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Purpose To show the feasibility of 3D-printed fixation masks for whole brain radiation therapy in a clinical setting and perform a first comparison to an established thermoplastic mask system. Methods Six patients were irradiated with whole brain radiotherapy using individually 3D-printed masks. Daily image guidance and position correction were performed prior to each irradiation fraction. The vectors of the daily position correction were compared to two collectives of patients, who were irradiated using the standard thermoplastic mask system (one cohort with head masks; one cohort with head and neck masks). Results The mean systematic errors in the experimental cohort ranged between 0.59 and 2.10 mm which is in a comparable range to the control groups (0.18 mm–0.68 mm and 0.34 mm–2.96 mm, respectively). The 3D-printed masks seem to be an alternative to the established thermoplastic mask systems. Nevertheless, further investigation will need to be performed. Conclusion The prevailing study showed a reliable and reproducible interfractional positioning accuracy using individually 3D-printed masks for whole brain irradiation in a clinical routine. Further investigations, especially concerning smaller target volumes or other areas of the body, need to be performed before using the system on a larger basis.

Purpose This work aims to develop a simple, anatomically and haptically realistic vascular phantom, compatible with intravascular and intracardiac ultrasound. The low-cost, dual-layered phantom bridges the gap between traditional wall-only and wall-less phantoms by showing both the vessel wall and surrounding tissue in ultrasound imaging. This phantom can better assist clinical tool training, testing of intravascular devices, blood flow studies, and validation of algorithms for intravascular and intracardiac surgical systems. Methods Polyvinyl alcohol cryogel (PVA-c) incorporating a scattering agent was used to obtain vessel and tissue-mimicking materials. Our specific design targeted the inferior vena cava and renal bifurcations which were modelled using CAD software. A custom mould and container were 3D-printed for shaping the desired vessel wall. Three phantoms were prepared by varying both the concentrations of scattering agent as well as the number of freeze–thaw cycles to which the phantom layers were subjected during the manufacturing process. Each phantom was evaluated using ultrasound imaging using the Foresight™ ICE probe. Geometrical validation was provided by comparing CAD design to a CT scan of the phantom. Results The desired vascular phantom was constructed using 2.5% and 0.05% scattering agent concentration in the vessel and tissue-mimicking layers, respectively. Imaging of the three phantoms showed that increasing the number of freeze–thaw cycles did not significantly enhance the image contrast. Comparison of the US images with their CT equivalents resulted in an average error of 0.9$${\,\mathrm{mm}}$$ mm for the lumen diameter. Conclusion The phantom is anatomically realistic when imaged with intracardiac ultrasound and provides a smooth lumen for the ultrasound probe and catheter to manoeuvre. The vascular phantom enables validation of intravascular and intracardiac image guidance systems. The simple construction technique also provides a workflow for designing complex, multi-layered arterial phantoms.

Purpose In minimally invasive spring-assisted craniectomy, surgeons plan the surgery by manually locating the cranial sutures. However, this approach is prone to error. Augmented reality (AR) could be used to visualize the cranial sutures and assist in the surgery planning. The purpose of our work is to develop an AR-based system to visualize cranial sutures, and to assess the accuracy and usability of using AR-based navigation for surgical guidance in minimally invasive spring-assisted craniectomy. Methods An AR system was developed that consists of an electromagnetic tracking system linked with a Microsoft HoloLens. The system was used to conduct a study with two skull phantoms. For each phantom, five sutures were annotated and visualized on the skull surface. Twelve participants assessed the system. For each participant, model alignment using six anatomical landmarks was performed, followed by the participant delineation of the visualized sutures. At the end, the participants filled a system usability scale (SUS) questionnaire. For evaluation, an independent optical tracking system was used and the delineated sutures were digitized and compared to the CT-annotated sutures. Results For a total of 120 delineated sutures, the distance of the annotated sutures to the planning reference was $$2.4\pm 1.2$$ 2.4 ± 1.2 mm. The average delineation time per suture was $$13\pm 5$$ 13 ± 5 s. For the system usability questionnaire, an average SUS score of 73 was obtained. Conclusion The developed AR-system has good accuracy (average 2.4 mm distance) and could be used in the OR. The system can assist in the pre-planning of minimally invasive craniosynostosis surgeries to locate cranial sutures accurately instead of the traditional approach of manual palpation. Although the conducted phantom study was designed to closely reflect the clinical setup in the OR, further clinical validation of the developed system is needed and will be addressed in a future work.

