Visualisation of intracerebral haemorrhage with flat-detector CT compared to multislice CT: results in 44 cases

Clinical Comparison of FD-CT and MS-CT in Aneurysmal Subarachnoid Haemorrhage: A Single Center Experience

Single-center comparison of postinterventional multislice computed tomography (MS-CT) and flat-detector computed tomography (FD-CT) in patients with subarachnoid haemorrhage (SAH) and endovascularly treated cerebral aneurysms with a focus on detection of posttherapeutical complications. Patients with endovascularly treated aneurysmal SAH undergoing both MS-CT and FD-CT within 24 h after intervention were included. Datasets were compared regarding image quality (IQ) as well as qualitative (detection of SAH, intracerebral haemorrhage [ICH], intraventricular haemorrhage [IVH], external ventricular drain [EVD] position, acute obstructive hydrocephalus [AOH]) and quantitative (cella media distance [CMD], modified Graeb score [GS]) parameters. 410 patients with endovascularly treated aneurysmal SAH were included. IQ was equal between MS-CT and FD-CT. FD-CT allowed equal detection of SAH and ICH in comparison to MS-CT. FD-CT allowed excellent detection of IVH and delineation of EVD position with strong agreement to MS-CT findings. FD-CT allowed equal detection of AOH in comparison to MS-CT. There was no significant difference of CMD and GS between FD-CT and MS-CT. Postinterventional FD-CT yields equivalent diagnostic value in patients with endovascular treated SAH as MS-CT. Enabling reliable detection of SAH-associated complications within the angiosuite, FD-CT might be an efficient and safe imaging modality in these clinical emergencies.

Immediate postinterventional flat-panel CT: Differentiation of hemorrhagic transformation from contrast exudation of acute ischemic stroke patients after thrombectomy

BACKGROUND

Flat-panel computed tomography (CT) is an available imaging modality immediately after endovascular thrombectomy without transferring patients to the CT room.

PURPOSE

To determine the accuracy of flat-panel CT scans in differentiating hemorrhagic transformation (HT) from contrast exudation after thrombectomy in patients with acute ischemic stroke (AIS).

MATERIAL AND METHODS

From January 2019 to December 2021, consecutive patients with AIS who received an immediate flat-panel CT scan and follow-up neuroimaging after thrombectomy were enrolled in our study. The receiver operating characteristic curve was adopted to assess the discriminating accuracy of characteristics of flat-panel CT for HT.

RESULTS

A total of 108 patients were enrolled in the study; 58 (53.7%) patients presented with hyperdense lesions on flat-panel CT. Patients with hyperdense lesions experienced a higher proportion of HT than patients without (58.7% vs. 10.0%; P < 0.001). Among all patients with hyperdensity on flat-panel CT, patients who experienced HT had higher average Hounsfield units (HUavg) (125 vs. 93; P = 0.001) and a higher proportion of mass effect (67.6 vs. 12.5; P < 0.001). The flat-panel CT differentiating HT from contrast exudation yielded a sensitivity of 87.2% and a negative predictive value of 90.0%. The area under the curve of HUavg, mass effect, and combination for differentiation of HT were 0.74, 0.78, and 0.83, respectively.

CONCLUSION

The hyperdensity on immediately post-thrombectomy flat-panel CT could differentiate HT from contrast exudation with an excellent negative predictive value. The ability of flat-panel CT in differentiating HT from contrast exudation was improved when combined with HUavg and mass effect.

OUP accepted manuscript

Background: Time is brain! This paradigm is forcing the development of strategies with potential to shorten the time from symptom onset to recanalization. One of these strategies is to transport select patients with acute ischaemic stroke directly to an angio-suite equipped with flat-detector computed tomography (FD-CT) to exclude intracranial haemorrhage, followed directly by invasive angiography and mechanical thrombectomy if large-vessel occlusion (LVO) is confirmed. Aim: To present existing published data about the direct transfer (DT) of stroke patients to angio-suites and to describe our initial experience with this stroke pathway. Methods: We performed a systematic PubMed search of trials that described DT of stroke patients to angio-suites and summarized the results of these trials. In January 2020, we implemented a new algorithm for acute ischaemic stroke care in our stroke centre. Select patients suitable for DT (National Institute of Health Stroke Scale score ≥10, time from symptom onset to door <4.5 h) were referred by neurologists directly to an angio-suite equipped with FD-CT. Patients treated using this algorithm were analysed and compared with patients treated using the standard protocol including CT and CT angiography in our centre. Results: We identified seven trials comparing the DT protocol with the standard protocol in stroke patients. Among the 628 patients treated using the DT protocol, 104 (16.5%) did not have LVO and did not undergo endovascular treatment (EVT). All the trials demonstrated a significant reduction in door-to-groin time with DT, compared with the standard protocol. This reduction ranged from 22 min (DT protocol: 33 min; standard protocol: 55 min) to 59 min (DT protocol: 22 min; standard protocol: 81 min). In three of five trials comparing the 90-day modified Rankin scale scores between the DT and standard imaging groups, this reduction in ischaemic time translated into better clinical outcomes, whereas the two other trials reported no such difference in scores. Between January 2020 and October 2021, 116 patients underwent EVT for acute ischaemic stroke in our centre. Among these patients, 65 (56%) met the criteria for DT (National Institutes of Health Stroke Scale score >10, symptom onset-to-door time <4.5 h), but only 7 (10.8%) were transported directly to the angio-suite. The reasons that many patients who met the criteria were not transported directly to the angio-suite were lack of personnel trained in FD-CT acquisition outside of working hours, ongoing procedures in the angio-suite, contraindication to the DT protocol due to atypical clinical presentation, and neurologist’s decision for obtain complete neurological imaging. All seven patients who were transported directly to the angio-suite had LVOs. The median time from door-to-groin-puncture was significantly lower with the DT protocol compared with the standard protocol {29 min [interquartile range (IQR): 25–31 min] vs. 71 min [IQR: 55–94 min]; P < 0.001}. None of the patients had symptomatic intracranial haemorrhage in the DT protocol group, compared with 7 (6.4%) patients in the standard protocol group. Direct transfer of acute ischaemic stroke patients to the angio-suite equipped with FD-CT seems to reduce the time from patient arrival in the hospital to groin puncture. This reduction in the ischaemic time translates into better clinical outcomes. However, more data are needed to confirm these results.

Accuracy and reliability of PBV ASPECTS, CBV ASPECTS and NCCT ASPECTS in acute ischaemic stroke: a matched-pair analysis

BACKGROUND AND PURPOSE

To investigate the reliability and accuracy of Alberta Stroke Program Early Computed Tomography Scores (ASPECTS) derived from flatpanel detector computed tomography pooled blood volume maps compared to non-contrast computed tomography and multidetector computed tomography perfusion cerebral blood volume maps.

METHODS

ASPECTS from pooled blood volume maps were evaluated retrospectively by two experienced readers for 37 consecutive patients with acute middle cerebral artery (MCA) M1 occlusion who underwent flatpanel detector computed tomography perfusion imaging before mechanical thrombectomy between November 2016 and February 2019. For comparison with ASPECTS from non-contrast computed tomography and cerebral blood volume maps, a matched-pair analysis according to pre-stroke modified Rankin scale, age, stroke severity, site of occlusion, time from stroke onset to imaging and final modified thrombolysis in cerebral infarction (mTICI) was performed in a separate group of patients who underwent multimodal computed tomography prior to mechanical thrombectomy between June 2015 and February 2019. Follow-up ASPECTS were derived from either non-contrast computed tomography or from magnetic resonance imaging (in seven patients) one day after mechanical thrombectomy.

