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

SuperDyna: Unlocking the Potential of Post-Treatment Device Evaluation

BACKGROUND

Current imaging algorithms for post-device evaluation are limited by either poor representation of the device or poor delineation of the treated vessel. Combining the high-resolution images from a traditional three-dimensional digital subtraction angiography (3D-DSA) protocol with the longer cone-beam computed tomography (CBCT) protocol may provide simultaneous visualization of both the device and the vessel content in a single volume, improving the accuracy and detail of the assessment. We aim here to review our use of this technique which we termed "SuperDyna".

METHODS

In this retrospective study, patients who underwent an endovascular procedure between February 2022 and January 2023 were identified. We analyzed patients who had both non-contrast CBCT and 3D-DSA post-treatment and collected information on pre-/post-blood urea nitrogen, creatinine, radiation dose, and the intervention type.

RESULTS

In 1 year, SuperDyna was performed in 52 (of 1935, 2.6%) patients, of which 72% were women, median age 60 years. The most common reason for the addition of the SuperDyna was for post-flow diversion assessment (n=39). Renal function tests showed no changes. The average total procedure radiation dose was 2.8 Gy, with 4% dose and ~20 mL of contrast attributed to the additional 3D-DSA needed to generate the SuperDyna.

CONCLUSIONS

The SuperDyna is a fusion imaging method that combines high-resolution CBCT and contrasted 3D-DSA to evaluate intracranial vasculature post-treatment. It allows for more comprehensive evaluation of the device position and apposition, aiding in treatment planning and patient education.

Flat-panel Detector Perfusion Imaging and Conventional Multidetector Perfusion Imaging in Patients with Acute Ischemic Stroke : A Comparative Study

PURPOSE

Flat-panel detector computed tomography (FDCT) is increasingly used in (neuro)interventional angiography suites. This study aimed to compare FDCT perfusion (FDCTP) with conventional multidetector computed tomography perfusion (MDCTP) in patients with acute ischemic stroke.

METHODS

In this study, 19 patients with large vessel occlusion in the anterior circulation who had undergone mechanical thrombectomy, baseline MDCTP and pre-interventional FDCTP were included. Hypoperfused tissue volumes were manually segmented on time to maximum (Tmax) and time to peak (TTP) maps based on the maximum visible extent. Absolute and relative thresholds were applied to the maximum visible extent on Tmax and relative cerebral blood flow (rCBF) maps to delineate penumbra volumes and volumes with a high likelihood of irreversible infarcted tissue ("core"). Standard comparative metrics were used to evaluate the performance of FDCTP.

RESULTS

Strong correlations and robust agreement were found between manually segmented volumes on MDCTP and FDCTP Tmax maps (r = 0.85, 95% CI 0.65-0.94, p < 0.001; ICC = 0.85, 95% CI 0.69-0.94) and TTP maps (r = 0.91, 95% CI 0.78-0.97, p < 0.001; ICC = 0.90, 95% CI 0.78-0.96); however, direct quantitative comparisons using thresholding showed lower correlations and weaker agreement (MDCTP versus FDCTP Tmax 6 s: r = 0.35, 95% CI -0.13-0.69, p = 0.15; ICC = 0.32, 95% CI 0.07-0.75). Normalization techniques improved results for Tmax maps (r = 0.78, 95% CI 0.50-0.91, p < 0.001; ICC = 0.77, 95% CI 0.55-0.91). Bland-Altman analyses indicated a slight systematic underestimation of FDCTP Tmax maximum visible extent volumes and slight overestimation of FDCTP TTP maximum visible extent volumes compared to MDCTP.

CONCLUSION

FDCTP and MDCTP provide qualitatively comparable volumetric results on Tmax and TTP maps; however, direct quantitative measurements of infarct core and hypoperfused tissue volumes showed lower correlations and agreement.

Virtual diluted cone beam CT for device apposition assessment during endovascular treatment of intracranial aneurysm: A technical note

The increasing use of embolization devices with suboptimal radio-opacity to treat intracranial aneurysm underscores the need for advanced imaging techniques to characterize device-vessel interactions more accurately. Contrast-diluted cone-beam CT is commonly used in neurointervention but requires additional technical refinements to improve endovascular treatment assessment. In this technical note, we describe the virtual dilution cone beam CT (VDCBCT), a technique that synthetizes non-contrast and contrast-enhanced CBCT images to virtually dilute iodinated contrast agents, thereby facilitating a more accurate assessment of embolization device apposition. Through a set of intracranial aneurysms treated with different embolization devices, we describe the VDCBCT protocol and its usefulness for device apposition confidence. VDCBCT may enhance the global understanding of neurovascular embolization treatments by providing improved visualization of target vessels and low-radio-opacity embolization devices, obviating the need for contrast dilution.

Value of Immediate Flat Panel Perfusion Imaging after Endovascular Therapy (AFTERMATH): A Proof of Concept Study

BACKGROUND AND PURPOSE

Potential utility of flat panel CT perfusion imaging (FPCT-PI) performed immediately after mechanical thrombectomy (MT) is unknown. We aimed to assess whether FPCT-PI obtained directly post-MT could provide additional potentially relevant information on tissue reperfusion status.

MATERIALS AND METHODS

This was a single-center analysis of all patients with consecutive acute stroke admitted between June 2019 and March 2021 who underwent MT and postinterventional FPCT-PI (n = 26). A core lab blinded to technical details and clinical data performed TICI grading on postinterventional DSA images and qualitatively assessed reperfusion on time-sensitive FPCT-PI maps. According to agreement between DSA and FPCT-PI, all patients were classified into 4 groups: hypoperfusion findings perfectly matched by location (group 1), hypoperfusion findings mismatched by location (group 2), complete reperfusion on DSA with hypoperfusion on FPCT-PI (group 3), and hypoperfusion on DSA with complete reperfusion on FPCT-PI (group 4).

