waashk/dblp huggingface dataset:
nonmagnetic rigid and flexible outer sheath with pneumatic interlocking mechanism for minimally invasive surgical approach. we developed a nonmagnetic rigid and flexible outer sheath with pneumatic interlocking mechanism using flexible toothed links and a wire-driven bending distal end. the outer sheath can be switched between rigid and flexible modes easily depending on surgical scenes, and the angle of its distal end can be controlled by three nylon wires. all components of flexible parts are made of mri-compatible nonmagnetic plastics. we manufactured the device with 300-mm long, 16-mm outer diameter, 7-mm inner diameter and 90-mm bending distal end. holding power of the device in rigid mode was maximum 3.6 n, which was sufficient for surgical tasks in body cavity. in vivo experiment using a swine, our device performed smooth insertion of a flexible endoscope and a biopsy forceps into reverse side of the liver, intestines and spleen with a curved path. in conclusion, our device shows availability of secure approach of surgical instruments into deep cavity.
methods for tractography-driven surface registration of brain structures. registration of brain structures should bring anatomically equivalent areas into correspondence which is usually done using information from structural mri modalities. correspondence can be improved by using other image modalities that provide complementary data. in this paper we propose and evaluate two novel surface registration algorithms which improve within-surface correspondence in brain structures. both approaches use a white-matter tract similarity function (derived from probabilistic tractography) to match areas of similar connectivity patterns. the two methods differ in the way the deformation field is calculated and in how the multi-scale registration framework is implemented. we validated both algorithms using artificial and real image examples, in both cases showing high registration consistency and the ability to find differences in thalamic sub-structures between alzheimer's disease and control subjects. the results suggest differences in thalamic connectivity predominantly in the medial dorsal parts of the left thalamus.
intra-operative multimodal non-rigid registration of the liver for navigated tumor ablation. ct guided tumor ablation of the liver often suffers from a lack of visualization of the target tumor and surrounding critical structures. this information is available on pre-operative contrast enhanced mr images and a non-rigid registration technique is desirable. however while registration methods have been successfully tested retrospectively on patient data, very few have been incorporated into clinical procedures. a non-rigid registration technique has been evaluated, optimized and validated to be able to perform registration of the liver between mr to ct images, and between intra-operative ct images. the method requires pre-processing and segmentation of the liver, and presents an accuracy of approximately 2mm. a clinical feasibility study has been conducted in 5 liver ablation cases. the method helps clinicians enhance interventional planning, confirm ablation probe location with respect to the tumor, and in the case of cryotherapy, evaluate tumor coverage by the ice ball.
optimal transseptal puncture location for robot-assisted left atrial catheter ablation. the preferred method of treatment for atrial fibrillation (af) is by catheter ablation wherein a catheter is guided into the left atrium through a transseptal puncture. however, the transseptal puncture constrains the catheter, thereby limiting its maneuverability and increasing the difficulty in reaching various locations in the left atrium. in this paper, we address the problem of choosing the optimal transseptal puncture location for performing cardiac ablation to obtain maximum maneuverability of the catheter. we have employed an optimization algorithm to maximize the global isotropy index (gii) to evaluate the optimal transseptal puncture location. as part of this algorithm, a novel kinematic model for the catheter has been developed based on a continuum robot model. preoperative mr/ct images of the heart are segmented using the open source image-guided therapy software, slicer 3, to obtain models of the left atrium and septal wall. these models are input to the optimization algorithm to evaluate the optimal transseptal puncture location. simulation results for the optimization algorithm are presented in this paper.
nonparametric intensity priors for level set segmentation of low contrast structures. segmentation of low contrast objects is an important task in clinical applications like lesion analysis and vascular wall remodeling analysis. several solutions to low contrast segmentation that exploit high-level information have been previously proposed, such as shape priors and generative models. in this work, we incorporate a priori distributions of intensity and low-level image information into a nonparametric dissimilarity measure that defines a local indicator function for the likelihood of belonging to a foreground object. we then integrate the indicator function into a level set formulation for segmenting low contrast structures. we apply the technique to the clinical problem of positive remodeling of the vessel wall in cardiac ct angiography images. we present results on a dataset of twenty five patient scans, showing improvement over conventional gradient-based level sets.
