Treatment of common femoral artery steno-occlusive disease: a comprehensive review of anatomical and hemodynamic considerations.

Open surgical repair, often in the form of endarterectomy, is still the gold standard for steno-occlusive disease in the common femoral artery, despite the success of lower-risk endovascular alternatives in other peripheral arterial regions. Stenting in the common femoral artery is not widely adopted due to the proximity of the artery to the mobile hip joint, and the perceived risk this has on the stent structure due to kinking. The purpose of this review was to assess how hip movement contributes to the anatomical and biomechanical challenges proposed in the common femoral artery, and how these challenges impact the hemodynamics with both open surgical and endovascular stent treatments. The findings demonstrated that the common femoral artery is a fixed arterial segment which does not bend or twist as previously perceived. However, high degrees of bending and twisting are evident in the vessels directly proximal and distal to the common femoral artery. Mechanical testing suggests that the latest generation braided Nitinol stents could be well-suited to these challenges. Both endarterectomy and stenting provide good hemodynamic results regarding limb perfusion. However, other hemodynamic parameters, such as wall shear stress, may not be optimized with either modality, increasing the risk of chronic restenosis. As a high proportion of common femoral artery disease extends into the adjacent arterial segments, further research is warranted to ascertain the optimum hemodynamic stent configuration, as a lower-risk alternative to open surgery.

Machine learning evaluation of LV outflow obstruction in hypertrophic cardiomyopathy using three-chamber cardiovascular magnetic resonance.

Left ventricular outflow tract obstruction (LVOTO) is common in hypertrophic cardiomyopathy (HCM), but relationships between anatomical metrics and obstruction are poorly understood. We aimed to develop machine learning methods to evaluate LVOTO in HCM patients and quantify relationships between anatomical metrics and obstruction. This retrospective analysis of 1905 participants of the HCM Registry quantified 11 anatomical metrics derived from 14 landmarks automatically detected on the three-chamber long axis cine CMR images. Linear and logistic regression was used to quantify strengths of relationships with the presence of LVOTO (defined by resting Doppler pressure drop of > 30 mmHg), using the area under the receiver operating characteristic (AUC). Intraclass correlation coefficients between the network predictions and three independent observers showed similar agreement to that between observers. The distance from anterior mitral valve leaflet tip to basal septum (AML-BS) was most highly correlated with Doppler pressure drop (R2 = 0.19, p < 10-5). Multivariate stepwise regression found the best predictive model included AML-BS, AML length to aortic valve diameter ratio, AML length to LV width ratio, and midventricular septal thickness metrics (AUC 0.84). Excluding AML-BS, metrics grouped according to septal hypertrophy, LV geometry, and AML anatomy each had similar associations with LVOTO (AUC 0.71, 0.71, 0.68 respectively, p = ns), significantly less than their combination (AUC 0.77, p < 0.05 for each). Anatomical metrics derived from a standard three-chamber CMR cine acquisition can be used to highlight risk of LVOTO, and suggest further investigation if necessary. A combination of geometric factors is required to provide the best risk prediction.

Creation of personalised rib prostheses using a statistical shape model and 3D printing: Case report.

Management of chest wall defects after oncologic resection can be challenging, depending on the size and location of the defect, as well as the method of reconstruction. This report presents the first clinical case where patient-specific rib prostheses were created using a computer program and statistical shape model of human ribs. A 64-year-old male was diagnosed with non-small-cell lung cancer originating in the right upper lobe and invading the lateral aspect of the 3rd, 4th, and 5th ribs. Prior to surgical resection, a statistical shape model of human ribs was created and used to synthesise rib models in the software MATLAB (MathWorks, Natick, MA, USA). The patient's age, weight, height, and sex, as well as the number and side of the ribs of interest, were the inputs to the program. Based on these data, the program generated digital models of the right 3rd, 4th, and 5th ribs. These models were 3D printed, and a silicone mould was created from them. The patient subsequently underwent right upper lobectomy with en bloc resection of the involved chest wall. During the operation, the silicone mould was used to produce rigid prostheses consisting of methyl methacrylate and two layers of polypropylene mesh in a "sandwich" fashion. The prosthetic patch was then implanted to cover the chest wall defect. Thirty days after the surgery, the patient has returned to his pre-disease performance and physical activities. The statistical shape model and 3D printing is an optimised 3D modelling method that can provide clinicians with a time-efficient technique to create personalised rib prostheses, without any expertise or prior software knowledge.

