Probe Contact Force Research Articles

Ultrasound Probe Movement Analysis Using Depth Camera with Compact Handle Design for Probe Contact Force Measurement.

The real-time information of the ultrasound probe movement and contact force during scanning is helpful for improving skill of medical professionals. This paper presents an affordable technique using an RGB-depth camera with the MediaPipe Hands framework for capturing the hand gesture to estimate the position and orientation of the ultrasound probe. The method does not require any additional marker which can interfere the motion and the feeling of handheld operation. The tracking accuracies of position and orientation were evaluated experimentally at different camera angles. The 3D printed handle was inserted into the grids of the XYZ plate and the tilt plate. Although the camera angle and the spatial position affect the accuracies, the maximum errors are always less than 7.5 mm and 10 degrees. The custom designed handle consisting of the inner and outer shells allows installation of the small three-axis force sensor for probe contact force measurement while scanning. The design is easy to assemble with an ultrasound probe without requiring any modification. The results of this work can be applied as a guideline for monitoring ultrasound training.

Tactile, Orientation, and Optical Sensor Fusion for Tactile Breast Image Mosaicking

Breast cancer screening using tactile imaging (TI) is an advancing field of low-cost noninvasive medical imaging. Utilizing arrays of capacitive pressure transducers to perform a differential stress measurement of suspicious tissue, TI has been shown to be effective in measuring lesion size and stiffness, and subsequent differentiation of malignant and benign conditions, in repeated clinical studies. In order to further improve the lesion classification accuracy of clinical TI, this article presents a novel method of mosaicking tactile images to form a large composite tactile map using the vein structure within the breast to spatially register tactile data. This article demonstrates practical nonrigid tactile image mosaicking, using probe contact force and relative orientation sensor fusion to correct for the tissue deformation during tactile scanning, miniaturized and applied to a pre-clinical TI prototype. Testing of the proposed TI prototype on representative, tissue-mimicking, and silicone breast phantoms, with varying baseline elasticity and internal vein structure, yields typical image registration accuracies of 0.33% ± 0.15%. In similar testing, the proposed system measures the background elasticity of the samples with worst case error < 4.5% over the range of 9–60 kPa, required for accurate lesion characterization. This work will lead into further clinical validation of TI for measurement and classification of in situ phantom and breast lesions, utilizing the delivered metrics from this work to improve differentiation accuracy.

Probe Contact Force Monitoring during Conductivity Measurements of the Left Atrial Appendage to Support the Design of Novel Diagnostic and Therapeutic Procedures.

The electrical properties of many biological tissues are freely available from the INRC and the IT’IS databases. However, particularly in lower frequency ranges, few studies have investigated the optimal measurement protocol or the key confounders that need to be controlled, monitored, and reported. However, preliminary work suggests that the contact force of the measurement probe on the tissue sample can affect the measurements. The aim of this paper is to investigate the conductivity change due to the probe contact force in detail. Twenty ex vivo bovine heart samples are used, and conductivity measurements are taken in the Left Atrial Appendage, a common target for medical device developments. The conductivity measurements reported in this work (between 0.14 S/m and 0.24 S/m) align with the literature. The average conductivity is observed to change by −21% as the contact force increases from 2 N to 10 N. In contrast, in conditions where the fluid concentration in the measurement area is expected to be lower, very small changes are observed (less than 2.5%). These results suggest that the LAA conductivity is affected by the contact force due to the fluid concentration in the tissue. This work suggests that contact force should be controlled for in all future experiments.

Comprehensive evaluation method of real-time non-reference ultrasound image involving soft tissue deformation

Ultrasound guided percutaneous interventional therapy has been widely used in clinic. Aiming at the problem of soft tissue deformation caused by probe contact force in robot-assisted ultrasound-guided therapy, a real-time non-reference ultrasound image evaluation method considering soft tissue deformation is proposed. On the basis of ultrasound image brightness and sharpness, a multi-dimensional ultrasound image evaluation index was designed, which incorporated the aggregation characteristics of the organization. In order to verify the effectiveness of the proposed method, ultrasound images of four different models were collected for experiments, including prostate phantom, phantom with cyst, pig liver tissue, and pig liver tissue with cyst. In addition, the correlation between subjective and objective evaluations was analyzed based on Spearman's rank correlation coefficient. Experimental results showed that the average evaluation time of a single image was 68.8 milliseconds. The evaluation time could satisfy real-time applications. The proposed method realizes the effective evaluation of real-time ultrasound image quality in robot-assisted therapy, and has good consistency with the evaluation of supervisors.

