Marker Registration Research Articles

Accuracy of robotic-assisted surgery for immediate implant placement in posterior teeth: a retrospective case series

BackgroundRobotic computer-assisted implant surgery (r-CAIS) is a revolutionary innovation in oral implantation; however, the clinical feasibility of r-CAIS for immediate implant placement (IIP) in posterior teeth has not been verified. Thus, this study aimed to evaluate the accuracy of r-CAIS for IIP in posterior tooth regions.MethodsPatients with posterior teeth to be extracted and indicated to undergo r-CAIS were evaluated. The patients had positioning markers installed in the oral cavity and underwent cone-beam computed tomography (CBCT). Subsequently, minimally invasive tooth extractions were performed, and an individualised surgical plan was generated in the robotic software. After marker registration, implantation surgery was performed by the robotic arm under the supervision and assistance of the surgeons. Finally, the deviations between the planned and placed implants were evaluated based on preoperative and postoperative CBCT data.ResultsA total of 12 patients were evaluated. No adverse events occurred during the surgery. The mean global coronal, global apical, and angular deviations were 0.46 ± 0.15 mm (95%CI:0.36 to 0.56 mm), 0.46 ± 0.14 mm (95%CI:0.37 to 0.54 mm), and 1.05 ± 0.55° (0.69 to 1.40°), respectively.ConclusionsUnder the limited conditions of this study, the r-CAIS exhibited high accuracy in posterior teeth IIP surgery. Further multicentre randomised controlled studies are required to confirm the feasibility of this technology.

The influence of radiographic marker registration versus a markerless trace registration method on the implant placement accuracy achieved by dynamic computer-assisted implant surgery. An in-vitro study

ObjectivesThis study aimed to compare the effect the radiographic marker registration (RMR) and markerless tracing registration (MTR) on implant placement accuracy using a dynamic computer-assisted implant surgery system (dCAIS). Additionally, this study aimed to assess the surgical time and whether the implant location influences the accuracy of the two registration methods. Methods136 dental implants were randomly allocated to the RMR or MTR group and were placed with a dCAIS in resin models. Preoperative and postoperative Cone Beam Computer Tomograms (CBCT) were overlaid and implant placement accuracy was assessed. Descriptive and multivariate analysis of the data was performed. ResultsSignificant differences (P < 0.001) were found for all accuracy variables except angular deviation (RMR:4.30° (SD:4.37°); MTR:3.89° (SD:3.32°)). The RMR had a mean 3D platform deviation of 1.53 mm (SD:0.98 mm) and mean apex 3D deviation of 1.63 mm (SD:1.05 mm) while the MTR had lower values (0.83 mm (SD:0.67 mm) and 1.07 mm (SD:0.86 mm), respectively). In the MTR group, implant placement in the anterior mandible was more accurate (p < 0.05). Additionally, MTR did not significantly increase the surgical time compared with RMR (P = 0.489). ConclusionsMTR seems to increase the accuracy of implant placement using dCAIS in comparison with the RMR method, without increasing the surgical time. The operated area seems to be relevant and might influence the implant deviations. Clinical significanceConsidering the limitations of this in-vitro study, MTR seems to provide a higher accuracy in implant placement using dCAIS without increasing the surgical time. Furthermore, this method does not require radiographic markers and allows re-registration during surgery.

Noctopus: a novel device and method for patient registration and navigation in image-guided cranial surgery.

A patient registration and real-time surgical navigation system and a novel device and method (Noctopus) is presented. With any tracking system technology and a patient/target-specific registration marker configuration, submillimetric target registration error (TRE), high-precise application accuracy for single or multiple anatomical targets in image-guided neurosurgery or ENT surgery is realized. The system utilizes the advantages of marker-based registration technique and allows to perform automatized patient registration using on the device attached and with patient scanned four fiducial markers. The best possible sensor/marker positions around the patient's head are determined for single or multiple region(s) of interest (target/s) in the anatomy. Once brought at the predetermined positions the device can be operated with any tracking system for registration purposes. Targeting accuracy was evaluated quantitatively at various target positions on a phantom skull. The target registration error (TRE) was measured on individual targets using an electromagnetic tracking system. The overall averaged TRE was 0.22 ± 0.08 mm for intraoperative measurements. An automatized patient registration system using optimized patient-/target-specific marker configurations is proposed. High-precision and user-error-free intraoperative surgical navigation with minimum number of registration markers and sensors is realized. The targeting accuracy is significantly improved in minimally invasive neurosurgical and ENT interventions.

