1. Salient Features of Soft Tissue Examination Velocity during Manual Palpation
Jelizaveta Konstantinova1, Kaspar Althoefer1, Prokar Dasgupta2, Thrishantha Nanayakkara1
1Centre for Robotics Research (CoRe), Dept. of Informatics, King’s College London
2MRC Centre for Transplantation, DTIMB and NIHR BRC, King’s College London

2. Outline Motivation Studies of Manual Palpation
Experimental setup
Results
Finite Element Simulations
Conclusions and Next Steps

3. Motivation
To detect tissue abnormalities and provide haptic feedback during robot-assisted minimally invasive surgery (RMIS) in real time;
Artificial probing or palpation should be introduced
Liu et al., 2010
Zbyszewski et al.,2011

4. Motivation
But:
Non-linear and non-homogeneous environment leads to high variability of tactile information;
The influence of probing behaviour on abnormality detection should be studied
Palpation velocity could be one of the parameters, defining the effectiveness of results during tactile examination

5. Manual Palpation Studies
To study the effect of velocity during manual palpation
Ten participants with at least five years of surgical experience
Silicone Phantom or Porcine Kidney sample with embedded hard nodules
Unidirectional movement
Three types of velocity: slow, natural and fast

6. Experimental Setup
To understand the impact of velocity during manual palpation of soft tissue
Computer to record and synchronise data
Force and torque sensor to record applied pressure
Microsoft Kinect camera to track position of the hand – mm accuracy for an average palpation velocity
Subject performs unidirectional palpation

7. Experiments on Manual Palpation

8. Results of manual palpation studies
Factors, which might influence the detection rate of hard nodules: - Applied force - Applied velocity - Palpation material

9. Results of manual palpation studies
Factors, which might influence the detection rate of hard nodules: - Applied force - Applied velocity - Palpation material (p<0.0001) Porcine kidney or silicone organ Palpation behaviour should be studied in conjunction with the given viscoelastic properties of environment

10. Results of manual palpation studies
Silicone phantom:
- Applied velocity (p<0.0001)
256 – 300 mm/s
69 % detection rate
Velocity, mm/s
300
200
100
144 – 220 mm/s
82 % detection rate
85 – 123 mm/s
87 % detection rate
Slow Natural Fast
Clusters of velocity magnitude across all experiments

11. Finite Element Simulations
To understand stress sensed by human finger
Slow velocity
Stress, Pa
5 mm deep
3 mm deep
Distance, mm
Slow: 100 mm/s
Hyperelastic Arruda-Boyce model
Hard nodules (r = 5mm): 3 and 5 mm deep
Velocity according to experiments
Natural: 180 mm/s
Fast: 280 mm/s

12. Conclusions and Next Steps
The impact of palpation velocity on the detection rate has been demonstrated
The detection rate of hard formations can be improved by using corresponding velocity startegy
What is the optimal tactile examination strategy to detect tumours in soft tissue?

13. Thank you for your attention