The Effects of Baseline Length in Computed Tomography Perfusion of Liver

Objective: Computed Tomography perfusion (CTp) of liver is very attractive for predictive and prognostic purposes, but motion artefacts and radiation dose connected to duration of examinations jeopardize the reproducibility of perfusion values, thwarting CTp daily application in clinics. The goal is showing to what extent these issues can be faced by shortening the CTp unenhanced stage (i.e., the baseline). Methods: 59 patients with colorectal cancer underwent undelayed hepatic CTp examinations. For each patient, fifteen virtual examinations E\u3c4 simulating different scan delays \u3c4 08[1..15] s were achieved from the undelayed original sequence E0. Absolute (AD), percentage (PD) and compound differences (CD\u3c4 ) were computed between E0 and each E\u3c4 for baseline and perfusion values and measured in HU and arbitrary units (a.u.), respectively. Patients were grouped and counted based on the differences achieved. Results: Maximum perfusion CD\u3c4<10 a.u. and baseline CD\u3c4<7 HU were achieved. For \u3c4 6410 s, maximum perfusion CD\u3c4 08[5,6) a.u. was found in one patient only as well as maximum baseline CD\u3c4 08[2,3) HU. Blood flow (BF), hepatic perfusion index and arterial BF showed the lowest CD\u3c4 , while portal BF and total BF the highest ones. PD is practically always higher than AD. Conclusion: The approach presented allows clinicians to design the shortest CTp acquisition protocol, selecting the highest delay compliant with the required accuracy for the chosen perfusion parameters, to limit patient\u2019s motion and improve image quality. Significance: A short CTp protocol allows strengthening the reliability of perfusion values, and correctness of clinical outcomes, advancing CTp introduction in the standard clinical practice