Reference Scan Research Articles

A high throughput phenotyping technique for banana cultivar Sukali Ndizi based on internal fruit quality attributes

Background: Sukali Ndizi quality traits such as Total soluble solid (TSS) content, pulp texture and sugar/acid (S/A) ratio are critical in quality assessment. Screening very large numbers of fruit genotypes has prompted the development of a high throughput method using Near Infrared spectrometry (NIRS). Results: The calibration procedure for the attributes of TSS, pulp texture and S/A ratio was optimized with respect to a reference sampling technique, scan averaging, spectral window, data pre-treatment and regression procedure. Calibration equations for all analytical characteristics were computed by NIR Software ISI Present WINISI using Modified Partial Least Squares (MPLS) and Partial Least Squares. The quality of calibration models were evaluated by Standard Error of Calibration and coefficient of determination parameters between the measured and the predicted values. The results obtained with FOSS NIR systems 2500 spectrometer (model DS 2500) using the 350-2500 nm range, showed good prediction of the quality traits TSS content, pulp texture and S/A ratio. The MPLS method produced satisfactory Calibration model performance for TSS, texture and S/A ratio, with typical Rc2 of 0.73%Brix, 0.69kgf and 0.7; and root mean squared standard error of calibration of 0.73%Brix, 0.25kgf and 5.36 respectively. This is a good set of quality traits predicting Sukali Ndizi quality with NIRS with robustness, as it was obtained by using diverse Ndizi populations. Conclusions: This can be a useful tool to phenotype large numbers of Ndizi hybrids per day, making it possible to reduce on the resources spent when utilizing organoleptic evaluation selection technique.

Attenuation Correction Using Template PET Registration for Brain PET: A Proof-of-Concept Study.

NeuroLF is a dedicated brain PET system with an octagonal prism shape housed in a scanner head that can be positioned around a patient's head. Because it does not have MR or CT capabilities, attenuation correction based on an estimation of the attenuation map is a crucial feature. In this article, we demonstrate this method on [18F]FDG PET brain scans performed with a low-resolution proof of concept prototype of NeuroLF called BPET. We perform an affine registration of a template PET scan to the uncorrected emission image, and then apply the resulting transform to the corresponding template attenuation map. Using a whole-body PET/CT system as reference, we quantitively show that this method yields comparable image quality (0.893 average correlation to reference scan) to using the reference µ-map as obtained from the CT scan of the imaged patient (0.908 average correlation). We conclude from this initial study that attenuation correction using template registration instead of a patient CT delivers similar results and is an option for patients undergoing brain PET.

Investigation of a water equivalent depth method for dosimetric accuracy evaluation of synthetic CT

PurposeTo provide a metric that reflects the dosimetric utility of the synthetic CT (sCT) and can be rapidly determined. MethodsRetrospective CT and atlas-based sCT of 62 (53 IMRT and 9 VMAT) prostate cancer patients were used. For image similarity measurements, the sCT and reference CT (rCT) were aligned using clinical registration parameters. Conventional image similarity metrics including the mean absolute error (MAE) and mean error (ME) were calculated. The water equivalent depth (WED) was automatically determined for each patient on the rCT and sCT as the distance from the skin surface to the treatment plan isocentre at 36 equidistant gantry angles, and the mean WED difference (ΔWED¯) between the two scans was calculated. Doses were calculated on each scan pair for the clinical plan in the treatment planning system. The image similarity measurements and ΔWED¯ were then compared to the isocentre dose difference (ΔDiso) between the two scans. ResultsWhile no particular relationship to dose was observed for the other image similarity metrics, the ME results showed a linear trend against ΔDiso with R2 = 0.6, and the 95 % prediction interval for ΔDiso between −1.2 and 1 %. The ΔWED¯ results showed an improved linear trend (R2 = 0.8) with a narrower 95 % prediction interval from −0.8 % to 0.8 %. ConclusionΔWED¯ highly correlates with ΔDiso for the reference and synthetic CT scans. This is easy to calculate automatically and does not require time-consuming dose calculations. Therefore, it can facilitate the process of developing and evaluating new sCT generation algorithms.

Deep learning-based motion quantification from k-space for fast model-based magnetic resonance imaging motion correction.

