Levy Ei

A proposed grading system for endovascular treatment of cerebral arteriovenous malformations: Buffalo score

Background: The Spetzler–Martin arteriovenous malformation (AVM) grading system has proven to be useful in guiding treatment of cerebral AVMs with craniotomy. It is based on anatomical characteristics each of which makes surgical resection of an AVM more difficult, namely, deep venous drainage, eloquence of surrounding tissue, and large nidus size. A higher score correlates with more complications after treatment. Although this grading system has proven reliable over time, it does not reflect the major determinants of risk associated with endovascular treatment. The authors developed a grading system unique to endovascular treatment of cerebral AVMs. Methods: The proposed grading system accounts for the principal AVM anatomical and physiological features that make endovascular embolization more difficult and, thus, the likelihood of complications greater. These include number of arterial pedicles, diameter of arterial pedicles, and eloquent location of AVM nidus. The proposed grading system was retrospectively applied to 50 patients undergoing endovascular AVM embolization, and its ability to predict complications was compared to the Spetzler–Martin grading system. Results: Perioperative complications among the 50 patients included 4 major and 9 minor complications. The proposed grading system was predictive of complication risk, with an increasing rate of perioperative complications associated with an increasing AVM grade. An improved correlation of perioperative complication incidence was noted with the proposed system (P = 0.002), when compared with the Spetzler–Martin grading system (P = 0.33). Conclusion: This grading system for the endovascular treatment of AVMs is simple, easily reproduced, and clinically valuable.

Feasibility, Safety, and Periprocedural Complications of Pipeline Embolization for Intracranial Aneurysm Treatment Under Conscious Sedation: University at Buffalo Neurosurgery Experience.

BACKGROUND: Endovascular Pipeline Embolization Device (PED) placement for intracranial aneurysms is performed under general anesthesia at most centers because of perceived improved image quality and patient safety. OBJECTIVE: To report the feasibility, safety, and outcomes associated with the use of the PED for intracranial aneurysms performed in awake patients after the administration of conscious sedation (CS) and a local anesthetic. METHODS: Between March 2012 and September 2014, 130 patients with 139 intracranial aneurysms (8 ruptured) were treated with the PED under CS at our institution. Procedure details and time (including duration, radiation exposure, and fluoroscopy) and procedure-related complications were retrospectively reviewed. RESULTS: A total of 155 PED deployment procedures were performed under CS. Treatment was successfully completed in all cases. Anesthesia was converted from CS to general anesthesia during 5 procedures. Mean interval from patient entry at the endovascular suite to procedure initiation was 18 minutes (range, 5 minutes-1 hour 10 minutes). Mean procedure length was 1 hour 25 minutes (range, 30 minutes-3 hours 51 minutes). Mean ± SD values for fluoroscopy time and radiation exposure were 36.17 ± 18.4 minutes and 1367 ± 897 mGy, respectively. The mean amount of contrast material administered was 211.37 ± 83.5 mL. Permanent neurological complications were seen in 4 patients (3%). CONCLUSION: In our experience, CS for PED placement for intracranial aneurysm treatment is feasible and safe. Procedure and fluoroscopy times and amount of radiation exposure are similar to or less than described in reports of PED placement under general anesthesia. CS allows direct neurological evaluation and earlier detection of and response to intraprocedural complications. ABBREVIATIONS: CS, conscious sedation GA, general anesthesia ICA, internal carotid artery PED, Pipeline Embolization Device

A Patient Dose-Reduction Technique for Neuroendovascular Image-Guided Interventions: Image-Quality Comparison Study

