Relationship between diameter asymmetry and blood flow in the pre-communicating (A1) segment of the anterior cerebral arteries.

BACKGROUND: Asymmetry in diameter between pre-communicating (A1) segments of the anterior cerebral arteries is related to anterior communicating artery aneurysm formation. Diameter asymmetry definitions vary and have not been related to blood flow measurements using the same imaging modality. We aimed to evaluate the relationship between A1-diameter asymmetry and blood flow asymmetry and to define a hemodynamically significant cut-off value for A1-diameter asymmetry. We assessed sex differences between different groups of A1-asymmetry. MATERIALS AND METHODS: 3-Tesla time-of-flight MRA and 4D-phase-contrast MRI were performed in 122 healthy participants. Diameter and blood flow measurements were performed halfway in both A1-segments. Participants were subdivided based on A1-diameter asymmetry: ≤10% (symmetric); 11-20%; 21-30%; 31-40%; and >40% (increasing asymmetry) groups. We studied the relationship between A1-diameter asymmetry and corresponding flow asymmetry (scatterplot and correlation). A hemodynamic-based cutoff value for A1-asymmetry was determined by comparing dominant A1 blood flow in the asymmetry groups to the mean blood flow of the symmetric A1-group (linear mixed-effects model). Sex-related differences in A1-diameter, blood flow and asymmetry were assessed with t-tests. RESULTS: A1-diameter asymmetry was linearly related to blood flow asymmetry between dominant and non-dominant sides. A1-diameter asymmetry >30% yielded statistically significant increased blood flow in the dominant A1 compared to symmetric A1s. Men had statistically significant larger A1-diameters, higher blood flow and a similar degree of A1-diameter asymmetry compared to women. CONCLUSION: A1-diameter asymmetry is linearly related to blood flow asymmetry. A >30% A1-asymmetry can be used as hemodynamically significant cut-off value. There were no sex-related differences in A1-diameter asymmetry.

Relationship between 3D Morphologic Change and 2D and 3D Growth of Unruptured Intracranial Aneurysms.

BACKGROUND AND PURPOSE: Untreated unruptured intracranial aneurysms are usually followed radiologically to detect aneurysm growth, which is associated with increased rupture risk. The ideal aneurysm size cutoff for defining growth remains unclear and also whether change in morphology should be part of the definition. We investigated the relationship between change in aneurysm size and 3D quantified morphologic changes during follow-up. MATERIALS AND METHODS: We performed 3D morphology measurements of unruptured intracranial aneurysms on baseline and follow-up TOF-MRAs. Morphology measurements included surface area, compactness, elongation, flatness, sphericity, shape index, and curvedness. We investigated the relation between morphologic change between baseline and follow-up scans and unruptured intracranial aneurysm growth, with 2D and 3D growth defined as a continuous variable (correlation statistics) and a categoric variable (t test statistics). Categoric growth was defined as ≥1-mm increase in 2D length or width. We assessed unruptured intracranial aneurysms that changed in morphology and the proportion of growing and nongrowing unruptured intracranial aneurysms with statistically significant morphologic change. RESULTS: We included 113 patients with 127 unruptured intracranial aneurysms. Continuous growth of unruptured intracranial aneurysms was related to an increase in surface area and flatness and a decrease in the shape index and curvedness. In 15 growing unruptured intracranial aneurysms (12%), curvedness changed significantly compared with nongrowing unruptured intracranial aneurysms. Of the 112 nongrowing unruptured intracranial aneurysms, 10 (9%) changed significantly in morphology (flatness, shape index, and curvedness). CONCLUSIONS: Growing unruptured intracranial aneurysms show morphologic change. However, nearly 10% of nongrowing unruptured intracranial aneurysms change in morphology, suggesting that they could be unstable. Future studies should investigate the best growth definition including morphologic change and size to predict aneurysm rupture.

Pulsatility Attenuation along the Carotid Siphon in Pseudoxanthoma Elasticum.

