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Biomedical subjects

D F Kallmes

Publications and source records attributed to D F Kallmes.

At least 91 records · Page 5Linked to original sources
PubMed1997

Thrombogenicity of hydrophilic and nonhydrophilic microcatheters and guiding catheters.

PURPOSE: To assess in a swine model the in vivo thrombogenicity of various microcatheters and guiding catheters as a function of catheter material, catheter coating, and duration of implantation. METHODS: Microcatheters (Tracker 18 and Fastracker 18, Target Therapeutics, Fremont, Calif; Magic 1.8, Balt, Montmorency, France; and Transit, Cordis Endovascular Systems, Miami Lakes, Fla) were placed through 6F guiding catheters (Fasguide, Target Therapeutics, and Envoy, Cordis Endovascular Systems) into the common carotid arteries of swine for 30 minutes (short term), 90 minutes (medium term), and 35 days (long term). Guiding catheters were implanted for 5 hours. At the end of the implantation periods the catheters were retracted and fixed for scanning electron microscopy. RESULTS: The surface of the Fastracker microcatheter was devoid of debris after both short- and medium-term implantation. The Tracker microcatheter had minimal accumulation of cellular elements whereas the Transit microcatheter showed moderate accumulation of nondeformed red blood cells. Neither the Tracker nor the Transit microcatheter showed evidence of increasing debris accumulation after medium-term implantation as compared with short-term implantation. The Magic microcatheter was coated with gross thrombus after both short- and medium-term implantation. The Fasguide guiding catheter was nearly devoid of debris, while the Envoy guiding catheter had moderate thrombus formation. Long-term implantation of the Fastracker microcatheter was well tolerated whereas that of the Transit catheter resulted in vessel occlusion. CONCLUSIONS: Hydrophilic microcatheters and guiding catheters are less thrombogenic than their nonhydrophilic counterparts, but not all hydrophilic coatings are equally hypothrombogenic. Degree of thrombogenicity depends on catheter material rather than surface morphology. Medium-term implantation did not yield increasing thrombus formation relative to short-term implantation.

Animals↗
PubMed1997

Cost-effectiveness of angiography performed during surgery for ruptured intracranial aneurysms.

PURPOSE: To calculate the incremental cost-utility ratio for routine angiography performed during surgery for ruptured cerebral aneurysms. METHODS: Decision-tree and Markov analyses based on a cohort simulation were used to determine the incremental cost-utility ratio of routine intraoperative angiography versus no angiography. Input data from the literature were estimated for the following variables: frequency of unexpected aneurysmal rests and branch artery occlusions; annual rate of rehemorrhage of partially clipped aneurysms; prevalence of clinically relevant infarction resulting from branch artery occlusion; efficacy of clip repositioning; morbidity associated with intraoperative angiography; morbidity and mortality associated with aneurysmal rehemorrhage; sensitivity of intraoperative angiography for aneurysmal rests; and costs of intraoperative angiography, added duration of surgery, ischemic cerebral infarction, aneurysmal rehemorrhage, and rehabilitation. Sensitivity analyses were performed for all relevant input variables. A societal perspective was used, and cost-utility ratios less than $50000/quality-adjusted life years (QALY) gained were considered acceptable. RESULTS: Baseline input variables resulted in an acceptable cost-utility ratio for routine intraoperative angiography ($19000/QALY). The input variables with greatest influence on the cost-utility ratio were frequency of branch artery occlusions, angiographic morbidity, and cost of angiography. However, the cost-utility ratio remained acceptable even over wide ranges of these input variables. Frequency of unexpected partially clipped aneurysms, efficacy of clip repositioning, and costs of stroke, rehemorrhage, and rehabilitation had relatively little impact on the analysis. CONCLUSION: Routine intraoperative angiography is cost-effective if performed in a manner consistent with low morbidity in a patient cohort harboring at least some unexpected branch artery occlusions that, if uncorrected, would result in clinically relevant cerebral infarctions.

Adult↗
PubMed1996

Molecular methods of enhancing lumbar spine fusion.

