lymph nodes have a systemic relapse risk that is higher than that of node-negative patients may be considered as an indication for systemic treatment. Most studies in the literature suggest that in patients with M(i) or ITC in their sentinel nodes who receive systemic therapy and whole breast radiotherapy, the risk of axillary relapse without axillary lymphadenectomy is under 2%. Given the fact that axillary lymphadenectomy is associated with a 5-25% risk of lymphoedema, we propose that a policy of close follow up should be adopted in these patients rather than axillary lymphadenectomy.

Research paper thumbnail of Changes in prefrontal cortical behaviour depend upon familiarity on a bimanual co-ordination task: an fNIRS study

NeuroImage, Jan 15, 2008

To investigate neurocognitive mechanisms associated with task-related expertise development, this... more To investigate neurocognitive mechanisms associated with task-related expertise development, this paper investigates serial changes in prefrontal activation patterns using functional near infrared spectroscopy (fNIRS). We evaluate cortical function in 62 healthy subjects with varying experience during serial evaluations of a knot-tying task. All tasks were performed bimanually and self paced, with fixed episodes of motor rest for five repetitions. Improvements in technical skill were evaluated using dexterity indices to quantify time, total movements and pathlength required to complete trials. Significant improvements in technical skills were observed in novices between the 2nd and 3rd trials, associated with increasing task familiarity. In trained subjects, minimal fluctuation in task-related oxyhaemoglobin (HbO(2)) and deoxyhaemoglobin (HHb) changes were observed in association with more stable task performance. In contrast, two significant transitions in prefrontal haemodynamic c...

Research paper thumbnail of The frontal cortex is activated during learning of endoscopic procedures (Ohuchida et al., Surgical Endoscopy , January 2009)

Surgical Endoscopy and Other Interventional Techniques, 2010

Research paper thumbnail of Functional Near Infrared Spectroscopy in Novice and Expert Surgeons – A Manifold Embedding Approach

Lecture Notes in Computer Science, 2007

Monitoring expertise development in surgery is likely to benefit from evaluations of cortical bra... more Monitoring expertise development in surgery is likely to benefit from evaluations of cortical brain function. Brain behaviour is dynamic and nonlinear. The aim of this paper is to evaluate the application of a nonlinear dimensionality reduction technique to enhance visualisation of multidimensional functional Near Infrared Spectroscopy (fNIRS) data. Manifold embedding is applied to prefrontal haemodynamic signals obtained during a surgical knot tying task from a group of 62 healthy subjects with varying surgical expertise. The proposed method makes no assumption about the functionality of the data set and is shown to be capable of recovering the intrinsic low dimensional structure of in vivo brain data. After manifold embedding, Earth Mover's Distance (EMD) is used to quantify different patterns of cortical behaviour associated with surgical expertise and analyse the degree of inter-hemispheric channel pair symmetry.

Research paper thumbnail of Cognitive burden estimation for visuomotor learning with fNIRS

Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention, 2010

Novel robotic technologies utilised in surgery need assessment for their effects on the user as w... more Novel robotic technologies utilised in surgery need assessment for their effects on the user as well as on technical performance. In this paper, the evolution in 'cognitive burden' across visuomotor learning is quantified using a combination of functional near infrared spectroscopy (fNIRS) and graph theory. The results demonstrate escalating costs within the activated cortical network during the intermediate phase of learning which is manifest as an increase in cognitive burden. This innovative application of graph theory and fNIRS enables the economic evaluation of brain behaviour underpinning task execution and how this may be impacted by novel technology and learning. Consequently, this may shed light on how robotic technologies improve human-machine interaction and augment minimally invasive surgical skills acquisition. This work has significant implications for the development and assessment of emergent robotic technologies at cortical level and in elucidating learning-...

Research paper thumbnail of Modelling Dynamic Fronto-Parietal Behaviour During Minimally Invasive Surgery – A Markovian Trip Distribution Approach

Lecture Notes in Computer Science, 2008

Learning to perform Minimally Invasive Surgery (MIS) requires considerable attention, concentrati... more Learning to perform Minimally Invasive Surgery (MIS) requires considerable attention, concentration and spatial ability. Theoretically, this leads to activation in executive control (prefrontal) and visuospatial (parietal) centres of the brain. A novel approach is presented in this paper for analysing the flow of fronto-parietal haemodynamic behaviour and the associated variability between subjects. Serially acquired functional Near Infrared Spectroscopy (fNIRS) data from fourteen laparoscopic novices at different stages of learning is projected into a low-dimensional 'geospace', where sequentially acquired data is mapped to different locations. A trip distribution matrix based on consecutive directed trips between locations in the geospace reveals confluent fronto-parietal haemodynamic changes and a gravity model is applied to populate this matrix. To model global convergence in haemodynamic behaviour, a Markov chain is constructed and by comparing sequential haemodynamic distributions to the Markov's stationary distribution, inter-subject variability in learning an MIS task can be identified.

