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1.
Phys Med Biol ; 68(21)2023 10 18.
Artigo em Inglês | MEDLINE | ID: mdl-37774711

RESUMO

Objective. Surgical guidewires are commonly used in placing fixation implants to stabilize fractures. Accurate positioning of these instruments is challenged by difficulties in 3D reckoning from 2D fluoroscopy. This work aims to enhance the accuracy and reduce exposure times by providing 3D navigation for guidewire placement from as little as two fluoroscopic images.Approach. Our approach combines machine learning-based segmentation with the geometric model of the imager to determine the 3D poses of guidewires. Instrument tips are encoded as individual keypoints, and the segmentation masks are processed to estimate the trajectory. Correspondence between detections in multiple views is established using the pre-calibrated system geometry, and the corresponding features are backprojected to obtain the 3D pose. Guidewire 3D directions were computed using both an analytical and an optimization-based method. The complete approach was evaluated in cadaveric specimens with respect to potential confounding effects from the imaging geometry and radiographic scene clutter due to other instruments.Main results. The detection network identified the guidewire tips within 2.2 mm and guidewire directions within 1.1°, in 2D detector coordinates. Feature correspondence rejected false detections, particularly in images with other instruments, to achieve 83% precision and 90% recall. Estimating the 3D direction via numerical optimization showed added robustness to guidewires aligned with the gantry rotation plane. Guidewire tips and directions were localized in 3D world coordinates with a median accuracy of 1.8 mm and 2.7°, respectively.Significance. The paper reports a new method for automatic 2D detection and 3D localization of guidewires from pairs of fluoroscopic images. Localized guidewires can be virtually overlaid on the patient's pre-operative 3D scan during the intervention. Accurate pose determination for multiple guidewires from two images offers to reduce radiation dose by minimizing the need for repeated imaging and provides quantitative feedback prior to implant placement.


Assuntos
Fraturas Ósseas , Procedimentos Ortopédicos , Cirurgia Assistida por Computador , Humanos , Procedimentos Ortopédicos/métodos , Cirurgia Assistida por Computador/métodos , Fraturas Ósseas/cirurgia , Fluoroscopia/métodos , Imageamento Tridimensional/métodos
2.
Mar Policy ; 140: 105054, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-35399704

RESUMO

The human response to the COVID-19 pandemic set in motion an unprecedented shift in human activity with unknown long-term effects. The impacts in marine systems are expected to be highly dynamic at local and global scales. However, in comparison to terrestrial ecosystems, we are not well-prepared to document these changes in marine and coastal environments. The problems are two-fold: 1) manual and siloed data collection and processing, and 2) reliance on marine professionals for observation and analysis. These problems are relevant beyond the pandemic and are a barrier to understanding rapidly evolving blue economies, the impacts of climate change, and the many other changes our modern-day oceans are undergoing. The "Our Ocean in COVID-19″ project, which aims to track human-ocean interactions throughout the pandemic, uses the new eOceans platform (eOceans.app) to overcome these barriers. Working at local scales, a global network of ocean scientists and citizen scientists are collaborating to monitor the ocean in near real-time. The purpose of this paper is to bring this project to the attention of the marine conservation community, researchers, and the public wanting to track changes in their area. As our team continues to grow, this project will provide important baselines and temporal patterns for ocean conservation, policy, and innovation as society transitions towards a new normal. It may also provide a proof-of-concept for real-time, collaborative ocean monitoring that breaks down silos between academia, government, and at-sea stakeholders to create a stronger and more democratic blue economy with communities more resilient to ocean and global change.

3.
Artigo em Inglês | MEDLINE | ID: mdl-36090307

RESUMO

Purpose: A method and prototype for a fluoroscopically-guided surgical robot is reported for assisting pelvic fracture fixation. The approach extends the compatibility of existing guidance methods with C-arms that are in mainstream use (without prior geometric calibration) using an online calibration of the C-arm geometry automated via registration to patient anatomy. We report the first preclinical studies of this method in cadaver for evaluation of geometric accuracy. Methods: The robot is placed over the patient within the imaging field-of-view and radiographs are acquired as the robot rotates an attached instrument. The radiographs are then used to perform an online geometric calibration via 3D-2D image registration, which solves for the intrinsic and extrinsic parameters of the C-arm imaging system with respect to the patient. The solved projective geometry is then be used to register the robot to the patient and drive the robot to planned trajectories. This method is applied to a robotic system consisting of a drill guide instrument for guidewire placement and evaluated in experiments using a cadaver specimen. Results: Robotic drill guide alignment to trajectories defined in the cadaver pelvis were accurate within 2 mm and 1° (on average) using the calibration-free approach. Conformance of trajectories within bone corridors was confirmed in cadaver by extrapolating the aligned drill guide trajectory into the cadaver pelvis. Conclusion: This study demonstrates the accuracy of image-guided robotic positioning without prior calibration of the C-arm gantry, facilitating the use of surgical robots with simpler imaging devices that cannot establish or maintain an offline calibration. Future work includes testing of the system in a clinical setting with trained orthopaedic surgeons and residents.

