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Biomedical subjects

M W de Haan

Publications and source records attributed to M W de Haan.

18 recordsLinked to original sources
PubMed2005

Autogenous options in secondary and tertiary access for haemodialysis.

OBJECTIVES: The world's haemodialysis population is growing rapidly so that in 2006, some 1.5 million interventions will be needed for access placement, revision and maintainance. Secondary and tertiary arteriovenous fistulas are becoming an integral part of vascular access especially in the elderly, comorbid population. METHODS: Venous conduits may have a more favourable outcome with fewer complications and revisions in comparison with accesses using prosthetic implants. Innovative surgical techniques, including vein transposition, translocation and elevation may add to this philosophy of creating exclusively autogenous vascular access.

Arteriovenous Shunt, Surgical↗
PubMed2005

Contemporary imaging techniques for the diagnosis of renal artery stenosis.

Renal artery stenosis (RAS) is a potentially curable cause of renovascular hypertension (RVH) and is caused by either atherosclerosis or fibromuscular dysplasia (FMD) in the vast majority of patients. Although intra-arterial digital subtraction angiography (IA-DSA) is still considered the standard of reference test for the anatomical diagnosis of RAS, noninvasive techniques such as MR angiography, CT angiography, and color-aided duplex ultrasonography are promising alternatives that also allow functional characterization of RAS. We provide an overview of these techniques and discuss their relative merits and shortcomings. Analysis of high-quality studies shows that both MR and CT angiography are significantly more accurate for the diagnosis of at least 50% atherosclerotic RAS than ultrasonographic techniques. The primary strength of ultrasonography at present is its suggested ability to predict functional recovery based on preinterventional resistance index measurements. A still unresolved issue is the detection of FMD. Because missing RVH may have serious consequences the most important requirement for a screening test is that it has high sensitivity.

Angiography↗
PubMed2003

Central vein obstruction in hemodialysis patients: results of radiological and surgical intervention.

BACKGROUND/AIMS: Symptomatic central venosus obstruction (CVO) in dialysis patients with arteriovenous fistulas (AVFs) leads to significant morbidity and patient inconvenience. We evaluated the results of surgical and radiological interventional treatment of symptomatic central venous obstruction. METHODS: Clinical data, site and length of vein obstruction, type and outcome of intervention were obtained from patient records. Patency rates of radiological and surgical treatment were calculated using Life Table survival analysis. RESULTS: In 28 patients with VH, 45 interventions (percutaneous intervention 30; surgical reconstruction 10; AVF closure five) were performed. Mean vessel obstruction length was 4.9 cm, mainly localized in the subclavian vein (55%). Initial clinical success rate of PTA and surgery was 92%, with complications after percutaneous transluminal angioplasty (PTA) on six occasions. Restenosis after PTA was observed in 39%. One-year primary and secondary patency after PTA was 50 and 63%, respectively. One-year primary patency after surgical reconstruction was 75%. CONCLUSION: Symptomatic CVO in dialysis patients with AVFs can be treated with a high success rate through radiological intervention. Surgical reconstruction is an appropriate alternative method in case of failed PTA.

Aged↗
PubMed2002

Renovascular disease in patients with hypertension: detection with duplex ultrasound.

The aim of this study was to evaluate the accuracy of duplex ultrasound for the diagnosis of renovascular disease in a cohort of hypertensive patients. In 78 patients suspected of renovascular hypertension on clinical grounds duplex ultrasound examination of the renal arteries was performed. Renal angiography was used as the standard of reference. Duplex ultrasound was inconclusive in 11 kidneys (7%). None of the supernumerary renal arteries was detected with duplex ultrasound. The overall prevalence of significant renovascular disease (> or =50% stenosis) was 20%. Based on the combination of parameters at thresholds commonly applied in current literature: ie PSV(max) >180 cm/sec and RAR >3.5 the overall sensitivity of duplex ultrasound for detection of haemodynamically significant renovascular disease was 50.0% with a specificity of 91.3% (PPV: 87.9%; NPV: 59.1). Lowering the thresholds for both parameters improved the test results at the cost of a significant increase of false positive examinations. In a population of hypertensive patients clinically suspected of renovascular hypertension, only limited results for duplex ultrasound could be acquired in the detection of renovascular disease. This result, in combination with the wide range of sensitivities and specificities published in international literature and the relatively large number of incomplete examinations does not support the general application of duplex ultrasound as a screening procedure for detection and assessment of renovascular disease.

Adult↗
PubMed2000

Three-dimensional contrast-enhanced moving-bed infusion-tracking (MoBI-track) peripheral MR angiography with flexible choice of imaging parameters for each field of view.

