The integration of diffuse reflectance spectroscopy into the electrosurgical knife used during breast-conserving surgery

Abstract

Among women, breast cancer has the highest incidence rate of all types of cancer worldwide. For 80% of these patients, a treatment option is the surgical procedure known as breast conserving surgery (BCS). Re-excision is required in 10-60% of these patients, as positive margins are encountered post-operatively, showing the need of an intra-operative margin assessment (IMA) technique. Diffuse Reflectance Spectroscopy (DRS) has proven to accurately discriminate real-time between malignant and non-malignant tissue. As electrosurgery (ES) is the main technique used for BCS, the incorporation of DRS into the electrosurgical knife (ESK) is desired. A ‘smart’ ESK has previously been developed, yet practical use was disturbed by tissue contamination of the integrated diffuse reflectance fibers during ES.

This thesis, therefore, examines the characteristics of this contamination and the effects on the desired integration. Clinical and research analyses were done, obtaining requirements for a re-design of the ‘smart’ ESK. Instruments, settings and methods of cleaning the ESK in the operating room have been observed and the influence of clinical parameters on the amount of tissue debris has been investigated. Tissue contamination on ESK blades used for BCS was analyzed with the use of DRS and Fourier Transform – Infrared spectroscopy (FTIR). The impact of this contamination was additionally determined by power measurements of the ‘smart’ ESK after cutting on samples of subcutaneous porcine tissue for several time intervals.

All measured spectra of the charring components adhering to the electrosurgical blades matched with proteins (best matching with hemoglobin and hydrolyzed proteins) and fatty acid esters adhering to the electrosurgical blades. Furthermore, significant decreased debris was found correlating with the date of surgery and the amount of times the ESK was cleaned. No significant influence was found of the amount of ES current used on the tissue debris, yet the intensity of the signal was expressively decreased with the increase of debris. During the power experiments, tissue debris on the ‘smart’ ES increased significantly over time while cutting. Polishing the fibers resulted in a fiber signal of only 43% of the maximal power.
Disturbance occurred already early within the normal usage time of surgical procedures, with 1.9% of the maximal power left after 2 minutes of cutting. Prevention of fiber contamination seemed most effective by avoiding direct contact of the fibers with tissue during ES.

Design challenges and requirements were obtained, resulting in three concepts aiming to overcome tissue adhering to the integrated fibers. Three prototypes were made and evaluated, which eventually led to a proposed re-design of the ‘smart’ ESK, containing integrated fibers which can be retracted into the casing when the knife is used to cut and is intermittently slided out for tissue contact to obtain DRS measurements. A working prototype was produced, which potentially overcomes the disrupted DRS measurements due to tissue contamination on the integrated fibers. Hence, a step is made towards the integration of DRS into the ESK. This will possibly have a positive impact on the margin assessment during surgery, which might reduce the number of re-excisions after BCS.