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Biomedical subjects

L M Boxt

Publications and source records attributed to L M Boxt.

81 records · Page 5Linked to original sources
PubMed1983

Intravenous digital subtraction angiography of the thoracic and abdominal aorta.

Intravenous digital subtraction angiography (IV DSA) is a new imaging modality that utilizes techniques of video image acquisition and computer image manipulation to provide anatomic information about blood vessels and organs. In many ways, it represents an electronic version of classic intravenous and film-subtraction angiography. As a means of imaging the thoracic and abdominal aorta, IV DSA has demonstrated great potential, particularly in vessels originally imaged by the former techniques. We have imaged the aorta in over 300 cases at Brigham and Women's Hospital, either alone, or in combination with other vessels in the course of work-up for vascular disease. Although experience has been limited, intravenous imaging of the aorta can be routinely performed, providing reliable and clinically significant information.

Aortic Dissection↗
PubMed1983

Long-term hepatic arterial infusion of 5-fluorodeoxyuridine for liver metastases using an implantable infusion pump.

Twenty-one patients with liver metastases of various histologies (predominantly colorectal carcinoma) underwent Infusaid pump implantation for long-term hepatic arterial 5-fluorodeoxyuridine (5-FUdR) infusion. Patients received 5-FUdR infusion on a 2-wk cycle alternating with a 2-wk saline--heparin infusion. A dosage of 0.2-0.3 mg/kg/day (average 0.23 mg/kg/day) was infused for a cumulative 5-FUdR administration of 1940 days. Six patients (29%) responded to therapy (five colorectal, one carcinoid); median response duration was 6 mo. Median survival for the treated group was 17 mo from diagnosis of liver metastases and 13 mo from pump implantation. Median survival among the six responding patients was 15 mo from diagnosis of liver metastases and 11 mo from pump implantation. Comparison of survival from the diagnosis of liver metastases of the treated group to ten patients found ineligible for the study by virtue of extrahepatic metastases revealed no significant difference in median (18 mo for ineligible group) or overall survival. However, median survival for the treated group after pump implantation (13 mo) was significantly better than the median survival of the ineligible group after evaluation for this study (4 mo). Toxicities of therapy included fatigue, anorexia, nausea, vomiting, toxic hepatitis, epigastric pain, and diarrhea. No patients died of toxicity, but six patients required hospitalization for management of pain or vomiting. No serious technical complications developed in any patient except separation of the infusion catheter at its junction with the pump in one patient, necessitating pump replacement for continuation of therapy. These survival data suggest identification of new anticancer agents for hepatic arterial infusion.

Adult↗
PubMed1982

Digital subtraction angiography: overview of technical principles.

The rapid development of equipment for digital subtraction angiography (DSA) has created a new diagnostic imaging method, the limits of which have not been scientifically determined. Yet through aggressive marketing, the technique is already beginning to permeate radiologic practice. The radiologist requires technical understanding of the instrumentation for informed judgment on clinical applications. DSA depends on the mating of high-resolution image-intensifier and television technology with computerized information manipulation and storage. In this overview, the individual components of the system are analyzed, from the generator to the image intensifier to the television system to the associated computer. By examining the role of each component, the current limitations and the areas of possible future development of DSA can be understood. This provides a basis for dealing with current technology and for evaluating the rapid technological changes that will occur over the next few years.

Angiography↗
PubMed1980

Radiographic findings in congenital lead poisoning.

Because lead crosses the placenta throughout pregnancy, the fetus is at risk for lead poisoning. A full term, asymptomatic child was born with congenital lead poisoning secondary to maternal pica. Radiographic findings of a dense cranial vault, lead lines, and delayed skeletal and deciduous dental development were noted at birth. After chelation therapy, when the patient was seven months old, radiographs revealed normal skeletal maturation. Tooth eruption did not occur until 15 months of age. Newborn infants with these radiographic findings should be screened for subclinical, congenital lead poisoning.

