3D Distance Research Articles

Proactive Surgical Management and Outcomes of Unilateral Zygomaticomaxillary Complex Fractures in Major Trauma Patients: A National Level I Center Experience.

Managing facial trauma in patients with severe polytrauma presents significant challenges due to competing priorities, poor systemic conditions, and delayed surgical timing. At a national level I trauma center, the authors evaluated the feasibility and outcomes of proactive surgical intervention for unilateral zygomaticomaxillary complex (ZMC) fractures in severe trauma patients. This retrospective study included 81 patients with unilateral ZMC fractures treated at a regional level I trauma center between October 2019 and August 2021. Patients were categorized into high and low trauma severity groups based on the injury severity score (ISS). Three-dimensional (3D) computed tomography analyses were performed to evaluate surgical outcomes, including dimensional distances (Dx, Dy, and Dz) and the Asymmetry Index. Of the 81 patients, 52 underwent surgical intervention. No significant differences were observed in 3D distances (Dx, Dy, and Dz) between the high and low ISS groups, both preoperatively and postoperatively. However, postoperative symmetry was superior in the high ISS group (P < 0.010). The average delay from injury to surgery was slightly longer in the high ISS group (8.69 versus 7.35 d, P = 0.248). Complications such as diplopia and paresthesia were more common in the high ISS group, but no significant differences in overall complication rates were observed between the groups. Proactive surgical management of unilateral ZMC fractures in major trauma patients is effective. Despite the systemic challenges in this population, timely intervention resulted in superior postoperative symmetry in the high ISS group and comparable 3D outcomes across trauma severities.

Investigating the potential of diffusion tensor atlases to generate anisotropic clinical tumor volumes in glioblastoma patients.

Diffusion tensor imaging (DTI) has been proposed to guide the anisotropic expansion from gross tumor volume to clinical target volume (CTV), aiming to integrate known tumor spread patterns into the CTV. This study investigate the potential of using a DTI atlas as an alternative to patient-specific DTI for generating anisotropic CTVs. The dataset consisted of twenty-eight newly diagnosed glioblastoma patients from a Danish national DTI protocol with post-operative T1-contrast and DTI imaging. Three different DTI atlases, spatially aligned to the patient images using deformable image registration, were considered as alternatives. Anisotropic CTVs were constructed to match the volume of a 15 mm isotropic expansion by generating 3D distance maps using either patient- or atlas-DTI as input to the shortest path solver. The degree of CTV anisotropy was controlled by the migration ratio, modeling tumor cell migration along the dominant white matter fiber direction extracted from DTI. The similarity between patient- and atlas-DTI CTVs was analyzed using the Dice Similarity Coefficient (DSC), with significance testing according to a Wilcoxon test. The median (range) DSC between anisotropic CTVs generated using patient-specific and atlas-based DTI was 0.96 (0.93-0.97), 0.96 (0.93-0.97), and 0.95 (0.93-0.97) for the three atlases, respectively (p 0.01), for a migration ratio of 10. The results remained consistent over the range of studied migration ratios (2 to 100). The high degree of similarity between all anisotropic CTVs indicates that atlas-DTI is a viable replacement for patient-specific DTI for incorporating fiber direction into the CTV.

Unilateral cleft lip and palate patients present cranial base modifications: a cross-sectional study.

The aim of this cross-sectional study was to perform a three-dimensional (3D) assessment of the cranial base of patients with unilateral cleft lip and palate (UCLP). Cone-beam computed tomography (CBCT) scans of 52 UCLP patients (21 females and 31 males; mean age, 10.0 ± 2.12 years) were compared with the scans of 72 individuals (24 females and 48 males; mean age, 11.0 ± 2.11 years) without CLP, matched by gender and age (control group, CG). The 3D Euclidean distances of anterior cranial base (N-S), posterior cranial base (S-Ba), total cranial base (N-Ba) lengths, cranial base width (Po-Po), as well as the cranial base flexure (NSBa), were measured using open-source software ITK-SNAP and 3D Slicer. Statistical analyses were carried out with the Student's t-test at a significance level of 5%. UCLP demonstrated shorter 3D distances than CG in the N-S, S-Ba, and N-Ba cranial base lengths (p < 0.001). In comparison with female CG, female UCLP had a smaller cranial base flexure (NSBa; p = 0.020). No statistically significant differences between UCLP and CG were found for the cranial base width (Po-Po). UCLP patients presented distinct morphological cranial base characteristics in comparison with CG. These results indicate that morphological and positioning changes in the maxillary bones are not solely attributable to the cleft and/or surgical procedures.