Computerized surgical navigation resection of pelvic region simulated bone tumors using skin fiducial marker registration: an in vitro cadaveric study.

Computerized surgical navigation system guidance can improve bone tumor surgical resection accuracy. This study compared the 10-mm planned resection margin agreement between simulated pelvic-region bone tumors (SPBT) resected using either skin fiducial markers or Kirschner (K)-wires inserted directly into osseous landmarks with navigational system registration under direct observation. We hypothesized that skin fiducial markers would display similar resection margin accuracy. Six cadaveric pelvises had one SPBT implanted into each supra-acetabular region. At the left hemi-pelvis, the skin fiducial marker group had guidance from markers placed over the pubic tubercle, the anterior superior iliac spine, the central and more posterior iliac crest, and the greater trochanter (5 markers). At the right hemi-pelvis, the K-wire group had guidance from 1.4-mm-diameter wires inserted into the pubic tubercle, and3 inserted along the iliac crest (4K-wires). The senior author, a fellowship-trained surgeon performed "en bloc" SPBT resections. The primary investigator, blinded to group assignment, measured actual resection margins. Twenty of 22 resection margins (91%) in the skin fiducial marker group were within the Bland-Altman plot 95% confidence interval for actual-planned margin mean difference (mean = -0.23mm; 95% confidence intervals = 2.8mm, - 3.3mm). Twenty-one of 22 resection margins (95%) in the K-wire group were within the 95% confidence interval of actual-planned margin mean difference (mean = 0.26mm; 95% confidence intervals = 1.7mm, - 1.1mm). Pelvic bone tumor resection with navigational guidance from skin fiducial markers placed over osseous landmarks provided similar accuracy to K-wires inserted into osseous landmarks. Further in vitro studies with different SPBT dimensions/locations and clinical studies will better delineate use efficacy.

Intraoperative mixed-reality spinal neuronavigation system: a novel navigation technique for spinal intradural pathologies.

The objective of this study was to assess the intraoperative accuracy and feasibility of 3D-printed marker-based mixed-reality neurosurgical navigation for spinal intradural pathologies. The authors produced 3D segmentations of spinal intradural tumors with neighboring structures by using combined CT and MRI, and preoperative registration of pathology and markers was successfully performed. A patient-specific, surgeon-facilitated application for mobile devices was built, and a mixed-reality light detection and ranging (LIDAR) camera on a mobile device was employed for cost-effective, high-accuracy spinal neuronavigation. Mobile device LIDAR cameras can successfully overlay images of virtual tumor segmentations according to the position of a 3D-printed marker. The surgeon can visualize and manipulate 3D segmentations of the pathology intraoperatively in 3D. A 3D-printed marker-based mixed-reality spinal neuronavigation technique was performed in spinal intradural pathology procedures and has potential to be clinically feasible and easy to use for surgeons, as well as being time saving, cost-effective, and highly precise for spinal surgical procedures.

Клиническое значение интегральной регистрации маркеров эндотоксического иммунитета и колонизационной резистентности буккальных эпителиоцитов при рецидивирующем бронхите у подростков

