AIMThe recent introduction to clinical practice of multidetector helical angio CT (MHACT) has generated a new interest in the diagnosis of carotid artery atherosclerosis. In recent years there has been a redefinition of the indications to carotid artery endarterectomy; there is a tendency to appraise plaque morphology and composition, and not only stenosis degree. The aim of this prospective study is to analyze the validity of MHACT in the diagnosis of atheromasic stenosis of the carotid bifurcation, in comparison with US color Doppler (USCD), digital subtraction angiography (DSA) and intraoperative evidence (OP). Special emphasis is given to the analysis of plaque composition and to precise evaluation of the stenosis percentage computed as an area rate on oblique reconstructions performed exactly orthogonal to the axis of the vessel at the point of maximal stenosis.METHODSTwenty-seven carotid stenosis (in 24 patients) were preoperatively evaluated by USCD, MHACT, DSA. We calculated the stenosis degree with USCD, by the ECST method, both as a diameter rate and as a bidimensional value. By MHACT we computed the percentage of stenosis as an area rate, in an MPR oblique plane orthogonal to the vessel axis, at the point of maximal stenosis; by DSA we used NASCET and the common carotid artery method (CC). DSA measurements have been mathematically converted as area rate (NASCET2 and CC2). All the patients were operated on with the eversion technique (EEA); it was always possible to obtain an intact cylindrical specimen of the plaque and to perform a reliable and accurate evaluation of the degree of stenosis by sectioning and measuring it on the desk. We gave a score to the presence and amount of lipid and calcium components, and these data were compared to those obtained with the different diagnostic instruments.RESULTSStatistical analysis of the 7 data sets showed an important underestimate of the angiographical method (DSA), even if the measurements were carried on by a precision caliper. The mathematical conversion of a linear stenosis rate into an area rate gives these values more reliability, indicating, as for NASCET2, non statistically significant differences when compared to surgical evidence, notwithstanding a high standard deviation. The rates obtained by USCD (area rate) and MHACT proved to be very accurate with respect to surgical evidence. In this study there was no significant difference in the detection of various components (lipid and calcium) of the atheromasic lesion, by MHACT and surgical evidence (OP).CONCLUSIONMHACT promises to be a very accurate instrument in the detection of plaque components and identification of the stenosis degree. It shows some limits in very calcific lesions and occasionally, in relevant cardiac failure, may be useless. Hence one feels the need to reassess the role of DSA, once considered the "gold standard", with more extensive prospective studies, including comparison with MHACT and USCD.

A methodology for patient-specific model reconstruction and computational mesh generation of arterial bifurcations from angio-CT scans is presented. Three-dimensional models were reconstructed with a level set technique, analyzed with a skeletoning algorithm and automatically decomposed into branches. Cooper scheme was then employed to generate high quality hexahedral mesh. We successfully applied our technique to the carotid bifurcations of two patients affected by severe atherosclerotic plaques. The proposed technique is fast, accurate and reproducible, and can be a useful tool for the evaluation of arterial fluid dynamics within conventional computed tomography investigations.

Vascular accesses (VA) for hemodialysis are usually created by native arteriovenous fistulas (AVF) or synthetic grafts. Maintaining patency of VA continues to be a major problem for patients with end-stage renal disease, since in these vessels thrombosis and intimal hyperplasia often occur. These lesions are frequently associated with disturbed flow that develops near bifurcations or sharp curvatures. We explored the possibility of investigating blood flow dynamics in a patient-specific model of end-to-end native AVF using computational fluid dynamics (CFD). Using digital subtraction angiographies of an AVF, we generated a three-dimensional meshwork for numerical analysis of blood flow. As input condition, a time-dependent blood waveform in the radial artery was derived from centerline velocity obtained during echo-color-Doppler ultrasound examination. The finite element solution was calculated using a fluid-dynamic software package. In the straight, afferent side of the radial artery wall shear stress ranged between 20 and 36 dynes/cm2, while on the inner surface of the bending zone it increased up to 350 dynes/cm2. On the venous side, proximal to the anastomosis, wall shear stress was oscillating between negative and positive values (from -12 dynes/cm2 to 112 dynes/cm2), while distal from the anastomosis, the wall shear stress returned within the physiologic range, ranging from 8 to 22 dynes/cm2. Areas of the vessel wall with very high shear stress gradient were identified on the bending zone of the radial artery and on the venous side, after the arteriovenous shunt. Secondary blood flows were also observed in these regions. CFD gave a detailed description of blood flow field and showed that this approach can be used for patient-specific analysis of blood vessels, to understand better the role of local hemodynamic conditions in the development of vascular lesions.