We compared velocity pulsatility, distensibility, and pulsatility attenuation along the intracranial ICA and MCA between 50 patients with pseudoxanthoma elasticum and 40 controls. Patients with pseudoxanthoma elasticum had higher pulsatility and lower distensibility at all measured locations, except for a similar distensibility at C4. The pulsatility attenuation over the siphon was similar between patients with pseudoxanthoma elasticum and controls. This finding suggests that other disease mechanisms are the main contributors to increased intracranial pulsatility in pseudoxanthoma elasticum.

Reliability and Agreement of 2D and 3D Measurements on MRAs for Growth Assessment of Unruptured Intracranial Aneurysms.

BACKGROUND AND PURPOSE: Reliable and reproducible measurement of unruptured intracranial aneurysm growth is important for unruptured intracranial aneurysm rupture risk assessment. This study aimed to compare the reliability and reproducibility of 2D and 3D growth measurements of unruptured intracranial aneurysms. MATERIALS AND METHODS: 2D height, width, and neck and 3D volume measurements of unruptured intracranial aneurysms on baseline and follow-up TOF-MRAs were performed by two observers. The reliability of individual 2D and 3D measurements and of change (growth) between paired scans was assessed (intraclass correlation coefficient) and stratified for aneurysm location. The smallest detectable change on 2D and 3D was determined. Proportions of growing aneurysms were compared, and Bland-Altman plots were created. RESULTS: Seventy-two patients with 84 unruptured intracranial aneurysms were included. The interobserver reliability was good-to-excellent for individual measurements (intraclass correlation coefficient > 0.70), poor for 2D change (intraclass correlation coefficient < 0.5), and good for 3D change (intraclass correlation coefficient = 0.76). For both 2D and 3D, the reliability was location-dependent and worse for irregularly shaped aneurysms. The smallest detectable changes for 2D height, width, and neck and 3D volume measurements were 1.5 , 2.0, and 1.9 mm and 0.06 mL, respectively. The proportion of growing unruptured intracranial aneurysms decreased from 10% to 2%, depending on the definition of growth (1 mm or the smallest detectable changes for 2D and 3D). CONCLUSIONS: The interobserver reliability of the size measurements of individual 2D and 3D unruptured intracranial aneurysms was good-to-excellent but lower for 2D and 3D growth measurements. For growth assessment, 3D measurements are more reliable than 2D measurements. The smallest detectable change for 2D measurements was larger than 1 mm, the current clinical definition of unruptured intracranial aneurysm growth.

Evolutionary algorithms and decision trees for predicting poor outcome after endovascular treatment for acute ischemic stroke.

Despite the large overall beneficial effects of endovascular treatment in patients with acute ischemic stroke, severe disability or death still occurs in almost one-third of patients. These patients, who might not benefit from treatment, have been previously identified with traditional logistic regression models, which may oversimplify relations between characteristics and outcome, or machine learning techniques, which may be difficult to interpret. We developed and evaluated a novel evolutionary algorithm for fuzzy decision trees to accurately identify patients with poor outcome after endovascular treatment, which was defined as having a modified Rankin Scale score (mRS) higher or equal to 5. The created decision trees have the benefit of being comprehensible, easily interpretable models, making its predictions easy to explain to patients and practitioners. Insights in the reason for the predicted outcome can encourage acceptance and adaptation in practice and help manage expectations after treatment. We compared our proposed method to CART, the benchmark decision tree algorithm, on classification accuracy and interpretability. The fuzzy decision tree significantly outperformed CART: using 5-fold cross-validation with on average 1090 patients in the training set and 273 patients in the test set, the fuzzy decision tree misclassified on average 77 (standard deviation of 7) patients compared to 83 (±7) using CART. The mean number of nodes (decision and leaf nodes) in the fuzzy decision tree was 11 (±2) compared to 26 (±1) for CART decision trees. With an average accuracy of 72% and much fewer nodes than CART, the developed evolutionary algorithm for fuzzy decision trees might be used to gain insights into the predictive value of patient characteristics and can contribute to the development of more accurate medical outcome prediction methods with improved clarity for practitioners and patients.

Sex differences in intracranial and extracranial atherosclerosis in patients with acute ischemic stroke.

