Motion-Tracking Machines and Sensors: Advancing Education Technology

      Graduate medical education is predominantly based on a time-based apprenticeship model, with implied acquisition of proficiency after a pre-set amount of clinical exposure. While motion metrics have been used previously to measure skill performance indicators, these assessments have largely been performed on a summative scale to describe the performance of complete tasks or procedures. By segmenting performances of interest and assessing the essential elements individually, a more comprehensive understanding of the aspects in need of improvement for a learner can be obtained. The purpose of this review is to discuss technologies applicable to motion tracking, their benefits and limitations, approaches to data processing, and potential applications based on recent improvements in this technology. Objective analysis of motion metrics may improve educational standards of learning and efficiency by both standardizing the feedback process for trainees and reducing the volume of instructors required to facilitate practice sessions. With rigorous validation and standardization, motion metric assessment may also prove useful to demonstrate competency in technical procedures as part of a comprehensive certification process.

      Key Words

      GRADUATE MEDICAL EDUCATION predominantly is based on a time-based apprenticeship model, with implied acquisition of proficiency after a preset amount of clinical exposure. Although motion metrics have been used previously to measure skill performance indicators, these assessments largely have been performed on a summative scale to describe the performance of complete tasks or procedures. By segmenting performances of interest and assessing the essential elements individually, a more comprehensive understanding of the aspects in need of improvement for a learner can be obtained. The purpose of this review is to discuss technologies applicable to motion tracking, their benefits and limitations, approaches to data processing, and potential applications based on recent improvements in this technology. Objective analysis of motion metrics may improve educational standards of learning and efficiency by both standardizing the feedback process for trainees and reducing the volume of instructors required to facilitate practice sessions. With rigorous validation and standardization, motion-metric assessment also may prove useful to demonstrate competency in technical procedures as part of a comprehensive certification process.

      Value of Motion Metrics

      The current graduate medical education model is based on a time-based apprenticeship model, with implied acquisition of proficiency after a predetermined duration of clinical exposure. Specifically for clinical procedures requiring psychomotor skills, subjective endpoint-based observer metrics are used to verify the presence of proficiency. With the availability of “mixed-reality” simulators, the value of motion metrics has been demonstrated in objectifying progression of skill acquisition for complex tasks.
      • Ma IWY
      • Brindle ME
      • Ronksley PE
      • et al.
      Use of simulation-based education to improve outcomes of central venous catheterization: A systematic review and meta-analysis.
      For example, motion-tracking technology has been used previously to analyze technique and performance in athletic sports.
      • Pueo B
      • Jimenez-Olmedo JM.
      Application of motion capture technology for sport performance analysis.
      Meanwhile, the National Aeronautics and Space Administration has used optical and inertial motion trackers to analyze astronauts’ navigation of the International Space Station to guide construction.

      Mamiit A. NASA hopes motion tracking tech will help it build better space stations. Available at: https://www.techtimes.com/articles/115732/20151212/nasa-hopes-motion-tracking-tech-will-help-it-build-better-space-stations.htm.

      Approaches to education based on objective quantification of skill progression can be used to distinguish learners who require more or less time to train.
      • Rebel A
      • DiLorenzo AN
      • Fragneto RY
      • et al.
      A competitive objective structured clinical examination event to generate an objective assessment of anesthesiology resident skills development.
      In such a competency-based, metric-driven model, training may be expedited, deliberate, and consistent regarding, identifying and successfully preparing trainees to achieve educational milestones.
      Although motion metrics have been used previously to measure skill performance indicators, such as path length and accelerations of hands and medical instruments, these assessments largely have been performed on a summative scale to describe the performance of complete tasks or procedures.
      • Garfjeld Roberts P
      • Alvand A
      • Gallieri M
      • et al.
      Objectively assessing intraoperative arthroscopic skills performance and the transfer of simulation training in knee arthroscopy: A randomized controlled trial.
      ,
      • Musits AN
      • Phrampus PE
      • Lutz JW
      • et al.
      Physician versus nonphysician instruction: evaluating an expert curriculum-competent facilitator model for simulation-based central venous catheter training.
      Little- to-no segmentation of these metric reports has been performed to assess skills and facets that represent essential elements of the complex psychomotor tasks or procedures. By segmenting performances of interest and assessing the essential elements individually, a more comprehensive understanding of the aspects in need of improvement for a learner can be obtained.
      • Matyal R
      • Mitchell JD
      • Hess PE
      • et al.
      Simulator-based transesophageal echocardiographic training with motion analysis: A curriculum-based approach.
      For example, motion analysis may be able to indicate a need to practice specifically obtaining venous access during central line placement, as opposed to retraining the entire procedure, enhancing the efficiency of training.
      The purpose of this review is to discuss technologies applicable to motion tracking, their benefits and limitations, approaches to data processing, and potential applications based on recent improvements in this technology. Although there has been limited exploration of motion tracking in patient care settings, applications of motion tracking mentioned here largely refer to training exercises in simulated environments.
      • Garfjeld Roberts P
      • Alvand A
      • Gallieri M
      • et al.
      Objectively assessing intraoperative arthroscopic skills performance and the transfer of simulation training in knee arthroscopy: A randomized controlled trial.
      ,
      • Chin KJ
      • Tse C
      • Chan V
      • et al.
      Hand motion analysis using the imperial college surgical assessment device: validation of a novel and objective performance measure in ultrasound-guided peripheral nerve blockade.
      Potential future applications in clinical medicine are mentioned in closing. Specific focus is placed on electromagnetic sensing devices, particularly the Polhemus Liberty (Polhemus, Colchester, VT), with which the authors have the most experience.

