Selection of patients with atherosclerotic carotid stenosis for revascularization is mainly based on the degree of luminal narrowing of the carotid artery. However, identification of other features ...of plaque apart from the degree of stenosis could enable better selection for intervention if they are also associated with the occurrence of stroke. Before these risk factors can possibly play a role in treatment decisions, their prognostic value needs to be proven. The purpose of this narrative review is to summarize current knowledge regarding the risk factors for stroke in patients with carotid stenosis, how they can be determined, and to what extent they predict stroke, based on recent literature. References for this review were identified by searches of PubMed between 1995 and October, 2016 and references from relevant articles. For each topic in this review different relevant search terms were used. The main search terms were ‘carotid stenosis’, ‘atherosclerosis’, ‘stroke risk’, and ‘vulnerable plaque’. Language was restricted to English. The final reference list was generated on the basis of relevance to the topics covered in this review.
Our aim was to determine whether use of the filter-based Sentinel™ Cerebral Protection System (CPS) during transcatheter aortic valve implantation (TAVI) can affect the early incidence of new brain ...lesions, as assessed by diffusion-weighted magnetic resonance imaging (DW-MRI), and neurocognitive performance.
From January 2013 to July 2015, 65 patients were randomised 1:1 to transfemoral TAVI with or without the Sentinel CPS. Patients underwent DW-MRI and extensive neurological examination, including neurocognitive testing one day before and five to seven days after TAVI. Follow-up DW-MRI and neurocognitive testing was completed in 57% and 80%, respectively. New brain lesions were found in 78% of patients with follow-up MRI. Patients with the Sentinel CPS had numerically fewer new lesions and a smaller total lesion volume (95 mm3 IQR 10-257 vs. 197 mm3 95-525). Overall, 27% of Sentinel CPS patients and 13% of control patients had no new lesions. Ten or more new brain lesions were found only in the control cohort (in 20% vs. 0% in the Sentinel CPS cohort, p=0.03). Neurocognitive deterioration was present in 4% of patients with Sentinel CPS vs. 27% of patients without (p=0.017). The filters captured debris in all patients with Sentinel CPS protection.
Filter-based embolic protection captures debris en route to the brain in all patients undergoing TAVI. This study suggests that its use can lead to fewer and overall smaller new brain lesions, as assessed by MRI, and preservation of neurocognitive performance early after TAVI.
Dutch trial register-ID: NTR4236. URL http://www.trialregister.nl/trialreg/admin/rctsearch.asp?Term=mistral.
Existing quantitative imaging biomarkers (QIBs) are associated with known biological tissue characteristics and follow a well-understood path of technical, biological and clinical validation before ...incorporation into clinical trials. In radiomics, novel data-driven processes extract numerous visually imperceptible statistical features from the imaging data with no a priori assumptions on their correlation with biological processes. The selection of relevant features (radiomic signature) and incorporation into clinical trials therefore requires additional considerations to ensure meaningful imaging endpoints. Also, the number of radiomic features tested means that power calculations would result in sample sizes impossible to achieve within clinical trials. This article examines how the process of standardising and validating data-driven imaging biomarkers differs from those based on biological associations. Radiomic signatures are best developed initially on datasets that represent diversity of acquisition protocols as well as diversity of disease and of normal findings, rather than within clinical trials with standardised and optimised protocols as this would risk the selection of radiomic features being linked to the imaging process rather than the pathology. Normalisation through discretisation and feature harmonisation are essential pre-processing steps. Biological correlation may be performed after the technical and clinical validity of a radiomic signature is established, but is not mandatory. Feature selection may be part of discovery within a radiomics-specific trial or represent exploratory endpoints within an established trial; a previously validated radiomic signature may even be used as a primary/secondary endpoint, particularly if associations are demonstrated with specific biological processes and pathways being targeted within clinical trials.
Key Points
• Data-driven processes like radiomics risk false discoveries due to high-dimensionality of the dataset compared to sample size, making adequate diversity of the data, cross-validation and external validation essential to mitigate the risks of spurious associations and overfitting.
• Use of radiomic signatures within clinical trials requires multistep standardisation of image acquisition, image analysis and data mining processes.
• Biological correlation may be established after clinical validation but is not mandatory.
Abstract Background Longitudinal data on the role of atherosclerosis in different vessel beds in the etiology of cognitive impairment and dementia are scarce and inconsistent. Methods Between ...2003–2006, 2364 nondemented persons underwent computed tomography of the coronaries, aortic arch, extracranial, and intracranial carotid arteries to quantify atherosclerotic calcification. Participants were followed for incident dementia (n = 90) until April 2012. At baseline and follow-up participants also underwent a cognitive test battery. Results Larger calcification volume in all vessels, except in the coronaries, was associated with a higher risk of dementia. After adjustment for relevant confounders, extracranial carotid artery calcification remained significantly associated with a higher risk of dementia hazard ratio per standard deviation increase in calcification volume: 1.37 (1.05, 1.79). Additional analyses for Alzheimer's disease only or censoring for stroke showed similar results. Larger calcification volumes were also associated with cognitive decline. Conclusions Atherosclerosis, in particular in the extracranial carotid arteries, is related to a higher risk of dementia and cognitive decline.
