Objective: The objective of this study was to assess the effects of pre–enhancement set point (T1) positioning on computed tomographic perfusion (CTp) parameter values.
Methods: The CTp data from 16 patients with neuroendocrine liver metastases were analyzed with distributed parameter modeling to yield tissue blood flow (BF), blood volume, mean transit time, permeability, and hepatic arterial fraction for tumor and normal liver, with displacements in T1 of ±0.5, ±1.0, ±2.0 seconds, relative to the reference standard. A linear mixed-effects model was used to assess the displacement effects.
Results: Effects on the CTp parameter values were variable: BF was not significantly affected, but T1 positions of ≥+1.0 second and −2.0 seconds or longer significantly affected the other CTp parameters (P ≤ 0.004). Mean differences in the CTp parameter values versus the reference standard for BF, blood volume, mean transit time, permeability, and hepatic arterial fraction ranged from −5.0% to 5.2%, −12.7% to 8.9%, −12.5% to 8.1%, −5.3% to 5.7%, and −12.9% to 26.0%, respectively.
Conclusions: CTp parameter values can be significantly affected by T1 positioning.
From the Departments of *Diagnostic Radiology, †Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX; ‡CT Research, GE Healthcare, Waukesha, WI; Departments of §Gastrointestinal Medical Oncology, and ∥Biostatistics, The University of Texas MD Anderson Cancer Center, Houston, TX.
Received for publication June 3, 2013; accepted November 19, 2013.
Reprints: Chaan S. Ng, MD, Department of Diagnostic Radiology, Unit 1473, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030-4009 (e-mail: firstname.lastname@example.org).
Supported in part by Genentech and Novartis.
Conflicts of Interest: Adam G. Chandler, PhD, is employed by GE Healthcare. The other authors report no conflicts of interest.