Alignment Discrepancies Research Articles

Effect of Virtual Casts Superimposition Strategies on the Estimation of IOS Accuracy in Complete-Arch Scans.

This study aims to assess the impact of three different strategies of best-fit (BF) alignments of virtual casts on the estimation of the accuracy of intraoral scanner (IOS) in complete-arch scans. A maxillary typodont, modified with an Implant Scan Body (ISB) in the retroincisive area, was digitized using a desktop scanner (SW Optor Lab) to obtain a reference STL file. The typodont was then scanned 10 times using two IOSs (Trios4, Itero). Each STL file obtained from the IOS was superimposed onto the reference cast using three methods in CloudCompare: full-arch BF (BF-full), BF at the starting tooth (BF-tooth), and BF at the ISB (BF-ISB). Discrepancies from the reference were recorded, and trueness and precision were compared for each method. Statistical analysis with the Kruskall-Wallis nonparametric test was performed (α = 0.05). The Kruskall-Wallis test (p ⟨0.05) revealed statistically significant differences in trueness and precision among the alignment methods. Post Hoc multiple comparison test p-values were all below the critical alpha value. Differences in BF methods lead to significantly different accuracy values of IOS complete-arch scans as different virtual casts' alignment discrepancy. BF-full had the highest accuracy followed by BF-ISB and BF-tooth.

Effects of alignment discrepancies on the weld quality in friction stir welding

Friction stir welding is a modern welding technology with which the joining partners are welded in the solid state. The technology is often employed in the aerospace industry due to the excellent mechanical properties of the weld. Process disturbances can cause irregularities in the weld quality. It is still a challenge to avoid part fit-up deviations as a result of part misalignments and tolerances. Several publications have investigated the effect of alignment discrepancies on the weld quality, for example, by introducing a gap between parts, a tool offset, or linearly misaligned sheets. Depending on the application, the effects of simultaneously occurring alignment discrepancies on the weld quality could be critical. In this work, three alignment discrepancies were investigated (gap, linearly misaligned sheets, tool offset). The weld quality was determined using tensile tests. Process data such as the process forces and the spindle torque were also measured during the welding experiments. The results showed that each of the alignment discrepancies had a negative impact on the weld quality. The simultaneous occurrence resulted in an even lower weld quality. Some alignment discrepancies can probably be detected in the future using process data (e.g., the lateral force).

Trainable Weka segmentation tool machine learning-enabled segmentation on features of orthopantomograms

<h3>Objective</h3> The aims of this research were to provide an in-depth analysis of the latest benchmarks in oral imaging by studying the segmentation of radiographs using Trainable Weka Segmentation and to accurately automate segmentation where it can be implemented on a large scale of clients in order to simplify radiological diagnosis. <h3>Study Design</h3> The experimentation was conducted by modifying open-source radiographs from the UFBA UESC DENTAL IMAGES dataset. In order to simulate realistic conditions such as noise affecting the regions of interest, panoramic radiographs were degraded and blurred with Gaussian noise. Accuracy was quantified by measuring the difference between the automated radiograph and the dentist-annotated image using MorphoLibJ. To ensure precision in results, automated predicted segmentations were observed by an oral maxillofacial radiologist and compared with the dentist-renditioning annotations of the panoramic images. <h3>Results</h3> The TWS classifier on radiographs with an average of 32 teeth and greater (Dice value of 0.66) and an average of less than 32 teeth (F1 score of 0.59) was significant. The calculated t-value for the Jaccard index was 2.78 and the t-value for the Dice score was 2.81. The results, considering the statistical scores, were due to the IV. The radiographs with 32 teeth and greater had higher IoU and F1 scores because there was less of a discrepancy in tooth alignment. <h3>Conclusions</h3> Segmentation of dental radiographs can be conducted by machine learning instead of manually. <b>Statement of Ethical Review</b> Ethical Review or exemption was not warranted for this study

Best-Fit Algorithm Influences on Virtual Casts' Alignment Discrepancies.

