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.
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.
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.
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.
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).
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.
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%.
In these healthy animals, measurement of CBV with C-arm CT compared well with measurements made with PCT.
Recent advances in flat panel detector angiographic equipment have provided the opportunity to obtain physiologic and anatomic information from angiographic examinations. To exploit this possibility, ...one must understand the factors that affect the bolus geometry of an intra-arterial injection of contrast medium. It was our purpose to examine these factors in a canine model.
Under an institutionally approved protocol conforming to Guide for the Care and Use of Laboratory Animals of the National Institutes of Health, 7 canines were placed under general anesthesia with isoflurane and propofol. Through a 5F catheter placed into the right common carotid artery, a series of biplane angiographic acquisitions was obtained to examine the effects caused by variation in the volume of injection, the rate of injection, the duration of injection, the concentration of contrast medium, and the catheter position on arterial, capillary, and venous opacification. The results of each injection protocol were determined from analysis of a time-contrast concentration curve derived from locations over an artery, in brain parenchyma, and over a vein. The curve was generated from 2D digital subtraction angiography acquisitions by using prototype software. The area under the curve, the amplitude of the curve, and the time to peak (TTP) were analyzed separately for each injection parameter.
Changes in the injection protocols resulted in predictable changes in the time-concentration curves. The injection parameter that contributed most to maximum opacification was the volume of contrast medium injected. When the injection rate was fixed and the volume was varied, there was an increase in opacification (maximal) proportional to the injected volume. The injected volume also had an indirect (secondary) impact on the temporal characteristics of the opacification. The time-concentration curve became wider, and the peak was shifted to the right as the injection duration increased. The impact of injected volume on maximal opacification was significant (P < .0001), regardless of the site of measurement (artery, tissue, and vein); however, the impact on the temporal characteristics of the time-concentration curve reached statistical significance only in measurements made in the artery and the vein (P < .05), but not in the tissue (P > .1). The impact of injected volume on maximal opacification became nonproportional in the tissue and vein when the volume was very large (>12 mL). Increasing the concentration of contrast medium resulted in a nonproportional increase in the height of the time-concentration curves (P < .05). Injection rate had an impact on both maximal opacification and TTP. The impact on TTP occurred only when the injection rate was very slow (1 mL/s). Changes of concentration had a similar impact on the time-concentration curve. Catheter position did not cause significant alterations in the shape of the curves.
There were predictable effects from modification of injection parameters on the contrast bolus geometry and on time-concentration curves as measured in an artery, brain parenchyma, or a vein. The amplitude, TTP, and area under the time-concentration curve depend mainly and proportionally on the amount of iodine traversing the vasculature per second. Other injection parameters were of less importance in defining bolus geometry. These findings mimic those observed in studies of parameters affecting bolus geometry following an intravenous injection.
Assessment of perfusion parameters is important in the selection of patients who are most likely to benefit from revascularization after an acute ischemic stroke. The aim of this study was to ...evaluate the feasibility of measuring cerebral perfusion parameters with the use of a novel high-speed C-arm CT acquisition in conjunction with a single intravenous injection of contrast.
Seven canines had experimentally induced focal ischemic regions confirmed by CT perfusion imaging. Four hours after ischemic injury creation, each subject underwent cerebral perfusion measurements with the use of standard perfusion CT, immediately followed by the use of C-arm CT. Cerebral blood flow and cerebral blood volume maps measured by C-arm CT were quantitatively and qualitatively compared with those measured by perfusion CT for 6 of the 7 canine subjects.
Results from independent observer evaluations of perfusion CT and C-arm perfusion maps show strong agreement between observers for identification of ischemic lesion location. Significant percentage agreement between observers for lesion detection and identification of perfusion mismatch between CBV and CBF maps indicate that the maps for both perfusion CT and C-arm are easy to interpret. Quantitative region of interest-based evaluation showed a strong correlation between the perfusion CT and C-arm CBV and CBF maps (R(2) = 0.68 and 0.85). C-arm measurements for both CBV and CBF were consistently overestimated when compared with perfusion CT.
Qualitative and quantitative measurements of CBF and CBV with the use of a C-arm CT acquisition and a single intravenous injection of contrast agent are feasible. Future improvements in flat detector technology and software algorithms probably will enable more accurate quantitative perfusion measurements with the use of C-arm CT.