OBJECTIVE:We have investigated recurrence of stroke in a consecutive series of young adults, aged 16 to 45 years, after a first cerebral infarction. METHODS:From January 1, 1988 to December 31, 1996 we submitted those patients to a diagnostic protocol including angiographic, cardiological, and haematological investigations. The patients were followed at 6 month intervals up to December 31, 1998. RESULTS:We have evaluated and followed-up 135 patients, 71 men and 64 women, who were 3.99% of all the admitted stroke patients. At 12 months after stroke, 83 patients had returned to work, 40 patients were mildly to moderately handicapped, 4 were using a wheel-chair, and 8 had died. Follow-up was 26 to 123 months (mean 68.8). Recurrence of stroke, always of ischaemic nature, was seen in 15 patients (11.1%), 3 to 76 months after the first stroke (mean 27.4), for an annual incidence of 2.26%. Recurrence was significantly associated with Partial Anterior Circulation Syndrome and Haematological subtype of first stroke (respectively, P = 0.0209 and P = 0.0135, chi2 test), but not with age (< or = or > 35 years) or risk factors. Repetition of stroke was never fatal, but it caused heavy disability in 13 patients, 8 of whom had completely or nearly completely recovered after the first event. CONCLUSIONS:Our data suggest that recurrence of stroke is a major clinical problem also for the patients aged less than 45 years and that it might be more frequent with specific clinical syndromes and etiologic subtypes of first stroke.

OBJECTIVES:To evaluate the presence of microembolic signals (MES) in the middle cerebral artery distal to a stented carotid artery late after stent deployment. MES may be a signal of thrombus formation at the stent level.PATIENTS AND METHODS:Two patient groups were studied with transcranial Doppler at different intervals after deployment of Palmaz stents or Wallstents for stenosis of the internal or common carotid artery. Group 1: from 6 to 12 months after stent deployment; Group 2: > 12 months after stenting.RESULTS:One out of 19 patients in Group 1 showed MES (5.0%); however, this patient also had two mechanical heart valves. None out of 17 patients in Group 2 had MES.CONCLUSIONS:Carotid stents seem to have a very low emboligenic potential after the early post-deployment period. This is a reassuring message for present and future patients harboring such stents.

Since 1989 we performed stereotactic radiotherapy treatments of cerebral arterovenous malformations (AVM), estimating three-dimensional (3-D) localization and shape of target volumes by the Leksell stereotactic helmet on two orthogonal radiographic projections. Due to the limitations of this method, we developed a new technique for the localization of the target volume using digital subtraction angiography (DSA) and digital image processing. To achieve this result we first developed a method to correct nonlinear distortion of DSA images using spatial relocation of image pixels based on a calibration grid. We then developed an algorithm for localization of the target volume using two independent DSA projections. Target volume coordinates in the helmet system are calculated using two DSA acquisitions taken with a free angle (approximately 90 degrees), one in the AP and the other in the LL direction. The helmet can be freely positioned between the x-ray source and the image plane. The projections of eight reference points inserted in the helmet at a known location, are used to calculate the transformation matrix between the two coordinate systems. We performed numerical and experimental validation of the system. A hypothetical random error (up to 2 mm) on image coordinates of the reference points allowed to determine that the error in target localization was less than 0.2 mm. Using DSA images of target points with a known location within a phantom, the error between calculated and actual location was, on average, 0.30+/-0.13 mm (mean+/-SD), with a maximum error of 0.49 mm. The results of numerical and experimental validations show that the system we have developed allows fast and accurate localization of the center of the target volume and it is suitable for efficient guiding during stereotactic radiosurgery of AVM.

OBJECTIVES:To report experience of intra-arterial thrombolysis for acute stroke, performed with a microcatheter navigated into the intracranial circulation to impale the clot.METHODS:Patients were selected on the following criteria: (1) clinical examination suggesting a large vessel occlusion in stroke patients between 18 and 75 years; (2) no radiographic signs of large actual ischaemia on CT at admission; (3) angiographically documented occlusion of the middle cerebral artery (MCA) stem or of the basilar artery (BA), without occlusion of the ipsilateral extracranial internal carotid artery or of both the vertebral arteries; (4) end of the entire procedure within six hours of stroke. 12 patients with acute stroke were recruited, eight of whom had occlusion of the MCA stem and four of the BA. Urokinase was used as the thrombolytic agent.RESULTS:Complete recanalisation in six MCA stem and in two BA occurred, and partial recanalisation in two MCA stem and one BA. There was no recanalisation in one BA. A clinically silent haemorrhage occurred in two patients, and a parenchymal haematoma in one patient, all in MCA occlusions. At four months five patients achieved self sufficiency (four with MCA and one with BA occlusion). Six patients were dependent (three totally), and one died.CONCLUSIONS:The strict criteria of eligibility allowing the enrollment of very few patients and the procedure itself, requiring particular neuroradiological expertise, make this procedure not routine. Nevertheless, the approach can be considered a possible option for patients with acute ischaemic stroke.

Si descrive un caso di occlusione delle vene cerebrali superficiali del gruppo ventro laterale, con particolare coinvolgimento della vena di Labbé. L'analisi della letteratura clinica e radiologica esistente su questa rara patologia consente di riferire su alcuni elementi di particolare originalità.