Real-time measurement of blood vessel occlusion during microsurgery

Abstract

Measurement and feedback of vascular properties during microsurgery is generally not available. We carried out real-time in vivo measurement and analysis of microsurgical occlusion of 1-2-mm diameter arteries and veins in rodents. A pair of forceps mounted with strain gauges was designed for applying and directly measuring the force on tissue. Forces between 0 and 450 mN were applied, with the device having a resolution of 0.5 mN. We performed in vivo experiments on the rat femoral (n = 5) and abdominal (n = 8) blood vessels to measure the elastic restoration force of the tissue in response to radial compression at different levels of force. On average, the minimum occlusion force was 57 mN for the rat artery. During steady application of force, the perturbations in the blood vessel due to heartbeat are visible in the force data. These force oscillations ranged between 1 and 3 mN around the mean steady-state force applied. It was determined that the magnitude of the Fourier spectral peak corresponding to heartbeat frequency can be used as a measure of the patency of the blood vessel, and can provide feedback to microsurgeons to avoid damage to the vessel by application of excess force.

MEMSurgery: An integrated test-bed for vascular surgery

“…This test-bed has been successfully used to provide training to non-skilled individuals to achieve desirable minimum occlusion force (MOF) (14) . The test-bed has yielded useful data on tissue properties, distinguishing the mechanical properties of veins and arteries (4) . Together, this information should lead to improvements in surgical procedures, Figure 8 Training simulator with indication of mechanical properties, the red point shows in real-time the position of force and displacement when users apply force to occlude the blood vessel.…”

“…We setup our experiment, calibrated the laser displacement sensor, and the force-sensing forceps, and collected data as described earlier (4) . The gradual displacement of the forceps and the resulting force were recorded and shown in Figure 5.…”

“…This problem is even more acute with the advent of a variety of minimally invasive coronary artery bypass procedures, where the surgeon's view and perception is blocked and thereby, the degree of difficulty in manipulating vessels increases. Because of the shortcomings of assisting technologies, excess force may unintentionally be applied when performing delicate operations such as the closure of these vessels or the exposure of the vascular endothelial surface (both necessary precursors to several procedures) (4) . This excess force may cause tissue damage, one of the major factors affecting the outcome of the surgery (5) .…”