OBJECTIVE: An optimal method for spinal fusion would induce rapid growth of bone via an osteoconductive and osteoinductive implant. This study examines the spinal fusion enhancement potential of some osteoconductive and osteoinductive biomaterials. METHODS: Four similar canines received unilateral posterolateral fusions on the left side at T13-L1 and L4-L5 and on the right side at L2-L3 and L6-L7. The experiments were grouped as follows: Group A, autogenous bone harvested from the iliac crest; Group B, autogenous bone and collagen; Group C, no implant; and Group D, autogenous bone, collagen, and recombinant human bone morphogenetic protein-2. Radiographic assessment, three-dimensional computed tomographic volumetric analysis, and biomechanical testing were performed at each level. RESULTS: For Groups A and B, the fusions demonstrated moderate bone formation at 6 and 12 weeks postoperatively. Group D fusions exhibited earlier and more dramatic increases in volume and radiodensity and eventually were comparable in size to the vertebral bodies. Average fusion volumes computed from three-dimensional computed tomographic analysis were: Group A = 1.243 cc, Group B = 0.900 cc, Group C = 0.000 cc, and Group D = 6.668 cc (P = 0.003 compared to Group A). Group D exhibited flexion and extension biomechanical properties much greater than controls. The addition of recombinant human bone morphogenetic protein-2 consistently yielded the strongest fused segments and, on average, enhanced extension stiffness by 626% and flexion stiffness by 1120% over controls. CONCLUSION: The most advantageous spinal fusion implant matrix consisted of recombinant human bone morphogenetic protein-2, autogenous bone, and collagen. Future investigators, however, need to examine the appropriate quantities of the individual components and clarify the efficacy of the matrix for the various types of spinal fusion approaches.

Animals↗
PubMed1996

Optimization of parameters for the detection of cerebral aneurysms: CT angiography of a model.

PURPOSE: To optimize parameters with computed tomographic angiography for the detection of cerebral aneurysms. MATERIALS AND METHODS: Model aneurysms were placed randomly at various branch points and scanned multiple times with spiral technique. The final analysis included 63 branch points and 22 aneurysms. Each spiral scan used a different parameter combination. Collimation ranged from 1.5 to 4.0 mm and pitch ranged from 1:1 to 1.5:1. Images were constructed with shaded surface display (SSD) and maximum intensity projection (MIP) algorithms and were interpreted by three readers for the presence or absence of aneurysm. RESULTS: The receiver operating characteristic (ROC) curve area for 1.5-mm collimation was greater than those of 3- or 4-mm collimation (P < .01 and P < .001, respectively). There was no statistically significant difference in the ROC curve areas between 3- and 4-mm collimation (P = .37). There was no statistically significant decrease in ROC curve area when increasing pitch from 1:1 to 1.5:1 for any value of collimation (P = .96). For all parameter combinations the ROC curve areas for SSD images was greater than that of MIP images (P < .0001). CONCLUSION: For cerebral aneurysm detection, narrow collimation is superior to wider collimation. Mild increases in pitch do not substantially degrade diagnostic accuracy. SSD offers improved diagnostic accuracy over MIP display in this model.

Algorithms↗
PubMed1996

Ruptured vertebrobasilar aneurysms: frequency of the nonaneurysmal perimesencephalic pattern of hemorrhage on CT scans.

