Validation of single reference variable flip angle (SR-VFA) dynamic T1 mapping with T2 * correction using a novel rotating phantom

PURPOSE

To validate single reference variable flip angle (SR-VFA) dynamic T1 mapping with and without T2 * correction against inversion recovery (IR) T1 measurements.

METHODS

A custom cylindrical phantom with three concentric compartments was filled with variably doped agar to produce a smooth spatial gradient of the T1 relaxation rate as a function of angle across each compartment. IR T1 , VFA T1 , and B1 + measurements were made on the phantom before rotation, and multi-echo stack-of-radial dynamic images were acquired during rotation via an MRI-compatible motor. B1 + -corrected SR-VFA and SR-VFA-T2 * T1 maps were computed from the sliding window reconstructed images and compared against rotationally registered IR and VFA T1 maps to determine the percentage error.

RESULTS

Both VFA and SR-VFA-T2 * T1 maps fell within 10% of IR T1 measurements for a low rotational speed, with a mean accuracy of 2.3% ± 2.6% and 2.8% ± 2.6%, respectively. Increasing rotational speed was found to decrease the accuracy due to increasing temporal smoothing over ranges where the T1 change had a nonconstant slope. SR-VFA T1 mapping was found to have similar accuracy as the SR-VFA-T2 * and VFA methods at low TEs (˜<2 ms), whereas accuracy degraded strongly with later TEs. T2 * correction of the SR-VFA T1 maps was found to consistently improve accuracy and precision, especially at later TEs.

CONCLUSION

SR-VFA-T2 * dynamic T1 mapping was found to be accurate against reference IR T1 measurements within 10% in an agar phantom. Further validation is needed in mixed fat-water phantoms and in vivo.

Deadwood Amount at Disturbance Plots after Sanitary Felling

Deadwood is an important component of forests that fulfils many ecosystem functions. The occurrence, amount and spatial distribution of deadwood in forest ecosystems depend on tree species composition, historical development and past management. In this presented study, we assessed the total amount of deadwood, including fine and coarse woody debris at five areas of predominantly broadleaved forests within the University Forest Enterprise of the Technical University in Zvolen, Slovakia that had been disturbed by windstorm Žofia in 2014. Windthrown wood was salvaged between May 2014 and October 2015. In the year 2018, we performed an inventory of deadwood that remained on-site after salvage logging. The mean volume of deadwood recorded at sample plots fluctuated between 35.96 m³/ha and 176.06 m³/ha and mean deadwood coverage values at individual disturbed areas ranged from 7.27 to 17.91%. In the work, we derived several models for the estimation of deadwood volume based on deadwood coverage and/or diameter, which showed that these characteristics are good proxies of deadwood volume. The tests, involving close-range photogrammetry methods for deadwood quantification, revealed that the number of pieces and the coverage of deadwood recorded in photos was significantly lower than the values derived from field measurements.

Effects of T2 * on accuracy and precision of dynamic T1 measurements using the single reference variable flip angle method - a simulation study

PURPOSE

To study in simulation and in theory the accuracy and precision of dynamic T₁ measurements obtained using the previously published single-reference variable flip angle (SR-VFA) technique, with a focus on the effects of dynamic changes in T₂ * on the calculation.

METHODS

Monte Carlo simulations were performed over 1000 noisy iterations for the VFA method, the SR-VFA method, and a proposed method, SR-VFA with a T₂ * correction (SR-VFA-T₂ *). Dynamic T₁ estimates were calculated analytically for each method, with signals modeled by the steady-state spoiled gradient echo equation. The mean and standard deviation of these estimates were calculated and compared to truth, while varying repetition time (TR), baseline and dynamic T₁ , echo time (TE), baseline and dynamic T₂ *, flip angles, and the number of averages on baseline scans. Additionally, the variance of T₁ in the SR-VFA and SR-VFA-T₂ * methods was derived analytically based on the theory of propagation of errors. This equation was used to produce an inverse-variance weighted linear combination to improve T₁ mapping precision in the SR-VFA-T₂ * method. Flip angle sensitivity of dynamic T₁ precision in the SR-VFA and SR-VFA-T₂ * methods was also performed.

RESULTS

Substantial bias can be produced by the SR-VFA method when the ratio of the T₂ * decay of the dynamic signal versus that of the baseline signals deviates from 1, with a 0.01 deviation leading to approximately a 1% bias in cases of high SNR and TR ≫ T₁ . This bias can be corrected by estimating the baseline and dynamic T₂ * values in this ratio via multi-echo measurements. The bias and precision of the SR-VFA-T₂ * method, when normalized to scan time, is found to rival and sometimes improve upon the two flip angle VFA method when an inverse variance weighted linear combination is applied across its multi-echo T₁ maps. The analytic variance equation presented is found to be accurate within 1% relative to the Monte Carlo simulations over a broad parameter space. Flip angle ranges that maximize SR-VFA and SR-VFA-T₂ * T₁ precision over a broad parameter space are given, and each is defined relative to TR and T₁ .

