Location Of Entry Point Research Articles

Toward Robust Partial-Image Based Template Matching Techniques for MRI-Guided Interventions.

We have developed an MRI-safe needle guidance toolkit for MRI-guided interventions intended to enable accurate positioning for needle-based procedures. The toolkit allows intuitive and accurate needle angulation and entry point positioning according to an MRI-based plan, using a flexible, patterned silicone 2D grid. The toolkit automatically matches the grid on MRI planning images with a physical silicon grid placed conformally on the patient's skin and provides the Interventional Radiologist an easy-to-use guide showing the needle entry point on the silicon grid as well as needle angle information. The radiologist can use this guide along with a 2-degree-of-freedom (rotation and angulation relative to the entry point) hand-held needle guide to place the needle into the anatomy of interest. The initial application that we are considering for this toolkit is arthrography, a diagnostic procedure to evaluate the joint space condition. However, this toolkit could be used for any needle-based and percutaneous procedures such as MRI-guided biopsy and facet joint injection. For matching the images, we adopt a transformation parameter estimation technique using the phase-only correlation method in the frequency domain. We investigated the robustness of this method against rotation, displacement, and Rician noise. The algorithm was able to successfully match all the dataset images. We also investigated the accuracy of identifying the entry point from registered template images as a prerequisite for a future targeting study. Application of the template matching algorithm to locate the needle entry points within the MRI dataset resulted in an average entry point location estimation accuracy of 0.12 ±0.2 mm. This promising result motivates a more detailed assessment of this algorithm in the future including a targeting study on a silicon phantom with embedded plastic targets to investigate the end-to-end accuracy of this automatic template matching algorithm in the interventional MRI room.

Percutaneous plantar fasciotomy: An anatomical study about its safety and efficacy

BackgroundPercutaneous plantar fasciotomy is one of the available options for recalcitrant cases of plantar fasciopathy, but there is a mismatch in the clinical results between different author’s experience, possibly due to variability when choosing the exact cutaneous entry point. The purpose of this study is to validate the plantar approach in the surgical treatment of plantar fasciopathy, describing a safe path and cutaneous entry point to perform a percutaneous plantar fasciotomy with a 2 mm incision testing the procedure on cadavers. Methodsa unicentric cross-sectional analytical study was conducted in 12 cadaveric feet to verify the accuracy of the percutaneous fasciotomy entry point. Independent variables analysed were: extent of fasciotomy, entry point location, spur resection, and soft tissues injuries. A double evaluation was performed: an indirect evaluation under fluoroscopic vision, and a direct evaluation after anatomical dissection. ResultsNo cases of plantar cortical lesion on the calcaneus was observed. Satisfactory fasciotomy was performed in 91.7% of the cases. An optimal entry point was noticed in all cases with a mean distance to the tip of tibial malleolus of 22.5 mm (±6.9; 35.1−12.1) and a mean distance to foot midline of 7.8 mm (±1.7; 11.8−5.1). No neurological nor vascular lesions were found. In all the feet, a laceration of the plantar part of flexor digitorum brevis muscle was noted. Conclusionthe plantar approach for percutaneous total plantar fasciotomy is a safe procedure. The current study provides an intraoperative guideline for minimising the possible risks.

A virtual reality-based data analysis for optimizing freehand external ventricular drain insertion.

This work exploits virtual reality technique to analyse and optimize the preoperative planning of freehand external ventricular drain (EVD) insertion. Based on the three-dimensional (3D) virtual brain models, neurosurgeons can directly observe the anatomical landmarks and complete the simulated EVD insertion. Simulation data is used to optimize preoperative planning parameters to ensure the surgical performance. We used the computed tomography (CT) scans to construct the 3D virtual brain models. A group of EVD insertions were simulated by inserting virtual catheters at different entry points. The key parameters including the location of entry point, the catheter orientation, the catheter tip position on lateral ventricles, and the insertion depth were recorded. A data analysis method was then applied to optimize these parameters, resulting in the optimal parameters for the EVD insertion. When the lateral distance of entry point ranged from 2.5 to 3cm, the success rate of 204 cases was 97.79%, which was higher than that of the classic method (59.52%). The optimal insertion angle towards the sagittal plane ranged from 10.46° to 12.73°. To prevent penetrating the lateral ventricles, the insertion depth was optimized to be 3.28 to 4.58cm. The proposed data analysis method is helpful to optimize the key parameters of the preoperative planning, and provides useful references for neurosurgeons to perform the freehand EVD insertion. The EVD insertion experiments on 3D printing model had a success rate of 93.75%, which verified the effectiveness of the data analysis.