To measure the influence of best-fit (BF) algorithms (entire dataset, 3 or 6 points landmark-based, or section-based BF) on virtual casts and their alignment discrepancies. A mandibular typodont was obtained and digitized by using an industrial scanner (GOM Atos Q 3D 12M). A control mesh was acquired. The typodont was digitized by using an intraoral scanner (TRIOS 4). Based on the alignment procedures, four groups were created: BF of the entire dataset (BF group), landmark-based BF using 3 reference points (LBF-3 group), or 6 reference points (LBF-6 group), and section-based BF (SBF group). The root mean square (RMS) error was calculated. One-way ANOVA and post hoc pairwise multi-comparison Tukey were used to analyze the data (α = 0.05). Significant RMS error mean value differences were found across the groups (p < 0.001). Tukey test revealed significant RMS error mean value differences between the BF and LBF-3 groups (p = 0.022), BF and LBF-6 groups (p < 0.001), LB-3 and LB-6 groups (p < 0.001), LBF-3 and SBF groups (p < 0.001), and LBF-6 and SBF groups (p < 0.001). The LBF-6 group had the lowest trueness, while SBF and BF groups obtained the highest trueness values. Furthermore, significant SD differences were revealed across the groups tested (p < 0.001). Tukey test revealed significant SD differences between the BF and LBF-6 groups (p < 0.001), LBF-3 and LB-6 groups (p < 0.001), LBF-3 and SBF groups (p = 0.004), and LBF-6 and SBF groups (p < 0.001). The BF and SBF groups showed equal and highest precision, while the LBF-6 group had the lowest precision. The best-fit algorithms tested influenced the virtual casts' alignment discrepancy. Entire dataset or section-based best-fit algorithms obtained the highest virtual casts' alignment trueness and precision compared with the landmark-based method.

The Accuracy and Clinical Success of Robotic-Assisted Total Knee Arthroplasty.

Background: Robotic-assisted total knee arthroplasty (rTKA) has emerged as a patient-specific customizable tool that enables 3-dimensional preoperative planning, intraoperative adjustment, robotic-assisted bone preparation, and soft-tissue protection. Haptic rTKA may enhance component positioning, but only a few small studies have examined patient satisfaction and clinical outcomes after haptic rTKA. Purpose: In patients who underwent haptic rTKA, we sought to evaluate (1) the discrepancy in alignment between the executed surgical plan and implanted alignment in the coronal and sagittal planes 1 year postoperatively and (2) patient-reported outcomes 2 years postoperatively. Methods: From a prospectively collected database, we reviewed 105 patients who underwent haptic rTKA from August 2016 to May 2017. Two fellowship-trained arthroplasty surgeons independently reviewed hip-to-ankle standing biplanar radiographs to measure overall limb alignment and individual tibial and femoral component alignment relative to the mechanical axis and compared this to the executed surgical plan. Patient-reported outcomes were collected preoperatively and at 2 years postoperatively using the Lower Activity Extremity Score (LEAS), Knee Injury and Osteoarthritis Outcome Score Junior (KOOS Jr.), and Numeric Pain Rating Scale (NPRS). Results: Mean patient age was 62.4 years, and mean body mass index was 30.6 kg/m2. Interobserver reliability was significant with a κ of 0.89. Absolute mean deviations in postoperative coronal alignment compared to intraoperative alignment were 0.625° ± 0.70° and 0.45° ± 0.50° for the tibia and femur, respectively. Absolute mean deviations in postoperative tibial sagittal alignment were 0.47° ± 0.76°. Overall mechanical alignment was 0.97° ± 1.79°. Outcomes in LEAS, KOOS Jr., and NPRS changed from 8 to 10, 78 to 88.3, and 8 to 1, respectively. Conclusions: Haptic rTKA demonstrated high reliability and accuracy (less than 1°) of tibial coronal, femoral coronal, and tibial sagittal component alignment postoperatively compared to the surgical plan. Patient-reported outcomes improved, as well. A more rigorous study on long-term outcomes is warranted.

