  This work presents an evaluation study using a force feedback evaluation
framework for a novel direct needle force volume rendering concept in the
context of liver puncture simulation. PTC/PTCD puncture interventions targeting
the bile ducts have been selected to illustrate this concept. The haptic
algorithms of the simulator system are based on (1) partially segmented patient
image data and (2) a non-linear spring model effective at organ borders. The
primary aim is to quantitatively evaluate force errors caused by our patient
modeling approach, in comparison to haptic force output obtained from using
gold-standard, completely manually-segmented data. The evaluation of the force
algorithms compared to a force output from fully manually segmented
gold-standard patient models, yields a low mean of 0.12 N root mean squared
force error and up to 1.6 N for systematic maximum absolute errors. Force
errors were evaluated on 31,222 preplanned test paths from 10 patients. Only
twelve percent of the emitted forces along these paths were affected by errors.
This is the first study evaluating haptic algorithms with deformable virtual
patients in silico. We prove haptic rendering plausibility on a very high
number of test paths. Important errors are below just noticeable differences
for the hand-arm system.
