Grundlagen der Embolisation und anderer verschließender Verfahren

Vascular embolizations are complex and sophisticated procedures and can be a powerful alternative or useful adjunct to surgery in many clinical situations. Hemorrhage, vascular malformations, and tumors are the main indications for embolization procedures. Establishing the correct indication for intervention as well as the proper embolic agent and the most suitable catheterization technique requires advanced knowledge in interventional radiology, and an interdisciplinary approach is a prerequisite. A broad spectrum of microcatheters and embolization materials is available for these therapies. The desired level of occlusion and the individual vascular territory determine the choice of mechanical devices, particles, or liquid substances. Sclerosing agents and thrombin are used in special situations such as varicoceles and pseudoaneurysms.     

Embolotherapy: principles and indications

Vascular embolizations are complex and sophisticated procedures and can be a powerful alternative or useful adjunct to surgery in many clinical situations. Hemorrhage, vascular malformations, and tumors are the main indications for embolization procedures. Establishing the correct indication for intervention as well as the proper embolic agent and the most suitable catheterization technique requires advanced knowledge in interventional radiology, and an interdisciplinary approach is a prerequisite. A broad spectrum of microcatheters and embolization materials is available for these therapies. The desired level of occlusion and the individual vascular territory determine the choice of mechanical devices, particles, or liquid substances. Sclerosing agents and thrombin are used in special situations such as varicoceles and pseudoaneurysms.     

How much intravenous contrast is needed in FDG-PET/CT?

Intravenous, iodinated contrast agents are used routinely for CT (ceCT) imaging but only applied reluctantly for FDG-PET/CT due to possible artefacts. Only for few oncological PET/CT indications, the role of IV contrast agent has been clarified. Essentially, if any knowledge regarding vascular structures or tumour invasion into adjacent structures are needed, a ceCT as part of the combined PET/CT exam should be implemented. However, for some indications like lymphoma, contrast seems not to be necessary. Therefore, imaging procedures for the use of IV contrast for PET/CT have to be adapted individually for each FDG-PET/CT indication to especially reduce unnecessary radiation burden to the patient.     

The histotoxicity of cyanoacrylates

Summary Cyanoacrylates, a group of rapidly polymerizing adhesives, have found widespread uses in oral and general surgery as well as surgical subspecialties, for example as hemostatic and anastomotic agents. They have been utilized most recently as materials for embolotherapy of complex cerebral and extra-cerebral vascular anomalies. The histopathology that results from their deposition in human tissues is thus an important consideration, and the subject of this review. Particular attention is given to the fate of cyanoacrylates in cerebral lesions after iatrogenic embolization procedures. The apparent toxicity of these plastics on blood vessel walls is discussed in relation to experimental observations. It is imperative that clinicians who use this group of substances evaluate their potential functions in the light of the pathologic findings.     

Management of vascular perforations that occur during neurointerventional procedures

This article describes a number of treatment strategies for the management of perforations that occur during neurointerventional procedures. During the past 5 years, we have performed over 1200 endovascular procedures to treat vascular disorders involving the brain and spinal cord (400 cerebral arteriovenous malformations, 230 tumors, 197 carotid cavernous fistulas, 183 aneurysms, 130 dural fistulas, 80 spinal arteriovenous malformations, 18 vein of Galen aneurysms, and 20 cases of vasospasm). Fifteen patients (1.1%) sustained a vascular perforation as a direct result of these procedures. Among these 15 patients, indications for endovascular treatment were six symptomatic arteriovenous malformations, two spinal cord arteriovenous malformations, two cavernous sinus dural fistulas, one transverse sinus fistula, one case of vasospasm following subarachnoid hemorrhage, one direct carotid cavernous fistula, one vein of Galen malformation, and one ruptured basilar artery aneurysm. The vascular perforations were grouped into three probable mechanisms: mechanical perforation of a normal vessel (six patients), mechanical disruption of a dysplastic vessel or aneurysm (five patients), and fluid overinjection (four patients). Treatment of the perforations included immediate reversal of anticoagulants (12 patients) and direct closure of the perforation site with coils (five patients). In addition, closure of the intravascular compartment adjacent to the perforation was achieved with coils (six patients), liquid adhesives (four patients), balloons (two patients), or particles (two patients). In two patients a detachable balloon was placed transiently across the perforation site for several minutes, deflated, and removed when no further extravasation was noted. Five patients were started on anticonvulsant therapy, two of whom have had a new onset seizure related to the perforation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Transvenous embolization of dural fistulas involving the transverse and sigmoid sinuses