Intra-scan rigid-body motion is a costly and ubiquitous problem in clinical magnetic resonance imaging (MRI) of thehead. State-of-the-art methods for retrospective motion correction in MRI are often computationally expensive or in the case of image-to-image deep learning (DL) based methods can be prone to undesired alterations of the image (hallucinations'). In this work we introduce a novel rigid-body motion correction method which combines the advantages of classical model-driven and data-consistency (DC) preserving approaches with a novel DL algorithm, to provide fast and robust retrospective motion correction. The proposed Motion Parameter Estimating Densenet (MoPED) retrospectively estimates subject head motion during MRI acquisitions using a DL network with DenseBlocks and multitask learning. It quantifies the 2D rigid in-plane motion parameters slice-wise for each echo train (ET) of a Cartesian T2-weighted 2D Turbo-Spin-Echo sequence. The network receives a center patch of the motion corrupted k-space as well as an additional motion-free low-resolution reference scan to provide the ground truth orientation. The supervised training utilizes motion simulations based on 28 acquisitions with subject-wise training, validation, and test data splits of 70%, 23%, and 7%. During inference, MoPED is embedded in an iterative DC-driven motion correction algorithm which alternatingly updates estimates of the motion parameters and motion-corrected low-resolution k-space data. The estimated motion parameters are then used to reconstruct the final motion correctedimage. The mean absolute/squared error and the Pearson correlation coefficient were used to analyze the motion parameter estimation quality on in-silico data in a quantitative evaluation. Structural similarity (SSIM), DC error and root mean squared error (RMSE) were used as metrics of image quality improvement. Furthermore, the generalization capability of the network was analyzed on two in-vivo motion volumes with 28 slices each and on one simulated T1-weightedvolume. The motion estimation achieves a Pearson correlation of 0.968 to the simulated ground-truth of the 2433 test data slices used. In-silico results indicate that MoPED decreases the time for the optimization by a factor of around 27 compared to a conventional method and is able to reduce the RMSE of the reconstructions and average DC error by more than a factor of two compared to uncorrected images. In-vivo experiments show a decrease in computation time by a factor of around 20, a RMSE decrease from 0.055 to 0.033 and an SSIM increase from 0.795 to 0.862. Furthermore, contrast independence is demonstrated as MoPED is also able to correct T1-weighted images in simulations without retraining. Due to the model-based correction, no hallucinations wereobserved. Incorporating DL in a model-based motion correction algorithm shows great benefit on the optimization and computation time. The k-space-based estimation also allows a data consistent correction and therefore avoids the risk of hallucinations of image-to-imageapproaches.

In vivo trueness and precision of full-arch implant scans using intraoral scanners with three different acquisition protocols

ObjectivesTo evaluate an in situ reference acquisition method for implant positions in complete edentulous maxillae using an industrial scanner and allowing for in vivo trueness analysis of the restorative workflow. To assess in vivo trueness and precision of intraoral scanners (IOS) using different acquisition protocols. Furthermore, to compare IOS trueness with impression-based models and implant-supported fixed dentures (IFD) in a parallel study on the same cohort using the same in situ reference scan. MethodsSix scan-bodies mounted to maxillary implants in five subjects were reference scanned (REF) using an industrial scanner. Subjects were scanned with IOS three times using three different protocols: control (CT), dental floss assisted (DF), and acrylic splint (SP). CAD-files of scan-bodies with inter-aligned analogues were geometry-aligned to REF, and SP. Scan-bodies were aligned to CT and DF in proprietary dental laboratory software and exported with analogue positions. Resulting six CAD-analogues per scan were Globally Aligned using a consistent geometry-based alignment. Deviations were computed after a Reference Point System Alignment at the implant/prosthetic platform for Cartesian axes with a linear Resultant. ResultsResultant trueness was CT: 41±11 µm, DF: 49±22 µm, SP: 55±8 µm. Resultant precision was CT: 48±7 µm, DF: 50±7 µm, SP: 45±6 µm. ConclusionsThis method is applicable for assessing trueness of maxillary full-arch implant scans in vivo. The CT protocol was most accurate. CT trueness showed no difference to digitised impression-based models in parallel study. CT was more accurate than IFD in a parallel study. CT displayed similar numerical trueness as existing in vitro studies. Clinical significanceUsing IOS to acquire full-arch implant scans is controversial. The modified protocol in this pilot shows promising results in the maxilla where great care was taken to manage non-attached tissues when a modified scanning pattern was used. However, other IOS may show varying results in vivo. A completed scan does not necessarily equate to an accurate scan.