      Motion-Tracking Technology

      Motion-tracking machines can be divided largely into two forms: optical and nonoptical. Optical systems typically use high-speed cameras to detect either infrared light reflection or emission, from which three-dimensional positional data can be extracted and postprocessed. Nonoptical systems typically rely on one of three methods of data acquisition to determine orientation and movement: electromagnetic, mechanical, and inertial mechanisms. Electromagnetic appliances detect the orientation of wired and/or wireless sensors by assessing the interaction between an emitted electric field and flowing current, as described in Faraday’s law. Mechanical systems operate by recording the orientation of a particular object with electrochemical potentiometers. Inertial mechanisms operate by recording orientation with gyroscopes and accelerometers, which then require various estimation techniques to approximate changes in position over time (Table 1).
      Table 1Advantages and Disadvantages of Various Tracking Modalities
      Tracking ModalityDescriptionProsCons
      Active marker (optical)Cameras record LED markers; motion capture software extrapolates positional data– Absolute positioning

      – High signal-to-noise ratio
      – High expense

      – Wires can obstruct complex movements
      Passive marker (optical)Cameras record light from reflective markers; software extrapolates positional data– Absolute positioning

      – No wires required for markers
      – High expense

      – Prone to occlusion
      Markerless (optical)Cameras record shadow from multiple angles; pattern recognition used to interpret positional data– Absolute positioning

      – Subject free from electrical equipment
      – High expense

      – Requires pattern recognition
      Electromagnetic (non-optical)Source emits electromagnetic field; sensors are recorded by changes in magnetic flux– Low expense

      – Durability and fidelity of sensors
      – Relative positioning

      – Prone to electric and magnetic interference
      Mechanical (non-optical)Embedded potentiometers measure relative position of equipped exoskeleton mold– Low expense–

      Highly replicable sensor positioning
      – Relative positioning

      – Restricted range of motion
      Inertial (non-optical)Gyroscopes and accelerometers record position and velocity of attached device– Low expense–

      Size & implantability
      – Relative positioning

      – Prone to positional drift and noise
      NOTE. Optical systems provide precise measurements of motion, with minimal obstruction to the wearer; however, they are relatively expensive and require advanced procedural planning. Nonoptical systems facilitate high-fidelity, low-cost motion tracking through portable, easily applied technology; however, they are prone to noise and distortion, and may restrict the dexterity of the wearer.
      Abbreviations: LED, light-emitting diode.

      Examples of Motion Trackers

      Manufacturers of motion-tracking technology include, for example, Natural Point (Corvallis, OR), Polhemus (Colchester, VT), Virtual Motion Lab (Dallas, TX), and Vicon Systems Ltd (UK) (Fig 1).

      OptiTrack Cameras. NaturalPoint, Inc. DBA OptiTrack. 2021. Retrieved from: https://optitrack.com/cameras/prime-41/indepth.html. Accessed 17 May, 2021.

      Polhemus Liberty. Polhemus Innovation in Motion. 2015. Retrieved from: https://polhemus.com/motion-tracking/all-trackers/liberty. Accessed 17 May, 2021.

      VMG 30. Virtual Motion Labs. 2021. Retrieved from: https://www.virtualmotionlabs.com/vr-gloves/vmg-30/. Accessed 17 May, 2021.

