L. Cirillo

GLISTR: Glioma Image Segmentation and Registration

We present a generative approach for simultaneously registering a probabilistic atlas of a healthy population to brain magnetic resonance (MR) scans showing glioma and segmenting the scans into tumor as well as healthy tissue labels. The proposed method is based on the expectation maximization (EM) algorithm that incorporates a glioma growth model for atlas seeding, a process which modifies the original atlas into one with tumor and edema adapted to best match a given set of patients images. The modified atlas is registered into the patient space and utilized for estimating the posterior probabilities of various tissue labels. EM iteratively refines the estimates of the posterior probabilities of tissue labels, the deformation field and the tumor growth model parameters. Hence, in addition to segmentation, the proposed method results in atlas registration and a low-dimensional description of the patient scans through estimation of tumor model parameters. We validate the method by automatically segmenting 10 MR scans and comparing the results to those produced by clinical experts and two state-of-the-art methods. The resulting segmentations of tumor and edema outperform the results of the reference methods, and achieve a similar accuracy from a second human rater. We additionally apply the method to 122 patients scans and report the estimated tumor model parameters and their relations with segmentation and registration results. Based on the results from this patient population, we construct a statistical atlas of the glioma by inverting the estimated deformation fields to warp the tumor segmentations of patients scans into a common space.

Epidemiology and genetics of intracranial aneurysms

Intracranial aneurysms are acquired lesions (5-10% of the population), a fraction of which rupture leading to subarachnoid hemorrhage with devastating consequences. Until now, the exact etiology of intracranial aneurysms formation remains unclear. The low incidence of subarachnoid hemorrhage in comparison with the prevalence of unruptured IAs suggests that the vast majority of intracranial aneurysms do not rupture and that identifying those at highest risk is important in defining the optimal management. The most important factors predicting rupture are aneurysm size and site. In addition to ambiental factors (smoking, excessive alcohol consumption and hypertension), epidemiological studies have demonstrated a familiar influence contributing to the pathogenesis of intracranial aneurysms, with increased frequency in first- and second-degree relatives of people with subarachnoid hemorrhage. In comparison to sporadic aneurysms, familial aneurysms tend to be larger, more often located at the middle cerebral artery, and more likely to be multiple. Other than familiar occurrence, there are several heritable conditions associated with intracranial aneurysm formation, including autosomal dominant polycystic kidney disease, neurofibromatosis type I, Marfan syndrome, multiple endocrine neoplasia type I, pseudoxanthoma elasticum, hereditary hemorrhagic telangiectasia, and Ehlers-Danlos syndrome type II and IV. The familial occurrence and the association with heritable conditions indicate that genetic factors may play a role in the development of intracranial aneurysms. Genome-wide linkage studies in families and sib pairs with intracranial aneurysms have identified several loci on chromosomes showing suggestive evidence of linkage, particularly on chromosomes 1p34.3-p36.13, 7q11, 19q13.3, and Xp22. For the loci on 1p34.3-p36.13 and 7q11, a moderate positive association with positional candidate genes has been demonstrated (perlecan gene, elastin gene, collagen type 1 A2 gene). Moreover, 3 of the polymorphisms analyzed in 2 genes (endothelial nitric oxide synthase T786C, interleukin-6 G572C, and interleukin-6 G174C) were found to be significantly associated with ruptured/unruptured aneurysms: the endothelial nitric oxide synthase gene single-nucleotide polymorphisms increased the risk, while IL-6 G174C seemed protective. More recently, two genomic loci (endothelin receptor A and cyclin-dependent kinase inhibitor 2BAS) have been found to be significantly associated with intracranial aneurysms in the Japanese population; endothelin-1 is a potent vasoconstrictor produced by the endothelial cells. Until now, there are no diagnostic tests for specific genetic risk factors to identify patients who are at a high risk of developing intracranial aneurysms. Knowledge of the genetic determinants may be useful in order to allow clues on stopping aneurysm formation and obtain diagnostic tools for identifying individuals at increased risk. Further multicenter studies have to be carried out.