Correlation of supine MRI and standing radiographs for cervical sagittal balance in myelopathy patients: a cross-sectional study.

Cervical sagittal alignment is correlated with myelopathy severity and used by spinal surgeons for surgical planification. Magnetic resonance imaging (MRI) is the gold standard for the evaluation of cervical myelopathy but may not be for the assessment of cervical sagittal balance compared to X-rays. The objective of this study was to assess the correlation of cervical alignment between supine MRI and standing radiographs in patients with cervical spondylotic myelopathy (CSM). Cobb, Jackson and Harrison methods were used to measure cervical sagittal alignment on supine MRI and standing radiographs of CSM adults. Cervical alignment was divided based on Cobb angle values on lordotic (> 4°), kyphotic (< - 4°) and rectitude (- 4° to 4°). Correlations between radiographic and MRI measurements were determined. Intra- and interobserver reliability were assessed and MRI and X-Ray-measured angles were compared. One hundred and thirty patients with CSM were reviewed. Correlations of cervical lordosis measures between radiographs and MRI were strong using the Cobb (0.65) and Jackson (0.63) methods, and moderate using the Harrison (0.37) method. Mean cervical lordosis angle was significantly lower on supine MRI compared to standing radiographs for all methods (Cobb 11.6 Rx vs. 9.2 MRI, Jackson 14.6 vs. 11.6, Harrison 23.5 vs. 19.9). Eighteen patients (15.4%) without lordosis on supine MRI presented lordosis on standing radiographs. A substantial proportion of patients has sagittal alignment discrepancies between supine MRI and standing radiographs. Therefore, standing radiographs of the cervical spine should always be included in surgical planning of CSM patients.

Retraction Notice: Immediate Postoperative Portable Radiograph After Total Knee Replacements: A Necessity or a Burden?

Background Total Knee Replacement (TKR) is one of the most commonly performed orthopaedic surgery(1). Immediate postoperative portable radiographs are performed after primary TKR in order to identify any potential complications and technical flaws. It also serves as a reference for comparison with subsequent radiographs. The aim of this study was to evaluate the clinical and economical value of these radiographs in TKR. It compares the quality of the portable radiograph, taken immediately post-operation, with in-suite radiographs taken 5-7 weeks post-operation. Methods In this retrospective study, a consecutive series of 389 TKR patients from January-2011 to March-2015 were reviewed. Radiological evaluation consisted of assessing the beam angle and the exposure on the images. Implant positioning was also compared by measuring the anatomical axis to look for component alignment discrepancies. Results The quality of the portable recovery room radiograph was overall inferior to the radiology suite radiograph regarding both beam angle and exposure. Component alignment discrepancies were also identified in the angle measurements between both types of radiographs. Conclusion Therefore, our study demonstrated that there is no clinical or financial value obtained from postoperative portable radiograph. Furthermore, Immediate recovery room radiographs should be avoided from being performed routinely and may only be used in cases where the surgeon is utilizing a new implant or technique. No external funding was provided for this study from any source.

Intraoperatively accurate limb alignment after opening wedge high tibial osteotomy can be lost by large knee joint line convergence angle during surgery.

