Simultaneous computer-assisted assessment of mucosal and serosal perfusion in a model of segmental colonic ischemia

BACKGROUND: Fluorescence-based enhanced reality (FLER) enables the quantification of fluorescence signal dynamics, which can be superimposed onto real-time laparoscopic images by using a virtual perfusion cartogram. The current practice of perfusion assessment relies on visualizing the bowel serosa. The aim of this experimental study was to quantify potential differences in mucosal and serosal perfusion levels in an ischemic colon segment. METHODS: An ischemic colon segment was created in 12 pigs. Simultaneous quantitative mucosal and serosal fluorescence imaging was obtained via intravenous indocyanine green injection (0.2 mg/kg), using two near-infrared camera systems, and computer-assisted FLER analysis. Lactate levels were measured in capillary blood of the colonic wall at seven regions of interest (ROIs) as determined with FLER perfusion cartography: the ischemic zone (I), the proximal and distal vascularized areas (PV, DV), and the 50% perfusion threshold proximally and distally at the mucosal and serosal side (P50M, P50S, D50M, D50S). RESULTS: The mean ischemic zone as measured (mm) for the mucosal side was significantly larger than the serosal one (56.3 ± 21.3 vs. 40.8 ± 14.9, p = 0.001) with significantly lower lactate values at the mucosal ROIs. There was a significant weak inverse correlation between lactate and slope values for the defined ROIs (r = - 0.2452, p = 0.0246). CONCLUSIONS: Mucosal ischemic zones were larger than serosal zones. These results suggest that an assessment of bowel perfusion from the serosal side only can underestimate the extent of ischemia. Further studies are required to predict the optimal resection margin and anastomotic site

Development of a handheld fiber-optic probe-based raman imaging instrumentation: raman chemlighter

Raman systems based on handheld fiber-optic probes offer advantages in terms of smaller sizes and easier access to the measurement sites, which are favorable for biomedical and clinical applications in the complex environment. However, there are several common drawbacks of applying probes for many applications: (1) The fixed working distance requires the user to maintain a certain working distance to acquire higher Raman signals; (2) The single-point-measurement ability restricts realizing a mapping or scanning procedure; (3) Lack of real-time data processing and a straightforward co-registering method to link the Raman information with the respective measurement position. The thesis proposed and experimentally demonstrated various approaches to overcome these drawbacks. A handheld fiber-optic Raman probe with an autofocus unit was presented to overcome the problem arising from using fixed-focus lenses, by using a liquid lens as the objective lens, which allows dynamical adjustment of the focal length of the probe. An implementation of a computer vision-based positional tracking to co-register the regular Raman spectroscopic measurements with the spatial location enables fast recording of a Raman image from a large tissue sample by combining positional tracking of the laser spot through brightfield images. The visualization of the Raman image has been extended to augmented and mixed reality and combined with a 3D reconstruction method and projector-based visualization to offer an intuitive and easily understandable way of presenting the Raman image. All these advances are substantial and highly beneficial to further drive the clinical translation of Raman spectroscopy as potential image-guided instrumentation

Creation of a Virtual Atlas of Neuroanatomy and Neurosurgical Techniques Using 3D Scanning Techniques