Treatment of Intracranial Aneurysms Using Flow-Diverting Silk Stents (BALT): a Single Centre Experience

The Silk stent (Balt, Montmorency, France) is a retractable device designed to achieve curative reconstruction of the parent artery associated with an intracranial aneurysm. We present our initial experience with the Silk flow-diverting stent in the management and follow-up of 25 patients presenting with intracranial aneurysms. Twenty-five patients (age range, 34–81 years; 24 female) were treated with the Silk flow-diverting device. Aneurysms ranged in size from small (5), large (10) and giant (10) and included wide-necked aneurysms, multiple, nonsaccular, and recurrent intracranial aneurysms. Nine aneurysms were treated for headache, 14 for mass effect. None presented with haemorrhage. All patients were pretreated with dual antiplatelet medications for at least 72 hours before surgery and continued taking both agents for at least three months after treatment. A total of 25 Silk stents were used. Control MR angiography and/or CT angiography was typically performed prior to discharge and at one, three, six and 12 months post treatment. A follow-up digital subtraction angiogram was performed between six and 19 months post treatment. Complete angiographic occlusion or subtotal occlusion was achieved in 15 patients in a time frame from three days to 12 months. Three deaths and one major complication were encountered during the study period. Two patients, all with cavernous giant aneurysms, experienced transient exacerbations of preexisting cranial neuropathies and headache after the Silk treatment. Both were treated with corticosteroids, and symptoms resolved completely within a month. In our experience the Silk stent has proven to be a valuable tool in the endovascular treatment of intracranial giant partially thrombosed aneurysms and aneurysms of the internal carotid artery cavernous segment presenting with mass effect. The time of complete occlusion of the aneurysms and the risk of the bleeding is currently not predictable.

Complications in the Treatment of Intracranial Aneurysms with Silk Stents: an Analysis of 30 Consecutive Patients

Flow-diverting stents (Silk and PED) have radically changed the approach to intracranial aneurysm treatment from the use of endosaccular materials to use of an extraaneurysmal endoluminal device. However, much debate surrounds the most appropriate indications for the use of FD stents and the problems raised by several possible complications. We analysed our technical difficulties and the early (less than ten days after treatment) and late complications encountered in 30 aneurysms treated comprising 13 giant lesions, 12 large, five with maximum diameters <10 mm and one blister-like aneurysm. In our experience the primary indications for the use of FD stents can be the symptomatic intracavernous giant aneurysms. Although the extracavernous carotid siphon aneurysms have major risk of bleeding, FD stents are indicated clearly explaining the risks to the patient in case of severe mass effect. There is a very complex assessment for aneurysms of the vertebrobasilar circulation.

Traumatic anterior glenohumeral instability: quantification of glenoid bone loss by spiral CT