Cadaveric Diagnostic Study of Subtle Syndesmotic Instability Using a 3-Dimensional Weight-Bearing CT Distance Mapping Algorithm.

The diagnosis of syndesmotic instability is challenging, and chronically unstable injuries can potentially lead to ankle arthritic degeneration. The objective of this cadaveric study was to utilize a 3-dimensional (3D) weight-bearing computed tomography (WBCT) distance mapping algorithm for the detection of subtle syndesmotic instability, induced by complete syndesmotic ligament sectioning and stressed by isolated axial load. We hypothesized that this algorithm would accurately detect subtle syndesmotic instability. Nineteen matched pairs of through-the-knee cadaveric specimens (38 legs) were utilized. Specimens were mounted in a frame that allowed simulated axial weight-bearing (356 N). Specimens were scanned using cone-beam WBCT in the normal pre-injury state and after complete syndesmotic ligament sectioning. The deltoid ligament was kept intact, and no external rotational stress was applied. Syndesmotic incisura and lateral gutter distances were assessed and compared between pre-injury ipsilateral, contralateral, and injured states using a 3D WBCT distance mapping algorithm. The receiver operating characteristic (ROC) curve and area under the curve (AUC) were calculated for the comparison of syndesmotic distance measurements between injured specimens and controls. P values of <0.05 were considered significant. Overall, significantly increased distances were observed in injured specimens when compared with controls, with average relative syndesmotic widening in injured specimens of 16.9% (p = 0.0003), 11.3% (p = 0.0015), 6.4% (p = 0.0027), and 2.9% (p = 0.037) at the first 1, 3, 5, and 10 cm (proximal to the apex of the distal tibial articular surface), respectively. Widening was more pronounced in the anterior aspect of the syndesmosis, where the diagnostic accuracy was found to be highest at the first 1 and 3 cm of the syndesmotic incisura, with AUC values ranging from 80.9% to 83.0% (p < 0.0001) and with threshold diagnostic values of relative syndesmotic widening as low as 0.43 mm. The newly proposed 3D WBCT distance mapping algorithm was able to accurately detect subtle syndesmotic instability in a cadaveric model of complete syndesmotic sectioning under isolated axial weight-bearing load. This algorithm needs to be further validated in patients with suspected traumatic syndesmotic instability. This cadaveric study demonstrated high diagnostic accuracy of a 3D WBCT distance mapping algorithm to detect subtle syndesmotic instability when stressed with isolated axial loading and in the absence of deltoid injury. The future use of this algorithm in patients with suspected unilateral traumatic syndesmotic instability could hopefully optimize the diagnosis and treatment decision-making.

Three-dimensional digital anatomical measurements of pterygoid plates and posterior maxillary region

BackgroundThe posterior maxilla and skull base is a region with a complex anatomy. Accurate resection of the pterygoid plate is critical during a maxillectomy procedure. However, there is a paucity of functional and anatomical studies on the pterygoid plate and skull base. This study aimed to investigate functional anatomy of the pterygoid plate and its surrounding structures in the posterior maxilla to provide a better understanding of surgical procedures in this region.Methods3D software was used to measure 3D distances, angles, and areas of key anatomical landmarks on CT images of 100 hemifaces. Morphological classification of pterygoid plates was then performed.ResultsResults of comparing right and left pterygoid plates revealed no significant differences in dimensions or angles. Comparisons between sexes revealed that a few parameters were significantly different (P< 0.01), including pterygoid height on the left side, distance from the zygomatico-maxillary buttress to the infraorbital fissure (Zy-IOF), and area of the left lateral pterygoid plate. The morphology of the lateral pterygoid plate was classified into four types based on the shape of the middle region: middle convex (42%), double concave (36%), flattened (10%), and middle concave (12%). The morphology of pterygoid plates was classified based on the divergence of medial and lateral pterygoid plates, with the narrow type (56%) being more common than the wide type in this study cohort.ConclusionsThis 3D digital anatomical study measured key landmarks for maxillary resection. Such measurement has never been reported. This anatomical study provides surgeons with information on the anatomy of the posterior maxilla and allows for safer and more accurate resection of the difficult-to-resect posterior maxilla.