Research paper thumbnail of Functional prefrontal reorganization accompanies learning-associated refinements in surgery: A manifold embedding approach

Computer Aided Surgery, 2008

The prefrontal cortex (PFC) is known to be vital for acquisition of visuomotor skills, but its ro... more The prefrontal cortex (PFC) is known to be vital for acquisition of visuomotor skills, but its role in the attainment of complex technical skills which comprise both perceptual and motor components, such as those associated with surgery, remains poorly understood. We hypothesized that the prefrontal response to a surgical knot-tying task would be highly dependent on technical expertise, and that activation would wane in the context of learning success following extended practice. The present series of experiments investigated this issue, using functional Near Infrared Spectroscopy (fNIRS) and dexterity analysis to compare the PFC responses and technical skill of expert and novice surgeons performing a surgical knot-tying task in a block design experiment. Applying a data-embedding technique known as Isomap and Earth Mover's Distance (EMD) analysis, marked differences in cortical hemodynamic responses between expert and novice surgeons have been found. To determine whether refinement in technical skill was associated with reduced PFC demands, a second experiment assessed the impact of pre- and post-training on the PFC responses in novices. Significant improvements (p < 0.01) were observed in all performance parameters following training. Smaller EMD distances were observed between expert surgeons and novices following training, suggesting an evolving pattern of cortical responses. A random effect model demonstrated a statistically significant decrease in relative changes of total hemoglobin (Delta HbT) [coefficient = -3.825, standard error (s.e.) = 0.8353, z = -4.58, p < 0.001] and oxygenated hemoglobin (Delta HbO(2)) [coefficient = -4.6815, s.e = 0.6781, z = -6.90, p < 0.001] and a significant increase in deoxygenated hemoglobin (Delta HHb) [coefficient = 0.8192, s.e = 0.3034, z = 2.66, p < 0.01] across training. The results indicate that learning-related refinements in technical performance are mediated by temporal reductions in prefrontal activation.

Research paper thumbnail of New Technologies for the Surgical Curriculum

World Journal of Surgery, 2008

The aim of a surgical residency program is to produce competent professionals displaying the cogn... more The aim of a surgical residency program is to produce competent professionals displaying the cognitive, technical, and personal skills required to meet the needs of society. Current changes to the delivery of healthcare necessitate the development of new models of training. These can be supported with the development of new technologies to train and assess surgical practitioners. This article describes recent developments within Imperial College London with regard to eye tracking, noninvasive brain imaging, and an innovative mentoring scheme for the new surgical curriculum. The concept of eye tracking is described, together with surgical application for this technique in terms of dexterity analysis during minimally invasive procedures. We have also begun to understand spatial localization within the brain cortex during surgical knot-tying tasks. The aim is to develop a map of the cortex with regard to surgical novices and experienced surgeons and then to develop the hypothesis that a translational process of cortical plasticity occurs during training. Finally, the article is intended to describe a training scheme that goes beyond dexterity, and moves toward the development of a successful surgeon through surgical mentoring. It is hoped that some of these tools will enhance

Research paper thumbnail of Emergency and Elective Laparoscopic Repair of Spigelian Hernias

Surgical Laparoscopy, Endoscopy & Percutaneous Techniques, 2009

Diagnosing spigelian hernias through physical examination can be particularly challenging. Increa... more Diagnosing spigelian hernias through physical examination can be particularly challenging. Increasingly, laparoscopy is being used to both confirm the diagnosis and carry out therapeutic repair. Here, we describe 2 cases of successful laparoscopic repair of spigelian hernias using an Endocatch assisted sutured technique. A review of the literature describing the role of laparoscopy in the management of spigelian hernia is also provided.

Research paper thumbnail of The ergonomics of natural orifice translumenal endoscopic surgery (NOTES) navigation in terms of performance, stress, and cognitive behavior

Surgery, 2011

Background. The evolution toward minimally invasive surgery and subsequently to natural orifice t... more Background. The evolution toward minimally invasive surgery and subsequently to natural orifice translumenal endoscopic surgery (NOTES) poses challenges to the surgeon in terms of increased task complexity requiring greater visuospatial and navigational ability. Neuroergonomics is the study of the brain and behavior at work, and establishing the baseline cortical response for NOTES procedures will help to ascertain whether technological innovation such as navigational aids can alleviate the taskinduced cognitive burden. The aims of the current study are to characterize the impact of navigation within a NOTES environment on the subject in terms of (1) performance, (2) stress, (3) prefrontal cortical activity, and (4) how this is influenced by expertise. Methods. In all, 29 subjects were assessed for performance, stress response, and prefrontal cortical activity during a NOTES navigational task within a validated NOTES simulator. Results. Experts performed significantly better than novices (P < .05). Expertise was not a predictor for overall changes in prefrontal cortical activity. The differences between experts and novices were modulated by the location of prefrontal cortical activity, with experts demonstrating more pronounced lateral prefrontal cortical activation compared with novices. Stress was not an independent predictor of changes in prefrontal cortical hemodynamics.

Research paper thumbnail of Changes in prefrontal cortical behaviour depend upon familiarity on a bimanual co-ordination task: An fNIRS study☆

NeuroImage, 2008

To investigate neurocognitive mechanisms associated with task-related expertise development, this... more To investigate neurocognitive mechanisms associated with task-related expertise development, this paper investigates serial changes in prefrontal activation patterns using functional near infrared spectroscopy (fNIRS). We evaluate cortical function in 62 healthy subjects with varying experience during serial evaluations of a knot-tying task. All tasks were performed bimanually and self paced, with fixed episodes of motor rest for five repetitions. Improvements in technical skill were evaluated using dexterity indices to quantify time, total movements and pathlength required to complete trials. Significant improvements in technical skills were observed in novices between the 2nd and 3rd trials, associated with increasing task familiarity. In trained subjects, minimal fluctuation in task-related oxyhaemoglobin (HbO 2 ) and deoxyhaemoglobin (HHb) changes were observed in association with more stable task performance. In contrast, two significant transitions in prefrontal haemodynamic change were observed in novices. Greater task-related increases in HbO 2 and decreases in HHb were identified on the second trial compared to the first. Relative decreases in HbO 2 and increases in HHb change were observed between the third and fourth, and fourth and fifth trials respectively. These data suggest that prefrontal processing across five knot-tying trials is influenced by the level of experience on a task. Modifications in prefrontal activation appear to confer technical performance adaptation in novices.

