Evaluation of Direct Haptic 4D Volume Rendering of Partially Segmented Data for Liver Puncture Simulation

Andre Mastmeyer,Heinz Handels,Dirk Fortmeier

doi:10.1038/s41598-017-00746-z

Abstract

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.

Highlights

We have presented the predecessor AcusVR-3D13 featuring fully manually-segmented patient models and our new simulator AcusVR-4D9 with simulated US imaging needle guidance as a valuable training and planning tool
We applied our methods to 10 patient (#1-#10) clinical CT data sets and compared the new haptics method using “partial segmentation masks augmented by our patient-specific transfer functions,” against the haptic algorithm based on gold-standard fully manually-segmented data
We introduce and report (1) segmentation errors using new local metrics, i.e. well-known measures are evaluated only on the planned puncture paths, rather than the full volume; (2) we show the axial force errors caused by these segmentation errors

Summary

Introduction

We have presented the predecessor AcusVR-3D13 featuring fully manually-segmented patient models and our new simulator AcusVR-4D9 with simulated US imaging needle guidance as a valuable training and planning tool. Needle deflection (bending), tissue deformation and non-axial forces[10, 16] are relevant for realistic, real-time, visuo-haptic simulations. These topics are beyond the scope of this work. We focus the quantitative haptic evaluation of the axial force output of our new simulator AcusVR-4D and generate a high number of test paths from ten test patients for the simulation of PTCD. Along these test paths, forces from reference and new haptic algorithms are calculated and compared. We think the design of the presented evaluation experiment is a practicable way to bridge the gap between qualitative and still missing quantitative evaluations of virtual haptic simulations

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Discussion

Conclusion