      Blue Trident. Vicon Motion Systems. 2021. Retrieved from: https://www.vicon.com/hardware/blue-trident/. Accessed 17 May, 2021.

      The authors’ institution has acquired the Polhemus Liberty for use in objective analyses of performance and informed feedback reports to enhance the teaching of medical procedures. Although each system has its own advantages and disadvantages, further details about this system are included based on the authors’ experience.
      Fig 1
      Fig. 1Commercially available motion-tracking machines. (A) OptiTrack Primex 41 (Natural Point, Corvallis, OR).

      OptiTrack Cameras. NaturalPoint, Inc. DBA OptiTrack. 2021. Retrieved from: https://optitrack.com/cameras/prime-41/indepth.html. Accessed 17 May, 2021.

      (B) Polhemus Liberty (Polhemus, Colchester, VT).

      Polhemus Liberty. Polhemus Innovation in Motion. 2015. Retrieved from: https://polhemus.com/motion-tracking/all-trackers/liberty. Accessed 17 May, 2021.

      (C) VMG 30 Virtual Reality Glove (Virtual Motion Lab, Dallas, TX).

      VMG 30. Virtual Motion Labs. 2021. Retrieved from: https://www.virtualmotionlabs.com/vr-gloves/vmg-30/. Accessed 17 May, 2021.

      (D) Blue Trident (Vicon Motion Systems Ltd., UK).

      Blue Trident. Vicon Motion Systems. 2021. Retrieved from: https://www.vicon.com/hardware/blue-trident/. Accessed 17 May, 2021.

      Device and Software Description of Polhemus Liberty

      • Software used to operate and interpret motion-tracking data is compatible with Macintosh (Apple Inc, Cupertino, CA) and Windows (Microsoft Corporation, Redmond, WA) operating systems (Fig 2).
        Fig 2
        Fig. 2PiMgr software used to record motion with the Polhemus Liberty. Position and orientation are recorded in the form of Cartesian coordinates, and Azimuth, Elevation, and Rotation, respectively. Sensors can be observed in real time with color references and signals to notify the presence of distortion in any sensor.
      • Sensors can be connected by wire, or wirelessly, to the motion tracker and recorded within a finite range to avoid distortion (Figs 2 and 3).
        Fig 3
        Fig. 3Electromagnetic sensors applied to the dorsum of both hands, right thumb, right forearm, needle plunger, and ultrasound probe during a central line procedure, using the Polhemus Liberty.
      • Motion recordings can be observed in real time, with a latency of 3.5 ms, as well as a static position and orientation accuracy of 0.76 mm and 0.15 degrees root mean square, respectively.
      • The motion-tracking device is capable of recording in six degrees of freedom, at a rate of 120 or 240 Hz, with up to 16 sensors at one time.
      • Sensors can be attached easily to record numerous objects or anatomic locations, with high fidelity, in real time (Fig 3).

      General Limitations to Motion-Tracking Technology

      The field of motion tracking is relatively novel and subject to broad limitations:
      • Motion tracking and kinematic analysis can be highly technical and may not be readily interpretable by the standard participant.
      • There currently are no validated standards for motion metric performance in medicine, which represents a barrier to its use in evaluating technical performance.
      • Although motion-tracking technology prospectively may reduce the cost of training, the initial investment may not be economically viable for some institutions.
      • Outputs of motion-metric data must be processed for interpretation; therefore, delaying feedback to users, as opposed to observer-based feedback that immediately can be provided. The availability of motion-metric feedback may be expedited significantly by the use of automated computing software.

      Technical Limitations to Motion-Tracking Machines

      Despite the numerous advantages of using motion-tracking systems in education and training, technical limitations include the following:
      • Marker-based optical systems require several nodes to be attached and in line of sight to track motion. If these nodes at any point are obstructed and lose line of sight, data are lost.
      • Electromagnetic systems are prone to signal distortion by metal objects, which may limit the physical range of use.
      • Mechanical systems generally hinder the operator’s range of motion, and may limit the user to particular joint movements (e.g., flexion and extension).
      • Inertial systems require extensive postprocessing to approximate positional data, account for drift, and filter noise and magnetic disturbance.