BACKGROUND AND PURPOSE: The ROI–dose-reduced intervention technique represents an extension of ROI fluoroscopy combining x-ray entrance skin dose reduction with spatially different recursive temporal filtering to reduce excessive image noise in the dose-reduced periphery in real-time. The aim of our study was to compare the image quality of simulated neurointerventions with regular and reduced radiation doses using a standard flat panel detector system. MATERIALS AND METHODS: Ten 3D-printed intracranial aneurysm models were generated on the basis of a single patient vasculature derived from intracranial DSA and CTA. The incident dose to each model was reduced using a 0.7-mm-thick copper attenuator with a circular ROI hole (10-mm diameter) in the middle mounted inside the Infinix C-arm. Each model was treated twice with a primary coiling intervention using ROI-dose-reduced intervention and regular-dose intervention protocols. Eighty images acquired at various intervention stages were shown twice to 2 neurointerventionalists who independently scored imaging qualities (visibility of aneurysm-parent vessel morphology, associated vessels, and/or devices used). Dose-reduction measurements were performed using an ionization chamber. RESULTS: A total integral dose reduction of 62% per frame was achieved. The mean scores for regular-dose intervention and ROI dose-reduced intervention images did not differ significantly, suggesting similar image quality. Overall intrarater agreement for all scored criteria was substantial (Kendall τ = 0.62887; P < .001). Overall interrater agreement for all criteria was fair (κ = 0.2816; 95% CI, 0.2060–0.3571). CONCLUSIONS: Substantial dose reduction (62%) with a live peripheral image was achieved without compromising feature visibility during neuroendovascular interventions.

TU‐A‐116‐06: Pre and Post‐Treatment Temporal Parametric Analysis of Neurovascular Disease Using Gamma Variate Fitting of Time Density Curves From DSA Sequences

PURPOSE To calculate temporal parameters of contrast flow, using digital subtraction angiography (DSA), and provide parametric imaging (PI) of pre-and post-treated neurovascular lesions to aid neuro-interventionalists decision. METHODS We developed a program to evaluate changes in contrast flow before and after treatment of neurovascular lesions. The program records each pixel value in a DSA sequence and fits the data with a gamma-variate function. Using the function we calculate parameters such as mean-transit-time (MTT), bolus-arrival-time (BAT) and time-to-peak (TTP) and generate PIs for each quantity. The program was used for pre and post-treatment parametric calculations for four representative neurovascular lesions: ischemic stroke, intracranial stenosis, arteriovenous malformation (AVM) and intracranial aneurysm treated with a flow diverter. Finally we compared the pre and post-treatment PIs for changes in temporal parameters of the contrast flow. RESULTS Processing times for a typical DSA acquisition at 10 frames per second were between 15 and 20 minutes. In the ischemic stroke and intracranial stenosis cases we observed increased flow after clot removal and balloon angioplasty respectively, BAT decreased by 2x while MTT and TTP decreased 1.5x as compared with the pre-treatment PI. For the AVM the venous arrival time increased three times after glue embolization, indicating decreased flow through the AVM. For the aneurysm treatment the MTT in the aneurysm dome was 5x larger compared with the pretreatment run indicating a reduced flow in the aneurysm. CONCLUSION Pre and post-treatment PIs showed significant differences, indicating reestablished flow for ischemic stroke and intracranial stenosis and decreased flow for the AVM and intracranial aneurysm. Execution time can be decreased significantly if software and hardware is optimized. This kind of information could be a very useful tool for treatment assistance during intracranial minimally invasive procedures in the angiographic suites where CT-perfusion is not immediately available. Support NIH-2R01EB002873; Support from NIH Grant 2R01EB002873.

New head equivalent phantom for task and image performance evaluation representative for neurovascular procedures occurring in the Circle of Willis.

Phantom equivalents of different human anatomical parts are routinely used for imaging system evaluation or dose calculations. The various recommendations on the generic phantom structure given by organizations such as the AAPM, are not always accurate when evaluating a very specific task. When we compared the AAPM head phantom containing 3 mm of aluminum to actual neuro-endovascular image guided interventions (neuro-EIGI) occurring in the Circle of Willis, we found that the system automatic exposure rate control (AERC) significantly underestimated the x-ray parameter selection. To build a more accurate phantom for neuro-EIGI, we reevaluated the amount of aluminum which must be included in the phantom. Human skulls were imaged at different angles, using various angiographic exposures, at kVs relevant to neuro-angiography. An aluminum step wedge was also imaged under identical conditions, and a correlation between the gray values of the imaged skulls and those of the aluminum step thicknesses was established. The average equivalent aluminum thickness for the skull samples for frontal projections in the Circle of Willis region was found to be about 13 mm. The results showed no significant changes in the average equivalent aluminum thickness with kV or mAs variation. When a uniform phantom using 13 mm aluminum and 15 cm acrylic was compared with an anthropomorphic head phantom the x-ray parameters selected by the AERC system were practically identical. These new findings indicate that for this specific task, the amount of aluminum included in the head equivalent must be increased substantially from 3 mm to a value of 13 mm.

