Optical techniques for 3D surface reconstruction in computer-assisted laparoscopic surgery

One of the main challenges for computer-assisted surgery (CAS) is to determine the intra-opera- tive morphology and motion of soft-tissues. This information is prerequisite to the registration of multi-modal patient-specific data for enhancing the surgeon’s navigation capabilites by observ- ing beyond exposed tissue surfaces and for providing intelligent control of robotic-assisted in- struments. In minimally invasive surgery (MIS), optical techniques are an increasingly attractive approach for in vivo 3D reconstruction of the soft-tissue surface geometry. This paper reviews the state-of-the-art methods for optical intra-operative 3D reconstruction in laparoscopic surgery and discusses the technical challenges and future perspectives towards clinical translation. With the recent paradigm shift of surgical practice towards MIS and new developments in 3D opti- cal imaging, this is a timely discussion about technologies that could facilitate complex CAS procedures in dynamic and deformable anatomical regions

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

A Compact Active Stereovision System with Dynamic Reconfiguration for Endoscopy or Colonoscopy Applications

International audienceA new concept of endoscopic device based on a compact optical probe which can capture 3D shape of objects using an active stereovision method is presented. The distinctive feature of this probe is its capability to dynamically switch between two distinct points of view. If the first measurement angle of view does not give results with sufficient quality, the system can switch to a second mode which sets distinct angle of view within less than 25 milliseconds. This feature consequently allows selecting the angle that provides the more useful 3D information and enhances the quality of the captured result. The instrumental setup of this measurement system and the reconstruction algorithms are presented in this paper. Then, the advantages of this new endoscopic probe are explained with an experimental 3D reconstruction of a coin's surface. Finally, first measurements on a phantom colon are provided. In future works, further miniaturization of the device and its integration into a real colonoscope will be implemented

Coherent microscopy by laser optical feedback imaging (LOFI) technique

The application of the non conventional imaging technique LOFI (Laser Optical Feedback Imaging) to coherent microscopy is presented. This simple and efficient technique using frequency-shifted optical feedback needs the sample to be scanned in order to obtain an image. The effects on magnitude and phase signals such as vignetting and field curvature occasioned by the scanning with galvanometric mirrors are discussed. A simple monitoring method based on phase images is proposed to find the optimal position of the scanner. Finally, some experimental results illustrating this technique are presented

Comparative validation of single-shot optical techniques for laparoscopic 3-D surface reconstruction

Intra-operative imaging techniques for obtaining the shape and morphology of soft-tissue surfaces in vivo are a key enabling technology for advanced surgical systems. Different optical techniques for 3-D surface reconstruction in laparoscopy have been proposed, however, so far no quantitative and comparative validation has been performed. Furthermore, robustness of the methods to clinically important factors like smoke or bleeding has not yet been assessed. To address these issues, we have formed a joint international initiative with the aim of validating different state-of-the-art passive and active reconstruction methods in a comparative manner. In this comprehensive in vitro study, we investigated reconstruction accuracy using different organs with various shape and texture and also tested reconstruction robustness with respect to a number of factors like the pose of the endoscope as well as the amount of blood or smoke present in the scene. The study suggests complementary advantages of the different techniques with respect to accuracy, robustness, point density, hardware complexity and computation time. While reconstruction accuracy under ideal conditions was generally high, robustness is a remaining issue to be addressed. Future work should include sensor fusion and in vivo validation studies in a specific clinical context. To trigger further research in surface reconstruction, stereoscopic data of the study will be made publically available at www.open-CAS.com upon publication of the paper