Positional Discrepancies Research Articles

Evaluating the Accuracy of Contour Ridgeline Positioning for Soil Conservation in the Northeast Black Soil Region of China

The Northeast black soil region is China’s vital commercial grain base. However, severe soil erosion on slope farmland poses a significant threat to this region’s sustainable agricultural productivity. The transition from traditional downslope ridging to contour ridging (briefly referred to as “contour ridging”) is one of the primary sustainable measures for preventing soil erosion on slope farmland. By integrating high-precision Digital Elevation Models (DEMs) and design standards, ArcMap can plan the orientation and position of contour ridgelines and estimate the reduction in soil erosion on slope farmland after implementing contour ridging. Therefore, the degree of discrepancy between the designed and implemented positions of the contour ridgelines directly affects the effectiveness of contour ridging and the precision in evaluating its impacts and benefits. This study aims to assess the position accuracy of contour ridgelines designed by ArcMap 10.5 (here after ArcMap) using high-precision DEMs obtained from unmanned aerial vehicles (UAV). For this purpose, three fields where contour ridging had already been implemented were selected in the Sanjiang Plain of Heilongjiang Province, China. CORS RTK was used to measure the XYZ coordinates of verification points along implemented ridges precisely. Those measured coordinates were compared with the designed ridgeline positions to analyze the positional discrepancies between the designed and implemented ridgelines. The results indicated the following: (1) The average slope gradient along contour ridgelines measured in the field (0.5~0.6°) was relatively close to that along the ridgelines designed using ArcMap (0.6°), and the elevation changes along most of the contour ridgelines showed a pattern of being higher in the middle and lower on both sides. (2) The positional offset between most of the measured and designed ridgelines was less than the width of a single ridge (1.3 m), and the median offset was one-third of the width of a single ridge. (3) The positional offset caused by the movement of ridging machinery could be larger than the offset resulting from the baseline setup, and verification points with larger positional offsets were often located at the edges of the plots as well as turns of the ridgelines. Therefore, during the designing ridgelines process, the turns should be made as smooth as possible. During ridging, reducing the speed at these turns to minimize errors and maintain the accuracy of the ridgeline was recommended. The findings of this study can provide a scientific basis to improve contour ridging design and effect prediction in slope farmland to control soil erosion and enhance agricultural sustainability.

Do the Various Indirect Bonding Techniques Provide the Same Accuracy for Orthodontic Bracket Placement? (Randomized Clinical Trial).

For orthodontic treatment to be effective, bracket placement must be precise to make the finishing stage easier, leading to an ideal occlusion with minimal intervention. This study aimed to evaluate the accuracy of manual and digital bracket positioning techniques utilizing computer-aided design and computer-aided manufacturing (CAD/CAM) jigs, 3D-printed indirect bonding trays (IBT), and double-layer vacuum-formed thermoplastic IBT. This study was done by scanning the dental arch of 30 orthodontic patients. The virtual setup and bracket positioning were performed with the Insignia™ system for ten patients, and 3D Maestro® software was used for the virtual setup of the remaining 20 patients. At the same time, the bracket positioning of 10 patients was done digitally by the 3D Maestro® software and the remaining 10 patients manually through the Ray Set® device. IBT were fabricated by CAD/CAM system, 3D printer, and vacuum-formed thermoplastic machine. A virtual bracket position was compared to the actual bracket position using the best-fit method of 3D digital superimposition in Geomagic® Control X™ (CX) software to determine how accurate it was in terms of linear and angular accuracy. Statistical analyses using SPSS 26.0 including Bland-Altman plots were used to assess the intra-examiner reproducibility. Shapiro-Wilk test was used to measure normality distribution. Wilcoxon matched-pairs signed rank test was used to analyze the differences between bracket positions within each group. Although there were obvious positional discrepancies between several readings, they were still within clinically acceptable ranges. All types of IBT would translate the planned position of the bracket from the digital and manual techniques to the teeth of patients with accepted precision in both linear and angular measurements; in addition, the error rate is about the same for all types of IBT. This trial is registered with NCT05549089.

