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Biomedical subjects

S G Imbesi

Publications and source records attributed to S G Imbesi.

12 recordsLinked to original sources
PubMed2006

Artifact simulating subarachnoid and intraventricular hemorrhage on single-shot, fast spin-echo fluid-attenuated inversion recovery images caused by head movement: A trap for the unwary.

BACKGROUND AND PURPOSE: Single-shot, fast spin-echo, fluid attenuated inversion recovery (SS-FSE-FLAIR) images are frequently used to detect disease in the brain and subarachnoid space in confused or uncooperative patients who may move during the examination. In some of these patients, high signal intensity areas are seen on good-quality images in the subarachnoid space and ventricular system in locations not associated with high CSF flow. These artifacts may simulate hemorrhage or leptomeningeal disease. The purpose of this article was to determine the cause of these artifacts, describe ways to recognize them, and find methods to reduce or eliminate them. METHODS: Healthy volunteers were studied on 6 occasions with conventional multisection FSE-FLAIR images and SS-FSE-FLAIR images while at rest and while nodding and rotating their heads at different speeds. In addition, SS-FSE-FLAIR images with different section widths of the initial inverting pulse and a non-section-selective initial inversion pulse were performed with the subjects moving their heads in the same way. The scans of 30 successive patients with acute neurologic syndromes who had been studied with SS-FSE-FLAIR sequences were reviewed for evidence of high signal intensity in the CSF in regions not associated with high CSF flow. RESULTS: Each of the volunteers showed areas of increased signal intensity in CSF at sites apart from those associated with rapid pulsatile CSF flow on SS-FSE-FLAIR images acquired during head motion. The images were otherwise virtually free of motion artifact. The use of a wider initial inversion pulse section and a non-section-selected initial inversion pulse reduced the extent of these artifacts. Nineteen of the 30 patients showed areas of high signal intensity in the CSF in regions not associated with highly pulsatile CSF flow. Six of these patients had negative lumbar punctures for blood and xanthochromia and normal CSF protein levels. CONCLUSION: High signal intensity artifacts may be seen in CSF as a result of head movement on otherwise artifact-free images when imaging uncooperative patients with SS-FSE-FLAIR sequences. These artifacts have a different mechanism and distribution from those caused by CSF pulsation and may simulate subarachnoid and intraventricular hemorrhage. Artifact recognition is aided by signs of patient motion during the examination. The artifacts can be reduced by use of increased section width and non-section-selective initial inversion pulses. Recognition of these artifacts is important, because the circumstances in which the SS-FSE-FLAIR sequence is used and the particular properties of the sequence may conspire to produce a trap for the unwary.

Adult↗
PubMed2005

Rapid prototyping to create vascular replicas from CT scan data: making tools to teach, rehearse, and choose treatment strategies.

Our goal was to develop and prove the accuracy of a system that would allow us to re-create live patient arterial pathology. Anatomically accurate replicas of blood vessels could allow physicians to teach and practice dangerous interventional techniques and might also be used to gather basic physiologic information. The preparation of replicas has, until now, depended on acquisition of fresh cadaver material. Using rapid prototyping, it should be able to replicate vascular pathology in a live patient. We obtained CT angiographic scan data from two patients with known arterial abnormalities. We took such data and, using proprietary software, created a 3D replica using a commercially available rapid prototyping machine. From the prototypes, using a lost wax technique, we created vessel replicas, placed those replicas in the CT scanner, then compared those images with the original scans. Comparison of the images made directly from the patient and from the replica showed that with each step, the relationships were maintained, remaining within 3% of the original, but some smoothing occurred in the final computer manipulation. From routinely obtainable CT angiographic data, it is possible to create accurate replicas of human vascular pathology with the aid of commercially available stereolithography equipment. Visual analysis of the images appeared to be as important as the measurements. With 64 and 128 slice detector scanners becoming available, acquisition times fall enough that we should be able to model rapidly moving structures such as the aortic root.

Angiography↗
PubMed2004

Manipulation of volume data to manufacture vascular replicas.

There are three reasons to create physical replicas of human anatomy: (1) to be able to better visualize the shape of a single organ, or a section of anatomy; (2) to be able to visualize the spatial relationships in three-dimensions; and (3) to use accurate replicas to practice or rehearse otherwise high-risk clinical procedures in the laboratory. This paper describes a project to fabricate a carotid artery. It discusses the gathering of data, the conversion to a volume, and the subsequent conversion to a manufacturable form.

California↗
PubMed2002

Development of a posterior cerebral artery aneurysm subsequent to occlusion of the contralateral internal carotid artery for giant cavernous aneurysm.

We report a case of a patient who developed a left posterior cerebral artery aneurysm 5 years after balloon occlusion of the right internal carotid artery for a giant cavernous aneurysm. The location of the new aneurysm was outside of the primary collateral pathways to the contralateral, proximally occluded, anterior circulation, illustrating the complexity of hemodynamic factors contributing to the development of intracranial saccular aneurysms. The appearance of an aneurysm in this setting supports the hypothesis that degenerative factors and hemodynamic stresses are important in the etiology of intracranial aneurysms.

Balloon Occlusion↗
PubMed2001

Analysis of slipstream flow in a wide-necked basilar artery aneurysm: evaluation of potential treatment regimens.

