Magnetic resonance angiography of a pulmonary artery stenosis late after cardiac surgery.
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Adult↗
Biomedical subjects
R J van Geuns
Publications and source records attributed to R J van Geuns.
Coronary artery fly-through using electron beam computed tomography.
BACKGROUND: Virtual reality techniques have recently been introduced into clinical medicine. This study examines the possibility of coronary artery fly-through using a dataset obtained by noninvasive coronary angiography with contrast-enhanced electron-beam computed tomography. METHODS AND RESULTS: Ten patients were examined, and 40 to 60 transaxial tomograms (thickness, 1.5 mm; in-plane pixel dimensions, approximately 0.5x0.5 mm) were obtained after intravenous contrast injection. The datasets were processed on a graphics workstation using volume-rendering software. For fly-throughs, the contrast-enhanced lumen was made transparent and other tissue was made opaque. Then, key frames were selected in a path through the vessel, with software interpolation of frames between key frames. A typical movie contained 150 to 300 frames (10 to 15 key frames). Fly-throughs of coronary bypass grafts (n=3), left anterior descending arteries (LAD; n=6), and the intermediate branch (n=1) were reconstructed. Coronary calcifications were seen in 3 patients. The fly-through of the intermediate branch, the bypass grafts, and one of the LADs did not show any irregularities. In 2 cases, a stenosis was visible in the LAD; its presence was confirmed by conventional coronary angiography. CONCLUSIONS: Recent developments in fast-volume rendering using special-purpose hardware in combination with noninvasive coronary angiography with electron beam computed tomography have provided the possibility of performing coronary artery fly-throughs.
Calcinosis↗
Images in Cardiovascular Medicine. Aberrant right subclavian artery mimics aortic dissection.
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Aged↗
Coronary arteries.
Coronary angiography (CA) is presently considered the gold standard for the assessment of the coronary arteries. However, the presence of ionizing radiation, its invasiveness and the small associated risk of morbidity prompted long ago the development of more patient-friendly imaging modalities. A promising technique, magnetic resonance imaging (MRI), has been regarded as the major modality in the coming decade. Although still in its infancy qualitatively, its flexibility and non-invasiveness opens the door for a comprehensive evaluation of the heart and the coronary arteries in one single sitting with high anatomical definition and excellent soft tissue contrast capabilities, double-oblique tomographic sections and the possibility to quantify an innumerable number of cardiovascular physiological parameters. Numerous ideas have been assessed, comprising breath-hold and free-breathing two-dimensional and three-dimensional measurements. New ongoing trials with intravascular contrast agents may provide for all these techniques the long-awaited essential boost for reliable magnetic resonance coronary angiography (MRCA). Introduction of parallel MRI acquisition techniques, such as simultaneous acquisition of spatial harmonics (SMASH) and sensitivity encoding (SENSE) may provide the speed enhancement required to shorten imaging time for all techniques explored to date.
Coronary Angiography↗
MR coronary angiography with breath-hold targeted volumes: preliminary clinical results.
PURPOSE: To assess the clinical value of a magnetic resonance (MR) coronary angiography strategy involving a small targeted volume to image one coronary segment in a single breath hold for the detection of greater than 50% stenosis. MATERIALS AND METHODS: Thirty-eight patients referred for elective coronary angiography were included. The coronary arteries were localized during single-breath-hold, three-dimensional imaging of the entire heart. MR coronary angiography was then performed along the major coronary branches with a double-oblique, three-dimensional, gradient-echo sequence. Conventional coronary angiography was the reference-standard method. RESULTS: Adequate visualization was achieved with MR coronary angiography in 85%-91% of the proximal coronary arterial branches and in 38%-76% of the middle and distal branches. Overall, 187 (69%) of 272 segments were suitable for comparison between conventional and MR coronary angiography. The diagnostic accuracy of MR coronary angiography for the detection of hemodynamically significant stenoses was 92%; sensitivity, 68%; and specificity, 97%. The sensitivity in individual segments was 50%-77%, whereas the specificity was 94%-100%. CONCLUSION: Adequate visualization of the major coronary arterial branches was possible in the majority of patients. The observed accuracy of MR coronary angiography for detection of hemodynamically significant coronary arterial stenosis is promising, but it needs to be higher before this modality can be used reliably in a clinical setting.
Adult↗
Magnetic resonance imaging of the coronary arteries: imaging planes and resulting anatomy in two-dimensional imaging.
Magnetic-resonance imaging techniques use different imaging planes than does conventional coronary angiography to acquire longer segments of a coronary artery in a single tomographic slice. At first sight, these planes appear rather puzzling, because the coronary arteries are displayed in unfamiliar orientations. In this article we will review the existing methodology for obtaining the orientations for the proximal coronary arteries and describe the associated anatomical landmarks that can be seen. Additional orientations for the middle segment of the circumflex and distal right coronary artery are introduced. These orientations are used both in various acquisition techniques and for evaluation of three-dimensional data when using multiplanar reformatting.
