A Comprehensive Study on Measurement Accuracy of Distributed Fiber Optic Sensors Embedded within Capillaries of Solid Structures

Embedding fiber optic sensors (FOSs) within parts for strain measurement is attracting widespread interest due to its great potential in the field of structural health monitoring (SHM). This work proposes a novel method of embedding FOSs using capillaries within solid structures and investigates fiber positions and orientation uncertainties within capillaries of different sizes and their influences on strain measurement accuracies. To investigate how the fiber positions and orientation variations influence strain measurement accuracy, both analytical and numerical models are utilized to predict strain distributions along embedded fibers at different positions and with different orientations within the specimen. To verify the predictions, a group of specimens made of Aluminum 6082 was prepared, and the specimens in each group had capillaries of 2 mm, 4 mm, and 6 mm diameters, respectively. Fibers were embedded within each specimen using the capillaries. Four-point bending static tests were conducted for each specimen with embedded FOSs, performing in situ strain measurement. Subsequently, the specimens were partitioned into several pieces, and the cross sections were observed to know the real positions of the embedded fiber. Finally, the strain predictions at the real locations of the fiber were compared with the measured strain from the embedded FOSs. The predicted strain distributions as a function of the fiber positions alone and as a function of both the fiber positions and orientations were compared to assess the influence of fiber orientation change. The results from a combination of analytical, numerical, and experimental techniques suggest that the fiber position from the capillary center is the main factor that can influence strain measurement accuracies of embedded FOSs, and potential fiber misalignments within the capillary had a negligible influence. The fiber position-induced measured error increases from 10.5% to 18.5% as the capillary diameter increases from 2 mm to 6 mm. A 2 mm capillary diameter is able to lead to the lowest measurement error in this study and maintains ease of embedding. In addition, it is found that the measured strain always lies within a strain window defined by the strain distribution along capillary boundaries when there are no cracks. This can be further studied for crack detection.

Respiratory Rate Estimation during Walking and Running Using Breathing Sounds Recorded with a Microphone

Emerging evidence suggests that respiratory frequency (f_R) is a valid marker of physical effort. This has stimulated interest in developing devices that allow athletes and exercise practitioners to monitor this vital sign. The numerous technical challenges posed by breathing monitoring in sporting scenarios (e.g., motion artifacts) require careful consideration of the variety of sensors potentially suitable for this purpose. Despite being less prone to motion artifacts than other sensors (e.g., strain sensors), microphone sensors have received limited attention so far. This paper proposes the use of a microphone embedded in a facemask for estimating f_R from breath sounds during walking and running. f_R was estimated in the time domain as the time elapsed between consecutive exhalation events retrieved from breathing sounds every 30 s. Data were collected from ten healthy subjects (both males and females) at rest and during walking (at 3 km/h and 6 km/h) and running (at 9 km/h and 12 km/h) activities. The reference respiratory signal was recorded with an orifice flowmeter. The mean absolute error (MAE), the mean of differences (MOD), and the limits of agreements (LOAs) were computed separately for each condition. Relatively good agreement was found between the proposed system and the reference system, with MAE and MOD values increasing with the increase in exercise intensity and ambient noise up to a maximum of 3.8 bpm (breaths per minute) and -2.0 bpm, respectively, during running at 12 km/h. When considering all the conditions together, we found an MAE of 1.7 bpm and an MOD ± LOAs of -0.24 ± 5.07 bpm. These findings suggest that microphone sensors can be considered among the suitable options for estimating f_R during exercise.

Accuracy of uncalibrated 2D digital subtraction angiography measurements on a novel biplane system compared to computed tomography angiography

BACKGROUND

2D digital subtraction angiography (DSA) images are the gold standard for neuroradiological vascular assessment and the basis of interventional procedures such as mechanical thrombectomy and cerebral aneurysm coiling. However, length measurements in projected DSA images are affected by the distance between the x-ray source, the object, and the detector. Precise coordination between all integrated parts of a novel biplane system makes it possible to accurately measure DSA distances without manual calibration. The aim of this study was to compare vascular diameter measurements in uncalibrated DSA images with computed tomography angiography (CTA).

METHODS

Consecutive patients undergoing interventional neuroradiological procedures were retrospectively included. Vascular diameter measurements in the image isocenter and periphery were performed. These measurements were repeated in picture archiving and communication system (PACS) on DSA images and maximum intensity pixel (MIP) CTA images.

RESULTS

Forty-two (42) consecutive patients with adequate DSA and CTA images were included in the final analysis. The correlation between vessel diameter measurements in the image isocenter (R² = 0.81/0.85, p < 0.0001/p < 0.0001 [Reader1/Reader2]), periphery (R² = 0.85/0.82, p < 0.0001/p < 0.0001 [Reader1/Reader2]), and all measurements combined (R² = 0.87/0.87, p < 0.0001/p < 0.0001 [Reader1/Reader2]) on DSA and CTA were strong and statistically significant. The interclass correlation coefficient for measurements performed by two independent reviewers was strong (ICC = 0.96, 95% CI 0.92-0.98).

CONCLUSIONS

The correlations between uncalibrated DSA measurements and CTA for vessel diameter were strong. In addition, there were strong correlations between these image types for repeated measurements in the image isocenter as well as image periphery for vessel diameter. Consequently, endovascular devices can be sized correctly without the need for pre-operative non-invasive imaging.

A Portable Pull-Out Soil Profile Moisture Sensor Based on High-Frequency Capacitance

Soil profile moisture is a crucial parameter of agricultural irrigation. To meet the demand of soil profile moisture, simple fast-sensing, and low-cost in situ detection, a portable pull-out soil profile moisture sensor was designed based on the principle of high-frequency capacitance. The sensor consists of a moisture-sensing probe and a data processing unit. The probe converts soil moisture into a frequency signal using an electromagnetic field. The data processing unit was designed for signal detection and transmitting moisture content data to a smartphone app. The data processing unit and the probe are connected by a tie rod with adjustable length, which can be moved up and down to measure the moisture content of different soil layers. According to indoor tests, the maximum detection height for the sensor was 130 mm, the maximum detection radius was 96 mm, and the degree of fitting (R²) of the constructed moisture measurement model was 0.972. In the verification tests, the root mean square error (RMSE) of the measured value of the sensor was 0.02 m³/m³, the mean bias error (MBE) was ±0.009 m³/m³, and the maximum error was ±0.039 m³/m³. According to the results, the sensor, which features a wide detection range and good accuracy, is well suited for the portable measurement of soil profile moisture.

Design and Testing of a Smart Facemask for Respiratory Monitoring during Cycling Exercise

Given the importance of respiratory frequency (f_R) as a valid marker of physical effort, there is a growing interest in developing wearable devices measuring f_R in applied exercise settings. Biosensors measuring chest wall movements are attracting attention as they can be integrated into textiles, but their susceptibility to motion artefacts may limit their use in some sporting activities. Hence, there is a need to exploit sensors with signals minimally affected by motion artefacts. We present the design and testing of a smart facemask embedding a temperature biosensor for f_R monitoring during cycling exercise. After laboratory bench tests, the proposed solution was tested on cyclists during a ramp incremental frequency test (RIFT) and high-intensity interval training (HIIT), both indoors and outdoors. A reference flowmeter was used to validate the f_R extracted from the temperature respiratory signal. The smart facemask showed good performance, both at a breath-by-breath level (MAPE = 2.56% and 1.64% during RIFT and HIIT, respectively) and on 30 s average f_R values (MAPE = 0.37% and 0.23% during RIFT and HIIT, respectively). Both accuracy and precision (MOD ± LOAs) were generally superior to those of other devices validated during exercise. These findings have important implications for exercise testing and management in different populations.