Research paper thumbnail of Assessment of the cerebral cortex during motor task behaviours in adults: A systematic review of functional near infrared spectroscopy (fNIRS) studies

NeuroImage, 2011

Functional near infrared spectroscopy (fNIRS) is an emerging tool for non-invasively monitoring t... more Functional near infrared spectroscopy (fNIRS) is an emerging tool for non-invasively monitoring the haemodynamic response to brain activation. The technique has been widely adopted to investigate cortical responses during motor tasks in health and disease. This systematic review provides a critical analysis of the research findings in the hope of summating relevant information, identifying consistent outcomes acquired using different spectrometers, clarifying data inconsistencies, and learning from the common challenges across disciplines. The spatiotemporal characteristics, reliability, repeatability and modulation of typical cortical response evoked by motor stimulation are all evaluated in detail. The review assesses the contribution of the technique to advancing our understanding of motor skill learning and control in the context of tasks of everyday living, athletic performance, and recovery from neurological illness. Finally, the limitations of current fNIRS technologies are examined and a series of recommendations for future studies are provided based upon the reviewed literature.

Research paper thumbnail of Gaze-Contingent Motor Channelling, haptic constraints and associated cognitive demand for robotic MIS

Medical Image Analysis, 2012

The success of MIS is coupled with an increasing demand on surgeons&amp;amp;amp;amp;amp;amp;a... more The success of MIS is coupled with an increasing demand on surgeons&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; manual dexterity and visuomotor coordination due to the complexity of instrument manipulations. The use of master-slave surgical robots has avoided many of the drawbacks of MIS, but at the same time, has increased the physical separation between the surgeon and the patient. Tissue deformation combined with restricted workspace and visibility of an already cluttered environment can raise critical issues related to surgical precision and safety. Reconnecting the essential visuomotor sensory feedback is important for the safe practice of robot-assisted MIS procedures. This paper introduces a novel gaze-contingent framework for real-time haptic feedback and virtual fixtures by transforming visual sensory information into physical constraints that can interact with the motor sensory channel. We demonstrate how motor tracking of deforming tissue can be made more effective and accurate through the concept of Gaze-Contingent Motor Channelling. The method is also extended to 3D by introducing the concept of Gaze-Contingent Haptic Constraints where eye gaze is used to dynamically prescribe and update safety boundaries during robot-assisted MIS without prior knowledge of the soft-tissue morphology. Initial validation results on both simulated and robot assisted phantom procedures demonstrate the potential clinical value of the technique. In order to assess the associated cognitive demand of the proposed concepts, functional Near-Infrared Spectroscopy is used and preliminary results are discussed.

Research paper thumbnail of The Neurocognitive Enhancement of Surgeons: An Ethical Perspective

Journal of Surgical Research, 2009

Neurocognitive enhancement is a rapidly expanding scientific field. The vast ethical implications... more Neurocognitive enhancement is a rapidly expanding scientific field. The vast ethical implications of this developing field for surgical practice have yet to be considered within the literature. This article outlines the reasons surgeons may, in the near future, consider using neurocognitive enhancement and addresses the resulting significant ethical implications of this. We do not seek to support or denounce the potential role of neurocognitive enhancement in surgeons, but to stimulate a debate, which, with ever-increasing levels of stimulant use in schools and colleges, and with a pharmaceutical industry driving the creation of new neuroactive products, has now become a necessity.

Research paper thumbnail of Skeletonization of radial and gastroepiploic conduits in coronary artery bypass surgery

Journal of Cardiothoracic Surgery, 2007

The use of a skeletonized internal thoracic artery in coronary artery bypass graft surgery has be... more The use of a skeletonized internal thoracic artery in coronary artery bypass graft surgery has been shown to confer certain advantages over a traditional pedicled technique, particularly in certain patient groups. Recent reports indicate that radial and gastroepiploic arteries can also be harvested using a skeletonized technique. The aim of this study is to systematically review the available evidence regarding the use of skeletonized radial and gastroepiploic arteries within coronary artery bypass surgery, focusing specifically on it's effect on conduit length and flow, levels of endothelial damage, graft patency and clinical outcome. Four electronic databases were systematically searched for studies reporting the utilisation of the skeletonization technique within coronary revascularisation surgery in humans. Reference lists of all identified studies were checked for any missing publications. There appears to be some evidence that skeletonization may improve angiographic patency, when compared with pedicled vessels in the short to mid-term. We have found no suggestion of increased complication rates or increased operating time. Skeletonization may increase the length of the conduit, and the number of sequential graft sites, but no clear clinical benefits are apparent. Our study suggests that there is not enough high quality or consistent evidence to currently advocate the application of this technique to radial or gastroepiploic conduits ahead of a traditional pedicled technique.

Research paper thumbnail of Anorectal symptoms during pregnancy: how important is trimester?

International Journal of Colorectal Disease, 2010

The frequency of anorectal symptoms amongst pregnant women has not been objectively investigated ... more The frequency of anorectal symptoms amongst pregnant women has not been objectively investigated in the United Kingdom. The aim of this study was to determine the frequency of anorectal symptoms during each trimester of pregnancy. Women attending the antenatal clinics at a London teaching hospital were asked to complete a questionnaire. The presence or absence of common anorectal symptoms experienced both before and during the current pregnancy together with demographic and pregnancy data was collected. Statistical analysis was performed using Fisher&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s exact test. Two hundred seventeen patients (first trimester n=75, second trimester n=70 and third trimester n=72) participated. A significant increase in the frequency of symptoms was observed in the third (43.1%) compared to the first (16.0%, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001) and second (22.9%, p=0.013) trimesters. The incidence of per rectal bleeding was significantly greater in the third trimester (30.6%) compared to the first (10.6%, p=0.004) and the second (12.9%, p=0.014) trimesters. Similarly, anal pain was significantly more frequent in the third trimester (34.7%) compared to the first (13.3%, p=0.003) and the second (12.9%, p=0.003) trimesters. The frequency of anorectal symptom reporting appears to increase as pregnancy progresses. Further investigation and research is warranted to determine the configuration of services that may be required to treat those affected.

