Volume rendering compared with maximum intensity projection for magnetic resonance angiography measurements of the abdominal aorta.

PURPOSE: To compare the volume rendering technique (VRT) with maximum intensity projection (MIP) for aortic diameter measurements in MR angiography (MRA) data sets. MATERIAL AND METHODS: Existing contrast-enhanced 3-dimensional MRA and digital subtraction angiography (DSA) data sets from 20 patients were analyzed. In each MRA data set, two aortic diameters were measured using MIP and VRT. Agreement with DSA measurements, dependence on rendering parameters, and interobserver agreement were assessed. RESULTS: Diameters measured on MIP with fixed parameters showed no significant difference compared with DSA and with freely selected parameters a slight overestimation relative to DSA. Diameters measured on VRT were larger than on DSA. For both MIP and VRT, the measurements depended on the chosen parameters. The error relative to DSA was larger for VRT than for MIP with fixed parameters but not with freely chosen parameters. Interobserver agreement did not differ significantly. CONCLUSIONS: VRT is not suitable for diameter measurements of the abdominal aorta with fixed parameter settings but may be useful with user-selected settings.

Long-term results after endovascular repair of abdominal aortic aneurysms with the Stentor and Vanguard stent-graft.

PURPOSE: To present a single institution experience of long-term results after endovascular repair of abdominal aortic aneurysms (AAA) with the Stentor and Vanguard stent-grafts. MATERIAL AND METHODS: Twenty-three patients (20 men, 3 women; mean age 68 years, range 53-81 years) were included in this prospective study. A first generation nitinol stent-graft (Stentor) was used in 12 patients and a second generation (Vanguard) in 11 patients. Follow-up was performed with magnetic resonance imaging (MRI) with contrast-enhanced MR angiography (CE MRA) at 1, 6, and 12 months, and thereafter annually (median follow-up 3 years; range 8 months to 8 years). A conventional radiograph of the abdomen was also performed. Before secondary intervention the findings on MRI with CE MRA were confirmed with spiral computed tomography (CT) and/or angiography (DSA). RESULTS: Only one patient (4%) had no complication. Endoleak was found in 15 patients (65%), graft migration in 8 (35%), and graft deformation in 18 (78%). Secondary endovascular repair was required in 7 patients (30%) and 7 (30%) were converted to open repair. CONCLUSION: Complications with the Stentor and Vanguard stent-grafts were common. Long-term follow-up of endovascularly repaired AAA is mandatory.

Costs in follow-up of endovascularly repaired abdominal aortic aneurysms. Magnetic resonance imaging with MR angiography versus EUROSTAR protocols.

AIM: Endovascular repair of abdominal aortic aneurysms (AAA) necessitates a long-term follow-up. These patients are often old and renal insufficiency is not unusual. Cost-effectiveness needs to be addressed in evaluating methods of follow-up. The aim of this study was to compare costs of 5 years follow-up with magnetic resonance imaging with contrast enhanced three-dimensional magnetic resonance angiography (MRI/MRA) with follow-up using CT with DSA, or CTA. We also assessed the impact of contrast media induced (CMI) nephropathy on follow-up costs. METHODS: We have implemented Swedish costs of CT with DSA, and CTA on the reported follow-up examinations from the EUROSTAR progress report 2000. The costs of follow-up with CT with DSA, or CTA were compared to a follow-up protocol with MRI/MRA. A cost analysis including a risk analysis of CMI nephropathy was made between MRI/MRA and CT with DSA, or CTA. RESULTS: Excluding the risk of CMI nephropathy, the 5 years follow-up cost in Euro ( ) with MRI/MRA ( 5715) is substantially higher than CT with DSA ( 3 095) or CTA ( 3573). The cost analysis favours MRI/MRA if the risk of CMI nephropathy from CT with DSA, or CTA is more than 5%. CONCLUSION: MRI/MRA can be cost-effective for follow-up of endovascularly repaired AAA depending on the risk of CMI nephropathy for CT with DSA, and CTA. MRI/MRA should be the method of choice for patients with pre-existing renal insufficiency.

