AI-support for the detection of intracranial large vessel occlusions: One-year prospective evaluation.

Purpose: Few studies have evaluated real-world performance of radiological AI-tools in clinical practice. Over one-year, we prospectively evaluated the use of AI software to support the detection of intracranial large vessel occlusions (LVO) on CT angiography (CTA). Method: Quantitative measures (user log-in attempts, AI standalone performance) and qualitative data (user surveys) were reviewed by a key-user group at three timepoints. A total of 491 CTA studies of 460 patients were included for analysis. Results: The overall accuracy of the AI-tool for LVO detection and localization was 87.6%, sensitivity 69.1% and specificity 91.2%. Out of 81 LVOs, 31 of 34 (91%) M1 occlusions were detected correctly, 19 of 38 (50%) M2 occlusions, and 6 of 9 (67%) ICA occlusions. The product was considered user-friendly. The diagnostic confidence of the users for LVO detection remained the same over the year. The last measured net promotor score was -56%. The use of the AI-tool fluctuated over the year with a declining trend. Conclusions: Our pragmatic approach of evaluating the AI-tool used in clinical practice, helped us to monitor the usage, to estimate the perceived added value by the users of the AI-tool, and to make an informed decision about the continuation of the use of the AI-tool.

Cerebral small vessel disease and perihematomal edema formation in spontaneous intracerebral hemorrhage.

Objective: Blood-brain barrier (BBB) dysfunction is implicated in the pathophysiology of cerebral small vessel disease (cSVD)-related intracerebral hemorrhage (ICH). The formation of perihematomal edema (PHE) is presumed to reflect acute BBB permeability following ICH. We aimed to assess the association between cSVD burden and PHE formation in patients with spontaneous ICH. Methods: We selected patients with spontaneous ICH who underwent 3T MRI imaging within 21 days after symptom onset from a prospective observational multicenter cohort study. We rated markers of cSVD (white matter hyperintensities, enlarged perivascular spaces, lacunes and cerebral microbleeds) and calculated the composite score as a measure of the total cSVD burden. Perihematomal edema formation was measured using the edema extension distance (EED). We assessed the association between the cSVD burden and the EED using a multivariable linear regression model adjusting for age, (log-transformed) ICH volume, ICH location (lobar vs. non-lobar), and interval between symptom onset and MRI. Results: We included 85 patients (mean age 63.5 years, 75.3% male). Median interval between symptom onset and MRI imaging was 6 days (IQR 1-19). Median ICH volume was 17.0 mL (IQR 1.4-88.6), and mean EED was 0.54 cm (SD 0.17). We found no association between the total cSVD burden and EED (B = -0.003, 95% CI -0.003-0.03, p = 0.83), nor for any of the individual radiological cSVD markers. Conclusion: We found no association between the cSVD burden and PHE formation. This implies that mechanisms other than BBB dysfunction are involved in the pathophysiology of PHE.

A review on imaging techniques and quantitative measurements for dynamic imaging of cerebral aneurysm pulsations.

Measurement of intracranial aneurysm wall motion may refine the current rupture risk estimation. A golden standard for measuring aneurysm pulsation is lacking. The aim is to evaluate magnitudes of aneurysm pulsation as published in current literature. Embase and PubMed were searched for publications containing quantitative measures of cardiac-cycle related cerebral aneurysm pulsation (no date or language restrictions). Eleven studies were included, covering 197 unruptured and untreated cerebral aneurysms. Quantitative pulsation measurements were extracted from the studies. Characteristics of the study population and aneurysms were taken into account, as well as the imaging modality, scanning technique and data processing methods used. A meta-analysis was performed of studies with similar methodologies and individual IA measures and locations. The magnitude of the absolute volume pulsations varied between 14 ± 9 mm3 and 106 ± 123 mm3 and the mean relative volume change varied between 5 and 36%. The meta-analysis revealed a positive correlation between size and absolute volume change. The relative volume change in Basilar artery aneurysms seems smaller. No authors were contacted for original study data and articles only describing visual pulsations were excluded. The variation in methodologies impedes an accurate estimation of the magnitude of IA pulsations. Validation of aneurysm pulsation measurement is crucial prior to clinical studies evaluating IA pulsatility in relation to IA rupture risk. Prerequisite is a reliable and robust imaging method with high spatial and temporal resolution and standardization of the image analysis methods.

