Charles M. Strother

Early treatment of ruptured aneurysms with Guglielmi detachable coils: effect on subsequent bleeding.

The major causes of mortality and morbidity in patients surviving the rupture of a saccular aneurysm are subsequent bleeding and vasospasm. The purpose of this study was to evaluate the influence of early treatment of ruptured aneurysms with Guglielmi detachable coils on the incidence of subsequent bleeding. Thirteen patients were treated within 72 hours of initial aneurysm rupture with Guglielmi detachable coils. Excluding three patients who died 2, 4, and 12 weeks after initial hemorrhage, all others have been followed up for intervals between 6 and 36 months (mean, 16 mo). None of these have had either clinical or radiographic evidence of subsequent bleeding. Assuming that there is a 30% incidence of subsequent bleeding in conservatively (nonsurgically) treated patients, the 0% subsequent bleed rate observed in this subgroup was significant at a P value of 0.01. Only one procedure-related complication occurred in this series, and 9 of 13 (69%) aneurysms were 100% occluded at the time of initial treatment. All aneurysms were at least 90% occluded at the end of initial treatment. In addition to reducing the risk of subsequent bleeding, early treatment facilitated the institution of an aggressive approach for management of both vasospasm and increased intracranial pressure. Patient outcome, as measured by the Glasgow Outcome Scale, was good in 9 of 13 (69%), poor in 1 of 13 (8%), and death in 3 of 13 (23%) patients. The results of this study suggest that early Guglielmi detachable coil treatment of ruptured aneurysms may be effective in reducing the incidence of subsequent bleeding and can be performed with a low incidence of complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer modeling of intracranial saccular and lateral aneurysms for the study of their hemodynamics.

There is strong evidence indicating hemodynamic stress as an underlying cause for saccular intracranial aneurysm growth, thrombosis, and/or rupture. We examined flow fields encountered in models of cerebral aneurysms having a lateral (originating from the side of an artery, not at a branch point) geometric configuration. Shear stress and pressure gradients acting on aneurysm walls under a variety of flow and geometric conditions were evaluated. For this purpose, a two-dimensional finite-element computer model of lateral aneurysms in a steady-flow state was developed. Three idealized aneurysm shapes were studied, half-spherical, spherical, and pear-shaped. The ostium width of the cerebral aneurysm, relative to the radius of the parent artery and the Reynolds number, were also varied. Maximal shear stresses and maximum pressures (for an ostium width of 2 times the radius of the parent artery) were typically found at the downstream site of the ostium, rather than at the dome of the aneurysm. In general, the highest shear stresses and the lowest pressures (at the distal portion of the ostium) were obtained in the spherical aneurysm, whereas the lowest shear stresses and the highest pressures were found in the half-spherical aneurysm. The location of maximal stresses (shear and pressure) at the distal region of the ostium suggests that growth and/or rupture may well proceed from this point. Such findings are in contrast to the commonly held opinion that aneurysm rupture occurs at the dome. Careful pathological investigation will need to be performed to clarify this finding. The results of this preliminary investigation also indicate that the flow field in lateral aneurysms is highly dependent on a number of factors related to flow and geometric parameters. Geometry seems to be a significant mediator of local magnitudes of stress. Thus, the tendency for growth or thrombosis may be influenced by variations in size or shape.

Early Treatment of Ruptured Aneurysms with Guglielmi Detachable Coils

ABSTRACTTHE MAJOR CAUSES of mortality and morbidity in patients surviving the rupture of a saccular aneurysm are subsequent bleeding and vasospasm. The purpose of this study was to evaluate the influence of early treatment of ruptured aneurysms with Guglielmi detachable coils on the incidence of sub

Real-time MR imaging-guided passive catheter tracking with use of gadolinium-filled catheters.

