A Rural and Global PACS provides its services in real-time and non real-time. Images transferred are usually provided in non real-time, requested prior to the consultation session. In this scenario, medical images (up to 4096x4096x8) and patient information are transferred to the destination within minutes. Typical resolution for a radiology modality is 2048x2048 pixel and 12 bits per pixel. This is an example of non real-time image transfer for storage or retrieval. Requests for image storage and retrieval occurs off-line and images are exchanged between an imaging equipment or workstation on a Local PACS and the database archive system on a Remote PACS. Local PACS users have access to an image directory service for image location. This scenario is used to retrieve image sets for research, education and diagnosis.
The rural virtual consultation service scenario involves two or more medical experts located respectively at a Local and Remote (rural) viewing workstation. These workstations can be located anywhere in the country. The physicians establish a consultation session for the purpose of examining images and recording a diagnosis. They both see the same image on their workstation screen. Each viewing workstation provides a pointer that allows the physician to point to parts of the image. When the physician moves the pointer, the Remote site sees the resulting movement of the pointer on their display. Additionally, workstations have image processing capabilities that allow the physicians to manipulate and analyze the image. These features are also displayed on the other monitors at the same time as the originating workstation. Voice interaction between the physicians takes place interactively. In order for all this to take place in real-time, the pointing commands, voice packets, and image processing parameters are transmitted to the remote site. Our tests shows round-trip delay times of less than 100 milliseconds for the image annotation commands, making the pointing operations real-time to the physicians. During the remote consultation and diagnosis session, the image annotation commands and voice are recorded and stored for later playback. The playback session can then be observed as it actually occurred. The session may include image annotation, such as graphics and text comments. Each physician has control over the parts of the session that are stored for the diagnosis.
Figure 2. shows the operations and services in the remote consultations scenario.
Virtual Consultation Services with Multi-Media viewing
In this scenario, a videoconference is conducted between
the Local and Remote physicians. Two uses are possible, 1) display video of the
two consulting physicians, and 2) display a live or recorded video of an
operative procedure. This video is displayed in a sub-window during a
consultation session. The digitized video is recorded at the Local WS site and
can be saved as part of the patient record and for layer review. This scenario
will require at least a T1 MBPS network to the rural sites, in order to display
slow scan motion video. The initial bandwidth of the ATEN is a T1 (1.544 MBPS)
links to the rural sites and the video conferencing will then operate at 5-8
frames per second. This scenario will be useful during ultrasound consultations.
The clinicians are able to access
image cases from a DBAS unit at University of Arizona.
A film scanner or digital
camera unit must be available
at the rural clinic for the
University of Arizona to provide
remote consultation services.
The images are digitized, formatted, and
transferred to the DBAS at the Local PACS at the University of Arizona for later
In rural clinics that have no Internet connection, a telephone line and 28.8 KBPS modem are used to access the nearest Local PACS network with a SLIP interface. The image annotation and real-time voice scenarios required at least a T1 speed to the rural sites. The viewing workstation performs the same as a direct Internet connection. For video services, T3 or greater network speeds are required for the remote sites.