coronary tree extraction using motion layer separation. fluoroscopic images contain useful information that is difficult to comprehend due to the collapse of the 3d information into 2d space. extracting the informative layers and analyzing them separately could significantly improve the task of understanding the image content. traditional digital subtraction angiography (dsa) is not applicable for coronary angiography because of heart beat and breathing motion. in this work, we propose a layer extraction method for separating transparent motion layers in fluoroscopic image sequences, so that coronary tree can be better visualized.. the method is based on the fact that different anatomical structures possess different motion patterns, e.g., heart is beating fast, while lung is breathing slower. a multiscale implementation is used to further improve the efficiency and accuracy. the proposed approach helps to enhance the visibility of the vessel tree, both visually and quantitatively.
tractography-based parcellation of the cortex using a spatially-informed dimension reduction of the connectivity matrix. determining cortical functional areas is an important goal for neurosciences and clinical neurosurgery. this paper presents a method for connectivity-based parcellation of the entire human cortical surface, exploiting the idea that each cortex region has a specific connection profile. the connectivity matrix of the cortex is computed using analytical q-ball-based tractography. the parcellation is achieved independently for each subject and applied to the subset of the cortical surface endowed with enough connections to estimate safely a connectivity profile, namely the top of the cortical gyri. the key point of the method lies in a twofold reduction of the connectivity matrix dimension. first, parcellation amounts to iterating the clustering of voronoï patches of the cortical surface into parcels endowed with homogeneous profiles. the parcels without intersection with the patch boundaries are selected for the final parcellation. before clustering a patch, the complete profiles are collapsed into short profiles indicating connectivity with a set of putative cortical areas. these areas are supposed to correspond to the catchment basins of the watershed of the density of connection to the patch computed on the cortical surface. the results obtained for several brains are compared visually using a coordinate system.
a novel global tractography algorithm based on an adaptive spin glass model. this paper introduces a novel framework for global diffusion mri tractography inspired from a spin glass model. the entire white matter fascicle map is parameterized by pieces of fibers called spins. spins are encouraged to move and rotate to align with the main fiber directions, and to assemble into longer chains of low curvature. moreover, they have the ability to adapt their quantity in regions where the spin concentration is not sufficient to correctly model the data. the optimal spin glass configuration is retrieved by an iterative minimization procedure, where chains are finally assimilated to fibers. as a result, all brain fibers appear as growing simultaneously until they merge with other fibers or reach the domain boundaries. in case of an ambiguity within a region like a crossing, the contribution of all neighboring fibers is used determine the correct neural pathway. this framework is tested on a mr phantom representing a 45° crossing and a real brain dataset. notably, the framework was able to retrieve the triple crossing between the callosal fibers, the corticospinal tract and the arcuate fasciculus.
towards interactive planning of coil embolization in brain aneurysms. many vascular pathologies can now be treated in a minimally invasive way thanks to interventional radiology. instead of open surgery, it allows to reach the lesion of the arteries with therapeutic devices through a catheter. as a particular case, intracranial aneurysms are treated by filling the localized widening of the artery with a set of coils to prevent a rupture due to the weakened arterial wall. considering the location of the lesion, close to the brain, and its very small size, the procedure requires a combination of careful planning and excellent technical skills. an interactive and reliable simulation, adapted to the patient anatomy, would be an interesting tool for helping the interventional neuroradiologist plan and rehearse a coil embolization procedure. this paper describes an original method to perform interactive simulations of coil embolization and proposes a clinical metric to quantitatively measure how the first coil fills the aneurysm. the simulation relies on an accurate reconstruction of the aneurysm anatomy and a real-time model of the coil for which sliding and friction contacts are taken into account. simulation results are compared to real embolization procedure and exhibit good adequacy.
parallax-free long bone x-ray image stitching. in this paper, we present a novel method to create parallax-free panoramic x-ray images of long bones during surgery by making the c-arm rotate around its x-ray source, relative to the patient's table. in order to ensure that the c-arm motion is a relative pure rotation around its x-ray source, we move the table to compensate for the translational part of the motion based on c-arm pose estimation, for which we employed a camera augmented mobile c-arm system [1] and a visual planar marker pattern. thus, we are able to produce a parallax-free panoramic x-ray image that preserves the property of linear perspective projection. we additionally implement a method to reduce the error caused by varying intrinsic parameters of c-arm x-ray imaging. the results show that our proposed method can generate a parallax-free panoramic x-ray image, independent of the configuration of bone structures and without the requirement of a fronto-parallel setup or any overlap in the x-ray images. the resulting panoramic images have a negligible difference (below 2 pixels) in the overlap between two consecutive individual x-ray images and have a high visual quality, which promises suitability for intra-operative clinical applications in orthopedic and trauma surgery.