RESULTS

Interrater agreement was best for non-contrast computed tomography ASPECTS (w-kappa = 0.74, vs. w-kappa = 0.63 for cerebral blood volume ASPECTS and w-kappa = 0.53 for pooled blood volume ASPECTS). Also, accuracy, defined as correlation between acute and follow-up ASPECTS, was best for non-contrast computed tomography ASPECTS (Spearman ρ = 0.86 (0.65-0.97), P < 0.001), while it was lower and comparable for pooled blood volume ASPECTS (ρ = 0.58 (0.32-0.79), P < 0.001) and cerebral blood volume ASPECTS (ρ = 0.52 (0.17-0.80), P = 0.001). It was noteworthy that cases of relevant infarct overestimation by two or more ASPECTS regions (compared to follow-up imaging) were observed for both acute pooled blood volume and cerebral blood volume ASPECTS but occurred more often for acute pooled blood volume ASPECTS (25% vs. 5%, P = 0.02).

CONCLUSION

Non-contrast computed tomography ASPECTS outperformed both pooled blood volume ASPECTS and cerebral blood volume ASPECTS in accuracy and reliability. Importantly, relevant infarct overestimation was observed more often in pooled blood volume ASPECTS than cerebral blood volume ASPECTS, limiting its present clinical applicability for acute stroke imaging.

Lens dose reduction with a bismuth shield in neuro cone-beam computed tomography: an investigation on optimum shield device placement conditions

This study aimed to determine the placement distance, number, and position of the bismuth shield for developing a lens protective device for cone-beam computed tomography (CBCT). To determine the dose reduction rate, the lens doses were measured using an anthropomorphic head phantom and a real-time dosimeter. The image quality assessment was determined by analyzing the change in the pixel value, caused by the bismuth shield, and the artifact index was calculated from the pixel value and image noise within various regions of interest in the head phantom. When the distance between the bismuth shield and the subject was increased, the image quality deteriorated less, but there was also a decrease in the lens dose reduction rate. Upon changing the number of bismuth shields from 1-ply to 2-ply, the dose reduction rate increased; however, there was a decrease in the image quality. Additionally, placing the bismuth shield outside of the subject improved the dose reduction rate without deteriorating the image quality. The optimum placement conditions of the bismuth shield were concluded as follows: positioned outside, placed 10 mm from the surface of the subject, and used a 1-ply bismuth shield. When these placement conditions were used, the lens dose reduction rate was 26.9 ± 0.36% (right-left average) for the "bismuth shield: separate". The protective device developed in this study will contribute to radiation dose reduction in CBCT scans.

Radioprotection of eye lens using protective material in neuro cone-beam computed tomography: Estimation of dose reduction rate and image quality

PURPOSE

In cerebral angiography, for diagnosis and interventional neuroradiology, cone-beam computed tomography (CBCT) scan is frequently performed for evaluating brain parenchyma, cerebral hemorrhage, and cerebral infarction. However, the patient's eye lens is more frequently exposed to excessive doses in these scans than in the previous angiography and interventional neuroradiology (INR) procedures. Hence, radioprotection for the lenses is needed. This study selects the most suitable eye lens protection material for CBCT from among nine materials by evaluating the dose reduction rate and image quality.

METHODS

To determine the dose reduction rate, the lens doses were measured using an anthropomorphic head phantom and a real-time dosimeter. For image quality assessment, the artifact index was calculated based on the pixel value and image noise within various regions of interest in a water phantom.

RESULTS

The protective materials exhibited dose reduction; however, streak artifacts were observed near the materials. The dose reduction rate and the degree of the artifact varied significantly depending on the protective material. The dose reduction rates were 14.6%, 14.2%, and 26.0% when bismuth shield: normal (bismuth shield in the shape of an eye mask), bismuth shield: separate (two separate bismuth shields), and lead goggles were used, respectively. The "separate" bismuth shield was found to be effective in dose reduction without lowering the image quality.

CONCLUSION

We found that bismuth shields and lead goggles are suitable protective devices for the optimal reduction of lens doses.

Diagnostic accuracy of flat-panel computed tomography in assessing cerebral perfusion in comparison with perfusion computed tomography and perfusion magnetic resonance: a systematic review

Purpose

Flat-panel computed tomography (FP-CT) is increasingly available in angiographic rooms and hybrid OR’s. Considering its easy access, cerebral imaging using FP-CT is an appealing modality for intra-procedural applications. The purpose of this systematic review is to assess the diagnostic accuracy of FP-CT compared with perfusion computed tomography (CTP) and perfusion magnetic resonance (MRP) in cerebral perfusion imaging.

Methods

We performed a systematic literature search in the Cochrane Library, MEDLINE, Embase, and Web of Science up to June 2019 for studies directly comparing FP-CT with either CTP or MRP in vivo. Methodological quality was assessed using the QUADAS-2 tool. Data on diagnostic accuracy was extracted and pooled if possible.

Results

We found 11 studies comparing FP-CT with CTP and 5 studies comparing FP-CT with MRP. Most articles were pilot or feasibility studies, focusing on scanning and contrast protocols. All patients studied showed signs of cerebrovascular disease. Half of the studies were animal trials. Quality assessment showed unclear to high risks of bias and low concerns regarding applicability. Five studies reported on diagnostic accuracy; FP-CT shows good sensitivity (range 0.84–1.00) and moderate specificity (range 0.63–0.88) in detecting cerebral blood volume (CBV) lesions.

Conclusions

Even though FP-CT provides similar CBV values and reconstructed blood volume maps as CTP in cerebrovascular disease, additional studies are required in order to reliably compare its diagnostic accuracy with cerebral perfusion imaging.

Electronic supplementary material

The online version of this article (10.1007/s00234-019-02285-y) contains supplementary material, which is available to authorized users.

ESTIMATION OF PATIENT LENS DOSE ASSOCIATED WITH C-ARM CONE-BEAM COMPUTED TOMOGRAPHY USAGE DURING INTERVENTIONAL NEURORADIOLOGY

The purpose of this study was to investigate the dose distribution and lens doses associated with C-arm cone-beam computed tomography (CBCT), using a head phantom, and to estimate the contribution ratio of C-arm CBCT to each patient's lens dose during interventional neuroradiology ('lens dose ratio') in 109 clinical cases. In the phantom study, the peak skin doses and respective right and left lens doses of C-arm CBCT were as follows: 63.0 ± 1.9 mGy, 19.7 ± 1.4 mGy and 21.9 ± 0.8 mGy in whole brain C-arm CBCT and 39.2 ± 1.4 mGy, 4.7 ± 0.9 mGy and 3.6 ± 0.3 mGy in high-resolution C-arm CBCT. In the clinical study, the lens dose ratios were 25.4 ± 8.7% in the right lens and 19.1 ± 9.8% in the left lens. This study shows that, on average, ~25% of patients' total lens dose was contributed by C-arm CBCT.

Intra-aneurysmal air after flow diversion treatment in intracranial aneurysms: incidence, characteristics and clinical significance

OBJECTIVE

To describe the rate and characteristics of air bubble retention (ABR) within cerebral aneurysms treated by flow diversion.

METHODS

Procedural flat detector CT (FDCT) studies were scrutinized for the presence of air bubbles (density < - 200 HU) in patients treated by flow diversion. Patients with intrasaccular treatment or previous clipping were excluded. Clinical outcomes, procedural angiograms, aneurysm characteristics and imaging features of air within the aneurysm were evaluated.

RESULTS

Bubbles were noted in 17.1% of 105 aneurysms in 85 FDCTs. Aneurysms with ABR were significantly larger (mean diameter: 18.9 versus 7.5 mm, P < 0.0001). There was a trend for the use of multiple devices during the treatment of these aneurysms (72.2% vs 49.4%, P = 0.071). All of the bubbles were located rostrally in the aneurysm sac and were smaller than 6 mm (mean diameter: 2.1 ± 1.3 mm). None of the patients had post-procedural neurological deterioration. The air had spontaneously disappeared on follow-up CT images (available in 12 patients) obtained at a mean follow-up duration of 48 h.

CONCLUSIONS

ABR is not infrequent in cerebral flow diversion procedures. It is a clinically silent and self-limited technical complication. We propose air entrapment or filtration through the flow diverter as causative factors.

