Purpose

We present a feasibility study for the visuo-haptic simulation of pedicle screw tract palpation in virtual reality, using an approach that requires no manual processing or segmentation of the volumetric medical data set.

Methods

In a first experiment, we quantified the forces and torques present during the palpation of a pedicle screw tract in a real boar vertebra. We equipped a ball-tipped pedicle probe with a 6-axis force/torque sensor and a motion capture marker cluster. We simultaneously recorded the pose of the probe relative to the vertebra and measured the generated forces and torques during palpation. This allowed us replaying the recorded palpation movements in our simulator and to fine-tune the haptic rendering to approximate the measured forces and torques. In a second experiment, we asked two neurosurgeons to palpate a virtual version of the same vertebra in our simulator, while we logged the forces and torques sent to the haptic device.

Results

In the experiments with the real vertebra, the maximum measured force along the longitudinal axis of the probe was 7.78 N and the maximum measured bending torque was 0.13 Nm. In an offline simulation of the motion of the pedicle probe recorded during the palpation of a real pedicle screw tract, our approach generated forces and torques that were similar in magnitude and progression to the measured ones. When surgeons tested our simulator, the distributions of the computed forces and torques were similar to the measured ones; however, higher forces and torques occurred more frequently.

Conclusions

We demonstrated the suitability of direct visual and haptic volume rendering to simulate a specific surgical procedure. Our approach of fine-tuning the simulation by measuring the forces and torques that are prevalent while palpating a real vertebra produced promising results.

中文翻译：

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使用直接视觉触觉体积渲染对椎弓根螺钉束触诊的力进行量化和模拟。

目的

我们提出了一项在虚拟现实中对椎弓根螺钉束触诊进行视觉触觉模拟的可行性研究，使用的方法不需要手动处理或分割立体医学数据集。

方法

在第一个实验中，我们量化了真实公猪椎骨中椎弓根螺钉束触诊过程中存在的力和扭矩。我们配备了带有 6 轴力/扭矩传感器和运动捕捉标记簇的球尖椎弓根探针。我们同时记录了探头相对于椎骨的姿势，并测量了触诊过程中产生的力和扭矩。这使我们能够在模拟器中重放记录的触诊运动，并微调触觉渲染以近似测量的力和扭矩。在第二个实验中，我们要求两名神经外科医生在模拟器中触诊同一椎骨的虚拟版本，同时记录发送到触觉设备的力和扭矩。

结果

在真实椎骨的实验中，沿探头纵轴的最大测量力为 7.78 N，最大测量弯曲扭矩为 0.13 Nm。在对真实椎弓根螺钉道触诊过程中记录的椎弓根探针运动的离线模拟中，我们的方法产生的力和扭矩在大小和进展上与测量的相似。当外科医生测试我们的模拟器时，计算的力和扭矩的分布与测量的相似；然而，更高的力和扭矩发生得更频繁。

结论

我们展示了直接视觉和触觉体积渲染模拟特定手术过程的适用性。我们通过测量触诊真实椎骨时普遍存在的力和扭矩来微调模拟的方法产生了有希望的结果。