Development of a catheter-based technique for endoluminal radiofrequency sealing of pancreatic duct

Is occlusion of the main pancreatic duct by thermal ablation really safe? A surgical innovation assessed according to IDEAL recommendations

INTRODUCTION

Pre-clinical studies suggest that thermal ablation of the main pancreatic duct (TAMPD) is more recommendable than glue for reducing postoperative pancreatic fistula (POPF). Our aims were (1) to analyze the changes in the pancreas of patients after TAMPD and (2) to correlate the clinical findings with those obtained from a study on an animal model.

MATERIALS AND METHODS

A retrospective early feasibility study of a marketed device for a novel clinical application was carried out on a small number of subjects (n = 8) in whom TAMPD was conducted to manage the pancreatic stump after a pancreatectoduodenectomy (PD). Morphological changes in the remaining pancreas were assessed by computed tomography for 365 days after TAMPD.

RESULTS

All the patients showed either Grade A or B POPF, which generally resolved within the first 30 days. The duct's maximum diameter significantly increased after TAMPD from 1.5 ± 0.8 mm to 8.6 ± 2.9 mm after 7 days (p = .025) and was then reduced to 2.6 ± 0.8 mm after 365 days PO (p < .0001). The animal model suggests that TAMPD induces dilation of the duct lumen by enzymatic digestion of ablated tissue after a few days and complete exocrine atrophy after a few weeks.

CONCLUSIONS

TAMPD leads to long-term exocrine pancreatic atrophy by completely occluding the duct. However, the ductal dilatation that occurred soon after TAMPD could even favor POPF, which suggests that TAMPD should be conducted several weeks before PD, ideally by digestive endoscopy.

Radiofrequency impedance monitoring of the biological tissues under local heating by optical radiation

Development of methods for simultaneous control of state of biological tissues during optical treatment is the important tasks in laser surgery. We introduce a novel approach for the monitoring of the state of biological tissues in the process of its local heating by optical radiation. It is based on measurements of the electrical radiofrequency impedance kinetics of the sample during irradiation. The obtained data are processed using interconnected mathematical modeling of corresponding thermodynamic, optical and electrical problems. Experimental applications of this approach, represented in the paper, reveal its high sensitivity, repeatability and consistency with the model. The introduced method can be used for the selection and optimization of radiation parameters of medical laser sources as an alternative or an addition to histological techniques. Radiofrequency impedance measurement can be used directly in the course of surgical operations for monitoring the treated tissues state, including its temperature and degree of damage.

Radiofrequency impedance spectroscopy of biological tissues under heating by homogeneous laser radiation

We have developed an original method to measure the temperature dependence of the biological tissue electrical properties based on its heating by homogeneous optical radiation.The conventional approach in hyperthermia research involves heating due to a thermal conductivity through the surface of the sample. The novel technique is based on the emission of heat sources in the sample volume caused by the absorption of optical radiation.The method was verified using chicken liver and aloe parenchyma samples, which were uniformly irradiated in a special chamber with an optically scattering inner coating. The electrical impedance of the samples was measured using a 4-electrode technique in the frequency range 100 Hz-1 MHz. In order to approximate and analyze the electrical impedance module, an equivalent electrical circuit based on the Cole-Cole function was used and the dependences of the approximation parameters on time and temperature were obtained. Applying the Arrhenius formulation to the kinetics of low-frequency resistance, we obtained the parameters of the kinetics of degradation of the biological tissues (critical temperatureTcrand activation energyEa):Ea=(16±4)·105J·mol^-1,Tcr=63±1°C for the aloe parenchyma andEa=(4.5±2)·105J·mol^-1,Tcr=83±1°Cfor the chicken liver.