BACKGROUND AND AIM: To investigate sex differences with respect to presence and location of atherosclerosis in acute ischemic stroke patients. METHODS: Participants with acute ischemic stroke were included from the Dutch acute stroke trial, a large prospective multicenter cohort study performed between May 2009 and August 2013. All patients received computed tomography/computed tomography-angiography within 9 h of stroke onset. We assessed presence of atherosclerosis in the intra- and extracranial internal carotid and vertebrobasilar arteries. In addition, we determined the burden of intracranial atherosclerosis by quantifying internal carotid and vertebrobasilar artery calcifications, resulting in calcium volumes. Prevalence ratios between women and men were calculated with Poisson regression analysis and adjusted prevalence ratio for potential confounders (age, hypertension, hyperlipidemia, diabetes, smoking, and alcohol use). RESULTS: We included 1397 patients with a mean age of 67 years, of whom 600 (43%) were women. Presence of atherosclerosis in intracranial vessel segments was found as frequently in women as in men (71% versus 72%, adjusted prevalence ratio 0.95; 95% CI 0.89-1.01). In addition, intracranial calcification volume did not differ between women and men in both intracranial internal carotid (large burden 35% versus 33%, adjusted prevalence ratio 0.93; 95% CI 0.73-1.19) and vertebrobasilar arteries (large burden 26% versus 40%, adjusted prevalence ratio 0.69; 95% CI 0.41-1.12). Extracranial atherosclerosis was less common in women than in men (74% versus 81%, adjusted prevalence ratio 0.86; 95% CI 0.81-0.92). CONCLUSIONS: In patients with acute ischemic stroke the prevalence of intracranial atherosclerosis does not differ between women and men, while extracranial atherosclerosis is less often present in women compared with men.

MRI Vessel Wall Imaging after Intra-Arterial Treatment for Acute Ischemic Stroke.

BACKGROUND AND PURPOSE: Vessel wall imaging is increasingly performed in the diagnostic work-up of patients with ischemic stroke. The aim of this study was to compare vessel wall enhancement after intra-arterial thrombosuction with that in patients not treated with thrombosuction. MATERIALS AND METHODS: From 2009 to 2017, forty-nine patients with an ischemic stroke underwent 7T MR imaging within 3 months after symptom onset as part of a prospective intracranial vessel wall imaging study. Fourteen of these patients underwent intra-arterial treatment using thrombosuction (intra-arterial treatment group). In the intra-arterial treatment group, vessel walls were evaluated for major vessel wall changes. All patients underwent pre- and postcontrast vessel wall imaging to assess enhancing foci of the vessel wall using coregistered subtraction images. A Wilcoxon signed rank test was performed to test for differences. RESULTS: In the intra-arterial treatment group, 11 of 14 patients (79%) showed vessel wall enhancement compared with 17 of 35 patients without intra-arterial treatment (49%). In the intra-arterial treatment group, more enhancing foci were detected on the ipsilateral side (n = 18.5) compared with the contralateral side (n = 3, P = .005). Enhancement was more often concentric on the ipsilateral side (n = 8) compared with contralateral side (n = 0, P = .01). No differences were found in the group without intra-arterial treatment between the number and configuration of ipsilateral and contralateral enhancing foci. CONCLUSIONS: Patients with intra-arterial treatment by means of thrombosuction showed more (concentric) enhancing foci of the vessel wall ipsilateral compared with contralateral to the treated artery than the patients without intra-arterial treatment, suggesting reactive changes of the vessel wall. This finding should be taken into account when assessing vessel wall MR images in patients with stroke.

Gadolinium Enhancement of the Aneurysm Wall in Unruptured Intracranial Aneurysms Is Associated with an Increased Risk of Aneurysm Instability: A Follow-Up Study.