CONCLUSIONS

Multi-echo SR-VFA-T₂ * T₁ mapping is found in simulation and theory to be a promising alternative to the VFA method that maintains speed of the SR-VFA method with accuracy and precision similar to the VFA method. This article is protected by copyright. All rights reserved.

A study on accuracy and precision of fluid volume measurements by nurses, patients and healthy persons in a clinical setting

AIM

To evaluate the accuracy and precision for assessing fluid intake by examining the ability of nurses, patients and healthy people to visually estimate fluid volumes, thereby reflecting the fluid monitoring process in clinical practice.

DESIGN

A cross-sectional study.

METHODS

This study used the convenience sampling method and involved twenty-five participants from three groups; nurses, patients and healthy people. The participants carried out a set of different visual volume assessments of two types of fluids using two fluid containers. The exact volumes were measured, and the results were compared with the target volumes.

RESULTS

High variations were observed in the fluid volume assessments for patients, nurses and healthy persons and also were observed to be an effect of environmental factors (fluid container or fluid type) on volume perceptions. This highlights the importance of finding new and innovative ways of measuring fluids for oral intake in a hospital setting, to ensure accurate and reliable data on fluid balance and thereby increase patient safety.

The "Painting by Numbers Method" for education of students in crown preparation

INTRODUCTION

No commercially available solution to improve the teaching of a crown preparation directly on typodont teeth exists at the moment. To fill this gap and support the supervisors of dental courses, a printable and inexpensive tooth was created for structured self-assessment. The aim of this study was to test this printable tooth under realistic pre-clinical situations.

MATERIALS AND METHODS

A two-coloured, double-layer practice tooth was developed. This tooth was consisting of a layer for a correct preparation and the crown. All printed teeth were produced with a stereolithographic printer. 35 voluntary second-year dental students in the second pre-clinical course in prosthodontics were randomly divided into two groups. All students had experience with typodont teeth and models. The first group was trained on four standard model teeth. The second group used model teeth for the first and fourth attempt and printed teeth for second and third attempt. The preparations of the students were scanned by an in-lab scanner and the surface deviations in contrast to a perfect preparation were measured. The differences between the first and fourth attempt were calculated. Benefits of the printed tooth were also evaluated by a questionnaire using German school grades completed by the students (1 = Excellent, 2 = Good, 3 = Satisfactory, 4 = Adequate, 5 = Poor, 6 = Unsatisfactory).

RESULTS

The workflow was feasible and cost-effective regarding the production of the printed teeth. The overall rating of the printed tooth in the questionnaire was good (Ø 2.1 ± 0.22). Students reported different advantages of this method in the free text. The comparison of the preparation between the first and fourth attempt showed that there was a significant better preparation with the printed teeth. The complete preparation had median values of 0.05 mm (Group1: standard model tooth) and -0.03 mm (Group2: printed tooth) (P = .005). Divided into single surfaces, the vestibular and occlusal regions were significantly better. The vestibular surface was 0.11 mm (Group1) and -0.04 mm (Group2) (P = .018). The occlusal surface was 0.13 mm (Group1) and -0.05 mm (Group2) (P = .009).

CONCLUSIONS

The aim of this study was fulfilled. The printed tooth was tested successfully in a pre-clinical course. The feasibility of this teaching concept was confirmed by the questionnaire and the analysis of the preparation form. A significant difference to a standard model tooth was measurable. The students had the possibility to learn a correct crown preparation on a standardised two-layered tooth with included preparation. This printed tooth enabled the students to control the crown preparation directly on their own.

Nanoscale Resolution 3D Snapshot Particle Tracking by Multifocal Microscopy

Accurate, precise, and rapid particle tracking in three dimensions remains a challenge; yet, its achievement will significantly enhance our understanding of living systems. We developed a multifocal microscopy (MFM) that allows snapshot acquisition of the imaging data, and an associated image processing approach, that together allow simultaneous 3D tracking of many fluorescent particles with nanoscale resolution. The 3D tracking was validated by measuring a known trajectory of a fluorescent bead with an axial accuracy of 19 nm through an image depth (axial range) of 3 μm and 4 nm precision of axial localization through an image depth of 4 μm. A second test obtained a uniform axial probability distribution and Brownian dynamics of beads diffusing in solution. We also validated the MFM approach by imaging fluorescent beads immobilized in gels and comparing the 3D localizations to their "ground truth" positions obtained from a confocal microscopy z-stack of finely spaced images. Finally, we applied our MFM and image processing approach to obtain 3D trajectories of insulin granules in pseudoislets of MIN6 cells to demonstrate its compatibility with complex biological systems. Our study demonstrates that multifocal microscopy allows rapid (video rate) and simultaneous 3D tracking of many "particles" with nanoscale accuracy and precision in a wide range of systems, including over spatial scales relevant to whole live cells.