Measurements before endovascular repair of abdominal aortic aneurysms. MR imaging with MRA vs. angiography and CT.

PURPOSE: 1) To compare measurements obtained with MR imaging (MRI)/contrast-enhanced MR angiography (CE MRA) with measurements obtained with angiography (DSA) and CT, for stent-graft sizing of abdominal aortic aneurysms (AAA). 2) To compare MRA measurements obtained with the two post processing techniques MIP (maximum intensity projection) and VRT (3D volume rendering technique). MATERIAL AND METHODS: The prospective study included 20 consecutive patients with AAA identified by DSA and CT as suitable for endovascular repair. For the study, MRI/CE MRA was performed. Five measurement variables for stent-graft sizing were chosen. Comparisons were made between MRI/CE MRA, DSA and CT, and between observers. Comparisons were also made between MIP and VRT. RESULTS: Significantly shorter lengths were obtained with MRA-MIP than with DSA. Three out of six diameter measurements were significantly smaller on MRI/CE MRA than on DSA and CT. No significant differences were found between the observers. One diameter measurement was significantly smaller on MIP than on VRT, while the other measurements showed no significant differences. CONCLUSION: The length measurements obtained with MRA-MIP were probably more correct than those with DSA. For more reliable diameter measurements with CE MRA, improvements of the technique, including VRT reconstructions and a standardized determination of the vessel boundaries, are needed.

Patient preferences for follow-up methods after endovascular repair of abdominal aortic aneurysms.

AIM: A fundamental and influential difference between open and endovascular repair of abdominal aortic aneurysms is the central role of imaging after endovascular repair. Willingness of the patient to return for further imaging is an important factor in choosing the method for follow-up. This study was undertaken to assess the subjective experiences of patients undergoing magnetic resonance imaging with contrast enhanced MR angiography, computed tomography and angiography (DSA) after endovascular repair of abdominal aortic aneurysms. METHODS: In a prospective study, 24 consecutive patients after endovascular repair of abdominal aortic aneurysms were invited to answer a questionnaire to qualitatively investigate the patient preferences for the follow-up methods, magnetic resonance imaging with contrast enhanced MR angiography, computed tomography and DSA. Nineteen patients (79%) answered. The questionnaire was constructed according to the principles and methods in nursing research and was developed as closed-ended multiple-choice questions with 4 alternatives, from most favorable to least favorable. The items of the questionnaire were based on interviews with radiographers in charge of each modality and concerned the most common patient experiences. RESULTS: The overall patient experience of magnetic resonance imaging with contrast enhanced MR angiography was more unpleasant than computed tomography. CONCLUSION: The overall patient experience showed no differences between magnetic resonance imaging with contrast enhanced MR angiography and DSA, or between computed tomography and DSA.

MR evaluation ex vivo and in vivo of a covered stent-graft for abdominal aortic aneurysms: ferromagnetism, heating, artifacts, and velocity mapping.

Magnetic resonance imaging (MRI) safety was evaluated at 1.5 T in a covered nickel titanium stent-graft (Vanguard) used for endovascular treatment of abdominal aortic aneurysms (AAAs). Imaging artifacts were assessed on MRI with contrast-enhanced (CE) three-dimensional (3D) MR angiography (MRA) and spiral computed tomography (CT) in 10 patients as well as ex vivo. Velocity mapping was performed in the suprarenal aorta and femoral arteries in 14 patients before and after stent-graft placement. For comparison it was also performed in six healthy volunteers. No ferromagnetism or heating was detected. Metal artifacts caused minimal image distortion on MRI/MRA. The artifacts disturbed image evaluation on CT at the graft bifurcation and graft limb junction. No significant differences in mean flow were found in patients before and after stent-graft placement. Our study indicates that MRI at 1.5 T may be performed safely in patients with the (Vanguard) stent-graft. MRI/MRA provides diagnostic image information. Velocity mapping is not included in our routine protocol.

Aortoenteric fistula caused by a ruptured stent-graft: a case report.

