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Biomedical subjects

R M MacMillan

Publications and source records attributed to R M MacMillan.

At least 19 recordsLinked to original sources
PubMed1992

Magnetic resonance imaging vs. ultrafast computed tomography for cardiac diagnosis.

Ultrafast computed tomography (CT) and magnetic resonance imaging (MRI) generate high resolution tomographic cardiac images. Ultrafast CT requires intravenous injection of x-ray contrast combined with an image acquisition time of 50 msec. MRI requires no contrast injection, but has relatively long acquisition times due to gating. Both technologies can be used to evaluate cardiac chamber and great vessel dimensions, intracardiac and extracardiac masses, ventricular hypertrophy, left ventricular mass, congenital heart disease, regional and global left ventricular function, right ventricular function and pericardium. MRI is highly useful for detection and semi-quantitation of valvular regurgitation while ultrafast CT is not. Aortic and mitral valve stenosis can be detected by both, but MRI is the preferred study. Though both techniques can be used to assess coronary artery bypass graft status, ultrafast CT is the preferred method. It is concluded that ultrafast CT and MRI have broad applications for cardiac diagnosis.

Coronary Disease↗
PubMed1992

Clinical application of magnetic resonance imaging of the heart and great vessels.

This report reviews the clinical applications of magnetic resonance imaging, (MRI) for the heart and great vessels based on the first 120 patients studied with 1.5 Tesla scanner. Cine scans were obtained in 85% of patients studied with the remainder having T1 spin-echo imaging. MRI provides high-resolution multiplanar images for defining abnormalities in cardiac structure and is especially useful for congenital heart disease. Cine MR evaluates cardiac dynamic functions such as left ventricular volumes and ejection fraction, left ventricular segmental wall motion, and valvular function. It is also useful for detection of aortic and pulmonary arterial disease and diseases of the pericardium. It is concluded that MR has broad applications for diagnosis of cardiac and great-vessel disorders.

Aorta, Thoracic↗
PubMed1992

Applications of MRI for diagnosis of cardiovascular diseases.

Magnetic resonance imaging (MRI) acquires high spatial resolution images of the heart from any part of the cardiac cycle and in any planar configuration without use of contrast. Sequential images through the cardiac cycle can be viewed as a cine.

Heart Diseases↗
PubMed1990

Coronary artery dissection--a case report.

Coronary artery dissection, both spontaneous and catheter-induced, is associated with a significant morbidity and mortality. The authors present a case of a middle-aged woman with spontaneous right coronary artery dissection causing inferior wall myocardial infarction and left coronary artery dissection at the time of coronary arteriography. It is suggested that emergency aortocoronary bypass surgery be performed preceded by insertion of an intra-aortic balloon in acute evolving cases where coronary anatomy is favorable to limit infarction and avert loss of life.

Aortic Dissection↗
PubMed1988

Assessment of global and regional left ventricular function in ischemic heart disease using ultrafast computed tomography.

Contrast-enhanced ultrafast computed tomography (CT) of the left ventricle was done in the long axis and short axis within one day of cardiac catheterization in 14 males with ischemic heart disease and a mean age of 58 years. Imaging was R wave-triggered at 58-msec intervals (13/level). Left ventriculography was performed in 30 degrees right anterior oblique (RAO) and 60 degrees left anterior oblique (LAO) caudal 12 degrees. CT left ventricular ejection fraction was measured using a modified Simpson's reconstruction of end-systolic and end-diastolic slices. Catheterization left ventricular ejection fraction was measured by area-length method. Six left ventricular segments (septal, apex, anterior, lateral, inferior, and posterior) were scored by different paired observers as follows: dyskinesis (-1), akinesis (0), moderate-severe hypokinesis (1), mild hypokinesis (2), and normal (3). Correlations of left ventricular ejection fraction for catheterization vs. long-axis CT and short-axis CT were r = .83 and r = .86, respectively. Seven of eight patients with transmural myocardial infarction were identified on CT by akinetic/dyskinetic segments. Eighty-four segments were scored. There was agreement (normal vs. abnormal) in 76 (90%). CT detected 47 normal segments vs. 51 by catheterization (92%), 11 akinetic/dyskinetic segments (92%), and 14 hypokinetic segments vs. 21 (67%). Wall motion scores between CT and catheterization differed by greater than 1 in 6 of 84 segments (7%). Therefore, ultrafast CT can accurately assess global and regional left ventricular function.

Cardiac Catheterization↗
PubMed1988

Preliminary experience in the use of ultrafast computed tomography to diagnose aortic valve stenosis.

