LPR: A CT and MR-Compatible Puncture Robot to Enhance Accuracy and Safety of Image-Guided Interventions

Image-guided percutaneous interventions are common procedures used for diagnosis or therapeutic purposes. The clinical demand for such interventions is growing since they are minimally invasive. To increase the quality of the operations and provide optimal accuracy and safety to patients, puncture robots may be very helpful. This paper presents a new robotic architecture designed to perform abdominal and thoracic punctures under computer tomography (CT) or MRI guidance. Innovations concerning the robotic architecture, materials, and energy sources are described. Segmentation and registration algorithms have been developed to localize the robot on images coming from CT or MRI devices, and a specific control loop is used to verify the movements and the positioning of the robot. The results of the initial experiments made under CT and MRI environments are presented.     

Central airway stenoses: preliminary results of spiral-CT-generated virtual bronchoscopy simulations in 29 patients

The purpose of this study was to determine the feasibility of using virtual bronchoscopy simulations to depict stenoses of the tracheobronchial tree. Virtual bronchoscopy simulations, based on ray casting, were applied to spiral-CT data sets of 29 patients presenting 41 stenoses of the central airways, proved with fiberoptic bronchoscopy. Simulations of the inner walls of the airways were of good quality in 27 of 29 patients. Airway stenoses were depicted in 39 of 41 cases. Evaluation of the length of stenoses and surrounding tissues required simultaneous display of multiplanar reformations. Virtual bronchoscopy provides a valuable road map for bronchoscopy, in an image format familiar to bronchoscopists.     

A general tool for the evaluation of spiral CT interpolation algorithms: revisiting the effect of pitch in multislice CT

While multislice spiral computed tomography (CT) scanners are provided by all major manufacturers, their specific interpolation algorithms have been rarely evaluated. Because the results published so far relate to distinct particular cases and differ significantly, there are contradictory recommendations about the choice of pitch in clinical practice. In this paper, we present a new tool for the evaluation of multislice spiral CT z-interpolation algorithms, and apply it to the four-slice case. Our software is based on the computation of a "Weighted Radiation Profile" (WRP), and compares WRP to an expected ideal profile in terms of widening and heterogeneity. It provides a unique scheme for analyzing a large variety of spiral CT acquisition procedures. Freely chosen parameters include: number of detector rows, detector collimation, nominal slice width, helical pitch, and interpolation algorithm with any filter shape and width. Moreover, it is possible to study any longitudinal and off-isocenter positions. Theoretical and experimental results show that WRP, more than Slice Sensitivity Profile (SSP), provides a comprehensive characterization of interpolation algorithms. WRP analysis demonstrates that commonly "preferred helical pitches" are actually nonoptimal regarding the formerly distinguished z-sampling gap reduction criterion. It is also shown that "narrow filter" interpolation algorithms do not enable a general preferred pitch discussion, since they present poor properties with large longitudinal and off-center variations. In the more stable case of "wide filter" interpolation algorithms, SSP width or WRP widening are shown to be almost constant. Therefore, optimal properties should no longer be sought in terms of these criteria. On the contrary, WRP heterogeneity is related to variable artifact phenomena and can pertinently characterize optimal pitches. In particular, the exemplary interpolation properties of pitch = 1 "wide filter" mode are demonstrated.