RESULTS

Detection of hypoperfusion (present/absent) concurred in 21/26 patients. Of these, reperfusion findings showed perfect agreement on location and size in 16 patients (group 1), while in 5 patients there was a mismatch by location (group 2). Of the remaining 5 patients with disagreement regarding the presence or absence of hypoperfusion, 3 were classified into group 3 and 2 into group 4. FPCT-PI findings could have avoided TICI overestimation in all false-positive operator-rated TICI 3 cases (10/26).

CONCLUSIONS

FPCT-PI may provide additional clinically relevant information in a considerable proportion of patients undergoing MT. Hence, FPCT-PI may complement the evaluation of reperfusion efficacy and potentially inform decision-making in the angiography suite.

Motion artifact correction for cone beam CT stroke imaging: a prospective series

BACKGROUND

Imaging assessment for acute ischemic stroke (AIS) patients in the angiosuite using cone beam CT (CBCT) has created increased interest since endovascular treatment became the first line therapy for proximal vessel occlusions. One of the main challenges of CBCT imaging in AIS patients is degraded image quality due to motion artifacts. This study aims to evaluate the prevalence of motion artifacts in CBCT stroke imaging and the effectiveness of a novel motion artifact correction algorithm for image quality improvement.

METHODS

Patients presenting with acute stroke symptoms and considered for endovascular treatment were included in the study. CBCT scans were performed using the angiosuite X-ray system. All CBCT scans were post-processed using a motion artifact correction algorithm. Motion artifacts were scored before and after processing using a 4-point scale.

RESULTS

We prospectively included 310 CBCT scans from acute stroke patients. 51% (n=159/310) of scans had motion artifacts, with 24% being moderate to severe. The post-processing algorithm improved motion artifacts in 91% of scans with motion (n=144/159), restoring clinical diagnostic capability in 34%. Overall, 76% of the scans were sufficient for clinical decision-making before correction, which improved to 93% (n=289/310) after post-processing with our algorithm.

CONCLUSIONS

Our results demonstrate that CBCT motion artifacts are significantly reduced using a novel post-processing algorithm, which improved brain CBCT image quality and diagnostic assessment for stroke. This is an important step on the road towards a direct-to-angio approach for endovascular thrombectomy (EVT) treatment.

Use of Dyna-computed tomography-assisted neuroendoscopic hematoma evacuation in the treatment of hypertensive intracerebral hemorrhage

The purpose of this study was to evaluate and summarize the technical characteristics and clinical efficacy of using Dyna-computed tomography (CT)-assisted neuroendoscopic hematoma evacuation to treat hypertensive intracerebral hemorrhage (HICH). We treated 42 consecutive patients with HICH who underwent neuroendoscopic hematoma evacuation in our department from March 1, 2020, to May 31, 2022. Patients were divided into two groups: Dyna-CT-assisted neuroendoscopic group (n = 18) and neuroendoscopic group (n = 24). Retrospective data, treatment efficacy, and outcomes were collected and compared between these two groups. The operative time in the Dyna-CT-assisted neuroendoscopic group was significantly shorter than the operative time in the neuroendoscopic group (mean time 131.6 ± 13.51 vs. 156.6 ± 19.25 min, P < 0.001). Dyna-CT-assisted neuroendoscopic group had significantly less intraoperative blood loss than the neuroendoscopic group (46.94 ± 10.42 vs. 106.46 ± 23.25, P = 0.003). Meanwhile, patients who underwent Dyna-CT-assisted neuroendoscopic had a comparable hematoma clearance rate to those who underwent neuroendoscopic (89.36 ± 7.31 vs. 68.87 ± 19.44%, P = 0.006). The incidence of complications in the Dyna-CT-assisted neuroendoscopic group (5.5%) was lower than in the neuroendoscopic group (12.5%), but the difference was not statistically significant (P = 0.129). Patients who underwent Dyna-CT-assisted neuroendoscopic hematoma evacuation had better 6-month functional outcomes, and the difference was significant (P = 0.004). Furthermore, multivariable analysis showed that younger age, smaller hematoma volume, and Dyna-CT-assisted neuroendoscopic were predictors of favorable 6-month outcomes in HICH patients. In the treatment of HICH, Dyna-CT-assisted hematoma evacuation appears to be safer and more effective than neuroendoscopic hematoma evacuation. Dyna-CT-assisted neuroendoscopic hematoma evacuation in hybrid operating rooms may improve the clinical effect and outcomes of patients with HICH.

Extended Multimodal Flat Detector CT Imaging in Acute Ischemic Stroke: A Pilot Study

By using Flat detector computed tomography (FD-CT), a one-stop-shop approach in the diagnostic workup of acute ischemic stroke (AIS) might be achieved. Although information on upstream vessels is warranted, dedicated FD-CT protocols which include the imaging of the cervical vasculature are still lacking. We aimed to prospectively evaluate the implementation of a new multimodal FD-CT protocol including cervical vessel imaging in AIS patients. In total, 16 patients were included in this study. Eight patients with AIS due to large vessel occlusion (LVO) prospectively received a fully multimodal FD-CT imaging, including non-enhanced flat detector computed tomography (NE-FDCT), dynamic perfusion flat detector computed tomography (FD-CTP) and flat detector computed tomography angiography (FD-CTA) including cervical imaging. For comparison of time metrics and image quality, eight AIS patients, which received multimodal CT imaging, were included retrospectively. Although image quality of NE-FDCT and FD-CTA was rated slightly lower than NE-CT and CTA, all FD-CT datasets were of diagnostic quality. Intracerebral hemorrhage exclusion and LVO detection was reliably possible. Median door-to-image time was comparable for the FD-CT group and the control group (CT:30 min, IQR27-58; FD-CT:44.5 min, IQR31-55, p = 0.491). Door-to-groin-puncture time (CT:79.5 min, IQR65-90; FD-CT:59.5 min, IQR51-67; p = 0.016) and image-to-groin-puncture time (CT:44 min, IQR30-50; FD-CT:14 min, IQR12-18; p < 0.001) were significantly shorter, when patients were directly transferred to the angiosuite, where FD-CT took place. Our study indicates that using a new fully multimodal FD-CT approach including imaging of cervical vessels for first-line imaging in AIS patients is feasible and comparable to multimodal CT imaging with substantial potential to streamline the stroke workflow.