A technique to image peripheral arteries with flexible choice of scan parameters for separate stations was developed based on moving-bed single-bolus three-dimensional gradient-recalled echo magnetic resonance angiography. A volunteer study yielded higher signal- and contrast-to-noise ratios, less venous enhancement, and better subjective interpretability compared with imaging with fixed parameters for each station. Additionally, six patients were imaged to test the feasibility of the new method in a clinical setting. Imaging peripheral arteries with the new technique in volunteers yielded better image quality and is feasible for patients.

Adult↗
PubMed2000

Motion of the proximal renal artery during the cardiac cycle.

In 48 hypertensive patients, the motion of the proximal renal artery during the cardiac cycle was quantified using two-dimensional quantitative flow (QF) measurements and automatic contour detection. Substantial translational motion was observed with an amplitude ranging from 1 to 4 mm. Since motion effectively reduces spatial resolution, the use of motion suppression techniques should be strongly considered for renal MR angiography. J. Magn. Reson. Imaging 2000;12:924-928.

Adult↗
PubMed2000

Renal artery blood flow: quantification with breath-hold or respiratory triggered phase-contrast MR imaging.

The aim of this study was to evaluate the validity and reproducibility of breath-hold and respiratory triggered phase-contrast (PC) MR imaging techniques in the measurement of renal artery blood flow. In 12 healthy subjects cardiac-gated PC flow measurements were obtained in the renal arteries using a breath-hold and a respiratory-triggered technique. The flow measurements were repeated in each renal artery separately. Comparison between the sum of flow measurements in the renal arteries and the difference in aortic flow measurements above and below the renal arteries served as an internal control. The flow measurements showed a good reproducibility both with the breath-hold (r=0.92, p < 0.0001) and with the respiratory-triggered (r = 0.91, p < 0.0001) technique. The validity of both methods was good and there was no statistically significant difference. Reproducible quantitative measurements of renal artery blood flow are possible with respiratory controlled, cardiac-gated, PC MR imaging.

Adult↗
PubMed1999

[Contrast-enhanced magnetic resonance angiography].

Contrast-enhanced magnetic resonance angiography (MRA) involves intravenous injection of a contrast medium that increases the signal intensity of blood by shortening its T1 value. With contrast-enhanced MRA the acquisition time is short (less than 40 s for the abdominal aorta and the iliac vessels) and the images obtained can be interpreted accurately. The contrast medium currently in use virtually never causes adverse effects and is not nephrotoxic. After obtaining a three-dimensional dataset projections can be made at will. In addition, the individual partitions should be evaluated. The postprocessing time is about 15 min per examination. Current clinical applications are diagnostic examination of (stenoses of) the aortic arch and its branches, the thoracic and abdominal aorta, the visceral vessels, the renal arteries and the peripheral arteries. The sensitivity and specificity of contrast-enhanced MRA in most studies amount to over 90%.

Aortic Diseases↗
PubMed1999

Peripheral MR angiography.

Atherosclerotic disease of the lower extremities is a common disorder in western society. Its debilitating nature calls for accurate diagnosis and treatment. The gold standard for diagnosing this disease by depiction of vessel morphology is X-ray angiography (either conventional or digital subtraction angiography). However, the invasive nature of this technique and the possible harmful effects of iodinated contrast agents have led to the idea that non-invasive MR angiography might be a good alternative for acquiring information about vessel morphology. Most extensively studied was time-of-flight MR angiography. Although first results with this technique were encouraging, it is now apparent that time-of-flight MR angiography is hampered by the virtue of which it exists, since blood flow not only generates vessel-to-background contrast, but is also the cause of disturbing artifacts. However, with the introduction of minimally invasive contrast-enhanced MR angiography, using gadolinium chelates to reduce the T1 of blood, image quality has improved dramatically. Moreover, using contrast-enhanced MR angiography, high-resolution three-dimensional data about the entire peripheral vascular tree can be obtained within several minutes, which might make MR angiography a true competitor of X-ray angiography as a diagnostic tool in the clinical work-up of a patient with complaints of peripheral atherosclerosis. The purpose of this article is to explain working mechanisms and usefulness of both time-of-flight and contrast-enhanced MR angiography.

Arterial Occlusive Diseases↗
PubMed1999

Interpretation of renal angiography by radiologists.