Flat Panel Detector Computed Tomography-Guided Placement of External Ventricular Drains Using the BrainLAB Headband and Precalibrated Disposable Stylet Instrument: A Cadaveric Feasibility Study

BACKGROUND

The standard freehand method for the insertion of external ventricular drains (EVDs) is associated with high rates of incorrect placement. Use of neuronavigation has been shown to reduce the rates of inaccurately positioned EVDs. We present a novel neuronavigation-based approach for EVD placement using flat panel detector computed tomography (FDCT) imaging.

METHODS

Four cadaveric heads were used for neuronavigated placement of EVDs using the BrainLAB reference headband in combination with laser surface registration and the precalibrated disposable stylet. In 2 cases, conventional multislice CT imaging was performed to reference neuronavigation. In the other 2 cases, preprocedural imaging was performed with FDCT. After inserting the EVDs, all heads were examined again with the identical imaging method as used before the procedure, followed by evaluation of catheter position.

RESULTS

Our data demonstrate that FDCT imaging provides adequate image quality for referencing neuronavigation and performing navigated neurosurgery. All EVDs showed an optimal position in the ipsilateral frontal horn. Use of a BrainLAB reference headband combined with laser surface registration and the precalibrated disposable stylet affords the advantage of not requiring rigid fixation in a clamp.

CONCLUSIONS

Our presented method is fast, accurate, and easy to use. Furthermore, this study is the first to demonstrate that navigated neurosurgery can be performed on the basis of FDCT imaging.

Accuracy of image-guided percutaneous injection into a phantom spinal cord utilizing flat panel detector CT with MR fusion and integrated navigational software

PURPOSE

To evaluate the accuracy of percutaneous fluoroscopic injection into the spinal cord of a spine phantom utilizing integrated navigational guidance from fused flat panel detector CT (FDCT) and MR datasets. Conventional and convection-enhanced delivery (CED) techniques were evaluated.

MATERIALS AND METHODS

FDCT and MR datasets of a swine thoracic spine phantom were co-registered using an integrated guidance system and surface to spinal cord target trajectory planning was performed on the fused images. Under real-time fluoroscopic guidance with pre-planned trajectory overlay, spinal cord targets were accessed via a coaxial technique. Final needle tip position was compared with a pre-determined target on 10 independent passes. In a subset of cases, contrast was injected into the central spinal cord with a 25G spinal needle or customized 200 µm inner diameter step design cannula for CED.

RESULTS

Average needle tip deviation from target measured 0.92±0.5 mm in the transverse, 0.47±0.4 mm in the anterior-posterior, and 1.67±1.2 mm in the craniocaudal dimension for an absolute distance error of 2.12±1.12 mm. CED resulted in elliptical intramedullary diffusion of contrast compared with primary reflux observed with standard needle injection.

CONCLUSIONS

These phantom feasibility data demonstrate a minimally invasive percutaneous approach for targeted injection into the spinal cord utilizing real-time fluoroscopy aided by overlay trajectories derived from fused MRI and FDCT data sets with a target error of 2.1 mm. Intramedullary diffusion of injectate in the spinal cord is facilitated with CED compared with standard injection technique. Pre-clinical studies in large animal models are warranted.

Optimized Management of Endovascular Treatment for Acute Ischemic Stroke

This manuscript describes a streamlined protocol for the management of patients with acute ischemic stroke, which aims at the minimization of time from hospital admission to reperfusion. Rapid restoration of cerebral blood flow is essential for the outcomes of patients with acute ischemic stroke. Endovascular treatment (EVT) has become the standard of care to accomplish this in patients with acute stroke due to large vessel occlusion (LVO). To achieve reperfusion of ischemic brain regions as fast as possible, all in-hospital time delays have to be carefully avoided. Therefore, management of patients with acute ischemic stroke was optimized with an interdisciplinary standard operating procedure (SOP). Stroke neurologists, diagnostic as well as interventional neuroradiologists, and anesthesiologists streamlined all necessary processes from patient admission and diagnosis to EVT of eligible patients. Target times for every step were established. Actually achieved times were prospectively recorded along with clinical data and imaging scores for all endovascularly treated stroke patients. These data were regularly analyzed and discussed in interdisciplinary team meetings. Potential issues were evaluated and all staff involved was trained to adhere to the SOP. This streamlined patient management approach and enhanced interdisciplinary collaboration reduced time from patient admission to reperfusion significantly and was accompanied by a beneficial effect on clinical outcomes.

Clinical Impact of Flat Panel Volume CT Angiography in Evaluating the Accurate Intraoperative Deployment of Flow-Diverter Stents

BACKGROUND AND PURPOSE

The deployment of flow-diverter stents may be difficult to analyse on regular DSA. The purpose of our study was to investigate the clinical impact of stent-dedicated flat panel volume CT angiography to evaluate intraoperatively the satisfactory deployment of flow-diverter stents.

MATERIALS AND METHODS

From January 2009 to April 2015, 83 consecutive patients (mean age, 51 years; 62 women) were treated in our institution with flow-diverter stents. Eighty-seven aneurysms (82 unruptured, 5 ruptured; 77 anterior, 10 posterior circulation) were treated in these 83 patients (4 patients had 2 aneurysms, both treated by means of flow-diverter stents). One patient was treated for a traumatic carotid cavernous fistula. In 80% of the cases (68/85) a flat panel volume CT angiography was performed in the angiographic suite just after the flow-diverter stent deployment. Stent visualization was assessed by 2 independent reviewers. The clinical impact of stent malapposition was evaluated.

RESULTS

Flow-diverter stent visualization was satisfactory in 73.5% of the cases. In 2 cases (2.9%) the flat panel volume CT angiography prompted the operator to perform an additional intrastent angioplasty for a condition that was previously underestimated. Four patients (4.7%) experienced acute thromboembolic complications; 3 others had delayed thromboembolic complications. Only 1 of these patients had thromboembolic complications (acute or delayed) related to stent misdeployment, which was easily managed intraoperatively with no clinical consequence.

CONCLUSIONS

Flat panel volume CT angiography is an interesting tool to depict flow-diverter stent misdeployment and may encourage the operator to perform intrastent angioplasty (2.9% of the cases in our experience) to reduce the risks of thromboembolic complications.

Latest generation of flat detector CT as a peri-interventional diagnostic tool: a comparative study with multidetector CT

Background and purpose

Flat detector CT (FDCT) has been used as a peri-interventional diagnostic tool in numerous studies with mixed results regarding image quality and detection of intracranial lesions. We compared the diagnostic aspects of the latest generation FDCT with standard multidetector CT (MDCT).

Materials and methods

102 patients were included in our retrospective study. All patients had undergone interventional procedures. FDCT was acquired peri-interventionally and compared with postinterventional MDCT regarding depiction of ventricular/subarachnoidal spaces, detection of intracranial hemorrhage, and delineation of ischemic lesions using an ordinal scale. Ischemic lesions were quantified with the Alberta Stroke Program Early CT Scale (ASPECTS) on both examinations. Two neuroradiologists with varying grades of experience and a medical student scored the anonymized images separately, blinded to the clinical history.

Results

The two methods were of equal diagnostic value regarding evaluation of the ventricular system and the subarachnoidal spaces. Subarachnoidal, intraventricular, and parenchymal hemorrhages were detected with a sensitivity of 95%, 97%, and 100% and specificity of 97%, 100%, and 99%, respectively, using FDCT. Gray–white differentiation was feasible in the majority of FDCT scans, and ischemic lesions were detected with a sensitivity of 71% on FDCT, compared with MDCT scans. The mean difference in ASPECTS values on FDCT and MDCT was 0.5 points (95% CI 0.12 to 0.88).

Conclusions

The latest generation of FDCT is a reliable and accurate tool for the detection of intracranial hemorrhage. Gray–white differentiation is feasible in the supratentorial region.

Optimized Flat-Detector CT in Stroke Imaging: Ready for First-Line Use?

