Effect of suprarenal fixation of aortic stent-grafts on the renal artery ostia: assessment of morphological changes by virtual intravascular endoscopy.

PURPOSE: To investigate the morphological effects of suprarenal fixation of aortic stent-grafts on the renal artery ostia (RaO) by analysis of suprarenal stent wire distribution and vascular calcification across the RaO using virtual intravascular endoscopy (VIE). METHODS: Fourteen consecutive patients (11 men; mean age 75 years) from a single institution were studied following endovascular aortic aneurysm repair (EVAR) using the Zenith endograft system from September 1999 to March 2002. Imaging assessment included computed tomographic (CT) measurement of renal artery intraluminal ostial diameter and quantification and analysis of uncovered stent struts across the RaO and radiological determination of RaO calcification. Morphological changes following EVAR at 3 time points (before and within 1 week after stent-grafting, and at the most recent follow-up) were compared for each patient to determine whether suprarenal stent struts or RaO calcification affected intraluminal ostial diameter. Renal function was assessed by temporal measurements of serum creatinine concentration and creatinine clearance. RESULTS: The renal ostium was distorted to variable degrees in all cases at a mean follow-up of 41+/-6.6 months. An increase in ostial diameter was identified in most patients if the right RaO was calcified when comparing the 1-week postoperative and most recent follow-up CT images (p<0.05). There was no direct relationship between the number of stent struts crossing the RaO and the morphological/dimensional changes (p>0.05). Renal function was not significantly affected. CONCLUSION: Patients undergoing suprarenal fixation of aortic stent-grafts experienced morphological changes of the RaO to a variable extent at midterm follow-up. Although the presence of stent struts did not significantly affect dimensional changes, we observed that calcification at the renal artery ostium may influence the development of atherosclerotic effects as a direct relationship between the calcification and ostial diameter. Future studies utilizing VIE to determine the long-term safety of this technique in these particular patients requires investigation.

Suprarenal fixation of endovascular aortic stent grafts: assessment of medium-term to long-term renal function by analysis of juxtarenal stent morphology.

OBJECTIVE: The effect of suprarenal stent fixation during endovascular aortic aneurysm repair (EVAR) on renal function remains unclear. A unique validated three-dimensional intraluminal imaging technique was used to analyze the effect of suprarenal stent position relative to renal artery orifices. Also analyzed was its medium-term to long-term effects on renal function. METHODS: The study cohort comprised 29 of 34 consecutive patients who underwent EVAR with the Zenith endograft system from September 1999 to March 2002 at a single institution. The precise locations of the uncovered suprarenal stent struts were assessed by a virtual endoscopic imaging technique. Anatomic and quantitative categorization of patients was made according to the configuration of uncovered stent struts across the renal artery ostia (RAO). The anatomic subgroups were defined as struts located centrally or peripherally across both RAO. The quantitative subgroups were defined as RAO crossed by multiple struts, a solitary strut, or no struts. The subgroups were compared for their renal function, as assessed by temporal measurements of serum creatinine concentration and creatinine clearance, and renal parenchymal perfusion defects, as assessed using contrast-enhanced computed tomography (CT). RESULTS: Mean follow-up was 52.7 months. Separate subgroup analysis for both anatomic and quantitative configurations did not demonstrate any significant difference in renal function between the different strut permutations (P > .05). Follow-up imaging confirmed one case of renal infarction secondary to an occluded accessory renal artery, although this patient had normal serum creatinine levels. CONCLUSION: RAO coverage by suprarenal uncovered stents does not appear to have a significant effect on renal function as evaluated by creatinine measurements in patients with normal preoperative renal function.

Image registration and subtraction for the visualization of change in diabetic retinopathy screening.

Diabetic retinopathy (DR) is a leading cause of blindness in people of working age in developed countries. DR is characterized by lesions of the retinal microvasculature. This paper describes a technique for visualizing the changes which occur in retinal pathology over a 1 year interval. Pairs of retinal images of the same eye were acuired 12 months apart within a DR screening programme. The images were normalized, registered and subtracted to generate a contrast-enhanced difference image displaying changes in retinal appearance. The normalization factor and registration error were quantified for 104 pairs of retinal images.

Diagnostic value of CT virtual intravascular endoscopy in aortic stent-grafting.

PURPOSE: To investigate the diagnostic value of postprocessing techniques for 3-dimensional (3D) computed tomography (CT), with emphasis on CT virtual intravascular endoscopy (VIE), in patients with abdominal aortic aneurysms (AAA) treated with suprarenal stent-grafts. METHODS: The preprocedural and postprocedural CT datasets from 47 AAA patients (40 men; mean age 75 years, range 61-87) undergoing aortic stent-grafting with suprarenal fixation were examined. The CT datasets were processed to create various 3D reconstructions: shaded surface display (SSD), maximum intensity projection (MIP), and VIE. Three independent radiologists assessed various diagnostic parameters for each 3D reconstruction method and compared them to axial CT images. RESULTS: Scores for VIE reconstructions were inferior to axial CT images in the visualization of normal arterial branches, measurement of the aneurysm diameter and neck length, as well as assessment of vessel patency and presence of endoleaks. VIE was rated superior to axial CT and other 3D imaging methods in visualizing the configuration of stent struts relative to the aortic branch ostia and the number of stent wires crossing the ostia in >80% of cases. CONCLUSIONS: VIE was not found to play a role in most preoperative situations compared to axial CT images. However, VIE provided additional postgrafting information on the 3D relationship of the suprarenal stent struts to the aortic branch ostia (in particular the renal and superior mesenteric arteries). VIE findings might aid clinicians in accurately assessing the effect of suprarenal stent-grafting on the renal arteries.