The purpose of this study was to assess early postoperative loss of achieved correction and associated factors after opening wedge high tibial osteotomy (OWHTO). OWHTO was performed in 121 patients with osteoarthritis of the knee (mean age 66years, 154 knees). Anteroposterior radiographs of the knee and full-length leg, and varus and valgus stress radiographs of the knee were taken, and the femorotibial angle (FTA), joint line convergence angle (JLCA), and medial proximal tibial angle (MPTA) were measured. The changes in the FTA, JLCA, and MPTA were defined as ΔFTA, ΔJLCA, and ΔMPTA. The ΔFTA and ΔJLCA at postoperative 0-2days were - 1.8 ± 1.2° and - 1.9 ± 1.4°, respectively. The ΔFTA, ΔJLCA and ΔMPTA at postoperative 1-12months were 0.9 ± 1.3°, 0.2 ± 1.2° and - 0.8 ± 0.8°, respectively. A positive correlation was found between ΔFTA and ΔJLCA at postoperative 0-2days (ρ = 0.642, P < 0.001) and at postoperative 1-12months (ρ = 0.402, P < 0.001). A negative correlation was found between ΔFTA and ΔMPTA at postoperative 1-12months (ρ = - 0.534, P < 0.001). A discrepancy in alignment represented by the FTA occurred in the supine radiographs between the day of surgery and postoperative 2days. Multiple regression analysis suggested that postoperative JLCA on the day of surgery was the factor related to early postoperative change of the FTA. This study demonstrated the early loss of achieved correction after OWHTO due to change of the JLCA, even if the accurate alignment is obtained intraoperatively.

Comparison of smile esthetics among celebrities, dentists, and dental students in a Han Chinese population

Statement of problemVarious components of smile esthetics have been evaluated. However, whether these components affect smile esthetics in Han Chinese celebrities, dentists, and dental students is unknown. PurposeThe purpose of this study was to evaluate the smile esthetics of celebrities, dentists, and dental students in a Han Chinese population. Material and methodsFrontal images of smiles were obtained from the Internet for the celebrity group, while images of dentists and dental students were collected for the dentist and dental student groups. The buccal and posterior corridor ratios, the alignment discrepancy between the commissural and interpupillary lines, the number of teeth revealed, the width ratio relative to the golden proportion, and the width-to-length ratios of maxillary anterior teeth were calculated by using a photo-editing software program. Statistical analysis was performed by using 2-way ANOVA and the Tukey HSD test (α=.05). ResultsEligible images were obtained for 81 celebrities, 83 dentists, and 78 dental students. The celebrities were found to have the highest buccal and posterior corridor ratios and reveal the least teeth in the smile among the 3 groups (all P<.001). The alignment discrepancy for celebrities was significantly less than that for dental students (P=.025). Moreover, the absolute difference of width ratios from the golden proportion was significantly different from 0 for all groups (all P<.001). ConclusionsSignificant differences were found in the smiles of Han Chinese celebrities, dentists, and dental students in regard to the buccal and posterior corridor ratios, the alignment discrepancy between the commissural and interpupillary lines, and the number of teeth revealed. Chinese celebrities tended to have a smile that displays to the second premolar, with a medium buccal corridor width.

Can intrinsic alignments of elongated low-mass galaxies be used to map the cosmic web at high redshift?

ABSTRACT Hubble Space Telescope observations show that low-mass ($M_*=10^9\!-\!10^{10}\, \mathrm{M}_{\odot }$) galaxies at high redshift (z = 1.0–2.5) tend to be elongated (prolate) rather than disky (oblate) or spheroidal. This is explained in zoom-in cosmological hydrodynamical simulations by the fact that these galaxies are forming in cosmic web filaments where accretion happens preferentially along the direction of elongation. We ask whether the elongated morphology of these galaxies allows them to be used as effective tracers of cosmic web filaments at high redshift via their intrinsic alignments. Using mock light cones and spectroscopically confirmed galaxy pairs from the Cosmic Assembly Near-infared Deep Extragalactic Legacy Survey (CANDELS), we test two types of alignments: (1) between the galaxy major axis and the direction to nearby galaxies of any mass and (2) between the major axes of nearby pairs of low-mass, likely prolate, galaxies. The mock light cones predict strong signals in 3D real space, 3D redshift space, and 2D projected redshift space for both types of alignments (assuming prolate galaxy orientations are the same as those of their host prolate haloes), but we do not detect significant alignment signals in CANDELS observations. However, we show that spectroscopic redshifts have been obtained for only a small fraction of highly elongated galaxies, and accounting for spectroscopic incompleteness and redshift errors significantly degrades the 2D mock signal. This may partly explain the alignment discrepancy and highlights one of several avenues for future work.