Background: Using flat-detector CT (FD-CT) for stroke imaging has the advantage that both diagnostic imaging and endovascular therapy can be performed directly within the Angio Suite without any patient transfer and time delay. Thus, stroke management could be speeded up significantly, and patient outcome might be improved. But as precondition for using FD-CT as primary imaging modality, a reliable exclusion of intracranial hemorrhage (ICH) has to be possible. This study aimed to investigate whether optimized native FD-CT, using a newly implemented reconstruction algorithm, may reliably detect ICH in stroke patients. Additionally, the potential to identify ischemic changes was evaluated. Methods: Cranial FD-CT scans were obtained in 102 patients presenting with acute ischemic stroke (n = 32), ICH (n = 45) or transient ischemic attack (n = 25). All scans were reconstructed with a newly implemented half-scan cone-beam algorithm. Two experienced neuroradiologists, unaware of clinical findings, evaluated independently the FD-CTs screening for hemorrhage or ischemic signs. The findings were correlated to CT, and rater and inter-rater agreement was assessed. Results: FD-CT demonstrated high sensitivity (95-100%) and specificity (100%) in detecting intracerebral and intraventricular hemorrhage (IVH). Overall, interobserver agreement (κ = 0.92) was almost perfect and rater agreement to CT highly significant (r = 0.81). One infratentorial ICH and 10 or 11 of 22 subarachnoid hemorrhages (SAHs) were missed of whom 7 were perimesencephalic. The sensitivity for detecting acute ischemic signs was poor in blinded readings (0 or 25%, respectively). Conclusions: Optimized FD-CT, using a newly implemented reconstruction algorithm, turned out as a reliable tool for detecting supratentorial ICH and IVH. However, detection of infratentorial ICH and perimesencephalic SAH is limited. The potential of FD-CT in detecting ischemic changes is poor in blinded readings. Thus, plain FD-CT seems insufficient as a standalone modality in acute stroke, but within a multimodal imaging approach primarily using the FD technology, native FD-CT seems capable to exclude reliably supratentorial hemorrhage. Currently, FD-CT imaging seems not yet ready for wide adoption, replacing regular CT, and should be reserved for selected patients. Furthermore, prospective evaluations are necessary to validate this approach in the clinical setting.

X-Ray Scatter Correction on Soft Tissue Images for Portable Cone Beam CT

Soft tissue images from portable cone beam computed tomography (CBCT) scanners can be used for diagnosis and detection of tumor, cancer, intracerebral hemorrhage, and so forth. Due to large field of view, X-ray scattering which is the main cause of artifacts degrades image quality, such as cupping artifacts, CT number inaccuracy, and low contrast, especially on soft tissue images. In this work, we propose the X-ray scatter correction method for improving soft tissue images. The X-ray scatter correction scheme to estimate X-ray scatter signals is based on the deconvolution technique using the maximum likelihood estimation maximization (MLEM) method. The scatter kernels are obtained by simulating the PMMA sheet on the Monte Carlo simulation (MCS) software. In the experiment, we used the QRM phantom to quantitatively compare with fan-beam CT (FBCT) data in terms of CT number values, contrast to noise ratio, cupping artifacts, and low contrast detectability. Moreover, the PH3 angiography phantom was also used to mimic human soft tissues in the brain. The reconstructed images with our proposed scatter correction show significant improvement on image quality. Thus the proposed scatter correction technique has high potential to detect soft tissues in the brain.

A novel reconstruction tool (syngo DynaCT Head Clear) in the post-processing of DynaCT images to reduce artefacts and improve image quality

BACKGROUND

Latest generations of flat detector (FD) neuroangiography systems are able to obtain CT-like images of the brain parenchyma. Owing to the geometry of the C-arm system, cone beam artifacts are common and reduce image quality, especially at the periphery of the field of view. An advanced reconstruction algorithm (syngo DynaCT Head Clear) tackles these artifacts by using a modified interpolation-based 3D correction algorithm to improve image quality.

MATERIALS AND METHODS

Eleven volumetric datasets from FD-CT scans were reconstructed with the standard algorithm as well as with the advanced algorithm. In a two-step data analysis process, two reviewers compared dedicated regions of the skull and brain in both reconstruction modes using a 5-point scale (1, much better; 5, much worse; advanced vs standard algorithm). Both reviewers were blinded to the reconstruction mode. In a second step, two additional observers independently evaluated image quality of the 3D data (non-comparative evaluation) in dedicated regions also using a 5-point scale (1, not diagnostically evaluable; 5, good quality, perfectly usable for diagnosis) for both reconstruction algorithms.

RESULTS

Both in the comparative evaluation of dedicated brain regions and in the independent analysis of the FD-CT datasets the observers rated a better image quality if the advanced algorithm was used. The improvement in image quality was statistically significant at both the supraganglionic (p=0.018) and the infratentorial (p=0.002) levels.

CONCLUSIONS

The advanced reconstruction algorithm reduces typical artifacts in FD-CT images and improves image quality at the periphery of the field of view.

Whole brain C-arm computed tomography parenchymal blood volume measurements

INTRODUCTION

C-arm flat detector computed tomography (FDCT) parenchymal blood volume (PBV) imaging in the neuro-interventional suite is a new technique for which detailed whole brain measurements have not been previously reported. This study aims to create a catalogue of PBV measurements for various anatomical regions encompassing the whole brain, using a three-dimensional volume-of-interest (3D-VOI) analysis.

METHODS

We acquired and analysed 30 C-arm FDCT datasets from 26 patients with aneurysmal subarachnoid haemorrhage (SAH), as part of a prospective study comparing C-arm computed tomography (CT) PBV with magnetic resonance perfusion-weighted imaging (MR-PWI). We calculated the PBV values for various brain regions with an automated analysis, using 58 pre-defined atlas-based 3D-VOIs encompassing the whole brain. VOIs partially or completely overlapping regions of magnetic resonance diffusion weighted imaging (MR-DWI) abnormality or magnetic resonance cerebral blood flow (MR-CBF) asymmetry were excluded from the analysis.

RESULTS

Of the 30 C-arm CT PBV datasets, 14 (54%; 12 patients) had areas of restricted diffusion, the majority of which were focal. The PBV values for the cerebral cortex and cerebral white matter were 4.01 ± 0.47 (mean ± SD) and 3.01 ± 0.39 ml per 100 ml. Lobar PBV values were: frontal lobe 4.2 ± 0.8, temporal lobe 4.2 ± 0.9, parietal lobe 3.9 ± 0.7 and occipital lobe 4.3 ± 0.8 ml/100 ml. The basal ganglia and brainstem PBV values were 3.4 ± 0.7 and 4.6 ± 0.6 ml/100 ml, respectively.

CONCLUSIONS

Compared with the typical reference cerebral blood volume (CBV) values reported in the literature for Positron Emission Tomography (PET), the PBV values were relatively high for the white matter and relatively low for the cortical grey matter. The reported catalogue of PBV values for various brain regions would be useful to inform future studies and could be used in clinical practice, when interpreting PBV maps.

Flat-Panel Computed Tomography (DYNA-CT) in Neuroradiology. From High-Resolution Imaging of Implants to One-Stop-Shopping for Acute Stroke

Originally aimed at improving standard radiography by providing higher absorption efficiency and a wider dynamic range, flat-panel detector technology has meanwhile got widely accepted in the neuroradiological community. Especially flat-panel detector computed tomography (FD-CT) using rotational C-arm mounted flat-panel detector technology is capable of volumetric imaging with a high spatial resolution. By providing CT-like images of the brain within the angio suite, FD-CT is able to rapidly visualize hemorrhage and may thus improve complication management without the need of patient transfer. As "Angiographic CT" FD-CT may be helpful during many diagnostic and neurointerventional procedures and for noninvasive monitoring and follow-up. In addition, spinal interventions and high-resolution imaging of the temporal bone might also benefit from FD-CT. Finally, using novel dynamic perfusion and angiographic protocols, FD-CT may provide functional information on brain perfusion and vasculature with the potential to replace standard imaging in selected acute stroke patients.