Research paper thumbnail of Recombinant activated factor VII: a solution to refractory haemorrhage in vascular surgery?

Post-operative haemorrhage is a recognised complication and independent predictor of outcome in c... more Post-operative haemorrhage is a recognised complication and independent predictor of outcome in complex vascular surgery. The off-license administration of activated Recombinant Factor VII (rFVIIa) to treat haemorrhage in other surgical settings has been investigated, but concerns over potential adverse events have limited its use in vascular surgery. This article reports rFVIIa&#39;s method of action and systematically reviews rFVIIa&#39;s role in complex vascular surgery. A systematic literature search identified articles reporting on rFVIIa administration within vascular surgery patients. Patient-specific data regarding transfusion requirements was extracted and pooled statistical analysis performed. 15 articles reporting 43 patients were identified. RFVIIa has been administered in open and endovascular procedures and in both elective and emergency settings. Major aortic surgery accounted for 75% of cases. The range of rFVIIa administered as a cumulative dose was large, as was the variation in initial dose. Transfusion data from 9 patients was pooled and analysed. Significant differences were found between pre- and post- rFVIIa for packed red cell transfusions (mean 29.2 vs. 8.2, p=0.015). Intra-arterial thrombosis was reported in 3 cases. RFVIIa may reduce haemorrhage in selected vascular surgical patients. Randomized controlled trials are justified to definitively investigate its role within this setting.

Research paper thumbnail of The effects of various leukocyte filtration strategies in cardiac surgery

European Journal of Cardio-Thoracic Surgery, 2007

It is known that cardiopulmonary bypass causes an inflammatory reaction with an associated morbid... more It is known that cardiopulmonary bypass causes an inflammatory reaction with an associated morbidity and mortality. Several antiinflammatory strategies have been implemented to reduce this response, including leukocyte removal from the circulation using specialised filters. The aim of this study is to systematically review the available evidence on leukocyte filtration in cardiac surgery, focusing on its effect on systemic inflammation and whether this has influenced clinical outcomes. Five electronic databases were systematically searched for studies reporting the effect of leukocyte filtration at any point within the cardiopulmonary bypass circuit in humans. Reference lists of all identified studies were checked for any missing publications. Two authors independently extracted the data from the included studies. Whilst systemic leukodepleting filters do not appear to consistently lower leukocyte counts, they may preferentially remove activated leukocytes. Small improvements in early post-operative lung function in patients receiving systemic leukodepletion have been reported, but this does not lead to reduced hospital stay or decreased mortality. There is substantial evidence that cardioplegic leukocyte filtration attenuates the reperfusion injury at a cellular level, but this has not been translated into clinical improvements. Finally, whilst various strategies involving multiple leukocyte filters, or the incorporation of pharmacological agents into leukocyte-depleting protocols have been evaluated, the current available results are not conclusive. Our study suggests that there is not enough high quality or consistent evidence to draw guidelines regarding the use of leukocyte-depleting filters within routine cardiac surgical practice. #

Research paper thumbnail of Diffuse optical imaging of the healthy and diseased breast: A systematic review

Breast Cancer Research and Treatment, 2008

Screening X-ray mammography is limited by false positives and negatives leading to unnecessary ph... more Screening X-ray mammography is limited by false positives and negatives leading to unnecessary physical and psychological morbidity. Diffuse Optical Imaging using harmless near infra red light, provides lesion detection based on functional abnormalities and represents a novel diagnostic arm that could compliment traditional mammography. Reviews of optical breast imaging have not been systematic, are focused mainly on technological developments, and have become superseded by rapid technological advancement. The aim of this study is to review clinically orientated studies involving approximately 2,000 women in whom Near InfraRed Spectroscopy has been used to evaluate the healthy or diseased bearing breast. The results suggest that approximately 85% of breast lesions are detectable on Optical Mammography. Spectroscopic resolution of tissue haemoglobin composition and oxygen saturation may improve the detectability of breast disease. Results confirm that breast lesions contain approximately twice the haemoglobin concentration of background tissue. Current evidence suggests that it is not possible to distinguish benign from malignant disease is using optical imaging techniques in isolation. Methods to improve the spatial resolution of Diffuse Optical Imaging, such as better spectral coverage with additional wavelengths, enhanced modelling of light transport in tissues and the use of extrinsic dyes may augment lesion detection and characterisation. Future research should involve large clinical trials to determine the overall sensitivity and specificity of optical imaging techniques as well as to establish patient satisfaction and economic viability.

Research paper thumbnail of Investigation of Partial Directed Coherence for Hand-Eye Coordination in Laparoscopic Training

Lecture Notes in Computer Science, 2008

Effective hand-eye coordination is an important aspect of training in laparoscopic surgery. This ... more Effective hand-eye coordination is an important aspect of training in laparoscopic surgery. This paper investigates the interdependency of the hand and eye movement along with the variability of their temporal relationships based on Granger-causality. Partial directed coherence is used to reveal the subtle effects of improvement in hand-eye coordination, where the causal relationship between instrument and eye movement gradually reverse during simple laparoscopic tasks. For assessing the practical value of the proposed technique for minimally invasive surgery, two laparoscopic experiments have been conducted to examine the ability of the trainees in handling mental rotation tasks, as well as dissection and manipulation skills in laparoscopic surgery. Detailed experimental results highlight the value of the technique in investigating handeye coordination in laparoscopic training, particularly during early motor learning for complex bimanual procedures.