Single-timepoint low-dimensional characterization and classification of acute versus chronic multiple sclerosis lesions using machine learning

Multiple sclerosis (MS) is a chronic inflammatory and neurodegenerative disease characterized by the appearance of focal lesions across the central nervous system. The discrimination of acute from chronic MS lesions may yield novel biomarkers of inflammatory disease activity which may support patient management in the clinical setting and provide endpoints in clinical trials. On a single timepoint and in the absence of a prior reference scan, existing methods for acute lesion detection rely on the segmentation of hyperintense foci on post-gadolinium T1-weighted magnetic resonance imaging (MRI), which may underestimate recent acute lesion activity. In this paper, we aim to improve the sensitivity of acute MS lesion detection in the single-timepoint setting, by developing a novel machine learning approach for the automatic detection of acute MS lesions, using single-timepoint conventional non-contrast T1- and T2-weighted brain MRI. The MRI input data are supplemented via the use of a convolutional neural network generating “lesion-free” reconstructions from original “lesion-present” scans using image inpainting. A multi-objective statistical ranking module evaluates the relevance of textural radiomic features from the core and periphery of lesion sites, compared within “lesion-free” versus “lesion-present” image pairs. Then, an ensemble classifier is optimized through a recursive loop seeking consensus both in the feature space (via a greedy feature-pruning approach) and in the classifier space (via model selection repeated after each pruning operation). This leads to the identification of a compact textural signature characterizing lesion phenotype. On the patch-level task of acute versus chronic MS lesion classification, our method achieves a balanced accuracy in the range of 74.3–74.6% on fully external validation cohorts.

APOE genotype and blood pressure influence global and regional cerebral blood flow in older adults post‐high lipid feeding

AbstractBackgroundBoth hypertension and the E4 allele of the APOE gene are known risk factors for Alzheimer’s disease (AD). We investigated the influence of these factors on global cerebral blood flow (CBF) and four prespecified areas (angular gyrus, hippocampus, posterior cingulate, temporal lobe) using arterial spin labeling (ASL) MRI both in fasting state and after ingestion of a high fat drink.MethodAfter fasting, 29 older adults (age 66.8 ± 4.1) underwent baseline and 1, 2, 3‐hour ASL MRI after ingestion of 1/2 cup heavy cream with comparable total and saturated fat to a high fat breakfast. We used pCASL MRI with background suppression to measure CBF in ml/100g/min. Imaging parameters were in accordance with the recommendations of ISMRM: label duration = 1.8 s, postlabeling delay = 2 s, labeling offset = 25‐30 mm, slices = 20, resolution = 3.5×3.5×5 mm3, SENSE‐factor = 2, TR/TE= 5000/18 ms. Finally, we acquired a reference scan (M0, 1 minute) identical to above scan but with TR = 10,000 ms and no labeling or background suppression. Statistical analyses included repeated measures ANOVA as well as cross‐sectional multiple regressions with robust estimators adjusting for age, E4 status, BMI, heart rate, systolic and diastolic blood pressure (DBP).ResultGlobal CBF decreased at 1‐, 2‐, and 3‐hours post‐lipid drink, compared to time 0 (RM ANOVA F=5.57, p=0.002). These findings were recapitulated in the posterior cingulate (F=3, p=0.036) and hippocampus (F=3.3, p= 0.025); this difference was not seen in the temporal lobe or angular gyrus. E4 genotype was significantly associated with lower global CBF at hour 2 and in three areas examined (Table). Additionally, higher DBP was associated with lower CBF globally and in all four areas (Table).ConclusionCBF decreased in response to lipid ingestion, both globally and in regions known to be important in AD, and this was exaggerated in individuals with the E4+ genotype and with elevated DBP. Further examination of E4 and blood pressure interactions are ongoing, as well as how these findings relate to cognitive performance.

A comparative study of quantitative metrics in chemical exchange saturation transfer imaging for grading gliomas in adults

PurposeTo evaluate the performance of different chemical exchange saturation transfer (CEST) metrics for grading gliomas with semiautomatically defined regions of interest (ROIs). MethodsThirty-eight adult subjects were included, including 23 high-grade gliomas and 15 low-grade gliomas confirmed by histopathology. The B0-corrected CEST z-spectra were first calculated with magnetization transfer ratio asymmetry (MTRasym) analysis at frequency offsets of 3.5, 3, 2.5, 2, 1.5, and 1 ppm to obtain the fit-free metrics and subsequently fitted with three Lorentzian functions denoting direct water saturation (DS), amide proton transfer (APT), and combined semisolid magnetization transfer and nuclear Overhauser enhancement (MT & NOE) effects to derive the fit-based metrics. Wilcoxon rank-sum test was performed to determine if a statistically significant difference was present in the CEST metrics between low- and high-grade gliomas. Receiver operating characteristic (ROC) curves were used to evaluate the differentiation of CEST metrics between low- and high-grade gliomas. Pearson correlation coefficients were employed to evaluate the correlations of CEST metrics. ResultsFor the fit-free metrics, the highest areas under the curve (AUCs) of 0.85, 0.88, and 0.88, corresponding to MTRasym, MTRnormref (normalization by the reference scan), and MTRRex (subtraction of inverse z-spectra), respectively, were obtained at 3 ppm across various frequency offsets. In addition, the AUCs generated from the fit-based metrics (0.88–0.90) were higher than those generated from the fit-free metrics at 3 ppm. ConclusionThe results of this preliminary study indicate that fit-free CEST metrics at 3 ppm are superior to the other frequency offsets for grading human brain gliomas. The fit-based metrics manifested improved differentiation between low- and high-grade gliomas compared to the fit-free CEST metrics.