Repositioning accuracy of the implant- and abutment-level prosthetic components used in conventional and digital workflows

ObjectivesTo evaluate the repositioning accuracy of the implant- and abutment-level impression components (impression abutments and implant scan bodies) and implant abutments (with and without anti-rotational hex index); also, to estimate the tightening torque influence on the positional stability of abutments. MethodsSeven types of prosthetic components (n = 7) [impression pick-up copings (PC), implant scan bodies (ISB), non‑hex and hex titanium base implant abutments (TB H and TB NH), multi-unit impression copings (MU PC), multi-unit implant scan bodies (MU ISB), and multi-unit caps (MU C) (Medentika GmbH)] were tested. For repositioning accuracy tests a coordinate measuring machine (CMM) was used. During assembly 15 Ncm torque for all components was applied. After measurement, only hex and non‑hex abutments were torqued to 25 Ncm and their coordinates were again recorded to assess torque influence. The procedure was repeated 7 times for each component. Linear and 3D deviations, angulation to the vertical axis, and axial rotation were calculated. The Kruskal-Wallis test was used to compare the measurements between the groups. A post-hoc test (Mann–Whitney U test) was used for pairwise comparison to determine the influence of the torque (α=0.05). ResultsImplant- and abutment-level components used for digital scans showed different positional discrepancies compared to ones used for conventional impressions and ranged from 10 to 37 µm. Hex abutments demonstrated statistically significantly lower 3D deviations (4.4 ± 7.1 µm) compared to non‑hex abutments (8.7 ± 6.1 µm). Torque influence was significantly lower for hex abutments than for non‑hex abutments. ConclusionsRepositioning inaccuracies were found in all implant- and abutment-level impression components (impression abutments and implant scan bodies) and all abutments (with and without anti-rotational hex index) tested. Final tightening of the components could cause further positional discrepancies. Clinical significanceThe misfit of the prosthetic components used in conventional and digital workflows stays in the clinically acceptable range. Even when multiple connections and disconnections on the track of the laboratory preparation is needed, it should not have a negative influence for single teeth reconstructions. However, in the complex cases with multiple implants, repetitive repositioning of the prosthetic components may lead to the accumulation of vertical, horizontal and rotational errors leading to the clinical problems with the passive fit of the final framework.

Deform2NeRF: Non-Rigid Deformation and 2D–3D Feature Fusion with Cross-Attention for Dynamic Human Reconstruction

Reconstructing dynamic human body models from multi-view videos poses a substantial challenge in the field of 3D computer vision. Currently, the Animatable NeRF method addresses this challenge by mapping observed points from the viewing space to a canonical space. However, this mapping introduces positional shifts in predicted points, resulting in artifacts, particularly in intricate areas. In this paper, we propose an innovative approach called Deform2NeRF that incorporates non-rigid deformation correction and image feature fusion modules into the Animatable NeRF framework to enhance the reconstruction of animatable human models. Firstly, we introduce a non-rigid deformation field network to address the issue of point position shift effectively. This network adeptly corrects positional discrepancies caused by non-rigid deformations. Secondly, we introduce a 2D–3D feature fusion learning module with cross-attention and integrate it with the NeRF network to mitigate artifacts in specific detailed regions. Our experimental results demonstrate that our method significantly improves the PSNR index by approximately 5% compared to representative methods in the field. This remarkable advancement underscores the profound importance of our approach in the domains of new view synthesis and digital human reconstruction.

Reliable Reference Areas for 3D Smiling Facial Model Alignment: Posed vs Natural Smile Expressions.

To evaluate the reliability of various reference areas for digital alignment between 3D resting and smiling facial models. 3D posed and natural smiling faces of 33 adults were registered to the respective neutral faces, using six matching strategies with different reference matching surfaces: nose (N), nose + central forehead (NFc), nose + whole forehead (NFw), nose + chin (NC), nose + central forehead + chin (NFcC), and nose + whole forehead + chin (NFwC). The positional discrepancies of the registered images were measured at the left and right pupil centers. Two-way ANOVA and post hoc multiple pairwise t test with Bonferroni correction (α = .05) were used to evaluate the measurements. As a result, the use of larger reference areas increases the trueness of image-matching, whereas there was no statistically significant difference between the matching strategies within the same smiling type. Meanwhile, the image registration of posed smiles resulted in fewer positional disparities than the natural smiles with significant differences observed for the registration using the NC and NFcC surface-based matching areas at the right pupil (P = .030 and .026, respectively). The findings of this study suggest that the reference surface areas and smiling types have some impact on the accuracy of 3D smiling facial image alignments. Large and evenly distributed matching surfaces are recommended for posed smiles, whereas caution should be taken when using the chin area as a reference surface for matching natural smile facial images.