Objectives Motion compensation is an interesting approach to improve treatments of moving structures. For example, target motion can substantially affect dose delivery in radiation therapy, where methods to detect and mitigate the motion are widely used. Recent advances in fast, volumetric ultrasound have rekindled the interest in ultrasound for motion tracking. We present a setup to evaluate ultrasound based motion tracking and we study the effect of imaging rate and motion artifacts on its performance. Methods We describe an experimental setup to acquire markerless 4D ultrasound data with precise ground truth from a robot and evaluate different real-world trajectories and system settings toward accurate motion estimation. We analyze motion artifacts in continuously acquired data by comparing to data recorded in a step-and-shoot fashion. Furthermore, we investigate the trade-off between the imaging frequency and resolution. Results The mean tracking errors show that continuously acquired data leads to similar results as data acquired in a step-and-shoot fashion. We report mean tracking errors up to 2.01 mm and 1.36 mm on the continuous data for the lower and higher resolution, respectively, while step-and-shoot data leads to mean tracking errors of 2.52 mm and 0.98 mm. Conclusions We perform a quantitative analysis of different system settings for motion tracking with 4D ultrasound. We can show that precise tracking is feasible and additional motion in continuously acquired data does not impair the tracking. Moreover, the analysis of the frequency resolution trade-off shows that a high imaging resolution is beneficial in ultrasound tracking.

PURPOSE: Accurate and efficient spine registration is crucial to success of spine image-guidance. However, changes in spine pose cause intervertebral motion that can lead to significant registration errors. In this study, we develop a geometrical rectification technique via non-linear principal component analysis (NLPCA) to achieve level-wise vertebral registration that is robust to large changes in spine pose. METHODS: We used explanted porcine spines and live pigs to develop and test our technique. Each sample was scanned with pre-operative CT (pCT) in an initial pose, and re-scanned with intraoperative stereovision (iSV) in a different surgical posture. Patient registration rectified arbitrary spinal postures in pCT and iSV into a common, neutral pose through a parameterized moving-frame approach. Topologically encoded depth projection 2D images were then generated to establish invertible point-to-pixel correspondences. Level-wise point correspondences between pCT and iSV vertebral surfaces were generated via 2D image registration. Finally, closed-form vertebral level-wise rigid registration was obtained by directly mapping 3D surface point pairs. Implanted mini screws were used as fiducial markers to measure registration accuracy. RESULTS: In 7 explanted porcine spines and 2 live animal surgeries (maximum in-spine pose change of 87.5 mm and 32.7 degrees averaged from all spines), average target registration errors (TRE) of 1.70±0.15 mm and 1.85±0.16 mm were achieved, respectively. The automated spine rectification took 3–5 mins, followed by an additional 30 secs for depth image projection and level-wise registration. CONCLUSION: Accuracy and efficiency of the proposed level-wise spine registration supports its application in human open spine surgeries. The registration framework, itself, may also be applicable to other intraoperative imaging modalities such as ultrasound and MRI, which may expand utility of the approach in spine registration in general.