      Postprocessing

      Motion analysis may be used to better interpret the composite parts of a procedure or skill through segmentation of key checkpoints and subsequent interrogation of recorded metric parameters. Imported data can be divided into segments using time stamps derived from the duration of each procedural checkpoint and the frame rate of the motion tracker. By multiplying the frame rate of the motion tracker by the duration of a segment, a precise period of motion can be extracted for analysis (Table 2). A number of parameters may be addressed thereafter, including path length, rotational sum, number of accelerations, and time, using a variety of software and equations.
      • Ebina K
      • Abe T
      • Higuchi M
      • et al.
      Motion analysis for better understanding of psychomotor skills in laparoscopy: Objective assessment-based simulation training using animal organs.
      Table 2Example of Segmentation in the Analysis of a Rapid Ultrasound for Shock and Hypotension (RUSH) Examination
      Rush Ultrasound ViewsTimestampFrame CountFrame SumFrame Reference
      Start01:18.72
      Parasternal long-axis02:20.6148751487614877
      Parasternal short-axis03:14.4129052778127782
      Apical 4-chamber03:38.457483352933530
      Subcostal 4-chamber03:55.440943762337624
      Subcostal inferior vena cava04:04.120863970939710
      Morrison’s pouch04:33.871264683546836
      Left upper-quadrant splenorenal04:43.523404917549176
      Long-axis suprarenal04:55.929695214452145
      Short-axis suprarenal04:59.68865303053031
      Left lung05:13.032145624456245
      Right lung05:32.0456060804
      NOTE. Timestamps from a video recording are used to identify ranges of frame data in which specific views were obtained. Precise interrogation of motions for each view are made possible.
      The advantage of segmentation is to allow motion analysis during any part or duration of interest in a given procedure. For example, transthoracic echocardiography examinations may be segmented to analyze probe motion for each view obtained. Similarly, central line procedures may be segmented to analyze probe motion while scanning for venous access. Task-based training traditionally is used to assess proficiency in isolated components of a procedure; this method often prevents learners from being immersed in executing the entire process. This barrier to learning is apparent in the disparity between simulation training and more broad clinical application.
      • Tokarczyk AJ
      • Greenberg SB.
      Use of mannequin-based simulators in anesthesiology.
      Segmentation allows for the precise interrogation of composite skills in a more immersive environment, wherein a complete procedure is performed and segmented later for analysis. This may allow for a more accurate assessment of skill acquisition in the performer.