Eleven patients with dural fistulas involving the transverse and sigmoid sinuses were treated by transvenous embolization with coils or liquid adhesives. Seven patients underwent preoperative embolization of the external supply followed by direct surgical exposure of the sinus: liquid adhesives were used in four patients and coils in the remaining three. Four of these patients had complete obliteration of their fistulas and there was 95% reduction in the remaining three. Four patients had transvenous placement of coils from a transfemoral approach. In three, the ipsilateral sigmoid sinus was thrombosed and a contralateral approach across the torcular herophili was used. Coils were used in all four patients; one patient also had liquid adhesives placed within the sinus. Complete cure was achieved in one patient, 95% reduction in another, and 50% and 40%, reductions in the remaining two. Two transient complications occurred, one related to venous occlusion secondary to liquid adhesives and another related to transient occlusion of the vestibular aqueduct. Obliteration of dural fistulas involving the transverse and sigmoid sinuses can be achieved by placement of embolic material within the involved sinus from a transvenous approach; both coils and liquid adhesives can achieve this goal.     

Transvenous embolization of dural fistulas involving the cavernous sinus

Because of the risks associated with arterial embolization of cavernous dural fistulas, we have sought an alternative method to promote fistula closure. Thirteen patients underwent transvenous embolization as a treatment for symptomatic cavernous dural fistulas. All procedures were performed from a femoral vein access through the inferior petrosal sinus or basilar plexus. In five patients the inferior petrosal sinus was not angiographically demonstrable; however, embolization was still possible through this route in two patients. The embolic agents used were detachable balloons in one patient, coils alone in five, coils and liquid adhesives in four, coils plus silk sutures in one, silk sutures alone in one, and liquid adhesives alone in one. Nine patients had follow-up angiograms, which showed complete obliteration of the fistulas and complete resolution of related symptoms. One patient had complete resolution of clinical symptoms but refused follow-up angiography. Another patient had 50% decrease in fistula flow on the follow-up angiogram and improvement in clinical symptoms. Two patients had complete fistula obliteration after embolization and progressive improvement in symptoms but follow-up angiograms had not been obtained. Follow-ups ranged from 1 to 97 months (mean, 15 months). Two complications were related to this treatment. An embolic stroke followed transient placement of a balloon in the internal carotid in one patient, and a second patient developed transient visual loss when the venous outflow pathways were occluded before fistula closure. The fistula was immediately closed with complete recovery of vision. With recent advances in microcatheter and embolic agent technology, transvenous closure of cavernous dural fistulas is now possible.(ABSTRACT TRUNCATED AT 250 WORDS)     

Off-label use of contrast agents

When contrast agents are approved, the label describes the approved indications and particular circumstances of use such as age, organ function or pregnancy. The use of contrast agents outside their labelled indications is increasing, namely with contrast agents used for MRI. The aim of this paper is to improve the knowledge about this topic. The basis for off-label use is the physician’s prerogative, which finds its basis in the “Declaration of Helsinki”. Off-label use is allowed under special conditions and might be even the medical state of the art. The necessity for off-label use will continue to increase for MR-contrast agents, as the regulatory requirements for approval of new indications continuously increase, and clinical trials for registration purposes are quite costly and time consuming. As a consequence, manufacturers will concentrate on clinical studies for the essential indications.     

Neuroimaging: do we really need new contrast agents for MRI?