360 Assessment of Pedicle Screw Placement Accuracy Utilizing a Novel Augmented Reality and Artificial Intelligence Surgical Guidance System

INTRODUCTION: The integration of artificial intelligence (AI) and augmented reality (AR) technologies in spine navigation has the potential to minimize pedicle screw misplacement, decrease radiation exposure, and improve procedural efficiency, addressing some of the challenges associated with spinal instrumentation. METHODS: Sixty lumbosacral pedicle screws were placed by 4 Orthopedics surgeons in 6 cadavers using the AR/AI surgical navigation system. Two CT intraoperative scans (before and after screw placement) of the cadaveric specimens were obtained for the study to measure the 3D positional and angular discrepancies between virtual and real screws. The validation procedure consisted of 3 steps: (1) automatic registration and 3D coordinate transformation, where the preop CT scan was aligned with the postop scan to determine the virtual screw 3D positions and orientations in postop scan; (2) analysis of the postop scan to determine the real screw 3D positions and orientations as they appeared in the scan volume; (3) automatic comparison between the 3D positions and orientations of the virtual and real screws. RESULTS: A one-sample t-test statistical analysis yielded a mean positional error of 2.16 mm ± 1.00 mm (99% CI: 1.81-2.49 mm), and a mean angular error of 1.49± 0.73° (99% CI: 1.25-1.74°). These results were independent of anatomical level, side, and surgeon. CONCLUSIONS: This study indicates that this AR/AI surgical guidance system provides mean positional and angular errors lower than 3.0 mm and 3.0° respectively, thus complying with FDA-required regulatory acceptance criteria. The system was FDA-cleared as a US 510k Orthopedic Stereotaxic Instrument.

Implant-Supported Overdentures: Current Status and Preclinical Testing of a Novel Attachment System.

Numerous attachment systems exist for implant-supported overdentures, with each having specific limitations in terms of retention, cost, wear, maintenance and cleanability. A retrospective analysis of patients restored with implant-supported overdentures using bars, telescopic crowns and Locator-type attachments was performed and the patients were interviewed. An in vitro strain gauge study compared telescopic crowns, Locator-type attachments and a novel flexible attachment system employing a shape memory alloy (NiTi) with respect to peri-implant strain development during insertion, loading and removal of an overdenture. A significantly lower number of attachment-related complications was observed in bars as compared to telescopic crowns (p = 0.00007) and Locator-type attachments (p = 0.00000), respectively. Greater overall patient satisfaction was noted in bar-retained restorations while Locator-type attachments led to lower levels of satisfaction regarding prosthesis retention. In vitro, telescopic crowns caused maximum strain development during prosthesis insertion and loading, while during removal this was observed in Locators with white retentive inserts. NiTi attachments caused significantly lower strain development during insertion as compared to telescopic crowns (p = 0.027). During loading, NiTi attachments caused significantly lower strain development than Locators with blue retentive inserts (p = 0.039). During removal, NiTi attachments caused significantly less strain development as compared to Locators with white retentive inserts (p = 0.027). Positional discrepancies between male and female attachment parts affected the retention and reaction force between both components, which may be minimized by using the novel NiTi attachment system. This may be beneficial in terms of component wear and implant loading.

Influence of implant diameter on accuracy of static implant guided surgery: An in vitro study