PURPOSE To test the hypothesis that real-time magnetic resonance (MR) imaging-guided passive catheter tracking is feasible with use of dilute gadolinium (Gd)-filled catheters, to determine the optimal Gd concentration required for tracking, and to measure catheter tip tracking accuracy. MATERIALS AND METHODS The authors tested a real-time, T1-weighted, two-dimensional, spoiled gradient-recalled echo MR imaging sequence suitable for tracking catheters. In a yogurt phantom, the authors placed 5-F catheters filled with 2%-12% Gd solutions. MR imaging was performed with and without use of a projection dephaser that suppressed background signal. The authors measured signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and enhancement ratio to determine the optimal Gd concentration for catheter depiction. Catheter tip tracking accuracy was measured in an acrylic phantom with use of linear regression analysis, with goodness of fit assessed statistically with the F test. RESULTS Peak catheter SNR, CNR, and enhancement ratios were obtained with 4%-6% Gd concentrations. Tip tracking accuracy was determined to be +/- 0.41 mm (R2 = 0.99; P < .0001). MR imaging reconstructions were displayed up to 3.1 frames/sec. CONCLUSIONS Accurate MR imaging-guided passive catheter tracking was feasible in real-time with use of dilute Gd-filled catheters. This technique may have application in MR imaging-guided endovascular procedures.

Flat Detector CT in the Evaluation of Brain Parenchyma, Intracranial Vasculature, and Cerebral Blood Volume: A Pilot Study in Patients with Acute Symptoms of Cerebral Ischemia

BACKGROUND AND PURPOSE: The viability of both brain parenchyma and vascular anatomy is important in estimating the risk and potential benefit of revascularization in patients with acute cerebral ischemia. We tested the hypothesis that when used in conjunction with IV contrast, FD-CT imaging would provide both anatomic and physiologic information that would correlate well with that obtained by using standard multisection CT techniques. MATERIALS AND METHODS: Imaging of brain parenchyma (FD-CT), cerebral vasculature (FD-CTA), and cerebral blood volume (FD-CBV) was performed in 10 patients. All patients also underwent conventional multisection CT, CTA, CTP (including CBV, CTP-CBV), and conventional catheter angiography. Correlation of the corresponding images was performed by 2 experienced neuroradiologists. RESULTS: There was good correlation of the CBV color maps and absolute values between FD-CBV and CTP-CBV (correlation coefficient, 0.72; P < .001). The Bland-Altman test showed a mean difference of CBV values between FD-CT and CTP-CBV of 0.04 ± 0.55 mL/100 mL. All vascular lesions identified with standard CTA were also visualized with FD-CTA. Visualization of brain parenchyma by using FD-CT was poor compared with that obtained by using standard CT. CONCLUSIONS: Both imaging of the cerebral vasculature and measurements of CBV by using FD-CT are feasible. The resulting vascular images and CBV measurements compared well with ones made by using standard CT techniques. The ability to measure CBV and also visualize cerebral vasculature in the angiography suite may offer significant advantages in the management of patients. FD-CT is not yet equivalent to CT for imaging of brain parenchyma.

MR-guided angioplasty of renal artery stenosis in a pig model: a feasibility study.

PURPOSE To test the hypothesis that magnetic resonance (MR) imaging can guide the percutaneous treatment of renal artery stenosis in a pig model. MATERIALS AND METHODS Ameroid constrictors were surgically placed around six renal arteries in four pigs. After 30-36 days, all stenoses were documented by conventional x-ray aortograms. MR-guided renal angioplasty was attempted for three stenoses. For these pigs, MR angiography was performed with use of contrast-enhanced three-dimensional (3D) techniques. The authors visualized catheters by filling them with dilute 4% gadolinium and imaging with two-dimensional (2D) and 3D MR fast spoiled gradient recalled echo techniques. Under MR guidance, the authors advanced a selective catheter into the affected renal artery and crossed the stenosis with a nitinol guide wire. Angioplasty was performed with a balloon catheter filled with dilute gadolinium. Stenosis and luminal diameter measurements were compared before and after angioplasty. RESULTS After ameroid constrictor placement, four significant stenoses, one mild stenosis, and one occlusion developed. Under MR guidance, the authors achieved technical success in performing three of three (100%) attempted dilations. After MR-guided angioplasty, the mean reduction in stenosis was 35% and the mean increase in luminal diameter was 1.6 mm. CONCLUSION Use of MR guidance for the angioplasty of renal artery stenosis in pigs is feasible.

