4D-DSA: Development and Current Neurovascular Applications.

Originally described by Davis et al in 2013, 4D-Digital Subtraction Angiography (4D-DSA) has developed into a commercially available application of DSA in the angiography suite. 4D-DSA provides the user with 3D time-resolved images, allowing observation of a contrast bolus at any desired viewing angle through the vasculature and at any time point during the acquisition (any view at any time). 4D-DSA mitigates some limitations that are intrinsic to both 2D- and 3D-DSA images. The clinical applications for 4D-DSA include evaluations of AVMs and AVFs, intracranial aneurysms, and atherosclerotic occlusive disease. Recent advances in blood flow quantification using 4D-DSA indicate that these data provide both the velocity and geometric information necessary for the quantification of blood flow. In this review, we will discuss the development, acquisition, reconstruction, and current neurovascular applications of 4D-DSA volumes.

Optimizing the Quality of 4D-DSA Temporal Information.

BACKGROUND AND PURPOSE: Quantification of blood flow using a 4D-DSA would be useful in the diagnosis and treatment of cerebrovascular diseases. A protocol optimizing identification of density variations in the time-density curves of a 4D-DSA has not been defined. Our purpose was to determine the contrast injection protocol most likely to result in the optimal pulsatility signal strength. MATERIALS AND METHODS: Two 3D-printed patient-specific models were used and connected to a pulsatile pump and flow system, which delivered 250-260 mL/min to the model. Contrast medium (Isovue, 370 mg I/mL, 75% dilution) was injected through a 6F catheter positioned upstream from the inlet of the model. 4D-DSA acquisitions were performed for the following injection rates: 1.5, 2.0, 2.5, 3.0 and 3.5 mL/s for 8 seconds. To determine pulsatility, we analyzed the time-density curve at the inlets using the oscillation amplitude and a previously described numeric metric, the sideband ratio. Vascular geometry from 4D-DSA reconstructions was compared with ground truth and micro-CT measurements of the model. Dimensionless numbers that characterize hemodynamics, Reynolds and Craya-Curtet, were calculated for each injection rate. RESULTS: The strongest pulsatility signal occurred with the 2.5 mL/s injections. The largest oscillation amplitudes were found with 2.0- and 2.5-mL/s injections. Geometric accuracy was best preserved with injection rates of >1.5 mL/s. CONCLUSIONS: An injection rate of 2.5 mL/s provided the strongest pulsatility signal in the 4D-DSA time-density curve. Geometric accuracy was best preserved with injection rates above 1.5 mL/s. These results may be useful in future in vivo studies of blood flow quantification.

Quantification of Blood Velocity with 4D Digital Subtraction Angiography Using the Shifted Least-Squares Method.

BACKGROUND AND PURPOSE: 4D-DSA provides time-resolved 3D-DSA volumes with high temporal and spatial resolutions. The purpose of this study is to investigate a shifted least squares method to estimate the blood velocity from the 4D DSA images. Quantitative validation was performed using a flow phantom with an ultrasonic flow probe as ground truth. Quantification of blood velocity in human internal carotid arteries was compared with measurements generated from 3D phase-contrast MR imaging. MATERIALS AND METHODS: The centerlines of selected vascular segments and the time concentration curves of each voxel along the centerlines were determined from the 4D-DSA dataset. The temporal shift required to achieve a minimum difference between any point and other points along the centerline of a segment was calculated. The temporal shift as a function of centerline point position was fit to a straight line to generate the velocity. The proposed shifted least-squares method was first validated using a flow phantom study. Blood velocities were also estimated in the 14 ICAs of human subjects who had both 4D-DSA and phase-contrast MR imaging studies. Linear regression and correlation analysis were performed on both the phantom study and clinical study, respectively. RESULTS: Mean velocities of the flow phantom calculated from 4D-DSA matched very well with ultrasonic flow probe measurements with 11% relative root mean square error. Mean blood velocities of ICAs calculated from 4D-DSA correlated well with phase-contrast MR imaging measurements with Pearson correlation coefficient r = 0.835. CONCLUSIONS: The availability of 4D-DSA provides the opportunity to use the shifted least-squares method to estimate velocity in vessels within a 3D volume.

