Biomedical subjects

G R Caputo

Publications and source records attributed to G R Caputo.

48 records · Page 3Linked to original sources

PubMed1990

Cardiac transplantation in situs inversus.

Transplantation of the heart was successfully performed in a patient with situs inversus of the viscera and atria. Anatomic constants common to all patients allowed the left atrium, pulmonary artery, and aorta to be joined as usual in the transplant operation. Systemic venous reconstruction was the crux of the operation. A composite superior vena cava was reconstructed on the right side from the recipient translocated superior vena cava, donor superior vena cava and innominate vein, and recipient in situ pericardium. The inferior vena cava was rerouted from the left side across the midline to the right through a composite conduit consisting of the recipient night atrium and in situ pericardium over the diaphragm. These reconstructed venous passageways have remained patent and unobstructed for 1 1/2 years after the operation.

Anastomosis, Surgical↗

PubMed1989

Efficient biphasic spin-echo magnetic resonance imaging.

The concept of temporal echo multiplexing is defined and used to develop rapid biphasic spin-echo sequences for imaging the heart. Three imaging sequences, based on four-echo and two-echo multiplexing and rapid single echo (i.e., conventional spin-echo imaging), are compared. Preliminary results indicate that two-echo multiplexing yields a significantly reduced acquisition time window with image quality that is only slightly inferior to single-echo imaging. Single-echo biphasic imaging results in the most consistent image quality.

Adult↗

PubMed1987

Coronary artery bypass graft patency: noninvasive evaluation with MR imaging.

A noninvasive means of determining coronary artery bypass graft (CABG) patency in symptomatic patients would be an important clinical asset. The accuracy of magnetic resonance (MR) imaging was evaluated for this purpose. Multiphasic electrocardiographically gated MR imaging examinations were performed in 25 patients with a total of 72 grafts. Transverse images of the heart at ten anatomic levels were obtained at five or six phases of the cardiac cycle. The MR images were read blindly to determine CABG patency versus occlusion, and these results were compared with those of coronary angiography performed within 2 months before the MR imaging. MR imaging correctly disclosed 43 patent grafts and 13 occluded grafts (predictive accuracy, 78%). Patency and occlusion were incorrectly diagnosed from MR imaging findings in five and four CABGs, respectively. CABG status could not be determined in seven (10%) grafts because the grafts were visualized at only one anatomic level. Thus, the accuracy of a definitive MR imaging evaluation was 91% (43 of 47 grafts) for patency determination and 72% (13 of 18 grafts) for occlusion determination. MR imaging appears to be a useful method for the noninvasive evaluation of CABGs.

Adult↗

PubMed1987

Measurement of canine left ventricular mass by using MR imaging.

This study assessed the capability of ECG-gated MR imaging for quantitating left ventricular mass by means of signal intensity-based and geometric methods for measuring left ventricular mass of normal dogs and dogs with left ventricular hypertrophy. Mass was measured on transverse images encompassing the left ventricle during both diastole and late systole. Partial-volume errors were minimized by measuring the length of the left ventricle on a sagittal image and weighting the mass of end slices accordingly. The range of postmortem left ventricular mass was 61-100 g. The linear relationship between postmortem left ventricular mass and mass measured via MR images correlated closely when MR imaging measurements were done at either end diastole (r = .94) or late systole (r = .94). The standard errors of the estimate were 13.7 and 14.7 g for images gated to end diastole and late systole, respectively. Inter- and intraobserver reproducibility showed excellent agreement (r = .93 and r = .89 for end diastole and r = .99 and r = .93 for late systole, respectively). Thus, left ventricular mass can be quantified accurately and reproducibly over a wide range of masses by using ECG-gated MR imaging.

Animals↗

PubMed1987

Measurement of myocardial infarct size at early and late time intervals using MR imaging: an experimental study in dogs.

The current study assessed the capability of ECG-gated MR imaging to quantitate both the percentage of the left ventricle involved by acute myocardial infarction and the mass of acute myocardial infarction at 3 and 21 days after coronary occlusion in dogs. Infarct mass was measured from gated transverse MR images using computer-generated calculated-T2 images. T2 images provided accentuation of the boundary between infarcted and normal myocardium as well as objective, reproducible calculation of image voxels representing infarcted myocardium. Postmortem and in vivo MR infarct mass and percentage correlated closely at 3 days (r = .98, SEE = 0.73 g; r = .97, SEE = 1.2%), and 21 days (r = .94, SEE = 1.54 g; r = .95, SEE = 1.61%). Left ventricular mass, infarct mass, and percentage of infarct were measured on end-diastolic MR images. Infarct mass at 3 and 21 days was not significantly different, with a mean deviation of 0.63 g. There was close intra- and interobserver reproducibility (r = .99 and r = .90, respectively) for measurement of infarct mass. The quantitative technique employed for determining the mass of acute myocardial infarctions, based on the different T2 relaxation times of infarcted and normal myocardium, provides for objective analysis and reproducibility. With this technique, MR provides an accurate method for assessing the mass of acute infarcts and the percentage of the left ventricle involved by the infarct both early and late after coronary occlusion.

