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In the embryonic period, several developmental anomalies of the cerebral arteries occur. The knowledge of these anatomic variations of the cerebral artery is important to avoid the unnecessary surgery and to undergo surgery or interventional radiology with safety. We reviewed 3000 MR angiographies and 700 cerebral angiographies of the previous 5 years to assess cerebral arterial system, and to illustrate the embryological development, imaging findings, occurrence, and clinical significance of the anatomic variation of the cerebral arteries. The normal development and variations of the cerebral arteries are depicted. Knowledge of the anatomic variations is important since it can influence surgical and interventional procedure.

Nanocomposites of polystyrene (PS) with up to 20 wt% organoclay were prepared by melt compounding in a co‐rotating, intermeshing twin‐screw extruder. Three grades of PS with different molecular weights were used. In this paper we discuss preparation and characterization of the mixtures. Residence time and its distribution were measured by ultrasonics (US). They were found to be independent of the PS grade, but the US attenuation and sound velocity varied with the organoclay loading. According to the XRD diffraction data, the organoclay was dispersed into two types of platelet stacks evidenced by the diffraction peaks at about 2θ = 2.1 and 5.5°, i.e., with the interlayer spacings of d001 = 4.20 and 1.6 nm, respectively. Since neat organoclay has d001 = 1.93 nm, the first peak indicates intercalation by PS and the other a collapse of the interlamellar gallery during compounding. The XRD spectra depended on the organoclay content, but not on PS grade. According to TEM analysis, the degree of intercalation of organoclay in the polymer matrix is highest for the low‐molecular‐weight polystyrene. TEM results also confirm the collapse of interlamellar spacing in parts of the samples. FT‐IR spectroscopy showed that there was some thermal degradation of the onium compound present in the nanoclay. Polym. Eng. Sci. 44:1046–1060, 2004. © 2004 Society of Plastics Engineers.

On angiography, two types of intrahepatic portosystemic venous shunt were seen: intrahepatic portal venous-hepatic venous communication and intrahepatic portal venous-perihepatic venous communication. Transcatheter embolization is effective for treatment of intrahepatic portosystemic venous shunt. Retrograde transcaval obliteration is the least invasive technique and is recommended as the first choice for treatment of portosystemic venous shunt except in patients with multiple shunts.

ABSTRACT. The aim of this study was to evaluate the anatomy of and normal variations in the craniocervical junction veins. We retrospectively reviewed 50 patients who underwent contrast-enhanced CT with a multidetector scanner. Axial and reconstructed images were evaluated by two neuroradiologists with special attention being paid to the existence and size of veins and their relationships with other venous branches around the craniocervical junction. The venous structures contributing to craniocervical junction venous drainage, including the inferior petrosal sinus (IPS), transverse-sigmoid sinus, jugular vein, condylar vein, marginal sinus and suboccipital cavernous sinus were well depicted in all cases. The occipital sinus (OS) was identified in 18 cases, including 4 cases of prominent-type OS. The IPS showed variations in drainage to the jugular vein through the jugular foramen or intraosseous course of occipital bone via the petroclival fissure. In all cases, the anterior condylar veins connected the anterior condylar confluence to the marginal sinus; however, a number of cases with asymmetry and agenesis in the posterior and lateral condylar veins were seen. The posterior condylar vein connected the suboccipital cavernous sinus to the sigmoid sinus or anterior condylar confluence. The posterior condylar canal in the occipital bone showed some differences, which were accompanied by variations in the posterior condylar veins. In conclusion, there are some anatomical variations in the venous structures of the craniocervical junction; knowledge of these differences is important for the diagnosis and treatment of skull base diseases. Contrast-enhanced CT using a multidetector scanner is useful for evaluating venous structures in the craniocervical junction. Intracranial veins and venous sinuses converge to form major dural sinuses, the transverse sinus and the sigmoid sinus, which drain into extracranial veins. These major dural sinuses are connected by other venous structures at the skull base. These venous structures form complex venous networks that drain intracranial venous flow into extracranial veins at the craniocervical junction [1]. These venous structures are also known to have an important role as collateral pathways in cases of venoocclusive disease. The typical relationships between the craniocervical junction veins are shown in Figure 1. Knowledge of the anatomical relationships and variations of these veins is necessary not only for radiological diagnosis, but also when considering surgical or endovascular treatment of skull base diseases. Some investigators have previously reported the anatomy of and variations in these veins using anatomical and radiological methods with conventional angiography or contrast-enhanced MRI [2][3][4][5][6][7][8]. CT has been recognised as inadequate for evaluations of the posterior fossa owing to artefacts from bony structures; however, recent applications of multidetector row CT (MDCT) enable us to evaluate the posterior fossa with thin-sectional axial images and/o...

