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Proceedings of the 2016 International Conference on Industrial Engineering and Operations Management
Kuala Lumpur, Malaysia, March 8-10, 2016
Sonographer Ergonomics: Assessment and workplace redesign
Sonographers work related musculoskeletal disorder reported in previous studies considerably. A large no of questioner based work mapped the injury profile of sonographers, among these studies approximately 65% - 96% sonographers reported suffering from some form of work related injuries[1][2]. These injuries includes the mild pain in joints, discomforts in muscles and tendons, swelling, loss of sensation, clumsiness etc. Some body parts such as neck, shoulder, wrist, upper back and arm are more prone to injury due to long duration scanning[3]. Main cause of these injuries are unfavourable postures, pinch grip, repetitive motion, forceful exertion, sonographer rotation schedule etc.[4][5]. From economic perspective WRMSD in sonographers results in huge financially losses, increased absences and negative emotional impact [6] And must be eradicated with an easily adoptable solution.
To counter the hazardous ergonomics of sonographers three types of approaches are identified - engineering intervention, administrative intervention and personal/behavioural intervention. Few engineering intervention been identified in the literature mostly in trial period proposing arm support system[7], articulating arm [8], ultrasound system[9], probe supporting robot [10] and voice scan system [11]. These solutions are effective but market adoption will not likely to happen anytime soon. Administrative interventions constitute small modules of ergonomic training/workshops, optimal scheduling etc. which needs awareness and coordination among healthcare units, manufacturing industries and sonographers.
Third and most easily adaptable, behavioural intervention for sonographers presented in few studies. Workplace redesign for sonographers have been proposed in [12] for diagnosis animals. Most recommendation made on the positioning of animals and equipment subjectively, [13] described importance of proper adjustment between equipment’s, patient and sonographer and provides a set of guidelines to prevent WRMSD, [14] recommends the individual sonographer approach to be more effective, [15] organized a workshop sharing various sonographer practices to deals with WRMD supporting individually customized workplace practices, [16] Proposed alexander technique to make aware the individuals for better work practice, [17] Concluded prevention to be the best cure for WRMSD. Above mentioned studies mostly focussed towards individual awareness and weight the individual for a better work practices but lacks a systemic approach towards individual intervention. Individual intervention is a multifactorial approach and requires individually customized solutions.
Most ultrasound machines available in the markets are equipped with customization ability but customization performed by user based on gut feeling which could leads to comfortable but hazardous postures. A systematic quantitative approach is lacking where a user can customized the workplace considering patient size, types of diagnosis, user’s anthropometry and room layout.
Therefore, the aim of this study was to access the sonographer’s ergonomics and develop a methodology for individual intervention. Particularly this study aims to optimize the sonographer’s workplace using weighted product model with DHM in
Proceedings of the 2016 International Conference on Industrial Engineering and Operations Management
Kuala Lumpur, Malaysia, March 8-10, 2016
order to decrease the rapid upper limb assessment (RULA) score and lower back (L4/L5) compression force. The advantage of proposed methodology is discussed in terms of adaptability and feasibility in later section.
II. METHODOLOGY
The proposed approach takes place in following order –
(1) Ergonomics assessment of sonographer’s workplace using DHM. Most commonly performed diagnosis are categorisedinto 4 types depends upon the targeting patient body parts since for different body parts different postures are required.
(2) A new approach to redesign the workplace is proposed here. Proposed algorithm is generic that can be applied to otherproblems as well. Quantitative and qualitative criteria are considered for a holistic approach.
(3) Abdominal and carotid diagnosis, two most severe and frequent diagnosis obtained is targeted using proposed algorithm.
A. Ergonomics assessment of sonographers
Three method of ergonomic assessment presents in most literatures – survey questioners, DHM simulation and sensor basedassessment. Sonographer’s assessment had been carried out using sensors (electromyography and joint angle meter, motion capture system and dynamometer) in [18] [19] [20] , deriving joint angles and stress data.
Only occurrence of DHM simulation applied on sonographers found in [21] assessing abdominal ultrasound.
