Multidetector CT angiography with perfusion analysis in the surveillance of renal artery stents

Purpose: To evaluate 4 perfusion parameters obtained by multidetector computed tomographic angiography (CTA) in the follow-up of patients after renal artery stenting. \ Methods: Thirty-three consecutive patients (20 women; mean age 64.3+/-10.7 years) with renal artery stents were included in this prospective pilot trial. CTA was performed in 21 patients on a 4-row scanner and in 12 patients on a 16-row scanner. Volume maximum intensity projections and curved planar reconstructions were used for morphological analysis. The initial contrast test bolus was used for perfusion imaging by placing 2 additional regions of interest in the cortex of each kidney. The maximum relative attenuation values (Hounsfield units [HU max]), the time-to-peak values, an attenuation ratio, and a time-to-peak ratio for each side were calculated. Results: Over a mean follow-up of 3.4+/-1.7 years, restenosis was detected in 4 (12.1%) of the 33 stents; in all 66 main renal arteries, 5 (7.5%) significant flow obstructions were detected. Interobserver agreement for all morphological parameters was excellent (kappa>0.8). Mean relative HU max for the cortical region of stented arteries was 63.7+/-29.7 (mean HU ratio 0.37+/-0.12); the mean TTP max was 32.9+/-7.4 seconds (mean ratio 0.76+/-0.10). None of the perfusion parameters differed significantly between patients with and without significant flow obstructions (p>0.05). Conclusions: Despite the excellent morphological information provided by multidetector CTA in the follow-up of renal stents, this modality does not provide hemodynamic information. Unfortunately, none of the evaluated perfusion parameters added any useful information in the follow-up after renal artery stenting.