Several trials involving patients with acute ischemic stroke have shown better functional outcomes with endovascular treatment than with conventional treatment at 90 days after initiation of ...treatment. However, results on long-term clinical outcomes are lacking.
We assessed clinical outcomes 2 years after patients were randomly assigned to receive either endovascular treatment (intervention group) or conventional treatment (control group) for acute ischemic stroke. The primary outcome was the score on the modified Rankin scale at 2 years; this scale measures functional outcome, with scores ranging from 0 (no symptoms) to 6 (death). Secondary outcomes included all-cause mortality and the quality of life at 2 years, as measured by means of a health utility index that is based on the European Quality of Life-5 Dimensions questionnaire (scores range from -0.329 to 1, with higher scores indicating better health).
Of the 500 patients who underwent randomization in the original trial, 2-year data for this extended follow-up trial were available for 391 patients (78.2%) and information on death was available for 459 patients (91.8%). The distribution of outcomes on the modified Rankin scale favored endovascular treatment over conventional treatment (adjusted common odds ratio, 1.68; 95% confidence interval CI, 1.15 to 2.45; P=0.007). There was no significant difference between the treatment groups in the percentage of patients who had an excellent outcome (i.e., a modified Rankin scale score of 0 or 1). The mean quality-of-life score was 0.48 among patients randomly assigned to endovascular treatment as compared with 0.38 among patients randomly assigned to conventional treatment (mean difference, 0.10; 95% CI, 0.03 to 0.16; P=0.006). The cumulative 2-year mortality rate was 26.0% in the intervention group and 31.0% in the control group (adjusted hazard ratio, 0.9; 95% CI, 0.6 to 1.2; P=0.46).
In this extended follow-up trial, the beneficial effect of endovascular treatment on functional outcome at 2 years in patients with acute ischemic stroke was similar to that reported at 90 days in the original trial. (Funded by the Netherlands Organization for Health Research and Development and others; MR CLEAN Current Controlled Trials number, ISRCTN10888758 , and Netherlands Trial Register number, NTR1804 , and MR CLEAN extended follow-up trial Netherlands Trial Register number, NTR5073 .).
Purpose
To optimize the diffusion‐weighting b values and postprocessing pipeline for hybrid intravoxel incoherent motion diffusion kurtosis imaging in the head and neck region.
Methods
Optimized ...diffusion‐weighting b value sets ranging between 5 and 30 b values were constructed by optimizing the Cramér‐Rao lower bound of the hybrid intravoxel incoherent motion diffusion kurtosis imaging model. With this model, the perfusion fraction, pseudodiffusion coefficient, diffusion coefficient, and kurtosis were estimated. Sixteen volunteers were scanned with a reference b value set and 3 repeats of the optimized sets, of which 1 with volunteers swallowing on purpose.
The effects of (1) b value optimization and number of b values, (2) registration type (none vs. intervolume vs. intra‐ and intervolume registration), and (3) manual swallowing artifact rejection on the parameter precision were assessed.
Results
The SD was higher in the reference set for perfusion fraction, diffusion coefficient, and kurtosis by a factor of 1.7, 1.5, and 2.3 compared to the optimized set, respectively. A smaller SD (factor 0.7) was seen in pseudodiffusion coefficient. The sets containing 15, 20, and 30 b values had comparable repeatability in all parameters, except pseudodiffusion coefficient, for which set size 30 was worse. Equal repeatability for the registration approaches was seen in all parameters of interest. Swallowing artifact rejection removed the bias when present.
Conclusion
To achieve optimal hybrid intravoxel incoherent motion diffusion kurtosis imaging in the head and neck region, b value optimization and swallowing artifact image rejection are beneficial. The optimized set of 15 b values yielded the optimal protocol efficiency, with a precision comparable to larger b value sets and a 50% reduction in scan time.
Objectives
In intrathecal drug delivery, visualization of the device has been performed with plain radiography. However, the visibility of the related structures can be problematic. In ...troubleshooting, after the contrast material injection via the catheter access port, a computed tomography (CT) scan has been used. In troubleshooting, we also used a non‐contrast CT scan with 2D and 3D reconstructions. With the current phantom study, we aimed to obtain high‐resolution imaging of a poor opaque catheter with the use of a low‐dose single‐energy 2D and 3D CT scan with limited radiation exposure as a substitute for plain radiography.
Materials and Methods
The catheter was placed into a fatty substance and mounted on an anthropomorphic abdomen phantom followed by CT with varying kVp settings and with added tin beam filtering. Dose levels corrected based on the spinal catheter tip on T8 would result in a calculated effective dose in the range of the mSv's calculated for the plain x‐ray examination.
Results
Ultimately, Sn100 kVp has the best trade‐off between visibility, artifacts, and noise for a fixed dose. Although 3D VRT imaging was challenging at this low dose level, we could make a full evaluation possible with complementary 2D projections.
