Addressing source-induced structural vibrations in an interventional X-ray system

Interventional radiology is a medical discipline, in which imaging equipment is used to diagnose and treat diseases throughout the human body. Dedicated systems, based on X-ray, computed tomography and ultrasound technology, allow for 2D and 3D imaging of (contrast enhanced) physical structures. Using these images, physicians are able to perform minimally invasive, image-guided therapy. Interventional X-ray systems typically feature an X-ray source and detector mounted to the ends of a C-shaped arm (C-arm). The C-arm is part of a larger structure, called stand. The X-ray source produces distinct disturbance forces at a specific frequency, which act upon the C-arm. This leads to vibrations of the stand, which could potentially result in acoustic noise and image quality degradation. As these effects could be clinically unacceptable, their extent is being investigated. Modal analyses have been performed to investigate the dynamic behaviour of the stand. This has revealed a number of eigenmodes with eigenfrequencies close to the excitation frequency of the X-ray source. These eigenmodes involve local deflections of the end of the C-arm, and the X-ray source interface. Two methods are explored to decrease the resonant effects corresponding to the excited eigenmodes. The first approach aims to apply Tuned Mass Dampers (TMD) to the C-arm. The second approach proposes local stiffness enhancement of the C-arm and the X-ray source interface, at similar mass and inertia. A comparison of the first approach (TMD) with the second, more classical approach, will be given in terms of the reduction in vibration levels during operation of the X-ray source.