We considered 4 types of diagnosis. Since diagnosis of different body parts needs adoption of particular types of postures, hence categorisation of diagnosis is necessary for an accurate and comprehensive assessment. DHM performed on following diagnosis-
Abdominal Ultrasound (obstetric ultrasound)-To see organs and vessels within the abdomen. Some of the organs seen arethe liver, gallbladder, kidney etc.
Pelvic and Transvaginal (TV) Ultrasound-To see organs and vessels within the pelvic region. Organs seen are the uterus,ovaries and nearby structures.
Carotid Doppler-To identify arteries in neck and measure the speed and direction of blood flow through those bloodvessels.
Venous Doppler-To see the larger veins in leg and arm.
Fig. 1. An abdominal diagnosis posture snapshot. Fig. 2. Recreation of above posture.
Proceedings of the 2016 International Conference on Industrial Engineering and Operations Management
Kuala Lumpur, Malaysia, March 8-10, 2016
A. 1. Results
RULA is a proven technique to evaluate the posture for neck, trunk and upper extremity. RULA results for current studies are summarized in table 2. Rating of 1 and 2 in RULA indicate accepted posture (green), 3 and 4 indicate further change(yellow), 5 and 6 indicate, the soon change required(orange) and 7 indicate immediate change. No one posture manages to score 1 or 2.
TABLE I. RULA Evaluation results (average and variance)
Types of Diagnosis Average Variance
Abdominal
Pelvic and TV
Carotid Venous
4.5
4.9
6.6 4.6
1.5
0.72 0.33
1.05
B. Ergonomics Redesign Methodology
This section describes an interactive optimization technique to optimize the sonographer workplace. Proposed methodology is inspired from [22] who used virtual manufacturing (VM) and Design of experiment (DOE) to optimized a fruit packing workstation and [23] proposing Interactive evolutionary computation (IEC) for ergonomic optimization.
We present a novel methodology to redesign the workstation. Proposed methodology uses fusion of Microsoft Kinect and inertial sensors to capture the motion and workplace information. Data is being imported into DHM. Weighted product model is applied to optimize the workstation design variables for DHM quantitative assessment (RULA analysis and Lower back analysis). Method incorporates Qualitative inputs from both designer & sonographer.
Fig. 4. Flow Chart for Proposed Redesign Methodology
Proceedings of the 2016 International Conference on Industrial Engineering and Operations Management
Kuala Lumpur, Malaysia, March 8-10, 2016
Carotid Diagnosis
CA1 Horizontal distance between patient bed and sonographer chair 5 30
CA2 Vertical distance between patient bed and sonographer chair 15 32
CB1 Height of ultrasound machine screen 85 125
CB2 Distance between sonographer and screen 85 115
CA3 Patient Bed angles from hip 15 30
We performed the simulation and iteratively generate the random solutions from DHM. As suggested into
methodology DHM optimization results are further evaluated by designers and user.
Result:
4 same and 1 different design factors are used for each diagnosis. AA1, AA2, AB2 and CA1, CA2 CA3, showed the major
contribution in postures. Optimum value for these factors are identified to reduce the awkward posture.
TABLE V. Qualitative assessment from designer and user.
Abdominal Diagnosis
Solution Set Fitness Function User Designer Final Weightage
S1 0.74 0.7 0.60 0.74
S2 0.74 0.80 0.70 0.74
S3 0.75 0.80 0.65 0.75
S4 0.77 0.90 0.80 0.77
Carotid Diagnosis
S1 0.72 0.9 0.76 0.71
S2 0.75 0.9 0.8 0.73
S3 0.72 0.8 0.7 0.67
S4 0.73 0.78 0.72 0.68
Following tables contains the random solution generated and tested on virtual platform to find out the best possible configuration between sonographer-patient-machine to improve the sonographer’s ergonomics.
TABLE VI. DHM optimization results for carotid diagnosis.
