Reduction of CT artifacts from cardiac implantable electronic devices using a combination of virtual monoenergetic images and post-processing algorithms.

OBJECTIVES: To evaluate the reduction of artifacts from cardiac implantable electronic devices (CIEDs) by virtual monoenergetic images (VMI), metal artifact reduction (MAR) algorithms, and their combination (VMIMAR) derived from spectral detector CT (SDCT) of the chest compared to conventional CT images (CI). METHODS: In this retrospective study, we included 34 patients (mean age 74.6 ± 8.6 years), who underwent a SDCT of the chest and had a CIED in place. CI, MAR, VMI, and VMIMAR (10 keV increment, range: 100-200 keV) were reconstructed. Mean and standard deviation of attenuation (HU) among hypo- and hyperdense artifacts adjacent to CIED generator and leads were determined using ROIs. Two radiologists qualitatively evaluated artifact reduction and diagnostic assessment of adjacent tissue. RESULTS: Compared to CI, MAR and VMIMAR ≥ 100 keV significantly increased attenuation in hypodense and significantly decreased attenuation in hyperdense artifacts at CIED generator and leads (p < 0.05). VMI ≥ 100 keV alone only significantly decreased hyperdense artifacts at the generator (p < 0.05). Qualitatively, VMI ≥ 100 keV, MAR, and VMIMAR ≥ 100 keV provided significant reduction of hyper- and hypodense artifacts resulting from the generator and improved diagnostic assessment of surrounding structures (p < 0.05). Diagnostic assessment of structures adjoining to the leads was only improved by MAR and VMIMAR 100 keV (p < 0.05), whereas keV values ≥ 140 with and without MAR significantly worsened diagnostic assessment (p < 0.05). CONCLUSIONS: The combination of VMI and MAR as well as MAR as a standalone approach provides effective reduction of artifacts from CIEDs. Still, higher keV values should be applied with caution due to a loss of soft tissue and vessel contrast along the leads. KEY POINTS: • The combination of VMI and MAR as well as MAR as a standalone approach enables effective reduction of artifacts from CIEDs. • Higher keV values of both VMI and VMIMAR at CIED leads should be applied with caution since diagnostic assessment can be hampered by a loss of soft tissue and vessel contrast. • Recommended keV values for CIED generators are between 140 and 200 keV and for leads around 100 keV.

Comparative Analysis of the Low-Profile Acclino Stent and the Enterprise Stent for the Treatment of Unruptured Intracranial Aneurysms.

OBJECTIVE: In preliminary studies, advanced intracranial stents appear to have a favorable safety profile for intracranial aneurysm treatment. This dual-center study is a head-to-head comparison of the low-profile Acandis Acclino stent (a third-generation stent) and the first- and second-generation Enterprise stent. METHODS: Patients who underwent stent-assisted coiling with either the Enterprise or the Acclino stent for unruptured aneurysms during an 8-year period were enrolled and compared for complications, clinical outcomes, and angiographic results. Primary outcome measures were ischemic stroke rate and mid-term complete occlusion rate. Propensity score adjustment was performed to account for small differences between the groups. RESULTS: Enterprise and Acclino stents were used in 48 cases each. The overall rate of thrombotic complications was higher in the Enterprise group than in the Acclino group (20.8% vs. 4.2%, HR: 6.6, 95%CI: 2.2-20.0, P = 0.01, adjusted P < 0.01), which translated into a higher rate of major ischemic stroke after Enterprise treatment (6.3% vs. 0%, HR: 2.1, 95%CI: 1.8-2.4, P = 0.08, adjusted P < 0.01). Mid-term and long-term angiographic follow-up showed complete occlusion rates of 83.3% and 75.0% for Enterprise and 89.2% and 75.9% for Acclino (both P > 0.05). Retreatment rates were 10.4% in the Enterprise group and 4.2% in the Acclino group (P = 0.42, adjusted P = 0.10). CONCLUSIONS: The results indicate a favorable safety profile of the Acclino over the Enterprise, justifying the use of advanced stent systems in clinical practice. However, further comparative studies of the Acclino and other competing stent systems are needed to draw a definitive conclusion on the state of stent-assisted coiling.

Immediate angiographic control after intra-arterial nimodipine administration underestimates the vasodilatory effect.