Recurrent bronchitis (RB) occupies one of the key places in the structure of nonspecific diseases of the respiratory tract and remains a significant medical and social problem in healthcare. The purpose — to investigate and evaluate the clinical significance of integral registration of markers of endotoxic immunity and colonization resistance of buccal epithelial cells (BE) in RB in adolescents. Material and methods. The study included 117 children (12–17 years old), including 78 with RB — the main group, 29 with acute bronchitis (AB) — the comparison group and 23 conditionally healthy children — the control group. The analysis of anamnestic, clinical, paraclinical data, verification of etiologically significant viruses, registration of artificial colonization of buccal epithelial cells (BE), colonization index (CI), micro-LAL test were carried out. Statistical processing of the results was carried out using the SPSS program. Results. A significant difference in markers of colonization resistance and anti-endotoxin protection was revealed in recurrent inflammation in the respiratory tract in comparison with AB in peers. In RB, the initial degree of Candida albicans adhesion to BE was significantly higher in relation to AB (p = 0.0427) and upon discharge from the hospital did not reach normative values, being significantly different from patients with AB (p = 0.0391). The high index of artificial colonization indicates the activation of allochthonous flora and disruption of the microbiota in the oral cavity, which negatively affects the body reactivity. In patients with RB, the titer of antiglycolipid antibodies significantly decreased and in 75% the values did not return to normal, while in AB they did not differ from the control. High levels of endotoxin were noted in RB compared to AB (p = 0.0317). Such patients were diagnosed with a more severe course of the disease with symptoms of endogenous intoxication and a long hospitalization period. Using the method of correlation analysis, a high direct relationship was established between artificial colonization and endotoxin concentration (r = 0.71). The relationship between these parameters in AB was significantly less pronounced (r = 0.3). The results obtained indicate close integration and mutual modulation of the local oral immunity and antiendotoxin defense. Conclusion. Integral registration of the markers of reactivity of specific anti-endotoxin immunity and colonization resistance reflect the severe inflammatory process in the respiratory tract and predict the risk of a chronic pathological process in the bronchopulmonary system.

MRI-based navigated cryosurgery of extra-abdominal desmoid tumors using skin fiducial markers: a case series of 15 cases

BackgroundPrecision surgery is becoming increasingly important in the field of Orthopaedic Oncology. Image-guided percutaneous cryosurgery (CRA) has emerged as a valid treatment modality for extra-abdominal desmoid tumors (EDTs). To date, most CRA procedures use CT-based guidance which fails to properly characterize tumor segments. Computer-guided MRI navigation can address this issue however, the lack of a fixed landmark for registration remains a challenge. Successful CRA correlates directly with precision approaches facilitated by intraoperative imaging guidance. This is the first study that attempts to assess the feasibility and efficacy of a novel approach of using skin fiducial markers to overcome the challenge of a MRI-based navigation CRA for symptomatic or progressive EDTs.MethodsIn this retrospective study conducted between 2018 and 2020, 11 patients at a single center with symptomatic or progressive EDTs were treated with CRA using intraoperative MRI navigation. Fifteen cryosurgery procedures were performed, each adhering to a personalized pre-operative plan. Total tumor size, viable and non-viable portions pre- and post-operation, and SF-36 questionnaire evaluating subjective health were recorded.ResultsAll CRAs demonstrated 100% adherence to the predetermined plan. Overall, tumor size decreased Median= -56.9% [-25.6, -72.4]) with a reduction in viable tissue, (Median= -80.4% [-53.3, -95.2]). Four patients required additional CRAs. Only one patient’s tumor did not reduce in size. One patient suffered from local muscle necrosis. Pre-operation, the average physical and mental scores 41.6 [29.4, 43] and 26.3 [17.6, 40.9] respectively. Post-operation, the average physical and mental scores were 53.4[38, 59.7] and 38 [31.2, 52.7] respectively.ConclusionThese findings provide an early indication of the feasibility and efficacy of performing percutaneous cryosurgery using skin fiducial marker registration for MRI-computed navigation to treat EDTs safely. Larger cohorts and multicenter evaluations are needed to determine the efficacy of this technique.