Dual-Layer Detector Cone-Beam CT Angiography for Stroke Assessment: First-in-Human Results (the Next Generation X-ray Imaging System Trial)

BACKGROUND AND PURPOSE

In patients with stroke, IV cone-beam CTA in the angiography suite could be an alternative to CTA to shorten the door-to-thrombectomy time. However, image quality in cone-beam CTA is typically limited by artifacts. This study evaluated a prototype dual-layer detector cone-beam CT angiography versus CTA in patients with stroke.

MATERIALS AND METHODS

A prospective, single-center trial enrolled consecutive patients with ischemic or hemorrhagic stroke on initial CT. Intracranial arterial segment vessel conspicuity and artifact presence were evaluated on dual-layer cone-beam CTA 70-keV virtual monoenergetic images and CTA. Eleven predetermined vessel segments were matched for every patient. Twelve patients were necessary to show noninferiority to CTA. Noninferiority was determined by the exact binomial test; the 1-sided lower performance boundary was prospectively set to 80% (98.75% CI).

RESULTS

Twenty-one patients had matched image sets (mean age, 72 years). After excluding examinations with movement or contrast media injection issues, all readers individually considered dual-layer cone-beam CT angiography noninferior to CTA (CI boundary, 93%, 84%, 80%, respectively) when evaluating arteries relevant in candidates for intracranial thrombectomy. Artifacts were more prevalent compared with CTA. The majority assessment rated each individual segment except M1 as having noninferior conspicuity compared with CTA.

CONCLUSIONS

In a single-center stroke setting, dual-layer detector cone-beam CTA virtual monoenergetic images are noninferior to CTA under certain conditions. Notably, the prototype is hampered by a long scan time and is not capable of contrast media bolus tracking. After excluding examinations with such scan issues, readers considered dual-layer detector cone-beam CTA noninferior to CTA, despite more artifacts.

Why Does It Shine?-A Prognostic Analysis about Predisposing Factors for Blood-Brain Barrier Damage after Revascularisation of Cerebral Large-Vessel Occlusion

BACKGROUND

Hyperdense lesions in CT after EVT of LVO are common. These lesions are predictors for haemorrhages and an equivalent of the final infarct. The aim of this study based on FDCT was the evaluation of predisposing factors for these lesions.

METHODS

Using a local database, 474 patients with mTICI ≥ 2B after EVT were recruited retrospectively. A postinterventional FDCT after recanalisation was analysed regarding such hyperdense lesions. This was correlated with a variety of items (demographics, past medical history, stroke assessment/treatment and short-/long-term follow-up).

RESULTS

Significant differences were present in NHISS at admission, regarding time window, ASPECTS in initial NECT, location of the LVO, CT-perfusion (penumbra, mismatch ratio), haemostatic parameters (INR, aPTT), duration of EVT, number of EVT attempts, TICI, affected brain region, volume of demarcation and FDCT-ASPECTS. The ICH-rate, the volume of demarcation in follow-up NECT and the mRS at 90 days differed in association with these hyperdensities. INR, the location of demarcation, the volume of demarcation and the FDCT-ASPECTS could be demonstrated as independent factors for the development of such lesions.

CONCLUSION

Our results support the prognostic value of hyperdense lesions after EVT. We identified the volume of the lesion, the affection of grey matter and the plasmatic coagulation system as independent factors for the development of such lesions.

Can flat-detector CT after successful endovascular treatment predict long-term outcome in patients with large vessel occlusion? An Alberta Stroke Programme Early CT Score-based study

PURPOSE

Recent studies postulate a high prognostic value of the Alberta Stroke Programme Early CT Score (ASPECTS) applied on non-contrast whole-brain flat-detector CT (FDCT) after successful endovascular treatment (EVT). The aim of this study was the evaluation of long-term patient outcome after endovascular treatment using postinterventional FDCT.

METHODS

Using a local database (Stroke Research Consortium in Northern Bavaria, STAMINA), 517 patients with successful endovascular treatment (modified Thrombolysis in Cerebral Infarction (mTICI) ≥ 2B) due to acute ischaemic stroke (AIS) and large vessel occlusion (LVO) of the anterior circulation were recruited retrospectively. In all cases, non-contrast FDCT after EVT was analysed with special focus at ASPECTS. These results were correlated with the functional outcome in long-term (modified Rankin Scale (mRS) shift from pre-stroke to 90 days after discharge).

RESULTS

A significant difference in FDCT-ASPECTS compared to the subgroup of favourable vs. unfavourable outcome (Δ mRS) (median ASPECTS 10 (10-9) vs. median ASPECTS 9 (10-7); p = 0,001) could be demonstrated. Multivariable regression analysis revealed FDCT-ASPECTS (OR 0.234, 95% CI - 0.102-0.008, p = 0.022) along with the NHISS at admission (OR 0.169, 95% CI 0.003-0.018, p = 0.008) as independent factors for a favourable outcome. Cut-off point for a favourable outcome (Δ mRS) was identified at an ASPECTS ≥ 8 (sensitivity 90.6%, specificity 35%).

