Impact of cone-beam computed tomography artifacts on dose calculation accuracy for lung cancer.

Background: To implement image-guided adaptive radiotherapy (IGART), many studies investigated dose calculations on cone-beam computed tomography (CBCT). A high HU accuracy is crucial for a high dose calculation accuracy and many imaging sites showed satisfactory results. It has been shown that the dose calculation accuracy for lung cancer lags behind.

Assessment of intra-fraction motion during frameless image guided Gamma Knife stereotactic radiosurgery.

As frameless stereotactic radiosurgery increase in use, the aim of this study was to evaluate intra-fraction motion through cone-beam CT (CBCT) and high-definition motion management (HDMM) systems. Intra-fraction motion measured between localization, repeat localization and post-treatment CBCTs were correlated to intra-faction motion indicated by the HDMM files using the Pearson coefficient (r). A total of 302 plans were reviewed from 263 patients (114 male, 149 female); 216 pairs of localization-repeat localization, and 260 localization-post-treatment CBCTs were analyzed against HDMM logs.

Monte Carlo analysis of beam blocking grid design parameters: Scatter estimation and the importance of electron backscatter.

Purpose: Beam blocking grids provide a simple and direct measurement of the scattered photon signal which degrades image quality in x-ray imaging systems, such as cone-beam CT (CBCT). This study evaluates the scatter estimation accuracy of the beam blocking method to optimize the design parameters of the grid system (e.g.

Preliminary Evaluation of a Novel Thermoplastic Mask System with Intra-fraction Motion Monitoring for Future Use with Image-Guided Gamma Knife.

Unlabelled: OBJECTIVES : A non-invasive immobilization system consisting of a thermoplastic mask with image-guidance using cone-beam CT (CBCT) and infrared (IR) tracking has been developed to ensure minimal inter- and intra-fractional movement during Gamma Knife radiosurgery. Prior to clinical use for patients on a Gamma Knife, this study clinically evaluates the accuracy and stability of this novel immobilization system with image-guidance in patients treated with standard fractionated radiation therapy on a linear accelerator.

Materials & Methods: This prospective cohort study evaluated adult patients planned for fractionated brain radiotherapy.

A combined dose calculation and verification method for a small animal precision irradiator based on onboard imaging.

Purpose: Novel small animal precision microirradiators (micro-IR) are becoming available for preclinical use and are often equipped with onboard imaging (OBI) devices. We investigated the use of OBI as a means to infer the accuracy of the delivered treatment plan.

Methods: Monte Carlo modeling of the micro-IR including an elliptical Gaussian electron beam incident on the x-ray tube was used to score dose and to continue photon transport to the plane of the OBI device.

Cone beam computed tomography image guidance system for a dedicated intracranial radiosurgery treatment unit.

Purpose: Image guidance has improved the precision of fractionated radiation treatment delivery on linear accelerators. Precise radiation delivery is particularly critical when high doses are delivered to complex shapes with steep dose gradients near critical structures, as is the case for intracranial radiosurgery. To reduce potential geometric uncertainties, a cone beam computed tomography (CT) image guidance system was developed in-house to generate high-resolution images of the head at the time of treatment, using a dedicated radiosurgery unit.

Geometric performance and efficiency of an optical tracking system for daily pre-treatment positioning in pelvic radiotherapy patients.

The purpose of this study was to characterize the accuracy of a novel in-house optical tracking system (OTS), and to determine its efficiency for daily pre-treatment positioning of pelvic radiotherapy patients compared to conventional optical distance indicator (ODI) methodology. The OTS is comprised of a passive infrared stereoscopic camera, and custom control software for use in assisting radiotherapy patient setup. Initially, the system was calibrated and tested for stability inside a radiation therapy treatment room.

Initial investigation of an automatic registration algorithm for surgical navigation.

The procedure required for registering a surgical navigation system prior to use in a surgical procedure is conventionally a time-consuming manual process that is prone to human errors and must be repeated as necessary through the course of a procedure. The conventional procedure becomes even more time consuming when intra-operative 3D imaging such as the C-arm cone-beam CT (CBCT) is introduced, as each updated volume set requires a new registration. To improve the speed and accuracy of registering image and world reference frames in image-guided surgery, a novel automatic registration algorithm was developed and investigated.

Automated 3-D reconstruction of the surface of live early-stage amphibian embryos.

Although three-dimensional (3-D) reconstructions of the surfaces of live embyos are vital to understanding embryo development, morphogenetic tissue movements and other factors have prevented the automation of this task. Here, we report an integrated set of software algorithms that overcome these challenges, making it possible to completely automate the reconstruction of embryo surfaces and other textured surfaces from multiview images. The process involves: 1) building accurate point correspondences using a robust deformable template block matching algorithm; 2) removing outliers using fundamental matrix calculations in conjunction with a RANSAC algorithm; 3) generating 3-D point clouds using a bundle adjustment algorithm that includes camera position and distortion corrections; 4) meshing the point clouds into triangulated surfaces using a Tight Cocone algorithm that produces water tight models; 5) refining surfaces using midpoint insertion and Laplacian smoothing algorithms; and 6) repeating these steps until a measure of convergence G, the rms difference between successive reconstructions, is below a specified threshold.

Multiview robotic microscope reveals the in-plane kinematics of amphibian neurulation.

A new robotic microscope system, called the Frogatron 3000, was developed to collect time-lapse images from arbitrary viewing angles over the surface of live embryos. Embryos are mounted at the center of a horizontal, fluid-filled, cylindrical glass chamber around which a camera with special optics traverses. To hold them at the center of the chamber and revolve them about a vertical axis, the embryos are placed on the end of a small vertical glass tube that is rotated under computer control.