Intra-arterial nimodipine administration is a widely used rescue therapy for cerebral vasospasm. Although it is known that its effect sets in with delay, there is little evidence in current literature. Our aim was to prove that the maximal vasodilatory effect is underestimated in direct angiographic controls. We reviewed all cases of intra-arterial nimodipine treatment for subarachnoid hemorrhage-related cerebral vasospasm between January 2021 and December 2022. Inclusion criteria were availability of digital subtraction angiography runs before and after nimodipine administration and a delayed run for the most affected vessel at the end of the procedure to decide on further escalation of therapy. We evaluated nimodipine dose, timing of administration and vessel diameters. Delayed runs were performed in 32 cases (19 patients) with a mean delay of 37.6 (± 16.6) min after nimodipine administration and a mean total nimodipine dose of 4.7 (± 1.2) mg. Vessel dilation was more pronounced in delayed vs. immediate controls, with greater changes in spastic vessel segments (n = 31: 113.5 (± 78.5%) vs. 32.2% (± 27.9%), p < 0.0001) vs. non-spastic vessel segments (n = 32: 23.1% (± 13.5%) vs. 13.3% (± 10.7%), p < 0.0001). In conclusion intra-arterially administered nimodipine seems to exert a delayed vasodilatory effect, which should be considered before escalation of therapy.

Analysis of Cerebral CT Based on Supervised Machine Learning as a Predictor of Outcome After Out-of-Hospital Cardiac Arrest.

BACKGROUND AND OBJECTIVES: In light of limited intensive care capacities and a lack of accurate prognostic tools to advise caregivers and family members responsibly, this study aims to determine whether automated cerebral CT (CCT) analysis allows prognostication after out-of-hospital cardiac arrest. METHODS: In this monocentric, retrospective cohort study, a supervised machine learning classifier based on an elastic net regularized logistic regression model for gray matter alterations on nonenhanced CCT obtained after cardiac arrest was trained using 10-fold cross-validation and tested on a hold-out sample (random split 75%/25%) for outcome prediction. Following the literature, a favorable outcome was defined as a cerebral performance category of 1-2 and a poor outcome of 3-5. The diagnostic accuracy was compared with established and guideline-recommended prognostic measures within the sample, that is, gray matter-white matter ratio (GWR), neuron-specific enolase (NSE), and neurofilament light chain (NfL) in serum. RESULTS: Of 279 adult patients, 132 who underwent CCT within 14 days of cardiac arrest with good imaging quality were identified. Our approach discriminated between favorable and poor outcomes with an area under the curve (AUC) of 0.73 (95% CI 0.59-0.82). Thus, the prognostic power outperformed the GWR (AUC 0.66, 95% CI 0.56-0.76). The biomarkers NfL, measured at days 1 and 2, and NSE, measured at day 2, exceeded the reliability of the imaging markers derived from CT (AUC NfL day 1: 0.87, 95% CI 0.75-0.99; AUC NfL day 2: 0.90, 95% CI 0.79-1.00; AUC NSE day: 2 0.78, 95% CI 0.62-0.94). DISCUSSION: Our data show that machine learning-assisted gray matter analysis of CCT images offers prognostic information after out-of-hospital cardiac arrest. Thus, CCT gray matter analysis could become a reliable and time-independent addition to the standard workup with serum biomarkers sampled at predefined time points. Prospective studies are warranted to replicate these findings.

First clinical experience with the Derivo 2heal embolization device for the treatment of intracranial aneurysms.

OBJECTIVE: The development of new flow-diverting devices with antithrombotic coatings may result in an improved safety profile, particularly a reduction in ischaemic stroke rates. The aim of this study was to evaluate our initial experience with the recently introduced coated Derivo® 2heal® Embolization Device (Acandis, Pforzheim, Germany). METHODS: This is a retrospective, single-centre analysis of patients with intracranial aneurysms undergoing Derivo® 2heal® Embolization Device treatment. Patient and aneurysm characteristics, procedural parameters, complications, and degree of initial and short-term aneurysm occlusion were evaluated on an intention-to-treat basis. RESULTS: A total of 16 unruptured aneurysms in 9 patients were treated with the Derivo® 2heal® Embolization Device in 10 treatment sessions. In one case the Derivo® 2heal® Embolization Device could not be deployed due to severe friction in the microcatheter. In all successful cases, one Derivo® 2heal® Embolization Device was sufficient to treat the target aneurysm and no additional coiling was performed. In-stent balloon angioplasty was performed in one procedure (10%) to improve vessel wall apposition. Twelve arterial side branches were covered in 9 procedures and all were patent at the end of the procedure. There were no clinical complications and no thromboembolic events during treatment. At the end of the procedure, contrast retention was observed in 13/16 (81%) aneurysms and at short-term follow-up, 6/9 (67%) were completely occluded. CONCLUSIONS: The preliminary results of the new Derivo® 2heal® Embolization Device appear promising and warrant further evaluation by multicentre studies with long-term follow-up.