PURPOSE: To determine the frequency of the computed tomographic (CT) pattern of nonaneurysmal perimesencephalic subarachnoid hemorrhage in the setting of ruptured posterior fossa aneurysms. MATERIALS AND METHODS: Four neuroradiologists independently and retrospectively reviewed cranial CT scans of 169 patients with ruptured vertebrobasilar aneurysms (44 cases of posteroinferior cerebellar artery aneurysm, 20 cases of superior cerebellar artery aneurysm, and 105 cases of basilar-tip aneurysm). RESULTS: The mean frequency of nonaneurysmal perimesencephalic pattern of subarachnoid hemorrhage in ruptured vertebrobasilar aneurysms was 7.1% (48 of 676 readings) among the four readers. The mean frequency of aneurysms with the pattern of hemorrhage for each location was as follows: basilar tip, 9.8% (41 of 420 readings); superior cerebellar artery, 5.0% (four of 80 readings); and posteroinferior cerebellar artery, 0%. In 75% (six of eight) of the cases in which the CT pattern of hemorrhage was deemed compatible by all readers with nonaneurysmal hemorrhage, the clinical presentation was mild. CONCLUSION: Because ruptured posterior fossa aneurysms manifest with the nonaneurysmal pattern of hemorrhage in approximately 10% of cases, a high degree of suspicion should be maintained even if the pattern of subarachnoid hemorrhage suggests a nonaneurysmal origin and clinical symptoms are mild.

Aneurysm, Ruptured↗
PubMed1996

Specificity of MR angiography as a confirmatory test of carotid artery stenosis.

PURPOSE: To estimate from available literature the specificity (true-negative rate) of MR angiography for detecting severe carotid artery stenoses when applied as a confirmatory test after screening with duplex Doppler sonography. METHODS: We reviewed the pertinent MR angiographic literature published between 1990 and 1994 and recalculated the specificity of MR angiography after deleting from the database results for normal vessels and for vessels with mild and moderate stenoses, since the study of these vessels is not germane to an exploration of the utility of MR angiography as a confirmatory test. RESULTS: Seventeen articles provided data for our analysis. We divided vessels into four categories on the basis of data supplied within each article. Seven of the articles provided data that could be configured to match the categories used in the North American Symptomatic Carotid Endarterectomy Trial (NASCET). In one study, the criterion of severe stenosis was more than 70% construction, but the moderate category was limited to stenoses of 50% to 69%. The remaining series defined severe stenoses as more than 80% (four series), more than 75% (two series), or more than 60% (three series) constriction. The stated specificity of MR angiography ranged from 64% to 100%. Before revision, 15 of 17 articles had stated specificity values above 75%. Our recalculated values ranged from 18% to 100%. Only seven of 17 studies would have had MR angiographic specificity of greater than 75%. Nine of 17 articles would have had specificities of less than 60%. For all articles specifically identifying vessels with false-positive findings at sonography, the specificity of MR angiography was 16%. CONCLUSION: To base specificity values for MR angiography as a confirmatory test of carotid artery stenosis on studies that include nondiseased vessels incurs spectrum bias. The actual specificity for MR angiography as a confirmatory test remains unknown, but it is lower than that reported in the literature.

Bias↗
PubMed1996

Acquired lumbar spinal stenosis.

Based on the individual clinical presentation and radiographic findings, an operation that completely decompresses the neural elements in the spinal canal and neural foramina followed by posterior, posterolateral, or interbody fusion, with or without instrumentation should be the procedure of choice in the future. The introduction of pharmacological agents to decrease scarring around the decompressed nerve roots will also increase the number of successful procedures. It must be stressed, however, that any new operative technique must be tested in a rigorous fashion, ideally with a prospective randomized clinical trial.

Humans↗
PubMedDate not supplied

In vivo evaluation of a new type I collagen hemostatic plug for high-risk, large-core biopsies.

PURPOSE: To evaluate in a swine model the hemostatic properties of a new, expansile type I collagen plug for use in high-risk renal biopsies. MATERIALS AND METHODS: Highly purified bovine type I collagen was formed into porous cylindrical plugs and compressed radially to fit into a 5-F delivery system. On hydration these collagen plugs demonstrated radial expansion with approximately 1,600% volumetric expansion ratio. Direct exposure of both kidneys was performed in a 25-kg swine, and a bolus of 3,000 U of heparin was administered to create a coagulopathic state. A 14-gauge Temno coaxial biopsy gun was utilized in performing nine pairs of renal biopsies. The first biopsy of each biopsy pair represented the control biopsy (without collagen plug placement), whereas the second biopsy of each pair represented the plugged biopsy. The presence and duration of hemorrhage from each biopsy site was monitored visually. RESULTS: The biopsy sites without collagen plug showed immediate hemorrhage in nine of nine cases (100%), and in two of nine cases (22%) pulsatile bleeding was noted. With the use of the collagen plug, seven of nine (78%) sites showed immediate hemorrhage, but in no case was pulsatile bleeding noted. Mean bleeding duration was 156 seconds for the control biopsies versus 73 seconds for the biopsy sites plugged with collagen (P = .03, Mann-Whitney rank sum test). Bleeding duration was less than 1 minute in only one of nine (11%) control biopsies compared to six of nine (67%) collagen plug biopsies. CONCLUSIONS: A recently developed, expansile collagen hemostatic plug significantly decreases the duration of hemorrhage at renal biopsy sites in an anticoagulated swine model.