Accuracy of flat panel detector CT with integrated navigational software with and without MR fusion for single-pass needle placement

PURPOSE

Fluoroscopic systems in modern interventional suites have the ability to perform flat panel detector CT (FDCT) with navigational guidance. Fusion with MR allows navigational guidance towards FDCT occult targets. We aim to evaluate the accuracy of this system using single-pass needle placement in a deep brain stimulation (DBS) phantom.

MATERIALS AND METHODS

MR was performed on a head phantom with DBS lead targets. The head phantom was placed into fixation and FDCT was performed. FDCT and MR datasets were automatically fused using the integrated guidance system (iGuide, Siemens). A DBS target was selected on the MR dataset. A 10 cm, 19 G needle was advanced by hand in a single pass using laser crosshair guidance. Radial error was visually assessed against measurement markers on the target and by a second FDCT. Ten needles were placed using CT-MR fusion and 10 needles were placed without MR fusion, with targeting based solely on FDCT and fusion steps repeated for every pass.

RESULTS

Mean radial error was 2.75±1.39 mm as defined by visual assessment to the centre of the DBS target and 2.80±1.43 mm as defined by FDCT to the centre of the selected target point. There were no statistically significant differences in error between MR fusion and non-MR guided series.

CONCLUSIONS

Single pass needle placement in a DBS phantom using FDCT guidance is associated with a radial error of approximately 2.5-3.0 mm at a depth of approximately 80 mm. This system could accurately target sub-centimetre intracranial lesions defined on MR.

Intravenous contrast media application using cone-beam computed tomography in a rabbit model

Purpose

This study was performed to evaluate the feasibility of visualizing soft tissue lesions and vascular structures using contrast-enhanced cone-beam computed tomography (CE-CBCT) after the intravenous administration of a contrast medium in an animal model.

Materials and Methods

CBCT was performed on six rabbits after a contrast medium was administered using an injection dose of 2 mL/kg body weight and an injection rate of 1 mL/s via the ear vein or femoral vein under general anesthesia. Artificial soft tissue lesions were created through the transplantation of autologous fatty tissue into the salivary gland. Volume rendering reconstruction, maximum intensity projection, and multiplanar reconstruction images were reconstructed and evaluated in order to visualize soft tissue contrast and vascular structures.

Results

The contrast enhancement of soft tissue was possible using all contrast medium injection parameters. An adequate contrast medium injection parameter for facilitating effective CE-CBCT was a 5-mL injection before exposure combined with a continuous 5-mL injection during scanning. Artificial soft tissue lesions were successfully created in the animals. The CE-CBCT images demonstrated adequate opacification of the soft tissues and vascular structures.

Conclusion

Despite limited soft tissue resolution, the opacification of vascular structures was observed and artificial soft tissue lesions were visualized with sufficient contrast to the surrounding structures. The vascular structures and soft tissue lesions appeared well delineated in the CE-CBCT images, which was probably due to the superior spatial resolution of CE-CBCT compared to other techniques, such as multislice computed tomography.

Early experience with low contrast imaging (LCI) technology during neuroendovascular interventional procedures

BACKGROUND AND PURPOSE

Early recognition of complications during intracranial neuroendovascular interventions is important for medical decision making and prompts administration of life-saving treatments. Low contrast imaging (LCI) provides computed tomographic (CT)-like images of anatomical brain structures, capable of detecting hydrocephalus and intracranial hemorrhage complications. We present our early experience with LCI using the Toshiba Infinix-i biplane angiographic suite during neurointerventional cases, including acute stroke interventions, aneurysm embolization, and subarachnoid hemorrhage management.

METHODS

Six patients underwent LCI during various neuroendovascular procedures. We describe clinical and imaging findings and provide visual comparison of LCI with conventional noncontrast cranial CT imaging.

RESULTS

Our initial experience shows that LCI is capable of detecting or excluding intracerebral hemorrhage and hydrocephalus during neurointerventional procedures as well as confirming ventriculostomy catheter placement when compared to noncontrast CT imaging. Motion artifact is a major limitation associated with this technology and can be overcome in part by performing shorter duration rotation sequences.

CONCLUSIONS

LCI is a promising tool in the arsenal of a neuroendovascular interventionist, especially when a complication is suspected during an intervention, potentially obviating the need for immediate transfer of the patient to a conventional CT scanner. Further studies comparing LCI with conventional noncontrast CT imaging are necessary.

Quantitative analysis of high-resolution, contrast-enhanced, cone-beam CT for the detection of intracranial in-stent hyperplasia

BACKGROUND

Intracranial in-stent hyperplasia is a stroke-associated complication that requires routine surveillance.

OBJECTIVE

To compare the results of in vivo experiments to determine the accuracy and precision of in-stent hyperplasia measurements obtained with modified C-arm contrast-enhanced, cone-beam CT (CE-CBCT) imaging with those obtained by 'gold standard' histomorphometry. Additionally, to carry out clinical analyses comparing this CE-CBCT protocol with digital subtraction angiography (DSA).

METHODS

A non-binned CE-CBCT protocol (VasoCT) was used that acquires x-ray images with a small field-of-view and applies a full-scale reconstruction algorithm providing high-resolution three-dimensional (3D) imaging with 100 µm isotropic voxels. In an vivo porcine model, VasoCT cross-sectional area measurements were compared with gold standard vessel histology. VasoCT and DSA were used to calculate in-stent stenosis in 23 imaging studies.

RESULTS

Porcine VasoCT cross-sectional stent, lumen, and in-stent hyperplasia areas strongly correlated with histological measurements (r(2)=0.97, 0.93, 0.90; slope=1.14, 1.07, and 0.76, respectively; p<0.0001). Clinical VasoCT percentage stenosis correlated well with DSA percentage stenosis (r(2)=0.84; slope=0.76), and the two techniques were free of consistent bias (Bland-Altman, bias=3.29%; 95% CI -14.75% to 21.33%). An illustrative clinical case demonstrated the advantages of VasoCT, including 3D capability and non-invasive IV contrast administration, for detection of in-stent hyperplasia.

CONCLUSIONS

C-arm VasoCT is a high-resolution 3D capable imaging technique that has been validated in an animal model for measurement of in-stent tissue growth. Successful clinical implementation of the protocol was performed in a small case series.

Artifact reduction of different metallic implants in flat detector C-arm CT

BACKGROUND AND PURPOSE

Flat detector CT has been increasingly used as a follow-up examination after endovascular intervention. Metal artifact reduction has been successfully demonstrated in coil mass cases, but only in a small series. We attempted to objectively and subjectively evaluate the feasibility of metal artifact reduction with various metallic objects and coil lengths.

MATERIALS AND METHODS

We retrospectively reprocessed the flat detector CT data of 28 patients (15 men, 13 women; mean age, 55.6 years) after they underwent endovascular treatment (20 coiling ± stent placement, 6 liquid embolizers) or shunt drainage (n = 2) between January 2009 and November 2011 by using a metal artifact reduction correction algorithm. We measured CT value ranges and noise by using region-of-interest methods, and 2 experienced neuroradiologists rated the degrees of improved imaging quality and artifact reduction by comparing uncorrected and corrected images.

RESULTS

After we applied the metal artifact reduction algorithm, the CT value ranges and the noise were substantially reduced (1815.3 ± 793.7 versus 231.7 ± 95.9 and 319.9 ± 136.6 versus 45.9 ± 14.0; both P < .001) regardless of the types of metallic objects and various sizes of coil masses. The rater study achieved an overall improvement of imaging quality and artifact reduction (85.7% and 78.6% of cases by 2 raters, respectively), with the greatest improvement in the coiling group, moderate improvement in the liquid embolizers, and the smallest improvement in ventricular shunting (overall agreement, 0.857).

CONCLUSIONS

The metal artifact reduction algorithm substantially reduced artifacts and improved the objective image quality in every studied case. It also allowed improved diagnostic confidence in most cases.