Probe contact forces during obstetric ultrasound scans - A design parameter for robot-assisted ultrasound

The ratio of experienced work-related musculoskeletal discomfort among obstetric sonographers has been reported to be as high as 80–90%. Risk factors are excessive probe contact forces long reach and static positions. Robot Assisted Ultrasound has potential to reduce the risks but in order to design such solutions, a critical need exists for a deeper understanding of the related risk factors. This involves quantification of the imposed transducer contact forces during obstetric scans. Thus, the objective of this study was to provide more accurate probe-contact force information through the recording of probe contact forces during scans of 40 pregnant women. Factors addressed were operator experience, subject Body Mass Index (BMI), foetus size, gestational age and the purpose of the scan. The BMI of the pregnant women had a significant correlation with the mean and maximum contact forces. The mean and maximum axial contact forces were 9.05 N and 37.63 N, respectively. The dependency of the applied transducer contact force versus the operator experience was found significant. The study results provide design information about required contact forces for robotic solutions to the ergonomic challenges of the sonographers.

Robotic Ultrasound Scanning With Real-Time Image-Based Force Adjustment: Quick Response for Enabling Physical Distancing During the COVID-19 Pandemic.

During an ultrasound (US) scan, the sonographer is in close contact with the patient, which puts them at risk of COVID-19 transmission. In this paper, we propose a robot-assisted system that automatically scans tissue, increasing sonographer/patient distance and decreasing contact duration between them. This method is developed as a quick response to the COVID-19 pandemic. It considers the preferences of the sonographers in terms of how US scanning is done and can be trained quickly for different applications. Our proposed system automatically scans the tissue using a dexterous robot arm that holds US probe. The system assesses the quality of the acquired US images in real-time. This US image feedback will be used to automatically adjust the US probe contact force based on the quality of the image frame. The quality assessment algorithm is based on three US image features: correlation, compression and noise characteristics. These US image features are input to the SVM classifier, and the robot arm will adjust the US scanning force based on the SVM output. The proposed system enables the sonographer to maintain a distance from the patient because the sonographer does not have to be holding the probe and pressing against the patient's body for any prolonged time. The SVM was trained using bovine and porcine biological tissue, the system was then tested experimentally on plastisol phantom tissue. The result of the experiments shows us that our proposed quality assessment algorithm successfully maintains US image quality and is fast enough for use in a robotic control loop.

Nanostethoscopy: Atomic Force Microscopy Probe Contact Force versus Measured Amplitude of Cardiomyocytic Contractions

Nanostethoscopy: Atomic Force Microscopy Probe Contact Force versus Measured Amplitude of Cardiomyocytic Contractions

Force and Position Control System for Freehand Ultrasound

A hand-held force-controlled ultrasound probe has been developed for medical imaging applications. The probe–patient contact force can be held constant to improve image stability, swept through a range, or cycled. The mechanical portion of the device consists of a ball screw linear actuator driven by a servo motor, along with a load cell, accelerometer, and limit switches. The performance of the system was assessed in terms of the frequency response to simulated sonographer hand motion and in hand-held image feature tracking during simulated patient motion. The system was found to attenuate contact force variation by 97% at 0.1 Hz, 83% at 1 Hz, and 33% 10 Hz, a range that spans the typical human hand tremor frequency spectrum. In studies with 15 human operators, the device applied the target contact force with ten times less variation than in conventional ultrasound imaging. An ergonomic, human-in-the-loop, imaging-workflow enhancing control scheme, which combines both force- and position-control, permits smooth making and breaking of probe–patient contact, and helps the operator keep the probe centered within its range of motion. By controlling ultrasound probe contact force and consequently the amount of tissue deformation, the system enhances the repeatability, usability, and diagnostic capabilities of ultrasound imaging.