4.
Med Image Anal ; 68: 101917, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33341493

RESUMO

PURPOSES: Surgical reduction of pelvic fracture is a challenging procedure, and accurate restoration of natural morphology is essential to obtaining positive functional outcome. The procedure often requires extensive preoperative planning, long fluoroscopic exposure time, and trial-and-error to achieve accurate reduction. We report a multi-body registration framework for reduction planning using preoperative CT and intraoperative guidance using routine 2D fluoroscopy that could help address such challenges. METHOD: The framework starts with semi-automatic segmentation of fractured bone fragments in preoperative CT using continuous max-flow. For reduction planning, a multi-to-one registration is performed to register bone fragments to an adaptive template that adjusts to patient-specific bone shapes and poses. The framework further registers bone fragments to intraoperative fluoroscopy to provide 2D fluoroscopy guidance and/or 3D navigation relative to the reduction plan. The framework was investigated in three studies: (1) a simulation study of 40 CT images simulating three fracture categories (unilateral two-body, unilateral three-body, and bilateral two-body); (2) a proof-of-concept cadaver study to mimic clinical scenario; and (3) a retrospective clinical study investigating feasibility in three cases of increasing severity and accuracy requirement. RESULTS: Segmentation of simulated pelvic fracture demonstrated Dice coefficient of 0.92±0.06. Reduction planning using the adaptive template achieved 2-3 mm and 2-3° error for the three fracture categories, significantly better than planning based on mirroring of contralateral anatomy. 3D-2D registration yielded ~2 mm and 0.5° accuracy, providing accurate guidance with respect to the preoperative reduction plan. The cadaver study and retrospective clinical study demonstrated comparable accuracy: ~0.90 Dice coefficient in segmentation, ~3 mm accuracy in reduction planning, and ~2 mm accuracy in 3D-2D registration. CONCLUSION: The registration framework demonstrated planning and guidance accuracy within clinical requirements in both simulation and clinical feasibility studies for a broad range of fracture-dislocation patterns. Using routinely acquired preoperative CT and intraoperative fluoroscopy, the framework could improve the accuracy of pelvic fracture reduction, reduce radiation dose, and could integrate well with common clinical workflow without the need for additional navigation systems.


Assuntos
Ortopedia , Cirurgia Assistida por Computador , Imagem Corporal , Fluoroscopia , Fixação de Fratura , Humanos , Imageamento Tridimensional , Estudos Retrospectivos , Tomografia Computadorizada por Raios X
5.
Artigo em Inglês | MEDLINE | ID: mdl-32476703

RESUMO

Pelvic trauma surgical procedures rely heavily on guidance with 2D fluoroscopy views for navigation in complex bone corridors. This "fluoro-hunting" paradigm results in extended radiation exposure and possible suboptimal guidewire placement from limited visualization of the fractures site with overlapped anatomy in 2D fluoroscopy. A novel computer vision-based navigation system for freehand guidewire insertion is proposed. The navigation framework is compatible with the rapid workflow in trauma surgery and bridges the gap between intraoperative fluoroscopy and preoperative CT images. The system uses a drill-mounted camera to detect and track poses of simple multimodality (optical/radiographic) markers for registration of the drill axis to fluoroscopy and, in turn, to CT. Surgical navigation is achieved with real-time display of the drill axis position on fluoroscopy views and, optionally, in 3D on the preoperative CT. The camera was corrected for lens distortion effects and calibrated for 3D pose estimation. Custom marker jigs were constructed to calibrate the drill axis and tooltip with respect to the camera frame. A testing platform for evaluation of the navigation system was developed, including a robotic arm for precise, repeatable, placement of the drill. Experiments were conducted for hand-eye calibration between the drill-mounted camera and the robot using the Park and Martin solver. Experiments using checkerboard calibration demonstrated subpixel accuracy [-0.01 ± 0.23 px] for camera distortion correction. The drill axis was calibrated using a cylindrical model and demonstrated sub-mm accuracy [0.14 ± 0.70 mm] and sub-degree angular deviation.

6.
Phys Med Biol ; 65(13): 135009, 2020 07 17.
Artigo em Inglês | MEDLINE | ID: mdl-32217833

RESUMO

Surgical reduction of pelvic dislocation is a challenging procedure with poor long-term prognosis if reduction does not accurately restore natural morphology. The procedure often requires long fluoroscopic exposure times and trial-and-error to achieve accurate reduction. We report a method to automatically compute the target pose of dislocated bones in preoperative CT and provide 3D guidance of reduction using routine 2D fluoroscopy. A pelvic statistical shape model (SSM) and a statistical pose model (SPM) were formed from an atlas of 40 pelvic CT images. Multi-body bone segmentation was achieved by mapping the SSM to a preoperative CT via an active shape model. The target reduction pose for the dislocated bone is estimated by fitting the poses of undislocated bones to the SPM. Intraoperatively, multiple bones are registered to fluoroscopy images via 3D-2D registration to obtain 3D pose estimates from 2D images. The method was examined in three studies: (1) a simulation study of 40 CT images simulating a range of dislocation patterns; (2) a pelvic phantom study with controlled dislocation of the left innominate bone; (3) a clinical case study investigating feasibility in images acquired during pelvic reduction surgery. Experiments investigated the accuracy of registration as a function of initialization error (capture range), image quality (radiation dose and image noise), and field of view (FOV) size. The simulation study achieved target pose estimation with translational error of median 2.3 mm (1.4 mm interquartile range, IQR) and rotational error of 2.1° (1.3° IQR). 3D-2D registration yielded 0.3 mm (0.2 mm IQR) in-plane and 0.3 mm (0.2 mm IQR) out-of-plane translational error, with in-plane capture range of ±50 mm and out-of-plane capture range of ±120 mm. The phantom study demonstrated 3D-2D target registration error of 2.5 mm (1.5 mm IQR), and the method was robust over a large dose range, down to 5 [Formula: see text]Gy/frame (an order of magnitude lower than the nominal fluoroscopic dose). The clinical feasibility study demonstrated accurate registration with both preoperative and intraoperative radiographs, yielding 3.1 mm (1.0 mm IQR) projection distance error with robust performance for FOV ranging from 340 × 340 mm2 to 170 × 170 mm2 (at the image plane). The method demonstrated accurate estimation of the target reduction pose in simulation, phantom, and a clinical feasibility study for a broad range of dislocation patterns, initialization error, dose levels, and FOV size. The system provides a novel means of guidance and assessment of pelvic reduction from routinely acquired preoperative CT and intraoperative fluoroscopy. The method has the potential to reduce radiation dose by minimizing trial-and-error and to improve outcomes by guiding more accurate reduction of joint dislocations.