Exposure of the lung to concentrations of ozone found in ambient air is known to cause toxicity to the epithelial cells of the lung. Because of the chemical reactivity of ozone, it likely reacts with ...target molecules in pulmonary surfactant, a lipid-rich material that lines the epithelial cells in the airways. Phospholipids containing unsaturated fatty acyl groups and cholesterol would be susceptible to attack by ozone, which may lead to the formation of cytotoxic products. Whereas free radicalderived oxidized cholesterol products have been frequently studied for their cytotoxic effects, ozonized cholesterol products have not been studied, although they could reasonably play a role in the toxicity of ozone. The reaction of ozone with cholesterol yielded a complex series of products including 3β-hydroxy-5-oxo-5,6-secocholestan-6-al, 5-hydroperoxy-B-homo-6-oxa-cholestan-3β,7a-diol, and 5β,6β-epoxycholesterol. Mass spectrometry and radioactive monitoring were used to identify the major cholesterol-derived product during the reaction of 2 ppm ozone in surfactant as 5β,6β-epoxycholesterol, which is only a minor product during ozonolysis of cholesterol in solution. A dose-dependent formation of 5β,6β-epoxycholesterol was also seen during direct exposure of intact cultured human bronchial epithelial cells (16-HBE) to ozone. Studies of the metabolism of this epoxide in lung epithelial cells yielded small amounts of the expected metabolite, cholestan-3β,5α,6β-triol, and more abundant levels of an unexpected metabolite, cholestan-6-oxo-3β,5α-diol. Both 5β,6β-epoxycholesterol and cholestan-6-oxo-3β,5α-diol were shown to be cytotoxic to cultured 16-HBE cells. A possible mechanism for cytotoxicity is the ability of these oxysterols to inhibit isoprenoid-based cholesterol biosynthesis in these cells.
The aim of this study was to evaluate the safety and efficacy of stent graft coverage of hypogastric artery in the management of aortoiliac aneurysms. Between January 2000 and December 2002, 98 ...patients underwent endovascular repair of aortoiliac aneurysms (EVAR). Of these, 24 (24.5%) required occlusion of one hypogastric artery to facilitate the endovascular repair. Based on the method of hypogastric artery occlusion, patients were divided in to two groups. Group A (13/24 = 54%) underwent standard coil embolization followed by hypogastric artery orifice coverage whereas group B (11/24 = 46) underwent hypogastric artery orifice coverage without coil embolization. Post-EVAR computed tomographic angiography (CTA) was used to determine occurrence of endoleaks from the hypogastric artery orifice and patency of superior gluteal artery in both groups. These findings were further correlated with presence or absence of gluteal claudication. There was no difference in age (p < 0.38) or iliac aneurysm size (p < 0.3). In group A (13 patients), occlusion of superior gluteal artery was seen in 6 (46%). Four of six (66%) patients developed severe gluteal claudication. Patients in group A were likely to require more than one intervention (p < 0.00036). No patients in group B developed occlusion of the superior gluteal artery (p < 0.04) or gluteal claudication (p < 0.046). No endoleaks were seen from the origins of hypogastric artery in either group. The follow-up period ranged from 2 to 35 months. Hypogastric artery orifice coverage without coil embolization effectively prevented retrograde endoleak without the occurrence of disabling gluteal claudication. Coil embolization of the hypogastric artery may be unnecessary during treatment of aortoiliac aneurysm.
CBV is a key parameter in distinguishing penumbra from ischemic core. The purpose of this study was to compare CBV measurements acquired with standard PCT with ones obtained with C-arm CT in a canine ...stroke model.
Under an institutionally approved protocol, unilateral MCA strokes were created in 10 canines. Four hours later, DWI was used to confirm the presence of an infarct. CBV maps acquired with PCT were compared with ones acquired by using C-arm CT. Three experienced observers, blinded to the technique used for acquisition, evaluated the CBV maps.
An ischemic stroke was achieved in 9 of the 10 animals. Areas of reduced CBV were detected in 70%-75% of the PCT studies and in 83%-87% of the C-arm CT examinations, with false-positives in 1.7% and 3.3%, respectively. False-negatives were found in 25% of the PCT and 12.2% of the C-arm CT studies. In all studies, there was a significant difference between the absolute CBV values in normal and abnormal tissue (P < .005) and no significant difference between PCT and C-arm CT CBV values in either the normal or the abnormal parenchyma (P > .05).
CBV measurements made with C-arm CT compare well with ones made with PCT. While further work is required both to fully validate the technique and to define its ultimate clinical value, it appears that it offers a feasible method for assessing CBV in the angiography suite.