Conventional and Deep-Learning-Based Image Reconstructions of Undersampled K-Space Data of the Lumbar Spine Using Compressed Sensing in MRI: A Comparative Study on 20 Subjects.

Compressed sensing accelerates magnetic resonance imaging (MRI) acquisition by undersampling of the k-space. Yet, excessive undersampling impairs image quality when using conventional reconstruction techniques. Deep-learning-based reconstruction methods might allow for stronger undersampling and thus faster MRI scans without loss of crucial image quality. We compared imaging approaches using parallel imaging (SENSE), a combination of parallel imaging and compressed sensing (COMPRESSED SENSE, CS), and a combination of CS and a deep-learning-based reconstruction (CS AI) on raw k-space data acquired at different undersampling factors. 3D T2-weighted images of the lumbar spine were obtained from 20 volunteers, including a 3D sequence (standard SENSE), as provided by the manufacturer, as well as accelerated 3D sequences (undersampling factors 4.5, 8, and 11) reconstructed with CS and CS AI. Subjective rating was performed using a 5-point Likert scale to evaluate anatomical structures and overall image impression. Objective rating was performed using apparent signal-to-noise and contrast-to-noise ratio (aSNR and aCNR) as well as root mean square error (RMSE) and structural-similarity index (SSIM). The CS AI 4.5 sequence was subjectively rated better than the standard in several categories and deep-learning-based reconstructions were subjectively rated better than conventional reconstructions in several categories for acceleration factors 8 and 11. In the objective rating, only aSNR of the bone showed a significant tendency towards better results of the deep-learning-based reconstructions. We conclude that CS in combination with deep-learning-based image reconstruction allows for stronger undersampling of k-space data without loss of image quality, and thus has potential for further scan time reduction.

Safety and efficacy of the fourth-generation Acandis Acclino flex plus stent for the treatment of complex intracranial aneurysms.

OBJECTIVE: The low-profile Acandis Acclino flex plus (AFP) is a fourth-generation laser-cut microstent with a flexible structure designed for the treatment of a wide variety of aneurysms. We report our single-center experience with this device in the treatment of complex aneurysms. METHODS: Twenty-eight patients were treated with the Acclino flex plus for 28 aneurysms. Aneurysm characteristics, technical success, complications, clinical outcome, and angiographic results were retrospectively analyzed. RESULTS: The cohort included 8 unruptured untreated aneurysms, 9 unruptured recurrent aneurysms, and 12 ruptured aneurysms with aneurysm diameters ranging from 3 to 23 mm. The anterior communicating artery was the most common location (52%). Stent deployment was successful in 28 cases (97%) with an average of 1.3 stents per aneurysm. The overall procedural complication rate was 17%, including 2 (6.8%) major clinical events (one ischaemic stroke and one aneurysm perforation) and one (3.4%) minor clinical event (one seizure). Angiographic results of 23 aneurysms at a mean of 6 months were complete occlusion in 74%, neck remnants in 13% and aneurysm remnants in 13%. Three patients were retreated. CONCLUSIONS: Given the complexity of the aneurysms, the use of the Acclino flex plus was feasible and associated with a favourable safety and efficacy profile. Further studies are needed to evaluate Acclino flex plus in other aneurysm subsets and to define its role in endovascular aneurysm treatment.

Angiographic Characteristics Associated with Rupture of Small Intracranial Aneurysms.

OBJECTIVE: Contrary to previous assumptions, there is increasing evidence that small intracranial aneurysms carry a relevant risk of rupture. The aim of this study was to identify angiographic characteristics of small ruptured aneurysms ≤7 mm and to evaluate their significance for clinical decision making. METHODS: A total of 385 patients with 149 unruptured and 236 ruptured intracranial aneurysms were retrospectively compared. Two- and three-dimensional digital subtraction angiography was used to determine aneurysm location, various size parameters, angulations, and morphology, as well as parent artery diameter. RESULTS: Aneurysms of the anterior communicating artery, the posterior inferior cerebellar artery, and the internal carotid artery terminus had a significantly increased prevalence among ruptured aneurysms. Ruptured aneurysms were characterized by a significantly larger aneurysm height (area under the curve [AUC] 0.60, P < 0.01) and aneurysm inclination angle (AUC 0.61, P = 0.02) in addition to a smaller dome (AUC 0.44, P = 0.02) and neck width (AUC 0.38, P < 0.01). Calculation of size ratios increases the predictive value for aneurysm rupture, with AUC values of 0.77 for aspect ratio (P < 0.01) and 0.76 for size ratio (P < 0.01). Aneurysm morphology was not a significant factor after multivariable adjustment (P = 0.20). Arterial hypertension was the only clinical risk factor significantly associated with rupture (P < 0.01). CONCLUSIONS: Of the numerous factors associated with aneurysm rupture, we propose aneurysmal location, aspect ratio (cut-off: 1.5), and aneurysm inclination angle as the most important morphological factors for assessing the rupture risk of small aneurysms because these factors have high AUC values and are robust to changes after rupture.