Purpose The initial registration of a 3D pre-operative CT model to a 2D laparoscopic video image in augmented reality systems for liver surgery needs to be fast, intuitive to perform and with minimal interruptions to the surgical intervention. Several recent methods have focussed on using easily recognisable landmarks across modalities. However, these methods still need manual annotation or manual alignment. We propose a novel, fully automatic pipeline for 3D–2D global registration in laparoscopic liver interventions. Methods Firstly, we train a fully convolutional network for the semantic detection of liver contours in laparoscopic images. Secondly, we propose a novel contour-based global registration algorithm to estimate the camera pose without any manual input during surgery. The contours used are the anterior ridge and the silhouette of the liver. Results We show excellent generalisation of the semantic contour detection on test data from 8 clinical cases. In quantitative experiments, the proposed contour-based registration can successfully estimate a global alignment with as little as 30% of the liver surface, a visibility ratio which is characteristic of laparoscopic interventions. Moreover, the proposed pipeline showed very promising results in clinical data from 5 laparoscopic interventions. Conclusions Our proposed automatic global registration could make augmented reality systems more intuitive and usable for surgeons and easier to translate to operating rooms. Yet, as the liver is deformed significantly during surgery, it will be very beneficial to incorporate deformation into our method for more accurate registration.

This article investigates the current state of the art of the use of auditory display in image-guided medical interventions. Auditory display is a means of conveying information using sound, and we review the use of this approach to support navigated interventions. We discuss the benefits and drawbacks of published systems and outline directions for future investigation. We undertook a review of scientific articles on the topic of auditory rendering in image-guided intervention. This includes methods for avoidance of risk structures and instrument placement and manipulation. The review did not include auditory display for status monitoring, for instance in anesthesia. We identified 15 publications in the course of the search. Most of the literature (60%) investigates the use of auditory display to convey distance of a tracked instrument to an object using proximity or safety margins. The remainder discuss continuous guidance for navigated instrument placement. Four of the articles present clinical evaluations, 11 present laboratory evaluations, and 3 present informal evaluation (2 present both laboratory and clinical evaluations). Auditory display is a growing field that has been largely neglected in research in image-guided intervention. Despite benefits of auditory displays reported in both the reviewed literature and non-medical fields, adoption in medicine has been slow. Future challenges include increasing interdisciplinary cooperation with auditory display investigators to develop more meaningful auditory display designs and comprehensive evaluations which target the benefits and drawbacks of auditory display in image guidance.

Purpose In the surgical treatment for lower-leg intra-articular fractures, the fragments have to be positioned and aligned to reconstruct the fractured bone as precisely as possible, to allow the joint to function correctly again. Standard procedures use 2D radiographs to estimate the desired reduction position of bone fragments. However, optimal correction in a 3D space requires 3D imaging. This paper introduces a new navigation system that uses pre-operative planning based on 3D CT data and intra-operative 3D guidance to virtually reduce lower-limb intra-articular fractures. Physical reduction in the fractures is then performed by our robotic system based on the virtual reduction. Methods 3D models of bone fragments are segmented from CT scan. Fragments are pre-operatively visualized on the screen and virtually manipulated by the surgeon through a dedicated GUI to achieve the virtual reduction in the fracture. Intra-operatively, the actual position of the bone fragments is provided by an optical tracker enabling real-time 3D guidance. The motion commands for the robot connected to the bone fragment are generated, and the fracture physically reduced based on the surgeon’s virtual reduction. To test the system, four femur models were fractured to obtain four different distal femur fracture types. Each one of them was subsequently reduced 20 times by a surgeon using our system. Results The navigation system allowed an orthopaedic surgeon to virtually reduce the fracture with a maximum residual positioning error of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$0.95 \pm 0.3\,\hbox {mm}$$\end{document}0.95±0.3mm (translational) and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1.4^{\circ } \pm 0.5^{\circ }$$\end{document}1.4∘±0.5∘ (rotational). Correspondent physical reductions resulted in an accuracy of 1.03 ± 0.2 mm and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1.56^{\circ }\pm 0.1^{\circ }$$\end{document}1.56∘±0.1∘, when the robot reduced the fracture. Conclusions Experimental outcome demonstrates the accuracy and effectiveness of the proposed navigation system, presenting a fracture reduction accuracy of about 1 mm and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1.5^{\circ }$$\end{document}1.5∘, and meeting the clinical requirements for distal femur fracture reduction procedures. Electronic supplementary material The online version of this article (doi:10.1007/s11548-016-1418-z) contains supplementary material, which is available to authorized users.