Neuroanatomy is one of the most challenging and fascinating topics within the human anatomy, due to the complexity and interconnection of the entire nervous system. The gold standard for learning neurosurgical anatomy is cadaveric dissections. Nevertheless, it has a high cost (needs of a laboratory, acquisition of cadavers, and fixation), is time-consuming, and is limited by sociocultural restrictions. Due to these disadvantages, other tools have been investigated to improve neuroanatomy learning. Three-dimensional modalities have gradually begun to supplement traditional 2-dimensional representations of dissections and illustrations. Volumetric models (VM) are the new frontier for neurosurgical education and training. Different workflows have been described to create these VMs -photogrammetry (PGM) and structured light scanning (SLS). In this study, we aimed to describe and use the currently available 3D scanning techniques to create a virtual atlas of neurosurgical anatomy. Dissections on post-mortem human heads and brains were performed at the skull base laboratories of Stanford University - NeuroTraIn Center and the University of California, San Francisco - SBCVL (skull base and cerebrovascular laboratory). Then VMs were created following either SLS or PGM workflow. Fiber tract reconstructions were also generated from DICOM using DSI-studio and incorporated into VMs from dissections. Moreover, common creative license materials models were used to simplify the understanding of the specific anatomical region. Both methods yielded VMs with suitable clarity and structural integrity for anatomical education, surgical illustration, and procedural simulation. We described the roadmap of SLS and PGM for creating volumetric models, including the required equipment and software. We have also provided step-by-step procedures on how users can post-processing and refine these images according to their specifications. The VMs generated were used for several publications, to describe the step-by-step of a specific neurosurgical approach and to enhance the understanding of an anatomical region and its function. These models were used in neuroanatomical education and research (workshops and publications). VMs offer a new, immersive, and innovative way to accurately visualize neuroanatomy. Given the straightforward workflow, the presently described techniques may serve as a reference point for an entirely new way of capturing and depicting neuroanatomy and offer new opportunities for the application of VMs in education, simulation, and surgical planning. The virtual atlas, divided into specific areas concerning different neurosurgical approaches (such as skull base, cortex and fiber tracts, and spine operative anatomy), will increase the viewer's understanding of neurosurgical anatomy. The described atlas is the first surgical collection of VMs from cadaveric dissections available in the medical field and could be a used as reference for future creation of analogous collection in the different medical subspeciality.La neuroanatomia è, grazie alle intricate connessioni che caratterizzano il sistema nervoso e alla sua affascinante complessità, una delle discipline più stimolanti della anatomia umana. Nonostante il gold standard per l’apprendimento dell’anatomia neurochirurgica sia ancora rappresentato dalle dissezioni cadaveriche, l’accessibilità a queste ultime rimane limitata, a causa della loro dispendiosità in termini di tempo e costi (necessità di un laboratorio, acquisizione di cadaveri e fissazione), e alle restrizioni socioculturali per la donazione di cadaveri. Al fine di far fronte a questi impedimenti, e con lo scopo di garantire su larga scala l’apprendimento tridimensionale della neuroanatomia, nel corso degli anni sono stati sviluppati nuovi strumenti e tecnologie. Le tradizionali rappresentazioni anatomiche bidimensionali sono state gradualmente sostituite dalle modalità 3-dimensionali (3D) – foto e video. Tra questi ultimi, i modelli volumetrici (VM) rappresentano la nuova frontiera per l'istruzione e la formazione neurochirurgica. Diversi metodi per creare questi VM sono stati descritti, tra cui la fotogrammetria (PGM) e la scansione a luce strutturata (SLS). Questo studio descrive l’utilizzo delle diverse tecniche di scansione 3D grazie alle quali è stato creato un atlante virtuale di anatomia neurochirurgica. Le dissezioni su teste e cervelli post-mortem sono state eseguite presso i laboratori di base cranica di Stanford University -NeuroTraIn Center e dell'Università della California, San Francisco - SBCVL. I VM dalle dissezioni sono stati creati seguendo i metodi di SLS e/o PGM. Modelli di fibra bianca sono stati generate utilizzando DICOM con il software DSI-studio e incorporati ai VM di dissezioni anatomiche. Inoltre, sono stati utilizzati VM tratti da common creative license material (materiale con licenze creative comuni) al fine di semplificare la comprensione di alcune regioni anatomiche. I VM generati con entrambi i metodi sono risultati adeguati, sia in termini di chiarezza che di integrità strutturale, per l’educazione anatomica, l’illustrazione medica e la simulazione chirurgica. Nel nostro lavoro sono stati esaustivamente descritti tutti gli step necessari, di entrambe le tecniche (SLS e PGM), per la creazione di VM, compresi le apparecchiature e i software utilizzati. Sono state inoltre descritte le tecniche di post-elaborazione e perfezionamento dei VM da poter utilizzare in base alle necessità richieste. I VM generati durante la realizzazione del nostro lavoro sono stati utilizzati per molteplici pubblicazioni, nella descrizione step-by-step di uno specifico approccio neurochirurgico o per migliorare la comprensione di una regione anatomica e della sua funzione. Questi modelli sono stati utilizzati a scopo didattico per la formazione neuroanatomica di studenti di medicina, specializzandi e giovani neurochirurghi. I VM offrono un modo nuovo, coinvolgente e innovativo con cui poter raggiungere un’accurata conoscenza tridimensionale della neuroanatomia. La metodologia delle due tecniche descritte può servire come punto di riferimento per un nuovo modo di acquisizione e rappresentazione della neuroanatomia, ed offrire nuove opportunità di utilizzo dei VM nella formazione didattica, nella simulazione e nella pianificazione chirurgica. L'atlante virtuale qui descritto, suddiviso in aree specifiche relative a diversi approcci neurochirurgici, aumenterà la comprensione dell'anatomia neurochirurgica da parte dello spettatore. Questa è la prima raccolta chirurgica di VM da dissezioni anatomiche disponibile in ambito medico e potrebbe essere utilizzato come riferimento per la futura creazione di analoga raccolta nelle diverse sotto specialità mediche