Development and Evaluation of a Rib Statistical Shape Model for Thoracic Surgery.

Patients with advanced cancer undergoing chest wall resection may require reconstruction. Currently, rib prostheses are created by segmenting computed tomography images, which is time-consuming and labour intensive. The aim was to optimise the production of digital rib models based on a patient's age, weight, height and gender. A statistical shape model of human ribs was created and used to synthetise rib models, which were compared to the ones produced by segmentation and mirroring. The segmentation took 11.56±1.60 min compared to 0.027 ±0.009 min using the new technique. The average mesh error between the mirroring technique and segmentation was 0.58±0.25 mm (right ribs), and 0.87±0.18 mm (left ribs), compared to 1.37±0.66 mm ( ) and 1.68 ±0.77 mm ( ), respectively, for the new technique. The new technique is promising for the efficiency and ease-of-use in the clinical environment. Clinical Relevance- This is an optimised 3D modelling method providing clinicians with a time-efficient technique to create patient-specific rib prostheses, without any expertise or software knowledge required.

Cardiac and placental imaging (CARP) in pregnancy to assess aetiology of preeclampsia.

INTRODUCTION: The CARP study aims to investigate placental function, cardiac function and fetal growth comprehensively during pregnancy, a time of maximal cardiac stress, to work towards disentangling the complex cardiac and placental interactions presenting in the aetiology of pre-eclampsia as well as predicting maternal Cardiovascular Disease (CVD) risk in later life. BACKGROUND: The involvement of the cardiovascular system in pre-eclampsia, one of the most serious complications of pregnancy, is evident. While the manifestations of pre-eclampsia during pregnancy (high blood pressure, multi-organ disease, and placental dysfunction) resolve after delivery, a lifelong elevated CVD risk remains. METHOD: An assessment including both cardiac and placental Magnetic Resonance Imaging (MRI) optimised for use in pregnancy and bespoke to the expected changes was developed. Simultaneous structural and functional MRI data from the placenta, the heart and the fetus were obtained in a total of 32 pregnant women (gestational ages from 18.1 to 37.5 weeks), including uncomplicated pregnancies and five cases with early onset pre-eclampsia. RESULTS: The achieved comprehensive MR acquisition was able to demonstrate a phenotype associated with pre-eclampsia linking both placental and cardiac factors, reduced mean T2* (p < 0.005), increased heterogeneity (p < 0.005) and a trend towards an increase in cardiac work, larger average mass (109.4 vs 93.65 gr), wall thickness (7.0 vs 6.4 mm), blood pool volume (135.7 vs 127.48 mL) and mass to volume ratio (0.82 vs 0.75). The cardiac output in the controls was, controlling for gestational age, positively correlated with placental volume (p < 0.05). DISCUSSION: The CARP study constitutes the first joint assessment of functional and structural properties of the cardiac system and the placenta during pregnancy. Early indications of cardiac remodelling in pre-eclampsia were demonstrated paving the way for larger studies.

Prenatal and Postnatal Cardiac Development in Offspring of Hypertensive Pregnancies.

Background Pregnancy complications such as preterm birth and fetal growth restriction are associated with altered prenatal and postnatal cardiac development. We studied whether there were changes related specifically to pregnancy hypertension. Methods and Results Left and right ventricular volumes, mass, and function were assessed at birth and 3 months of age by echocardiography in 134 term-born infants. Fifty-four had been born to mothers who had normotensive pregnancy and 80 had a diagnosis of preeclampsia or pregnancy-induced hypertension. Differences between groups were interpreted, taking into account severity of pregnancy disorder, sex, body size, and blood pressure. Left and right ventricular mass indexed to body surface area (LVMI and RVMI) were similar in both groups at birth (LVMI 20.9±3.7 versus 20.6±4.0 g/m2, P=0.64, RVMI 17.5±3.7 versus 18.1±4.7 g/m2, P=0.57). However, right ventricular end diastolic volume index was significantly smaller in those born to hypertensive pregnancy (16.8±5.3 versus 12.7±4.7 mL/m2, P=0.001), persisting at 3 months of age (16.4±3.2 versus 14.4±4.8 mL/m2, P=0.04). By 3 months of age these infants also had significantly greater LVMI and RVMI (LVMI 24.9±4.6 versus 26.8±4.9 g/m2, P=0.04; RVMI 17.1±4.2 versus 21.1±3.9 g/m2, P<0.001). Differences in RVMI and right ventricular end diastolic volume index at 3 months, but not left ventricular measures, correlated with severity of the hypertensive disorder. No differences in systolic or diastolic function were evident. Conclusions Infants born at term to a hypertensive pregnancy have evidence of both prenatal and postnatal differences in cardiac development, with right ventricular changes proportional to the severity of the pregnancy disorder. Whether differences persist long term as well as their underlying cause and relationship to increased cardiovascular risk requires further study.