On the origin of certain Early Iron Age populations of Western Siberia. Part I. Synchronic analysis

Ten male Early Iron Age cranial samples from Western Siberia — early Bol’shaya Rechka (Zavyalovo), three Kamen’, three Sargat, Gorokhovo, Kashino, and Kulay — were compared with 62 samples of the same period from adjacent territories using the D2 distance measure corrected for sample size. The distance matrix was subjected to nonmetric multidimensional scaling and cluster analysis. A new graphic method of combining two-dimensional representation with clustering is proposed. The vast majority of samples are arranged into two clusters, unequal in size. The morphologically “western” one includes 67 samples, the morphologically “eastern” one, four. All Western Siberian groups of the Early Iron Age, except Kulay, fall into the central part of the “western” cluster, evidently attesting to admixture between them; Kulay belongs to the “eastern” cluster, taking an isolated position within it. Within the “western” cluster”, two vectors of between-group variation are observed. The first one evidences admixture of two autochthonous components, Bol’shaya Rechka (Zavyalovo) and Kulay, with Saka immigrants. resulting in the emergence of the Kamen’ populations, among which the Novosibirsk population is not closer to Early Bol’shaya Rechka (Zavyalovo) but further from it than are the other two Kamen’ groups. The second vector mirrors the decline of the Andronovo component, mostly expressed in the Tagar samples. This vector links the Pazyryk group from the Ursul Ri­ver, obviously Tagar by origin, with Sargat, Kashino, and early Bol’shaya Rechka (Zavyalovo). The origin of the latter group could have been affected by pre-Sauromatians; that of Sargat and Kashino, by Sauromato-Sarmatian tribes. Gorokhovo is intermediate between the two vectors. Kulay is opposed to other Western Siberian populations, showing the highest concentration of eastern traits and resembling only two Altai-Sayan groups — Kopto and Kara-Koba. The Permian tendency of Kashino is not supported. Resemblance betweet Kamen’, early Sargat, and early Ananyino may be related to the “Uralic” tendency displayed by cranial nonmetrics in these Western Siberian groups.

RetSeg3D: Retention-based 3D semantic segmentation for autonomous driving

LiDAR semantic segmentation is one of the crucial tasks for scene understanding in autonomous driving. Recent trends suggest that voxel- or fusion-based methods obtain improved performance. However, the fusion-based methods are computationally expensive. On the other hand, the voxel-based methods uniformly employ local operators (e.g., 3D SparseConv) without considering the varying-density property of LiDAR point clouds, which result in inferior performance, specifically on far away sparse points due to limited receptive field. To tackle this issue, we propose novel retention block to capture long-range dependencies, maintain the receptive field of far away sparse points and design RetSeg3D, a retention-based 3D semantic segmentation model for autonomous driving. Instead of vanilla attention mechanism to model long-range dependencies, inspired by RetNet, we design cubic window multi-scale retentive self-attention (CW-MSRetSA) module with bidirectional and 3D explicit decay mechanism to introduce 3D spatial distance related prior information into the model to improve not only the receptive field but also the model capacity. Our novel retention block maintains the receptive field which significantly improve the performance of far away sparse points. We conduct extensive experiments and analysis on three large-scale datasets: SemanticKITTI, nuScenes and Waymo. Our method not only outperforms existing methods on far away sparse points but also on close and medium distance points and efficiently runs in real time at 52.1 FPS on a RTX 4090 GPU.

Investigation of intrafractional spinal cord and spinal canal movement during stereotactic MR-guided online adaptive radiotherapy for kidney cancer.

This study aimed to investigate the intrafractional movement of the spinal cord and spinal canal during MR-guided online adaptive radiotherapy (MRgART) for kidney cancer. All patients who received stereotactic MRgART for kidney cancer between February 2022 and February 2024 were included in this study. Patients received 30-42 Gy in 3-fraction MRgART for kidney cancer using the Elekta Unity, which is equipped with a linear accelerator and a 1.5 Tesla MRI. MRI scans were performed at three points during each fraction: for online planning, position verification, and posttreatment assessment. The spinal cord was contoured from the upper edge of Th12 to the medullary cone, and the spinal canal was contoured from Th12 to L3, using the first MRI. These contours were adjusted to the second and third MR images via deformable image registration, and movements were measured. Margins were determined via the formula "1.3×Σ+0.5×σ" and 95% prediction intervals. A total of 22 patients (66 fractions) were analyzed. The median interval between the first and third MRI scans were 38 minutes. The mean ± standard deviation of the spinal cord movements after this interval were -0.01 ± 0.06 for the x-axis (right-left), 0.01 ± 0.14 for the y-axis (caudal-cranial), 0.07 ± 0.05 for the z-axis (posterior-anterior), and 0.15 ± 0.08 for the 3D distance, respectively. The correlation coefficients of the 3D distance between the spinal cord and the spinal canal was high (0.92). The calculated planning organ at risk volume margin for all directions was 0.11 cm for spinal cord. The 95% prediction intervals for the x-axis, y-axis, and z-axis were -0.11-0.09 cm, -0.23-0.25 cm and -0.14-0.03 cm, respectively. Margins are necessary in MRgART to compensate for intrafractional movement and ensure safe treatment delivery.

