Real-time cannula navigation in biological tissue with high temporal and spatial resolution based on impedance spectroscopy

Abstract

In many medical applications a well-directed positioning of a cannula in body tissue is mandatory. Especially the accurate placing of the cannula tip in the tissue is important for efficient drug delivery or for accessing blood vessels and nerves. This paper presents a new approach for a universal cannula navigation system based on tissue classification on the cannula tip by impedance spectroscopy. The cannula serves as coaxial, open ended waveguide which is connected to remote measurement equipment. Objective of the new system is to reach a high spatial and temporal resolution for dynamic cannula guidance. Therefore the proposed coaxial cannula design has been analyzed by Finite Element Simulation to investigate the sensitivity of the cannula tip. For fast tissue impedance spectrum measurement the Time-Domain-Reflectometry method is used in order to achieve a high temporal resolution. Measurement data derived in the laboratory is analyzed and interpreted using the general Cole-Cole model for tissue. Based on the results we propose to use a chirp signal for impedance measurement in order to improve the sensitivity of the system towards specific tissue properties.

Spatial sensitivity distribution assessment and Monte Carlo simulations for needle‐based bioimpedance imaging during venipuncture using the finite element method

“…Various designs of hollow needles for blood sampling exist in which there is an active electrode in the cannula of the needle, resulting in a coaxial layout. [30][31][32][33][34][35][36] Liu et al 23 simulated an insertion procedure through heterogeneous tissue with three tissue types and two coaxial cannulas acting as a bipolar electrode pair. Similarly to Høyum et al, 27 the voltage distribution was used to represent the sensitivity.…”

“…The heterogeneity in itself was homogeneous, which does not properly represent the inhomogeneous microstructure of real tissue. Various designs of hollow needles for blood sampling exist in which there is an active electrode in the cannula of the needle, resulting in a coaxial layout 30–36 . Liu et al 23 simulated an insertion procedure through heterogeneous tissue with three tissue types and two coaxial cannulas acting as a bipolar electrode pair.…”

Broadband spectroscopy of dynamic impedances with short chirp pulses

“…Bioimpedance spectroscopy enables us to characterize biological matter, including label-free identification of fast moving bioparticles in the microfluidic lab-on-a-chip (LoC) (Sun et al 2009, Min et al 2009, see figure 1(a), and taking spectral impedance snapshots of the beating heart or the pulsating cardiovascular and/or pulmonary system (Min et al 2007a, Kink et al 2011 at different moments and several locations (figure 1(b)) for obtaining cycle-by-cycle impedance spectrograms at predetermined time instances of pulmonary or cardiac cycles. Also bioimpedance-based needle guidance during transcutaneous surgical interventions requires short-term real-time spectroscopy (Trebbels et al 2010). Short broadband excitation is preferred when the speed of analysis is important (Min et al 2008, Nahvi and Hoyle 2008, Pliquett et al 2000, Sun et al 2009.…”