Assuntos
Imageamento Tridimensional/métodos , Luxações Articulares/diagnóstico por imagem , Luxações Articulares/cirurgia , Procedimentos Ortopédicos , Pelve/lesões , Pelve/cirurgia , Cirurgia Assistida por Computador , Algoritmos , Fluoroscopia , Humanos , Imagens de Fantasmas
7.
Int J Comput Assist Radiol Surg ; 15(1): 1-14, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31741287

RESUMO

PURPOSE: A strong foundation in the fundamental principles of medical intervention combined with genuine exposure to real clinical systems and procedures will improve engineering students' capability for informed innovation on clinical problems. To help build such a foundation, a new course (dubbed Surgineering) was developed to convey fundamental principles of surgery, interventional radiology (IR), and radiation therapy, with an emphasis on experiential learning, hands-on with real clinical systems, exposure to clinicians, and visits to real operating theaters. The concept, structure, and outcomes of the course of the first run of the first semester of the course are described. METHOD: The course included six segments spanning fundamental concepts and cutting-edge approaches in a spectrum of surgical specialties, body and neurological IR, and radiation therapy. Each class involved a minimum of didactic content and an emphasis on hands-on experience with instrumentation, equipment, surgical approaches, anatomical models, dissection, and visits to clinical theaters. Outcomes on the quality of the course and areas for continuing improvement were assessed by student surveys (5-point Likert scores and word-cloud representations of free response) as well as feedback from clinical collaborators. RESULT: Surveys assessed four key areas of feedback on the course and were analyzed quantitatively and in word-cloud representations of: (1) best aspects (hands-on experience with surgeons); (2) worst aspects (quizzes and reading materials); (3) areas for improvement (projects, quizzes, and background on anatomy); and (4) what prospective students should know (a lot background reading for every class). Five-point Likert scores from survey respondents (16/19 students) indicated: overall quality of the course 4.63 ± 0.72 (median 5.00); instructor teaching effectiveness 4.06 ± 1.06 (median 4.00); intellectual challenge 4.19 ± 0.40 (median 4.00); and workload somewhat heavier (62.5%) compared to other courses. Novel elements of the course included the opportunity to engage with clinical faculty and participate in realistic laboratory exercises, work with clinical instruments and equipment, and visit real operating theaters. An additional measure of the success of the course was evidenced by surveys and a strong escalation in enrollment in the following year. CONCLUSIONS: The Surgineering course presents an important addition to upper-level engineering curricula and a valuable opportunity for engineering students to gain hands-on experience and interaction with clinical experts. Close partnership with clinical faculty was essential to the schedule and logistics of the course as well as to the continuity of concepts delivered over the semester. The knowledge and experience gained provides stronger foundation for identification of un-met clinical needs and ideation of new engineering approaches in medicine. The course also provides a valuable prerequisite to higher-level coursework in systems engineering, human factors, and data science applied to medicine.


Assuntos
Engenharia Biomédica/educação , Currículo , Educação de Pós-Graduação em Medicina/métodos , Aprendizagem Baseada em Problemas/métodos , Humanos , Estudos Prospectivos
8.
Med Phys ; 47(3): 958-974, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31863480