BACKGROUND AND PURPOSE: Previous studies have suggested that gadolinium enhancement of the wall of unruptured intracranial aneurysms on MR imaging may reflect aneurysm wall instability. However, all previous studies were cross-sectional. In this longitudinal study, we investigated whether aneurysm wall enhancement is associated with an increased risk of aneurysm instability. MATERIALS AND METHODS: We included all patients 18 years of age or older with ≥1 unruptured aneurysm from the University Medical Center Utrecht, the Netherlands, who were included in 2 previous studies with either 3T or 7T aneurysm wall MR imaging and for whom it was decided not to treat the aneurysm but to monitor it with follow-up imaging. We investigated the risk of growth or rupture during follow-up of aneurysms with and without gadolinium enhancement of the aneurysm wall at baseline and calculated the risk difference between the 2 groups with corresponding 95% confidence intervals. RESULTS: We included 57 patients with 65 unruptured intracranial aneurysms. After a median follow-up of 27 months (interquartile range, 20-31 months), growth (n = 2) or rupture (n = 2) was observed in 4 of 19 aneurysms (21%; 95% CI, 6%-54%) with wall enhancement and in zero of 46 aneurysms (0%; 95% CI, 0%-8%) without enhancement (risk difference, 21%; 95% CI, 3%-39%). CONCLUSIONS: Gadolinium enhancement of the aneurysm wall on MR imaging is associated with an increased risk of aneurysm instability. The absence of wall enhancement makes it unlikely that the aneurysm will grow or rupture in the short term. Larger studies are needed to investigate whether aneurysm wall enhancement is an independent predictor of aneurysm instability.

Diagnostic accuracy of point-of-care ultrasound for evaluation of early blood-induced joint changes: Comparison with MRI.

INTRODUCTION: Recurrent joint bleeding is the hallmark of haemophilia. Synovial hypertrophy observed with Magnetic Resonance Imaging (MRI) is associated with an increased risk of future joint bleeding. AIM: The aim of this study was to investigate whether point-of-care ultrasound (POC-US) is an accurate alternative for MRI for the detection of early joint changes. METHODS: In this single centre diagnostic accuracy study, bilateral knees and ankles of haemophilia patients with no or minimal arthropathy on X-rays were scanned using POC-US and 3 Tesla MRI. POC-US was performed by 1 medical doctor, blinded for MRI, according to the "Haemophilia Early Arthropathy Detection with Ultrasound" (HEAD-US) protocol. MRIs were independently scored by 2 radiologists, blinded for clinical data and ultrasound results. Diagnostic accuracy parameters were calculated with 95% confidence intervals (CI). RESULTS: Knees and ankles of 24 haemophilia patients (96 joints), aged 18-34, were studied. Synovial hypertrophy on MRI was observed in 20% of joints. POC-US for synovial tissue was correct (overall accuracy) in 97% (CI: 91-99) with a positive predictive value of 94% (CI: 73-100) and a negative predictive value of 97% (CI: 91-100). The overall accuracy of POC-US for cartilage abnormalities was 91% (CI: 83-96) and for bone surface irregularities 97% (CI: 91-99). CONCLUSION: POC-US could accurately assess synovial hypertrophy, bone surface irregularities and cartilage abnormalities in haemophilia patients with limited joint disease. As POC-US is an accurate and available alternative for MRI, it can be used for routine evaluation of early joint changes.

How visual search relates to visual diagnostic performance: a narrative systematic review of eye-tracking research in radiology.

Eye tracking research has been conducted for decades to gain understanding of visual diagnosis such as in radiology. For educational purposes, it is important to identify visual search patterns that are related to high perceptual performance and to identify effective teaching strategies. This review of eye-tracking literature in the radiology domain aims to identify visual search patterns associated with high perceptual performance. Databases PubMed, EMBASE, ERIC, PsycINFO, Scopus and Web of Science were searched using 'visual perception' OR 'eye tracking' AND 'radiology' and synonyms. Two authors independently screened search results and included eye tracking studies concerning visual skills in radiology published between January 1, 1994 and July 31, 2015. Two authors independently assessed study quality with the Medical Education Research Study Quality Instrument, and extracted study data with respect to design, participant and task characteristics, and variables. A thematic analysis was conducted to extract and arrange study results, and a textual narrative synthesis was applied for data integration and interpretation. The search resulted in 22 relevant full-text articles. Thematic analysis resulted in six themes that informed the relation between visual search and level of expertise: (1) time on task, (2) eye movement characteristics of experts, (3) differences in visual attention, (4) visual search patterns, (5) search patterns in cross sectional stack imaging, and (6) teaching visual search strategies. Expert search was found to be characterized by a global-focal search pattern, which represents an initial global impression, followed by a detailed, focal search-to-find mode. Specific task-related search patterns, like drilling through CT scans and systematic search in chest X-rays, were found to be related to high expert levels. One study investigated teaching of visual search strategies, and did not find a significant effect on perceptual performance. Eye tracking literature in radiology indicates several search patterns are related to high levels of expertise, but teaching novices to search as an expert may not be effective. Experimental research is needed to find out which search strategies can improve image perception in learners.