Development of a multi-objective model for the design of sustainable supply chains: the case of perishable food products

The role of sustainability in the function of a company and more specifically a food company is pivotal for its financial performance. The environmental issues as well as the potential economic gains from the implementation of its principles ask for the use of multiple instruments that have been developed to green supply chains. Moreover, social issues also arise and involve the food companies social responsibility, as this can be realized through the supply of fresh products that meet consumption security standards. On this basis, the strategic design of these companies’ supply chains can assists them towards meeting their sustainability objectives as it may lead to the selection of transportation modes, location of entry points and distribution centers, and flows between the nodes of the networks under cost, environmental and social impact minimization criteria. Under this context the purpose of this manuscript is to develop and employ a multi-objective (namely cost, social-time and emission minimization) mixed integer linear programming decision-making model for the network design of sustainable supply chains of perishable food products. The specific model was implemented in the case of a fruits importer in the North-Eastern European region considering its geographical settings. To synopsize and according to our findings the suggested model is an easy to use decision-making tool that leads to a whole set of possible solutions incorporating trade-offs between three aspects of sustainability.

Computer-assisted pedicle screw trajectory planning using CT-inferred bone density: A demonstration against surgical outcomes.

Image-guided spine surgery and preoperative computer-assisted planning provide spine surgeons with tools to improve the safety, accuracy, and reliability of pedicle screw placement. The purpose of this study is to demonstrate a computer-assisted pedicle screw placement planning tool in comparison to screws as delivered by a spine surgeon. We describe a novel computer-assisted tool for preoperative pedicle screw placement planning in computed tomography (CT) images, designed with respect to the vertebral shape and structure, and augmented with respect to the considerations of surgical practice. The approach is based on three-dimensional (3D) modeling of the vertebral body and pedicles, and planning of the pedicle screw size and insertion trajectory by maximizing the screw fastening strength, evaluated through CT-inferred bone density maps. The approach is augmented by yielding screw plans consistent with the straight-forward surgical technique of aligning screws parallel to vertebral endplates, and the screw entry points following the spinal curvature to facilitate rod attachment. For a cohort of 25 patients, placement plans were retrospectively obtained for 204 pedicle screws with the computer-assisted tool from preoperative CT images, while reference trajectories of inserted pedicle screws were reconstructed in 3D from postoperative biplanar radiographs. The best performing version of the computer-assisted tool achieved clinically acceptable preoperative pedicle screw placement plans in 96.6% of the cases, while the comparison to the postoperative reconstructions resulted in 3.4±2.5mm for the screw entry point location, 2.7±1.6mm for the screw crossing point location, and 7.4±5.3∘ for the screw sagittal inclination (mean absolute difference±standard deviation). Quantitative comparison revealed that the preoperative placement plans are consistent with the postoperative results, and that the computer-assisted tool integrating bone density and surgical constraints can successfully incorporate important aspects of pedicle screw placement. The results therefore confirm the accuracy of the tool prior to being integrated in an image-guidance system.

Associations between Optic Nerve Head–Related Anatomical Parameters and Refractive Error over the Full Range of Glaucoma Severity

