Research Article
Jae Kim*
Abstract
Minimally invasive surgeries provide lower morbidity and faster recovery compared to conventional surgeries. Since 1995, the cholecystectomy procedure shifted from conventional to minimally invasive by 80%. Despite its popularity and benefits, minimally invasive surgeries have major complications, including vessel and organ injury from difficulties in distinguishing between the two. Currently, a decision to distinguish between vessel and nonvessels is mainly based on surgeon’s experience and anatomical landmarks. Such methods can not only delay the operation time but also increase the number of medical errors due to subjectivity, especially for physicians-intraining. The purpose of this study is to introduce a sensor that can help distinguish blood vessels from non-blood vessel with a novel approach called “noninvasive impedance-based blood vessel detection”. This approach utilizes a cost-effective, constant current source and voltage sensor that can offer a quick and non-invasive way to distinguish blood vessels during minimally invasive surgeries. A unique characteristic of blood vessels is its pulsation. By capturing periodic dilation of the blood vessel, the validity of the blood vessel can be confirmed. Dilation of blood vessels not only changes flow resistance but also electrical resistance of blood vessel. By using a 50-100 uA current source with frequency from 1 kHz to 10 MHz, small change in electrical resistance can be captured by a voltage detector. The detected periodic signal is compared to a reference value. If the signal is higher than the reference value, then the CMOS-based digital counter is used to determine whether the pulse is periodic enough to be signaled as a blood vessel. Based on Ohm’s law, Poiseuille’s law, resistivity, and elasticity characteristics of blood vessel, minimal distention and changes in electrical resistance of the blood vessel based on pulse pressure can be analyzed. The minimum current needed to detect the change in resistance is mathematically deduced and compared with the measured results. Another potential benefit of this approach is its versatility. Impedance-based sensing can easily be integrated into current minimally invasive instruments to avoid the necessity of additional equipment.