PURPOSE Treatment of vascular malformations requires the placement of a needle within vessels which may be as small as 1 mm, with the current state of the art relying exclusively on two-dimensional fluoroscopy images for guidance. We hypothesize that the combination of stereotactic image guidance with existing targeting methods will result in faster and more reproducible needle placements, as well as reduced radiationexposure, when compared to standard methods based on fluoroscopy alone. METHODS The proposed navigation approach was evaluated in a phantom experiment designed to allow direct comparison with the conventional method. An anatomical phantom of the left forearm was constructed, including an independent control mechanism to indicate the attainment of the target position. Three interventionalists (one inexperienced, two of them frequently practice the conventional fluoroscopic technique) performed 45 targeting attempts utilizing the combined and 45 targeting attempts utilizing the standard approaches. RESULTS In all 45 attempts, the users were able to reach the target when utilizing the combined approach. In two cases, targeting was stopped after 15 min without reaching the target when utilizing only the C-arm. The inexperienced user was faster when utilizing the combined approach and applied significantly less radiation than when utilizing the conventional approach. Conversely, both experienced users were faster when using the conventional approach, in one case significantly so, with no significant difference in radiation dose when compared to the combined approach. CONCLUSIONS This work presents an initial evaluation of a combined navigation fluoroscopy targeting technique in a phantom study. The results suggest that, especially for inexperienced interventionalists, navigation may help to reduce the time and the radiation dose. Future work will focus on the improvement and clinical evaluation of the proposed method.

Minimally invasive alternatives are now available for many complex surgeries. These approaches are enabled by the increasing availability of intra-operative image guidance. Yet, fluoroscopic X-rays suffer from projective transformation and thus cannot provide direct views onto anatomy. Surgeons could highly benefit from additional information, such as the anatomical landmark locations in the projections, to support intra-operative decision making. However, detecting landmarks is challenging since the viewing direction changes substantially between views leading to varying appearance of the same landmark. Therefore, and to the best of our knowledge, view-independent anatomical landmark detection has not been investigated yet. In this work, we propose a novel approach to detect multiple anatomical landmarks in X-ray images from arbitrary viewing directions. To this end, a sequential prediction framework based on convolutional neural networks is employed to simultaneously regress all landmark locations. For training, synthetic X-rays are generated with a physically accurate forward model that allows direct application of the trained model to real X-ray images of the pelvis. View invariance is achieved via data augmentation by sampling viewing angles on a spherical segment of $$120^\circ \times 90^\circ $$ . On synthetic data, a mean prediction error of 5.6 ± 4.5 mm is achieved. Further, we demonstrate that the trained model can be directly applied to real X-rays and show that these detections define correspondences to a respective CT volume, which allows for analytic estimation of the 11 degree of freedom projective mapping. We present the first tool to detect anatomical landmarks in X-ray images independent of their viewing direction. Access to this information during surgery may benefit decision making and constitutes a first step toward global initialization of 2D/3D registration without the need of calibration. As such, the proposed concept has a strong prospect to facilitate and enhance applications and methods in the realm of image-guided surgery.

