Computed tomographic perfusion analysis is an imaging procedure that allows functional evaluation of tissue vascularity on the basis of temporal changes in tissue attenuation after IV injection of contrast medium. In human patients with acute pancreatitis, CT perfusion analysis allows detection of pancreatic ischemia with excellent sensitivity (100%) and specificity (95.3%).1,2 Ischemic pancreatic tissue has lower perfusion variable values than normal pancreatic tissue, and there is a high probability that tissue ischemia will lead to necrosis; consequently, this finding is associated with a poor prognosis.2 Early detection of pancreatic ischemia allows early intensive treatment to help prevent severe complications and improve prognosis.2 To the authors' knowledge, only 1 study3 has investigated canine pancreatic perfusion by means of CT perfusion analysis. That study3 investigated the applicability of CT perfusion algorithms such as the maximum slope and deconvolution methods for evaluation of pancreatic perfusion in dogs; pancreatic blood flow, blood volume, and mean transit time were measured in Beagles by use of CT with a 5-mm slice thickness.3 We are aware of no other studies on the protocol for CT perfusion analysis of the pancreas in dogs.
The maximum slope method is a compartmental analytic method used for quantification of CT perfusion.1,4 This mathematical modeling technique obtains time-attenuation data from arterial input and estimates perfusion from the maximum slope on the basis of a single compartment model.1,4 Because CT perfusion analysis estimates tissue perfusion with theoretical assumptions, there can be a difference between CT perfusion analysis-derived data and actual tissue perfusion owing to technical factors.4 Image noise and patient motion can affect the reliability of CT perfusion data.1,4 Slice thickness is an important technical factor influencing CT perfusion analysis-derived data. In general, a slice thickness of ≤ 5 mm is recommended in most CT perfusion analysis protocols to provide an ideal spatial resolution and signal-to-noise ratio in humans.5 In practice, slice thickness is set to 5 to 10 mm for CT perfusion, regardless of the patient's size.1,6 However, slice thickness is proportional to the magnitude of partial volume artifact, and small anatomic structures need a < 5-mm slice thickness for CT perfusion.7 Results of a previous study8 on the application of CT perfusion analysis in the diagnosis of lung, rectal, or renal cancer in human patients reveal that different slice-thickness reconstructions induce significant variability in perfusion variables, particularly transit time. However, variability was smaller when the difference between slice thickness was smaller (eg, 1.25 vs 2.5 mm or 2.5 vs 5 mm) than when it was larger (eg, 1.25 vs 5 mm).
Because the pancreas in dogs has a thin, elongated conformation and is < 10 mm thick, CT perfusion analysis with 5- to 10-mm slice thicknesses can induce a marked partial volume effect.9 The purpose of the study reported here was to investigate the effect of slice thickness on pancreatic CT perfusion analysis in healthy dogs to assess the applicability of a thin slice (selected as 2.4 mm) for CT perfusion analysis of the pancreas in healthy dogs. We hypothesized that there would be no significant difference in pancreatic perfusion variables obtained with 2.4-mm and 4.8-mm slice thicknesses.
This research was supported by the Animal Medical Institute of Chonnam National University and by the Basic Science Research Program through the National Research Foundation of Korea, funded by the Ministry of Science, ICT, and Future Planning (NRF-2018R1A2B6006775).
The authors declare that there were no conflicts of interest.
Intraclass correlation coefficient
Region of interest
SNAP cPL test, Idexx Laboratories Inc, Westbrook, Me.
Zoletil, Virbac, Carros, France.
Domitor, Orion Corp, Espoo, Finland.
Terrell, Piramal Critical Care Inc, Bethlehem, Pa.
Emotion 16, Siemens, Forchheim, Germany.
Omnipaque 300, GE Healthcare, Oslo, Norway.
Optivantage DH, Liebel-Flarsheim Co, Cincinnati, Ohio.
Syngo body perfusion CT, Siemens, Forchheim, Germany.
SPSS Statistics, version 23, IBM Corp, Armonk, NY.
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