      Breaking Down Barriers to Motion Tracking in Medicine

      Modern motion trackers now are capable of recording the position, orientation, and movements of multiple sensors with increased frame rate, decreased latency, and improved accuracy. Furthermore, tracker-specific improvements include increased range of recording in electromagnetic systems, increased mobility in mechanical systems, and decreased price in optical systems. These advances counter previous limitations and allow for significantly more precise interrogation of crucial elements of procedures, permitting use in myriad applications (Table 1). Furthermore, as opposed to embedded sensors in simulators, external motion trackers can be used to record and interpret motion freely in variable environments and fields of interest. These and a number of other technologic improvements have the potential to further the approach toward competency-based training and objective, individualized feedback that is both efficient and readily interpretable.
      Although motion tracking has been used to assess proficiency in highly dexterous procedures such as surgical intervention, these analyses traditionally have relied on expensive, optical motion trackers or simulation technology.
      • Sánchez-Margallo JA
      • Sánchez-Margallo FM
      • Oropesa I
      • et al.
      Objective assessment based on motion-related metrics and technical performance in laparoscopic suturing.
      ,
      • D'Angelo A-LD
      • Rutherford DN
      • Ray RD
      • et al.
      Idle time: An underdeveloped performance metric for assessing surgical skill.
      For example, reflective markers were attached to forceps, scissors, and needle holders to record motion during suturing, tissue resection, and needling in a previous study that demonstrated significant differences in path length and the number of accelerations between novices and experts.
      • Ebina K
      • Abe T
      • Higuchi M
      • et al.
      Motion analysis for better understanding of psychomotor skills in laparoscopy: Objective assessment-based simulation training using animal organs.
      Historically, nonoptical systems have been restricted somewhat to global interpretation of procedures with gross motor movements. This was due in part to the methods and interpretation of data collection being relatively limited regarding obstruction from wiring, noise, electromagnetic interference (distortion), the convoluted postprocessing of high-volume outputs of data, and the nature of their interpretation as summative rather than segmented.
      • Welch G
      • Foxlin E.
      Motion tracking: No silver bullet, but a respectable arsenal.
      The recent commercial availability of multifaceted nonoptical motion trackers has expanded the potential applications of kinematic analysis to include finer-motor movements of several moving parts.
      • Shaharan S
      • Nugent E
      • Ryan DM
      • et al.
      Basic surgical skill retention: can patriot motion tracking system provide an objective measurement for it?.
      Earlier work with proprietary electromagnetic systems included regional nerve blocks and central venous catheterization, but these and other areas now can be explored in greater detail and higher fidelity.
      • Chin KJ
      • Tse C
      • Chan V
      • et al.
      Hand motion analysis using the imperial college surgical assessment device: validation of a novel and objective performance measure in ultrasound-guided peripheral nerve blockade.
      ,
      • Shaharan S
      • Nugent E
      • Ryan DM
      • et al.
      Basic surgical skill retention: can patriot motion tracking system provide an objective measurement for it?.
      ,
      • Clinkard D
      • Holden M
      • Ungi T
      • et al.
      The development and validation of hand motion analysis to evaluate competency in central line catheterization.
      In turn, retention of skills, such as suturing, have been evaluated reliably using electromagnetic tracking of novices’ dorsums.
      • Shaharan S
      • Nugent E
      • Ryan DM
      • et al.
      Basic surgical skill retention: can patriot motion tracking system provide an objective measurement for it?.
      The authors anecdotally have integrated live model motion analysis as a means of training Rapid Ultrasound for Shock and Hypotension (RUSH) examinations in broader ultrasound skills training courses.
      • Fatima H
      • Kuppalli S
      • Baribeau V
      • et al.
      Comprehensive ultrasound course for special operations combat and tactical medics [in press].
      These recordings are possible within a physical recording range fit for numerous medical applications (Fig 4).
      Fig 4
      Fig. 4Demarcated area for use in motion-tracking applications. Fidelity is highest within the demarcated area but can be expanded significantly by avoiding metallic objects and wiring.
      Traditionally, multiple faculty members are present during training sessions to provide subjective feedback based on observation of a trainee’s performance. This native approach has significant room for improvement, particularly regarding the time required from faculty and interrater reliability.
      • Groenier M
      • Brummer L
      • Bunting BP
      • et al.
      Reliability of observational assessment methods for outcome-based assessment of surgical skill: Systematic review and meta-analyses.
      In light of the coronavirus disease 2019 pandemic, training programs have been required to facilitate lower-volume sessions, decreasing efficiency and further increasing the burden on faculty time by necessity of smaller student-to-faculty ratios.
      • Martinelli SM
      • Chen F
      • Isaak RS
      • et al.
      Educating anesthesiologists during the coronavirus disease 2019 pandemic and beyond.
      In response to novel challenges introduced by the pandemic, adaptive approaches are necessary to maintain effectiveness and improve educational standards of learning and efficiency. Objective analysis of motion metrics may both reduce the volume of instructors required to facilitate practice sessions and standardize the feedback process for trainees. This may be accomplished by partially substituting motion-metric analysis for instructor feedback, allowing for an increased number of training sessions and noninferior change in logistic and fiscal demand. In essence, the total volume and efficiency of training could be maintained while reducing the time required from faculty and abiding by protocols intended to limit unnecessary exposures.

      Conclusion

      Potential applications of motion tracking beyond what has been performed readily include the establishment of proficiency standards of kinematic performance. These may further the approach toward competency-based education and objective feedback for learners. Comparisons of motion-metric parameters, including path length, rotational sum, and number of accelerations, to previously validated measures of performance, such as global rating scales and time, may yield indicators of plasticity and proficiency in learners. Standardized metrics of performance may be used to elucidate an individual’s strengths and weaknesses both overall and in particular segments of procedures, facilitating a more deliberate feedback and learning process. With rigorous validation and standardization, motion-metric assessment also may prove useful to demonstrate competency in technical procedures as part of a comprehensive certification process. Despite motion metrics existing largely as an endpoint metric to date, there exists the possibility for application in evaluating performance of clinical procedures on actual patients. Moving forward, motion analysis could be used for providing objective feedback in training, debriefing after procedures, and evaluating clinical competence.

      Acknowledgments

      The authors thank the trainees who participated in pilot studies using the technology described in this article. They also thank the Department of Anesthesia, Critical Care and Pain Medicine and the Department of Radiology at Beth Israel Deaconess Medical Center for their support of this initiative.

      Conflict of Interest

      None.

      References

        • Ma IWY
        • Brindle ME
        • Ronksley PE
        • et al.
        Use of simulation-based education to improve outcomes of central venous catheterization: A systematic review and meta-analysis.
        Acad Med. 2011; 86: 1137-1147
        • Pueo B
        • Jimenez-Olmedo JM.
        Application of motion capture technology for sport performance analysis.
        Retos Nuevas Tendencias Educación Física Deporte Recreación. 2017; : 241-247
      1. Mamiit A. NASA hopes motion tracking tech will help it build better space stations. Available at: https://www.techtimes.com/articles/115732/20151212/nasa-hopes-motion-tracking-tech-will-help-it-build-better-space-stations.htm.