CONCLUSION

For patients with LVO and successful EVT, FDCT-ASPECTS was found to be highly reliable in predicting long-term outcome.

Evaluation of Sine Spin flat detector CT imaging compared with multidetector CT

BACKGROUND

Flat detector computed tomography (FDCT) is widely used for periprocedural imaging in the angiography suite. Sine Spin FDCT (SFDCT) is the latest generation of cone beam CT using a double oblique trajectory for image acquisition to reduce artefacts and improve soft tissue brain imaging. This study compared the effective dose, image quality and diagnostic performance of the latest generation of SFDCT with multidetector CT (MDCT).

METHODS

An anthropomorphic phantom equipped with MOSFET detectors was used to measure the effective dose of the new 7sDCT Sine Spin protocol on a latest generation biplane angiographic C-arm system. Diagnostic performance was evaluated on periprocedurally acquired SFDCT for depiction of anatomical details, detection of hemorrhage, and ischemia and was compared with preprocedurally acquired MDCT. Inter- and intra-rater correlation as well as sensitivity and specificity were calculated.

RESULTS

Both modalities showed equal diagnostic performance in the supratentorial ventricular system. SFDCT provided inferior image quality in grey-white matter differentiation and infratentorial structures. Intraventricular, subarachnoid and parenchymal hemorrhages were diagnosed with a sensitivity of 83.3%, 84.2% and 75% and a specificity of 97.3%, 80.0% and 100%, respectively; early ischemic lesions with a sensitivity of 73.3% and specificity 94.7%. The effective dose measured for the 7sDCT Sine Spin protocol was 2 mSv.

CONCLUSIONS

Our findings confirm the high diagnostic sensitivity and specificity of SFDCT in detecting intracranial hemorrhage and early ischemic lesions. The delineation of grey-white matter differentiation and infratentorial structures remains a limiting factor. In comparison to previous studies, the new 7sDCT Sine Spin protocol showed a lower effective dose.

Can angiographic Flat Detector Computed Tomography blood volume measurement be used to predict final infarct size in acute ischemic stroke?

INTRODUCTION AND PURPOSE

Flat detector computed tomography (FD-CT) technology is becoming more widely available in the angiography suites of comprehensive stroke centers. In patients with acute ischemic stroke (AIS), who are referred for endovascular therapy (EVT), FD-CT generates cerebral pooled blood volume (PBV) maps, which might help in predicting the final infarct area. We retrospectively analyzed pre- and post-recanalization therapy quantitative PBV measurements in both the infarcted and hypoperfused brain areas of AIS patients referred for EVT.

MATERIALS AND METHODS

We included AIS patients with large vessel occlusion in the anterior circulation referred for EVT from primary stroke centers to our comprehensive stroke center. The pre- and post-recanalization FD-CT regional relative PBV (rPBV) values were measured between ipsilateral lesional and contralateral non-lesional areas based on final infarct area on post EVT follow-up cross-sectional imaging. Statistical analysis was performed to identify differences in PBV values between infarcted and non-infarcted, recanalized brain areas.

RESULTS

We included 20 AIS patients. Mean age was 63 years (ranging from 36 to 86 years). The mean pre- EVT rPBV value was 0.57 (±0.40) for infarcted areas and 0.75 (±0.43) for hypoperfusion areas. The mean differences (Δ) between pre- and post-EVT rPBV values for infarcted and hypoperfused areas were respectively 0.69 (±0.59) and 0.69 (±0.90). We found no significant differences (p > 0.05) between pre-EVT rPBV and ΔrPBV values of infarct areas and hypoperfusion areas.

CONCLUSION

Angiographic PBV mapping is useful for the detection of cerebral perfusion deficits, especially in combination with the fill run images. However, we were not able to distinguish irreversibly infarcted tissue from potentially salvageable, hypoperfused brain tissue based on quantitative PBV measurement in AIS patients.

Flat Detector CT with Cerebral Pooled Blood Volume Perfusion in the Angiography Suite: From Diagnostics to Treatment Monitoring

C-arm flat-panel detector computed tomographic (CT) imaging in the angiography suite increasingly plays an important part during interventional neuroradiological procedures. In addition to conventional angiographic imaging of blood vessels, flat detector CT (FD CT) imaging allows simultaneous 3D visualization of parenchymal and vascular structures of the brain. Next to imaging of anatomical structures, it is also possible to perform FD CT perfusion imaging of the brain by means of cerebral blood volume (CBV) or pooled blood volume (PBV) mapping during steady state contrast administration. This enables more adequate decision making during interventional neuroradiological procedures, based on real-time insights into brain perfusion on the spot, obviating time consuming and often difficult transportation of the (anesthetized) patient to conventional cross-sectional imaging modalities. In this paper we review the literature about the nature of FD CT PBV mapping in patients and demonstrate its current use for diagnosis and treatment monitoring in interventional neuroradiology.

Principles, techniques and applications of high resolution cone beam CT angiography in the neuroangio suite

The aim of this review is to describe the acquisition and reformatting of state of the art high resolution cone beam CT (HR-CBCT) and demonstrate its role in multiple neurovascular conditions as a tool to improve the understanding of disease and guide therapeutic decisions. First, we will review the basic principle of CBCT acquisition, followed by the injection protocols and the reformatting paradigms. Next, multiple applications in different pathological conditions such as aneurysms, arteriovenous malformations, dural arteriovenous fistulas, and stroke will be described. HR-CBCT angiography, widely available, is uniquely useful in certain clinical scenarios to improve the understanding of disease and guide therapeutic decisions. It rapidly is becoming an essential tool for the contemporary neurointerventionalist.AChoAho.