Accuracy and precision of electrical permittivity mapping at 3T: the impact of three B 1 + mapping techniques

Purpose

To investigate the sequence‐specific impact of B1+ amplitude mapping on the accuracy and precision of permittivity reconstruction at 3T in the pelvic region.

Methods

B1+ maps obtained with actual flip angle imaging (AFI), Bloch–Siegert (BS), and dual refocusing echo acquisition mode (DREAM) sequences, set to a clinically feasible scan time of 5 minutes, were compared in terms of accuracy and precision with electromagnetic and Bloch simulations and MR measurements. Permittivity maps were reconstructed based on these B1+ maps with Helmholtz‐based electrical properties tomography. Accuracy and precision in permittivity were assessed. A 2‐compartment phantom with properties and size similar to the human pelvis was used for both simulations and measurements. Measurements were also performed on a female volunteer’s pelvis.

Results

Accuracy was evaluated with noiseless simulations on the phantom. The maximum B1+ bias relative to the true B1+ distribution was 1% for AFI and BS and 6% to 15% for DREAM. This caused an average permittivity bias relative to the true permittivity of 7% to 20% for AFI and BS and 12% to 35% for DREAM. Precision was assessed in MR experiments. The lowest standard deviation in permittivity, found in the phantom for BS, measured 22.4 relative units and corresponded to a standard deviation in B1+ of 0.2% of the B1+ average value. As regards B1+ precision, in vivo and phantom measurements were comparable.

Conclusions

Our simulation framework quantitatively predicts the different impact of B1+ mapping techniques on permittivity reconstruction and shows high sensitivity of permittivity reconstructions to sequence‐specific bias and noise perturbation in the B1+ map. These findings are supported by the experimental results.

Using virtual reality for drug discovery: a promising new outlet for novel leads

Introduction: Virtual reality (VR) environments are increasingly being used by researchers in various fields in addition to being increasingly integrated into various areas of human life, ranging from videogames to different industrial uses. VR can be used to create interactive and multimodal sensory stimuli and thus offers unique advantages over other computer-based approaches for scientific research and molecular-level applications. Consequently, VR is starting to be used in novel drug development, such as in drug discovery, and rational drug design. Areas covered: In this review, the authors discuss the basic development of VR technology, including the available hardware and software. The latest advances of VR technology in novel drug development are then detailed, and the VR programs that can be applied in relevant studies are highlighted. Expert opinion: VR will lead to a revolution in pharmaceutical development. However, there are still obstacles to the successful and extensive application of VR to drug development, including the demand for further improvements to the available hardware and software and the various limitations described with regard to accuracy and precision. As technology continues to improve, the barriers to the widespread adoption of VR will diminish and VR technologies will play an increasingly important role in novel drug development.

Blood Pressure Recording Practices Among Dental Hygiene Students

Purpose: The purpose of this study was to compare three different types of blood pressure (BP) recording devices (an automated arm cuff, an automated wrist cuff, and a manual cuff / stethoscope combination) for accuracy, patient comfort, and ease of operation.Methods: Three types of sphygmomanometers were tested on 150 study participants (n=150) obtained from the patients presenting for dental hygiene services at an urban dental school in the Midwest. Descriptive statistics were calculated for all variables of interest by cuff type. Repeated measures ANOVA using the Greenhouse-Geisser adjustment were used to test for differences in means in BP and rating measure by cuff type. Post-hoc comparisons using Tukey's procedure were calculated to determine pair-wise differences. An association between the cuff type and convenience rating was evaluated using the Chi-square test, and between cuff type and convenience rating using the Fisher's exact test.Results: There was a significant difference in systolic BP recording by cuff type (p<0.001). The automatic wrist cuff recorded an average of 11.30mm and 8.76mm HG higher systolic BP than the standard cuff and the automatic arm cuff respectively (p<0.001 for both). There was no significant difference in the systolic BP readings between the standard and automatic arm cuff (p=0.226) nor was there a significant difference in diastolic BP by cuff type (p=0.137).Conclusion: Blood pressure cuff readings with traditional sphygmomanometer and stethoscope or an automated brachial cuff are comparable while wrist cuff BP readings deviated significantly. For consistency in blood pressure readings, the three different cuff types are not interchangeable.

