Biomedical subjects

P M van Ooijen

Publications and source records attributed to P M van Ooijen.

8 recordsLinked to original sources

PubMed2000

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↗

PubMed2000

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↗

PubMed1999

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↗

PubMed1999

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↗

PubMed1999

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↗

PubMedDate not supplied

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↗

PubMedDate not supplied

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↗

PubMedDate not supplied

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↗