Enhanced Precision in Genioplasty: A Novel Intraoperative Spatial Repositioning Using Computer-Aided Design and Manufacturing Technology and a Holographic Mixed Reality Application

Genioplasty is performed for the orthognathic surgical correction of dentofacial deformities. This article reports a safe and accurate method for genioplasty combining a novel three-dimensional (3D) device with mixed reality (MR)-assisted surgery using a registration marker and a head-mounted display. Four types of devices were designed based on the virtual operation: a surgical splint with a connector; an osteotomy device; a repositioning device; and a registration marker. Microsoft HoloLens 2 and Holoeyes MD were used to project holograms created using computed tomography (CT) data onto the surgical field to improve the accuracy of the computer-aided designed and manufactured (CAD/CAM) surgical guides. After making an incision on the oral vestibule, the splint was fitted on the teeth and the osteotomy device was mounted at the junction site, placed directly on the exposed mandible bone surface. Temporary screws were fixed into the screw hole. An ultrasonic cutting instrument was used for the osteotomy. After separating the bone, a repositioning device was connected to the splint junction and bone segment, and repositioning was performed. At the time of repositioning, the registration marker was connected to the splint junction, and mandible repositioning was confirmed three-dimensionally through HoloLens 2 into the position specified in the virtual surgery. The rate of overlay error between the preoperative virtual operation and one-month postoperative CT data within 2 mm was 100%. CAD/CAM combined with MR enabled accurate genioplasty.

CT-based radiostereometric analysis for assessing midfoot kinematics: precision compared with marker-based radiostereometry.

3-dimensional midfoot motion is hard to evaluate in clinical practice. We present a new computed tomography (CT)-based radiostereometric analysis (CT-RSA) technique to examine in vivo midfoot kinematics during single-leg stance and compare it with marker-based radiostereometry (RSA). 8 patients were examined with bilateral non- and full-weight-bearing CT images of the midfoot. 1st tarsometatarsal motion was analyzed using a surface-registration technique (CT-RSA). As all patients had unilateral tantalum markers in the 1st cuneiform (C1) and 1st metatarsal (M1), comparison of precision with markerbased RSA was performed. CT-RSA precision was evaluated with surface registration of both C1-M1 bone and C1-M1 tantalum markers, while RSA precision was determined with C1-M1 markers only. Additionally, to remove motion bias, we evaluated intrasegmental CT-RSA precision by comparing proximal with distal part of M1. Under physical load, the primary movement for the 1st tarsometatarsal joint was M1 dorsiflexion (mean 1.4°), adduction (mean 1.4°), and dorsal translation (mean 1.1 mm). CT-RSA precision, using surface bone or markers, was in the range of 0.3-0.7 mm for translation and 0.6-1.6° for rotation. In comparison, RSA precision was in the range of 0.4-0.9 mm for translation and 1.0-1.7° for rotation. Finally, intrasegmental CT-RSA precision was in the range of 0.1-0.2 mm for translation and 0.4-0.5° for rotation. CT-RSA is a valid and precise, non-invasive method to measure midfoot kinematics when compared with conventional RSA.

Accuracy Evaluation Trial of Mixed Reality-Guided Spinal Puncture Technology.

To evaluate the accuracy of mixed reality (MR)-guided visualization technology for spinal puncture (MRsp). MRsp involved the following three steps: 1. Lumbar spine computed tomography (CT) data were obtained to reconstruct virtual 3D images, which were imported into a HoloLens (2nd gen). 2. The patented MR system quickly recognized the spatial orientation and superimposed the virtual image over the real spine in the HoloLens. 3. The operator performed the spinal puncture with structural information provided by the virtual image. A posture fixation cushion was used to keep the subjects' lateral decubitus position consistent. 12 subjects were recruited to verify the setup error and the registration error. The setup error was calculated using the first two CT scans and measuring the displacement of two location markers. The projection points of the upper edge of the L3 spinous process (L3↑), the lower edge of the L3 spinous process (L3↓), and the lower edge of the L4 spinous process (L4↓) in the virtual image were positioned and marked on the skin as the registration markers. A third CT scan was performed to determine the registration error by measuring the displacement between the three registration markers and the corresponding real spinous process edges. The setup errors in the position of the cranial location marker between CT scans along the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) axes of the CT bed measured 0.09 ± 0.06 cm, 0.30 ± 0.28 cm, and 0.22 ± 0.12 cm, respectively, while those of the position of the caudal location marker measured 0.08 ± 0.06 cm, 0.29 ± 0.18 cm, and 0.18 ± 0.10 cm, respectively. The registration errors between the three registration markers and the subject's real L3↑, L3↓, and L4↓ were 0.11 ± 0.09 cm, 0.15 ± 0.13 cm, and 0.13 ± 0.10 cm, respectively, in the SI direction. This MR-guided visualization technology for spinal puncture can accurately and quickly superimpose the reconstructed 3D CT images over a real human spine.