SURGICAL NAVIGATION AND AUGMENTED REALITY FOR MARGINS CONTROL IN HEAD AND NECK CANCER

I tumori maligni del distretto testa-collo rappresentano un insieme di lesioni dalle diverse caratteristiche patologiche, epidemiologiche e prognostiche. Per una porzione considerevole di tali patologie, l’intervento chirurgico finalizzato all’asportazione completa del tumore rappresenta l’elemento chiave del trattamento, quand’anche esso includa altre modalità quali la radioterapia e la terapia sistemica. La qualità dell’atto chirurgico ablativo è pertanto essenziale al fine di garantire le massime chance di cura al paziente. Nell’ambito della chirurgia oncologica, la qualità delle ablazioni viene misurata attraverso l’analisi dello stato dei margini di resezione. Oltre a rappresentare un surrogato della qualità della resezione chirurgica, lo stato dei margini di resezione ha notevoli implicazioni da un punto di vista clinico e prognostico. Infatti, il coinvolgimento dei margini di resezione da parte della neoplasia rappresenta invariabilmente un fattore prognostico sfavorevole, oltre che implicare la necessità di intensificare i trattamenti postchirurgici (e.g., ponendo indicazione alla chemioradioterapia adiuvante), comportando una maggiore tossicità per il paziente. La proporzione di resezioni con margini positivi (i.e., coinvolti dalla neoplasia) nel distretto testa-collo è tra le più elevate in ambito di chirurgia oncologica. In tale contesto si pone l’obiettivo del dottorato di cui questa tesi riporta i risultati. Le due tecnologie di cui si è analizzata l’utilità in termini di ottimizzazione dello stato dei margini di resezione sono la navigazione chirurgica con rendering tridimensionale e la realtà aumentata basata sulla videoproiezione di immagini. Le sperimentazioni sono state svolte parzialmente presso l’Università degli Studi di Brescia, parzialmente presso l’Azienda Ospedale Università di Padova e parzialmente presso l’University Health Network (Toronto, Ontario, Canada). I risultati delle sperimentazioni incluse in questo elaborato dimostrano che l'impiego della navigazione chirurgica con rendering tridimensionale nel contesto di procedure oncologiche ablative cervico-cefaliche risulta associata ad un vantaggio significativo in termini di riduzione della frequenza di margini positivi. Al contrario, le tecniche di realtà aumentata basata sulla videoproiezione, nell'ambito della sperimentazione preclinica effettuata, non sono risultate associate a vantaggi sufficienti per poter considerare tale tecnologia per la traslazione clinica.Head and neck malignancies are an heterogeneous group of tumors. Surgery represents the mainstay of treatment for the large majority of head and neck cancers, with ablation being aimed at removing completely the tumor. Radiotherapy and systemic therapy have also a substantial role in the multidisciplinary management of head and neck cancers. The quality of surgical ablation is intimately related to margin status evaluated at a microscopic level. Indeed, margin involvement has a remarkably negative effect on prognosis of patients and mandates the escalation of postoperative treatment by adding concomitant chemotherapy to radiotherapy and accordingly increasing the toxicity of overall treatment. The rate of margin involvement in the head and neck is among the highest in the entire field of surgical oncology. In this context, the present PhD project was aimed at testing the utility of 2 technologies, namely surgical navigation with 3-dimensional rendering and pico projector-based augmented reality, in decreasing the rate of involved margins during oncologic surgical ablations in the craniofacial area. Experiments were performed in the University of Brescia, University of Padua, and University Health Network (Toronto, Ontario, Canada). The research activities completed in the context of this PhD course demonstrated that surgical navigation with 3-dimensional rendering confers a higher quality to oncologic ablations in the head and neck, irrespective of the open or endoscopic surgical technique. The benefits deriving from this implementation come with no relevant drawbacks from a logistical and practical standpoint, nor were major adverse events observed. Thus, implementation of this technology into the standard care is the logical proposed step forward. However, the genuine presence of a prognostic advantage needs longer and larger study to be formally addressed. On the other hand, pico projector-based augmented reality showed no sufficient advantages to encourage translation into the clinical setting. Although observing a clear practical advantage deriving from the projection of osteotomy lines onto the surgical field, no substantial benefits were measured when comparing this technology with surgical navigation with 3-dimensional rendering. Yet recognizing a potential value of this technology from an educational standpoint, the performance displayed in the preclinical setting in terms of surgical margins optimization is not in favor of a clinical translation with this specific aim

