Ultra-early tranexamic acid after subarachnoid haemorrhage (ULTRA): a randomised controlled trial.

BACKGROUND: In patients with aneurysmal subarachnoid haemorrhage, short-term antifibrinolytic therapy with tranexamic acid has been shown to reduce the risk of rebleeding. However, whether this treatment improves clinical outcome is unclear. We investigated whether ultra-early, short-term treatment with tranexamic acid improves clinical outcome at 6 months. METHODS: In this multicentre prospective, randomised, controlled, open-label trial with masked outcome assessment, adult patients with spontaneous CT-proven subarachnoid haemorrhage in eight treatment centres and 16 referring hospitals in the Netherlands were randomly assigned to treatment with tranexamic acid in addition to care as usual (tranexamic acid group) or care as usual only (control group). Tranexamic acid was started immediately after diagnosis in the presenting hospital (1 g bolus, followed by continuous infusion of 1 g every 8 h, terminated immediately before aneurysm treatment, or 24 h after start of the medication, whichever came first). The primary endpoint was clinical outcome at 6 months, assessed by the modified Rankin Scale, dichotomised into a good (0-3) or poor (4-6) clinical outcome. Both primary and safety analyses were according to intention to treat. This trial is registered at ClinicalTrials.gov, NCT02684812. FINDINGS: Between July 24, 2013, and July 29, 2019, we enrolled 955 patients; 480 patients were randomly assigned to tranexamic acid and 475 patients to the control group. In the intention-to-treat analysis, good clinical outcome was observed in 287 (60%) of 475 patients in the tranexamic acid group, and 300 (64%) of 470 patients in the control group (treatment centre adjusted odds ratio 0·86, 95% CI 0·66-1·12). Rebleeding after randomisation and before aneurysm treatment occurred in 49 (10%) patients in the tranexamic acid and in 66 (14%) patients in the control group (odds ratio 0·71, 95% CI 0·48-1·04). Other serious adverse events were comparable between groups. INTERPRETATION: In patients with CT-proven subarachnoid haemorrhage, presumably caused by a ruptured aneurysm, ultra-early, short-term tranexamic acid treatment did not improve clinical outcome at 6 months, as measured by the modified Rankin Scale. FUNDING: Fonds NutsOhra.

High Early Fluid Input After Aneurysmal Subarachnoid Hemorrhage: Combined Report of Association With Delayed Cerebral Ischemia and Feasibility of Cardiac Output-Guided Fluid Restriction.

BACKGROUND: Guidelines on the management of aneurysmal subarachnoid hemorrhage (aSAH) recommend euvolemia, whereas hypervolemia may cause harm. We investigated whether high early fluid input is associated with delayed cerebral ischemia (DCI), and if fluid input can be safely decreased using transpulmonary thermodilution (TPT). METHODS: We retrospectively included aSAH patients treated at an academic intensive care unit (2007-2011; cohort 1) or managed with TPT (2011-2013; cohort 2). Local guidelines recommended fluid input of 3 L daily. More fluids were administered when daily fluid balance fell below +500 mL. In cohort 2, fluid input in high-risk patients was guided by cardiac output measured by TPT per a strict protocol. Associations of fluid input and balance with DCI were analyzed with multivariable logistic regression (cohort 1), and changes in hemodynamic indices after institution of TPT assessed with linear mixed models (cohort 2). RESULTS: Cumulative fluid input 0 to 72 hours after admission was associated with DCI in cohort 1 (n=223; odds ratio [OR] 1.19/L; 95% confidence interval 1.07-1.32), whereas cumulative fluid balance was not. In cohort 2 (23 patients), using TPT fluid input could be decreased from 6.0 ± 1.0 L before to 3.4 ± 0.3 L; P = .012), while preload parameters and consciousness remained stable. CONCLUSION: High early fluid input was associated with DCI. Invasive hemodynamic monitoring was feasible to reduce fluid input while maintaining preload. These results indicate that fluid loading beyond a normal preload occurs, may increase DCI risk, and can be minimized with TPT.

High sensitivity and specificity of 4D-CTA in the detection of cranial arteriovenous shunts.