RELATIONSHIP OF ABSOLUTE AND RELATIVE LOWER EXTREMITIES STRENGTH AND THE EFFICIENCY OF VAULT PERFORMANCE IN GYMNASTICS

The aim of this research was to examine the relationship between absolute and relative lower extremity strength and the efficiency of gymnastics vault performance. Thirty healthy, physically active male students (age: 20.84 ± 0.99 years; height: 179.46 ± 5.91 cm; body weight: 73.88 ± 6.43 kg) from the Faculty of Sports and Physical Education participated in the study. Absolute lower extremity strength was assessed by measuring the maximum load lifted (in kg) during a back squat (1RM). Relative lower extremity strength was calculated by dividing the estimated 1RM back squat by the participant's body weight (1RM/BW). Two types of vaults—the squat through (ST) and the front handspring (FHS)—were used to evaluate vault performance efficiency. Three criterion variables were applied: (d1) distance from the springboard in front of the vault, (d2) distance of landing beyond the vault, (d1 - d2) the difference between d1 and d2, and (pt) overall vault performance rating. The results showed statistically significant and strong correlations between both absolute and relative lower extremity strength and the variables measuring vault performance efficiency. The strongest correlations were observed for (d1), followed by (d2), (pt), and (d1 - d2). These findings can serve as guidelines for developing both absolute and relative lower extremity strength, which may lead to improved performance in gymnastics vaults.

Personalised High Tibial Osteotomy Surgery Is Accurate: An Assessment Using 3D Distance Mapping

Early-stage knee osteoarthritis is often suitable for treatment with high tibial osteotomy (HTO). This is an effective joint-preserving treatment, resulting in good postoperative outcomes. To overcome the limitations of traditional HTO, the surgical technique and correction accuracy can be enhanced by personalised procedures using three-dimensional digital planning and metal additive manufacturing, The purpose of this clinical trial study was to evaluate the three-dimensional accuracy of a new personalised HTO procedure, using modern imaging techniques, 3D modelling, and distance map analysis (DMA). Twenty-five patients were treated with the personalised HTO procedure. Before surgery and after 6 months, they underwent clinical evaluation scoring, radiographic imaging, and computed-tomography scanning to generate morphological models. Specifically, preoperative tibia models were used to plan the tibia correction and the design and position of the fixation plate. Preoperative, planned, and postoperative models were imported in computer-aided and designing software (Geomagic ControlTM 2014, 3D Systems, Rock Hill, SC, USA) for DMA implementation to assess geometrical differences between model surfaces. A very good reproduction of the planned tibia morphology was achieved postoperatively (average differences between −0.9 mm and 1.4 mm). DMA values associated with fixation-plate deformation were less than 1 mm, similar to those for plate-to-tibia surface-contour matching. Overall, personalised digitally planned HTO utilising three-dimensional printed surgical guides and plates enables accurate planned correction and plate placement.

Distance Mapping of Subtalar Joint after Total Ankle Arthroplasty - A Pilot Study