SUPER-SENSITIVE REGISTRATION OF POLYFUNCTIONAL MAGNETIC NANOMATERIALS FOR THE RAPID DETERMINATION OF MOLECULAR MARKERS OF DISEASES

Magnetic particles (MPs) based on superparamagnetic iron oxide nanocrystals are increasingly used in modern research for the development of express technologies for high-precision determination of the concentration of biomolecules. In this work, we developed a universal method for using MPs as polyfunctional agents that perform several different functions in one analysis for topical issues of biochemical and medical diagnostics, based on the original technology of ultrasensitive detection of nonlinear magnetic nanomaterials. The method was tested for the rapid quantitative registration of cardiac markers and SARS-CoV-2-associated molecular markers in complex matrices. The proposed method is promising for creating test systems for prehospital monitoring, particularly for emergency molecular diagnostics in patients with suspected acute myocardial infarction, as well as for the rapid detection of coronavirus infection.

Diagnostics of Oxidative Stress by Laser Optical-Acoustic Spectroscopy

The results of the registration of oxidative stress volatile molecular markers (NOx, C 2 H 6 , and C 5 H 12 ) in exhaled air by optical-acoustic spectroscopy are presented. Aerobic physical exercises were chosen as a method of oxidative stress activation. Three time points were studied: before exercises, immediately after exercises, and after 25 min rest. It was shown that there is a statistically significant increase in the studied markers concentrations in the exhaled air immediately after the exercises. After the rest, statistically significant differences are observed in relation to the initial state only for a part of these markers. This is most likely caused by different recovery of the subjects after the exercises and insufficient rest time. Thus, this instrumental approach is promising for non-invasive registration of markers of oxidative stress.

Conclusion or Illusion: Quantifying Uncertainty in Inverse Analyses From Marker-Based Motion Capture due to Errors in Marker Registration and Model Scaling.

Estimating kinematics from optical motion capture with skin-mounted markers, referred to as an inverse kinematic (IK) calculation, is the most common experimental technique in human motion analysis. Kinematics are often used to diagnose movement disorders and plan treatment strategies. In many such applications, small differences in joint angles can be clinically significant. Kinematics are also used to estimate joint powers, muscle forces, and other quantities of interest that cannot typically be measured directly. Thus, the accuracy and reproducibility of IK calculations are critical. In this work, we isolate and quantify the uncertainty in joint angles, moments, and powers due to two sources of error during IK analyses: errors in the placement of markers on the model (marker registration) and errors in the dimensions of the model’s body segments (model scaling). We demonstrate that IK solutions are best presented as a distribution of equally probable trajectories when these sources of modeling uncertainty are considered. Notably, a substantial amount of uncertainty exists in the computed kinematics and kinetics even if low marker tracking errors are achieved. For example, considering only 2 cm of marker registration uncertainty, peak ankle plantarflexion angle varied by 15.9°, peak ankle plantarflexion moment varied by 26.6 N⋅m, and peak ankle power at push off varied by 75.9 W during healthy gait. This uncertainty can directly impact the classification of patient movements and the evaluation of training or device effectiveness, such as calculations of push-off power. We provide scripts in OpenSim so that others can reproduce our results and quantify the effect of modeling uncertainty in their own studies.

Target registration errors in navigation-assisted mandibular surgery according to the tracking methods and the type of markers: experiments using human dry mandibular bone.