Color-Mapping of 4D-CTA for the Detection of Cranial Arteriovenous Shunts.

BACKGROUND AND PURPOSE: 4D CT angiography is increasingly used in clinical practice for the assessment of different neurovascular disorders. Optimized processing of 4D-CTA is crucial for diagnostic interpretation because of the large amount of data that is generated. A color-mapping method for 4D-CTA is presented for improved and enhanced visualization of the cerebral vasculature hemodynamics. This method was applied to detect cranial AVFs. MATERIALS AND METHODS: All patients who underwent both 4D-CTA and DSA in our hospital from 2011 to 2018 for the clinical suspicion of a cranial AVF or carotid cavernous fistula were retrospectively collected. Temporal information in the cerebral vasculature was visualized using a patient-specific color scale. All color-maps were evaluated by 3 observers for the presence or absence of an AVF or carotid cavernous fistula. The presence or absence of cortical venous reflux was evaluated as a secondary outcome measure. RESULTS: In total, 31 patients were included, 21 patients with and 10 without an AVF. Arterialization of venous structures in AVFs was accurately visualized using color-mapping. There was high sensitivity (86%-100%) and moderate-to-high specificity (70%-100%) for the detection of AVFs on color-mapping 4D-CTA, even without the availability of dynamic subtraction rendering. The diagnostic performance of the 3 observers in the detection of cortical venous reflux was variable (sensitivity, 43%-88%; specificity, 60%-80%). CONCLUSIONS: Arterialization of venous structures can be visualized using color-mapping of 4D-CTA and proves to be accurate for the detection of cranial AVFs. This finding makes color-mapping a promising visualization technique for assessing temporal hemodynamics in 4D-CTA.

Identification of the pedunculopontine nucleus and surrounding white matter tracts on 7T diffusion tensor imaging, combined with histological validation.

BACKGROUND: The pedunculopontine nucleus (PPN) has been studied as a possible target for deep brain stimulation (DBS) for Parkinson's disease (PD). However, identifying the PPN can be challenging as the PPN is poorly visualized on conventional or even high-resolution MR scans. From histological studies it is known that the PPN is surrounded by major white matter tracts, which could function as possible anatomical landmarks. METHODS: This study aimed to localize the PPN using 7T magnetic resonance (MR) imaging and diffusion tensor imaging (DTI) of its white matter borders in one post-mortem brain. Histological validation of the same specimen was performed. The PPN was segmented in both spaces, after which the two masks were compared using the Dice Similarity Index (DSI). The DSI compared the similarity of two samples on an inter-individual level and validated the MR findings. The error in distance between the center of the two 3D segmentations was measured by use of the Euclidean distance. RESULTS: The PPN can be found in between the superior cerebellar peduncle and the medial lemniscus on both the FA-maps of the DTI images and the histological sections. The histological transverse sections showed to be superior to recognize the PPN (DSI: 1.0). The DTI images have a DSI of 0.82. The overlap-masks of both spaces showed a DSI of 0.32, whereas the concatenation-masks of both spaces showed a remarkable overlap, a DSI of 0.94. Euclidean distance of the overlap- and concatenation-mask in the two spaces showed to be 1.29 mm and 1.59 mm, respectively. CONCLUSION: This study supports previous findings that the PPN can be identified using FA-maps of DTI images. For possible clinical application in DBS localization, in vivo validation of the findings of our study is needed.

Subtraction CTA: An Alternative Imaging Option for the Follow-Up of Flow-Diverter-Treated Aneurysms?