The behaviour of T2* and T2 relaxation time in extrinsic foot muscles under continuous exercise: A prospective analysis during extended running.

OBJECTIVES: Previous studies on T2* and T2 relaxation time of the muscles have shown that exercise leads to an initial increase, presumably representing different intramuscular physiological processes such as increase in intracellular volume or blood oxygenation level dependent effects with a subsequent decrease after cessation of exercise. Their behaviour during prolonged exercise is still unknown but could provide important information for example about the pathophysiology of overuse injuries. The aim of this study was to evaluate the temporal course of T2* and T2 relaxation time in extrinsic foot muscles during prolonged exercise and determine the optimal mapping technique. METHODS: Ten participants had to run a total of 75 minutes at their individual highest possible running speed, with interleaved MR scans at baseline and after 2.5, 5, 10, 15, 45 and 75 minutes. The examined extrinsic foot muscles were manually segmented, and relaxation time were analysed regarding its respective time course. RESULTS: T2* and T2 relaxation time showed an initial increase, followed by a plateau phase between 2.5 and 15 minutes and a subsequent decrease. For the T2* relaxation time, this pattern was also apparent, but less pronounced, with more muscles not reaching significance (p<0.05) when comparing different time points. CONCLUSIONS: T2* and T2 relaxation time showed a similar course with an initial rapid increase, a plateau phase and a subsequent decrease under prolonged exercise. Moderate but long-term muscular activity appears to have a weaker effect on T2* relaxation time than on T2 relaxation time.

WEB embolization of very broad-based intracranial aneurysms with a dome-to-neck ratio ≤ 1.1.

OBJECTIVE: The Woven EndoBridge (WEB) is a well-studied intrasaccular device for endovascular treatment of wide-necked bifurcation aneurysms. We evaluated the feasibility, safety and efficacy of the WEB for the treatment of very broad-based aneurysms with a dome-to-neck ratio ≤ 1.1. METHODS: Thirty-four aneurysms treated at three neurovascular centers were retrospectively identified. The mean aneurysm size was 5.5 ± 1.6 mm with a mean neck width of 4.7 ± 1.5 and a mean dome-to-neck ratio of 1.0 ± 0.1. The primary outcome measures were immediate technical treatment success by WEB only, complete or near-complete occlusion at 6-month follow-up and ischemic stroke. RESULTS: Aneurysm embolization by WEB only was technically feasible in 79.4%. Additional stenting was required in 14.7%. In two aneurysms (5.9%), WEB implantation failed, and the aneurysm was treated by stent- and balloon-assisted coiling, respectively. Thromboembolic events occurred during 5 interventions (14.7%), all of these performed in ruptured aneurysms. One patient (2.9%) remained asymptomatic (follow-up modified Rankin scale [mRS] score: 0), 2 patients (5.9%) had a transient deficit (mRS 0 and 1, respectively), and 2 (5.9%) had a disabling ischemic stroke (mRS 3, respectively). Mid-term angiographic follow-up of 29 patients (4.0 ± 2.6 months, range: 2-9 months) showed complete occlusion (WEB occlusion scale [WOS] A) in 41.4%, near-complete occlusion (WOS B) in 34.5%, a neck remnant (WOS C) in 10.3%, and aneurysm remnants (WOS D) in 13.8%. CONCLUSIONS: WEB embolization of very broad-necked aneurysms was technically feasible and could be achieved by WEB only in the majority of cases. Considering the challenging anatomy of very broad-based aneurysms, the WEB procedure was reasonably safe and efficient.

Virtual non-contrast reconstructions improve differentiation between vascular enhancement and calcifications in stereotactic planning CT scans of cystic intracranial tumors.