Image-guidance systems (IGS) have gained widespread use in endoscopic sinus surgery (ESS) and have been thoroughly analysed. In this study, we looked for a new parameter to determine if patients could directly benefit from the use of IGS during primary ESS. We questioned if IGS could improve the quality of ESS in chronic rhinosinusitis (CRS) patients via allowing a more comprehensive treatment of all involved sinus compartments. In a pilot feasibility study, we evaluated uncomplicated CRS patients following primary ESS with and without IGS between January 2011 and June 2012 using preoperative and postoperative CT scans. The preoperative CT scans identified the sinus compartments requiring surgery. The postoperative CT scans were used to evaluate the treatment effect in these compartments. From these data, we calculated a missing ratio (missed compartments/compartments requiring surgery) for each patient. Of the 169 ESS patients who were treated, ten patients were retrospectively identified as complying with the inclusion and exclusion criteria following ESS with IGS. Ten patients treated without IGS were then randomly chosen. The median missing ratio for non-IGS patients was 36%, and for IGS patients, the median missing ratio was 0% (p = 0.046). However, the missing ratio was depended on the number of compartments requiring surgery. Stratification of the number of compartments requiring surgery resulted in an exact p value of 0.13. IGS could help the surgeon to more completely address diseased sinus compartments. For better scientific merit, a comparative study of ESS with and without IGS seems feasible, using the proposed failing score missed compartments/compartments requiring surgery as the primary outcome parameter.

© 2015, CARS. Purpose: In order to assist in the identification of renal vasculature and tumour boundaries in robot-assisted partial nephrectomy, robust ultrasound probe calibration and tracking methods are introduced. Contemporaneous image guidance during these crucial stages of the procedure should ultimately lead to improved safety and quality of outcome for the patient, through reduced positive margin rates, segmental clamping, shorter ischaemic times and nephron-sparing resection. Methods: Small KeyDot markers with circular dot patterns are attached to a miniature pickup ultrasound probe. Generic probe calibration is superseded by a more robust scheme based on a sequence of physical transducer measurements. Motion prediction combined with a reduced region-of-interest in the endoscopic video feed facilitates real-time tracking and registration performance at full HD resolutions. Results: Quantitative analysis confirms that circular dot patterns result in an improved translational and rotational working envelope, in comparison with the previous chessboard pattern implementation. Furthermore, increased robustness is observed with respect to prevailing illumination levels and out-of-focus images due to relatively small endoscopic depths of field. Conclusion: Circular dot patterns should be employed in this context as they result in improved performance and robustness. This facilitates clinical usage and interpretation of the combined video and ultrasound overlay. The efficacy of the overall system is demonstrated in the first human clinical case.

Interventional MRI has significant potential for image guidance of iliac angioplasty and related vascular procedures. A technology framework with in-room image display, control, communication and MRI-guided intervention techniques was designed and tested for its potential to provide safe, fast and efficient MRI-guided angioplasty of the iliac arteries. A 1.5-T MRI scanner was adapted for interactive imaging during endovascular procedures using new or modified interventional devices such as guidewires and catheters. A perfused vascular phantom was used for testing. Pre-, intra- and post-procedural visualization and measurement of vascular morphology and flow was implemented. A detailed analysis of X-ray fluoroscopic angiography workflow was conducted and applied. Two interventional radiologists and one physician in training performed 39 procedures. All procedures were timed and analyzed. MRI-guided iliac angioplasty procedures were successfully performed with progressive adaptation of techniques and workflow. The workflow, setup and protocol enabled a reduction in table time for a dedicated MRI-guided procedure to 6 min 33 s with a mean procedure time of 9 min 2 s, comparable to the mean procedure time of 8 min 42 s for the standard X-ray-guided procedure. MRI-guided iliac vascular interventions were found to be feasible and practical using this framework and optimized workflow. In particular, the real-time flow analysis was found to be helpful for pre- and post-interventional assessments. Design optimization of the catheters and in vivo experiments are required before clinical evaluation.