RESUMO

PURPOSE: To characterize the radiation dose and three-dimensional (3D) imaging performance of a recently developed mobile, isocentric C-arm equipped with a flat-panel detector (FPD) for intraoperative cone-beam computed tomography (CBCT) (Cios Spin 3D, Siemens Healthineers) and to identify potential improvements in 3D imaging protocols for pertinent imaging tasks. METHODS: The C-arm features a 30 × 30 cm2 FPD and isocentric gantry with computer-controlled motorization of rotation (0-195°), angulation (±220°), and height (0-45 cm). Geometric calibration was assessed in terms of 9 degrees of freedom of the x-ray source and detector in CBCT scans, and the reproducibility of geometric calibration was evaluated. Standard and custom scan protocols were evaluated, with variation in the number of projections (100-400) and mAs per view (0.05-1.65 mAs). Image reconstruction was based on 3D filtered backprojection using "smooth," "normal," and "sharp" reconstruction filters as well as a custom, two-dimensional 2D isotropic filter. Imaging performance was evaluated in terms of uniformity, gray value correspondence with Hounsfield units (HU), contrast, noise (noise-power spectrum, NPS), spatial resolution (modulation transfer function, MTF), and noise-equivalent quanta (NEQ). Performance tradeoffs among protocols were visualized in anthropomorphic phantoms for various anatomical sites and imaging tasks. RESULTS: Geometric calibration showed a high degree of reproducibility despite ~19 mm gantry flex over a nominal semicircular orbit. The dose for a CBCT scan varied from ~0.8-4.7 mGy for head protocols to ~6-38 mGy for body protocols. The MTF was consistent with sub-mm spatial resolution, with f10 (frequency at which MTF = 10%) equal to 0.64 mm-1 , 1.0 mm-1 , and 1.5 mm-1 for smooth, standard, and sharp filters respectively. Implementation of a custom 2D isotropic filter improved CNR ~ 50-60% for both head and body protocols and provided more isotropic resolution and noise characteristics. The NPS and NEQ quantified the 3D noise performance and provided a guide to protocol selection, confirmed in images of anthropomorphic phantoms. Alternative scan protocols were identified according to body site and task - for example, lower-dose body protocols (<3 mGy) sufficient for visualization of bone structures. CONCLUSION: The studies provided objective assessment of the dose and 3D imaging performance of a new C-arm, offering an important basis for clinical deployment and a benchmark for quality assurance. Modifications to standard 3D imaging protocols were identified that may improve performance or reduce radiation dose for pertinent imaging tasks.


Assuntos
Tomografia Computadorizada de Feixe Cônico/instrumentação , Imageamento Tridimensional , Doses de Radiação , Fluoroscopia , Humanos , Período Intraoperatório , Imagens de Fantasmas
9.
Artigo em Inglês | MEDLINE | ID: mdl-33612913

RESUMO

PURPOSE: We investigate an application of multisource extremity Cone-Beam CT (CBCT) with capability of weight-bearing tomographic imaging to obtain quantitative measurements of load-induced deformation of metal internal fixation hardware (e.g. tibial plate). Such measurements are desirable to improve the detection of delayed fusion or non-union of fractures, potentially facilitating earlier return to weight-bearing activities. METHODS: To measure the deformation, we perform a deformable 3D-2D registration of a prior model of the implant to its CBCT projections under load-bearing. This Known-Component Registration (KC-Reg) framework avoids potential errors that emerge when the deformation is estimated directly from 3D reconstructions with metal artifacts. The 3D-2D registration involves a free-form deformable (FFD) point cloud model of the implant and a 3D cubic B-spline representation of the deformation. Gradient correlation is used as the optimization metric for the registration. The proposed approach was tested in experimental studies on the extremity CBCT system. A custom jig was designed to apply controlled axial loads to a fracture model, emulating weight-bearing imaging scenarios. Performance evaluation involved a Sawbone tibia phantom with an ~4 mm fracture gap. The model was fixed with a locking plate and imaged under five loading conditions. To investigate performance in the presence of confounding background gradients, additional experiments were performed with a pre-deformed femoral plate placed in a water bath with Ca bone mineral density inserts. Errors were measured using eight reference BBs for the tibial plate, and surface point distances for the femoral plate, where a prior model of deformed implant was available for comparison. RESULTS: Both in the loaded tibial plate case and for the femoral plate with confounding background gradients, the proposed KC-Reg framework estimated implant deformations with errors of <0.2 mm for the majority of the investigated deformation magnitudes (error range 0.14 - 0.25 mm). The accuracy was comparable between 3D-2D registrations performed from 12 x-ray views and registrations obtained from as few as 3 views. This was likely enabled by the unique three-source x-ray unit on the extremity CBCT scanner, which implements two off-central-plane focal spots that provided oblique views of the field-of-view to aid implant pose estimation. CONCLUSION: Accurate measurements of fracture hardware deformations under physiological weight-bearing are feasible using an extremity CBCT scanner and FFD 3D-2D registration. The resulting deformed implant models can be incorporated into tomographic reconstructions to reduce metal artifacts and improve quantification of the mineral content of fracture callus in CBCT volumes.

10.
Artigo em Inglês | MEDLINE | ID: mdl-36082206

RESUMO

Purpose: We report the initial development of an image-based solution for robotic assistance of pelvic fracture fixation. The approach uses intraoperative radiographs, preoperative CT, and an end effector of known design to align the robot with target trajectories in CT. The method extends previous work to solve the robot-to-patient registration from a single radiographic view (without C-arm rotation) and addresses the workflow challenges associated with integrating robotic assistance in orthopaedic trauma surgery in a form that could be broadly applicable to isocentric or non-isocentric C-arms. Methods: The proposed method uses 3D-2D known-component registration to localize a robot end effector with respect to the patient by: (1) exploiting the extended size and complex features of pelvic anatomy to register the patient; and (2) capturing multiple end effector poses using precise robotic manipulation. These transformations, along with an offline hand-eye calibration of the end effector, are used to calculate target robot poses that align the end effector with planned trajectories in the patient CT. Geometric accuracy of the registrations was independently evaluated for the patient and the robot in phantom studies. Results: The resulting translational difference between the ground truth and patient registrations of a pelvis phantom using a single (AP) view was 1.3 mm, compared to 0.4 mm using dual (AP+Lat) views. Registration of the robot in air (i.e., no background anatomy) with five unique end effector poses achieved mean translational difference ~1.4 mm for K-wire placement in the pelvis, comparable to tracker-based margins of error (commonly ~2 mm). Conclusions: The proposed approach is feasible based on the accuracy of the patient and robot registrations and is a preliminary step in developing an image-guided robotic guidance system that more naturally fits the workflow of fluoroscopically guided orthopaedic trauma surgery. Future work will involve end-to-end development of the proposed guidance system and assessment of the system with delivery of K-wires in cadaver studies.