PurposeTo evaluate the associations between optic disc (OD)-related anatomical parameters (interartery angle [IAA] between superior and inferior temporal retinal arteries, OD tilt [TL], rotation [ROT], and torsion [TO], OD surface curvature [CUR], and central retinal vessel trunk entry point location [CRVTL] on OD) and the spherical equivalent of refractive error (SE), and to assess the impact of glaucoma severity on these relationships.MethodsCirrus optical coherence tomography (OCT) fundus images and 24-2 visual fields of 438 patients were included. Ellipses were fitted to OD borders. IAA was calculated between marked retinal artery locations on a circle around OD. Blood vessel entry point on OD was marked to locate CRVTL. TL was measured as the angle between the lines fitted to OD clinical boundary and the Bruch's membrane edges on the horizontal B-scans. Ellipse rotation relative to the vertical axis defined ROT. Angle between the long axis of OD and the interartery line defined TO. CUR was determined by the inner limiting membrane on the horizontal B-scans. Linear regression models evaluated by Bayes Factors (BF) were used to determine the covariance structure between the parameters and SE as well as possible impacts of mean deviation (MD).ResultsOur results showed that CRVTL had the strongest relationship with SE, followed by ROT, TL, and IAA (BFs: 3.59 × 107, 2645, 1126, and 248, respectively). MD did not significantly modulate the relationship between ONH parameters and SE.ConclusionOur results suggest that SE should be considered when interpreting the OD and its circumpapillary region for diagnostic purposes.Translational RelevanceThe reported relationships between OD-related parameters and ametropia may help to decrease false-positive clinical diagnoses of optic neuropathies.

Can surface electromyography improve surgery planning? Electromyographic assessment and intraoperative verification of the nerve bundle entry point location of the gracilis muscle

Purpose: To verify the precision of surface electromyography (sEMG) in locating the innervation zone of the gracilis muscle, by comparing the location of the IZ estimated by means of sEMG with in vivo location of the nerve bundle entry point in patients before graciloplasty procedure due to fecal incontinence. Methods: Nine patients who qualified for the graciloplasty procedure underwent sEMG on both gracilis muscle before their operations. During surgery the nerve bundle was identified by means of electrical stimulation. The distance between the proximal attachment and the nerve entry point into the muscle’s body was measured. Both measurements (sEMG and in vivo identification) were compared for each subject. Results: On average, the IZ was located 65.5mm from the proximal attachment. The mean difference in location of the innervation zones in each individual was 10±9.7mm, maximal – 30mm, the difference being statistically significant (p=0.017). It was intraoperatively confirmed, that the nerve entered the muscle an average of 62mm from the proximal attachment. The largest difference between the EMG IZ estimation and nerve bundle entry point was 5mm (mean difference 2.8mm, p=0.767). Conclusion: Preoperative surface electromyography of both gracilis muscles is a safe, precise and reliable method of assessing the location of the innervation zones of the gracilis muscles. The asymmetry of the IZ location in left and right muscles may be important in context of technical aspects of the graciloplasty procedure.

New software applications for interchangeable instrumentation in spinal stereotaxis.

Computer image-guided surgery has been widely accepted because it allows the surgeon to track an instrument through unvisualized critical structures of a patient in real-time, thus minimizing the risk of injury. Current spinal and cranial image-guided surgery is, however, limited by the lack of surgical instruments and software applications that would allow rapid interchange of useful instruments to perform the procedures. Most image-guided systems utilize a single standard probe or a few pre-defined instruments that are not necessarily useful for performing the actual surgical procedure. Present image-guided technology for screw placement in spinal surgery utilizes the standard probe only to confirm the entry point location and view the planned trajectory of the screw. The surgeon then resumes the procedure using standard surgical instruments to drill, tap and place screws without the benefit of image guidance. Our clinical laboratory experience with spinal image-guided surgery indicates that there is potential for error between each of these procedural steps of screw placement. Despite accurately locating an entry point, any deviation in the trajectory during drilling of a pilot hole, tapping or screw placement may result in significant errors in screw placement and potential neurovascular injury. We have developed custom software applications and universal hardware adaptation devices for spinal image-guided surgery that allow the use of standard instruments for intraoperative guidance. Utilizing universal dynamic registration hardware and software, standard surgical instruments are adapted for real-time image guided surgery. An array of light emitting diodes can be attached to essentially any rigid instrument with a definable tip and then calibrated to the system for intraoperative use. Laboratory tests using a cadaveric model indicate a difference in accuracy of less than 1.0 mm between the standard probe and a dynamically registered custom instrument and an absolute mean error of less than 2.0 mm for the image-guided system which is clinically insignificant in most cases. This technology is a significant step forward as it allows the surgeon to use a full array of instruments with image guidance and will ultimately make spinal and intracranial surgery safer and more accurate.