In vitro scan accuracy and time efficiency in various implant-supported fixed partial denture situations

ObjectivesTo compare the accuracy and time efficiency of different digital workflows in 3 implant-supported fixed partial denture situations. MethodsThree partially edentulous maxillary models with 2 implants (Model 1: implants at lateral incisor sites; Model 2: implants at right canine and first molar sites; Model 3: implants at right first premolar and first molar sites) were digitized (ATOS Capsule 200MV120, n=1) for reference scans. Test scans were performed for direct (Primescan (DDW-P) and Trios 3 (DDW-T)) and indirect (IDW) digital workflows (n=14). For IDW, stone casts (type IV) were obtained from vinylsiloxanether impressions and digitized (S600 Arti). The scan/impression and post processing times were recorded. Reference and test scans were superimposed (GOM Inspect) to calculate 3D point, inter-implant distance, and angular deviations. Kruskal-Wallis and Mann-Whitney tests were used for trueness and precision analyses (α=.05). ResultsTested workflows affected trueness (P≤.030) and precision (P<.001) of scans (3D point, inter-implant distance, and angular deviations) within models. DDW-P had the highest accuracy (3D point deviations) for models 1 and 3 (P≤.046). IDW had the lowest accuracy for model 2 (P<.01). DDW-P had the highest accuracy (inter-implant distance deviations) for model 3 (P≤.048). Direct digital workflow mostly led to lower angular deviations (P≤.040), and higher precision for models 2 (mesiodistal direction) and 3 (P<.001). The time for direct digital workflow was shorter (P<.001), DDW-P being more efficient than DDW-T (P=.008). ConclusionDirect digital workflow was more accurate and efficient than indirect digital workflow in tested partial edentulism situations with 2 implants. Clinical significanceTested intraoral scanners can be recommended for accurate and efficient impressions of anterior and posterior 3- or 4-unit implant-supported fixed partial dentures.

Understanding the Benefit of Magnetic Resonance-guided Adaptive Radiotherapy in Rectal Cancer Patients: a Single-centre Study

AimsNeoadjuvant chemoradiotherapy followed by surgery is the mainstay of treatment for patients with rectal cancer. Standard clinical target volume (CTV) to planning target volume (PTV) margins of 10 mm are used to accommodate inter- and intrafraction motion of target. Treating on magnetic resonance-integrated linear accelerators (MR-linacs) allows for online manual recontouring and adaptation (MRgART) enabling the reduction of PTV margins. The aim of this study was to investigate motion of the primary CTV (CTVA; gross tumour volume and macroscopic nodes with 10 mm expansion to cover microscopic disease) in order to develop a simultaneous integrated boost protocol for use on MR-linacs. Materials and methodsPatients suitable for neoadjuvant chemoradiotherapy were recruited for treatment on MR-linac using a two-phase technique; only the five phase 1 fractions on MR-linac were used for analysis. Intrafraction motion of CTVA was measured between pre-treatment and post-treatment MRI scans. In MRgART, isotropically expanded pre-treatment PTV margins from 1 to 10 mm were rigidly propagated to post-treatment MRI to determine overlap with 95% of CTVA. The PTV margin was considered acceptable if overlap was >95% in 90% of fractions. To understand the benefit of MRgART, the same methodology was repeated using a reference computed tomography planning scan for pre-treatment imaging. ResultsIn total, nine patients were recruited between January 2018 and December 2020 with T3a-T4, N0–N2, M0 disease. Forty-five fractions were analysed in total. The median motion across all planes was 0 mm, demonstrating minimal intrafraction motion. A PTV margin of 3 and 5mm was found to be acceptable in 96 and 98% of fractions, respectively. When comparing to the computed tomography reference scan, the analysis found that PTV margins to 5 and 10 mm only acceptably covered 51 and 76% of fractions, respectively. ConclusionPTV margins can be reduced to 3–5 mm in MRgART for rectal cancer treatment on MR-linac within an simultaneous integrated boost protocol.