11.
Phys Med Biol ; 64(16): 165021, 2019 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-31287092

RESUMO

Intraoperative cone-beam CT (CBCT) is increasingly used for surgical navigation and validation of device placement. In spinal deformity correction, CBCT provides visualization of pedicle screws and fixation rods in relation to adjacent anatomy. This work reports and evaluates a method that uses prior information regarding such surgical instrumentation for improved metal artifact reduction (MAR). The known-component MAR (KC-MAR) approach achieves precise localization of instrumentation in projection images using rigid or deformable 3D-2D registration of component models, thereby overcoming residual errors associated with segmentation-based methods. Projection data containing metal components are processed via 2D inpainting of the detector signal, followed by 3D filtered back-projection (FBP). Phantom studies were performed to identify nominal algorithm parameters and quantitatively investigate performance over a range of component material composition and size. A cadaver study emulating screw and rod placement in spinal deformity correction was conducted to evaluate performance under realistic clinical imaging conditions. KC-MAR demonstrated reduction in artifacts (standard deviation in voxel values) across a range of component types and dose levels, reducing the artifact to 5-10 HU. Accurate component delineation was demonstrated for rigid (screw) and deformable (rod) models with sub-mm registration errors, and a single-pixel dilation of the projected components was found to compensate for partial-volume effects. Artifacts associated with spine screws and rods were reduced by 40%-80% in cadaver studies, and the resulting images demonstrated markedly improved visualization of instrumentation (e.g. screw threads) within cortical margins. The KC-MAR algorithm combines knowledge of surgical instrumentation with 3D image reconstruction in a manner that overcomes potential pitfalls of segmentation. The approach is compatible with FBP-thereby maintaining simplicity in a manner that is consistent with surgical workflow-or more sophisticated model-based reconstruction methods that could further improve image quality and/or help reduce radiation dose.


Assuntos
Artefatos , Tomografia Computadorizada de Feixe Cônico , Metais , Intensificação de Imagem Radiográfica/métodos , Idoso , Algoritmos , Humanos , Imageamento Tridimensional , Masculino , Parafusos Pediculares , Imagens de Fantasmas , Coluna Vertebral/cirurgia
12.
Phys Med Biol ; 64(9): 095022, 2019 05 02.
Artigo em Inglês | MEDLINE | ID: mdl-30921783

RESUMO

Percutaneous screw fixation in pelvic trauma surgery is a challenging procedure that often requires long fluoroscopic exposure times and trial-and-error insertion attempts along narrow bone corridors of the pelvis. We report a method to automatically plan surgical trajectories using preoperative CT and assist device placement by augmenting the fluoroscopic scene with planned trajectories. A pelvic shape atlas was formed from 40 CT images and used to construct a statistical shape model (SSM). Each member of the atlas included expert definition of volumetric regions representing safe trajectory within bone corridors for fixating 10 common fracture patterns. Patient-specific planning is obtained by mapping the SSM to the (un-segmented) patient CT via active shape model (ASM) registration and free-form deformation (FFD), and the resulting transformation is used to transfer the atlas trajectory volumes to the patient CT. Fluoroscopic images acquired during K-wire placement are in turn augmented with projection of the planned trajectories via 3D-2D registration. Registration performance was evaluated via leave-one-out cross-validation over the 40-member atlas, computing the root mean square error (RMSE) in pelvic surface alignment (volumetric registration error), the positive predicted value (PPV) of volumetric trajectories within bone corridors (safety of the automatically planned trajectories), and the distance between trajectories within the planned volume and the bone cortex (absence of breach). A cadaver study was conducted in which K-wires were placed under fluoroscopic guidance to validate 3D-2D registration accuracy and evaluate the potential utility of augmented fluoroscopy with planned trajectories. The leave-one-out cross-validation achieved surface RMSE of 2.2 ± 0.3 mm after ASM registration and 1.8 ± 0.2 mm after FFD refinement. Automatically determined surgical plans conformed within bone corridors with PPV > 90% and centerline trajectory within 3-5 mm of the bone cortex. 3D-2D registration in the cadaver study achieved 0.3 ± 0.8 mm accuracy (in-plane translation) and <4° accuracy (in-plane rotation). Fluoroscopic images augmented with planning data exhibited >90% conformance of volumetric planning data overlay within bone, and all centerline trajectories were within safe corridors. The approach yields a method for both automatic planning of pelvic fracture fixation and augmentation of fluoroscopy for improved surgical precision and safety. The method does not require segmentation of the patient CT, operates without additional hardware (e.g. tracking systems), and is consistent with common workflow in fluoroscopically guided procedures. The approach has the potential to reduce operating time and radiation dose by minimizing trial-and-error attempts in percutaneous screw placement.


