Michael Söderman

Brain imaging with a flat detector C-arm

IntroductionWe present the first clinical results from brain tissue imaging with a novel functionality in the angiography room, the XperCT.MethodsXperCT is a flat detector C-arm volume acquisition functionality integrated with the angiography equipment. We assessed brain images from 42 patients examined with computed tomography (CT) and XperCT.ResultsIn all patients, XperCT had significantly more beam hardening and reconstruction artifacts than CT, in particular in the posterior fossa. Contrast resolution was better on CT images. Hemorrhage, edema, and ventricular size could be assessed with XperCT in all patients, but CT was superior also in this aspect. In four of the last 12 cases, after the latest software upgrade, it was possible to differentiate between supra-tentorial grey and white substance on XperCT images.ConclusionCT was superior to XperCT regarding brain soft tissue imaging. However, XperCT could in some cases discriminate between grey and white substance. XperCT is a useful new functionality in interventional neuroradiology. In the clinical setting, it improves patient safety by allowing almost instant access to CT-like brain imaging in the angiography room. It can be life saving in situations where complications during an interventional procedure prompt for immediate action.

Radiation dose in neuroangiography using image noise reduction technology: a population study based on 614 patients

IntroductionThe purpose of this study was to quantify the reduction in patient radiation dose by X-ray imaging technology using image noise reduction and system settings for neuroangiography and to assess its impact on the working habits of the physician.MethodsRadiation dose data from 190 neuroangiographies and 112 interventional neuroprocedures performed with state-of-the-art image processing and reference system settings were collected for the period January–June 2010. The system was then configured with extra image noise reduction algorithms and system settings, which enabled radiation dose reduction without loss of image quality. Radiation dose data from 174 neuroangiographies and 138 interventional neuroprocedures were collected for the period January–June 2012. Procedures were classified as diagnostic or interventional. Patient radiation exposure was quantified using cumulative dose area product and cumulative air kerma. Impact on working habits of the physician was quantified using fluoroscopy time and number of digital subtraction angiography (DSA) images.ResultsThe optimized system settings provided significant reduction in dose indicators versus reference system settings (p<0.001): from 124 to 47 Gy cm2 and from 0.78 to 0.27 Gy for neuroangiography, and from 328 to 109 Gy cm2 and from 2.71 to 0.89 Gy for interventional neuroradiology. Differences were not significant between the two systems with regard to fluoroscopy time or number of DSA images.ConclusionX-ray imaging technology using an image noise reduction algorithm and system settings provided approximately 60% radiation dose reduction in neuroangiography and interventional neuroradiology, without affecting the working habits of the physician.

Epidural needle with embedded optical fibers for spectroscopic differentiation of tissue: ex vivo feasibility study

Epidural injection is commonly used to provide intraoperative anesthesia, postoperative and obstetric analgesia, and to treat acute radicular pain. Identification of the epidural space is typically carried out using the loss of resistance (LOR) technique, but the usefulness of this technique is limited by false LOR and the inability to reliably detect intravascular or subarachnoid needle placement. In this study, we present a novel epidural needle that allows for the acquisition of optical reflectance spectra from tissue close to the beveled surface. This needle has optical fibers embedded in the cannula that deliver and receive light. With two spectrometers, light received from tissue is resolved across the wavelength range of 500 to 1600 nm. To determine the feasibility of optical tissue differentiation, spectra were acquired from porcine tissues during a post mortem laminectomy. The spectra were processed with an algorithm that derives estimates of the hemoglobin and lipid concentrations. The results of this study suggest that the optical epidural needle has the potential to improve the accuracy of epidural space identification.

Identification of the epidural space with optical spectroscopy: an in vivo swine study.

Background:Accurate identification of the epidural space is critical for safe and effective epidural anesthesia or treatment of acute lumbar radicular pain with epidural steroid injections. The loss-of-resistance technique is commonly used, but it is known to be unreliable. Even when it is performed in conjunction with two-dimensional fluoroscopic guidance, determining when the needle tip enters the epidural space can be challenging. In this swine study, we investigated whether the epidural space can be identified with optical spectroscopy, using a custom needle with optical fibers integrated into the cannula. Methods:Insertion of the needle tip into the epidural space was performed with midline and paramedian approaches in a swine. In each insertion, optical spectra were acquired at different insertion depths, and anatomical localization of the needle was determined by three-dimensional imaging with rotational C-arm computed tomography. Optical spectra that included both visible and near-infrared wavelength ranges were processed to derive estimates of the blood and lipid volume fractions. Results:In all insertions, the transition of the needle tip to the epidural space from an adjacent tissue structure (interspinous ligament or the ligamentum flavum) was found to be associated with an increase in the lipid volume fraction. These increases, which ranged from 1.6- to 3.0-fold, were statistically significant (P = 0.0020). Lipid fractions obtained from the epidural space were 1.9- to 20-fold higher than those obtained from muscle (P = 0.0013). Accidental penetration of an epidural vein during one insertion coincided with a high blood volume fraction. Conclusions:The spectroscopic information obtained with the optical spinal needle is complementary to fluoroscopic images, and it could potentially allow for reliable identification of the epidural space during needle placement.