Research paper thumbnail of Is the presence of small volume disease in the sentinel node an indication for axillary clearance?

The finding of micrometastases (M(i)) and isolated tumour cells (ITC) within the axillary lymph n... more The finding of micrometastases (M(i)) and isolated tumour cells (ITC) within the axillary lymph nodes of patients with breast cancer has raised the question whether either/both have some prognostic significance. Several studies have shown that compared to node-negative patients, prognosis is significantly poorer in patients with M(i) and ITC. The fact that patients with M(i)/ITC in their sentinel lymph nodes have a systemic relapse risk that is higher than that of node-negative patients may be considered as an indication for systemic treatment. Most studies in the literature suggest that in patients with M(i) or ITC in their sentinel nodes who receive systemic therapy and whole breast radiotherapy, the risk of axillary relapse without axillary lymphadenectomy is under 2%. Given the fact that axillary lymphadenectomy is associated with a 5-25% risk of lymphoedema, we propose that a policy of close follow up should be adopted in these patients rather than axillary lymphadenectomy.

Research paper thumbnail of Changes in prefrontal cortical behaviour depend upon familiarity on a bimanual co-ordination task: an fNIRS study

NeuroImage, Jan 15, 2008

To investigate neurocognitive mechanisms associated with task-related expertise development, this... more To investigate neurocognitive mechanisms associated with task-related expertise development, this paper investigates serial changes in prefrontal activation patterns using functional near infrared spectroscopy (fNIRS). We evaluate cortical function in 62 healthy subjects with varying experience during serial evaluations of a knot-tying task. All tasks were performed bimanually and self paced, with fixed episodes of motor rest for five repetitions. Improvements in technical skill were evaluated using dexterity indices to quantify time, total movements and pathlength required to complete trials. Significant improvements in technical skills were observed in novices between the 2nd and 3rd trials, associated with increasing task familiarity. In trained subjects, minimal fluctuation in task-related oxyhaemoglobin (HbO(2)) and deoxyhaemoglobin (HHb) changes were observed in association with more stable task performance. In contrast, two significant transitions in prefrontal haemodynamic c...

Research paper thumbnail of The frontal cortex is activated during learning of endoscopic procedures (Ohuchida et al., Surgical Endoscopy , January 2009)

Surgical Endoscopy and Other Interventional Techniques, 2010

Research paper thumbnail of Functional Near Infrared Spectroscopy in Novice and Expert Surgeons – A Manifold Embedding Approach

Lecture Notes in Computer Science, 2007

Monitoring expertise development in surgery is likely to benefit from evaluations of cortical bra... more Monitoring expertise development in surgery is likely to benefit from evaluations of cortical brain function. Brain behaviour is dynamic and nonlinear. The aim of this paper is to evaluate the application of a nonlinear dimensionality reduction technique to enhance visualisation of multidimensional functional Near Infrared Spectroscopy (fNIRS) data. Manifold embedding is applied to prefrontal haemodynamic signals obtained during a surgical knot tying task from a group of 62 healthy subjects with varying surgical expertise. The proposed method makes no assumption about the functionality of the data set and is shown to be capable of recovering the intrinsic low dimensional structure of in vivo brain data. After manifold embedding, Earth Mover's Distance (EMD) is used to quantify different patterns of cortical behaviour associated with surgical expertise and analyse the degree of inter-hemispheric channel pair symmetry.

Research paper thumbnail of Cognitive burden estimation for visuomotor learning with fNIRS

Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention, 2010

Novel robotic technologies utilised in surgery need assessment for their effects on the user as w... more Novel robotic technologies utilised in surgery need assessment for their effects on the user as well as on technical performance. In this paper, the evolution in 'cognitive burden' across visuomotor learning is quantified using a combination of functional near infrared spectroscopy (fNIRS) and graph theory. The results demonstrate escalating costs within the activated cortical network during the intermediate phase of learning which is manifest as an increase in cognitive burden. This innovative application of graph theory and fNIRS enables the economic evaluation of brain behaviour underpinning task execution and how this may be impacted by novel technology and learning. Consequently, this may shed light on how robotic technologies improve human-machine interaction and augment minimally invasive surgical skills acquisition. This work has significant implications for the development and assessment of emergent robotic technologies at cortical level and in elucidating learning-...

Research paper thumbnail of Modelling Dynamic Fronto-Parietal Behaviour During Minimally Invasive Surgery – A Markovian Trip Distribution Approach

Lecture Notes in Computer Science, 2008

Learning to perform Minimally Invasive Surgery (MIS) requires considerable attention, concentrati... more Learning to perform Minimally Invasive Surgery (MIS) requires considerable attention, concentration and spatial ability. Theoretically, this leads to activation in executive control (prefrontal) and visuospatial (parietal) centres of the brain. A novel approach is presented in this paper for analysing the flow of fronto-parietal haemodynamic behaviour and the associated variability between subjects. Serially acquired functional Near Infrared Spectroscopy (fNIRS) data from fourteen laparoscopic novices at different stages of learning is projected into a low-dimensional 'geospace', where sequentially acquired data is mapped to different locations. A trip distribution matrix based on consecutive directed trips between locations in the geospace reveals confluent fronto-parietal haemodynamic changes and a gravity model is applied to populate this matrix. To model global convergence in haemodynamic behaviour, a Markov chain is constructed and by comparing sequential haemodynamic distributions to the Markov's stationary distribution, inter-subject variability in learning an MIS task can be identified.