Assuntos
Fluoroscopia/métodos , Fraturas Ósseas/cirurgia , Processamento de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Pelve/cirurgia , Cirurgia Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Adolescente , Adulto , Idoso , Algoritmos , Parafusos Ósseos , Cadáver , Feminino , Fraturas Ósseas/diagnóstico por imagem , Fraturas Ósseas/patologia , Humanos , Masculino , Pessoa de Meia-Idade , Pelve/diagnóstico por imagem , Pelve/patologia , Adulto Jovem
13.
Artigo em Inglês | MEDLINE | ID: mdl-34290470

RESUMO

PURPOSE: Intraoperative 2D virtual long-film (VLF) imaging is investigated for 3D guidance and confirmation of the surgical product in spinal deformity correction. Multi-slot-scan geometry (rather than a single-slot "topogram") is exploited to produce parallax views of the scene for accurate 3D colocalization from a single radiograph. METHODS: The multi-slot approach uses additional angled collimator apertures to form fan-beams with disparate views (parallax) of anatomy and instrumentation and to extend field-of-view beyond the linear motion limits. Combined with a knowledge of surgical implants (pedicle screws and/or spinal rods modeled as "known components"), 3D-2D image registration is used to solve for pose estimates via optimization of image gradient correlation. Experiments were conducted in cadaver studies emulating the system geometry of the O-arm (Medtronic, Minneapolis MN). RESULTS: Experiments demonstrated feasibility of multi-slot VLF and quantified the geometric accuracy of 3D-2D registration using VLF acquisitions. Registration of pedicle screws from a single VLF yielded mean target registration error of (2.0±0.7) mm, comparable to the accuracy of surgical trackers and registration using multiple radiographs (e.g., AP and LAT). CONCLUSIONS: 3D-2D registration in a single VLF image offers a promising new solution for image guidance in spinal deformity correction. The ability to accurately resolve pose from a single view absolves workflow challenges of multiple-view registration and suggests application beyond spine surgery, such as reduction of long-bone fractures.

14.
Unfallchirurg ; 121(4): 264-270, 2018 Apr.
Artigo em Alemão | MEDLINE | ID: mdl-29500506

RESUMO

BACKGROUND: Despite great advances in the development of hardware and software components, surgical navigation systems have only seen limited use in current clinical settings due to their reported complexity, difficulty of integration into clinical workflows and questionable advantages over traditional imaging modalities. OBJECTIVES: Development of augmented reality (AR) visualization for surgical navigation without the need for infrared (IR) tracking markers and comparison of the navigation system to conventional imaging. MATERIAL AND METHODS: Novel navigation system combining a cone beam computed tomography (CBCT) capable C­arm with a red-green-blue depth (RGBD) camera. Testing of the device by Kirschner wire (K-wire) placement in phantoms and evaluation of the necessary operating time, number of fluoroscopic images and overall radiation dose were compared to conventional x­ray imaging. RESULTS: We found a significant reduction of the required time, number of fluoroscopic images and overall radiation dose in 3D AR navigation in comparison to x­ray imaging. CONCLUSION: Our AR navigation using RGBD cameras offers a flexible and intuitive visualization of the operating field for the navigated osteosynthesis without IR tracking markers, enabling surgeons to complete operations quicker and with a lower radiation exposure to the patient and surgical staff.


Assuntos
Fixação Interna de Fraturas/métodos , Fraturas Ósseas/cirurgia , Interpretação de Imagem Assistida por Computador/métodos , Imageamento Tridimensional , Procedimentos Cirúrgicos Minimamente Invasivos/métodos , Ossos Pélvicos/lesões , Tomografia Computadorizada de Feixe Cônico/instrumentação , Fixação Interna de Fraturas/instrumentação , Fraturas Ósseas/diagnóstico por imagem , Humanos , Interpretação de Imagem Assistida por Computador/instrumentação , Imageamento Tridimensional/instrumentação , Procedimentos Cirúrgicos Minimamente Invasivos/instrumentação , Ossos Pélvicos/diagnóstico por imagem , Ossos Pélvicos/cirurgia , Cirurgia Assistida por Computador/instrumentação , Interface Usuário-Computador
15.
Artigo em Inglês | MEDLINE | ID: mdl-34290469

RESUMO

PURPOSE: Model-based image registration and reconstruction offer strong potential for improved safety and precision in image-guided interventions. Advantages include reduced radiation dose, improved soft-tissue visibility (detection of complications), and accurate guidance with/without a dedicated navigation system. This work reports the development and performance of such methods on an O-arm system for intraoperative imaging and translates them to first clinical studies. METHODS: Two novel methodologies predicate the work: (1) Known-Component Registration (KC-Reg) for 3D localization of the patient and interventional devices from 2D radiographs; and (2) Penalized-Likelihood reconstruction (PLH) for improved 3D image quality and dose reduction. A thorough assessment of geometric stability, dosimetry, and image quality was performed to define algorithm parameters for imaging and guidance protocols. Laboratory studies included: evaluation of KC-Reg in localization of spine screws delivered in cadaver; and PLH performance in contrast, noise, and resolution in phantoms/cadaver compared to filtered backprojection (FBP). RESULTS: KC-Reg was shown to successfully register screw implants within ~1 mm based on as few as 3 radiographs. PLH was shown to improve soft-tissue visibility (61% improvement in CNR) compared to FBP at matched resolution. Cadaver studies verified the selection of algorithm parameters and the methods were successfully translated to clinical studies under an IRB protocol. CONCLUSIONS: Model-based registration and reconstruction approaches were shown to reduce dose and provide improved visualization of anatomy and surgical instrumentation. Immediate future work will focus on further integration of KC-Reg and PLH for Known-Component Reconstruction (KC-Recon) to provide high-quality intraoperative imaging in the presence of dense instrumentation.