Renal arteriovenous (AV) shunt, a rare pathologic condition, is divided into two categories, traumatic and nontraumatic, and can cause massive hematuria, retroperitoneal hemorrhage, pain, and high-output heart failure. Although transcatheter embolization is a less-invasive and effective treatment option, it has a potential risk of complications, including renal infarction and pulmonary embolism, and a potential risk of recanalization. The successful embolization of renal AV shunt requires a complete occlusion of the shunted vessel while preventing the migration of embolic materials and preserving normal renal arterial branches, which depends on the selection of adequate techniques and embolic materials for individual cases, based on the etiology and imaging angioarchitecture of the renal AV shunts. A classification of AV malformations in the extremities and body trunk could precisely correspond with the angioarchitecture of the nontraumatic renal AV shunts. The selection of techniques and choice of adequate embolic materials such as coils, vascular plugs, and liquid materials are determined on the basis of cause (eg, traumatic vs nontraumatic), the classification, and some other aspects of the angioarchitecture of renal AV shunts, including the flow and size of the fistulas, multiplicity of the feeders, and endovascular accessibility to the target lesions. Computed tomographic angiography and selective digital subtraction angiography can provide precise information about the angioarchitecture of renal AV shunts before treatment. Color Doppler ultrasonography and time-resolved three-dimensional contrast-enhanced magnetic resonance angiography represent useful tools for screening and follow-up examinations of renal AV shunts after embolization. In this article, the classifications, imaging features, and an endovascular treatment strategy based on the angioarchitecture of renal AV shunts are described.

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IntroductionSpinal ventral epidural arteriovenous fistulas (EDAVFs) are relatively rare spinal vascular lesions. We investigated the angioarchitecture of spinal ventral EDAVFs and show the results of endovascular treatment.MethodsWe reviewed six consecutive patients (four males and two females; mean age, 67.3 years) with spinal ventral EDAVFs treated at our institutions from May 2011 to October 2012. All patients presented with progressive myelopathy. The findings of angiography, including 3D/2D reformatted images, treatments, and outcomes, were investigated. A literature review focused on the angioarchitecture and treatment of spinal ventral EDAVFs is also presented.ResultsThe EDAVFs were located in the ventral epidural space at the L1–L5 levels. All EDAVFs were supplied by the dorsal somatic branches from multiple segmental arteries. The ventral somatic branches and the radiculomeningeal arteries also supplied the AVFs in two patients. The AVFs drained via an epidural venous pouch into the perimedullary vein in four patients and into both the perimedullary vein and paravertebral veins in two patients. Four cases without paravertebral drainage were treated by transarterial embolization with diluted glue, and two cases with perimedullary and paravertebral drainages were treated by transvenous embolization alone or in combination with transarterial embolization. An angiographic cure was obtained in all patients. Clinical symptoms resolved in two patients, markedly improved in three patients, and minimally improved in one patient.ConclusionIn our limited experience, spinal ventral EDAVFs were primarily fed by somatic branches. EDAVFs can be successfully treated by endovascular techniques selected based on the drainage type of the AVF.