Augmented reality technology in image-guided therapy: State-of-the-art review.

Image-guided therapies have been on the rise in recent years as they can achieve higher accuracy and are less invasive than traditional methods. By combining augmented reality technology with image-guided therapy, more organs, and tissues can be observed by surgeons to improve surgical accuracy. In this review, 233 publications (dated from 2015 to 2020) on the design and application of augmented reality-based systems for image-guided therapy, including both research prototypes and commercial products, were considered for review. Based on their functions and applications. Sixteen studies were selected. The engineering specifications and applications were analyzed and summarized for each study. Finally, future directions and existing challenges in the field were summarized and discussed

Intraoperative Endoscopic Augmented Reality in Third Ventriculostomy

In neurosurgery, as a result of the brain-shift, the preoperative patient models used as a intraoperative reference change. A meaningful use of the preoperative virtual models during the operation requires for a model update. The NEAR project, Neuroendoscopy towards Augmented Reality, describes a new camera calibration model for high distorted lenses and introduces the concept of active endoscopes endowed with with navigation, camera calibration, augmented reality and triangulation modules

INTERFACE DESIGN FOR A VIRTUAL REALITY-ENHANCED IMAGE-GUIDED SURGERY PLATFORM USING SURGEON-CONTROLLED VIEWING TECHNIQUES

Initiative has been taken to develop a VR-guided cardiac interface that will display and deliver information without affecting the surgeons’ natural workflow while yielding better accuracy and task completion time than the existing setup. This paper discusses the design process, the development of comparable user interface prototypes as well as an evaluation methodology that can measure user performance and workload for each of the suggested display concepts. User-based studies and expert recommendations are used in conjunction to es­ tablish design guidelines for our VR-guided surgical platform. As a result, a better understanding of autonomous view control, depth display, and use of virtual context, is attained. In addition, three proposed interfaces have been developed to allow a surgeon to control the view of the virtual environment intra-operatively. Comparative evaluation of the three implemented interface prototypes in a simulated surgical task scenario, revealed performance advantages for stereoscopic and monoscopic biplanar display conditions, as well as the differences between three types of control modalities. One particular interface prototype demonstrated significant improvement in task performance. Design recommendations are made for this interface as well as the others as we prepare for prospective development iterations

