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T Leiner

Publications and source records attributed to T Leiner.

15 recordsLinked to original sources
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↗
PubMed2005

Magnetic resonance imaging of atherosclerosis.

Abundant data now link composition of the vascular wall, rather than the degree of luminal narrowing, with the risk for acute ischemic syndromes in the coronary, central nervous system, and peripheral arterial beds. Over the past few years, magnetic resonance angiography has evolved as a well-established method to determine the location and severity of advanced, lumen-encroaching atherosclerotic lesions. In addition, more recent studies have shown that high spatial resolution, multisequence MRI is also a promising tool for noninvasive, serial imaging of the aortic and carotid vessel wall, which potentially can be applied in the clinical setting. Because of the limited spatial resolution of current MRI techniques, characterization of coronary vessel wall atherosclerosis, however, is not yet possible and remains the holy grail of plaque imaging. Recent technical developments in MRI technology such as dedicated surface coils, the introduction of 3.0-T high-field systems and parallel imaging, as well as developments in the field of molecular imaging such as contrast agents targeted to specific plaque constituents, are likely to lead to the necessary improvements in signal to noise ratio, imaging speed, and specificity. These improvements will ultimately lead to more widespread application of this technology in clinical practice. In the present review, the current status and future role of MRI for plaque detection and characterization are summarized.

Arteriosclerosis↗
PubMed2003

Patients' preferences for MR angiography and duplex US in the work-up of peripheral arterial disease.

PURPOSE: To measure patients' preferences for magnetic resonance (MR) angiography and duplex ultrasound (US) in the imaging work-up of peripheral arterial disease (PAD). METHODS: Ninety-eight patients, who underwent both MR angiography and duplex US, received a questionnaire by mail and their preferences for imaging work-up were assessed in a telephone interview. The questionnaire consisted of one question on which imaging test they preferred, a rating scale score ranging from 0 (not bothersome at all) to 10 (extremely bothersome), and specific questions on whether patients experienced discomfort due to the imaging work-up. Responses were presented as means and frequencies, and differences were tested by non-parametric tests. RESULTS: Half of the patient population (50%) had no preference for MR angiography or duplex US, 41% had a preference for MR angiography, and 9% had a preference for duplex US. The average rating scale scores for MR angiography (1.6) and duplex US (1.7) were not significantly different (p=0.53). Four out of 98 (4%) patients responded that they experienced pain during the MR angiography versus 18 (18%) for duplex US (p=0.001). Eight out of 98 (8%) patients responded that they were anxious during the MR angiography versus 1 (1%) for duplex US (p=0.02). CONCLUSION: The results suggest that the majority of patients have no preference between MR angiography and duplex US in the diagnostic work-up of PAD. Among patients who do have a preference, MR angiography was preferred over duplex US.

Female↗
PubMed2001

Need for background suppression in contrast-enhanced peripheral magnetic resonance angiography.

To determine if background suppression is beneficial for peripheral magnetic resonance angiography (pMRA), nonsubtracted, subtracted, and fat-saturated contrast-enhanced (CE) pMRA were compared in 10 patients with peripheral arterial disease. Signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs), as well as venous enhancement and subjective interpretability, were determined in a station-by-station fashion for each technique. In three patients X-ray angiography was available as a standard of reference. SNRs and CNRs were significantly higher for fat-saturated vs. the other two techniques (P = 0.005). Subjective interpretability was best for subtracted data sets in the lower-leg station. In the iliac station, fat-saturated data sets were considered to have significantly lower interpretability than subtracted data sets. Venous enhancement occurred significantly more often in the lower-leg station with the fat-saturated technique. The value of subtraction depends on the hardware one has available and is a useful tool if dedicated surface coils are used. Background suppression by means of magnitude subtraction leads to the best lower-leg image interpretability. Care must be taken to avoid venous enhancement in the lower-leg station when using fat saturation.

Arterial Occlusive Diseases↗
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

Peripheral arterial disease: meta-analysis of the diagnostic performance of MR angiography.

PURPOSE: To summarize the overall diagnostic performance of magnetic resonance (MR) angiography in the evaluation of peripheral arteriosclerotic occlusive disease and to identify the most important sources of variation in diagnostic accuracy between studies. MATERIALS AND METHODS: A search strategy in MEDLINE and citation tracking were used to identify relevant English-language articles published since 1991. Each article was critically appraised for examination, patient, and study design characteristics. The accuracy data from different studies were analyzed by constructing summary receiver operating characteristic curves; multiple linear regression was used to examine the variation between study results. RESULTS: Twenty-three studies were included. There was much heterogeneity in the study results, which could not be explained as differences in the threshold for a positive result. About half of the variation was due to the type of MR angiographic examination and the extent of image evaluation. The relative diagnostic odds ratio (DOR) for three-dimensional (3D) gadolinium-enhanced MR angiography compared with two-dimensional (2D) time-of-flight MR angiography was 7.46 (95% CI: 2.48, 22.20). The relative DOR for review of transverse source images or multiplanar reformations in addition to maximum intensity projections (MIPs) compared with the use of only MIPs for image evaluation was 4.53 (95% CI: 1.46, 13.87). CONCLUSION: The diagnostic accuracy of 3D gadolinium-enhanced MR angiography is superior to that of 2D time-of-flight MR angiography. Also, the review of transverse source images or use of additional postprocessing techniques, such as multiplanar reformation, results in significantly better diagnostic performance.

Arterial Occlusive Diseases↗
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

MR angiography of run-off vessels.

Magnetic resonance angiography has taken a huge step forward since the introduction of contrast-enhanced MR angiography using gadolinium chelates. The more conventional MR angiographic techniques, such as time-of-flight and phase-contrast MR angiography, have been ousted by contrast-enhanced MR angiography in most vascular areas. However, in imaging the lower extremities, the major obstacle is the length of the vascular tree. In order to cover the entire peripheral vasculature, at least two to three fields of view are required. Using contrast-enhanced MR angiography, the best results are obtained if the vessels of interest are imaged during passage of a bolus of contrast material. Vessel-to-background contrast in subsequent acquisitions using subsequent injections of contrast material is hampered by recirculation and leakage of previously injected gadolinium, enhancing both the venous system and surrounding tissue. To overcome this problem several research groups have come up with various solutions. The three main strategies employed can be classified as either bolus catch, bolus chase, or bolus track techniques. The purpose of this article is to explain working mechanisms of the three bolus imaging strategies for imaging both inflow and outflow vessels of the lower extremities, to show their advantages and disadvantages, and to review results described in the literature in imaging patients using these techniques.

Contrast Media↗
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↗
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↗