Immediate Postoperative Portable Radiograph After Total Knee Replacements: A Necessity or a Burden?

Background:Total Knee Replacement (TKR) is one of the most commonly performed orthopaedic surgery(1). Immediate postoperative portable radiographs are performed after primary TKR in order to identify any potential complications and technical flaws. It also serves as a reference for comparison with subsequent radiographs. The aim of this study was to evaluate the clinical and economical value of these radiographs in TKR. It compares the quality of the portable radiograph, taken immediately post-operation, with in-suite radiographs taken 5-7 weeks post-operationMethods:In this retrospective study, a consecutive series of 389 TKR patients from January-2011 to March-2015 were reviewed. Radiological evaluation consisted of assessing the beam angle and the exposure on the images. Implant positioning was also compared by measuring the anatomical axis to look for component alignment discrepancies.Results:The quality of the portable recovery room radiograph was overall inferior to the radiology suite radiograph regarding both beam angle and exposure. Component alignment discrepancies were also identified in the angle measurements between both types of radiographs.Conclusion:Therefore, our study demonstrated that there is no clinical or financial value obtained from postoperative portable radiograph. Furthermore, Immediate recovery room radiographs should be avoided from being performed routinely and may only be used in cases where the surgeon is utilizing a new implant or technique. No external funding was provided for this study from any source.

Aesthetic rehabilitation through dentogingival prosthesis for patients with high smile line

OBJECTIVE: This report aimed to present a case of functional and aesthetic rehabilitation of anterior maxillary region through dentogingival prosthesis in a patient with high smile line.CASE DESCRIPTION: Patient female, 65 years old, had aesthetic complaints related to fixed partial denture from upper left canine to upper right lateral incisor. The patient reported loss of upper central incisors due to periodontal disease progression. Clinical and radiographic examination showed marginal leakage, discrepancy in teeth proportion, dental inclination and alignment, and excessive prolongation of the cervical-incisal direction, plus a resorbed alveolar ridge, in both volume and height, in the described area. Faced with these conditions, it was decided to perform a fixed partial dentogingival denture, restoring harmony and smile functionality.CONCLUSION: After a 1-year follow up, maintenance of functional and aesthetic aspects of the prosthesis was observed.

A Brief Exposure to Leftward Prismatic Adaptation Enhances the Representation of the Ipsilateral, Right Visual Field in the Right Inferior Parietal Lobule.

A brief exposure to rightward prismatic adaptation (PA) was shown to shift visual field representation within the inferior parietal lobule (IPL) from the right to the left hemisphere. This change in hemispheric dominance could be interpreted as (1) a general effect of discrepancy in visuomotor alignment caused by PA or (2) a direction-specific effect of rightward PA. To test these hypotheses, we compared the effects of rightward and leftward PA on visual representation in normal human subjects. Three groups of normal subjects underwent an fMRI evaluation using a simple visual detection task before and after brief PA exposure using leftward- or rightward-deviating prisms or no prisms (L-PA, R-PA, neutral groups). A two-way ANOVA group × session revealed a significant interaction suggesting that PA-induced modulation is direction specific. Post hoc analysis showed that L-PA enhanced the representation of the right visual field within the right IPL. Thus, a brief exposure to L-PA enhanced right hemispheric dominance within the ventral attentional system, which is the opposite effect of the previously described shift in hemispheric dominance following R-PA. The direction-specific effects suggest that the underlying neural mechanisms involve the fine-tuning of specific visuomotor networks. The enhancement of right hemispheric dominance following L-PA offers a parsimonious explanation for neglect-like symptoms described previously in normal subjects.