Value of routine ultrasound in detecting early joint changes in children with haemophilia using the 'Haemophilia Early Arthropathy Detection with UltraSound' protocol.

INTRODUCTION: Patients with haemophilia tend to bleed in large joints even during prophylactic replacement therapy. Detection of early blood-induced joint changes may improve monitoring of treatment. The aim of this study was to explore the value of routine ultrasound in detecting early joint abnormalities in children with haemophilia on prophylaxis. METHODS: Sixty-four joints in 32 children with haemophilia were examined by one operator using the Haemophilia Early Arthropathy Detection with UltraSound protocol during annual multidisciplinary follow-up. Based on reported bleeding, the joint with the highest risk of blood-induced joint damage and the contralateral joint were examined. At the same day, clinical function was assessed according to the Haemophilia Joint Health Score (HJHS). RESULTS: Median age was 11.5 years (range = 5.5-16.4). Out of the 64 examined joints, one ankle was excluded because of previous surgery. Median lifetime joint bleeds/joint was three (interquartile ranges = 1-5). Clinical function of most joints was perfect: only 7/49 joints with reported bleeds scored positive due to swelling, muscle atrophy and/or range of motion loss (HJHS range = 1-2 points). Ultrasound showed abnormalities in 5/49 joints with reported bleeding, and 4/5 showed positive HJHS scores. Ultrasound abnormalities were present in 1/56 joints (1.8%, CI: 0.1-9.6%) without loss of clinical function. CONCLUSION: Ultrasound abnormalities were found during routine evaluation of joints in children with haemophilia on prophylaxis. Most joints with ultrasound abnormalities showed low HJHS scores too. Ultrasound could be used to evaluate whether minimal losses of clinical function might be caused by anatomical changes.

Improving head and neck CTA with hybrid and model-based iterative reconstruction techniques.

AIM: To compare image quality of head and neck computed tomography angiography (CTA) reconstructed with filtered back projection (FBP), hybrid iterative reconstruction (HIR) and model-based iterative reconstruction (MIR) algorithms. MATERIALS AND METHODS: The raw data of 34 studies were simultaneously reconstructed with FBP, HIR (iDose(4), Philips Healthcare, Best, the Netherlands), and with a prototype version of a MIR algorithm (IMR, Philips Healthcare). Objective (contrast-to-noise ratio [CNR], vascular contrast, automatic vessel analysis [AVA], stenosis grade) and subjective image quality (ranking at level of the circle of Willis, carotid bifurcation, and shoulder) of the five reconstructions were compared using repeated-measures analysis of variance (ANOVA) and post-hoc analysis. RESULTS: Vascular contrast was significantly higher in both the circle of Willis and carotid bifurcation with both levels of MIR compared to the other reconstruction methods (all p<0.0001). The CNR was highest for high MIR, followed by low MIR, high HIR, mid HIR and FBP (p<0.001 except low MIR versus high HIR; p>0.33). AVA showed most complete carotids in both MIR-levels, followed by high HIR (p>0.08), mid HIR (p<0.023) and FBP (p<0.010), vertebral arteries completeness was similar (p=0.40 and p=0.06). Stenosis grade showed no significant differences (p=0.16). High HIR showed the best subjective image quality at the circle of Willis and carotid bifurcation level, followed by mid HIR. At shoulder level, low MIR and high HIR were ranked best, followed by high MIR. CONCLUSION: Objectively, MIR significantly improved the overall image quality, reduced image noise, and improved automated vessel analysis, whereas FBP showed the lowest objective image quality. Subjectively, the highest level of HIR was considered superior at the level of the circle of Willis and the carotid bifurcation, and along with the lowest level of MIR for the origins of the neck arteries at shoulder level.