Accelerometer-Based Physical Activity Assessment During Intermittent Conditions: Effect of Epoch Length on Energy Expenditure Estimate

Purpose: This study analyzed the effect of epoch length on energy expenditure (EE) estimates and on the moderate-to-vigorous physical activity (MVPA) measure obtained from EE estimates during accelerometer-based assessment. Methods: Ten active students exercised on a treadmill for four 5-min bouts, using two effort intensities (running and walking) and two physical activity (PA) patterns (continuous or intermittent) wearing an accelerometer. The criterion measure of EE was achieved using indirect calorimetry. Data obtained from the accelerometer were reintegrated into 1-sec, 10-sec, 30-sec and 60-sec epochs. Results: During the running intermittent condition, EE and MVPA estimates from the accelerometer were no different from the criterion measure with 30- and 60-sec epoch lengths but they were different with shorter epoch lengths. During the walking intermittent condition, no difference was observed between EE estimates and the criterion measure, regardless of the epoch length. During the running continuous condition, EE estimated from the accelerometer was significantly lower than the EE obtained with the criterion measure, regardless of the epoch length. During the walking continuous condition, no difference was observed. Conclusion: During the intermittent running condition, longer epoch lengths gave the best EE and MVPA estimates. This conclusion is contrary to the current general view that shorter epochs are the most accurate for PA assessment. However, PA estimates are closer to an external load estimates whereas EE estimates are closer to the internal load estimate. Depending on the objective of their study, researchers should be aware of these findings.

Wearable Electrocardiography for Physical Activity Monitoring: Definition of Validation Protocol and Automatic Classification

Wearable devices are rapidly spreading thanks to multiple advantages. Their use is expanding in several fields, from medicine to personal assessment and sport applications. At present, more and more wearable devices acquire an electrocardiographic (ECG) signal (in correspondence to the wrist), providing potentially useful information from a diagnostic point of view, particularly in sport medicine and in rehabilitation fields. They are remarkably relevant, being perceived as a common watch and, hence, considered neither intrusive nor a cause of the so-called "white coat effect". Their validation and metrological characterization are fundamental; hence, this work aims at defining a validation protocol tested on a commercial smartwatch (Samsung Galaxy Watch3, Samsung Electronics Italia S.p.A., Milan, Italy) with respect to a gold standard device (Zephyr BioHarness 3.0, Zephyr Technology Corporation, Annapolis, MD, USA, accuracy of ±1 bpm), reporting results on 30 subjects. The metrological performance is provided, supporting final users to properly interpret the results. Moreover, machine learning and deep learning models are used to discriminate between resting and activity-related ECG signals. The results confirm the possibility of using heart rate data from wearable sensors for activity identification (best results obtained by Random Forest, with accuracy of 0.81, recall of 0.80, and precision of 0.81, even using ECG signals of limited duration, i.e., 30 s). Moreover, the effectiveness of the proposed validation protocol to evaluate measurement accuracy and precision in a wide measurement range is verified. A bias of -1 bpm and an experimental standard deviation of 11 bpm (corresponding to an experimental standard deviation of the mean of ≈0 bpm) were found for the Samsung Galaxy Watch3, indicating a good performance from a metrological point of view.

Comparing a Fitbit Wearable to an Electrocardiogram Gold Standard as a Measure of Heart Rate Under Psychological Stress: A Validation Study

BACKGROUND

Wearable devices collect physiological and behavioral data that have the potential to identify individuals at risk of declining mental health and well-being. Past research has mainly focused on assessing the accuracy and the agreement of heart rate (HR) measurement of wearables under different physical exercise conditions. However, the capacity of wearables to sense physiological changes, assessed by increasing HR, caused by a stressful event has not been thoroughly studied.

OBJECTIVE

This study followed 3 objectives: (1) to test the ability of a wearable device (Fitbit Versa 2) to sense an increase in HR upon induction of psychological stress in the laboratory; (2) to assess the accuracy of the wearable device to capture short-term HR variations caused by psychological stress compared to a gold-standard electrocardiogram (ECG) measure (Biopac); and (3) to quantify the degree of agreement between the wearable device and the gold-standard ECG measure across different experimental conditions.

METHODS

Participants underwent the Trier Social Stress Test protocol, which consists of an oral phase, an arithmetic stress phase, an anticipation phase, and 2 relaxation phases (at the beginning and the end). During the stress protocol, the participants wore a Fitbit Versa 2 and were also connected to a Biopac. A mixed-effect modeling approach was used (1) to assess the effect of experimental conditions on HR, (2) to estimate several metrics of accuracy, and (3) to assess the agreement: the Bland-Altman limits of agreement (LoA), the concordance correlation coefficient, the coverage probability, the total deviation index, and the coefficient of an individual agreement. Mean absolute error and mean absolute percent error were calculated as accuracy indices.

RESULTS

A total of 34 university students were recruited for this study (64% of participants were female with a mean age of 26.8 years, SD 8.3). Overall, the results showed significant HR variations across experimental phases. Post hoc tests revealed significant pairwise differences for all phases. Accuracy analyses revealed acceptable accuracy according to the analyzed metrics of accuracy for the Fitbit Versa 2 to capture the short-term variations in psychological stress levels. However, poor indices of agreement between the Fitbit Versa 2 and the Biopac were found.

CONCLUSIONS

Overall, the results support the use of the Fitbit Versa 2 to capture short-term stress variations. The Fitbit device showed acceptable levels of accuracy but poor agreement with an ECG gold standard. Greater inaccuracy and smaller agreement were found for stressful experimental conditions that induced a higher HR. Fitbit devices can be used in research to measure HR variations caused by stress, although they cannot replace an ECG instrument when precision is of utmost importance.

Association of Intra-individual Differences in Estimated GFR by Creatinine Versus Cystatin C With Incident Heart Failure

RATIONALE & OBJECTIVE

Lower estimated glomerular filtration rate (eGFR) is associated with heart failure (HF) risk. However, eGFR based on cystatin C (eGFRcys) and creatinine (eGFRcr) may differ substantially within an individual. The clinical implications of these differences for risk of HF among persons with chronic kidney disease (CKD) are unknown.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

4,512 adults with CKD and without prevalent HF who enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study.

EXPOSURE

Difference in GFR estimates (eGFRdiff; ie, eGFRcys minus eGFRcr).

OUTCOME

Incident HF hospitalization.

ANALYTICAL APPROACH

Fine-Gray proportional subhazards regression was used to investigate the associations of baseline, time-updated, and slope of eGFRdiff with incident HF.

RESULTS

Of 4,512 participants, one-third had eGFRcys and eGFRcr values that differed by over 15 mL/min/1.73 m2. In multivariable-adjusted models, each 15 mL/min/1.73 m2 lower baseline eGFRdiff was associated with higher risk of incident HF hospitalization (hazard ratio [HR], 1.20 [95% CI, 1.07-1.34]). In time-updated analyses, those with eGFRdiff less than -15 mL/min/1.73 m2 had higher risk of incident HF hospitalization (HR, 1.99 [95% CI, 1.39-2.86]), and those with eGFRdiff ≥15 mL/min/1.73 m2 had lower risk of incident HF hospitalization (HR, 0.67 [95% CI, 0.49-0.91]) compared with participants with similar eGFRcys and eGFRcr. Participants with faster declines in eGFRcys relative to eGFRcr had higher risk of incident HF (HR, 1.49 [95% CI, 1.19-1.85]) compared with those in whom eGFRcys and eGFRcr declined in parallel.

LIMITATIONS

Entry into the CRIC Study was determined by eGFRcr, which constrained the range of baseline eGFRcr-but not eGFRcys-values.

CONCLUSIONS

Among persons with CKD who have large differences between eGFRcys and eGFRcr, risk for incident HF is more strongly associated with eGFRcys. Diverging slopes between eGFRcys and eGFRcr over time are also independently associated with risk of incident HF.

