Robotic intrafractional US guidance for liver SABR: System design, beam avoidance, and clinical imaging.

Purpose: To present a system for robotic 4D ultrasound (US) imaging concurrent with radiotherapy beam delivery and estimate the proportion of liver stereotactic ablative body radiotherapy (SABR) cases in which robotic US image guidance can be deployed without interfering with clinically used VMAT beam configurations.

Methods: The image guidance hardware comprises a 4D US machine, an optical tracking system for measuring US probe pose, and a custom-designed robot for acquiring hands-free US volumes. In software, a simulation environment incorporating the LINAC, couch, planning CT, and robotic US guidance hardware was developed.

Interactive initialization of 2D/3D rigid registration.

Purpose: Registration is one of the key technical components in an image-guided navigation system. A large number of 2D/3D registration algorithms have been previously proposed, but have not been able to transition into clinical practice. The authors identify the primary reason for the lack of adoption with the prerequisite for a sufficiently accurate initial transformation, mean target registration error of about 10 mm or less.

Multiple-object 2-D-3-D registration for noninvasive pose identification of fracture fragments.

This paper presents a multiple-object 2-D-3-D registration technique for noninvasively identifying the poses of fracture fragments in the space of a preoperative treatment plan. The plan is made by manipulating and aligning computer models of individual fracture fragments that are segmented from a diagnostic computed tomography. The registration technique iteratively updates the treatment plan and matches its digitally reconstructed radiographs to a small number of intraoperative fluoroscopic images.

A new representation of intensity atlas for GPU-accelerated instance generation.

Fast instance generation is a key requirement in atlas-based registration and other problems that need a large number of atlas instances. This paper describes a new method to represent and construct intensity atlases. Both geometry and intensity information are represented using B-spline deformation lattices; intensities are approximated using the multi-level B-spline approximation algorithm during model creation and the parallel computation capability of modern graphics processing units is used to accelerate the process of instance generation.

Registration of a statistical shape model of the lumbar spine to 3D ultrasound images.

Motivation: Spinal needle injections are technically demanding procedures. The use of ultrasound image guidance without prior CT and MR imagery promises to improve the efficacy and safety of these procedures in an affordable manner.

Methodology: We propose to create a statistical shape model of the lumbar spine and warp this atlas to patient-specific ultrasound images during the needle placement procedure.

Prediction of the repair surface over cartilage defects: a comparison of three methods in a sheep model.

Defects in articular cartilage can be repaired through osteochondral transplantation (mosaic arthroplasty), where osteochondral plugs from non-weight-bearing areas of the joint are transferred to the defect site. Incongruity between the plug surface and the adjacent cartilage results in increased contact pressures and poorer outcomes. We compare three methods to predict the desired repair surface for use in computer-assisted mosaic arthroplasty: manual estimation, a cubic spline surface, and a statistical shape atlas of the knee.

A robust technique for 2D-3D registration.

A robust 2D-3D registration method with a wide capture range is presented. The method registers pre-operatively collected 3D computed tomography (CT) data sets of a single bone fragment to its intra-operative fluoroscope images. The registration technique relies on hardware rendering of CT data on consumer-grade graphics cards to generate digitally reconstructed radiographs (DRRs) in real time.

A new method for CT to fluoroscope registration based on unscented Kalman filter.

We propose a new method for CT to fluoroscope registration which is very robust and has a wide capture range. The method relies on the Unscented Kalman Filter to search for an optimal registration solution and on modern commodity graphics cards for fast generation of digitally reconstructed radiographs. We extensively test our method using three different anatomical data sets and compare it with an implementation of the commonly used simplex-based method.