Statement of problemStatic guided implant surgery may be the most accurate method of implant placement to date. However, within the same guided implant system, whether accuracy is affected when placing a larger diameter implant that requires more drills than a smaller diameter implant is unclear. PurposeThe purpose of this in vitro study was to evaluate the influence of implant diameter on the angulation and 3-dimensional (3D) deviations of posterior single implant placement using static guided surgery. Material and methodsA polyurethane dental cast was made with an edentulous site at the maxillary right first molar position. Identical implant planning for each of 3 dental implant diameters 3.3, 4.1, and 4.8 mm (Straumann BLT) were made, and surgical guides for each implant diameters were fabricated by stereolithography. Fifteen implants of each diameter (N=45) were placed in simulated casts. A scan body was placed and the cast was scanned using an intraoral scanner. The positional discrepancies of implant placement, including angulation as well as 3D implant cervical and apex area deviations, were compared with the planned position. Linear ANOVA single factor analysis (ɑ=.05) was used, and box plots were made. ResultsThe ranges of angulation deviations for 3.3-, 4.1-, and 4.8-mm implants were 3.6 degrees to 6.0 degrees, 3.7 degrees to 7.7 degrees, and 3.1 degrees to 6.7 degrees, respectively. The ranges of 3D implant entry deviations of 3.3-, 4.1-, and 4.8-mm implants were 0.96 to 1.4, 0.85 to 1.72, and 0.89 to 1.78 mm, respectively. The ranges of 3D implant apex of 3.3-, 4.1-, and 4.8-mm implants were 0.63 to 1.21, 0.64 to 1.48, and 0.48 to 1.27 mm, respectively. No statistically significant differences were found in any of the 3 measurements: P=.67 for deviation in angulation; P=.27 for 3D implant deviation of entry; and P=.3 for 3D implant deviation of the apex. ConclusionsImplant diameters had no significant effect on placement deviations when a single posterior static guided surgery was used.

Optimizing a Feature-Based Motion Tracking System for Prospective Head Motion Estimation in MRI and PET/MRI

Patient head motion during magnetic resonance imaging (MRI) of the brain causes artifacts that limit diagnostic value. Prospective motion correction can, in principle, allow artifact-free imaging for any MRI sequence. Optical motion tracking systems are effective at measuring head motion for prospective motion correction but normally rely on attached markers, which are cumbersome and can move relative to the head. In this study, we optimized and benchmarked an optical motion tracking system that uses in-bore stereo-optical cameras to track feature patches on the forehead rather than attached markers. Feature patches were applied to the forehead in the form of an easily removable ink stamp or temporary tattoo. This approach has flexibility in camera positioning and allows tracking of a variety of surfaces on the human face, even those lacking prominent contours. This is advantageous given the limited space and line-of-sight with typical head coils. We optimized the accuracy and efficiency of two key components of the method: 1) the geometry of the stereo camera setup and 2) the feature detection and matching algorithm used for pose estimation. The absolute accuracy of the optimized feature-based method was compared with a commercial marker-based motion tracking system. Estimates of head motion of 15 volunteers simultaneously tracked by the two systems resulted in average positional discrepancies of less than 3 mm using a stamp and submillimeter average discrepancy using a feature-dense tattoo. These results suggest the feasibility of obtaining accurate head motion data for prospective motion compensated MRI using optimized feature-based motion tracking.

A tool for patient-specific prediction of delivery discrepancies in machine parameters using trajectory log files.

Multileaf collimator (MLC) delivery discrepancy between planned and actual (delivered) positions have detrimental effect on the accuracy of dose distributions for both IMRT and VMAT. In this study, we evaluated the consistency of MLC delivery discrepancies over the course of treatment and over time to verify that a predictive machine learning model would be applicable throughout the course of treatment. Next, the MLC and gantry positions recorded in prior trajectory log files were analyzed to build a machine learning algorithm to predict MLC positional discrepancies during delivery for a new treatment plan. An open source tool was developed and released to predict the MLC positional discrepancies at treatment delivery for any given plan. Trajectory log files of 142 IMRT plans and 125 VMAT plans from 9 Varian TrueBeam linear accelerators were collected and analyzed. The consistency of delivery discrepancy over patient-specific quality assurance (QA) and patient treatment deliveries was evaluated. Data were binned by treatment site and machine type to determine their relationship with MLC and gantry angle discrepancies. Motion-related parameters including MLC velocity, MLC acceleration, control point, dose rate, and gravity vector, gantry velocity and gantry acceleration, where applicable, were analyzed to evaluate correlations with MLC and gantry discrepancies. Several regression models, such as simple/multiple linear regression, decision tree, and ensemble method (boosted tree and bagged tree model) were used to develop a machine learning algorithm to predict MLC discrepancy based on MLC motion parameters. MLC discrepancies at patient-specific QA differed from those at patient treatment deliveries by a small (mean=0.0021±0.0036mm, P=0.0089 for IMRT; mean=0.0010±0.0016mm, P=0.0003 for VMAT) but statistically significant amount, likely due to setting the gantry angle to zero for QA in IMRT. MLC motion parameters, MLC velocity and gravity vector, showed significant correlation (P<0.001) with MLC discrepancy, especially MLC velocity, which had an approximately linear relationship (slope = -0.0027, P<0.001, R2 =0.79). Incorporating MLC motion parameters, the final generalized model trained by data from all linear accelerators can predict MLC discrepancy to a high degree of accuracy with high correlation (R2 =0.86) between predicted and actual MLC discrepancies. The same prediction results were found across different treatment sites and linear accelerators. We have developed a machine learning model using trajectory log files to predict the MLC discrepancies during delivery. This model has been a released as a research tool in which a DICOM-RT with predicted MLC positions can be generated using the original DICOM-RT file as input. This tool can be used to simulate radiotherapy treatment delivery and may be useful for studies evaluating plan robustness and dosimetric uncertainties from treatment delivery.