Temporal changes within mechanical dyssynchrony and rotational mechanics in Takotsubo syndrome: A cardiovascular magnetic resonance imaging study.

BACKGROUND: The pathophysiological significance of dyssynchrony and rotation in Takotsubo syndrome (TTS) is unknown. We aimed to define the influence of cardiovascular magnetic resonance feature tracking (CMR-FT) dyssynchrony and rotational mechanics in acute and during clinical course of TTS. METHODS: This multicenter study included 152 TTS patients undergoing CMR (mean 3 days after symptom onset). Apical, midventricular and basal short axis views were analysed in a core-laboratory. Systolic torsion, diastolic recoil and dyssynchrony expressed as circumferential and radial uniformity ratio estimates (CURE and RURE: 0 to 1; 1 = perfect synchrony) were compared to a matched control group (n = 21). Follow-up CMR (n = 20 patients; mean 62 days, SD 7.2) and general follow-up (n = 136; mean 3.3 years, SD 2.4) were performed. RESULTS: CURE was initially reduced compared to controls (p = 0.001) and recovered at follow-up (p < 0.001) as opposed to RURE (p = 0.116 and p = 0.179). CURE and RURE discriminated between ballooning patterns (p = 0.001 and p = 0.045). Recoil was generally impaired during the acute phase (p = 0.015), torsion only in highly dyssynchronous patients (p = 0.024). Diabetes (p = 0.007), physical triggers (p = 0.013) and malignancies (p = 0.001) predicted mortality. The latter showed a distinct association with impaired torsion (p = 0.042) and dyssynchrony (p = 0.047). Physical triggers and malignancies were related to biventricular impairment (p = 0.004 and p = 0.026), showing higher dyssynchrony (p < 0.01), greater reduction of left ventricular function (p < 0.001) and a strong trend towards increased mortality (p = 0.074). CONCLUSION: Transient circumferential dyssynchrony and impaired rotational mechanics are distinct features of TTS with different severities according to the pattern of ballooning. Patients with malignancies and precipitating physical triggers frequently show biventricular affection, greater dyssynchrony and high mortality risk.

Right ventricular morphology and function following stage I palliation with a modified Blalock-Taussig shunt versus a right ventricle-to-pulmonary artery conduit.

OBJECTIVES: The Norwood procedure for hypoplastic left heart syndrome (HLHS) is performed either via a right ventricle-to-pulmonary artery (RVPA) conduit or a modified Blalock-Taussig (MBT) shunt. Cardiac magnetic resonance (CMR) data was used to assess the effects of the RVPA conduit on ventricular shape and function through a computational analysis of anatomy and assessment of indices of strain. METHODS: A retrospective analysis of 93 CMR scans of subjects with HLHS was performed (59 with MBT shunt, 34 with RVPA conduit), incorporating data at varying stages of surgery from two congenital centres. Longitudinal and short-axis cine images were used to create a computational cardiac atlas and assess global strain. RESULTS: Those receiving an RVPA conduit had significant differences (P< 0.0001) in the shape of the RV corresponding to increased ventricular dilatation (P = 0.001) and increased sphericity (P = 0.006). Differences were evident only following completion of stage II surgery. Despite preserved ejection fraction in both groups, functional strain in the RVPA conduit group compared with that in the MBT shunt group was reduced across multiple ventricular axes, including a reduced systolic longitudinal strain rate (P< 0.0001), reduced diastolic longitudinal strain rate (P = 0.0001) and reduced midventricular systolic circumferential strain (P < 0.0001). CONCLUSIONS: Computational modelling analysis reveals differences in ventricular remodelling in patients with HLHS undergoing an RVPA conduit insertion with focal scarring and volume loading leading to decreased functional markers of strain. The need for continued surveillance is warranted, as deleterious effects may not become apparent until later years.