Study on the CHZ-II Gravimeter and Its Calibrations along Forward and Reverse Overlapping Survey Lines

The moving-base gravimeter is one of the key instruments used for Earth gravity survey. The accuracy of the survey data is closely related to the calibration precision of several key parameters, such as the damping delay time, the drift coefficient, the gravity scale factor, and the measurement accuracy. This paper will introduce the development of the CHZ-II gravimeter system in which a cylindrical sampling mass suspended vertically by a zero-length spring acts as a sensitive probe to measure specific force. Meanwhile, a GNSS (Global Navigation Satellite System) positioning system is employed to monitor the carrier motion and to remove the inertia acceleration. In order to achieve high-precision calibrations for the key parameters, a new calibration method performed along forward and reverse overlapping lines is proposed, which is used to calibrate the above parameters and to estimate the measurement accuracy of the instrument used for a normal gravity survey. The calibration principle and the shipboard calibration data processing method are introduced. The calibration was performed for three moving-base gravimeters and the corresponding results are determined, indicating that the method can significantly improve the accuracy of the parameters. For the CHZ-II gravimeter, the measurement accuracy of the survey is 0.471 mGal (1 mGal = 10^-5 m/s²), which improved by 19.5% after applying the calibrated parameters. This method is also practical for use with aviation, marine and even vehicle-carried moving-base gravimeters.

Evaluation of a Linear Measurement Tool in Virtual Reality for Assessment of Multimodality Imaging Data-A Phantom Study

This study aimed to evaluate the accuracy and reliability of a virtual reality (VR) system line measurement tool using phantom data across three cardiac imaging modalities: three-dimensional echocardiography (3DE), computed tomography (CT) and magnetic resonance imaging (MRI). The same phantoms were also measured using industry-standard image visualisation software packages. Two participants performed blinded measurements on volume-rendered images of standard phantoms both in VR and on an industry-standard image visualisation platform. The intra- and interrater reliability of the VR measurement method was evaluated by intraclass correlation coefficient (ICC) and coefficient of variance (CV). Measurement accuracy was analysed using Bland−Altman and mean absolute percentage error (MAPE). VR measurements showed good intra- and interobserver reliability (ICC ≥ 0.99, p < 0.05; CV < 10%) across all imaging modalities. MAPE for VR measurements compared to ground truth were 1.6%, 1.6% and 7.7% in MRI, CT and 3DE datasets, respectively. Bland−Altman analysis demonstrated no systematic measurement bias in CT or MRI data in VR compared to ground truth. A small bias toward smaller measurements in 3DE data was seen in both VR (mean −0.52 mm [−0.16 to −0.88]) and the standard platform (mean −0.22 mm [−0.03 to −0.40]) when compared to ground truth. Limits of agreement for measurements across all modalities were similar in VR and standard software. This study has shown good measurement accuracy and reliability of VR in CT and MRI data with a higher MAPE for 3DE data. This may relate to the overall smaller measurement dimensions within the 3DE phantom. Further evaluation is required of all modalities for assessment of measurements <10 mm.

Item Selection With Collaborative Filtering in On-The-Fly Multistage Adaptive Testing

An important design feature in the implementation of both computerized adaptive testing and multistage adaptive testing is the use of an appropriate method for item selection. The item selection method is expected to select the most optimal items depending on the examinees' ability level while considering other design features (e.g., item exposure and item bank utilization). This study introduced collaborative filtering (CF) as a new method for item selection in the on-the-fly assembled multistage adaptive testing framework. The user-based CF (UBCF) and item-based CF (IBCF) methods were compared to the maximum Fisher information method based on the accuracy of ability estimation, item exposure rates, and item bank utilization under different test conditions (e.g., item bank size, test length, and the sparseness of training data). The simulation results indicated that the UBCF method outperformed the traditional item selection methods regarding measurement accuracy. Also, the IBCF method showed the most superior performance in terms of item bank utilization. Limitations of the current study and the directions for future research are discussed.

Performance of the 2021 Race-Free CKD-EPI Creatinine- and Cystatin C-Based Estimated GFR Equations Among Kidney Transplant Recipients

RATIONALE & OBJECTIVE

Race-free estimated glomerular filtration rate (eGFR) equations incorporating creatinine with and without cystatin C were recently developed and recommended for routine use. However, the performance of these equations among kidney transplant recipients (KTRs) remains unknown.

STUDY DESIGN

Cross-sectional study to validate the 2021 race-free Chronic Kidney Disease (CKD) Epidemiology Collaboration (CKD-EPI) eGFR equation based on creatinine alone (eGFR_cr) or based on creatinine and cystatin C (eGFR_cr-cys) among KTRs.

SETTING & PARTICIPANTS

KTRs in stable condition (N = 415) from Canada and New Zealand with same-day measurements of creatinine, cystatin C, and glomerular filtration rate (GFR) using radiolabeled diethylenetriaminepentaacetic acid.

TESTS COMPARED

The 2009 CKD-EPI eGFR_cr, 2021 CKD-EPI eGFR_cr, 2012 CKD-EPI eGFR_cr-cys, 2021 CKD-EPI eGFR_cr-cys, 2012 CKD-EPI eGFR_cys, and Modification of Diet in Renal Disease (MDRD) Study eGFR equations were compared with measured GFR.

OUTCOMES

Bias, precision, accuracy, and correct classification by CKD stage. Bias was defined as the difference between estimated and measured GFR. Precision was represented by the interquartile range. Accuracy was defined as the percentages of participants with eGFRs within 10%/20%/30% (P₁₀/P₂₀/P₃₀) of measured GFR, root mean square error, and mean absolute error.

RESULTS

87% of patients studied were White, 3% Black, and 10% other races. Mean measured GFR was 53 ± 19 (SD) mL/min/1.73 m². The 2009 and 2021 CKD-EPI eGFR_cr equations demonstrated similar median bias (-2.3 vs -0.2 mL/min/1.73 m², respectively), precision (14.5 vs 14.9 mL/min/1.73 m²), and accuracy (P₁₀/P₂₀/P₃₀, 32%/65%/84% vs 33%/63%/84%). The 2012 and 2021 CKD-EPI eGFR_cr-cys equations also demonstrated similar median bias (-3.6 vs 0.3 mL/min/1.73 m², respectively), precision (13.3 vs 14.3 mL/min/1.73 m²), and accuracy (P₁₀/P₂₀/P₃₀, 32%/63%/80% vs 32%/67%/83%). No clear difference in performance was detected between the 2021 CKD-EPI eGFR_cr and eGFR_cr-cys equations among KTRs. The proportion of correct classification by CKD stage was similar across all eGFR equations.

LIMITATIONS

Moderate sample size, few patients had a GFR <30 mL/min/1.73 m², and the large majority of patients were White.

CONCLUSIONS

Among KTRs, the 2021 race-free CKD-EPI eGFR equations perform similarly to the previous CKD-EPI equations that included race correction terms. No significant difference in performance was observed between the 2021 CKD-EPI eGFR_cr and eGFR_cr-cys equations in the kidney transplant population.

Comparative Analysis on the Effect of Surface Reflectance for Laser 3D Scanner Calibrator

The calibrator is one of the most important factors in the calibration of various laser 3D scanning instruments. The requirements for the diffuse reflection surface are emphasized in many national standards. In this study, spherical calibrator and plane calibrator comparative measurement experiments were carried out. The black ceramic standard sphere, white ceramic standard sphere, metal standard sphere, metal standard plane, and white ceramic standard plane were used to test the laser 3D scanner. In the spherical calibrator comparative measurement experiments, the results indicate that the RMS of the white ceramic spherical calibrator with a reflectance of approximately 60% is 10 times that of the metal spherical calibrator with the reflectance of approximately 15%, and the RMS of the black ceramic spherical calibrator with reflectance of approximately 11% is of the same order as the metal spherical calibrator. In the plane calibrators comparative measurement experiments, the RMS of the flatness measurement is 0.077 mm for the metal plane calibrator with a reflectance of 15%, and 2.915 mm for ceramic plane calibrator with a reflectance of 60%. The results show that when the optimal measurement distance and incident angle are selected, the reflectance of the calibrator has a great effect on the measurement results, regardless of the outlines or profiles. Based on the experiments, it is recommended to use the spherical calibrator or the standard plane with a reflectance of around 18% as the standard, which can obtain reasonable results. In addition, it is necessary to clearly provide the material category and surface reflectance information of the standard when calibrating the scanner according to the measurement standard.