Measurement of perfusion parameters is typically done using an intravenous injection of contrast medium. This purpose of this study was to evaluate the feasibility of measuring regional and global ...CBV using C-arm CT with IA injections of contrast medium.
Twelve canines were studied. CBV measurement was performed using standard PCT, and then using C-arm CT with IV and IA contrast. Values obtained using C-arm CT were compared with those using PCT.
C-arm CT CBV maps using IA injections required less contrast than ones with IV injections. PCT and C-arm CT using IV and AA injections provided comparable maps. In controls, C-arm CT with a CCA or VA injection provided comparable maps to PCT. In animals with a stroke, a CCA or VA injection did not provide maps comparable to ones made with PCT. IV and AA C-arm CT showed excellent quantitative agreement with PCT, while CCA and VA C-arm CT studies did not.
Measurement of global CBV using C-arm CT in conjunction with either an IV or an AA injection was feasible in controls and dogs with a stroke. Measurement of regional CBV with C-arm CT using either CCA or VA injection, in normal canines, provided CBV maps qualitatively comparable with those obtained with PCT; the absolute CBV values from these maps were in poor agreement with PCT measurements. Valid measurement of CBV using C-arm CT requires all tissue in a target region to be fully and equally opacified during any acquisition. Using CCA or VA injections, it was impossible to document if and when this had been achieved. CBV measurements using these routes of injection were therefore not reliable.
Ozone toxicity in the lung is thought to be mediated by products derived from the reaction of ozone with components of the lung epithelial lining fluid. Cholesterol is an abundant component of this ...epithelial lining fluid, and it is susceptible to ozonolysis, yielding several stable products including 3beta-hydroxy-5-oxo-5,6-secocholestan-6-al and 5beta,6beta-epoxycholesterol. Both 5beta,6beta-epoxycholesterol and its metabolite, cholestan-6-oxo-3,5-diol, have been shown to cause cytotoxicity in vitro, suggesting that they may be potential mediators of ozone toxicity in vivo. An ozone-sensitive mouse strain, C57BL/6J, was exposed to varying concentrations of ozone (0.5-3.0 ppm), and subsequently the levels of these cholesterol ozonolysis products were quantitated by electrospray ionization mass spectrometry in bronchoalveolar lavage fluid, lavaged cells, and lung homogenate. An ozone dose-dependent formation of these biologically active oxysterols was observed in vivo, supporting a role for these compounds in ozone toxicity. Since the 5beta,6beta-epoxycholesterol metabolite, cholestan-6-oxo-3,5-diol, was isobaric with other cholesterol ozonolysis products, 3beta-hydroxy-5-oxo-5,6-secocholestan-6-al and its aldol condensation product, 3beta-hydroxy-5beta-hydroxy-B-norcholestan-6beta-carboxaldehyde, detailed mass spectral analysis using electron impact ionization was utilized to differentiate these isobaric cholesterol ozonolysis products. The specific detection of cholestan-6-oxo-3,5-diol in lung homogenate after ozone exposure established formation of 5beta,6beta-epoxycholesterol within the lung after exposure to 0.5 ppm ozone.
The most successful method for measuring absolute blood flow rate through the retinal circulation has been the use of radioactive microspheres. The purpose of this study was to develop a microsphere ...method that did not have the drawbacks associated with radioactivity and to use this method to make measurements of retinal blood flow in the cat. Blood flow measurements were made by injecting 15-μm-diameter polystyrene microspheres into the left ventricle of anesthetized, artificially ventilated cats. These microspheres were labeled with one of three fluorescent dyes. Retinal blood flow measurements were made by determining the number of spheres that were embedded in the retina and comparing them to the number found in a reference sample. Spheres in the retina were counted by making retinal whole mounts and taking retinal images with a CCD camera mounted on an epifluorescence microscope equipped with filter sets appropriate for imaging the dyes used to label the spheres. Blood flow measurements made under normal conditions showed a mean retinal blood flow of 19.8 ± 12.4 ml/min 100 g tissue (mean ± SD; n = 15 cats). Since the retinal circulation perfuses only the inner half of the retina, the effective flow rate in that region is about twice this value. RBF increased during hypoxemia (PaO2 < 42 mm Hg) to 336% of the normoxic value on average. Analysis of sphere deposition patterns showed that the central retina had a higher blood flow than the peripheral retina, although this difference was significant only during hypoxemia. We conclude that even with a relatively small number of spheres deposited in the retina, the technique can reveal important properties of the retinal circulation.
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