BACKGROUND AND PURPOSE: This was a pilot study to explore the diagnostic accuracy and safety of subtraction CTA combined with a single-energy metal artifact reduction algorithm (SEMAR) compared to DSA for the evaluation of intracranial aneurysm occlusion after flow diverter treatment. MATERIALS AND METHODS: We included patients treated with a flow diverter for an unruptured intracranial aneurysm between November 2015 and November 2016. The patient cohort comprised 2 groups: those who underwent follow-up imaging 1 month after flow-diverter treatment and those with a known residual intracranial aneurysm after flow diverter treatment who underwent imaging at regular follow-ups. Full-brain subtraction CTA was performed on a 320-detector row CT system. A low-dose non-enhanced volume acquisition was followed by a contrast-enhanced volume CTA. Iterative and noise-reduction filters, SEMAR, and SURESubtraction algorithms were applied. DSA was performed on a flat panel C-arm angiography system. Standard posteroanterior, lateral, 3D, and detailed 2D acquisitions were performed. Imaging was independently scored by 2 clinicians. Aneurysm occlusion (Raymond scale) was our primary outcome parameter. RESULTS: Thirteen intracranial aneurysms were evaluated with subtraction CTA and DSA. Nine aneurysm remnants were demonstrated by both subtraction CTA and DSA. The sensitivity and specificity of subtraction CTA for the detection of aneurysm occlusion were 100% (95% CI, 82.41%-100%) and 100% (95% CI, 67.55%-100%), respectively. Agreement between readers was perfect (κ = 1.0). The smallest neck remnant detected on subtraction CTA was 1.2 mm. No complications occurred. CONCLUSIONS: Subtraction CTA with single-electron metal artifact reduction is effective in the reduction of metal artifacts of flow diverters and might therefore be a viable alternative in the assessment of intracranial aneurysm occlusion after flow diverter treatment.

Brain imaging in comatose survivors of cardiac arrest: Pathophysiological correlates and prognostic properties.

INTRODUCTION: Hypoxic-ischemic brain injury is the main cause of death and disability of comatose patients after cardiac arrest. Early and reliable prognostication is challenging. Common prognostic tools include clinical neurological examination and electrophysiological measures. Brain imaging is well established for diagnosis of focal cerebral ischemia but has so far not found worldwide application in this patient group. OBJECTIVE: To review the value of Computed Tomography (CT), Magnetic Resonance Imaging (MRI), and Positron Emission Tomography (PET) for early prediction of neurological outcome of comatose survivors of cardiac arrest. METHODS: A literature search was performed to identify publications on CT, MRI or PET in comatose patients after cardiac arrest. RESULTS: We included evidence from 51 articles, 21 on CT, 27 on MRI, 1 on CT and MRI, and 2 on PET imaging. Studies varied regarding timing of measurements, choice of determinants, and cut-off values predicting poor outcome. Most studies were small (n = 6-398) and retrospective (60%). In general, cytotoxic oedema, defined by a grey-white matter ratio <1.10, derived from CT, or MRI-diffusion weighted imaging <650 × 10-6 mm2/s in >10% of the brain could differentiate between patients with favourable and unfavourable outcomes on a group level within 1-3 days after cardiac arrest. Advanced imaging techniques such as functional MRI or diffusion tensor imaging show promising results, but need further evaluation. CONCLUSION: CT derived grey-white matter ratio and MRI based measures of diffusivity and connectivity hold promise to improve outcome prediction after cardiac arrest. Prospective validation studies in a multivariable approach are needed to determine the additional value for the individual patient.

[A woman with reversible encephalopathy]. / Een vrouw met reversibele encefalopathie.

A 72-year-old woman who recently had been treated with metronidazole presented with subacute dysarthria, gait ataxia and encephalopathy with severe anxiety. Head MRI showed symmetrical T2-hyperintensities. Under suspicion of a metronidazole-induced encephalopathy, metronidazole was stopped immediately. The patient recovered completely and follow-up MRI showed complete resolution of T2-hyperintensities.

Timing-Invariant CT Angiography Derived from CT Perfusion Imaging in Acute Stroke: A Diagnostic Performance Study.

BACKGROUND AND PURPOSE: Timing-invariant (or delay-insensitive) CT angiography derived from CT perfusion data may obviate a separate cranial CTA in acute stroke, thus enhancing patient safety by reducing total examination time, radiation dose, and volume of contrast material. We assessed the diagnostic accuracy of timing-invariant CTA for detecting intracranial artery occlusion in acute ischemic stroke, to examine whether standard CTA can be omitted. MATERIALS AND METHODS: Patients with suspected ischemic stroke were prospectively enrolled and underwent CTA and CTP imaging at admission. Timing-invariant CTA was derived from the CTP data. Five neuroradiologic observers assessed all images for the presence and location of intracranial artery occlusion in a blinded and randomized manner. Sensitivity and specificity of timing-invariant CTA and standard CTA were calculated by using an independent expert panel as the reference standard. Interrater agreement was determined by using κ statistics. RESULTS: We included 108 patients with 47 vessel occlusions. Overall, standard CTA and timing-invariant CTA provided similar high diagnostic accuracy for occlusion detection with a sensitivity of 96% (95% CI, 90%-100%) and a specificity of 100% (99%-100%) for standard CTA and a sensitivity of 98% (95% CI, 94%-100%) and a specificity of 100% (95% CI, 100%-100%) for timing-invariant CTA. For proximal large-vessel occlusions, defined as occlusions of the ICA, basilar artery, and M1, the sensitivity and specificity were 100% (95% CI, 100%-100%) for both techniques. Interrater agreement was good for both techniques (mean κ value, 0.75 and 0.76). CONCLUSIONS: Timing-invariant CTA derived from CTP data provides diagnostic accuracy similar to that of standard CTA for the detection of artery occlusions in acute stroke.