The use of exogenous contrast media in magnetic resonance imaging of the brain has brought dramatic improvement in the sensitivity of detection and delineation of pathological structures, such as primary and metastatic brain tumors, inflammation and ischemia. Disruption of the blood brain barrier leads to accumulation of the intravenously injected contrast material in the extravascular space, leading to signal enhancement. Magnetic resonance angiography benefits from T(1)-shortening effects of contrast agent, improving small vessel depiction and providing vascular visualization even in situations of slow flow. High speed dynamic MRI after bolus injection of contrast media allows tracer kinetic modeling of cerebral perfusion. Progressive enhancement over serial post-contrast imaging allows modeling of vascular permeability and thus quantitative estimation of the severity of blood brain barrier disruption. With such an array of capabilities and ever improving technical abilities, it seems that the role of contrast agents in MR neuroimaging is established and the development of new agents may be superfluous. However, new agents are being developed with prolonged intravascular residence times, and with in-vivo binding of ever-increasing specificity. Intravascular, or blood pool, agents are likely to benefit magnetic resonance angiography of the carotid and cerebral vessels; future agents may allow the visualization of therapeutic drug delivery, the monitoring of, for example, gene expression, and the imaging evaluation of treatment efficacy. So while there is a substantial body of work that can be performed with currently available contrast agents, especially in conjunction with optimized image acquisition strategies, post processing, and mathematical analysis, there are still unrealized opportunities for novel contrast agent introduction, particularly those exploiting biological specificity. This article reviews the current use of contrast media in magnetic resonance neuroimaging, discusses some of the developing strategies for new applications of imaging with these agents and finally offers some views and indications for contrast agents currently under development, as well as some speculation on unsolved problems in neuroimaging, and opportunities for novel contrast agents.     

Magnetic resonance angiography (MRA) in renally impaired patients: when and how

Magnetic resonance angiography (MRA) and NSF in renally impaired patients have a close relationship due to the frequent coincidence of vascular and renal pathologies, the relatively large amount of contrast media applied and the delayed excretion. The date of the first NSF cases described in literature falls into the development of multi-stationary MRA—an investigation that requested multiple bolus injections or one large bolus of the contrast agent. It is therefore easily understood that NSF was regarded initially as possible complication of MRA.

A review on the history of MRA is presented and various techniques for MRA are described. While many neuroradiological indications can be solved by native MRA, most angiographic indications throughout the body rely on the application of intravenous contrast agents.

The paper discusses options for alternative methods in vascular imaging and offers guidelines for patients with renal impairment. NSF must always be balanced versus the outcome of an investigation, respectively versus the outcome of a denied MRA. Moreover, in patients with chronic kidney disease (CKD) and a proper justification for a vascular investigation, neither CT angiography nor DSA should replace MRA. Restrictions in contrast media dose for CKD patients are mandatory and obviously reduce the risk of NSF. Gadolinium-based contrast agents with lower stability are now contraindicated in patients with reduced renal function. The role of blood pool agents is under evaluation.

Since the awareness of the new disease grew over the last year, radiologists were able to reduce the number of newly diagnosed NSF cases by more careful consideration of contrast application and agent in renally impaired patients, which gives hope that NSF can be avoided by respecting some easy rules.     

Transvenous embolization of direct carotid cavernous fistulas

Of 165 cases of direct carotid cavernous fistula, 14 (8.5%) were treated from a transvenous approach. Twelve of these were treated through the inferior petrosal sinus and one through the superior ophthalmic vein. In one patient, both approaches were used. The embolic agents were as follows: five patients had balloons only, four patients had minicoils alone, three patients had coils and liquid adhesives, one had balloons and coils, and one had balloons and liquid adhesives. Among the patients who were treated from a transvenous approach, three had an occluded carotid artery caused by trauma, nine failed transarterial balloon attempts, and one had a prior trapping procedure. In the remaining patient, who had Ehlers-Danlos syndrome, a transarterial approach was judged to be too dangerous. This patient suffered a fatal pontine hemorrhage after subtotal transvenous occlusion of the carotid cavernous fistula with diversion of flow into cortical veins. Another complication occurred when the inferior petrosal sinus was perforated during catheterization, causing a small subarachnoid hemorrhage. The tear was immediately closed with minicoils, and surgical exposure and embolization resulted in complete cure. Of the remaining 12 patients treated, 11 were completely cured and one showed angiographic and clinical improvement. Transarterial balloon embolization remains the procedure of choice in the treatment of symptomatic carotid cavernous fistulas; however, transvenous embolization is an alternative when the arterial route fails.     