Conclusions
We could correctly identify the catheter and related structures, which supports the investigation of this in vivo and side‐by‐side evaluation with plain radiography. If found superior, then this technique may be able to replace plain radiography, while providing better visualization and acceptable radiation exposure.
Conflict of Interest
Dr. Delhaas reports personal fees from Medtronic Inc., as a previous consultant, outside the submitted work; Prof. van der Lugt reports grants from GE Healthcare, Siemens, Stryker, Medtronic, and Penumbra outside the submitted work.
Aging and vascular risk factors contribute to arterial stiffening. Increased arterial stiffness exposes the small vessels in the brain to abnormal flow pulsations and, as such, may contribute to the ...pathogenesis of cerebral small vessel disease. In a population-based study, we investigated the association between arterial stiffness, as measured by aortic pulse wave velocity (aPWV), and small vessel disease.
Overall, 1460 participants (mean age, 58.2 years) underwent aPWV measurement and brain MRI scanning. We calculated aPWV by measuring time differences and distances between pulse waves in the carotid and femoral arteries. Using automated MRI analysis, we obtained white matter lesion volumes. Infarcts and microbleeds were rated visually. We used linear and logistic regression models to associate aPWV with small vessel disease, adjusting for age, sex, mean arterial pressure, and heart rate and additionally for cardiovascular risk factors. Subsequently, we explored associations in strata of hypertension.
In the study group, higher aPWV was associated with larger white matter lesion volume (difference in volume per SD increase in aPWV 0.07; 95% CI, 0.02-0.12) but not with lacunar infarcts or microbleeds. In persons with uncontrolled hypertension, higher aPWV was significantly associated with larger white matter lesion volume (difference in volume per SD increase in aPWV 0.09; 95% CI, 0.00-0.18), deep or infratentorial microbleeds (OR, 2.13; 95% CI, 1.16-3.91), and to a lesser extent also with lacunar infarcts (OR, 1.63; 95% CI, 0.98-2.70). No such associations were present in persons with controlled hypertension or without hypertension.
In our study, increased arterial stiffness is associated with a larger volume of white matter lesions.
•Interest in hypofractionated radiotherapy with more heterogeneous dose distributions is increasing.•Existing osteoradionecrosis (ORN) risk models cannot be applied to non-standard fractionation ...schemes and dose distributions.•EUD can be used to better distinguish between ORN and non-ORN in a single model.•EUD(a = 8), teeth extraction, and mandibular volume were factors significantly associated to ORN.
Osteoradionecrosis (ORN) of the mandible is a severe complication following radiotherapy (RT). With a renewed interest in hypofractionation for head and neck radiotherapy, more information concerning ORN development after high fraction doses is important. The aim of this explorative study was to develop a model for ORN risk prediction applicable across different fractionation schemes using Equivalent Uniform Doses (EUD).
We performed a retrospective cohort study in 334 oropharyngeal squamous cell carcinoma (OPSCC) patients treated with either a hypofractionated Stereotactic Body Radiation Therapy (HF-SBRT) boost or conventional Intensity Modulated Radiation Therapy (IMRT). ORN was scored with the CTCAE v5.0. HF-SBRT and IMRT dose distributions were converted into equivalent dose in 2 Gy fractions (α/β = 0.85 Gy) and analyzed using EUD. The parameter a that led to an EUD that best discriminated patients with and without grade ≥ 2 ORN was selected. Patient and treatment-related risk factors of ORN were analyzed with uni- and multivariable regression analysis.
A total of 32 patients (9.6%) developed ORN grade ≥ 2. An EUD(a = 8) best discriminated between ORN and non-ORN (AUC = 0.71). In multivariable regression, pre-RT extractions (SHR = 2.34; p = 0.012), mandibular volume (SHR = 1.04; p = 0.003), and the EUD(a = 8) (SHR = 1.14; p < 0.001) were significantly associated with ORN.
Risk models for ORN based on conventional DVH parameters cannot be directly applied to HF-SBRT fractionation schemes and dose distributions. However, after correcting for fractionation and non-uniform dose distributions using EUD, a single model can distinguish between ORN and non-ORN after conventionally fractionated radiotherapy and hypofractionated boost treatments.
Purpose
Our aim is to automatically align digital subtraction angiography (DSA) series, recorded before and after endovascular thrombectomy. Such alignment may enable quantification of procedural ...success.
Methods
Firstly, we examine the inherent limitations for image registration, caused by the projective characteristics of DSA imaging, in a representative set of image pairs from thrombectomy procedures. Secondly, we develop and assess various image registration methods (SIFT, ORB). We assess these methods using manually annotated point correspondences for thrombectomy image pairs.
Results
Linear transformations that account for scale differences are effective in aligning DSA sequences. Two anatomical landmarks can be reliably identified for registration using a U-net. Point-based registration using SIFT and ORB proves to be most effective for DSA registration and are applicable to recordings for all patient sub-types. Image-based techniques are less effective and did not refine the results of the best point-based registration method.
Conclusion
We developed and assessed an automated image registration approach for cerebral DSA sequences, recorded before and after endovascular thrombectomy. Accurate results were obtained for approximately 85% of our image pairs.
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