PURPOSE: In a prospective cohort study, we evaluated the diagnostic accuracy of time-resolved CT angiography (4D-CTA) compared to digital subtraction angiography (DSA) for detecting cranial arteriovenous shunts. MATERIAL AND METHODS: Patients were enrolled if a DSA had been ordered querying either a dural arteriovenous fistula (dAVF) or a cerebral arteriovenous malformation (bAVM). After enrolment, both a DSA and a 4D-CTA were performed. Both studies were evaluated using a standardized form. If a dAVF or bAVM was found, its classification, angioarchitectural details, and treatment options were recorded. RESULTS: Ninety-eight patients were enrolled and 76 full datasets were acquired. DSA demonstrated a shunting lesion in 28 out of 76 cases (prevalence 37%). 4D-CTA demonstrated all but two of these lesions (sensitivity of 93%) and produced one false positive (specificity of 98%). These numbers yielded a positive predictive value (PPV) of 96% and a negative predictive value (NPV) of 96%. Significant doubt regarding the 4D-CTA diagnosis was reported in 6.6% of all cases and both false-negative 4D-CTA results were characterized by such doubt. CONCLUSIONS: 4D-CTA has very high sensitivity and specificity for the detection of intracranial arteriovenous shunts. Based on these results, 4D-CTA may replace DSA imaging as a first modality in the diagnostic workup in a large number of patients suspected of a cranial dAVF or bAVM, especially if there is no doubt regarding the 4D-CTA diagnosis. KEY POINTS: • 4D-CTA was shown to have a high diagnostic accuracy and is an appropriate, less invasive replacement for DSA as a diagnostic tool for cranial arteriovenous shunts in the majority of suspected cases. • Doubt regarding the 4D-CTA result should prompt additional DSA imaging, as it is associated with false negatives. • False-positive 4D-CTA results are rare, but do exist.

Current accuracy of surface matching compared to adhesive markers in patient-to-image registration.

OBJECT: In the past, the accuracy of surface matching has been shown to be disappointing. We aimed to determine whether this had improved over the years by assessing application accuracy of current navigation systems, using either surface matching or point-pair matching. METHODS: Eleven patients, scheduled for intracranial surgery, were included in this study after a power analysis had shown this small number to be sufficient. Prior to surgery, one additional fiducial marker was placed on the scalp, the "target marker," where the entry point of surgery was to be expected. Using one of three different navigation systems, two patient-to-image registration procedures were performed: one based on surface matching and one based on point-pair matching. Each registration procedure was followed by the digitization of the target marker's location, allowing calculation of the target registration error. If the system offered surface matching improvement, this was always used; and for the two systems that routinely offer an estimate of neuronavigation accuracy, this was also recorded. RESULTS: The error in localizing the target marker using point-pair matching or surface matching was respectively 2.49 mm and 5.35 mm, on average (p < 0.001). In those four cases where an attempt was made to improve the surface matching, the error increased to 6.35 mm, on average. For the seven cases where the system estimated accuracy, this estimate did not correlate with target registration error (R2 = 0.04, p = 0.67). CONCLUSION: The accuracy of navigation systems has not improved over the last decade, with surface matching consistently yielding errors that are twice as large as when point-pair matching with adhesive markers is used. These errors are not reliably reflected by the systems own prediction, when offered. These results are important to make an informed choice between image-to-patient registration strategies, depending on the type of surgery at hand.

The use of 4D-CTA in the diagnostic work-up of brain arteriovenous malformations.