缺血性脑血管病介入治疗的思考

缺血性脑血管病的介入治疗,为该病患者带来了一种新的治疗方法,以其微创的理念、较好的疗效得到认可.由于进行该类治疗的医师学科分散,侧重点可能有所不同,造成治疗指征有偏差.为了使其健康发展,需要重视治疗指征,综合各学科最新知识,更新治疗理念,特别要以脑功能的恢复和改善为主,规范手术操作.     

Percutaneous transluminal angioplasty of crural arteries

The authors dilated 103 stenosed crural arteries in 71 patients. Primary success was defined as traversing and reducing the lesion to a residual stenosis of less than 30%. This was achieved in 96% of cases. Complications included one vessel rupture and one occluding intimal flap, which were treated by the vascular surgeon with bypass and venous patch, respectively. One hematoma at the puncture site was treated surgically because of its size. With modern materials such as steerable guide wires and low-profile balloon catheters, dilation of crural arteries has become safe. Until now, the indications for percutaneous transluminal angioplasty (PTA) of crural arteries have been limited to Fontaine stages III and IV disease. The authors believe that the indications for PTA in Fontaine stage IIb disease are justified, especially if intervention improves outflow after a more proximal recanalizing procedure is performed.     

颈动脉16层螺旋CT成像和应用

随着多层螺旋CT的不断发展,多层螺旋CT成像及血管造影已成为颈动脉疾病的主要检查方法,研究证明CTA在评价颈动脉的狭窄和闭塞上与DSA有高度的一致性,可常规用来评价颈动脉狭窄等病变.同时CTA还可用来评价颈部血管外伤,可以发现颈部血管部分或完全闭塞、假性动脉瘤、夹层、动静脉瘘等,以及颈部软组织、气道、颈髓椎管等部位的病变,可作为怀疑颈部血管外伤但暂无手术指征的无创性检查方法.     

Contrast-enhanced MRI of the lung

The lung has long been neglected by MR imaging. This is due to unique intrinsic difficulties: (1) signal loss due to cardiac pulsation and respiration; (2) susceptibility artifacts caused by multiple air-tissue interfaces; (3) low proton density. There are many MR strategies to overcome these problems. They consist of breath-hold imaging, respiratory and cardiac gating procedures, use of short repetition and echo times, increase of the relaxivity of existing spins by administration of intravenous contrast agents, and enrichment of spin density by hyperpolarized noble gases or oxygen. Improvements in scanner performance and frequent use of contrast media have increased the interest in MR imaging and MR angiography of the lung. They can be used on a routine basis for the following indications: characterization of pulmonary nodules, staging of bronchogenic carcinoma, in particular assessment of chest wall invasion; evaluation of inflammatory activity in interstitial lung disease; acute pulmonary embolism, chronic thromboembolic pulmonary hypertension, vascular involvement in malignant disease; vascular abnormalities. Future perspectives include perfusion imaging using extracellular or intravascular (blood pool) contrast agents and ventilation imaging using inhalation of hyperpolarized noble gases, of paramagnetic oxygen or of aerosolized contrast agents. These techniques represent new approaches to functional lung imaging. The combination of visualization of morphology and functional assessment of ventilation and perfusion is unequalled by any other technique.     

Ultrasound contrast agents

Two concepts of microbubble stabilization led to reproducible, industrially manufactured contrast agents, and to the transpulmonary stability of agents after intravenous injection. The albumin microencapsulation concept is represented by Albunex (Molecular Biosystems, San Diego, CA), the saccharide microparticle concept is represented by SH U 454 (Echovist and its transpulmonary derivative SH U 508 A, Schering AG, Berlin, FRG). In the past year, the first reported clinical studies of the transpulmonary agents have demonstrated their safety and efficacy. Further, the results of contrast-enhanced pulsed wave and color Doppler studies bring prospects of further improvements in vascular Doppler examinations. The patency of fallopian tubes was assessed with transvaginal scanning and transcervical injection of echogenic contrast agents. The feasibility of sonographic perfusion imaging of different organs (eg, myocardium, liver, tumors) was demonstrated using invasive injection techniques. Thus, ultrasound contrast agents are a new diagnostic tool in sonography and have a broad spectrum of potential indications.     