OBJECTIVE: Different radiologists may show considerable variation in their interpretation of renal angiograms. We therefore wished to establish the reliability of their interpretation. DESIGN: Assessment of the intra- and inter-observer agreement of the interpretation of renal angiograms. SETTING: Tertiary referral university hospital. PATIENTS: Hypertensive patients suspected of renovascular hypertension on clinical grounds or on the basis of renography. INTERVENTIONS: Patients were prospectively selected to undergo a renal angiography via the femoral approach. MAIN OUTCOME MEASURES: Intra- and inter-observer agreement of the degree and site of stenosis. RESULTS: The difference between two estimates of the degree of stenosis ranged from 0 to 65% for the individual readers and from 0 to 75% between two readers. When the site of greatest stenosis was in the origin of the renal artery, the intra-observer agreement kappa ranged from 0.54-0.71, the inter-observer agreement across multiple readers being 0.43. In a post hoc analysis using two different cut-off points of stenosis (50 or 70%), the intra- and inter-observer agreement was better at the 70% cut-off-point. In a subset of patients with stenosis and a renin ratio greater than 1.5, both the intra- and inter-observer agreement were much better than when all angiograms were considered. CONCLUSIONS: Assessment of the diagnostic performance of three experienced radiologists in their interpretation of renal artery angiograms indicates that the intra- and inter-observer agreement with respect to their estimates of the degree of stenosis and the site of greatest stenosis are rather poor but their diagnostic performance improves in patients with stenosis and a renin ratio greater than 1.5. There is a need for more objective assessment of renal artery lesions.

Angiography↗
PubMed1998

Peripheral vascular tree stenoses: detection with subtracted and nonsubtracted MR angiography.

PURPOSE: To compare subtracted and nonsubtracted gadolinium-enhanced magnetic resonance (MR) angiography and cardiac-synchronized time-of-flight MR angiography for help in detecting pelvic-region stenoses. MATERIALS AND METHODS: Twenty-eight patients with intermittent claudication underwent MR angiography with a 1.5-T system; two-dimensional cardiac-synchronized time-of-flight MR angiograms and three-dimensional MR angiograms (without and with gadolinium enhancement) were obtained. Subtracted images were obtained by subtracting unenhanced data from enhanced data of identical volumes, and maximum intensity projection images were constructed, which two observers independently evaluated in blinded fashion, with conventional angiographic results as the reference standard. RESULTS: Sensitivity and specificity for grading of hemodynamically significant stenoses (> or = 50% lumen reduction) on subtracted MR angiograms were 94% and 93%, respectively. Sensitivity of subtracted images was significantly higher compared with that of time-of-flight images (P < .05) but not with that of nonsubtracted images. Contrast-to-noise ratio on subtracted images was significantly higher compared with that on nonsubtracted images (P < .05) but not with that on time-of-flight images. There was good correlation between stenosis length measurements on gadolinium-enhanced MR angiograms and those on conventional angiograms. CONCLUSION: Subtracted MR angiography is superior to cardiac-synchronized time-of-flight MR angiography for imaging of iliac and upper femoral arteries and provides higher contrast-to-noise ratio, fewer artifacts, and easier image interpretability than nonsubtracted MR angiography.

Angiography↗
PubMed1998

Peripheral vascular tree stenoses: evaluation with moving-bed infusion-tracking MR angiography.

PURPOSE: To evaluate a magnetic resonance (MR) angiographic technique for imaging of the peripheral arteries with gadolinium enhancement. MATERIALS AND METHODS: Moving-bed infusion-tracking MR angiograms were obtained in 15 healthy volunteers and in 28 patients with intermittent claudication before and during slow infusion of contrast material. Lower- and upper-leg and pelvic regions were imaged. Unenhanced images were subtracted from gadolinium-enhanced images, and maximum intensity projection images were generated. Image quality was evaluated subjectively and objectively, and maximum intensity projection images were compared with conventional angiograms, which served as the standard of reference. RESULTS: Moving-bed infusion-tracking MR angiography proved to be a robust technique, and image quality on maximum intensity projection images was comparable with that on conventional angiograms. Sensitivity and specificity for grading hemodynamically significant stenoses were 93% and 98%, respectively, with excellent interobserver agreement. CONCLUSION: Moving-bed infusion-tracking MR angiography can be used to image all peripheral arteries in 4 minutes by using a small amount of contrast material and a conventional 1.5-T MR imager.

Constriction, Pathologic↗
PubMed1997

MR angiography of the iliac and upper femoral arteries using four different inflow techniques.

OBJECTIVE: The purpose of this study was to compare two inflow MR angiography pulse sequences obtained with and without systolic synchronization. We also compared these two MR angiography pulse sequences with conventional angiography. SUBJECTS AND METHODS: Thirty-one consecutive patients who were scheduled for conventional angiography because of symptomatic atherosclerotic occlusive disease of the iliac or femoral artery underwent MR angiography using four different MR angiography techniques. These techniques consisted of a multiple two-dimensional inversion prepulse gradient-recalled echo technique (turbo field-echo) obtained with and without systolic synchronization and a multiple two-dimensional gradient-recalled echo technique (fast field-echo) obtained with and without systolic synchronization. We then compared image quality and our ability to detect and grade degree and length of stenosis, using conventional angiography as the gold standard. RESULTS: The systolic-synchronized turbo field-echo sequence produced the best results both objectively and subjectively. Comparing systolic-synchronized turbo field-echo and fast field-echo techniques with conventional angiography regarding detection and grading degree of stenoses, we found no statistically significant differences. CONCLUSION: Systolic synchronization proved to be of significant importance for image quality. The systolic-synchronized turbo field-echo pulse sequence proved to be superior to the other three MR angiography techniques.