Target delineation for radiosurgery of a small brain arteriovenous malformation using high-resolution contrast-enhanced cone beam CT

Three years following endovascular embolization of a 3 mm ruptured arteriovenous malformation (AVM) of the left superior colliculus in a 42-year-old man, digital subtraction angiography showed continuous regrowth of the lesion. Thin-slice MRI acquired for treatment planning did not show the AVM nidus. The patient was brought back to the angiography suite for high-resolution contrast-enhanced cone beam CT (VasoCT) acquired using an angiographic c-arm system. The lesion and nidus were visualized with VasoCT. MRI, CT and VasoCT data were transferred to radiation planning software and mutually co-registered. The nidus was annotated for radiation on VasoCT data by an experienced neurointerventional radiologist and a dose/treatment plan was completed. Due to image registration, the treatment area could be directly adopted into the MRI and CT data. The AVM was completely obliterated 10 months following completion of the radiosurgery treatment.

Target delineation for radiosurgery of a small brain arteriovenous malformation using high-resolution contrast-enhanced cone beam CT

Three years following endovascular embolization of a 3 mm ruptured arteriovenous malformation (AVM) of the left superior colliculus in a 42-year-old man, digital subtraction angiography showed continuous regrowth of the lesion. Thin-slice MRI acquired for treatment planning did not show the AVM nidus. The patient was brought back to the angiography suite for high-resolution contrast-enhanced cone beam CT (VasoCT) acquired using an angiographic c-arm system. The lesion and nidus were visualized with VasoCT. MRI, CT and VasoCT data were transferred to radiation planning software and mutually co-registered. The nidus was annotated for radiation on VasoCT data by an experienced neurointerventional radiologist and a dose/treatment plan was completed. Due to image registration, the treatment area could be directly adopted into the MRI and CT data. The AVM was completely obliterated 10 months following completion of the radiosurgery treatment.

A prospective, multicenter pilot study investigating the utility of flat detector derived parenchymal blood volume maps to estimate cerebral blood volume in stroke patients

Purpose

Newer flat panel angiographic detector (FD) systems have the capability to generate parenchymal blood volume (PBV) maps. The ability to generate these maps in the angiographic suite has the potential to markedly expedite the triage and treatment of patients with acute ischemic stroke. The present study compares FP-PBV maps with cerebral blood volume (CBV) maps derived using standard dynamic CT perfusion (CTP) in a population of patients with stroke.

Methods

56 patients with cerebrovascular ischemic disease at two participating institutions prospectively underwent both standard dynamic CTP imaging followed by FD-PBV imaging (syngo Neuro PBV IR; Siemens, Erlangen, Germany) under a protocol approved by both institutional review boards. The feasibility of the FD system to generate PBV maps was assessed. The radiation doses for both studies were compared. The sensitivity and specificity of the PBV technique to detect (1) any blood volume deficit and (2) a blood volume deficit greater than one-third of a vascular territory, were defined using standard dynamic CTP CBV maps as the gold standard.

Results

Of the 56 patients imaged, PBV maps were technically adequate in 42 (75%). The 14 inadequate studies were not interpretable secondary to patient motion/positioning (n=4), an injection issue (n=2), or another reason (n=8). The average dose for FD-PBV was 219 mGy (median 208) versus 204 mGy (median 201) for CT-CBV. On CT-CBV maps 26 of 42 had a CBV deficit (61.9%) and 15 (35.7%) had a deficit that accounted for greater than one-third of a vascular territory. FD-PBV maps were 100% sensitive and 81.3% specific to detect any CBV deficit and 100% sensitive and 62.9% specific to detect any CBV deficit of greater than one-third of a territory.

Conclusions

PBV maps can be generated using FP systems. The average radiation dose is similar to a standard CTP examination. PBV maps have a high sensitivity for detecting CBV deficits defined by conventional CTP. PBV maps often overestimate the size of CBV deficits. We hypothesize that the FP protocol initiates PBV imaging prior to complete saturation of the blood volume in areas perfused via indirect pathways (ie, leptomeningeal collaterals), resulting in an overestimation of CBV deficits, particularly in the setting of large vessel occlusion.

Integrated flat detector CT and live fluoroscopic-guided external ventricular drain placement within the neuroangiography suite

Purpose

To demonstrate the feasibility of the application of integrated flat detector (FD) CT and fluoroscopic guidance (iGuide) for the placement of external ventricular drains (EVD) within the neuroangiography suite.

Methods

A retrospective review of a prospectively maintained endovascular database identified six patients who underwent EVD placement using iGuide. Patient characteristics, operator, number of passes, accuracy of placement, immediate and delayed periprocedural complications and radiation exposure were assessed.

Results

Five patients with subarachnoid hemorrhage and one patient with a large cerebellar infarct (average age 45.5 years (range 39–53), four women) underwent EVD placement within the angiography suite using iGuide. Four procedures were performed by a neuroradiologist and two by a neurosurgeon. All catheters were placed with a single pass and all terminated within the frontal horn of the ipsilateral lateral ventricle. No parenchymal or intraventricular hemorrhages were encountered after catheter placement. No patients experienced any immediate or delayed periprocedural complications. Radiation exposure related to the FD CTs required for placement was 593.7 mGy (range 539–673).

Conclusions

EVD placement under combined CT and fluoroscopic control within the neuroangiography suite is feasible. The technique predictably allows optimized EVD catheter placement with a single pass. We propose that this technique could improve the accuracy, and potentially reduce the complications, of EVD insertion in cerebrovascular patients.

C-arm CT measurement of cerebral blood volume and cerebral blood flow using a novel high-speed acquisition and a single intravenous contrast injection

BACKGROUND AND PURPOSE

Assessment of perfusion parameters is important in the selection of patients who are most likely to benefit from revascularization after an acute ischemic stroke. The aim of this study was to evaluate the feasibility of measuring cerebral perfusion parameters with the use of a novel high-speed C-arm CT acquisition in conjunction with a single intravenous injection of contrast.

MATERIALS AND METHODS

Seven canines had experimentally induced focal ischemic regions confirmed by CT perfusion imaging. Four hours after ischemic injury creation, each subject underwent cerebral perfusion measurements with the use of standard perfusion CT, immediately followed by the use of C-arm CT. Cerebral blood flow and cerebral blood volume maps measured by C-arm CT were quantitatively and qualitatively compared with those measured by perfusion CT for 6 of the 7 canine subjects.

RESULTS

Results from independent observer evaluations of perfusion CT and C-arm perfusion maps show strong agreement between observers for identification of ischemic lesion location. Significant percentage agreement between observers for lesion detection and identification of perfusion mismatch between CBV and CBF maps indicate that the maps for both perfusion CT and C-arm are easy to interpret. Quantitative region of interest-based evaluation showed a strong correlation between the perfusion CT and C-arm CBV and CBF maps (R(2) = 0.68 and 0.85). C-arm measurements for both CBV and CBF were consistently overestimated when compared with perfusion CT.

CONCLUSIONS

Qualitative and quantitative measurements of CBF and CBV with the use of a C-arm CT acquisition and a single intravenous injection of contrast agent are feasible. Future improvements in flat detector technology and software algorithms probably will enable more accurate quantitative perfusion measurements with the use of C-arm CT.

Toward the era of a one-stop imaging service using an angiography suite for neurovascular disorders

Transportation of patients requiring multiple diagnostic and imaging-guided therapeutic modalities is unavoidable in current radiological practice. This clinical scenario causes time delays and increased risk in the management of stroke and other neurovascular emergencies. Since the emergence of flat-detector technology in imaging practice in recent decades, studies have proven that flat-detector X-ray angiography in conjunction with contrast medium injection and specialized reconstruction algorithms can provide not only high-quality and high-resolution CT-like images but also functional information. This improvement in imaging technology allows quantitative assessment of intracranial hemodynamics and, subsequently in the same imaging session, provides treatment guidance for patients with neurovascular disorders by using only a flat-detector angiographic suite-a so-called one-stop quantitative imaging service (OSIS). In this paper, we review the recent developments in the field of flat-detector imaging and share our experience of applying this technology in neurovascular disorders such as acute ischemic stroke, cerebral aneurysm, and stenoocclusive carotid diseases.