diffusion tensor field registration in the presence of uncertainty. we propose a novel method for deformable tensor---to---tensor registration of diffusion tensor imaging (dti) data. our registration method considers estimated diffusion tensors as normally distributed random variables whose covariance matrices describe uncertainties in the mean estimated tensor due to factors such as noise in diffusion weighted images (dwis), tissue diffusion properties, and experimental design. the dissimilarity between distributions of tensors in two different voxels is computed using the kullback-leibler divergence to drive a deformable registration process, which is not only affected by principal diffusivities and principal directions, but also the underlying dwi properties. we in general do not assume the positive definite nature of the tensor space given the pervasive influence of noise and other factors. results indicate that the proposed metric weights voxels more heavily whose diffusion tensors are estimated with greater certainty and exhibit anisotropic diffusion behavior thus, intrinsically favoring coherent white matter regions whose tensors are estimated with high confidence.
biomechanically constrained groupwise us to ct registration of the lumbar spine. registration of intraoperative ultrasound (us) with preoperative computed tomography (ct) data for interventional guidance is a subject of immense interest, particularly for percutaneous spinal injections. we propose a biomechanically constrained group-wise registration of us to ct images of the lumbar spine. each vertebra in ct is treated as a sub-volume and transformed individually. the sub-volumes are then reconstructed into a single volume. the algorithm simulates an us image from the ct data at each iteration of the registration. this simulated us image is used to calculate an intensity based similarity metric with the real us image. a biomechanical model is used to constrain the displacement of the vertebrae relative to one another. covariance matrix adaption - evolution strategy (cma-es) is utilized as the optimization strategy. validation is performed on ct and us images from a phantom designed to preserve realistic curvatures of the spine. the technique is able to register initial misalignments of up to 20mm with a success rate of 82%, and those of up to 10mm with a success rate of 98.6%.
temporal estimation of the 3d guide-wire position using 2d x-ray images. we present a method for realtime online 3d reconstruction of a guide-wire or catheter using 2d x-ray images, which do not have to be recorded from different viewpoints. no special catheters or sensors are needed. given a 3d patient data set and the projection parameters, we use recursive probability density propagation to estimate a probability distribution of the current positions of guide-wire parts. based on this distribution, we extract the optimal guide-wire position using regularization techniques. we describe the guide-wire position by a uniform cubic b-spline. experiments on simulated and phantom data demonstrate the high accuracy and robustness of our approach.
a robust solution to multi-modal image registration by combining mutual information with multi-scale derivatives. in this paper we present a novel method for performing image registration of different modalities. mutual information (mi) is an established method for performing such registration. however, it is recognised that standard mi is not without some problems, in particular it does not utilise spatial information within the images. various modifications have been proposed to resolve this, however these only offer slight improvement to the accuracy of registration. we present feature neighbourhood mutual information (fnmi) that combines both image structure and spatial neighbourhood information which is efficiently incorporated into mutual information by approximating the joint distribution with a covariance matrix (c.f. russakoff's regional mutual information). results show that our approach offers a very high level of accuracy that improves greatly on previous methods. in comparison to regional mi, our method also improves runtime for more demanding registration problems where a higher neighbourhood radius is required. we demonstrate our method using retinal fundus photographs and scanning laser ophthalmoscopy images, two modalities that have received little attention in registration literature. registration of these images would improve accuracy when performing demarcation of the optic nerve head for detecting such diseases as glaucoma.
groupwise registration and atlas construction of 4th-order tensor fields using the r riemannian metric. registration of diffusion-weighted mr images (dw-mri) can be achieved by registering the corresponding 2nd-order diffusion tensor images (dti). however, it has been shown that higher-order diffusion tensors (e.g. order-4) outperform the traditional dti in approximating complex fiber structures such as fiber crossings. in this paper we present a novel method for unbiased group-wise non-rigid registration and atlas construction of 4th-order diffusion tensor fields. to the best of our knowledge there is no other existing method to achieve this task. first we define a metric on the space of positive-valued functions based on the riemannian metric of real positive numbers (denoted by r + ). then, we use this metric in a novel functional minimization method for non-rigid 4th-order tensor field registration. we define a cost function that accounts for the 4th-order tensor re-orientation during the registration process and has analytic derivatives with respect to the transformation parameters. finally, the tensor field atlas is computed as the minimizer of the variance defined using the riemannian metric. we quantitatively compare the proposed method with other techniques that register scalar-valued or diffusion tensor (rank-2) representations of the dwmri.