Statement of ESMINT and ESNR regarding recent trials evaluating the endovascular treatment at the acute stage of ischemic stroke

Three recent, simultaneous publications report the neutral results of three randomized studies (SYNTHESIS Expansion, Interventional Management of Stroke (IMS) III, and Mechanical Retrieval and Recanalization of Stroke Clots Using Embolectomy (MR RESCUE)) comparing IV thrombolysis therapy or standard care (MR RESCUE) to the endovascular treatment (EVT) of acute ischemic stroke (AIS) [1–3]. The results of these three trials might lead to the erroneous conclusion that endovascular treatment has no or little place in the management of AIS. However, careful analysis of the IMS III, SYNTHESIS, and MR RESCUE studies is mandatory prior to assessment of the value of EVT of AIS. Also, the limits of the current and future trials should be outlined. The European Society of Minimally Invasive Neurological Therapy (ESMINT) and European Society of Neuroradiology (ESNR) represent the interventional neuroradiology community in Europe and have engaged in the definition of rules regarding trials evaluating the EVT of AIS [4, 5]. It is clearly their role to provide a precise analysis of recent and future trials. In the last 20 years, treatment of AIS has evolved to include neuroprotection, IV thrombolysis (IVT), and endovascular treatment. Despite numerous studies of a very large number

Optical Detection of the Brachial Plexus for Peripheral Nerve Blocks An In Vivo Swine Study

Background and Objectives: Accurate identification of nerves is critical to ensure safe and effective delivery of regional anesthesia during peripheral nerve blocks. Nerve stimulation is commonly used, but it is not perfect. Even when nerve stimulation is performed in conjunction with ultrasound guidance, determining when the needle tip is at the nerve target region can be challenging. In this in vivo pilot study, we investigated whether close proximity to the brachial plexus and penetration of the axillary artery can be identified with optical reflectance spectroscopy, using a custom needle stylet with integrated optical fibers. Methods: Ultrasound-guided insertions to place the needle tip near the brachial plexus at the axillary level were performed at multiple locations in 2 swine, with the stylet positioned in the cannula of a 20-gauge stimulation needle. During each insertion, optical reflectance spectra were acquired with the needle tip in skeletal muscle, at the surface of muscle fascia, and at the nerve target region; confirmation of the final needle position was provided by nerve stimulation. In addition, an insertion to the lumen of the axillary artery was performed in a third swine. Differences in the spectra were quantified with lipid and hemoglobin parameters that provide contrast for optical absorption by the respective chromophores. Results: The transition of the needle tip from skeletal muscle to the nerve target region was associated with higher lipid parameter values (P < 0.001) and lower hemoglobin parameter values (P < 0.001). The transition of the needle tip from muscle fascia to the nerve target region was associated with higher lipid parameter values (P = 0.001). Intraluminal access of the axillary artery was associated with an elevated hemoglobin parameter. Conclusions: Spectroscopic information obtained with the optical needle is distinct from nerve stimulation and complementary to ultrasound imaging, and it could potentially allow for reliable identification of the injection site during peripheral nerve blocks.

Results of an International Survey on the Investigation and Endovascular Management of Cerebral Vasospasm and Delayed Cerebral Ischemia