Tele-operated ultrasound scans using a robotic probe and an ADSL or satellite link. Application to abdominal, pelvic, vascular, fetal and cardiac organs

The ratio of experienced work-related musculoskeletal discomfort among obstetric sonographers has been reported to be as high as 80–90%. Risk factors are excessive probe contact forces long reach and static positions. Robot Assisted Ultrasound has potential to reduce the risks but in order to design such solutions, a critical need exists for a deeper understanding of the related risk factors. This involves quantification of the imposed transducer contact forces during obstetric scans. Thus, the objective of this study was to provide more accurate probe-contact force information through the recording of probe contact forces during scans of 40 pregnant women. Factors addressed were operator experience, subject Body Mass Index (BMI), foetus size, gestational age and the purpose of the scan. The BMI of the pregnant women had a significant correlation with the mean and maximum contact forces. The mean and maximum axial contact forces were 9.05 N and 37.63 N, respectively. The dependency of the applied transducer contact force versus the operator experience was found significant. The study results provide design information about required contact forces for robotic solutions to the ergonomic challenges of the sonographers.

Improved Micromachined Terahertz On-Wafer Probe Using Integrated Strain Sensor

This paper introduces an improved method for monitoring and controlling the contact condition of terahertz on-wafer probes to enhance the measurement repeatability as well as probe lifetime. This method enables accurate contact force and contact angle measurements without modification to the standard probe station. Both probe contact force and contact angle are crucial for RF measurement repeatability. Repeatable probe contact force can be achieved by properly monitoring and controlling the strain generated at designated positions on the terahertz probe due to probe deformation induced by contacting the test substrate. Contact angle can be measured by asymmetrical strain on symmetrical positions of the probe when the probe is contacting the test substrate with angular misalignment. In this work a WR-1.5 (500 GHz-750 GHz) probe with integrated strain sensor is developed and tested. Mechanical tests show that the integrated sensors have a contact force resolution of 0.2 mN and a contact angle resolution of 0.05 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> about the center. RF tests show that repeatable measurements can be achieved with 3 mN contact force after adjusting probe contact angle using the integrated sensors, as compared to a previously reported value of 15 mN.

Electric contact stability of anti-wear probes

For the practical realization of precise processes or devices utilizing scanning nanoprobes, not only improvement in the wear resistance of the probe tip but also a stable electric contact at the sliding probe electrode is required. To meet both these requirements, the authors developed an anti-wear probe having a supporting Si tip and a metal electrode, both of which slide on the substrate simultaneously. Probes with various electrode materials were evaluated to investigate the key factors of the material choice for maintaining good electric contact over a long sliding distance. The results show that the optimal management of material hardness, surface roughness, and probe contact force was important to realize an optimum performance from the probe.

Robotic system for inspection of test objects with unknown geometry using NDT methods

PurposeThe purpose of this paper is to develop a portable non‐destructive testing (NDT) robotic arm that can be carried by climbing and walking robots (CLAWAR). The arm is required to maintain, during a scanning trajectory, a desired NDT probe contact force and orientation to evaluate defects in geometrically complex industrial infrastructure and products such as turbine blades.Design/methodology/approachA seven‐axis arm transportable by CLAWAR was developed to deploy NDT probes with suitable dexterity. It was equipped with a force sensor to scan a complex shape by keeping the NDT probe normal to the surface while maintaining a constant contact force with it. Two approaches were used. One used permanent magnet adhesion to obtain secure contact while the other used position‐force‐moment (PFM) feedback to adapt the arm.FindingsTests were performed on turbine blades with eddy‐current inspection techniques to assess the quality of defect data using manual inspection and automated inspection. Significant improvements in the quality of inspection were observed when using robotic scanning as compared to manual inspection.Practical implicationsThe results have practical implications for the remote inspection of very large infrastructures such as petrochemical storage tanks, bridges, pressure vessels, etc. or where the inspection is performed in hazardous environments and the test surface is not known a priori with any accuracy.Originality/valueThe work is a novel application of the PFM control of a seven‐axis robot arm to scan unknown contoured surfaces to ensure reliable NDT data acquisition at scanning speeds of up to 0.5 mm s−1.