Clinical Evaluation of an Innovative Metal-Artifact-Reduction Algorithm in FD-CT Angiography in Cerebral Aneurysms Treated by Endovascular Coiling or Surgical Clipping

Treated cerebral aneurysms (IA) require follow-up imaging to ensure occlusion. Metal artifacts complicate radiologic assessment. Our aim was to evaluate an innovative metal-artifact-reduction (iMAR) algorithm for flat-detector computed tomography angiography (FD-CTA) regarding image quality (IQ) and detection of aneurysm residua/reperfusion in comparison to 2D digital subtraction angiography (DSA). Patients with IAs treated by endovascular coiling or clipping underwent both FD-CTA and DSA. FD-CTA datasets were postprocessed with/without iMAR algorithm (MAR+/MAR−). Evaluation of all FD-CTA and DSA datasets regarding qualitative (IQ, MAR) and quantitative (coil package diameter/CPD) parameters was performed. Aneurysm occlusion was assessed for each dataset and compared to DSA findings. In total, 40 IAs were analyzed (ncoiling = 24; nclipping = 16). All iMAR+ datasets demonstrated significantly better IQ (pIQ coiling < 0.0001; pIQ clipping < 0.0001). iMAR significantly reduced the metal-artifact burden but did not affect the CPD. iMAR significantly improved the detection of aneurysm residua/reperfusion with excellent agreement with DSA (naneurysm detection MAR+/MAR−/DSA = 22/1/26). The iMAR algorithm significantly improves IQ by effective reduction of metal artifacts in FD-CTA datasets. The proposed algorithm enables reliable detection of aneurysm residua/reperfusion with good agreement to DSA. Thus, iMAR can help to reduce the need for invasive follow-up in treated IAs.

Change your Angle of View : Sinusoidal C-Arm Movement in Cranial Flat-panel CT to Improve Image Quality

BACKGROUND

Artifacts from surrounding bony structures, especially from the petrous bones, regularly impair soft tissue computed tomography (CT) imaging of the middle and posterior fossa. This affects flat-panel CT in particular. Sinusoidal movement of the C‑arm during acquisition (i.e. craniocaudal tilting along with semicircular rotation) is supposed to reduce artifacts, thus enhancing soft tissue imaging quality.

METHODS

In the work-up of ischemic stroke or subarachnoid hemorrhage 40 patients underwent multi-slice CT (MS-CT) and either plain circular (cFP-CT; n = 20) or sinusoidal (sFP-CT; n = 20) flat-panel CT within a short interval. Two independent readers analyzed MS-CT and FP-CT datasets for recognizability of eight different brain structures and three typical types of artifacts according to a predetermined score.

RESULTS

Interrater reliability was moderate for cFP-CT (κ = 0.575) and good to very good for ratings of MS-CT and sFP-CT (κ = 0.651 to κ = 1). MS-CT was rated to be significantly better than cFP-CT and sFP-CT (p < 0.0001) in the overall score. Yet, sFP-CT was rated to be significantly superior to cFP-CT (overall p < 0.0001) regarding most anatomical regions and petrous bone artifacts.

CONCLUSION

Compared to a standard circular protocol, sinusoidal C‑arm movement in cranial FP-CT can significantly reduce artifacts in the posterior fossa and, moreover, can improve visualization of most supratentorial and infratentorial anatomical structures.

In vitro measurements of radiation exposure with different modalities (computed tomography, cone beam computed tomography) for imaging the petrous bone with a pediatric anthropomorphic phantom

BACKGROUND

Various imaging modalities, such as multi-detector computed tomography (CT) and cone beam CT are commonly used in infants for the diagnosis of hearing loss and surgical planning of implantation hearing aid devices, with differing results.

OBJECTIVE

We compared three different imaging modalities available in our institution, including a high-class CT scanner, a mid-class CT scanner and an angiography system with a cone beam CT option, for image quality and radiation exposure in a phantom study.

MATERIALS AND METHODS

While scanning an anthropomorphic phantom imitating a 1-year-old child with vendor-provided routine protocols, organ doses, surface doses and effective doses were determined for these three modalities with thermoluminescent dosimeters. The image quality was evaluated using the signal difference to noise ratio (SDNR) and the spatial resolution of a line-pair insert in the phantom head. The dose efficiency, defined as the ratio of SDNR and effective dose, was also compared.

RESULTS

The organ and surface doses were lowest with the high-class CT protocol, but the image quality was the worst. Image quality was best with the cone beam CT protocol, which, however, had the highest radiation exposure in this study, whereas the mid-class CT was in between.

CONCLUSION

Based on our results, high-end CT should be used for surgical planning because it has the lowest dose, while the image quality is still sufficient for this purpose. However, if highest image quality is needed and required, e.g., by ENT surgeons, the other modalities should be considered.

Complications of Mechanical Thrombectomy in Acute Ischemic Stroke

Multiple randomized clinical trials have supported the use of mechanical thrombectomy (MT) as standard of care in the treatment of large vessel occlusion acute ischemic stroke. Optimal outcomes depend not only on early reperfusion therapy but also on post thrombectomy care. Early recognition of post MT complications including reperfusion hemorrhage, cerebral edema and large space occupying infarcts, and access site complications can guide early initiation of lifesaving therapies that can improve neurologic outcomes. Knowledge of common complications and their management is essential for stroke neurologists and critical care providers to ensure optimal outcomes. We present a review of the available literature evaluating the common complications in patients undergoing MT with emphasis on early recognition and management.