Data collection, handling, and fitting strategies to optimize accuracy and precision of oxygen uptake kinetics estimation from breath-by-breath measurements

Phase 2 pulmonary oxygen uptake kinetics (ϕ2 τV̇o_2P) reflect muscle oxygen consumption dynamics and are sensitive to changes in state of training or health. This study identified an unbiased method for data collection, handling, and fitting to optimize V̇o_2P kinetics estimation. A validated computational model of V̇o_2P kinetics and a Monte Carlo approach simulated 2 × 10⁵ moderate-intensity transitions using a distribution of metabolic and circulatory parameters spanning normal health. Effects of averaging (interpolation, binning, stacking, or separate fitting of up to 10 transitions) and fitting procedures (biexponential fitting, or ϕ2 isolation by time removal, statistical, or derivative methods followed by monoexponential fitting) on accuracy and precision of V̇o_2P kinetics estimation were assessed. The optimal strategy to maximize accuracy and precision of τV̇o_2P estimation was 1-s interpolation of 4 bouts, ensemble averaged, with the first 20 s of exercise data removed. Contradictory to previous advice, we found optimal fitting procedures removed no more than 20 s of ϕ1 data. Averaging method was less critical: interpolation, binning, and stacking gave similar results, each with greater accuracy compared with analyzing repeated bouts separately. The optimal procedure resulted in ϕ2 τV̇o_2P estimates for transitions from an unloaded or loaded baseline that averaged 1.97 ± 2.08 and 1.04 ± 2.30 s from true, but were within 2 s of true in only 47-62% of simulations. Optimized 95% confidence intervals for τV̇o_2P ranged from 4.08 to 4.51 s, suggesting a minimally important difference of ~5 s to determine significant changes in τV̇o_2P during interventional and comparative studies.NEW & NOTEWORTHY We identified an unbiased method to maximize accuracy and precision of oxygen uptake kinetics (τV̇o_2P) estimation. The optimum number of bouts to average was four; interpolation, bin, and stacking averaging methods gave similar results. Contradictory to previous advice, we found that optimal fitting procedures removed no more than 20 s of phase 1 data. Our data suggest a minimally important difference of ~5 s to determine significant changes in τV̇o_2P during interventional and comparative studies.

Customization of UWB 3D-RTLS Based on the New Uncertainty Model of the AoA Ranging Technique

The increased potential and effectiveness of Real-time Locating Systems (RTLSs) substantially influence their application spectrum. They are widely used, inter alia, in the industrial sector, healthcare, home care, and in logistic and security applications. The research aims to develop an analytical method to customize UWB-based RTLS, in order to improve their localization performance in terms of accuracy and precision. The analytical uncertainty model of Angle of Arrival (AoA) localization in a 3D indoor space, which is the foundation of the customization concept, is established in a working environment. Additionally, a suitable angular-based 3D localization algorithm is introduced. The paper investigates the following issues: the influence of the proposed correction vector on the localization accuracy; the impact of the system's configuration and LS's relative deployment on the localization precision distribution map. The advantages of the method are verified by comparing them with a reference commercial RTLS localization engine. The results of simulations and physical experiments prove the value of the proposed customization method. The research confirms that the analytical uncertainty model is the valid representation of RTLS' localization uncertainty in terms of accuracy and precision and can be useful for its performance improvement. The research shows, that the Angle of Arrival localization in a 3D indoor space applying the simple angular-based localization algorithm and correction vector improves of localization accuracy and precision in a way that the system challenges the reference hardware advanced localization engine. Moreover, the research guides the deployment of location sensors to enhance the localization precision.

Radiostereometric analysis using clinical radiographic views: Validation measuring total hip replacement wear

Radiostereometric analysis (RSA) is a stereo X-ray technique used in clinical research studies to evaluate micro-motion and wear of orthopaedic implants within bone. While highly accurate and precise, its adoption has been limited due to technical requirements such as the need for implanted marker beads and radiograph view angles determined by a calibration cage. We propose a new technique that separates the calibration procedure from the patient examination, enabling clinical radiograph views to be used for RSA measurements. The concept of a reference plate was adapted to establish the link between calibration procedure and patient examination procedure for cassette radiography, which may not be necessary for digital radiography. A hip wear phantom was used to validate this technique by comparing the error and repeatability of the novel procedure with that of conventional RSA. Femoral head penetration was measured versus the acetabular cup (head/cup) and marker beads in the acetabular liner (head/liner). Conventional RSA had lower inferior-superior average error (p = 0.03 for head/cup) while the modified RSA had lower anterior-posterior average error (p = 0.01). Average error was greater but not significantly so for the medial-lateral (p = 0.06) and 3D (p = 0.97) measurements. The head/liner method had lower average errors (p < 0.0001) for both procedures, but did not affect repeatability, which was similar between techniques. The novel procedure's average error and repeatability was therefore, similar to conventional RSA. This new technique could be applied to any joint with two clinical radiograph view angles pending further validation in subjects. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1521-1528, 2016.