This study was conducted to evaluate the accuracy of navigation process according to the type of tracking methods and registration markers. The target registration errors (TREs) were measured at seven anatomical landmarks of the mandible. Four different experiments were performed to obtain the TREs using two tracking methods, the optical tracker (Polaris) and the electromagnetic (EM) tracker (Aurora), and two types of registration markers, invasive and noninvasive markers. All comparisons of TREs were statistically analyzed using SPSS and Python-based statistical package. The average TRE values obtained from the four experiments were as follows: (1) 0.85mm (± 0.07) using invasive marker and Aurora, (2) 1.06mm (± 0.12) using invasive marker and Polaris, (3) 1.43mm (± 0.15) using noninvasive marker and Aurora, and (4) 1.57mm (± 0.23) using noninvasive marker and Polaris. Comparisons between all the experimental results revealed statistically significant differences except for the type of tracking system. Although the comparison between the modality of the tracking system showed no significant differences, the EM-based approach consistently demonstrated better performances than the optical type in all comparisons. This study demonstrates that irrespective of the tracking modality, using invasive marker is a better choice in terms of accuracy. When using noninvasive marker, it is important to consider the increased TREs. In this study, the noninvasive marker caused a maximum increment of TREs of 0.81mm compared with the invasive marker. Furthermore, using an EM-based tracker with invasive marker may result in the best accuracy for navigation.

Accuracy evaluation of 3D-printed noninvasive adhesive marker for dynamic navigation implant surgery in a maxillary edentulous model: An in vitro study

Dynamic computer-aided implant surgery (DCAIS) can improve dental implantation accuracy and reduce surgical risks. In the registration procedure of DCAIS, the type and the number of registration markers significantly impact the accuracy of DCAIS. One problem of DCAIS in clinical application is that only invasive screw markers can be used for implantation in edentulous patients. It could cause additional trauma, scar formation and usually increase patient discomfort. In this experiment, a personalized 3D-printed edentulous maxillary model was used for simulating clinical situations, and a 3D-printed noninvasive adhesive marker (3D-PNAM) was designed to figure out the above problem. In this research, six target screws were implanted into the model's maxillary alveolar ridge as targets for accuracy analysis. This study used target registration error (TRE) as an index to evaluate the accuracy of invasive screw makers and noninvasive adhesive markers. Results showed that 3D-PNAMs had the same accuracy as screw markers, and placing at least six registration markers in the maxilla was needed for good registration accuracy. The registration markers should be further improved and designed according to application areas' clinical needs and anatomical characteristics in future clinical studies.

Computer-Assisted Dental Implant Placement Following Free Flap Reconstruction: Virtual Planning, CAD/CAM Templates, Dynamic Navigation and Augmented Reality.

Image-guided surgery, prosthetic-based virtual planning, 3D printing, and CAD/CAM technology are changing head and neck ablative and reconstructive surgical oncology. Due to quality-of-life improvement, dental implant rehabilitation could be considered in every patient treated with curative intent. Accurate implant placement is mandatory for prosthesis long-term stability and success in oncologic patients. We present a prospective study, with a novel workflow, comprising 11 patients reconstructed with free flaps and 56 osseointegrated implants placed in bone flaps or remnant jaws (iliac crest, fibula, radial forearm, anterolateral thigh). Starting from CT data and jaw plaster model scanning, virtual dental prosthesis was designed. Then prosthetically driven dental implacement was also virtually planned and transferred to the patient by means of intraoperative infrared optical navigation (first four patients), and a combination of conventional static teeth supported 3D-printed acrylic guide stent, intraoperative dynamic navigation, and augmented reality for final intraoperative verification (last 7 patients). Coronal, apical, and angular deviation between virtual surgical planning and final guided intraoperative position was measured on each implant. There is a clear learning curve for surgeons when applying guided methods. Initial only-navigated cases achieved low accuracy but were comparable to non-guided freehand positioning due to jig registration instability. Subsequent dynamic navigation cases combining highly stable acrylic static guides as reference and registration markers result in the highest accuracy with a 1–1.5-mm deviation at the insertion point. Smartphone-based augmented reality visualization is a valuable tool for intraoperative visualization and final verification, although it is still a difficult technique for guiding surgery. A fixed screw-retained ideal dental prosthesis was achieved in every case as virtually planned. Implant placement, the final step in free flap oncological reconstruction, could be accurately planned and placed with image-guided surgery, 3D printing, and CAD/CAM technology. The learning curve could be overcome with preclinical laboratory training, but virtually designed and 3D-printed tracer registration stability is crucial for accurate and predictable results. Applying these concepts to our difficult oncologic patient subgroup with deep anatomic alterations ended in comparable results as those reported in non-oncologic patients.