Animals↗

PubMed1985

Measurement of left ventricular volume using single-photon emission computed tomography.

A count-based method for measuring left ventricular (LV) volume using technetium-99m-labeled red cells and ungated single-photon emission computed tomography is described. The tomographic slices were used to determine the counts per milliliter in the center of the left ventricle and total LV counts, which were used to derive mean LV volume. End-diastolic and end-systolic volumes were calculated from the mean volume using the LV time-activity curve from planar gated blood pool images. Phantom evaluation with simulated LV volumes (50 to 400 ml) in air, in a phantom filled with water, with 10% background, and with a simulated right ventricle, showed excellent accuracy. For clinical validation, 30 patients underwent electrocardiographically gated planar and nongated tomographic acquisition of the cardiac blood pool followed by single-plane cineangiography. For end-diastolic and end-systolic volumes combined, the correlation with cineangiography showed a standard error of the estimate (SEE) of 24 ml and 14 ml, respectively. Mean intra- and interobserver deviation was 12 ml and 14 ml (SEE 13 ml and 16 ml), respectively. It is concluded that this noninvasive count-based technique, requiring no assumptions regarding LV geometry, is an accurate and reproducible way to measure LV volume.

Adult↗

PubMed1983

Value of partial ejection fraction, volume increment, and regional wall motion in identifying patients with clinically significant coronary artery disease.

Recent studies suggest that the partial ejection fraction (EF) in early systole is a more sensitive index of left ventricular (LV) dysfunction than the holosystolic EF. We examined LV volume, partial EF, and volume increment at each of 12 time points in systole to determine which parameter best distinguishes normal subjects from patients with coronary artery disease (CAD). Contrast ventriculograms, obtained either in the right anterior oblique projection (60 frames/sec) or in the biplane projection (30 frames/sec), of 58 normal subjects and 68 patients with CAD were studied. The endocardial contour in each frame of a sinus beat was traced to derive a volume curve. At each twelfth of systole, LV volume was extrapolated from the curve and the partial EF was calculated. The increment in volume between successive time points was also calculated. Both partial EF and LV volume in patients with CAD became progressively more abnormal with time; peak abnormality occurred at end-systole. In a subgroup of patients with CAD who had normal holosystolic EF, both partial EF and volume were normal throughout systole. The increment in volume with each twelfth of systole in patients with CAD deviated less than 1 SD from normal throughout systole. Thus, maximum abnormality in partial EF and volume occurs at end-systole. Of the parameters of global LV function tested, holosystolic EF best distinguishes patients with CAD from normal subjects. However, regional wall motion measured in the area of interest is more sensitive to localized abnormality, the severity of which may be overestimated or underestimated by the EF due to hyperkinesis or hypokinesis in other regions of the left ventricle.

Cardiac Catheterization↗

PubMedDate not supplied

Flow pattern analysis in the abdominal aorta with velocity-encoded cine MR imaging.

The sites of deposition of atherosclerotic plaque on the aortic wall are considered to be influenced by secondary and retrograde flow patterns that cause regions of altered shear stress. To detect secondary flow patterns and areas of retrograde flow in the abdominal aorta, velocity-encoded cine (VEC) magnetic resonance (MR) imaging was performed at five different levels of the abdominal aorta in nine healthy volunteers. Net retrograde flow (expressed as a percentage of antegrade flow) increased from proximal to distal levels and was maximal (13.8% +/- 11.8) just distal to the origin of the renal arteries. An increase in the duration of retrograde flow over the cardiac cycle was observed from proximal to distal levels. Whereas retrograde flow was present at end systole and early diastole in each volunteer at every level, the duration and amount of retrograde flow during diastole showed high interindividual variation. Such differences suggest the possibility of variable vascular geometric risk factors in the population for the development of atherosclerotic plaque. The location of retrograde flow in the abdominal aorta demonstrated in vivo with VEC MR imaging was close to that obtained with in vitro flow visualization studies in models of the abdominal aorta.

Adult↗

PubMedDate not supplied

MR measurement of blood flow in the true and false channel in chronic aortic dissection.

Velocity encoded (VEC) cine MR imaging is a new noninvasive technique for the quantification of blood flow velocity in the cardiovascular system. Six patients with type B aortic dissection underwent VEC cine MR imaging at 1.5 T. This technique provides cine MR magnitude and VEC phase images at approximately 16 equally spaced intervals during an average cardiac cycle. A region of interest encompassing a vascular structure, i.e., false channel, provides a spatially averaged velocity for the time interval at which the image was acquired. Interpretation of velocity values from the 16 intervals during the cardiac cycle provides a temporally average velocity. Velocity mapping across the aortic lumen in these six cases showed average spatial and temporal velocity of 13.4 +/- 1.49 cm/s in the true channel and 3.1 +/- 0.84 cm/s in the false channel (p less than 0.05). The peak systolic velocity (temporal peak) was 43.6 +/- 7.20 cm/s in the true channel and 14.3 +/- 2.30 cm/s in the false channel (p less than 0.05). The flow volume per cardiac cycle was not significantly different between the ture (23.1 +/- 5.04 ml/cycle) and false channel (27.1 +/- 10.14 ml/cycle). There was substantial retrograde flow in the false channel of two patients. The intraobserver and interobserver variability was less than 10% (r = 0.98 to 0.99) for the measurement of flow parameters in both the true and the false channel. We conclude that VEC cine MR imaging demonstrates substantial differences in the hemodynamic pattern in the true and false channel in aortic dissection.

