Evaluation of aterosclerotic renal artery stenoses after application of intravascular stent with spiral CT angiography

Purpose: The purpose of this study is to explore the sufficiency of CTA in evaluating stent-renal artery relation, stent completeness and stent patency in cases where intravascular is applied because of narrow renal artery in controls after stent. Materials and Methods: In this study 15 cases are included 12 of whom male and 3 of whom female and ages between 40-78 (average 58.4 ± 10.4) patients where metallic stent is applied dates between August 1996-March 2001 to renal artery because of narrow renal artery. All cases are explored with spiral CTA in 1. day - 44. month controls. The spiral CTA exploration is done in two phases where first phase is data collection and second phase is application of post-processing to collected data. MPR, MIP, SSD and VIE images are constructed by post-processing. Furthermore for all cases stent length is measured in oblique MPR images obtained in coronal plane and stent diameter is measured in 1 mm reconstructed standard axial images. In order to evaluate and compare with renal artery and aorta contrasting stent patency in aorta, in renal artery section of stent distal and in opposite renal artery, density measurements have been carried out in all cases. Kidneys, in the scope of its dimensions, being contrasted, cortical width have been evaluated in all cases. Results: In all cases when stent lengths and measured stent is made free are compared, the difference is found to be changing between 0 and 1 mm in diameter measurements the difference is found to be changing between 0 -0.7 mm. In three cases related with the insufficient dilatation of stent, stent diameter have been observed to be decreasing. In the scope of visibility of stent lumen, MPR and thickened MIP images are compared. Stent lumen is best viewed in axial plane oblique MPR images. In one cases, related with the angle between stent and aorta this plane is imaged as sagittal or coronal. In ten cases where MIP images are obtained by increasing section width, the plane the stent lumen is best viewed is the axial plane that is lying between 1.5-2.1 mm widths. In one case this plane is the sagittal and coronal plane which is 1.8 mm width related with the angle between aorta and stent.102 In 14 cases when evaluating all the images obtained stent is viewed as patent. In one case at the proximal of renal artery occlusion is identified and contrasting in stent lumen can not be showed. In one case we observed stenosis at the proximal of stent in M PR images. In all cases in MPR and MIP images, because stent which had high attenuation have been observed differently from intraluminal contrast agent but calcification could not be identified. In all cases the continuity of vascular structures in stent distal has been best viewed in MIP images of 7.3-10.7 mm width. SSD and stent, intraluminal contrast agent and vascular wall calcification could not be identified when density is considered. Stent has been observed wider compared to diameter of renal artery and overflowing in the contour. Stent has been observed as patent with VIE in 14 cases. In one case occlusion has been showed in stent proximal. In one case, the bilateral accessory arteries detected in angiography have been observed both in MIP and SSD. In one case where stent occlusion have been detected dimension of the kidney where stent exist observed to be diminishing. In three cases in which their angiography stenosis at the opposite has been detected stenosis segment has been showed in MIP and SSD. In all cases kidneys have been observed at the phase of nephrogram. In one case where stent occlusion exists, density values have been observed clearly as low in the measurements of distal side neighbourhood. Conclusion: Spiral CTA together with scanning parameters and postprocessing applications can be applied as an noninvasive method in stent completeness, stent patency and in evaluation relation between stent-renal artery.