Validation of a patient-specific system for mandible-first bimaxillary surgery: ramus and implant positioning precision assessment and guide design comparison

In orthognathic surgery, the use of patient-specific osteosynthesis devices is a novel approach used to transfer the virtual surgical plan to the patient. The aim of this study is to analyse the quality of mandibular anatomy reproduction using a mandible-first mandibular-PSI guided procedure on 22 patients. Three different positioning guide designs were compared in terms of osteosynthesis plate positioning and mandibular anatomical outcome. PSIs and positioning guides were designed according to virtual surgical plan and 3D printed using biocompatible materials. A CBCT scan was performed 1 month after surgery and postoperative mandibular models were segmented for comparison against the surgical plan. A precision comparison was carried out among the three groups. Correlations between obtained rami and plates discrepancies and between planned rami displacements and obtained rami discrepancies were calculated. Intraoperatively, all PSIs were successfully applied. The procedure was found to be accurate in planned mandibular anatomy reproduction. Different guide designs did not differ in mandibular outcome precision. Plate positional discrepancies influenced the corresponding ramus position, mainly in roll angle and vertical translation. Ramus planned displacement was found to be a further potential source of inaccuracy, possibly due to osteosynthesis surface interference.

Experimental Work for Evaluation the Time Saving Between Different GPS Techniques for Makkah- Jeddah Region

Nowadays, there are available in technology, devices, Techniques such as GNSS and CORS and use the VRS techniques. Although for previous technology, some application just needs for the ordinary GPS techniques. So, the current research work is done by field experiments to assess the time saving and accuracy between GPS different techniques such as Stop &amp; Go, Kinematic, and Kinematic ON THE FLY Techniques especially in mountain areas like MAKKAH region. There are three post-processed GPS kinematic techniques. These techniques are stop &amp;go, kinematic, and kinematic on the fly techniques. Stop&amp; go and kinematic techniques require the so-called initialization process, which must be repeated in each cycle slip due to satellite-signal blockage. This is a time consuming and practically reduces the surveying productivity. On the other hand, the kinematic on the fly technique does not require the initialization process. This leads to increase the surveying productivity. The current paper makes a comparative study between GPS stop &amp;go, kinematic, and kinematic on the fly techniques, from points of view of accuracy, time elapsed for the initialization process, observation time for each surveyed point and the surveying productivity. The results supported by appropriate statistical tests showed that positional discrepancies between stop-go and kinematic techniques have mean value of 22 mm  (S.D) of ± 7 mm. Also, the positional discrepancies between the stop&amp; go and kinematic on the techniques are statically and practically insignificant, where the results showed that the positional discrepancy between the two techniques has a mean value of 22 mm with  (S.D) of ± 2 mm. In this context, the kinematic on the fly technique is increasing the surveying due to using a recording data of about 3-seconds for each surveying point, and also because this technique does not require any initialization process which takes a lot of time especially in case of surveying near tree, road, mountains, and advertising frames specially when internet and communication with the CORS station is missed or disconnected. Finally, in case the issues to use RTK or VRS due to communication problems specially the regions within mountains areas such as MAKKAH in this situation the GPS kinematic on the fly technique is highly recommended to replace the stop-go and kinematic techniques, in all the surveying works of medium scale. Also, the distance between the surveyed point and the reference receiver does not affect the resulted coordinates for about 7 km.