Dural arteriovenous fistulas involving the inferior petrosal sinus: angiographic findings in six patients

We report the angiographic findings from six patients with intracranial dural arteriovenous fistulas of the inferior petrosal sinus and describe the clinical presentation, vascular anatomy, and embolization techniques used in the treatment of this disorder. Dural arteriovenous fistulas at this site are rare; of 105 patients diagnosed with this abnormality, only six had lesions involving the inferior petrosal sinus. The patients included three men and three women, ranging in age from 41 to 75 years. Patients presented with bruit, proptosis, abducens palsy, or loss of vision, and symptoms were present for up to 1 year prior to diagnosis. These presentations were similar to cavernous sinus arteriovenous fistulas. The arterial supply in all cases was from branches of the external carotid artery and in three cases from the meningohypophyseal trunk of the internal carotid artery. Venous drainage in four patients was via the cavernous sinus to the superior ophthalmic vein. The remaining two patients had drainage primarily to the jugular bulb. In four patients treatment was performed by introducing wire coils into the fistula from the transvenous route. This approach could be used even though the inferior petrosal sinus was thrombosed. One patient, treated early in the series, had only transarterial embolization with both liquid adhesives and particulate embolic agents. One patient had an asymptomatic fistula that was not treated. All patients were cured, as evidenced both angiographically and clinically during the follow-up period. Three patients experienced complications from angiography and treatment: two had transverse sinus thrombosis and one had a transient ischemic attack.     

Therapeutic embolization for vascular trauma of the head and neck

Therapeutic embolization is an effective and relatively safe method for managing many cases of head and neck trauma. In the last 5 years, 78 traumatic vascular lesions--10 arterial transections and 68 arteriovenous fistula--were treated by intravascular embolization at four medical centers. Selection of embolic materials is discussed and different types of lesions are illustrated. Treatment was successful in every instance. Complications were limited to one case of cerebral infarction and two cases of temporary oculomotor weakness. The indications for embolization have widened beyond life-threatening hemorrhage alone, and continued improvement in techniques and embolic agents should see an increased use of this form of treatment.     

Modafinil in sports: ethical considerations

Performance enhancing agents are prohibited in athletic competition so that only athletic skills can determine outcomes. Modafinil is a novel non-addicting psychostimulant approved for treatment of narcolepsy. Does its use, especially for medical indications, violate the Olympic Movement Anti-Doping Code? This is discussed with reference to a current high profile case.     

Liver MRI: From basic protocol to advanced techniques

Liver MR is a well-established modality with multiparametric capabilities. However, to take advantage of its full capacity, it is mandatory to master the technique and optimize imaging protocols, apply advanced imaging concepts and understand the use of different contrast media. Physiologic artefacts although inherent to upper abdominal studies can be minimized using triggering techniques and new strategies for motion control. For standardization, the liver MR protocol should include motion-resistant T2-w sequences, in-op phase GRE T1 and T2-w fast spin echo sequences with fat suppression. Diffusion-weighted imaging (DWI) is mandatory, especially for detection of sub-centimetre metastases. Contrast-enhanced MR is the cornerstone of liver MR, especially for lesion characterization. Although extracellular agents are the most extensively used contrast agents, hepatobiliary contrast media can provide an extra-layer of functional diagnostic information adding to the diagnostic value of liver MR. The use of high field strength (3T) increases SNR but is more challenging especially concerning artefact control. Quantitative MR belongs to the new and evolving field of radiomics where the use of emerging biomarkers such as perfusion or DWI can derive new information regarding disease detection, prognostication and evaluation of tumour response. This information can overcome some of the limitations of current tests, especially when using vascular disruptive agents for oncologic treatment assessment. MR is, today, a robust, mature, multiparametric imaging modality where clinical applications have greatly expanded from morphology to advanced imaging. This new concept should be acknowledged by all those involved in producing high quality, high-end liver MR studies.