INTRODUCTION: We aimed to evaluate the use of time-resolved whole-head CT angiography (4D-CTA) in patients with an untreated arteriovenous malformation of the brain (bAVM), as demonstrated by catheter angiography (DSA). METHODS: Seventeen patients with a DSA-proven bAVM were enrolled. These were subjected to 4D-CTA imaging using a 320 detector row CT scanner. Using a standardized scoring sheet, all studies were analyzed by a panel of three readers. This panel was blind to the DSA results at the time of reading the 4D-CTA. RESULTS: 4D-CTA detected all bAVMs. With regard to the Spetzler-Martin grade, 4D-CTA disagreed with DSA in only one case, where deep venous drainage was missed. Further discrepancies between 4D-CTA and DSA analyses included underestimation of the nidus size in small lesions (four cases), misinterpretation of a feeding vessel (one case), misinterpretation of indirect feeding through pial collaterals (three cases) and oversight of mild arterial enlargement (two cases). 4D-CTA correctly distinguished low-flow from high-flow lesions and detected dural/transosseous feeding (one case), venous narrowing (one case) and venous pouches (nine cases). CONCLUSION: In this series, 4D-CTA was able to detect all bAVMs. Although some angioarchitectural details were missed or misinterpreted when compared to DSA, 4D-CTA evaluation was sufficiently accurate to diagnose the shunt and classify it. Moreover, 4D-CTA adds cross-sectional imaging and perfusion maps, helpful in treatment planning. 4D-CTA appears to be a valuable new adjunct in the non-invasive diagnostic work-up of bAVMs and their follow-up when managed conservatively.

Tranexamic Acid After Aneurysmal Subarachnoid Hemorrhage: Post-Hoc Analysis of the ULTRA Trial.

BACKGROUND AND OBJECTIVES: The ULTRA-trial showed that ultra-early and short-term tranexamic acid treatment after subarachnoid hemorrhage did not improve clinical outcome at six months. An expected proportion of the included patients had non-aneurysmal subarachnoid hemorrhage In this post-hoc study, we will investigate whether ultra-early and short-term tranexamic acid treatment in patients with aneurysmal subarachnoid hemorrhage improves clinical outcome at six months. METHODS: The ULTRA-trial is a multicenter, prospective, randomized, controlled, open-label trial with blinded outcome assessment, conducted between July 24, 2013 and January 20, 2020. After confirmation of subarachnoid hemorrhage on non-contrast computer tomography, patients were allocated to either ultra-early and short-term tranexamic acid treatment with usual care, or usual care only. In this post-hoc analysis, we included all ULTRA-participants with a confirmed aneurysm on CT angiography and/or digital subtraction angiography. The primary endpoint was clinical outcome at six months, assessed by the modified Rankin Scale, dichotomized into good (0-3) and poor (4-6) outcome. RESULTS: Of the 813 ULTRA-trial patients who had an aneurysmal subarachnoid hemorrhage, 409 (50%) were assigned to the tranexamic acid group and 404 (50%) to the control group. In the intention-to-treat analysis, 233 of 405 (58%) patients in the tranexamic acid group and 238 of 399 (60%) patients in the control group had a good clinical outcome (adjusted odds ratio (aOR) 0·92; 95% confidence interval (C.I.) 0·69 to 1·24). None of the secondary outcomes showed significant differences between the treatment groups: excellent clinical outcome (mRS 0-2) aOR 0.76, 95% C.I. 0.57-1.03, all-cause mortality at 30 days aOR 0.91, 95% C.I. 0.65-1.28), all-cause mortality at six months aOR 1.10 (95% C.I. 0.80-1.52). DISCUSSION: Ultra-early and short-term tranexamic acid treatment did not improve clinical outcome at six months in patients with aneurysmal subarachnoid hemorrhage and therefore, cannot be recommended. TRIAL REGISTRATION: ClinicalTrials.gov (NCT02684812; submission date February 18, 2016, first patient enrollment on July 24th, 2013). CLASSIFICATION OF EVIDENCE: This study provides Class II evidence that tranexamic acid does not improve outcomes in patients presenting with aneurysmal subarachnoid hemorrhage.

Current Accuracy of Augmented Reality Neuronavigation Systems: Systematic Review and Meta-Analysis.

