Our overall research goal is to devise a robust method of tracking and compensating patient motion by combining an emission data based approach with a visual tracking system (VTS) that provides an independent estimate of motion. Herein, we present the latest hardware configuration of the VTS, a test of the accuracy of motion tracking by it, and our solution for synchronization between the SPECT and the optical acquisitions. The current version of the VTS includes stereo imaging with sets of optical network cameras with attached light sources, a SPECT/VTS calibration phantom, a black stretchable garment with reflective spheres to track chest motion, and a computer to control the cameras. The computer also stores the JPEG files generated by the optical cameras with synchronization to the list-mode acquisition of events on our SPECT system. Five Axis PTZ 2130 network cameras (Axis Communications AB, Lund, Sweden) were used to track motion of spheres with a highly retro-reflective coating using stereo methods. The calibration phantom is comprised of seven reflective spheres designed such that radioactivity can be added to the tip of the mounts holding the spheres. This phantom is used to determine the transformation to be applied to convert the motion detected by the VTS into the SPECT coordinates system. The ability of the VTS to track motion was assessed by comparing its results to those of the Polaris infra-red tracking system (Northern Digital Inc. Waterloo, ON, Canada). The difference in the motions assessed by the two systems was generally less than 1mm. Synchronization was assessed in two ways. First, optical cameras were aimed at a digital clock and the elapsed time estimated by the cameras was compared to the actual time shown by the clock in the images. Second, synchronization was also assessed by moving a radioactive and reflective sphere three times during concurrent VTS and SPECT acquisitions and comparing the time at which motion occurred in the optical and SPECT images. The results show that optical and SPECT images stay synchronized within a 150 ms range. The 100Mbit network load is less than 10%, and the computer's CPU load is between 15 and 25%; thus, the VTS can be improved by adding more cameras or by increasing the image size and/or resolution while keeping an acquisition rate of 30 images per second per camera.
Our overall research goal is to devise a robust method of tracking and compensating patient motion by combining an emission data based approach with a visual tracking system (VTS) that provides an independent estimate of motion. Herein, we present the latest hardware configuration of the VTS, a test of the accuracy of motion tracking by it, and our solution for synchronization between the SPECT and the optical acquisitions. The current version of the VTS includes stereo imaging with sets of optical network cameras with attached light sources, a SPECT/VTS calibration phantom, a black stretchable garment with reflective spheres to track chest motion, and a computer to control the cameras. The computer also stores the JPEG files generated by the optical cameras with synchronization to the list-mode acquisition of events on our SPECT system. Five Axis PTZ 2130 network cameras (Axis Communications AB, Lund, Sweden) were used to track motion of spheres with a highly retro-reflective coating using stereo methods. The calibration phantom is comprised of seven reflective spheres designed such that radioactivity can be added to the tip of the mounts holding the spheres. This phantom is used to determine the transformation to be applied to convert the motion detected by the VTS into the SPECT coordinates system. The ability of the VTS to track motion was assessed by comparing its results to those of the Polaris infra-red tracking system (Northern Digital Inc. Waterloo, ON, Canada). The difference in the motions assessed by the two systems was generally less than 1mm. Synchronization was assessed in two ways. First, optical cameras were aimed at a digital clock and the elapsed time estimated by the cameras was compared to the actual time shown by the clock in the images. Second, synchronization was also assessed by moving a radioactive and reflective sphere three times during concurrent VTS and SPECT acquisitions and comparing the time at which motion occurred in the optical and SPECT images. The results show that optical and SPECT images stay synchronized within a 150 ms range. The 100Mbit network load is less than 10%, and the computer's CPU load is between 15 and 25%; thus, the VTS can be improved by adding more cameras or by increasing the image size and/or resolution while keeping an acquisition rate of 30 images per second per camera.
The ATA is an induction accelerator designed to produce 70 ns pulses of electrons at currents of 10 kA and energies in excess of 50 MeV. The accelerator is capable of operating at an average rate of 5 Hz or at 1 kHz for ten pulses. The parameters were chosen primarily to provide the experimental basis for advancing the understanding of electron beam propaga tion physics. The 85 m accelerator has been under construction for the past four years and has adopted mainly an Improved version of the ETA technology to satisfy the required parameters. Initial operation of the facility and the energy conversion system from primary power to axial electric field will be described; recent advances in magnetic switching which hive beer incorporated in the injector will also be dlscusseo.
Patient motion, which causes artifacts in reconstructed images, can be a serious problem in SPECT imaging. If patient motion can be detected and quantified, the reconstruction algorithm can compensate for the motion. In previous work, we described a prototype system for tracking patient motion. In this paper, we present a real-time multithreaded Visual Tracking System (VTS) that will be suitable for deployment in clinical trials. The VTS tracks patients using multiple video images and image processing techniques, calculating patient motion in three-dimensional space. High performance is achieved by acquiring and processing images in parallel. Our system will incorporate up to five optical cameras monitoring the patient. Each camera is associated with a thread of control within the VTS. Thus, video images can be acquired asynchronously. As images are acquired, they are stored in buffers until needed. Another processing thread is responsible for requesting images from a specific time, and processing those images as a stereo set. The SPECT system operates in list mode. In this mode, all detected events are stored in a long list together with an event timestamp. Thus, it is possible to temporally register the time-stamped images with the detected activity in order to rebin the SPECT data to compensate for patient motion.
The DARPA Battlefield Awareness and Data Dissemination (BADD) Phase II Program will provide the next generation multimedia information management architecture to support the wa.rfighter. One goal of this architecture is proactive dissemination of information to the warfighter through strategies such as multicast and "smart push and pull" designed to minimize latency and make maximum use of available communications bandwidth. Another goal is to support integration of information from widely distributed legacy repositories. This will enable the next generation of battlefield awareness applications to form a common operational view of the battlefield to aid joint service and/or multi-national peacekeeping forces.This paper discusses the approach we are taking to realize such an architecture for BADD. Our architecture and its implementation, known as the Distributed Dissemination Services (DDS) are based on two key concepts: a global database schema and an intelligent, proactive caching scheme. A global schema provides a common logical view of the information space in which the warfighter operates. This schema (or subsets of it) is shared by all warfighters through a distributed object database providing local access to all relevant metadata. This approach provides both scalablity to a large number of warfighters, and it supports tethered as well as autonomous operations. By utilizing DDS information integration services that provide transparent access to legacy databases, related information from multiple "stovepipe" systems are now available to battlefield awareness applications.The second key concept embedded in our architecture is an intelligent, hierarchical caching system supported by proactive dissemination management services which push both lightweight and heavyweight data such as imagery and video to warfighters based on their information profiles. The goal of this approach is to transparently and proactively stage data which is likely to be requested by the warfighter in caches which are physically close to the warfighter. Through a global schema and intelligent caching, the BADD DDS architecture will provide a virtual information repository in which warfighter access to information is both fast and transparent with respect to its original source.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.