PubMed Health⌕ Search

Biomedical subjects

L M Boxt

Publications and source records attributed to L M Boxt.

At least 19 recordsLinked to original sources
PubMed2000

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.

Adult↗
PubMed2000

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.

Heart Valve Diseases↗
PubMed1999

Radiology of the right ventricle.

RV changes may be generalized into dilatation and hypertrophy. Increased preload results in ventricular dilatation. Increased afterload causes hypertrophy. Change in the shape of the RV resulting from increased afterload and myocardial hypertrophy induces tricuspid regurgitation, which superimposes changes of chamber dilatation onto those of hypertrophy. Sustained ventricular dilatation and hypertrophy frequently progresses to RV failure. In these cases, RV systolic function decreases in association with elevation of RV and right atrial diastolic pressure. Changes in the wall thickness and shape of the RV are variable, and depend upon the severity of the volume or pressure load presented, as well as its duration and rate of progression. Because the RV is an anterior cardiac structure, it occupies little of any heart border. Therefore, the sensitivity of plain film examination to RV disease is limited. Inferential diagnosis of RV disease can often be made based upon identification of other radiographic changes, notably the state of the pulmonary circulation, and the position of the heart in the chest. Conventional contrast right ventriculography may be used to assess the size and position of the RV, as well as associated acquired and congenital lesions that result in RV dysfunction. Due to the unusual shape of the RV cavity, however, and the unpredictable manner in which it dilates, accurate quantitative analysis by this technique is limited. Furthermore, the common association between RV disease and pulmonary hypertension limits the applicability of this imaging technique for evaluating patients with RV disease. Multiplanar MR imaging allows direct demonstration of changes in RV size and wall morphology. Furthermore, application of Simpson's rule to tomographic slices acquired at ventricular diastole and systole allows direct, accurate, and reproducible quantitative analysis of ventricular volume and myocardial mass, allowing radiographic assessment in patients for diagnosis, as well as longitudinally during medical management or after surgical treatment for congenital and acquired diseases that result in RV dysfunction.

Cardiac Output, Low↗
PubMed1999

MR imaging of adult patients with congenital heart disease.

Although the incidence of congenital heart disease remains constant among newborns, improved medical and surgical techniques have dramatically prolonged life expectancy and produced a new, growing group of patients harboring these lesions: adults with congenital heart disease. Conventional imaging techniques in these patients may be limited because of patient size, chest configuration, or poor ventricular function. MR imaging provides a noninvasive means of directly demonstrating their developmental abnormalities and the sequelae of pathophysiologic changes caused by these lesions. Combined use of spin echo and gradient reversal echo acquisition techniques allows complete evaluation of cardiac morphology and function in these patients. An new medical and surgical therapies prolong the lives of these patients, the role of MR imaging for physiologic assessment and surgical planning will expand further.

Adult↗