Adult↗

PubMedDate not supplied

Cine gradient refocused echo (GRE) imaging of intravascular masses: differentiation between tumor and nontumor thrombus.

Spin echo MR imaging has not permitted reliable differentiation between intraluminal blood clot and tumor thrombus. This study assessed the role of ECG referenced repetitive gradient refocused echo (cine GRE) imaging for the differentiation of intravascular tumor from blood clot. Cine GRE images were reviewed in 23 patients, 11 of whom had intravascular tumor and 12 of whom had intravascular blood clots. Percentage contrast between the lesion and skeletal muscle as the reference tissue was determined from a subjective review of the images and objective signal intensity measurements. Intravascular clots were found to be lower in signal intensity than muscle (mean -55 +/- 29%). Intravascular tumors showed higher signal intensity relative to muscle (mean +17 +/- 9%) with the exception of myxomas (n = 2), which had signal intensity values relative to muscle as low as clots (mean -41 +/- 17%). Three masses in the inferior vena cava were composed of central tumor and peripheral clot; the two components could be differentiated with cine GRE imaging. Cine GRE imaging provides adequate signal intensity differences to visualize intravascular masses and helps to differentiate intravascular clot from tumor thrombus. However, if the tumor contains substantial amounts of iron, then the signal is also low and consequently clot and thrombus may not be distinguishable. This can occur in some atrial myxomas.

Diagnosis, Differential↗

PubMedDate not supplied

Enhancement of thoracic masses using nonionic MR contrast agents.

OBJECTIVE: This study evaluated the effect of a new nonionic MR contrast medium, gadodiamide injection (Omniscan; Sanofi-Winthrop), on enhancement of thoracic masses on T1-weighted SE images. MATERIALS AND METHODS: Gadodiamide injection was administered intravenously at a dose of 0.2 mmol/kg to 26 patients with thoracic masses. The T1-weighted images with and without fat suppression and T2-weighted images obtained before contrast medium injection were compared with T1-weighted images obtained at 5, 30, and 45 min and a T1-weighted fat-suppressed image at 10 min after administration of the contrast medium. Enhancement of the thoracic masses and image quality were quantified by measuring signal intensity, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) using muscle and fat as reference tissues. RESULTS: The SNR of the masses increased significantly (p < 0.001) following contrast material injection both on standard T1-weighted sequences and on T1-weighted fat-suppressed images when compared with the precontrast T1-weighted images with and without fat suppression. The CNR (reference tissue muscle) improved significantly (p < 0.001) after contrast medium injection and persisted for 45 min on T1-weighted images compared with those prior to contrast medium. However, there was no significant difference in CNR between the T2-weighted images obtained before and the T1-weighted images obtained after contrast agent administration. On the other hand, the SNR of contrast-enhanced images was significantly better than that of the T2-weighted images. When fat was used as a reference tissue, CNR of the thoracic masses decreased significantly. CONCLUSION: This study shows that gadodiamide injection caused significant enhancement of thoracic masses on T1-weighted images, which rendered high signal intensity to the masses similar to the appearance on T2-weighted images. In comparison with the T2-weighted images, SNR was significantly improved.

Adolescent↗

PubMedDate not supplied

Assessment of popliteal arterial occlusive disease with 2D time-of-flight MRA.

OBJECTIVE: The purpose of this study was to evaluate both morphology and blood flow in peripheral arteries with occlusive lesions using MR angiography (MRA) and velocity-encoded cine MRI. MATERIALS AND METHODS: Two-dimensional time-of-flight MRA and velocity-encoded cine MRI were performed in nine patients with peripheral arterial occlusive disease. Findings on MR angiograms were verified by conventional angiography. RESULTS: All the stenotic lesions in the popliteal arteries were depicted by MRA. The degree of the stenoses in the artery was overestimated by MRA. Major collateral circulations were demonstrated. Velocity-encoded cine MRI provided flow velocity information on the arteries above and below the stenoses. The flow velocity waveform was monophasic above and below the stenosis. The peak systolic velocity in the artery below the stenosis was reduced compared with that above the stenosis (p < 0.05). CONCLUSION: The combination of MRA and velocity-encoded cine MRI has clinical potential for the evaluation of peripheral arterial occlusive disease.

Adult↗