Needles used in medical percutaneous procedures are brought to deform because of its interactions with inhomogeneous and anisotropic tissues. In this paper, the first step of the development of a new generation of tools for assistance in the realization of gestures taking into account these deformations are presented. We provide a new approach for determining, in “real time” and in 3D, the shape of an instrumented needle inserted into a complex tissue by using strain microgauges. The knowledge of the real time local deformation from these strain microgauges would improve the current navigation systems by considering not only the rigid needles but also the flexible ones. Our aim is to reconstruct in real time the instrumented needle shape in order to help tracking and steering during a medical intervention.

In this paper, we describe a method enabling to optimally position the strain microgauges of an instrumented needle using a 3D force distribution basis, in order to explain the forces applied on the needle during an intervention.

Needles used in medical percutaneous procedures are brought to deform because of its interactions with inhomogeneous and anisotropic tissues. In this paper, the premises of the development of a new generation of tools for assistance in the realization of gestures taking into account these deformation are presented. We provide a new approach for determining, in real time and in 3D, the shape of an instrumented needle inserted into a complex tissue by using strain gauges. The knowledge of the real time local deformation from these strain gauges would improve the current navigation systems by considering not only the rigid needles but also the flexible needles. Our aim is to reconstruct in real time the instrumented needle shape in order to track and to steer it during a medical intervention.

In this paper, the static interaction forces between a medical needle and soft tissue during CT (Computerized Tomography) guided insertion are studied. More precisely a set of linearly independent elements describing the forces (a basis) is identified. This forms a generic basis from which any forces that act on a static needle (that is not fixed at its base and that is inserted into human tissue) can be described accurately. To achieve this purpose, the same needle was inserted 62 times into fresh porcine shoulder tissue and CT scans were acquired after each push to determine the final trajectory of the needle. From this set of trajectories, a generic static force basis was determined by using static Beam, B-spline theories and Principal Component Analysis (PCA). This generic basis was first validated on theoretical simulations and then on 20 different needles inserted into in vivo human tissues during real clinical interventions. Such a basis could be of use to highlight the forces acting all along the length of a needle inserted into a complex tissue and enables models of needle deflection to be developed. These models could be used in the development of automated robot assisted and/or image guided strategies for needle steering.

The aim of this study is to determine a generic static loading basis applied on a medical needle inserted into human tissue during a percutaneous procedure. Such a basis can be worthwhile to highlight the forces effectively encountered in a medical act and may be useful to develop models of needle deflection or medium deformation.

This paper introduces a new patient-mounted CT and MRI guided interventional radiology robot for percutaneous needle interventions. The 5 DOF robot uses ultrasonic motors and pneumatics to position the needle and then insert it progressively. The needle position and inclination can be registered in the images using two strategically placed fiducials visible in both imaging modalities. A first prototype is presented and described in terms of its sterilization, CT and MRI compatibility, and precision. Tests showed that 1) it is entirely sterilizable with hydrogen peroxide gas, 2) no image artifacts or deformations are noticeable in the CT and MRI images, 3) does not affect the SNR of MR images, and 4) its mechanical error is less than 5mm.