Investigation of Measurement Accuracy of Bridge Deformation Using UAV-Based Oblique Photography Technique

This paper investigates the measurement accuracy of unmanned aerial vehicle-based oblique photography (UAVOP) in bridge deformation identifications. A simply supported concrete beam model was selected and measured using the UAVOP technique. The influences of several parameters, such as overall flight altitude (h), local shooting distance (d), partial image overlap (λ), and arrangement of control points, on the quality of the reconstructed three-dimensional (3D) beam model, were presented and discussed. Experimental results indicated that the quality of the reconstructed 3D model was significantly improved by the fusion overall-partial flight routes (FR), of which the reconstructed model quality was 46.7% higher than those with the single flight route (SR). Despite the minimal impact of overall flight altitude, the reconstructed model quality prominently varied with the local shooting distance, partial image overlap, and control points arrangement. As the d decreased from 12 m to 8 m, the model quality was improved by 48.2%, and an improvement of 42.5% was also achieved by increasing the λ from 70% to 80%. The reconstructed model quality of UAVOP with the global-plane control points was 78.4% and 38.4%, respectively, higher than those with the linear and regional control points. Furthermore, an optimized scheme of UAVOP with control points in global-plane arrangement and FR (h = 50 m, d = 8 m, and λ = 80%) was recommended. A comparison between the results measured by the UAVOP and the total station showed maximum identification errors of 1.3 mm. The study's outcomes are expected to serve as potential references for future applications of UAVOP in bridge measurements.

Prediction of VO2max From Submaximal Exercise Using the Smartphone Application Myworkout GO: Validation Study of a Digital Health Method

BACKGROUND

Physical inactivity remains the largest risk factor for the development of cardiovascular disease worldwide. Wearable devices have become a popular method of measuring activity-based outcomes and facilitating behavior change to increase cardiorespiratory fitness (CRF) or maximal oxygen consumption (VO_2max) and reduce weight. However, it is critical to determine their accuracy in measuring these variables.

OBJECTIVE

This study aimed to determine the accuracy of using a smartphone and the application Myworkout GO for submaximal prediction of VO_2max.

METHODS

Participants included 162 healthy volunteers: 58 women and 104 men (17-73 years old). The study consisted of 3 experimental tests randomized to 3 separate days. One-day VO_2max was assessed with Metamax II, with the participant walking or running on the treadmill. On the 2 other days, the application Myworkout GO used standardized high aerobic intensity interval training (HIIT) on the treadmill to predict VO_2max.

RESULTS

There were no significant differences between directly measured VO_2max (mean 49, SD 14 mL/kg/min) compared with the VO_2max predicted by Myworkout GO (mean 50, SD 14 mL/kg/min). The direct and predicted VO_2max values were highly correlated, with an R² of 0.97 (P<.001) and standard error of the estimate (SEE) of 2.2 mL/kg/min, with no sex differences.

CONCLUSIONS

Myworkout GO accurately calculated VO_2max, with an SEE of 4.5% in the total group. The submaximal HIIT session (4 x 4 minutes) incorporated in the application was tolerated well by the participants. We present health care providers and their patients with a more accurate and practical version of health risk estimation. This might increase physical activity and improve exercise habits in the general population.

Ex-vivo aortic root and coronary artery cast measurement to validate the accuracy of virtual imaging

BACKGROUND AND AIM OF THE STUDY

To investigate the accuracy of two methods of measuring features in cardiac anatomy, using an objective standard cast model.

METHODS

We made a silicone cast using a swine heart. Computerized tomography data of the solidified cast were processed through virtual reality (VR) software and through two-dimensional multiplanar-reconstruction (2D-MPR), and all measurements were compared against physical measurements of the cast.

RESULTS

The cast perfectly demonstrated the fine detail of the aortic valve and the proximal parts of coronary arteries. Anatomical features were measured by 3D-VR, 2D-MPR, and directly on the cast. Measurement differences between 2D-MPR and the cast were on average at least 3.6 times larger than those between 3D-VR and the cast.

CONCLUSIONS

Based on the observed accuracy, 3D-VR measurements seem considerably more accurate than the current standard 2D-MPR, and 3D-VR may be considered as the next gold standard for 3D measurement of cardiac anatomy in vivo.

Assessing agreement among crime scene measurement methods

A critical concern with crime scene documentation is the accuracy with which a crime scene can be reconstructed. Here, we discuss the accuracy of eight documentation methods as a function of measurement distance between reference ground targets in an outdoor scene. The relative accuracy of each documentation method was assessed with respect to a widely accepted and well-established standard method for land surveying, Total Station, from which measurements served as "ground truth" or reference data. For the majority of methods, the actual relative difference between measurements when compared to Total Station was small (less than a quarter of an inch). Measurements from FARO LiDAR agreed the most with to those of Total Station, while drone without the use of ground control points (GCPs) agreed the least. GCPs or a reference scale were also found to be important in mitigating increasing imprecision with increasing distance when measuring between two targets ~9-85 ft apart via drone and orthomosaic methods. Additionally, there were no statistical differences in the use of 2D (horizontal) or 3D (slope) measurement configurations for the Total Station. Overall, linear regression of difference plots did not reveal meaningful correlation between increasing distance measured and the error of a method when compared to Total Station. As more measurement methods become available, and the need for training and validating new tools become a necessity, these results point to the importance of establishing a ground truth or known distance range on which crime scene measurement methods can be validated.

Validation of a smart shirt for heart rate variability measurements at rest and during exercise

Heart rate variability (HRV) monitoring is a promising option to estimate the autonomic nervous system regulation responding to exercise. Textiles with embedded sensors recording heartbeat intervals are a simple tool for data collection. So-called smart shirts offer comfort for a daily use and are managed easily. Their measurement accuracy for HRV calculation at rest is promising but remains questionable during exercise. Therefore, the present study validated the Ambiotex smart shirt using HRV indices (RMSSD, rel. HF power and rel. LF power) during exercise. Eighty-three healthy participants (31 ± 6 years; 39 females, 44 males) completed an incremental exercise test on a bicycle ergometer wearing the smart shirt and an electrocardiogram simultaneously. We compared HRV indices of segments at rest (5 min), at warm-up (3 min) and twice at the exercise test (each 5 min). At rest and at warm-up, we observed excellent linear relationship (r > 0.96; R² > 0.94), excellent relative reliability (ICC ≥ 0.98; α ≥ 0.98) and acceptable agreement (bias < 10%). During the exercise test, measurement accuracy declined with increasing intensity but remained high (> 0.8), although results for partial HRV indices were insufficient. In addition, percentage bias was unacceptable during exercise test. However, the findings support the validity of the smart shirt for measuring HRV especially at rest and at warm-up. We suggest using the smart shirt for monitoring HRV indices on a daily basis but caution should be taken in the interpretation of HRV indices obtained during moderate to vigorous exercise intensities. This article is protected by copyright. All rights reserved.

Procedure Proposal for Minimising the Dynamic Error of Second-Order Sensors

This paper proposes the procedure for minimising the dynamic error in the time and frequency domains, based on the example of a second-order sensor. Our procedure includes three main steps: modelling of the sensors using the Monte Carlo (MC) method; determination of the maximum value of the dynamic error using the integral-square criterion (ISC); and optimisation of the parameters of the sensor model by minimising the ISC. The uncertainties associated with the modelling procedure and the MC method are also considered. The mathematical formulae necessary for implementation in a given programming language (MathCad, MATLAB, C, etc.) are presented in detail. The proposed procedure was implemented in the frequency domain, using MathCad 15, and applied to the example of the Althen 731-207 accelerometer. Validation of the proposed procedure was carried out using a digital signal processor of type TMS320C6713. The proposed procedure can increase the accuracy of the signal processing obtained at the output of sensors applied to a wide range of measurements.

