Electrical resistance of human soft tissue sarcomas: an ex vivo study on surgical specimens

Abstract

This paper presents a study about electrical resistance, which using fixed electrode geometry could be correlated to the tissue resistivity, of different histological types of human soft tissue sarcomas measured during electroporation. The same voltage pulse sequence was applied to the tumor mass shortly after surgical resection by means of a voltage pulse generator currently used in clinical practice for electrochemotherapy that uses reversible electroporation. The voltage pulses were applied by means of a standard hexagonal electrode composed by seven, 20-mm-long equispaced needles. Irrespective of tumor size, the electrode applies electric pulses to the same volume of tissue. The resistance value was computed from the voltage and current recorded by the pulse generator, and it was correlated with the histological characteristics of the tumor tissue which was assessed by a dedicated pathologist. Some differences in resistance values, which could be correlated to a difference in tissue resistivity, were noticed according to sarcoma histotype. Lipomatous tumors (i.e., those rich in adipose tissue) displayed the highest resistance values (up to 1700 Ω), whereas in the other soft tissue sarcomas, such as those originating from muscle, nerve sheath, or fibrous tissue, the electrical resistance measured was between 40 and 110 Ω. A variability in resistance was found also within the same histotype. Among lipomatous tumors, the presence of myxoid tissue between adipocytes reduced the electrical resistance (e.g., 50-100 Ω). This work represents the first step in order to explore the difference in tissue electrical properties of STS. These results may be used to verify whether tuning electric field intensity according to the specific STS histotype could improve tissue electroporation and ultimately treatment efficacy.

Membrane permeabilization of mammalian cells using bursts of high magnetic field pulses

“…However, these applications require direct contact between the applicator, electrodes and the biological sample. Therefore, despite many applications, the methodology has considerable limitations such as the dependence of PEF distribution on the dielectric properties of the sample (Corovic et al, 2013; Peyman et al, 2015; Campana et al, 2016a; Liu et al, 2016), presence of electrochemical reactions in the electrode-electrolyte or tissue interfaces (Pataro et al, 2015) and the possibility of electrical breakdown between the electrodes (Guenther et al, 2015; Rubinsky et al, 2016). …”

Ablation of soft tissue tumours by long needle variable electrode-geometry electrochemotherapy: final report from a single-arm, single-centre phase-2 study

“…Our results have the obvious limitations of a single-arm phase 2 design and include its small scale, patient heterogeneity, the absence of a control group and independent radiological review, the novelty of the procedure, which inevitably implied a learning phase as in other therapies 32 and on-study technique modifications. Admittedly, other variables might have influenced treatment outcome, including distribution of bleomycin and electric current within inhomogeneous tumour tissues 37 , and a discrepancy between pre-treatment plan and actual electrode placement. On this regard, a preliminary experience in patients with liver metastases suggests that US scan holds promise for real-time assessment of the electroporation process 38 , while experimental evidence in animal models indicates that magnetic resonance electrical impedance tomography (MREIT) may be a reliable instrument to predict electric field distribution 39 .…”

Electric field distribution study in inhomogeneous biological tissues

“…Eight voltage pulses were applied to the electrode plates by means of a voltage pulse generator (EPS01 manufactured by Igea, Carpi, Italy), and the corresponding current was measured. From voltage and current values, the resistance was computed as in Campana et al, and the corresponding conductivity ( σ = ρ −1 , ρ resistivity) was computed using Equation , by means of Ohm law and the model for resistance, R , of a parallelepiped sample with length L (7.5 mm) and section A (10 × 11.3 mm) as in Campana et al: …”

“…The pulse parameters are chosen as in Castiello et al 15 and Ongaro et al 35 The F I G U R E 1 A, Samples prepared. B, Set-up for electrical conductivity measurements 34 voltage pulses were applied by means of an electrode formed by a pair of needles, 1-cm long with a diameter of 0.5 mm, similar to the model in Figure 2, where the cylinder with a diameter of 9 mm was casted with one of the gels in Table 1. Two samples for each of the four gels in Table 1 were prepared.…”