C-arm flat-panel CT arthrography of the wrist and elbow: first experiences in human cadavers

OBJECTIVE

To determine the optimal intra-articular iodine concentration for C-arm flat-panel computed tomography (FPCT) arthrography using advanced joint phantoms and to evaluate its application in human cadaveric wrists and elbows. Multi-detector (MD) CT served as the standard of reference.

MATERIALS AND METHODS

Joint phantoms and 10 human cadaveric wrist and elbow joints were scanned with C-arm FPCT (5-s, 8-s, and 20-s runs) and standard MDCT using different and optimal concentrations of iodinated contrast material. CT numbers of contrast material, tissue, and noise were measured and contrast-to-noise ratios (CNR) calculated for quantitative analysis. Image and depiction of cartilage, bone, and soft tissues were rated. Radiation doses were compared.

RESULTS

In FPCT, iodine concentrations positively correlated with CT numbers and noise of contrast material and with radiation dose (r = 0.713-0.996, p < 0.05 each). At an iodine concentration of 45 mg/ml, CNR of cartilage and soft tissues were highest for all FPCT acquisitions and higher than in MDCT. The 20-s FPCT run performed best for image quality and depiction of anatomical structures and was rated overall equal to MDCT (p = 0.857).

CONCLUSION

The optimal iodine concentration for C-arm FPCT arthrography in this study is 45 mg/ml, leading to superior CNR and image quality for an optimal FPCT protocol compared with standard MDCT arthrography in human cadaveric joints.

Does preinterventional flat-panel computer tomography pooled blood volume mapping predict final infarct volume after mechanical thrombectomy in acute cerebral artery occlusion?

PURPOSE

Decreased cerebral blood volume is known to be a predictor for final infarct volume in acute cerebral artery occlusion. To evaluate the predictability of final infarct volume in patients with acute occlusion of the middle cerebral artery (MCA) or the distal internal carotid artery (ICA) and successful endovascular recanalization, pooled blood volume (PBV) was measured using flat-panel detector computed tomography (FPD CT).

MATERIALS AND METHODS

Twenty patients with acute unilateral occlusion of the MCA or distal ACI without demarcated infarction, as proven by CT at admission, and successful Thrombolysis in cerebral infarction score (TICI 2b or 3) endovascular thrombectomy were included. Cerebral PBV maps were acquired from each patient immediately before endovascular thrombectomy. Twenty-four hours after recanalization, each patient underwent multislice CT to visualize final infarct volume. Extent of the areas of decreased PBV was compared with the final infarct volume proven by follow-up CT the next day.

RESULTS

In 15 of 20 patients, areas of distinct PBV decrease corresponded to final infarct volume. In 5 patients, areas of decreased PBV overestimated final extension of ischemia probably due to inappropriate timing of data acquisition and misery perfusion.

CONCLUSION

PBV mapping using FPD CT is a promising tool to predict areas of irrecoverable brain parenchyma in acute thromboembolic stroke. Further validation is necessary before routine use for decision making for interventional thrombectomy.

Intraprocedural angiographic CT as a valuable tool in the course of endovascular treatment of direct sinus cavernous fistulas

This investigation aimed to demonstrate the potential of intraprocedural angiographic CT in monitoring complex endovascular coil embolization of direct carotid cavernous fistulas. Angiographic CT was performed as a dual rotational 5 s run with intraarterial contrast medium injection in two patients during endovascular coil embolization of direct carotid cavernous fistulas. Intraprocedural angiographic CT was considered helpful if conventional 2D series were not conclusive concerning coil position or if a precise delineation of the parent artery was impossible due to a complex anatomy or overlying coil material. During postprocessing multiplanar reformatted and dual volume images of angiographic CT were reconstructed. Angiographic CT turned out to be superior in the intraprocedural visualization of accidental coil migration into the parent artery where conventional 2D-DSA series failed to reliably detect coil protrusion. The delineation of coil protrusion by angiographic CT allowed immediate correct coil repositioning to prevent parent artery compromising. Angiographic CT can function as a valuable intraprocedurally feasible tool during complex coil embolizations of direct carotid cavernous fistulas. It allows the precise visualization of the cerebral vasculature and any accidental coil protrusion can be determined accurately in cases where conventional 2D-DSA series are unclear or compromised. Thus angiographic CT might contribute substantially to reduce procedural complications and to increase safety in the management of endovascular treatment of direct carotid cavernous fistulas.

Subarachnoid hyperattenuation on flat panel detector-based conebeam CT immediately after uneventful coil embolization of unruptured intracranial aneurysms

BACKGROUND AND PURPOSE

Flat panel detector-based CBCT can provide CT-like images of the brain without transferring patients from the angiography suite to a conventional CT facility. Conventional brain CT after uneventful endovascular treatment sometimes shows focal subarachnoid hyperattenuation with contrast leakage, mimicking SAH. Differentiating this finding from SAH is important for immediate postprocedural medical management. We investigated CBCT for detecting subarachnoid hyperattenuation immediately after coil embolization of unruptured cerebral aneurysms.

MATERIALS AND METHODS

Thirty-six patients with unruptured cerebral aneurysms undergoing CBCT immediately after uncomplicated coil embolization were included. The relationship between the presence of subarachnoid hyperattenuation and total volume of contrast medium injected, aneurysm size and location, and balloon and stent assistance during embolization was investigated. Statistical analyses were performed with the χ(2) test (P < .05).

RESULTS

Nine of the 36 patients (25.0%) showed focal subarachnoid hyperattenuation within the relevant parent artery territory harboring the aneurysm. Subarachnoid hyperattenuation locations included the ipsilateral superior frontal sulcus (n = 5), the bilateral superior frontal sulcus (n = 1), and the ipsilateral superior frontal and precentral sulci (n = 3). Statistically significant differences were observed between the presence of a subarachnoid hyperattenuation and the total volume of contrast medium injected (P < .001) and aneurysm size (P < .05).

CONCLUSIONS

Subarachnoid hyperattenuation can be detected by CBCT immediately after coil embolization for unruptured aneurysms. The increased amounts of contrast medium to be given before CBCT and the specific location of the hyperattenuation may help differentiate benign subarachnoid contrast leakage from SAH.

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.

Angiographic CT for intraprocedural monitoring of complex neuroendovascular procedures

SUMMARY Evolving techniques in interventional neuroradiology have widened therapeutic options, allowing treatment even in complex cases. Complex neuroendovascular procedures (eg, stent-assisted coiling, stent placement in X- or Y-techniques) require precise delineation of cerebral vasculature and devices. However, because of the complex anatomy or if an ideal projection is not possible, visualization of the parent artery might be difficult. We present 2 complex cases of basilar tip aneurysm in which ACT proved to be beneficial in the intraprocedural monitoring of stent-assisted coil embolization.

Applicability of tableside flat panel detector CT parenchymal cerebral blood volume measurement in neurovascular interventions: preliminary clinical experience

BACKGROUND AND PURPOSE

CBV is a vital perfusion parameter in estimating the viability of brain parenchyma (eg, in cases of ischemic stroke or after interventional vessel occlusion). Recent technologic advances allow parenchymal CBV imaging tableside in the angiography suite just before, during, or after an interventional procedure. The aim of this work was to analyze our preliminary clinical experience with this new imaging tool in different neurovascular interventions.

MATERIALS AND METHODS

FPD-CBV measurement was performed on a biplane FPD angiographic system. Eighteen patients (11 women, 7 men) were examined (age range, 18-86 years; median, 58.7 years). In the 10 patients with stroke, the extent of intracranial hypoperfusion was evaluated. The remaining 8 patients had an intracranial hemorrhage; periprocedural CBV was evaluated during the course of interventional treatment.

RESULTS

In the 18 cases studied, 23 CBV measurements were performed. Twenty acquisitions were of sufficient diagnostic quality. The remaining 3 acquisitions failed technically, 1 due to motion artifacts and 2 due to injection technique and/or hardware failure.