BACKGROUNDnDelayed cerebral ischemia (DCI) is a major cause of morbidity and mortality in aneurysmal subarachnoid hemorrhage. Endovascular management of this condition offers a new hope in preventing adverse outcome; however, a uniform standard of practice is lacking owing to a paucity of clinical trials. We conducted an international survey on the use of investigative and endovascular techniques in the treatment of DCI to assess the variability of current practice.nnnMETHODSnNeurovascular neurosurgeons and neuroradiologists were contacted through professional societies from America, United Kingdom, Europe, and Australasia. Members were invited to complete a 13-item questionnaire regarding screening techniques, first-line and second-line therapies in endovascular intervention, and the role of angioplasty. Answers were compared using χ(2) testing for nonparametric data.nnnRESULTSnData from 344 respondents from 32 countries were analyzed: 167 non-United States and 177 U.S.nnnRESPONDENTSnMore than half of all clinicians had 10+ years of experience in units with a mixture of higher and lower case volumes. Daily transcranial Doppler ultrasonography was the most commonly used screening technique by both U.S. (70%) and non-U.S. (53%) practitioners. Verapamil was the most common first-line therapy in the United States, whereas nimodipine was most popular in non-U.S. countries. Angioplasty was performed by 83% of non-U.S. and 91% of U.S. clinicians in the treatment of vasospasm; however, more U.S. clinicians reported using angioplasty for distal vasospasm.nnnCONCLUSIONSnTreatment practices for DCI vary considerably, with the greatest variability in the choice of agent for intra-arterial therapy. Our data demonstrate the wide variation of approaches in use at present. However, without further clinical trials and development of a uniform standard of best practice, variability in treatment and outcome for DCI is likely to continue.

Multiple intracranial arteriovenous malformations: a case report.

Multiple intracranial arteriovenous malformations are rare. There are a few cases in the literature with up to three malformations in one patient. A child with seven separate cerebral malformations is now described. There was no history of haemorrhage, but only of febrile seizures. The malformations were discovered at CT and verified at angiography. Six were selected for stereotaxic irradiation with the multicobalt unit. The seventh was considered too big for irradiation and suitable for surgery.

High-resolution 3D X-ray imaging of intracranial nitinol stents

IntroductionTo assess an optimized 3D imaging protocol for intracranial nitinol stents in 3D C-arm flat detector imaging. For this purpose, an image quality simulation and an in vitro study was carried out.MethodsNitinol stents of various brands were placed inside an anthropomorphic head phantom, using iodine contrast. Experiments with objects were preceded by image quality and dose simulations. We varied X-ray imaging parameters in a commercially interventional X-ray system to set 3D image quality in the contrast–noise–sharpness space. Beam quality was varied to evaluate contrast of the stents while keeping absorbed dose below recommended values. Two detector formats were used, paired with an appropriate pixel size and X-ray focus size. Zoomed reconstructions were carried out and snapshot images acquired. High contrast spatial resolution was assessed with a CT phantom.ResultsWe found an optimal protocol for imaging intracranial nitinol stents. Contrast resolution was optimized for nickel–titanium-containing stents. A high spatial resolution larger than 2.1xa0lp/mm allows struts to be visualized. We obtained images of stents of various brands and a representative set of images is shown. Independent of the make, struts can be imaged with virtually continuous strokes. Measured absorbed doses are shown to be lower than 50xa0mGy Computed Tomography Dose Index (CTDI).ConclusionBy balancing the modulation transfer of the imaging components and tuning the high-contrast imaging capabilities, we have shown that thin nitinol stent wires can be reconstructed with high contrast-to-noise ratio and good detail, while keeping radiation doses within recommended values. Experimental results compare well with imaging simulations.

Plea of the defence—critical comments on the interpretation of EVA3S, SPACE and ICSS

Three randomised controlled trials (RCTs) comparing outcomes after carotid artery stenting (CAS) with carotid endarterectomy (CEA) have recently been published. Recent systematic reviews have recommended that CAS is no longer justified for patients suitable for CEA. Indeed, in many centres, pooled data of RCTs show higher peri-operative risk of performing CAS vs. CEA with comparable long-term efficacy. Due to limitations in SPACE, EVA3S and ICSS study design and conduct, the inferiority of CAS to CEA as a method remains inconclusive. The goal of this review is not to discredit these trials but to develop a more differentiated and critical interpretation of the data and to create more discussion. It will discuss the necessity of RCTs for Interventional Neuroradiology in general and particular problems in study design (non-inferiority design and interpretation of results, clinical equipoise, study endpoints), practical study conduct difficulties (operator and centre experience, antiaggregation, timing of treatment) and the interpretation of the results (relation of internal and external validity, procedural complexity, the 68-year surprise, longer-term outcome). A premature rejection of CAS based on the data from these studies could harm future patients who would have had benefited from this procedure. For the time being, there is no reason why centres with good and independently controlled track records should stop performing CAS. Designing a single cooperative European trial that incorporates the lessons learned would be major step forward.