Deep brain stimulation (DBS) surgery utilizes image guidance via bone-implanted fiducial markers to achieve the desired submillimetric accuracy and to provide means for attaching microstereotactic frames. For maximal benefit, the markers must be inserted to the correct depth since over-insertion leads to stripping and under-insertion leads to instability.The purpose of the study was to test clinically a depth-release drive system, the PosiSeat™, versus manual insertion (pilot hole followed by manual screwing until tactile determined correct seating) for implanting fiducial markers into the bone.With institutional review board approval, the PosiSeat™ was used to implant markers in 15 DBS patients (57 fiducials). On post-insertion CT scans, the depth of the gap between the shoulder of the fiducial markers and the closest bone surface was measured. Similar depth measurements were performed on the CT scans of 64 DBS patients (250 fiducials), who underwent manual fiducial insertion.Median of shoulder-to-bone distance for PosiSeat™ and manual insertion group were 0.03 and 1.06 mm, respectively. Fifty percent of the fiducials had the shoulder-to-bone distances within 0.01-0.09 mm range for the PosiSeat group and 0.04-1.45 mm range for the manual insertion group. These differences were statistically significant.A depth-release drive system achieves more consistent placement of bone-implanted fiducial markers than manual insertion.

Inaccurate placement of external ventricular drains (EVDs) is a common issue in cerebrospinal diversion procedures. The conventional freehand technique results in a high fraction of sub-optimally placed catheters, and the use of image guidance can improve these results. The purpose of this paper is the validation of the use of an average model for guidance of EVD procedures. Three neurosurgeons have tested the model-based technique on three normal volunteers, and we have compared the model-based technique to the freehand technique and neuronavigation based on volunteer-specific images. Our results show that the surgeons perform significantly better when using the model-based technique than when using the freehand technique. Our results suggest that the use of an average model may improve the accuracy of catheter placements. However, further refinement of the method and testing in a clinical setting is required.

Purpose In this paper, we propose a pilot study for transcatheter aortic valve implantation guided by an augmented magnetic tracking system (MTS) with a dynamic aortic model and intra-operative ultrasound (US) images. Methods The dynamic 3D aortic model is constructed from the preoperative 4D computed tomography, which is animated according to the real-time electrocardiograph (ECG) input of patient. Before the procedure, the US probe calibration is performed to map the US image coordinate to the tracked device coordinate. A temporal alignment is performed to synchronize the ECG signals, the intra-operative US image and the tracking information. Thereafter, with the assistance of synchronized ECG signals, the spatial registration is performed by using a feature-based registration. Then the augmented MTS guides the surgeon to confidently position and deploy the transcatheter aortic valve prosthesis to the target. Results The approach was validated by US probe calibration evaluation and animal study. The US calibration accuracy achieved $$1.37\pm 0.43\, \text{ mm}$$ , whereas in the animal study on three porcine subjects, fiducial, target, deployment distance and tilting errors reached $$3.16\pm 0.55\,\text{ mm}$$ , $$3.80\pm 1.83\,\text{ mm}$$ , $$3.13\pm 1.12\,\text{ mm}$$ and $$5.87\pm 2.35^{\circ }$$ , respectively. Conclusion Our pilot study has revealed that the proposed approach is feasible and accurate for delivery and deployment of transcatheter aortic valve prosthesis.

We developed an image-guided intervention robot system that can be operated in a magnetic resonance (MR) imaging gantry. The system incorporates a bendable needle intervention robot for breast cancer patients that overcomes the space limitations of the MR gantry. Most breast coil designs for breast MR imaging have side openings to allow manual localization. However, for many intervention procedures, the patient must be removed from the gantry. A robotic manipulation system with integrated image guidance software was developed. Our robotic manipulator was designed to be slim, so as to fit between the patient’s side and the MR gantry wall. Only non-magnetic materials were used, and an electromagnetic shield was employed for cables and circuits. The image guidance software was built using open source libraries. In situ feasibility tests were performed in a 3-T MR system. One target point in the breast phantom was chosen by the clinician for each experiment, and our robot moved the needle close to the target point. Without image-guided feedback control, the needle end could not hit the target point (distance = 5 mm) in the first experiment. Using our robotic system, the needle hits the target lesion of the breast phantom at a distance of 2.3 mm from the same target point using image-guided feedback. The second experiment was performed using other target points, and the distance between the final needle end point and the target point was 0.8 mm. We successfully developed an MR-guided needle intervention robot for breast cancer patients. Further research will allow the expansion of these interventions.