time-of-flight 3-d endoscopy. this paper describes the first accomplishment of the time-of-flight (tof) measurement principle via endoscope optics. the applicability of the approach is verified by in-vitro experiments. off-the-shelf tof camera sensors enable the per-pixel, on-chip, real-time, marker-less acquisition of distance information. the transfer of the emerging tof measurement technique to endoscope optics is the basis for a new generation of tof rigid or flexible 3-d endoscopes. no modification of the endoscope optic itself is necessary as only an enhancement of illumination unit and image sensors is necessary. the major contribution of this paper is threefold: first, the accomplishment of the tof measurement principle via endoscope optics; second, the development and validation of a complete calibration and post-processing routine; third, accomplishment of extensive in-vitro experiments. currently, a depth measurement precision of 0.89 mm at 20 fps with 3072 3-d points is achieved.
prediction of the repair surface over cartilage defects: a comparison of three methods in a sheep model. defects in articular cartilage can be repaired through osteochondral transplantation (mosaic arthroplasty), where osteochondral plugs from non-weight-bearing areas of the joint are transferred to the defect site. incongruity between the plug surface and the adjacent cartilage results in increased contact pressures and poorer outcomes. we compare three methods to predict the desired repair surface for use in computer-assisted mosaic arthroplasty: manual estimation, a cubic spline surface, and a statistical shape atlas of the knee. the cubic spline was found to most accurately match the pre-impact cartilage surface; the atlas was found to match least accurately.
think global, act local; projectome estimation with bluematter. estimating the complete set of white matter fascicles (the projectome) from diffusion data requires evaluating an enormous number of potential pathways; consequently, most algorithms use computationally efficient greedy methods to search for pathways. the limitation of this approach is that critical global parameters - such as data prediction error and white matter volume conservation - are not taken into account. we describe bluematter, a parallel algorithm for global projectome evaluation, which uniquely accounts for global prediction error and volume conservation. leveraging the bluegene/l supercomputing architecture, bluematter explores a massive database of 180 billion candidate fascicles. the candidates are derived from several sources, including atlases and mutliple tractography algorithms. using bluematter we created the highest resolution, volume-conserved projectome of the human brain.
prostate biopsy assistance system with gland deformation estimation for enhanced precision. computer-assisted prostate biopsies became a very active research area during the last years. prostate tracking makes it possible to overcome several drawbacks of the current standard transrectal ultrasound (trus) biopsy procedure, namely the insufficient targeting accuracy which may lead to a biopsy distribution of poor quality, the very approximate knowledge about the actual location of the sampled tissues which makes it difficult to implement focal therapy strategies based on biopsy results, and finally the difficulty to precisely reach non-ultrasound (us) targets stemming from different modalities, statistical atlases or previous biopsy series. the prostate tracking systems presented so far are limited to rigid transformation tracking. however, the gland can get considerably deformed during the intervention because of us probe pressure and patient movements. we propose to use 3d us combined with image-based elastic registration to estimate these deformations. a fast elastic registration algorithm that copes with the frequently occurring us shadows is presented. a patient cohort study was performed, which yielded a statistically significant in-vivo accuracy of 0.83±0.54mm.
statistically deformable 2d/3d registration for accurate determination of post-operative cup orientation from single standard x-ray radiograph. the widely used procedure of evaluation of cup orientation following total hip arthroplasty using single standard anteroposterior (ap) radiograph is known inaccurate, largely due to the wide variability in individual pelvic orientation relative to x-ray plate. 2d/3d rigid image registration methods have been introduced for an accurate determination of the post-operative cup alignment with respect to an anatomical reference extracted from the ct data. although encouraging results have been reported, their extensive usage in clinical routine is still limited. this may be explained by their requirement of a cad model of the prosthesis, which is often difficult to be organized from the manufacturer due to the proprietary issue, and by their requirement of a pre-operative ct scan, which is not available for most retrospective studies. to address these issues, we developed and validated a statistically deformable 2d/3d registration approach for accurate determination of post-operative cup orientation. no cad model and pre-operative ct data is required any more. quantitative and qualitative results evaluated on cadaveric and clinical datasets are given, which indicate the validity of the approach.
multi-modal registration based ultrasound mosaicing. recent us systems allow the real-time acquisition of volume data, either by freehand 3d techniques or novel transducer hardware. however, the acquisition of large volumes is limited by the field of view of the us transducer and anatomical scanning windows into the patient. mosaicing of several 3d us scans has been proposed to generate large us volumes. still, us imaging specific characteristics and artifacts make it challenging to create high quality mosaics. for many clinical cases, especially interventions, additional high quality ct data is available. in this paper we present a novel multi-variate, multi-modal 3d us registration and mosaicing approach, which reduces the effects of ultrasound imaging artifacts on mosaic quality, by incorporating information from co-registered ct.