Aged↗
PubMed1996

Renovascular disease in patients with hypertension: detection with systolic and diastolic gating in three-dimensional, phase-contrast MR angiography.

PURPOSE: To evaluate the usefulness of three-dimensional, phase-contrast magnetic resonance (MR) angiography performed with cardiac synchronization in the assessment of renal arteries. MATERIALS AND METHODS: Thirty-eight patients (24 men, 14 women) underwent three-dimensional, phase-contrast MR angiography without gating and with systolic and diastolic gating. Conventional angiography was used as the standard of reference. RESULTS: The sensitivity for the detection of all stenoses (> 0%) was 93% with systolic, 92% with diastolic, and 77% without gating. However, there was no difference between the three techniques in the diagnosis of hemodynamically significant stenoses (> 50%). The mean arterial length depicted was significantly better with diastolic gating than with either of the other techniques (P < .0001). Vascular disease was significantly overestimated with systolic gating relative to estimation without (P = .030) or with diastolic (P = .008) gating. CONCLUSION: Three-dimensional, phase-contrast MR angiography provides good image quality and enables assessment of renovascular disease. Cardiac gating has limited improvement of these results.

Angiography↗
PubMed1989

Effect of one-HLA-DR-antigen-matched and completely HLA-DR-mismatched blood transfusions on survival of heart and kidney allografts.

Blood transfusions can influence the survival of organ allografts favorably, in spite of the danger of sensitization. We investigated the influence of HLA compatibility between blood donors and transfusion recipients on the production of HLA antibodies and on graft survival. Among recipients of transfusions who shared one HLA-DR antigen with their respective donors, antibodies developed in 6 of 28 who had received one transfusion, in 2 of 16 who had received three transfusions, and in 4 of 24 who had undergone renal transplantation. Among recipients who were mismatched with their donors for both HLA-DR antigens, the rate of sensitization was significantly higher in all three of these groups (18 of 30, P = 0.02; 12 of 16, P = 0.0007; and 12 of 22, P = 0.001). The survival of kidney allografts among graft recipients who were given transfusions and shared one HLA-DR antigen with their blood donors (81 percent at five years) was significantly higher than among recipients who were given transfusions and were mismatched for both HLA-DR antigens (57 percent; P = 0.02) or among recipients who were not given transfusions (45 percent; P = 0.001). There was no difference in graft survival between patients who received transfusions mismatched for two HLA-DR antigens and those who were not given transfusions. We conclude that allograft survival can be improved by pretransplantation blood transfusion when the transfusion recipients share at least one HLA-DR antigen with their donors. In view of the increased rate of sensitization and the lack of improvement in graft survival, the transfusion of blood mismatched for two HLA-DR antigens appears to be contraindicated in candidates for transplantation.

Antibody Formation↗
PubMedDate not supplied

The benefit of STent placement and blood pressure and lipid-lowering for the prevention of progression of renal dysfunction caused by Atherosclerotic ostial stenosis of the Renal artery. The STAR-study: rationale and study design.

BACKGROUND: Atherosclerotic renal artery stenosis (ARAS) is associated with progressive loss of renal function and is one of the most important causes of renal failure in the elderly. Current treatment includes restoration of the renal arterial lumen by endovascular stent placement. However, this treatment only affects damage caused by ARAS due to the stenosis and ensuing post-stenotic ischemia. ARAS patients have severe general vascular disease. Atherosclerosis and hypertension can also damage the kidney parenchyma causing renal failure. Medical treatment focuses on the latter. Lipid-lowering drugs (statins) could reduce renal failure progression and could reduce the overall high cardiovascular risk. The additional effect on preserving renal function of stent placement as compared to medical therapy alone is unknown. Therefore, the STAR-study aims to compare the effects of renal artery stent placement together with medication vs. medication alone on renal function in ARAS patients. METHOD: Patients with an ARAS of > or = 50% and renal failure (creatinine (Cr) clearance < 80 mL/min/1.73 m2) are randomly assigned to stent placement with medication or to medication alone. Medication consists of statins, anti-hypertensive drugs and antiplatelet therapy. Patients are followed for 2 yrs with extended follow-up to 5 yrs. The primary outcome of this study is a reduction in Cr clearance > 20% compared to baseline. This trial will include 140 patients.

Angioplasty, Balloon↗