Department of Electrical Engineering and Information Technologies, University of Naples Federico II, Via Claudio, 21, 80125 Napoli, Italy.
Sensors (Basel). 2022 May 20;22(10):3880. doi: 10.3390/s22103880.
During surgical procedures, real-time estimation of the current position of a metal lead within the patient's body is obtained by radiographic imaging. The inherent opacity of metal objects allows their visualization using X-ray fluoroscopic devices. Although fluoroscopy uses reduced radiation intensities, the overall X-ray dose delivered during prolonged exposure times poses risks to the safety of patients and physicians. This study proposes a potential alternative to real-time visualization of a lead inside the human body. In principle, by making a weak current flow through the lead and measuring the related magnetic field generated outside the body, it is possible to trace the position of the lead. This hypothesis was verified experimentally via two tests: one carried out on a curved copper wire in air and one carried out on a real pacemaker lead in a saline solution. In the second test, a pacemaker lead and a large return electrode were placed in a tank filled with a saline solution that reproduced the mean resistivity of the human torso. In both tests, a current flowed through the lead, which consisted of square pulses with short duration, to avoid any neuro-muscular stimulation effects in a real scenario. A small coil with a ferrite core was moved along a grid of points over a plastic sheet and placed just above the lead to sample the spatial amplitude distribution of the magnetic induction field produced by the lead. For each measurement point, the main coil axis was oriented along the and axes of the plane to estimate the related components of the magnetic induction field. The two matrices of measurements along the and axes were further processed to obtain an estimate of lead positioning. The preliminary results of this study support the scientific hypothesis since the positions of the leads were accurately estimated. This encourages to deepen the investigation and overcome some limitations of this feasibility study.
在手术过程中，通过放射成像获得金属引导线在患者体内当前位置的实时估计。金属物体的固有不透明度允许使用 X 射线透视设备对其进行可视化。尽管透视使用的辐射强度降低，但在长时间曝光期间，所传递的总 X 射线剂量对患者和医生的安全构成风险。本研究提出了一种替代实时可视化人体内部引导线的潜在方法。原则上，通过使弱电流流过引导线并测量体外产生的相关磁场，就可以跟踪引导线的位置。这一假设通过两个测试得到了实验验证：一个在空气中对弯曲的铜丝进行测试，另一个在盐溶液中对实际起搏器引导线进行测试。在第二个测试中，将起搏器引导线和一个大的返回电极放置在充满盐溶液的罐中，该溶液复制了人体躯干的平均电阻率。在这两个测试中，引导线中都有电流流过，该电流由持续时间短的方波脉冲组成，以避免在实际场景中出现任何神经肌肉刺激效应。一个带有铁氧体芯的小线圈在塑料片上的网格上移动，并放置在引导线上方，以采样由引导线产生的磁感应强度的空间幅度分布。对于每个测量点，主线圈轴沿平面的 和 轴定向，以估计磁感应场的相关分量。沿 和 轴的两个测量矩阵进一步处理，以获得引导线定位的估计值。该研究的初步结果支持科学假设，因为准确估计了引导线的位置。这鼓励进一步深入调查并克服这项可行性研究的一些限制。
