ADSL and cable modems found to optimize DICOM image transfer

Teleradiology is sometimes a better idea in theory than in practice. Using even the fastest modem, transmitting and receiving huge uncompressed DICOM images - which can be several million bytes in length - can take hours over a phone line.

Hoping to find a way to improve data communications rates, researchers at Emory University evaluated ADSL (asymmetrical digital subscriber line) and cable modem transfer of DICOM images.

Dr. Eric F. Mutz, an Emory radiologist, and colleagues connected the homes of two radiologists in Houston to a hospital workstation in Atlanta using a commercially available cable modem from MediaOne and an ADSL modem from BellSouth Telecommunications. Then, as reported at the RSNA meeting last month, a 20-image fully uncompressed DICOM head CT data set was sent from an Advantage Windows 3.1 workstation to the radiologists' home computers, each running eFilm DICOM servers from Toronto General Hospital.

The study concluded that ADSL and cable modem transfers of radiology studies using the commercial Internet as a transfer medium are suitable for timely review of full DICOM data sets and can be used to expand the range of teleradiology consultations.

In fact, both ADSL and cable modem connections operated somewhat faster than previously reported satellite transfer rates of 316 Kbits per second for a similar data set, Mutz said. (The earlier work was reported in J Digit Imaging 1999 May;12(2 suppl 1):195-196.)

The full 16-bit DICOM images were viewed with bone, brain, and soft-tissue windows.

To minimize the chances of hitting bottlenecks during peak usage hours, the same image data were transmitted at different times on three separate days: a Saturday, Sunday, and Wednesday.

ADSL transfer speed was found to be slightly higher than the cable modem for transfer of the 20-image CT data set.

The best results For ADSL were obtained at 10 a.m. on Saturday, when a transfer rate from the hospital workstation of 92 seconds (915 Kbits/second) was achieved, while the slowest rate, 106 seconds (763 Kbits/second), was found on Sunday at 8 p.m. The average for ADSL transmission of all 20 CT images from the workstation was 100.5, corresponding to a transfer rate of 837 Kbits/second, Mutz said.

For the Atlanta cable modem transfer, the average time for the 20 images was 140.2 seconds, corresponding to a transfer rate of 600 Kbits/second. The average Houston cable modem rate was 104.5 seconds.