An iterative approach based on contextual information for matching multi‐scale polygonal object datasets

AbstractObject matching facilitates spatial data integration, updating, evaluation, and management. However, data to be matched often originate from different sources and present problems with regard to positional discrepancies and different levels of detail. To resolve these problems, this article designs an iterative matching framework that effectively combines the advantages of the contextual information and an artificial neural network. The proposed method can correctly aggregate one‐to‐many (1:N) and many‐to‐many (M:N) potential matching pairs using contextual information in the presence of positional discrepancies and a high spatial distribution density. This method iteratively detects new landmark pairs (matched pairs), based on the prior landmark pairs as references, until all landmark pairs are obtained. Our approach has been experimentally validated using two topographic datasets at 1:50 and 1:10k. It outperformed a method based on a back‐propagation neural network. The precision increased by 4.5% and the recall increased by 21.6%, respectively.

Accuracy of Three Bracket Transfer Media for Indirect Bonding Techniques (IDB) Fabricated by Three-Dimensional Printing

To evaluate and compare the accuracy of bracket placement in three bracket transfer media techniques for indirect bonding. A total of 300 brackets were bonded on dental casts by indirect bonding techniques using three different bracket transfer media. The bracket positions were simulated by digital software. In the first two methods, digital models were designed with two types of markers, one with fully mocked up bracket (container method), and another with only marked bracket margins (marker method), then the models were printed out by a three-dimensional (3D) printer using pink resin and bracket transfer trays were vacuum formed on these models with polyvinylsiloxane. In the third methods, digital software was used to design full arch transfer trays, and printed by a stereolithographic 3D printer using elastic resin. With the transfer trays, the brackets were bonded onto dental stone casts, and a 3D model scanner was used to capture the final bracket positions on the casts. Superimpositions between the planned and actual bracket positions were done. Nonparametric statistical analyses were used to determine whether there were significant differences between planned and actual bracket positions and between the three methods. All significant differences in bracket position were less than 0.31 mm and most (95%) were less than 0.08 mm. Significant differences between all three methods were found. Indirect bonding methods using digital software combined with 3D printing show good accuracy with clinically insignificant positional discrepancies of less than 0.5mm.

Impact of Immobilization on Interfractional Errors for Upper Extremity Soft Tissue Sarcoma Radiation Therapy

Introduction/BackgroundOwing to the rare nature and presentation of upper extremity soft tissue sarcomas (STSs) and the high mobility of associated anatomy, various patient positioning strategies are used for radiation therapy. The purpose of this study is to measure the interfractional setup errors associated with upper extremity sarcomas using different immobilization methods through cone-beam computed tomography (CBCT) images. MethodsAll patients treated with daily CBCT guidance for upper extremity STSs during 2014–2015 were identified and triaged based on type of immobilization. After defining an optimal region of interest for image registration, daily CBCT images were automatically registered to reference CT images to quantify positional discrepancies. Means and standard deviations were calculated, and one-way analysis of variance was calculated to determine significance of data. ResultsSeventeen patients with upper extremity sarcoma met inclusion criteria: 13 were treated to the shoulder/axilla/upper arm and 4 to the arm/elbow/forearm. Three main types of immobilization were identified: vacuum cradle with custom thermoplastic shell, vacuum cradle alone, and no immobilization accessory used. Patient repositioning occurred if translational and rotational displacements were larger than 1 mm and 5°, respectively, as per institutional guidelines. Patient repositioning rates were 18% for vacuum cradle with thermoplastic shells, 15% for vacuum cradles only, and 6% for no immobilization accessories. Mean translational displacements in right/left (R/L), superior/inferior (S/I), and anterior/posterior (A/P) directions were −0.04 ± 0.33 cm, 0.32 ± 0.33 cm, and 0.12 ± 0.25 cm for vacuum cradle with thermoplastic shell; 0.25 ± 0.10 cm, −0.07 ± 0.22 cm, and 0.00 ± 0.17 cm for vacuum cradle alone; and 0.14 ± 0.15 cm, 0.08 ± 0.45 cm, and −0.01 ± 0.24 cm for no immobilization. For all patients, rotational displacements in the pitch, roll, and yaw were 0.15 ± 1.99°, 0.31 ± 2.11°, and −0.21 ± 1.76°, respectively. There were significant (P < .05) differences in systematic error values for all translational and rotational axes between immobilization methods. ConclusionLarge interfractional errors, especially in the rotational axes, were observed, regardless of immobilization strategy. Small study population and unequal representation of different parts of the upper extremity are identified limitations. The need for better immobilization techniques for upper extremity STS treatments is clearly demonstrated.