PURPOSE: To report a case of aortoenteric fistula secondary to endovascular abdominal aortic aneurysm (AAA) exclusion using the Stentor bifurcated endovascular graft. METHODS AND RESULTS: Seventeen months after a successful endovascular AAA procedure, a male patient developed upper gastrointestinal bleeding. An aortoenteric fistula was diagnosed. At operation, the endograft fabric was found to be ruptured in an area of suture disruption between the nitinol stents. Coincidentally, a pre-existing inflammatory process might have caused adhesions between the bowel and the aortic wall, predisposing to fistula formation. The patient recovered after placement of a conventional aortic graft. CONCLUSIONS: Suture disruption between the internal support stents is a recognized complication in the first-generation Stentor device. Although the case described here is probably not typical of the consequences of this sequela, it does reinforce the need for continual periodic imaging to check for signs of graft disruption in Stentor endografts.

Magnetic resonance imaging and MR angiography of endoluminally treated abdominal aortic aneurysms.

OBJECTIVES: To evaluate magnetic resonance imaging (MRI) with gadolinium-based contrast medium-enhanced MR angiography (MRA) for the follow-up of endoluminally treated abdominal aortic aneurysms. DESIGN: MRI/MRA, angiography and computed tomography (CT) were performed 1 month after endoluminal stent-graft placement. MRI/MRA was repeated at 6 and 12 months and angiography and CT were added to confirm unexpected findings. MATERIALS: Fifteen male patients with endoluminally treated abdominal aortic aneurysms. METHODS: MRI with MRA, spiral CT with transverse images and angiography were performed. RESULTS: MRI/MRA demonstrated changes of stent-graft morphology, aortic neck- and aneurysmal diameter, stent-graft blood flow, stent-graft leakage, blood flow in lumbar arteries, intra-aneurysmal thrombus, periaortic inflammation and vertebral body infarction. For most of these features MRI/MRA provided more information than angiography and/or CT. MRI was the only method demonstrating thrombus reorganisation and vertebral body infarction. CONCLUSIONS: MRI with MRA provides the relevant information needed for follow-up of endoluminally treated abdominal aortic aneurysms (AAA). This may be the method of choice because of its use of contrast media with very low nephrotoxicity, lack of ionising radiation and non-invasiveness.

[Endovascular technique in aortic aneurysm. A promising alternative to open surgery]. / Endovaskulär teknik vid aortaaneurysm. Lovande alternativ till öppen kirurgi.

The article consists in a presentation of endovascular surgery for abdominal aortic aneurysm repair in 23 cases. Two cases required conversion to open surgery, but the procedure could be completed in the remaining 21 cases, with a current duration of follow-up of up to 30 months. There was early leakage in one case, and late leakage in five cases. Late conversion has been necessary in three instances, and supplementary endovascular measures have been required in a further two instances. All complications have occurred in those cases operated during the first half of the study period. Modification of the endoprosthesis used and increasing skill have reduced both operation time and the complication rate. Intensive care is no longer required, and the median duration of hospitalisation is three days. Follow-up with magnetic resonance imaging has yielded new and important information.

Reflux, stricture and glomerular filtration rate after two antireflux techniques in continent urinary reconstruction using the right colon.

In the present study the incidence of reflux, stricture formation and changes in glomerular filtration rate in patients with the submucosal tunnel or the Camey-Le Duc technique of ureteric implantation into the caecum/detubularized right colon used for continent cutaneous diversion/orthotopic bladder substitution was investigated. Reflux was found in two renal units and ureterointestinal stenosis occurred in five renal units after submucosal tunnel ureteric implantation. After Camey-Le Duc ureteric implantation, one renal unit showed reflux and none had stenosis of the ureterointestinal anastomosis during follow-up. Mean glomerular filtration rate (ml/min/1.73 m2) fell from 98 to 85 in the submucosal tunnel group and from 88 to 81 in the Camey-Le Duc group after mean follow-ups of 9 and 5 years, respectively. Both methods of ureteric implantation in this study were effective in preventing reflux, and renal function was well preserved in both groups. The absence of ureterointestinal strictures in the Camey-Le Duc group is encouraging and indicates that this is a reliable method for reflux prevention.