Quantification of facial and smile esthetics

Statement of problemWhether deviations in alignment discrepancy, width-to-length ratio, application of the golden proportion, or number of teeth revealed in smile affect attractiveness is yet unknown. PurposeThe purpose of this analytical study was to quantify dental and facial esthetics to determine whether individuals identified as having superior smiles display differences in alignment discrepancies (angulation between interpupillary and commissure line); width-to-length ratios of maxillary anterior teeth; application of the golden proportion (approximately 1.618:1); and number of teeth revealed in an animated smile when compared with an average population. Material and methodsAn Internet search for “best smile” and “celebrity” identified 108 celebrities. Photographs showing smiles within 10 degrees of a frontal view were collected, while photographs of dental students were used for the control group. Alignment discrepancies, widths and lengths of the anterior teeth, and number of teeth revealed in an animated smile were measured with photo-editing software, and ratios were calculated. The groups were compared with repeated-measures ANOVA, the Mann-Whitney U test, and the Wilcoxon signed-rank test (α=.05). ResultsUsable photographs were obtained for 90 celebrities (58 women, 32 men) and compared with photographs of 97 dental students (54 women, 43 men). Statistically significant differences were found for alignment discrepancies (celebrities 0.97, students 1.25, P=.034) and for the number of teeth displayed (P=.049); 22.2% of the celebrities revealed 12 teeth, versus 6.2% of the students. In both groups, significant differences from the golden ratio (1.618:1) for the width of the central incisor/lateral incisor right and left and for the width of the lateral incisor/canine right and left were observed through 95% confidence intervals. Sex and left-right were nonsignificant factors. ConclusionsCelebrities identified as having a best smile had smaller mean alignment discrepancies and revealed a greater number of teeth in an animated smile than dental students.

Comparison of surface matching and target matching for image-guided pelvic radiation therapy for both supine and prone patient positions.

We investigate the difference between surface matching and target matching for pelvic radiation image guidance. The uniqueness of our study is that all patients have multiple CT‐on‐rails (CTOR) scans to compare to corresponding AlignRT images. Ten patients receiving pelvic radiation were enrolled in this study. Two simulation CT scans were performed in supine and prone positions for each patient. Body surface contours were generated in treatment planning system and exported to AlignRT to serve as reference images. During treatment day, the patient was aligned to treatment isocenter with room lasers, and then scanned with both CTOR and AlignRT. Image‐guidance shifts were calculated for both modalities by comparison to the simulation CT and the differences between them were analyzed for both supine and prone positions, respectively. These procedures were performed for each patient once per week for five weeks. The difference of patient displacement between AlignRT and CTOR was analyzed. For supine position, five patients had an average difference of displacement between AlignRT and CTOR along any direction (vertical, longitudinal, and lateral) greater than 0.5 cm, and one patient greater than 1 cm. Four patients had a maximum difference greater than 1 cm. For prone position, seven patients had an average difference greater than 0.5 cm, and three patients greater than 1 cm. Nine patients had a maximum difference greater than 1 cm. The difference of displacement between AlignRT and CTOR was greater for the prone position than for the supine position. For the patients studied here, surface matching does not appear to be an advisable image‐guidance approach for pelvic radiation therapy for patients with either supine or prone position. There appears to be a potential for large alignment discrepancies (up to 2.25 cm) between surface matching and target matching.PACS number(s): 87.55.‐x

Leg length discrepancy and lower limb alignment after total hip arthroplasty in unilateral hip osteoarthritis patients