Supervised classification of psychomotor competence in minimally invasive surgery based on instruments motion analysis.

BACKGROUND: Objective assessment of psychomotor skills has become an important challenge in the training of minimally invasive surgical (MIS) techniques. Currently, no gold standard defining surgical competence exists for classifying residents according to their surgical skills. Supervised classification has been proposed as a means for objectively establishing competence thresholds in psychomotor skills evaluation. This report presents a study comparing three classification methods for establishing their validity in a set of tasks for basic skills' assessment. METHODS: Linear discriminant analysis (LDA), support vector machines (SVM), and adaptive neuro-fuzzy inference systems (ANFIS) were used. A total of 42 participants, divided into an experienced group (4 expert surgeons and 14 residents with >10 laparoscopic surgeries performed) and a nonexperienced group (16 students and 8 residents with <10 laparoscopic surgeries performed), performed three box trainer tasks validated for assessment of MIS psychomotor skills. Instrument movements were captured using the TrEndo tracking system, and nine motion analysis parameters (MAPs) were analyzed. The performance of the classifiers was measured by leave-one-out cross-validation using the scores obtained by the participants. RESULTS: The mean accuracy performances of the classifiers were 71 % (LDA), 78.2 % (SVM), and 71.7 % (ANFIS). No statistically significant differences in the performance were identified between the classifiers. CONCLUSIONS: The three proposed classifiers showed good performance in the discrimination of skills, especially when information from all MAPs and tasks combined were considered. A correlation between the surgeons' previous experience and their execution of the tasks could be ascertained from results. However, misclassifications across all the classifiers could imply the existence of other factors influencing psychomotor competence.

Relevance of motion-related assessment metrics in laparoscopic surgery.

INTRODUCTION: Motion metrics have become an important source of information when addressing the assessment of surgical expertise. However, their direct relationship with the different surgical skills has not been fully explored. The purpose of this study is to investigate the relevance of motion-related metrics in the evaluation processes of basic psychomotor laparoscopic skills and their correlation with the different abilities sought to measure. METHODS: A framework for task definition and metric analysis is proposed. An explorative survey was first conducted with a board of experts to identify metrics to assess basic psychomotor skills. Based on the output of that survey, 3 novel tasks for surgical assessment were designed. Face and construct validation was performed, with focus on motion-related metrics. Tasks were performed by 42 participants (16 novices, 22 residents, and 4 experts). Movements of the laparoscopic instruments were registered with the TrEndo tracking system and analyzed. RESULTS: Time, path length, and depth showed construct validity for all 3 tasks. Motion smoothness and idle time also showed validity for tasks involving bimanual coordination and tasks requiring a more tactical approach, respectively. Additionally, motion smoothness and average speed showed a high internal consistency, proving them to be the most task-independent of all the metrics analyzed. CONCLUSION: Motion metrics are complementary and valid for assessing basic psychomotor skills, and their relevance depends on the skill being evaluated. A larger clinical implementation, combined with quality performance information, will give more insight on the relevance of the results shown in this study.

EVA: laparoscopic instrument tracking based on Endoscopic Video Analysis for psychomotor skills assessment.

INTRODUCTION: The EVA (Endoscopic Video Analysis) tracking system is a new system for extracting motions of laparoscopic instruments based on nonobtrusive video tracking. The feasibility of using EVA in laparoscopic settings has been tested in a box trainer setup. METHODS: EVA makes use of an algorithm that employs information of the laparoscopic instrument's shaft edges in the image, the instrument's insertion point, and the camera's optical center to track the three-dimensional position of the instrument tip. A validation study of EVA comprised a comparison of the measurements achieved with EVA and the TrEndo tracking system. To this end, 42 participants (16 novices, 22 residents, and 4 experts) were asked to perform a peg transfer task in a box trainer. Ten motion-based metrics were used to assess their performance. RESULTS: Construct validation of the EVA has been obtained for seven motion-based metrics. Concurrent validation revealed that there is a strong correlation between the results obtained by EVA and the TrEndo for metrics, such as path length (ρ = 0.97), average speed (ρ = 0.94), or economy of volume (ρ = 0.85), proving the viability of EVA. CONCLUSIONS: EVA has been successfully validated in a box trainer setup, showing the potential of endoscopic video analysis to assess laparoscopic psychomotor skills. The results encourage further implementation of video tracking in training setups and image-guided surgery.

