Virtual sonography through the Internet: volume compression issues.
BACKGROUND
Three-dimensional ultrasound images allow virtual sonography even at a distance. However, the size of final 3-D files limits their transmission through slow networks such as the Internet.


OBJECTIVE
To analyze compression techniques that transform ultrasound images into small 3-D volumes that can be transmitted through the Internet without loss of relevant medical information.


METHODS
Samples were selected from ultrasound examinations performed during, 1999-2000, in the Obstetrics and Gynecology Department at the University Hospital in La Laguna, Canary Islands, Spain. The conventional ultrasound video output was recorded at 25 fps (frames per second) on a PC, producing 100- to 120-MB files (for from 500 to 550 frames). Processing to obtain 3-D images progressively reduced file size.


RESULTS
The original frames passed through different compression stages: selecting the region of interest, rendering techniques, and compression for storage. Final 3-D volumes reached 1:25 compression rates (1.5- to 2-MB files). Those volumes need 7 to 8 minutes to be transmitted through the Internet at a mean data throughput of 6.6 Kbytes per second. At the receiving site, virtual sonography is possible using orthogonal projections or oblique cuts.


CONCLUSIONS
Modern volume-rendering techniques allowed distant virtual sonography through the Internet. This is the result of their efficient data compression that maintains its attractiveness as a main criterion for distant diagnosis.
Ferrer-Roca
O
O
Pathology, University of La Laguna, Tenerife, 38071, Canary Islands, Spain. catai@teide.net
Vilarchao-Cavia
J
J
Troyano-Luque
J M
JM
Clavijo
M
M
D000465:Algorithms; D016477:Artifacts; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods; D016247:Information Storage and Retrieval / Q000379:methods; D020407:Internet / Q000639:trends*; D011247:Pregnancy; D011873:Radiology Information Systems / Q000295:instrumentation; D019112:Teleradiology / Q000295:instrumentation / Q000379:methods; D016216:Ultrasonography, Prenatal / Q000295:instrumentation / Q000379:methods*