Combined and hybrid marker models for radiostereometry assessment of polyethylene liner motion in dual mobility hip prosthesis: a proof-of-concept study

BackgroundInvestigation of polyethylene liner movement in total hip arthroplasty requires bead-marking for radiographic visibility of the liner. However, occlusion of markers poses a challenge for marker registration in radiographs.MethodsThe polyethylene of a dual mobility acetabular system was marked with twelve 1-mm tantalum markers (four groups of three markers) using a custom-made drill guide. Liner motion in a phantom and a patient was investigated with dynamic radiostereometry analysis (dRSA) at 1-year follow-up and static radiostereometry analysis (sRSA) postoperatively and at 1- and 2-year follow-up. A combined marker configuration (CMC) model was calculated from the registered positions of the liner markers and the femoral head in several images. Furthermore, the CMC model and the theoretic marker positions from computer-assisted models of the drill guide were combined in a hybrid model.ResultsThe CMC model included eleven markers in the phantom and nine markers in the patient, which was sufficient for dRSA. Liner movement in the phantom followed liner contact with the femoral neck, while liner movement in the patient was independent. The hybrid model was necessary to determine liner orientation in sRSA recordings, which clearly changed from postoperative to 1- and 2-year follow-up even though the patient was positioned similarly.ConclusionPolyethylene liner motion in dual mobility hip prosthesis can be assessed with CMC models in dRSA recordings. In sRSA, the liner position between follow-ups is unpredictable and analysis requires inclusion of all markers in the model, accomplished with a hybrid marker model.Trial registrationClinicalTrials.gov [NCT02301182], 25 October 2015.

Automated Intrafraction Motion Detection in 3D and Correction Using Monoscopic X-Ray Imaging Improves Accuracy and Efficiency of for High-Dose Prostate SBRT

Automated marker detection allows real time image guidance for treatment setup in 6D and intra-beam monitoring in 3D on a standard linear accelerator. This study retrospectively assessed the accuracy and efficiency of automated marker registration vs. manual match from a group of treated prostate SBRT patients.An automated marker detection scheme was developed by reconstructing a 3D marker model from orthogonal paired images for pre-treatment setup alignment using iterative closest point (ICP). The 3D marker model was back-projected to monoscopic x-ray images acquired during treatment. 3D marker motion was estimated from the consecutive (40o gantry angle apart) monoscopic x-ray images. Standard treatment was 2 arc Volumetric-modulated arc therapy (VMAT) plan prescribed to 8 Gy per fraction (x5). From 9 SBRT prostate patients, 135 paired images and 810 monoscopic x-ray images were analyzed using the automated scheme by comparing to the 3D marker model of planning image. A subgroup of the data set (5 patients, 12 fractions, 235 monoscopic images) were re-aligned to 3D marker position of setup images from the automated program to compare marker motion without realignment, which had minor residual setup error after manual match. Paired sample Wilcoxon ranked test was run to evaluate the improvement of using automated alignment, P-value < 0.05 was considered significant.Using automated marker match as reference, the residual setup error after manual match of the entire group (135 paired images) was (0.3 ± 0.6) mm, (0.1 ± 0.7) mm, (0.2 ± 0.8) mm in lateral (Lat), longitudinal (Long), vertical (Vert) directions, and (-2.6 ± 5.0)o, (-0.1 ± 2.8)o, (-1.3 ± 3.0)o in pitch, yaw, roll directions, respectively. The centroid of the marker position had an error of (0.2 ± 1.2) mm, (-0.6 ± 1.3) mm, (0.7 ± 1.4) mm in Lat, Long, Vert directions, respectively, during treatment (from 810 images). Treatment error at Lat, Long, Vert directions had stronger correlation with setup error in Lat & roll (-0.57 & -0.18), in Long & yaw (-0.49 & -0.25), and in Vert & roll (0.48 & 0.31), respectively. The magnitude of the improvement for individual fraction of the subgroup (235 images) using automated setup correction was 0.4 mm, 0.4 mm, 0.4 mm in Lat (P < 0.01), Long (P = 0.04), Vert (P = 0.39). The fraction of the treatment time that the marker centroid had a positional error of more than 2mm (a tolerance which triggered treatment interruption) was 9.5%, 18.5%, 12% in Lat, Long, Vert directions, respectively, using manual setup match, and 2.5%, 8.5%, 0.5% using automated setup match.This study demonstrated the ability of automated marker match to improve the accuracy and efficiency of prostate SBRT during treatment using monoscopic x-ray image. The improvement of treatment accuracy was 0.4 mm in each (X, Y, and Z) dimension. The improvement treatment efficiency was 50% reduction of treatment interruption which needs re-imaging. In addition, auto-registration saves manual markers alignment time.