Predictors of reperfusion in patients with acute ischemic stroke.

BACKGROUND AND PURPOSE: Ischemic stroke studies emphasize a difference between reperfusion and recanalization, but predictors of reperfusion have not been elucidated. The aim of this study was to evaluate the relationship between reperfusion and recanalization and identify predictors of reperfusion. MATERIALS AND METHODS: From the Dutch Acute Stroke Study, 178 patients were selected with an MCA territory deficit on admission CTP and day 3 follow-up CTP and CTA. Reperfusion was evaluated on CTP, and recanalization on CTA, follow-up imaging. Reperfusion percentages were calculated in patients with and without recanalization. Patient admission and treatment characteristics and admission CT imaging parameters were collected. Their association with complete reperfusion was analyzed by using univariate and multivariate logistic regression. RESULTS: Sixty percent of patients with complete recanalization showed complete reperfusion (relative risk, 2.60; 95% CI, 1.63-4.13). Approximately one-third of patients showed some discrepancy between recanalization and reperfusion status. Lower NIHSS score (OR, 1.06; 95% CI, 1.01-1.11), smaller infarct core size (OR, 3.11; 95% CI, 1.46-6.66; and OR, 2.40; 95% CI, 1.14-5.02), smaller total ischemic area (OR, 4.20; 95% CI, 1.91-9.22; and OR, 2.35; 95% CI, 1.12-4.91), lower clot burden (OR, 1.35; 95% CI, 1.14-1.58), distal thrombus location (OR, 3.02; 95% CI, 1.76-5.20), and good collateral score (OR, 2.84; 95% CI, 1.34-6.02) significantly increased the odds of complete reperfusion. In multivariate analysis, only total ischemic area (OR, 6.12; 95% CI, 2.69-13.93; and OR, 1.91; 95% CI, 0.91-4.02) was an independent predictor of complete reperfusion. CONCLUSIONS: Recanalization and reperfusion are strongly associated but not always equivalent in ischemic stroke. A smaller total ischemic area is the only independent predictor of complete reperfusion.

Predictive value of thrombus attenuation on thin-slice non-contrast CT for persistent occlusion after intravenous thrombolysis.

BACKGROUND: In stroke erythrocyte-rich thrombi are more sensitive to intravenous thrombolysis with recombinant tissue plasminogen activator (IV-rtPA) and have higher density on non-contrast CT (NCCT). We investigated the relationship between thrombus density and recanalization and whether persistent occlusions can be predicted by Hounsfield unit (HU) measurements. METHODS: In 88 IV-rtPA-treated patients with intracranial ICA or MCA occluding thrombus and follow-up imaging, thrombus and contralateral vessel attenuation measurements were performed on thin-slice NCCT. Mean absolute and relative HU were compared between patients with persistent occlusion (modified Thrombolysis in Cerebral Infarction system, grade 0/1/2a) and recanalization (grade 2b/3). Univariate and multivariate (adjusted for stroke subtype, clot burden score, occlusion site and time to thrombolysis) odds ratios for persistent occlusion were calculated. Additional prognostic value for persistent occlusion was estimated by adding HU measurements to the area under the curve (AUC) of known determinants and calculating optimal cut-off values. RESULTS: Patients with persistent occlusion (n = 19) had significant lower mean HU (absolute 52.2 ± 9.5, relative 1.29 ± 0.20) compared to recanalization (absolute 63.1 ± 10.7, relative 1.54 ± 0.23, both p < 0.0001). Odds ratios for persistent occlusion were 3.1 (95% confidence interval, CI 1.6-6.0) univariate and 3.1 (95% CI 1.7-5.7) multivariate per 10 absolute HU decrease and 3.2 (95% CI 1.6-6.5) univariate and 4.1 (95% CI 1.8-9.1) multivariate per 0.20 relative HU decrease. Attenuation measurements significantly increased the AUC (0.67) of the known determinants to 0.84 (absolute HU) and 0.86 (relative HU). Cut-off values of <56.5 absolute HU and <1.38 relative HU showed optimal predictive values for persistent occlusion. CONCLUSIONS: Thrombus density is related to recanalization rate. Lower absolute and relative HU are independently related to persistent occlusion and HU measurements significantly increase discriminative performances of known recanalization determinants.