Susceptibility-weighted imaging improves the diagnostic accuracy of 3T brain MRI in the work-up of parkinsonism.

BACKGROUND AND PURPOSE: The differentiation between Parkinson disease and atypical parkinsonian syndromes can be challenging in clinical practice, especially in early disease stages. Brain MR imaging can help to increase certainty about the diagnosis. Our goal was to evaluate the added value of SWI in relation to conventional 3T brain MR imaging for the diagnostic work-up of early-stage parkinsonism. MATERIALS AND METHODS: This was a prospective observational cohort study of 65 patients presenting with parkinsonism but with an uncertain initial clinical diagnosis. At baseline, 3T brain MR imaging with conventional and SWI sequences was performed. After clinical follow-up, probable diagnoses could be made in 56 patients, 38 patients diagnosed with Parkinson disease and 18 patients diagnosed with atypical parkinsonian syndromes, including 12 patients diagnosed with multiple system atrophy-parkinsonian form. In addition, 13 healthy controls were evaluated with SWI. Abnormal findings on conventional brain MR imaging were grouped into disease-specific scores. SWI was analyzed by a region-of-interest method of different brain structures. One-way ANOVA was performed to analyze group differences. Receiver operating characteristic analyses were performed to evaluate the diagnostic accuracy of conventional brain MR imaging separately and combined with SWI. RESULTS: Disease-specific scores of conventional brain MR imaging had a high specificity for atypical parkinsonian syndromes (80%-90%), but sensitivity was limited (50%-80%). The mean SWI signal intensity of the putamen was significantly lower for multiple system atrophy-parkinsonian form than for Parkinson disease and controls (P < .001). The presence of severe dorsal putaminal hypointensity improved the accuracy of brain MR imaging: The area under the curve was increased from 0.75 to 0.83 for identifying multiple system atrophy-parkinsonian form, and it was increased from 0.76 to 0.82 for identifying atypical parkinsonian syndromes as a group. CONCLUSIONS: SWI improves the diagnostic accuracy of 3T brain MR imaging in the work-up of parkinsonism by identifying severe putaminal hypointensity as a sign indicative of multiple system atrophy-parkinsonian form.

Ancillary investigations to diagnose parkinsonism: a prospective clinical study.

Various ancillary investigations can assist clinicians in the differential diagnosis of patients with parkinsonism. It is unknown which test offers greatest diagnostic value in clinical practice. We included 156 consecutive patients with parkinsonism, but with an initially uncertain diagnosis. At baseline, all patients underwent extensive clinical testing and the following ancillary investigations: brain magnetic resonance imaging (MRI); (123)I-iodobenzamide single photon-emission computed tomography (IBZM-SPECT); analysis of cerebrospinal fluid (CSF); and anal sphincter electromyography (EMG). The final diagnosis was established after 3-year follow-up by two movement disorder specialists, according to international consensus criteria. We determined the diagnostic value by comparing the baseline clinical parameters and ancillary studies with the final diagnosis. Out of a potential 138 parameters, univariate analysis identified 35 parameters that discriminated Parkinson's disease (PD, n = 62) and atypical parkinsonism (AP, n = 94), with AUC of 0.55-0.81. Stepwise logistic regression showed that the combination of tandem gait, axial UPDRS subscore, slow saccadic eye movements and dysphagia yielded an AUC of 0.93, adjusted for optimism. The combination of tandem gait and axial UDPRS subscore yielded an AUC of 0.90. None of the ancillary investigations alone or in combination with clinical testing improved this clinically based diagnostic accuracy, not even in a subgroup of patients with the greatest diagnostic uncertainty at baseline. Our study demonstrates that a comprehensive set of clinical tests provides good accuracy to differentiate PD from AP. Our results also suggest that routine MRI, IBZM-SPECT, CSF analysis and anal sphincter EMG do not improve this diagnostic accuracy. Future work should evaluate the possible diagnostic value of more advanced diagnostic tests.