Appearance Modelling and Reconstruction for Navigation in Minimally Invasive Surgery

Minimally invasive surgery is playing an increasingly important role for patient care. Whilst its direct patient benefit in terms of reduced trauma, improved recovery and shortened hospitalisation has been well established, there is a sustained need for improved training of the existing procedures and the development of new smart instruments to tackle the issue of visualisation, ergonomic control, haptic and tactile feedback. For endoscopic intervention, the small field of view in the presence of a complex anatomy can easily introduce disorientation to the operator as the tortuous access pathway is not always easy to predict and control with standard endoscopes. Effective training through simulation devices, based on either virtual reality or mixed-reality simulators, can help to improve the spatial awareness, consistency and safety of these procedures. This thesis examines the use of endoscopic videos for both simulation and navigation purposes. More specifically, it addresses the challenging problem of how to build high-fidelity subject-specific simulation environments for improved training and skills assessment. Issues related to mesh parameterisation and texture blending are investigated. With the maturity of computer vision in terms of both 3D shape reconstruction and localisation and mapping, vision-based techniques have enjoyed significant interest in recent years for surgical navigation. The thesis also tackles the problem of how to use vision-based techniques for providing a detailed 3D map and dynamically expanded field of view to improve spatial awareness and avoid operator disorientation. The key advantage of this approach is that it does not require additional hardware, and thus introduces minimal interference to the existing surgical workflow. The derived 3D map can be effectively integrated with pre-operative data, allowing both global and local 3D navigation by taking into account tissue structural and appearance changes. Both simulation and laboratory-based experiments are conducted throughout this research to assess the practical value of the method proposed

Visual Perception and Cognition in Image-Guided Intervention

Surgical image visualization and interaction systems can dramatically affect the efficacy and efficiency of surgical training, planning, and interventions. This is even more profound in the case of minimally-invasive surgery where restricted access to the operative field in conjunction with limited field of view necessitate a visualization medium to provide patient-specific information at any given moment. Unfortunately, little research has been devoted to studying human factors associated with medical image displays and the need for a robust, intuitive visualization and interaction interfaces has remained largely unfulfilled to this day. Failure to engineer efficient medical solutions and design intuitive visualization interfaces is argued to be one of the major barriers to the meaningful transfer of innovative technology to the operating room. This thesis was, therefore, motivated by the need to study various cognitive and perceptual aspects of human factors in surgical image visualization systems, to increase the efficiency and effectiveness of medical interfaces, and ultimately to improve patient outcomes. To this end, we chose four different minimally-invasive interventions in the realm of surgical training, planning, training for planning, and navigation: The first chapter involves the use of stereoendoscopes to reduce morbidity in endoscopic third ventriculostomy. The results of this study suggest that, compared with conventional endoscopes, the detection of the basilar artery on the surface of the third ventricle can be facilitated with the use of stereoendoscopes, increasing the safety of targeting in third ventriculostomy procedures. In the second chapter, a contour enhancement technique is described to improve preoperative planning of arteriovenous malformation interventions. The proposed method, particularly when combined with stereopsis, is shown to increase the speed and accuracy of understanding the spatial relationship between vascular structures. In the third chapter, an augmented-reality system is proposed to facilitate the training of planning brain tumour resection. The results of our user study indicate that the proposed system improves subjects\u27 performance, particularly novices\u27, in formulating the optimal point of entry and surgical path independent of the sensorimotor tasks performed. In the last chapter, the role of fully-immersive simulation environments on the surgeons\u27 non-technical skills to perform vertebroplasty procedure is investigated. Our results suggest that while training surgeons may increase their technical skills, the introduction of crisis scenarios significantly disturbs the performance, emphasizing the need of realistic simulation environments as part of training curriculum