PubMed Health⌕ Search

Biomedical subjects

C W Kerber

Publications and source records attributed to C W Kerber.

At least 19 recordsLinked to original sources
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

Liquid acrylic adhesive agents in interventional neuroradiology.

Treating patients with brain arteriovenous malformations by the deposition of liquid embolic agents, particularly cyanoacrylates, requires judgment, technical expertise, and experience. Even though the first deposition of cyanoacrylate in human brain arteries occurred more than 25 years ago, the relative rarity of the disease and the high risk for complications has kept this procedure from being universally applied. Physicians are fortunate that, within the past year, new and better catheters have become available, and with the promise of approved cyanoacrylate devices that are now being evaluated, the future looks bright. This article reviews the history, chemistry, and uses of cyanoacrylate.

Acrylates↗
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

Observations on control of N2 and N3 neck disease in squamous cell carcinoma of the head and neck by intra-arterial chemoradiation.

Patients with head and neck squamous cell cancer with N2 and N3 neck disease have a poor prognosis and are at risk to fail regionally despite combined surgery and radiation. Twenty-two patients with N2 and N3 neck disease (and T3-4 primaries) were treated with intra-arterial, high-dose cisplatin (CDDP), 150 mg/m2 per week for 4 weeks, and concurrent radiation. All patients were followed for at least 2 years or until death from any cause. Twenty patients had a complete response at the primary site. Two of the 20 with a complete response later had a neck recurrence and died. Five patients with palpable nodes after treatment underwent fine-needle aspiration (FNA), one of which was positive and two suggestive of cancer. Six neck dissections were performed in this group, only two of which had positive nodes. This chemoradiation protocol may offer reasonable control of N2 and N3 neck disease in advanced head and neck squamous cell cancer. Neck dissection appeared to be necessary in only those patients with nodes 8 weeks after treatment in whom FNA was positive or suggestive of cancer. Because of the relatively small size of this series, additional accrual and monitoring of such patients is planned.

Adolescent↗
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↗
PubMed1998

An organ-preserving selective arterial chemotherapy strategy for head and neck cancer.

PURPOSE: Squamous cancer of the upper aerodigestive tract is a disheartening disease. Despite our best efforts, the long-term survival rate remains only 15% to 40%, and surgical cures often decrease the quality of life owing to the loss of swallowing and speech organs. A better understanding of tumor dynamics and the discovery that thiosulfate can neutralize cisplatin led us to develop a treatment plan that combines a rapid superselective high-dose intraarterial delivery of cisplatin (CDDP), simultaneous intravenous infusion of its antagonist, thiosulfate, and radiation therapy. METHODS: Patients with advanced head and neck squamous cancer were entered into the protocol after a multidisciplinary evaluation that included CT or MR imaging. Forty-two patients constituted the first cohort. After baseline angiography, an arterial acceptance test determined the maximum infusion rate that the tumor's nutrient artery would accept. CDDP was then infused at that rate, usually within 3 to 5 minutes, while the antagonist thiosulfate was given intravenously. In the second cohort of 85 patients with stage 3 or 4 previously untreated and unresectable disease, local radiation was added to the treatment plan. The radiation dose (180-200 cGy/d x 35) was delivered regionally on the basis of the known radiosensitizing effect of CDDP. RESULTS: Cohort 1 allowed us to develop the infusion technique and to establish a dose quantity and delivery frequency. When 150 mg/m2 was administered weekly for 4 weeks, no severe toxicity was found. In cohort 2, 72 (92%) of the remaining 78 patients had complete disappearance of their tumor. Seventeen severe toxic events were associated with 323 femoral catheterizations. One patient died of pulmonary embolus, precluding follow-up evaluation. Six patients had neurologic sequelae, three with transient and three with permanent strokes. CONCLUSION: Rapid superselective chemotherapy with CDDP combined with a circulatory systemic antagonist allowed delivery of an antitumoral drug directly into the lesion while protecting the kidneys and bone marrow from the agent's systemic effects. Use of a dose regimen of 150 mg CDDP/m2 per week for 4 weeks resulted in the disappearance of a large percentage of advanced squamous cancers.