Methods and tools for objective assessment of psychomotor skills in laparoscopic surgery.

Training and assessment paradigms for laparoscopic surgical skills are evolving from traditional mentor-trainee tutorship towards structured, more objective and safer programs. Accreditation of surgeons requires reaching a consensus on metrics and tasks used to assess surgeons' psychomotor skills. Ongoing development of tracking systems and software solutions has allowed for the expansion of novel training and assessment means in laparoscopy. The current challenge is to adapt and include these systems within training programs, and to exploit their possibilities for evaluation purposes. This paper describes the state of the art in research on measuring and assessing psychomotor laparoscopic skills. It gives an overview on tracking systems as well as on metrics and advanced statistical and machine learning techniques employed for evaluation purposes. The later ones have a potential to be used as an aid in deciding on the surgical competence level, which is an important aspect when accreditation of the surgeons in particular, and patient safety in general, are considered. The prospective of these methods and tools make them complementary means for surgical assessment of motor skills, especially in the early stages of training. Successful examples such as the Fundamentals of Laparoscopic Surgery should help drive a paradigm change to structured curricula based on objective parameters. These may improve the accreditation of new surgeons, as well as optimize their already overloaded training schedules.

Laparoscopic video analysis for training and image-guided surgery.

Automatic analysis of Minimally Invasive Surgical video has the potential to drive new solutions for alleviating needs of safe and reproducible training programs, objective and transparent evaluation systems and navigation tools to assist surgeons and improve patient safety. Surgical video is an always available source of information, which can be used without any additional intrusive hardware in the operating room. This paper is focused on surgical video analysis methods and techniques. It describes authors' contributions in two key aspects, the 3D reconstruction of the surgical field and the segmentation and tracking of tools and organs based on laparoscopic video images. Results are given to illustrate the potential of this field of research, like the calculi of the 3D position and orientation of a tool from its 2D image, or the translation of a preoperative resection plan into a hepatectomy surgical procedure using the shading information of the image. Research efforts are required to further develop these technologies in order to harness all the valuable information available in any video-based surgery.

Collaborative co-design of emerging multi-technologies for surgery.

The EU Research Training Network on Augmented Reality in Surgery (ARIS*ER) was established with two aims: (1) to develop next-generation novel image guidance (augmented reality based on medical images) and cross-linked robotic systems (automatic control loops guided by information sensed from the patient) and (2) to educate young researchers in the user-centred, multidisciplinary design of emerging technologies for minimally invasive surgery (MIS) and intervention radiology. Collaborations between engineers, Human Factors specialists, industrial designers and medical end users were foreseen, but actual methodologies had to be developed. Three applications were used as development vehicles and as demonstrators. The resulting teamwork and process of identifying requirements, finding solutions (in technology and workflow), and shifting between these to optimize and speed development towards quality of care were studied. The ARIS*ER approach solves current problems in collaborative teams, taking a systems approach, and manages the overview of requirements and solutions, which is too complex to manage centrally.

Use of the Resection Map system as guidance during hepatectomy.

BACKGROUND: The objective of this work is to evaluate a new concept of intraoperative three-dimensional (3D) visualization system to support hepatectomy. The Resection Map aims to provide accurate cartography for surgeons, who can therefore anticipate risks, increase their confidence and achieve safer liver resection. METHODS: In an experimental prospective cohort study, ten consecutive patients admitted for hepatectomy to three European hospitals were selected. Liver structures (portal veins, hepatic veins, tumours and parenchyma) were segmented from a recent computed tomography (CT) study of each patient. The surgeon planned the resection preoperatively and read the Resection Map as reference guidance during the procedure. Objective (amount of bleeding, tumour resection margin and operating time) and subjective parameters were retrieved after each case. RESULTS: Three different surgeons operated on seven patients with the navigation aid of the Resection Map. Veins displayed in the Resection Map were identified during the surgical procedure in 70.1% of cases, depending mainly on size. Surgeons were able to track resection progress and experienced improved orientation and increased confidence during the procedure. CONCLUSIONS: The Resection Map is a pragmatic solution to enhance the orientation and confidence of the surgeon. Further studies are needed to demonstrate improvement in patient safety.

