Drazenko Babic

Live 3D Guidance in the Interventional Radiology Suite

OBJECTIVE The development of a C-arm cone-beam CT unit coupled with flat detectors has markedly increased anatomic visualization capabilities for interventional radiology procedures. We present technology in which fluoroscopy and 3D imaging from a cone-beam CT-flat-detector C-arm unit are combined with an integrated tracking and navigation system. A description of the technology and representative clinical cases are presented. CONCLUSION This new combination further increases interventional radiologic capabilities because it provides real-time procedural evaluation and tracking.

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.

3D roadmap in neuroangiography: technique and clinical interest

We present the first clinical results obtained with a novel technique: the three-dimensional [3D] roadmap. The major difference from the standard 2D digital roadmap technique is that the newly developed 3D roadmap is based on a rotational angiography acquisition technique with the two-dimensional [2D] fluoroscopic image as an overlay. Data required for an accurate superimposition of the previously acquired 3D reconstructed image on the interactively made 2D fluoroscopy image, in real time, are stored in the 3D workstation and constitute the calibration dataset. Both datasets are spatially aligned in real time; thus, the 3D image is accurately superimposed on the 2D fluoroscopic image regardless of any change in C-arm position or magnification. The principal advantage of the described roadmap method is that one contrast injection allows the C-arm to be positioned anywhere in the space and allows alterations in the distance between the x-ray tube and the image intensifier as well as changes in image magnification. In the clinical setting, the 3D roadmap facilitated intravascular neuronavigation with concurrent reduction of procedure time and use of contrast medium.

Contrast-Enhanced Angiographic Cone-Beam CT of Cerebrovascular Stents: Experimental Optimization and Clinical Application

BACKGROUND AND PURPOSE: With modern imaging techniques, visualization of neurovascular stents remains challenging. We present a method for contrast-enhanced C-arm CBCT that provides detailed and simultaneous visualization of neurovascular stents and host arteries. MATERIALS AND METHODS: CBCT was performed with a rotational angiography system by acquiring 620 projection frames over a 200° arc at 80 kVp and a total of 260 mAs. A superselective intra-arterial contrast injection protocol was optimized in swine experiments and implemented in 57 clinical examinations. High-resolution 3D reconstructions were evaluated by 3 blinded interventional neuroradiologists. Reviewers rated the images by answering questions related to both the quality of the stent and artery visualization and the clinical utility of the images. Raw agreement statistics, ICC, and κ statistics were computed for the questionnaire results. RESULTS: Of 57 clinical evaluations, 5 were not evaluated due to the use of large balloon-mounted stents (n = 4) and a failed contrast injection (n = 1). In 50 of 52 evaluated examinations, the reviewers agreed that simultaneous stent and vessel visualization was of diagnostic quality. There was strong agreement that stent–vessel wall apposition could be assessed (κ = 0.79). CBCT detected contrast filling defects (κ = 0.85) and vascular calcification (κ = 0.68). Artifacts resulting from the aneurysm coil mass impaired the delineation of adjacent structures (κ = 0.72). CONCLUSIONS: We have developed a technique that enables simultaneous clinically useful imaging of neurovascular stents and their host arteries that is unobtainable with other current imaging modalities. Further improvements are required to reduce artifacts from large coil masses due to x-ray scattering.

Validation of 3D multimodality roadmapping in interventional neuroradiology

Three-dimensional multimodality roadmapping is entering clinical routine utilization for neuro-vascular treatment. Its purpose is to navigate intra-arterial and intra-venous endovascular devices through complex vascular anatomy by fusing pre-operative computed tomography (CT) or magnetic resonance (MR) with the live fluoroscopy image. The fused image presents the real-time position of the intra-vascular devices together with the patients 3D vascular morphology and its soft-tissue context. This paper investigates the effectiveness, accuracy, robustness and computation times of the described methods in order to assess their suitability for the intended clinical purpose: accurate interventional navigation. The mutual information-based 3D-3D registration proved to be of sub-voxel accuracy and yielded an average registration error of 0.515 mm and the live machine-based 2D-3D registration delivered an average error of less than 0.2 mm. The capture range of the image-based 3D-3D registration was investigated to characterize its robustness, and yielded an extent of 35 mm and 25° for >80% of the datasets for registration of 3D rotational angiography (3DRA) with CT, and 15 mm and 20° for >80% of the datasets for registration of 3DRA with MR data. The image-based 3D-3D registration could be computed within 8 s, while applying the machine-based 2D-3D registration only took 1.5 µs, which makes them very suitable for interventional use.