Antineoplastic Agents↗
PubMed1997

Arteriovenous malformation model for training and research.

PURPOSE: To develop an arteriovenous malformation (AVM) model for teaching embolization techniques and for researching and developing new interventional devices. METHODS: Open pore cellulose sponges 2 to 5 cm in diameter were coated with a watertight elastomer. One to three afferent tubes (arteries) and one large efferent tube (vein) allowed insertion of the model into a circuit of pulsatile, flowing, non-Newtonian fluid. Using fluoroscopy and angiographic imaging, five neuroradiologists practiced occluding the AVM nidus with a variety of techniques and cyanoacrylate mixtures. RESULTS: The model appeared and behaved like a human brain AVM. Attempts to teach liquid adhesive techniques were successful, and though they were stressful for the trainee, failure had none of the disastrous sequelae that attend training with human subjects. CONCLUSION: The AVM training and research model is of value in introducing physicians to the techniques needed for endovascular cyanoacrylate therapy: it allows users to develop skills at their own rates, and permits safe "failure-mode" learning.

Angiography, Digital Subtraction↗
PubMed1996

Flow dynamics in a fatal aneurysm of the basilar artery.

PURPOSE: To examine the flow dynamics in a fatal aneurysm of the basilar artery in humans. METHODS: We made transparent elastic replicas of the vertebrobasilar arteries of an elderly patient who died of a ruptured aneurysm in the basilar artery. Using non-Newtonian fluid, physiological pulsatile flow volumes and profiles, and isobaric dyes and particles, we observed and recorded the slipstreams as they entered the aneurysm while changing relative flow in the vertebral arteries. Finally, we placed clips on the aneurysm, leaving residuals (or dog-ears), and observed the slipstreams. RESULTS: The aneurysm originated laterally from the greater curvature of a tortuous basilar artery, measured 19 x 11 x 12 mm, and had a Murphy's teat at the apex, the rupture site. The neck measured 10 x 4 mm, about the diameter of the basilar artery. Slipstreams joined at the confluence of the vertebral arteries, formed helical flow patterns, and entered the aneurysm violently, striking the apex. They then passed proximally around the sac walls, then centrally, and finally reentered the basilar artery to pass distally. Altering the relative flows in the vertebral arteries could modify and prevent slipstream flow into the aneurysm. When a dog-ear was created by incorrect placement of an aneurysm clip, slipstreams entered only dog-ears that lay distal to the clip. Correctly placed clips excluded the aneurysm from the circulation, but did not return the flow dynamics to normal. CONCLUSION: High-velocity slipstreams strike aneurysms at their rupture site and have an impact on distal but not proximal dog-ears. Modifying relative flow may prevent aneurysmal filling. Further, a knowledge of flow dynamics may allow us to predict which aneurysms are at risk of enlarging and rupturing, and may help guide proper therapy.

Aged↗
PubMed1995

Design and evaluation of a flow phantom.

RATIONALE AND OBJECTIVES: We constructed a near-anatomically correct large-vessel phantom to perform repeatable flow dynamics research examinations by angiography, magnetic resonance (MR) angiography, and computed tomography (CT) angiography. METHODS: An internal carotid artery was constructed within a head phantom. The internal carotid artery branches into a middle and an anterior cerebral artery; the former trifurcates and ends in the superior sagittal sinus, and the latter ends in the inferior sagittal sinus. A transverse and sigmoid sinus drains the model. All four vessels connecting the arterial and venous vessels have variable flow-constricting ligatures placed around them. These ligatures are accessible on the skull surface. The skull cavity is filled with a silicone polymer that is isodense to brain on CT scans and isointense on most MR images. RESULTS: The flow in the phantom's vessels may be varied in a repeatable manner. Multiple scan sequences may be performed without the image degradation caused by patient motion. The homogeneity of the filler polymer allows visualization of flow-related artifacts that may be hidden by complex human anatomy. CONCLUSION: Preliminary images of each modality show promise for use of the phantom in imaging research on large-vessel flow dynamics.