Objective Open heart bypass graft surgery is the standard treatment for advanced cases of coronary heart disease. Optimal placement of the bypass graft anastomosis is very important for the success of the procedure. Therefore, detailed and precise knowledge about the path and morphology of the target vessel is crucial for the operating surgeon.

Purpose The development of the CyberKnife technology, a combination of image guidance and industrial robotics, led to a paradigm shift in radiosurgery.

Neuronavigation with display of intraoperative structures, instrument locations, orientation and relationships to nearby structures can increase anatomic precision while enhancing the surgeon’s confidence and his/her perception of safety. Combination of neuronavigation with functional imaging provides multimodal guidance for surgery of cerebral lesions. We evaluated the impact of functional MRI (fMRI) on surgical decision making and outcome. A neuronavigational device (StealthStation (tm), Medtronic Inc.) was used as platform to merge fMRI data with anatomic images, and to implement intraoperative multimodal guidance. In a 52-month period, where 977 surgical procedures were performed with the aid of neuronavigation, 88 patients underwent image-guided procedures using multimodal guidance. Patient, surgical and outcome data of this series was prospectively collected. Evaluation of 88 procedures on cerebral lesions in complex regions where fMRI data were integrated using the navigation system demonstrated that the additional information was presented in a user-friendly way. Computer assisted fMRI integration was found to be especially helpful in planning the best approach, in assessing alternative approaches, and in defining the extent of the surgical exposure. Furthermore, the surgeons found it more effective to interpret fMRI information when shown in a navigation system as compared to the traditional display on a light board or monitor. Multimodal navigation enhanced by fMRI was judged useful for optimization of surgery of cerebral lesions, especially in and around eloquent regions by experienced neurosurgeons.

© 2015, CARS. Purpose: Epidural and spinal anesthesia are common procedures that require a needle to be inserted into the patient’s spine to deliver an anesthetic. Traditionally, these procedures were performed without image guidance, using only palpation to identify the correct vertebral interspace. More recently, ultrasound has seen widespread use in guiding spinal needle interventions. Dural pulsation is a valuable cue for finding a path through the vertebral interspace and for determining needle insertion depth. However, dural pulsation is challenging to detect and not perceptible in many cases. Here, a method for automatically detecting very subtle dural pulsation from live ultrasound video is presented. Methods: A periodic model is fit to the B-mode intenstity values through extended Kalman filtering. The fitted frequencies and amplitudes are used to detect and visualize dural pulsation. The method is validated retrospectively on synthetic and human video and used in real time on an interventional spinal phantom. Results: This method was capable of quickly identifying subtle dural pulsation and was robust to background noise and motion. The pulsation visualization reduced both the normalized path length and number of attempts required in a mock epidural procedure. Conclusion: This technique is able to localize the dura and help find a clear needle trajectory to the epidural space. It can be run in real time on commercial ultrasound systems and has the potential to improve ultrasound guidance of spine needle interventions.

Dynamic implants for the human spine are used to re-establish regular segmental motion. However, the results have often been unsatisfactory and complications such as screw loosening are common. Individualisation of appliances and precision implantation are needed to improve the outcome of this procedure. Computer simulation, virtual implant optimisation and image guidance were used to improve the technique. A human lumbar spine computer model was developed using multi-body simulation software. The model simulates spinal motion under load and degenerative changes. After virtual degeneration of a L4/5 segment, virtual pedicle screw-based implants were introduced. The implants’ positions and properties were iteratively optimised. The resulting implant positions were used as operative plan for image guidance and finally implemented in a physical spine model. In the simulation, the introduction and optimisation of virtually designed dynamic implants could partly compensate for the effects of virtual lumbar segment degeneration. The optimised operative plan was exported to two different image-guidance systems for transfer to a physical spine model. Three-dimensional computer graphic simulation is a feasible means to develop operative plans for dynamic spinal stabilization. These operative plans can be transferred to commercially available image-guidance systems for use in implantation of physical implants in a spine model. This concept has important potential in the design of operative plans and implants for individualised dynamic spine stabilization surgery.

