New computer system for in-beam PET data evaluation at GSI

The reconstruction of in-beam PET data acquired during the therapeutic irradiation with heavy ions at GSI Darmstadt requires high computational power since the PET images have to be available as shortly as possible after finishing a fractionated irradiation, however, at the latest before applying the next daily dose fraction. Furthermore, the number of patients treated per day (up to 15) increases steadly and more sophisticated and thus time consuming reconstruction techniques as e.g. the scatter correction introduced recently [1] and new real-time data evaluation concepts [2] are applied. Therefore, we have adapted our data processing software to a state-of-the-art computer system (Hewlett-Packard Linux cluster located at the computing centre of FZR). The cluster consists of 40 CPUs, from which up to 4 can be exclusively occupied by a user and it has been working for the routine PET data processing for heavy ion therapy since 2002. However, there remain two drawbacks: (i) The data transfer of the raw PET-data from the GSI to FZR and the retransfer of the reconstructed images to GSI depends on a reliable long-distance data transmission. (ii) The effectiveness of the PET data evaluation correlates with the load of the local network which is of course not so efficient like a direct connection to a PC. These disadvantages can be overcome by means of an onsite computer system placed at the therapy facility of GSI Darmstadt. Such a system provides a better in-time data evaluation [2] since it simplifies the data handling and it fastens the interactive calculation of deviations between planned and applied dose. Thus, we have installed in 2003 a new dual processor workstation (Fujitsu Siemens Celsius R610) with Intel Xeon processors of 3.06GHz equipped with 4GB DDR-SDRAM memory and a fast redundant SCSI RAID-1 storage disk array with a capacity of 122GB that is sufficient to store data for future beam-times (each ≈ 5GB). The workstation is connected via a Gigabit Ethernet LAN network device to the intranet of the therapy facility and it is protected against hacker attacks from outside using the GSI-Firewall. For archiving the data the internal DVD Burner is used. It allows to write media with a size of 4.7GByte which is sufficient to store all PET relevant patient data of one beam-time on one disk. The Linux operating system has been installed since it provides a high level of transparency and compatibility to the existing source codes and the shell scripts. Furthermore,