Cerebral Angiography↗
PubMed1994

Blood flow dynamics in the vertebrobasilar system: correlation of a transparent elastic model and MR angiography.

PURPOSE: To describe the flow patterns in a model of the vertebrobasilar artery and use these observations to explain the appearance of the flow on the MR images. METHODS: We created an anatomically precise, transparent elastic model of the human vertebrobasilar artery containing a basilar tip aneurysm and perfused the model with non-Newtonian fluid which has similar rheologic properties to blood. Flow patterns in the vessels were directly observed. MR angiogram images were obtained with commercially available two-dimensional time-of-flight, three-dimensional time-of-flight, and 3-D phase-contrast MR angiographic pulse sequences, and they were correlated with the directly seen flow patterns. Quantitative flow velocity measurements were performed with 2-D cine phase-contrast MR angiography and correlated with the flow measured with an electromagnetic flow meter. RESULTS: Visualization studies showed the dye stream patterns in the vertebrobasilar arteries to be extremely complex and variable. During the MR experiments we found that often the same segment of a vessel could appear very different depending on the pulse sequence. In some instances, the model experiments helped to explain the MR appearance of the vessels. Flow profiles measured with 2-D cine phase contrast were found to be consistent with those measured directly with an electromagnetic flow meter. CONCLUSION: Clear elastic models can be used to duplicate the flow in human cranial vessels and thus provide a unique means to observe these flow patterns directly. The flow patterns helped to explain the variation in appearance of the vessels and the artifacts with different MR angiography pulse sequences. The artifacts depend on both the geometry of the vessel and the flow pattern within it. Two-dimensional cine phase-contrast MR provides temporal flow field information that is directly related to physiological information about flow volumes and velocity patterns.

Adult↗
PubMed1994

Flow dynamics for radiologists. II. Practical considerations in the live human.

Although the rules about flows seem complex and even at times suggest chaos, some general principles can be extracted and used by the radiologist. Normal arteries damp disturbances, tolerate our catheters well, and generally cause the blood's slipstreams to swirl. It seems that the swirls and the energy that accompanies the passage of those swirls are prime determiners of the development of degenerative changes, most importantly of atherosclerosis and berry aneurysms. Knowing this, we now must direct our research to look beyond today's practical applications and this simplistic summary. Radiologists who trained during the angiography era are often incredulous when they see the richness of information found in physiologic flow models. For years, contrast agents have hidden the elegant complexity of blood flow. Now, however, we have two new powerful machines: the Doppler gray-scale ultrasound and the MR scanner. These machines routinely demonstrate flow data that we do not as yet use. As angiographers we have a natural and unconscious bias to make images produced by our new machines look like the classic angiogram. It is a powerful and pervasive bias. We still call angiography our "gold standard." We must overcome that bias. As valuable as angiography has been to radiology, it may no longer be our benchmark. A new standard is ready to be developed. The MR scanner even now not only allows calculation of global flow in vessels but also analyzes individual slipstreams. The images shown here are only the beginning. Keep our old mindset, and the limits and utility of the MR scanner will not be explored by radiologists. However, if we physicians, especially radiologists, reenter the field of fluid dynamics, all of science and our patients will benefit. We have broad shoulders to stand on and see into the future. Harvey, Hales, Galen, and Poiseuille: all were physicians; they added immeasurably to the foundations of rheology and our understanding of flowing blood. We must be willing to do likewise.

Aging↗
PubMed1993

Pulsatile flow artifacts in 3D magnetic resonance imaging.

