title: Differences in perfusion CT parameter values with commercial software upgrades: a preliminary report about algorithm consistency and stability.
abstract: BACKGROUND
  Computed tomographic perfusion (CTp) imaging is a promising technique that allows functional imaging, as an adjunct to a morphologic CT examination, that can be used as an aid to carefully evaluate the response to therapy in oncologic patients. Considering this statement, it could be desirable that the measurements obtained with the CT perfusion software, and their upgrades, are consistent and reproducible.
  
  
  OBJECTIVE
  To determine how commercial software upgrades impact on algorithm consistency and stability among the three version upgrades of the same platform in a preliminary study.
  
  
  METHODS
  Blood volume (BV), blood flow (BF), mean transit time (MTT), and permeability surface area product (PS) were calculated with repeated measurements (n = 1119) while truncating the time density curve at different time values in six CT perfusion studies using CT perfusion software version 4D (CT Perfusion 4D), then repeated with the previous version (CT Perfusion 3.0 and CT Perfusion 4.0), using a fixed ROI both for arterial input and target lesion. The software upgrades were compared in pairs by applying a Kolmogorov-Smirnov test to all the parameters measured. Stability and reliability of the three versions were verified through the variation of the truncated parameters.
  
  
  RESULTS
  The three software versions provided different parent distributions for approximately 80% of the 72 parameters measured. A complete agreement was found only for one patient in version 3.0 vs. 4.0 and 3.0 vs. 4D. Perfusion 4.0 vs. 4D: a complete agreement was found only in two cases. Parameters obtained with Perfusion 4D always showed the lowest standard deviation in all temporal intervals and also for all individual parameters.
  
  
  CONCLUSIONS
  The three versions of the same platform tested yield different perfusion measurements. Thus, our preliminary results show that Perfusion 4D version uses a stable deconvolution algorithm to provide more reliable measurements.
authors.affiliation: Department of Human Pathology and Oncology, Section of Radiological Sciences, University of Siena, Siena.
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Mazzei
authors.forename: Nevada Cioffi
authors.initials: NC
authors.lastname: Squitieri
authors.forename: Eleonora
authors.initials: E
authors.lastname: Sani
authors.forename: Susanna
authors.initials: S
authors.lastname: Guerrini
authors.forename: Giusi
authors.initials: G
authors.lastname: Imbriaco
authors.forename: Duccio
authors.initials: D
authors.lastname: Di Lucia
authors.forename: Andrea
authors.initials: A
authors.lastname: Guasti
authors.forename: Francesco Giuseppe
authors.initials: FG
authors.lastname: Mazzei
authors.forename: Luca
authors.initials: L
authors.lastname: Volterrani
mesh_terms: D000465:Algorithms; D001783:Blood Flow Velocity; D001810:Blood Volume; D002292:Carcinoma, Renal Cell / Q000098:blood supply / Q000000981:diagnostic imaging*; D003287:Contrast Media; D006801:Humans; D007479:Iopamidol; D007680:Kidney Neoplasms / Q000098:blood supply / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D015203:Reproducibility of Results; D012984:Software; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D003287:Contrast Media; D007479:Iopamidol
keywords: Perfusion imaging; multidetector computed tomography; oncology; software