16.
Artigo em Inglês | MEDLINE | ID: mdl-31337926

RESUMO

PURPOSE: In-vivo evaluation of bone microarchitecture remains challenging because of limited resolution of conventional orthopaedic imaging modalities. We investigate the performance of flat-panel detector extremity Cone-Beam CT (CBCT) in quantitative analysis of trabecular bone. To enable accurate morphometry of fine trabecular bone architecture, advanced CBCT pre-processing and segmentation algorithms are developed. METHODS: The study involved 35 transilliac bone biopsy samples imaged on extremity CBCT (voxel size 75 µm, imaging dose ~13 mGy) and gold standard µCT (voxel size 7.67 µm). CBCT image segmentation was performed using (i) global Otsu's thresholding, (ii) Bernsen's local thresholding, (iii) Bernsen's local thresholding with additional histogram-based global pre-thresholding, and (iv) the same as (iii) but combined with contrast enhancement using a Laplacian Pyramid. Correlations between extremity CBCT with the different segmentation algorithms and gold standard µCT were investigated for measurements of Bone Volume over Total Volume (BV/TV), Trabecular Thickness (Tb.Th), Trabecular Spacing (Tb.Sp), and Trabecular Number (Tb.N). RESULTS: The combination of local thresholding with global pre-thresholding and Laplacian contrast enhancement outperformed other CBCT segmentation methods. Using this optimal segmentation scheme, strong correlation between extremity CBCT and µCT was achieved, with Pearson coefficients of 0.93 for BV/TV, 0.89 for Tb.Th, 0.91 for Tb.Sp, and 0.88 for Tb.N (all results statistically significant). Compared to a simple global CBCT segmentation using Otsu's algorithm, the advanced segmentation method achieved ~20% improvement in the correlation coefficient for Tb.Th and ~50% improvement for Tb.Sp. CONCLUSIONS: Extremity CBCT combined with advanced image pre-processing and segmentation achieves high correlation with gold standard µCT in measurements of trabecular microstructure. This motivates ongoing development of clinical applications of extremity CBCT in in-vivo evaluation of bone health e.g. in early osteoarthritis and osteoporosis.

17.
Phys Med Biol ; 62(23): 9018-9038, 2017 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-29058687

RESUMO

Percutaneous pelvic screw placement is challenging due to narrow bone corridors surrounded by vulnerable structures and difficult visual interpretation of complex anatomical shapes in 2D x-ray projection images. To address these challenges, a system for planning, guidance, and quality assurance (QA) is presented, providing functionality analogous to surgical navigation, but based on robust 3D-2D image registration techniques using fluoroscopy images already acquired in routine workflow. Two novel aspects of the system are investigated: automatic planning of pelvic screw trajectories and the ability to account for deformation of surgical devices (K-wire deflection). Atlas-based registration is used to calculate a patient-specific plan of screw trajectories in preoperative CT. 3D-2D registration aligns the patient to CT within the projective geometry of intraoperative fluoroscopy. Deformable known-component registration (dKC-Reg) localizes the surgical device, and the combination of plan and device location is used to provide guidance and QA. A leave-one-out analysis evaluated the accuracy of automatic planning, and a cadaver experiment compared the accuracy of dKC-Reg to rigid approaches (e.g. optical tracking). Surgical plans conformed within the bone cortex by 3-4 mm for the narrowest corridor (superior pubic ramus) and >5 mm for the widest corridor (tear drop). The dKC-Reg algorithm localized the K-wire tip within 1.1 mm and 1.4° and was consistently more accurate than rigid-body tracking (errors up to 9 mm). The system was shown to automatically compute reliable screw trajectories and accurately localize deformed surgical devices (K-wires). Such capability could improve guidance and QA in orthopaedic surgery, where workflow is impeded by manual planning, conventional tool trackers add complexity and cost, rigid tool assumptions are often inaccurate, and qualitative interpretation of complex anatomy from 2D projections is prone to trial-and-error with extended fluoroscopy time.