A method for image-guided positioning of cochlear specimens in insertion test benches using 3D printed stands

Abstract Cochlear implants include an electrode array (EA) which needs to be inserted into the cochlea. Insertion tests using artificial cochlear models (ACM) or ex vivo specimens are widely used methods during EA development to characterize EA design properties, including insertion forces. Measured forces are directly linked to the orientation of the cochlear lumen with respect to the insertion axis of the test bench. While desired insertion directions in ACM experiments can be predefined by design, specimens are individually shaped and the cochlear lumen is embedded invisibly. Therefore, a new method for accurate, individual specimen positioning is required. A key element of the proposed method is a customizable pose setting adapter (PSA) used to adjust the specimen’s fine positioning. After rigid fixation of the specimen to a holder featuring spherical registration markers and subsequent cone beam computed tomography the desired insertion direction is planned. The planned data is used to calculate the individual shape of the PSA. Finally, the PSA is 3D printed and mounted between force sensor and specimen holder to correctly align the specimen to the test bench’s insertion axis. All necessary hard- and software have been developed including the specimen holder, a software for registration and trajectory planning, and a custom Matlab script whose output drives a parametric CAD file of the PSA. Positioning accuracy was determined in a first trial using 10 virtual trajectories and was found to be 0.23 ± 0.12 mm and 0.38 ± 0.17°. The presented stereotactic positioning procedure enables high repeatability in future ex vivo insertion experiments due to accurate, image-guided control of the insertion direction.

Comparison of Dental Surface Image Registration and Fiducial Marker Registration: An In Vivo Accuracy Study of Static Computer-Assisted Implant Surgery.

This study compared the accuracy of static computer-assisted implant surgery (sCAIS) planned through dental surface image registration and fiducial marker registration. Stone models of 30 patients were converted into digital dental casts by using a desktop scanner. Cone-beam computed tomography (CBCT) was performed and superimposed to the digital dental casts with two methods: matching the dental surface images or matching the fiducial markers on a stereolithographic radiographic template. Following the implant planning, stereolithographic surgical guides were fabricated, and 56 fully guided implants were inserted by the same doctor. Deviations between planned and inserted implants were measured and compared using postoperative CBCT images. After adjustment for other potential influencing factors, compared with the fiducial marker registration group, significantly larger mean lateral deviations were noted in the dental surface registration group at both the implant platform and apex (p = 0.0188 and 0.0371, respectively). However, the mean lateral deviations for the dental surface registration (0.83 ± 0.51 mm at implant platform and 1.24 ± 0.68 mm at implant apex) were comparable to the literature. In conclusion, our findings indicate that although sCAIS planned using dental surface image registration was not statistically as accurate as that using fiducial marker registration, its accuracy was satisfactory for clinical use.