Adolescent↗
PubMedDate not supplied

Three-dimensional echocardiographic volume computation by polyhedral surface reconstruction: in vitro validation and comparison to magnetic resonance imaging.

Two-dimensional echocardiographic methods of left ventricular volume computation are limited by geometric assumptions and image plane positioning error in the nonvisualized dimension. We evaluated a three-dimensional (3D echocardiographic method that addresses these limitations. Our method uses a volume computation algorithm based on polyhedral surface reconstruction (PSR) and nonparallel, unequally spaced, nonintersecting short-axis planes. Seventeen balloon phantoms were subjected to volume computation by the 3D echocardiography-PSR method and by magnetic resonance imaging (MRI) and compared to true volumes determined by water displacement. The results for 3D echocardiography-PSR were: accuracy = 2.27%, interobserver variability = 4.33%, r = 0.999, SEE = 2.45 ml, and p less than 0.001. Results for MRI were 8.01%, 13.78%, r = 0.995, SEE = 7.01 ml, and p less than 0.001. There was no statistically significant difference between the methods. We conclude that precise image plane positioning and use of the 3D echocardiographic-PSR volume computation method achieves high accuracy and reproducibility in vitro. The excellent in vitro correlation between 3D echocardiography-PSR and MRI indicates that MRI may also serve as an in vivo standard of comparison.

Cardiac Volume↗
PubMedDate not supplied

Feasibility of a two-dimensional echocardiographic method for the clinical assessment of right ventricular volume and function in children.

The relative ease of acquisition and safety of two-dimensional echocardiography has established it as the mainstay for routine cardiac imaging. Translation of imaging data into useful quantitative information, however, requires fitting the ventricle to a specific geometric model. Because of its complex shape and anterior position, many attempts at right ventricular quantitation by two-dimensional echocardiography have been criticized as impractical and not reproducible. A simple method incorporating subcostal and apical imaging was introduced in 1984. This approach appeared to combine accuracy and practicability but was never validated in a clinical setting because of the difficulties of subcostal imaging in adults. This study assessed the feasibility and accuracy of this technique in the pediatric population. Results of volume comparison to values derived by magnetic resonance imaging were r = 0.96, standard error of the estimate (SEE) = 19.3 ml, and mean difference = 15 +/- 19.4 ml and r = 0.97, SEE = 12.3 ml, and bias = 5 +/- 11.8 ml for diastolic and systolic volumes, respectively. Comparison of estimates of ejection fraction with magnetic resonance imaging demonstrated r = 0.90, SEE = 5.9%, and bias = 3% +/- 5.7%. Interobserver and intraobserver variability was 9.9% and 8.2%, respectively, for systolic volumes and 11.5% and 8.9%, respectively, for diastolic volumes. Evaluation of right ventricular size and function by this approach is comparable to determinations by magnetic resonance imaging and may be clinically useful in the management of pediatric patients.

Adolescent↗
PubMedDate not supplied

Computer-assisted, operator-interactive technique for calculating pulmonary arterial taper.

We have developed a computer-assisted, operator-interactive technique which performs fast, precise computations of pulmonary artery taper. Individual 35-mm cineframes from balloon-occlusion pulmonary arteriograms are digitized into a 640 X 480 matrix in 8-bit depth and loaded into a VAX 11/780 computer for analysis. After operator identification of the arterial segment, an automated process of caliber analysis is initiated. By fitting a cubic spline function to the densitometric profiles extracted from the arterial segment, serial arterial cross-sectional diameters are calculated from the mathematically-derived points along the fitted curves. Spurious profiles, caused by sectioning at bifurcations, can be overridden by an operator-interactive subroutine. Taper is derived from the slope of the least-squares fit of vessel caliber with respect to its distance along the arterial segment. Results obtained by calculations from the computer-assisted caliber measurements were compared with those obtained by hand-tracing the same vessel segments. Correlation between computer-traced inflection points and hand-traced taper was very significant (r = .96, n = 13, P less than 0.001).

Child, Preschool↗
PubMedDate not supplied

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.

Aortic Diseases↗