BACKGROUND: Augmented reality neuronavigation (ARN) systems can overlay three-dimensional anatomy and disease without the need for a two-dimensional external monitor. Accuracy is crucial for their clinical applicability. We performed a systematic review regarding the reported accuracy of ARN systems and compared them with the accuracy of conventional infrared neuronavigation (CIN). METHODS: PubMed and Embase were searched for ARN and CIN systems. For ARN, type of system, method of patient-to-image registration, accuracy method, and accuracy of the system were noted. For CIN, navigation accuracy, expressed as target registration error (TRE), was noted. A meta-analysis was performed comparing the TRE of ARN and CIN systems. RESULTS: Thirty-five studies were included, 12 for ARN and 23 for CIN. ARN systems could be divided into head-mounted display and heads-up display. In ARN, 4 methods were encountered for patient-to-image registration, of which point-pair matching was the one most frequently used. Five methods for assessing accuracy were described. Ninety-four TRE measurements of ARN systems were compared with 9058 TRE measurements of CIN systems. Mean TRE was 2.5 mm (95% confidence interval, 0.7-4.4) for ARN systems and 2.6 mm (95% confidence interval, 2.1-3.1) for CIN systems. CONCLUSIONS: In ARN, there seems to be lack of agreement regarding the best method to assess accuracy. Nevertheless, ARN systems seem able to achieve an accuracy comparable to CIN systems. Future studies should be prospective and compare TREs, which should be measured in a standardized fashion.

Auditory feedback during frameless image-guided surgery in a phantom model and initial clinical experience.

In this study the authors measured the effect of auditory feedback during image-guided surgery (IGS) in a phantom model and in a clinical setting. In the phantom setup, advanced IGS with complementary auditory feedback was compared with results obtained with 2 routine forms of IGS, either with an on-screen image display or with image injection via a microscope. The effect was measured by means of volumetric resection assessments. The authors also present their first clinical data concerning the effects of complementary auditory feedback on instrument handling during image-guided neurosurgery. When using image-injection through the microscope for navigation, however, resection quality was significantly worse. In the clinical portion of the study, the authors performed resections of cerebral mass lesions in 6 patients with the aid of auditory feedback. Instrument tip speeds were slightly (although significantly) influenced by this feedback during resection. Overall, the participating neurosurgeons reported that the auditory feedback helped in decision-making during resection without negatively influencing instrument use. Postoperative volumetric imaging studies revealed resection rates of > or = 95% when IGS with auditory feedback was used. There was only a minor amount of brain shift, and postoperative resection volumes corresponded well with the preoperative intentions of the neurosurgeon. Although the results of phantom surgery with auditory feedback revealed no significant effect on resection quality or extent, auditory cues may help prevent damage to eloquent brain structures.

Dynamic CT angiography and CT perfusion employing a 320-detector row CT: protocol and current clinical applications.

The aim of this study is to report the authors' initial clinical experience of a 320-detector row computed tomography (CT) scanner in cerebrovascular disorders. Volumetric CT using the full 160-mm width of the 320 detector rows enables full brain coverage in a single rotation that allows for combined time-resolved whole-brain perfusion and four-dimensional CT angiography (CTA). The protocol for the combined dynamic CTA and CT perfusion (CTP) is presented, and its potential applications in stroke, stenoocclusive disease, arteriovenous malformations and dural shunts are reviewed based on clinical examples. The combined CTA/CTP data can provide visualization of dynamic flow and perfusion as well as motion of an entire volume at very short time intervals which is of importance in a variety of pathologies with altered cerebral hemodynamics. The broad coverage enabled by 320 detector rows offers z-axis coverage allowing for whole-brain perfusion and subtracted dynamic angiography of the entire intracranial circulation.

The Incidence of Cranial Arteriovenous Shunts in Patients With Pulsatile Tinnitus: A Prospective Observational Study.