Proceedings of the 2016 International Conference on Industrial Engineering and Operations Management
Kuala Lumpur, Malaysia, March 8-10, 2016
5 20 123 104 18 4.8 0.267 1480 0.71 0.62
10 21 98 86 16 4.3 0.35 1377 0.72 0.68
11 15 94 89 22 3.9 0.417 1458 0.71 0.71
9 16 88 98 19 4.2 0.367 1519 0.70 0.68
21 28 113 111 27 4.8 0.267 1674 0.68 0.62
30 32 125 115 30 6.3 0.017 2415 0.57 0.27
TABLE VI. DHM optimization results for abdominal diagnosis
AA1 AA2 AB1 AB2 AC1
Fitness Function
18 21 102 84 15 4.99 0.24 1569 0.69 0.60
28 25 120 84 15 4.5 0.32 1800 0.66 0.64
29 30 110 100 29 6 0.07 1753 0.67 0.41
18 21 118 84 30 5.3 0.18 1590 0.69 0.56
16 24 109 70 15 4.3 0.35 1676 0.68 0.66
13 21 118 100 24 3.9 0.42 1514 0.70 0.71
8 26 96 75 15 4.11 0.38 1591 0.69 0.68
11 21 11 75 30 3.58 0.47 1507 0.70 0.73
8 11 90 84 10 3.5 0.48 1504 0.70 0.74
8 21 99 84 18 3.8 0.43 1542 0.70 0.71
21 11 114 84 19 3.5 0.48 1431 0.72 0.74
18 21 121 60 15 3.4 0.50 1410 0.72 0.75
8 15 90 65 15 3.2 0.53 1320 0.73 0.77
8 10 97 75 30 4 0.40 1420 0.72 0.70
18 19 94 84 21 3.7 0.45 1435 0.71 0.72
24 11 103 60 10 4.1 0.38 1422 0.72 0.69
10 11 92 65 15 3.6 0.47 1503 0.70 0.73
17 11 116 75 28 4.2 0.37 1588 0.69 0.68
24 18 120 88 25 5.2 0.20 1632 0.69 0.57
30 30 122 100 30 6.2 0.03 1932 0.64 0.34
III. CONCLUSION
Ergonomic intervention strategies proposed had been tried for two cases and successfully provides a set of design variables to improve the sonographer ergonomics. A 50% percentile sonographer doing abdominal and carotid diagnosis can adopt these parameters to improve the ergonomics.
The work presented here is a small step towards integrating state of the art yet cheap motion capture system and virtual platform to cater the ergonomic issues and intervene at individual level.
IV. DISCUSSION
Used methodology successfully reduced the awkward posture to some extents however sometimes when grip force is too high, lower back objective function cannot be minimized. Also some awkward postures are still arriving for short durations. To overcome these shortcomings users mind propagate towards more innovative solutions. The method may be used as a systematic way to arrive towards product based solutions by exactly identifying the problematic behaviour.
Integration of DHM into Interactive evolutionary techniques could be a potential path for more optimal solutions. Interactive input from designers and sonographers can be reduced using neural networking. Also simulation time in DHM is fairly enough to prevent the quick adoption of method for every individual. However a database considering ergonomically optimized design variables for 5, 50, 95 percentile sonographer will be sufficient enough. Methodology needs to be followed for other diagnosis procedure as well with lesser no of assumptions.
A system comprising advanced artificial intelligence tools, motion capture hardware system such as Microsoft Kinect or Vicon and DHM tools such as Siemens Jack or Catia can comprehensively approve the ergonomics.
[24] J. Village and C. Trask, “Ergonomic analysis of postural and muscular loads to diagnostic sonographers,” Int. J. Ind. Ergon., vol. 37, no.9–10, pp. 781–789, Sep. 2007.
BIOGRAPHY
Anchal Patil graduated from Indian Institute of Tecnology Delhi India. He earned Master of Technology in industrial engineering from IIT
Delhi and Bachelor of Technology in industrial engineering and management from National Institute of Technology Kuruskhetra. His area
of research interests are biomechnaics and motor control, ergonomics, Operation Research and advanced optimization techniques.
P V M Rao is an Professor in Mechanical Engineering Department at Indian Institute of Technology Delhi India. He earned B.E. from college
of engineering, Osmania University, M.Tech from Indian Institute of Technology BHU and Ph.D. from Indian Institute of Technology