Animals↗
PubMedDate not supplied

The fate of neuroradiologic abstracts presented at national meetings in 1993: rate of subsequent publication in peer-reviewed, indexed journals.

BACKGROUND AND PURPOSE: Abstract presentations are a valuable means of rapidly conveying new information; however, abstracts that fail to eventually become published are of little use to the general medical community. Our goals were to determine the publication rate of neuroradiologic papers originally presented at national meetings in 1993 and to assess publication rate as a function of neuroradiologic subspecialty and study design. METHODS: Proceedings from the 1993 ASNR and RSNA meetings were reviewed. A MEDLINE search encompassing 1993-1997 was performed cross-referencing lead author and at least one text word based on the abstract title. All ASNR and RSNA neuroradiologic abstracts were included. Study type, subspecialty classification, and sample size were tabulated. Publication rate, based on study design and neuroradiologic subspecialty, was compared with overall publication rate. Median duration from meeting presentation to publication was calculated, and the journals of publication were noted. RESULTS: Thirty-seven percent of ASNR abstracts and 33% of RSNA neuroradiologic abstracts were published as articles in indexed medical journals. Publication rates among neuroradiologic subspecialty types were not significantly different. Prospective studies presented at the ASNR were published at a higher rate than were retrospective studies. There was no difference between the publication rate of experimental versus clinical studies. Neuroradiologic abstracts were published less frequently than were abstracts within other medical specialties. Median time between abstract presentation and publication was 15 months. CONCLUSION: Approximately one third of neuroradiologic abstracts presented at national meetings in 1993 were published in indexed journals. This rate is lower than that of abstracts from medical specialties other than radiology.

Abstracting and Indexing↗
PubMedDate not supplied

Value of bone scan imaging in predicting pain relief from percutaneous vertebroplasty in osteoporotic vertebral fractures.

BACKGROUND AND PURPOSE: Patient selection for percutaneous vertebroplasty is often complicated by the presence of multiple fractures or non-localizing pain. Our purpose was to determine whether increased activity revealed by bone scan imaging is predictive of a positive clinical response to percutaneous vertebroplasty. METHODS: A retrospective chart review conducted at our institution yielded 28 vertebroplasty treatment sessions that had been performed after obtaining bone scan imaging for painful, osteoporotic compression fractures in 27 patients. Thirty-five compression fractures were treated during these 28 treatment sessions. In all cases, increased activity was revealed by bone scan imaging before treatment with vertebroplasty. Positive outcome was defined as subjective decrease in pain severity and/or increased level of patient mobility. RESULTS: Subjective pain relief was noted in 26 (93%) of 28 treatment sessions. In 14 (100%) of 14 cases with quantifiable pain levels, pain improved at least 3 points on a 10-point scale (range of improvement, 3-10 points; mean improvement, 7.4 points). Among the remaining 14 treatment sessions in which patients were unable or unwilling to quantify pain severity, the pain relief was described as complete or excellent pain relief in 11 (78%) of 14 cases. In 14 (100%) of 14 cases for which semiquantitative assessment of mobility was available, mobility improved at least one level (5-point graded scale; range of improvement, 1-4 points; mean improvement, 1.7 points). CONCLUSIONS: Increased activity revealed by bone scan imaging is highly predictive of positive clinical response to percutaneous vertebroplasty.