An innovative gynecological HDR brachytherapy applicator system for treatment delivery and real-time verification

The multichannel vaginal cylinder (MVC) applicator employed for gynecological high dose rate (HDR) brachytherapy increases dose delivery complexity, and thus makes the treatment more prone to errors. A quality assurance (QA) procedure tracking the source throughout dose delivery can detect dwell position and time errors in the multiple channels of the applicator.A new MVC system with integrated real time in vivo treatment delivery QA has been developed based on diodes embedded on the outer surface of the MVC. It has been pre-calibrated and verified using a non-clinical treatment plan with consecutive test positions and dwell times within each catheter, followed by the delivery of ten clinical plans of adjuvant vaginal cuff brachytherapy following hysterectomy for endometrial cancer.The non-clinical verification showed overall mean dwell position and time discrepancies between the nominal and measured treatment of −0.2 ± 0.5 mm and −0.1 ± 0.1 s (k = 1), respectively. The clinical plans showed mean positional discrepancies of 0.2 ± 0.4 and 0.0 ± 0.8 mm, for the central and peripheral catheters, respectively, and mean dwell time discrepancies of −0.1 ± 0.2 and −0.0 ± 0.1 s for central and peripheral catheters, respectively.The innovative prototype of the MVC system has shown the ability to track the source with sub-mm and sub-second accuracy, and demonstrated potential for its incorporation into the clinical routine.

Stereotactic Body Radiation Therapy for Non-Spine Bone Metastases: A Single Institution's Experience

Purpose/Aim: Liver cancer patients with minimal amplitude of breathing or unable to tolerate breath-hold for radiotherapy are treated free-breathing with image guided SBRT. The purpose of this study is to assess the accuracy and reproducibility of automated registration of 3D versus 4D CBCT in target localization for free-breathing liver stereotactic body radiotherapy (SBRT). Method/Process: Daily localization CBCT images are acquired and any positional discrepancies corrected prior to treatment delivery for free-breathing liver SBRT. For image-guided radiotherapy (IGRT) at our institution, amplitudes of breathing 5 mm undergo 3D-CBCT acquisition while larger breathers (> 5 mm) utilize a 4D-CBCT workflow for target localization. Retrospective analysis of translational (T) and rotational (R) displacements of treated fractions was performed through 3 methods: 3D-CBCT dual registration using bony anatomy (T+R) and average liver position (T+R); 3D-CBCT registration using average liver position (T+R) followed by 4D-CBCT registration to the liver exhale position (T); and 4D-CBCT registration to the liver exhale position (T). Each retrospective image registration was performed automatically by the imaging software, and evaluated by three independent observers who performed manual adjustments to ensure clinical target coverage. Krippendorff’s alpha was used to assess agreement between the methods. Results/Benefits/Challenges: Ten liver cancer patients treated for 30-50 Gy over 5 or 6 fractions, with amplitudes of breathing motion ranging from 3.6 13 mm, were included. A total of 54 CBCT images were analyzed by each observer. Mean (+/SD) observer disagreement for 3D-CBCT dual registration was 1.1 0.8 mm, 2.1 1.3 mm, and 1.4 1.3 mm in the right-left, cranio-caudal and anterior posterior direction respectively. Agreement between observers was very high with Krippendorff’s alpha greater than 0.81 in all directions. Dual registration on 3D-CBCT and 4D-CBCT of the liver produced similar shifts; the root-mean-square (RMS) difference between mean manual and automatic techniques was 0.75mm in a 3D vector. Registration using 4D-CBCT to the liver exhale position alone produced an RMS observer error of 0.72 mm. Automatic matches of 3D and 4D liver registrations converged at small amplitudes, indicating a single 4DCBCT workflow is sufficient for any amplitude of breathing motion. Inter-observer variability between the 3 observers and automatic imaging software matches was smallest with 4D-CBCT liver exhale registration alone. Conclusion/Impact/Outcomes: Automatic registration using 4D-CBCT provides accurate target localization and is unaffected by larger breathing amplitudes as seen with 3D-CBCT image registration. Fourdimensional CBCT reduces the inter-observer variability and potential for systematic error, making it a desirable approach for free breathing liver IG-SBRT.