Microwave ablation is used for the treatment of hypersplenism. Image guidance and ablation volume assessment is important to ensure that the ablation is successful. The accuracy of 3D ultrasound (US) and magnetic resonance imaging (MRI) in determining the parameters for microwave ablation were compared in a canine splenomegaly model.Microwave ablation of the spleen was performed on 13 dogs with congestive splenomegaly. Several combinations of power output and ablation time were used: 60 W for 300 s, 50 W for 360 s and 40 W for 450 s. The ablation zone volume was measured by 3D US and 3D MRI immediately after microwave ablation, and at 1, 2 and 8 weeks thereafter.Compared with 3D MRI, the ablation zone reconstruction rate was lower with 3D US (92 vs. 100%). However, there was no significant difference was found in the ablation volume calculated soon after the treatment and 1 week and 2 months later.3D US may be useful for quantifying the volume of microwave ablation zones in the spleens of experimental animals and appears promising as an alterative modality to MRI for clinical examinations.

Percutaneous lung biopsies (PLBs) performed for the evaluation of pulmonary masses require image guidance to avoid critical structures. A new CT navigation system (SIRIO, “Sistema robotizzato assistito per il puntamento intraoperatorio”) for PLBs was validated. The local Institutional Review Board approved this retrospective study. Image-guided PLBs in 197 patients were performed with a CT navigation system (SIRIO). The procedures were reviewed based on the number of CT scans, patients’ radiation exposure and procedural time recorded. Comparison was performed with a group of 72 patients undergoing standard CT-guided PLBs. Sensitivity, specificity and overall diagnostic accuracy were assessed in both groups. SIRIO-guided PLBs showed a significant reduction in procedure time, number of required CT scans and the radiation dose administered to patients ( $$p

In the treatment of small bone fractures, such as the scaphoid bone, conventional navigation is limited by its dependence on fixed reference arrays. We introduce a new technique based on reference markers in surgical instruments. If visible on a standard fluoroscopic image, static trajectories are overlaid in this image to guide implant insertions. Fixed markers are not required. The purpose of this study was to identify the possible advantages of the new guidance technique.For this study, 20 artificial hand specimens were randomized into two groups and blinded with polyurethane foam: 10 were treated conventionally and 10 were image guided. We used a clip containing radiopaque markers, which was detected by the system's workstation. A static trajectory was displayed consecutively in the fluoroscopic image to serve as an aiming device. Secondly, we included 3 patients with fractures of the scaphoid bone to test the integrability of this novel method in a clinical setting.In the experimental setup, trajectory guidance reduced the duration of surgery and radiation exposure. Furthermore, it reduced the perforation rate. Accuracy was not improved by the new technique. For clinical cases, the system was integrated into the accommodated surgical workflow and rated as very helpful by users.The system helped reduce the misplacement rate and the emission of radiation. The main limitations were that trajectories were not displayed in real time and could only be shown in a single fluoroscopic image. However, the system is simple and can be easily integrated into the surgical workflow.

Purpose Laparoscopic liver resection has significant advantages over open surgery due to less patient trauma and faster recovery times, yet is difficult for most lesions due to the restricted field of view and lack of haptic feedback. Image guidance provides a potential solution but is challenging in a soft deforming organ such as the liver. In this paper, we therefore propose a laparoscopic ultrasound (LUS) image guidance system and study the feasibility of a locally rigid registration for laparoscopic liver surgery.