Research paper thumbnail of Functional prefrontal reorganization accompanies learning-associated refinements in surgery: A manifold embedding approach

Computer Aided Surgery, 2008

The prefrontal cortex (PFC) is known to be vital for acquisition of visuomotor skills, but its ro... more The prefrontal cortex (PFC) is known to be vital for acquisition of visuomotor skills, but its role in the attainment of complex technical skills which comprise both perceptual and motor components, such as those associated with surgery, remains poorly understood. We hypothesized that the prefrontal response to a surgical knot-tying task would be highly dependent on technical expertise, and that activation would wane in the context of learning success following extended practice. The present series of experiments investigated this issue, using functional Near Infrared Spectroscopy (fNIRS) and dexterity analysis to compare the PFC responses and technical skill of expert and novice surgeons performing a surgical knot-tying task in a block design experiment. Applying a data-embedding technique known as Isomap and Earth Mover&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s Distance (EMD) analysis, marked differences in cortical hemodynamic responses between expert and novice surgeons have been found. To determine whether refinement in technical skill was associated with reduced PFC demands, a second experiment assessed the impact of pre- and post-training on the PFC responses in novices. Significant improvements (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01) were observed in all performance parameters following training. Smaller EMD distances were observed between expert surgeons and novices following training, suggesting an evolving pattern of cortical responses. A random effect model demonstrated a statistically significant decrease in relative changes of total hemoglobin (Delta HbT) [coefficient = -3.825, standard error (s.e.) = 0.8353, z = -4.58, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001] and oxygenated hemoglobin (Delta HbO(2)) [coefficient = -4.6815, s.e = 0.6781, z = -6.90, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001] and a significant increase in deoxygenated hemoglobin (Delta HHb) [coefficient = 0.8192, s.e = 0.3034, z = 2.66, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01] across training. The results indicate that learning-related refinements in technical performance are mediated by temporal reductions in prefrontal activation.

Research paper thumbnail of New Technologies for the Surgical Curriculum

World Journal of Surgery, 2008

The aim of a surgical residency program is to produce competent professionals displaying the cogn... more The aim of a surgical residency program is to produce competent professionals displaying the cognitive, technical, and personal skills required to meet the needs of society. Current changes to the delivery of healthcare necessitate the development of new models of training. These can be supported with the development of new technologies to train and assess surgical practitioners. This article describes recent developments within Imperial College London with regard to eye tracking, noninvasive brain imaging, and an innovative mentoring scheme for the new surgical curriculum. The concept of eye tracking is described, together with surgical application for this technique in terms of dexterity analysis during minimally invasive procedures. We have also begun to understand spatial localization within the brain cortex during surgical knot-tying tasks. The aim is to develop a map of the cortex with regard to surgical novices and experienced surgeons and then to develop the hypothesis that a translational process of cortical plasticity occurs during training. Finally, the article is intended to describe a training scheme that goes beyond dexterity, and moves toward the development of a successful surgeon through surgical mentoring. It is hoped that some of these tools will enhance

Research paper thumbnail of Emergency and Elective Laparoscopic Repair of Spigelian Hernias

Surgical Laparoscopy, Endoscopy & Percutaneous Techniques, 2009

Diagnosing spigelian hernias through physical examination can be particularly challenging. Increa... more Diagnosing spigelian hernias through physical examination can be particularly challenging. Increasingly, laparoscopy is being used to both confirm the diagnosis and carry out therapeutic repair. Here, we describe 2 cases of successful laparoscopic repair of spigelian hernias using an Endocatch assisted sutured technique. A review of the literature describing the role of laparoscopy in the management of spigelian hernia is also provided.

Research paper thumbnail of The ergonomics of natural orifice translumenal endoscopic surgery (NOTES) navigation in terms of performance, stress, and cognitive behavior

Surgery, 2011

Background. The evolution toward minimally invasive surgery and subsequently to natural orifice t... more Background. The evolution toward minimally invasive surgery and subsequently to natural orifice translumenal endoscopic surgery (NOTES) poses challenges to the surgeon in terms of increased task complexity requiring greater visuospatial and navigational ability. Neuroergonomics is the study of the brain and behavior at work, and establishing the baseline cortical response for NOTES procedures will help to ascertain whether technological innovation such as navigational aids can alleviate the taskinduced cognitive burden. The aims of the current study are to characterize the impact of navigation within a NOTES environment on the subject in terms of (1) performance, (2) stress, (3) prefrontal cortical activity, and (4) how this is influenced by expertise. Methods. In all, 29 subjects were assessed for performance, stress response, and prefrontal cortical activity during a NOTES navigational task within a validated NOTES simulator. Results. Experts performed significantly better than novices (P < .05). Expertise was not a predictor for overall changes in prefrontal cortical activity. The differences between experts and novices were modulated by the location of prefrontal cortical activity, with experts demonstrating more pronounced lateral prefrontal cortical activation compared with novices. Stress was not an independent predictor of changes in prefrontal cortical hemodynamics.

