Developing a Breast Phantom to Test and Validate the Smart Electrosurgical Knife

Abstract

Previous studies show that the smart electrosurgical knife, which adds diffuse reflectance spectroscopy to the traditional electrosurgical knife, is a promising technique for breast-conserving surgery, namely it enables real-time tissue characterization while cutting. More specifically, based on the fat/water-ratio, it enables intraoperative healthy from malignant tissue discrimination, therefore potentially reducing the re-excision rate with breast-conserving surgery procedures. However, the smart electrosurgical knife cannot be used on patients yet since it has not been validated yet. Several studies suggest phantoms are ideal for validation of systems including imaging systems like diffuse reflectance spectroscopy. Hence, for this master thesis, the objective was to develop a breast phantom that enables validation of the smart electrosurgical knife.

Firstly, it was found that a study which enables validation of the smart electrosurgical knife, should mimic a breast-conserving surgery procedure including a breast phantom, so that the potential of the intraoperative margin assessment technique ‘’ diffuse reflectance spectroscopy ‘’, added to the traditional electrosurgical knife, could sufficiently be tested. For such a study to take place, it was found that the phantom should have a similar size and shape as human breasts containing a tumour. With regard to pre- and postoperative margin assessment, the phantom should have a contrast between the tumour and healthy phantom, which enables size, border, and location assessment of the phantom tumour upfront and residual tumour inspection after surgery. Intraoperatively, the phantom should have a significant difference in fat/water-ratio between the tumour and healthy phantom. This enables us to assess diffuse reflectance spectroscopy with its capability in discriminating healthy from malignant tissue. Furthermore, visually and mechanically, there should be a minimal difference between the tumour and healthy phantom, which eliminates the possibility of using the intraoperative margin assessment techniques, palpation and visual inspection. Finally, the phantom should have similar mechanical- electrically conductive and thermo tolerance properties as real breast tissue. This will result in realistic haptic feedback and tissue effects with electrosurgery.

To develop such a phantom, various fat/water-ratios of water and lard, in combination with various additives such as guar gum, agar, gelatin and barium sulphate, were produced and tested. It turned out that agar in combination with water, lard, and the contrast agent barium sulphate, enables breast phantom production, that meets all the aforementioned phantom requirements. More specifically, the final phantom is a breast-shaped phantom with a realistic size and shape, consisting of healthy tissue with a tumour inclusion. The healthy tissue is composed of 50% lard, 50% water and then 5% agar by weight of water, whereas the tumour is composed of 20% lard, 80% water and then 3% agar- and 5% barium sulphate by weight of water. Since this phantom meets all requirements, it enables the design of a study that subsequently enables extensive testing and further validation of the smart electrosurgical knife.