Category: Hindfoot; Ankle Arthritis Introduction/Purpose: Patients with ankle arthritis often present with concomitant subtalar joint deformity, as the subtalar joint may compensate for ankle malalignment. This compensation in the subtalar joint may manifest as joint space narrowing and sinus tarsi impingement. The objective of this study was to use 3D distance maps (DMs) from weightbearing computed tomography (WBCT) images to see if altering alignment of the tibiotalar joint with total ankle arthroplasty alters alignment of the subtalar joint. We hypothesized that, in patients with ankle arthritis, improving alignment of the tibiotalar joint from total ankle arthroplasty would increase the mean distances across the subtalar joint, indicative of improved alignment. Methods: A retrospective review of WBCT data of randomly selected patients who underwent total ankle arthroplasty between February 2022-July 2023 was performed as a pilot study. Using principal components analysis, the calcaneus was divided into 9 regions on the posterior facet, 4 regions in the sinus tarsi, 1 region in the middle facet, and 1 region in the anterior facet of the subtalar joint, as shown in Figure 1. 3D distance technique was used to objectively measure joint space across the subtalar joint. DMs were measured in millimeters, and DMs of the posterior facet and sinus tarsi were also averaged. Descriptive analysis was performed. Results: A total of 15 patients were included – 10 patients with preoperative and 5 patients with postoperative WBCT scans. The mean DMs in all regions increased postoperatively, showing a trend toward improved alignment. The greatest change in mean DM was seen in the middle facet articulation, from 1.78 mm preoperatively to 2.44mm postoperatively. The sinus tarsi was the second highest change, from a mean DM of 2.45 mm preoperatively to 2.80 postoperatively. Conclusion: This pilot study demonstrates that improved tibiotalar alignment through total ankle arthroplasty results in changes in the subtalar joint. Further study with adequate power is warranted to quantify the effect that improved tibiotalar alignment has on subtalar alignment.

Automated body measurement of beef cattle based on keypoint detection and local point cloud clustering

Abstract Body size parameters of beef cattle are crucial for assessing growth status and breeding value. In actual farming environments, the various postures of beef cattle and complex backgrounds can affect the accuracy and stability of non-contact body measurement methods. Therefore, this paper proposes a novel method called the cattle body measurement method (CBMM), which combines keypoint detection with local point cloud clustering. First, a keypoint detection model based on YOLOv8-SimBiFPN is constructed. This model enhances the feature extraction and fusion capabilities of YOLOv8-pose by introducing SimAM and BiFPN into the backbone and neck networks, respectively, and realizes 2D keypoint detection for beef cattle in various postures. Second, a 3D keypoint-locating algorithm based on Density-based spatial clustering of applications with noise (DBSCAN) is proposed. This algorithm utilizes 2D keypoints, depth maps and camera parameters to generate local point clouds, which are then clustered using DBSCAN to segment cattle body point clouds, thereby relocating the 3D keypoints based on their positional features. Finally, body size parameters are calculated based on the 3D keypoints and distance formulae. In our experiment, the mean average precision (mAP@0.5) of YOLOv8-SimBiFPN reached 99.1% on an Angus beef cattle keypoint detection dataset. The mean absolute percentage errors for measuring beef cattle withers height, hip height, body depth, body length, and oblique body length using the CBMM were 4.37%, 4.96%, 6.47%, 4.84%, and 4.14%, respectively. In summary, our method can achieve non-contact body measurement for beef cattle in a free-moving state with high accuracy and stability.

Digital 3D Hologram Generation Using Spatial and Elevation Information

The evolution of cartography poses challenges in representing three-dimensional terrain accurately on traditional two-dimensional maps. Providing an accurate 3D view of the area, coupled with essential geographic information, is vital for rapid and accurate decision-making in emergency management and response. Holography offers a promising solution by providing immersive three-dimensional visualizations. The field of hologram mapping, although novel, is still developing. Given its nascent stage, several limitations are evident. This study addresses one such limitation—inaccuracies in distance measurement—by presenting a hologram map that integrates two-dimensional and three-dimensional information. Accurate distance information on maps is critical for operational success. We aimed to improve hologram maps by integrating contour lines. Our approach allows users to measure distances from near-perpendicular angles while viewing 3D features from other perspectives. We review current advancements in hologram mapping, highlight existing limitations, and introduce our innovative solution designed to enhance both accuracy and usability. Our experiment resulted in a hologram map that accurately depicts a 3D environment, integrates contour lines, and allows for distance and slope angle measurements. The hologram map fills the research gap by providing accurate 3D visualization and distance measurement, signifying a major advancement in hologram mapping.