Some of the important features of how pulsatile flow generates artifacts in three-dimensional magnetic resonance imaging are analyzed and demonstrated. Time variations in the magnetic resonance signal during the heart cycle lead to more complex patterns of artifacts in 3D imaging than in 2D imaging. The appearance and location of these artifacts within the image volume are shown to be describable as displacements along a line in a plane parallel to that defined by the phase and volume encode directions. The angle of the line in the plane depends solely upon the imaging parameters while the ghost displacement along the line is proportional to the signal modulation frequency. Aliasing of these ghosts leads to a variety of artifact patterns which are sensitive to the pulsation period and repetition time of the pulse sequence. Numerical simulations of these effects were found to be in good agreement with experimental images of an elastic model of a human carotid artery under simulated physiological conditions and with images of two human subjects.

Aged↗
PubMed1992

Multimodality treatment of deep periventricular cerebral arteriovenous malformations.

The surgical treatment of arteriovenous malformations (AVMs) located in deep periventricular regions such as the basal ganglia is associated with marked morbidity and mortality. Approaches through critical brain regions afford limited exposure of the lesions, while surgical dissection is sometimes complicated by acute severe brain swelling and/or hemorrhage in the surrounding tissues. In our approach to deep AVMs, our regimen has evolved from direct staged microsurgical excision under routine fentanyl-N2O-relaxant anesthesia (first four patients) to the use of elective high-dose barbiturate anesthesia (subsequent 12 patients). In the first group of four patients, 11 operations were performed. Two patients improved, one of whom returned to normal neurologically. There were three episodes of acute brain swelling and/or hemorrhage. One patient died as a result, and another deteriorated. In the second group of 12 patients, all but two lesions were completely excised. Among the 10 patients in whom the AVM was completely excised, seven improved, six of whom achieved a good to excellent outcome, with two regaining full neurologic function. Three patients worsened (one as the result of acute brain swelling and/or hemorrhage). There was no death in this group. Only one incidence of acute brain swelling and/or hemorrhage occurred in 26 operations. Even though the number of patients is too small in the first group for meaningful statistical comparison, our intraoperative observations and postoperative results suggest that our evolved multimodality regimen, such as staged excision and the use of elective high-dose barbiturates, was likely to have contributed to the improved treatment results of these formidable lesions.

Adolescent↗
PubMed1991

Hemodynamics of the central nervous system arteriovenous malformation nidus during particulate embolization. A computer model.

We have modelled the hemodynamics of the nidus of the central nervous system (CNS) arteriovenous malformation (AVM) during the process of particulate embolization. The model accurately reproduces the visually apparent incremental slowing observed during such embolization of CNS AVMs. The model is simple and proposes that the nidus is composed of many identical microchannels. As the microchannels are occluded by particles at a constant rate, the rate of change of flow reduction with each bolus of emboli constantly increases exponentially. A rapid reduction in apparent flow rate occurs immediately prior to complete occlusion. With a more accurate understanding of the working of the nidus of CNS AVMs we can increase the safety of therapeutic particulate embolization.

Cerebrovascular Circulation↗
PubMed1991

The anatomy of the cauda equina on CT scans and MRI.

The nerve roots of the cauda equina may be visualised by contrast-enhanced CT scans and by surface-coil MRI. We have identified the pattern of anatomy from L2-L3 to L5-S1 in 10 human cadaver specimens and correlated this with anatomical dissections. Individual roots are slightly more distinct on contrast-enhanced CT than on surface-coil MRI. There is a crescentic oblique pattern of nerve roots at the lower lumbar levels which is still apparent in the more crowded proximal sections. In all cases, the axial images correlated precisely with the dissections. Current imaging modalities can help the clinical understanding and management of abnormalities in this region of the spine.

Adult↗
PubMed1989

A case of hemorrhagic pineal cyst: MR/CT correlation.

A 30-year-old male had a headache for one month and was evaluated with both computed tomography (CT) and magnetic resonance (MR). These scans demonstrated an obstructing pineal cyst containing layered acute and subacute blood products by MR criteria. The concurrent scans allowed correlation between CT and MR findings in this rare complication of an unusual entity, explained his headache (and the development of later upward gaze paresis), provided a precise surgical/anatomic approach, and gave a good final clinical result. The report illustrates appropriate CT and MR images and pathological specimen.

Adult↗