Movies acquired from fundus imaging using Indocyanine Green (ICG) and a scanning laser ophthalmoscope provide information for identifying vascular and other retinal abnormalities. Today, the main limitation of this modality is that it requires esoteric training for interpretation. A straightforward interpretation of these movies by objective measurements would aid in eliminating this training barrier. A software program has been developed and tested that produces and visualizes 2D maps of perfusion measures. The program corrects for frame-to-frame misalignment caused by eye motion, including rigid misalignment and warp. The alignment method uses a cross-correlation operation that automatically detects the distance due to motion between adjacent frames. The d-ICG movie is further corrected by removing flicker and vignetting artifacts. Each pixel in the corrected movie sequence is fit with a least-squares spline to yield a smooth intensity temporal profile. From the dynamics of these intensity curves, several perfusion measures are calculated. The most effective of these measures include a metric that represents the amount of time required for a vessel to fill with dye, a metric that represents the diffusion of dye, and a metric that is affected by local blood volume. These metrics are calculated from movies acquired before and after treatment for a neovascular condition. A comparison of these before and after measures may someday provide information to the clinician that helps them to evaluate disease progression and response to treatment.

This paper describes deployment of a Medical Doctor's Workstation (MDWS) hosting access to the Institute's radiology image and information system testbed. On-line acquisition of CT, MR and CR images for the physician's patients was supported. JPEG-compressed images reduced image data communications requirements by a factor of ten. Image interpretation at the remote site was supported by access to on-line radiology reports. The communications link to the MDWS was provided by a pair of Combinet ethernet-to-ISDN bridges interfaced to a basic rate (two B channel) ISDN line. Results of two successive trials in a referring physician's office are reported, along with the steps taken to improve limitations identified by the system's user.

Objective: Mathematical models for the delineation of regional myocardial perfusion and metabolism with PET require faithful reconstruction of arterial and myocardial time-activity curves following administration of radiotracers. High temporal resolution is often required in such measurements. Many commercially available tomographs exhibit long dead times that limit their count rate capabilities. To overcome these limitations, we developed and tested a whole-body tomographic device (Super PET 3000-E) with high count rate capabilities. The use of cesium fluoride scintillation detectors coupled with a one-to-one detector photomultiplier configuration reduces the system resolving and dead times. Materials and Methods: The Super PET 3000-E was subjected to a series of tests with phantoms to determine its resolution, sensitivity, linearity, count rate capabilities, dead time, and random coincidence contribution. Results: The system sensitivity is 136 kcounts/s/mu Ci/ml and its transverse and longitudinal resolutions are 8.5 and 10.5 mm full width at half-maximum, respectively. The system can easily record a total event rate of 2.0 Mcounts/s with minimal dead time loss and excellent linearity. Conclusion: The system fulfills its design goals and allows the very high count rate performance needed for the application of the physiological models used in our cardiac studies.

A new computer system designed for Posi- tron Emission Tomography (PET) devices that utilize list- mode data acquisition and Time-of-Flight(ToF) information is presented. The approach uses commercially available subsys- tems, all supported by hardware and software industry stan- dards. The host supports a VME-based disk farm that provides inexpensive disk storage operating at high transfer rates capa- ble of easily supporting list-mode data collection. All software development as well as the production environment is suppomd entirely under UNIX. All code development uses the C language. Graphical user interfxes are developed under X-Windows, Version 11. Images and data which are produced by the scanner are easily transferred to other environments via etheme$ link and 'KP/lP. Benchmark results show an increase in list-mode data collection rates, while decreasing the loss associated with the collection protocol. Image reconstruction times are shown to decrease markedly. Overall cost is also decreased. This allows a very flexible approach to system selection, enabling the researcher to choose any standards-based plat- form which provides a satisfactory cost-performance ratio. 1. The Importance of Industry Standards

A new image-reconstruction algorithm for time-of-flight (TOF) assisted positron-emission tomography is presented. This linear algorithm differs from previously published linear algorithms in the way the angular information of the measurements is used. The needed computations are reduced by coalescing data having angles within a range into a smaller number of group angles. This angle-reduction is made possible by the additional TOF measurement. It is shown that in the limit as the numer of groups is very large this reduced-angle weighting algorithm is the same as the confidence-weighting algorithm [1]. Similarly, if the data are grouped into a single angular range, the new algorithm is the same as the most-likely-position algorithm [1].