2A1-A10 手術支援のための超音波プローブ保持ロボットの開発 : プローブ押し当て力の計測とその最適力の決定

2A1-A10 手術支援のための超音波プローブ保持ロボットの開発 : プローブ押し当て力の計測とその最適力の決定

Normative vibrotactile thresholds measured at five European test centres.

To compare vibrotactile thresholds between five international test centres, to determine causes of variability, and to provide normative data for use by health professionals. Vibrotactile thresholds were measured on various fingers in 1,008 subjects at 31.5 Hz (2,531 measurements) and at 125 Hz (2,807 measurements). Three centres used the up-and-down method of limits, rate of change of stimulus 3dB/s, to obtain vibrotactile thresholds. The push force on the surround was 2 N, the probe contact force was 1 N and the probe diameter was 6 mm concentric to a 10-mm diameter hole in the surround. One centre used an up-and-down method of limits with a 5-dB step and a 1.26-mm diameter probe with no surround. Another centre used a stepping algorithm, no surround, and the force on the 6-mm-diameter probe was unspecified. The 31.5-Hz thresholds and 125-Hz thresholds, expressed in dB, were similar between centres using similar methods. There were small (<5 dB) differences in vibrotactile thresholds between male and female subjects, between white-collar and blue-collar workers and between fingers. Both 31.5-Hz and 125-Hz thresholds increased with age; the mean effect of age on 31.5-Hz thresholds was approximately 2 dB over 25 years, while the effect of age on 125 Hz-thresholds was as high as 10 dB over 25 years. Vibrotactile thresholds are influenced by measurement method but can be similar at different centres if similar methods are used. Effects of measurement location and gender are often negligible. Thresholds depend on age, but over the range of ages considered, only the effect on 125-Hz thresholds is sufficient for correction; methods of correcting for age are given. These normative data may be used to assist the diagnosis of peripheral neuropathy involving vibrotactile sensation.

Vibration Perception Thresholds Assessed by Two Different Methods in Healthy Subjects

The values of vibration perception threshold (VPT) should be related to the equipment and methods of measurement that differ between European countries. ISO Standard 13091-1-2001 specifies the general guidelines regarding device facilities and measurement methodology. This study was designed to compare VPTs in healthy subjects by using two different methods of measurement. The first one was a standard technique applied currently in Poland and the second one was based on the principles of the International Standard ISO 13091-1-2001. The study comprised 187 healthy subjects, aged 17–57 years, not occupationally exposed to vibration. Both measurements of VPTs were performed using the same equipment (P-8, EmsonMat). The main differences in methodology between the Polish standard method and the method of ISO included: different mode of stimuli presentation (ascending in standard vs. Bekesy in ISO method), frequency range applied (63–500 Hz vs. 4–125 Hz), probe contact force (larger in Polish method), probe diameter (12 mm vs. 5 mm) and its surface (plane vs. rough). The results obtained found that the mean VPTs differed significantly at the overlapping frequencies depending on the method used, the differences varied from 2.2 to 6.4 dB at frequencies 125 and 250Hz, respectively. The correlation between the thresholds obtained by both methods at these frequencies was moderate (correlation coefficients about 0.6), although statistically significant. In the ISO method, the best VPTs were found at 4 and 125 Hz. There was a poor correlation between the thresholds at the extreme frequencies (i.e. 125 and 4 Hz) and rather high between adjacent frequencies (i.e. 25 and 32 Hz). Age, weight and height were significant covariates in both measurements. The model to calculate the normative values of VPTs adjusted for explanatory factors was set up in this study. It was concluded that different methods of VPT measurement are not comparable. The ISO method seems to supply more information about skin receptors and different kinds of tough sense than the Polish standard method. In order to perform international cohort studies there is a need to establish a unified standardised method of vibrotactile sense assessment.