        • Rebel A
        • DiLorenzo AN
        • Fragneto RY
        • et al.
        A competitive objective structured clinical examination event to generate an objective assessment of anesthesiology resident skills development.
        A A Case Rep. 2016; 6: 313-319
        • Garfjeld Roberts P
        • Alvand A
        • Gallieri M
        • et al.
        Objectively assessing intraoperative arthroscopic skills performance and the transfer of simulation training in knee arthroscopy: A randomized controlled trial.
        Arthroscopy. 2019; 35 (e1): 1197-1209
        • Musits AN
        • Phrampus PE
        • Lutz JW
        • et al.
        Physician versus nonphysician instruction: evaluating an expert curriculum-competent facilitator model for simulation-based central venous catheter training.
        Simul Healthc. 2019; 14: 228-234
        • Matyal R
        • Mitchell JD
        • Hess PE
        • et al.
        Simulator-based transesophageal echocardiographic training with motion analysis: A curriculum-based approach.
        Anesthesiology. 2014; 121: 389-399
        • Chin KJ
        • Tse C
        • Chan V
        • et al.
        Hand motion analysis using the imperial college surgical assessment device: validation of a novel and objective performance measure in ultrasound-guided peripheral nerve blockade.
        Reg Anesth Pain Med. 2011; 36: 213-219
      2. OptiTrack Cameras. NaturalPoint, Inc. DBA OptiTrack. 2021. Retrieved from: https://optitrack.com/cameras/prime-41/indepth.html. Accessed 17 May, 2021.

      3. Polhemus Liberty. Polhemus Innovation in Motion. 2015. Retrieved from: https://polhemus.com/motion-tracking/all-trackers/liberty. Accessed 17 May, 2021.

      4. VMG 30. Virtual Motion Labs. 2021. Retrieved from: https://www.virtualmotionlabs.com/vr-gloves/vmg-30/. Accessed 17 May, 2021.

      5. Blue Trident. Vicon Motion Systems. 2021. Retrieved from: https://www.vicon.com/hardware/blue-trident/. Accessed 17 May, 2021.

        • Ebina K
        • Abe T
        • Higuchi M
        • et al.
        Motion analysis for better understanding of psychomotor skills in laparoscopy: Objective assessment-based simulation training using animal organs.
        Surg Endosc. 2021; 35: 4399-4416
        • Tokarczyk AJ
        • Greenberg SB.
        Use of mannequin-based simulators in anesthesiology.
        Dis Mon. 2011; 57: 706-714
        • Sánchez-Margallo JA
        • Sánchez-Margallo FM
        • Oropesa I
        • et al.
        Objective assessment based on motion-related metrics and technical performance in laparoscopic suturing.
        Int J Comput Assist Radiol Surg. 2017; 12: 307-314
        • D'Angelo A-LD
        • Rutherford DN
        • Ray RD
        • et al.
        Idle time: An underdeveloped performance metric for assessing surgical skill.
        Am J Surg. 2015; 209: 645-651
        • Welch G
        • Foxlin E.
        Motion tracking: No silver bullet, but a respectable arsenal.
        IEEE Comput Graph Appl. 2002; 22: 24-38
        • Shaharan S
        • Nugent E
        • Ryan DM
        • et al.
        Basic surgical skill retention: can patriot motion tracking system provide an objective measurement for it?.
        J Surg Educ. 2016; 73: 245-249
        • Clinkard D
        • Holden M
        • Ungi T
        • et al.
        The development and validation of hand motion analysis to evaluate competency in central line catheterization.
        Acad Emerg Med. 2015; 22: 212-218
        • Fatima H
        • Kuppalli S
        • Baribeau V
        • et al.
        Comprehensive ultrasound course for special operations combat and tactical medics [in press].
        J Spec Oper Med. Accepted for publication. 2021; (May)
        • Groenier M
        • Brummer L
        • Bunting BP
        • et al.
        Reliability of observational assessment methods for outcome-based assessment of surgical skill: Systematic review and meta-analyses.
        J Surg Educ. 2020; 77: 189-201
        • Martinelli SM
        • Chen F
        • Isaak RS
        • et al.
        Educating anesthesiologists during the coronavirus disease 2019 pandemic and beyond.
        Anesth Analg. 2021; 132: 585-593