Assessment of Cervical Screw Trajectory Using 3-Dimensional Software Planning

Objective: It is important and helpful for surgeons to understand the correlation between spinal anatomy and screw trajectory before surgery. We aimed to assess a simple technique using 3D imaging software available on the hospital intranet for visual and quantitative feedback to prepare surgeons for an appropriate entry point and safe trajectory when placing cervical screws. Methods: A total of 59 cervical screws were inserted from C1 to T1 in 12 consecutive patients using this technique. First, a single CT optimal slice was selected from 3D CT images of the cervical spine to determine the intervals of bilateral entry points and lateral angle. Next, this 3D image was rotated to the lateral angle. Finally, bone was cut out on the entry point using subtractive manipulation, which removed the core of the pedicle or lateral mass. Screw trajectory was indicated, and surgeons could assess the correlation between surface landmarks, spinal anatomy, and screw trajectory. Posterior cervical fusion was performed using fluoroscopy. Postoperative outcomes and incidence of complications were retrospectively assessed. Results: One perforation (1.4%) was identified on postoperative CT images. No vascular injuries occurred. Differences in the intended entry point location and lateral angle of the screw from actual postoperative values were 1.49 ± 1.23 mm and 5.46。 ± 4.46。, respectively. Conclusions: A novel 3D CT imaging assessment underwent in cervical screw fixation. This technique is easily accessible on the hospital intranet and provides training in cervical screw placement for fellows. Surgeons can simulate screw placement and share surgical strategy.

Surgical Entry Spot Location Developer Software for Neurosurgeries

Neurosurgery is a complex and delicate craft where a neurosurgeon needs to reach the tumors or lesion present deep inside the brain with precision, accuracy and safety, minimizing the damage caused to the brain tissues. The entry point and the trajectory of the tool above the skull are crucial in the case of neurosurgeries as a small error can cause death of the patient since there are number of major blood vessels and nerve cells present beneath the skull. So, as a first level for performing the neurosurgery, the entry spot and the trajectory of the surgical tool need to be fixed. This work focuses on the development of software which will help in extracting the entry point location for the surgical tool above the skull in neurosurgeries. Initially a 3D image of the patient was reconstructed from number of 2D head CT slices by the software using contour slicing and isosufacing techniques. Then, using this software the surgeons can extract the location of the entry spot from the developed 3D image. Also the surgeon can check and verify the entry spot location before actually performing the surgery. A GUI was also developed for this software which makes it easy to handle even for a common man. Using this GUI the surgeon can easily determine the location and these coordinate points can be serially transmitted to the controller for performing robotic surgeries.

Decision support system to divide a large network into suitable District Metered Areas

This paper presents a new approach to divide large Water Distribution Networks (WDN) into suitable District Metered Areas (DMAs). It uses a hydraulic simulator and two operational models to identify the optimal number of DMAs, their entry points and boundary valves, and the network reinforcement/replacement needs throughout the project plan. The first model divides the WDN into suitable DMAs based on graph theory concepts and some user-defined criteria. The second model uses a simulated annealing algorithm to identify the optimal number and location of entry points and boundary valves, and the pipes reinforcement/replacement, necessary to meet the velocity and pressure requirements. The objective function is the difference between the economic benefits in terms of water loss reduction (arising from the average pressure reduction) and the cost of implementing the DMAs. To illustrate the proposed methodology, the results from a hypothetical case study are presented and discussed.

Subaxial cervical pedicle screw insertion with newly defined entry point and trajectory: accuracy evaluation in cadavers