Eight patients, mean age 72 years, with aortic valve stenosis were studied by ultrafast CT 1 day after cardiac catheterization. After injection of radiographic contrast material through a peripheral vein, two contiguous eight-level R wave-triggered cine mode scans in the short axis were acquired, starting above the aortic valve and continuing through the apex of the left ventricle. Seven of eight patients, all with calcified aortic valves, had a detectable central orifice. Catheterization-derived aortic valve areas were within 0.25 cm2 of the CT valve areas in six of seven. LV mass was measured by ultrafast CT in the eight patients with aortic valve stenosis (121.6 +/- 18.2 gm/m2) and was found to be significantly higher (p less than 0.0001) than that in a group of eight subjects with normal LV function, no history of hypertension, and normal ECGs (73.0 +/- 13.1 gm/m2). It is concluded that in selected cases ultrafast CT can contribute to the assessment of severity of calcific aortic stenosis by measurement of LV mass and valve area.

Aged↗
PubMed1988

Determinants of left ventricular ejection fraction by ultrafast computed tomography.

Twenty-seven patients had left ventricular ejection fraction (LVEF) measured by catheterization, single-plane angiography, and ultrafast computed tomography (cine CT). Twelve patients (mean age sixty-two years) had LVEF measured by use of the cine CT long-axis view LAV), and 15 patients (mean age fifty-eight years) had LVEF measured by use of the cine CT transaxial view (TAV). Cine CT LVEF was measured by means of two methods of edge detection (M1 and M2). A significant correlation was found between single-plane angiography and cine CT LAV LVEF (M1, r = .96; M2, r = .93). A lesser correlation was found for catheterization vs TAV cine CT LVEF (M1, r = .77; M2, r = .81). There was no significant difference between the two methods of edge detection for determining LVEF (M1 vs M2: LAV, r = .98; TAV, r = .94); however, there was significant variability in cavity volumes. Therefore, the LAV is superior to the TAV for measurement of LVEF by cine CT; however, different methods of edge detection, though affecting volumes, may not affect LVEF.

Cardiac Catheterization↗
PubMed1987

Demonstration of mitral and aortic valves by ultrafast computed tomography.

Contrast medium-enhanced ultrafast computed tomography has sufficient spatial and temporal resolution to permit imaging of the mitral and aortic valves. The conventional transaxial planar scan projection is not adequate for this purpose. This communication describes the planar configurations and technique required to image the mitral and aortic valves by ultrafast computed tomography.

Aortic Valve↗
PubMed1986

Quantitation of shunting at the atrial level using rapid acquisition computed tomography with comparison with cardiac catheterization.

Contrast-enhanced rapid acquisition computed tomography was employed to quantitate intracardiac shunts in two adult patients. Contrast medium was injected through a median antecubital vein and data were accumulated using the R wave-triggered flow mode. Time-density curves from a region of interest were generated by a gamma variate fit method and areas under the curves were calculated. Comparisons of calculated left to right shunts (Cases 1 and 2) with results of computed tomography and right to left shunt (Case 2) with cardiac catheterization data resulted in close agreement. This is the first report of quantitation of intracardiac shunts at the atrial level in humans by rapid acquisition computed tomography.

Adult↗
PubMed1986

Heart evaluation by cine CT: use of two new oblique views.

Two new oblique views on cine computed tomography for examination of the left ventricle of the heart are described. A short-axis view sections the left ventricle transversely, demonstrating all the ventricular walls; a long-axis view sections the left ventricle longitudinally, demonstrating the mitral valve, proximal aortic root, aortic outflow tract, and ventricular apex. These views are produced by a combination of table slew and patient positioning. Reproducible short-axis views were obtained in 16 healthy volunteers and 11 patients. Long-axis views were obtained in 11 patients. Patient studies in the long-and short-axis views were compared with results from angiocardiography, with nearly identical findings.

Adult↗
PubMed1986

Demonstration of mitral valve function by cine computed tomography using a new long axis view.

Comparison was made between contrast enhanced cine computed tomography (Cine/CT) and echocardiography in the imaging of the mitral valve in 14 patients. The mitral valve was seen in all 14 patients by Cine/CT using a new long axis view. There was agreement with echocardiography in 12 patients. Abnormalities in mitral valve movement were detected by Cine/CT. Left atrial size and contraction was measured by Cine/CT with a difference in left atrial ejection fraction observed between 13 patients with no evidence of mitral disease and 3 patients with mitral disease.

Adult↗
PubMed1986

Acute hemodynamic effects of nifedipine during supine exercise in patients with prior myocardial infarction.

