A fast and accurate fusion of intra-operative images with a pre-operative data is a key component of computer-aided interventions which aim at improving the outcomes of the intervention while reducing the patient's discomfort. In this paper, we focus on the problematic of the intra-operative navigation during abdominal surgery, which requires an accurate registration of tissues undergoing large deformations. Such a scenario occurs in the case of partial hepatectomy: to facilitate the access to the pathology, e.g. a tumor located in the posterior part of the right lobe, the surgery is performed on a patient in lateral position. Due to the change in patient's position, the resection plan based on the pre-operative CT scan acquired in the supine position must be updated to account for the deformations. We suppose that an imaging modality, such as the cone-beam CT, provides the information about the intra-operative shape of an organ, however, due to the reduced radiation dose and contrast, the actual locations of the internal structures necessary to update the planning are not available. To this end, we propose a method allowing for fast registration of the pre-operative data represented by a detailed 3D model of the liver and its internal structure and the actual configuration given by the organ surface extracted from the intra-operative image. The algorithm behind the method combines the iterative closest point technique with a biomechanical model based on a co-rotational formulation of linear elasticity which accounts for large deformations of the tissue. The performance, robustness and accuracy of the method is quantitatively assessed on a control semi-synthetic dataset with known ground truth and a real dataset composed of nine pairs of abdominal CT scans acquired in supine and flank positions. It is shown that the proposed surface-matching method is capable of reducing the target registration error evaluated of the internal structures of the organ from more than 40 mm to less then 10 mm. Moreover, the control data is used to demonstrate the compatibility of the method with intra-operative clinical scenario, while the real datasets are utilized to study the impact of parametrization on the accuracy of the method. The method is also compared to a state-of-the art intensity-based registration technique in terms of accuracy and performance.
- MeSH
- algoritmy MeSH
- analýza metodou konečných prvků MeSH
- biomechanika MeSH
- břicho diagnostické zobrazování chirurgie MeSH
- chirurgie s pomocí počítače metody MeSH
- elastografie * MeSH
- lidé MeSH
- nemoci jater diagnostické zobrazování chirurgie MeSH
- peroperační doba MeSH
- počítačová rentgenová tomografie * MeSH
- počítačová simulace MeSH
- počítačová tomografie s kuželovým svazkem * MeSH
- polohování pacienta MeSH
- rentgenový obraz - interpretace počítačová metody MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- validační studie MeSH
In image-guided percutaneous interventions, a precise planning of the needle path is a key factor to a successful intervention. In this paper we propose a novel method for computing a patient-specific optimal path for such interventions, accounting for both the deformation of the needle and soft tissues due to the insertion of the needle in the body. To achieve this objective, we propose an optimization method for estimating preoperatively a curved trajectory allowing to reach a target even in the case of tissue motion and needle bending. Needle insertions are simulated and regarded as evaluations of the objective function by the iterative planning process. In order to test the planning algorithm, it is coupled with a fast needle insertion simulation involving a flexible needle model and soft tissue finite element modeling, and experimented on the use-case of thermal ablation of liver tumors. Our algorithm has been successfully tested on twelve datasets of patient-specific geometries. Fast convergence to the actual optimal solution has been shown. This method is designed to be adapted to a wide range of percutaneous interventions.
- MeSH
- ablace MeSH
- algoritmy * MeSH
- anatomické modely * MeSH
- chirurgie s pomocí počítače metody MeSH
- játra patofyziologie chirurgie MeSH
- lidé MeSH
- nádory jater chirurgie MeSH
- počítačová simulace * MeSH
- předoperační období * MeSH
- uživatelské rozhraní počítače MeSH
- zobrazování trojrozměrné MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
During the minimally-invasive liver surgery, only the partial surface view of the liver is usually provided to the surgeon via the laparoscopic camera. Therefore, it is necessary to estimate the actual position of the internal structures such as tumors and vessels from the pre-operative images. Nevertheless, such task can be highly challenging since during the intervention, the abdominal organs undergo important deformations due to the pneumoperitoneum, respiratory and cardiac motion and the interaction with the surgical tools. Therefore, a reliable automatic system for intra-operative guidance requires fast and reliable registration of the pre- and intra-operative data. In this paper we present a complete pipeline for the registration of pre-operative patient-specific image data to the sparse and incomplete intra-operative data. While the intra-operative data is represented by a point cloud extracted from the stereo-endoscopic images, the pre-operative data is used to reconstruct a biomechanical model which is necessary for accurate estimation of the position of the internal structures, considering the actual deformations. This model takes into account the patient-specific liver anatomy composed of parenchyma, vascularization and capsule, and is enriched with anatomical boundary conditions transferred from an atlas. The registration process employs the iterative closest point technique together with a penalty-based method. We perform a quantitative assessment based on the evaluation of the target registration error on synthetic data as well as a qualitative assessment on real patient data. We demonstrate that the proposed registration method provides good results in terms of both accuracy and robustness w.r.t. the quality of the intra-operative data.