Influence of the Angulation and Insertion Depth of Implants on the 3D Trueness of Conventional and Digital Impressions

To study the influence of insertion depth and implant angulation on the 3D trueness of models obtained with different impression techniques. Four different reference models (model 1: parallel, depth of 1.5 mm; model 2: parallel, depth of 4 mm; model 3: 20-degree angle, depth of 1.5 mm; and model 4: 20-degree angle, depth of 4 mm) of partially edentulous maxillae were generated by altering implant angulations and subgingival depths. All scans of reference models were done with a laboratory scanner, and obtained data were exported into standard tessellation language format to be used as virtual reference images. Impressions were obtained from each reference model via three conventional techniques (closed tray [CT], non-hexed open tray [NHOT], and hexed open tray [HOT]) and one digital technique (intraoral scanning [IOS]). A total of 160 impressions were made. The reference and experimental scan data were superimposed by using the best-fit alignment algorithm. Angular (AD), linear (LD), and 3D (RMS) deviations were computed, and obtained data were statistically analyzed. In premolar implant sites, AD and LD values were significantly affected by model type (P ≤ .001 for AD and LD) and impression technique (P = .001 for AD, P = .002 for LD). However, no significant interaction was detected (P = .703 for AD, P = .768 for LD). Model 1 (0.44 ± 0.25 for AD, 7.79 ± 6.29 for LD) and the NHOT technique (0.49 ± 0.43 for AD, 9.04 ± 8.14 for LD) exhibited the lowest mean AD and LD values. In molar implant sites, AD and LD values were significantly affected by model type (P ≤ .001 for AD and LD) and impression technique (P ≤ .001 for AD and LD), as well as by their interaction terms (P = .037 for AD, P = .005 for LD). Considering interaction terms, while the highest and lowest mean AD values were exhibited by IOS-model 4 (1.56 ± 0.25) and NHOTmodel 2 (0.46 ± 0.28), respectively, the highest and lowest mean LD values were exhibited by CT-model 4 (41.40 ± 14.48) and NHOT-model 2 (8.03 ± 4.86), respectively. RMS estimate values were significantly influenced by model type (P ≤ .001) and impression technique (P ≤ .001), as well as by their interaction terms (P = .019). The highest and lowest mean RMS values were exhibited by IOS-model 4 (70.02 ± 4.74) and NHOT-model 2 (25.96 ± 17.67), respectively. In the case of angulated and deeply placed implants, splinted NHOT and HOT techniques can be recommended for better trueness.

Accelerated 4D-flow MRI with 3-point encoding enabled bymachine learning.

To investigate the acceleration of 4D-flow MRI using a convolutional neural network (CNN) that produces three directional velocities from three flow encodings, without requiring a fourth reference scan measuring background phase. A fully 3D CNN using a U-net architecture was trained in a block-wise fashion to take complex images from three flow encodings and to produce three real-valued images for each velocity component. Using neurovascular 4D-flow scans (n=144), the CNN was trained to predict velocities computed from four flow encodings by standard reconstruction including correction for residual background phase offsets. Methods to optimize loss functions were investigated, including magnitude, complex difference, and uniform velocity weightings. Subsequently, 3-point encoding was evaluated using cross validation of pixelwise correlation, flow measurements in major arteries, and in experiments with data at differing acceleration rates than the training data. The CNN-produced 3-point velocities showed excellent agreements with the 4-point velocities, both qualitatively in velocity images, in flow rate measures, and quantitatively in regression analysis (slope=0.96, R2 =0.992). Optimizing the training to focus on vessel velocities rather than the global velocity error and improved the correlation of velocity within vessels themselves. The lowest error was observed when the loss function used uniform velocity weighting, in which the magnitude-weighted inverse of the velocity frequency uniformly distributed weighting across all velocity ranges. When applied to highly accelerated data, the 3-point network maintained a high correlation with ground truth data and demonstrated a denoising effect. The 4D-flow MRI can be accelerated using machine learning requiring only three flow encodings to produce three-directional velocity maps with small errors.