Comparison of vessel contrast measured with a scanning-beam digital x-ray system and an image intensifier/television system.

Vessel contrast was measured in the fluoroscopic images produced by a scanning-beam digital x-ray (SBDX) system and an image intensifier/television (II/TV) based system. The SBDX system electronically scans a series of pencil x-ray beams across the patient, each of which is directed at a distant small-area detector array. The reduction in detected scatter achieved with this geometry was expected to provide an increase in image contrast. Vessel contrast was evaluated from images of a phantom containing iodinated tubes. The vessels were inserted into an acrylic stack to provide a patient-mimicking scattering medium. Vessel diameter ranged from 0.3 to 3.1 mm. Images were acquired at 100 kVp with the SBDX and II/TV systems and averaged to reduce x-ray noise. The II/TV system was operated in the 6-in. image intensifier mode with an anti-scatter grid. The increase in contrast in the SBDX images, expressed as a ratio of the measured SBDX and II/TV contrasts, ranged from 1.63 to 1.79 for individual vessels. This agreed well with a prediction of the contrast improvement ratio for this experiment, based on measurements of the scatter fraction, object-plane line spread functions, and consideration of the source spectrum and detector absorption properties. The predicted contrast improvement ratio for SBDX relative to II/TV images was 1.62 to 1.77.

Morphological, biochemical, and molecular changes in endothelial cells after alpha-particle irradiation.

The response of cultured bovine aortic endothelial (BAE) cells after exposure to alpha-particle radiation from chelated 212Bi has been evaluated. The results suggest that even relatively high doses of alpha-particle radiation from 212Bi (20-72 Gy) cause only minor acute changes in the morphology of BAE cells (light and electron microscopy) under conditions of confluent monolayer growth. Significant morphological changes can be detected in cells that detach from the monolayer, though it is unclear whether these changes represent a genuine response to irradiation or reflect the causes or effects of monolayer detachment with the consequent loss of intercellular biochemical communication. After alpha-particle irradiation (20-40 Gy) angiotensin-converting-enzyme activity was not detectable in the monolayer culture medium but was significantly decreased within the cell monolayer. Neutral-elution-assay data demonstrated that DNA double-strand-break (DSB) damage occurred in these cells and that about 35% of the DSBs were repairable.

Urokinase binding and receptor identification in cultured endothelial cells.

Recombinant human single-chain urokinase (rscu-PA), two-chain urokinase (tcu-PA), and diisopropyl-fluorophosphate-treated tcu-PA (DFP-tcu-PA) bound to cultured human and porcine endothelial cells in a rapid, saturable, dose-dependent and reversible manner. Analysis of specific binding results in cultured human umbilical vein endothelial cells (HUVECs) gave the following estimated values for Kd and Bmax: 0.57 +/- 0.08 nM (mean +/- S.E.) and 188,000 +/- 18,000 sites/cell for 125I-labeled rscu-PA; 0.54 +/- 0.10 nM and 132,000 +/- 23,900 sites/cells for 125I-labeled tcu-PA; 0.89 +/- 0.14 nM and 143,000 +/- 30,300 sites/cell for 125I-labeled DFP-tcu-PA, respectively. Values for Kd were similar for primary and subcultured (six passages) HUVECs, but Bmax values were lower in subcultured HUVECs. Similar Kd values were found in cultured porcine endothelial cells; however, Bmax values varied depending on the endothelial cell type. All 125I-labeled urokinase forms yielded similar cross-linked approximately 110-kDa ligand-receptor complexes with cultured HUVECs, and 125I-labeled DFP-tcu-PA bound to a single major approximately 55-kDa protein in whole-cell lysates (ligand blotting/autoradiography), suggesting the presence of a single major approximately 55-kDa urokinase receptor in cultured HUVECs. The approximately 55-kDa urokinase receptor, isolated from several separate batches of cultured HUVECs (3-5 micrograms of protein, approximately 1 x 10(9) cells), by ligand affinity chromatography, exhibited the following properties: retained biologic activity as evidenced by its ability to bind 125I-labeled rscu-PA by ligand blotting/autoradiography and formation of a cross-linked 125I-labeled approximately 110-kDa rscu-PA-receptor complex; single-chain approximately 55-kDa protein, following reduction; complete conversion to and formation of a single major deglycosylated approximately 35-kDa protein, following treatment with N-glycanase.