CONCLUSIONS

FPD-CBV measurement in the angiography suite provides a feasible and helpful tool for peri-interventional neuroimaging. It extends the intraprocedural imaging modalities to the level of tissue perfusion. However, the technique has technical limitations and shows room for improvement in the future.

Feasibility of cerebral blood volume mapping by flat panel detector CT in the angiography suite: first experience in patients with acute middle cerebral artery occlusions

BACKGROUND AND PURPOSE

A new FPCT application offers the possibility of perfusion (FPCT CBV) and parenchymal (FPCT) imaging within the angiography suite. We tested the hypothesis that findings in FPCT CBV and FPCT would correlate with those obtained using MSCT and PCT.

MATERIALS AND METHODS

In 16 patients with acute MCA occlusion, FPCT CBV was performed immediately posttreatment. The volume of tissue having abnormal CBV values was determined by FPCT CBV and PCT images. Stroke volume on follow-up MSCT was determined, CBV values in the effected parenchyma were measured, and FPCT images were reviewed.

RESULTS

In 6 cases, we found a FPCT CBV value identical or higher (hyperemia) in comparison with the contralateral side. In 10 cases, we found CBV lesions with values lower (oligemia) than the contralateral brain tissue. We found a high correlation of CBV lesion volume on FPCT CBV images to stroke volume on follow-up MSCT (r = 0.9, P < .05) in the oligemia group. Absolute FPCT CBV and PCT CBV values were comparable and showed good correlation (r = 0.9, P < .05). In 8 patients, contrast medium extravasation was visible.

CONCLUSIONS

The new FPCT application allows assessment of CBV in acute stroke patients. Our initial results indicate that these measurements may predict final infarct volume. The ability to assess this key parameter of cerebral perfusion within the angiographic suite may improve the management of these patients.

Frameless multimodal image guidance of localized convection-enhanced delivery of therapeutics in the brain

INTRODUCTION

Convection-enhanced delivery (CED) has been shown to be an effective method of administering macromolecular compounds into the brain that are unable to cross the blood-brain barrier. Because the administration is highly localized, accurate cannula placement by minimally invasive surgery is an important requisite. This paper reports on the use of an angiographic c-arm system which enables truly frameless multimodal image guidance during CED surgery.

METHODS

A microcannula was placed into the striatum of five sheep under real-time fluoroscopic guidance using imaging data previously acquired by cone beam computed tomography (CBCT) and MRI, enabling three-dimensional navigation. After introduction of the cannula, high resolution CBCT was performed and registered with MRI to confirm the position of the cannula tip and to make adjustments as necessary. Adeno-associated viral vector-10, designed to deliver small-hairpin micro RNA (shRNAmir), was mixed with 2.0 mM gadolinium (Gd) and infused at a rate of 3 μl/min for a total of 100 μl. Upon completion, the animals were transferred to an MR scanner to assess the approximate distribution by measuring the volume of spread of Gd.

RESULTS

The cannula was successfully introduced under multimodal image guidance. High resolution CBCT enabled validation of the cannula position and Gd-enhanced MRI after CED confirmed localized administration of the therapy.

CONCLUSION

A microcannula for CED was introduced into the striatum of five sheep under multimodal image guidance. The non-alloy 300 μm diameter cannula tip was well visualized using CBCT, enabling confirmation of the position of the end of the tip in the area of interest.

Quantitative evaluation of C-arm CT cerebral blood volume in a canine model of ischemic stroke

BACKGROUND AND PURPOSE

Previous studies have shown the feasibility of assessing qualitative CBV measurements in the angiography suite by using FPD-CBCT systems. We have investigated the correlation of FPD-CBCT CBV lesion volumes to the infarct volume.

MATERIALS AND METHODS

Unilateral strokes were created in 7 adult dogs. MR imaging and FPD-CBCT data were obtained after MCA occlusion. FPD-CBCT CBV and ADC maps were generated for all subjects. The animals were sacrificed immediately following the last imaging study to measure infarct volume on histology. The reliability of FPD-CBCT-based lesion volume measurements was compared with those measured histologically by using regression and Bland-Altman analysis.

RESULTS

The best correlation (R(2) = 0.72) between lesion volumes assessed with FPD-CBCT and histology was established with a threshold of mean healthy CBV - 2.5 × SD. These results were inferior to the correlation of lesion volumes measured with ADC and histology (R(2) = 0.99). Bland-Altman analysis showed that the agreement of ADC-derived lesion volumes with histology was superior to the agreement of FPD-CBCT-derived lesion volumes with histology.

CONCLUSIONS

We correlated FPD-CBCT measurements of CBV and MR ADC lesion volumes with histologically assessed infarct volume. As expected, ADC is a very accurate and precise method for determining the extent of infarction. FPD-CBCT CBV lesion volumes are correlated to the size of the infarct. Improvement of FPD-CBCT image quality provides an opportunity to establish quantitative CBV measurement in the angiography suite.

The value of flat-detector computed tomography during catheterisation of congenital heart disease

OBJECTIVES

To analyse the diagnostic utility of flat-detector computed tomography imaging (FD-CT) in patients with congenital heart disease, including the value of image fusion to overlay three-dimensional (3D) reconstructions on fluoroscopic images during catheter-based interventions.

METHODS

We retrospectively analysed 62 consecutive paediatric patients in whom FD-CT was used during catheterisation of congenital heart disease. Expert operators rated the clinical value of FD-CT over conventional fluoroscopic imaging. Added radiation exposure and contrast medium volume were evaluated.

RESULTS

During a 12-month period, FD-CT was performed in 62 out of 303 cardiac catheterisations. Median patient age was 3.5 years. In 32/62 cases, FD-CT was used for diagnostic purposes, in 30/62 cases it was used in the context of interventions. Diagnostic utility was never rated as "misleading". It was classified as "not useful" in six cases (9.7%), "useful" in 18 cases (29.0%), "very useful" in 37 cases (59.7%) and "essential" in one case (1.6%). The median added dose-area product was 111.0 μGym(2), the required additional quantity of contrast medium was 1.6 ml/kg.

CONCLUSION

FD-CT provides useful diagnostic information in most of the patients investigated for congenital heart disease. The added radiation exposure and contrast medium volume are reasonable.

Clinical evaluation of flat-panel detector compared with multislice computed tomography in 65 patients with acute intracranial hemorrhage: initial results

Object

The goal in this study was to compare flat-panel detector (FD) CT with multislice (MS) CT in the visualization of intracerebral hemorrhage (ICH), subarachnoid hemorrhage (SAH), intraventricular hemorrhage, and external ventricular drains (EVDs) to evaluate the diagnostic quality and limitations of the new FD CT imaging modality.

Methods

Neuroimages obtained in 65 patients, including 24 with EVDs, were reviewed by 2 independent, experienced clinicians. Lesions in all patients were investigated with FD CT and MS CT. The numbers of slices positive for ICH and SAH were counted, and for ICH the diameter and area of the lesion was measured. The positioning of drains was assessed. The presence of ventricular blood was noted. Statistical analysis was performed by calculating the Pearson correlation coefficient (r) to evaluate the level of inter- and intraobserver agreement, and linear regression analysis was done to visualize the results of the numbers of ICH- and SAH-positive slices.

Results

The authors found high interobserver agreement regarding the number of slices with evidence of ICH (r = 0.89 for MS CT, r = 0.78 for FD CT) and SAH (r = 0.88 for MS CT, r = 0.9 for FD CT). Thin layers of blood in the ventricles were not detected on FD CT in 36.4% of cases. Six of 7 perimesencephalic SAHs were not seen on FD CT scans. The EVDs could be assessed with both modalities in 83.3% of cases, but the position of the drain could not be determined with FD CT in 16.7% (4 of 24 cases).

Conclusions

In some respects, FD CT is of limited use for the visualization of intracranial hemorrhage. However, despite limited contrast resolution, ICH and EVDs can be reliably demonstrated. Perimesencephalic SAH and thin layers of blood in the occipital horns may not be detected using FD CT. Further evaluation and improvement of the image quality is necessary before FD CT will provide identical quality in comparison with MS CT.