OBJECTIVES: Finding the underlying cause for pulsatile tinnitus can be challenging. We aimed to determine the incidence of arteriovenous shunts, i.e., arteriovenous malformations (AVMs) or dural arteriovenous fistulas (dAVFs), in patients referred for catheter angiography (digital subtraction angiography [DSA]). Furthermore, we assessed which clinical features were predictive for the presence of such a lesion. STUDY DESIGN AND METHODS: Fifty-one patients with pulsatile tinnitus, who were referred to us for DSA to exclude an arteriovenous shunt, were enrolled, prospectively. MAIN OUTCOME MEASURES: DSA determined the presence of a dAVF or AVM. Clinical characteristics were recorded systematically and all patients underwent a physical examination. RESULTS: Fifty patients were included in the final analyses. While no AVMs were found, a dAVF was found in 12 cases (24%). Three of these demonstrated cortical venous reflux, thus requiring treatment due to the risk of hemorrhage. In three cases (6%), DSA demonstrated a non-arteriovenous-shunt abnormality, likely causing the tinnitus. The odds of having a dAVF were significantly raised by unilaterality, objective bruit, and the ability to influence the tinnitus with compression. Unilaterality even had a negative predictive value of 1 and, if used as selection criterion, would have raised dAVF prevalence from 24 to 32%. CONCLUSION: In a tertiary care setting, the prevalence of dAVFs in patients with pulsatile tinnitus is not negligible. Thus, patients with unilateral pulsatile tinnitus should be offered dynamic vascular imaging to rule out a dAVF. Especially, since some of these patients are at risk of intracranial hemorrhage and treatment options exist.

Application accuracy in frameless image-guided neurosurgery: a comparison study of three patient-to-image registration methods.

OBJECT: The aim of this study was to compare three patient-to-image registration methods in frameless stereotaxy in terms of their application accuracy (the accuracy with which the position of a target can be determined intraoperatively). In frameless stereotaxy, imaging information is transposed to the surgical field to show the spatial position of a localizer or surgical instrument. The mathematical relationship between the image volume and the surgical working space is calculated using a rigid body transformation algorithm, based on point-pair matching or surface matching. METHODS: Fifty patients who were scheduled to undergo a frameless image-guided neurosurgical procedure were included in the study. Prior to surgery, the patients underwent either computerized tomography (CT) scanning or magnetic resonance (MR) imaging with widely distributed adhesive fiducial markers on the scalp. An extra fiducial marker was placed on the head as a target, as near as possible to the intracranial lesion. Prior to each surgical procedure, an optical tracking system was used to perform three separate patient-to-image registration procedures, using anatomical landmarks, adhesive markers, or surface matching. Subsequent to each registration, the target registration error (TRE), defined as the Euclidean distance between the image space coordinates and world space coordinates of the target marker, was determined. Independent of target location or imaging modality, mean application accuracy (+/- standard deviation) was 2.49 +/- 1.07 mm when using adhesive markers. Using the other two registration strategies, mean TREs were significantly larger (surface matching, 5.03 +/- 2.30 mm; anatomical landmarks, 4.97 +/- 2.29 mm; p < 0.001 for both). CONCLUSIONS: The results of this study show that skin adhesive fiducial marker registration is the most accurate noninvasive registration method. When images from an earlier study are to be used and accuracy may be slightly compromised, anatomical landmarks and surface matching are equally accurate alternatives.

Image-guided vascular neurosurgery based on three-dimensional rotational angiography. Technical note.

Three-dimensional rotational angiography is capable of exquisite visualization of cerebral blood vessels and their pathophysiology. Unfortunately, images obtained using this modality typically show a small region of interest without exterior landmarks to allow patient-to-image registration, precluding their use for neuronavigation purposes. The aim of this study was to find an alternative technique to enable 3D rotational angiography-guided vascular neurosurgery. Three-dimensional rotational angiograms were obtained in an angiographic suite with direct navigation capabilities. After image acquisition, a navigated pointer was used to touch fiducial positions on the patient's head. These positions were located outside the image volume but could nevertheless be transformed into image coordinates and stored in the navigation system. Prior to surgery, the data set was transferred to the navigation system in the operating room, and the same fiducial positions were touched again to complete the patient-to-image registration. This technique was tested on a Perspex phantom representing the cerebral vascular tree and on two patients with an intracranial aneurysm. In both the phantom and patients, the neuronavigation system provided 3D images representing the vascular tree in its correct orientation, that is, the orientation seen by the neurosurgeon through the microscope. In one patient, tissue shift was clearly observed without significant changes in the orientation of the structures. Results in this study demonstrate the feasibility of using 3D rotational angiography data sets for neuronavigation purposes. Determining the benefit of this type of navigation should be the subject of future studies.

