1Department of Neurosurgery, Medical University Vienna; and.
2Austrian Center of Medical Innovation and Technology, Wiener Neustadt, Austria.
J Neurosurg. 2020 Jul 17;134(6):1951-1958. doi: 10.3171/2020.4.JNS20394. Print 2021 Jun 1.
Electromagnetic (EM) navigation provides the advantages of continuous guidance and tip-tracking of instruments. The current solutions for patient reference trackers are suboptimal, as they are either invasively screwed to the bone or less accurate if attached to the skin. The authors present a novel EM reference method with the tracker rigidly but not invasively positioned inside the nasal cavity.
The nasal tracker (NT) consists of the EM coil array of the AxiEM tracker plugged into a nasal tamponade, which is then inserted into the inferior nasal meatus. Initially, a proof-of-concept study was performed on two cadaveric skull bases. The stability of the NT was assessed in simulated surgical situations, for example, prone, supine, and lateral patient positioning and skin traction. A deviation ≤ 2 mm was judged sufficiently accurate for clinical trial. Thus, a feasibility study was performed in the clinical setting. Positional changes of the NT and a standard skin-adhesive tracker (ST) relative to a ground-truth reference tracker were recorded throughout routine surgical procedures. The accuracy of the NT and ST was compared at different stages of surgery.
Ex vivo, the NT proved to be highly stable in all simulated surgical situations (median deviation 0.4 mm, range 0.0-2.0 mm). In 13 routine clinical cases, the NT was significantly more stable than the ST (median deviation at procedure end 1.3 mm, range 0.5-3.0 mm vs 4.0 mm, range 1.2-11.2 mm, p = 0.002). The loss of accuracy of the ST was highest during draping and flap fixation.
Application of the EM endonasal patient tracker was found to be feasible with high procedural stability ex vivo as well as in the clinical setting. This innovation combines the advantages of high precision and noninvasiveness and may, in the future, enhance EM navigation for neurosurgery.
电磁（EM）导航具有连续引导和器械尖端跟踪的优势。目前患者参考跟踪器的解决方案并不理想，因为它们要么通过侵入性方式拧到骨头上，要么如果贴在皮肤上则精度较低。作者提出了一种新颖的 EM 参考方法，将跟踪器刚性地但非侵入性地定位在鼻腔内。
鼻腔跟踪器（NT）由 AxiEM 跟踪器的 EM 线圈阵列组成，插入鼻腔填塞物中，然后插入下鼻道。最初，在两个尸体颅底上进行了概念验证研究。在模拟手术情况下评估 NT 的稳定性，例如，俯卧、仰卧和侧卧位以及皮肤牵引。偏差≤2mm 被认为足以进行临床试验。因此，在临床环境中进行了可行性研究。在整个常规手术过程中，记录 NT 和标准皮肤粘贴跟踪器（ST）相对于地面真实参考跟踪器的位置变化。比较了 NT 和 ST 在不同手术阶段的准确性。
在离体研究中，NT 在所有模拟手术情况下均表现出高度稳定性（中位数偏差 0.4mm，范围 0.0-2.0mm）。在 13 例常规临床病例中，NT 明显比 ST 更稳定（手术结束时的中位数偏差为 1.3mm，范围为 0.5-3.0mm 与 4.0mm，范围为 1.2-11.2mm，p=0.002）。在铺单和皮瓣固定期间，ST 的准确性损失最大。
EM 经鼻患者跟踪器的应用在离体和临床环境中都具有很高的程序稳定性，被证明是可行的。这项创新结合了高精度和非侵入性的优势，将来可能会增强神经外科的 EM 导航。