Interpretation of radiological images: towards a framework of knowledge and skills.

The knowledge and skills that are required for radiological image interpretation are not well documented, even though medical imaging is gaining importance. This study aims to develop a comprehensive framework of knowledge and skills, required for two-dimensional and multiplanar image interpretation in radiology. A mixed-method study approach was applied. First, a literature search was performed to identify knowledge and skills that are important for image interpretation. Three databases, PubMed, PsycINFO and Embase, were searched for studies using synonyms of image interpretation skills or visual expertise combined with synonyms of radiology. Empirical or review studies concerning knowledge and skills for medical image interpretation were included and relevant knowledge and skill items were extracted. Second, a preliminary framework was built and discussed with nine selective experts in individual semi-structured interviews. The expert team consisted of four radiologists, one radiology resident, two education scientists, one cognitive psychologist and one neuropsychologist. The framework was optimised based on the experts comments. Finally, the framework was applied to empirical data, derived from verbal protocols of ten clerks interpreting two-dimensional and multiplanar radiological images. In consensus meetings adjustments were made to resolve discrepancies of the framework with the verbal protocol data. We designed a framework with three main components of image interpretation: perception, analysis and synthesis. The literature study provided four knowledge and twelve skill items. As a result of the expert interviews, one skill item was added and formulations of existing items were adjusted. The think-aloud experiment showed that all knowledge items and three of the skill items were applied within all three main components of the image interpretation process. The remaining framework items were apparent only within one of the main components. After combining two knowledge items, we finally identified three knowledge items and thirteen skills, essential for image interpretation by trainees. The framework can serve as a guideline for education and assessment of two- and three-dimensional image interpretation. Further validation of the framework in larger study groups with different levels of expertise is needed.

Is joint effusion on MRI specific for haemophilia?

Magnetic resonance imaging (MRI) scores for haemophilic arthropathy are useful for evaluation of early and moderate arthropathy. The most recent additive International Prophylaxis Study Group (IPSG) MRI scale for haemophilic arthropathy includes joint effusion. However, it is unknown whether joint effusion is haemophilia specific. Correct interpretation of joint effusion is needed for outcome assessment of prophylactic therapies in haemophilia care. The aim of this study was to compare joint effusion on MRI between young adults with haemophilia and healthy controls. MRI's of both knees and ankles of 26 haemophilic patients (104 joints) and 30 healthy active men (120 joints) were assessed. Scans in both groups were performed in 2009/2010 and 2012 respectively. Joint effusion was measured and scored according to the MRI atlas referred by the IPSG MRI scale for haemophilic arthropathy. Median age of haemophilic patients and healthy controls was 21 and 24 years respectively. In haemophilic patients 23% of knees and 22% of ankles showed joint effusion. Healthy controls had significantly more positive scores for knee effusion (67%, P < 0.01) and a comparable scores for effusion in the ankle (17%). Joint effusion according to criteria of the IPSG MRI scale was observed significantly more often in knees of healthy controls, while findings in ankles were similar. These data suggest that joint effusion in knees and ankles is not haemophilia specific. Inclusion of joint effusion in the MRI scale is expected to reduce its specificity for haemophilic arthropathy.

Relationship between thrombus attenuation and different stroke subtypes.