The effect of respiration-induced target motion on 3D magnetic resonance images used to guide radiotherapy

3D Magnetic Resonance Imaging (MRI) is used in radiation therapy for reference planning and, lately, for adaptive treatments on MR accelerators. This study aimed to investigate the impact of different types of respiratory motion on the apparent target position and extent in such scans. An MRI motion phantom with a 30mm diameter target was used to simulate cranial-caudal (CC) motion and imaged at an MR-Linac using a standard clinically released 3D T2w sequence. Scans were acquired for each combination of functions (sin(t), sin4(t) and sin12(t)), peak-to-peak amplitudes(5, 10, 15 and 20mm), and periods (4, 5 and 6s). Furthermore, respiration CC motion patterns fromtwo patients were used. Motion functions were shifted such that the time average target position would match a static reference scan at 0-position. The target was automatically identified in coronal and sagittal images using k-means clustering. The mean position and area of the target were calculated and compared to the reference scan. Artefacts increased with amplitude and depended on the motion type. Sin(t) and sin4(t) oscillations resulted in a blurring of the target, which led to an increased target area, while sin12(t) motion did not show significant changes in the target area. However, for the sin12(t) motion, the offset in apparent position was prominent, while that was not the case for the sin(t) and sin4(t) motion. The patient respiration motion profiles showed similar trends. In 3D MRI, target motion can change apparent tumour extent and apparent position. The changes increase with motion amplitude and depend on the motion type.

Comparative evaluation of the accuracy of the dental arch display using modern intraoral three-dimensional scanners

BACKGROUND: At present, modern dentists used dental intraoral three-dimensional (3D) scanners routinely in their daily work. Obtaining an optical 3D image of the teeth and dentition helps avoid errors at the stage of obtaining traditional silicone impressions and significantly reduces the level of discomfort during dental procedures. Intraoral scanner systems are commercially available today. Despite their advantages over traditional silicone impressions, the accuracy of the optical impressions obtained during total and subtotal prosthetics on the upper and lower jaw are still questionable.&#x0D; AIM: This study aimed to evaluate the accuracy of scanning models of the patients dentition obtained using intraoral scanners and to determine the currently available models of digital devices that are optimal in terms of price and quality.&#x0D; MATERIAL AND METHODS: The reference scan (master model) was an optical image of the reference model of the upper jaw of a patient with a full dentition made by additive 3D-printing technology obtained using a laboratory scanner. To level out the shrinkage errors of photopolymerization materials, the resulting model was scanned on the same day using intraoral scanners selected for the study. The obtained scan results were compared with the reference scan of the control group. Based on the measurements made at reference points, the average error value relative to the master model and its precision were calculated for each scanner. In addition to the average values, the error parameters of the scanners in the frontal and chewing sections were calculated, as well as the arc error, which was equal to the difference in the values of the discrepancy at the reference points at which the maximum and minimum values were obtained. The cost and availability of scanners on the domestic market, under the sanctions policy of foreign countries, were also considered.&#x0D; RESULTS: The CEREC Primescan AC scanner showed the best accuracy according to the results of model discrepancies. It has an average error of 13.727.34. The arc error was 18.8 microns, and the discrepancies in the frontal area and chewing area were 18 and 6.8 microns, respectively. 3Shape Trios 3 scanner has the closest accuracy, with an average error of 16.285.94 microns. The error value of Aoralscan 3 was 42.0818.34 microns, its arc accuracy was 65 microns, and the discrepancies in the frontal and chewing areas were 33 and 55.1 microns, respectively. Emerald S Mode C had an average error of 35.8422.29 microns, which was higher than that of Medit i500 and Aoralscan 3; however, Aoralscan 3 showed better precision (18.34 microns versus 22.29 microns). According to the comparison results of the models in the MeshLab program, CEREC Primescan AC showed the smallest median of distances (18 microns). The TRIOS 3 and Emerald S Mode C differed from the standard by an average of 29 microns, and Aoralscan 3 scanners had of 33 microns and Medit i500 had 41 microns.&#x0D; CONCLUSION: The precision of Aoralscan 3 scanner, which is the best among its analogs in the price category, makes it the most affordable scanner for dental surgical, orthodontic, and orthopedic fields. CEREC Primescan AC is the leader of the premium scanners involved in the study and available in the dental market.

