J. Doornbos

Diagnostic significance of gadolinium-DTPA (diethylenetriamine penta-acetic acid) enhanced magnetic resonance imaging in thrombolytic treatment for acute myocardial infarction: its potential in assessing reperfusion.

The diagnostic value of gadolinium-DTPA (diethylenetriamine penta-acetic acid) enhanced magnetic resonance imaging in patients treated by thrombolysis for acute myocardial infarction was assessed in 27 consecutive patients who had a first acute myocardial infarction (14 anterior, 13 inferior) and who underwent thrombolytic treatment and coronary arteriography within 4 hours of the onset of symptoms. Magnetic resonance imaging was performed 93 hours (range 15-241) after the onset of symptoms. A Philips Gyroscan (0.5 T) was used, and spin echo measurements (echo time 30 ms) were made before and 20 minutes after intravenous injection of 0.1 mmol/kg gadolinium-DTPA. In all patients contrast enhancement of the infarcted areas was seen after Gd-DTPA. The signal intensities of the infarcted and normal values were used to calculate the intensity ratios. Mean (SD) intensity ratios after Gd-DTPA were significantly increased (1.15 (0.17) v 1.52 (0.29). Intensity ratios were higher in the 17 patients who underwent magnetic resonance imaging more than 72 hours after the onset of symptoms than in the 10 who underwent magnetic resonance imaging earlier, the difference being significantly greater after administration of Gd-DTPA (1.38 (0.12) v 1.61 (0.34). When patients were classified according to the site and size of the infarcted areas, or to reperfusion (n = 19) versus non-reperfusion (n = 8), the intensity ratios both before and after Gd-DTPA did not show significant differences. Magnetic resonance imaging with Gd-DTPA improved the identification of acutely infarcted areas, but with current techniques did not identify patients in whom thrombolytic treatment was successful.

Right ventricular hypertrophy and diastolic dysfunction in arterial switch patients without pulmonary artery stenosis

Objective: To assess pulmonary flow dynamics and right ventricular (RV) function in patients without significant anatomical narrowing of the pulmonary arteries late after the arterial switch operation (ASO) by using magnetic resonance imaging (MRI). Methods: 17 patients (mean (SD), 16.5 (3.6) years after ASO) and 17 matched healthy subjects were included. MRI was used to assess flow across the pulmonary trunk, RV systolic and diastolic function, and RV mass. Results: Increased peak flow velocity (>1.5 m/s) was found across the pulmonary trunk in 14 of 17 patients. Increased RV mass was found in ASO patients: 14.9 (3.4) vs 10.0 (2.6) g/m2 in normal subjects (p<0.01). Delayed RV relaxation was found after ASO: mean tricuspid valve E/A peak flow velocity ratio = 1.60 (0.96) vs 1.92 (0.61) in normal subjects (p = 0.03), and E-deceleration gradients = −1.69 (0.73) vs −2.66 (0.96) (p<0.01). After ASO, RV mass correlated with pulmonary trunk peak flow velocity (r = 0.49, p<0.01) and tricuspid valve E-deceleration gradients (r = 0.35, p = 0.04). RV systolic function was well preserved in patients (ejection fraction = 53 (7)% vs 52 (8)% in normal subjects, p = 0.72). Conclusions: Increased peak flow velocity in the pulmonary trunk was often observed late after ASO, even in the absence of significant pulmonary artery stenosis. Haemodynamic consequences were RV hypertrophy and RV relaxation abnormalities as early markers of disease, while systolic RV function was well preserved.

Magnetic resonance imaging of ischemic heart disease : Why cardiac magnetic resonance imaging will play a significant role in the management of patients with coronary artery disease

The role of magnetic resonance imaging in the diagnosis of ischemic heart disease has great potential impact on patient management, because a number of aspects of ischemic heart disease can be evaluated in one imaging session. High resolution coronary magnetic resonance angiography is currently available, although several technical improvements are awaited to make the technique routinely applicable. A major advance will probably include the availability of magnetic resonance blood pool contrast agents to improve vessel visualization. Contrast media, in combination with either first pass or delayed myocardial scanning, will also play an important role in myocardial perfusion imaging. Functional magnetic resonance assessment of regional and global ventricular function is currently a well-established technique and is considered a new gold standard, which may impact on routine cardiology practice. This review summarizes some of the recent magnetic resonance developments for evaluating various aspects of ischemic heart disease, including magnetic resonance coronary angiography, flow imaging, and imaging of myocardial perfusion and function.