SUMMARY: A replica of a lethal wide-necked basilar artery aneurysm was created by casting a deceased patient's brain vessels and then placing the replica in a circuit of pulsating optically clear non-Newtonian fluid. Individual fluid slipstreams were opacified with isobaric dyes, and images were recorded on film. Studies were completed on the vascular replica, then were repeated, first after placement of a stent across the aneurysm neck and then after placement of Guglielmi detachable coils into the aneurysm sac through the stent. The slipstreams entered the untreated aneurysm via the distal aneurysm neck (the inflow zone), impacting against the distal lateral aneurysm wall. When the stent was placed across the aneurysm neck, the slipstreams lost coherence and did not strike the aneurysm sidewall. Placing the coils further disturbed and reduced aneurysmal flow, especially when the coils filled the inflow zone at the distal lateral aneurysm sac.

Blood Flow Velocity↗
PubMed2000

Spinal oligodendroglioma with gliomatosis in a child. Case report.

The authors present a rare case of oligodendrogliomatosis in a child, which they believe originated from a primary spinal cord tumor. At 2.5 years of age this boy developed poor balance, neck stiffness, and a regression in developmental milestones. A computerized tomography (CT) scan of the head initially revealed ventriculomegaly and multiple cystic cerebellar lesions. In addition, magnetic resonance (MR) imaging revealed a cystic intramedullary lesion involving the cervical spinal cord. A CT scan of the head and an MR image obtained 3 years later demonstrated diffuse small cysts on the surface of the brainstem, cerebellum, medial temporal and inferior frontal cortices, subcortical white matter, and corpus callosum suggestive of leptomeningeal tumor spread. Analysis of pathological specimens obtained at surgery showed neoplastic glial cells with small, uniform nuclei and perinuclear clear zones. The cells appeared to migrate along the subpial space but no tumor cells were present in the subarachnoid space. These findings were compatible with a diagnosis of oligodendrogliomatosis cerebri. Despite having a complicated course, chemotherapy with carboplatin has provided the patient with long-term palliation and a high quality of life. This case may represent the fifth report in the literature of oligodendrogliomatosis occurring in a child but only the third occurring with a spinal primary tumor.

Brain Neoplasms↗
PubMed1999

Analysis of slipstream flow in two ruptured intracranial cerebral aneurysms.

Replicas of ruptured posterior communicating and basilar artery aneurysms were created from cadaveric specimens and then were placed in a circuit of pulsating non-Newtonian fluid. Individual fluid slipstreams were opacified with isobaric dyes, and images were recorded on film. The slipstreams entered the distal aneurysm neck with impact against the distal lateral wall of the aneurysm. They then swirled slowly in a reverse vortical pattern within the aneurysm sac. Fluid exited the aneurysm at the proximal neck. The flow pattern clearly shows the impact zone of entering slipstreams (the point of aneurysm rupture) and provides information pertaining to aneurysm growth and formation.

Aneurysm, Ruptured↗
PubMed1998

Why do ulcerated atherosclerotic carotid artery plaques embolize? A flow dynamics study.

PURPOSE: We describe and analyze flow dynamics and pressure relationships in an ulcerated atherosclerotic human carotid bulb. METHODS: Replicas of an ulcerated atherosclerotic human carotid bulb were created using the lost wax technique. The resulting replicas were placed in a circuit of pulsating non-Newtonian fluid and flows were adjusted to replicate human physiological flow profiles. Common carotid artery total flow volumes of 400, 600, and 800 mL/min were studied. Slipstreams were opacified with isobaric dyes. Images were recorded on 35 mm film and on super VHS video. A pressure recording device was calibrated; data were received from needles placed radially and longitudinally in the common carotid artery, narrowed bulb/ulcer, and internal carotid artery. Multiple pressure recordings were obtained in the replicas. RESULTS: Measurements of the replica showed a 59% diameter stenosis and an 88% area stenosis of the carotid bulb with a shallow 3.3-mm ulcer. Analysis of flow in the common carotid artery showed undisturbed slipstreams, but as these streams entered the narrowed carotid bulb they crowded together and accelerated significantly. This accelerated jet continued for at least two vessel diameters into the more normal portions of the internal carotid artery, where flow remained disturbed peripherally and often assumed a helical pattern but was nonturbulent. As fluid entered the narrowed bulb, radial pressures decreased. Most important, at peak systole, lower radial pressure with a vortex circulation was found at the ulceration. CONCLUSION: This combination of events (ie, slowly swirling fluid within the ulcer, allowing platelet aggregates to form, and the intermittent Bernoulli effect, pulling the aggregates into the rapidly flowing blood) may help explain how ulcerated carotid plaques lead to embolic stroke.

Arteriosclerosis↗
PubMedDate not supplied

Flow dynamics in a lethal anterior communicating artery aneurysm.

We describe and analyze the flow dynamics in replicas of a human anterior communicating artery aneurysm. The replicas were placed in a circuit of pulsating non-Newtonian fluid, and flows were adjusted to replicate human physiologic parameters. Individual slipstreams were opacified with isobaric dyes, and images were recorded on film and by CT/MR angiography. When flow in the afferent (internal carotid) and efferent (anterior and middle cerebral) arteries was bilaterally equal, slipstreams rarely entered the aneurysm. When flow in either the afferent or efferent vessels was not symmetrical, however, slipstreams entered the aneurysm neck, impinged upon the aneurysm dome, and swirled within the aneurysm. Unequal flow in carotid or cerebral systems may be necessary to direct pathologic, fluid slipstreams into an aneurysm.

Aneurysm, Ruptured↗