Aged↗
PubMedDate not supplied

Elastase-induced saccular aneurysms in rabbits: comparison of geometric features with those of human aneurysms.

BACKGROUND AND PURPOSE: The development of more effective intracranial aneurysm therapy depends on the ability to test various intravascular occlusion devices and techniques in preclinical animal models. This requires the creation of experimental aneurysms, which, ideally, should mimic the size and geometric features of human intracranial aneurysms. The purpose of this study was to characterize the morphologic features of elastase-induced saccular aneurysms in rabbits to determine whether the morphology of such aneurysms mimics that of human intracranial aneurysms. METHODS: Elastase-induced saccular aneurysms were created in 40 New Zealand white rabbits. Intravenous digital subtraction angiography was performed 14 days after surgery. Relative to an external sizing device, the following dimensions were determined: aneurysm dome (height and width), aneurysm neck diameter, and parent artery diameter. Based on maximal diameter, aneurysms were categorized as small (2.0-4.9 mm), medium-sized (5.0-9.9 mm), or large (10-16 mm), and as narrow-necked (<4.0 mm neck width) or wide-necked (>4.0 mm neck width). Mean dome-neck ratio was calculated and compared with that of human aneurysms. RESULTS: All aneurysm cavities were angiographically patent. Widths of the cavities ranged from 2.5 to 7.1 mm (mean, 4.1 +/- 1.2 mm); heights ranged from 3.0 to 15.6 mm (mean, 8.8 +/- 2.6 mm). Three (7.5%) of 40 aneurysms were small, 20 (50%) were medium-sized, and 17 (42.5%) were large. Twenty-two (55%) of 40 aneurysms were small-necked, and 18 (45%) were wide-necked. Mean dome-neck ratio was 1.13 +/- 0.54. Mean parent artery diameter was 4.3 +/- 1.4 mm. CONCLUSION: Saccular aneurysms of sizes similar to that of human intracranial aneurysms were reliably created using a simple method of vessel ligation and elastase injury. Neck sizes varied with both large and small-necked aneurysms created.

Angiography, Digital Subtraction↗
PubMedDate not supplied

Age of fracture and clinical outcomes of percutaneous vertebroplasty.

BACKGROUND AND PURPOSE: The patient populations that are most likely to benefit from percutaneous vertebroplasty (PVP) are uncertain. Our purpose was to evaluate the effect of the age of vertebral compression fracture (VCF) on clinical improvement after PVP. METHODS: We performed a retrospective review of charts of patients who had undergone PVP for painful osteoporotic VCFs at our institution. The preprocedural and postprocedural outcome measurements of pain, mobility, and analgesic use were compared for 80 treatment sessions in 75 patients (122 total vertebrae treated). We assessed the association between the duration of pain before PVP and postprocedural outcomes by using multivariable analysis. RESULTS: Age of fracture at time of PVP was not independently associated with postprocedural pain or activity. Increasing age of fracture was independently associated with slightly greater postprocedural analgesic requirement, at least for patients who required narcotics at baseline before PVP. Greater preprocedural analgesic requirement was independently associated with greater postprocedural analgesic requirement. Reduced preprocedural mobility was independently associated with reduced postprocedural mobility. CONCLUSION: PVP is a highly efficacious therapy for relief of pain and improvement in mobility, regardless of fracture age. PVP also is efficacious in reducing analgesic requirement, although this effect may be slightly blunted in patients who require narcotics before the procedure and in those who have older fractures.

Adult↗
PubMedDate not supplied

Use of the ulnar artery as an alternative access site for cerebral angiography.

Although the common femoral artery is the easiest and most widely accepted access site for cerebral angiography, atherosclerotic, aortoiliac, or femoral artery disease can preclude this approach. We describe our experience using the ulnar artery access site in a patient with bilateral aortoiliac occlusive disease. This article may be useful to neuroradiologists who encounter difficulty with other arterial access sites. A description of the technique and a review of the pertinent literature are provided.

Aged↗