BackgroundLeg length discrepancy (LLD) following total hip arthroplasty (THA) is a leading cause of patient dissatisfaction. However, no reports have described the influence of lower limb alignment on LLD after THA. In the present study, we firstly investigated the change in lower limb alignment after THA. Secondly, we determined the influence of lower limb alignment on LLD after THA. Thirdly, we evaluated the influence of LLD in the entire lower leg on the clinical outcomes after THA. MethodsWe followed up with 54 unilateral hip osteoarthritis (OA) patients 1year after THA. For the radiological assessment of LLD and lower limb alignment, we obtained anteroposterior radiographs of the pelvis and both lower legs in entirety in a standing position before and 1year after THA. The Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Medical Outcomes Study Short-Form 36-Item Health Survey (SF-36) were also obtained to assess the clinical outcome. ResutsThe alignment of the affected leg, which was more valgus than the unaffected leg before THA, tended toward varus after THA, and the discrepancy between the lower limb alignments on both sides decreased. However, the alignment discrepancies that remained after THA influenced the LLD measured on the radiograph of the entire lower leg, and this LLD influenced the clinical outcome as measured by the HHS and the WOMAC score. ConclusionsLLD in the entire lower leg should be corrected for a better clinical outcome after THA.

Intra- and post-operative accuracy assessments of two different patient-specific instrumentation systems for total knee replacement

The aim of this study is to assess and compare the accuracy of two different patient-specific instrumentation (PSI) systems for total knee replacement, both intra-operatively for bone preparation and post-operatively for final component alignment. Twenty-five patients were treated according to a computer tomography (CT)-based PSI system (group A) and 25 to a magnetic resonance imaging (MRI)/X-ray-based system (group B). Alignments on the three anatomical planes and resection thickness at the cutting blocks and at the resulting bone cuts were recorded intra-operatively by a standard surgical navigation system. Alignments of the prosthetic components and mechanical axis were also measured post-operatively on radiographs. These measurements at both the femur and tibia were compared with those of the corresponding pre-operative planning, considering discrepancies larger than 3° as outliers. In both groups, the mean absolute differences between pre-operatively planned alignments and corresponding intra- and post-operative measurements ranged from a minimum of 1.2° to a maximum of 2.9° in all three anatomical planes. In both groups and in both femur and tibia, the plane with the smallest percentage of outliers was the coronal, maximum 17%. The comparison between two groups was statistically significant (p = 0.02) in the femoral sagittal plane, where group B showed smaller alignment discrepancies at the cutting blocks. Both PSI systems showed good alignments in the coronal plane in all stages. For a few measurements, a better performance was observed in the MRI/X-ray-based system than in the CT-based system. I.

A further investigation of the centroid‐to‐centroid method for stereotactic lung radiotherapy: A phantom study

Our previous study [B. Lu et al., "A patient alignment solution for lung SBRT setups based on a deformable registration technique," Med. Phys. 39(12), 7379-7389 (2012)] proposed a deformable-registration-based patient setup strategy called the centroid-to-centroid (CTC) method, which can perform an accurate alignment of internal-target-volume (ITV) centroids between averaged four-dimensional computed tomography and cone-beam computed tomography (CBCT) images. Scenarios with variations between CBCT and simulation CT caused by irregular breathing and/or tumor change were not specifically considered in the patient study [B. Lu et al., "A patient alignment solution for lung SBRT setups based on a deformable registration technique," Med. Phys. 39(12), 7379-7389 (2012)] due to the lack of both a sufficiently large patient data sample and a method of tumor tracking. The aim of this study is to thoroughly investigate and compare the impacts of breathing pattern and tumor change on both the CTC and the translation-only (T-only) gray-value mode strategies by employing a four-dimensional (4D) lung phantom. A sophisticated anthropomorphic 4D phantom (CIRS Dynamic Thorax Phantom model 008) was employed to simulate all desired respiratory variations. The variation scenarios were classified into four groups: inspiration to expiration ratio (IE ratio) change, tumor trajectory change, tumor position change, tumor size change, and the combination of these changes. For each category the authors designed several scenarios to demonstrate the effects of different levels of breathing variation on both of the T-only and the CTC methods. Each scenario utilized 4DCT and CBCT scans. The ITV centroid alignment discrepancies for CTC and T-only were evaluated. The dose-volume-histograms (DVHs) of ITVs for two extreme cases were analyzed. Except for some extreme cases in the combined group, the accuracy of the CTC registration was about 2 mm for all cases for both the single and the combined scenarios. The performance of the CTC method was insensitive to region-of-registration (ROR) size selections, as suggested by the comparable accuracy between 1 and 2 cm expansions of the ROR selections for the method. The T-only method was suitable for some single scenarios, such as trajectory variation, position variation, and size variation. However, for combined scenarios and/or a large variation in the IE ratio, the T-only method failed to produce reasonable registration results (within 3 mm). The discrepancy was close to, or even greater than, 1 cm. In addition, unlike the CTC method, the T-only method was sensitive to the ROR size selection. The DVH analysis suggested that a large ITV to PTV margin should be considered if a breathing pattern variation is observed. The phantom study demonstrated that the CTC method was reliable for scenarios in which breathing pattern variation was involved. The T-only gray value method worked for some scenarios, but not for scenarios that involved an IE ratio variation. For scenarios involving position variation, the T-only method worked only with a careful selection of the ROR, whereas the CTC method was independent of ROR size as long as the ITVs were included in the ROR. One indication of the dose consequence analysis was that a large ITV to PTV margin should be considered if a breathing pattern variation is observed.