In vivo human coronary magnetic resonance angiography at 7 Tesla

Introduction. Cardiac MRI at high fields faces many challenges including the lack of commercially available body RF coils, increased sample-induced B1 inhomogeneity, increased magnetic susceptibility effects which make imaging with balanced sequences difficult, and SAR limitations. However, if these can be at least partially overcome, then the higher signal-to-noise is advantageous both for imaging and localized spectroscopy. Here we investigate the feasibility of acquiring coronary magnetic resonance angiography (CMRA) scans, a promising technique for the non-invasive visualization of the coronary anatomy (1), in volunteers at 7 tesla (T) on a time-scale acceptable for clinical studies.

High field MR carotid vessel wall imaging: reproducibility of five different MR-weightings

Magnetic Resonance Imaging (MRI) has emerged as a promising noninvasive imaging modality for the serial assessment of vessel wall thickness in the carotid artery as an early marker of atherosclerosis. For clinical application of this technique, Scan-Rescan reproducibility is paramount. Currently, a multicontrast protocol, including a combination of MR-weightings is used as reference standard for quantitative and morphologic measurements.

Ultrafast Magnetic Resonance Imaging of the Heart

Magnetic resonance imaging (MRI) provides an excellent tool for the evaluation of the heart. A wide array of fast MR techniques have become available for examining coronary artery anatomy and flow, cardiac function, myocardial perfusion, and metabolism. Cardiac MRI methods may be divided into conventional methods, such as spin-echo sequences, and fast-imaging methods, including echo-planar-imaging (EPI) and fast gradient-echo sequences. The acquisition and display of the information available by these techniques within a single comprehensive imaging session may provide a useful test for guiding patient management in a cost-effective manner. Until now most studies have focused on the feasibility and optimization of MR technology for assessing the heart and its most significant disease processes. Further technological progress in acquiring and processing the multitude of data obtained during an MR examination is still required.

Noninvasive imaging of coronary artery anomalies

Determination of the course of an aberrant coronary artery using coronary arteriography is often difficult. Fast gradient echo magnetic resonance (MR) angiography, however, can be a useful additional technique in case coronary arteriography is inconclusive. In this chapter, the different types of coronary artery anomalies are reviewed, arteriographic criteria are discussed, the technique of fast gradient echo MR angiography is described, results with this technique are shown and the various other additional diagnostic techniques are discussed.

Cardiac through-plane motion: comparison of long- and short-axis MR images of the left ventricle

Left ventricular (LV) long-axis shortening produces cardiac motion through fixed short-axis sections, complicating accurate quantification of myocardial and wall-motion parameters with MRI. Therefore, LV long-axis length and shortening was studied in both long- and short-axis end-diastolic (ED) and end-systolic (ES) MRI scans. A group of 38 male volunteers underwent gradient-echo cine-MRI: single-slice long-axis and multi-slice short-axis. The LV dimensions were directly measured in the long-axis images using epicardial and endocardial contours. The position of the apex and the base (aortic valve) were assessed in the sections of the short-axis scan. The LV dimensions as measured on both long- and short-axis scans showed a correlation of r = 0.62 for ED and r = 0.69 for ES. Relative LV shortening between long- and short-axis scans showed a poor correlation (r = 0.22). These results suggest that short-axis MRI is not sufficient to accurately assess through-plane motion. Therefore, long-axis images are needed for optimal quantification of myocardial and wall-motion parameters.

Myocardial Perfusion Assessed By Nuclear Magnetic Resonance

In 1946 the groups of Bloch (6) and Purcell (35) described independently from each other a phenomenon which is known as Nuclear Magnetic Resonance. It appeared that certain atomic nuclei, when placed in a strong magnetic field, absorb electromagnetic waves of a particular frequency (radiowaves, 1–100 MegaHerz) and re-emit some of the absorbed energy in the form of radiosignals with the same frequency. In fact this resembles the resonance of a tuning fork when the right tone is struck.