PurposeWe evaluated the role of computed tomography (CT) for quantifying glenoid bone defects in patients with anterior glenohumeral instability and assisting in planning the most appropriate type of surgery.Materials and methodsFrom January to November 2006, 93 patients were studied by spiral CT with multiplanar reconstructions (MPR) for recurrent posttraumatic anteroinferior instability, chronic multidirectional instability and recurrent glenohumeral dislocation after surgical stabilisation.ResultsQuantitative CT enabled us to measure bone defects of the anteroinferior glenoid in terms of area (mm2) or surface percentage. Glenoid osseous defects were classified as small (<15%), medium (15%–20%), and large (>20%).ConclusionsCT quantification of glenoid bone loss is very accurate as well as rapid, simple and easily reproducible. CT therefore provides an important contribution to preoperative selection of patients, assisting in directing those with <20% bone loss towards arthroscopic capsular repair.RiassuntoObiettivoValutare l’efficacia della TC nel quantificare esattamente il deficit osseo glenoideo in pazienti con instabilità gleno-omerale antero-inferiore, per la pianificazione del corretto approccio chirurgico.Materiali e metodiNel periodo compreso tra gennaio e novembre 2006, sono stati sottoposti a TC spirale e successive elaborazioni MPR (Multi-Planar-Recostruction), 93 pazienti giunti alla nostra osservazione per instabilità recidivante post-traumatica anteroinferiore, instabilità cronica multidirezionale e recidiva di lussazione dopo intervento di stabilizzazione.RisultatiLa valutazione quantitativa ha permesso di calcolare con esattezza il deficit osseo del bordo glenoideo antero-inferiore in termini di area (espressa in mm2) o di percentuale di superficie. Le dimensioni del difetto sono stato classificate come: piccolo (<15%), medio (tra il 15% ed il 20%) e grande (>20%).ConclusioniLa metodica da noi utilizzata rende possibile quantificare con estrema precisione il deficit osseo, con una tecnica semplice, rapida e facilmente riproducibile, fornendo così un contributo fondamentale nella selezione pre-operatoria dei pazienti, indirizzando verso l’intervento di capsuloplastica artroscopica i pazienti con un difetto osseo inferiore al 20%.

Comparison of 3D TOF-MRA and 3D CE-MRA at 3 T for imaging of intracranial aneurysms

PURPOSE To compare 3T elliptical-centric CE MRA with 3T TOF MRA for the detection and characterization of unruptured intracranial aneurysms (UIAs), by using digital subtracted angiography (DSA) as reference. MATERIALS AND METHODS Twenty-nine patients (12 male, 17 female; mean age: 62 years) with 41 aneurysms (34 saccular, 7 fusiform; mean diameter: 8.85 mm [range 2.0-26.4mm]) were evaluated with MRA at 3T each underwent 3D TOF-MRA examination without contrast and then a 3D contrast-enhanced (CE-MRA) examination with 0.1mmol/kg bodyweight gadobenate dimeglumine and k-space elliptic mapping (Contrast ENhanced Timing Robust Angiography [CENTRA]). Both TOF and CE-MRA images were used to evaluate morphologic features that impact the risk of rupture and the selection of a treatment. Almost half (20/41) of UIAs were located in the internal carotid artery, 7 in the anterior communicating artery, 9 in the middle cerebral artery and 4 in the vertebro-basilar arterial system. All patients also underwent DSA before or after the MR examination. RESULTS The CE-MRA results were in all cases consistent with the DSA dataset. No differences were noted between 3D TOF-MRA and CE-MRA concerning the detection and location of the 41 aneurysms or visualization of the parental artery. Differences were apparent concerning the visualization of morphologic features, especially for large aneurysms (>13 mm). An irregular sac shape was demonstrated for 21 aneurysms on CE-MRA but only 13/21 aneurysms on 3D TOF-MRA. Likewise, CE-MRA permitted visualization of an aneurismal neck and calculation of the sac/neck ratio for all 34 aneurysms with a neck demonstrated at DSA. Conversely, a neck was visible for only 24/34 aneurysms at 3D TOF-MRA. 3D CE-MRA detected 15 aneurysms with branches originating from the sac and/or neck, whereas branches were recognized in only 12/15 aneurysms at 3D TOF-MRA. CONCLUSION For evaluation of intracranial aneurysms at 3T, 3D CE-MRA is superior to 3D TOF-MRA for assessment of sac shape, detection of aneurysmal neck, and visualization of branches originating from the sac or neck itself, if the size of the aneurysm is greater than 13 mm. 3T 3D CE-MRA is as accurate and effective as DSA for the evaluation of UIAs.

