:: transferring dicom images to pcs
ImPACT have used DICOM to transfer the images obtained at CT scanner assessments to our laptop UNIX workstation, and more recently, a lap top PC. These images are then analysed for the standard ImPACT image quality parameters (image noise, spatial resolution, axial and helical z-sensitivity) using custom written software.
A number of people have asked us what is needed to get images off their scanners, or other DICOM equipment onto their desktop computers. This page describes the equipment, software and techniques required. The description is for computers running Windows 95/98/NT/2000, but the general principles are the same for a UNIX, LINUX or Mac computer. Equally, our experience is mainly with CT, but the same approaches are required for MR, Digital II, or any digital imaging device capable of DICOM image transfer.
What you will need:
- A modern (Pentium or newer) computer, preferably a lap top. CT image files are approx 1/2 MB each in size, so plenty of hard disk space may be required if many images are to be transferred.
- A network card - for a laptop, a PCMCIA interface is the norm, although it may be built in. TCP/IP network protocol must be installed - check using Start -> Settings -> Control Panel and double clicking on Network. TCP/IP should be listed in the Protocols section.
- Network cable - twisted pair cable with a connector is the most common, but coaxial cables may also be used. Check the local network type.
- Network socket on the same network as the CT scanner.
- CT scanner or workstation that is capable of sending DICOM images. In DICOM parlance, it has to support the DICOM storage service class as a service class user (SCU). Most scanners that have DICOM capablities are capable of DICOM storage SCU.
- Software for the PC that supports DICOM storage service class as a service class provider (SCP). ImPACT use the DICOM toolkit software provided (free of charge) by the OFFIS group at the University of Oldenburg. The files can be downloaded here - download and unzip the executable binaries, as well as the source code which contains the documentation. Only one program is actually used - STORESCP.EXE. On our set up this is controlled using a batch file, USESTORESCP.BAT that can be downloaded as a zip file (1k). Note that there are now two versions of USESTORESCP; one is for DICOM toolkit version 3.5 and greater, the other for older versions. The difference is due to a minor change in syntax between the different versions.
- Software to view and/or manipulate the DICOM images once they are on the PC. Osiris is a good general purpose image viewer. ImPACT use the IDL programming language to do our image analysis - not cheap, but very versatile and with good DICOM facilities.
Procedure
The following is a fairly extensive procedure description - this is an attempt to explain the reason for some of the steps, and to keep to instructions as general as possible.
Scanner or Workstation settings
Generally it should be possible to transfer images from any imaging devices on a DICOM network to your PC - the choice is not always obvious. Workstations can often be easier to set up, as it is common for them to be routinely used to look at images from a range of devices, whereas the scanner is usually a supplier of images. Often it is necessary to hunt round the different set up menus, to find a Network or DICOM setup option. Sometimes, it is not possible to do this without going into service mode - manufacturer help is usually needed in this situation.
For most systems, you need to create a new storage device, give it a name and set a number of options. The options that need to be set vary from device to device, but in general, there are two main settings necessary, IP address and port number. These should match up to the settings on the PC. There may be other settings, such as calling and responding Application Title (AET), but it is usually possible to use the defaults. There is also sometimes a selector to say what services the device provides. In our case, the laptop is acting as a storage service class provider (it provides the DICOM storage service class - it is the SCP; the workstation or scanner will use that service - it is the SCU).
PC setup
STORESCP.EXE and USESTORESCP.BAT should be put in the same directory, preferably c:\dicom\. Other directories can be used, but USESTORESCP.BAT will need to be edited. A directory is needed to store the transferred images. c:\imges\transfer is the default, again, this can be changed by editing USESTORESCP.BAT.
Before the PC can connect to the scanner or workstation, the IP address needs to be set (more info on IP addresses). To change the PC's IP address, select Start -> Settings -> Control Panel. Double click on the 'Network' control panel item, select the TCP/IP protocol, and press the Properties button. The TCP/IP properties box appears, and allows you to change the setting marked 'IP address:' to one that is compatible with the local settings. Click OK, then OK again. Depending on the operating system, you may need to reboot the PC. The IP setting should now be correct.
The second setting that it may be necessary to make (although the default is usually OK) is the Port number. When using TCP/IP to communicate data, each piece of information has a destination address (the IP address) and a Port number (e.g. web site 'http' data is often sent on port 80). It is not particularly important which port number you use, as long as it is the same at both ends of the communication chain. DICOM often uses port 104, and this is the standard port we use. If you are working on a scanner or workstation that is determined to use some other port number, it is possible to change it on the laptop, by editing the line 'set port=104' to the appropriate number.
Before switching, the PC on, it should be connected to the local area network using the network cable.
To start the STORESCP.EXE program, double click on 'USESTORESCP.BAT' icon. This brings up a DOS window, with 'waiting for data on port 104!' at the top. The PC can then be left in this state while images are being sent to it, and various pieces of information will flash up on this screen, showing that image transfer is taking place. The images will appear in the directory c:\images\transfer, and explorer will show this directory slowly filling up.
Transferring images
Once the settings have been confirmed, it is time to try to transfer an image. Again, this varies on different units - but generally, you will need to be in the patient browser, where you will be able to select images, series or patients. With an image selected, you then have to either 'push' or 'archive' the image. A choice of destinations for the image is then usually given - select your PC, and confirm. The image should then be transferred - if this is working correctly, activity in the StoreSCP window on the laptop should let you know it is being receive. Look in c:\images\transfer for the files being transferred - each file should be approx 512 - 530kB in size. File names are normally something like CT.1.2.392.200036.9116.2.2.2.1762619180.961732103.121216.
Viewing images
To confirm that the image has been transferred correctly, use Osiris, or another DICOM viewer to open the image. Don't worry if Osiris shows an all white or all black screen - select Display -> Adjust Colors..., and alter window width and window level settings as appropriate. If this test image has benn transferred correctly, it should now be possible to transfer whole patients or series at a time.
More information on IP addresses
The IP address is the 'name' of the computer on the network used by the TCP/IP network protocol. It consists of four numbers, from 0 to 255, each separated by a full stop, e.g. 192.9.200.255. The reason this has to be changed is that in order to communicate in a simple manner, the first three of the numbers need to be the same as the scanner or workstation that the images will be transferred from. Therefore, it is necessary to find out the IP address of the scanner (e.g. in a particular situation, the CT scanner is 10.12.120.1, and the workstation 10.12.120.2; when transferring data, the PC is set up as 10.12.120.3). Care should be taken, especially in a hospital setting, not to duplicate an IP address that is already in use.