Effect of velocity control on kinesthetic lung tumour localization

Restricted access during minimally invasive surgery precludes manual palpation, making the localization of lung tumours challenging. This paper investigates the force sensing performance that would allow an instrumented kinesthetic probe to localize tumours based on stiffness variations of the lung parenchyma. Agar injected into ex vivo porcine lungs produced a model approximating commonly encountered tumours. Using both constant and variable velocity approaches, force-deformation data were collected from multiple sites at various palpation depths, before and after the tumours were injected. Analysis showed an increase in force after the tumours were injected, ranging from 0.07 to 0.16 N at 7 mm. A constant palpation velocity minimized exponential stress decay at constant depths, facilitating easier comparisons between measurements. A sensing range of 0 to 2 N, with 0.01 N resolution should allow a kinesthetic palpation probe to resolve local tissue stiffness changes that suggest an underlying tumour.