Research paper thumbnail of Changes in prefrontal cortical behaviour depend upon familiarity on a bimanual co-ordination task: An fNIRS study☆

NeuroImage, 2008

To investigate neurocognitive mechanisms associated with task-related expertise development, this... more To investigate neurocognitive mechanisms associated with task-related expertise development, this paper investigates serial changes in prefrontal activation patterns using functional near infrared spectroscopy (fNIRS). We evaluate cortical function in 62 healthy subjects with varying experience during serial evaluations of a knot-tying task. All tasks were performed bimanually and self paced, with fixed episodes of motor rest for five repetitions. Improvements in technical skill were evaluated using dexterity indices to quantify time, total movements and pathlength required to complete trials. Significant improvements in technical skills were observed in novices between the 2nd and 3rd trials, associated with increasing task familiarity. In trained subjects, minimal fluctuation in task-related oxyhaemoglobin (HbO 2 ) and deoxyhaemoglobin (HHb) changes were observed in association with more stable task performance. In contrast, two significant transitions in prefrontal haemodynamic change were observed in novices. Greater task-related increases in HbO 2 and decreases in HHb were identified on the second trial compared to the first. Relative decreases in HbO 2 and increases in HHb change were observed between the third and fourth, and fourth and fifth trials respectively. These data suggest that prefrontal processing across five knot-tying trials is influenced by the level of experience on a task. Modifications in prefrontal activation appear to confer technical performance adaptation in novices.

Research paper thumbnail of Assessment of the cerebral cortex during motor task behaviours in adults: A systematic review of functional near infrared spectroscopy (fNIRS) studies

NeuroImage, 2011

Functional near infrared spectroscopy (fNIRS) is an emerging tool for non-invasively monitoring t... more Functional near infrared spectroscopy (fNIRS) is an emerging tool for non-invasively monitoring the haemodynamic response to brain activation. The technique has been widely adopted to investigate cortical responses during motor tasks in health and disease. This systematic review provides a critical analysis of the research findings in the hope of summating relevant information, identifying consistent outcomes acquired using different spectrometers, clarifying data inconsistencies, and learning from the common challenges across disciplines. The spatiotemporal characteristics, reliability, repeatability and modulation of typical cortical response evoked by motor stimulation are all evaluated in detail. The review assesses the contribution of the technique to advancing our understanding of motor skill learning and control in the context of tasks of everyday living, athletic performance, and recovery from neurological illness. Finally, the limitations of current fNIRS technologies are examined and a series of recommendations for future studies are provided based upon the reviewed literature.

Research paper thumbnail of Gaze-Contingent Motor Channelling, haptic constraints and associated cognitive demand for robotic MIS

Medical Image Analysis, 2012

The success of MIS is coupled with an increasing demand on surgeons&amp;amp;amp;amp;amp;amp;a... more The success of MIS is coupled with an increasing demand on surgeons&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; manual dexterity and visuomotor coordination due to the complexity of instrument manipulations. The use of master-slave surgical robots has avoided many of the drawbacks of MIS, but at the same time, has increased the physical separation between the surgeon and the patient. Tissue deformation combined with restricted workspace and visibility of an already cluttered environment can raise critical issues related to surgical precision and safety. Reconnecting the essential visuomotor sensory feedback is important for the safe practice of robot-assisted MIS procedures. This paper introduces a novel gaze-contingent framework for real-time haptic feedback and virtual fixtures by transforming visual sensory information into physical constraints that can interact with the motor sensory channel. We demonstrate how motor tracking of deforming tissue can be made more effective and accurate through the concept of Gaze-Contingent Motor Channelling. The method is also extended to 3D by introducing the concept of Gaze-Contingent Haptic Constraints where eye gaze is used to dynamically prescribe and update safety boundaries during robot-assisted MIS without prior knowledge of the soft-tissue morphology. Initial validation results on both simulated and robot assisted phantom procedures demonstrate the potential clinical value of the technique. In order to assess the associated cognitive demand of the proposed concepts, functional Near-Infrared Spectroscopy is used and preliminary results are discussed.

Research paper thumbnail of The Neurocognitive Enhancement of Surgeons: An Ethical Perspective

Journal of Surgical Research, 2009

Neurocognitive enhancement is a rapidly expanding scientific field. The vast ethical implications... more Neurocognitive enhancement is a rapidly expanding scientific field. The vast ethical implications of this developing field for surgical practice have yet to be considered within the literature. This article outlines the reasons surgeons may, in the near future, consider using neurocognitive enhancement and addresses the resulting significant ethical implications of this. We do not seek to support or denounce the potential role of neurocognitive enhancement in surgeons, but to stimulate a debate, which, with ever-increasing levels of stimulant use in schools and colleges, and with a pharmaceutical industry driving the creation of new neuroactive products, has now become a necessity.

Research paper thumbnail of Skeletonization of radial and gastroepiploic conduits in coronary artery bypass surgery

Journal of Cardiothoracic Surgery, 2007

The use of a skeletonized internal thoracic artery in coronary artery bypass graft surgery has be... more The use of a skeletonized internal thoracic artery in coronary artery bypass graft surgery has been shown to confer certain advantages over a traditional pedicled technique, particularly in certain patient groups. Recent reports indicate that radial and gastroepiploic arteries can also be harvested using a skeletonized technique. The aim of this study is to systematically review the available evidence regarding the use of skeletonized radial and gastroepiploic arteries within coronary artery bypass surgery, focusing specifically on it's effect on conduit length and flow, levels of endothelial damage, graft patency and clinical outcome. Four electronic databases were systematically searched for studies reporting the utilisation of the skeletonization technique within coronary revascularisation surgery in humans. Reference lists of all identified studies were checked for any missing publications. There appears to be some evidence that skeletonization may improve angiographic patency, when compared with pedicled vessels in the short to mid-term. We have found no suggestion of increased complication rates or increased operating time. Skeletonization may increase the length of the conduit, and the number of sequential graft sites, but no clear clinical benefits are apparent. Our study suggests that there is not enough high quality or consistent evidence to currently advocate the application of this technique to radial or gastroepiploic conduits ahead of a traditional pedicled technique.

Research paper thumbnail of Anorectal symptoms during pregnancy: how important is trimester?