Influence of the surface humidity, implant angulation, and interimplant distance on the accuracy and scanning time of complete-arch implant scans

ObjectivesTo assess the influence of implant angulation, humidity, and interimplant distance on the accuracy and scanning time of complete-arch implant scans. MethodsA definitive cast with 4 parallel implant abutment analogs (P group), and another cast with 4 angulated (up to 30 degrees) implant abutment analogs (NP group) were digitized by using a scanner (7Series) (reference scans). Two subgroups were created: dry (D subgroup) and wet (W subgroup). For the D subgroup, the casts were digitized without altering the surface humidity by using an intraoral scanner (IOS) (TRIOS 3). For the W subgroup, the cast surface was humidified with artificial saliva and digitized by using the same IOS. The interimplant distance discrepancies were assessed by computing linear and angular measurements. Trueness data was analyzed using 3-way ANOVA followed by the pairwise comparison Tukey tests. The Bartlett test, followed by the pairwise comparison tests, was used to assess the precision (α=.05). ResultsRegarding the trueness, implant angulation (P<.001) and inter-implant distance measurement (P<.001) influenced the linear discrepancies. Implant angulation (P=.002), humidity conditions (P<.001), and inter-implant distance (P=.001) influenced the angular discrepancies. Regarding the precision, significant differences in the variance of linear and angular measurements and inter-implant distances were found. Humidity conditions (P<.001) influenced the scanning time. ConclusionsImplant angulation, humidity, and interimplant distance influenced the accuracy and scanning time of complete-arch implant scans. Parallel implants resulted in higher trueness and precision values. Dry conditions resulted in slightly higher scanning trueness and precision and shorter scanning time. Clinical significanceDrying the surface being scanned increases intraoral scanning accuracy and decreases intraoral scanning time.

Scanning Accuracy of 10 Intraoral Scanners for Single-crown and Three-unit Fixed Denture Preparations: An In Vitro Study.

To evaluate the accuracy of 10 intraoral scanners for single-crown and three-unit preparation models. A maxillary partially edentulous model was fabricated. A dental cast scanner was used to obtain standard tessellation language (STL) data. Ten intraoral scanners, namely Trios 2 (TR2; 3Shape, Copenhagen, Denmark), True Definition (TD; 3M, Saint Paul, MN, USA), CEREC AC Omnicam (OM; Dentsply Sirona, Charlotte, NC, USA), Organical Scan Oral (OS; R+K, Berlin, Germany), PlanScan (PS; Planmeca, Helsinki, Finland), DWIOP (DW; Dental Wings, Montreal, Canada), Xianlin (XL; Hangzhou Xianlin, Hangzhou, China), DL-100 (DL; Guangzhou Longcheng, Guangzhou, China), Trios 3 (TR3; 3Shape) and i500 (MD; MEDIT, Seoul, South Korea) were used to obtain stereolithography data as test groups. Trueness, precision and surface accuracy were evaluated by deviation analysis using 3D image processing software. One tooth with a three-unit preparation for each test group was registered with the reference scan data, and the absolute distance from another tooth was calculated as the absolute accuracy. The data were analysed using a Mann-Whitney U test and Dunn-Bonferroni test (α = 0.05). The best trueness, precision and surface accuracy of scanning single crown preparation were recorded with TD (trueness 2.9 μm and precision 1.9 μm) and XL (surface accuracy 20.3 ± 2.9 μm). The best trueness, precision, surface accuracy and absolute accuracy of three-unit preparations were recorded with TD (2.6 μm), XL (1.9 μm), OM (27.1 ± 5.2 μm) and TR3 (79.2 ± 19.6 μm), respectively. There was no statistically significant difference in trueness between single- and multiple-unit preparations for any of the intraoral scanners (P > 0.05). A statistically significant difference in the surface accuracy between single and multiple preparations was found for TR2, TD, OM, DW, XL, DL and MD (P < 0.05). The trueness and precision of intraoral scanners for scanning three-unit preparations were nearly the same as those for single-crown preparations; however, with the exception of OS, PS and TR3, the surface accuracy of single-crown preparations was significantly better than that for three-unit preparations.

Artifact suppression in readout-segmented consistentK-tspace EPSI (RS-COKE) for fast 1 H spectroscopic imagingat7 T.