Parametric Color Coding of Digital Subtraction Angiography

BACKGROUND AND PURPOSE: Color has been shown to facilitate both visual search and recognition tasks. It was our purpose to examine the impact of a color-coding algorithm on the interpretation of 2D-DSA acquisitions by experienced and inexperienced observers. MATERIALS AND METHODS: Twenty-six 2D-DSA acquisitions obtained as part of routine clinical care from subjects with a variety of cerebrovascular disease processes were selected from an internal data base so as to include a variety of disease states (aneurysms, AVMs, fistulas, stenosis, occlusions, dissections, and tumors). Three experienced and 3 less experienced observers were each shown the acquisitions on a prerelease version of a commercially available double-monitor workstation (XWP, Siemens Healthcare). Acquisitions were presented first as a subtracted image series and then as a single composite color-coded image of the entire acquisition. Observers were then asked a series of questions designed to assess the value of the color-coded images for the following purposes: 1) to enhance their ability to make a diagnosis, 2) to have confidence in their diagnosis, 3) to plan a treatment, and 4) to judge the effect of a treatment. The results were analyzed by using 1-sample Wilcoxon tests. RESULTS: Color-coded images enhanced the ease of evaluating treatment success in >40% of cases (P < .0001). They also had a statistically significant impact on treatment planning, making planning easier in >20% of the cases (P = .0069). In >20% of the examples, color-coding made diagnosis and treatment planning easier for all readers (P < .0001). Color-coding also increased the confidence of diagnosis compared with the use of DSA alone (P = .056). The impact of this was greater for the naïve readers than for the expert readers. CONCLUSIONS: At no additional cost in x-ray dose or contrast medium, color-coding of DSA enhanced the conspicuity of findings on DSA images. It was particularly useful in situations in which there was a complex flow pattern and in evaluation of pre- and posttreatment acquisitions. Its full potential remains to be defined.

C-Arm CT Measurement of Cerebral Blood Volume: An Experimental Study in Canines

BACKGROUND AND PURPOSE: Cerebral blood volume (CBV) is an important parameter in estimating the viability of brain tissue following an ischemic event. We tested the hypothesis that C-arm CT measurements of CBV would correlate well with those made with perfusion CT (PCT). MATERIALS AND METHODS: CBV was measured in 12 canines by using PCT and C-arm CT. Two measurements with each technique were made on each animal; a different injection protocol was used for each of these techniques. PCT was performed by using a 64-section V-scanner. C-arm CT was performed by using a biplane Artis dBA system. PCT images were transferred to a commercially available workstation for postprocessing and analysis; C-arm CT images were transferred to a commercially available workstation for postprocessing and analysis by using prototype software. From each animal, 2 sections from each technique were selected for analysis. RESULTS: There was good agreement of both the color maps and absolute numbers between the 2 techniques. The maximum and mean deviations of values between the 2 techniques for the first 5 animals were 30.20% and 7.82%; for the second 7 animals, these values were 26.79% and 7.40%. The maximum and mean deviations between the 2 C-arm CT studies performed on the first 5 animals were 33.15% and 12.24%; for the second 7 animals, these values were 41.15% and 10.89%. CONCLUSIONS: In these healthy animals, measurement of CBV with C-arm CT compared well with measurements made with PCT.