From Fully Physical to Virtual Sensing for Water Quality Assessment: A Comprehensive Review of the Relevant State-of-the-Art

Rapid urbanization, industrial development, and climate change have resulted in water pollution and in the quality deterioration of surface and groundwater at an alarming rate, deeming its quick, accurate, and inexpensive detection imperative. Despite the latest developments in sensor technologies, real-time determination of certain parameters is not easy or uneconomical. In such cases, the use of data-derived virtual sensors can be an effective alternative. In this paper, the feasibility of virtual sensing for water quality assessment is reviewed. The review focuses on the overview of key water quality parameters for a particular use case and the development of the corresponding cost estimates for their monitoring. The review further evaluates the current state-of-the-art in terms of the modeling approaches used, parameters studied, and whether the inputs were pre-processed by interrogating relevant literature published between 2001 and 2021. The review identified artificial neural networks, random forest, and multiple linear regression as dominant machine learning techniques used for developing inferential models. The survey also highlights the need for a comprehensive virtual sensing system in an internet of things environment. Thus, the review formulates the specification book for the advanced water quality assessment process (that involves a virtual sensing module) that can enable near real-time monitoring of water quality.

Effect of equalization filters on measurements with kerma-area product meter in a cardiovascular angiography system

Purpose

This study aimed to evaluate the effect of equalization filters (EFs) on the kerma‐area product (KAPQKM) and incident air‐kerma (Ka,i,QKM) using a kerma‐area product (KAP) meter. In addition, potential underestimations of the Ka,i,QKM values by EFs were identified.

Materials and methods

A portable flat‐panel detector (FPD) was placed to measure the X‐ray beam area (A) and EFs dimension at patient entrance reference point (PERP). Afterward, a 6‐cm³ external ionization chamber was placed to measure incident air‐kerma (Ka,i,Qext) at PERP instead of the portable FPD. KAP reading and Ka,i,Qext were simultaneously measured at several X‐ray beam qualities with and without EFs. The X‐ray beam quality correction factor by KAP meter (kQ,Q0KM) was calculated by A, Ka,i,Qext and KAP reading to acquire the KAPQKM and Ka,i,QKM. Upon completion of the measurements, KAPQKM, Ka,i,QKM, and Ka,i,Qext were plotted as functions of tube potential, spectral filter, and EFs dimension. Moreover, Ka,i,QKM/Ka,i,Qext values were calculated to evaluate the Ka,i,QKM underestimation.

Results

The kQ,Q0KM values increased with an increase in the X‐ray tube potential and spectral filter, and the maximum kQ,Q0KM was 1.18. KAPQKM and Ka,i,QKM decreased as functions of EFs dimension, whereas Ka,i,Qext was almost constant. Ka,i,QKM/Ka,i,Qext decreased with an increase in EFs dimension but increased with an increase in tube potential and spectral filter, and the range was 0.55–1.01.

Conclusions

Ka,i,QKM value was up to approximately two times lower than the Ka,i,Qext values by EFs. When using the Ka,i,QKM value, the potential Ka,i,QKM underestimation with EFs should be considered.

A New Method to Balance Measurement Accuracy and Attribute Coverage in Cognitive Diagnostic Computerized Adaptive Testing

As one of the important research areas of cognitive diagnosis assessment, cognitive diagnostic computerized adaptive testing (CD-CAT) has received much attention in recent years. Measurement accuracy is the major theme in CD-CAT, and both the item selection method and the attribute coverage have a crucial effect on measurement accuracy. A new attribute coverage index, the ratio of test length to the number of attributes (RTA), is introduced in the current study. RTA is appropriate when the item pool comprises many items that measure multiple attributes where it can both produce acceptable measurement accuracy and balance the attribute coverage. With simulations, the new index is compared to the original item selection method (ORI) and the attribute balance index (ABI), which have been proposed in previous studies. The results show that (1) the RTA method produces comparable measurement accuracy to the ORI method under most item selection methods; (2) the RTA method produces higher measurement accuracy than the ABI method for most item selection methods, with the exception of the mutual information item selection method; (3) the RTA method prefers items that measure multiple attributes, compared to the ORI and ABI methods, while the ABI prefers items that measure a single attribute; and (4) the RTA method performs better than the ORI method with respect to attribute coverage, while it performs worse than the ABI with long tests.

On the Use of Dynamic Calibration to Correct Drop Counter Rain Gauge Measurements

Dynamic calibration was performed in the laboratory on two catching-type drop counter rain gauges manufactured as high-sensitivity and fast response instruments by Ogawa Seiki Co. Ltd. (Japan) and the Chilbolton Rutherford Appleton Laboratory (UK). Adjustment procedures were developed to meet the recommendations of the World Meteorological Organization (WMO) for rainfall intensity measurements at the one-minute time resolution. A dynamic calibration curve was derived for each instrument to provide the drop volume variation as a function of the measured drop releasing frequency. The trueness of measurements was improved using a post-processing adjustment algorithm and made compatible with the WMO recommended maximum admissible error. The impact of dynamic calibration on the rainfall amount measured in the field at the annual and the event scale was calculated for instruments operating at two experimental sites. The rainfall climatology at the site is found to be crucial in determining the magnitude of the measurement bias, with a predominant overestimation at the low to intermediate rainfall intensity range.

Binary Restrictive Threshold Method for Item Exposure Control in Cognitive Diagnostic Computerized Adaptive Testing

Although classification accuracy is a critical issue in cognitive diagnostic computerized adaptive testing, attention has increasingly shifted to item exposure control to ensure test security. In this study, we developed the binary restrictive threshold (BRT) method to balance measurement accuracy and item exposure. In addition, a simulation study was conducted to evaluate its performance. The results indicated that the BRT method performed better than the restrictive progressive (RP) and stratified dynamic binary searching (SDBS) approaches but worse than the restrictive threshold (RT) method in terms of classification accuracy. With respect to item exposure control, the BRT method exhibited noticeably stronger performance compared with the RT method, even though its performance was not as high as that of the RP and SDBS methods.

Influence of the Duration and Timing of Data Collection on Accelerometer-Measured Physical Activity, Sedentary Time and Associated Insulin Resistance

Accelerometry is a commonly used method to determine physical activity in clinical studies, but the duration and timing of measurement have seldom been addressed. We aimed to evaluate possible changes in the measured outcomes and associations with insulin resistance during four weeks of accelerometry data collection. This study included 143 participants (median age of 59 (IQR9) years; mean BMI of 30.7 (SD4) kg/m²; 41 men). Sedentary and standing time, breaks in sedentary time, and different intensities of physical activity were measured with hip-worn accelerometers. Differences in the accelerometer-based results between weeks 1, 2, 3 and 4 were analyzed by mixed models, differences during winter and summer by two-way ANOVA, and the associations between insulin resistance and cumulative means of accelerometer results during weeks 1 to 4 by linear models. Mean accelerometry duration was 24 (SD3) days. Sedentary time decreased after three weeks of measurement. More physical activity was measured during summer compared to winter. The associations between insulin resistance and sedentary behavior and light physical activity were non-significant after the first week of measurement, but the associations turned significant in two to three weeks. If the purpose of data collection is to reveal associations between accelerometer-measured outcomes and tenuous health outcomes, such as insulin sensitivity, data collection for at least three weeks may be needed.

A Clinical Evaluation of Cone-beam Computed Tomography: Implications for Endodontic Microsurgery

INTRODUCTION

Cone-beam computed tomographic (CBCT) imaging is a valuable diagnostic tool for endodontics. Some studies report that CBCT images have limitations in representing the true clinical presentation. This prospective, in vivo study compared limited field of view (LFOV) CBCT measurements with clinical measurements made during endodontic surgery.

METHODS

Eighty-seven subjects requiring endodontic surgery and LFOV CBCT acquisition of the surgical site were enrolled. Data collection involved clinicians answering standardized questions during the radiographic and surgical assessment. Intraoperatively, data were collected and photographically documented. Postoperatively, CBCT scans were evaluated by 3 calibrated, board-certified specialists: 2 endodontists and 1 oral and maxillofacial radiologist. The 2 subsets of data were compared through statistical analysis to quantify their relationship.

RESULTS

The subjects included 65 maxillary and 29 mandibular teeth from 87 subjects: 25 women and 62 men with an average age of 42 years old. The CBCT evaluators correctly identified the presence or absence of buccal plate fenestrations with 91.0% accuracy (95% confidence interval, 83.1-96.0) with 89.4% sensitivity and 92.9% specificity. The area of fenestrations measured clinically (mean = 19.6 ± 33.4 mm²) was generally larger than the area measured by CBCT imaging (mean across CBCT evaluators = 12.2 ± 19.1 mm²). Fenestration size in the maxillary arch was more likely to be underestimated than in the mandibular arch (P < .0001). Vertical bone height was also underestimated when measured on CBCT imaging.