Lipolyzed hypertriglyceridemic serum and triglyceride-rich lipoprotein cause lipid accumulation in and are cytotoxic to cultured human endothelial cells. High density lipoproteins inhibit this cytotoxicity.

The cytotoxic effect of hypertriglyceridemic (HTG) serum and triglyceride-rich lipoprotein (TG-rich lipoprotein) lipolyzed in vitro by purified lipoprotein lipase on cultured human umbilical vein endothelial cells (HUVECs) was studied. When confluent cultures of HUVECs (8.4 x 10(4)/cm2) were incubated in the presence of control (non-lipolyzed HTG serum) or lipolyzed HTG serum or TG-rich lipoprotein, the lipolyzed HTG serum or TG-rich lipoprotein was cytotoxic to the HUVECs as indicated by their detachment from the culture dish; the lipolyzed serum at 10% of the culture medium or lipolyzed TG-rich lipoprotein at 75 micrograms cholesterol/ml caused the detachment of all (100%) of the cells from the culture dish after a 24 h incubation. Control (non-lipolyzed) HTG serum or non-lipolyzed TG-rich lipoprotein at the same or higher concentration was not cytotoxic to the cells. The HUVECs incubated for 48 h with low (sublethal) doses of lipolyzed TG-rich lipoprotein (10-50 micrograms cholesterol/ml) contained massive lipid inclusions; no lipid inclusions were seen within the cells when the culture medium contained control non-lipolyzed TG-rich lipoproteins. Finally, when high density lipoprotein (HDL) was added to the culture medium at the same concentration as the cytotoxic lipolyzed TG-rich lipoprotein (75 micrograms cholesterol/ml), the cytotoxic effect of the lipolyzed TG-rich lipoprotein was inhibited. These data suggest that the interaction of endothelial cells with lipolytic remnants of TG-rich lipoprotein may play a role in the pathogenesis of atherosclerosis and that HDL may play an important role in inhibition of the endothelial cell injury produced by the lipolytic remnants of TG-rich lipoprotein.

A monoclonal antigen-binding T cell immunoprotein: antigenic relatedness to T cell receptor beta chain FR1 V and J peptide segments: physicochemical distinctiveness from classical immunoglobulins and T cell receptor heterodimers.

The monoclonal murine T cell hybridoma, 51H7D, was previously shown to bind the arsazobenzene hapten and to produce a soluble antigen-binding molecule. In this paper we characterize this antigen-binding immunoprotein for its relationship to known T cell receptors serologically, using antibodies specific for variable region framework, or joining region peptides predicted from gene sequence and by biochemical means. The 51H7D cell expresses a protein with subunit size of approximately 31,000, that reacts antigenically with affinity-purified antibodies directed against synthetic first framework and joining segment peptides, corresponding to the gene sequence of the T cell receptor beta chain, YT35. This molecule does not react with affinity-purified antibodies directed against murine immunoglobulin, framework 1 sequences of alpha and gamma T cell receptors, or with antibodies against synthetic heavy chain joining segments. The subunit of mol. wt. 31,000 can form higher aggregates, notably in the mol. wt range of 60,000-70,000, depending upon extraction conditions. The soluble form of the antigen-binding molecule bears the J beta cross-reactive determinant and occurs predominantly as a charge restricted molecular species of approximate mol. wt 60,000-70,000. The purified molecule has a blocked N-terminus, but quantitative statistical analysis of its amino acid composition indicates a closer relatedness to T cell receptor beta chains and other antigen-binding T cell products, than it has to alpha, gamma or delta TCR chains. No evidence for more than one type of polypeptide chain was found and the polymerization is not dependent upon the formation of disulfide bonds. These studies raise the possibility that antigen-binding soluble T cell molecules might belong to a new family of immunoproteins, that is related to, but distinct from, classical immunoglobulins and alpha beta or gamma delta heterodimers.