Treatment of arteriovenous malformations with stereotactic radiosurgery employing both magnetic resonance angiography and standard angiography as a database

Twenty-one arteriovenous malformations were prospectively evaluated using magnetic resonance angiography and compared with stereotactic angiography. The goals were to establish the feasibility of magnetic resonance angiography, compare it to stereotactic angiography, employ magnetic resonance angiography in follow-up, and semiquantify flow. A correlative evaluation between flow and response to stereotactic radiosurgery was carried out. Phase contrast angiograms were obtained at flow velocities of 400, 200, 100, 60, and 20 cm/sec. The fractionated velocities provided images that selectively demonstrated the arterial and venous components of the arteriovenous malformations. Qualitative assessment of the velocity within the arteriovenous malformations and the presence of fistulae were also determined by multiple velocity images. In addition, 3-dimensional time-of-flight magnetic resonance angiograms were obtained to define the exact size and shape of the nidus. This technique also permitted evaluation of the nidus and feeding arteries for the presence of low flow aneurysms. Correlation between the two imaging modalities was carried out by subjective and semiquantitative estimation of flow velocity and estimation of nidus size. The following velocity parameters were employed: fast, intermediate, slow, and none (arteriovenous malformation obliterated). In 19 of 21 (90.5%) arteriovenous malformations, magnetic resonance angiography was equal or superior to stereotactic angiography for flow quantification and visualization of the nidus. Only 2 of 21 arteriovenous malformations were better demonstrated by stereotactic angiography than by magnetic resonance angiography (failure rate of 9.5%). The nidus size in one case was clearly underestimated by stereotactic angiography and would have resulted in a geographic miss without magnetic resonance angiography. Seven post-radiosurgery arteriovenous malformations were evaluated for follow-up with both magnetic resonance angiography and stereotactic angiography. In 6 of 7 arteriovenous malformations, magnetic resonance angiography response matched stereotactic angiography response. Correlation of flow with outcome was carried out for 14 arteriovenous malformations using magnetic resonance angiography only. Interestingly, all nine arteriovenous malformations with intermediate or slow flow demonstrated partial or complete obliteration; whereas only 3 of 5 fast flow arteriovenous malformations achieved a response with a median follow-up of 10 months. This early analysis suggests that slower flowing arteriovenous malformations may obliterate faster after stereotactic radiosurgery and flow parameters could be employed to predict response. In conclusion, magnetic resonance angiography permits semiquantitative flow velocity assessment and may therefore be superior to stereotactic angiography. An additional advantage of magnetic resonance angiography is the generation of serial transverse images which can replace the conventional CT scan employed for stereotactic radiosurgery treatment planning.(ABSTRACT TRUNCATED AT 400 WORDS)

Determination of Optimal Injection Parameters for Intraarterial Gadolinium-enhanced MR Angiography

PURPOSE Rapid vascular depiction with use of a minimum of gadolinium (Gd) contrast agent will be required to generate road-map vascular images for magnetic resonance (MR) imaging-guided endovascular interventions. The objective of this study was to optimize intraarterial injections of MR contrast agent during magnetic resonance angiography (MRA), obtained during interventions, by determining the optimal Gd vascular concentration ([Gd]) for vessel depiction. MATERIALS AND METHODS The authors derived theoretical expressions to estimate the [Gd] resulting in maximal signal in blood. A model was developed to account for flow dilution to estimate [Gd] given the injected Gd concentration, injection rate, and the blood flow rate. Experiments in four animals (three dogs, one pig) were conducted to verify this model with use of both time-resolved two-dimensional (2D) thick-slab and single-phase three-dimensional (3D) MRA acquisitions. The authors also determined the optimal [Gd] required for vessel depiction in animal models. RESULTS The theoretical expressions yielded optimal [Gd] of 10.2 mmol/L in blood. The animal experiments used the flow dilution model and examined signal enhancement in the aorta and the renal and iliac arteries. Maximal enhancement occurred at [Gd] = 16.2 +/- 4.0 mmol/L (mean +/- SE). CONCLUSIONS The theoretically predicted values for [Gd]optimal and the flow dilution model were successfully validated. The relationship between injected [Gd], injection rate, and blood flow rate permits rapid intraarterial administration of contrast material, using less overall contrast material than with standard intravenous Gd-enhanced MRA.