PURPOSE: To assess the diagnostic value of spectral-detector CT (SDCT) derived virtual non-contrast images (VNC) for differentiation between vascular enhancement and wall calcifications of cystic intracranial tumors in contrast-enhanced stereotactic planning examinations. METHOD: 48 patients with cystic intracranial tumors who underwent stereotactic SDCT examinations between 02/2017 and 02/2020 were retrospectively included. In each patient, two separate hyperattenuating structures along the cyst wall were defined as either enhancement or calcification, respectively, using reference MRI examinations. Quantitative analysis was performed ROI-based in conventional images (CI) and VNC. In the subjective analysis, two radiologists diagnosed the predefined peri-cystic structures in binary decisions as either enhancement or calcification using CI and the combination of CI and VNC, and rated diagnostic confidence, image noise and removal of iodine in VNC. Moreover, a potential diagnostic benefit of VNC was indicated. RESULTS: Attenuation in CI was higher as compared to VNC across all assessed ROI (all p < 0.01). In VNC, CNR between calcification and white matter was significantly higher as compared to CNR between vascular enhancement and white matter (2.6 vs 1.3, p < 0.01), while there was no significant difference in CI. In the qualitative assessment, diagnostic accuracy was significantly higher using both VNC and CI compared to using CI alone. Raters reported less image noise in VNC as compared to CI. An additional diagnostic benefit of VNC was indicated in 84.4 % of all cases. CONCLUSIONS: SDCT-derived VNC images facilitate differentiation between peri-cystic contrast enhancement in blood vessels and calcifications in stereotactic planning scans of cystic intracranial tumors.

Comparative Analysis of the Pipeline and the Derivo Flow Diverters for the Treatment of Unruptured Intracranial Aneurysms-A Multicentric Study.

OBJECTIVE: Flow diversion represents a safe and efficient technique for the endovascular treatment of complex intracranial aneurysms. This study compares 2 competing flow diverters, the Pipeline embolization device (PED) and the Derivo Embolization Device (DED) regarding technical aspects, clinical outcome, and angiographic results. METHODS: A total of 111 patients with unruptured aneurysms were treated with the PED (n = 62) or the DED (n = 49) between 2011 and 2019. Procedural specifics, complication rates, functional outcome, and aneurysm occlusion were evaluated retrospectively. RESULTS: Flow-diverter implantation was technically successful in all patients. There were no significant differences regarding baseline characteristics, adjunctive coiling, and fluoroscopy time. Multiple devices were more often used in the PED group (35.6%) than in the DED group (4.1%, P < 0.001). Procedural adverse events occurred in 4 cases of each group (PED: 5.5%, DED: 8.2%, P = 0.713), including 3 thromboembolic events and 1 hemorrhagic event per group. Morbidity rates were similar between the 2 groups (PED: 2.7%, DED: 4.1%, P = 1.0). There was no procedural mortality. At 6-month follow-up, complete or near-complete occlusion (O'Kelly-Marotta scale C+D) was achieved in 79.0% (49/62) after PED implantation and 80.0% (32/40) after DED implantation (P = 0.354). CONCLUSIONS: In regard to complication rates, functional outcome, and aneurysm occlusion, no significant differences were found between the PED and DED collective.

Phantomless assessment of volumetric bone mineral density using virtual non-contrast images from spectral detector computed tomography.

OBJECTIVE: To evaluate phantomless assessment of volumetric bone mineral density (vBMD) based on virtual non-contrast images of arterial (VNCa) and venous phase (VNCv) derived from spectral detector CT in comparison to true non-contrast (TNC) images and adjusted venous phase conventional images (CIV(adjusted)). METHODS: 104 consecutive patients who underwent triphasic spectral detector CT between January 2018 and April 2019 were retrospectively included. TNC, VNCa, VNCv and venous phase images (CIV) were reconstructed. vBMD was obtained by two radiologists using an FDA/CE-cleared software. Average vBMD of the first three lumbar vertebrae was determined in each reconstruction; vBMD of CIV was adjusted for contrast enhancement as suggested earlier. RESULTS: vBMD values obtained from CIV(adjusted) are comparable to vBMD values derived from TNC images (91.79 ± 36.52 vs 90.16 ± 41.71 mg/cm3, p = 1.00); however, vBMD values derived from VNCa and VNCv (42.20 ± 22.50 and 41.98 ± 23.3 mg/cm3 respectively) were significantly lower as compared to vBMD values from TNC and CIV(adjusted) (all p ≤ 0.01). CONCLUSION: Spectral detector CT-derived virtual non-contrast images systematically underestimate vBMD and therefore should not be used without appropriate adjustments. Adjusted venous phase images provide reliable results and may be utilized for an opportunistic BMD screening in CT examinations. ADVANCES IN KNOWLEDGE: Adjustments of venous phase images facilitate opportunistic assessment of vBMD, while spectral detector CT-derived VNC images systematically underestimate vBMD.