Detection of human and marmoset immunoglobulin heavy chain by a polyclonal antiserum to a marmoset immunoglobulin-related T cell product.

We show that a polyclonal rabbit antiserum raised against a purified monoclonal T cell component from a lower primate (cotton-topped marmoset) reacts by immunoblot transfer (Western Blot analysis) with serum immunoglobulin of man and marmoset. The antigenic component had an approximate mass of 68 kilodaltons and was isolated by immune-affinity chromatography from culture fluid in which the marmoset T cell leukemia 70-N2 had been grown. The reaction with human serum immunoglobulin is with a subset of the IgG molecules and is localized to the gamma heavy chain. The reaction with marmoset serum immunoglobulin is predominantly directed against the heavy chain, but slight reactivity is also noted against the light chains. These results substantiate reports of serological cross-reactions between immunoglobulin-like T cell receptors and classical immunoglobulins and illustrate the similarity between immunoglobulins of man and those of a distantly related New World primate.

Identification of a low molecular weight polypeptide of pregnant bovine uterine origin (LMW-UDF): influence on coagulation system in vitro. Part I.

Acidified extracts of pregnant bovine uterus were found to contain a heparin-affinity polypeptide(s). The eluted peak was assayed in the Chandler loop method for whole blood and fibrin thrombus generation. Significant differences in the mean weight and size of whole blood thrombi (243.5 +/- 50 mg and 3.5 cm +/- 0.6 cm) occurred with 1 microgram of purified polypeptide when compared to control samples containing albumin (47.87 +/- .30 g and 0.8 cm +/- 0.3 cm). This activity was detected by the Chandler loop method with 100 ng to 10 micrograms of protein when analyzed in a dose-response fashion. When tested for fibrin thrombus formation this activity persisted. Experiments with 125I fibrinogen revealed no net increase or decrease of uptake into whole blood thrombi when purified polypeptide was added. The heparin-affinity polypeptide(s) possessed a molecular weight of approximately 6-4 kDa when examined by SDS-PAGE. We have therefore designated this polypeptide as low molecular weight-uterine derived factor (LMW-UDF).

The effect of hyperlipoproteinemia on thrombolysis: in vitro studies using purified lipoproteins from normolipemic donors.

To determine whether or not lipoproteins affect thrombolysis in vitro using Chandler's loop method, VLDL, LDL, and HDL fractions from healthy male donors were obtained by ultracentrifugation. The lipoproteins were used to enrich whole blood or fibrin thrombi radiolabeled with 125-I-fibrinogen. Lipoprotein-enriched or unenriched thrombi were perfused in rotating Chandler loops with lipoprotein-enriched or unenriched plasma, respectively. Lysis was initiated by adding high molecular weight urokinase or single chain pro-urokinase to the perfusion medium. In some experiments, plasminogen was also added. Variation in the amounts of these activators and plasminogen permitted study of the effect of lipoproteins over a range of thrombolysis. No consistent statistically significant difference in the degree or time course of lysis of lipoprotein-enriched vs. unenriched thrombi or perfusion media was found. These studies, using normal lipoproteins, do not preclude the possibility that lipoproteins from patients with type IIa, IIb, or IV hyperlipoproteinemia may be genetically abnormal or may function pathologically, resulting in an effect on thrombolysis.

The sagittal split osteotomy of the mandible.

Modifications of the sagittal split osteotomy of the mandible have essentially reduced the major drawbacks of the procedure, such as condyle displacement, short-term skeletal relapse, and protracted maxillomandibular fixation and mental nerve dysesthesia. These techniques have proved effective over a period of 4 years in fifty-seven patients treated.