CT Perfusion in the Treatment of a Swine Model of Unilateral Renal Artery Stenosis: Validation with Microspheres

Abstract

To assess the feasibility of using current computed tomography (CT) perfusion techniques for evaluating unilateral renal artery stenosis (RAS) with assessment of pre- and posttreatment perfusion and to compare those results against the standard of microsphere injection. Six juvenile swine with surgically created right RAS were examined in a combined angiography-CT suite. CT perfusion, injection of fluorescent microspheres, and digital subtraction angiography were performed before and after release of the stenosis. Cortical horseshoe-shaped regions of interest were used to measure blood flow (in milliliters/[100 g min]). Two cortical samples (superior and inferior) from each kidney were excised and sent to a reference laboratory for microsphere analysis. The relative blood flow ratio (RBFR) and posttherapy increase in blood flow were determined. The Pearson product correlation was calculated to compare the absolute blood flow, pretherapy RBFR, and posttherapy increase in blood flow between the two techniques. Bland-Altman analysis of the absolute blood flow measurements was performed. Forty-eight blood flow measurements showed moderate correlation (r = 0.712, P < .001). However, Bland-Altman plots (bias, -19.21; limits of agreement, -156.1 to 117.7 mL/[100 g . min]) showed poor agreement. Measurements of RBFR with CT correlated well with microsphere data. Pretherapy RBFR showed moderate correlation with microsphere data (r = 0.859, P < .001, n = 12), whereas the posttherapy increase in blood flow was highly correlated (r = 0.898, P < .001, n = 12). CT perfusion and microspheres produce similar indexes of relative renal cortical perfusion when normalized to the unaffected kidney. Further work is needed to determine the clinical utility of CT perfusion for pre- and posttherapy decision making.