The Agreement Measure γcat a Complement to γ Focused on Categorization of a Continuum

Agreement on unitizing, where several annotators freely put units of various sizes and categories on a continuum, is difficult to assess because of the simultaneaous discrepancies in positioning and categorizing. The recent agreement measure γ offers an overall solution that simultaneously takes into account positions and categories. In this article, I propose the additional coefficient γ cat, which complements γ by assessing the agreement on categorization of a continuum, putting aside positional discrepancies. When applied to pure categorization (with predefined units), γ cat behaves the same way as the famous dedicated Krippendorff's α, even with missing values, which proves its consistency. A variation of γ cat is also proposed that provides an in-depth assessment of categorizing for each individual category. The entire family of γ coefficients is implemented in free software.

Development of a surgical navigation system for corrective osteotomy based on augmented reality

This study develops a novel navigation system for corrective osteotomy surgery based on augmented reality. By combining camera calibration and optical tracking technologies, we can provide a superimposed view of virtual 3D models with the resection plan onto the real patient, whereby both positional and rotational discrepancies between the surgical plan and current cutting plane are displayed. To test the feasibility of the developed system, the quantitative accuracy assessments were performed by using a custommade grid phantom and a mockup model. The assessment using the custom-made grid phantom showed stable root mean square error (RMSE) between virtual points and corresponding real points regardless of the viewing angle (1.31 ± 0.29 mm; mean ± s.d.) and the phantom-to-camera distance (1.17 ± 0.31 mm; mean ± s.d.). The assessment using the mockup model with five human subjects showed small positional and rotational discrepancies between the cutting plan and real cutting plane (0.59 ± 0.39 mm and 1.31° ± 0.38°; mean ± s.d.).

Functional Imaging in Radiotherapy in the Netherlands: Availability and Impact on Clinical Practice

AimsFunctional imaging with positron emission tomography/computed tomography (PET/CT) and multiparametric magnetic resonance (mpMR) is increasingly applied for radiotherapy purposes. However, evidence and experience are still limited, and this may lead to clinically relevant differences in accessibility, interpretation and decision making. We investigated the current patterns of care in functional imaging for radiotherapy in the Netherlands in a care evaluation study. Materials and methodsThe availability of functional imaging in radiotherapy centres in the Netherlands was evaluated; features available in >80% of academic and >80% of non-academic centres were considered standard of care. The impact of functional imaging on clinical decision making was evaluated using case questionnaires on lung, head/neck, breast and prostate cancer, with multiple-choice questions on primary tumour delineation, nodal involvement, distant metastasis and incidental findings. Radiation oncologists were allowed to discuss cases in a multidisciplinary approach. Ordinal answers were evaluated by median and interquartile range (IQR) to identify the extent and variability of clinical impact; additional patterns were evaluated descriptively. ResultsInformation was collected from 18 radiotherapy centres in the Netherlands (all except two). PET/CT was available for radiotherapy purposes to 94% of centres; 67% in the treatment position and 61% with integrated planning CT. mpMR was available to all centres; 61% in the treatment position. Technologists collaborated between departments to acquire PET/CT or mpMR for radiotherapy in 89%. All sites could carry out image registration for target definition. Functional imaging generally showed a high clinical impact (average median 4.3, scale 1–6) and good observer agreement (average IQR 1.1, scale 0–6). However, several issues resulted in ignoring functional imaging (e.g. positional discrepancies, central necrosis) or poor observer agreement (atelectasis, diagnostic discrepancies, conformation strategies). ConclusionsAccess to functional imaging with PET/CT and mpMR for radiotherapy purposes, with collaborating technologists and multimodal delineation, can be considered standard of care in the Netherlands. For several specific clinical situations, the interpretation of images may benefit from further standardisation.