MDCT angiography assessment of renal artery in-stent restenosis: can we reduce the radiation exposure burden? A feasibility study.

Aim: We explored the feasibility of renal artery multidetector computed tomography (MDCT) and detection of in-stent restenosis at low exposure settings.

Patients/methods: Sixteen patients with 19 renal artery stents underwent CT angiography. A biphasic protocol was performed including arteriographic acquisition at standard 120 kVp and a late-arterial scan at 100 kVp (n=9) or 80 kVp (n=7). Images were reconstructed under various algorithms. Signal-to-noise and contrast-to-noise ratios (SNR, CNR) were determined within stent, aorta and renal arteries. Image quality and the presence of restenosis were assessed. Volume CT dose-index was recorded and dose reduction (DR%) between phases was calculated.

Results: Ten patients presented with Hounsfield values >250 HU in all segments, phases and reconstructions and were further evaluated. The 120 kVp protocol performed better in all vessels and reconstruction algorithms. SNR at 120 kVp (B31f) did not differ significantly compared to 100 kVp (B31f). CNR within stent was borderline compromised at 100 kVp (p=0.042). All but two image sets (at 80 kVp) were considered diagnostic. Minor loss of subjective image quality was noticed at 100 kVp. No difference in assessment of restenosis was observed between 120 kVp and the diagnostic low-exposure scans. Mean DR% was estimated 45% at 100 kVp and 77% at 80 kVp.

Conclusions: Renal MDCT angiography and stent-restenosis assessment are feasible at 100 kVp with minor loss of image quality and almost half radiation exposure.