Jeannette Bakker

Quantitative analysis of vascular morphology from 3D MR angiograms: In vitro and in vivo results.

A 3D model‐based approach for quantification of vascular morphology from several MRA acquisition protocols was evaluated. Accuracy, reproducibility, and influence of the image acquisition techniques were studied via in vitro experiments with ground truth diameters and the measurements of two expert readers as reference. The performance of the method was similar to or more accurate than the manual assessments and reproducibility was also improved. The methodology was applied to stenosis grading of carotid arteries from CE MRA data. In 11 patients, the approach was compared to manual scores (NASCET criterion) on CE MRA and DSA images, with the result that the model‐based technique correlates better with DSA than the manual scores. Spearmans correlation coefficient was 0.91 (P < 0.001) for the model‐based technique and DSA vs. 0.80 and 0.84 (P < 0.001) between the manual scores and DSA. From the results it can be concluded that the approach is a promising objective technique to assess geometrical vascular parameters, including degree of stenosis. Magn Reson Med 45:311–322, 2001.

Duplex Ultrasonography in Assessing Restenosis of Renal Artery Stents

Purpose: To determine the accuracy and optimal threshold values of duplex ultrasonography (US) in assessing restenosis of renal artery stents.Methods: Twenty-four consecutive patients with 33 renal arteries that had previously been treated with placement of a Palmaz stent underwent duplex US prior to intraarterial digital subtraction angiography (DSA), which was the reference standard. Diagnostic accuracy of in-stent peak systolic velocity (PSV) and reno-aortic ratio (RAR=PSV renal stent/PSV aorta) in detecting τ; 50% in-stent restenosis were evaluated by the receiver operating characteristic curve. Sensitivity and specificity were determined using the optimal threshold values, and using published threshold values: RAR τ; 3.5 and in-stent PSV τ; 180 cm/sec.Results: Six examinations were technically inadequate. Nine stents had residual or restenosis τ; 50% at DSA. The two duplex parameters were equally accurate since areas under the curves were similar (0.943). With optimal threshold values of 226 cm/sec for PSV and 2.7 for RAR, sensitivities and specificities were 100% and 90%, and 100% and 84%, respectively. Using the published duplex criteria resulted in sensitivities and specificities of 100% and 74% for PSV, and 50% and 89% for RAR.Conclusion: Duplex US is a sensitive modality for detecting in-stent restenosis if laboratory-specific threshold values are used.

The Erasme Study: A Multicenter Study on the Safety and Technical Results of the Palmaz Stent Used for the Treatment of Atherosclerotic Ostial Renal Artery Stenosis

AbstractPurpose: To assess, in a multicenter setting, safety, technical results, and restenosis rate of the Palmaz stent for treatment of atherosclerotic ostial renal artery stenosis. Methods: Ten centers enrolled 106 patients (120 treated renal artery stenoses) in the study. Patient selection was based on unsuccessful percutaneous transluminal renal angioplasty (residual stenosis ≥ 20%) performed for treatment of ostial stenosis ≥ 50%, in patients with hypertension and/or impaired renal function. Safety was assessed by means of the complication rate, and technical results by the number of successful stent placements and occurrence of restenosis (>50%) at intraarterial angiographic follow-up. Results: Stent placement was successful (n=112) or partially successful (n=5) in 117 (98%) arteries. Complications occurred in 19 procedures; seven were of serious clinical significance. Angiographic follow-up was performed in 89 of 117 (76%) cases, at a mean of 8 months (range 2.5–18 months). Fifteen stents (16.9%) showed restenosis (at a mean of 8.5 months), of which 10 were successfully redilated. Conclusion: Renal artery stenting has a high technical success rate, a complication rate comparable to percutaneous transluminal renal angioplasty, and a low rate of restenosis at 8 months angiographic follow-up.

Optimal scan delay in spiral CT for the diagnosis of acute pulmonary embolism.

Purpose The purpose of this work was to assess whether easily obtained clinical parameters can predict optimal scan delay for contrast-enhanced spiral CT of pulmonary arteries and to compare image quality between individualized contrast timing versus a fixed scan delay. Method We used an individualized delay in 85 patients by measuring the contrast transit time through the pulmonary circulation (Group A) and assessed the correlation between transit time and clinical parameters. In 56 patients (Group B), we used a 20 s fixed scan delay. The CT examinations of both groups were compared with regard to image quality. Results Contrast transit times (mean 10.5 s, range 4–26 s) did not correlate significantly with heart rate, blood pressure, body length, weight, body surface area, or cardiac function. Although contrast transit times were significantly related to gender and age, only 14.8% of the variation could be explained by these clinical parameters. Data of 57 patients in Group A and 50 patients in Group B were available for analysis. Image quality was not significantly different between Groups A and B, which was good, moderate, and poor in 61, 32, and 7% in Group A and 60, 34, and 6% in Group B, respectively (p = 1.0). Conclusion One cannot predict individual scan delay from easily obtainable clinical parameters. Fortunately, a 20 s fixed scan delay provides equal image quality as individualized contrast timing.

MR urography for the preoperative evaluation of living renal donors

Abstract. The purpose of this study was to assess the image quality and diagnostic value of MR urography in detecting abnormalities of the urinary collecting system relevant for the preoperative evaluation of living renal donors. Study subjects were selected from the existing intravenous urography (IVU) reports: 18 consecutive patients with a duplication or another abnormality of the collecting system and 20 consecutive patients with normal anatomy. They underwent a respiratory-triggered 3D T2-weighted fast spin-echo acquisition after oral administration of furosemide, without and with abdominal compression. The MR images were evaluated by two independent blinded observers. The IVU was used as the standard of reference. Image quality of the MR urograms with compression was overall better than those without compression, and the former were regarded as adequate for the evaluation of small filling defects and deformities of the pelvis and calyces in 76–81% of the kidneys and 74–79% of the patients. Both observers correctly diagnosed all 13 kidneys with a partial or complete duplication. The image quality of MR urography was inadequate to evaluate the calyces and pelvis for small filling defects or deformities in approximately 25% of the patients; however, the technique was accurate in the detection of abnormalities of the urinary collecting system relevant for the preoperative evaluation of living renal donors.