Computed tomography and magnetic resonance imaging of patients with valvular heart disease.

Although computed tomographic (CT) and magnetic resonance (MR) evaluation of patients with valvular heart disease is almost never performed as a first line of diagnostic intervention, their performance does provide important morphologic and physiologic information concerning the etiology and the current status of the valvular dysfunction. Evaluation of chamber and great artery size as well as ventricular wall thickness provide the basis for diagnosing and analyzing severity of valvular heart disease. Furthermore, additional findings, including calcification and evidence of interstitial pulmonary edema, increase diagnostic sensitivity and confidence in diagnosis. MR examination has the advantage over CT of providing direct demonstration of the signal void jets of dysfunctional valves, as well as a means of quantitating regional and global ventricular function and severity of valvular pressure gradients.

Primer on cardiac magnetic resonance imaging: how to perform the examination.

Cardiac magnetic resonance imaging is made possible by utilizing an external signal, the patient's own electrocardiogram, to time image acquisition. ECG gated cardiac magnetic resonance examination may be performed using spin-echo or gradient reversal techniques or their newer k-space segmented variants. Spin-echo techniques provide the highest contrast between rapidly moving blood and the cardiac chambers and arteries and veins containing the blood, but are of relatively low temporal resolution. Gradient reversal acquisition, however, provides higher temporal resolution ideal for evaluating changes in myocardial thickening, ventricular wall motion abnormalities, and changes in chamber volume through the cardiac cycle; gradient reversal technique has significantly lower contrast resolution. Careful attention to the details of image acquisition will provide high-quality images of the heart and great arteries from which important morphologic and physiological information may be obtained, aiding in the diagnosis and management of patients with cardiovascular disease.

Cardiac MR imaging: a guide for the beginner.

The complex motion of the heart during contraction is a serious challenge to the diagnostic radiologist and to the capabilities of the magnetic resonance (MR) imaging unit itself, but electrocardiographic (ECG) gating "stops" motion and thus allows acquisition of diagnostic-quality images. Attention to placement of chest-wall ECG electrodes and the course of ECG leads from the patient will maximize the quality of the gating signal and result in better-quality images. Before commencing the MR imaging examination, the clinical questions for the examination must be identified so that a clinical protocol can be applied to acquire relevant morphologic and physiologic data. In addition to the standard orthogonal views (axial, coronal, and sagittal), oblique and complex sections parallel and orthogonal to intrinsic cardiac axes may be necessary to portray the relevant anatomy to best advantage. Construction of these views requires an understanding of basic normal and pathologic cardiac anatomy. If care is taken in the planning and execution of the MR imaging examination, the radiologist will be able to exploit this exciting technology to its full noninvasive potential.