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Biomedical subjects

D J Widder

Publications and source records attributed to D J Widder.

14 recordsLinked to original sources
PubMed1987

Magnetite albumin microspheres: a new MR contrast material.

A superparamagnetic MR contrast agent was synthesized by incorporating 150-250-A particles of magnetite (Fe3O4, Fe2O3) in 1-5 microns human serum albumin microspheres. Magnetite albumin microspheres (MAM) target almost exclusively to the reticuloendothelial system after IV administration, are stable in vitro and in vivo, and possess a long shelf life. The agent has a large magnetic susceptibility effect that selectively reduces T2 with little effect on T1. Biodistribution studies that use a dose of 20 mg MAM/kg show prompt clearance from the blood pool with marked decrease in T2 for rat liver (40%) and spleen (45%) with a small decrease in liver (5%) and spleen (10%) T1 values. Pulmonary T1 and T2 decrease transiently over the first 24 hr, while no significant changes were observed in other tissues. Imaging of a rabbit VX2 tumor model resulted in a 200% increase in the contrast ratio of VX2 tumor to normal liver on T2-weighted and mixed T1-/T2-weighted pulse sequences after administration of contrast agent. The extreme potency, excellent targeting, and apparent lack of toxicity of this agent suggest that MAM probably will have a clinical application in detecting focal hepatic and splenic lesions.

Animals↗
PubMed1987

Magnetite albumin suspension: a superparamagnetic oral MR contrast agent.

Suspensions of magnetite albumin microspheres (MAM), a new biodegradable particulate iron superparamagnetic MR contrast material, were evaluated in vitro and in vivo as an oral contrast agent. MAM is stable over a broad range of pH and tolerates proteolytic enzyme exposure over 24 hr in vitro. MAM possesses a much larger magnetic moment than do paramagnetic contrast agents. The transverse relaxation rate (R2) of MAM can be as much as 40 times the longitudinal relaxation rate (R1). In vitro spectroscopy studies confirm the potency of MAM in promoting T2 relaxation at concentrations of 10-1000 mg/l. Preliminary studies in rabbits and dogs show that in contrast to oral gadolinium-DTPA, which causes increased signal in bowel, MAM causes marked signal loss in the stomach and small bowel on both T1- and T2-weighted pulse sequences. Radionuclide labeling studies of MAM suspension with 99mTc show no evidence of absorption of MAM suspension from the gastrointestinal tract in small animals. Superparamagnetic suspensions such as MAM that reduce bowel signal on T1- and T2-weighted pulse sequences offer the unique benefit of reducing motion artifacts throughout the gastrointestinal tract, which should allow for improved evaluation of intra- and retroperitoneal diseases, particularly with high-field strength and gradient-echo "fast-scan techniques." Unlike paramagnetic material, MAM appears effective as a small-bowel contrast material.

Administration, Oral↗
PubMed1986

Microbubbles as a contrast agent for neurosonography and ultrasound-guided catheter manipulation: in vitro studies.

Tissue-equivalent ultrasound phantoms, including models of the ventricular system and cyst phantoms, may be useful for developing expertise in both biopsy procedures and shunt catheter placement that use ultrasound guidance. These phantoms have been constructed (1) to assess the ability to position biopsy needles and manipulate shunt catheters with conventional angiographic guidewires and (2) to evaluate the usefulness of microbubbles as an ultrasound contrast agent. Optimal catheter and needle position and catheter patency are demonstrated with microbubbles generated by hand injection of small volumes of saline, a safe ultrasound contrast agent that, to our knowledge, has not been previously exploited in neurosonography. Microbubbles can define biopsy needle location without direct imaging of the biopsy needle; they can also define the extent of communication or separation of fluid-filled or loculated spaces.

Air↗
PubMed1986

Assessment of ventricular shunt patency by sonography: a new noninvasive test.

This report describes a new test of patency of the ventricular component of a ventriculoperitoneal shunt that precludes injection into the shunt reservoir. Preliminary clinical experience confirms that digital compression of the ventricular shunt reservoir (Cordis standard and pediatric reservoir), while occluding the shunt distal to the reservoir, generates microbubbles that increase the echogenicity of the catheter, demonstrating shunt patency. In vitro, the extrusion of microbubbles from catheter side holes can be imaged during digital compression of the reservoir, but so far this has not been imaged in patients as a direct sign of shunt patency. A sonographic means of assessing shunt function offers the advantage of simultaneously imaging the ventricular catheter, determining its location, and assessing the etiology of shunt failure. Its usefulness is limited to pediatric cases in which an adequate transfontanelle cranial sonographic study can be obtained and to individuals with large craniotomy defects.

Adolescent↗
PubMed1983

Spontaneous nontraumatic rupture of the thoracic aorta.

Spontaneous nontraumatic rupture of the thoracic aorta is a rare, life-threatening condition for which emergency diagnostic and therapeutic measures are indicated. The entity should be considered in the differential diagnosis of patients presenting with chest pain and signs of pericardial tamponade.

Aorta, Thoracic↗
PubMed1982

The Carman-Kirklin ulcer revisited: computed tomographic correlation.

A patient with ulcerating gastric adenocarcinoma presented with the classic features of a Carman-Kirklin meniscus sign on an upper GI series. Clinical staging with computed tomography (CT) provided an opportunity to examine the anatomic appearance of this often confusing finding.

Adenocarcinoma↗
PubMedDate not supplied

MR of hemorrhage.

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Hemorrhage↗