Registration of ultrasound and computed tomography for guidance of laparoscopic liver surgery

Laparoscopic Ultrasound (LUS) imaging is a standard tool used for image-guidance during laparoscopic liver resection, as it provides real-time information on the internal structure of the liver. However, LUS probes are di cult to handle and their resulting images hard to interpret. Additionally, some anatomical targets such as tumours are not always visible, making the LUS guidance less e ective. To solve this problem, registration between the LUS images and a pre-operative Computed Tomography (CT) scan using information from blood vessels has been previously proposed. By merging these two modalities, the relative position between the LUS images and the anatomy of CT is obtained and both can be used to guide the surgeon. The problem of LUS to CT registration is specially challenging, as besides being a multi-modal registration, the eld of view of LUS is signi cantly smaller than that of CT. Therefore, this problem becomes poorly constrained and typically an accurate initialisation is needed. Also, the liver is highly deformed during laparoscopy, complicating the problem further. So far, the methods presented in the literature are not clinically feasible as they depend on manually set correspondences between both images. In this thesis, a solution for this registration problem that may be more transferable to the clinic is proposed. Firstly, traditional registration approaches comprised of manual initialisation and optimisation of a cost function are studied. Secondly, it is demonstrated that a globally optimal registration without a manual initialisation is possible. Finally, a new globally optimal solution that does not require commonly used tracking technologies is proposed and validated. The resulting approach provides clinical value as it does not require manual interaction in the operating room or tracking devices. Furthermore, the proposed method could potentially be applied to other image-guidance problems that require registration between ultrasound and a pre-operative scan

Organ-focused mutual information for nonrigid multimodal registration of liver CT and Gd–EOB–DTPA-enhanced MRI

Accurate detection of liver lesions is of great importance in hepatic surgery planning. Recent studies have shown that the detection rate of liver lesions is significantly higher in gadoxetic acid-enhanced magnetic resonance imaging (Gd–EOB–DTPA-enhanced MRI) than in contrast-enhanced portal-phase computed tomography (CT); however, the latter remains essential because of its high specificity, good performance in estimating liver volumes and better vessel visibility. To characterize liver lesions using both the above image modalities, we propose a multimodal nonrigid registration framework using organ-focused mutual information (OF-MI). This proposal tries to improve mutual information (MI) based registration by adding spatial information, benefiting from the availability of expert liver segmentation in clinical protocols. The incorporation of an additional information channel containing liver segmentation information was studied. A dataset of real clinical images and simulated images was used in the validation process. A Gd–EOB–DTPA-enhanced MRI simulation framework is presented. To evaluate results, warping index errors were calculated for the simulated data, and landmark-based and surface-based errors were calculated for the real data. An improvement of the registration accuracy for OF-MI as compared with MI was found for both simulated and real datasets. Statistical significance of the difference was tested and confirmed in the simulated dataset (p < 0.01)

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

Advancements and Breakthroughs in Ultrasound Imaging

Ultrasonic imaging is a powerful diagnostic tool available to medical practitioners, engineers and researchers today. Due to the relative safety, and the non-invasive nature, ultrasonic imaging has become one of the most rapidly advancing technologies. These rapid advances are directly related to the parallel advancements in electronics, computing, and transducer technology together with sophisticated signal processing techniques. This book focuses on state of the art developments in ultrasonic imaging applications and underlying technologies presented by leading practitioners and researchers from many parts of the world

SUBJECT-SPECIFIC 4D ULTRASOUND LIVER MODEL AND DYNAMIC PHANTOM FOR ROBOTIC-ASSISTED LIVER BIOPSY STUDY

Ph.DDOCTOR OF PHILOSOPH

Real-time Biomechanical Modeling for Intraoperative Soft Tissue Registration

Computer assisted surgery systems intraoperatively support the surgeon by providing information on the location of hidden risk and target structures during surgery. However, soft tissue deformations make intraoperative registration (and thus intraoperative navigation) difficult. In this work, a novel, biomechanics based approach for real-time soft tissue registration from sparse intraoperative sensor data such as stereo endoscopic images is presented to overcome this problem

I Simulatori in realtà virtuale: un ausilio nella formazione chirurgica

Negli ultimi anni la necessità di formazione in campo laparoscopico ha spinto verso la creazione di simulatori chirurgici di diversa fattura e diversa complessità. Al momento molti di questi sono disponibili in commercio. Ognuna di questi ha il proprio design, struttura e programma di formazione. L'evoluzione è rappresentata dall’utilizzo della Realtà Virtuale, che mima l'azione reale e lavora sulle diverse competenze acquisite durante i corsi di formazione e l’esperienza chirurgica al campo operatorio. Il ruolo della formazione "sicura ed efficiente" è necessario nel corso di una specializzazione in chirurgia e durante la formazione continua. La simulazione in realtà virtuale è in grado di offrire un numero infinito di scenari chirurgici. I simulatori chirurgici in realtà virtuale di ultima generazione sono forniti di percorsi di formazione graduali che guidano lo specializzando nell’acquisizione di manualità “fine” nei singoli tasks fino alla procedura completa “full task” di un intervento chirurgico, ad esempio una colecistectomia. In questo studio abbiamo voluto testare la validità di un’acquisizione graduale di tecnica manuale “step by step” rispetto all’esercizio diretto solo su una procedura completa mediante l’ausilio di un simulatore in Virtual Reality, il LapMentor®(Simbionix,Israele). Specializzandi in Chirurgia Generale privi di esperienza precedente in laparoscopia hanno ottenuto risultati migliori sulla procedura completa della colecistectomia laparoscopica procedendo durante il corso step by step rispetto a coloro che hanno eseguito la procedura completa “full task” direttamente. Il nostro studio conferma che una buona esperienza e la conoscenza delle capacità tecniche di base nel campo della formazione laparoscopica migliorano le prestazioni nella procedura completa.In the last years the need for training in laparoscopy has led to the creation of surgical simulators of varying complexity and different bill. Currently, many of these are commercially available. Each of these has its own design, structure and training program. The trend is the use of virtual reality, which mimics the real action and work on various skills acquired during the training and experience in the surgical operating field. The role of training on safe and efficient "is necessary in the course of specialization in surgery and during the training. The simulation in virtual reality is able to offer an infinite number of surgical scenarios. The surgical simulators in virtual reality are equipped with the latest training courses that guide the gradual specializing in the acquisition of manual skills "end" in the individual tasks to complete procedure "full task" for surgery, such as a cholecystectomy. In this study we wanted to test the validity of the gradual acquisition of technical manual "step by step" only on a direct comparison with the whole procedure with the help of a mortgage in Virtual Reality, the LapMentor ® (Simbionix, Israel) .Specializing in general surgery with no previous experience in laparoscopy have performed better on the whole procedure of laparoscopic cholecystectomy during the course of proceeding step by step than those who performed the procedure complete "full task" directly. Our study confirms that a good experience and knowledge of basic technical skills in training laparoscopic improve performance in the whole procedure

Multi-Modality Imaging: A Software Fusion and Image-Guided Therapy Perspective

With the introduction of computers in medical imaging, which were popularized with the presentation of Hounsfield's ground-breaking work in 1971, numerical image reconstruction and analysis of medical images became a vital part of medical imaging research. While mathematical aspects of reconstruction dominated research in the beginning, a growing body of literature attests to the progress made over the past 30 years in image fusion. This article describes the historical development of non-deformable software-based image co-registration and it's role in the context of hybrid imaging and provides an outlook on future developments