Sunday, October 21, 2007

New DICOM Compression and Transfer Server

So, for the last two weeks or so a friend and I have been working on a secure file transfer server to host connections from mobile ultrasound units across the state. The initial problem revolved around the DICOM protocol itself...bulky and bandwidth intensive. Even with 512 up, it was taking 15-20 minutes to submit one study to our Radiologist in the upstate. As we continue to grow, the limitation becomes more and more restrictive. The design we came up with is ingeniously simple...move the entire DICOM directory directly from the modality onto a laptop via a crossover cable and a DICOM SCU association, since its local it's relatively quick. Once stored on the laptops file system, the user will open our secure client. The client has three simple operations: Connect, Transfer, and Upload reports. Its' what goes on behind the scenes that is critical. We wanted to be able to access the file system of our remote Server at our home office from each mobile client. All transferred data is strongly encrypted, and for optimal bandwidth utilization the uploaded/downloaded files are compressed/decompressed transparently during the transmission. The standard FTP protocol seems to be too limited and slow. We built in low-level access to the remote files as if they were local. Essentially, the client zips up the entire DICOM directory, connects to a secure FTP server, transfers the ZIP file, and closes the connection. The Server decrypts the file and unzips the file, recreating the DICOM directory on the host server. the PACS server points to the shared directory behind the firewall. Typical files get around 46% compression, and the transfer time is cut from nearly 20 minutes down to about 4 minutes. We tested with a four hop trace route and a 280Mb compressed file. Extreme performance. Most of the low level file sharing and encryption is using the BigSpeed component.