Successful placement of cervical pedicle screws requires accurate identification of both entry point and trajectory. However, literature has not provided consistent recommendations regarding the direction of pedicle screw insertion and entry point location. The objective of this study was to define a guideline regarding the optimal entry point and trajectory in placing subaxial cervical pedicle screws and to evaluate the screw accuracy in cadaver cervical spines. The guideline for entry point and trajectory for each vertebra was established based on the recently published morphometric data. Six fresh frozen cervical spines (C3-C7) were used. There were two men and four women. After posterior exposure, the entry point was determined and the cortical bone of the entry point was removed using a 2-mm burr. Pilot holes were created with a cervical probe based on the guideline using fluoroscopy. After tapping, 3.5-mm screws with appropriate length were inserted. After screw insertion, every vertebra was dissected and inspected for pedicle breach. The pedicle width, height, pedicle transverse angulation and actual screw insertion angle were measured. A total of 60 pedicle screws were inserted. No statistical difference in pedicle width and height was found between the left and right sides for each level. The overall accuracy of pedicle screws was 83.3%. The remaining 13.3% screws had noncritical breach, and 3.3% had critical breach. The critical breach was not caused by the guideline. There was no statistical difference between the pedicle transverse angulation and the actual screw trajectory created using the guideline. There was statistical difference in pedicle width between the breach and non-breach screws. In conclusion, high success rate of subaxial cervical pedicle screw placement can be achieved using the recently proposed operative guideline and oblique views of fluoroscopy. However, careful preoperative planning and good surgical skills are still required to ensure screw placement accuracy and to reduce the risk of neural and vascular injury.

Correct anatomical location of entry point for antegrade femoral nailing

Closed intramedullary nailing is a well-accepted method of treatment for femoral shaft fractures. The issue of the correct entry point for antegrade nailing remains a matter of controversy, and the literature is confusing. We reviewed the opinions of 100 orthopaedic surgeons by means of questionnaires. Only four surgeons were able to identify and label their respective entry points for femoral nailing correctly, possibly because of incorrect illustration in publications or errors in terminology. Although the piriformis fossa appears to be the ideal entry point, the importance of exact localisation in the sagittal plane, centered over the axis of medullary canal, cannot be overlooked.

Geometric analysis of potential error in using femoral intramedullary guides in total knee arthroplasty

Abstract: Proper component orientation is necessary for the long-term success of a total knee arthroplasty. Femoral component placement has used jigging systems that are based on intramedullary and extramedullary guides. The intramedullary system has been shown to foster more accurate and reproducible placement of the femoral component. This study analyzed and quantified the potential error of the intramedullary guide system. Geometric data of the human femur were obtained from radiographs of 45 cadaver femora in the anteroposterior and lateral views. The correct entry point of the intramedullary rod in the distal femur is the midaxial line of the femoral canal on anteroposterior and lateral radiographs. The position of this point in relation to the mediolateral and anteroposterior dimensions of the distal femur was calculated as a ratio. The average calculated ratios were anteroposterior, 0.53 offset medially; lateral, 0.32 offset anterior. Mathematical models were constructed to quantify the potential varus valgus and flexion extension error of the guide rods. Variables investigated were entry point location, guide rod diameter, guide rod length, and rotation. The surgeon must be cognizant of these potential sources of error to maximize the accuracy of the femoral intramedullary jigging system.

Data on dynamics of the subcloud Venus atmosphere from Venera Spaceprobe measurements

This paper presents the principal results of wind velocity and turbulence measurements in the Venus atmosphere during the Venera flights. Based on one-way Doppler measurements wind estimations were obtained as a difference of the measured and computed descent velocity values. The computation of free parachute descent velocity was performed by an independent method that utilized aerodynamics of the spaceprobes and the pressure-temperature measurements of the Venus atmosphere. Entry point location, dynamics of the parachute-spaceprobe system as well as frequency instability of the on-board crystal oscillators are basic factors which influenced the accuracy of wind and turbulence estimations. Venera 4 measured a strong wind (up to 40–50 m sec −1) and turbulence at 0.7–4 bar levels (40–50km altitude); within the measurement errors neither wind nor turbulence were found at altitudes lower than 40 km. Venera 5 and Venera 6 Doppler data indicated very smooth velocity changes during the whole descent without noticeable signs of turbulence. Venera 7 measured a zonal wind component; values 5–14 m sec −1 were obtained at 38–53 km altitudes; below 38 km the wind velocity was zero. Estimation of wind velocity near the planet surface (0–3.5 km) leads to value of 0–2.5 m sec −1. Based on an analysis of the apparatus construction characteristics and the radio signal variation during impact upon the Venus surface, values of 2–80 kg cm −2 were obtained for the bearing strength of the soil.