Differences in perfusion CT parameter values with commercial software upgrades: algorithm consistency and stability.

Computed tomographic (CT) perfusion imaging is a widely applied technique for the evaluation of acute ischemic stroke patients and to assess other brain diseases, including tumors. It is also a promising technique that realizes functional imaging, as an adjunct to a morfologic CT examination, that can be used as an aid to carefully evaluate the response to therapy in oncologic patients, especially with the new therapies. This technique has increased in the past few years, thanks to the diffusion of commercial Perfusion CT software platforms that are now integrated into a clinical reporting workstation. Although one of the advantages of CT perfusion imaging is it's ability to allow quantitative results, it has been reported that the CT perfusion imaging maps and relative quantitative results were significantly different among commercial software programs, provided by various CT manufacturers, using different algorithms, even when using identical source data, presumably because of differences in tracerdelay sensitivity and between different versions of the same software platform. V. Goh et al have demonstrated that upgrades of the same software (version 3.0 and 4.0 of perfusion software GE Healthcare Technologies) may alter the derived parameter values in colorectal cancer because of the introduction of T0, the time difference in arrival of contrast within the input vessel and the tissue of interest in version 4.0. Beyond this previous study and considering the recent introduction of the new version of upgrades of a widely-used commercial software platform (Perfusion 4.0 to 4D; GE Healthcare Technologies), the aim of our study was to determine how commercial software upgrades impact on algorithm consistency and stability among the three version upgrades of the same software platform (versions 3.0, 4.0 and 4D; Perfusion CT software, GE Healthcare Technologies).