Effectiveness of neuronavigation in resecting solitary intracerebral contrast-enhancing tumors: a randomized controlled trial.

OBJECT: The goal of this study was to assess the impact of neuronavigation on the cytoreductive treatment of solitary contrast-enhancing intracerebral tumors and outcomes of this treatment in cases in which neuronavigation was preoperatively judged to be redundant. METHODS: The authors conducted a prospective randomized study in which 45 patients, each harboring a solitary contrast-enhancing intracerebral tumor, were randomized for surgery with or without neuronavigation. Peri- and postoperative parameters under investigation included the following: duration of the procedure; surgeon's estimate of the usefulness of neuronavigation; quantification of the extent of resection, determined using magnetic resonance imaging; and the postoperative course, as evaluated by neurological examinations, the patient's quality-of-life self-assessment, application of the Barthel index and the Karnofsky Performance Scale score, and the patient's time of death. The mean amount of residual tumor tissue was 28.9% for standard surgery (SS) and 13.8% for surgery involving neuronavigation (SN). The corresponding mean amounts of residual contrast-enhancing tumor tissue were 29.2 and 24.4%, respectively. These differences were not significant. Gross-total removal (GTR) was achieved in five patients who underwent SS and in three who underwent SN. Median survival was significantly shorter in the SN group (5.6 months compared with 9 months, unadjusted hazard ratio = 1.6); however, this difference may be attributable to the coincidental early death of three patients in the SN group. No discernible important effect on the patients' 3-month postoperative course was identified. CONCLUSIONS: There is no rationale for the routine use of neuronavigation to improve the extent of tumor resection and prognosis in patients harboring a solitary enhancing intracerebral lesion when neuronavigation is not already deemed advantageous because of the size or location of the lesion.

Brain shift estimation in image-guided neurosurgery using 3-D ultrasound.

Intraoperative brain deformation is one of the most important causes affecting the overall accuracy of image-guided neurosurgical procedures. One option for correcting for this deformation is to acquire three-dimensional (3-D) ultrasound data during the operation and use this data to update the information provided by the preoperatively acquired MR data. For 12 patients 3-D ultrasound images have been reconstructed from freehand sweeps acquired during neurosurgical procedures. Ultrasound data acquired prior to and after opening the dura, but prior to surgery, have been quantitatively compared to the preoperatively acquired MR data to estimate the rigid component of brain shift at the first stages of surgery. Prior to opening the dura the average brain shift measured was 3.0 mm parallel to the direction of gravity, with a maximum of 7.5 mm, and 3.9 mm perpendicular to the direction of gravity, with a maximum of 8.2 mm. After opening the dura the shift increased on average 0.2 mm parallel to the direction of gravity and 1.4 mm perpendicular to the direction of gravity. Brain shift can be detected by acquiring 3-D ultrasound data during image-guided neurosurgery. Therefore, it can be used as a basis for correcting image data and preoperative planning for intraoperative deformations.

Segmentation of tumors in magnetic resonance brain images using an interactive multiscale watershed algorithm.

RATIONALE AND OBJECTIVE: This article presents the evaluation of an interactive multiscale watershed segmentation algorithm for segmenting tumors in magnetic resonance brain images of patients scheduled for neuronavigational procedures. MATERIALS AND METHODS: The watershed method is compared with manual delineation with respect to accuracy, repeatability, and efficiency. RESULTS: In the 20 patients included in this study, the measured volume of the tumors ranged from 2.7 to 81.9 cm(3). A comparison of the tumor volumes measured with watershed segmentation to the volumes measured with manual delineation shows that the two methods are interchangeable according to the Bland and Altman criterion, and thus equally accurate. The repeatability of the watershed method and the manual method are compared by looking at the similarity of the segmented volumes. The similarity for intraobserver and interobserver variability for watershed segmentation is 96.4% and 95.3%, respectively, compared with 93.5% and 90.0% for manual outlining, from which it may be concluded that the watershed method is more repeatable. Moreover, the watershed algorithm is on average three times faster than manual outlining. CONCLUSION: The watershed method has an accuracy comparable to that of manual delineation and outperforms manual outlining on the criteria of repeatability and efficiency.