Fast proton (1 H) MRSI is an important diagnostic tool for clinical investigations, providing metabolic and spatial information. MRSI at 7T benefits from increased SNR and improved separation of peaks but requires larger spectral widths. RS-COKE (Readout-Segmented Consistent K-t space Epsi) is an echo planar spectroscopic imaging (Epsi) variant capable to support the spectral width required for human brain metabolites spectra at 7T. However, mismatches between readout segments lead to artifacts, particularly when subcutaneous lipid signals are not suppressed. In this study, these mismatches and their effects are analyzed and reduced. The following corrections to the data were performed: i) frequency-dependent phase corrections; ii) k-space trajectory corrections, derived from short reference scans; and iii) smoothing of data at segment transitions to mitigate the effect of residual mismatches. The improvement was evaluated by performing single-slice RS-COKE on a head-shaped phantom with a "lipid" layer and healthy subjects, using varying resolutions and durations ranging from 4.1 × 4.7 × 15 mm3 in 5:46 min to 3.1 × 3.3 × 15 mm3 in 13:07 min. Artifacts arising from the readout-segmented acquisition were substantially reduced, thus providing high-quality spectroscopic imaging in phantom and human scans. LCModel fitting of the human data resulted in a relative Cramer-Rao lower bounds within 6% for NAA, Cr, and Cho images in the majority of the voxels. Using the new reference scans and reconstruction steps, RS-COKE was able to deliver fast 1 H MRSI at 7T, overcoming the spectral width limitation of standard EPSI at this field strength.

Valuable Techniques for Repeatable Absorbance Measurements

Spectroscopy offers a range of available techniques that can be differentiated by the use or omission of reference spectra. This differentiation means that techniques such as Raman or fluorescence typically look at raw intensity outputs, whereas techniques such as transmission or reflectance require some reference scan to calculate those relative outputs. Within the group of referenced spectral techniques, absorbance is easily one of the most common and offers much value because of the concentration dependence of Beer’s Law. However, this value is only properly captured when system components and samples are made to be repeatable, both for the reference scans and live acquisitions. This article discusses several useful techniques to establish this repeatability, including proper cuvette and probe handling, component setup, and sample considerations. By optimizing repeatability of the measurement system, the observed concentration values calculated from absorbance outputs are much more accurate and relevant to the sample being measured.

In vitro scanning accuracy using different aids for multiple implants in the edentulous arch.

Optical impressions of implants in the edentulous arch are challenged by the absence of distinct surface morphology between multiple implant scan bodies. The purpose of this in vitro study was to evaluate a newly developed scan aid in various designs and colors to improve the accuracy of multi-implant scans. A universal scan aid in three different designs (circular, square, irregular) and three different materials (colors: beige, gray, white) was applied to the implant scan bodies of a master model of six implants in an edentulous maxilla. Ten scans using an intra-oral scanner of each scan aid were acquired. Reference scanning was performed using a desktop optical scanner. Alignment of scans was performed at the first scan body in a three-dimensional modeling and inspection software and deviations for trueness and precision were calculated using the signed nearest-neighbor method and then statistically analyzed (α=.05). Overall, the beige irregular scan aid had the highest trueness and showed significant differences compared to unsplinted scans. The precision showed more heterogenous results and decreased when using the scan aid. Ease of use was observed with the irregular gray scan aid due to its increased elongation at break. The evaluated scan aid led to improved trueness when compared to unsplinted scans. Even though the irregular design in beige color showed highest trueness, the poor fracture strength of the tested material requires further improvement.

Effect of Scanned Area and Operator on the Accuracy of Dentate Arch Scans with a Single Implant.

Studies have shown the effect of the operator and scanned areas on the accuracy of single implant scans. However, the knowledge on the scan accuracy of the remaining dental arch during single implant scans, which may affect the occlusion, is limited. The aim of this study was to investigate the effect of scanned areas and the operator on the scan accuracy of a dentate arch while scanning a single implant. A dentate model with an anterior implant was digitized with a laboratory scanner (reference scan). Three operators with similar experience performed 10 complete- and 10 partial-arch scans (left 2nd molar to right canine) with an intraoral scanner (TRIOS 3), and these scans were superimposed over the reference. The accuracy was analyzed at 22 points in complete-arch and at 16 points in partial-arch scans on 2nd molars and incisors. Data were evaluated with 2-way ANOVA and Tukey HSD tests (α = 0.05). The trueness of the total scanned area was higher in partial- than in complete-arch scans (p < 0.001). The trueness and precision of the scans were higher in the anterior site compared with the posterior in complete- (trueness: p ≤ 0.022, precision: p ≤ 0.003) and partial-arch (trueness: p ≤ 0.016, precision: p ≤ 0.016) scans of each operator and when the operator scan data were pooled. The complete-arch scan’s precision was not influenced by the operator (p ≥ 0.029), whereas the partial-arch scans of operator 1 and 2 were significantly different (p = 0.036). Trueness was higher in partial- compared with complete-arch scans, but their precision was similar. Accuracy was higher in the anterior site regardless of the scan being a partial- or a complete-arch. The operator’s effect on the accuracy of partial- and complete-arch scans was small.