Direct Transfer to Angiosuite in Acute Stroke: Why, When, and How?

Time to reperfusion is one of the strongest predictors of functional outcome in acute stroke due to a large vessel occlusion (LVO). Direct transfer to angiography suite (DTAS) protocols have shown encouraging results in reducing in-hospital delays. DTAS allows bypassing of conventional imaging in the emergency room by ruling out an intracranial hemorrhage or a large established infarct with imaging performed before transfer to the thrombectomy-capable center in the angiography suite using flat-panel CT (FP-CT). The rate of patients with stroke code primarily admitted to a comprehensive stroke center with a large ischemic established lesion is <10% within 6 hours from onset and remains <20% among patients with LVO or transferred from a primary stroke center. At the same time, stroke severity is an acceptable predictor of LVO. Therefore, ideal DTAS candidates are patients admitted in the early window with severe symptoms. The main difference between protocols adopted in different centers is the inclusion of FP-CT angiography to confirm an LVO before femoral puncture. While some centers advocate for FP-CT angiography, others favor additional time saving by directly assessing the presence of LVO with an angiogram. The latter, however, leads to unnecessary arterial punctures in patients with no LVO (3%-22% depending on selection criteria). Independently of these different imaging protocols, DTAS has been shown to be effective and safe in improving in-hospital workflow, achieving a reduction of door-to-puncture time as low as 16 minutes without safety concerns. The impact of DTAS on long-term functional outcomes varies between published studies, and randomized controlled trials are warranted to examine the benefit of DTAS.

Performance characterization of a prototype dual-layer cone-beam computed tomography system

PURPOSE

Conventional cone-beam computed tomography CT (CBCT) provides limited discrimination between low-contrast tissues. Furthermore, it is limited to full-spectrum energy integration. A dual-energy CBCT system could be used to separate photon energy spectra with the potential to increase the visibility of clinically relevant features and acquire additional information relevant in a multitude of clinical imaging applications. In this work, the performance of a novel dual-layer dual-energy CBCT (DL-DE-CBCT) C-arm system is characterized for the first time.

METHODS

A prototype dual-layer detector was fitted into a commercial interventional C-arm CBCT system to enable DL-DE-CBCT acquisitions. DL-DE reconstructions were derived from material-decomposed Compton scatter and photoelectric base functions. The modulation transfer function (MTF) of the prototype DL-DE-CBCT was compared to that of a commercial CBCT. Noise and uniformity characteristics were evaluated using a cylindrical water phantom. Effective atomic numbers and electron densities were estimated in clinically relevant tissue substitutes. Iodine quantification was performed (for 0.5-15 mg/ml concentrations) and virtual noncontrast (VNC) images were evaluated. Finally, contrast-to-noise ratios (CNR) and CT number accuracies were estimated.

RESULTS

The prototype and commercial CBCT showed similar spatial resolution, with a mean 10% MTF of 5.98 cycles/cm and 6.28 cycles/cm, respectively, using a commercial standard reconstruction. The lowest noise was seen in the 80 keV virtual monoenergetic images (VMI) (7.40 HU) and the most uniform images were seen at VMI 60 keV (4.74 HU) or VMI 80 keV (1.98 HU), depending on the uniformity measure used. For all the tissue substitutes measured, the mean accuracy in effective atomic number was 98.2% (SD 1.2%) and the mean accuracy in electron density was 100.3% (SD 0.9%). Iodine quantification images showed a mean difference of -0.1 (SD 0.5) mg/ml compared to the true iodine concentration for all blood and iodine-containing objects. For VNC images, all blood substitutes containing iodine averaged a CT number of 43.2 HU, whereas a blood-only substitute measured 44.8 HU. All water-containing iodine substitutes measured a mean CT number of 2.6 in the VNC images. A noise-suppressed dataset showed a CNR peak at VMI 40 keV and low at VMI 120 keV. In the same dataset without noise suppression applied, a peak in CNR was obtained at VMI 70 keV and a low at VMI 120 keV. The estimated CT numbers of various clinically relevant objects were generally very close to the calculated CT number.

CONCLUSIONS

The performance of a prototype dual-layer dual-energy C-arm CBCT system was characterized. Spatial resolution and noise were comparable with a commercially available C-arm CBCT system, while offering dual-energy capability. Iodine quantifications, effective atomic numbers, and electron densities were in good agreement with expected values, indicating that the system can be used to reliably evaluate the material composition of clinically relevant tissues. The VNC and monoenergetic images indicate a consistent ability to separate clinically relevant tissues. The results presented indicate that the system could find utility in diagnostic, interventional, and radiotherapy planning settings.

Simulation of superselective catheterization for cerebrovascular lesions using a virtual injection software

Background

This report addresses the feasibility of virtual injection software based on contrast-enhanced cone-beam CTs (CBCTs) in the context of cerebrovascular lesion embolization. Intracranial arteriovenous malformation (AVM), dural arteriovenous fistula (AVF) and mycotic aneurysm embolization cases with CBCTs performed between 2013 and 2020 were retrospectively reviewed. Cerebrovascular lesions were reviewed by 2 neurointerventionalists using a dedicated virtual injection software (EmboASSIST, GE Healthcare; Chicago, IL). Points of Interest (POIs) surrounding the vascular lesions were first identified. The software then automatically displayed POI-associated vascular traces from vessel roots to selected POIs. Vascular segments and reason for POI identification were recorded. Using 2D multiplanar reconstructions from CBCTs, the accuracy of vascular traces was assessed. Clinical utility metrics were recorded on a 3-point Likert scale from 1 (no benefit) to 3 (very beneficial).