Multifaceted control of focal points along an arbitrary 3D curved trajectory

Metalenses can integrate the functionalities of multiple optical components thanks to the unprecedented capability of optical metasurfaces in light control. With the rapid development of optical metasurfaces, metalenses continue to evolve. Polarization and color play a very important role in understanding optics and serve as valuable tools for gaining insights into our world. Benefiting from the design flexibility of metasurfaces, we propose and experimentally demonstrate a super metalens that can realize multifaceted control of focal points along any 3D curved trajectory. The wavelengths and polarization states of all focal points are engineered in a desirable manner. The super metalens can simultaneously realize customized 3D positioning, polarization states, and wavelengths of focal points, which are experimentally demonstrated with incident wavelengths ranging from 501 to 700 nm. We further showcase the application of the developed super metalenses in 3D optical distance measurement. The compact nature of metasurfaces and unique properties of the proposed super metalenses hold promise to dramatically miniaturize and simplify the optical architecture for applications in optical metrology, imaging, detection, and security.

Robust localization of poorly visible tumor in fiducial free stereotactic body radiation therapy

Background and purposeEffective respiratory motion management reduces healthy tissue toxicity and ensures sufficient dose delivery to lung cancer cells in pulmonary stereotactic body radiation therapy (SBRT) with high fractional doses. An articulated robotic arm paired with an X-ray imaging system is designed for real-time motion-tracking (RTMT) dose delivery. However, small tumors (<15 mm) or tumors at challenging locations may not be visible in the X-ray images, disqualifying patients with such tumors from RTMT dose delivery unless fiducials are implanted via an invasive procedure. To track these practically invisible lung tumors in SBRT, we hereby develop a deep learning-enabled template-free tracking framework, SAFE Track. MethodsSAFE Track is a fully supervised framework that trains a generalizable prior for template-free target localization. Two sub-stages are incorporated in SAFE Track, including the initial pretraining on two large-scale medical image datasets (DeepLesion and Node21) followed by fine-tuning on our in-house dataset. A two-stage detector, Faster R-CNN, with a backbone of ResNet50, was selected as our detection network. 94 patients (415 fractions; 40,348 total frames) with low tumor visibility who thus had implanted fiducials were included. The cohort is categorized by the longest dimension of the tumor (<10 mm, 10–15 mm and > 15 mm). The patients were split into training (n = 66) and testing (n = 28) sets. We simulated fiducial-free tumors by removing the fiducials from the X-ray images. We classified the patients into two groups – fiducial implanted inside tumors and implanted outside tumors. To ensure the rigor of our experiment design, we only conducted fiducial removal simulation in training patients and utilized patients with fiducial implanted outside of the tumors for testing. Commercial Xsight Lung Tracking (XLT) and a Deep Match were included for comparison. ResultsSAFE Track achieves promising outcomes to as accurate as 1.23±1.32 mm 3D distance in testing patients with tumor size > 15 mm where Deep Match is at 4.75±1.67 mm and XLT is at 12.23±4.58 mm 3D distance. Even for the most challenging tumor size (<10 mm), SAFE Track maintains its robustness at 1.82 plus or minus 1.67 mm 3D distance, where Deep Match is at 5.32 plus or minus 2.32 mm, and XLT is at 24.83±12.95 mm 3D distance. Moreover, SAFE Track can detect some considerably challenging cases where the tumor is almost invisible or overlapped with dense anatomies. ConclusionSAFE Track is a robust, clinically compatible, fiducial-free, and template-free tracking framework that is applicable to patients with small tumors or tumors obscured by overlapped anatomies in SBRT.

Trueness of Intraoral Scanners in Different Scan Patterns for Full-Arch Digital Implant Impressions.

The optimal scan pattern for full-arch digital implant impressions remains to be determined. This study aimed to analyze the effects of different scan patterns on the trueness of intraoral scanners for full-arch digital implant impressions. A maxillary plaster model with 4 implant analogs was employed as the master model. Scan bodies were attached to the master model and scanned with a laboratory scanner to obtain reference data. Test scans were obtained using 3 different scan patterns with Cerec Primescan and Trios 3. Each test datum was superimposed onto the reference data. The trueness was assessed by determining the 3D distance and angular deviations between the test and reference data. Significant differences in 3D distance deviation were detected among the scan patterns for both scanners. Significant differences in angle deviation were detected among the scan patterns for the Cerec Primescan, whereas it was not substantial for the Trios 3. Cerec Primescan exhibited superior trueness across all scan patterns compared with Trios 3. The zigzag pattern resulted in more accurate scans for the Cerec Primescan, whereas both the zigzag and occlusal-palatal-buccal patterns showed higher accuracy for the Trios 3.