Understanding perceptual boundaries in laparoscopic surgery.

Human perceptual capabilities related to the laparoscopic interaction paradigm are not well known. Its study is important for the design of virtual reality simulators, and for the specification of augmented reality applications that overcome current limitations and provide a supersensing to the surgeon. As part of this work, this article addresses the study of laparoscopic pulling forces. Two definitions are proposed to focalize the problem: the perceptual fidelity boundary, limit of human perceptual capabilities, and the Utile fidelity boundary, that encapsulates the perceived aspects actually used by surgeons to guide an operation. The study is then aimed to define the perceptual fidelity boundary of laparoscopic pulling forces. This is approached with an experimental design in which surgeons assess the resistance against pulling of four different tissues, which are characterized with both in vivo interaction forces and ex vivo tissue biomechanical properties. A logarithmic law of tissue consistency perception is found comparing subjective valorizations with objective parameters. A model of this perception is developed identifying what the main parameters are: the grade of fixation of the organ, the tissue stiffness, the amount of tissue bitten, and the organ mass being pulled. These results are a clear requirement analysis for the force feedback algorithm of a virtual reality laparoscopic simulator. Finally, some discussion is raised about the suitability of augmented reality applications around this surgical gesture.

SINERGIA laparoscopic virtual reality simulator: didactic design and technical development.

VR laparoscopic simulators have demonstrated its validity in recent studies, and research should be directed towards a high training effectiveness and efficacy. In this direction, an insight into simulators' didactic design and technical development is provided, by describing the methodology followed in the building of the SINERGIA simulator. It departs from a clear analysis of training needs driven by a surgical training curriculum. Existing solutions and validation studies are an important reference for the definition of specifications, which are described with a suitable use of simulation technologies. Five new didactic exercises are proposed to train some of the basic laparoscopic skills. Simulator construction has required existing algorithms and the development of a particle-based biomechanical model, called PARSYS, and a collision handling solution based in a multi-point strategy. The resulting VR laparoscopic simulator includes new exercises and enhanced simulation technologies, and is finding a very good acceptance among surgeons.

Conceptual framework for laparoscopic VR simulators.

Availability of YR laparoscopic simulation for surgical training has increased significantly. Nevertheless, few studies have explored such simulators' requirements and the degree of fidelity necessary to provide effective educational tools. The authors aim to identify which didactic resources available in YR simulation technologies are most important for laparoscopic training.

Virtual reality thread simulation for laparoscopic suturing training.

The level of realism in virtual reality trainers might not be proportional to its didactic value. As an example, three exercises to train suturing skills are proposed in this article. They use a discrete thread model with a simple but good enough behaviour, and constitute a training means for three laparoscopic skills: (1) Accurate grasping, which trains grasping a precise point in the thread. (2) Coordinated Pulling, which trains tightening the thread co-ordinately and in different space orientations; and (3) Knotting, which allow the surgeon to practice this manoeuvre. These three exercises, found interesting among experts in surgical training, are now being validated in MIS workshops at the Minimally Invasive Surgery Centre of Cáceres (Spain).

Study of laparoscopic forces perception for defining simulation fidelity.

One of the most controversial dilemmas in virtual reality laparoscopic simulators design is the incorporation of force feedback (FF). This issue is approached with an experimental design in which surgeons assess the resistance against pulling of four different tissues, which are characterized with the acquisition of interaction forces. Comparing subjective assessments with objective force parameters we aim to determine the fidelity boundary beyond which no more realism is necessary in simulation. Interaction pulling forces of four tissues have been characterized, which can constitute a basis for requirements of a FF algorithm. Results have also led to the hypothesis that surgeons are able to differentiate tissues and perceive somesthesic information although resulting interaction forces are of the same magnitude than interferences like trocar friction.