Hernandez D J, Sinkov V A, Roberts W W, Allaf M E, Patriciu A, Jarrett T W, Kavoussi L R, Stoianovici D
James Buchanan Brady Urological Institute, The Johns Hopkins Medical Institutions, Baltimore, Maryland, USA.
J Urol. 2001 Oct;166(4):1520-3.
The traditional method of percutaneous renal access requires freehand needle placement guided by C-arm fluoroscopy, ultrasonography, or computerized tomography. This approach provides limited objective means for verifying successful access. We developed an impedance based percutaneous Smart Needle system and successfully used it to confirm collecting system access in ex vivo porcine kidneys.
The Smart Needle consists of a modified 18 gauge percutaneous access needle with the inner stylet electrically insulated from the outer sheath. Impedance is measured between the exposed stylet tip and sheath using Model 4275 LCR meter (Hewlett-Packard, Sunnyvale, California). An ex vivo porcine kidney was distended by continuous gravity infusion of 100 cm. water saline from a catheter passed through the parenchyma into the collecting system. The Smart Needle was gradually inserted into the kidney to measure depth precisely using a robotic needle placement system, while impedance was measured continuously.
The Smart Needle was inserted 4 times in each of 4 kidneys. When the needle penetrated the distended collecting system in 11 of 16 attempts, a characteristic sharp drop in resistivity was noted from 1.9 to 1.1 ohm m. Entry into the collecting system was confirmed by removing the stylet and observing fluid flow from the sheath. This characteristic impedance change was observed only at successful entry into the collecting system.
A characteristic sharp drop in impedance signifies successful entry into the collecting system. The Smart Needle system may prove useful for percutaneous kidney access.
经皮肾穿刺的传统方法需要在C形臂荧光透视、超声或计算机断层扫描引导下徒手放置穿刺针。这种方法提供的验证穿刺成功的客观手段有限。我们开发了一种基于阻抗的经皮智能穿刺针系统，并成功地用它在离体猪肾中确认进入集合系统。
智能穿刺针由一根改良的18号经皮穿刺针组成，内芯针与外套管电绝缘。使用4275型LCR测量仪（惠普公司，加利福尼亚州桑尼维尔）测量暴露的芯针尖端与外套管之间的阻抗。通过将一根导管穿过肾实质插入集合系统，以100厘米水柱的生理盐水持续重力输注使离体猪肾充盈。使用机器人穿刺针放置系统将智能穿刺针逐渐插入肾脏以精确测量深度，同时持续测量阻抗。
在4个肾脏中每个肾脏穿刺4次。在16次尝试中有11次穿刺针进入充盈的集合系统时，观察到电阻率从1.9欧姆·米显著下降至1.1欧姆·米。拔出芯针并观察到外套管有液体流出，证实进入了集合系统。仅在成功进入集合系统时观察到这种特征性的阻抗变化。
阻抗的特征性急剧下降表明成功进入集合系统。智能穿刺针系统可能对经皮肾穿刺有用。