The use of flow-diverting stents in the treatment of giant cerebral aneurysms: Preliminary results

The treatment of giant cerebral aneurysms has always been a challenge for neurosurgeons and neuroradiologists. Flow-diverting stents (Silk; Pipeline Embolization Device) are new endovascular devices introduced for the treatment of intracranial aneurysms without release of intrasaccular coils. They are tubular bimetallic endoluminal devices with low porosity. We have employed these stents in the Neuroradiology Unit of Bellaria Hospital (Bologna, Italy) since the end of 2008, treating nine patients with giant carotid cerebral aneurysms using nine Silk stents as soon as the device obtained the CE mark. All patients were pretreated with dual antiplatelet medications before surgery. The Silk stents were deployed through a 4F Balt introducer, which ensured an uneventful and very quick procedure. Control CT angiography or MR angiography was typically performed at discharge and one, three, six and 12 months after treatment. Post-treatment results were: four complete occlusions, three near complete occlusions (residual neck flow) with reduced volume of the aneurysm and two more than 50% reduction of intra-aneurysmal flow. A fatal hemorrhagic complication occurred in one patient, probably due to the antiplatelet treatment. The Silk stent seems a very interesting curative device to treat giant aneurysms with preservation of the parent artery and small adjacent branches. Technical improvements will certainly reduce the thrombogenic effect with the related risks.

A Minimally Invasive Treatment for Lumbar Disc Herniation: DiscoGel® Chemonucleolysis in Patients Unresponsive to Chemonucleolysis with Oxygen-Ozone:

A multitude of therapies is available to treat disc herniation, ranging from conservative methods (medication and physical therapy) to minimally invasive (percutaneous) treatments and surgery. O2-O3 chemonucleolysis (O2-O3 therapy) is one of the minimally invasive treatments with the best cost/benefit ratio and lowest complication rate. Another substance recently made available exploiting the chemical properties of pure ethanol is DiscoGel®, a radiopaque gelified ethanol more viscous than absolute alcohol 8,9. The present study aimed to assess the therapeutic outcome of DiscoGel® chemonucleolysis in patients with lumbar disc herniation unresponsive to O2-O3 therapy. Thirty-two patients aged between 20 and 79 years were treated by DiscoGel® chemonucleolysis between December 2008 and January 2010. The treatment was successful (improvement in pain) in 24 out of 32 patients. DiscoGel® is safe and easy to handle and there were no complications related to product diffusivity outside the treatment site. The therapeutic success rate of DiscoGel® chemonucleolysis in patients unresponsive to O2-O3 therapy was satisfactory. Among other methods used to treat lumbar disc herniation, DiscoGel® chemonucleolysis can be deemed an intermediate procedure bridging conservative medical treatments and surgery.

3T MRI in the Evaluation of Brain Aneurysms Treated with Flow-Diverting Stents: Preliminary Experience

Deployment of stents across the neck of intracranial aneurysms to isolate the lesion from the circulation is a recently introduced endovascular treatment. These devices are known as flow-diverting stents because the stent mesh design drastically slows the blood flow within the aneurysm sac, thereby stimulating thrombus formation. Treated aneurysms require close follow-up monitoring using an effective minimally invasive method. We devised a dedicated follow-up protocol using a high field strength magnetic resonance system (MR) with gadolinium administration to monitor 11 patients treated by insertion of flow-diverting stents. Findings were compared with the results of a reference imaging procedure (CT angiography). MR accurately demonstrated patency of the stent lumen and monitored the evolution of the aneurysmal sac in all patients. Gadolinium administration proved essential in two patients to depict the complete exclusion of the flow within the aneurysmal sac.

Covered Stent Implantation for the Treatment of Direct Carotid-Cavernous Fistula and Its Mid-Term Follow-up

Carotid-cavernous fistulas are abnormal arteriovenous communications either directly between the internal carotid artery and the cavernous sinus or between the dural branches of the internal and external carotid arteries. These fistulas predominantly present with ocular manifestations and they are treated mainly by endovascular techniques in most cases. A detailed review of the literature allowed us to make a complete analysis of the information available on the topic. We describe a case of a direct carotid-cavernous fistula occluded by endovascular implantation of a covered stent, showing the persistence of results after three years.