International Journal of Colorectal Disease, 2010

The frequency of anorectal symptoms amongst pregnant women has not been objectively investigated ... more The frequency of anorectal symptoms amongst pregnant women has not been objectively investigated in the United Kingdom. The aim of this study was to determine the frequency of anorectal symptoms during each trimester of pregnancy. Women attending the antenatal clinics at a London teaching hospital were asked to complete a questionnaire. The presence or absence of common anorectal symptoms experienced both before and during the current pregnancy together with demographic and pregnancy data was collected. Statistical analysis was performed using Fisher&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s exact test. Two hundred seventeen patients (first trimester n=75, second trimester n=70 and third trimester n=72) participated. A significant increase in the frequency of symptoms was observed in the third (43.1%) compared to the first (16.0%, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001) and second (22.9%, p=0.013) trimesters. The incidence of per rectal bleeding was significantly greater in the third trimester (30.6%) compared to the first (10.6%, p=0.004) and the second (12.9%, p=0.014) trimesters. Similarly, anal pain was significantly more frequent in the third trimester (34.7%) compared to the first (13.3%, p=0.003) and the second (12.9%, p=0.003) trimesters. The frequency of anorectal symptom reporting appears to increase as pregnancy progresses. Further investigation and research is warranted to determine the configuration of services that may be required to treat those affected.

Research paper thumbnail of Recombinant activated factor VII: a solution to refractory haemorrhage in vascular surgery?

Post-operative haemorrhage is a recognised complication and independent predictor of outcome in c... more Post-operative haemorrhage is a recognised complication and independent predictor of outcome in complex vascular surgery. The off-license administration of activated Recombinant Factor VII (rFVIIa) to treat haemorrhage in other surgical settings has been investigated, but concerns over potential adverse events have limited its use in vascular surgery. This article reports rFVIIa&#39;s method of action and systematically reviews rFVIIa&#39;s role in complex vascular surgery. A systematic literature search identified articles reporting on rFVIIa administration within vascular surgery patients. Patient-specific data regarding transfusion requirements was extracted and pooled statistical analysis performed. 15 articles reporting 43 patients were identified. RFVIIa has been administered in open and endovascular procedures and in both elective and emergency settings. Major aortic surgery accounted for 75% of cases. The range of rFVIIa administered as a cumulative dose was large, as was the variation in initial dose. Transfusion data from 9 patients was pooled and analysed. Significant differences were found between pre- and post- rFVIIa for packed red cell transfusions (mean 29.2 vs. 8.2, p=0.015). Intra-arterial thrombosis was reported in 3 cases. RFVIIa may reduce haemorrhage in selected vascular surgical patients. Randomized controlled trials are justified to definitively investigate its role within this setting.

Research paper thumbnail of The effects of various leukocyte filtration strategies in cardiac surgery

European Journal of Cardio-Thoracic Surgery, 2007

It is known that cardiopulmonary bypass causes an inflammatory reaction with an associated morbid... more It is known that cardiopulmonary bypass causes an inflammatory reaction with an associated morbidity and mortality. Several antiinflammatory strategies have been implemented to reduce this response, including leukocyte removal from the circulation using specialised filters. The aim of this study is to systematically review the available evidence on leukocyte filtration in cardiac surgery, focusing on its effect on systemic inflammation and whether this has influenced clinical outcomes. Five electronic databases were systematically searched for studies reporting the effect of leukocyte filtration at any point within the cardiopulmonary bypass circuit in humans. Reference lists of all identified studies were checked for any missing publications. Two authors independently extracted the data from the included studies. Whilst systemic leukodepleting filters do not appear to consistently lower leukocyte counts, they may preferentially remove activated leukocytes. Small improvements in early post-operative lung function in patients receiving systemic leukodepletion have been reported, but this does not lead to reduced hospital stay or decreased mortality. There is substantial evidence that cardioplegic leukocyte filtration attenuates the reperfusion injury at a cellular level, but this has not been translated into clinical improvements. Finally, whilst various strategies involving multiple leukocyte filters, or the incorporation of pharmacological agents into leukocyte-depleting protocols have been evaluated, the current available results are not conclusive. Our study suggests that there is not enough high quality or consistent evidence to draw guidelines regarding the use of leukocyte-depleting filters within routine cardiac surgical practice. #

Research paper thumbnail of Diffuse optical imaging of the healthy and diseased breast: A systematic review

Breast Cancer Research and Treatment, 2008

Screening X-ray mammography is limited by false positives and negatives leading to unnecessary ph... more Screening X-ray mammography is limited by false positives and negatives leading to unnecessary physical and psychological morbidity. Diffuse Optical Imaging using harmless near infra red light, provides lesion detection based on functional abnormalities and represents a novel diagnostic arm that could compliment traditional mammography. Reviews of optical breast imaging have not been systematic, are focused mainly on technological developments, and have become superseded by rapid technological advancement. The aim of this study is to review clinically orientated studies involving approximately 2,000 women in whom Near InfraRed Spectroscopy has been used to evaluate the healthy or diseased bearing breast. The results suggest that approximately 85% of breast lesions are detectable on Optical Mammography. Spectroscopic resolution of tissue haemoglobin composition and oxygen saturation may improve the detectability of breast disease. Results confirm that breast lesions contain approximately twice the haemoglobin concentration of background tissue. Current evidence suggests that it is not possible to distinguish benign from malignant disease is using optical imaging techniques in isolation. Methods to improve the spatial resolution of Diffuse Optical Imaging, such as better spectral coverage with additional wavelengths, enhanced modelling of light transport in tissues and the use of extrinsic dyes may augment lesion detection and characterisation. Future research should involve large clinical trials to determine the overall sensitivity and specificity of optical imaging techniques as well as to establish patient satisfaction and economic viability.