This research aims to support chest computed tomography (CT) medical checkups to decrease the death rate by
lung cancer. We have developed a remote cooperative reading system for lung cancer screening over the Internet, a
secure transmission function, and a cooperative reading environment. It is called the Network-based Reading System. A
telemedicine system involves many issues, such as network costs and data security if we use it over the Internet, which
is an open network. In Japan, broadband access is widespread and its cost is the lowest in the world. We developed our
system considering human machine interface and security. It consists of data entry terminals, a database server, a computer
aided diagnosis (CAD) system, and some reading terminals. It uses a secure Digital Imaging and Communication
in Medicine (DICOM) encrypting method and Public Key Infrastructure (PKI) based secure DICOM image data distribution.
We carried out an experimental trial over the Japan Gigabit Network (JGN), which is the testbed for the Japanese
next-generation network, and conducted verification experiments of secure screening image distribution, some kinds of
data addition, and remote cooperative reading. We found that network bandwidth of about 1.5 Mbps enabled distribution
of screening images and cooperative reading and that the encryption and image distribution methods we proposed
were applicable to the encryption and distribution of general DICOM images via the Internet.