Twelve male patients age 36-66, 8 on clinical doses of beta blocker, with old transmural myocardial infarction underwent rest and matched workload exercise before and 30 min after 20 mg sublingual nifedipine during cardiac catheterization. For the group, resting heart rate, aortic pressure, pulmonary wedge pressure, systemic vascular resistance, cardiac index, and left ventricular ejection fraction were normal. Exercise duration was 12.5 +/- 1.5 min. Comparing exercise before and after nifedipine, heart rate, cardiac index, and mean velocity circumferential fiber shortening increased, while mean aortic pressure, systemic vascular resistance, pulmonary wedge pressure, right atrial pressure, left ventricular end-diastolic volume and left ventricular end-systolic volume decreased with no significant change in double product, pulmonary arteriolar resistance and left ventricular ejection fraction. Therefore, for the range of left ventricular dysfunction in this study group and with 8 patients concurrently on beta blocker, nifedipine 20 mg s.l. produced significant improvement in hemodynamics at rest and exercise.

Adult↗
PubMed1986

Comparison of left ventricular ejection fraction by cine computed tomography and single plane right anterior oblique ventriculography.

Cine Computed Tomography (CCT) is a minimally invasive technique which offers high temporal (50 msec scan time) and spatial (2 line pairs) resolution. Left ventricular ejection fraction (LVEF) has been determined by this technique in dogs and normal subjects but no comparison has been made with contrast left ventriculography by cardiac catheterization. Ten patients, 9 male and 1 female, mean age 61 (range 46-70) had LVEF determined by both single plane RAO left ventriculography and CCT. Patients were studied in the fasting state, on different days without change in medication. LVEF by CCT was determined in the long axis, a new view which has been developed for CCT to be comparable to the RAO view of contrast left ventriculography by catheterization. This view is obtained by positioning the patient head first into the scanner, supine, with a counterclockwise table slew (20 degrees) without table tilt. Contrast is introduced via a median antecubital vein, and injected in a prolonged bolus of 7-13 seconds dependent on arm to heart circulation time. Scans are performed in the cine mode (17 frames/sec) timed during maximal opacification of the right and left ventricles. Four or six contiguous levels are imaged as required to slice the entire left ventricular cavity. End-systolic and end-diastolic frames are identified. Left ventricular cavity areas are determined by computerized planimetry after the Hounsfield level number is set at half the difference between the contrast in the cavity and the myocardium and setting the window width at one giving a black and white image. Left ventricular end-diastolic volume (LVEDV) and end-systolic volume (LVESV) per slice are summated to obtain LVEDV and LVESV from which LVEF is desired.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1986

Rapid acquisition computed tomographic assessment of left ventricular regional wall motion using a new long axis view.

A long axis view to demonstrate left ventricular regional wall motion was devised for the ultrafast CT scanner. The patients are positioned supine, head first, into the scanner. The scan table is slewed 20 degrees counter-clockwise in the horizontal plane without tilt. A bolus of contrast is injected via a median antecubital vein. Contiguous level R wave triggered cine studies are obtained during peak passage of contrast through the heart to image the entire left ventricular cavity. Fourteen patients had left ventricular wall motion compared by long axis CT and RAO 30 degrees single plane ventriculography at catheterization. In all cases, regional wall motion in comparable segments by both methods was in agreement. It is concluded that the ultrafast CT long axis view permits diagnosis of left ventricular regional wall motion abnormalities. This view images the apex and sections the interventricular septum and lateral free wall horizontally. Unlike conventional CT views, it is comparable to the RAO left ventriculogram.

Cardiac Catheterization↗
PubMed1986

Angiographic recognition of ostial left main coronary artery stenosis: case report.

Ostial left main coronary stenosis has a poor prognosis and increased mortality rate with coronary arteriography. Due to its anatomic location, visualization of the stenosis may be difficult. A high index of suspicion based upon only a few signs should prompt the physician to perform certain maneuvers to obtain the correct diagnosis. Four illustrative cases are presented and discussed.

Aged↗
PubMed1986

The functional and anatomic evaluation of the cardiovascular system with rapid-acquisition computed tomography (cine CT).

Cine CT combines the advantages of digital cross-sectional imaging with those of angiography. It provides vivid portrayal of complex anatomic relationships as well as important functional data not easily obtainable elsewhere, including quantitation of myocardial wall thickening and regional myocardial blood flow. The blood flow in major vessels following coronary artery bypass graft surgery and cardiac output have been quantified with accuracy. The future of cine CT will depend ultimately on controlled studies comparing this technique with other modalities, including echocardiography, magnetic resonance imaging, radionuclide angiocardiography, and contrast-enhanced catheter angiography.

Blood Flow Velocity↗