Using the Fingerprinting Method to Customize RTLS Based on the AoA Ranging Technique

Real-time Locating Systems (RTLSs) have the ability to precisely locate the position of things and people in real time. They are needed for security and emergency applications, but also for healthcare and home care appliances. The research aims for developing an analytical method to customize RTLSs, in order to improve localization performance in terms of precision. The proposed method is based on Angle of Arrival (AoA), a ranging technique and fingerprinting method along with an analytically defined uncertainty of AoA, and a localization uncertainty map. The presented solution includes three main concerns: geometry of indoor space, RTLS arrangement, and a statistical approach to localization precision of a pair of location sensors using an AoA signal. An evaluation of the implementation of the customized RTLS validates the analytical model of the fingerprinting map. The results of simulations and physical experiments verify the proposed method. The research confirms that the analytically established fingerprint map is the valid representation of RTLS’ performance in terms of precision. Furthermore, the research demonstrates an impact of workspace geometry and workspace layout onto the RTLS’ performance. Moreover, the studies show how the size and shape of a workspace and the placement of the calibration point affect the fingerprint map. Withal, the performance investigation defines the most effective arrangement of location sensors and its influence on localization precision.

Reliability of CAD CAM technology in assessing crown preparations in a preclinical dental school environment

In order to use CAD CAM (Computer Aided Design, Computer Aided Manufacturing) technology as an assessment tool when evaluating the preclinical performance of dental students, it is imperative that one has confidence in the reliability of the process. In this study, a variety of alignment methods were compared to determine both the consistency and accuracy of each method. Although the "Tooth Dots Diagonal" method exhibited the best precision (coefficient of variation=5.4 percent), it also represented the least accurate method when compared to the other methods tested. Using "Small Dots Diagonal" on the gingiva appears to be the best option, exhibiting an acceptable coefficient of variation (17.6 percent) and a high degree of accuracy in terms of tolerance (mean ± standard deviation=0.163 ± 0.029). Based on the results of this study, further investigation of CAD CAM technology for the purpose of assessment and education of dental students is recommended.

Is the simple auger coring method reliable for below-ground standing biomass estimation in Eucalyptus forest plantations?

BACKGROUND AND AIMS

Despite their importance for plant production, estimations of below-ground biomass and its distribution in the soil are still difficult and time consuming, and no single reliable methodology is available for different root types. To identify the best method for root biomass estimations, four different methods, with labour requirements, were tested at the same location.

METHODS

The four methods, applied in a 6-year-old Eucalyptus plantation in Congo, were based on different soil sampling volumes: auger (8 cm in diameter), monolith (25 × 25 cm quadrate), half Voronoi trench (1·5 m(3)) and a full Voronoi trench (3 m(3)), chosen as the reference method.

KEY RESULTS

With the reference method (0-1m deep), fine-root biomass (FRB, diameter <2 mm) was estimated at 1·8 t ha(-1), medium-root biomass (MRB diameter 2-10 mm) at 2·0 t ha(-1), coarse-root biomass (CRB, diameter >10 mm) at 5·6 t ha(-1) and stump biomass at 6·8 t ha(-1). Total below-ground biomass was estimated at 16·2 t ha(-1) (root : shoot ratio equal to 0·23) for this 800 tree ha(-1) eucalypt plantation density. The density of FRB was very high (0·56 t ha(-1)) in the top soil horizon (0-3 cm layer) and decreased greatly (0·3 t ha(-1)) with depth (50-100 cm). Without labour requirement considerations, no significant differences were found between the four methods for FRB and MRB; however, CRB was better estimated by the half and full Voronoi trenches. When labour requirements were considered, the most effective method was auger coring for FRB, whereas the half and full Voronoi trenches were the most appropriate methods for MRB and CRB, respectively.

CONCLUSIONS

As CRB combined with stumps amounted to 78 % of total below-ground biomass, a full Voronoi trench is strongly recommended when estimating total standing root biomass. Conversely, for FRB estimation, auger coring is recommended with a design pattern accounting for the spatial variability of fine-root distribution.