CONCLUSIONS

Based on the findings of this study, LFOV CBCT imaging accurately identifies the presence or absence of buccal plate fenestrations, yet, when a fenestration is present, underestimates its area.

A High Accuracy Ion Conductance Imaging Method Based on the Approach Curve Spectrum

Scanning ion conductance microscopy (SICM), as an emerging non-contact in situ topography measurement tool with nano resolution, has been increasingly used in recent years in biomedicine, electrochemistry and materials science. In the conventional measurement method of SICM, the sample topography is constructed according to the position of the probe at the feedback threshold of the ion current. Nevertheless, for different structures, a constant threshold cannot maintain a constant probe-sample distance. This phenomenon makes the measurement topography inconsistent with the real sample surface. In order to solve this problem and improve the measurement accuracy of SICM, a new ion conductance imaging method based on the approach curve spectrum is proposed in this work. In the new method, the local feature around the measurement point is firstly evaluated according to the change rate of ion current. Secondly, based on the local feature, the corresponding approach curve is searched from the prior approach curve spectrum to accurately evaluate the distance between the probe and the sample. Finally, the sample topography is constructed by the probe position subtracting the probe-sample distance. In this paper, we verify the feasibility of the new imaging method by combining finite element theory and experiments. To examine the measurement accuracy, the standard strip silicon and cylindrical polydimethylsiloxane (PDMS) samples are tested, and the improved imaging method can obtain the topography closer to the real samples and reduce the volumetric measurement error by 5.4%. The implementation of the new imaging method will further promote SICM application in related research fields.

Seismic Discrimination between Earthquakes and Explosions Using Support Vector Machine

The discrimination between earthquakes and explosions is a serious issue in seismic signal analysis. This paper proposes a seismic discrimination method using support vector machine (SVM), wherein the amplitudes of the P-wave and the S-wave of the seismic signals are selected as feature vectors. Furthermore, to improve the seismic discrimination performance using a heterodyne laser interferometer for seismic wave detection, the Hough transform is applied as a compensation method for the periodic nonlinearity error caused by the frequency-mixing in the laser interferometric seismometer. In the testing procedure, different kernel functions of SVM are used to discriminate between earthquakes and explosions. The outstanding performance of a laser interferometer and Hough transform method for precision seismic measurement and nonlinearity error compensation is confirmed through some experiments using a linear vibration stage. In addition, the effectiveness of the proposed discrimination method using a heterodyne laser interferometer is verified through a receiver operating characteristic curve and other performance indices obtained from practical experiments.

Blood Pressure Measurement: A KDOQI Perspective

The majority of patients with chronic kidney disease (CKD) have elevated blood pressure (BP). In patients with CKD, hypertension is associated with increased risk for cardiovascular disease, progression of CKD, and all-cause mortality. New guidelines from the American College of Cardiology/American Heart Association (ACC/AHA) recommend new thresholds and targets for the diagnosis and treatment of hypertension in patients with and without CKD. A new aspect of the guidelines is the recommendation for measurement of out-of-office BP to confirm the diagnosis of hypertension and guide therapy. In this KDOQI (Kidney Disease Outcomes Quality Initiative) perspective, we review the recommendations for accurate BP measurement in the office, at home, and with ambulatory BP monitoring. Regardless of location, validated devices and appropriate cuff sizes should be used. In the clinic and at home, proper patient preparation and positioning are critical. Patients should receive information about the importance of BP measurement techniques and be encouraged to advocate for adherence to guideline recommendations. Implementing appropriate BP measurement in routine practice is feasible and should be incorporated in system-wide efforts to improve the care of patients with hypertension. Hypertension is the number 1 chronic disease risk factor in the world; BP measurements in the office, at home, and with ambulatory BP monitoring should adhere to recommendations from the AHA.

Selection of the Best Model of Distribution of Measurement Points in Contact Coordinate Measurements of Free-Form Surfaces of Products

The article presents a new method for determining the distribution of measurement points, which can be used in the case of contact coordinate measurements of curvilinear surfaces of products. The developed method is based on multi-criteria decision analysis. In the case of the new method, the selection of the distribution of measurement points on free-form surfaces is carried out based on the analysis of five different criteria. The selection of the best model of the distribution of measurement points results from the accuracy of coordinate measurements, the time needed to complete measurement tasks, the number of measurement points, the accuracy of the substitute surface representing the measured free-form surface and the area where measurement points are located. The purpose of using the developed method of the distribution of measurement points is to increase the performance of coordinate measurements primarily by increasing the automation of strategy planning of measurements of curvilinear surfaces and improving the accuracy of measurements of free-form surfaces of products. The new method takes into account various aspects of coordinate measurements to determine the final model of the distribution of measurement points on measured surfaces of products, thereby increasing the probability of the proper determination (i.e., identifying the highest deviations of a product) of the location of measurement points on the surfaces of a measured object. The paper presents an example of the application of the created method, which concerns the selection of the best model of the distribution of measurement points on a selected free-form surface. This example is based on, among others, the results of experimental investigations, which were carried out by using the ACCURA II coordinate measuring machine equipped with the VAST XXT measuring probe and the Calypso measurement software. The results of investigations indicate a significant reduction in time of coordinate measurements of products when using the new method for determining the distribution of measurement points. However, shortening the time of coordinate measurements does not reduce their accuracy.

Digital Magnetic Compass Integration with Stationary, Land-Based Electro-Optical Multi-Sensor Surveillance System

Multi-sensor imaging systems using the global navigation satellite system (GNSS) and digital magnetic compass (DMC) for geo-referencing have an important role and wide application in long-range surveillance systems. To achieve the required system heading accuracy, the specific magnetic compass calibration and compensation procedures, which highly depend on the application conditions, should be applied. The DMC compensation technique suitable for the operation environment is described and different technical solutions are studied. The application of the swinging procedure was shown as a good solution for DMC compensation in a given application. The selected DMC was built into a system to be experimentally evaluated, both under laboratory and field conditions. The implementation of the compensation procedure and magnetic sensor integration in systems is described. The heading accuracy measurement results show that DMC could be successfully integrated and used in long-range surveillance systems providing required geo-referencing data.

Evaluation of the cone-beam computed tomography accuracy in measuring soft tissue thickness in different areas of the jaws

Purpose:

Due to the extensive use of cone-beam computed tomography (CBCT) in dentistry, especially in measuring thicknesses of hard and soft tissues, and the fact that CBCT has low contrast resolution, the aim of this study was to evaluate the accuracy of CBCT in measuring soft tissue thickness.

Materials and Methods:

In this cross-sectional study, pink baseplate wax as a soft tissue simulation was overlaid in different areas of the jaws on the dry human skull, and the probe was used to determine the thicknesses of 1, 2, 3, and 5 mm. These thicknesses were then measured accurately with a digital caliper by one person four times at interval of a week. The skull was scanned using two CBCT scanners, and the different thicknesses of wax were measured by two observers four times with a week interval. The CBCT measurements were compared with digital caliper measurements as a reference.

Results:

Statistical analysis showed no significant difference between CBCT and digital caliper measurements for thickness < 2 mm (P > 0.05).

Conclusions:

Statistically, the difference between digital caliper and CBCT measurements was < 0.1 mm, but this difference is not clinically important. The accuracy of CBCT in measuring soft tissue thickness was 0.1 mm.