Total bolus extraction method improves arterial image quality in dynamic CTAs derived from whole-brain CTP data.

Background and Purposes. The 320-detector row CT scanner enables visualization of whole-brain hemodynamic information (dynamic CT angiography (CTA) derived from CT perfusion scans). However, arterial image quality in dynamic CTA (dCTA) is inferior to arterial image quality in standard CTA. This study evaluates whether the arterial image quality can be improved by using a total bolus extraction (ToBE) method. Materials and Methods. DCTAs of 15 patients, who presented with signs of acute cerebral ischemia, were derived from 320-slice CT perfusion scans using both the standard subtraction method and the proposed ToBE method. Two neurointerventionalists blinded to the scan type scored the arterial image quality on a 5-point scale in the 4D dCTAs in consensus. Arteries were divided into four categories: (I) large extradural, (II) intradural (large, medium, and small), (III) communicating arteries, and (IV) cerebellar and ophthalmic arteries. Results. Quality of extradural and intradural arteries was significantly higher in the ToBE dCTAs than in the standard dCTAs (extradural P = 0.001, large intradural P < 0.001, medium intradural P < 0.001, and small intradural P < 0.001). Conclusion. The 4D dCTAs derived with the total bolus extraction (ToBE) method provide hemodynamic information combined with improved arterial image quality as compared to standard 4D dCTAs.

Intravascular functional maps of common neurovascular lesions derived from volumetric 4D CT data.

PURPOSE: Current computed tomography angiography (CTA) postprocessing tools do not support quantitative assessment of intravascular physiology. Dynamic volumetric CT, acquired at a sufficiently high temporal resolution, is ideal for such analysis. Following preliminary experiments in flow phantoms, we examine the segmentation of blood vessels from 4D CT angiography by curve fit and encoding of functional blood flow information into the resulting functional intravascular maps. MATERIALS AND METHODS: Flow phantoms were constructed consisting of a single pipe input and 4 simultaneous outputs of varying flow rates. Two outflow pipe diameters were tested. Bolus transit time (TT), time to peak (TTP), and time of arrival (TOA) were analyzed using contrast bolus profiles generated from 4D volumetric CT examinations on a 320 detector scanner in regions of interest placed 10 cm apart in all outflow pipes. Six subjects with various neurovascular lesions were next examined using a volumetric contrast-enhanced 4D CT angiography protocol. Segmentation was performed by quadratic curve fit after comparative analysis and optimization of the segmentation technique using quadratic curves, the gamma variate function, and a simplified formulation of the gamma variate function. After segmentation, quantitative analysis of spatially congruent intravascular voxels including TTP, rise, TT, and slope of the contrast upstroke was employed to encode physiologic information into the segmentations and produce intravascular functional maps. Comparison was made in each case to the patient's routine imaging. RESULTS: Increasing volumetric flow rates correspond to reduction of bolus TT in flow phantoms. TT elongation was observed as the contrast bolus moved distally in all pipes, with greater elongation seen at slower flow rates and larger pipe diameters. A greater difference was observed between TTP proximally and distally in pipes compared with TOA, an effect most prominent at slower flow rates and larger pipe lumens, and thus TTP was chosen for functional encoding into segmentations of the clinical series. In vivo, the quadratic function demonstrated the lowest coefficient of variation when fit to intravascular time density series and outperformed 2 formulations of the gamma variate function. After segmentation with quadratic curves, Gaussian distributions were chosen over gamma variate functions to characterize contrast bolus profiles while neglecting recirculation and to calculate functional parameters for spatial encoding. Intravascular functional maps free of bone artifacts were created in every case that demonstrated all appropriate vessels and showed agreement with conventional imaging modalities in terms of vessel delineation and the diagnosis of vascular pathology. The most useful and interesting functional maps are discussed in each case. CONCLUSIONS: The above approach to quantitative CT angiography provides a method of evaluating dynamic CTA data by means of intravascular functional maps. The techniques are broadly applicable in the clinical assessment of a variety of vascular diseases.