Implant placement using mixed reality-based dynamic navigation: A proof of concept

Objectives: To present the first clinical application of a novel mixed reality-based dynamic navigation (MR-DN) system in the rehabilitation of a single tooth gap.Methods: The protocol consisted of the following: (1) three-dimensional patient data acquisition using intraoral scanning (IOS) and cone-beam computed tomography (CBCT), (2) implant planning using guided surgery software, (3) holography-guided implant placement using the novel MR-DN system (ANNA®, MARS Dental, Haifa, Israel) and (4) placement accuracy verification.Results: The novel MR-DN system was safe and time-efficient, as the surgery took 30 min from anaesthesia to suturing. The accuracy of implant placement was high with minimal deviations recorded in the three planes of space compared to the presurgical planning: the error at the entry point planar distance (XY) was 0.381 mm, and the entry point planar distance (Z) was 0.173 mm, for a 3D entry point distance (En) of 0.417 mm. A 3D apex deviation (An) of 0.193 mm was registered, with an angle difference of 1.852°Conclusions: This proof-of-concept study demonstrated the clinical feasibility of MR-DN for guided implant placement in single tooth gaps. Further clinical studies on a large sample of patients are needed to confirm these positive preliminary results.Statement of clinical relevance: The use of MR-DN can change the perspectives of guided dental implant surgery as a possible alternative to the classic static and dynamic guided surgical techniques for the rehabilitation of single tooth gaps.

Poster 251: Tibial Tuberosity to Trochlear Groove Distance (TT-TG): A Patellar Instability Gold Standard Prone to Errors?

Objectives: For decades, tibial tuberosity–trochlear groove (TT-TG) distance has been the gold standard for clinical decision-making in patellar instability. Therefore, the accuracy of the metric has large implications for patient care. Numerous studies and reviews have pointed out potential sources of measurement error in TT-TG, such as differences in landmark selection, flexion of the knee while measuring, and axial alignment of the knee in the scanner. Most studies have reported high interrater reliability (IRR) for landmark selection to justify using TT-TG as a clinical metric without detailing errors within the scan. These errors, such as axial alignment of the knee, occur because TT-TG simplifies a 3-dimensional (3D) feature using a 2-dimensional (2D) measurement. To date, no studies have analyzed how these simplification errors translate into clinical practice. The objective of this study is to develop a 3D method to quantify the discrepancy between classic TT-TG measured in 2D (2D TT-TG) and the true TT-TG measured in 3D (3D TT-TG). In addition, we quantify the change in measured TT-TG depending on whether the most proximal, the most distal, or an intermediate point in the trochlear groove is chosen. Methods: High resolution computed tomography (CT) scans of 20 patients with lateral patellofemoral instability and of 20 control knees from the New Mexico Decedent Image Database were segmented, and 3D models created. The femoral posterior condyles, proximal, middle, and distal trochlear groove, tibial shaft center, and tibial intercondylar tubercles were marked on each model. These landmarks are the basis for a 3D TT-TG measurement analogous to TT-TG measured on axial CT slices. 3D TT-TG distance was measured perpendicular to the longitudinal tibial axis (chosen to minimize the influence of Q-angle and, therefore, sex) and the corresponding posterior femoral condyle line for all 3D models. 2D TT-TG was measured perpendicular to the posterior condyle line on axial slices, using the same landmarks as true TT-TG. In addition, the coronal angle between the tibia longitudinal axis and the corresponding axis of the scanner was calculated. TT-TG measurements were carried out for the most proximal and most distal points as well as the midpoint of the trochlear groove. Significant differences between patients and controls were analyzed with a Mann-Whitney U test. P values &lt;0.01 were considered significant to account for multiple hypotheses testing. Differences between 2D and 3D TT-TG were correlated with Pearson coefficients. The study was regarded as exempt by the institutional review board. Results: Table 1 summarizes the results for 2D TT-TG and 3D TT-TG, their differences, and the corresponding alignment angle. In some patients, the trochlear groove is curved, causing variation in 2D and 3D TT-TG, reducing TT-TG of up to 11.3 mm (3.2 ± 3.6 TT-TG) when measuring the most proximal point of the trochlea compared to the most distal point or midpoint of the trochlear groove. In controls, the maximum reduction was 5.8 mm (1.5 ± 1.2 mm). The difference between 2D and 3D TT-TG was significant between patients and controls (p &lt; 0.01). Angular malalignment was not significantly different between patients and controls (p = 0.603). Patients’ trochleae were significantly more curved compared with controls. Patients’ difference between 2D and 3D had a correlation R value to angular malalignment of 0.85 (p &lt; 0.01) (controls R value: 0.88, p &lt; 0.01). Conclusions: The current 2D method of measuring TT-TG is strongly influenced by the orientation of the patient’s knee in the scanner. For nearly one-third of patients, the error resulting from orientation changes was &gt;5 mm – more than the mean difference between the patient and control groups. Differences between 2D and 3D TT-TG were significantly correlated with scanner-tibia alignment. Knees that were correctly positioned within the scanner showed minimal differences between 2D and 3D TT-TG, showing that the current method of measuring TT-TG can be used in clinical practice if a robust radiological protocol is in place to ensure proper tibial axis alignment. However, due to the significant difference between 2D and 3D TT-TG population values and the inconsistent thresholds defined in studies without exclusion criteria for patient knee alignment, the use of TT-TG must be reevaluated. Variation of the proximity of the point within the trochlea can cause differences in TT-TG of &gt;10 mm. Universal agreement on where to measure is necessary to achieve a standard in clinical decision-making; choosing a distal point reduces error and variation overall. Due to current limitations of the sample, we cannot yet estimate error prevalence. This study shows that the radiological metric TT-TG, the cornerstone of clinical decision-making in patellar instability, is susceptible to errors caused by patient-scanner alignment. Robust radiological protocols can be used to minimize this error.