Manual fish length measurement accuracy for adult river fish using an acoustic camera (DIDSON)

Total lengths (L_T ) of 50 free-swimming fish in a tank, silver carp Hypophthalmichthys molitrix and rainbow trout Oncorhynchus mykiss, were measured using a DIDSON (Dual-frequency IDentification SONar) camera. Using Sound Metrics software, multiple measurements of each fish (L_T , side aspect angle and distance from the camera) at different times were analysed by two experienced operators while a subset of data was analysed by two inexperienced operators. The main result showed high variability in intra-fish L_T measurements. The number of measurements required to minimise errors and to obtain robust fish measurements (true L_T  ± 3 cm) was estimated by a bootstrap method. Three to five measurements per fish were recommended for fish surveys in rivers. In this experimental study, aiming to reproduce river conditions, no evidence of fish position (side aspect angle and distance from the camera) effect was detected, but an operator effect (partially explained by training) was observed. General linear mixed models also showed that lengths of the smallest fish (L_T  < 57 cm) were overestimated and lengths of the largest fish (L_T  > 57 cm) were underestimated in comparison with their true lengths. In conclusion, we highlight that this technology, like any monitoring methods, returns imperfect observations. We advise DIDSON users to ensure that measurements are carried out correctly in order to draw accurate conclusion from this new technology.

Modeling the Influence of Oil Film, Position and Orientation Parameters on the Accuracy of a Laser Triangulation Probe

The laser triangulation probe conveniently obtains surface topography data of a measured target. However, compared to the touch probe, its reliability and accuracy can be negatively affected by various factors associated with the object being measured and the probe itself. In this paper, to identify potential compensation strategies to improve the accuracy of depth measurement for laser triangulation probe, the measuring errors caused by an oil film on the measured surface, and the probe’s position and orientation parameters with respect to the measuring object (including scan depth, incident angle, and azimuth angle), were studied. A theoretical model based on the geometrical optics, and an empirical model from the error evaluations, were established to quantitatively characterize the error influence of oil film and probe’s parameters, respectively. We also investigated the influence pattern of different filtering methods with several comparison experiments. The verification procedures, measuring both a free-form surface (chevron-corrugated plate) and a gauge block covered with an oil film, demonstrate that these models and measurement suggestions are viable methods for predicting theoretical error and can be used as compensation references to improve the accuracy of depth measurement to the laser triangulation probe.

Radiostereometric analysis using clinical radiographic views: Validation with model-based radiostereometric analysis for the knee

Radiostereometric analysis is a sophisticated radiographic technique with high measurement accuracy. In order to improve the accessibility of radiostereometric analysis for clinical use, a modified radiostereometric analysis procedure has been previously proposed that enables clinical radiographic views to be used for radiostereometric analysis. It has been successfully validated for its application to the hip wear study with the conventional bead-based radiostereometric analysis environment using computed radiography. In this study, we describe the implementation and validation of this technique for the knee study with the model-based radiostereometric analysis environment using digital radiography. A knee-joint phantom with 6 degrees of freedom was examined, and the bias and repeatability/reproducibility of the modified radiostereometric analysis approach were investigated following the newly updated ASTM recommendations. The bias parameters (mean ± 95% confidence interval) ranged from 0.008 ± 0.003 mm to 0.027 ± 0.006 mm for translation and from 0.014° ± 0.007° to 0.040° ± 0.020° for rotation. The repeatability standard deviation ranged from 0.004 to 0.020 mm for translation and from 0.005° to 0.015° for rotation. The 95% repeatability limit ranged from 0.011 to 0.055 mm for translation and from 0.014° to 0.041° for rotation. The reproducibility standard deviation ranged from 0.004 to 0.023 mm for translation and from 0.006° to 0.040° for rotation. The 95% reproducibility limit ranged from 0.012 to 0.063 mm for translation and from 0.016° to 0.112° for rotation. The modified procedure allows routine clinical radiographs to be used for radiostereometric analysis, which provides the possibility of adding quantitative measurements to current patient registries.

Improving Color Accuracy of Colorimetric Sensors

Accurate measurements of reflectance and color require spectrophotometers with prices often exceeding $3000. Recently, new “color instruments” became available with much lower prices, thanks to the availability of inexpensive colorimetric sensors. We investigated the Node+ChromaPro and the Color Muse, launched in 2015 and 2016 by Variable Inc. Both instruments are colorimeters, combining a colorimetric sensor with LED lighting. We investigated color accuracy compared to a high-end spectrophotometer from BYK Gardner. With different sets of samples we find for the Node an average value of dE_CMC (1:1) = 1.50, and a maximum of 7.86, when comparing with the 45° geometry of the spectrophotometer. Utilizing measurement data on the Spectral Power Distributions of the LEDs, we developed three methods to improve color accuracy as compared to the spectrophotometer data. We used these methods on different sets of samples with various degrees of gloss, both for training the models underlying the methods and for independent tests of model accuracy. Average color accuracy of the Node+ChromaPro improves from dE_CMC (1:1) = 1.82 to 1.16 with respect to spectrophotometer data. The percentage of samples with dE_CMC (1:1) < 1.0 increases from 30.9% (uncorrected) to 64%. With the improved color accuracy, these sensors become useful for many more applications.

Application of High-Throughput Seebeck Microprobe Measurements on Thermoelectric Half-Heusler Thin Film Combinatorial Material Libraries

In view of the variety and complexity of thermoelectric (TE) material systems, combinatorial approaches to materials development come to the fore for identifying new promising compounds. The success of this approach is related to the availability and reliability of high-throughput characterization methods for identifying interrelations between materials structures and properties within the composition spread libraries. A meaningful characterization starts with determination of the Seebeck coefficient as a major feature of TE materials. Its measurement, and hence the accuracy and detectability of promising material compositions, may be strongly affected by thermal and electrical measurement conditions. This work illustrates the interrelated effects of the substrate material, the layer thickness, and spatial property distributions of thin film composition spread libraries, which are studied experimentally by local thermopower scans by means of the Potential and Seebeck Microprobe (PSM). The study is complemented by numerical evaluation. Material libraries of the half-Heusler compound system Ti-Ni-Sn were deposited on selected substrates (Si, AlN, Al₂O₃) by magnetron sputtering. Assuming homogeneous properties of a film, significant decrease of the detected thermopower S_m can be expected on substrates with higher thermal conductivity, yielding an underestimation of materials thermopower between 15% and 50%, according to FEM (finite element methods) simulations. Thermally poor conducting substrates provide a better accuracy with thermopower underestimates lower than 8%, but suffer from a lower spatial resolution. According to FEM simulations, local scanning of sharp thermopower peaks on lowly conductive substrates is linked to an additional deviation of the measured thermopower of up to 70% compared to homogeneous films, which is 66% higher than for corresponding cases on substrates with higher thermal conductivity of this study.

Analysis of the Light Propagation Model of the Optical Voltage Sensor for Suppressing Unreciprocal Errors

An improved temperature-insensitive optical voltage sensor (OVS) with a reciprocal dual-crystal sensing method is proposed. The inducing principle of OVS reciprocity degradation is expounded by taking the different temperature fields of two crystals and the axis-errors of optical components into consideration. The key parameters pertaining to the system reciprocity degeneration in the dual-crystal sensing unit are investigated in order to optimize the optical sensing model based on the Maxwell's electromagnetic theory. The influencing principle of axis-angle errors on the system nonlinearity in the Pockels phase transfer unit is analyzed. Moreover, a novel axis-angle compensation method is proposed to improve the OVS measurement precision according to the simulation results. The experiment results show that the measurement precision of OVS is superior to ±0.2% in the temperature range from −40 °C to +60 °C, which demonstrates the excellent temperature stability of the designed voltage sensing system.

An Inexpensive, Stable, and Accurate Relative Humidity Measurement Method for Challenging Environments

In this research, an improved psychrometer is developed to solve practical issues arising in the relative humidity measurement of challenging drying environments for meat manufacturing in agricultural and agri-food industries. The design in this research focused on the structure of the improved psychrometer, signal conversion, and calculation methods. The experimental results showed the effect of varying psychrometer structure on relative humidity measurement accuracy. An industrial application to dry-cured meat products demonstrated the effective performance of the improved psychrometer being used as a relative humidity measurement sensor in meat-drying rooms. In a drying environment for meat manufacturing, the achieved measurement accuracy for relative humidity using the improved psychrometer was ±0.6%. The system test results showed that the improved psychrometer can provide reliable and long-term stable relative humidity measurements with high accuracy in the drying system of meat products.

Noninvasive measurement of intracranial pressure via the pulsatility index on transcranial Doppler sonography: Is improvement possible?