Evaluation of intracranial aneurysm coil embolization in phantoms and patients using a high-resolution Microangiographic Fluoroscope (MAF).

Intracranial aneurysm (IA) embolization using Gugliemi Detachable Coils (GDC) under x-ray fluoroscopic guidance is one of the most important neuro-vascular interventions. Coil deposition accuracy is key and could benefit substantially from higher resolution imagers such as the micro-angiographic fluoroscope (MAF). The effect of MAF guidance improvement over the use of standard Flat Panels (FP) is challenging to assess for such a complex procedure. We propose and investigate a new metric, inter-frame cross-correlation sensitivity (CCS), to compare detector performance for such procedures. Pixel (P) and histogram (H) CCSs were calculated as one minus the cross-correlation coefficients between pixel values and histograms for the region of interest at successive procedure steps. IA treatment using GDCs was simulated using an anthropomorphic head phantom which includes an aneurysm. GDCs were deposited in steps of 3 cm and the procedure was imaged with a FP and the MAF. To measure sensitivity to detect progress of the procedure by change in images of successive steps, an ROI was selected over the aneurysm location and pixel-value and histogram changes were calculated after each step. For the FP, after 4 steps, the H and P CCSs between successive steps were practically zero, indicating that there were no significant changes in the observed images. For the MAF, H and P CCSs were greater than zero even after 10 steps (30 cm GDC), indicating observable changes. Further, the proposed quantification method was applied for evaluation of seven patients imaged using the MAF, yielding similar results (H and P CCSs greater than zero after the last GDC deposition). The proposed metric indicates that the MAF can offer better guidance during such procedures.

TU‐C‐211‐06: Practical Operational Considerations for Clinical Usage of the Micro‐ Angio Fluoroscope (MAF) in Neuro‐Vascular Interventions

Purpose: To demonstrate a C‐arm mounted, high‐resolution, microangiographic‐fluoroscope (MAF) during neuro‐vascular clinical interventions (NVCI) with increased x‐ray tube output while still using the small focal spot. Method and Materials: The MAF consisting of a 300 μm CsI input phosphor coupled to a micro‐channel‐plate light image‐ intensifier, in turn coupled to a CCDsensor through a minifying fiber‐optic taper was mounted on a clinical C‐arm. To take advantage of the MAFs high resolution, the small focal spot must be used. In general NVCIs require x‐ray tubes to use near maximum available mAs during fluoroscopy and angiography even with a larger focal spot. To tackle the problem we implemented a variable temporal filter (TF) and modified imaging protocols to enable use of the small focal spot. For DSA we increased the frame rate to 15 fps with the maximum mAs available and implemented a 3‐frame TF. For short but critical fluoroscopy durations where high resolution was essential for guiding a NVCI such as stent deployment, we used the small focal spot with a low exposure angiography protocol at (2– 4)X fluoroscopy settings which we refer to as High Definition (HD) mode. Results: The variable temporal filtering was used successfully during fluoroscopy to compensate for mAs limitations. Depending on patient motion we used TF weights between 3 and 7. Temporally‐filtered, high‐speed angiograms allowed visualization of fine vasculature details better than the standard imager. HD mode was used during stent deployments allowing visualization of detailed stent structure which normally is not visible using standard x‐ray imagers. Conclusions: X‐ray output limitations during NVCI were overcome by a combination TF and x‐ray protocol modification to meet the MAF high‐resolution requirements. The imaging improvements were significant with patients benefiting from more accurate treatments or in one case the elimination of an additional costly procedure. NIH Grants R01‐EB008425, R01‐EB002873.