Strong association between genomic 3D structure and CRISPR cleavage efficiency.

CRISPR is a gene editing technology which enables precise in-vivo genome editing; but its potential is hampered by its relatively low specificity and sensitivity. Improving CRISPR's on-target and off-target effects requires a better understanding of its mechanism and determinants. Here we demonstrate, for the first time, the chromosomal 3D spatial structure's association with CRISPR's cleavage efficiency, and its predictive capabilities. We used high-resolution Hi-C data to estimate the 3D distance between different regions in the human genome and utilized these spatial properties to generate 3D-based features, characterizing each region's density. We evaluated these features based on empirical, in-vivo CRISPR efficiency data and compared them to 425 features used in state-of-the-art models. The 3D features ranked in the top 13% of the features, and significantly improved the predictive power of LASSO and xgboost models trained with these features. The features indicated that sites with lower spatial density demonstrated higher efficiency. Understanding how CRISPR is affected by the 3D DNA structure provides insight into CRISPR's mechanism in general and improves our ability to correctly predict CRISPR's cleavage as well as design sgRNAs for therapeutic and scientific use.

Effect of 3D printer, implant analog and angulation on the accuracy of analog position in implant casts

Objectives: To evaluate the accumulative effect of 3D printer, implant analog systems, and implant angulation on the accuracy of analog position in implant casts.Methods: A reference cast, presenting a case of a three-unit implant-supported prosthesis, was scanned with a coordinate measurement machine, producing the first reference data set (CMM, n = 1). The second reference data set (n = 10) was prepared using an intraoral scanner (IOS) (Trios4). Test quadrant casts were produced using three DLP type 3D printers, Max (MAX UV385), Pro (PRO 4K65 UV), and Nex (NextDent 5100), and three implant analog systems, El (Elos), Nt (Nt-trading), and St (Straumann) (n = 90). Stone casts were also produced via analog impressions (Stone, n = 10). After digitization, the accuracy of 3D distance, local angulation (angle between implants) and global angulation (angle between the implant center axis and an axis perpendicular to the global plane) was evaluated by comparing the reference (CMM, IOS), test (3D print), and control (Stone) groups using metrology software. Data were statistically analyzed using three-way ANOVA and Tukey`s tests (α = 0.05).Results: IOS was truer in 3D implant distance and more precise in capturing local angulation than Stone (p ≤ 0.05). Other measurements were similar between both groups (p > 0.05). The amount of error introduced in the workflow by IOS and 3D printing was mostly similar (p > 0.05). 3D printed casts had similar or even higher accuracy than Stone group (p > 0.05). In most cases, higher trueness was achieved when using PRO 4K65 UV 3D printer and Elos implant analog system (p ≤ 0.05).Conclusion: 3D printer, implant analog system, and implant angulation have a significant effect on the accuracy of analog position in implant casts. Limited-span implant-supported cases could be reproduced digitally with similar accuracy as conventional methods.Clinical significance: A fully digital workflow with a carefully selected 3D printer and implant analog system can increase the accuracy of digitally produced implant casts with comparable accuracy to conventional workflow.