Assuntos
Algoritmos , Parafusos Ósseos , Processamento de Imagem Assistida por Computador/métodos , Pelve/cirurgia , Garantia da Qualidade dos Cuidados de Saúde , Cirurgia Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Cadáver , Fluoroscopia/métodos , Humanos , Imageamento Tridimensional/métodos , Pelve/diagnóstico por imagem
18.
Artigo em Inglês | MEDLINE | ID: mdl-28989221

RESUMO

Pelvic Kirschner wire (K-wire) insertion is a challenging surgical task requiring interpretation of complex 3D anatomical shape from 2D projections (fluoroscopy) and delivery of device trajectories within fairly narrow bone corridors in proximity to adjacent nerves and vessels. Over long trajectories (~10-25 cm), K-wires tend to curve (deform), making conventional rigid navigation inaccurate at the tip location. A system is presented that provides accurate 3D localization and guidance of rigid or deformable surgical devices ("components" - e.g., K-wires) based on 3D-2D registration. The patient is registered to a preoperative CT image by virtually projecting digitally reconstructed radiographs (DRRs) and matching to two or more intraoperative x-ray projections. The K-wire is localized using an analogous procedure matching DRRs of a deformably parametrized model for the device component (deformable known-component registration, or dKC-Reg). A cadaver study was performed in which a K-wire trajectory was delivered in the pelvis. The system demonstrated target registration error (TRE) of 2.1 ± 0.3 mm in location of the K-wire tip (median ± interquartile range, IQR) and 0.8 ± 1.4° in orientation at the tip (median ± IQR), providing functionality analogous to surgical tracking/navigation using imaging systems already in the surgical arsenal without reliance on a surgical tracker. The method offers quantitative 3D guidance using images (e.g., inlet/outlet views) already acquired in the standard of care, potentially extending the advantages of navigation to broader utilization in trauma surgery to improve surgical precision and safety.

19.
Proc SPIE Int Soc Opt Eng ; 101352017 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-28572694

RESUMO

INTRODUCTION: Fluoroscopically guided procedures often involve repeated acquisitions for C-arm positioning at the cost of radiation exposure and time in the operating room. A virtual fluoroscopy system is reported with the potential of reducing dose and time spent in C-arm positioning, utilizing three key advances: robust 3D-2D registration to a preoperative CT; real-time forward projection on GPU; and a motorized mobile C-arm with encoder feedback on C-arm orientation. METHOD: Geometric calibration of the C-arm was performed offline in two rotational directions (orbit α, orbit ß). Patient registration was performed using image-based 3D-2D registration with an initially acquired radiograph of the patient. This approach for patient registration eliminated the requirement for external tracking devices inside the operating room, allowing virtual fluoroscopy using commonly available systems in fluoroscopically guided procedures within standard surgical workflow. Geometric accuracy was evaluated in terms of projection distance error (PDE) in anatomical fiducials. A pilot study was conducted to evaluate the utility of virtual fluoroscopy to aid C-arm positioning in image guided surgery, assessing potential improvements in time, dose, and agreement between the virtual and desired view. RESULTS: The overall geometric accuracy of DRRs in comparison to the actual radiographs at various C-arm positions was PDE (mean ± std) = 1.6 ± 1.1 mm. The conventional approach required on average 8.0 ± 4.5 radiographs spent "fluoro hunting" to obtain the desired view. Positioning accuracy improved from 2.6° ± 2.3° (in α) and 4.1° ± 5.1° (in ß) in the conventional approach to 1.5° ± 1.3° and 1.8° ± 1.7°, respectively, with the virtual fluoroscopy approach. CONCLUSION: Virtual fluoroscopy could improve accuracy of C-arm positioning and save time and radiation dose in the operating room. Such a system could be valuable to training of fluoroscopy technicians as well as intraoperative use in fluoroscopically guided procedures.

20.
Phys Med Biol ; 62(7): 2871-2891, 2017 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-28177300

RESUMO

Spinal screw placement is a challenging task due to small bone corridors and high risk of neurological or vascular complications, benefiting from precision guidance/navigation and quality assurance (QA). Implicit to both guidance and QA is the definition of a surgical plan-i.e. the desired trajectories and device selection for target vertebrae-conventionally requiring time-consuming manual annotations by a skilled surgeon. We propose automation of such planning by deriving the pedicle trajectory and device selection from a patient's preoperative CT or MRI. An atlas of vertebrae surfaces was created to provide the underlying basis for automatic planning-in this work, comprising 40 exemplary vertebrae at three levels of the spine (T7, T8, and L3). The atlas was enriched with ideal trajectory annotations for 60 pedicles in total. To define trajectories for a given patient, sparse deformation fields from the atlas surfaces to the input (CT or MR image) are applied on the annotated trajectories. Mean value coordinates are used to interpolate dense deformation fields. The pose of a straight trajectory is optimized by image-based registration to an accumulated volume of the deformed annotations. For evaluation, input deformation fields were created using coherent point drift (CPD) to perform a leave-one-out analysis over the atlas surfaces. CPD registration demonstrated surface error of 0.89 ± 0.10 mm (median ± interquartile range) for T7/T8 and 1.29 ± 0.15 mm for L3. At the pedicle center, registered trajectories deviated from the expert reference by 0.56 ± 0.63 mm (T7/T8) and 1.12 ± 0.67 mm (L3). The predicted maximum screw diameter differed by 0.45 ± 0.62 mm (T7/T8), and 1.26 ± 1.19 mm (L3). The automated planning method avoided screw collisions in all cases and demonstrated close agreement overall with expert reference plans, offering a potentially valuable tool in support of surgical guidance and QA.


Assuntos
Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Parafusos Pediculares/estatística & dados numéricos , Fusão Vertebral/instrumentação , Fusão Vertebral/métodos , Coluna Vertebral/diagnóstico por imagem , Tomografia Computadorizada por Raios X/métodos , Humanos
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