Coronary Vessels↗
Magnetic resonance imaging of the coronary arteries: clinical results from three dimensional evaluation of a respiratory gated technique.
BACKGROUND: Magnetic resonance coronary angiography is challenging because of the motion of the vessels during cardiac contraction and respiration. Additional challenges are the small calibre of the arteries and their complex three dimensional course. Respiratory gating, turboflash acquisition, and volume rendering techniques may meet the necessary requirements for appropriate visualisation. OBJECTIVE: To determine the diagnostic accuracy of respiratory gated magnetic resonance imaging (MRI) for the detection of significant coronary artery stenoses evaluated with three dimensional postprocessing software. METHODS: 32 patients referred for elective coronary angiography were studied with a retrospective respiratory gated three dimensional gradient echo MRI technique. Resolution was 1.9 x 1.25 x 2 mm. After manual segmentation three dimensional evaluation was performed with a volume rendering technique. RESULTS: Overall 74% (range 50% to 90%) of the proximal and mid coronary artery segments were visualised with an image quality suitable for further analysis. Sensitivity and specificity for the detection of significant stenoses were 50% and 91%, respectively. CONCLUSIONS: Volume rendering of respiratory gated MRI techniques allows adequate visualisation of the coronary arteries in patients with a regular breathing pattern. Significant lesions in the major coronary artery branches can be identified with a moderate sensitivity and a high specificity.
Adult↗
In vivo assessment of three dimensional coronary anatomy using electron beam computed tomography after intravenous contrast administration.
Intravenous coronary angiography with electron beam computed tomography (EBCT) allows for the non-invasive visualisation of coronary arteries. With dedicated computer hardware and software, three dimensional renderings of the coronary arteries can be constructed, starting from the individual transaxial tomograms. This article describes image acquisition, postprocessing techniques, and the results of clinical studies. EBCT coronary angiography is a promising coronary artery imaging technique. Currently it is a reasonably robust technique for the visualisation and assessment of the left main and left anterior descending coronary artery. The right and circumflex coronary arteries can be visualised less consistently. Improvements in image acquisition and postprocessing techniques are expected to improve visualisation and diagnostic accuracy of the technique.
Contrast Media↗
Magnetic resonance imaging of the coronary arteries: anatomy of the coronary arteries and veins in three-dimensional imaging.
Magnetic resonance imaging of coronary arteries will visualize, besides the arteries, the myocardium, blood in the cavities and cardiac veins. This will hamper the application of projectional visualization techniques such as those used in conventional coronary angiography. Volume rendering, a different visualization technique, can be used to create a three-dimensional impression of a magnetic resonance data set on a two-dimensional surface. In this article, we will review the volume-rendering technique and anatomy of the coronary arteries and veins in the obtained images. Also we will discuss the relation between arteries and veins and the possible sites of confusion.
Animals↗
Intravenous coronary angiography by electron beam computed tomography: a clinical evaluation.
BACKGROUND: -Noninvasive detection of coronary stenoses with electron beam CT (EBCT) after intravenous injection of contrast medium has recently emerged. We sought to determine the diagnostic accuracy of EBCT angiography in the clinical setting using conventional coronary angiography as the "gold standard." METHODS AND RESULTS: Thirty-seven patients (30 men) were investigated. After intravenous injection of 150 mL of contrast medium, 40 to 60 consecutive transaxial tomograms, covering the proximal and middle parts of the coronary arteries, were obtained with ECG triggering at end diastole during breath-holding. Three-dimensional reconstructions of the proximal and middle parts of the arteries were compared with the conventional angiograms. Of the 259 proximal and middle coronary segments, 211 (81%) were analyzable by EBCT. Of the left anterior descending coronary artery (LAD) segments, 95% were assessable. Right coronary artery (RCA) and left circumflex artery (LCx) segments were assessable in 66% and 76%, respectively. Overall sensitivity and specificity to detect a >50% diameter stenosis were 77% and 94%, respectively. This was 82% and 92% for the LAD, 60% and 97% for the RCA, and 83% and 89% for the LCx (all figures based on assessable lesions). CONCLUSIONS: Intravenous EBCT coronary angiography is a promising coronary imaging technique. The technique is not yet robust enough to be an alternative to conventional coronary angiography. It can detect and rule out significant coronary artery disease of the left main proximal and mid portions of the LAD with good accuracy.
Adult↗
Coronary arteries.