Aggressive intracranial dural arteriovenous fistula presenting with cerebrospinal fluid rhinorrhea: case report.

OBJECTIVE: This is the first report of an aggressive dural arteriovenous fistula presenting with rhinorrhea. It demonstrates the importance of recognizing increased intracranial pressure, and its underlying cause, as the predisposing factor to a spontaneous cerebrospinal fluid leak because this carries implications for management. CLINICAL PRESENTATION: Ten years after minor trauma and directly after an intercontinental flight, a 43-year-old woman presented with rhinorrhea. Right-sided pulsatile tinnitus had been present for the past 9 years. Imaging demonstrated an intracranial dural arteriovenous fistula of the right transverse sinus with cortical venous reflux. Magnetic resonance imaging findings indicated long-standing increased intracranial pressure. INTERVENTION: The fistula was treated by endovascular means, using both transvenous and transarterial approaches, which led to immediate relief of the tinnitus and resolution of the rhinorrhea within 4 days. CONCLUSION: A dural arteriovenous fistula should be included in the differential diagnosis of underlying causes of increased intracranial pressure when examining a patient with a cerebrospinal fluid leak. Treatment of the fistula should precede attempts to treat the rhinorrhea, especially if the fistula has cortical venous reflux.

The impact of workflow and volumetric feedback on frameless image-guided neurosurgery.

OBJECTIVE: During image-guided neurosurgery, if the surgeon is not fully orientated to the surgical position, he or she will briefly shift attention toward the visualization interface of an image guidance station, receiving only momentary "point-in-space" information. The aim of this study was to develop a novel visual interface for neuronavigation during brain tumor surgery, enabling intraoperative feedback on the entire progress of surgery relative to the anatomy of the brain and its pathology, regardless of the interval at which the surgeon chooses to look. METHODS: New software written in Java (Sun Microsystems, Inc., Santa Clara, CA) was developed to visualize the cumulative recorded instrument positions intraoperatively. This allowed surgeons to see all previous instrument positions during the elapsed surgery. This new interactive interface was then used in 17 frameless image-guided neurosurgical procedures. The purpose of the first 11 cases was to obtain clinical experience with this new interface. In these cases, workflow and volumetric feedback (WVF) were available at the surgeons' discretion (Protocol A). In the next 6 cases, WVF was provided only after a complete resection was claimed (Protocol B). RESULTS: With the novel interactive interface, dynamics of surgical resection, displacement of cortical anatomy, and digitized functional data could be visualized intraoperatively. In the first group (Protocol A), surgeons expressed the view that WVF had affected their decision making and aided resection (10 of 11 cases). In 3 of 6 cases in the second group (Protocol B), tumor resections were extended after evaluation of WVF. By digitizing the cortical surface, an impression of the cortical shift could be acquired in all 17 cases. The maximal cortical shift measured 20 mm, but it typically varied between 0 and 10 mm. CONCLUSION: Our first clinical results suggest that the embedding of WVF contributes to improvement of surgical awareness and tumor resection in image-guided neurosurgery in a swift and simple manner.

The effect of repetitive manual fiducial localization on target localization in image space.

OBJECTIVE: In this clinical study, we quantify intra- and interobserver variability of manual fiducial localization in image space, as the effect of repetitive manual fiducial localization is still unclear, especially on a target position. METHODS: After uploading eight imaging datasets with a total of 56 skin adhesive fiducial markers in a commercially available image-guidance system, the centroids of the fiducial markers were tagged. This task was executed repeatedly at three separate moments by six different observers. The fiducial localization variability and its target shift effect in image space were determined out of 1008 tagged fiducial markers. RESULTS: The maximal intraobserver target shift effect measured 0.72 +/- 0.14 mm in computed tomographic image space and 0.95 +/- 0.21 mm in magnetic resonance image space. CONCLUSION: If a fiducial tagging task is well understood, repetitive manual detection of fiducial markers can be done with a low intraobserver fiducial localization variability, resulting in a submillimetric effect on a target position, either in computed tomographic or magnetic resonance image space. Therefore, we think it is justified to determine the centroids of a skin adhesive fiducial marker in the image space by hand.