Utility of VasoCT in the treatment of intracranial aneurysm with flow-diverter stents.

OBJECT The small size and tortuous anatomy of intracranial arteries require that flow-diverter stents in the intracranial vasculature have a low profile, high flexibility, and excellent trackability. However, these features limit the degree of radiopacity that can be incorporated into the stents. Visualization of these stents and the degree of stent deployment using conventional radiographic techniques is suboptimal. To overcome this drawback, the authors used a new combined angiography/CT suite that uses flat-panel detector technology for higher resolution angiography. METHODS The authors present their preliminary experience in the imaging of flow-diverter stents in 31 patients in whom VasoCT was used with a new flat-panel detector angiographic system. RESULTS Intraarterial VasoCT was performed after flow-diverter stent deployment in all cases. In 4 of these cases, balloon angioplasty or telescopic stent deployment-related decisions were made after checking VasoCT images. At 3- and 6-month follow-up in 27 patients, digital subtraction angiography was performed in 12 patients and intravenous VasoCT in 11 patients. Twenty-three of 31 patients had their aneurysm occluded during short-term follow-up, and 4 of the 31 patients still had minimal residual filling of the aneurysms. None of the 27 patients had stenosis of the parent artery. CONCLUSIONS The authors found that VasoCT provides clear visualization of flow-diverter stents. The images obtained both intraarterially and intravenously are very promising. The initial results provide a high confidence and reproducibility rate for further utilization of this new technique.

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.

Evaluation of stent visibility by flat panel detector CT in patients treated for intracranial aneurysms

IntroductionThis study aimed to evaluate the visibility of stents using high-resolution computed tomography (CT) acquisitions acquired with flat panel detector (XperCT, Allura series, Philips Healthcare, The Netherlands) for endovascular treatment of intracranial aneurysms.MethodsOn a 24-month period, 48 patients endovascularly treated by coiling and stenting (59 stents) for intracranial aneurysms were explored by flat panel detector CT technique. A sequence of 620 2D images was acquired over an angle of 240° using a 1,024 × 1,024 pixel matrix detector within a 48-cm field of view. The images were retrospectively analyzed independently by two neuroradiologists. Evaluation criteria were percentage of visualization of the stents and stent deployment (kinking or unsatisfactory deployment of the stent).ResultsEvaluation of the stent was feasible for all the patients. Stent visibility by XperCT was overall estimated at 76% of the stent length.Difficulties to analyze the stents were related to coil artifacts but not to packing density or aneurysm location. Stent length visualization was higher when the acquisition was performed before additional coiling (P < 0.0001). Mild kinking/misdeployment was noticed in 22% of the cases.ConclusionXperCT technique provides multiplanar and 3D reconstructions that allows for a satisfying visualization of intracranial stents. This CT-like acquisition should be performed after the stent deployment and before coiling, in order to obtain better stent visualization.

Percutaneous vertebroplasty: preliminary experiences with rotational acquisitions and 3D reconstructions for therapy control.

Percutaneous vertebroplasty (PVP) is carried out under fluoroscopic control in most centers. The exclusion of implant leakage and the assessment of implant distribution might be difficult to assess based on two-dimensional radiographic projection images only. We evaluated the feasibility of performing a follow-up examination after PVP with rotational acquisitions and volumetric reconstructions in the angio suite. Twenty consecutive patients underwent standard PVP procedures under fluoroscopic control. Immediate postprocedure evaluation of the implant distribution in the angio suite (BV 3000; Philips, The Netherlands) was performed using rotational acquisitions (typical parameters for the image acquisition included a 17-cm field-of-view, 200 acquired images for a total angular range of 180°). Postprocessing of acquired volumetric datasets included multiplanar reconstruction (MPR), maximum intensity projection (MIP), and volume rendering technique (VRT) images that were displayed as two-dimensional slabs or as entire three-dimensional volumes. Image evaluation included lesion and implant assessment with special attention given to implant leakage. Findings from rotational acquisitions were compared to findings from postinterventional CT. The time to perform and to postprocess the rotational acquisitions was in all cases less then 10 min. Assessment of implant distribution after PVP using rotational image acquisition methods and volumetric reconstructions was possible in all patients. Cement distribution and potential leakage sites were visualized best on MIP images presented as slabs. From a total of 33 detected leakages with CT, 30 could be correctly detected by rotational image acquisition. Rotational image acquisitions and volumetric reconstruction methods provided a fast method to control radiographically the result of PVP in our cases.