Conventional coronary angiography (CA) is the standard of excellence for the evaluation of coronary artery disease. However, non-invasive imaging modalities have developed that can play an important clinical role in the diagnosis. Magnetic resonance imaging (MRI) can offer a comprehensive evaluation of the heart and the coronary arteries by virtue of its high soft tissue contrast capabilities, double-oblique tomographic sections and the possibility of quantifying physiological parameters without need of ionizing radiation. Magnetic resonance coronary arteriography (MRCA) using breath-hold and free-breathing techniques has been investigated but is still in the experimental phase; its precise role for the assessment of coronary stenosis must still be identified. Nonetheless, MRCA has proven clinically relevant in determining the course of anomalous coronary arteries and the patency of coronary artery bypass grafts. Novel intravascular contrast agents promise faster coverage of the cardiac anatomy and may provide a long-awaited boost for MRCA. Contrast-enhanced electron-beam computed tomography (EBT), another competing imaging modality, is now being subjected to widespread evaluation following initially encouraging results.
Coronary Angiography↗
Breath-hold coronary MR angiography with volume-targeted imaging.
PURPOSE: To illustrate a new concept for fast coronary artery screening with breath-hold volume targeted magnetic resonance (MR) imaging. MATERIALS AND METHODS: Ten volunteers and 25 patients were imaged at a field strength of 1.5 T with an MR system with phased-array-coil reception and capable of echo-planar imaging. End-expiration breath-hold volume localization of the entire heart was performed with three-dimensional (3D) multishot segmented echo-planar imaging in 16-22 heartbeats. Interaction with a multiplaner reformation platform provided the optimal double-oblique volumes necessary to target seven coronary artery segments. Each segment was evaluated with 24-mm-thick volumes and breath holds at end expiration and magnetization transfer-enhanced 3D turbo fast low-angle shot imaging in 21 heartbeats. An intravascular contrast agent was used in eight patients to improve blood-myocardium contrast for the heart volume localizer acquisitions. RESULTS: The entire coronary tree was consistently covered in fewer than 13 breath holds. The scheme was successful in all volunteers and in 22 patients who could achieve adequate breath hold. With end-expiration acquisitions, the prescribed 24-mm-thick volumes were reproducible for all coronary segments in all cooperative subjects. CONCLUSION: Despite its status as the indisputable standard of reference for the detection of coronary artery disease, conventional coronary angiography remains costly and highly invasive, with associated risks of major complications, including stroke and death. Breath-hold volume targeted acquisitions permit rapid localization and coverage of the entire coronary tree with adequate resolution for evaluating the coronary arteries.
Adult↗
Intravenous coronary angiography using electron beam computed tomography.
Intravenous coronary angiography with electron beam computed tomography (EBCT) allows for the noninvasive visualisation of coronary arteries. With dedicated computer hardware and software, three-dimensional renderings of the coronary arteries, veins, and other cardiac structures can be constructed from the individual transaxial tomograms. Interest in this technique is growing, and recently a number of clinical studies have been published comparing EBCT coronary angiography with conventional cine-coronary angiography. In this article, image acquisition, postprocessing techniques, and the results of recently published clinical studies are discussed. EBCT coronary angiography is a promising imaging technique of coronary arteries. Currently, it is a reasonably robust technique for the visualization and assessment of the left main and left anterior descending coronary artery. However, at the moment a relatively high proportion of the right and circumflex coronary angiograms are noninterpretable. Improvements in image acquisition and postprocessing techniques are expected to improve visualization and diagnostic accuracy of the technique.
Beta Particles↗
Basic principles of magnetic resonance imaging.
Magnetic resonance imaging (MRI) is a noninvasive imaging technique that is becoming more and more important in clinical cardiology. Physicians must understand the basic principles of MRI before reliable use in practice is possible. Therefore, we will give an introduction to basic MRI principles necessary to understand the difficulties of cardiac MRI. First the generation of a signal by the combination of a strong magnetic field, radiofrequency pulses, and temporary changes in the magnetic field is explained. Then, the processes of localization of different points in an image, resolution, and signal-to-noise ratio are highlighted. Finally, the influence of tissue characteristics such as T1 and T2 on the contrast of an image are discussed.
Cardiovascular Diseases↗
Magnetic resonance imaging of the coronary arteries: techniques and results.
Recently a new noninvasive imaging technique, magnetic resonance imaging (MRI) has been developed that has the potential to assess the coronary arteries. MRI of the coronary arteries is a challenging task because of the motion of the vessels during cardiac contraction and the motion of the heart with respiration. Several two-dimensional and three-dimensional acquisition techniques have been developed to overcome these problems. In this article we will describe different conventional MR techniques such as spin-echo and gradient-echo imaging. Also, we will describe new developments in MRI as ultrafast breathhold techniques using echo planar imaging or targeted volume scanning. Other new developments are respiratory gating techniques with or without respiratory motion correction. Finally, we will review the results of these techniques in the detection of coronary artery bypass graft patency, coronary artery stenosis, and the evaluation of coronary artery anomalies.
Coronary Artery Disease↗