INTRODUCTION: More insights in the etiopathogenesis of thrombi could be helpful in the treatment of patients with acute ischemic stroke. The aim of our study was to determine the relationship between presence of a hyperdense vessel sign and thrombus density with different stroke subtypes. METHODS: We included 123 patients with acute ischemic anterior circulation stroke and a visible occlusion on CT-angiography caused by cardioembolism (n = 53), large artery atherosclerosis (n = 55), or dissection (n = 15). Presence or absence of a hyperdense vessel sign was assessed and thrombus density was measured in Hounsfield Units (HU) on non-contrast 1 mm thin slices CT. Subsequently, occurrence of hyperdense vessel sign and thrombus density (absolute HU and rHU (=HU thrombus/HU contralateral)) were related with stroke subtypes. RESULTS: The presence of hyperdense vessel signs differed significantly among subtypes and was found in 45, 64 and 93 % of patients with cardioembolism, large artery atherosclerosis and dissection, respectively (p = 0.003). The mean HU and rHU (+95 % CI) of the thrombi in all vessels were respectively 56.1 (53.2-59.0) and 1.39 (1.33-1.45) in cardioembolism, 64.6 (62.2-66.9) and 1.59 (1.54-1.64) in large artery atherosclerosis and 76.4 (73.0-79.8) and 1.88 (1.79-1.97) in dissection (p < 0.0001). We found the same significant ranking order in the density of thrombi with hyperdense vessel signs (mean HU and rHU (+95 % CI), respectively): cardioembolism 61.3 (57.4-65.3) and 1.49 (57.4-65.3); large artery atherosclerosis 67.3 (64.9-69.7) and 1.65 (1.58-1.71); dissection 76.4 (72.6-80.1) and 1.89 (1.79-1.99, p < 0.0001). CONCLUSION: Presence of a hyperdense vessel sign and thrombus density are related to stroke subtype.

Diagnostic accuracy of CT perfusion imaging for detecting acute ischemic stroke: a systematic review and meta-analysis.

BACKGROUND: The aim of the current study was to determine the sensitivity and specificity of CT perfusion (CTP) for the detection of ischemic stroke by performing a systematic review and meta-analysis of published reports. METHODS: We searched PubMed, Embase and the Cochrane library using the terms 'perfusion computed tomography', 'ischemic stroke' and synonyms. We included studies that: (1) reported original data, (2) studied the diagnostic value of CTP for detecting ischemic stroke, (3) used MRI-DWI, follow-up MRI or follow-up CT as the reference standard, (4) included at least 10 patients who were suspected of ischemic stroke, and (5) reported the number of true positives, true negatives, false positives and false negatives for the diagnosis of ischemic stroke. RESULTS: Fifteen studies were finally included in the current review with a total of 1,107 patients. A pooled analysis resulted in a sensitivity of 80% (95% confidence interval, CI: 72-86%) and a specificity of 95% (95% CI: 86-98%). Almost two thirds of the false negatives were due to small lacunar infarcts; the remaining false negatives were mostly due to limited coverage. CONCLUSIONS: The current systematic review shows that CTP has a high sensitivity and a very high specificity for detecting infarcts.

Changes in cerebral perfusion around the time of delayed cerebral ischemia in subarachnoid hemorrhage patients.

BACKGROUND: Because the pathogenesis of delayed cerebral ischemia (DCI) after subarachnoid hemorrhage (SAH) is unclear, we studied cerebral perfusion at different time points around the occurrence of DCI. METHODS: We prospectively enrolled 53 patients admitted to the University Medical Center Utrecht who underwent CT perfusion (CTP) scans on admission, and within 2 weeks after hemorrhage on 2 scheduled time points or during clinical deterioration. The occurrence of DCI was assessed according to predefined criteria by 2 neurological observers blinded to perfusion results. Clinically stable patients (no-DCI) served as reference, and patients with other causes of deterioration (n = 11) were excluded. In DCI patients, the day of DCI onset and in no-DCI patients the median day of DCI onset was taken as t = 0. Scans made before and after DCI were clustered into 5 additional time points. At each time point, cerebral blood volume (CBV) and flow (CBF), and mean transit time (MTT) were measured, and absolute and relative (interhemispheric asymmetry) values were compared between DCI and no-DCI patients. RESULTS: Absolute CBF was lower and MTT was higher in the 18 DCI patients than in the 24 no-DCI patients before, during and after DCI. MTT asymmetry increased during DCI and partially recovered afterwards in DCI patients while it remained constant in no-DCI patients. Absolute and relative CBV remained constant in both groups. CONCLUSIONS: Our findings suggest that DCI patients already have diffusely worse perfusion (absolute values) than no-DCI patients before focal worsening (increased asymmetry) occurs and becomes symptomatic. The partial recovery in the measured areas suggests that DCI can be partly reversible.