Results

Nine cases (7 AVM, 1 AVF, 1 mycotic aneurysm) were reviewed, with 26 POIs selected. Three POIs were in 2nd order segments, 8 POIs in 3rd order segments and 15 POIs in 4th order segments of their respective arteries. The reviewers rated all 26 POI traces – involving a total of 90 vascular segments – as accurate. The average utility score across the 8 questions were 2.7 and 2.8 respectively from each reviewer, acknowledging the software’s potential benefit in cerebrovascular embolization procedural planning.

Conclusion

The operators considered CBCT-based virtual injection software clinically useful and accurate in guiding and planning cerebrovascular lesion embolization in this retrospective review. Future prospective studies in larger cohorts are warranted for validation of this modality.

Direct Transfer to Angio-Suite Versus Computed Tomography–Transit in Patients Receiving Mechanical Thrombectomy

Background and Purpose:

To quantify workflow metrics in patients receiving stroke imaging (noncontrast-enhanced computed tomography [CT] and CT-angiography) in either a computed-tomography scanner suite (CT-Transit [CTT]) or an angio-suite (direct transfer to angio-suite—[DTAS]—using flat-panel CT) before undergoing mechanical thrombectomy.

Methods:

Prospective, single-center investigator initiated randomized controlled trial in a comprehensive stroke center focusing on time from imaging to groin puncture (primary end point) and time from hospital admission to final angiographic result (secondary end point) in patients receiving mechanical thrombectomy for anterior circulation large vessel occlusion after randomization to the CTT or DTAS pathway.

Results:

The trial was stopped early after the enrollment of n=60 patients (CTT: n=34/60 [56.7 %]; DTAS: n=26/60 [43.3%]) of n=110 planned patients because of a preplanned interim analysis. Time from imaging to groin puncture was shorter in DTAS-patients (in minutes, median [interquartile range]: CTT: 26 [23–32]; DTAS: 19 [15–23]; P value: 0.001). Time from hospital admission to stroke imaging was longer in patients randomized to DTAS (in minutes, mean [SD]: CTT: 12 [13]; DTAS: 21 [14], P value: 0.007). Time from hospital admission to final angiographic reperfusion was comparable between patient groups (CTT: 78 [58–92], DTAS: 80 [66–118]; P value: 0.067).

Conclusions:

This trial showed a reduction in time from imaging to groin-puncture when patients are transferred directly to the angiosuite for advanced stroke-imaging compared with imaging in a CT scanner suite. This time saving was outweighed by a longer admission to imaging time and could not translate into a shorter time to final angiographic reperfusion in this trial.

Utility of Immediate Postprocedural Cone Beam Computed Tomography Scan in the Detection of Ischemic and Hemorrhagic Complications in Pediatric Neurointerventional Surgery

BACKGROUND

Cone beam computed tomography (CBCT) imaging is used commonly in neurointerventional surgery for rapid intraprocedural assessment and planning of intracranial interventions. Our goal was to evaluate the ability of immediate postprocedural CBCT scan in assessing potential complications in pediatric patients.

METHODS

A retrospective review was completed to include all pediatric patients at our hospital with an immediate postprocedural CBCT scan with the Artis Q system. Demographic, clinical, and imaging data were examined. CBCT images were reviewed by 3 independent neurointerventionalists to assess ventricular system/subarachnoid spaces, gray-white differentiation, and ischemia or hemorrhage if present. Each assessment was rated qualitatively on a 4-point scale and was compared with conventional computed tomography (cCT) scan when available. Interrater reliability was assessed and radiation dose data were reviewed.

RESULTS

Thirty-five patients were included with an average age of 11.0 ± 5.1 years (median, 10.9; range, 1.1-18 years). Of the patients, 54.3% were boys; 34.3% were Hispanic and 34.3% were non-Hispanic white. Diagnoses included a variety of vascular pathologies. CBCT scan had a mean score of 2.69 ± 0.54 out of 3 for ventricular and subarachnoid space assessment with a combined interrater reliability of 0.82, 1.71 ± 1.38 for hemorrhage with a combined interrater reliability of 1.00, and 0.52 ± 0.60 for gray-white differentiation with a combined interrater reliability of 0.79.

CONCLUSIONS

Immediate postprocedural CBCT images were adequate to detect ventricular size/subarachnoid spaces changes and large volume hemorrhage compared with cCT scan in pediatric patients. However, there are limitations using immediate CBCT images to detect small volume hemorrhage and ischemic changes.

Neuroimaging of Acute Stroke

Acute stroke is the clinical manifestation of disrupted blood flow or bleeding in the central nervous system. Imaging supports the clinical diagnosis and can aide in acute treatment decision making and guide information on prognosis. Features that are delineated include the parenchyma and the blood vessels. Parenchymal characteristics include early ischemic changes, established infarct and tissue at risk (penumbra), and hemorrhage. Vessel pathology includes arterial and venous steno-occlusive disease and vascular malformations. In the presence of a vessel occlusion, vessel imaging can assess collateral flow. This article outlines the role of neuroimaging as applied to patients presenting with acute stroke.

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.

Optimizing contrast-enhanced cone-beam CT protocol to facilitate simultaneous visualization of neurovascular pathologies and surrounding structures of interest

OBJECTIVE

Contrast-enhanced cone-beam computed tomography (CBCT) imaging is commonly used for evaluating neurovascular stents and their relationship to the parent artery or vascular pathologies such as arteriovenous malformations (AVMs) and dural arteriovenous fistulas (dAVFs) in the context of surrounding anatomical structures. The purpose of this study was to understand the effects of varying concentrations of contrast medium used in CBCT imaging for optimal visualization of various endovascular devices and anatomical pathologies.