4D-CTA in neurovascular disease: a review.

CT angiography is a widely used technique for the noninvasive evaluation of neurovascular pathology. Because CTA is a snapshot of arterial contrast enhancement, information on flow dynamics is limited. Dynamic CTA techniques, also referred to as 4D-CTA, have become available for clinical practice in recent years. This article provides a description of 4D-CTA techniques and a review of the available literature on the application of 4D-CTA for the evaluation of intracranial vascular malformations and hemorrhagic and ischemic stroke. Most of the research performed to date consists of observational cohort studies or descriptive case series. These studies show that intracranial vascular malformations can be adequately depicted and classified by 4D-CTA, with DSA as the reference standard. In ischemic stroke, 4D-CTA better estimates thrombus burden and the presence of collateral vessels than conventional CTA. In intracranial hemorrhage, 4D-CTA improves the detection of the "spot" sign, which represents active ongoing bleeding.

MRA versus DSA for follow-up of coiled intracranial aneurysms: a meta-analysis.

MR angiography is proposed as a safer and less expensive alternative to the reference standard, DSA, in the follow-up of intracranial aneurysms treated with endovascular coil occlusion. We performed a systematic review and meta-analysis to evaluate the accuracy of TOF-MRA and contrast-enhanced MRA in detecting residual flow in the follow-up of coiled intracranial aneurysms. Literature was reviewed through the PubMed, Cochrane, and EMBASE data bases. In comparison with DSA, the sensitivity of TOF-MRA was 86% (95% CI: 82-89%), with a specificity of 84% (95% CI: 81-88%), for the detection of any recurrent flow. For contrast-enhanced MRA, the sensitivity and specificity were 86% (95% CI: 82-89%) and 89% (95% CI: 85-92%), respectively. Both TOF-MRA and contrast-enhanced MRA are shown to be highly accurate for detection of any recanalization in intracranial aneurysms treated with endovascular coil occlusion.

The additional value of three time point color coding in dynamic contrast-enhanced MRI of the breast for inexperienced and experienced readers.

PURPOSE: To evaluate the additional value of the color coding of dynamic data using the 3TP method in the evaluation of contrast-enhanced breast MRI for readers with different levels of experience. MATERIALS AND METHODS: A total of 52 lesions were included in this study, 25 malignant and 27 benign. All lesions were evaluated by four readers on two different workstations for the evaluation of dynamic breast MRI; one displaying the subtracted images and relative enhancement versus time curves and one displaying the subtracted images together with the 3TP color coding projected onto pre-contrast T1 images. Readers with different levels of experience were used. The diagnostic performance of both workstations was evaluated using ROC curve analyses. Interobserver variations were evaluated using kappa statistics. RESULTS: All lesions were detected by all four readers on both workstations. The diagnostic performance found in the inexperienced readers improved significantly when using the 3TP evaluations (p=0.04 and p=0.03). No significant difference was found for the more experienced readers (p=0.94 and p=0.54). The level of agreement between the readers improved significantly when using the 3TP evaluation method (p=0.01). CONCLUSION: Even though the 3TP color coding did not improve the diagnostic performance of the more experienced readers, this study clearly shows its value for inexperienced readers. The use of 3TP color coding is therefore recommended for inexperienced readers.

Treatment of a traumatic carotid-cavernous fistula with a covered stent: some considerations. Case report.

SUMMARY: This article discusses some considerations concerning covered stent placement in a patient with a traumatic direct carotid-cavernous fistula. Our case supports recent reports in the literature that covered stent placement can be an acceptable alternative when detachable balloon occlusion or coil occlusion of a direct carotid-cavernous fistula fails or cannot be done. Positioning of a covered stent in the internal carotid artery can be technically challenging. No specific covered stents for neurovascular use have been designed or registered. Because of limited experience with covered stent placement in the carotid artery the optimal preventive and therapeutic strategies for thromboembolic complications are not known.