PURPOSE

We hypothesized that using hemodynamic variables could improve the prediction of intracranial pressure (ICP) from the middle cerebral artery pulsatility index (PI) measured with transcranial Doppler sonography.

METHODS

In this prospective study, 39 patients with traumatic brain injury were routinely examined with transcranial Doppler sonography, and the middle cerebral artery PI was calculated. A multivariate model including hematocrit, mean arterial blood pressure, heart rate, and arterial CO2 pressure (PaCO2 ) was evaluated.

RESULTS

Thirty-nine comatose patients (16 women and 23 men; age range 18-73 years; median 44 years) were included, and 234 data pairs (consisting of ICP and corresponding PI values) were analyzed. ICP ranged from -3 mmHg to +52 mmHg, and PI from 0.6 to 2.85. We found a significant but weak correlation between PI and the square root of ICP (R(2) between 0.29 and 0.34, p < 0.0001). A slightly stronger correlation was detected when hemodynamic variables were incorporated (R(2) between 0.37 and 0.43). Of these variables, mean arterial blood pressure had the most significant influence.

CONCLUSIONS

In this study, PI was not a sufficiently strong predictor of ICP to be used in clinical practice. Its reliability did not improve even when hemodynamic variables were considered. Therefore, we recommend abandoning the use of PI for the noninvasive measurement of ICP in clinical practice.

Caregiver report versus clinician impression: disagreements in rating neuropsychiatric symptoms in Alzheimer's disease patients

BACKGROUND

The measurement of neuropsychiatric symptoms (NPS) in dementia is often based on caregiver report. Challenges associated with providing care may bias the caregiver's recognition and reporting of symptoms. Given potential problems associated with caregiver report, clinicians may improve measurement by drawing from a wider array of available data and by applying clinical judgment.

OBJECTIVE

The objective of this study is to evaluate potential disagreements between caregiver report and clinician impression when rating psychopathological manifestations from the same patient with dementia.

METHODS

Three hundred twelve participants (156 patients with Alzheimer's disease [AD] and 156 caregivers) were studied using the Neuropsychiatric Inventory-Clinician Rating Scale. We considered disagreement to be present when caregiver ratings were significantly higher or lower (p < 0.05) than NPS ratings by clinicians of the same patient. To evaluate whether disagreements were related to dementia severity, we repeated comparisons across levels defined by the clinical dementia rating.

RESULTS

The most common disagreements involved ratings of agitation, depression, anxiety, apathy, irritability, and aberrant motor behavior especially in patients with mild dementia. There were fewer discrepancies in moderate or severe dementia. The most consistent disagreements involved global ratings of depression where caregiver scores ranged from +22.5 higher to -4.5 lower than clinician rating.

CONCLUSIONS

Caregivers may have incomplete perception of patient NPS mainly in mild dementia. NPS ratings might be confounded by cultural beliefs, sometimes leading caregiver to interpret symptoms as part of "normal" aging.

Assessing Conifer Ray Parenchyma for Ecological Studies: Pitfalls and Guidelines

Ray parenchyma is an essential tissue for tree functioning and survival. This living tissue plays a major role for storage and transport of water, nutrients, and non-structural carbohydrates (NSC), thus regulating xylem hydraulics and growth. However, despite the importance of rays for tree carbon and water relations, methodological challenges hamper knowledge about ray intra- and inter-tree variability and its ecological meaning. In this study we provide a methodological toolbox for soundly quantifying spatial and temporal variability of different ray features. Anatomical ray features were surveyed in different cutting planes (cross-sectional, tangential, and radial) using quantitative image analysis on stem-wood micro-sections sampled from 41 mature Scots pines (Pinus sylvestris). The percentage of ray surface (PERPAR), a proxy for ray volume, was compared among cutting planes and between early- and latewood to assess measurement-induced variability. Different tangential ray metrics were correlated to assess their similarities. The accuracy of cross-sectional and tangential measurements for PERPAR estimates as a function of number of samples and the measured wood surface was assessed using bootstrapping statistical technique. Tangential sections offered the best 3D insight of ray integration into the xylem and provided the most accurate estimates of PERPAR, with 10 samples of 4 mm(2) showing an estimate within ±6.0% of the true mean PERPAR (relative 95% confidence interval, CI95), and 20 samples of 4 mm(2) showing a CI95 of ±4.3%. Cross-sections were most efficient for establishment of time series, and facilitated comparisons with other widely used xylem anatomical features. Earlywood had significantly lower PERPAR (5.77 vs. 6.18%) and marginally fewer initiating rays than latewood. In comparison to tangential sections, PERPAR was systematically overestimated (6.50 vs. 4.92%) and required approximately twice the sample area for similar accuracy. Radial cuttings provided the least accurate PERPAR estimates. This evaluation of ray parenchyma in conifers and the presented guidelines regarding data accuracy as a function of measured wood surface and number of samples represent an important methodological reference for ray quantification, which will ultimately improve the understanding of the fundamental role of ray parenchyma tissue for the performance and survival of trees growing in stressed environments.

Effects of coordinate-system construction methods on postoperative computed tomography evaluation of implant orientation after total hip arthroplasty

OBJECTIVE

In total hip arthroplasty, it is important to assess postoperative implant orientation. The computed tomography-based (CT-based) three-dimensional (3D) templating method using 3D preoperative planning software is generally recommended. In this method, postoperative implant orientation within a bony coordinate system can be measured by overlaying a 3D computerized model of the implant on a real postoperative CT image of the implant. The bony coordinate system consists of several reference points (RPs) marked on a CT image of the bone surface. Therefore, preoperative and postoperative coordinate systems do not always match. We investigated how the difference between coordinate systems constructed from RPs chosen by manual methods (M1 and M2) and those constructed by the computer matching method influences the results of measurement validation.

METHODS

In M1, postoperative RPs were chosen without a specific tool in a single planning module. In M2, postoperative RPs were chosen with as little deviation as possible from preoperative RPs, verifying preoperative RPs on another monitor.

RESULTS

M1 and M2 produced mean errors in acetabular cup inclination of 0.7° ± 0.5° and 0.5° ± 0.3°, respectively, and mean errors in cup anteversion of 1.3° ± 1.2° and 0.5° ± 0.4°, respectively, which were statistically significant differences. M1 and M2 produced mean errors in femoral stem anteversion of 2.4° ± 2.0° and 2.7° ± 2.1°, respectively, not a significant difference, but these errors were larger than errors in cup orientation.

DISCUSSION

We recommend referring to preoperative RPs when choosing postoperative RPs. Surgeons must be aware that for evaluation of postoperative stem anteversion, manual methods may produce considerable error.

Accuracy of temperature measurement in the cardiopulmonary bypass circuit

Oxygenator arterial outlet blood temperature is routinely measured in the cardiopulmonary bypass (CPB) circuit as a surrogate for the temperature of the arterial blood delivered to sensitive organs such as the brain. The aim of this study was to evaluate the accuracy of the temperature thermistors used in the Terumo Capiox SX25 oxygenator and to compare the temperature measured at the outlet of the oxygenator using the Capiox CX*TL Luer Thermistor with temperatures measured at distal sites. Five experimental stages were performed in vitro to achieve this aim. Under our experimental conditions, the luer thermistors accurately measured the temperature as referenced by a precision thermometer. In the CPB circuit, the difference between arterial outlet and reference thermometer temperature varied with outlet temperature over-reading at low temperatures and under reading at high temperatures. There was negligible heat loss (-0.4+/-0.1degrees C) measured at 4.5 m from the arterial outlet. The Terumo Capiox CX*TL Luer Thermistor is an accurate and reliable instrument for measuring temperature when incorporated into the Capiox Oxygenator. The accuracy in the measurement of temperature using these thermistors is affected by the thermistor immersion depth. Under reading of the arterial blood temperature by approximately 0.5 degrees C should be considered at normothermic temperatures, to avoid exceeding the maximum arterial blood temperature as described by institutional protocols. The accuracy of blood temperature measurements should be considered for all oxygenator arterial outlet temperature probes.