1. Limitations for manual and telemanipulator-assisted motion tracking—implications for endoscopic beating-heart surgery 
Stephan Jacobs, MD, David Holzhey, MD, Bob B Kiaii, MD, Joerg F Onnasch, MD, Thomas Walther, MD, PhD, Friedrich W Mohr, MD, PhD, Volkmar Falk, MD, PhD 
The Annals of Thoracic Surgery 
Volume 76, Issue 6, Pages (December 2003)
DOI: /S (03)

2. Fig 1
Description of Fitt's law. The operator is asked to move from a starting point to a target. The width (W) of the target in which the operator wishes to terminate the movement and the distance (A) between the two points determine the difficulty of the task (a). By increasing the width of the target the index of difficulty (ID) decreases (b). Similarily, by decreasing the distance towards the target, the ID is decreased (c). Fitt's law predicts that an increase in the index of difficulty results in an increase of movement time.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

3. Fig 2
Endoscopic trainer consisting of a moving plate with a fixed task pad. Design of two point tapping task in a vertical, diagonal, and horizontal direction and the meander figure are displayed.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

4. Fig 3
Regression lines and correlation coefficients (r) for manual and telemanipulator (TM)-assisted two point tapping tasks at rest for diagonal, horizontal, and vertical directions. As Fitt's law describes a linear relationship where the delay constant is the intersection of the straight line with the y-axis and the information processing constant represents the slope of the straight line. Heavy dashed line = TM diagonal (r = 0.97); heavy solid line = TM horizontal (r = 0.98); dash-dot line = TM vertical (r = 0.81); light dashed line = manual diagonal (r = 0.99); broken line = manual horizontal (r = 0.89); light solid line = manual vertical (r = 0.98).
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

5. Fig 4
Time (T) to touch two targets in a vertical line. A is the distance from the starting point to the target (distance the needle has to move). With increasing distance to the target (A3 > A2 > A1) the index of difficulty and thus the time to perform the task increases. The distance between two points is 2.5 mm for vertical direction. Results are shown at rest and with variing frequencies (35 and 60 beats per minute) and amplitudes. Solid bars = A1, 2.5 mm; open bars = A2, 5.0 mm; hatched bars = A3, 7.5 mm.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

6. Fig 5
Number of errors for a more complex task (meander) at rest and different frequencies (35 and 60 beats per minute) and amplitudes for manual and telemanipulator-assisted control and motion tracking.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

7. Fig 6
Mean number of errors at different scaling rates. The number of errors at the two point tapping task in a vertical, diagonal, and horizontal direction decreased when the scaling rate was changed from 1:1 over 3:1 to 5:1.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

8. Fig 7
Structural model of tracking and control tasks. For tracking tasks (a) the operator follows a moving object. The manual response is preceded by signal reception and a decision making process. The manual movements are transmitted to the target system by the control panels and the effector devices of the telemanipulator. The current state of the target system is perceived by the operator closing the feedback loop. For the control task (b) the internal (wish) or external (command) goal is to change the state of an object. The information and motion flow as well as the feedback are similar as for tracking tasks. The effect on the object is additionally influenced by its behavior and structural texture (inherited dynamics). Both control and tracking tasks occur simultaneously and have impact on each other during beating heart surgery.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )

9. Fig 8
Feedback-loop for the operator performing a manual task (a). Visual and tactile signals are received. A decision is made followed by a response. The effect on the object is immediately seen or felt and thus fed back to the operator. By using a telemanipulator (b) the response of the operator is further processed. This causes a system related delay and the effect on the object is indirect. Additionally, with most telemanipulators fine tactile feedback is lacking and the operator has to rely mostly on indirect visual signals that are displayed on a video monitor.
The Annals of Thoracic Surgery  , DOI: ( /S (03) )