- MeSH
- biologické modely * MeSH
- individualizovaná medicína metody MeSH
- játra chirurgie MeSH
- lidé MeSH
- miniinvazivní chirurgické výkony metody MeSH
- Check Tag
- lidé MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
Accurate biomechanical modeling of liver is of paramount interest in pre-operative planning or computer-aided per-operative guidance. Since the liver is an organ composed of three different components (parenchyma, vascularization and Glisson's capsule), an efficient and realistic simulation of its behaviour is a challenging task. In this paper we propose a complete model of liver where each component is modelled with different type of finite elements chosen according to the nature and mechanical properties of the component. The elements of different types are coupled via mechanical mapping encoded in the global stiffness matrix. In the result section, we first focus on simulation of Glisson's capsule using constant-strain triangular elements: we compare the model to a detailed non-real-time model and also reproduce previously published aspiration test showing the importance of the capsule. Finally, we demonstrate that the proposed complete liver model can be used in a real-time simulation.
In the previous paper [11], a method for geometrical and transducer-time-delay auto-calibration of an ultrasonic computed tomography (USCT) system has been described, aiming at calibration of individual ultrasonic (US) transducer positions. The present contribution describes a novel modification of the method utilizing the particular USCT system concept: the exactly known spatial relations among transducers grouped in each of the transducer array systems (TASes). The algorithms used for the calibration remain based on the principles similar to the global positioning system (GPS) navigation, however, the positions and orientations of complete TASes are calibrated, rather than individual positions of transducers. This way, the number of unknowns is substantially reduced while the number of available equations remains unchanged. Consequently, a solution substantially more robust with respect to measurement noise can be obtained based on this highly overdetermined equation system. The method is capable of calibrating the individual positions of all ultrasonic transducers via their positions in TASes as well as their individual time delays at once during sc. empty measurement, without a need for any particular arrangements, e.g. calibration phantoms.
The contribution presents further results in developing the exact means for simulating the realistic situation in the USCT (ultrasonic computed tomography) imaging system, aiming both at evaluating the approximations used in the existing USCT image reconstruction methods as to their precision and also (in a longer perspective) at iterative improvement of the obtained images via continuum mechanics based feedback. The mathematical models, generalised in comparison with [1], emerging from the transparent physical background, are presented for inhomogeneous media incorporating both the object tissue and the surrounding fluid. The equations are already general enough to employ complex nonlinear phenomena in three-dimensional space; and linearised 3D simulations (giving rise to wave equation, WE) have been performed enabling first conclusions on the feasibility of this approach with respect to the available computing resources. Some of the results of the numerical solution of the WE in 3D by means of the finite-element method show in local detail the diffraction phenomena on acoustic-impedance inhomogeneities. The spatial extent of the simulations is basically limited only by the available computing resources. The hardware requirements and related practical limitations are mentioned together with a few examples of presently available results. Together with conclusions, further perspectives of this branch of the USCT research are suggested.
- MeSH
- algoritmy MeSH
- biologické modely MeSH
- financování organizované MeSH
- interpretace obrazu počítačem metody MeSH
- počítačová simulace MeSH
- refraktometrie metody MeSH
- reprodukovatelnost výsledků MeSH
- senzitivita a specificita MeSH
- tomografie metody MeSH
- ultrasonografie metody MeSH
- vylepšení obrazu metody MeSH
- zobrazování trojrozměrné metody MeSH
This paper presents a method for geometrical and time-delay auto-calibration of an ultrasonic computed tomography (USCT) system. The algorithms used for the calibration are based on the principles similar to the global positioning system (GPS) navigation. Ultrasonic transmitters and receivers in USCT can be viewed like satellite transmitters and mobile receiver units in GPS. However, unlike in GPS, none of the positions of the transmitters or receivers in USCT are assumed to be known and all are the to-be-calibrated unknowns. The presented method is capable of calibrating the positions of all ultrasonic transducers and their individual time delays at once. No calibration phantoms are necessary.
- MeSH
- algoritmy MeSH
- časové faktory MeSH
- design vybavení MeSH
- financování organizované MeSH
- kalibrace MeSH
- počítačová rentgenová tomografie metody přístrojové vybavení MeSH
- počítačová simulace MeSH
- počítačové zpracování signálu MeSH
- reprodukovatelnost výsledků MeSH
- rozpoznávání automatizované MeSH
- statistické modely MeSH
- teoretické modely MeSH
- ultrasonografie metody přístrojové vybavení MeSH
- ultrazvuk MeSH
- zobrazování trojrozměrné metody MeSH