Three-Dimensional Image Registration as a Tool for Forensic Odontology

Frequently, human dentition is utilized for victim identification. This report introduces a new human identification technique based on the principle of 3-dimensional (3D) image registration of the dentition. With the aid of a dry human skull, postmortem (PM) and antemortem (AM) scenarios were assumed. The skull in its initial state composed the PM scenario. Virtual 3D PM images were reconstructed from medical CT images. The AM scenario was achieved by reconstructing the missing hard and soft tissues of the skull by dental waxes. Virtual 3D AM images were obtained by laser surface scanning. The virtual PM and AM images were registered at 2 levels: arch level and tooth level. At arch level, the deviation between the 2 images was 0.147 mm for the maxilla and 0.166 mm for the mandible. At tooth level, the deviation average ranged from 0.077 to 0.237 mm. Qualitatively, even image fit was observed for the arches, intact teeth, and teeth with minimal deficiencies. As the tooth defect increased, the alignment discrepancy increased. It is concluded that 3D image registration ensured an accurate superimposition of the 3D images and can be used as a robust tool for forensic identification.

Bisphosphonates as a risk factor for adverse orthodontic outcomes: A retrospective cohort study

Bisphosphonates are a class of drugs commonly prescribed to treat osteoporosis. They act by decreasing the resorption of bone. Since tooth movement depends on bone remodeling, these drugs can impact orthodontic treatment. The purpose of this study was to evaluate the extent to which bisphosphonate therapy is a risk factor for poor orthodontic outcomes. Orthodontists were invited to participate in the study by performing case reviews of women over age 50 who were treated from 2002 through 2008. Women who used bisphosphonates were compared with women who did not have a history of bisphosphonate use. Outcomes assessed included treatment time, osteonecrosis of the jaws, incisor alignment, incomplete space closure, and root parallelism. The records for 20 subjects with bisphosphonate exposure were collected, as well as records for 93 subjects without bisphosphonate exposure. In patients undergoing extractions, treatment times were significantly longer if they had a history of bisphosphonate use. No occurrences of osteonecrosis of the jaws were reported, nor did patients end treatment with incisor alignment discrepancies greater than 1 mm, regardless of bisphosphonate exposure. Among patients with extractions or initial spacing, there were higher odds of incomplete space closure (odds ratio, 13) and poor root parallelism (odds ratio, 26) at the end of treatment for patients using bisphosphonates. Bisphosphonate use is associated with longer treatment times among extraction patients, increased odds of poor space closure, and increased odds of poor root parallelism.