METHODS

Thirty-five patients with various neurovascular pathologies were included in the study. Contrast-enhanced CBCT images (20 s DR, Siemens syngo DynaCT, Siemens AG, Forchheim, Germany) were acquired in all cases, with varying dilutions of contrast medium, from 1% to 30%. The injection rate was kept constant at 3 cc/sec with an X-ray delay of two sec, and a total volume of 66 cc of diluted contrast was administered. Results from visual and quantitative analysis were reported.

RESULTS

Ten percent dilution of contrast medium resulted in the best image differentiation between flow-diverter devices and the parent artery. Concentrations as low as 2.5% contrast medium also resulted in identifying AVMs in the context of the surrounding brain parenchyma, whereas 20% to 30% dilution provided the best visualization of residual AVMs with prior Onyx embolization and dAVFs in the presence of bony structures.

CONCLUSIONS

Simultaneous visualization of brain parenchyma, bony structures, devices, and pathological anatomy using contrast-enhanced CBCT imaging is feasible with appropriate doses of iodinated contrast, and should be tailored to the individual case based on the goals of CBCT.

Flat detector CT and its applications in the endovascular treatment of wide-necked intracranial aneurysms-A literature review

Flat detector CT (FDCT) provides cross sectional imaging within an angiographic suite and is increasingly gaining popularity in various areas of interventional radiology, as an alternative imaging modality. Its relatively high spatial resolution improves visualization of intraluminal devices such as intracranial stents or flow-diverters. Device deployment and positioning, in relation to the parent vessel and surrounding structures, are easily assessible with FDCT. Furthermore, with contrast agent administration, it expands the diagnostic capabilities of this new imaging tool. However, beam-hardening artifacts is a major limitation in some cases. The examination can be performed both during the endovascular procedure and for pre- and post-treatment imaging. Intravenous contrast agent injection reduces the risk of complications, making it possible to perform this examination in the outpatient settings. The aim of this paper is to present an overview of published studies reporting experience with FDCT in the field of endovascular neurosurgery and in particular, FDCT's contribution in treatment of wide-necked intracranial aneurysms. The authors have focused specifically on stent-assisted coiling and flow-diverter implantation, since obtaining proper parent vessel wall apposition of these devices is essential for short- and long-term procedural outcomes.

[Modern imaging of the temporal bone]

This article describes the current significance of computed tomography (CT), magnetic resonance imaging (MRI), cone beam CT, digital subtraction angiography (DSA), and special X‑rays in the diagnostics of temporal bone diseases. The latter is obsolete for diagnostic intentions. Possibilities and limitations in terms of detection and/or depiction of the extent of inflammatory, traumatic, tumorous, and postoperative pathologies are discussed. A concrete question and conveyance of clinical findings influence the choice of the method to be applied in the individual case. Malformations of the middle ear can only be detected noninvasively by CT or cone beam CT. These are also the methods that may support the diagnosis of otosclerosis in clinically unclear cases. MRI is the method of choice for pathologies of the inner ear and internal auditory canal, including inner ear malformations. At present, only in few institutions is a successful visualization of endolymphatic hydrops in Menière's disease realized.

C-Arm Conebeam CT Perfusion Imaging in the Angiographic Suite: A Comparison with Multidetector CT Perfusion Imaging

BACKGROUND AND PURPOSE

Perfusion imaging in the angiography suite may provide a way to reduce time from stroke onset to endovascular revascularization of patients with large-vessel occlusion. Our purpose was to compare conebeam CT perfusion with multidetector CT perfusion.

MATERIALS AND METHODS

Data from 7 subjects with both multidetector CT perfusion and conebeam CT perfusion were retrospectively processed and analyzed. Two algorithms were used to enhance temporal resolution and temporal sampling density and reduce the noise of conebeam CT data before generating perfusion maps. Two readers performed qualitative image-quality evaluation on maps by using a 5-point scale. ROIs indicating CBF/CBV abnormalities were drawn. Quantitative analyses were performed by using the Sørensen-Dice coefficients to quantify the similarity of abnormalities. A noninferiority hypothesis was tested to compare conebeam CT perfusion against multidetector CT perfusion.

RESULTS

Average image-quality scores for multidetector CT perfusion and conebeam CT perfusion images were 2.4 and 2.3, respectively. The average confidence score in diagnosis was 1.4 for both multidetector CT and conebeam CT; the average confidence scores for the presence of a CBV/CBF mismatch were 1.7 (κ = 0.50) and 1.5 (κ = 0.64). For multidetector CT perfusion and conebeam CT perfusion maps, the average scores of confidence in making treatment decisions were 1.4 (κ = 0.79) and 1.3 (κ = 0.90). The area under the visual grading characteristic for the above 4 qualitative quality scores showed an average area under visual grading characteristic of 0.50, with 95% confidence level cover centered at the mean for both readers. The Sørensen-Dice coefficient for CBF maps was 0.81, and for CBV maps, 0.55.

CONCLUSIONS

After postprocessing methods were applied to enhance image quality for conebeam CT perfusion maps, the conebeam CT perfusion maps were not inferior to those generated from multidetector CT perfusion.

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.

[Imaging-based indications for interventional treatment of stroke]

The indications for mechanical thrombectomy are based on a proximal vessel occlusion in the absence of extensive ischemic damage in the corresponding dependent vascular territory. The maximum extent of early ischemic edema for which endovascular treatment is still useful is not clear from the studies. A benefit of mechanical thrombectomy can be safely assumed with an ASPECT score of 6-10, possibly also with lower scores. A more complex imaging with assessment of the status of collateral vessels or perfusion abnormality is scientifically interesting but usually not necessary for clinical decision-making for endovascular stroke treatment within the first 6 h after symptom onset.